JP5391970B2 - Moving object detection device and pixel similarity determination method - Google Patents

Description

  The present invention relates to a moving object detection apparatus that detects a moving object in an image based on a color moving image, and a method for determining the similarity of pixels used in the moving object detection apparatus.

  In a surveillance system using a video camera or the like, a technique for automatically detecting a moving object existing in a surveillance area has become important. If automatic detection of a moving object becomes possible, it can be used for processing for identifying whether the object is a vehicle or a human. Further, in the case of a vehicle, the number can be read to identify the vehicle, and in the case of a human, the present invention can be applied to a process for identifying an individual. It is also possible to automatically zoom in and track the detected suspicious person.

  The basic principle of detecting a moving object is to recognize a time-varying region by comparing a frame-unit input image given in time series with a background image prepared in advance and obtaining the difference between them. There is to do. However, when it is used for an outdoor monitoring system or the like, illumination fluctuations occur due to time or weather, so that accurate object detection cannot always be performed. Thus, for example, Patent Document 1 below discloses a technique of dividing an input image in units of frames into small regions and performing pixel value statistical processing in units of each small region to estimate illumination variation. In Patent Document 2 below, an input image in units of frames is divided into blocks, an average value of pixel values is obtained for each block, and the block is moved by comparing with an average of pixel values of a background image. A method for determining whether or not an object is included is disclosed.

  On the other hand, Non-Patent Document 1 below discloses a method of comparing an input image and a background image in units of pixels and determining whether or not the pixel is a pixel constituting a moving object. Specifically, when the pixel values of both pixels to be compared are similar, the pixel is a pixel constituting the background, and when the pixel values are not similar, the pixel is a pixel constituting a moving object. Is determined. At this time, the pixel similarity determination is performed by plotting coordinate points corresponding to both pixel values in a three-dimensional color space, and determining whether one coordinate point is in the vicinity region of the other coordinate point. It is done by examining.

JP-A-7-302328 JP 2009-048240 A

Kim K, Chalidabhongse T H, Harwood D, Davis L S. "Background Modeling and Subtraction by Codebook Construction" Proceedings of International Conference on Image Processing, Singapore. IEEE, 2004. 5: 3061-3064

  In the methods disclosed in Patent Documents 1 and 2 described above, the input image is subjected to statistical processing such as taking a histogram of pixel values in small regions or block units, and the feature amount obtained by the statistical processing is calculated. Since it is necessary to estimate the area of the moving object by applying it to a complicated model, there is a problem that the arithmetic processing becomes extremely complicated. For this reason, a general processor takes a long processing time, and it is difficult to perform processing in real time. Further, in order to perform more accurate detection, it is necessary to store an input image over many frames, and a large-capacity image buffer memory is required. For this reason, it is unsuitable for use in an inexpensive monitoring system for real-time monitoring.

  On the other hand, in the method disclosed in Non-Patent Document 1 described above, since it is only necessary to perform comparison in units of pixels, it is not necessary to perform complicated statistical processing or build a complicated model. However, in order to determine the similarity of pixels, geometric calculation in a three-dimensional color space is required, and in order to perform real-time processing using an inexpensive processor, the calculation processing load is still heavy. . In particular, operations including trigonometric functions are extremely heavy processing for an inexpensive general-purpose processor. In addition, since the statistical processing in units of regions is omitted and detection is performed based only on the comparison results in units of pixels, there is a problem that the detection is likely to be affected by lighting fluctuations due to time and weather, and erroneous detection is likely to occur.

  Therefore, an object of the present invention is to provide a moving object detection device that can perform more accurate detection while reducing the burden of calculation processing. It is another object of the present invention to provide a pixel similarity determination method that can be used in such a moving object detection device.

(1) A first aspect of the present invention provides a moving object detection device that detects a moving object for a moving image.
An image input unit for inputting a color original image in units of frames continuously given in time series as aggregate data of pixels having pixel values of three primary colors;
An original image storage unit for sequentially storing the input original images;
Based on a plurality of original images input in the past, an average image creation unit that sequentially creates an average image having average characteristics of these original images;
An average image storage unit for sequentially storing the created average images;
An image comparison unit that compares the original image stored in the original image storage unit with the average image stored in the average image storage unit and creates a mask image that distinguishes the foreground region and the background region;
A mask image storage for storing the mask image;
An image output unit for outputting a mask image;
Provided,
The image comparison unit
A pixel value reading unit that reads a pixel value of a pixel at a predetermined position of one image to be compared as a reference pixel value, and reads a pixel value of a pixel at a predetermined position of the other image to be compared as a comparison pixel value;
A similarity determination unit that determines whether or not the comparison pixel value is within a predetermined similarity range set for the reference pixel value;
When the similarity determination unit determines that the pixel value of the pixel at the predetermined position constituting the mask image is within the similar range, the pixel value indicating the background area is determined. When the similarity determination unit determines that the pixel value is outside the similarity range, A pixel value writing unit for writing the pixel value indicating the foreground region into the mask image storage unit,
Composed by
In the three-dimensional coordinate system in which the similarity determination unit takes each pixel value of the three primary colors on each coordinate axis, the reference point Q located at the coordinate corresponding to the reference pixel value and the comparison point q located at the coordinate corresponding to the comparison pixel value When the positional relationship between the spheroid E having a predetermined size centered on the reference point Q and the comparison point q is examined, and it can be determined that the comparison point q is located outside the spheroid E or its approximate body, If it is determined that it is outside the similar range and it can be determined that it is located inside, it is determined that it is within the similar range ,
In addition, the similarity determination unit multiplies a distance D between the origin O of the three-dimensional coordinate system and the reference point Q by a predetermined parameter h (where h <1) to obtain a value α = h · D as a major axis radius. And an ellipse having a minor axis radius of β = k · D obtained by multiplying a predetermined parameter k (where k <h), the major axis overlaps the reference axis Z connecting the origin O and the reference point Q. In this way, the spheroid E is defined by arranging the reference point Q to be the center point and rotating it around the reference axis Z.

(2) According to a second aspect of the present invention, in the moving object detection device according to the first aspect described above,
The average image creation unit
When the i-th original image P (i) is input (i = 1, 2,...), Pixels at corresponding positions in the past original image including the original image P (i) To calculate a weighted average value of pixel values for each color, and create an i-th average image A (i) composed of a collection of pixels having the average value,
When the (i + 1) -th original image P (i + 1) is input, the image comparison unit compares the original image P (i + 1) with the i-th average image A (i), The (i + 1) th mask image M (i + 1) is created.

(3) According to a third aspect of the present invention, in the moving object detection device according to the second aspect described above,
The average image creation unit
When the first original image P (1) is input, the original image P (1) is stored in the average image storage unit as the first average image A (1) as it is,
Thereafter, every time the i-th original image P (i) is input (i = 2, 3,...), The i-th average image A (i) is
a (i) = (1-w) .a (i-1) + w.p (i)
(However, a (i) is the average image A (i)
A pixel value of a predetermined color of a pixel at a predetermined position,
a (i-1) is the average image A (i-1)
The pixel value of the predetermined color of the pixel at the predetermined position,
p (i) is the original image P (i)
The pixel value of the predetermined color of the pixel at the predetermined position,
w is a parameter indicating a predetermined weight (w <1))
It is made using the following arithmetic expression.

(4) According to a fourth aspect of the present invention, in the moving object detection device according to the first to third aspects described above,
Similarity judgment part,
“The comparison point q is located inside the sphere C1 with the origin O as the center and the radius (D−α)” or “the comparison point q is located outside the sphere C2 with the origin O as the center and the radius (D + α)”. A first condition determining unit that determines whether or not the first condition is satisfied;
When the first condition determination unit makes a negative determination, “the comparison point q is outside the cone ξ or its approximated body that is in contact with the spheroid E with the origin O as the vertex and the reference axis Z as the central axis. A second condition determining unit that determines whether or not the second condition “located” is satisfied;
The third condition determining unit that determines whether or not the third condition “the comparison point q is located outside the spheroid E” is satisfied when the second condition determining unit makes a negative determination. When,
When any of the first condition determination unit, the second condition determination unit, and the third condition determination unit makes a positive determination, a determination value indicating a determination result that the similarity is out of the similar range is output. A determination value output unit that outputs a determination value indicating a determination result that is within the similar range when all of the condition determination unit, the second condition determination unit, and the third condition determination unit perform a negative determination;
It is made up by.

(5) According to a fifth aspect of the present invention, in the moving object detection device according to the fourth aspect described above,
When the distance between the origin O and the reference point Q is D, and the distance between the origin O and the comparison point q is d,
The first condition determination unit
(1-h) ² · D ² > d ² or
(1 + h) ² · D ² <d ²
The calculation for determining whether or not the above condition is satisfied is performed.

(6) According to a sixth aspect of the present invention, in the moving object detection device according to the fourth aspect described above,
When the second condition determination unit determines that the circle constituting the intersection line of the spherical surface C3 having the radius D centered on the origin O and the spheroid E is the intersection line S, “the origin O is the vertex, the reference axis Whether or not the second condition that the comparison point q is located outside the cone ξ ′ passing through the circle of intersection S with Z as the central axis is satisfied is determined.

(7) According to a seventh aspect of the present invention, in the moving object detection device according to the sixth aspect described above,
The second condition determination unit performs an approximate determination using an approximate expression in which the distance f between an arbitrary point on the intersection circle S and the reference point Q is equal to the minor axis radius β. is there.

(8) According to an eighth aspect of the present invention, in the moving object detection device according to the seventh aspect described above,
The reference pixel value indicating the coordinates of the reference point Q is (R, G, B), the comparison pixel value indicating the coordinates of the comparison point q is (r, g, b), the distance between the origin O and the reference point Q is D, When the distance between the origin O and the comparison point q is d,
The second condition determination unit
γ = (R · r + G · g + B · b)
As
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2
The calculation for determining whether or not the above condition is satisfied is performed.

(9) According to a ninth aspect of the present invention, in the moving object detection device according to the fourth aspect described above,
The reference pixel value indicating the coordinates of the reference point Q is (R, G, B), the comparison pixel value indicating the coordinates of the comparison point q is (r, g, b), the distance between the origin O and the reference point Q is D, When the distance between the origin O and the comparison point q is d,
The third condition determination unit
α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
γ = (R · r + G · g + B · b)
As
β ² · x ² + α ² · y ² -α ² · β ² > 0
The calculation for determining whether or not the above condition is satisfied is performed.

(10) According to a tenth aspect of the present invention, in the moving object detection device according to the first to third aspects described above,
Similarity judgment part,
A parameter holding unit for holding values of parameters h and k;
Based on the reference pixel value (R, G, B) and the comparison pixel value (r, g, b) read by the pixel value reading unit,
D ² = R ² + G ² + B ² and
d ² = r ² + g ² + b ²
A basic calculation unit for calculating the value D ² and the value d ² ,
By using the value of the parameter h to the basic computation unit is held at the value D ² and the value d ² and the parameter holding section calculated,
(1-h) ² · D ² > d ² or
(1 + h) ² · D ² <d ²
A first condition determination unit that performs an operation for determining whether or not the condition is satisfied;
Based on the reference pixel value (R, G, B) and the comparison pixel value (r, g, b) read by the pixel value reading unit when the first condition determining unit makes a negative determination,
γ = R · r + G · g + B · b
To calculate the value γ, using the value D ² and the value d ² calculated by the basic calculation unit, the value of the parameter k held in the parameter holding unit, and the value γ,
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2
A second condition determination unit that performs an operation for determining whether or not the condition is satisfied,
If the second condition determination unit makes a negative determination, values and determining a second condition of parameters h and k basic operation unit is held at the value D ² and the value d ² and the parameter holding unit calculated Using the value γ calculated by the
α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
And using the calculation result,
β ² · x ² + α ² · y ² -α ² · β ² > 0
A third condition determination unit that performs an operation for determining whether or not the condition is satisfied,
When any of the first condition determination unit, the second condition determination unit, and the third condition determination unit makes a positive determination, a determination value indicating a determination result that the similarity is out of the similar range is output. A determination value output unit that outputs a determination value indicating a determination result that is within the similar range when all of the condition determination unit, the second condition determination unit, and the third condition determination unit perform a negative determination;
It is made up by.

(11) An eleventh aspect of the present invention is the moving object detection apparatus according to the fifth, eighth to tenth aspects described above.
For some or all arithmetic expressions containing inequality signs, use arithmetic expressions that use “inequality sign ≧” instead of “inequality sign>”, or arithmetic expressions that use “inequality sign ≦” instead of “inequality sign <”. It is a thing.

(12) According to a twelfth aspect of the present invention, in the moving object detection device according to the first to eleventh aspects described above,
A parameter setting unit for setting the parameters “w” or “h and k” or all of them to an arbitrary value by a user operation input is further provided.

(13) According to a thirteenth aspect of the present invention, in the moving object detection device according to the first to twelfth aspects described above,
The pixel value reading unit reads the pixel value of the pixel of the original image as the reference pixel value, and reads the pixel value of the pixel of the average image as the comparison pixel value.

(14) In a fourteenth aspect of the present invention, the moving object detection device according to the first to thirteenth aspects is configured by incorporating a program into a computer.

(15) According to a fifteenth aspect of the present invention, the moving object detection device according to the first to thirteenth aspects is configured by a semiconductor integrated circuit.

(16) A sixteenth aspect of the present invention is a first color pixel having pixel values (R, G, B) of three primary colors and a second color having pixel values (r, g, b) of three primary colors. In the pixel similarity determination method for determining similarity with a color pixel,
A preparatory stage in which a computer captures values of pixel values (R, G, B) and (r, g, b);
In a three-dimensional coordinate system in which each pixel value of the three primary colors is taken as each coordinate axis, the computer has a spheroid E of a predetermined size centered on a reference point Q having coordinates corresponding to the pixel values (R, G, B) or A positional relationship determination step for examining whether the latter is inside or outside the former with respect to the approximation and the comparison point q having coordinates corresponding to the pixel value (r, g, b);
When the computer determines that the comparison point q is outside the spheroid E or its approximate body, the computer outputs a determination result that the first color pixel and the second color pixel are dissimilar, and rotates. A determination result output stage for outputting a determination result that the first color pixel and the second color pixel are similar when it is determined that the comparison point q is inside the ellipsoid E or its approximate body;
To carry out the,
In the positional relationship determination stage, a value α = h · D obtained by multiplying the distance D between the origin O of the three-dimensional coordinate system and the reference point Q by a predetermined parameter h (where h <1) is set as the major axis radius, An ellipse whose minor axis radius is a value β = k · D obtained by multiplying a predetermined parameter k (where k <h) is set so that the major axis overlaps the reference axis Z connecting the origin O and the reference point Q. In addition, a spheroid E obtained by rotating around the reference axis Z is defined so that the reference point Q is the center point.

(17) According to a seventeenth aspect of the present invention, in the pixel similarity determination method according to the sixteenth aspect described above,
The positional relationship judgment stage
“The comparison point q is located inside the sphere C1 with the origin O as the center and the radius (D−α)” or “the comparison point q is located outside the sphere C2 with the origin O as the center and the radius (D + α)”. A first condition determination stage for determining whether or not a first condition is satisfied;
When a negative determination is made in the first condition determination stage, “the comparison point q is outside the cone ξ or its approximated body that is in contact with the spheroid E with a circle with the origin O as the apex and the reference axis Z as the central axis. A second condition determination step for determining whether or not a second condition “is located” is satisfied;
Third condition determination for determining whether or not the third condition “the comparison point q is located outside the spheroid E” is satisfied when a negative determination is made in the second condition determination stage. Stages,
Composed by
In the determination result output stage, when a positive determination is made in any of the first condition determination stage, the second condition determination stage, and the third condition determination stage, the first color pixel and the second color When the determination result that the pixel is dissimilar is output and negative determination is made in all of the first condition determination stage, the second condition determination stage, and the third condition determination stage, the first color A determination result indicating that the pixel and the second color pixel are similar is output.

(18) According to an eighteenth aspect of the present invention, in the pixel similarity determination method according to the seventeenth aspect described above,
In the first condition determination stage,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
And when
(1-h) ² · D ² > d ² or
(1 + h) ² · D ² <d ²
The calculation for determining whether or not the above condition is satisfied is performed.

(19) According to a nineteenth aspect of the present invention, in the pixel similarity determination method according to the seventeenth aspect described above,
In the second condition determination stage,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² ),
γ = (R · r + G · g + B · b)
And when
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2
The calculation for determining whether or not the above condition is satisfied is performed.

(20) According to a twentieth aspect of the present invention, in the pixel similarity determination method according to the seventeenth aspect described above,
In the third condition determination stage,
α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
γ = (R · r + G · g + B · b)
And when
β ² · x ² + α ² · y ² -α ² · β ² > 0
The calculation for determining whether or not the above condition is satisfied is performed.

(21) In a twenty-first aspect of the present invention, a first color pixel having each pixel value (R, G, B) of the three primary colors and a second color having each pixel value (r, g, b) of the three primary colors In the pixel similarity determination method for determining similarity with a color pixel,
A preparatory stage in which a computer captures values of parameters h (h <1) and k (k <h), pixel values (R, G, B) and (r, g, b);
Computer
(1-h) ² · (R ² + G ² + B ² )> (r ² + g ² + b ² ) or (1 + h) ² · (R ² + G ² + B ² ) <(r ² + g ² + b ² )
A first condition determination stage for determining whether or not the condition is satisfied,
When a negative determination is made in the first condition determination stage, the computer
(R · r + G · g + B · b) ² /
((R ² + G ² + B ² ) · (r ² + g ² + b ² ))
^{<(1-k 2/2} ) 2
A second condition determination stage for determining whether or not the condition is satisfied,
If a negative determination is made in the second condition determination stage, the computer
β ² · x ² + α ² · y ² -α ² · β ² > 0
However, α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
γ = (R · r + G · g + B · b)
A third condition determination stage for determining whether or not the condition is satisfied;
If the computer makes a positive determination in any of the first condition determination stage, the second condition determination stage, and the third condition determination stage, the first color pixel and the second color pixel are A determination result of dissimilarity is output, and when negative determination is made in all of the first condition determination stage, the second condition determination stage, and the third condition determination stage, the first color pixel and the first color pixel A determination result output stage for outputting a determination result that the two color pixels are similar;
Is to do.

(22) According to a twenty-second aspect of the present invention, in the pixel similarity determination method according to the eighteenth to twenty-first aspects described above,
For some or all arithmetic expressions containing inequality signs, use arithmetic expressions that use “inequality sign ≧” instead of “inequality sign>”, or arithmetic expressions that use “inequality sign ≦” instead of “inequality sign <”. It is a thing.

  According to the pixel similarity determination method according to the present invention, in the three-dimensional color space, a coordinate point plotting the other pixel value is placed in a spheroid centered on the coordinate point plotting one pixel value. Since the determination of the similarity of the color pixel to be compared is performed based on whether or not, it is possible to perform the similarity determination suitable for detecting the moving object while reducing the burden of the arithmetic processing become. In addition, since the moving object detection device according to the present invention employs a detection method that adopts the above-described pixel similarity determination method, it is possible to more accurately detect a moving object while reducing the burden of calculation processing. become.

It is a top view which shows the example of a detection of the moving object about a moving image. It is a figure which shows the basic principle of the moving object detection in this invention. It is a figure which shows an example of the production method of the average image used as an image which shows a background in this invention. It is a figure which shows the pixel value transition process of 1 pixel on the average image produced based on the method shown in FIG. It is a figure which shows the pixel value determination process of the mask image in this invention. It is a three-dimensional color space figure which shows the prior art example of the similarity determination method of a pixel. It is a three-dimensional color space figure which shows another prior art example of the similarity determination method of a pixel. It is a three-dimensional color space diagram showing a first application example of a pixel similarity determination method for use in moving object detection according to the present invention. It is a three-dimensional color space figure which shows the 2nd application example of the similarity determination method of the pixel used for the moving object detection which concerns on this invention. FIG. 3 is a three-dimensional color space diagram illustrating a pixel similarity determination method according to the present invention. It is sectional drawing which shows the advantage of the spheroid model of this invention with respect to the conventional cylinder model. It is sectional drawing which shows the 1st condition determination principle at the time of using a spheroid model. It is a figure which shows the determination type | formula based on the 1st condition determination principle shown in FIG. It is sectional drawing which shows the 2nd condition determination principle at the time of using a spheroid model. FIG. 15 is a diagram illustrating a first process for deriving a determination formula based on the second condition determination principle illustrated in FIG. 14. FIG. 15 is a diagram showing a second process for deriving a determination formula based on the second condition determination principle shown in FIG. 14. It is a figure which shows the determination type based on the 2nd condition determination principle shown in FIG. It is sectional drawing which shows the 3rd condition determination principle at the time of using a spheroid model. It is a figure which shows the determination formula based on the 3rd condition determination principle shown in FIG. It is a flowchart which shows the practical procedure of the similarity determination method of the pixel which concerns on this invention. It is a block diagram which shows the basic composition of the moving object detection apparatus which concerns on this invention. It is a block diagram which shows the detailed structure of the similarity determination part 220 in the apparatus shown in FIG.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

<<< §1. Basic principle of moving object detection >>
First, the basic principle of moving object detection according to the present invention will be described. This basic principle is for detecting a moving object in a moving image, and it is assumed that a color image in units of frames is given continuously in time series as a collection of pixels having pixel values of three primary colors. Yes.

  For example, assume that images P10, P20, P30, and P40 in units of frames are given in this order as shown on the left side of FIG. The illustrated example shows a photographed image by a fixed-point video camera installed on the street, and shows a state in which one vehicle (moving object) passes from right to left. Note that in the case of a general video camera, captured images are output continuously at a cycle of about 30 frames per second, so in practice, a large number of frame images can be obtained at finer time intervals. However, for convenience of explanation, it is assumed that four frame images P10, P20, P30, and P40 are given in order as shown in the figure.

  Looking at these four images, the image P10 is only the background of the city, but in the image P20, since a part of the vehicle has entered the right side, the image is a part of the vehicle overlapped on the background. Similarly, the images P30 and P40 are images in which vehicles overlap on the background. Since the background is stationary, it is common for the images P10 to P40. However, since the vehicle is a moving object, the images P10 to P40 are different. Here, on each image, the area constituting the background is referred to as the background area B, and the area constituting the vehicle (moving object) is referred to as the foreground area F.

  The object of the moving object detection in the present invention is to distinguish the background area B and the foreground area F from each of the given images P10 to P40. The images M10 to M40 shown on the right side of FIG. 1 are images showing the distinction between the background region B and the foreground region F with respect to the images P10 to P40 shown on the left side, respectively. The hatched area in the figure is the background area B, and the white area is the foreground area F. Since it is only necessary to identify which region, these images M10 to M40 are given as binary images. For example, if the pixel value “0” is given to the pixels belonging to the background area B and the pixel value “1” is given to the pixels belonging to the foreground area F, the images M10 to M40 are 1-bit pixels. It can be prepared as image data consisting of a collection of pixels having values.

  According to the present invention, a corresponding binary image can be created for each given frame image. After all, the essence of the moving object detection process according to the present invention is a process of creating a binary image indicating the distinction between the background area B and the foreground area F for each color image continuously given in time series. be able to. Therefore, hereinafter, for convenience, a color image continuously given in time series is referred to as an “original image”, and a binary image created based on the “original image” is referred to as a “mask image”.

  In the example shown in FIG. 1, an example in which mask images M10 to M40 are created for each of the original images P10 to P40 is shown. By using these mask images, it is possible to recognize which area on the original image is a moving object, so you can grasp the shape and size of the moving object, zoom up the moving object part, and set the vehicle number. It is possible to perform processing for confirming or specifying a person. In addition, it is possible to track a moving object on the screen while zooming up, or to grasp a moving path.

  Of course, it is difficult to create such a mask image from only one original image. For example, when only the illustrated original image P20 is given as a still image, the human brain can recognize the presence of the vehicle from various information, but the presence of the vehicle is detected by the computer from only this one still image. In order to recognize this, processing based on a complicated algorithm is required. Therefore, as described above, a general moving object detection algorithm employs a method of determining a difference area between the input image and the background image and determining the difference area as a moving object area (foreground area F). .

  For example, if the original image P10 is designated as a background image in advance, the difference area is recognized as the foreground area F by comparing the original image P20 when the original image P20 is input, and a mask image M20 as shown in the figure is obtained. Can be created. As described above, as a method for recognizing a difference region, a method of performing statistical processing of pixel values in units of small regions is also known. However, by comparing the input image and the background image in units of pixels, the pixels of both pixels are compared. When the values are similar, it is assumed that the pixel is a pixel constituting the background region B, and when the values are not similar, it is most preferable that the pixel is a pixel constituting the foreground region F constituting the moving object. It is a simple method. The present invention is also premised on adopting such a pixel-by-pixel comparison method.

  As a background image, it is possible to use a still image that has been captured in a state in which no moving object exists in advance (for example, the state shown in the image P10). However, due to factors such as weather and time, the lighting environment is constantly changing. Since it changes, it is inappropriate to continue to use a still image taken at a specific time point as a background image. Therefore, usually, a method is employed in which an average image having an average characteristic of these original images is created based on a plurality of original images input in the past, and this average image is used as a background image. In the present invention, the average image obtained by such a method is used as a background image. Since the average image is sequentially updated each time a new image is input, it always functions as an optimum background image at that time.

  FIG. 2 is a diagram showing the basic principle of moving object detection in the present invention. Here, the images P (1), P (2),..., P (i-2), P (i-1), and P (i) shown in the upper part of the figure are given continuously in time series. A frame-unit original image is shown, and a state in which images for i frames from the first original image P (1) to the i-th original image P (i) have been given is shown. . On the other hand, the image P (i + 1) shown on the left in the middle of the figure is the (i + 1) th original image newly given, and the image A (i) shown on the right of the middle of the figure is the past shown in the upper part of the figure. Is an average image having an average characteristic of the original images P (1) to P (i) for i frames given to.

  The mask image M (i + 1) for the newly input original image P (i + 1) is created by comparing the original image P (i + 1) and the average image A (i). The lower part of FIG. 2 shows the mask image M (i + 1) created in this way. Specifically, the pixel value of each pixel on the original image P (i + 1) is compared with the pixel value of the corresponding pixel on the average image A (i). A pixel value indicating B (for example, “0”) is given, and a pixel value indicating the foreground area F (for example, “1”) is given to a pixel determined to be outside the similar range, thereby forming a mask made of a binary image An image M (i + 1) may be created.

  Subsequently, when the (i + 2) th original image P (i + 2) is input, an average image A () having an average characteristic up to the (i + 1) th original image P (i + 1) input in the past. i + 1) is newly created, and the mask image M (i + 2) is created by comparing the original image P (i + 2) with the average image A (i + 1). In this way, since the average image is sequentially updated, even if the lighting environment changes due to factors such as weather and time, it can function as a background image suitable for each time point.

  Note that when creating an average image, it is preferable to perform weighting along a time series, and obtain a weighted average with the latest original image information weighted. For example, if an average is obtained by giving a weight of 1 for an original image input in the past 10 minutes and a weight of 0 for an original image input before that, an average image for the original image obtained in the latest 10 minutes is always obtained. It can be obtained and can cope with a change in the lighting environment. Of course, the weights can be set finely so that the latest original image always has a higher weight.

  After all, in the case of the example shown in FIG. 2, when creating the average image, when the i-th original image P (i) is input (i = 1, 2,...), For the past original image including the image P (i), the weighted average value of the pixel values for each color of the pixels at the corresponding positions is calculated, and the i-th pixel composed of a collection of pixels having the average value. An average image A (i) may be created. When the (i + 1) -th mask image M (i + 1) is created for the (i + 1) -th original image P (i + 1), the original image P (i + 1) and the i-th average image A What is necessary is just to compare (i).

  However, if a moving image is input at a general frame rate of 30 frames per second, even if it is an original image for the past 10 minutes, in order to store all the image data, the image data buffer Considerable storage capacity is required. Therefore, practically, when the i-th original image P (i) is given, the (i−1) -th average image A (i−1) and the i-th original image P ( Based on the two images i), a method of creating the i-th average image A (i) is adopted. FIG. 3 is a diagram illustrating an example of an average image creation method based on such a method.

First, when the first original image P (1) is given, the original image P (1) is processed as it is as the first average image A (1). Then, every time the i-th original image P (i) shown in the upper right of FIG. 3 is inputted (i = 2, 3,...), The (i−) shown in the upper left of FIG. 1) The i-th average image A (i) shown in the middle part of FIG. 3 is shown in the lower part of FIG.
a (i) = (1-w) .a (i-1) + w.p (i) Formula (1)
It may be created using the following arithmetic expression. Here, a (i) is a pixel value of a predetermined color of a pixel at a predetermined position of the average image A (i), and a (i-1) is a pixel value of the pixel at the predetermined position of the average image A (i-1). The pixel value of the predetermined color, p (i) is the pixel value of the predetermined color of the pixel at the predetermined position of the original image P (i), and w is a parameter (w <1) indicating a predetermined weight.

  In short, the pixel value a (i−1) of the (i−1) -th average image A (i−1) calculated for the original image up to the original image P (i−1) given immediately before, For the pixel value p (i) of the i-th original image P (i) that is newly given, an average value considering the weight w is calculated, and the calculated value is used as the i-th average image A (i). The process of setting the pixel value a (i) is performed. Thus, every time a new original image P (i) is input, the average image A (i) is updated, and only the immediately preceding average image A (i-1) is used for the update. By doing so, it is not necessary to store and hold past original image data for several frames, so that it is possible to greatly save the capacity of the buffer necessary for processing.

  As shown in FIG. 3, as the value of the weight w is increased, the pixel value of the latest original image P (i) greatly affects the pixel value of the average image A (i). FIG. 4 is a diagram showing a pixel value transition process of one pixel on the average image created based on the method shown in FIG. In this example, a specific example in which the weight w = 0.01 is shown.

  For example, if the pixel value of the pixel at the specific position of the first (i = 1) original image P (1) is p (1) = 100, the specific of the first average image A (1) is specified. The pixel value a (1) of the pixel at the position is a (1) = 100 as it is. Subsequently, assuming that the pixel value of the pixel at the specific position of the second original image P (2) is p (2) = 100, the pixel at the specific position of the second average image A (2). The pixel value a (2) is calculated as a weighted average “0.99 × 100 + 0.01 × 100” between a (1) and p (2), so that a (2) = 100.

  In the illustrated example, since the pixel value at the specific position of the original image remains 100 from p (1) to p (4), the pixel value at the specific position of the average image is also a (1) to a Maintain 100 until (4). However, in the fifth original image P (5), the pixel value a (5) of the fifth average image A (5) is changed in the lower part of FIG. As shown in the equation, a (5) = 101 is obtained by calculating the weighted average “0.99 × 100 + 0.01 × 200” of a (4) and p (5). Further, since the pixel value p (6) = p (7) = 200 is maintained in the sixth original image P (6) and the seventh original image P (7), the lower part of FIG. As shown in the equation, in the sixth average image A (6) and the seventh average image A (7), the pixel value a (6) = 102 and the pixel value a (7) = 103 gradually increase. doing.

  As in this example, when the weight w is set to a value of about 0.01, even if the pixel value of the original image changes abruptly, the pixel value of the average image does not change immediately, and the pixel value of the original image It will approach you slowly. Therefore, as in the example shown in FIG. 1, even if a moving image through which the vehicle passes is given, the transient pixel value change does not cause a large change in the pixel value of the average image, and the average image It can serve as an image. On the other hand, if the lighting environment changes, such as when the time changes from daytime to dusk, the change persists across many frame images, so the average image pixel value also changes following the change. become. Therefore, an average image suitable for a daytime background image is obtained during the daytime, and an average image suitable for a sunset background image is obtained at dusk.

  The mask image in the present invention is created by comparing individual original images using the average image created by such a method as a background image. FIG. 5 is a diagram showing a pixel value determination process of the mask image created in this way. The mask image M (i) for the i-th original image P (i) is a binary image composed of a collection of pixels having pixel values determined by the following method. That is, the pixel value m (i) of the pixel at the specific position of the mask image M (i) is equal to the pixel value p (i) of the pixel at the specific position of the original image P (i) and the average image A (i−1). ) Is compared with the pixel value a (i-1) of the pixel at the specific position, and if both pixel values are within the similar range, a pixel value indicating that the pixel is in the background region B (for example, If both pixel values are outside the similar range, a pixel value (for example, “1”) indicating a pixel in the foreground area F is given.

  Actually, since the original image is a color image having pixel values of three primary colors (for example, in the case of the RGB color system, pixel values of three colors R, G, and B), the original image P (i ) And the pixel value a (i) of each pixel constituting the average image A (i) are each composed of three independent values for each color. It will be. Then, the calculation of Expression (1) is executed independently for each color. For example, the pixel value a (i) of a pixel at a specific position on the average image A (i) is composed of three sets of pixel values, an R color pixel value, a G color pixel value, and a B color pixel value. The R pixel value is a value obtained as a weighted average of the R pixel values of the past original image.

  Therefore, the comparison between the pixel value p (i) and the pixel value a (i−1) in FIG. 5 is not a simple comparison between two values, but a comparison between three sets of pixel values and three sets of pixel values. become. Naturally, the pixel similarity determination is processing for determining whether or not the three sets of pixel values are similar to each other. A feature of the present invention resides in a method for determining similarity between these three sets of pixel values. Hereinafter, this similarity determination method will be described in detail in Section 2.

<<< §2. Pixel similarity determination method >>>
Now, as described in §1, in the present invention, the original image (input image) and the average image (background image) are compared in pixel units, and if both pixels are similar, the pixels in the background region B, In the case of dissimilarity, it is determined that the pixel is in the foreground area F. As described above, the method for determining similarity in units of pixels is simpler than the method of obtaining feature amounts in units of regions, and the calculation burden is relatively light. However, since the pixel similarity determination is a factor that affects the detection accuracy of the moving object, it is very important to determine how much the range is determined as the “similar range”.

  For example, in §1, when the image P10 in FIG. 1 is an average image (background image) and the image P20 is an original image (input image), a mask image like the image M20 is obtained by comparing the two images. Stated. Here, the foreground area F of the mask image M20 is an area in which the pixels are determined to be out of the similar range as a result of comparing the images P10 and P20, and the background image B is an area in which the pixels are determined to be in the similar range. It is. In this case, a correct mask image cannot be obtained unless the similar range is set appropriately.

  That is, in FIG. 1, the exact same image is drawn in the background part, but in an actual landscape, the lighting environment due to sunlight changes due to the movement of the clouds, and the position and orientation of the leaves of the trees change slightly due to the wind. . Therefore, if the criteria for judging whether or not the pixels are similar is strict, an erroneous determination of being out of the similar range occurs even though it is actually the background portion, and the pixels in the foreground area F are recognized. On the other hand, if the criteria for judging whether or not a pixel is similar is relaxed, an erroneous determination that it is in the foreground portion but within the similar range occurs, and the pixel in the background region B is recognized.

  In addition, in the case of a color image, as described above, the similarity of pixels needs to be performed based on a comparison between three pixel values of one pixel and three pixel values of the other pixel. It is possible to set a similar similarity criterion. The determination accuracy also varies depending on what kind of similarity determination criterion is adopted. Usually, such pixel comparison of color images is performed by plotting coordinate points corresponding to both pixel values in a three-dimensional color space and examining the spatial positional relationship between the two coordinate points. Hereinafter, there will be described several methods for determining similarity in the color space when each pixel has a RGB color system pixel value.

  FIG. 6 is a three-dimensional color space diagram showing the simplest method for determining similarity of pixels. As illustrated, coordinate points A and P are plotted in an RGB three-dimensional orthogonal coordinate system in which the pixel values of the three primary colors R, G, and B are taken as coordinate axes. Here, the coordinate point A (Ra, Ga, Ba) is a point obtained by plotting pixel values (Ra, Ga, Ba) of pixels on the average image A indicating the background, and the coordinate point P (Rp, Gp, Bp). ) Is a point in which pixel values (Rp, Gp, Bp) of pixels on the original image P to be determined are plotted.

  Here, if the distance between the two points A and P in the three-dimensional color space is δ, the distance δ is an index indicating the similarity between the two pixels. If δ = 0, both pixels have exactly the same pixel value, and the overall similarity of the three pixel values decreases as δ increases. Therefore, if a predetermined threshold value δth is set in advance and it is determined that δ <δth is within the similar range and δ ≧ δth is out of the similar range, a temporary determination criterion can be set. .

  Alternatively, starting from the origin O, a vector Va going to the coordinate point A and a vector Vp going to the coordinate point P are defined, and an angle θ formed by both vectors Va and Vp is used as an index indicating the similarity between both pixels. You can also. When θ = 0, the two points A and P are not necessarily the same point, but are points on the same straight line passing through the origin O. Therefore, the hues of both pixels determined by at least the blend ratio of the three primary colors R, G, and B are used. Will be similar. Eventually, if θ is small, the similarity of hue will increase. Therefore, like the criterion using index δ, a predetermined threshold θth is set in advance, and if θ <θth, If it is determined that θ ≧ θth is outside the similar range, a temporary determination criterion can be set.

  However, when such a simple similarity determination method based on the distance δ and the angle θ is used for a moving object detection process in a general live-action image, it may be difficult to obtain a satisfactory detection result. Are known. This means that, with only simple parameter values such as distance δ and angle θ, appropriate judgment criteria corresponding to the actual shooting environment, such as changes in the lighting environment due to sunlight and changes in light and darkness due to wind, etc. should be set. This is because it is difficult.

  In order to deal with such a problem, the aforementioned non-patent document 1 proposes a similarity determination method using a cylindrical model in order to set a more appropriate determination criterion. FIG. 7 is a three-dimensional color space diagram showing the basic principle of the method using this cylindrical model. In FIG. 7, as in FIG. 6, the pixel values (Ra, Ga, Ba) of the pixels on the average image A indicating the background are plotted as the coordinate point A, and the pixels on the original image P to be determined are plotted. Pixel values (Rp, Gp, Bp) are plotted as coordinate points P. Here again, the vectors Va and Vp are vectors from the origin O toward the points A and P.

In this model, a cylinder C having a length L with a predetermined radius around a coordinate point A is defined as shown in the figure. In other words, the cylinder C is a cylinder arranged such that the reference axis Z defined on the vector Va is the central axis and the center point is at the coordinate point A. Then, the space area inside the cylinder C is defined as a similar range of pixels constituting the average image A indicating the background. Therefore, as in the example shown in the figure, a pixel having a pixel value corresponding to the coordinate point P is determined to be outside the similar range because it is located outside the cylinder C, and recognized as a pixel constituting the foreground region F. become. On the contrary, if the coordinate point P is located inside the cylinder C, it is determined to be within the similar range and is recognized as a pixel constituting the background region B.

  A feature of this cylindrical model is that a cylindrical region having a reference axis Z facing the direction of the vector Va as a longitudinal direction is set. The radius of the cylinder C functions as a parameter for determining the hue similarity range, and the length L functions as a parameter for determining the brightness similarity range. As described above, in an actual scene, the pixel value of the background region B will vary temporally due to changes in the lighting environment due to sunlight, changes in brightness such as trees due to the wind, and so on. , It is considered to have a greater effect on brightness than hue. Therefore, as in this model, it makes sense to set the similarity range based on the cylinder C having the reference axis Z as the longitudinal direction.

  However, even if this cylindrical model is used, it is difficult to completely eliminate the influence of illumination fluctuation due to time, weather, etc., and there still remains a problem that erroneous detection occurs. Further, in order to determine whether the coordinate point P is located inside or outside the cylinder C, geometric calculation in a three-dimensional color space is required, and real-time operation is performed using an inexpensive processor. The processing load is heavy to perform the processing. In particular, operations including trigonometric functions are extremely heavy processing for an inexpensive general-purpose processor. In order to cope with such a problem, the present invention proposes a pixel similarity determination method using a new model.

  The most important feature of the pixel similarity determination method according to the present invention is that a spheroid is used instead of the cylinder C of the cylinder model shown in FIG. FIG. 8 is a three-dimensional color space diagram showing a spheroid model in which the cylinder C shown in FIG. 7 is replaced with a spheroid Ea. Here, the spheroid Ea indicating the similar range is an ellipse having the coordinate point A indicating the pixel value of the average image A as the center point and the reference axis Za defined on the vector Va as the major axis direction. It is a rotating body obtained by rotating using Za as a rotation axis. The size of the spheroid Ea is defined by the length La1 in the major axis direction and the length La2 in the minor axis direction.

Even when this spheroid model is used, the similarity determination method is the same as the above-described determination method using the cylindrical model, and the pixels plotted in the inner area of the spheroid Ea are coordinate points. A pixel having a pixel value corresponding to A is determined as a similar pixel. Specifically, in the case of the illustrated example, a pixel having a pixel value corresponding to the coordinate point P is determined to be outside the similar range because it is located outside the spheroid Ea, and the pixels constituting the foreground region F are Certified. On the other hand, if the coordinate point P is located inside the spheroid Ea, it is determined to be within the similar range and recognized as a pixel constituting the background region B.

  On the other hand, FIG. 9 is a three-dimensional color space diagram showing variations of the spheroid model shown in FIG. As shown in the figure, a spheroid Ep indicating a similar range in this model has a coordinate point P indicating a pixel value of the original image P to be determined as a center point, and a reference axis Zp defined on the vector Vp as a major axis It is a rotating body obtained by rotating an ellipse as a direction around a reference axis Zp as a rotation axis. The size of the spheroid Ep is defined by the length Lp1 in the major axis direction and the length Lp2 in the minor axis direction.

  In the case of the model shown in FIG. 8, a spheroid Ea indicating a similar range is defined on the basis of the coordinate point A on which the pixel values (Ra, Ga, Ba) of the average image A indicating the background are plotted, and is a comparison target. While it has been determined whether the coordinate point P on which the pixel values (Rp, Gp, Bp) of the original image P are plotted is inside or outside the spheroid Ea, the model shown in FIG. In this case, a spheroid Ep indicating a similar range is defined with reference to the coordinate point P on which the pixel value (Rp, Gp, Bp) of the original image P to be compared is plotted, and shows the background. It is determined whether the coordinate point A on which the pixel values (Ra, Ga, Ba) of the average image A are plotted is inside or outside the spheroid Ep.

  In short, the former takes a method of determining whether or not the pixel of the newly input original image P is in the similar range of the pixels of the past average image A indicating the background, whereas the latter is A method of determining whether or not the pixels of the past average image A indicating the background are within the similar range of the pixels of the newly input original image P is taken. After all, the only difference between the two is in which of the two pixels to be compared is used as a reference to define the spheroid.

  Therefore, in the following description, of the two images to be compared, the pixel value of one image is expressed as a reference pixel value (R, G, B), and the pixel value of the other image is expressed as a comparison pixel value (r , G, b). Also, the coordinate point Q (R, G, B) on which the reference pixel value (R, G, B) is plotted in the three-dimensional color space is called the reference point Q, and the comparison pixel value (r, g, b) is plotted. The coordinate point q (r, g, b) is referred to as a comparison point q. The similarity determination is made based on the positional relationship between the spheroid defined around the reference point Q and the comparison point q.

  FIG. 10 is a three-dimensional color space diagram illustrating a spheroid model according to the present invention in accordance with such general notation. If the vector V starting from the origin O and going to the reference point Q is a vector V, the reference axis Z is an axis on the vector V. The spheroid E is a rotator obtained by rotating an ellipse having the reference point Q as the center point and the reference axis Z defined on the vector V as the major axis direction with the reference axis Z as the rotation axis. It is. Here, if the comparison point q (r, g, b) is located inside the spheroid E, both pixels are determined to be within the similar range, and if located outside the spheroid E, both pixels are similar. Determined to be out of range.

  The model shown in FIG. 8 uses the pixel value of the pixel a (i-1) on the average image A (i-1) as the reference pixel value (R, G, B) when performing the similarity determination shown in FIG. The reference point Q (R, G, B) is plotted, and the pixel value of the pixel p (i) on the original image P (i) is set as the comparison pixel value (r, g, b). , B) are plotted. On the other hand, the model shown in FIG. 9 uses the pixel value of the pixel p (i) on the original image P (i) as the reference pixel value (R, G, B) when performing the similarity determination shown in FIG. ) Is plotted as a reference point Q (R, G, B), and the pixel value of the pixel a (i−1) on the average image A (i−1) is set as a comparison pixel value (r, g, b). q (r, g, b) is plotted.

  Compared to the conventional cylindrical model shown in FIG. 7, the spheroid model of the present invention shown in FIG. 10 has the following two advantages. The first advantage is that, when used in the pixel similarity determination process in the moving object detection method described in §1, it is possible to detect a moving object more accurately without the influence of illumination fluctuations due to time or weather. It is a point to become.

  Actually, the inventor of the present application has detected a moving object that adopts the similarity determination process based on the cylindrical model shown in FIG. 7 and various types based on the spheroid model shown in FIG. When an attempt was made to detect a moving object incorporating the rejection determination process, an experimental result in which the latter detection was more accurate was obtained. This is considered because in the case of a cylindrical model, there is a high possibility that erroneous detection is performed in the peripheral edge region in the longitudinal direction of the cylinder.

  FIG. 11 is a cross-sectional view showing the advantages of the spheroid model over the cylindrical model. In the example shown in the figure, when the cross section of the cylinder C and the cross section of the spheroid E are compared, all of them are figures having the reference point Q as the center and the direction of the reference axis Z as the longitudinal direction, but the figure is hatched. It can be seen that the area is determined to be the inner area in the cylinder C, whereas it is determined to be the outer area in the spheroid E. Therefore, when the comparison point q is located in the hatched area, it is determined that the comparison point q is within the similar range on the one hand and is outside the similar range on the other hand. Of course, which judgment result is correct cannot be generally determined, but at least as long as it is used for detection processing of a moving object using a real image, the latter judgment result may be a correct result. It will be expensive.

  That is, in the case of a cylindrical model, when the comparison point q is located in the hatched area in the figure, the pixel to be determined is similar to the background image, and thus is a pixel in the background area B. It is considered that there is a relatively high probability that a pixel that is dissimilar to the background image and should have been a pixel in the foreground area F. As shown in FIG. 11, when compared with cross-sectional shapes, the cross section of the spheroid E is an ellipse made of a curved surface, whereas the cross section of the cylinder C is a rectangle made of a straight line. It can be understood intuitively that an ellipse having a curved cross section is more suitable as the boundary line for the determination.

  In this way, at least when used for detection processing of a moving object based on a live-action image, the first advantage is obtained that the detection accuracy of the spheroid model is improved compared to the cylindrical model. On the other hand, the second advantage obtained by adopting the spheroid model is that the calculation burden can be reduced. The details of the second advantage will be described in §3. Here, one of the devices that contributes to the reduction of the calculation burden will be briefly described.

  This contrivance is to set the size of the spheroid E to a value proportional to the distance D between the origin O of the three-dimensional coordinate system and the reference point Q. Specifically, as shown in FIG. 10, a value α = h · D obtained by multiplying the distance D by a predetermined parameter h (where h <1) is a major axis radius, and a predetermined parameter k (where k An ellipse having a minor axis radius of β = k · D obtained by multiplying <h) so that the major axis overlaps the reference axis Z connecting the origin O and the reference point Q, and the reference point Q is the center The spheroid E may be defined by arranging it to be a point and rotating it around the reference axis Z.

  When the size of the spheroid E is determined under such conditions, the size of the spheroid E increases as the reference point Q moves away from the origin O, and the similarity range increases accordingly. This means that the higher the lightness, that is, the highlight portion of the image, the wider the similar range. However, in practice, there is no problem even if such a similar range is set. On the other hand, the calculation burden for determining whether or not it is within the similar range, that is, whether it is inside or outside of the spheroid E is set such that the long axis radius is α = h · D and the short axis radius is β = k · D. (That is, by setting the size of the ellipse to a value proportional to the distance D), it can be greatly reduced. Details will be described in §3.

  By the way, according to an experiment conducted by the inventor of the present application, when the size of the spheroid E is set to a value proportional to the distance D, it is detected by using the model of FIG. 9 rather than the model of FIG. It was found that the accuracy was improved. When the model of FIG. 9 is adopted, the reference point Q (R, G, B) in FIG. 10 is a point plotted with the pixel value of the pixel of the original image P to be determined as the reference pixel value, and is a comparison point. q (r, g, b) is a point where the pixel values of the pixels of the average image A serving as the background are plotted as comparison pixel values.

  As described above, the model in FIG. 8 and the model in FIG. 9 are different in that the spheroid is defined based on the pixel of the original image P or the pixel of the average image A. Moreover, if the size of the spheroid is set to a value proportional to the distance D, the size of the defined spheroid will be different. That is, the length La1 in the major axis direction and the length La2 in the minor axis direction of the spheroid Ea in the model shown in FIG. 8 are obtained by multiplying the length of the vector Va by the parameters 2h and 2k, respectively. On the other hand, the length Lp1 in the major axis direction and the length Lp2 in the minor axis direction of the spheroid Ep in the model shown in FIG. 9 are obtained by multiplying the length of the vector Vp by parameters 2h and 2k, respectively. Accordingly, in the case of the illustrated example, the size of the spheroid Ep is larger than the size of the spheroid Ea, and a wider similarity range is set.

  Of course, from a common sense, the model shown in FIG. 8 will generally be adopted rather than the model shown in FIG. That is, a similar range that can be regarded as a background is defined in advance as a spheroid Ea, and it is determined whether or not a point P indicating a pixel of a newly input image falls within this similar range. The general idea is to recognize whether or not the pixel is a point on a moving object. On the other hand, the model shown in FIG. 9 determines a similar range of pixels of a newly input image as a spheroid Eb and determines whether or not a point A indicating a background pixel is included therein. It can be said to be the opposite of the method based on general common sense.

  However, according to experiments conducted by the inventors of the present application, it is better to adopt the model shown in FIG. 9 than to adopt the model shown in FIG. 8 as long as it is used for detection processing of a moving object using at least a photographed image. More correct judgment results were obtained. This is because, when the pixel value a (i) of the average image A is determined by the method shown in the equation (1) of FIG. 3, the newly input original image P is caused by factors such as sunlight and wind. Even if the pixel value p (i) greatly fluctuates, it takes a certain amount of time for the pixel value a (i) to follow the fluctuation (for example, see the table in FIG. 4). It is considered that it is possible to make a correct determination if the width is determined according to the pixel value p (i) of the original image P instead of the pixel value a (i) of the average image A indicating the background.

  As described above, in the pixel similarity determination processing method used for detecting a moving object, as compared to the conventional method using a cylindrical model, as an advantage of the present invention that uses a spheroid model, illumination variation due to time, weather, etc. The first advantage that a more accurate moving object can be detected without the influence of the above is described, and the second advantage that the calculation burden can be reduced is also briefly described. In the following §3, details on this second advantage will be described.

<<< §3. Practical similarity judgment procedure >>>
In general, in determining whether a point is inside or outside a cylinder in a three-dimensional space, or when determining whether it is inside or outside a spheroid, the coordinate value is The geometric operation used is required. However, when determining whether it is inside or outside the spheroid, it is possible to greatly reduce the calculation burden by devising the calculation formula and incorporating approximate calculation in part. . Here, in the spheroid model shown in FIG. 10, is the comparison point q (r, g, b) inside the spheroid E defined with the reference point Q (R, G, B) as the center? A practical procedure to determine whether it is outside is described.

  The procedure described here is composed of three condition determination stages. FIG. 12 is a cross-sectional view showing the principle of the first condition determination stage. In the figure, the origin O shown below is the origin O of the RGB three-dimensional orthogonal coordinate system shown in the three-dimensional color space diagram of FIG. 10, and the reference point Q (R, G, B) is on the coordinate system. ) And a comparison point q (r, g, b) are plotted (coordinate axes are not shown). The reference axis Z is a line connecting the origin O and the reference point Q, and the spheroid E is an ellipse centered on the reference point Q with the reference axis Z as the major axis direction and the reference axis Z as the rotation axis. It is a rotating body obtained by rotating as. An ellipse having a cross section in the figure is an ellipse having a major axis radius α and a minor axis radius β. As described in §2, when the distance between the origin O and the reference point Q is D, a predetermined ellipse is shown. Are set such that α = h · D (where h <1) and β = k · D (where k <h).

  In the first condition determination stage, it is determined whether or not the comparison point q is within the hatched area in the figure. That is, since the hatched area in the lower part of the figure is “the inner area of the sphere C1 having the radius (D−α) centered on the origin O”, if the distance between the origin O and the comparison point q is d, “D If the condition of “−α> d” is satisfied, the comparison point q is located inside the sphere C1. The sphere C1 is a sphere that is in contact with the spheroid E at the closest point E1 with respect to the origin O of the spheroid E, and the inner area of the sphere C1 is naturally the outer area of the spheroid E. On the other hand, since the hatched area in the upper part of the figure is “the outer area of the sphere C2 having the radius (D + α) centered on the origin O” and the distance between the origin O and the comparison point q is d, “D + α <d If the condition “is satisfied, the comparison point q is located outside the sphere C2. The sphere C2 is a sphere in contact with the spheroid E at the farthest contact point E2 with respect to the origin O of the spheroid E, and the outer region of the sphere C2 is naturally the outer region of the spheroid E.

FIG. 13 is a diagram showing a determination formula based on the first condition determination principle shown in FIG. FIG. 13A shows a deformation process of the conditional expression “D−α> d” for the comparison point q to be in the inner region of the sphere C1. That is, if α = h · D is substituted, the conditional expression becomes “(1−h) · D> d”, and if both sides are squared,
(1-h) ² · D ² > d ² Formula (2)
Is obtained. On the other hand, FIG. 13B shows a deformation process of the conditional expression “D + α <d” for the comparison point q being in the outer region of the sphere C2. That is, if α = h · D is substituted, the conditional expression becomes “(1 + h) · D <d”, and if both sides are squared,
(1 + h) ² · D ² <d ² formula (3)
Is obtained.

Here, since the coordinate value of the reference point Q is (R, G, B) and the coordinate value of the comparison point q is (r, g, b), as shown in FIG.
D = √ (R ² + G ² + B ² )
d = √ (r ² + g ² + b ² )
And if both sides are squared,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
It becomes. Therefore, if Equation (2) and Equation (3) are rewritten, as shown in FIG.
(1-h) ² · (R ² + G ² + B ² )
> (R ² + g ² + b ² ) Formula (2 ′)
(1 + h) ² · (R ² + G ² + B ² )
<(R ² + g ² + b ² ) Formula (3 ′)
The following conditional expression is obtained. Here, h is a predetermined parameter set in advance, and (R, G, B) and (r, g, b) are coordinate values of the reference point Q and the comparison point q (that is, 2 to be compared). The pixel values of the three primary colors of one pixel). Since the expressions (2 ′) and (3 ′) are arithmetic expressions composed only of a square operation and a sum / difference operation, the calculation burden is very light.

  Thus, when a result satisfying either of the conditions of the formula (2 ′) or the formula (3 ′) is obtained, it can be determined that the comparison point q is located outside the spheroid E. It can be determined that it is outside the similar range.

  On the other hand, when neither of the conditions of the expressions (2 ′) and (3 ′) is satisfied, the comparison point q is located in the region outside the sphere C1 and inside the sphere C2 in FIG. Therefore, in that case, the second condition determination step described below is continued.

  FIG. 14 is a sectional view showing the principle of the second condition determination stage. In the second condition determination stage, it is determined whether or not the comparison point q is within the hatched area of FIG. This hatching area is an area defined as "the outer area of the cone ξ with the origin O as the apex and the reference axis Z as the central axis and in contact with the spheroid E with a circle". The half apex angle of the cone ξ is the angle φ as shown in the figure. In the illustrated cross-sectional view, a state where the cone ξ is in contact with the ellipse E at the contact point T is shown, but in actuality, the cone ξ and the spheroid E are in line contact with a tangent circle T. . The relationship between the cone ξ and the spheroid E in the three-dimensional space can be easily understood by considering the state in which the egg is inserted into the cone.

  Eventually, in this second condition determination stage, it is determined whether the comparison point q is inside or outside the cone ξ. The position of the tangent circle T where the cone ξ and the spheroid E contact each other can be obtained by geometric calculation, and a geometric equation indicating the cone ξ passing through the tangent circle T can also be obtained. It is. However, such an equation becomes a relatively complex expression. Therefore, here, instead of the cone ξ, an approximate determination using a cone ξ ′ indicated by a broken line in FIG. 14 is performed to reduce the calculation burden.

  The cone ξ drawn with a solid line in FIG. 14 is a figure that touches the spheroid E with a tangent circle T, whereas the cone ξ ′ drawn with a broken line is a figure that intersects the spheroid E with an intersection line S . Here, the intersecting circle S is a circle constituting an intersecting line between the spheroid E3 and the spherical surface C3 having a radius D centered on the origin O, and an arbitrary point on the intersecting circle S with the reference point Q. Is f as shown in the figure. After all, in this approximate determination, a determination is made as to whether or not the comparison point q is located outside the cone ξ ′ passing through the intersection circle S with the origin O as the apex and the reference axis Z as the central axis. It will be.

  As shown in the figure, the half apex angle φ ′ of the cone ξ ′ is slightly smaller than the half apex angle φ of the cone ξ, and the cone ξ ′ becomes a slightly smaller cone than the cone ξ. For this reason, in the case of the points “outside the cone ξ ′” and “inside the cone ξ”, although it is actually a point inside the spheroid E, the approximate determination method substituting the cone ξ ′ Therefore, it is determined that the point is outside the spheroid E. Therefore, from the viewpoint of “strictly determining the inside and outside of the spheroid E”, the determination method substituting the cone ξ ′ is inaccurate. However, since the spheroid E itself is not a solid having a function of detecting a moving object strictly, it provides only one index, so an approximate determination method that substitutes the cone ξ ′. Even if is used, there will be no major hindrance.

Consider a specific method for geometrically determining whether the comparison point q is inside or outside the cone ξ ′. Now, as shown in FIG. 15 (a), consider a general triangle with three side lengths a, b, and c, respectively. Here, if the angle between the two sides b and c is φ, according to the cosine theorem,
cos φ = (b ² + c ² −a ² ) / 2bc Equation (4)
Holds.

Next, consider the triangle OQS shown in FIG. FIG. 15B shows the triangle OQS shown in FIG. 14 as it is extracted. As described above, the intersecting circle S is an intersecting line between the spheroid E3 and the spherical surface C3 having the radius D centered on the origin O, so that the distance between the two points OS is equal to the distance between the two points OQ and becomes D. Become. Therefore, the triangle OQS is an isosceles triangle, the included angle between the two equal sides is φ ′, and the length of the third side is f. Applying the cosine theorem shown in Equation (4) to this triangle OQS,
cos φ ′ = (D ² + D ² −f ² ) / 2D ² formula (5)
Holds.

Here, it can be seen from FIG. 14 that the length f is close to the minor axis radius β of the spheroid E. Thus, approximately, if f≈β, then β = k · D, so f≈k · D. As shown in the lower right of FIG.
^{cos φ '≒ 1-k 2} /2 Equation (6)
The following formula is obtained.

  Next, consider the triangle OQq shown in FIG. In FIG. 16, the four points O, Q, S, and q shown in FIG. 14 are extracted and plotted as they are. The distance between the two points OQ is D, and the distance between the two points Oq is d. Here, an angle between two sides having the lengths D and d is θ, and a length of the third side is t. Further, the angle φ ′ formed by the line segment OQ and the line segment OS is the half apex angle of the cone ξ ′ described above.

Now, in FIG. 14, using the cone ξ ′ instead of the cone ξ and obtaining the condition for the comparison point q to be in the hatched region, it can be seen that θ> φ ′. Here, if the coordinate values (pixel values) R, G, B, r, g, b are positive values, the angles θ and φ ′ are both acute angles. As described on the right side of FIG. 16, generally, if θ and φ ′ are positive acute angles, when θ> φ ′, “cos θ <cos φ ′” and “cos ² θ <cos ² φ”. ''. The equation ^{(6), cos 2 φ '} ≒ (1-k 2/2) because it is ^2, after all,
^{cos 2 θ <(1-k} 2/2) 2 Equation (7)
Can be approximately determined that the comparison point q is in the outer region of the cone ξ ′.
Subsequently, if the cosine theorem of Equation (4) is applied to the triangle OQq shown in FIG. 16, as shown in the lower part of FIG.
cos θ = (D ² + d ² −t ² ) / (2 · D · d) Equation (8)
Holds. At this time, as described in FIG.
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
t ² = (R−r) ² + (G−g) ² + (B−b) ²
So, substituting this into equation (8)
cos θ = γ / (D · d) Equation (9)
(However, γ = R ・ r + G ・ g + B ・ b)
Is obtained. If both sides of equation (9) are squared,
cos ² θ = γ ² / (D ² · d ² ) Formula (10)
It is. Therefore, from equation (7),
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2 Equation (11)
Can be approximately determined that the comparison point q is in the outer region of the cone ξ ′. Here, if γ, D, and d are rewritten using pixel values, as shown in the lower part of FIG.
(R · r + G · g + B · b) ² /
((R ² + G ² + B ² ) · (r ² + g ² + b ² ))
^{<(1-k 2/2} ) 2 formula (11 ')
Can be approximately determined that the comparison point q is in the outer region of the cone ξ ′.

  As described above, in FIG. 14, the cone ξ ′ can be approximately substituted for the cone ξ. Therefore, if the above equation (11 ′) is established, the comparison point q is located in the outer region of the spheroid E. It is possible to make an approximate determination that there is. Of course, this approximate determination result is not a strict determination result because it is a determination result obtained by substituting the cone ξ ′ for the cone ξ and approximating f≈β. However, since the spheroid E itself is not a solid having a function of detecting a moving object strictly, even if such an approximate determination is performed, no major trouble occurs. In other words, the approximate determination method described above is a method for determining whether or not the comparison point q is located outside the approximate ellipsoid E instead of determining whether or not the comparison point q is outside the spheroid E. become.

  When a result satisfying the expression (11 ′) is obtained in this way, it can be determined that the comparison point q is located outside the approximated body of the spheroid E, so Judgment can be made.

  On the other hand, if the expression (11 ′) is not satisfied, the comparison point q is approximately determined to be located inside the non-hatched cone ξ in FIG. Three condition determination steps are performed.

  FIG. 18 is a sectional view showing the principle of the third condition determination stage. In the third condition determination stage, it is determined whether or not the comparison point q is within the hatched area of FIG. This hatching area is an outer area of the spheroid E, and so the third condition determination stage is an original determination stage that should be performed as the similarity determination using the spheroid model described in §2. . For this reason, the expression used for the condition determination is an expression using an elliptical equation, which is inevitably slightly more complicated than the conventional condition determination expression.

  As shown in FIG. 18, a local XY two-dimensional orthogonal coordinate system having an origin at the position of the reference point Q and defined on the paper surface is taken, and an ellipse E and a comparison point q are taken on this two-dimensional coordinate system. Let's consider the positional relationship with. Here, the X axis is a coordinate axis in the major axis direction of the spheroid E, and the Y axis is a coordinate axis in the minor axis direction of the spheroid E. Of course, the coordinates of the reference point Q in the XY coordinate system are (0, 0). Therefore, the comparison point q has a three-dimensional coordinate value q (r, g, b) in the RGB three-dimensional orthogonal coordinate system, and a two-dimensional coordinate value q (x, y) in the XY local coordinate system. .

Here, when the coordinate value (x, y) of the comparison point q is expressed using the distance D between the two points OQ, the distance d between the two points Oq, and the included angle θ, it is also shown in the lower right of FIG. As you did
x = D−d · cos θ, y = d · sin θ Equation (12)
Holds. On the other hand, as shown in FIG.
x ² / α ² + y ² / β ² = 1 Formula (13)
So that
f (x, y) = β ² · x ² + α ² · y ² −α ² · β ² Formula (14)
If the following judgment formula is defined, the comparison point q is
If f (x, y) <0, the point inside the ellipse
If f (x, y) = 0, the point on the ellipse
If f (x, y)> 0, it is a point outside the ellipse. Therefore,
β ² · x ² + α ² · y ² -α ² · β ² > 0 Formula (15)
Then, the comparison point q is a point outside the ellipse. Here, even if the XY local coordinate system is rotated about the reference axis Z as the central axis, the above equation is still true, and therefore the equation (15) can be extended to a three-dimensional solid. That is, if the condition of Expression (15) is satisfied, the comparison point q is a point in the outer region of the spheroid E.

In equation (15), the value of each variable can be obtained as follows, as shown in the lower half of FIG. First, since α = h · D and β = k · D,
α ² = h ² · D ² , β ² = k ² · D ² (16)
It is. On the other hand, since x = D−d · cos θ from equation (12), if both sides are squared,
x ² = D ² + d ² · cos ² θ-2Dd · cos θ
And substituting Equation (9) and Equation (10) into this,
x ² = D ² + γ ² / D ² −2γ Formula (17)
(Where γ = R · r + G · g + B · b). Also, from equation (12), y = d · sin θ, so if both sides are squared,
y ² = d ² · sin ² θ = d ² · (1-cos ² θ)
And substituting equation (10) into this,
y ² = d ² −γ ² / D ² formula (18)
(Where γ = R · r + G · g + B · b).

Thus, after calculating the values of α ² , β ² , x ² , and y ² according to Equations (16) to (18), if the condition determination equation of Equation (15) is calculated, the comparison point q is Whether the point is in the inner region or the outer region of the spheroid E can be determined.

  FIG. 20 is a flowchart showing the procedure of the practical similarity determination method according to the present invention described so far. According to this similarity determination method, the first color pixel having each pixel value (R, G, B) of the three primary colors, and the second color pixel having each pixel value (r, g, b) of the three primary colors, Similarity determination can be performed. In practice, each procedure shown in FIG. 20 is executed by a computer.

  First, in step S11, parameters h and k for determining the size of the spheroid E are set. As described above, the parameter h is a value (h <1) that determines the major axis radius α of the spheroid E, and the major axis radius is determined by the equation α = h · D. The parameter k is a value (k <h) that determines the minor axis radius β of the spheroid E, and the minor axis radius is determined by the equation β = k · D. The values of these parameters h and k are the characteristics of the background image (for example, the type of outdoor or indoor, city or suburb), and the characteristics of the foreground image that enters as a moving object (for example, whether it is a vehicle or a human, Therefore, the value is set as appropriate so that the highest possible detection accuracy can be obtained. According to experiments conducted by the present inventor, in the case of general applications, relatively high detection accuracy can be achieved by setting h = 0.45 to 0.20 and k = 0.15 to 0.05. Is obtained.

  In step S12, the coordinate values (R, G, B) and (r, g, b) of the reference point Q (R, G, B) and the comparison point q (r, g, b) are captured. These coordinate values are values given as pixel values of the three primary colors of the two color images. Once these coordinate values are captured, the preparation stage is complete. That is, the parameters h (h <1) and k (k <h) and the pixel values (R, G, B) and (r, g, b) are taken into the computer, and these values are obtained. This completes the preparation for executing the following arithmetic processing.

  Hereinafter, as shown in FIG. 10, the procedure shown in steps S13 to S18 has coordinates corresponding to pixel values (R, G, B) in a three-dimensional coordinate system in which the pixel values of the three primary colors are taken as coordinate axes. For the spheroid E of a predetermined size centered on the reference point Q and the comparison point q having coordinates corresponding to the pixel value (r, g, b), whether the latter is inside or outside the former This is the procedure of the positional relationship determination stage to be examined.

  Specifically, as described above, the value α = h · D obtained by multiplying the distance D between the origin O of the three-dimensional coordinate system and the reference point Q by a predetermined parameter h (where h <1) is long. An ellipse having a short axis radius of β = k · D, which is obtained by multiplying a predetermined parameter k (where k <h), is a long axis on a reference axis Z connecting the origin O and the reference point Q. Are arranged so that the reference points Q are the center points, and a spheroid E obtained by rotating around the reference axis Z is defined. Then, it is determined whether the comparison point q is inside or outside the spheroid E. Actually, since the approximation as described above is performed, instead of the spheroid E, it is logically determined whether the approximate body is inside or outside. This positional relationship determination stage includes three condition determination stages.

First, in the first condition determination stage shown in step S13, as shown in FIG. 12, “the comparison point q is located inside the sphere C1 having the radius (D−α) around the origin O” or “the origin O It is determined whether or not the condition that the comparison point q is located outside the sphere C2 having the radius (D + α) as the center ”is satisfied. For that purpose, as explained in FIG.
(1-h) ² · D ² > d ² Formula (2)
Or
(1 + h) ² · D ² <d ² formula (3)
An operation for determining whether or not the above condition is satisfied may be performed. here,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
Therefore, after all, as described in the block of step S13,
(1-h) ² · (R ² + G ² + B ² )> (r ² + g ² + b ² ) Formula (2 ′)
Or (1 + h) ² · (R ² + G ² + B ² ) <(r ² + g ² + b ² ) Formula (3 ′)
An operation for determining whether or not the above condition is satisfied may be performed.

  If a positive determination is made in the first condition determination stage shown in step S13 (when the condition of expression (2 ′) or expression (3 ′) is satisfied), the process proceeds from step S14 to step S19. The positional relationship determination step ends. On the other hand, if a negative determination is made, the process proceeds from step S14 to step S15.

  In the second condition determination stage shown in step S15, as shown in FIG. 14, “the comparison point q is outside the cone ξ with the origin O as the apex and the reference axis Z as the central axis and in contact with the spheroid E with a circle. It is determined whether or not the second condition “located” is satisfied. However, as described above, in practice, an expression that uses a cone ξ ′ instead of the cone ξ and approximates f≈β is used. When such an approximate determination method is employed, the second condition is that the comparison point q is located outside the approximated body of the spheroid E.

If this approximate determination method is adopted, as shown in FIG.
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2 Equation (11)
An operation for determining whether or not the above condition is satisfied may be performed. here,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² ),
γ = (R · r + G · g + B · b)
Therefore, after all, as described in the block of step S15,
(R · r + G · g + B · b) ² /
((R ² + G ² + B ² ) · (r ² + g ² + b ² ))
^{<(1-k 2/2} ) 2 formula (11 ')
An operation for determining whether or not the above condition is satisfied may be performed.

  If an affirmative determination is made in the second condition determination step shown in step S15 (when the condition of expression (11 ′) is satisfied), the process proceeds from step S16 to step S19, and the positional relationship determination step is performed. End. On the other hand, if a negative determination is made, the process proceeds from step S16 to step S17.

In the third condition determination stage shown in step S17, as shown in FIG. 18, it is determined whether or not the third condition “the comparison point q is located outside the spheroid E” is satisfied. . To do so, as described in the block of step S17,
β ² · x ² + α ² · y ² -α ² · β ² > 0 Formula (15)
An operation for determining whether or not the above condition is satisfied may be performed. Here, as explained in FIG.
α ² = h ² · D ² , β ² = k ² · D ² (16)
x ² = D ² + γ ² / D ² -2γ Formula (17)
y ² = d ² −γ ² / D ² formula (18)
And as already mentioned,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
γ = (R · r + G · g + B · b)
It is.

  If a positive determination is made in the third condition determination stage shown in step S17 (when the condition of expression (15) is satisfied), the process proceeds from step S18 to step S19, and the positional relationship determination stage is terminated. To do. On the other hand, if a negative determination is made, the process proceeds from step S18 to step S20, and the positional relationship determination stage is also terminated.

  What should be noted here is that the condition determination formulas performed in the first to third condition determination stages described above include only addition / subtraction / multiplication / division calculations. In other words, it does not include any square root or trigonometric function operations that are included in general geometric operations. Therefore, the burden on the arithmetic unit is relatively light, and real-time processing is possible even when an inexpensive processor is used.

  Finally, the determination result output stage shown in step S19 or step S20 is performed. That is, as described above, when a positive determination is made in any of the first condition determination stage (step S13), the second condition determination stage (step S15), and the third condition determination stage (step S17). Advances to step S19, and a determination result that the first color pixel and the second color pixel are dissimilar is output. On the other hand, if a negative determination is made in all of the first condition determination stage (step S13), the second condition determination stage (step S15), and the third condition determination stage (step S17), The process proceeds to S20, and a determination result that the first color pixel and the second color pixel are similar is output.

  In short, according to the procedure shown in the flowchart of FIG. 20, when it is determined that the comparison point q is outside the spheroid E or its approximate body, the first color pixel and the second color pixel Is output as a non-similar determination result, and it is determined that the comparison point q is inside the spheroid E or its approximated body, the first color pixel is similar to the second color pixel. Will be output. The second condition determination stage in step S15 is executed only when a negative determination is made in the first condition determination stage in step S13. Similarly, the third condition determination stage in step S17 is performed in step S15. Since this process is executed only when a negative determination is made in the second condition determination stage, it is possible to omit a useless calculation and to reduce the calculation burden.

In particular, when an operation is performed in which the values of the parameters h and k are fixed values, the values of (1−h) ² and (1 + h) ² used in the arithmetic expressions (2 ′) and (3 ′) in step S13, step S15 the value of using the arithmetic expression (11 ') (1-k 2/2) 2 of, it is possible to be prepared as a predetermined constant, it is possible to further reduce the computation load. Actually, if the value of (R ² + G ² + B ² ) and the value of (r ² + g ² + b ² ) are calculated first, the calculation formulas (2 ′) and (3 ′) in step S13 are related. The calculation is a very simple calculation using the above constants. Similarly, in the calculation related to the calculation formula (11 ′) in step S15, if the value of (R · r + G · g + B · b) is calculated, the already calculated value (R ² + G ² + B ² ) and By using the value of (r ² + g ² + b ² ) and the above constant, the calculation becomes extremely simple.

<<< §4. Configuration of Moving Object Detection Device According to the Present Invention >>
Here, the configuration of the moving object detection device according to the present invention will be described with reference to the block diagram of FIG. This apparatus has a function of detecting a moving object for a given moving image, and as illustrated, an image input unit 110, an original image storage unit 120, an average image creation unit 130, an average image storage unit 140, and an image comparison unit 200. , A mask image storage unit 310, an image output unit 320, and a parameter setting unit 330.

  The image input unit 110 is a component that inputs a frame-unit color original image P continuously given in time series as pixel aggregate data having pixel values of the three primary colors. The original image storage unit 120 This is a component that sequentially stores the input original image. On the other hand, the average image creation unit 130 is a component that sequentially creates an average image A having an average characteristic of these original images based on a plurality of original images P input in the past. Is a component that sequentially stores the created average image A.

  Specific processing functions of these components are as already described in §1. The original image storage unit 120 and the average image storage unit 140 can be configured by a buffer memory. If the average image creation unit 130 sequentially creates an average image using the weight w as a parameter by the method shown in FIG. 3 and stores it in the average image storage unit 140, the original image storage unit 120 includes Since only the latest original image necessary for processing is always stored, and only the latest average image A necessary for processing is always stored in the average image storage unit 140. Capacity can be saved.

  The image comparison unit 200 compares the original image P stored in the original image storage unit 120 with the average image A stored in the average image storage unit 140, and distinguishes the foreground region F from the background region B. It is a component that fulfills the function of creating M, and is composed of a pixel value reading unit 210, an similarity determination unit 220, and a pixel value writing unit 230, as shown.

  The pixel value reading unit 210 selects one of a pair of images to be compared (that is, the original image P stored in the original image storage unit 120 and the average image A stored in the average image storage unit 140). The pixel value of a pixel at a predetermined position in one image is read as a reference pixel value (R, G, B), and the pixel value of a pixel at a corresponding position in the other image is read as a comparison pixel value (r, g, b). Process.

  As described above, when the model shown in FIG. 8 is adopted, the pixel value of the pixel of the average image A is read as the reference pixel value (R, G, B), and the pixel value of the pixel of the original image P is compared with the comparison pixel value. It will be read out as (r, g, b). On the other hand, when the model shown in FIG. 9 is adopted, on the contrary, the pixel value of the pixel of the original image P is read as the reference pixel value (R, G, B), and the pixel value of the pixel of the average image A is The comparison pixel value (r, g, b) is read out. As already described in §2, in practice, it is preferable to adopt the model shown in FIG.

  The similarity determination unit 220 performs a process of determining whether or not the comparison pixel value (r, g, b) is within a predetermined similar range set for the reference pixel value (R, G, B). Specifically, as shown in FIG. 10, in a three-dimensional coordinate system in which the pixel values of the three primary colors are taken on the coordinate axes, a reference point Q (located at a coordinate corresponding to the reference pixel value (R, G, B). R, G, B) and a comparison point q (r, g, b) located at coordinates corresponding to the comparison pixel value (r, g, b), and a spheroid of a predetermined size centered on the reference point Q When the positional relationship between E and the comparison point q is examined, and it can be determined that the comparison point q is located outside the spheroid E or its approximate body, it is determined that it is outside the similar range, and it can be determined that it is located inside. Is determined to be within the similar range. At this time, the size of the spheroid E is determined with reference to the parameters h and k.

  Then, the pixel value writing unit 230 responds to the determination result of the similarity determination unit 220 as the pixel value of a pixel at a predetermined position (position to be read by the pixel value reading unit 210) constituting the mask image M. A value is set and written into the mask image storage unit 310. That is, the pixel value (eg, “0”) indicating the background region B is determined when the similarity determination unit 220 determines that it is within the similar range, and the foreground region when the similarity determination unit 220 determines that it is outside the similarity range. The pixel value (for example, “1”) indicating F is written into the mask image storage unit 310.

  The mask image storage unit 310 is a component that stores the mask image M created in this way, and the image output unit 320 is a component that outputs the mask image M.

  On the other hand, the parameter setting unit 330 uses the parameter w (weight w shown in FIG. 3) used for the average image creation process by the average image creation unit 130 and the parameter h used for the similarity determination process of the similarity determination unit 220. , K (values for determining the major axis radius α and the minor axis radius β shown in FIG. 10) are set to arbitrary values by user operation input. The user can obtain a detection result with higher accuracy by adjusting the values of these parameters w, h, and k as necessary. However, some or all of these parameters can be fixed values. In an embodiment in which all parameter values are fixed values, the parameter setting unit 330 need not be provided.

  In practice, the moving object detection apparatus shown in FIG. 21 can be constructed by incorporating a dedicated program into the computer. The components shown in the blocks in FIG. 21 are the hardware and software of the computer. It can be realized by a combination of Of course, this moving object detection device can also be configured as a semiconductor integrated circuit.

  FIG. 22 is a block diagram showing a detailed configuration of the similarity determination unit 220 in the apparatus shown in FIG. As shown in the figure, the similarity determination unit 220 includes a basic calculation unit 221, a first condition determination unit 222, a second condition determination unit 223, a third condition determination unit 224, a determination value output unit 225, and a parameter holding unit. 226.

  The parameter holding unit 226 is a component that holds the values of the parameters h and k. When the parameter setting unit 330 shown in FIG. 21 is provided, the parameter h and k values set by the parameter setting unit 330 are provided. Is written in the parameter holding unit 226. When the values of the parameters h and k are fixed, the fixed values are held in the parameter holding unit 226.

Based on the reference pixel value (R, G, B) and the comparison pixel value (r, g, b) read by the pixel value reading unit 210 shown in FIG.
D ² = R ² + G ² + B ² and
d ² = r ² + g ² + b ²
Performed becomes operational, a component that calculates a value D ² and the value d ^2. The values D ² and d ² calculated here are used in calculations in the first condition determination unit 222, the second condition determination unit 223, and the third condition determination unit 224.

As shown in FIG. 12, the first condition determination unit 222 “comparison point q is located inside the sphere C1 with the origin O as the center and the radius (D−α)” or “the radius with the origin O as the center ( It is a component that determines whether or not the first condition that the comparison point q is located outside the sphere C2 of D + α) is satisfied. For this purpose, the value D ² and the value d ² calculated by the basic calculation unit 221 and the value of the parameter h held in the parameter holding unit 226 are used.
(1-h) ² · D ² > d ² Formula (2)
Or
(1 + h) ² · D ² <d ² formula (3)
An operation for determining whether or not the condition is satisfied is performed. Then, when an affirmative determination is made that “condition is satisfied”, the determination result is notified to the determination value output unit 225. On the other hand, when a negative determination is made that “the condition is not satisfied”, the determination result is notified to the second condition determination unit 223.

  The second condition determination unit 223 is a component that executes the condition determination process only when a negative determination result “not satisfied” is notified from the first condition determination unit 222. The purpose of the processing performed here is, as shown in FIG. 14, "the comparison point q is located outside the cone ξ with the origin O as the apex and the reference axis Z as the central axis and in contact with the spheroid E with a circle." It is to determine whether or not the second condition is satisfied. However, in practice, in order to reduce the calculation burden, it is preferable to perform the determination using the cone ξ ′ instead of the cone ξ.

  That is, when a circle constituting an intersection line of the spherical surface C3 having a radius D centered on the origin O and the spheroid E is defined as an intersection circle S, “the origin O is the vertex, the reference axis Z is the central axis, It may be determined whether or not the second condition that the comparison point q is located outside the cone ξ ′ passing through the intersection circle S is satisfied. At this time, in order to further reduce the calculation burden, an approximate determination is performed using an approximate expression in which the distance f between an arbitrary point on the intersection circle S and the reference point Q is equal to the minor axis radius β. Is preferable.

When such an approximate determination is performed, the second condition determination unit 223 includes the reference pixel value (R, G, B) and the comparison pixel value (r, g) read by the pixel value reading unit 210 illustrated in FIG. , B)
γ = R · r + G · g + B · b
And the value γ is calculated, and the value D ² and the value d ² calculated by the basic calculation unit 221, the value of the parameter k held in the parameter holding unit 226, and the calculated value γ are used. And
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2 Equation (11)
An operation for determining whether or not the above condition is satisfied may be performed. After all, the condition indicated by the arithmetic expression of the equation (11) is that “the comparison point q is outside the approximated body of the cone ξ that is in contact with the spheroid E and the circle with the origin O as the apex and the reference axis Z as the central axis. It is a condition of “position”.

  When the second condition determination unit 223 makes an affirmative determination that “condition is satisfied”, the determination result is notified to the determination value output unit 225. On the other hand, when a negative determination is made that “the condition is not satisfied”, the determination result is notified to the third condition determining unit 224 together with the value of γ.

The third condition determination unit 224 is a component that executes the condition determination process only when the second condition determination unit 223 reports a negative determination result “not satisfied”. The purpose of the processing performed here is to determine whether or not the third condition “the comparison point q is located outside the spheroid E” is satisfied, as shown in FIG. Therefore, the third condition determination unit 224 includes the values D ² and d ² calculated by the basic calculation unit 221, the values of the parameters h and k held in the parameter holding unit 226, and the second condition determination unit. Using the value γ calculated by 223,
α ² = h ² · D ² , β ² = k ² · D ² (16)
x ² = D ² + γ ² / D ² -2γ Formula (17)
y ² = d ² −γ ² / D ² formula (18)
And using the calculation result,
β ² · x ² + α ² · y ² -α ² · β ² > 0 Formula (15)
An operation for determining whether or not the condition is satisfied is performed.

  Then, an affirmative determination result of “condition satisfaction” or a negative determination result of “condition not satisfied” in the third condition determination unit 224 is notified to the determination value output unit 225.

  The determination value output unit 225 is similar when one of the first condition determination unit 222, the second condition determination unit 223, and the third condition determination unit 224 makes an affirmative determination that the condition is satisfied. A determination value (for example, “1”) indicating a determination result of out of range is output, and all of the first condition determination unit 222, the second condition determination unit 223, and the third condition determination unit 224 When a negative determination is made as “z”, a determination value (for example, “0”) indicating a determination result within the similar range is output. These determination values are written as pixel values of the mask image M in the mask image storage unit 310 by the pixel value writing unit 230 as shown in FIG.

  As described above, the condition determination formula includes only addition / subtraction / division / division operations, and therefore, it is not necessary to perform square root extraction operations or trigonometric function operations necessary for general geometric operations. Therefore, the burden on the arithmetic unit is relatively light, and real-time processing is possible even when the similarity determination unit 220 is configured using an inexpensive processor.

<<< §5. Modified example >>>
Although the present invention has been described based on the basic embodiment, finally, some modifications of the present invention will be described.

  First of all, the condition judgment expressions described so far include arithmetic expressions including “inequality sign>” and “inequality sign <”. For some or all of these arithmetic expressions, instead of “inequality sign>”. An arithmetic expression using “inequality sign ≧” or an arithmetic expression using “inequality sign ≦” instead of “inequality sign <” may be used. That is, each condition determination expression indicates whether the comparison point q is in the inner region or the outer region of some graphic, but the point on the boundary surface of the graphic is included in the inner region of the graphic. However, it may be included in the outer region.

  In the embodiments described so far, for the sake of convenience, symbols (R, G, B) or (r, g, b) are used as symbols indicating the three primary colors, but these symbols are not necessarily (red, It does not mean the three primary colors (green, blue). In general, an image captured by a video camera is given as data consisting of a set of pixels having pixel values of the three primary colors (red, green, and blue). The present invention is not limited to the color system using the three primary colors, but can be applied to other color systems using the three primary colors composed of other colors. In this case, the symbols (R, G, B) or (r, g, b) used in each arithmetic expression indicate the pixel values of the three primary colors of the other color systems.

110: Image input unit 120: Original image storage unit 130: Average image creation unit 140: Average image storage unit 200: Image comparison unit 210: Pixel value reading unit 220: Similarity determination unit 221: Basic calculation unit 222: First Condition determination unit 223: second condition determination unit 224: third condition determination unit 225: determination value output unit 226: parameter holding unit 230: pixel value writing unit 310: mask image storage unit 320: image output unit 330: Parameter setting unit A (1) to A (i): average image (background image)
A, A (Ra, Ga, Ba): A coordinate point indicating the pixel value of the average image a: One side a (i-1) of a triangle, a (i): Pixel value B of one pixel constituting the average image B: Background area / pixel values of the three primary colors (reference pixel values)
b: Pixel value of three primary colors (comparison pixel value) / one side of triangle C: cylinder C1, C2 of cylinder model: sphere C3: spherical surface c: one side of triangle D: distance between origin O and reference point Q d: origin O Distances E, Ea, Ep with comparison point q: spheroid E1: closest point of spheroid E2: farthest point of spheroid E: foreground area f: any point on intersection circle S Distance G with reference point Q: Pixel value of three primary colors (reference pixel value)
g: Three primary color pixel values (comparison pixel values)
h: Parameter for determining the major axis radius α of the spheroid E k: Parameter for determining the minor axis radius β of the spheroid E: Length La of the cylinder C La1: Length La2 of the spheroid Ea in the major axis direction: Length in the minor axis direction of the spheroid Ea Lp1: Length in the major axis direction of the spheroid Ep: Lp2: Length in the minor axis direction of the spheroid Ep: Mask images M (1) to M (i) , M (i + 1), M10 to M40: Mask image m (i): Pixel value of one pixel constituting the mask image O: Origin point of RGB coordinate system constituting the three-dimensional color space P: Original image / original image Coordinate points P (1) to P (i), P (i + 1), P10 to P40 indicating pixel values: original image (input image)
P (Rp, Gp, Bp): Coordinate point p (i) indicating the pixel value of the original image Q: Pixel value of one pixel constituting the original image Q: Reference point (with pixel value (R, G, B) Coordinate point)
q: Comparison point (coordinate point with pixel values (r, g, b))
R: Pixel value of three primary colors (reference pixel value)
r: Pixel value of three primary colors (comparison pixel value)
S: Circle of intersection (intersection line of spherical surface C3 and spheroid E)
S11 to S20: Steps T in the flowchart: Tangent circle (tangent between cone ξ and spheroid E)
t: distance between reference point Q and comparison point q: vector Va indicating reference pixel value Va: vector Vp indicating average image pixel value Vp: vector indicating pixel value of original image w: parameter indicating weight X: coordinate axis x : Variable Y of elliptic equation Y: Coordinate axis y: Variable Z, Za, Zp of elliptic equation: Reference axis α: Long axis radius of spheroid E β: Short axis radius γ of spheroid E: Calculated value δ: Coordinate point Distance θ: Angle ξ, ξ ′: Cone φ, φ ′: Half apex angle of cone

Claims (22)

A moving object detection device for detecting a moving object for a moving image,
An image input unit for inputting a color original image in units of frames continuously given in time series as aggregate data of pixels having pixel values of three primary colors;
An original image storage unit for sequentially storing the input original images;
Based on a plurality of original images input in the past, an average image creation unit that sequentially creates an average image having average characteristics of these original images;
An average image storage unit for sequentially storing the created average images;
An image comparison unit that compares the original image stored in the original image storage unit with the average image stored in the average image storage unit and creates a mask image that distinguishes a foreground region and a background region;
A mask image storage for storing the mask image;
An image output unit for outputting the mask image;
With
The image comparison unit
A pixel value reading unit that reads a pixel value of a pixel at a predetermined position of one image to be compared as a reference pixel value, and reads a pixel value of the pixel at the predetermined position of the other image to be compared as a comparison pixel value;
A similarity determination unit that determines whether or not the comparison pixel value is within a predetermined similar range set for the reference pixel value;
When the similarity determination unit determines that the pixel value of the pixel at the predetermined position constituting the mask image is within the similar range, the pixel value indicating the background area is determined to be out of the similarity range. A pixel value writing unit that writes a pixel value indicating a foreground region to the mask image storage unit, respectively,
Have
In the three-dimensional coordinate system in which the similarity determination unit takes each pixel value of the three primary colors on each coordinate axis, the reference point Q located at the coordinate corresponding to the reference pixel value and the coordinate corresponding to the comparison pixel value The comparison point q is taken, the positional relationship between the spheroid E having a predetermined size centered on the reference point Q and the comparison point q is examined, and the comparison point q is outside the spheroid E or its approximate body. If it can be determined that it is located in, it is determined that it is outside the similar range, and if it can be determined that it is located inside, it is determined that it is within the similar range ,
The similarity determination unit multiplies the distance D between the origin O of the three-dimensional coordinate system and the reference point Q by a predetermined parameter h (where h <1) to obtain a value α = h · D. On the reference axis Z connecting the origin O and the reference point Q, an ellipse having a long axis radius and a value β = k · D obtained by multiplying a predetermined parameter k (where k <h) is the short axis radius The moving object detection is characterized in that the ellipsoid E is defined by rotating around the reference axis Z so that the long axis and the reference point Q become the center point. apparatus. The moving object detection device according to claim 1,
The average image creation unit
When the i-th original image P (i) is input (i = 1, 2,...), Pixels at corresponding positions in the past original image including the original image P (i) To calculate a weighted average value of pixel values for each color, and create an i-th average image A (i) composed of a collection of pixels having the average value,
When the (i + 1) -th original image P (i + 1) is input, the image comparison unit compares the original image P (i + 1) with the i-th average image A (i), i + 1) A moving object detection apparatus for generating a mask image M (i + 1). The moving object detection device according to claim 2,
The average image creation unit
When the first original image P (1) is input, the original image P (1) is stored in the average image storage unit as the first average image A (1) as it is,
Thereafter, every time the i-th original image P (i) is input (i = 2, 3,...), The i-th average image A (i) is
a (i) = (1-w) .a (i-1) + w.p (i)
(However, a (i) is the average image A (i)
A pixel value of a predetermined color of a pixel at a predetermined position,
a (i-1) is the average image A (i-1)
A pixel value of the predetermined color of the pixel at the predetermined position;
p (i) is the original image P (i)
A pixel value of the predetermined color of the pixel at the predetermined position;
w is a parameter indicating a predetermined weight (w <1))
A moving object detection device, which is created using an arithmetic expression In the moving object detection apparatus in any one of Claims 1-3 ,
The similarity determination unit
“The comparison point q is located inside the sphere C1 with the origin O as the center and the radius (D−α)” or “the comparison point q is located outside the sphere C2 with the origin O as the center and the radius (D + α)”. A first condition determining unit that determines whether or not the first condition is satisfied;
If the first condition determination unit makes a negative determination, “the comparison point q is located outside the cone ξ or its approximate body that is in contact with the spheroid E with a circle with the origin O as the apex and the reference axis Z as the central axis. A second condition determining unit that determines whether or not the second condition that “is located” is satisfied;
Third condition determination for determining whether or not the third condition “the comparison point q is located outside the spheroid E” is satisfied when the second condition determination unit makes a negative determination. And
When any one of the first condition determination unit, the second condition determination unit, and the third condition determination unit makes a positive determination, a determination value indicating a determination result that is not in the similar range is output. When a negative determination is made by all of the first condition determination unit, the second condition determination unit, and the third condition determination unit, a determination value indicating a determination result within the similar range is output. A judgment value output unit;
A moving object detection apparatus comprising: The moving object detection device according to claim 4 ,
When the distance between the origin O and the reference point Q is D, and the distance between the origin O and the comparison point q is d,
The first condition determination unit
(1-h) ² · D ² > d ² or
(1 + h) ² · D ² <d ²
A moving object detection device that performs an operation for determining whether or not the condition is satisfied. The moving object detection device according to claim 4 ,
When the second condition determination unit determines that the circle constituting the intersection line of the spherical surface C3 having the radius D centered on the origin O and the spheroid E is the intersection line S, “the origin O is the vertex, the reference axis A moving object detecting apparatus, wherein whether or not a second condition that a comparison point q is located outside a cone ξ ′ passing through the circle of intersection S with Z as a central axis is satisfied is determined. The moving object detection device according to claim 6 ,
The second condition determination unit performs an approximate determination using an approximate expression in which a distance f between an arbitrary point on the intersection circle S and the reference point Q is equal to the minor axis radius β. Moving object detection device. The moving object detection device according to claim 7 ,
The reference pixel value indicating the coordinates of the reference point Q is (R, G, B), the comparison pixel value indicating the coordinates of the comparison point q is (r, g, b), the distance between the origin O and the reference point Q is D, When the distance between the origin O and the comparison point q is d,
The second condition determination unit
γ = (R · r + G · g + B · b)
As
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2
A moving object detection device that performs an operation for determining whether or not the condition is satisfied. The moving object detection device according to claim 4 ,
The reference pixel value indicating the coordinates of the reference point Q is (R, G, B), the comparison pixel value indicating the coordinates of the comparison point q is (r, g, b), the distance between the origin O and the reference point Q is D, When the distance between the origin O and the comparison point q is d,
The third condition determination unit
α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
γ = (R · r + G · g + B · b)
As
β ² · x ² + α ² · y ² -α ² · β ² > 0
A moving object detection device that performs an operation for determining whether or not the condition is satisfied. In the moving object detection apparatus in any one of Claims 1-3 ,
The similarity determination unit
A parameter holding unit for holding values of parameters h and k;
Based on the reference pixel value (R, G, B) and the comparison pixel value (r, g, b) read by the pixel value reading unit,
D ² = R ² + G ² + B ² and
d ² = r ² + g ² + b ²
A basic calculation unit for calculating the value D ² and the value d ² ,
By using the value of the parameter h to the basic computation unit is held to the value D ² and the value d ² calculated in the parameter holding unit,
(1-h) ² · D ² > d ² or
(1 + h) ² · D ² <d ²
A first condition determination unit that performs an operation for determining whether or not the condition is satisfied;
Based on the reference pixel value (R, G, B) and the comparison pixel value (r, g, b) read by the pixel value reading unit when the first condition determining unit makes a negative determination,
γ = R · r + G · g + B · b
To calculate the value γ, using the value D ² and the value d ² calculated by the basic calculation unit, the value of the parameter k held in the parameter holding unit, and the value γ,
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2
A second condition determination unit that performs an operation for determining whether or not the condition is satisfied,
When the second condition determination unit makes a negative determination, the value D ² and the value d ² calculated by the basic calculation unit, the values of the parameters h and k held in the parameter holding unit, and the first Using the value γ calculated by the condition determining unit 2,
α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
And using the calculation result,
β ² · x ² + α ² · y ² -α ² · β ² > 0
A third condition determination unit that performs an operation for determining whether or not the condition is satisfied,
When any one of the first condition determination unit, the second condition determination unit, and the third condition determination unit makes a positive determination, a determination value indicating a determination result that is not in the similar range is output. When a negative determination is made by all of the first condition determination unit, the second condition determination unit, and the third condition determination unit, a determination value indicating a determination result within the similar range is output. A judgment value output unit;
A moving object detection apparatus comprising: In the moving object detection apparatus in any one of Claim 5, 8-10 ,
For some or all of the arithmetic expressions including the inequality sign, use an arithmetic expression using the inequality sign ≧ in place of the inequality sign>, or an arithmetic expression using the inequality sign ≦ in place of the inequality sign <. A moving object detection device. In the moving object detection apparatus in any one of Claims 1-11 ,
A moving object detection apparatus further comprising a parameter setting unit that sets parameters “w” or “h and k” or all of them to an arbitrary value by a user operation input. In the moving object detection apparatus in any one of Claims 1-12 ,
A moving object detection device, wherein a pixel value reading unit reads a pixel value of a pixel of an original image as a reference pixel value, and reads a pixel value of a pixel of an average image as a comparison pixel value. A program for operating a computer as the moving object detection device according to claim 1 . A semiconductor integrated circuit that functions as the moving object detection device according to claim 1 . A method for determining similarity between a first color pixel having each pixel value (R, G, B) of the three primary colors and a second color pixel having each pixel value (r, g, b) of the three primary colors. There,
A preparatory stage in which a computer captures values of pixel values (R, G, B) and (r, g, b);
In a three-dimensional coordinate system in which the computer takes the pixel values of the three primary colors as the coordinate axes, a spheroid E having a predetermined size centered on a reference point Q having coordinates corresponding to the pixel values (R, G, B). Alternatively, with respect to the approximate body and the comparison point q having coordinates corresponding to the pixel value (r, g, b), a positional relationship determination step for checking whether the latter is inside or outside the former,
When the computer determines that the comparison point q is outside the spheroid E or its approximate body, the determination result is that the first color pixel and the second color pixel are dissimilar. And when it is determined that the comparison point q is inside the spheroid E or its approximated body, a determination result that the first color pixel and the second color pixel are similar is output. A judgment result output stage to perform,
Have
In the positional relationship determination step, a value α = h · D obtained by multiplying a distance D between the origin O of the three-dimensional coordinate system and the reference point Q by a predetermined parameter h (where h <1) is a long axis. An ellipse having a radius β and a short axis radius of a value β = k · D obtained by multiplying by a predetermined parameter k (where k <h) is long on a reference axis Z connecting the origin O and the reference point Q. A class of pixels characterized by defining a spheroid E that is arranged such that the axes overlap and the reference point Q is the center point and is rotated about the reference axis Z. Negation method. The method of determining similarity of pixels according to claim 16 .
The positional relationship determination stage
“The comparison point q is located inside the sphere C1 with the origin O as the center and the radius (D−α)” or “the comparison point q is located outside the sphere C2 with the origin O as the center and the radius (D + α)”. A first condition determination stage for determining whether or not a first condition is satisfied;
When a negative determination is made in the first condition determination step, “a comparison point outside the cone ξ or its approximated body that touches the spheroid E with a circle with the origin O as the apex and the reference axis Z as the central axis. a second condition determining step for determining whether or not a second condition that “q is located” is satisfied;
The third condition for determining whether or not the third condition “the comparison point q is located outside the spheroid E” is satisfied when a negative determination is made in the second condition determination step. A judgment stage;
Have
In the determination result output stage, when an affirmative determination is made in any of the first condition determination stage, the second condition determination stage, and the third condition determination stage, the first color pixel and A determination result that the second color pixel is dissimilar is output, and a negative determination is made in all of the first condition determination step, the second condition determination step, and the third condition determination step. In this case, the pixel similarity determination method outputs a determination result that the first color pixel and the second color pixel are similar. The pixel similarity determination method according to claim 17 ,
In the first condition determination stage,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
And when
(1-h) ² · D ² > d ² or
(1 + h) ² · D ² <d ²
A pixel similarity determination method characterized by performing an operation for determining whether or not the above condition is satisfied. The pixel similarity determination method according to claim 17 ,
In the second condition determination stage,
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² ),
γ = (R · r + G · g + B · b)
And when
^{γ 2 / (D 2 · d} 2) <(1-k 2/2) 2
A pixel similarity determination method characterized by performing an operation for determining whether or not the above condition is satisfied. The pixel similarity determination method according to claim 17 ,
In the third condition determination stage,
α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
γ = (R · r + G · g + B · b)
And when
β ² · x ² + α ² · y ² -α ² · β ² > 0
A pixel similarity determination method characterized by performing an operation for determining whether or not the above condition is satisfied. A method for determining similarity between a first color pixel having each pixel value (R, G, B) of the three primary colors and a second color pixel having each pixel value (r, g, b) of the three primary colors. There,
A preparatory stage in which a computer captures values of parameters h (h <1) and k (k <h), pixel values (R, G, B) and (r, g, b);
Computer
(1-h) ² · (R ² + G ² + B ² )> (r ² + g ² + b ² ) or (1 + h) ² · (R ² + G ² + B ² ) <(r ² + g ² + b ² )
A first condition determination stage for determining whether or not the condition is satisfied,
When a negative determination is made in the first condition determination step, the computer
(R · r + G · g + B · b) ² /
((R ² + G ² + B ² ) · (r ² + g ² + b ² ))
^{<(1-k 2/2} ) 2
A second condition determination stage for determining whether or not the condition is satisfied,
When a negative determination is made in the second condition determination step, the computer
β ² · x ² + α ² · y ² -α ² · β ² > 0
However, α ² = h ² · D ²
β ² = k ² · D ²
x ² = D ² + γ ² / D ² -2γ
y ² = d ² −γ ² / D ²
D ² = (R ² + G ² + B ² )
d ² = (r ² + g ² + b ² )
γ = (R · r + G · g + B · b)
A third condition determination stage for determining whether or not the condition is satisfied;
If the computer makes a positive determination in any of the first condition determination stage, the second condition determination stage, and the third condition determination stage, the first color pixel and the second color pixel When the determination result that the color pixel is dissimilar is output, and negative determination is made in all of the first condition determination stage, the second condition determination stage, and the third condition determination stage, A determination result output step for outputting a determination result that the first color pixel is similar to the second color pixel;
A method for determining similarity of pixels. In the pixel similarity determination method according to any one of claims 18 to 21 ,
For some or all of the arithmetic expressions including the inequality sign, use an arithmetic expression using the inequality sign ≧ in place of the inequality sign>, or an arithmetic expression using the inequality sign ≦ in place of the inequality sign <. A feature similarity determination method.

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