JP6322356B2 - Vanishing point position calculation method and distance measurement method - Google Patents

Description

  The present invention relates to a vanishing point position calculation method and a distance measurement method.

  2. Description of the Related Art Conventionally, a method for measuring an inter-vehicle distance between a host vehicle and a preceding vehicle using an image of a preceding vehicle obtained by imaging the front of the host vehicle is known (see, for example, Patent Document 1).

JP 2002-117392 A

  Hereinafter, a conventional inter-vehicle distance measuring method recognized by the inventor of the present invention will be described with reference to FIGS. 9 and 10. FIG. 9 is an explanatory diagram for explaining a conventional inter-vehicle distance measuring method, and FIG. 10 is a schematic diagram showing an image captured from the attachment point O in FIG.

  The inter-vehicle distance measurement method described below is as a horizontal distance from an attachment point O of a camera (not shown) attached to the host vehicle to an intersection S between a vertical line passing through the rear end of the preceding vehicle and the ground. The purpose is to calculate the value of the defined inter-vehicle distance Z (see FIG. 9).

  First, the relationship between FIG. 9 and FIG. 10 will be described. A two-dot chain line C extending from the attachment point O in FIG. 9 indicates the optical axis of the camera. An arc-shaped dotted line connecting the point P and the point R indicates a range that can be imaged by the camera fixed to the attachment point O. That is, ∠POR represents the angle of view of the image captured by the camera. An image obtained by capturing a range from the point P to a predetermined point Q on the ground in the angle of view is used for measuring the inter-vehicle distance as an image obtained by capturing the preceding vehicle. That is, as shown in FIG. 10, in the image obtained by imaging the preceding vehicle, the point P is located at the upper end of the image, and the point Q is located at the lower end of the image. 9 and 10 indicate the position of the vanishing point. The vanishing point is a point where the position of the subject in the image converges when the subject is moved to an infinite point, and theoretically exists at an infinite distance. In the measurement of the inter-vehicle distance Z, the host vehicle on which the camera is mounted and the preceding vehicle that is the subject move on a road that is formed substantially horizontally. For this reason, the vanishing point is located on a straight line extending from the point O in the horizontal direction. A one-dot chain line D in FIG. 9 is a line segment extending from the point O in the horizontal direction, and indicates the direction in which the vanishing point is seen from the camera. As shown in FIGS. 9 and 10, the vanishing point is located at the intersection F between the dotted line PR and the alternate long and short dash line D on the image. Hereinafter, in this specification, the intersection point F defined on the image will be referred to as a vanishing point F for the sake of simplicity. The position of the vanishing point F in the image, that is, which point on the image obtained by copying the dotted line connecting the point P and the point Q by the camera, is the angle formed by the optical axis C of the camera and the horizontal plane. That is, it is determined according to the mounting angle of the camera in the pitch direction.

Next, a calculation method for measuring the inter-vehicle distance Z will be described.
It is assumed that the value of the ground height H at which the camera is mounted and the value of the horizontal distance Z0 from the camera mounting point O to the point Q located at the lower end of the image are known. At this time, as can be seen from FIG. 9, the size of the angle of view b corresponding to ∠FOQ is equal to the size of the elevation angle when the point O is viewed from the point Q. Accordingly, the value of the angle of view b is obtained by the following (Equation 1).
(Equation 1)
b = arctan (H / Z0)

Further, based on the image obtained by imaging the preceding vehicle shown in FIG. 10, the value of the length Y1 from the vanishing point F to the point S in the image and the length Y2 from the vanishing point F to the point Q in the image. And the ratio of. More specifically, the ratio is obtained based on the pixels constituting the image. A general image is expressed by arranging pixels which are the minimum units constituting a digital image, and is configured by arranging, for example, 640 pixels in the horizontal direction and 480 pixels in the vertical direction. In the conventional inter-vehicle distance measurement method, the ratio of the number of pixels existing from the vanishing point F to the point S in the image of the preceding vehicle and the number of pixels existing from the vanishing point F to the point Q is obtained. The ratio of Y1 and Y2 is obtained. The ratio of Y2 to Y1 thus obtained is considered to be equal to the ratio of the angle of view b to the angle of view a corresponding to ∠FOS in the conventional inter-vehicle distance calculation method (see FIG. 9). That is, in the conventional inter-vehicle distance measurement method, it is considered that the ratio of the length on the image obtained by imaging the preceding vehicle is equal to the ratio of the angle of view corresponding to the length. In this case, the value of the angle of view a is obtained by the following (Equation 2).
(Equation 2)
a = b × Y1 / Y2

The field angle a is equal to the elevation angle when the point O is viewed from the point S as can be seen from FIG. Therefore, the value of the inter-vehicle distance Z is obtained by the following (Equation 3).
(Equation 3)
Z = H / tan (a)

  As described above, according to the conventional inter-vehicle distance measurement method, the value of the ground height H at which the camera is mounted and the horizontal distance Z0 from the camera mounting point O to the point Q located at the lower end of the image. If the value is known, the value of the inter-vehicle distance Z can be calculated based on an image obtained by imaging the preceding vehicle.

  However, in the conventional inter-vehicle distance measurement method, as described above, the value of the horizontal distance Z0 from the camera attachment point O to the point Q located at the lower end of the image needs to be measured in advance and known. Therefore, the operator has to measure the distance Z0 from the camera attachment point O to the point Q located at the lower end of the image when the camera is attached or at the time of initial setting.

  However, when the camera is mounted or initially set, it may be difficult to measure the distance Z0, such as when there is an obstacle at the point Q located at the lower end of the image. For this reason, in the conventional inter-vehicle distance measurement method, it is necessary to stop the vehicle at a point that satisfies the measurement conditions and measure the distance Z0. This may be a burden on the operator.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a vanishing point position calculation method and a distance measurement method that can reduce the burden on the operator.

In order to achieve the above-described object, the vanishing point position calculating method according to the present invention is characterized by the following (1).
(1) an imaging means by obtain a reference image obtained by photographing the reference point is any point on the ground, the reference picture on by the position of the reference point on the reference image is specified by the tap operation Obtaining position information of the reference point at
Obtaining a value of the reference distance is a horizontal distance of the imaging means ground clearance of values attached, from a position attached 及 beauty said imaging means to said reference point,
Calculating a value of the angle of view α in the ground height direction from the vanishing point F1 defined in the reference image to the reference point based on a ratio between the ground height value and the reference distance;
The number D1 of pixels existing in the ground high direction from the upper end of the reference image to the reference point in the reference image specified based on the acquired position information of the reference point, and the imaging means Calculating the value of the angle of view β in the ground high direction from the upper end of the reference image to the reference point based on correspondence data between each pixel and the angle of view in the captured image;
By subtracting the value of the angle of view α from the value of the angle of view β, the value of the angle of view γ in the ground high direction from the upper end of the reference image to the vanishing point F1 is calculated, and the value of the angle of view γ Calculating the number D2 of pixels existing in the ground high direction between the upper end of the reference image and the vanishing point F1 in the reference image based on the correspondence data;
A vanishing point position calculating step for calculating a position of the vanishing point F1 in the reference image,
The correspondence data is imaged by the imaging means obtained based on a first correspondence relationship acquired in advance between an angle in the height direction from the optical axis of the imaging means and the angle of view per pixel at that angle. The second correspondence between each pixel in the vertical direction of the image and the angle of view per pixel in that pixel.

In order to achieve the above-described object, the distance measuring method according to the present invention is characterized by the following (2 ) .
(2) The vanishing point position calculating step provided in the vanishing point position calculating method according to (1),
A measurement distance calculation step;
A distance measuring method comprising:
The measurement distance calculating step includes:
Obtaining a measurement image obtained by imaging a value of the ground height and a measurement point which is an arbitrary point on the ground by the imaging means;
The reference image from the upper end of the reference image calculated in the vanishing point position calculation step is calculated from the number D3 of pixels existing in the height direction from the upper end of the measurement image to the measurement point in the measurement image. Is determined in the measurement image obtained by subtracting the number D2 of pixels existing in the height direction above the vanishing point F1, and the position in the measurement image is the vanishing point F1 in the reference image. On the basis of the number D4 of pixels existing in the height direction above the ground from the vanishing point F2 that is the same as the position to the measurement point in the measurement image, and the second correspondence relationship as the correspondence data, The value of the angle of view θ in the ground height direction from the vanishing point F2 to the measurement point is calculated, and based on the value of the angle of view θ and the value of the ground height, the position from which the imaging unit is attached is calculated. Water to measuring point Calculating a value of the measurement distance L2, which is a distance in the flat direction;
Including .

  In the vanishing point position calculation method having the configuration (1) above, the reference point is calculated from the value of the ground height to which the imaging unit is attached, the reference image obtained by imaging the reference point by the imaging unit, and the position at which the imaging unit is attached. The position of the vanishing point F1 in the reference image is calculated based on the value of the reference distance that is the distance in the horizontal direction up to and the correspondence data between each pixel and the angle of view in the image captured by the imaging unit. .

In the distance measuring method having the above configuration (2), the value of the ground height to which the imaging means is attached, the reference image obtained by imaging the reference point by the imaging means, and the position from the position where the imaging means is attached to the reference point. Measured based on the value of the reference distance, which is the distance in the horizontal direction, the correspondence data between each pixel and the angle of view in the image captured by the imaging unit, and the measurement image obtained by imaging the measurement point by the imaging unit A distance value is calculated .

  According to the vanishing point position calculating method and the distance measuring method of the present invention, it is possible to provide a vanishing point position calculating method and a distance measuring method that can reduce the burden on the practitioner.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is a block diagram illustrating a hardware configuration example of an inter-vehicle distance measurement system according to an embodiment of the present invention. FIG. 2 is a flowchart showing processing in the vanishing point position calculating step. FIG. 3 is an explanatory diagram for explaining a vanishing point position calculating method in the vanishing point position calculating step. FIG. 4 is a schematic diagram illustrating an example of a reference image. FIG. 5 is a diagram illustrating an example of a correspondence relationship between each pixel and an angle of view in an image. FIG. 6 is a flowchart showing processing in the measurement distance calculation step. FIG. 7 is an explanatory diagram for explaining a measurement distance calculation method in the measurement distance calculation step. FIG. 8 is a schematic diagram illustrating an example of a measurement image. FIG. 9 is an explanatory diagram for explaining a conventional inter-vehicle distance measurement method. FIG. 10 is a schematic diagram showing an image captured from the attachment point O in FIG.

  A vanishing point position calculating method and a distance measuring system 1 using a distance measuring method according to an embodiment of the present invention will be described below with reference to the drawings.

First, an outline of the inter-vehicle distance measurement system 1 will be described.
The inter-vehicle distance measurement system 1 is based on an image obtained by imaging the front of the vehicle with the camera 11 attached to the host vehicle, from the attachment point O of the camera 11 to the intersection S between the vertical line passing through the rear end of the preceding vehicle and the ground. This is a system for calculating the value of the inter-vehicle distance L2 defined as the horizontal distance (see FIG. 7).

  A two-dot chain line C extending from the attachment point O in FIGS. 3 and 7 indicates the optical axis of the camera 11. A dotted line connecting the point P and the point Q indicates a range that can be captured by the camera 11. That is, ∠POQ indicates the angle of view of the image captured by the camera 11. An image obtained by capturing a range from the point P to a predetermined point Q on the ground in the angle of view is used for measuring the inter-vehicle distance L2 as an image obtained by imaging the front of the vehicle. That is, as shown in FIGS. 4 and 8, in the captured image, the point P is located at the upper end of the image and the point Q is located at the lower end of the image. The points P and Q are located side by side in the vertical direction on the captured image. Reference numeral F1 shown in FIG. 4 and reference numeral F2 shown in FIG. 8 indicate the positions of vanishing points determined in the image. In the measurement of the inter-vehicle distance L2, the host vehicle on which the camera 11 is mounted and the preceding vehicle that is the subject move on a road that is formed substantially horizontally. For this reason, vanishing points F1 and F2 are located on a straight line extending from point O in the horizontal direction. 3 and 7 is a line segment extending in the horizontal direction from the point O, and indicates the directions of the vanishing points F1 and F2 viewed from the camera 11. The positions of the vanishing points F1, F2 in the image are determined according to the angle formed by the optical axis C of the camera 11 and the horizontal plane.

Next, the configuration of each part of the inter-vehicle distance measurement system 1 will be described.
FIG. 1 is a diagram illustrating a hardware configuration example of an inter-vehicle distance measurement system 1 according to the present embodiment. As shown in FIG. 1, the inter-vehicle distance measurement system 1 according to this embodiment includes a camera 11, an image recognition unit 100, a drive recorder 200, and a terminal 300.

  The camera 11 is a camera as imaging means for imaging the front of the vehicle. The camera 11 includes a lens that bends and focuses light, and an image sensor that detects the light focused by the lens and converts the light into an electrical signal. The camera 11 captures an object and conforms to the NTSC (National Television System Committee) standard. Output video signal. For example, as shown in FIGS. 3 and 7, the camera 11 is attached to the front portion of the vehicle at a position and an angle at which a preceding vehicle can be imaged. In the present embodiment, the image captured by the camera 11 is configured by arranging 640 pixels in the horizontal direction and 480 pixels in the vertical direction.

  The image recognition unit 100 includes a video amplifier 101, an NTSC decoder 102, an image processing circuit 103, a microcomputer 104, a ROM 105, a RAM 106, and a power supply circuit 107 as main components.

  The drive recorder 200 includes a main decoder 201, a data processing unit 202, a communication processing unit 203, a ROM 204, a RAM 205, and a vehicle signal interface 206 as main components.

  The terminal 300 is a terminal including a display unit (not shown) that displays various information such as images and an operation unit (not shown) that accepts various operation inputs, and is used in a vanishing point position calculating step described later. It is done. In the present embodiment, the display unit and the operation unit are integrally configured as a touch panel, and a color two-dimensional display screen in which a large number of micro display cells configured by a liquid crystal device are arranged in the X direction and the Y direction. It is comprised by. By controlling the display state of a large number of minute display cells for each cell, desired information such as graphics, characters, images, etc. can be displayed graphically on the two-dimensional display screen. The terminal 300 is connected to the image recognition unit 100 and the drive recorder 200. The terminal 300 receives the processed video signal output from the image processing circuit 103 and displays an image as shown in FIG. 4 by two-dimensional screen display. In addition, the terminal 300 accepts a tap operation for designating an arbitrary point on the touch panel and an input operation for characters or symbols by tapping a character or symbol displayed on the touch panel. The terminal 300 outputs an input signal corresponding to the accepted operation to the microcomputer 104 via a communication network (CAN (Controller Area Network)) on the vehicle. Specific display contents and operation of the terminal 300 will be described later.

  The video amplifier 101 receives an NTSC standard video signal output from the camera 11 and outputs a video signal amplified to a necessary level. The output of the video amplifier 101 is connected to the video input of the drive recorder 200 and the input of the NTSC decoder 102.

  The NTSC decoder 102 processes the NTSC standard video signal input from the video amplifier 101 to extract a plurality of signal components (Y, Cb, Cr) included in the video signal, and performs A / D conversion. A digital image signal that can be used for image processing is generated.

  The image processing circuit 103 is a dedicated large-scale integrated circuit (LSI (Large Scale Integration)) having a function for performing image processing such as calculation of the inter-vehicle distance L2. The image processing circuit 103 executes, for example, the process of the vanishing point position calculating step shown in FIG. 2 based on the input image data to calculate the positions of the vanishing points F1 and F2 in the image, or shown in FIG. A function necessary for executing the process of the measurement distance calculation step and calculating the value of the inter-vehicle distance L2 is provided.

  The image processing circuit 103 is connected to a ROM (Read Only Memory) 105 which is a read-only memory and a RAM (Random Access memory) 106 which is a rewritable memory. The ROM 105 holds a program executed by the image processing circuit 103 in the vanishing point position calculating step and the measurement distance calculating step, and constant data used by the image processing circuit 103 in each process. For example, the ROM 105 holds a data table shown in FIG. The RAM 106 is used to hold image data processed by the image processing circuit 103 and temporary data being processed in the vanishing point position calculating step and the measurement distance calculating step.

  The microcomputer (microcomputer) 104 has a CAN (Controller Area Network) standard communication function, and performs communication between the drive recorder 200 and the terminal 300. For example, the microcomputer 104 receives a signal including operation input information output from the terminal 300.

  In the drive recorder 200, the main decoder 201 processes the NTSC standard video signal output from the video amplifier 101 in the image recognition unit 100, and a plurality of signal components (Y, Cb, Cr) included in the video signal are processed. Each is extracted and subjected to A / D conversion to generate a digital image signal that can be processed by the data processing unit 202.

  The data processing unit 202 includes a microcomputer, and mainly performs processing for sequentially inputting image data output from the main decoder 201, compressing and recording the image data. A ROM 204 connected to the data processing unit 202 holds in advance a program executed by the data processing unit 202, various constant data used by the data processing unit 202, and the like. The RAM 205 is used to hold temporary data such as data being processed. As for data such as operation information including an image finally recorded by the drive recorder 200 and inter-vehicle distance information, for example, a non-volatile memory is mounted on a memory card (not shown) that is detachably attached to the drive recorder 200. Saved in.

  The communication processing unit 203 is configured by a microcomputer having a CAN standard communication function, and communicates with the image recognition unit 100 connected thereto via a communication network (CAN) on the vehicle. Do. In addition, bidirectional communication is performed between the communication processing unit 203 and the data processing unit 202, and information is exchanged as necessary.

  The vehicle signal interface 206 receives various signals output from the vehicle side and converts them into signals that can be processed by the data processing unit 202, or converts various signals output from the data processing unit 202 into signals that can be processed by the vehicle side. Process. Signals handled by the vehicle signal interface 206 as operation information include trigger output, ignition (IGN), manual switch (SW), brake, turn signal L side, turn signal R side, vehicle speed pulse, and the like.

Next, a specific operation of the inter-vehicle distance measurement system 1 according to this embodiment will be described.
The inter-vehicle distance measurement system 1 according to the present embodiment generally executes two processes, a process in a vanishing point position calculating step and a process in a measured distance calculating step. In the process in the vanishing point position calculating step, the position of the vanishing point on the image is calculated, and in the process in the measuring distance calculating step, the value of the inter-vehicle distance L2 is calculated with reference to the position of the vanishing point calculated in the vanishing point position calculating step. To do. In the following, first, the vanishing point position calculating step will be described.

(Disappearance point calculation step)
FIG. 2 is a flowchart showing processing in the vanishing point position calculating step.
Schematically, in the vanishing point position calculating step, the position of the vanishing point F1 determined in the reference image, which is an image obtained by imaging the reference point T that is an arbitrary point on the ground by the camera 11, is calculated. Here, the reference point T may be any point as long as it is captured by the camera 11 and appears on the reference image, and the position of the reference point T on the reference image is an operation input to the terminal 300 as described later. It is determined according to. Further, in the present embodiment, the calculation of the position of the vanishing point F1 in the vanishing point position calculating step is executed when, for example, the camera 11 is attached to the vehicle and the operation of the inter-vehicle distance measuring system 1 is started. It is executed before executing the process in the step. That is, the vanishing point position calculating step is executed as a pre-process of the measuring distance calculating step for calculating the inter-vehicle distance L2 based on the measurement image obtained by imaging the preceding vehicle.

Hereinafter, specific processing in the vanishing point position calculating step will be described.
In step S <b> 21, first, the image processing circuit 103 receives a reference image from the camera 11 via the video amplifier 101 and the NTSC decoder 102. Thereafter, the image processing circuit 103 outputs the processed video signal to the terminal 300. The terminal 300 receives the processed video signal output from the image processing circuit 103 and displays a reference image as shown in FIG. FIG. 4 is a schematic diagram showing an example of the reference image. The point F, the point P, the point Q, and the arrow shown in the figure are not actually displayed on the terminal 300. When the position information of the reference point T on the reference image specified by the operator's operation input to the terminal 300 is received after the display of the reference image, the terminal 300 sends a signal including the position information to the image processing circuit 103. Output via the computer 104. The designation of the position of the reference point T is performed, for example, by the operator specifying one point on the reference image displayed on the touch panel included in the terminal 300 by a tap operation. For example, the reference point T can be set by placing an object as a mark on the ground within the range imaged by the camera 11 and specifying one arbitrary point on the object on the reference image. Thereafter, the image processing circuit 103 receives the signal output from the terminal 300. In the processing of the inter-vehicle distance measurement system 1 according to the present embodiment, the position of the reference point T in the reference image in the horizontal direction does not affect the processing result. Therefore, the image processing circuit 103 processes the position information by regarding the intersection of the straight line extending from the point where the position information is received as the reference point T and the line segment PQ as the reference point T. That is, the reference point T is always located on the line segment PQ. Through the above processing, in step S21, the image processing circuit 103 receives the reference image in which the position of the reference point T is determined.

  In step S22, the image processing circuit 103 determines whether or not the value of the ground height H to which the camera 11 is attached has been input. The value of the ground height H is input to the terminal 300 by the operator. As a result of the determination, when it is determined that the value of the ground height H has not been input, the process of step S22 is repeated again. On the other hand, if it is determined that the value of the ground height H has been input, the received value of the ground height H is held in the RAM 106, and the process of step S23 is executed.

  In step S23, the image processing circuit 103 determines whether or not a value of a reference distance L1 (see FIG. 3), which is a horizontal distance from the attachment point O of the camera 11 to the reference point T, is input. The value of the reference distance L1 is input to the terminal 300 by the operator. As a result of the determination, when it is determined that the reference distance L1 value has not been input, the process of step S22 is repeated again. On the other hand, if it is determined by the determination that the value of the reference distance L1 has been input, the received value of the reference distance L1 is held in the RAM 106, and the process of step S24 is executed.

In step S24, the image processing circuit 103 displays the image in the ground height direction from the vanishing point F1 to the reference point T based on the ratio between the value of the ground height H received in step S22 and the reference distance L1 received in step S23. The value of the angle α (∠F1OT) is calculated (see FIG. 3). As can be seen from FIG. 3, the angle of view α is equal to the angle of elevation when the point O is viewed from the reference point T. Therefore, the image processing circuit 103 calculates the value of the angle of view α by the following (Equation 4).
(Equation 4)
α = arctan (H / L1)

  In step S25, the image processing circuit 103 calculates the number D1 of pixels existing in the height direction from the point P located at the upper end of the reference image to the reference point T based on the reference image received in step S21. To do. More specifically, the image processing circuit 103 calculates the number D1 of pixels by counting the number of pixels existing in the range indicated by the arrow E1 in FIG.

  In step S <b> 26, the image processing circuit 103 reads a data table (see FIG. 5) held in the ROM 105. The data table shown in FIG. 5 is a data table as correspondence data including correspondence information between each pixel and an angle of view in an image captured by the camera 11 as information. In FIG. 5, the leftmost column indicates the angle in the ground height direction from the optical axis, and the angle of view of the camera 11 is divided every 5 °. The center column indicates the number of pixels included in the section. The rightmost column shows the angle of view per pixel in the section. This data table is calculated according to the characteristics (for example, distortion) of the lens provided in the camera 11 and is stored in the ROM 105 in advance.

In step S27, the image processing circuit 103 determines the height in the ground direction from the point P positioned at the upper end of the reference image to the reference point T based on the number of pixels D1 calculated in step S25 and the data table read in step S26. The angle of view β is calculated. More specifically, for example, referring to the data table, when the angle per pixel is added for each pixel from the point P to the point Q, and the number of pixels reaches D1. The angle obtained by integrating the angle?
In the present embodiment, the angle of view β is calculated by the following relational expression (Equation 5) that approximates the relationship between the number D1 of pixels and the angle of view β. The relational expression is obtained according to the data table shown in FIG. In the present embodiment, the relational expression is held in the ROM 105 in advance, and is read out in step S26 instead of the data table as the correspondence data between each pixel and the angle of view in the image. By using a relational expression that directly defines the relationship between the number of pixels D1 and the angle of view β, the calculation time and the load on the image processing circuit 103 are reduced as compared with the case where a data table is used.
(Equation 5)
β = 0.0000001898 * D1 ³ -0.000136 * D1 ² + 0.191675 * D1

In step S28, the image processing circuit 103 subtracts the value of the angle of view α calculated in step S24 from the value of the angle of view data calculated in step S27, thereby eliminating the vanishing point F1 from the point P positioned at the upper end of the reference image. The angle of view γ in the high direction above the ground is calculated. That is, the image processing circuit 103 calculates the value of the angle of view γ by the following (Equation 6).
(Equation 6)
γ = β-α

In step S29, the image processing circuit 103 determines between the point P located at the upper end of the reference image and the vanishing point F1 based on the value of the angle of view γ calculated in step S28 and the data table read in step S26. The number D2 of pixels existing in the ground high direction is calculated. That is, the number D2 of pixels existing in the range indicated by the arrow E2 in FIG. 4 is calculated. More specifically, for example, with reference to the data table, the angle per pixel of the pixel is added for each pixel from the point P to the point Q, and the integrated angle value is represented by the angle of view γ. The number of accumulated pixels at the time when this value is reached may be D2.
In the present embodiment, the number of pixels D2 is calculated by the following relational expression (Equation 7) that approximates the relationship between the angle of view γ and the number of pixels D2. The relational expression is obtained according to the data table shown in FIG. In the present embodiment, the relational expression is held in the ROM 105 in advance, and is read out in step S26 instead of the data table as the correspondence data between each pixel and the angle of view in the image. By using a relational expression that directly defines the relationship between the angle of view γ and the number of pixels D2, the calculation time and the load on the image processing circuit 103 are reduced as compared with the case where a data table is used.
(Equation 7)
D2 = −0.000232 * γ ³ + 0.028332 * γ ² + 5.1225 * γ

  With the above processing, the number D2 of pixels existing in the high direction above the ground between the point P positioned at the upper end of the reference image and the vanishing point F1 is calculated. That is, the position of the vanishing point F1 in the reference image is calculated. The image processing circuit 103 holds the calculated value D2 of pixels in the RAM 106 and ends the vanishing point position calculating step.

(Measurement distance calculation step)
FIG. 6 is a flowchart showing processing in the measurement distance calculation step.
Schematically, in the measurement distance calculation step, measurement is performed from the attachment point O of the camera 11 based on a measurement image that is an image of the measurement point S that is the intersection of the vertical line passing through the rear end of the preceding vehicle and the ground. An inter-vehicle distance L2 defined as a horizontal distance to the point S is calculated (see FIG. 7). In the measurement distance calculation step, the inter-vehicle distance L2 is calculated as the measurement distance.

  The process of the measurement distance calculation step is executed in a state where the attachment angle in the pitch direction of the camera 11 in the measurement distance calculation step and the attachment angle in the pitch direction of the camera 11 in the vanishing point position calculation step are the same. For example, when the attachment angle of the camera 11 is not changed between the vanishing point position calculating step for executing the preprocessing and the measuring distance calculating step for calculating the measurement distance, this state is set. At this time, the position of the vanishing point F2 in the measurement image is the same as the position of the vanishing point F1 in the reference image. Therefore, the number of pixels existing in the height direction from the point P located at the upper end of the measurement image to the vanishing point F2 is equal to the value of the number of pixels D2 calculated in the vanishing point position calculating step.

Hereinafter, specific processing in the measurement distance calculation step will be described.
In step S <b> 31, the image processing circuit 103 receives a measurement image from the camera 11 via the video amplifier 101 and the NTSC decoder 102.

  In step S32, the image processing circuit 103 reads the value of the ground height H held in the RAM 106 in step S22.

In step S33, the image processing circuit 103 calculates the number D 4 pixels existing in the ground clearance direction between the vanishing point F2 to the measurement point. In the present embodiment, the image processing circuit 103 specifies the position of the vanishing point F2 on the image by a known image recognition method.

  In step S33a, the image processing circuit 103 calculates the number D3 of pixels existing in the height direction from the point P located at the upper end of the measurement image to the measurement point S based on the measurement image. More specifically, the image processing circuit 103 calculates the number D3 of pixels by counting the number of pixels existing in the range indicated by the arrow E3 in FIG.

  In step S33b, the image processing circuit 103 reads the value of the number of pixels D2 held in the RAM 106 in the vanishing point position calculating step.

In step S33c, the value of the number of pixels D2 read in step S33b is subtracted from the value of the number of pixels D3 calculated in step S33a, thereby existing in the high direction from the vanishing point F2 to the measurement point S. The number D4 of pixels is obtained. That is, the image processing circuit 103 calculates the value of the number of pixels D4 from (Equation 8).
(Equation 8)
D4 = D3-D2

  In step S <b> 34, the image processing circuit 103 reads a data table held in the ROM 105.

  In step S35, the value of the angle of view θ in the height direction from the vanishing point F2 to the measurement point S is calculated based on the value of the number of pixels D4 calculated in step S33c and the data table read in step S34. More specifically, for example, referring to the data table, the angle per pixel of the pixel is added for each pixel from the vanishing point F2 to the point Q, and the number of pixels reaches D4. The angle accumulated at the angle may be set as the angle of view θ. Similarly to step S27 and step S29, the angle of view θ may be calculated by a relational expression that approximates the relationship between the number of pixels D4 and the angle of view θ. In the present embodiment, the field angle value corresponding to the pixel number D3 is calculated based on the equation (5) in step S27, and the field angle γ value corresponding to the pixel number D2 is subtracted from the calculated value. As a result, the angle of view θ is calculated.

In step S36, the image processing circuit 103 calculates the value of the inter-vehicle distance L2, which is the measurement distance, based on the value of the ground height H received in step S32 and the value of the angle of view θ calculated in step S35. As can be seen from FIG. 7, the angle of view θ is equal to the angle of elevation when viewing point O from measurement point S. Therefore, the image processing circuit 103 calculates the value of the inter-vehicle distance L2 by the following (Equation 10).
(Equation 10)
L2 = H / tan (θ)

  With the above process, the value of the inter-vehicle distance L2 is calculated. The image processing circuit 103 outputs the value of the inter-vehicle distance L2 calculated in step S36 to the data processing unit 202 via the microcomputer 104 and the communication processing unit 203, and ends the measurement distance calculating step.

  The data processing unit 202 of the drive recorder 200 uses the received value of the inter-vehicle distance L2 as operation information, and executes a process for realizing a function as a drive recorder.

  Below, the effect | action and effect of the vanishing point position calculation method which concerns on embodiment of this invention, and the inter-vehicle distance measurement system 1 using the ranging method are demonstrated.

The vanishing point position calculation method used by the inter-vehicle distance measurement system 1 according to the present embodiment is a reference obtained by imaging the value of the ground height H to which the camera 11 is attached and the reference point T that is an arbitrary point on the ground by the camera 11. Steps S21 to S23 for obtaining the image and the value of the reference distance L1 which is the horizontal distance from the point O where the camera 11 is attached to the reference point T, and the value of the ground height H and the reference distance L1. And the step S24 for calculating the value of the angle of view α in the height direction from the vanishing point F1 to the reference point T determined in the reference image, and the reference image from the point P positioned at the upper end of the reference image. A reference image based on the number D1 of pixels existing in the height direction above the reference point T in the middle and a data table that is correspondence data between each pixel and the angle of view in the image captured by the camera 11 of Steps S25 to S27 for calculating the value of the angle of view β in the height direction from the point P positioned at the end to the reference point T, and subtracting the value of the angle of view α from the value of the angle of view β. The value of the angle of view γ in the height direction from the point P located at the upper end to the vanishing point F1 is calculated, and based on the value of the angle of view γ and the corresponding data, from the point P located at the upper end of the reference image A vanishing point position calculating step for calculating the position of the vanishing point F1 in the reference image, including steps S28 and S29 for calculating the number D2 of pixels existing in the height direction above the vanishing point F1 in the reference image. Is provided.
Accordingly, the value of the ground height H to which the camera 11 is attached, the reference image obtained by capturing the reference point T by the camera 11, and the horizontal distance from the point O where the camera 11 is attached to the reference point T. The position of the vanishing point F1 in the reference image is calculated on the basis of the value of the reference distance L1 and the correspondence data between each pixel and the angle of view in the image captured by the camera 11.
As a result, in the vanishing point position calculation method used by the inter-vehicle distance measurement system 1 according to the present embodiment, the operator can move from the camera attachment point to the point positioned at the lower end of the image as in the conventional inter-vehicle distance measurement method. There is no need to measure a predetermined distance. Instead, it is only necessary to measure a distance from a point captured by the camera 11 and appearing on the reference image to an arbitrarily selectable reference point T. For this reason, the vanishing point position calculation method used by the inter-vehicle distance measurement system 1 according to the present embodiment has milder measurement conditions than the conventional inter-vehicle distance measurement method. Therefore, according to the vanishing point position calculation method used by the inter-vehicle distance measurement system 1 according to the present embodiment, a vanishing point position calculation method that can reduce the burden on the operator can be provided.

Further, the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment is a distance measuring method including a vanishing point position calculating step and a measurement distance calculating step provided in the vanishing point position calculating method. The distance calculation step is defined in the measurement image, step S31 and step S32 in which the measurement image obtained by capturing the value of the ground height H and the measurement point S which is an arbitrary point on the ground by the camera 11 is determined in the measurement image. The number D3 of pixels existing in the height direction above the ground from the vanishing point F2 whose position in the image is the same as the position of the vanishing point F1 in the reference image to the measuring point S in the measurement image, and a data table as corresponding data , The value of the angle of view θ in the ground height direction from the vanishing point F2 to the measurement point S is calculated, and the position where the camera 11 is attached is calculated based on the value of the angle of view θ and the value of the ground height H. In Steps S33 to S36 for calculating the value of the inter-vehicle distance L2, which is the horizontal distance from the point O to the measurement point S, as the value of the measurement distance.
Accordingly, the value of the ground height H to which the camera 11 is attached, the reference image obtained by capturing the reference point T by the camera 11, and the horizontal distance from the point O where the camera 11 is attached to the reference point T. Based on the value of the reference distance L1, which is a data table corresponding to each pixel and the angle of view in the image captured by the camera 11, and the measurement image obtained by capturing the measurement point S by the camera 11. A value of the inter-vehicle distance L2, which is a distance, is calculated.
As a result, in the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment, the operator determines in advance from the camera attachment point to a point positioned at the lower end of the image as in the conventional inter-vehicle distance measuring method. It is not necessary to measure the measured distance, but instead, it is only necessary to measure the distance from the point captured by the camera 11 and appearing on the reference image to the arbitrarily selectable reference point T. For this reason, the distance measurement method used by the inter-vehicle distance measurement system 1 according to the present embodiment has milder measurement conditions than the conventional inter-vehicle distance measurement method. Therefore, according to the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment, it is possible to provide a vanishing point position calculating method that can reduce the burden on the operator.
Further, in the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment, the ratio of the length on the image is equal to the ratio of the angle of view corresponding to the length as in the conventional inter-vehicle distance measuring method. Rather than calculating the value of the inter-vehicle distance, the value of the inter-vehicle distance is calculated based on the relationship between each pixel on the image and the angle of view. For this reason, according to the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment, the value of the inter-vehicle distance can be calculated with higher accuracy than the conventional inter-vehicle distance measuring method.

In addition, the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment images the value of the ground height H to which the camera 11 is attached and the measuring point S that is an arbitrary point on the ground by the camera 11. Steps S31 and S32 for acquiring the measurement image, the number D3 of pixels existing in the height direction from the vanishing point F2 determined in the measurement image to the measurement point S in the measurement image, and the camera 11 capture the image. On the basis of the data table that is the correspondence data between each pixel and the angle of view in the obtained image, the value of the angle of view θ in the height direction from the vanishing point F2 to the measurement point S is calculated. Steps S33 to S33, in which the value of the inter-vehicle distance L2, which is the distance in the horizontal direction from the point O where the camera 11 is mounted to the measurement point S, is calculated as the value of the measurement distance based on the value of the ground height H. S36 And including.
Thereby, the value of the ground height to which the camera 11 is attached, the measurement image obtained by imaging the measurement point S by the camera 11, and the data table that is the correspondence data between each pixel and the angle of view in the image taken by the camera 11 , The value of the inter-vehicle distance L2, which is the measurement distance, is calculated.
As a result, in the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment, the ratio of the length on the image is equal to the ratio of the angle of view corresponding to the length as in the conventional inter-vehicle distance measuring method. Therefore, the value of the inter-vehicle distance is calculated based on the relationship between each pixel on the image and the angle of view. For this reason, according to the distance measuring method used by the inter-vehicle distance measuring system 1 according to the present embodiment, the value of the inter-vehicle distance can be calculated with higher accuracy than the conventional inter-vehicle distance measuring method.

  The technical scope of the present invention is not limited to the embodiment described above. The above-described embodiments can be accompanied by various modifications and improvements within the technical scope of the present invention.

  For example, the vanishing point position calculating method and the inter-vehicle distance measuring system 1 using the distance measuring method according to the embodiment of the present invention calculate the value of the inter-vehicle distance L2 from the attachment point O of the camera 11 to the preceding vehicle. Although the system is a vanishing point position calculation method and distance measurement method according to the present invention, the distance from the attachment position of the imaging means to an arbitrary point appearing on the image captured by the imaging means is measured. Can be used. That is, it is applicable not only when measuring the distance to the preceding vehicle but also when measuring the distance to an arbitrary measurement target.

  In the inter-vehicle distance measuring system 1 using the vanishing point position calculating method and the distance measuring method according to the embodiment of the present invention, the calculation of the position of the vanishing point F1 in the vanishing point position calculating step is performed by attaching the camera 11 to the vehicle. The vanishing point position calculation step only needs to be executed before the processing in the measurement distance calculation step is performed, and the operation of the inter-vehicle distance measurement system 1 is performed. It may be executed after the start.

  Further, in the inter-vehicle distance measurement system 1 using the vanishing point position calculating method and the distance measuring method according to the embodiment of the present invention, after calculating the positions of the vanishing points F1, F2 in the image by the vanishing point position calculating step, The inter-vehicle distance L2 that is the measurement distance is calculated by the measurement distance calculation step. However, when the position of the vanishing point in the image is known in advance, the process of the vanishing point position calculation step is omitted and the measurement distance calculation step The measurement distance can be calculated only by this. In this case, in step S33b, the image processing circuit 103 reads the value of the number of pixels D2 previously held in the ROM 106 instead of reading the value of the number of pixels D2 held in the RAM 106 in the vanishing point position calculating step. What is necessary is just composition. As the vanishing point position calculating method, various known methods can be used.

  Further, the processing order in the vanishing point position calculation step shown in FIG. 2 and the processing order in the measurement distance calculation step shown in FIG. 6 are examples, and it goes without saying that the processing order is not limited to this. For example, the order of steps S21 to S23 in the vanishing point position calculating step can be exchanged, and the order of steps S24 to S26 can also be exchanged. In addition, the order of step S31 and step S32 in the measurement distance calculation step can be exchanged, the order of step S33a and step S33b can be exchanged, and the order of step S33 and step S34 can be exchanged.

1 Vehicle Distance Measurement System 11 Camera 100 Image Recognition Unit 101 Video Amplifier 102 NTSC Decoder 103 Image Processing Circuit 104 Microcomputer 105 ROM
106 RAM
107 power supply circuit 200 drive recorder 201 main decoder 202 data processing unit 203 communication processing unit 204 ROM
205 RAM
206 Vehicle signal interface 300 terminal

Claims (2)

Obtain a reference image obtained by photographing the reference point is any point on the ground by an imaging means, the reference on the reference image by the position of the reference point on the reference image is specified by the tap operation Obtaining point location information;
Obtaining a value of the reference distance is a horizontal distance of the imaging means ground clearance of values attached, from a position attached 及 beauty said imaging means to said reference point,
Calculating a value of the angle of view α in the ground height direction from the vanishing point F1 defined in the reference image to the reference point based on a ratio between the ground height value and the reference distance;
The number D1 of pixels existing in the ground high direction from the upper end of the reference image to the reference point in the reference image specified based on the acquired position information of the reference point, and the imaging means Calculating the value of the angle of view β in the ground high direction from the upper end of the reference image to the reference point based on correspondence data between each pixel and the angle of view in the captured image;
By subtracting the value of the angle of view α from the value of the angle of view β, the value of the angle of view γ in the ground high direction from the upper end of the reference image to the vanishing point F1 is calculated, and the value of the angle of view γ Calculating the number D2 of pixels existing in the ground high direction between the upper end of the reference image and the vanishing point F1 in the reference image based on the correspondence data;
A vanishing point position calculating step for calculating a position of the vanishing point F1 in the reference image,
The correspondence data is imaged by the imaging means obtained based on a first correspondence relationship acquired in advance between an angle in the height direction from the optical axis of the imaging means and the angle of view per pixel at that angle. A vanishing point position calculation method using a second correspondence relationship between each pixel in the vertical direction of an image and a field angle per pixel in the pixel. The vanishing point position calculating step provided in the vanishing point position calculating method according to claim 1;
A measurement distance calculation step;
A distance measuring method comprising:
The measurement distance calculating step includes:
Obtaining a measurement image obtained by imaging a value of the ground height and a measurement point which is an arbitrary point on the ground by the imaging means;
The reference image from the upper end of the reference image calculated in the vanishing point position calculation step is calculated from the number D3 of pixels existing in the height direction from the upper end of the measurement image to the measurement point in the measurement image. Is determined in the measurement image obtained by subtracting the number D2 of pixels existing in the height direction above the vanishing point F1, and the position in the measurement image is the vanishing point F1 in the reference image. On the basis of the number D4 of pixels existing in the height direction above the ground from the vanishing point F2 that is the same as the position to the measurement point in the measurement image, and the second correspondence relationship as the correspondence data, The value of the angle of view θ in the ground height direction from the vanishing point F2 to the measurement point is calculated, and based on the value of the angle of view θ and the value of the ground height, the position from which the imaging unit is attached is calculated. Water to measuring point Calculating a value of the measurement distance L2, which is a distance in the flat direction;
Ranging method characterized by including.

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