JP3705591B2 - Method and apparatus for detecting reference position of annular image by omnidirectional imaging - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for detecting a reference position necessary for converting an annular image obtained by omnidirectional imaging using a omnidirectional imaging lens (PAL) into a panoramic image.
[0002]
[Problems to be solved by the invention]
An image photographed using the omnidirectional imaging lens becomes a ring image as shown in FIG. This annular image is converted into a panorama developed image using MPU as shown in FIG. At the time of this image conversion, as shown in FIG. 1, if the reference position for image conversion consisting of the center coordinate position and the position of the inner circle and the outer circle is adapted to the annular image, the MPU will be shown in FIG. However, if the reference position is in an incompatible state as shown in FIG. 3, the panorama developed image becomes a curved distortion image as shown in FIG. End up.
[0003]
Conventionally, in order to eliminate such curvature distortion of a panoramic developed image, adjustment of mechanical attachment is performed to increase the accuracy of the mechanical attachment position of the omnidirectional imaging optical system and the image sensor, or an annular image is displayed. The reference position of the development area was determined by visual display on the display.
[0004]
An object of the present invention has been made in view of the above, and is an annular by omnidirectional imaging that absorbs adjustment work after installation of an imaging optical system and an imaging element using software technology and does not require mechanical hardware adjustment. An object of the present invention is to provide an image reference position detection method and apparatus.
[0005]
Another object of the present invention is a method and apparatus for detecting the reference position of an annular image by omnidirectional imaging, which automatically detects and determines the reference position in the annular image when the annular image is converted into a panoramic developed image. Is to provide.
[0006]
[Means for Solving the Problems]
According to the present invention, in a predetermined region at the center of the annular image photographed by the omnidirectional imaging apparatus, the radius of the circular pattern is changed while moving the center coordinates, and the circle that best fits the inner circle of the annular image. The center of the circle is the center coordinate of the ring image, the radius is the radius of the inner circle of the ring image, and the circular pattern is centered on the center coordinate and outside the inner circle. By changing the radius of the outer circle to the radius of the outer circle that best fits the outer circle, the inner circle and outer circle representing the development area of the annular image taken by the omnidirectional imaging device to the panoramic image are displayed. A method and an apparatus for detecting a reference position of an annular image by omnidirectional imaging, in which the positions and the center positions of the circles are obtained.
[0007]
According to one embodiment of the present invention, a circular image is converted into an image in which the contours representing the inner circle and the outer circle are actualized, and the radius of the inner circle in the actualized image is changed while moving the center coordinates. The circle that best matches the inner circle in the manifestation image is selected, and the center and radius of the circle are set as the center coordinate and the radius of the inner circle of the ring image, and then the center coordinate is the center. By gradually increasing the radius of the circular pattern from the inner circle radius to the radius of the outer circle of the annular image, the radius of the circle that best matches the outer circle of the actualized image is set as the center coordinate of the annular image. Provided is a method and apparatus for detecting a reference position of an annular image by omnidirectional imaging, in which an inner circle radius and an outer circle radius are obtained to determine a reference position representing a development area on a panoramic image.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 5 is a block diagram showing an overall configuration including a reference position detection device for an annular image by omnidirectional imaging according to the present invention.
[0009]
In FIG. 5, the omnidirectional imaging lens 1 receives a light beam from a subject in all directions of 360 degrees around and displays a subject image on the image sensor 2. The image sensor 2 converts the subject image into an electrical signal and transfers it to the MPU 3 as digital image data. The MPU 3 holds the digital image data in a memory as a circular image as shown in FIG. 1, and converts it into a panoramic developed image as shown in FIG. This panoramic image is displayed on the display 4.
[0010]
When converting the annular image of FIG. 1 into the panorama developed image of FIG. 2, it is important to correctly set the reference position including the center coordinate position, inner circle position, and outer circle position of the annular image added to the figure. is there. This reference position can consist of center coordinates, inner circle radius and outer circle radius.
[0011]
In the present invention, the reference position is obtained by using the software technology by the MPU 3 in FIG. 5, and the operation flow is shown in FIG. Hereinafter, the present invention will be described in detail with reference to the drawings.
[0012]
In step 10 of FIG. 6, a noise removal filter is applied to the annular image (the inner circle and the outer circle are not shown) as shown in FIG. The noise removal filter removes noise from an image having noise such as black and white dots in the image. For example, a median filter can be used. The median filter, for example, performs an operation for all pixels by setting the fifth (median value) when the densities of 9 adjacent 3 × 3 pixels are arranged in ascending order to the density value of the center pixel. As a result, the density value that is too large or small like noise is eliminated, so that an image from which noise is removed can be obtained.
[0013]
Next, the annular image uses the edge extraction filter to reveal the edges of the inner and outer circles. This edge extraction filter is composed of differential filters in the horizontal and vertical directions. In step 11 of FIG. 6, when all pixels are filtered using a horizontal differential filter having a filter matrix as shown in FIG. 7A, vertical line segments are obtained as shown in FIG. Is emphasized. Next, in step 12, when all pixels are filtered using a longitudinal differential filter having a filter matrix as shown in FIG. 7B, the horizontal line segment is emphasized as shown in FIG. 8B. The formed image is formed. In step 13, by adding these two differential images in the horizontal and vertical directions, a contour image in which the contours of the inner and outer circles of the annular image are emphasized can be formed as shown in FIG. .
[0014]
In step 14 of FIG. 6, a circle pattern is formed, the radius is changed at each moving point while moving the center point of this circle, and the density of each pixel on the circumference of the circle pattern at each changing point is added. Find the density addition value for each circle. The density addition value becomes the largest when the circle pattern overlaps the inner circle of the annular image. Since the purpose of this step is to find the center coordinates and the radius of the inner circle of the annular image, if the height of the image is H, the movement range of the center point is ± H × 0. The range is 25. Further, the range of change of the radius of the circular pattern is set to be a range larger than H × 0.1 and smaller than H × 0.25. FIG. 9 shows how the center moves and the radius of the circle changes. Note that the radius of the circular pattern may be gradually changed, and the center position may be moved at each radius change point. In step 14, a density average value may be obtained instead of the density addition value.
[0015]
In step 15, the largest density addition value obtained in step 14 is selected, the center of the circle pattern is set as the center coordinate of the annular image, and the radius of the circle is set as the radius of the inner circle of the annular image. And
[0016]
In step 16, the circular pattern centered on the center coordinate is changed so that its radius gradually increases from the length of the inner circle radius +1, and pixels along the circumference of the circular pattern at the change point of each radius. The average value of the concentration values is obtained. Note that the radius of the circular pattern may be gradually reduced from the maximum radius, or an added value may be obtained instead of the density value.
[0017]
In step 17, when the average density value at each change point of the radius obtained in step 16 is plotted with the radius R on the horizontal axis and the density average value on the vertical axis, a histogram is drawn as shown in FIG. In step 18, a one-dimensional differential filter is applied to the histogram obtained in step 16 to form a histogram in which the edge portion is emphasized as shown in FIG.
[0018]
The principle of the one-dimensional differentiation in step 18 will be described in more detail based on FIG. FIG. 12B is a bar graph showing the density average value in the vicinity of a certain edge before the one-dimensional differential filter is applied. When this value is represented by a numerical value, it is as shown in the middle column of FIG. The upper column of (a) shows the characteristics of the one-dimensional differential filter (edge extraction filter). The result of calculation while moving this filter characteristic column one by one in order from the left end is as shown in the lower column of FIG. In FIG. 12, it is considered that the distribution in the contour portion of the contour image is as shown in FIG. Here, the position 11 has the highest density average value. When a one-dimensional differential filter is applied to this, the maximum is obtained at the position 4 as shown in FIG. Originally, it is preferable to set the radius of the outer circle of the contour image at the edge portion of the contour portion, and therefore it is preferable that a peak appears at the edge portion as shown in FIG.
[0019]
Therefore, in step 19 of FIG. 6, the circle with the radius 4 having the highest density average value in the differential histogram is selected, and the radius of the circle is determined as the radius of the outer circle of the annular image.
[0020]
As described above, the reference position of the annular image including the center coordinate position of the annular image, the radius of the inner circle, and the radius of the outer circle can be calculated.
[0021]
If the image data of only the area designated by the reference position of the annular image determined as described above, that is, the development area of the annular image to the panoramic image is transferred to another device, The transfer speed can be improved.
[0022]
【The invention's effect】
According to the present invention, since the center coordinate position of the annular image, the radius of the inner circle, and the radius of the outer circle can be automatically calculated using software technology, mechanical adjustment is not necessary. In addition, an operation for visually determining the development area of the annular image becomes unnecessary.
[Brief description of the drawings]
FIG. 1 is a diagram showing a normal development region of an annular image photographed by an omnidirectional imaging lens.
FIG. 2 is a view showing a panoramic developed image obtained by converting the annular image of FIG. 1 into a rectangle.
FIG. 3 is a diagram showing an annular image showing a state in which an inappropriate development area is designated.
4 is a view showing a panorama development image obtained as a result of specifying an inappropriate development area as shown in FIG. 3; FIG.
FIG. 5 is a block diagram showing a schematic configuration of the present invention.
FIG. 6 is a flowchart showing a procedure for carrying out the present invention.
FIG. 7 is a diagram illustrating a filter matrix of a differential filter for obtaining a contour image.
FIG. 8 is a diagram illustrating a process of obtaining a contour image when a differential filter is applied in the vertical direction and the horizontal direction.
FIG. 9 is a diagram for explaining an operation for obtaining the center coordinates of the contour image and the radius of the inner circle;
FIG. 10 is a histogram used for obtaining an outer circle radius of a contour image.
11 is a histogram after the histogram of FIG. 10 is applied to a one-dimensional differential filter.
FIG. 12 is a diagram for explaining the principle of obtaining an outer circle of a contour image by applying a one-dimensional differential filter to a histogram.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Omnidirectional imaging lens 2 Imaging element 3 MPU
4 display

Claims (9)

A method for detecting a reference position of an annular image by omnidirectional imaging,
Capturing an annular image with an omnidirectional imaging device;
Processing the captured annular image into a contour image in which the contours of the inner and outer circles of the annular image are clarified;
Selecting a circle that best fits the contour of the contour image based on a circle whose center and radius vary;
Using the center coordinates of the selected circle and the radius thereof to obtain a reference position for designating a development area of the annular image when the annular image is developed into a panoramic image;
The selection step includes
In a predetermined region at the center of the annular image, an addition value or an average value of density values of pixels on the circle is obtained at each change point of the circle whose radius changes while moving the center, and the addition value or the average value A first step of selecting a circle showing the maximum value in the circle, and setting the center coordinate and radius of the selected circle as the center coordinate of the annular image and the radius of the inner circle, respectively;
A histogram is formed with respect to an addition value or an average value of density values of pixels on a circle whose center is the center coordinate of the circle selected in the first step and whose radius is larger than the radius of the selected circle. And a second step of applying a differential filter to the histogram to form a differential histogram, wherein the radius of the circle corresponding to the maximum point of the histogram is the radius of the outer circle of the annular image.   The method according to claim 1, wherein the reference position is a center coordinate position, an inner circle position, and an outer circle position of the annular image.   The method according to claim 1, wherein the reference position is a center coordinate position of the annular image, a radius of the inner circle from the center coordinate, and a radius of the outer circle from the center coordinate.   The method according to claim 1, wherein the image processing step applies an edge extraction filter to the annular image.   The method according to claim 1, wherein the image processing step applies an edge extraction filter after applying a noise removal filter to the annular image.   6. The method according to claim 4, wherein the step of applying the edge extraction filter forms a differential image by applying a lateral differential filter and a vertical differential filter to the annular image, and sums the differential images. To obtain the contour image. An apparatus for detecting a reference position of an annular image by omnidirectional imaging,
An omnidirectional imaging device that captures a ring image;
Means for processing the captured annular image into a contour image in which the contours of the inner and outer circles of the annular image are clarified;
Means for selecting a circle that best fits the contour of the contour image based on a circle of varying center and radius;
Means for obtaining a reference position for designating a development area of the annular image when the annular image is developed into a panoramic image using the center coordinates of the selected circle and its radius;
The means for selecting is:
In a predetermined region at the center of the annular image, an addition value or an average value of density values of pixels on the circle is obtained at each change point of the circle whose radius changes while moving the center, and the addition value or the average value A first means for selecting the circle showing the maximum value in the circle, and setting the center coordinate and radius of the selected circle as the center coordinate of the annular image and the radius of the inner circle, respectively;
A histogram is formed with respect to an addition value or an average value of density values of pixels on a circle whose center is the center coordinate of the circle selected by the first means and whose radius is larger than the radius of the selected circle. And a second means for applying a differential filter to the histogram to form a differential histogram, wherein the radius of the circle corresponding to the maximum point of the histogram is the radius of the outer circle of the annular image.   8. The apparatus according to claim 7, wherein the processing means is an edge extraction filter that makes the inner circle and the outer circle of the contour image obvious.   9. The apparatus according to claim 8, wherein the edge extraction filter includes: a horizontal differential filter that reveals a vertical line segment; and a vertical differential filter that uses the horizontal line segment as a building material. Means for obtaining the contour image by taking the sum of the annular images obtained by the above-mentioned method.

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