JP3648563B2 - 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. It is to provide.
[0006]
[Means for Solving the Problems]
According to one aspect of the present invention, an omnidirectional imaging lens in which, for example, a high-purity red annular reference line is printed along the upper and lower (or inner and outer limits) positions corresponding to the boundary of the imaging region on the surface. When a landscape or the like is photographed using, a red inner annular reference line and an outer annular reference line appear at the inner and outer boundaries of the photographing region in the obtained annular image. This annular image is binarized and converted into an image in which only the red inner annular reference line and the outer annular reference line are extracted, and the center representing the development area of the annular image into the panoramic image using this converted image A method and apparatus for detecting a reference position of an annular image by omnidirectional imaging, in which coordinates, an inner circle radius, and an outer circle radius are obtained.
[0007]
According to another aspect of the present invention, an omnidirectional imaging device having an inner wall surface surrounded by a single color enclosure is photographed to obtain an annular image in which the imaging region is clarified, and the annular image is obtained. A method and apparatus for detecting a reference position of an annular image by omnidirectional imaging for determining a reference position representing a development area to a panoramic image composed of a center coordinate, an inner circle radius, and an outer circle radius of a ring image that is subsequently taken provide.
[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 consists of center coordinates, inner circle radius and outer circle radius.
[0011]
In the omnidirectional imaging lens 1 of FIG. 5, as shown in FIG. 6, incident light 10 is incident from an incident glass surface 11, reflected by a reflecting surface 12, and further reflected by a reflecting surface on the upper surface to be guided to an imaging optical system. It is burned. The reflecting surface 12 is mirror coated. When the omnidirectional imaging lens 1 is viewed from the side, the mirror coating 6 is formed in a belt shape as shown in FIG. 7A, and when viewed from the bottom, the mirror coating 6 is formed in an annular shape as shown in FIG. 7B.
[0012]
FIG. 7 shows the omnidirectional imaging lens 1, (a) is a side view thereof, and (b) is a bottom view thereof. On the surface of the omnidirectional imaging lens 1, as shown in FIG. 7, the inner annular reference line 7 and the outer annular reference line 8 are adjacent to the mirror coating 6 and correspond to the boundary between the imaging region and the non-imaging region. To print. The inner and outer annular reference lines 7, 8 may be located just outside the mirror coating 6. The annular reference lines 7 and 8 may be printed on the incident glass surface instead of the mirror coating portion.
[0013]
As the color of the circular reference line, it is preferable to use a color that is relatively difficult to exist in a general landscape, for example, a high-purity red color, but other colors such as a high-purity color are used according to the environment in which the system is used. Blue or the like may be used. That is, the color of the annular reference line can be given a threshold value that can distinguish between the annular reference line and other images in the binarization process described later and leave only the annular reference line. Selected.
[0014]
The thickness of the annular reference line only needs to ensure the number of pixels that can be processed, and is preferably about 0.5 mm from the viewpoint of ease of image processing. The annular reference lines 7 and 8 can be printed by a mask method.
[0015]
When a landscape is photographed using the omnidirectional imaging lens 1 provided with the annular reference lines 7 and 8 as described above, two annular reference lines are imprinted in the annular image as shown in FIG. In FIG. 8, the annular reference line is imprinted just outside the inner and outer circles of the annular image. Hereinafter, the operation procedure of the MPU 3 for obtaining the reference position indicating the development area to the panoramic image, that is, the center coordinates, the inner circle radius and the outer circle radius using the annular image shown in FIG. 8 will be described with reference to the flowchart of FIG.
[0016]
In FIG. 9, the annular image shown in FIG. 8 taken in step S1 is held in the MPU 3 as digital data representing the color and density for each pixel. Next, in step S2, the original image of FIG. 8 is binarized according to a program held in the MPU. This binarization process binarizes the density level of each pixel with a threshold as a boundary. A pixel having a density equal to or higher than the threshold is set to black, and a pixel having a density lower than the threshold is set to white. Perform the process. When the color of the annular reference line is red, in the binarization process, if the threshold value is selected so that red with a purity of 90% or more is regarded as red, the pixel threshold value is RGB (255 * 0.90). 255 * 0.10, 255 * 0.10). When blue is selected as the color of the mark, the threshold value of the pixel is set to RGB (255 * 0.10, 255 * 0...) So that blue having a purity of 90% or more is regarded as blue in the binarization process. 10, 255 * 0.90). As described above, when the color of the annular reference line is changed, it is necessary to change the binarization threshold according to the color.
[0017]
Specifically, in the binarization threshold RGB (255 * 0.90, 255 * 0.10, 255 * 0.10), the density component of a certain pixel is red R? When 255 * 0.90, green G <255 * 0.10, and blue B <255 * 0.10, the pixel is processed as a graphic part (black), and the other part as a background part (white) It is processed. When the annular image in FIG. 8 is binarized in this way, an inner annular reference line and an outer annular reference line are displayed as shown in FIG. The center coordinates, the inner circle radius, and the outer circle radius representing the development area when the annular image is developed into the panoramic image are obtained by the method described later based on the inner annular reference line and the outer annular reference line.
[0018]
Next, a method and apparatus for directly capturing a captured image area in a ring image will be described.
[0019]
As shown in FIG. 11, the omnidirectional imaging device 14 including the omnidirectional lens 1 and the imaging device 2 is positioned inside a white, translucent cylindrical case 15, and is photographed by the omnidirectional imaging device 14 in this state. As a result, the 360 ° surrounding subject turns white, and as shown in FIG. 12, an annular image in which the effective image area and the invalid image area to be imprinted are clearly distinguished can be obtained.
[0020]
The cylindrical case 15 may be provided with a lid 16 as shown in FIG. 11 (b), or as shown in FIG. 11 (c), the annular illuminating body 17 surrounds the translucent cylindrical case and If the contrast of the annular image is increased from the outside, the annular image shown in FIG. 12 becomes clearer. Further, as shown in FIG. 12D, an illuminating body 18 may be attached to the lid 16 so that an annular image as shown in FIG. 12 can be obtained even if the surroundings are not bright.
[0021]
The cylindrical case 15 may be formed of a material such as translucent acrylic or a semitransparent member made of a material that irregularly reflects. The case 15 is not necessarily a case-like object as long as it can surround the omnidirectional imaging device 14. Further, the case 15 may be a rectangular object instead of a cylinder, or may be a polygonal object.
[0022]
Based on the annular image shown in FIG. 12 taken as described above, the center coordinates, the inner circle radius, and the outer circle radius for defining the reference position when the annular image as shown in FIG. It can be determined by the method described.
[0023]
A method and apparatus for determining the center coordinates, inner circle radius, and outer circle radius defining the development region from the annular image to the panoramic image shown in FIG. 10 or FIG. 12 will be described below.
[0024]
Referring to FIG. 14, in step 20, search is performed in order from the center coordinates of the image in FIG. 10 or 12 toward the four corners of the image as indicated by solid lines in FIG. Record the coordinates in memory. In this way, the coordinates of the four points on the inner circle can be obtained. The center coordinates here are, for example, the position of coordinates (100, 100) when the pixel is 200 × 200, and the coordinates of the search position from there can be easily determined.
[0025]
In step 21, an equation of a circle passing through any three of the four points on the inner circle obtained as described above is obtained by a conventionally known method. As a result, inner circle information including the center coordinate position and radius of the inner circle can be calculated.
[0026]
Next, at step 22, the edge of the outer circle is detected by searching as shown by the broken line in FIG. 13 from the inner circle obtained previously toward the centrifugal direction, and the coordinates of the edge are obtained. In step 23, the radius of the outer circle is obtained from the edge coordinates of the outer circle and the center coordinates of the inner circle. The search in this case is performed toward the four corners starting from the radius of the inner circle on the straight line from the center coordinates of the image toward the four corners, and any three of the four points on the outer circle obtained as a result of the search. The equation of the outer circle may be calculated using points, or the average value of the radii of the outer circle obtained from the four points may be obtained as the radius of the outer circle.
[0027]
In step 20, the edge of the outer circle may be detected first, and then the edge of the inner circle may be detected by searching from the center coordinates in step 22. Further, the search direction may be performed from the four corners toward the center. In particular, as shown in FIGS. 10 and 12, when the annular outer circle or the annular inner circle has a certain width, the four points of the effective image area of the annular image are on a straight line connecting the center and the four corners of the image. It is preferable to search from the center to the center or toward the four corners. Note that the search is not necessarily performed on a straight line connecting the center and the four corners, and at least three radiations from the center may be searched.
[0028]
Next, another embodiment for obtaining center coordinates, inner circle radii, and outer circle radii that define a development area of a ring image to a panoramic image will be described with reference to FIG.
[0029]
In step 30 of FIG. 15, an edge extraction filter is applied to the annular image shown in FIGS. The edge extraction filter subtracts the density of adjacent pixels to obtain a density difference, and acts to extract an edge portion, that is, an outline of an image in which the density changes rapidly. Therefore, by applying the edge extraction filter, the image of FIG. 10 becomes as shown in FIG. 16A, and the image of FIG. 12 becomes as shown in FIG. In FIG. 16, the effective image area, that is, the development area of the annular image is an annular portion 36 between the inner circle 37 and the outer circle 38. Therefore, in step 31, a circle pattern is formed, and the center point of the circle is moved near the center of the image, and the radius of the circle is changed gradually from the center of the development area at each moving point, The density addition value of each circle is obtained by adding the density of each pixel on the circumference of the circle pattern at the change point. 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. In addition, the change range of the radius of the circular pattern is set to a range smaller than H × 0.25 and larger than H × 0.1. 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 31, a density average value may be obtained instead of the density addition value.
[0030]
In step 32, the largest one of the density addition values obtained in step 31 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 the radius of the inner circle of the annular image. And
[0031]
In step 33, 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.
[0032]
In step 34, the radius of the circle having the maximum density average value is determined as the radius of the outer circle.
[0033]
As described above, the reference position of the annular image including the center coordinate position of the annular image, the inner circle radius, and the outer circle radius can be calculated.
[0034]
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.
[0035]
【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 an explanatory diagram for explaining an optical system of an omnidirectional imaging lens according to the present invention.
FIG. 7 is a diagram illustrating a state where an annular reference line according to the present invention is printed on an omnidirectional imaging lens.
FIG. 8 is a diagram showing a ring image in the case of imaging using the omnidirectional imaging lens shown in FIG.
FIG. 9 is a flowchart showing a part of a procedure for carrying out the present invention.
10 is a diagram showing an image obtained as a result of performing binarization processing on the annular image shown in FIG. 8;
FIG. 11 is an explanatory diagram showing another embodiment of the present invention.
12 is a view showing a ring image taken using the configuration shown in FIG. 11. FIG.
FIG. 13 is a diagram for explaining a concept of obtaining a reference position using FIG. 10 or FIG.
FIG. 14 is a flowchart for carrying out the method shown in FIG. 13;
FIG. 15 is a flowchart showing another embodiment of the present invention.
16 is an explanatory diagram of one step in FIG. 15;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Omnidirectional imaging lens 2 Imaging element 3 MPU
4 display

Claims (3)

Imaging an annular image using an omnidirectional imaging lens with an annular reference line printed along a surface position corresponding to the inner and outer boundaries of the imaging and non-imaging regions;
Extracting the boundary in the annular image by extracting an image of the annular reference line from the annular image;
Obtaining a reference position for designating a development area of the annular image when developing the annular image into a panoramic image based on the position of the boundary extracted from the annular image;
A method for detecting a reference position of an annular image by omnidirectional imaging. The reference position detection method according to claim 1,
In the step of extracting the boundary, an image of the annular reference line is obtained by performing binarization processing on the annular image using a threshold value for distinguishing the color of the annular reference line from the annular image other than the annular reference line. A method for detecting a reference position, comprising the step of extracting. An omnidirectional imaging device that captures an annular image using an omnidirectional imaging lens printed with an annular reference line along a surface position corresponding to the inner and outer boundaries of the imaging region and the non-imaging region;
By extracting the image of the annular reference line from the annular image captured by the omnidirectional imaging device, the boundary in the annular image is extracted, and the annular image is developed into a panoramic image based on the position of the boundary. Means for obtaining a reference position for designating a development area of the annular image when
An apparatus for detecting a reference position of an annular image by omnidirectional imaging.

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