JP3745301B2 - 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 an annular image as shown in FIG. This annular image is converted into a panoramic developed image using an MPU as shown in FIG. At the time of this image conversion, as shown in FIG. 2, if the reference position for image conversion consisting of the center coordinate position and the position of the inner circle and the outer circle matches the annular image, the MPU will be shown in FIG. However, if the reference position is in an incompatible state as shown in FIG. 4, 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, an annular image captured by an omnidirectional imaging device is subjected to image processing on a contour image in which the contours of an inner circle and an outer circle representing a development area for a panoramic image are clearly expressed, and the contour image An annular image reference position detection method and apparatus based on omnidirectional imaging, in which an outer circle, an inner circle, and a center are obtained based on the above.
[0007]
According to one embodiment of the present invention, contour images in which the contours in the inner circle and the outer circle of the annular image photographed by the omnidirectional imaging device are clarified using the sharpening filter are obtained, and each contour image is further obtained. Using the threshold value corresponding to the average value of the density values of the pixels, the contour image is binarized and image processing is performed on the binarized image in which the inner circle and the outer circle are clearly expressed. A method and an apparatus for detecting a reference position of an annular image by omnidirectional imaging, in which a reference position including an outer circle, an inner circle, and a center is obtained based on a digitized image.
[0008]
According to another embodiment of the present invention, in determining the reference position of the annular image, the contour position of the outer circle is searched from the at least three points around the image where the inner circle and the outer circle are sharpened toward the center. Calculate the equation of the circle representing the position of the outer circle using the three points where the outer circle was detected, calculate the center coordinates of the outer circle, and then move from the determined center coordinates to the centrifugal direction. The inner circle radius or inner circle equation is calculated using the points on the inner circle detected by searching the inner circle, and the reference is composed of the center coordinates of the annular image, the position of the inner circle, and the position of the outer circle. A method and an apparatus for detecting a reference position of an annular image by omnidirectional imaging for obtaining a position are provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an overall configuration including an annular image reference position detection apparatus based on omnidirectional imaging according to the present invention.
[0010]
In FIG. 1, the omnidirectional imaging lens 1 receives light rays 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. 2 and converts it into a panoramic developed image as shown in FIG. This panoramic image is displayed on the display 4.
[0011]
When converting the annular image of FIG. 2 into the panorama developed image of FIG. 3, it is important to correctly set the reference position consisting of the center point position, inner circle position and outer circle position of the annular image added to the figure. is there. In other words, it can be said that the reference position includes the center coordinates, the inner circle radius, and the outer circle radius.
[0012]
In the present invention, the reference position is determined by using software technology, and the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 6 is an original image of an annular image photographed through the omnidirectional imaging lens 1 and the image sensor 2 and corresponds to FIGS. 2 and 4. This annular image is processed by the MPU 3 according to the flowchart shown in FIG.
[0014]
In step S1 of FIG. 7, the original image of FIG. 6 is subjected to a sharpening filter. As the sharpening filter, for example, a filter matrix of 3 × 3 pixels may be used as shown in (a) or (b) of FIG. In this case, a value obtained by multiplying nine pixels including eight pixels around a certain pixel by the numerical value shown in the filter matrix (a) or (b) is used as a density value of the pixel, and calculation is performed for all the pixels. To do. The filter matrix shown in FIG. 8 has a positive median value and a negative value around it, so that the calculation result shows a large difference in density value between adjacent pixels. For this reason, the change in density value at the contour portion or the like becomes large, and the contour is emphasized. The filter matrix may be in the form of 5 × 5 pixels as shown in FIG. By performing the sharpening filter processing in this way, it is possible to obtain a ring image as shown in FIG. 9 in which the contours of the outer circle and the inner circle are emphasized.
[0015]
Next, in step 2 of FIG. 7, an edge extraction filter is further applied to the sharpened annular image shown in FIG. The edge extraction filter operates to extract an edge portion, that is, an outline of an image, and the density difference in the outline portion changes abruptly. Therefore, when the adjacent pixel values are subtracted, the density value difference becomes large and is extracted as an outline. Is. By applying the edge extraction filter to the sharpened annular image in this way, a contour image as shown in FIG. 10 can be obtained. Each pixel of the contour image is represented by a density value from 0 to 255.
[0016]
Next, in step S3, an average value Th of density values is calculated for all pixels of the contour image. However, pixels with a density value of 0 are excluded from the average value calculation. In step S4, the average value Th is set as a threshold value, pixels having a density value larger than this are set to white (density value 255), and pixels having a density value lower than this are set to black (density value 0) to be binary The binarized image is obtained as shown in FIG.
[0017]
Next, in step S5, as shown in FIG. 12, the search is performed sequentially from the four corners of the binarized image toward the center coordinates, and the coordinates where the edge of the contour of the outer circle is found are stored in the memory. To do. In this way, the coordinates of the four points on the outer circle can be obtained. The central coordinates here are, for example, the positions of the coordinates (100, 100) when the pixel is 200 × 200. In step S6, an equation of a circle passing through any three of the four points on the outer circle obtained as described above is obtained by a conventionally known method. As a result, outer circle information including the center coordinate position and radius of the outer circle can be calculated.
[0018]
Next, in step S7, the binarized image is searched in the centrifugal direction from the center coordinates of the outer circle obtained previously to detect the edge of the inner circle, and the radius of the inner circle is obtained in step S8. The search in this case may be performed from the center coordinates toward the four corners, and the inner circle equation may be calculated using any three of the four points on the inner circle obtained as a result of the search, Further, the radius of the inner circle obtained from the average value of the radius of the inner circle obtained from the four points may be used.
[0019]
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 detected.
[0020]
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 increased. Can be improved.
[0021]
【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 block diagram showing a schematic configuration of the present invention.
FIG. 2 is a diagram showing an annular image photographed by an omnidirectional imaging lens and showing a normal development region.
FIG. 3 is a view showing a panoramic developed image obtained by converting the annular image of FIG. 2 into a rectangle.
FIG. 4 is a diagram showing an annular image showing a state in which an inappropriate development area is designated.
FIG. 5 is a view showing a panorama developed image obtained as a result of designating an inappropriate development region as shown in FIG. 4;
FIG. 6 is a diagram illustrating an annular image photographed by an omnidirectional imaging lens.
FIG. 7 is a flowchart showing an operation procedure according to the present invention.
FIG. 8 is a diagram illustrating a filter matrix of a sharpening filter.
FIG. 9 is a diagram showing an annular image that has been subjected to a sharpening filter.
FIG. 10 is a diagram showing a contour image obtained by applying an edge extraction filter;
FIG. 11 is a diagram illustrating a binarized image obtained by binarizing the contour image.
FIG. 12 is an explanatory diagram illustrating the concept of searching from the four corners toward the center.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Omnidirectional imaging lens 2 Imaging element 3 MPU
4 display

Claims (2)

A method for detecting a reference position of an annular image by omnidirectional imaging,
An imaging step of capturing an annular image by an omnidirectional imaging means;
A processing step of processing the annular image into an image in which the contours of the inner circle and the outer circle of the annular image are clarified by information processing means;
A calculation step of calculating a reference position for designating a development area of the annular image when the annular image is converted into a panoramic development image using the contour in the processed image by the information processing means;
The calculating step includes:
Searching the processed image from the four corners of the processed image sequentially toward the center to detect points on the contour of the outer circle;
Calculating an outer circle equation based on at least three points on the detected contour of the outer circle;
Calculating the center coordinate position and radius of the outer circle from the calculated outer circle equation;
Searching the processed image in the centrifugal direction from the central coordinate position to detect the contour of the inner circle, and calculating the radius of the inner circle;
A reference position detecting method characterized by comprising : An apparatus for detecting a reference position of an annular image by omnidirectional imaging,
  An omnidirectional imaging means for imaging a ring image;
  Processing means for processing the annular image into an image in which the contours of the inner circle and outer circle of the annular image are clarified, and outputting the processed image;
  Calculating means for calculating a reference position for designating a development area of the annular image when the annular image is converted into a panoramic developed image using the contour in the processed image;
  The calculating means includes
  Means for searching a processed image from the four corners of the processed image in order toward the center and detecting points on the contour of the outer circle;
  Means for calculating an outer circle equation based on at least three points on the detected contour of the outer circle;
  Means for calculating the center coordinate position and radius of the outer circle from the calculated outer circle equation;
  Means for searching the processed image in a centrifugal direction from the central coordinate position to detect an outline of the inner circle, and calculating a radius of the inner circle;
  A reference position detecting device comprising:

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