JPH01302474A - Method for correcting image distortion - Google Patents

Abstract

PURPOSE:To analyze measuring values such as sizes and shapes obtained from an image by correcting the image pickup distortion of image data obtained by an image pickup means on the basis of an image pickup distortion characteristic inherent in an image pickup means picking up the image. CONSTITUTION:An eyeground image is photographed by an eyeground camera 1 and an image signal is digitized by an A/D converter 2 and stored in a data processing part 3. The processing part 3 corrects image distortion based upon distortion aberration data inherent in the camera 1 and stored in a data memory 4 and the corrected image data are stored in the memory 4 by operating a keyboard 5. Simultaneously, an eyeground image correcting at its prescribed distortion aberration is displayed on a monitor 6. In order to correct the distortion, a distortion DELTAr in a radius direction generated by the distortion aberration in accordance with each optical axis height of a radius (r) from the center of the image is previously measured by the processing part 3 and stored in the memory 4. At the time of executing data processing, the positional information of a digital image signal is corrected by the displacement value DELTAr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image distortion correction method for correcting distortion caused by distortion of a lens system in an image captured by, for example, a fundus camera.

[Prior Art] Conventionally, for example, an image taken by a fundus camera or the like is directly recorded on a film or the like without any particular correction, resulting in a distorted image due to distortion of the lens system. . Therefore, it is inaccurate to measure fundus vascular diameters using such distorted images, and since the distortion aberration value differs depending on the model of the imaging lens system used in the device, it is difficult to measure the fundus vascular diameter etc. It is also difficult to compare.

Furthermore, when comparing a visual field chart measured by a perimeter meter with a fundus image as shown in FIG. 9, there is a drawback that positional correspondence cannot be established due to the influence of distortion of the fundus image. Furthermore, the fact that the position of the papilla and the position of the macula in the visual field chart and the fundus image are mirror images in the vertical direction is also a cause of difficulty in matching.

[Object of the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional example, correct image distortion caused by distortion aberration of the lens system, and enable analysis of various measured values such as dimensions and shapes from images. An object of the present invention is to provide an image distortion correction method that makes it possible to correct image distortion.

[Summary of the Invention] The gist of the present invention to achieve the above-mentioned object is to correct the imaging distortion of image data obtained by the imaging means based on the inherent imaging distortion characteristics of the imaging means that captured the image. This is an image distortion correction method characterized by:

[Embodiments of the Invention] The method according to the present invention will be explained in detail based on the embodiments illustrated in FIGS. 1 to 8.

FIG. 1 shows a block circuit diagram of an image distortion correction device for carrying out the method according to the present invention when applied to a fundus camera. The digital output of the A/D converter 2 is connected to a data processing section 3 such as a microcomputer.

The data processing unit 3 includes a data memory 4, an input terminal and 1.
A keyboard 5 and a television monitor 6 as an output terminal are respectively connected.

First, a fundus image is taken by the fundus camera 1, and A/
The image signal is digitized by the D converter 2 and input to the data processing section 3. In the data processing unit 3, image distortion is corrected based on the distortion aberration data stored in the data memory 4 specific to the fundus camera 1, and the corrected image data is stored in the data memory 4 by operations using the keyboard 5, etc. , a fundus image with distortion aberrations corrected as shown in FIG. 2 is displayed on the television monitor 6.

As a distortion correction method by the data processing unit 3, for example, corresponding to each optical axis height, that is, the position of radius r from the image center,
Displacement Δr in the radial direction caused by distortion aberration is measured or calculated in advance and stored in the data memory 4 or the like as distortion aberration data, and during data processing, the position information of the digital image signal is calculated by the displacement Δτ. Correct only.

Furthermore, if a plurality of pieces of data obtained by photographing a part of the same fundus are stored in the data memory 4, each image will have its distortion aberration corrected.

Even when partial images a, b, and c are connected and displayed simultaneously on the screen of the television monitor 6 as shown in FIG. , it is possible to create wide-angle Nogunorama photos.

Furthermore, by specifying an arbitrary blood vessel in the image as shown in FIG. 4 using an input means such as a keyboard 5 or a mouse (not shown), a highly accurate blood vessel diameter d (without distortion) can be obtained. measurements can be performed. Similarly, as shown in FIG. 5, it is also possible to measure the circumferential length and area of a hemorrhagic spot e or a white spot f.

Next, the above measurement and data processing operations will be explained with reference to the flowchart of FIG. 6, centering on the data processing section 3. The data processing unit 3 starts operating according to the program, and in step 100 it becomes possible to select whether or not to input a new fundus image using the keyboard 5. When the input of a fundus image is specified using the keyboard 5, an image signal from the fundus camera 1 is input in the next step 101, and the image signal is converted into a digital signal by the A/D converter 2 in the next step 102. Continued 1. Then, in step 103, the above-described image distortion is corrected, and the process proceeds to the next step 104. Note that if the fundus image is not input in step 100, the process directly jumps from step 100 to step 104.

In step 104, it is possible to select by inputting from the keyboard 5 whether or not to superimpose images as shown in FIG. When superimposition is instructed by the keyboard 5, the data memory 4 is
In the next step 106 in which a plurality of image data stored in the image data are superimposed, it is possible to select whether or not to store the image data created by the superposition in the data memory 4 by inputting from the keyboard 5. If the image data is not stored, the current image data is displayed on the television monitor 6 in the next step 107, and then the data processing operation is ended.

On the other hand, if superposition is not performed in step 104,
If the superimposed image data is to be stored in the data memory 4 in step 106, the process jumps to step 108, and the currently image-processed data is stored in the data memory 4.

Subsequently, in step 109, it is possible to select whether or not to display an image on the television monitor 6 using the keyboard 5, and when display is instructed, the process jumps to the previously described step 107, and the same operation is performed thereafter.

If no display is to be performed, it is possible to select whether to proceed to the first step IO and repeat the measurement and data processing operations, or to terminate. If repeat measurement is instructed, the process returns to step 100 and the above operations are repeated, and if an instruction is given to end, the data processing section 3 ends the operation.

FIG. 7 is a block circuit configuration diagram of a modified embodiment of FIG. 1, in which the data processing section 3 is further added with an image mirror image reversal processing function, and a printer 7 is connected as an output terminal. The other configurations and functions are the same as in FIG. 1, and the same reference numerals indicate the same members.

According to the data processing section 3 having such a configuration, it is possible to perform upper and lower mirror image inversion processing on the fundus image shown in FIG. 2 as shown in FIG. 8 and output it from the printer 7. Therefore,
The correspondence between the positions of the visual field chart measured by a perimetry and the fundus image as shown in FIG. 9 is easy and effective for comparative analysis because the fundus image is mirror-inverted in the vertical direction.

In addition, if the magnification of the visual field chart and the fundus image are different, it is possible to match the magnification of the fundus image with the visual field chart using known image processing technology, and if either one is output using a transparent film, they can be overlapped. You can also see the correspondence relationship. Furthermore, if the image output by the printer 7 can be selected as either a monochrome image or a color image, it is convenient for one-overlapping comparison.

Note that the present invention is not limited to fundus images, and can be applied to, for example, images of the anterior segment of an eye to be examined, or to fields other than ophthalmological equipment.

[Effects of the Invention] As explained above, the image distortion correction method according to the present invention can correct the distortion aberration of the imaging system through image processing. Measurement is possible. Furthermore, it is also possible to separately capture partial images of a plurality of locations on the object to be imaged and to form a single image by superimposing the plurality of images without any deviation. Furthermore,
By performing mirror image inversion processing on images, it becomes easy to compare images that are mirror images in the vertical direction, such as a visual field chart of a perimeter meter and a fundus image.

[Brief explanation of the drawing]

1 to 8 show an embodiment of the image distortion correction method according to the present invention, in which FIG. 1 is a block circuit configuration diagram, FIG. 2 is a front view of a corrected image, and FIG. 3 is a diagram of an image distortion correction method. 4 and 5 are partially enlarged views of images, FIG. 6 is a flowchart of the operation, and FIG. 7 is a block circuit configuration diagram of another embodiment. Figure 8 is a front view of the image subjected to mirror image reversal processing;
The figure is a front view of the visual field chart. Reference numeral 2 is an A/D converter, 3 is a data processing unit, 4 is a data memory, 5 is a keyboard, 6 is a television monitor, and 7 is a printer. Patent applicant: Canon Corporation Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. An image distortion correction method, which comprises correcting imaging distortion of image data obtained by the imaging means based on the inherent imaging distortion characteristics of the imaging means that captured the image. 2. The imaging distortion correction method according to claim 1, wherein a plurality of image data corrected for imaging distortion are synthesized to form an image having a wide field of view.