Image processor for correcting distortion of central portion of image and preventing marginal portion of the image from protruding

• US 5,818,527 A
• Filed: 12/19/1995
• Issued: 10/06/1998
• Est. Priority Date: 12/21/1994
• Status: Expired due to Fees

• Current Assignee: Olympus Optical Company Ltd. (Olympus Corporation)
• Original Assignee: Olympus Optical Company Ltd. (Olympus Corporation)
• Inventors: Yamaguchi, Tatsuya, Watanabe, Hiroyuki, Okada, Mitsumasa, Tomizawa, Masaomi
• Primary Examiner(s): GARBER, WENDY RAE
• Application Number:
  US08/574,639
• Time in Patent Office: 1,022 Days
• Field of Search: 348/335, 348/241, 348/231, 348/340, 348/222, 382/293
• US Class Current: 348/335
• CPC Class Codes: A61B 1/05 characterised by the image sensor, e.g. camera, being in the distal end portion
• CPC Class Codes: H04N 23/555 for picking-up images in sites, inaccessible due to their dimensions or hazardous conditions, e.g. endoscopes or borescopes
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation
• CPC Class Codes: H04N 25/61 the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"
• CPC Class Codes: H04N 3/2335 with calculating means
• CPC Class Codes: H04N 5/2628 Alteration of picture size, shape, position or orientation, e.g. zooming, rotation, rolling, perspective, translation

Abstract

A distorted optical image formed on an image pickup surface by an optical system is photoelectrically converted by an image pickup device and written in memory cells of an image memory designated by write addresses. When the optical image is read, the image quality at the central portion is improved and the image is prevented from missing at the marginal portion so that the image can preferably be observed by correcting the distortion of an image in the area at the central side of the image pickup surface due to the optical system by read addresses obtained by converting the write addresses and preventing an image in the area at the marginal side from protrusion.

Claims

1. An image processor comprising:

a first correcting section for performing electrical correction of distortion according to a first correction characteristic of an optical system in a first closed area at the central side in an image area set correspondingly to an image pickup surface of an image pickup device for an electrical image generated as a result of the fact that an optical image formed on said image pickup surface of said image pickup device by said optical system is photoelectrically converted by said image pickup device, said electrical correction of distortion being performed according to said first correction characteristic so that the image in said first closed area may be enlarged; and

a second correcting section for performing electrical correction of distortion according to a second correction characteristic for said electrical image in a second closed area at the marginal side outside of said first closed area in said image area so that said second closed area does not protrude outside of said image area, said correction being performed according to said second correction characteristic so that the image in said second closed area may be contracted.

2. The image processor according to claim 1, wherein said image area is an area equivalent to the area of said image pickup surface.

3. The image processor according to claim 1, wherein image storage means for storing image data corresponding to said image and an address conversion circuit for performing each correction when said first and second correcting sections convert address values for reading said image data from said image storage means are further included.

4. The image processor according to claim 3, wherein said address conversion circuit has an address conversion data storing section for storing address conversion data for converting said address values.

5. The image processor according to claim 4, wherein said address conversion data storing section is a ROM.

6. The image processor according to claim 1, wherein said first closed area is a circle.

7. The image processor according to claim 1, wherein said first and second correcting sections have an information storing section for storing information to correct some areas line-symmetric to the horizontal axis or vertical axis passing through the approximate center of said image area and a correction circuit for correcting other areas in said image area by using said line-symmetric characteristic and referring to said information.

8. The image processor according to claim 1, wherein said first correcting section corrects a barrel distortion.

9. The image processor according to claim 7, wherein said information storing section stores address conversion information for geometrically moving various portions of images in said first and second closed areas and said correction circuit computes said address conversion information and corrects various portions of images in said other areas.

10. The image processor according to claim 4, wherein said address conversion data storing section is removable from said image processor.

11. The image processor according to claim 10, wherein said address conversion data storing section is integrally replaced with said optical system when said optical system is replaceable.

12. The image processor according to claim 7, wherein said information storing section stores address conversion information for correction and said correction circuit has an addition circuit for adding a predetermined offset value to a computed address by referring to address conversion information when each picture element to be processed is spatially moved and corrected.

13. The image processor according to claim 7, wherein a moving circuit is included which makes it possible to optionally move the horizontal axis and/or the vertical axis passing through the center of said image area vertically and/or horizontally.

14. The image processor according to claim 1, wherein said first and second correcting sections perform corrections corresponding to imaging characteristics of said optical system when the imaging characteristics of said optical system can be changed.

15. The image processor according to claim 1, wherein a processing information holding section for dividing said image captured by said image pickup device into four areas of top, bottom, right, and left and holding processing information necessary for the processing for correction of images in at least one of the four areas is included and the whole image is corrected by obtaining the processing information for images in three remaining areas from the processing information stored in said processing-information holding section by means of arithmetic.

16. The image processor according to claim 1, wherein said second correcting section corrects images in said second closed area at correction degrees different in the horizontal and vertical directions.

17. The image processor according to claim 1, wherein said first correcting section corrects images in said first closed area by electrically correcting the distortion of said optical system and enlarges the whole image and said second correcting section compresses the images in said second closed area up to a degree in which only the presence of an object can be recognized.

18. The image processor according to claim 1, wherein said second correcting section processes the images in said second closed area so that the color tones of them are different from those of the images corrected by said first correcting section.

19. The image processor according to claim 1, wherein boundaries between the images corrected by said first correcting section and the images corrected by said second correcting section are displayed.

20. The image processor according to claim 1, wherein said first correcting section corrects the distortion of said optical system by further enlarging an image in said first closed area as the correcting section goes away from the center of said image.

21. The image processor according to claim 1, wherein said first correcting section corrects the distortion of said optical system by further contracting an image in said first closed area as the correcting section approaches the center of said image.

22. The image processor according to claim 1, wherein said first correcting section corrects the distortion of said optical system by further contracting the image in said first closed area as the image approaches the center of the image in an area nearby the center of it and enlarging the image as the image goes away from the center in areas other than the area nearby the center.

23. The image processor according to claim 1, wherein a second corrected image obtained by correcting a distortion of the central portion of said image or distortion corrected image is further superimposed on part of said image or a corrected image generated by said first and second correcting sections and displayed.

24. An image pickup device comprising:

an optical system for capturing an optical image of an object;

image pickup means for receiving the optical image captured by the optical system with its image pickup surface, converting the optical image into electric image pickup signals, and outputting the signals;

image storage means for storing the image pickup signals output from said image pickup means;

read and write control means for controlling the read and write operations of said image storage means; and

correction and control means constituting said read and write control means to apply a first correction characteristic for electrically correcting the optical distortion of said optical system to an image in a first area at the central side of said image pickup surface about the center of the optical axis of said optical system and a second correction characteristic for electrically correcting an image in a second area at the marginal side of said first area so that the image does not go out of an area set correspondingly to the area of said image pickup surface by controlling at least one of the write operation and read operation of said image storage means, said correction of distortion according to said first correction characteristic being performed so that the image in said first area may be enlarged, and said correction according to said second correction characteristic being performed so that the image in said second area may be contracted.

25. The image pickup device according to claim 24, wherein said first correction characteristic is a correction for an optical distortion aberration of said optical system.

26. The image pickup device according to claim 25, wherein said correction and control means applies the first correction characteristic for decreasing said distortion aberration to the image in said first area and the second correction characteristic with a characteristic opposite to the first correction characteristic for decreasing the distortion aberration to the image in said second area.

27. The image pickup device according to claim 24, wherein the image in said second area is contracted or enlarged and output from said image storage means.

28. The image pickup device according to claim 24, wherein said correction and control means has a read pulse generating section for generating a read pulse to read image data stored in said image storage means at a predetermined cycle and a read address generating section for outputting the read address in said image storage means as a function of the read pulse generation timing.

29. The image pickup device according to claim 28, wherein the function form of said function has a characteristic opposite to the correction for decreasing the distortion aberration of said optical system for the image in said first area and decreasing the distortion aberration for the image in said second area and said correction and control means contracts or enlarges image data corresponding to almost the whole of the image in said second area and outputs the data by reading the image data from said image storage means with said read address.

30. The image pickup device according to claim 24, wherein said correction and control means has a processing information holding section for storing a relative position between the position of each point of an optical image formed by said optical system and the position of an ideally formed optical image as processing information for the image in said first area and storing a displacement value for displacing the position of each point of the optical image formed by said optical system as processing information so as to output image data corresponding to almost the entire optical image formed by said optical system for the image in said second area and corrects and controls at least one of the write operation and read operation of said image storage means in accordance with the processing information stored in the processing information holding section.

31. The image pickup device according to claim 28, wherein the function form of said function is an approximate expression obtained by approximating said distortion aberration by a polynomial of the distance from the center of said first area on the central area of the storage area of said image storage means for the image in said first area.

32. The image pickup device according to claim 28, wherein said correction and control means is able to translate said function in the direction of the generation timing axis of said read pulse in order to decrease correction errors of said distortion aberration due to the inconsistency between the central axis of said optical system and the center of the image pickup surface of said image pickup means.

33. The image pickup device according to claim 28, wherein said correction and control means is able to translate said function in the direction of said read address axis in order to change the positions of a corrected image read out of said image storage means.

34. The image pickup device according to claim 28, wherein said correction and control means is able to multiply said function by any factor in the direction of said read address axis in order to change the magnifications of the corrected image read out of said image storage means.

35. An endoscope system comprising:

an endoscope having an optical system for capturing an optical image of an object arranged at an end of a slender inserting portion and image pickup means for receiving an optical image formed by said optical system, converting the image into electrical picture signals, and outputting the signals;

image storage means for storing said picture signals output from said image pickup means;

read and write control means for controlling read operation and write operation of said image storage means; and

correction and control means constituting said read and write control means to correct and control at least one of the read operation and write operation of said image storage means so as to correct the image in the first area at the central side of said image pickup surface according to a first correction characteristic and the image in the second area at the marginal side of said first area according to a second correction characteristic which is not equivalent to said first correction characteristic, said correction of optical distortion according to said first correction characteristic being performed so that the image in said first area may be enlarged, and said correction according to said second correction characteristic being performed so that the image in said second area may be contracted.

36. The endoscope system according to claim 35, wherein said endoscope is an electronic endoscope in which said image pickup device is arranged at the imaging position of said optical system.

37. The endoscope system according to claim 35, wherein said endoscope is a TV-camera-mounted endoscope comprising an optical endoscope having image transmission means for optically transmitting an optical image formed by said optical system, an imaging optical system mounted on said optical endoscope to form said optical image transmitted by image transmission means, and a TV camera in which said image pickup device is arranged at the imaging position of said imaging optical system.

38. The endoscope system according to claim 35, wherein said correction and control means has a switching section for switching types of corrections for said optical distortion to correct the distortion correspondingly to the type of said optical system of said endoscope.

39. The endoscope system according to claim 38, wherein said correction and control means has a discriminating section for discriminating the type of said optical system of said endoscope and said switching section is switched by the discriminating section and correction is controlled.

40. An image processor for correcting an optical distortion of an image captured by an optical system in accordance with information processing, wherein the optical distortion is changed at the central portion of the image according to a first correction characteristic and the marginal portion of the image according to a second correction characteristic not equivalent to said first correction characteristic, said correction of optical distortion according to said first correction characteristic being performed so that the image of said central portion may be enlarged, and said correction according to said second correction characteristic being performed so that the image at said marginal portion may be contracted.