Image processing apparatus and its processing method

• US 20020015111A1
• Filed: 06/29/2001
• Published: 02/07/2002
• Est. Priority Date: 06/30/2000
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Harada, Yoshihito
• Granted Patent: US 7,133,072 B2
• Time in Patent Office: Days
• US Class Current: 348/642
• CPC Class Codes: H04N 25/63 applied to dark current

Abstract

This invention relates to an image processing apparatus for processing an image sensed by an image sensing element such as a CCD sensor, and the apparatus includes a dark correction circuit for making dark correction of the image, a defect correction circuit for correcting a defective pixel in the image using other pixels, and a controller for controlling the shares of dark correction by the dark correction circuit and defect correction by the defect correction circuit on the basis of information which pertains to image sensing (e.g., ISO speed, temperature, and accumulation time).

Claims

1. An image processing apparatus which processes an image, comprising:

an image sensing element having a plurality of photoelectric conversion units;

a first correction unit which corrects a signal from the photoelectric conversion unit, a dark level of which reaches a predetermined level, using signals from other photoelectric conversion units, the dark level being a level of a signal output from said image sensing element in the dark; and

a controller which changes the predetermined level in accordance with information that pertains to image sensing.

2. The apparatus according to claim 1, further comprising a second correction unit which subtracts a second signal output from said image sensing element in the dark from a first signal output from said image sensing element.

3. The apparatus according to claim 1, wherein the information that pertains to image sensing includes at least one of three factors, i.e., a temperature, an accumulation time of said image sensing element, and an ISO speed.

4. The apparatus according to claim 1, wherein the information that pertains to image sensing includes three factors, i.e., a temperature, an accumulation time of said image sensing element, and an ISO speed.

5. The apparatus according to claim 1, wherein said controller comprises:

a plurality of defective pixel tables prepared in correspondence with a plurality of image sensing conditions; and

a defective pixel instruction unit which selects one defective pixel table from said plurality of defective pixel tables on the basis of the information that pertains to image sensing, and indicates a defective pixel to be corrected by said first correction unit thereto on the basis of the selected defective pixel table.

6. The apparatus according to claim 5, wherein the information that pertains to image sensing includes at least one of three factors, i.e., a temperature, an accumulation time of said image sensing element, and an ISO speed.

7. The apparatus according to claim 5, wherein the information that pertains to image sensing includes three factors, i.e., a temperature, an accumulation time of said image sensing element, and an ISO speed.

8. The apparatus according to claim 1, wherein said first correction unit determines a pixel value of a defective pixel to be corrected on the basis of surrounding pixels of that defective pixel.

9. The apparatus according to claim 7, wherein said first correction unit determines a pixel value of a defective pixel to be corrected on the basis of an average value of surrounding pixels of that defective pixel.

10. The apparatus according to claim 1, wherein said image sensing element includes a CCD sensor.

11. The apparatus according to claim 1, wherein said image sensing element includes a CMOS sensor.

13. The apparatus according to claim 12, wherein said controller controls the gain in association with the number of defective pixels in said defect correction unit.

14. The apparatus according to claim 12, wherein said controller controls the number of defective pixels in said defect correction unit in association with the gain.

15. The apparatus according to claim 12, wherein said controller comprises:

a plurality of defective pixel tables prepared in correspondence with a plurality of image sensing conditions; and

a defective pixel instruction unit which selects one defective pixel table from said plurality of defective pixel tables on the basis of information that pertains to image sensing, and indicates a defective pixel to be corrected by said defect correction unit thereto on the basis of the selected defective pixel table.

16. The apparatus according to claim 15, wherein said defect correction unit determines a pixel value of a defective pixel to be corrected on the basis of surrounding pixels of that defective pixel.

17. The apparatus according to claim 12, wherein said image sensing element includes a CCD sensor.

18. The apparatus according to claim 12, wherein said image sensing element includes a CMOS sensor.

20. The method according to claim 19, further comprising second correcting a second signal, subtracting the second signal output from the image sensing element in the dark from a first signal output from the image sensing element.

21. The method according to claim 19, wherein the information that pertains to image sensing includes at least one of three factors, i.e., a temperature, an accumulation time of the image sensing element, and an ISO speed.

22. The method according to claim 19, wherein the information that pertains to image sensing includes three factors, i.e., a temperature, an accumulation time of the image sensing element, and an ISO speed.

23. The method according to claim 19, wherein one defective pixel table is selected from a plurality of defective pixel tables prepared in correspondence with a plurality of image sensing conditions on the basis of the information that pertains to image sensing, and a defective pixel to be corrected is specified on the basis of the selected defective pixel table.

24. The method according to claim 23, wherein the information that pertains to image sensing includes at least one of three factors, i.e., a temperature, an accumulation time of the image sensing element, and an ISO speed.

25. The method according to claim 23, wherein the information that pertains to image sensing includes three factors, i.e., a temperature, an accumulation time of the image sensing element, and an ISO speed.

26. The method according to claim 19, wherein a pixel value of a defective pixel to be corrected is determined on the basis of surrounding pixels of that defective pixel.

27. The method according to claim 26, wherein a pixel value of a defective pixel to be corrected is determined on the basis of an average value of surrounding pixels of that defective pixel.

28. The method according to claim 19, wherein the image sensing element includes a CCD sensor.

29. The method according to claim 19, wherein the image sensing element includes a CMOS sensor.

33. The method according to claim 28, wherein one defective pixel table is selected from a plurality of defective pixel tables prepared in correspondence with a plurality of image sensing conditions on the basis of information that pertains to image sensing, and a defective pixel to be corrected is specified on the basis of the selected defective pixel table.

34. The method according to claim 33, wherein a pixel value of a defective pixel to be corrected is determined on the basis of surrounding pixels of that defective pixel.

35. The method according to claim 28, wherein the image sensing element includes a CCD sensor.

36. The method according to claim 28, wherein the image sensing element includes a CMOS sensor.

12. An image processing apparatus which processes an image, comprising:

an image sensing element which senses an object;

a defect correction unit which corrects a defective pixel in the image using other pixels; and

a controller which controls a gain of a signal output from said image sensing element and the number of defective pixels in said defect correction unit in association with each other.

19. An image processing method which processes an image sensed by an image sensing element having a plurality of photoelectric conversion units, comprising:

first correcting a signal from the photoelectric conversion unit, a dark level of which reaches a predetermined level, using signals from other photoelectric conversion units, the dark level being a level of a signal output from the image sensing element in the dark; and

changing the predetermined level in accordance with information that pertains to image sensing.

30. An image processing method which processes an image sensed by an image sensing element for sensing an object, comprising:

correcting a defective pixel in the image using other pixels; and

controlling a gain of a signal output from the image sensing element and the number of defective pixels in the defect correction step in association with each other.

31. The method according to claim 30, wherein the gain is controlled in association with the number of defective pixels to be corrected.

32. The method according to claim 30, wherein the number of defective pixels to be corrected is controlled in association with the gain.

37. A memory medium that stores software for implementing an image processing method which processes an image sensed by an image sensing element, said software comprising:

correcting a signal from a photoelectric conversion unit, a dark level of which reaches a predetermined level, using signals from other photoelectric conversion units, the dark level being a level of a signal output from the image sensing element in the dark; and

changing the predetermined level in accordance with information that pertains to image sensing.

38. A memory medium that stores software adapted to implement an image processing method which processes an image sensed by an image sensing element, said software comprising:

correcting a defective pixel in the image using other pixels; and

controlling a gain of a signal output from the image sensing element and the number of defective pixels in association with each other.

39. Software adapted to implement an image processing method which processes an image sensed by an image sensing element, comprising:

correcting a signal from a photoelectric conversion unit, a dark level of which reaches a predetermined level, using signals from other photoelectric conversion units, the dark level being a level of a signal output from the image sensing element in the dark; and

changing the predetermined level in accordance with information that pertains to image sensing.

40. Software adapted to implement an image processing method which processes an image sensed by an image sensing element, comprising:

correcting a defective pixel in the image using other pixels; and

controlling a gain of a signal output from the image sensing element and the number of defective pixels in association with each other.