Image sensing apparatus

• US 5,442,397 A
• Filed: 05/18/1994
• Issued: 08/15/1995
• Est. Priority Date: 03/11/1988
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Fujiwara, Akihiro, Suda, Hirofumi, Kaneda, Kitahiro, Toyama, Masamichi, Homma, Hideo, Yamada, Kunihiko, Yoshimura, Katsuji
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): LEE, CHEUKFAN
• Application Number:
  US08/245,813
• Time in Patent Office: 454 Days
• Field of Search: 348/363, 348/362, 250/201.2, 250/203.1, 250/203.3, 250/203.6, 250/203.7, 250/203.5, 354/403
• US Class Current: 348/363
• CPC Class Codes: G01S 3/7864 T.V. type tracking systems
• CPC Class Codes: G02B 7/36 using image sharpness techniques , e.g. image processing techniques for generating autofocus signals image data processing per se G06T; in cameras having a solid state image sensor H04N23/67
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/675 comprising setting of focusing regions
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation

Abstract

An image sensing apparatus operating with adaptive selection of a first tracing algorithm in which an object image is traced by moving a detecting area capable of being movably set on an image sensing plane in such a manner that the luminance level difference between the inside and the outside of that area becomes maximum and a second tracing algorithm in which the object image is traced by moving the position of the detecting area in such a manner that a point at which a contrast becomes maximum comes to coincide with a central portion of the detecting are depending on the state of the image sensing plane. The threshold values for changing over between the first tracing algorithm and the second tracing algorithm are made to have a hysteresis characteristic.

Claims

1. An object tracing device for tracing an object image on an image sensing plane, comprising:

(A) setting means for movably setting a detecting area on said image sensing plane;

(B) first object tracing means, having means for respectively detecting luminance level between the inside and outside of said detecting area, for controlling said setting means to vary a set position of said detecting area on said image sensing plane so that the difference in luminance level between the inside and the outside of said detecting area becomes greater;

(C) second object tracing means for controlling said setting means to vary the set position of said detecting area on said image sensing plane so that a position at which a contrast on said image sensing plane becomes maximum coincides with a central portion of said detecting area; and

(D) control means for selectively operating one of said first object tracing means and said second object tracing means.

2. A device according to claim 1, wherein said first object tracing means sets said detecting area to a position at which the difference in average luminance level between the inside and the outside of said detecting area becomes maximum.

3. A device according to claim 2, wherein said first object tracing means controls said setting means to perform such a wobbling that said detecting area is shifted upward, downward, to the left and to the right in units of a predetermined distance repeatedly, to control said setting means to move said detecting area to the set position where the difference in average luminance level between the inside and the outside of said detecting area becomes maximum.

4. A device according to claim 3, wherein said first object tracing means includes gate circuits for extracting the respective image signals corresponding to the inside and the outside of said detecting area, integration circuits for integrating the respective image signals output from said gate circuits, correction circuits for correcting the error caused on the basis of the difference in area between the inside and the outside of said detecting area so as to normalize the integrated value output from said correction circuits, and a subtracting circuit for obtaining the difference between outputs of said correction circuits.

5. A device according to claim 1, wherein said second object tracing means sets the position of said detecting area so that a position where a contrast on said detecting area becomes maximum coincides with a central portion of said detecting area.

6. A device according to claim 5, wherein said second object tracing means includes horizontal peak-value/peak-position detecting means having a sample-and-hold circuit in holding a peak value in every one horizontal scanning in said detecting area and a counter for detecting a position at which said peak value is detected in said one horizontal scanning, and vertical peak-value/peak-position detecting means having a sample-and-hold circuit for holding a peak value in every one vertical scanning in said detecting area and a counter for detecting a position at which said peak value is detected in said one vertical scanning.

7. A device according to claim 1, wherein said control means selects one of said first and said second object tracing means in accordance with a state of said image sensing plane.

8. A device according to claim 7, further comprising integration means for integrating luminance signal components corresponding to the inside and the outside of said detecting area, and wherein said control means, responsive to a difference in integrated luminance level integrated by said integration means between the inside and the outside of said detecting area, adaptively selects one of said first object tracing means and said second object tracing means.

9. A device according to claim 8, wherein said control means selects said first object tracing means when the difference in average luminance level between the inside and the outside of said detecting area is larger than a predetermined value, and selects said second object tracing means when said difference in average luminance level is not larger than said predetermined value.

10. A device according to claim 1, further comprising focus detecting means for detecting the degree of focus to the object image on the basis of an image signal corresponding to the inside of said detecting area.

11. A device according to claim 10, wherein said focus detecting means detects the degree of focus on the basis of the quantity of a high-frequency component in said image signal.

12. An object tracing type automatic focusing device for keeping an object image in an in-focus state by tracing the object image on an image sensing plane, comprising:

(A) means for movably setting a focus detecting area on said image sensing plane;

(B) setting means for movably setting an object tracing area on said image sensing plane;

(C) first object tracing means, having means for respectively detecting luminance level between the inside and outside of said object tracing area , for controlling said setting means to vary a set position of said object tracing area on said image sensing plane so that the difference in luminance level between the inside and the outside of said object tracing area becomes greater;

(D) second object tracing means for controlling said setting means to vary the set position of said object tracing area on said image sensing plane so that a position at which a contrast on said image sensing plane becomes maximum coincides with a central portion of said object tracing area;

(E) control means for selectively operating one of said first object tracing means and said second object tracing means; and

(F) means for setting said focus detecting area to a position in said object tracing area.

13. A device according to claim 12, wherein said object tracing area serves also as said focus detecting area.

14. A device according to claim 12, wherein said first object tracing means sets said object tracing area to a position at which the difference in average luminance level between the inside and the outside of said object tracing area becomes maximum.

15. A device according to claim 14, wherein said first object tracing means controls said setting means to perform such a wobbling that said object tracing area is shifted upward, downward, to the right, to the left in units of a predetermined distance repeatedly, and to move said object tracing area to the shifting position at which the difference in average luminance level between the inside and the outside of said object tracing area becomes maximum.

16. A device according to claim 15, wherein said first object tracing means includes gate circuits for extracting the respective image signals corresponding to the inside and the outside of said object tracing area, integrating circuits for integrating the respective image signals output from said gate circuits, correction circuits for correcting the error caused on the basis of the difference in area between the inside and the outside of said object tracing area so as to normalize the integrated value output from said correction circuits, and a subtracting circuit for obtaining the difference between outputs of said correction circuits.

17. A device according to claim 12, wherein said second object tracing means sets the position of said object tracing area so that a position at which a contrast on said object tracing area becomes maximum coincides with a central portion of said object tracing area.

18. A device according to claim 17, wherein said second object tracing means includes horizontal peak-value/peak-position detecting means having a sample-and-hold circuit for holding a peak value in every one horizontal scanning in said object tracing area and a counter for detecting a position at which said peak value is detected in said one horizontal scanning, and vertical peak-value/peak-position detecting means having a sample-and-hold circuit for holding a peak value in every one vertical scanning in said object tracing area and a counter for detecting a position at which said peak value is detected in said one vertical scanning.

19. A device according to claim 12, wherein said control means selects one of said first and said second object tracing means in accordance with a state of said image sensing plane.

20. A device according to claim 19, wherein said first object tracking means has integration circuits for respectively detecting average luminance level of the inside and outside of said object tracing area, and said control means adaptively selects one of said first object tracing means and said second object tracing means in response to a difference in integrated luminance level between the inside and the outside of said object tracing area integrated by said integration circuits.

21. A device according to claim 20, wherein said control means selects said first object tracing means when the difference in average luminance level between the inside and the outside of said object tracing area is larger than a predetermined value, and selects said second object tracing means when said difference in average luminance level is not larger than said predetermined value.

22. An automatic focusing device for focusing on an object image on an image sensing plane by tracing the object image, comprising:

(A) focus detecting means for detecting an in focus state on the basis of an image signal corresponding to a focus detecting area set on said image sensing plane;

(B) first area setting means for varying the position of said set focus detecting area on said image sensing plane so that the difference in average luminance level between the inside and the outside of said focus detecting area becomes larger;

(C) second area setting means for varying the position of said set focus detecting area on said image sensing plane so that a contrast of a central portion of said focus detecting area on said image sensing plane becomes maximum; and

(D) control means for selectively operating one of said first area setting means and said second area setting means.

23. A device according to claim 22, wherein said first area setting means sets said focus detecting area so that the difference in average luminance level between the inside and the outside of said focus detecting area becomes maximum.

24. A device according to claim 22, wherein said control means selects one of said first and said second area setting means in accordance with a state of said image sensing plane.

25. A device according to claim 24, wherein said control means selects said first area setting means when the difference in average luminance level between the inside and the outside of said focus detecting area is larger than a predetermined value, and selects said second area setting means when said difference in average luminance level is not larger than said predetermined value.

26. An object tracing device for tracing an object image on an image sensing plane, comprising:

(A) first object tracing means for varying a set position of a detecting area on said image sensing plane so that the difference in luminance level between the inside and the outside of said detecting area becomes larger;

(B) second object tracing means for varying the set position of said detecting area on said image sensing plane so that a contrast of a central portion of said detecting area on said image sensing plane becomes maximum; and

(C) control means for selectively operating one of said first object tracing means and said second object tracing means, wherein;

a selecting operation of said control means has a hysteresis characteristic in which a threshold value at which a selection is changed from said first object tracing means to said second object tracing means differs from a threshold value at which a selection is changed from said second object tracing means to said first object tracing means.

27. A device according to claim 26, wherein said first object tracing means sets said detecting area so that the difference in average luminance level between the inside and the outside of said detecting area becomes maximum.

28. A device according to claim 27, wherein said first object tracing means controls said setting means to perform such a wobbling that said detecting area is shifted upward, downward, to the left and to the right in units of a predetermined distance repeatedly, and to move said detecting area to the position of said detecting area at which the difference in average luminance level between the inside and the outside of said detecting area becomes maximum.

29. A device according to claim 28, wherein said first object tracing means includes gate circuits for extracting the respective image signals corresponding to the inside and the outside of said detecting area, integration circuits for integrating the respective image signals output from said gate circuits, area correction circuits for correcting the difference in area between the inside and the outside of said detecting area with respect to integrated values output from said integration circuits, and a subtracting circuit for obtaining the difference between outputs of said area correction circuits.

30. A device according to claim 26, wherein said second object tracing means sets the position of said detecting area so that a contrast of a central portion of said detecting area on said image sensing plane becomes maximum.

31. A device according to claim 30, wherein said second object tracing means includes horizontal peak-value/peak-position detecting means having a sample-and-hold circuit for holding a peak value in every one horizontal scanning in said detecting area and a counter for detecting a position at which said peak value is detected in said one horizontal scanning, and vertical peak-value/peak-position detecting means having a sample-and-hold circuit for holding a peak value in every one vertical scanning in said detecting area and a counter for detecting a position at which said peak value is detected in said one vertical scanning.

32. A device according to claim 26, wherein said control means, responsive to the difference in luminance level between the inside and the outside of said detecting area, adaptively selects one of said first object tracing means and said second object tracing means.

33. A device according to claim 32, wherein said control means selects said first object tracing means when the difference in average luminance level between the inside and the outside of said detecting area is larger than a predetermined value, and selects said second object tracing means when said difference in average luminance level is not larger than said predetermined value.

34. A device according to claim 33, further comprising focus detecting means for detecting a degree of focus to of said object image on the basis of a high frequency component of an image signal corresponding to the inside of said detecting area.

35. An image sensing apparatus comprising:

(A) first tracing means for detecting a feature of an image on an image sensing plane and for tracing a motion of said feature;

(B) second tracing means for detecting a feature of said image having a different detection characteristic from that of said first tracing means; and

(C) control means for selectively operating one of said first tracing means and said second tracing means in accordance with a detecting condition of the image on said image sensing plane on the basis of detecting information of said first or second tracing means, in which a selecting operation of said control means has a hysteresis characteristic in changing operation between said first and second tracing means.

36. An apparatus according to claim 35,

said first tracing means detects said feature and traces said feature in a first detecting area so that a difference in luminance level between the inside and the outside of the first detecting area becomes maximum, and wherein said second tracing means detects said feature and traces said feature in a second detecting area so that a contrast of a central portion of said second detecting area becomes maximum.

37. An apparatus according to claim 36, wherein said control means selects one of said first and said second tracing means in accordance with the difference in luminance level between the inside and the outside of said second detecting area.

38. A device according to claim 37 in which said first and second detecting areas are common with said detecting area.

39. An apparatus according to claim 35, wherein said detecting area is a focus detecting area.

40. An apparatus according to claim 35, wherein said detecting area is a light measuring area.

41. An automatic focus detecting device, comprising:

(A) image sensing means for sensing an object image formed on an image sensing plane and for photo-electrically converting said object image into an image signal and outputting said image signal;

(B) focus detecting means for extracting a predetermined signal component varying according to a focus condition from the image signal corresponding to a detecting area set on said image sensing plane; and

(C) detecting area setting means having a first mode for setting said detecting area on said image sensing plane on the basis of a first algorithm and having a second mode for setting said detecting area on the basis of a second algorithm different from said first algorithm wherein said detecting area setting means has a hysteresis characteristic in the changing operation between said first and second modes.

42. A device according to claim 41, wherein said detecting area setting means includes level detecting means for detecting an average luminance level inside and outside of said detecting area and wherein said detecting area is set at a position where a difference in luminance level between the inside and the outside of said detecting area detected by said level detecting means in said first mode becomes maximum.

43. A device according to claim 41, wherein said detecting area setting means includes peak detecting means for detecting a peak value of a high frequency component in said image signal corresponding to said detecting area, and said detecting area is set at a peak detecting position detected by said peak detecting means in said second mode.

44. An automatic exposure control device, comprising:

(A) image sensing means for sensing an object image formed on an image sensing plane and for photo-electrically converting said object image into an image signal and outputting said image signal;

(B) exposure detecting means for extracting a predetermined signal component according to an exposure condition from the image signal corresponding to a detecting area set on said image sensing plane; and

(C) detecting area setting means having a first mode for setting said detecting area on said image sensing plane according to a first algorithm and a second mode for setting said detecting area according to a second algorithm different from said first algorithm.

45. A device according to claim 44, wherein said detecting area setting means has a hysteresis characteristic in the changing operation between said first mode and said second mode.

46. A device according to claim 45, wherein said detecting area setting means includes level detecting means for detecting an average luminance level inside and outside of said detecting area and wherein said detecting area is set at a position where a difference in luminance level between the inside and the outside of said detecting area detected by said level detecting means in said first mode becomes maximum.

47. A device according to claim 45, wherein said detecting area setting means includes peak detecting means for detecting a peak value of a high frequency component in said image signal corresponding to said detecting area, and said detecting area is set at a peak detecting position detected by said peak detecting means in said second mode.

48. A video camera device comprising:

(A) image sensing means for sensing an object image formed on an image sensing plane and for photo-electrically converting said object image into an image signal and outputting said image signal;

(B) detecting means for extracting a predetermined signal component according to a photographing condition from the image signal corresponding to a detecting area set on said image sensing plane; and

(C) detecting area setting means having a first mode for setting said detecting area on said image sensing plane according to a first algorithm and a second mode for setting said detecting area according to a second algorithm different from said first algorithm, said detecting area setting means having a hysteresis characteristic in changing operation between said first mode and said second mode.

49. A device according to claim 48, wherein said detecting area is a focus detecting area.

50. A device according to claim 49, wherein said detecting area is an exposure detecting area.