Methods and systems for detecting bright objects and/or adaptively modifying video camera exposure

• US 20070258007A1
• Filed: 05/03/2006
• Published: 11/08/2007
• Est. Priority Date: 05/03/2006
• Status: Active Grant

• Current Assignee: UTC Fire & Security Americas Corporation, Inc. (Carrier Global Corporation)
• Original Assignee: UTC Fire & Security Americas Corporation, Inc. (Carrier Global Corporation)
• Inventors: Horowitz, Michael, Justiss, Joseph
• Granted Patent: US 8,004,575 B2
• Time in Patent Office: Days
• US Class Current: 348/364
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation

Abstract

Methods and systems for automatically detecting the presence or absence of a bright object in the field of view of a video camera and/or for adaptively modifying video camera exposure level. A video camera system may be configured to enter and exit an adaptive exposure modification mode upon detection of the presence of a bright object in the field of view of a video camera.

Claims

1. A method for modifying a default exposure level of a video image, comprising:

determining the number of bright luma samples in said video image having a default exposure; and

modifying said default exposure level of said video image based on a comparison of said number of bright luma samples in said video image to an exposure modification threshold number of luma samples.

2. The method of claim 1, further comprising darkening said default exposure level of said video image if said number of bright luma samples in said video image is at least one of greater than or equal to said exposure modification threshold number of luma samples.

3. The method of claim 2, further comprising determining the number of bright luma samples in said video image after said darkening of said exposure level;

and then further darkening said exposure level of said video image if said number of bright luma samples in said video image is at least of one greater than or equal to said exposure modification threshold number of luma samples.

4. The method of claim 2, wherein said video image is generated by a video camera system and represents a scene in the field of view of said video camera;

and wherein said method further comprises;

determining if said scene is a low light scene; and

darkening said default exposure level of said video image if said scene is determined to be a low light scene and if said number of bright luma samples in said video image is at least of one greater than or equal to said threshold number of luma samples;

or

not darkening said default exposure level of said video image if said scene is not determined to be a low light scene, or if said number of bright luma samples in said video image is less than said exposure modification threshold number of luma samples.

5. The method of claim 1, further comprising first determining if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image prior to modifying said default exposure level of said video image based on a comparison of said number of bright luma samples in said video image to said exposure modification threshold number of luma samples.

6. The method of claim 5, wherein said method further comprises comparing the number of bright luma samples determined to be in said video image to a minimum number of bright luma samples to determine if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image, said minimum number of bright luma samples being indicative of the presence of at least one bright object in said video image.

7. The method of claim 6, wherein said bright object comprises an automobile license plate.

8. The method of claim 6, wherein said minimum number of bright luma samples is a number of bright luma samples determined by empirical measurement to be indicative of the presence of a bright object in a video image.

9. The method of claim 2, wherein said threshold number of luma samples is a number of luma samples determined by empirical measurement.

10. A method for detecting bright objects in a video image, comprising:

determining the number of bright luma samples in said video image; and

then determining if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image.

11. The method of claim 10, wherein said determining the number of bright luma samples in said video image comprises determining the number of bright luma samples in said video image that have a brightness greater than a brightness threshold.

12. The method of claim 10, wherein said method further comprises comparing the number of bright luma samples determined to be in said video image to a minimum number of bright luma samples to determine if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image, said minimum number of bright luma samples being indicative of the presence of at least one bright object in said video image.

13. The method of claim 12, wherein said bright object comprises an automobile license plate.

14. The method of claim 12, further comprising darkening a default exposure of said video image based on said comparison of the number of bright luma samples determined to be in said video image to said minimum number of bright luma samples when a result of said comparison indicates the presence of said license plate in said video image.

15. The method of claim 12, wherein said minimum number of bright luma samples is a number of bright luma samples determined by empirical measurement to be indicative of the presence of a bright object in a video image.

16. The method of claim 10, further comprising modifying a default exposure of said video image based on a determination that said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image.

17. A system configured to modify a default exposure level of a video image, said system comprising logic configured to:

determine the number of bright luma samples in said video image having a default exposure; and

modify said default exposure level of said video image based on a comparison of said number of bright luma samples in said video image to a exposure modification threshold number of luma samples.

18. The system of claim 17, wherein said logic is further configured to darken said default exposure level of said video image if said number of bright luma samples in said video image is at least one of greater than or equal to said exposure modification threshold number of luma samples.

19. The system of claim 18, wherein said logic is further configured to determine the number of bright luma samples in said video image after said darkening of said exposure level;

and then to further darken said exposure level of said video image if said number of bright luma samples in said video image is at least of one greater than or equal to said exposure modification threshold number of luma samples.

20. The system of claim 18, wherein said video image is generated by a video camera system and represents a scene in the field of view of said video camera;

and wherein said logic is further configured to;

determine if said scene is a low light scene; and

darken said default exposure level of said video image if said scene is determined to be a low light scene and if said number of bright luma samples in said video image is at least of one greater than or equal to said threshold number of luma samples;

or

not darken said default exposure level of said video image if said scene is not determined to be a low light scene, or if said number of bright luma samples in said video image is less than said exposure modification threshold number of luma samples.

21. The system of claim 17, wherein said logic is further configured to first determine if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image prior to modifying said default exposure level of said video image based on a comparison of said number of bright luma samples in said video image to said exposure modification threshold number of luma samples.

22. The system of claim 21, wherein said logic is further configured to compare the number of bright luma samples determined to be in said video image to a minimum number of bright luma samples to determine if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image, said minimum number of bright luma samples being indicative of the presence of at least one bright object in said video image.

23. The system of claim 22, wherein said bright object comprises an automobile license plate.

24. The system of claim 22, wherein said minimum number of bright luma samples is a number of bright luma samples determined by empirical measurement to be indicative of the presence of a bright object in a video image.

25. The system of claim 18, wherein said threshold number of luma samples is a number of luma samples determined by empirical measurement.

26. The system of claim 17, wherein said system comprises a part of a video camera system.

27. A system configured to detect bright objects in a video image, said system comprising logic configured to:

determine the number of bright luma samples in said video image; and

then determine if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image.

28. The system of claim 27, wherein said logic is configured to determine the number of bright luma samples in said video image by determining the number of bright luma samples in said video image that have a brightness greater than a brightness threshold.

29. The system of claim 27, wherein said logic is further configured to compare the number of bright luma samples determined to be in said video image to a minimum number of bright luma samples to determine if said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image, said minimum number of bright luma samples being indicative of the presence of at least one bright object in said video image.

30. The system of claim 29, wherein said bright object comprises an automobile license plate.

31. The system of claim 30, wherein said logic is further configured to darken a default exposure of said video image based on said comparison of the number of bright luma samples determined to be in said video image to said minimum number of bright luma samples when a result of said comparison indicates the presence of said license plate in said video image.

32. The system of claim 29, wherein said minimum number of bright luma samples is a number of bright luma samples determined by empirical measurement to be indicative of the presence of a bright object in a video image.

33. The system of claim 27, wherein said logic is further configured to modify a default exposure of said video image based on a determination that said number of bright luma samples in said video image is indicative of the presence of at least one bright object in said video image.

34. The system of claim 33, wherein said bright object comprises an automobile license plate.

35. The system of claim 27, wherein said system comprises part of a video camera system.