Method, apparatus and system providing adjustment of pixel defect map

• US 7,932,938 B2
• Filed: 08/25/2006
• Issued: 04/26/2011
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Subbotin, Igor
• Primary Examiner(s): Ometz; David L
• Assistant Examiner(s): Chon; Peter
• Application Number:
  US11/509,712
• Publication Number:
  US 20080049125A1
• Time in Patent Office: 1,705 Days
• Field of Search: 348/175, 348/176, 348/177, 348/178, 348/179, 348/180, 348/187, 348/189, 348/241, 348/243, 348/244, 348/246, 348/247, 348/250, 348/251
• US Class Current: 348/247
• CPC Class Codes: H04N 25/68 applied to defects
• CPC Class Codes: H04N 25/683 by defect estimation performed on the scene signal, e.g. real time or on the fly detection

Abstract

A method, apparatus and system that allows for the identification of defective pixels, for example, defective pixel clusters, in an imager device. The method, apparatus and system determine, during use of the imager device, that a pixel defect, e.g., cluster defect, exists and accurately maps the location of the defective pixel. By analyzing more than one frame of an image, the method increases the accuracy of the defect mapping, which is used to improve the quality of the resulting image data.

Claims

1. A method of adjusting a pixel array defect map comprising:

storing an initial pixel defect map corresponding to a pixel sensor array;

obtaining pixel output signals from said pixel sensor array;

using said pixel output signals to determine current defective pixel locations in accordance with pixel defect criteria;

for every current defective pixel location;

if the corresponding location in the stored pixel defect map was previously marked as defective, comparing the data of the corresponding location in the stored pixel defect map with the data of said respective current defective pixel location, updating the mark for the corresponding location in the map to indicate a true defect if the compared stored data is the same as the compared current data, and removing the defect mark for the corresponding location in the map if the compared stored data is different from the compared current data; and

if the corresponding location in the map was not previously marked as defective, marking the corresponding location in the map as defective; and

storing the pixel defect map.

2. The method of claim 1, wherein using, comparing, updating, removing, and marking operations are performed on a pixel-by-pixel basis using the pixel output signals.

3. The method of claim 1, wherein using the pixel output signals to determine current defective pixel locations in accordance with pixel defect criteria comprises determining current cluster defect locations.

4. The method of claim 3, wherein determining current cluster defect locations includes examining the pixel output signals for a pixel-under-test and immediately surrounding pixels.

5. The method of claim 3, further comprising identifying a type of pixel defect cluster if it is determined that a pixel defect cluster exists.

6. The method of claim 5, further comparing the type of defect cluster to data on a type of cluster at the location in the stored pixel defect map.

7. The method of claim 5, wherein identifying a type of pixel defect cluster comprises comparing the obtained pixel output signals to threshold bright and dark values.

8. The method of claim 3, wherein for each pixel in the array, data is saved in the map that includes data related to pixel location, pixel defect type, and pixel cluster information.

9. The method of claim 1, further comprising determining whether conditions for detecting a pixel defect meet pre-determined criteria.

10. The method of claim 9, wherein determining whether conditions for detecting a pixel defect meet pre-determined criteria comprises determining if an imaged scene has an overly bright or overly dark spot associated with said location.

11. The method of claim 3, wherein removing the defective mark for the corresponding location in the map comprises removing a cluster defect from the map.

12. The method of claim 1, wherein updating the mark for the corresponding location in the map to indicate a true defect comprises marking the corresponding location as a “

TRUE DEFECT”

on said map.

13. The method of claim 1, wherein the pixel defect criteria comprises minimum and maximum threshold values for the pixel output signals.

14. The method of claim 1, wherein the method is performed during use of an imager device.

15. The method of claim 1, wherein the pixel defect criteria comprises a minimum deviation in the pixel output signal for each pixel from the pixel output signals of pixels surrounding the pixel.

16. A method of operating an imager device comprising:

saving a pre-trigger pixel defect map having a location for each of a plurality of pixel sensors in an imager device;

perceiving a triggering event;

subsequently obtaining at least one pixel output signal from a pixel-under-test associated with a first location in said map;

determining whether a pixel defect cluster is currently detected at the location for the pixel-under-test; and

updating the pre-trigger defect map after the triggering event with data created based on the act of determining if a pixel defect cluster is detected, wherein if a pixel defect cluster is detected at the location, said updating comprises determining a type of the pixel defect cluster, removing a cluster defect from the map if it is determined that the type of the pixel defect cluster is different than a type of defect cluster associated with the location in the pre-trigger defect map.

17. The method of claim 16, wherein the pre-triggering event comprises a change in an imaged scene.

18. The method of claim 16, wherein the pre-triggering event comprises sensing motion.

19. The method of claim 16, wherein if a pixel defect cluster is detected based on the at least one pixel output signal, said updating further comprises:

determining if the type was previously present at the location in the pre-trigger defect map.

20. The method of claim 16, wherein if a pixel defect cluster is not detected, determining if a cluster is sited at the location in the pre-trigger defect map.

21. The method of claim 19, wherein updating the pre-trigger defect map comprises marking a cluster defect as a “

TRUE DEFECT”

on the map if the type was previously present at the location in the pre-trigger defect map and the type matches the type of defect cluster associated with the location in the pre-trigger defect map.

22. The method of claim 16, further comprising comparing a pixel output signal for the pixel-under-test to at least one pixel defect threshold value.

23. The method of claim 16, further comprising comparing a pixel output signal for the pixel-under-test to a pixel output signal for a plurality of neighboring pixels.

24. The method of claim 21, further comprising substituting values for the pixel output signal for at least one pixel marked “

TRUE DEFECT.”

25. An imager device comprising:

an array of pixel image sensors for creating a plurality of signals in response to an applied image;

a circuit for sensing a triggering event;

a memory for storing a pre-trigger pixel defect map, the map having data on a plurality of locations, each location corresponding a pixel image sensor in the array; and

a circuit for obtaining a plurality of pixel output signals for a first location and at least one neighboring location of a pixel image sensor array, determining whether a pixel defect cluster exists at the first location, comparing data in the pre-trigger pixel defect map associated with the first location and the at least one neighboring location to current data based on the obtained pixel output signals, and updating the pixel defect map based on the determination of whether a pixel defect cluster exists at the first location, wherein the updating comprises determining a type of the pixel defect cluster, removing a cluster defect from the map if it is determined that the type of the pixel defect cluster is different than a type of the defect cluster associated with the location in the pre-trigger defect map.

26. The imager device of claim 25, wherein the circuit is also constructed for determining whether a pixel cluster defect currently exists for each location of the map.

27. The imager device of claim 25, wherein the circuit is also constructed for determining if the type was previously present at the location in the pre-trigger defect map if a pixel defect cluster exists at the location.

28. The imager device of claim 27, wherein the circuit is also constructed for marking a defect cluster as a true cluster when it is determined during the comparison that the cluster has the same characteristics as found in the pre-trigger map data for the location.

29. The imager device of claim 25, wherein the pre-triggering event comprises a change in an imaged scene.

30. The imager device of claim 25, wherein the circuit for sensing the pre-triggering event comprises a motion sensor.

31. The imager device of claim 26, wherein for each pixel image sensor, the data in the pre-trigger defect map includes data related to:

pixel sensor location, pixel defect type, and pixel cluster information.

32. The imager device of claim 25, wherein the memory for storing a pre-trigger pixel defect map also stores criteria for determining whether a pixel defect exists at each pixel sensor location in the array.

33. A camera system, comprising:

an array of image sensors for creating a plurality of signals in response to an applied image;

a memory for storing a pixel defect map, the map having data on a plurality of image sensors in the array; and

a pixel signal processor for processing said pixel output signals,

wherein the processor is designed for;

using the pixel output signals to locate current pixel defects in accordance with pixel defect criteria;

for every current pixel defect;

if the corresponding location in the stored pixel defect map was previously marked as defective, comparing saved data for the corresponding location in the stored pixel defect map to current data of said respective current pixel defect, updating the mark for the corresponding location in the map to indicate a true defect if the compared saved data is the same as the compared current data, and removing the defect mark for the corresponding location in the map if the compared saved data is different from the compared current data; and

if the corresponding location in the map was not previously marked as defective, marking the corresponding location in the map as defective; and

storing the pixel defect map if updates were made to the pixel defect map.

34. The camera system of claim 33, wherein the processor is further designed for determining current cluster defect locations.

35. The camera system of claim 34, wherein the pixel defect map is stored in a non-volatile memory element on a chip with the image sensor array.

36. The camera system of claim 34, wherein the defect map is stored in a volatile memory element on a chip with the image sensor array.

37. The camera system of claim 33, wherein the processor is designed for automatically repeating a pixel defect map update process on a pixel-by-pixel basis for each pixel in the image sensor array.

38. The camera system of claim 33, wherein the memory further stores the pixel defect criteria.

39. The camera system of claim 38, wherein the pixel defect criteria includes a bright and a dark pixel output signal threshold value.

40. The camera system of claim 33, further comprising a motion sensor circuit.