Method, apparatus and system providing adjustment of pixel defect map

• US 9,781,365 B2
• Filed: 10/17/2013
• Issued: 10/03/2017
• 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): Haliyur, Padma
• Application Number:
  US14/056,447
• Publication Number:
  US 20140043506A1
• Time in Patent Office: 1,447 Days
• Field of Search: 348175, 348176, 348177, 348178, 348179, 348180, 348187, 348189, 348241, 348243, 348244, 348246, 348247, 348250, 348251
• 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 the pixel sensor array, wherein the pixel output signals represent an imaged scene;

using the pixel output signals to determine current defective pixel locations in accordance with pixel defect criteria and independent of the stored pixel defect map, wherein the current defective pixel locations correspond to a marking of “

DEFECT”

or “

TRUE DEFECT,”

checking whether a condition exists based on the pixel output signals and a predetermined threshold, wherein the condition represents a cause external to the imaged scene that affects detection of the defective pixel locations and whether the current defective pixel locations correspond to the “

TRUE DEFECT”

marking;

comparing the stored pixel defect map with the said current defective pixel locations;

determining if the stored pixel defect map needs adjusting by using the results of the comparison and the results of the determination of whether the condition exists; and

updating and storing the pixel defect map if adjusting is determined to be necessary.

2. The method of claim 1, wherein using, comparing, determining, and updating 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 of current defective pixel locations in accordance with pixel defect criteria and independent of the stored pixel defect map 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 1, 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, wherein the condition is at least one of a condition associated with one or more pixels reaching saturation, a condition associated with a dark pixel defect, or a condition associated with a bright pixel defect.

10. The method of claim 9, wherein the condition is a pixel reaching saturation.

11. The method of claim 1, wherein updating the pixel defect map comprises removing a cluster defect from the map if the comparison of data in the stored pixel defect map and current data are different.

12. The method of claim 1, wherein updating the pixel defect map comprises marking a pixel defect as a “

TRUE DEFECT”

on said map if the comparison of data in the stored pixel defect map and current data are the same.

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 trigger event;

subsequently obtaining at least one pixel output signal from a pixel-under-test associated with a first location in the map, wherein the at least one pixel output signal represents an imaged scene;

determining whether a true pixel defect cluster is currently detected at the location for the pixel-under-test, wherein determining whether a true pixel defect cluster is currently detected includes—

using the at least one output signal from the pixel-under test to determine whether a pixel defect cluster is currently detected at the location for the pixel-under-test independently from the saved pre-trigger pixel defect map, wherein the at least one output signal at the location corresponds to a marking of “

DEFECT”

or “

TRUE DEFECT”

, and

checking whether a condition exists based on the pixel output signals and a predetermined threshold, wherein the condition represents a cause external to the imaged scene that affects detection of the defective pixel locations; and

updating the pre-trigger defect map after the triggering event with the data created based on the act of determining if a true pixel defect cluster is detected and the results of the determination of whether the condition exists.

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, the method further comprises:

determining a type of the pixel defect cluster; and

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

20. 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 the pixel sensor array, wherein the pixel output signals represent an imaged scene;

using the pixel output signals to determine current defective pixel locations in accordance with pixel defect criteria and independent of the stored pixel defect map, wherein the current defective pixel locations correspond to a marking of “

DEFECT”

or “

TRUE DEFECT,”

checking whether a condition exists based on the pixel output signals and a predetermined threshold, wherein the condition represents a cause external to the imaged scene that affects detection of the defective pixel locations and whether the current defective pixel locations correspond to the “

TRUE DEFECT”

marking;

comparing the stored pixel defect map with the current defective pixel locations, wherein if a pixel defect cluster is not detected, the method further comprises determining if a cluster is sited at the location in the stored pixel defect map;

determining if the stored pixel defect map needs adjusting by using the results of the comparison and the results of the determination of whether the condition exists; and

updating and storing the pixel defect map if adjusting is determined to be necessary, wherein updating the pixel defect map comprises removing a cluster defect from the map if it is determined that the type of defect is different than a type of defect cluster associated with the location in the pixel defect map, or marking a cluster defect as the “

TRUE DEFECT”

on the map if it is determined that the type of defect is the same as a type of defect cluster associated with the location in the pixel defect map.