Hi-speed deterministic approach in detecting defective pixels within an image sensor

• US 6,381,357 B1
• Filed: 02/26/1999
• Issued: 04/30/2002
• Est. Priority Date: 02/26/1999
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Tan, Yap-Peng, Acharya, Tinku
• Primary Examiner(s): Mancuso, Joseph
• Assistant Examiner(s): Bali, Vikkram
• Application Number:
  US09/258,636
• Time in Patent Office: 1,159 Days
• Field of Search: 382/141-149, 358/482, 358/483, 358/406, 348/246, 348/247, 348/264
• US Class Current: 382/141
• CPC Class Codes: H04N 25/68 applied to defects

Abstract

What is disclosed is a method including downloading a sequence of images from an image sensor, and then marking on a map a pixel location of the sensor defective if a Defective Vote score exceeds a first threshold, the score tallied over all captured images. The defective pixel map is stored on a host computer, which performs the defective pixel detection on behalf of the sensor, rather than directly on the device incorporating the image sensor.

Claims

1. A method comprising:

downloading a sequence of images from an image sensor;

determining for each image of the sequence of images a minimum neighboring distance about a pixel by computing an absolute value of intensity value differences between said pixel location and each of a set of neighboring pixel locations in said each image and finding a minimum among said absolute value of intensity value differences, said minimum set to be the minimum neighboring distance; and

marking on a map the pixel location of said sensor defective if a Defective Vote score incorporating the minimum neighboring distance exceeds a first threshold, said score tallied over all said captured images, wherein incorporating the minimum neighboring distance includes increasing said Defective Vote score by one if said minimum neighboring distance exceeds a second threshold.

2. A method according to claim 1 wherein downloading includes:

connecting said sensor to a host computer; and

capturing said images using said sensor.

3. A method according to claim 2 wherein capturing of images includes increasing the exposure time of s aid sensor to a given scene when detecting Stuck Low defects.

4. A method according to claim 2 wherein capturing of images includes decreasing the exposure time of said sensor to a given scene when detecting Stuck High defects.

5. A method according to claim 1 wherein the neighborhood of said neighboring pixels is determined in accordance with the color plane association of said pixel location whose defectiveness is being determined.

6. A method according to claim 5 wherein said minimum is chosen not to be the lowest ranking difference.

7. A method according to claim 1 wherein said sensor is arranged in a Bayer pattern.

8. A method according to claim 1 wherein said first threshold is the number of images downloaded divided by a fixed number, said fixed number determined by the level of false positive and false negative rate.

9. A method according to claim 1 wherein said sensor is incorporated in a digital camera.

10. An article comprising a computer readable medium having

instructions stored thereon which when executed causes:

downloading a sequence of images from an image sensor;

determining for each image of the sequence of images a minimum neighboring distance about a pixel by computing an absolute value of intensity value differences between said pixel location and each of a set of neighboring pixel locations in said each image and finding a minimum among said absolute value of intensity value differences, said minimum set to be the minimum neighboring distance; and

marking on a map the pixel location of said sensor defective if a Defective Vote score incorporating the minimum neighboring distances exceeds a first threshold, said score tallied overall said captured images, wherein incorporating the minimum neighboring distance includes increasing said Defective Vote score by one if said minimum neighboring distance exceeds a second threshold.

11. An article according to claim 10 wherein said downloading is caused by:

connecting said sensor to a host computer; and

capturing said images using said sensor.

12. A system comprising:

a memory capable of storing instructions and data related to defective pixel detection;

a processor coupled to said memory, said processor adapted to execute said instructions and manipulate said data to determine which pixels of an image sensor are defective, said instructions including;

downloading a sequence of images from an image sensor;

determining for each image of the sequence of images a minimum neighboring distance about a pixel by computing an absolute value of intensity value differences between said pixel location and each of a set of neighboring pixel locations in said each image and finding a minimum among said absolute value of intensity value differences, said minimum set to be the minimum neighboring distance; and

marking on a map the pixel location of said sensor defective if a Defective Vote score incorporating the minimum neighboring distance exceeds a first threshold, said score tallied overall said captured images, wherein incorporating the minimum neighboring distance includes increasing said Defective Vote score by one if said minimum neighboring distance exceeds a second threshold.

13. A system according to claim 12 further comprising:

an image sensor providing data in the form of pixel intensity values, said sensor adapted to capture each said image.

14. A system according to claim 13, comprising:

a defective pixel location memory adapted to store locations of pixels determined defective.

15. A system according to claim 14 wherein image captures of said sensor are corrected in those pixel locations determined to be defective.