System and method for detecting and correcting defective pixels in a digital image sensor

• US 20060126127A1
• Filed: 12/09/2004
• Published: 06/15/2006
• Est. Priority Date: 12/09/2004
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Zhang, Xuemei, Kakarala, Ramakrishna, Ying, Bond Yu Pong, Stanback, John H.
• Granted Patent: US 7,460,688 B2
• Time in Patent Office: Days
• US Class Current: 358/474
• CPC Class Codes: H04N 25/68 applied to defects

Abstract

A digital image sensor comprising an array of pixels and a processor is provided. The array of pixels comprises a current pixel in a first color plane that is configured to produce a current sensor value, a first plurality of pixels in the first color plane that is configured to produce a first plurality of sensor values, and a second plurality of pixels in the second color plane that is configured to produce a second plurality of sensor values. The processor is configured to generate a plurality of estimate values using the first plurality of sensor values and a plurality of intensity ratios associated with the second plurality of sensor values, and the processor is configured to determine whether the current pixel is defective using the plurality of estimate values and the current sensor value.

Claims

1. A digital image sensor comprising:

an array of pixels comprising a current pixel in a first color plane that is configured to produce a current sensor value, a first plurality of pixels in the first color plane that is configured to produce a first plurality of sensor values, and a second plurality of pixels in the second color plane that is configured to produce a second plurality of sensor values; and

a processor configured to generate a plurality of estimate values using the first plurality of sensor values and a plurality of intensity ratios associated with the second plurality of sensor values, and the processor configured to determine whether the current pixel is defective using the plurality of estimate values and the current sensor value.

2. The digital image sensor of claim 1 wherein the processor is configured to generate each of the plurality of estimate values by multiplying one of the first plurality of sensor values by one of the plurality of intensity ratios.

3. The digital image sensor of claim 1 wherein the processor is configured to generate each of the plurality of intensity ratios by dividing a first value generated from a first set of the second plurality of sensor values by a second value generated from a second set of the second plurality of sensor values.

4. The digital image sensor of claim 3 wherein the first value is selected from a first group consisting of a mean, a mean where extreme values are excluded, and a median generated from the first set of the second plurality of sensor values, and wherein the second value is selected from a second group consisting of a mean, a mean where extreme values are excluded, and a median generated from the second set of the second plurality of sensor values.

5. The digital image sensor of claim 1 wherein the processor is configured to replace the current sensor value with one of the plurality of estimate values in response to determining that the current pixel is defective.

6. The digital image sensor of claim 5 wherein the one of the plurality of estimate values is selected from a group consisting of a mean value, a mean value where extreme values are excluded, and a median value of the plurality of estimate values.

7. The digital image sensor of claim 1 wherein the processor is configured to compute a threshold value from the plurality of estimate values, and wherein the processor is configured to determine whether the current pixel is defective using the threshold value.

8. The digital image sensor of claim 1 wherein the processor is configured to compute a minimum value of the plurality of estimate values and a maximum value of the a plurality of estimate values, and wherein the processor is configured to determine whether the current pixel is defective using the minimum value and the maximum value.

9. The digital image sensor of claim 1 further comprising:

a buffer configured to receive the current sensor value, the first plurality of sensor values, and the second plurality of sensor values from the array, the buffer configured to provide the current sensor value, the first plurality of sensor values to the processor, and the second plurality of sensor values to the processor.

19. The system of claim 3 wherein the first value is selected from a first group consisting of a mean, a mean where extreme values are excluded, and a median generated from the first set of the second plurality of sensor values, and wherein the second value is selected from a second group consisting of a mean, a mean where extreme values are excluded, and a median generated from the second set of the second plurality of sensor values.

20. The system of claim 1 wherein the digital image system is configured to replace the current sensor value with one of the plurality of estimate values in response to determining that the current pixel is defective.

10. A method for detecting a defective pixel in an array of pixels comprising a current pixel in a first color plane that is configured to produce a current sensor value, a first plurality of pixels in a second color plane that is configured to produce a first plurality of sensor values, and a second plurality of pixels in the first color plane that is configured to produce a second plurality of sensor values, the method comprising:

generating a plurality of estimate values using the first plurality of sensor values and a plurality of intensity ratios associated with the second plurality of sensor values; and

determining whether the current pixel is defective using the plurality of estimate values and the current sensor value.

11. The method of claim 10 further comprising:

generating each of the plurality of estimate values by multiplying one of the first plurality of sensor values by one of the plurality of intensity ratios.

12. The method of claim 10 further comprising:

computing the plurality of intensity ratios by dividing a first value generated from a first set of the second plurality of sensor values by a second value generated from a second set of the second plurality of sensor values.

13. The method of claim 12 wherein the first value is selected from a first group consisting of a mean, a mean where extreme values are excluded, and a median generated from the first set of the second plurality of sensor values, and wherein the second value is selected from a second group consisting of a mean, a mean where extreme values are excluded, and a median generated from the second set of the second plurality of sensor values.

14. The method of claim 10 further comprising:

replacing the current sensor value with one of the plurality of estimate values in response to determining that the current pixel is defective.

15. The method of claim 14 wherein the one of the plurality of estimate values is selected from a group consisting of a mean value, a mean value where extreme values are excluded, and a median value of the plurality of estimate values.

16. The method of claim 10 further comprising:

computing a minimum value of the plurality of estimate values and a maximum value of the a plurality of estimate values; and

determining whether the current pixel is defective using the minimum value and the maximum value.

17. A system comprising:

a digital image system having an array of pixels arranged in rows and columns, the array of pixels comprising a current pixel in a first color plane that is configured to produce a current sensor value associated with an image, a first plurality of pixels in the first color plane that is configured to produce a first plurality of sensor values associated with the image, and a second plurality of pixels in a second color plane that is configured to produce a second plurality of sensor values associated with the image, the digital image system configured to compute a plurality of estimate values using the first plurality of sensor values and a plurality of intensity ratios associated with the second color plane, and the digital image system configured to determine whether the current pixel is defective using the plurality of estimate values and the current sensor value; and

a processing system configured to receive the image from the digital image system.

18. The system of claim 17 wherein the digital image system is configured to generate each of the plurality of intensity ratios by dividing a first value generated from a first set of the second plurality of sensor values by a second value generated from a second set of the second plurality of sensor values.