Method and apparatus for improving low-light performance for small pixel image sensors

• US 20080278591A1
• Filed: 05/09/2007
• Published: 11/13/2008
• Est. Priority Date: 05/09/2007
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Barna, Sandor L., Campbell, Scott P., Agranov, Gennady
• Granted Patent: US 8,462,220 B2
• Time in Patent Office: Days
• US Class Current: 348/216.1
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/76 by influencing the image signals
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

Method and apparatuses processing pixel values from a captured image include receiving an array of digital pixel values corresponding to a captured image, and computing a rolling sum of the array of pixel values. Computing a rolling sum includes selecting successive groupings of the pixel values, each grouping comprising N×M pixel values, summing pixel values in each of the successive groupings, and forming an output image using the summed pixel values.

Claims

1. A method of processing pixel values from a captured image, the method comprising:

receiving an array of digital pixel values corresponding to a captured image; and

computing a rolling sum of the array of pixel values,

wherein computing a rolling sum comprises;

selecting successive groupings of the pixel values, each grouping comprising N×

M pixel values;

summing pixel values in each of the successive groupings; and

forming an output image using the summed pixel values.

2. The method of claim 1, wherein the successive groupings of pixel values are displaced from an adjacent grouping of pixel values by one pixel value in a first direction of the array.

3. The method of claim 1, wherein the successive groupings of pixel values are displaced from an adjacent grouping of pixel values by one pixel value in a second direction of the array.

4. The method of claim 1, wherein the successive groupings of pixel values are displaced from an adjacent grouping of pixel values by more than one pixel value.

5. The method of claim 1, wherein the rolling sum is computed in response to a predetermined detected lighting condition.

6. The method of claim 1, wherein the rolling sum is computed in response to a predetermined lens characteristic.

7. The method of claim 1, wherein the rolling sum is computed in response to a predetermined detected noise condition.

8. The method of claim 1, wherein the array of pixel values comprises an array of monochromatic pixel values.

9. The method of claim 1, wherein the array of pixel values comprises an array of red, blue, and green pixel values.

10. The method of claim 1, wherein:

the array of pixel values comprises an array of demosaiced pixel values; and

the summing comprises separately summing same-color components within a grouping.

11. The method of claim 1, wherein the summing of pixel values comprises separately summing same-color pixel values within a grouping.

12. A method of reducing noise in a captured image comprising:

receiving an array of digital pixel values corresponding to a captured image;

selecting a first set of pixel values;

computing a first summed pixel value for the first set of pixel values;

selecting a second set of pixel values, the second set of pixel values differing from the first set of pixel values by location, number, pattern, shape, size, color component, or a combination of two or more of location, number, pattern, shape, size, or color component;

computing a second summed pixel value for the second set of pixel values; and

forming an output image using the summed pixel values.

13. An apparatus for processing pixel values in a captured image comprising:

a processing circuit configured to calculate a rolling sum of an array of digital pixel values corresponding to a captured image,

wherein calculating a rolling sum comprises;

selecting successive clusters of the pixel values, each cluster comprising N×

M pixel values;

summing pixel values in each of the successive clusters; and

forming an output image using the summed pixel values.

14. The apparatus of claim 13, wherein the successive clusters of pixel values are displaced from an adjacent cluster of pixel values by one pixel value in a first direction of the array.

15. The apparatus of claim 13, wherein the successive clusters of pixel values are displaced from an adjacent cluster of pixel values by one pixel value in a second direction of the array.

16. The apparatus of claim 13, wherein the successive clusters of pixel values are displaced from an adjacent cluster of pixel values by more than one pixel value.

17. The apparatus of claim 13, wherein the rolling sum is computed in response to a predetermined detected lighting condition.

18. The apparatus of claim 13, wherein the rolling sum is computed in response to a predetermined a lens characteristic.

19. The apparatus of claim 13, wherein the rolling sum is computed in response to a predetermined detected noise condition.

20. The apparatus of claim 13, wherein the array of pixel values comprises an array of monochromatic pixel values.

21. The apparatus of claim 13, wherein the array of pixel values comprises an array of red, blue, and green pixel values.

23. The apparatus of claim 13, wherein the summing of pixel values comprises separately summing same-color pixel values within a cluster.

22. (canceled)

24. An imaging system comprising:

a pixel array and readout circuit for capturing image data;

a receiving circuit configured to receive an array of digital pixel values corresponding to a captured image from the readout circuit; and

a processing circuit configured to;

select successive groupings of pixel values of the array of pixel values, each grouping comprising N×

M pixel values, where N and M are integers;

sum pixel values in each of the successive groupings; and

form an output image using the summed pixel values.

29. The imaging system of claim 24, wherein the imaging system comprises a digital camera.

30. The imaging system of claim 29, further comprising a lens for focusing an image on the pixel array.

25-28. -28. (canceled)