Image sensor with flexible pixel summing

• US 9,319,611 B2
• Filed: 03/14/2013
• Issued: 04/19/2016
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Fan, Xiaofeng
• Primary Examiner(s): Sohn, Seung C
• Application Number:
  US13/830,748
• Publication Number:
  US 20140263951A1
• Time in Patent Office: 1,132 Days
• Field of Search: 250/208.1, 348/308
• US Class Current: 1/1
• CPC Class Codes: H04N 25/46 by combining or binning pixels
• CPC Class Codes: H04N 25/57 Control of the dynamic range
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array

Abstract

An image sensor can include pixels that are grouped into subsets of pixels, with each subset including three or more pixels. A method for asymmetrical high dynamic range imaging can include capturing an image of a subject scene using a single integration time for all of the pixels. In a subset of pixels, charge in N pixels is read out and summed together. N represents a number that is between two and one less than a total number of pixels in the subset. Un-summed charge is read out from one pixel in the subset. The un-summed charge and the summed charge are combined when producing a high dynamic range image.

Claims

1. A method for performing flexible pixel summing in an image sensor that includes a plurality of pixels grouped into subsets of pixels with each subset of pixels including three or more pixels operably connected to a separate common node, the method comprising:

in a subset of pixels, selecting, in real time and based on one or more criterion, N pixels to include in a summing operation, where N represents a number that is between two and a total number of pixels in the subset of pixels;

summing charge in the N pixels together by transferring the charge from the N pixels to the common node; and

reading out the summed charge from the common node.

2. The method as in claim 1, wherein the summed charge on the common node represents one color.

3. The method as in claim 1, wherein the summed charge on the common node represents two or more colors.

4. A method for asymmetrical high dynamic range imaging using an image sensor that includes a plurality of pixels, wherein the pixels are grouped into subsets of pixels and each subset includes three or more pixels, the method comprising:

capturing an image of a subject scene using a single integration time for the plurality of pixels; and

in a subset of pixels, reading out charge from N pixels selected from the subset and summing the charge together, wherein selection is based, at least in part, on one or more criterion and wherein N represents a number that is between two and one less than a total number of pixels in the subset of pixels;

reading out un-summed charge from one pixel in the subset of pixels; and

combining the un-summed charge with the summed charge when producing a high dynamic range image.

5. The method as in claim 4, wherein the summed charge is associated with one color.

6. The method as in claim 4, wherein the summed charge is associated with two or more colors.

7. The method as in claim 4, further comprising selecting which N pixels in the subset of pixels to sum prior to summing the charge in the N pixels together.

8. The method as in claim 7, wherein the selected N pixels are associated with one color.

9. A method for asymmetrical high dynamic range imaging using an image sensor that includes a plurality of pixels grouped into subsets of pixels and each subset includes three or more pixels operably connected to a separate common node, the method comprising:

capturing an image of a subject scene using a single integration time for the plurality of pixels; and

in a subset of pixels, summing charge in N pixels together by transferring the charge from the N pixels to the common node, wherein the N pixels are selected in real time based, at least in part, on one or more criterion and wherein N represents a number that is between two and one less than a total number of pixels in the subset of pixels;

reading out the summed charge from the common node;

reading out un-summed charge from one pixel in the subset of pixels; and

combining the un-summed charge with the summed charge when producing a high dynamic range image.

10. The method as in claim 9, wherein the summed charge on the common node is associated with one color.

11. The method as in claim 9, wherein the summed charge on the common node is associated with two or more colors.

12. The method as in claim 9, further comprising selecting which N pixels in the subset of pixels to sum prior to summing the charge in the N pixels together.

13. An image sensor, comprising:

an imaging area that includes a plurality of pixels, wherein the pixels are grouped into subsets of pixels with each subset including three or more pixels operably connected to a separate common node; and

a processor for selecting N pixels to include in a summing operation, the pixels being selected in real time and based, at least in part, on one or more criterion.

14. The image sensor as in claim 13, further comprising readout circuitry operably connected to each common node.

15. The image sensor as in claim 13, wherein each readout circuitry operably connected to each common node includes a sense region operably connected to the common node and a readout transistor having a gate connected to the sense region.

16. The image sensor as in claim 13, wherein where N represents a number that is between two and a total number of pixels in a subset of pixels.

17. The image sensor as in claim 13, wherein where N represents a number that is between two and one less than a total number of pixels in a subset of pixels.

18. The image sensor as in claim 13, wherein each pixel includes a photodetector and a transfer transistor, wherein the transfer transistor is connected between the photodetector and a respective common node.

19. The image sensor as in claim 18, wherein a sense region is connected to each common node.

20. The image sensor as in claim 13, wherein the one or more criterion comprises one or more of:

lighting conditions;

filter elements in a color filter array; and

image resolution.