Dark-emulation image sensor

Patent metadata

Field	Value
Publication number	US-10356350-B2
Application number	US-201816051344-A
Country	US
Kind code	B2
Filing date	Jul 31, 2018
Priority date	Feb 7, 2014
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

Photocharge is accumulated within an image sensor pixel array during a first exposure interval. At conclusion of the first exposure interval, accumulated photocharge is discarded from a first subset of the pixels to emulate absence of incident light with respect to those pixels. After discarding accumulated photocharge from the first subset of the pixels, first and second readout signals are generated, the first readout signals corresponding to respective pixels not included in the first subset and indicative of photocharge accumulated therein, and the second readout signals corresponding to respective pixels included in the first subset.

First claim

What is claimed is:

1. A method of operation within an integrated-circuit image sensor, the method comprising:
accumulating photocharge within an array of pixels during a first exposure interval;
at conclusion of the first exposure interval, discarding accumulated photocharge from a first subset of the pixels to emulate absence of incident light with respect to the first subset of the pixels; and
after discarding accumulated photocharge from the first subset of the pixels, generating (i) first readout signals corresponding to respective pixels not included in the first subset and indicative of photocharge accumulated therein, and (ii) second readout signals corresponding to respective pixels included in the first subset.

2. The method of claim 1 further comprising:
accumulating photocharge within the array of pixels during a second exposure interval;
at conclusion of the second exposure interval, discarding accumulated photocharge from a second subset of the pixels to emulate absence of incident light with respect to the second subset of the pixels, the second subset of the pixels including pixels not included in the first subset of the pixels; and
after discarding accumulated photocharge from the second subset of the pixels, generating (i) third readout signals corresponding to respective pixels not included in the second subset and indicative of photocharge accumulated therein, and (ii) fourth readout signals corresponding to respective pixels included in the second subset.

3. The method of claim 1 wherein the array of pixels comprises pixels arranged in rows and columns and wherein discarding accumulated photocharge from the first subset of the pixels comprises discarding photocharge from one or more pixels disposed at selected columns within a first row of the array of pixels, and wherein generating the first and second readout signals comprises concurrently generating (i) respective first readout signals corresponding to the one or more pixels disposed at the selected columns within the first row of the array of pixels and (ii) respective second readout signals corresponding to pixels within the first row other than the one or more pixels disposed at the selected columns.

4. The method claim 3 wherein discarding photocharge from one or more pixels disposed at selected columns within the first row of the array of pixels comprises pseudo-randomly selecting the one or more pixels disposed at selected columns within the first row after conclusion of an exposure interval that precedes the first exposure interval.

5. The method of claim 3 wherein discarding photocharge from one or more pixels disposed at selected columns within the first row of the array of pixels comprises selecting, as the one or more pixels disposed at selected columns within the first row, at least one pixel within each of a plurality of sets of M contiguous pixels.

6. The method of claim 3 wherein discarding photocharge from one or more pixels disposed at selected columns within the first row of the array of pixels comprises exclusively selecting, as the one or more pixels disposed at selected columns within the first row, pixels associated with a green color filter element.

7. The method of claim 1 wherein discarding accumulated photocharge from the first subset of the pixels comprises:
transferring photocharge accumulated within respective photodetectors of the pixels of the first subset to respective floating diffusion nodes associated with the pixels of the first subset; and
switchably coupling the respective floating diffusion nodes associated with the pixels of the first subset to a reset voltage node to remove the photocharge from the respective floating diffusion nodes.

8. The method of claim 7 wherein the pixels of the first subset comprise at least one pixel disposed in a first row of pixels within the pixel array, the first row of pixels additionally including a plurality of pixels not included within the first subset, and wherein switchably coupling the respective floating diffusion nodes associated with the pixels of the first subset to the reset voltage node comprises switchably coupling a floating diffusion node associated with the at least one pixel to the reset voltage node concurrently with switchably coupling to the reset voltage node other floating diffusion nodes associated with the plurality of pixels not included with the first subset.

9. The method of claim 8 wherein generating the second readout signals comprises generating a correlated double sample readout signal with respect to each of the plurality of pixels within the first row not included in the first subset.

10. The method of claim 9 wherein generating the correlated double sample readout signal with respect to each of the plurality of pixels within the first row not included in the first subset comprises, for a first pixel of the plurality of pixels within the first row not included in the first subset:
generating a reset-level readout signal indicative of a reset state of the floating diffusion node associated with the first pixel after switchably coupling the floating diffusion node associated with the first pixel to the reset voltage node;
transferring accumulated photocharge from the photodetector of the first pixel to the floating diffusion node associated with the first pixel; and
generating a photocharge readout signal indicative of the accumulated photocharge transferred from the photodetector of the first pixel to the floating diffusion node associated with the first pixel.

11. An integrated-circuit image sensor comprising:
an array of pixels to accumulate photocharge during a first exposure interval; and
control circuitry coupled to the array of pixels to:
discard, at conclusion of the first exposure interval, accumulated photocharge from a first subset of pixels within the array to emulate absence of incident light with respect to the first subset of pixels; and
generate, after discarding accumulated photocharge from the first subset of pixels, (i) first readout signals corresponding to respective pixels within the array not included in the first subset and indicative of photocharge accumulated therein, and (ii) second readout signals corresponding to respective pixels included in the first subset.

12. The integrated-circuit image sensor of claim 11 wherein the array of pixels are further to accumulate photocharge during a second exposure interval, and wherein the control circuitry is further to:
discard, at conclusion of the second exposure interval, accumulated photocharge from a second subset of pixels within the array to emulate absence of incident light with respect to the second subset of pixels, the second subset of pixels including pixels not included in the first subset of pixels; and
generate, after discarding accumulated photocharge from the second subset of pixels, (i) third readout signals corresponding to respective pixels within the array not included in the second subset and indicative of photocharge accumulated therein, and (ii) fourth readout signals corresponding to respective pixels included in the second subset.

13. The integrated-circuit image sensor of claim 11 wherein the array of pixels comprises pixels arranged in rows and columns and wherein the control circuitry to discard accumulated photocharge from the first subset of pixels comprises circuitry to discard photocharge from one or more of the pixels disposed at selected columns within a first row of the array of pixels, and wherein the control circuitry to generate the first and second readout signals comprises circuitry to concurrently generate (i) respective first readout signals correspondin

Assignees

• Rambus Inc

Inventors

• Guidash Michael
• Endsley Jay
• Ladd John
• Vogelsang Thomas
• Smith Craig M

Classifications

• H04N25/617 Primary

  for reducing electromagnetic interference, e.g. clocking noise · CPC title

• H04N25/76 Primary

  Addressed sensors, e.g. MOS or CMOS sensors · CPC title

• H04N25/583 Primary

  with different integration times · CPC title

• H04N5/378

  Electricity · mapped topic

• H04N5/3765

  Electricity · mapped topic