Oversampled high dynamic-range image sensor

Patent metadata

Field	Value
Publication number	US-2017195596-A1
Application number	US-201515312778-A
Country	US
Kind code	A1
Filing date	May 21, 2015
Priority date	May 27, 2014
Publication date	Jul 6, 2017
Grant date	—

Abstract

In an integrated-circuit image sensor having a pixel array, a first subframe readout policy is selected from among a plurality of subframe readout policies, each of the subframe readout policies specifying a first number of subframes of image data to be readout from the pixel array for each output image frame and respective exposure durations for each of the first number of subframes of image data, wherein a shortest one of the exposure durations is uniform for each of the subframe readout policies. Each of the first number of subframes of image data is read out from the pixel array following the respective exposure durations thereof while applying a respective analog readout gain. The analog readout gain applied during readout of at least a first subframe of the first number of subframes is scaled according to a ratio of the shortest one of the exposure durations to the exposure duration of the first subframe.

First claim

1 . A method of operation within an integrated-circuit image sensor having a pixel array, the method comprising:
selecting, as a readout policy of the integrated-circuit image sensor, a first subframe readout policy from among a plurality of subframe readout policies, each of the subframe readout policies specifying a first number of subframes of image data to be readout from the pixel array for each output image frame and respective exposure durations for each of the first number of subframes of image data, wherein a shortest one of the exposure durations is uniform for each of the subframe readout policies; and reading out each of the first number of subframes of image data from the pixel array following the respective exposure durations thereof and while applying a respective analog readout gain, including scaling the analog readout gain applied during readout of at least a first subframe of the first number of subframes according to a ratio of the shortest one of the exposure durations to the exposure duration of the first subframe.

2 . The method of claim 1 further comprising summing image data read out of the pixel array for all but a second subframe of the first number of subframes to produce a composite subframe.

3 . The method of claim 2 further comprising comparing the summed image data of the composite subframe with image data read out of the pixel array for the second subframe to identify object motion within a scene represented by the summed image data and the image data read out for the second subframe.

4 . The method of claim 3 further comprising, summing the summed image data of the composite subframe with the image data read out for the second subframe to produce reconstructed image data corresponding to regions of the scene for which image data from the second subframe is below saturation and determined to lack object motion, and producing reconstructed image data corresponding to regions of the scene in which image data from the second subframe is saturated or object motion was identified without including the image data read out for the second subframe.

5 . The method of claim 2 wherein summing the image data read out of the pixel array for all but the second subframe comprises digitally scaling image data read out for the first subframe by a scaling factor based on the analog readout gain applied during readout of the first subframe.

6 . The method of claim 5 wherein digitally scaling the image data read out for the first subframe by a scaling factor based on the analog readout gain applied during readout of the first subframe comprises digitally scaling the image data read out for the first subframe by a scaling factor that is an inverse of the ratio of the shortest one of the exposure durations to the exposure duration of the first subframe.

7 . The method of claim 1 wherein selecting the first subframe readout policy from among the plurality of subframe readout policies comprises determining a brightness level of a scene to be captured by the integrated-circuit image sensor and selecting from among the plurality of subframe readout policies based at least in part on the brightness level.

8 . The method of claim 1 wherein, for each of the plurality of subframe readout policies, the respective exposure durations for each of the first number of subframes of image data transpire sequentially over a uniform frame interval.

9 . An integrated-circuit image sensor to generate one or more output images corresponding to a scene, the integrated-circuit image sensor comprising:
a pixel array; subframe policy selection circuitry to select, as a readout policy of the image sensor, a first subframe readout policy from among a plurality of subframe readout policies, each of the subframe readout policies specifying a first number of subframes of image data to be readout from the pixel array for each of the output images and respective exposure durations for each of the first number of subframes of image data, wherein a shortest one of the exposure durations is uniform for each of the subframe readout policies; and readout circuitry to read out each of the first number of subframes of image data from the pixel array following the respective exposure durations thereof and while applying a respective analog readout gain, the readout circuitry including gain control circuitry to scale the analog readout gain applied during readout of at least a first subframe of the first number of subframes according to a ratio of the shortest one of the exposure durations to the exposure duration of the first subframe.

10 . The integrated-circuit image sensor of claim 9 further comprising reconstruction circuitry to sum image data read out of the pixel array for all but a second subframe of the first number of subframes to produce a composite subframe.

11 . The integrated-circuit image sensor of claim 10 further wherein the reconstruction circuitry comprises logic to compare the summed image data of the composite subframe with image data read out of the pixel array for the second subframe to identify object motion within a scene represented by the summed image data and the image data read out for the second subframe.

12 . The integrated-circuit image sensor of claim 11 wherein the reconstruction circuitry further comprises logic to (i) sum the summed image data of the composite subframe with the image data read out for the second subframe to produce reconstructed image data corresponding to regions of the scene for which image data from the second subframe is below saturation and determined to lack object motion and (ii) produce reconstructed image data corresponding to regions of the scene in which image data from the second subframe is saturated or object motion was identified without including the image data read out for the second subframe.

13 . The integrated-circuit image sensor of claim 10 wherein the reconstruction circuitry to sum the image data read out of the pixel array for all but the second subframe comprises digital gain circuitry to digitally scale image data read out for the first subframe by a scaling factor based on the analog readout gain applied during readout of the first subframe.

14 . The integrated-circuit image sensor of claim 13 wherein the digital gain circuitry to digitally scale the image data read out for the first subframe by a scaling factor based on the analog readout gain applied during readout of the first subframe comprises circuitry to digitally scale the image data read out for the first subframe by a scaling factor that is an inverse of the ratio of the shortest one of the exposure durations to the exposure duration of the first subframe.

15 . The integrated-circuit image sensor of claim 9 wherein the subframe policy selection circuitry to select the first subframe readout policy from among the plurality of subframe readout policies comprises circuitry to select from among the plurality of subframe readout policies based at least in part on a brightness level determine a brightness level of the scene.

16 . The integrated-circuit image sensor of claim 9 wherein, for each of the plurality of subframe readout policies, the respective exposure durations for each of the first number of subframes of image data are to transpire sequentially over a uniform frame interval.

17 - 32 . (canceled)

33 . A method of operation within an integrated-circuit image sensor having a pixel array comprising multiple rows, the method comprising:
for a first image frame, operating each pixel array row in at least a subset of the multiple r

Assignees

• Rambus Inc

Inventors

• Vogelsang Thomas
• Smith Craig M

Classifications

• H04N25/583

  with different integration times · CPC title

• H04N25/70

  SSIS architectures; Circuits associated therewith · CPC title

• H04N25/46 Primary

  by combining or binning pixels · CPC title

• H04N25/589 Primary

  with different integration times, e.g. short and long exposures · CPC title

• H04N25/778

  comprising amplifiers shared between a plurality of pixels, i.e. at least one part of the amplifier must be on the sensor array itself · CPC title