High dynamic range imaging pixels with multiple exposures

Patent metadata

Field	Value
Publication number	US-10356344-B1
Application number	US-201816008221-A
Country	US
Kind code	B1
Filing date	Jun 14, 2018
Priority date	Jun 14, 2018
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

Image sensors may have high dynamic range (HDR) functionality. To implement the high dynamic range functionality, the image sensor may use multiple exposure imaging. In multiple exposure imaging, multiple images are captured with an image sensor at different exposure times and are later combined into a single high dynamic range image. Image data from one or more exposures in a multi-exposure imaging scheme may be used to determine that subsequent exposures will not produce useful information. To conserve power in the image sensor, certain readout circuitry such as analog-to-digital converter circuitry and column memory may be disabled during readout of the exposures that are determined to not produce useful information.

First claim

What is claimed is:

1. An image sensor comprising:
a pixel array that includes rows and columns of imaging pixels, wherein the imaging pixels are configured to capture image data in an image frame using at least first and second exposures;
readout circuitry coupled to the pixel array, wherein the readout circuitry is configured to, for each exposure, read analog image data from the pixel array, convert the analog image data to digital image data, and output the digital image data; and
control circuitry configured to receive digital image data associated with the first exposure and selectively disable the readout circuitry during a readout of the second exposure based on the digital image data associated with the first exposure.

2. The image sensor defined in claim 1 , wherein the readout circuitry comprises a plurality of analog-to-digital converters and memory.

3. The image sensor defined in claim 1 , wherein the readout circuitry is configured to selectively disable the plurality of analog-to-digital converters and the memory during a readout of the second exposure based on the digital image data associated with the first exposure.

4. The image sensor defined in claim 3 , further comprising a buffer that is configured to receive the digital image data from the memory.

5. The image sensor defined in claim 3 , wherein portions of the memory that are disabled output a default value to the buffer.

6. The image sensor defined in claim 5 , further comprising processing circuitry that is configured to receive the digital image data from the buffer.

7. The image sensor defined in claim 6 , wherein the processing circuitry is configured to combine the digital image data from each exposure into a single high dynamic range image value.

8. The image sensor defined in claim 1 , wherein the control circuitry is configured to compare the digital image data associated with the first exposure to at least one threshold, and wherein the control circuitry is configured to selectively disable the readout circuitry during the readout of the second exposure based on a comparison of the digital image data associated with the first exposure to the at least one threshold.

9. The image sensor defined in claim 8 , wherein the digital image data associated with the first exposure comprises a plurality of digital image data values each associated with a respective imaging pixel and wherein the control circuitry is configured to compare each digital image data value to a threshold and disable the readout circuitry associated with the imaging pixel associated with the respective digital image data value if the digital image data value is less than the threshold.

10. The image sensor defined in claim 8 , wherein the digital image data associated with the first exposure comprises a plurality of digital image data values each associated with a respective imaging pixel and wherein the control circuitry is configured to compare each digital image data value to a threshold and disable the readout circuitry associated with the imaging pixel associated with the respective digital image data value if the digital image data value is greater than the threshold.

11. The image sensor defined in claim 8 , wherein the digital image data associated with the first exposure comprises a plurality of sets of digital image data values each associated with a respective subset of imaging pixels and wherein the control circuitry is configured to compare each set of the digital image data values to the at least one threshold and disable the readout circuitry associated with the subset of imaging pixels associated with the respective set of digital image data values based on the comparison.

12. A method of operating an image sensor with a plurality of imaging pixels, comprising:
obtaining image data for at least one imaging pixel of the plurality of imaging pixels in an exposure;
comparing the image data for the at least one imaging pixel to a threshold; and
disabling readout circuitry associated with the at least one imaging pixel for at least one subsequent exposure based on the comparison between the image data for the at least one imaging pixel and the threshold.

13. The method defined in claim 12 , wherein the exposure is longer than the at least one subsequent exposure, wherein comparing the image data for the at least one imaging pixel to the threshold comprises determining if the image data for the at least one imaging pixel is below the threshold, and wherein disabling the readout circuitry associated with the at least one imaging pixel for the at least one subsequent exposure based on the comparison between the image data for the at least one imaging pixel and the threshold comprises disabling the readout circuitry associated with the at least one imaging pixel for the at least one subsequent exposure in response to determining that the image data for the at least one imaging pixel is below the threshold.

14. The method defined in claim 13 , further comprising:
obtaining additional image data for at least one additional imaging pixel of the plurality of imaging pixels in the exposure;
comparing the additional image data for the at least one additional imaging pixel to the threshold; and
enabling readout circuitry associated with the at least one additional imaging pixel for the at least one subsequent exposure based on the comparison between the additional image data for the at least one additional imaging pixel and the threshold.

15. The method defined in claim 14 , wherein comparing the additional image data for the at least one additional imaging pixel to the threshold comprises determining if the additional image data for the at least one additional imaging pixel is below the threshold and wherein enabling the readout circuitry associated with the at least one additional imaging pixel for the at least one subsequent exposure based on the comparison between the additional image data for the at least one additional imaging pixel and the threshold comprises enabling the readout circuitry associated with the at least one additional imaging pixel for the at least one subsequent exposure in response to determining that the additional image data for the at least one imaging pixel is not below the threshold.

16. The method defined in claim 15 wherein the exposure is a first exposure and the at least one subsequent exposure includes a second exposure and a third exposure, the method further comprising:
obtaining second additional image data for the at least one additional imaging pixel of the plurality of imaging pixels in the second exposure;
comparing the second additional image data for the at least one additional imaging pixel to a second threshold; and
disabling readout circuitry associated with the at least one additional imaging pixel for the third exposure based on the comparison between the second image data for the at least one additional imaging pixel and the second threshold.

17. The method defined in claim 12 , wherein the exposure is shorter than the at least one subsequent exposure, wherein comparing the image data for the at least one imaging pixel to the threshold comprises determining if the image data for the at least one imaging pixel is above the threshold, and wherein disabling the readout circuitry associated with the at least one imaging pixel for the at least one subsequent exposure based on the comparison between the image data for the at least one imaging pixel and the threshold comprises disabling the readout circuitry associated with the at least one imaging pixel for the at least one subsequent exp

Assignees

• Semiconductor Components Ind Llc

Inventors

• Bowers Gabriel
• Hizume Koji

Classifications

• H04N25/709

  Circuitry for control of the power supply · CPC title

• H04N23/741

  by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors · CPC title

• H04N25/767

  Horizontal readout lines, multiplexers or registers · CPC title

• H04N23/651 Primary

  for reducing power consumption by affecting camera operations, e.g. sleep mode, hibernation mode or power off of selective parts of the camera · CPC title

• H04N25/589 Primary

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