High dynamic range image sensor with full resolution recovery

• US 9,413,992 B2
• Filed: 04/02/2014
• Issued: 08/09/2016
• Est. Priority Date: 05/20/2013
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Kuang, Jiangtao, Wu, Donghui, Wang, Chao, Funatsu, Eiichi
• Primary Examiner(s): Haskins, Twyler
• Assistant Examiner(s): Chiu, Wesley J
• Application Number:
  US14/243,480
• Publication Number:
  US 20140340553A1
• Time in Patent Office: 860 Days
• US Class Current: 1/1
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 25/581 acquired simultaneously
• CPC Class Codes: H04N 25/583 with different integration times
• CPC Class Codes: H04N 25/585 with pixels having different sensitivities within the sensor, e.g. fast or slow pixels or pixels having different sizes

Abstract

A method of reading pixel data from a pixel array includes exposing each one of a plurality of regions of pixels a respective exposure time. Pixel data is read from the plurality of regions of pixels. The pixel data is interpolated from a first one of the plurality of regions of pixels to determine the pixel data of the regions of pixels other than the first one of the plurality of regions of pixels to generate a first image having the first exposure time. The pixel data is interpolated from the second one of the plurality of regions of pixels to determine the pixel data of the regions of pixels other than the second one of the plurality of regions to generate a second image having the second exposure time. The images are combined to produce a high dynamic range image.

Claims

1. A method of reading pixel data from a pixel array including a plurality of pixels, wherein the plurality of pixels is organized into a plurality of regions of pixels arranged in a pattern in the pixel array, the method comprising:

exposing each one of a plurality of regions of pixels for a respective one of a plurality of exposure times;

reading pixel data from the plurality of regions of pixels;

for each respective one of the plurality of exposure times, determining an exposure ratio for each one of the plurality of regions of pixels, wherein the exposure ratio for each one of the plurality of regions of pixels for each respective one of the plurality of exposure times is equal to respective one of the plurality of exposure times divided by the exposure time for said one of the plurality regions of pixels;

for each respective one of the plurality of exposure times, substituting the pixel data for each one of the plurality of regions of pixels for which the exposure ratio is less than a first threshold with the pixel data from said one of the plurality of regions of pixels multiplied by the exposure ratio for said one of the plurality of regions of pixels to generate an image in a plurality of images for each respective one of the plurality of exposure times;

for each respective one of the plurality of exposure times, substituting the pixel data for each one of the plurality of regions of pixels for which the exposure ratio is greater than a second threshold with an interpolation of the pixel data from the one of the plurality of regions of pixels having said respective one of the plurality of exposure times to generate the image in the plurality of images for each respective one of the plurality of exposure times; and

combining the plurality of images to produce a high dynamic range image.

2. The method of claim 1 further comprising for each respective one of the plurality of exposure times, substituting the pixel data for each one of the plurality of regions of pixels for which the exposure ratio is greater than the first threshold and less than the second threshold with a combination of the pixel data from said one of the plurality of regions of pixels multiplied by the exposure ratio for said one of the plurality of regions of pixels and the interpolation of the pixel data from the one of the plurality of regions of pixels having said respective one of the plurality of exposure times.

3. The method of claim 1 wherein a pixel response of each one of the plurality of pixels in the pixel array is linear with respect to exposure time.

4. The method of claim 1 wherein said combining the plurality of images comprises performing a tone-mapping process on the plurality of images to compress a dynamic range of the high dynamic range image.

5. An imaging system, comprising:

a pixel array including a plurality of pixels, wherein the plurality of pixels is organized into a plurality of regions of pixels arranged in a pattern in the pixel array;

control circuitry coupled to the pixel array to control operation of the pixel array, wherein the control circuitry is coupled to expose each one of a plurality of regions of pixels for a respective one of a plurality of exposure times; and

readout circuitry coupled to the pixel array to readout pixel data from the plurality of regions of pixels, the imaging system coupled to;

for each respective one of the plurality of exposure times, determine an exposure ratio for each one of the plurality of regions of pixels, wherein the exposure ratio for each one of the plurality of regions of pixels for each respective one of the plurality of exposure times is equal to respective one of the plurality of exposure times divided by the exposure time for said one of the plurality regions of pixels;

for each respective one of the plurality of exposure times, substituting the pixel data for each one of the plurality of regions of pixels for which the exposure ratio is less than a first threshold with the pixel data from said one of the plurality of regions of pixels multiplied by the exposure ratio for said one of the plurality of regions of pixels to generate an image in a plurality of images for each respective one of the plurality of exposure times;

for each respective one of the plurality of exposure times, substitute the pixel data for each one of the plurality of regions of pixels for which the exposure ratio is greater than a second threshold with an interpolation of the pixel data from the one of the plurality of regions of pixels having said respective one of the plurality of exposure times to generate the image in the plurality of images for each respective one of the plurality of exposure times; and

combine the plurality of images to produce a high dynamic range image.

6. The imaging system of claim 5 further comprising function logic coupled to the readout circuitry to store high dynamic range image data readout from the plurality of pixels.

7. The imaging system of claim 5 wherein the imaging system is further coupled to, for each respective one of the plurality of exposure times, substitute the pixel data for each one of the plurality of regions of pixels for which the exposure ratio is greater than the first threshold and less than the second threshold with a combination of the pixel data from said one of the plurality of regions of pixels multiplied by the exposure ratio for said one of the plurality of regions of pixels and the interpolation of the pixel data from the one of the plurality of regions of pixels having said respective one of the plurality of exposure times.

8. The imaging system of claim 5 wherein a pixel response of each one of the plurality of pixels in the pixel array is linear with respect to exposure time.

9. The imaging system of claim 5 wherein the imaging system is further coupled to perform a tone-mapping process on the plurality of images to compress a dynamic range of the high dynamic range image to combine the plurality of images.