Determining exposure time in a digital camera

• US 8,675,122 B2
• Filed: 01/16/2009
• Issued: 03/18/2014
• Est. Priority Date: 01/16/2009
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kroepfl, Michael, Ponticelli, Martin Josef, Hegenbarth, Hannes, Kimchi, Gur, Curlander, John Charles
• Primary Examiner(s): LaBalle, Clayton E
• Assistant Examiner(s): Hancock, Dennis
• Application Number:
  US12/354,797
• Publication Number:
  US 20100182444A1
• Time in Patent Office: 1,887 Days
• Field of Search: 348/362, 396/213
• US Class Current: 348/362
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 23/90 Arrangement of cameras or camera modules, e.g. multiple cameras in TV studios or sports stadiums
• CPC Class Codes: H04N 25/46 by combining or binning pixels

Abstract

A digital camera described herein includes an analyzer component that analyzes a histogram of a first image, wherein the first image has a first resolution. The digital camera also includes a setter component that sets an exposure time for capturing a second image based at least in part upon the analysis of the histogram of the first image, wherein the second image has a second resolution, and wherein the first resolution of the first image is less than the second resolution of the second image.

Claims

1. A system comprising:

a processor; and

a memory that comprises a plurality of components that are executed by the processor, the plurality of components comprising;

a partitioner component that partitions a first image into partitions, wherein the first image is captured by an image sensor of a digital camera, the first image having a first resolution;

a weight assigner component that assigns respective weights to the partitions; and

a setter component that determines respective exposures times for the plurality of partitions based upon the respective weights, and sets an exposure time for capturing a second image by the image sensor of the digital camera based at least in part upon the respective exposure times, the second image having a second resolution, the second resolution being greater than the first resolution.

2. The system of claim 1, the plurality of components further comprising:

an analyzer component that analyzes a histogram of the first image, wherein the setter component further sets the exposure time for capturing the second image in the image sensor of the digital camera based at least in part upon the analysis of the histogram of the first image.

3. The system of claim 2, the plurality of components further comprising a histogram generator component that generates the histogram, wherein the histogram includes a plurality of different intensity values and a number of occurrences in the first image of the plurality of different intensity values.

4. The system of claim 3, wherein the analysis undertaken by the analyzer component comprises determining a white point value, wherein the white point value corresponds to an intensity value where a predefined percentage of bins have an intensity value no higher than the determined white point value.

5. The system of claim 4, wherein the setter component further sets the exposure time for capturing the second image based at least in part upon the determined white point value.

6. The system of claim 5, wherein the setter component further sets the exposure time for capturing the second image based at least in part upon an exposure time used to capture the first image.

7. The system of claim 6, wherein the setter component further sets the exposure time for capturing the second image based at least in part upon a binning factor used to cause the first image to be of the first resolution.

8. The system of claim 7, wherein the setter component further sets the exposure time for capturing the second image based at least in part upon a target gray value of the second image.

9. The system of claim 1, the plurality of components further comprising a configuration component that configures the digital camera to capture the first image at the first resolution.

10. The system of claim 9, the plurality of components further comprising a binner component that bins intensity values from cells in the image sensor to cause the first image to be of the first resolution.

11. The system of claim 1, wherein the setter component is configured to set an exposure time for the first image.

12. The system of claim 11, wherein the setter component is configured to set the exposure time for the first image at approximately ten microseconds.

13. A method comprising acts that are executed by at least one processor, the acts comprising:

capturing a first image using an image sensor of a digital camera, the first image having a first resolution;

partitioning the first image into at least a first partition and a second partition;

assigning a first weight to the first partition;

assigning a second weight to the second partition;

determining a first exposure time for the first partition;

determining a second exposure time for the second partition;

determining an exposure time for a second image based at least in part upon the first exposure time, the second exposure time, the first weight, and the second weight; and

capturing the second image using the image sensor of the digital camera using the determined exposure time, the second imaging having a second resolution, the second resolution greater than the first resolution.

14. The method of claim 13, wherein the second image is captured within twenty milliseconds of the first image being captured.

15. The method of claim 13, the acts further comprising using binning to cause the first image to be of the first resolution.

16. The method of claim 15, the acts further comprising setting an exposure time of ten microseconds for capturing the first image.

17. The method of claim 15, the acts further comprising:

generating a histogram that includes a number of occurrences of intensity of charges pertaining to a plurality of bins; and

further determining the exposure time for the second image based at least in part upon the histogram.

18. A camera comprising a computer-readable medium, the computer-readable medium comprising instructions that, when executed by a processor, cause the processor to perform acts comprising:

capturing a first image in an image sensor, the first image having a first resolution;

partitioning the first image into at least a first partition and a second partition;

assigning a first weight to the first partition;

assigning a second weight to the second partition;

determining a first exposure time for the first partition;

determining a second exposure time for the second partition; and

determining an exposure time for a second image based at least in part upon the first exposure time, the second exposure time, the first weight, and the second weight, the second image having a second resolution, the second resolution being higher than the first resolution; and

capturing the second image in the image sensor using the exposure time determined for the second image.

19. The camera of claim 18 comprised by a mobile telephone.

20. The camera of claim 18 configured to capture images of the second resolution at a frame rate between five and twenty five frames per second.