System and Method For Independent Image Sensor Parameter Control in Regions of Interest

• US 20090225189A1
• Filed: 03/05/2008
• Published: 09/10/2009
• Est. Priority Date: 03/05/2008
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Morin, Jeffrey L.
• Granted Patent: US 8,441,535 B2
• Time in Patent Office: Days
• US Class Current: 348/229.100
• CPC Class Codes: G03B 7/003 setting of both shutter and diaphragm G03B7/02 - G03B7/22 take precedence
• CPC Class Codes: H04N 25/44 by partially reading an SSIS array
• CPC Class Codes: H04N 25/443 by reading pixels from selected 2D regions of the array, e.g. for windowing or digital zooming
• CPC Class Codes: H04N 25/46 by combining or binning pixels

Abstract

An image sensing systems supports independently setting sensor parameters in two or more different regions of interest. In one implementation resolution, exposure time, and gain are independently selectable in each region of interest. Independently setting exposure time and gain in different regions of interest improves image recognition when there are large difference in the illumination of objects within an image. Independently setting resolution permits the resolution to be selectively increased in regions of interest requiring high resolution in order to reduce the pixel data bandwidth and processing requirements.

Claims

1. An image sensing system, comprising:

an image sensor having an array of pixels to capture images;

a controller to independently set image sensor parameters in a plurality of regions of interest with the controller selecting default image sensor parameters in other portions of the image outside of the plurality of regions of interest; and

a processor receiving image data from the image sensor, the processor identifying regions of interest and providing control signals to the image sensor to selectively adjust image sensor parameters in each of the plurality of regions of interest.

2. The image sensing system of claim 1, wherein the controller selects a minimum pixel resolution and a pixel exposure time across an image and independently sets a local pixel exposure time and pixel resolution in each region of interest.

3. The image sensing system of claim 2, wherein the controller selects resolution by selecting a pixel sub-sampling rate.

4. The image sensing system of claim 2, wherein a gain is selectively adjusted in each region of interest.

5. The image sensing system of claim 2, wherein a minimum pixel resolution is at least a factor of four lower than a maximum image sensor resolution for a region of interest.

6. The image sensing system of claim 2, wherein a minimum pixel resolution is at least a factor of ten lower than a maximum image sensor resolution for a region of interest.

7. The image sensing system of claim 2, wherein for a plurality of regions of interest each region of interest has gain, exposure time, and resolution independently selected based on an image recognition detection task.

8. The image sensing system of claim 7, wherein each image recognition detection task is a forward looking camera automobile detection task selected from the group consisting of pedestrian detection, headlight detection, stop light detection, road sign detection, license plate detection, brake light detection, and lane detection.

9. The image sensing system of claim 2 in combination with an infrared light source, the image sensor being sensitive to infrared light.

10. The image sensing system of claim 2, wherein exposure time in regions of interest is based on at least one of an average value or a histogram.

11. The image sensing system of claim 2, wherein resolution in a region of interest is iteratively increased in steps until an image recognition criterion is satisfied.

12. The image sensing system of claim 2, wherein resolution in a region of interest is increased from the minimum image resolution to the maximum image resolution.

13. An image sensing system, comprising:

an image sensor having an array of pixels to capture images and a controller to selectively adjust the pixel resolution and exposure time in regions of interest in response to a control signal;

the image sensor having a maximum achievable pixel resolution determined by the array of pixels with the image sensor providing pixel data at a reduced pixel resolution in areas outside of regions of interest to reduce an average data rate of pixel data output from the image sensor for processing.

14. The image sensing system of claim 13, wherein said image sensor sub-samples pixels in areas outside of regions of interest.

15. The image sensing system of claim 14, wherein said image sensor increases pixel resolution in a region of interest by selectively increasing the sub-sampling rate in the selected region of interest.

16. The image sensing system of claim 13, further comprising an image processor, the image processor receiving pixel data from the image sensor, analyzing images, and providing control signals to the image sensor to adjust pixel resolution and exposure time in regions of interest.

17. An image sensing system, comprising:

an image sensor having an array of pixels to capture images and including a controller to independently set a local pixel exposure time and pixel resolution in a plurality of regions of interest, the image sensor having a maximum achievable pixel resolution determined by the array of pixels with the image sensor providing pixel data at a reduced pixel resolution in areas outside of regions of interest to reduce an average data rate of pixel data output from the image sensor for processing; and

an image processor including image analysis modules to support a plurality of different automobile image recognition detection tasks, the image processor receiving image data from the image sensor, identifying regions of interest for the different image recognition detection tasks, determining adjustments to exposure time, resolution, and gain for each region of interest to perform a selected image recognition detection task, and providing control signals to the image sensor to selectively adjust the resolution and exposure time in each region of interest.

18. The image sensing system of claim 17, wherein the automobile image recognition detection tasks are selected from the group consisting of pedestrian detection, headlight detection, stop light detection, road sign detection, license plate detection, brake light detection, and lane detection.

19. An image sensing system to support forward-looking automobile camera applications under illumination conditions in which there is a large range of variation in light intensity from different objects in an image, comprising:

an image sensor having an array of pixels to capture images and including a controller to independently set a local pixel exposure time and gain in multiple regions of interest; and

an image processor including image analysis modules to support multiple different automobile image recognition detection tasks, the image processor receiving image data from the image sensor, identifying regions of interest for the different image recognition detection tasks, determining adjustments to exposure time and gain for each region of interest to perform a selected image recognition detection task, and providing control signals to the image sensor to selectively adjust the pixel exposure time and gain in each region of interest.

20. The image sensing system of claim 19, wherein the automobile image recognition detection tasks are selected from the group consisting of pedestrian detection, headlight detection, stop light detection, road sign detection, license plate detection, brake light detection, and lane detection.

21. A method of operating an image sensor, comprising:

identifying regions of interest in an image, each region of interest corresponding to an image recognition detection task;

for each region of interest, selecting a minimum pixel resolution, pixel exposure time, and pixel gain based on the corresponding image recognition detection task; and

adjusting the minimum pixel resolution, pixel exposure time, and pixel gain in each region of interest based on the selection.

22. The method of claim 21, further comprising selecting a pixel resolution in image areas outside of regions of interest to have a reduced pixel resolution.

23. The method of claim 21, wherein said adjusting is performed iteratively over a sequence of images until an image recognition criterion is satisfied for each region of interest.