SYSTEM AND METHOD FOR IMAGE CORRECTION

• US 20100265358A1
• Filed: 04/01/2010
• Published: 10/21/2010
• Est. Priority Date: 04/16/2009
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: Ing, Elena, Takemoto, Sohei, He, Hu, Cabral, Brian
• Granted Patent: US 8,749,662 B2
• Time in Patent Office: Days
• US Class Current: 348/223.100
• CPC Class Codes: G06T 17/30 Polynomial surface description
• CPC Class Codes: H04N 17/00 Diagnosis, testing or measuring for television systems or their details
• CPC Class Codes: H04N 25/61 the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"

Abstract

A system and method for correcting image data. Embodiments of the present invention provide calibration and image correction to overcome various lens effects including lens shading and lens imperfections. In one embodiment, the correction of image data is performed via utilization of a spline surface (e.g., Bezier surface). The use of spline surfaces facilitates efficient hardware implementation. The image correction may be performed on a per channel and illumination type basis. In another embodiment, the present invention provides a method for determine a spline surface to be used for calibrating an image signal processor to be used in correcting image data.

Claims

1. A method of image signal processing, said method comprising:

receiving image data from an optical image sensor and wherein said image data comprises data for one or more color channels;

accessing a Bezier patch array, wherein said Bezier patch array comprises control points for each of said one or more color channels, wherein said control points define a surface which is a reciprocal function for correcting a lens shading distortion; and

utilizing said Bezier patch array with said image data to produce corrected image data.

2. A method as described in claim 1 wherein said Bezier patch array comprises patches of a bi-cubic Bezier form.

3. A method as described in claim 1 wherein said Bezier patch array comprises 100 control points and wherein said Bezier patch array comprises 9 patches.

4. A method as described in claim 1 wherein a portion of said control points are located on boundaries of a Bezier patch of said Bezier Patch array and are shared between Bezier patches.

5. A method as described in claim 1 wherein said optical sensor is a complementary metal-oxide-semiconductor (CMOS) sensor.

6. A method as described in claim 1 wherein said optical sensor is a charge-coupled device (CCD) sensor.

7. A method as described in claim 1 wherein said Bezier patch array comprises a respective Bezier surface for each color channel.

8. A method as described in claim 1 wherein said Bezier patch array comprises a respective Bezier surface for each illumination type.

9. A method as described in claim 8 wherein said illumination type is selected from the group consisting of:

tungsten, florescent and daylight.

10. A method of calibrating an image signal processor, said method comprising:

passing light from a uniform field through a lens;

sampling light passing through said lens with a digital optical sensor;

determining a plurality of reciprocal values for a plurality of sensor locations; and

determining a plurality of control points based on said reciprocal values, wherein said plurality of control points define a surface based on said plurality of reciprocal values and wherein said surface is operable to be used for correcting a subsequent image detected by said digital optical sensor using said lens.

11. A method as described in claim 10 wherein said surface is a Bezier surface comprising a plurality of patches.

12. A method as described in claim 10 wherein said Bezier surface is bi-cubic in form.

13. A method as described in claim 11 wherein a portion of said control points are located within a boundary of a Bezier patch of said Bezier surface and are shared between Bezier patches of said Bezier surface.

14. A method as described in claim 10 wherein said plurality of control points are determined on a per channel basis.

15. A method as described in claim 10 wherein said plurality of control points are determined on an illumination type basis.

16. A image signal processing system comprising:

an optical sensor operable to capture image data;

a processing unit operable to receive image data from said optical sensor and wherein said processing unit is operable to process said image data to correct for lens shading distortion based on a plurality of values defining a plurality of reciprocal surfaces;

a channel selector for selecting image data of a single color channel for said processing unit to receive; and

a memory operable to store said plurality of values wherein said plurality of reciprocal surfaces comprise a respective surface for each of a plurality of color channels.

17. A image signal processing system as described in claim 16 wherein said plurality of reciprocal surfaces comprise a respective surface for each of a plurality of lighting conditions.

18. A image signal processing system as described in claim 16 wherein said reciprocal surface is a Bezier surface.

19. A image signal processing system as described in claim 18 wherein said Bezier surface comprises a plurality of Bezier patches having one or more control points on a boundary of said plurality of Bezier patches and shared between two Bezier patches.

20. A image signal processing system as described in claim 16 wherein said processing unit is operable to correct said image data on a per color channel basis.