System and method for calibrating a camera

• US 20090027504A1
• Filed: 07/25/2007
• Published: 01/29/2009
• Est. Priority Date: 07/25/2007
• Status: Abandoned Application

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Lim, Suk Hwan, Chang, Nelson Liang An, Damera-Venkata, Niranjan
• Application Number:
  US11/880,933
• Publication Number:
  US 20090027504A1
• Time in Patent Office: Days
• US Class Current: 348/187
• CPC Class Codes: H04N 17/002 for television cameras

Abstract

A method of calibrating a camera includes capturing a set of dark images at each of a plurality of different exposure settings, thereby generating a plurality of sets of dark images. Each set of dark images is averaged, thereby generating a fixed pattern noise image corresponding to each one of the exposure settings. The method includes determining fixed pattern noise for at least one pixel of the camera based on an exposure setting of the camera and at least one of the fixed pattern noise images.

Claims

1. A method of calibrating a camera, comprising:

capturing a set of dark images at each of a plurality of different exposure settings, thereby generating a plurality of sets of dark images;

averaging each set of dark images, thereby generating a fixed pattern noise image corresponding to each one of the exposure settings; and

determining fixed pattern noise for at least one pixel of the camera based on an exposure setting of the camera and at least one of the fixed pattern noise images.

2. The method of claim 1, and further comprising:

determining an equation for each pixel of the camera for determining fixed pattern noise at that pixel as a function of exposure based on the fixed pattern noise images.

3. The method of claim 2, and further comprising:

removing fixed pattern noise from images captured by the camera based on the determined equations, thereby generating corresponding compensated images.

4. The method of claim 3, and further comprising:

measuring at least one characteristic of a projector in a multi-projector system based on the compensated images.

5. The method of claim 4, wherein the at least one characteristic comprises a gamma curve of the projector.

6. The method of claim 2, wherein the equation for each pixel comprises a polynomial equation.

7. The method of claim 6, wherein the polynomial equation is a cubic polynomial equation.

8. The method of claim 7, wherein the cubic polynomial equation comprises:

FPN(u,v)=a(u,v)+b(u,v)*e+c(u,v)*e²+d(u,v)*e³

where;

(u,v)=indices for identifying pixel location;

FPN(u,v)=value of fixed pattern noise for pixel (u,v);

a, b, c, and d=stored parameter values; and

e=exposure value.

9. The method of claim 2, wherein the equation for each pixel includes a plurality of parameter values, and wherein the parameter values are stored in a lookup table.

10. The method of claim 2, wherein the equation for each pixel includes a plurality of parameter values that are determined using a least squares technique.

11. The method of claim 1, and further comprising:

determining a transfer curve of the camera as a function of exposure.

12. The method of claim 11, and further comprising:

determining an offset value based on the transfer curve, wherein the offset value represents an amount that the transfer curve is offset from the origin along a y-axis; and

compensating images captured by the camera based on the offset value.

13. The method of claim 1, and further comprising:

storing the fixed pattern noise images;

identifying a current exposure setting of the camera; and

identifying at least one of the stored fixed pattern noise images based on the identified exposure setting.

14. The method of claim 13, and further comprising:

removing fixed pattern noise from an image captured by the camera based on the identified at least one fixed pattern noise image.

15. The method of claim 13, wherein the identified at least one fixed pattern noise image comprises a plurality of fixed pattern noise images, and wherein the method further comprises:

performing an interpolation operation on the plurality of fixed pattern noise images, thereby generating a fixed pattern noise image corresponding to the identified exposure setting.

16. A camera system, comprising:

a camera configured to capture a set of dark images at each of a plurality of different exposure settings, thereby generating a plurality of sets of dark images; and

a calibration unit configured to average each set of dark images, thereby generating an average image corresponding to each exposure setting, the calibration unit configured to use the average images to determine a set of values for each pixel of the camera for determining fixed pattern noise at that pixel as a function of exposure.

17. The camera system of claim 16, wherein the calibration unit is configured to remove fixed pattern noise from images captured by the camera based on the determined values for each pixel, thereby generating corresponding compensated images.

18. The camera system of claim 17, wherein the calibration unit is configured to measure at least one characteristic of a projector in a multi-projector system based on the compensated images.

19. The camera system of claim 16, wherein the determined set of values for each pixel comprise parameter values for use in a polynomial equation for determining fixed pattern noise as a function of exposure.

20. A computer-readable medium having computer-executable instructions for performing a method of determining fixed pattern noise contained in an image captured by a camera, the method comprising:

receiving an exposure value representing an exposure setting of the camera during the capture of the image;

receiving a plurality of sets of parameter values, each set of parameter values corresponding to one pixel of the camera; and

determining a fixed pattern noise value for each pixel of the camera based on the exposure value and the set of parameter values corresponding to the pixel.