Digital Camera Patent

Method and apparatus for producing calibration data for a digital camera

Digital Camera Patent Abstract

Producing calibration data (to remove vignetting, e.g., color-dependent vignetting) for a digital camera includes: arranging, in front of the camera, a white reference surface that is to be imaged; capturing, via the camera, a characteristic array of data corresponding to an image of the reference surface for each color that the camera can image; and manipulating each characteristic array to reduce a total amount of data representing the reference image.

Digital Camera Patent Claims

What is claimed is:

1. A method of producing calibration data for a digital camera, the method comprising: arranging, in front of said camera, a reference surface that is to be imaged; capturing, via said camera, a characteristic array of data corresponding to an image of said reference surface for each color that said camera can image; and doing to each characteristic array at least the following, dividing the characteristic array into a plurality of blocks, and determining a representative value for each block as a function of data within said block and without translation thereof to the frequency domain, and arranging the representative values as a reduced array.

2. The method of claim 1, wherein said manipulating is performed entirely by processing circuitry within said camera or entirely by a processor external to said camera.

3. The method of claim 1, wherein each block is the same size, and wherein said size is predetermined to substantially ensure less than about 1% variation in pixel magnitudes within each block.

4. The method of claim 3, wherein said size is one of 32.times.32 and 64.times.64.

5. The method of claim 1, further comprising: storing each characteristic array as a calibration array corresponding to said reference image.

6. The method of claim 5, wherein, for each calibration array, said storing also stores an indication of values to which parameters of said camera parameters were set when the respective characteristic arrays were captured.

7. The method of claim 6, wherein said parameters are zoom setting and aperture setting.

8. The method of claim 7, wherein said zoom setting can include the values wide, medium and telephoto, and said aperture can include two values A and B, and wherein said combinations are: wide zoom and aperture A; medium zoom and aperture A; telephoto zoom and aperture A; wide zoom and aperture B; medium zoom and aperture B; and telephoto zoom and aperture B.

9. The method of claim 1, the method further comprising: iteratively repeating the steps of arranging and capturing for a plurality of combinations of values to which parameters of said camera parameters are set when the respective characteristic arrays are captured.

10. The method of claim 9, wherein said parameters are zoom setting and aperture setting.

11. The method of claim 10, wherein said zoom setting can take the values wide, medium and telephoto, and said aperture can take two values A and B, and wherein said combinations are: wide zoom and aperture A; medium zoom and aperture A; telephoto zoom and aperture A; wide zoom and aperture B; medium zoom and aperture B; and telephoto zoom and aperture B.

12. The method of claim 1, wherein said camera can image a red array, a green array and a blue array.

13. A computer-readable medium having code portions embodied thereon that, when read by a processor, cause said processor to perform the method of claim 1.

14. A method of producing calibration data for a digital camera, the method comprising: arranging, in front of said camera, a reference surface that is to be imaged: capturing, via said camera, a characteristic array of data corresponding to an image of said reference surface for each color that said camera can image; and doing to each characteristic array at least the following, dividing the characteristic array into a plurality of blocks, and determining a representative value for each block as a function of data within said block, and arranging the representative values as a reduced array. wherein said determining includes at least the following, choosing a sub-block of data within the block; processing the pixel magnitudes within said block to achieve a result; and setting said representative value equal to the result.

15. The method of claim 14, wherein a size of said sub-block is 8.times.8.

16. The method of claim 14, wherein said sub-block is centered on the block.

17. The method of claim 14, wherein said processing is averaging and said result is the average.

18. The method of claim 14, wherein said processing includes: low pass filtering said pixel magnitudes within said block; and selecting the median value in the filtered data as said result.

19. A system of producing calibration data for a digital camera, the system comprising: a reference surface that is to be imaged; an imager to capture a characteristic array of data corresponding to an image of said reference surface for each color that said camera can image; and processing circuitry, present at least one of within said camera and external to said camera, to do to each characteristic array at least the following, divide the characteristic array into a plurality of blocks, determine a representative value for each block as a function of data within said block and without translation thereof to the frequency domain, and arrange the representative values as a reduced array.

20. The system of claim 19, wherein said imager can image a red array, a green array and a blue array.

21. The system of claim 19, wherein each block is the same size, and wherein said size is predetermined to substantially ensure less than about 1% variation in pixel magnitudes within each block.

22. The system of claim 21, wherein said size is one of 32.times.32 and 64.times.64.

23. The system of claim 19, further comprising: at least one memory the characteristic arrays as a calibration array corresponding to said reference image.

24. The system of claim 23, wherein, for each calibration array, indications of values to which parameters of said camera parameters were set when the respective characteristic arrays were captured are stored in said at least one memory.

25. The system of claim 24, wherein said parameters are zoom setting and aperture setting.

26. The system of claim 25, wherein said zoom setting can include the values wide, medium and telephoto, and said aperture can include two values A and B, and wherein said combinations are: wide zoom and aperture A; medium zoom and aperture A; telephoto zoom and aperture A; wide zoom and aperture B; medium zoom and aperture B; and telephoto zoom and aperture B.

27. The system of claim 19, wherein said imager and said processing circuitry are operable to iteratively capture and manipulate characteristic arrays for a plurality of combinations of values to which parameters of said camera parameters are set upon capture.

28. The system of claim 27, wherein said parameters are zoom setting and aperture setting.

29. The system of claim 28, wherein said zoom setting can take the values wide, medium and telephoto, and said aperture can take two values A and B, and wherein said combinations are: wide zoom and aperture A; medium zoom and aperture A; telephoto zoom and aperture A; wide zoom and aperture B; medium zoom and aperture B; and telephoto zoom and aperture B.

30. A system of producing calibration data for a digital camera, the system comprising: a reference surface that is to be imaged; an imager to capture a characteristic array of data corresponding to an image of said reference surface for each color that said camera can image; and processing circuitry, present at least one of within said camera and external to said camera, to do to each characteristic array at least the following, divide the characteristic array into a plurality of blocks. determine a representative value for each block as a function of data within said block, and arrange the representative values as a reduced array; wherein, when determining, said processing circuitry is operable to4 do at least the following, choose a sub-block of data within the block, process the pixel magnitudes within said block to achieve a result, and set said representative value equal to the result.

31. The system of claim 30, wherein a size of said sub-block is 8.times.8.

32. The system of claim 30, wherein said sub-block is centered on the block.

33. The system of claim 30, wherein, when processing, said processing circuitry is operable to average such that said result is the average.

34. The system of claim 30, wherein, when processing, said processing circuitry is operable to: low-pass filter said pixel magnitudes within said block; and select the median value in the filtered data as said result.

35. A method of producing calibration data for a digital camera, the method comprising: arranging, in front of said camera, a reference surface that is to be imaged; capturing, via said camera, a characteristic array of data corresponding to an image of said reference surface for each color that said camera can image; modeling the characteristic arrays with polynomial equations, respectively, the coefficients of the respective polynomial equations together representing a reduction in the total amount of data representing said reference image; and storing the coefficients of the respective polynomial equations, the stored coefficients of the respective polynomial equations representing respective calibration polynomials.

36. The method of claim 35, wherein said polynomial is at least a second order polynomial.

37. The method of claim 35, wherein said modeling includes processing the respective characteristic array via the MATLAB brand of mathematical analysis software.

38. The method of claim 35, further comprising: storing the polynomial coefficients as a calibration polynomial corresponding to said reference image.

39. The method of claim 35, wherein, for each calibration polynomial, said storing also stores an indication of values to which parameters of said camera parameters were set when the respective characteristic arrays were captured.

40. The method of claim 39, wherein said parameters are zoom setting and aperture setting.

41. The method of claim 40, wherein said