Correction of non-uniform sensitivity in an image array

• US 20060033005A1
• Filed: 08/11/2004
• Published: 02/16/2006
• Est. Priority Date: 08/11/2004
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Ovsiannikov, Ilia, Subbotin, Igor, Jerdev, Dmitri
• Granted Patent: US 7,609,302 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: H04N 25/61 the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"

Abstract

An improved non-uniform sensitivity correction algorithm for use in an imager device (e.g., a CMOS APS). The algorithm provides zones having flexible boundaries which can be reconfigured depending upon the type of lens being used in a given application. Each pixel within each zone is multiplied by a correction factor dependent upon the particular zone while the pixel is being read out from the array. The amount of sensitivity adjustment required for a given pixel depends on the type of lens being used, and the same correction unit can be used with multiple lenses where the zone boundaries and the correction factors are adjusted for each lens. In addition, the algorithm makes adjustments to the zone boundaries based upon a misalignment between the centers of the lens being used and the APS array.

Claims

1. An imager device, comprising:

a pixel array; and

a programmable sensitivity correction unit coupled to said pixel array for correcting sensitivity of at least one pixel in said pixel array, and wherein

said sensitivity correction unit is configured to be used with more than one type of lens useable with said pixel array.

2. The imager device of claim 1 further comprising:

a memory device coupled to said sensitivity correction unit for storing at least one correction value for correcting at least one corresponding pixel value.

3. The imager device of claim 2, wherein said memory device comprises at least one register.

4. The imager device of claim 1 further comprising:

a column bus coupling at least one pixel of said pixel array and said sensitivity correction unit.

5. The imager device of claim 4 further comprising:

a sample and hold circuit coupled to said sensitivity correction unit for receiving corrected pixel signals;

an analog-to-digital converter coupled to said sample and hold circuit for converting sampled corrected pixel signals to digital format; and

a pixel processor for processing said digital corrected pixel signals.

6. The imager device of claim 1, wherein said sensitivity correction unit is configured to apply correction values to said pixel signals, wherein the correction values are generated by dividing said pixel array into a plurality of zones, wherein

each of said plurality of zones contains more than one pixel;

and wherein

each pixel in a given zone requires a similar degree of sensitivity correcting.

7. The imager device of claim 6, wherein said correction values are generated by dividing said pixel array into a first number of zones when said pixel array is used with a first type of lens, wherein each of said first number of zones respectively contains a predetermined plurality of pixels of said pixel array.

8. The imager device of claim 7, wherein said correction values are generated by dividing said pixel array into a second number of zones different from said first number of zones, when said pixel array is used with a second type of lens different from said first type of lens, and wherein

each of said second number of zones respectively contains a predetermined plurality of pixels of said pixel array different from said pixels associated with said first number of zones.

9. The imager device of claim 7, wherein said first number of zones comprises eight zones in the x-direction and eight zones in the y-direction.

10. The imager device of claim 1, wherein said sensitivity correction unit is configured to correct for any misalignment between respective centers of said pixel array and a lens used with said pixel array.

11. The imager device of claim 1, wherein said imager device is incorporated onto an imager chip.

12. The imager device of claim 1, wherein said imager device comprises a CMOS imager.

13. The imager device of claim 1, wherein said imager device comprises a CCD imager.

14. The imager device of claim 1, wherein said sensitivity correction unit is configured to adjust a degree of correcting depending upon an amount of light received by said pixel array.

15. An imager device, comprising:

a pixel array; and

a programmable sensitivity correction unit coupled to said pixel array for applying a correction factor to at least one pixel signal read out from said pixel array, wherein said programmable sensitivity correction unit is programmable to be used with a plurality of different lenses capable of being used with said pixel array.

16. The imager device of claim 15, wherein said progammable sensitivity correction unit is configured to multiply at least one correction factor by said at least one pixel signal.

17. The imager device of claim 15, wherein said programmable sensitivity correction unit is configured to divide said pixel array into a plurality of zones and wherein boundaries of said plurality of zones are programmable depending upon a type of lens being used with said pixel array.

18. A method of correcting sensitivity of pixels of an imager device, the method comprising:

determining which of a plurality of types of lenses is being used with a pixel array;

programming a sensitivity correction unit used with said pixel array to correspond to a first type of lens being used with said pixel array, wherein said first type of lens is one of a plurality of types of lenses capable of being used with said pixel array and said sensitivity correction unit; and

correcting sensitivity of at least one pixel of said pixel array.

19. The method of claim 18 further comprising:

forwarding at least one corrected pixel signal to a sample and hold circuit;

converting an output of said sample and hold circuit to digital format; and

conducting further pixel processing of a digital version of said at least one corrected pixel signal.

20. The method of claim 18, wherein said act of determining comprises:

determining that a first type of lens, of a plurality of lenses capable of being used with said pixel array, is being used with said pixel array.

21. The method of claim 20, wherein said act of programming a sensitivity correction unit comprises:

dividing said pixel array into a first plurality of zones, said first plurality of zones being predetermined based upon said first type of lens being used, where each zone contains a plurality of pixels and where the pixels of each zone require a similar degree of sensitivity correction as compared with pixels of the other zones.

22. The method of claim 21 further comprising:

determining that a second type of lens different from said first type of lens, of said plurality of lenses capable of being used with said pixel array, is being used with said pixel array; and

dividing said pixel array into a second plurality of zones different from said first plurality of zones, said second plurality of zones being predetermined based upon said second type of lens being used, where each zone contains a plurality of pixels and where the pixels of each zone require a similar degree of sensitivity correction as compared with pixels of other zones.

23. The method of claim 18, wherein said act of programming comprises:

assigning respective correction function values to each pixel of said pixel array, wherein said respective correction function values correspond to said first type of lens.

24. The method of claim 23, wherein said act of assigning comprises:

storing an initial correction function value corresponding to at least a first pixel of said pixel array; and

storing a first derivative of said initial correction function value corresponding to a correction function value of at least a second pixel of said pixel array.

25. The method of claim 24 further comprising:

storing a first derivative of said correction function value of said at least a second pixel corresponding to a correction function value of at least a third pixel of said pixel array; and

storing a second derivative of said correction function value of said at least a second pixel corresponding to said correction function value of said at least a third pixel of said pixel array.

26. The method of claim 18, wherein said act of correcting further comprises:

multiplying a first pixel value being read out from a first pixel of said pixel array by a first correction function value corresponding to said first pixel.

27. The method of claim 18, wherein said act of correcting further comprises:

adjusting a degree of correcting depending upon an amount of light received by said pixel array.

28. The method of claim 21, wherein said act of dividing further comprises:

determining that respective centers of said first type of lens and said pixel array are misaligned; and

adjusting respective boundaries of said first plurality of zones based on the misalignment of the centers of the first type of lens and the pixel array.

29. A method of correcting sensitivity of pixels of an imager device, the method comprising:

determining which lens of a plurality of lenses capable of being used with a given pixel array is being used with said given pixel array;

programming a sensitivity correction unit for use with the lens being used with the pixel array;

reading out at least one pixel signal from a pixel array; and

applying a correction factor to at least one pixel signal read out from said pixel array.

30. The method of claim 29, wherein said act of applying comprises multiplying said at least one correction factor by said at least one pixel.

31. The method of claim 29 further comprising:

dividing said pixel array into a plurality of zones and wherein the correction factor applied to said at least one pixel signal depends on which zone said pixel signal was read from.

32. A method of forming an imager device, the method comprising:

coupling a programmable sensitivity correction unit to a pixel array for correcting sensitivity of at least one pixel in said pixel array, wherein said sensitivity correction unit is configured to be used with more than one type of lens useable with said pixel array.

33. The method of claim 32 further comprising:

coupling a storage device to said sensitivity correction unit for storing at least one correction value for correcting at least one pixel value.

34. A semiconductor chip, comprising:

a pixel array; and

a programmable sensitivity correction unit coupled to said pixel array for correcting sensitivity of at least one pixel in said pixel array, and wherein

said sensitivity correction unit is configured to be used with more than one type of lens useable with said pixel array.

35. The chip of claim 34 further comprising:

a memory device coupled to said sensitivity correction unit for storing at least one correction value for correcting at least one corresponding pixel value.

36. The chip of claim 35, wherein said memory device comprises at least one register.

37. The chip of claim 34 further comprising:

a column bus coupling at least one pixel of said pixel array and said sensitivity correction unit.

38. The chip of claim 37 further comprising:

a sample and hold circuit coupled to said sensitivity correction unit for receiving corrected pixel signals;

an analog-to-digital converter coupled to said sample and hold circuit for converting sampled corrected pixel signals to digital format; and

a pixel processor for processing said digital corrected pixel signals.

39. The chip of claim 34, wherein said sensitivity correction unit is configured to apply correction values to said pixel signals, wherein the correction values are generated by dividing said pixel array into a plurality of zones, wherein

each of said plurality of zones contains more than one pixel;

and wherein

each pixel in a given zone requires a similar degree of sensitivity correcting.

40. The chip of claim 39, wherein said correction values are generated by dividing said pixel array into a first number of zones when said pixel array is used with a first type of lens, wherein each of said first number of zones respectively contains a predetermined plurality of pixels of said pixel array.

41. The chip of claim 40, wherein said correction values are generated by dividing said pixel array into a second number of zones different from said first number of zones, when said pixel array is used with a second type of lens different from said first type of lens, and wherein

each of said second number of zones respectively contains a predetermined plurality of pixels of said pixel array different from said pixels associated with said first number of zones.

42. The chip of claim 40, wherein said first number of zones comprises eight zones in the x-direction and eight zones in the y-direction.

43. The chip of claim 34, wherein said sensitivity correction unit is configured to correct for any misalignment between respective centers of said pixel array and a lens used with said pixel array.

44. The chip of claim 34, wherein said pixel array comprises a pixel array of a CMOS imager.

45. The chip of claim 34, wherein said pixel array comprises a pixel array of a CCD imager.

46. A processor system, comprising:

a processor;

an imager device coupled to said processor, said imager device comprising;

a pixel array; and

a programmable sensitivity correction unit coupled to said pixel array for correcting sensitivity of at least one pixel in said pixel array, and wherein

said sensitivity correction unit is configured to be used with more than one type of lens useable with said pixel array.

47. The processor system of claim 46, wherein said imager device further comprises:

a memory device coupled to said sensitivity correction unit for storing at least one correction value for correcting at least one corresponding pixel value.

48. The processor system of claim 47, wherein said memory device comprises at least one register.

49. The processor system of claim 46, wherein said imager device further comprises:

a column bus coupling at least one pixel of said pixel array and said sensitivity correction unit.

50. The processor system of claim 49, wherein said imager device further comprises:

a sample and hold circuit coupled to said sensitivity correction unit for receiving corrected pixel signals;

an analog-to-digital converter coupled to said sample and hold circuit for converting sampled corrected pixel signals to digital format; and

a pixel processor for processing said digital corrected pixel signals.

51. The processor system of claim 46, wherein said correction values are generated by dividing said pixel array into a plurality of zones, wherein

each of said plurality of zones contains more than one pixel;

and wherein

each pixel in a given zone requires a similar degree of sensitivity correcting.

52. The processor system of claim 51, wherein said correction values are generated by dividing said pixel array into a first number of zones when said pixel array is used with a first type of lens, wherein each of said first number of zones respectively contains a predetermined plurality of pixels of said pixel array.

53. The processor system of claim 52, wherein said correction values are generated by dividing said pixel array into a second number of zones different from said first number of zones, when said pixel array is used with a second type of lens different from said first type of lens, and wherein

each of said second number of zones respectively contains a predetermined plurality of pixels of said pixel array different from said pixels associated with said first number of zones.

54. The processor system of claim 52, wherein said first number of zones comprises eight zones in the x-direction and eight zones in the y-direction.

55. The processor system of claim 46, wherein said sensitivity correction unit is configured to correct for any misalignment between respective centers of said pixel array and a lens used with said pixel array.

56. The processor system of claim 46, wherein said imager device comprises a CMOS imager.

57. The processor system of claim 46, wherein said imager device comprises a CCD imager.