USRE38180EExpiredUtility

Recalibrating a multi-color imaging system

Assignee: KODAK POLYCHROME GRAPHICS LLCPriority: May 1, 1995Filed: Oct 16, 2000Granted: Jul 15, 2003

Est. expiryMay 1, 2015(expired)· nominal 20-yr term from priority

Inventors:Christopher J. Edge

H04N 1/40006H04N 1/6036H04N 1/6033

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Claims

Abstract

An apparatus and method for calibrating a multi-color imaging system are provided. The multi-color imaging system is capable of applying different colorants to a substrate based on a plurality of input color values. The input color values control amounts of the colorants to be applied to the substrate by the imaging system. A subset of the input color values is selected and used to control the imaging system to apply one or more of the different colorants to the substrate, thereby forming a plurality of different color patches on the substrate. The subset of input color values is selected such that one of more of the different color patches is formed by application of a combination of at least two of the different colorants to the substrate. Color values are measured for each of the different color patches, and compared to reference color values, representing a calibrated condition of the imaging system. An error value is calculated. The error value represents a deviation of the measured color values from the reference color values. The input color values for each colorant then are independently adjusted to reduce the error value to a predetermined degree.

Claims

exact text as granted — not AI-modified

What is claimed is:

1. A computer readable medium encoded with a computer program arranged such that, upon execution of the computer program, a processor performs a method for recalibrating a multi-color imaging system, wherein the imaging system is capable of forming different colors based on input color values, and wherein the input color values control amounts of the colors formed by the imaging system, the method comprising:
controlling the imaging system to form different color combinations by combining two or more of the different colors;
controlling a measuring device to measure color values for each of the different color combinations;
comparing each of the measured color values to corresponding reference color values, the reference color values representing a calibrated condition of the imaging system;
calculating an error value representing a deviation of the measured color values from the reference color values; and
adjusting one or more of the input color values to reduce the error value to a predetermined degree, wherein the adjustment of the input color values for one of the colors is performed independently of the adjustment of the input color values for others of the colors.

2. The computer medium of claim 1 , wherein the adjusting act further includes:
accessing a color correction lookup table, wherein the color correction lookup table has a plurality of dimensions, each of the dimensions mapping at least a collection of the input color values to corrected input color values for one of the different colors, and
adjusting the corrected input color values of the correction lookup table to reduce the error value to the predetermined degree.

3. The computer readable medium of claim 1 , wherein one or more of the different color combinations includes a combination of at least three of the different colors.

4. The computer readable medium of claim 1 , wherein the different color combinations consist of less than seven different color combinations.

5. The computer readable medium of claim 1 , wherein the different color combinations consist of less than eight different color combinations.

6. The computer readable medium of claim 1 , wherein the different color combinations consist of less than nineteen different color combinations.

7. The computer readable medium of claim 1 , wherein the different color combinations consist of less than twenty-three different color combinations.

8. The computer readable medium of claim 1 , wherein:
one of the different color combinations includes a combination of at least three of the different colors in highlight-tone amounts,
one of the different color combinations includes a combination of at least three of the different colors in quarter-tone amounts, and
one of the different color combinations includes a combination of at least three of the different colors in mid-tone amounts.

9. The computer readable medium of claim 8 , wherein one of the different color combinations includes a combination of at least three of the different colors in three-quarter tone amounts.

10. The computer readable medium of claim 9 , wherein:
each of a first subset of the different color combinations includes a single one of the different colors in a highlight-tone amount,
each of a second subset of the different color combinations includes a single one of the different colors in a quarter-tone amount, and
each of a third subset of the different color combinations includes a single one of the different colors in a mid-tone amount.

11. The computer readable medium of claim 10 , wherein each of a plurality of the different color combinations includes a single one of the different colorants in a three-quarter tone amount.

12. The computer readable medium of claim 8 , wherein:
one of the different color combinations includes a combination of a first and a second of the different colors in saturated-tone amounts,
one of the different color combinations includes a combination of the first and a third of the different colors in saturated-tone amounts, and
one of the different color combinations includes a combination of the second and the third of the different colors in saturated-tone amounts.

13. The computer readable medium of claim 1 , wherein:
one of the different color combinations includes a combination of a first and a second of the different colorants in saturated-tone amounts,
one of the different color combinations includes a combination of the first and a third of the different colorants in saturated-tone amounts, and
one of the different color combinations includes a combination of the second and the third of the different colorants in saturated-tone amounts.

14. The computer readable medium of claim 1 , wherein the different colors comprise cyan, magenta, yellow, and black colorants.

15. The computer readable medium of claim 1 , wherein the act of controlling the measuring device includes controlling the measuring device to measure the color values in one of a plurality of system-independent color coordinate systems including L*a*b* and XYZ.

16. The computer readable medium of claim 1 , wherein the act of controlling the measuring device includes controlling the measuring device to measure the color values in one of a plurality of system-dependent color coordinate systems including RGB and density CMY, the method further comprising converting the measured color values into one of a plurality of system independent color coordinate systems including L*a*b* and XYZ.

17. A method for recalibrating a multi-color imaging system, wherein the imaging system is capable of outputting different colors based on input color values, the method comprising:
forming different color combinations, wherein one or more of the different color combinations includes at least two of the different colors;
measuring color values for each of the different color combinations;
comparing each of the measured color values to corresponding reference color values that represent a calibrated condition of the imaging system;
calculating an error value that represents a deviation of the measured color values from the reference color values; and
adjusting one or more of the input color values to reduce the error value to a predetermined degree, wherein the adjustment of the input color values for one of the colors is performed independently of the adjustment of the input color values for others of the colors.

18. The method of claim 17 , wherein the forming act includes forming one or more of the different color combinations by a combination of at least three of the different colors.

19. The method of claim 17 , wherein the forming act includes:
forming one of the different color combinations by a combination of at least three of the different colors in highlight-tone amounts,
forming one of the different color combinations by a combination of at least three of the different colors in quarter-tone amounts,
forming one of the different color combinations by a combination of at least three of the different colors in mid-tone amounts, and
forming one of the different color combinations by a combination of at least three of the different colors in three-quarter tone amounts.

20. A computer readable medium encoded with a computer program arranged such that, upon execution of the computer program, a processor performs a method for recalibrating a multi-color imaging system, the imaging system configured to output colors based on corresponding input color values, the method comprising:
controlling the imaging system to form different color combinations, wherein one or more of the different color combinations includes at least two of the different colors;
controlling a measuring device to measure color values for each of the different color combinations;
comparing each of the measured color values to corresponding reference color values that represent a calibrated condition of the imaging system;
calculating an error value that represents a deviation of the measured color values from the reference color values; and
adjusting one or more of the input color values to reduce the error value to a predetermined degree, wherein the adjustment of the input color values for one of the colors is performed independently of the adjustment of the input color values for others of the colors.

21. The computer readable medium of claim 20 , wherein one or more of the different color combination includes a combination of at least three of the different colors.

22. The computer readable medium of claim 20 , wherein:
one of the different color combination includes a combination of at least three of the different colors in highlight-tone amounts,
one of the different color combinations includes a combination of at least three of the different colors in quarter-tone amounts,
one of the different color combinations includes a combination of at least three of the different colors in mid-tone amounts, and
one of the different color combination includes a combination of at least three of the different colors in three-quarter tone amounts.

23. A method comprising:

forming color combinations by outputting two or more colors on an output device based on corresponding input color values;

receiving information characterizing a color response of the output device; and

adjusting one or more of the input color values based on the received information,

wherein the adjustment of the input color values for one of the colors is performed independently of the adjustment of the input color values for others of the colors.

24. The method of claim 23 wherein the information is a color value for at least one of the color combinations, and further wherein adjusting the input color values comprises:

comparing the color value to a corresponding reference color value; and

calculating an error value representing a deviation of the color value from the reference color value.

25. The method of claim 23 wherein receiving color information includes measuring the color values for each of the color combinations.

26. The method of claim 23 , wherein forming color combinations includes printing color patches on a substrate.

27. The method of claim 23 , wherein adjusting the input color values includes:

accessing a color correction lookup table, wherein the color correction lookup table has a plurality of dimensions, each of the dimensions mapping at least a collection of the input color values to corrected input color values for one of the different colors, and

adjusting the corrected input color values of the correction lookup table to reduce the error value to the predetermined degree.

28. The method of claim 23 , wherein one or more of the different color combinations includes a combination of at least three of the different colors.

29. The method of claim 23 , wherein the different color combinations consist of less than seven different color combinations.

30. The method of claim 23 , wherein the different color combinations consist of less than eight different color combinations.

31. The method of claim 23 , wherein the different color combinations consist of less than nineteen different color combinations.

32. The method of claim 23 , wherein the different color combinations consist of less than twenty- three different color combinations.

33. The method of claim 23 , wherein;
one of the different color combinations includes a combination of at least three of the different colors in highlight - tone amounts,
one of the different color combinations includes a combination of at least three of the different colors in quarter - tone amounts, and
one of the different color combinations includes a combination of at least three of the different colors in mid - tone amounts.

34. The method of claim 33 , wherein one of the different color combinations includes a combination of at least three of the different colors in three- quarter tone amounts.

35. The method of claim 34 , wherein:
each of a first subset of the different color combinations includes a single one of the different colors in a highlight - tone amount,
each of a second subset of the different color combinations includes a single one of the different colors in a quarter - tone amount, and
each of a third subset of the different color combinations includes a single one of the different colors in a mid - tone amount.

36. The method of claim 35 , wherein each of a plurality of the different color combinations includes a single one of the different colorants in a three- quarter tone amount.

37. The method of claim 23 , wherein:
one of the different color combinations includes a combination of a first and a second of the different colors in saturated - tone amounts,
one of the different color combinations includes a combination of the first and a third of the different colors in saturated - tone amounts, and
one of the different color combinations includes a combination of the second and the third of the different colors in saturated - tone amounts.

38. The method of claim 23 , wherein the different colors comprise cyan, magenta, yellow, and black colorants.

39. The method of claim 24 , wherein measuring the color values includes measuring the color values in one of a plurality of system- independent color coordinate systems including L*a*b* and XYZ.

40. The method of claim 24 , wherein measuring the color values includes measuring the color values in one of a plurality of system- dependent color coordinate systems including RGB and density CMY, the method further comprising converting the color values into one of a plurality of system independent color coordinate systems including L*a*b* and XYZ.

41. A system comprising:

an output device configured to output colors based on corresponding input color values; and a calibration device configured to control the output device to form color combinations of two or more colors, wherein the calibration device is further configured to receive information characterizing a color response of the output device and adjust one or more of the input color values based on the received information, wherein the calibration device adjusts the input color values for one of the colors independently from the adjustment of the input color values for others of the colors.

42. The system of claim 41 , wherein the information is a color value for at least one of the color combinations and the calibration module is further configured to calculate an error value by comparing at least one of the color values to a corresponding reference color value and to adjust one or more of the input color values to reduce the error value to a predetermined degree.

43. The system of claim 41 further including a measuring device to measure the color values for each of the color combinations.

44. The system of claim 41 , wherein the output device is configured to print the color combinations on a substrate.

45. The system of claim 41 , wherein the calibration device is configured to access a color correction lookup table having a plurality of dimensions, each dimension mapping at least a collection of the input color values to corrected input color values for one of the different colors, and wherein the calibration device is further configured to adjust the corrected input color values of the correction lookup table.

46. The system of claim 41 , wherein one or more of the different color combinations includes a combination of at least three of the different colors.

47. The system of claim 41 , wherein the different color combinations consist of less than seven different color combinations.

48. The system of claim 41 , wherein the different color combinations consist of less than eight different color combinations.

49. The system of claim 41 , wherein the different color combinations consist of less than nineteen different color combinations.

50. The system of claim 41 , wherein the different color combinations consist of less than twenty- three different color combinations.

51. The system of claim 41 , wherein:
one of the different color combinations includes a combination of at least three of the different colors in highlight - tone amounts,
one of the different color combinations includes a combination of at least three of the different colors in quarter - tone amounts, and
one of the different color combinations includes a combination of at least three of the different colors in mid - tone amounts.

52. The system of claim 51 , wherein one of the different color combinations includes a combination of at least three of the different colors in three- quarter tone amounts.

53. The system of claim 41 , wherein each of a plurality of the different color combinations includes a single one of the different colorants in a three- quarter tone amount.

54. The system of claim 53 , wherein:
one of the different color combinations includes a combination of a first and a second of the different colors in saturated - tone amounts,
one of the different color combinations includes a combination of the first and a third of the different colors in saturated - tone amounts, and
one of the different color combinations includes a combination of the second and the third of the different colors in saturated - tone amounts.

55. The system of claim 41 , wherein:
one of the different color combinations includes a combination of a first and a second of the different colorants in saturated - tone amounts,
one of the different color combinations includes a combination of the first and a third of the different colorants in saturated - tone amounts, and
one of the different color combinations includes a combination of the second and the third of the different colorants in saturated - tone amounts.

56. The system of claim 41 , wherein the different colors comprise cyan, magenta, yellow, and black colorants.

57. The system of claim 42 , wherein the measuring devices measures the color values in one of a plurality of system- independent color coordinate systems including L*a*b* and XYZ.

58. The system of claim 42 , wherein in one of a plurality of system- dependent color coordinate systems including RGB and density CMY, the calibration module converting the color values into one of a plurality of system independent color coordinate systems including L*a*b* and XYZ.

59. A medium containing instructions to cause a programmable processor to:

form color combinations by outputting two or more colors on an output device based on corresponding input color values;

receive information characterizing a color response of the output device; and

adjust one or more of the input color values based on the received information, wherein the adjustment of the input color values for one of the colors is performed independently of the adjustment of the input color values for others of the colors.

60. The medium of claim 59 wherein the information is a color value for at least one of the color combinations, and further wherein the medium contains instructions to cause the programmable processor to:

compare the color value to a corresponding reference color value; and

calculate an error value representing a deviation of the color value from the reference color value.

61. The medium of claim 59 further including instructions to cause the processor to measure the color values for each of the color combinations.

62. The medium of claim 59 , further including instructions to cause the processor to print color patches on a substrate.

63. The medium of claim 59 , further including instructions to cause the processor to

access a color correction lookup table, wherein the color correction lookup table has a plurality of dimensions, each of the dimensions mapping at least a collection of the input color values to corrected input color values for one of the different colors, and

adjust the corrected input color values of the correction lookup table to reduce the error value to the predetermined degree.

64. The medium of claim 59 , wherein one or more of the different color combinations includes a combination of at least three of the different colors.

65. The medium of claim 59 , wherein the different color combinations consist of less than seven different color combinations.

66. The medium of claim 59 , wherein the different color combinations consist of less than eight different color combinations.

67. The medium of claim 59 , wherein the different color combinations consist of less than nineteen different color combinations.

68. The medium of claim 59 , wherein the different color combinations consist of less than twenty- three different color combinations.

69. The medium of claim 59 , wherein:
one of the different color combinations includes a combination of at least three of the different colors in highlight - tone amounts,
one of the different color combinations includes a combination of at least three of the different colors in quarter - tone amounts, and
one of the different color combinations includes a combination of at least three of the different colors in mid - tone amounts.

70. The medium of claim 69 , wherein one of the different color combinations includes a combination of at least three of the different colors in three- quarter tone amounts.

71. The medium of claim 59 , wherein the medium is a storage medium.

72. The medium of claim 59 , wherein the medium is a transmission medium.

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