Method of and apparatus for correcting color of print medium, and proofer used therein

• US 20010028471A1
• Filed: 05/09/2001
• Published: 10/11/2001
• Est. Priority Date: 12/15/1997
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Hirokazu, Kondo
• Granted Patent: US 7,345,798 B2
• Time in Patent Office: Days
• US Class Current: 358/1.13
• CPC Class Codes: B41F 33/0036 Devices for scanning or checking the printed matter for quality control
• CPC Class Codes: B41F 7/18 specially adapted for proof printing

Abstract

Even if the color of a print sheet to be actually used for printing is lighter than the color of a sheet according to a given standard printing profile, a printer outputs a proof on a dedicated sheet where the difference between the sheet colors has been corrected. Specifically, after input image data are converted to calorimetric data by a printing profile, the difference between the sheet colors is corrected by one-dimensional LUTs. Input/output gradients (straight lines) incorporated in the one-dimensional LUTs are represented by Xα/X0, Yα/Y0, Zα/Z0 where Xα, Yα, Zα indicate colorimetric values of the color of the print sheet to be actually used for printing and X0, Y0, Z0 indicate calorimetric values of the color of a standard print sheet used to generate the print profile. The difference between the sheet color according to the standard printing profile and the sheet color to be actually used for printing.

Claims

1. A method of correcting the color of a print medium, comprising the steps of:

converting device-dependent image data to first colorimetric data with color converting means given to a standard print medium;

thereafter, converting said first colorimetric data to second colorimetric data with color correcting means to correct the difference between the color of a desired print medium and the color of said standard print medium; and

producing a proof on which the difference between the color of said desired print medium and the color of said standard print medium has been corrected, on a proof medium with an image output device based on said second calorimetric data;

wherein said color correcting means comprises one-dimensional lookup tables for converting said first colorimetric data to said second colorimetric data.

3. A method according to

claim 1

, wherein said color correcting means is generated by outputting color patches, whose calorimetric values are varied in a calorimetric color space about the color of the standard print medium, with said image output device, and comparing the color of the desired print medium with the colors of the color patches on the proof medium.

5. A method according to

claim 3

, wherein said color patches outputted on said proof medium comprise color patches whose colorimetric values L*a*b* are varied in a CIELAB color space about the color of said standard print medium.

29. The method of

claim 3

, wherein a color of a central color patch is the same as a color of the standard print medium.

30. The method of

claim 29

, wherein the color patches comprise three-dimensional calorimetric values of L*a*b* and color patches are arranged as a*-b* planes in respective cross sections of different L*-axes values.

31. The method of

claim 30

, wherein each color patch is assigned an integer as a relative position from the central color patch according to each axis of L*a*b* for showing increment/decrement intervals of a colorimetric value and the color of the desired print medium is compared with the color patches, and wherein when no color patch is the same as the color of the desired print medium, a value between two closest color patches which is close to the color of the desired print medium is described as a real number to describe a colorimetric value of the desired print medium.

32. The method of

claim 31

, wherein a color difference Δ

E in adjacent color patches on each axis of L*a*b* has value between 1.5 and 2.0, inclusive.

2. A method of correcting the color of a print medium, comprising the steps of:

converting device-dependent image data, which have been converted in gradation with respect to each color in order to match desired printing conditions by gradation converting means, to first calorimetric data with color converting means corresponding to standard printing conditions given to a standard print medium;

thereafter, converting said first colorimetric data to second calorimetric data with color correcting means to correct the difference between the color of a desired print medium and the color of said standard print medium; and

producing a proof on which the difference between the color of said desired print medium and the color of said standard print medium has been corrected, on a proof medium with an image output device based on said second colorimetric data.

4. A method according to

claim 2

, wherein said color correcting means is generated by outputting color patches, whose colorimetric values are varied in a colorimetric color space about the color of the standard print medium, with said image output device, and comparing the color of the desired print medium with the colors of the color patches on the proof medium.

6. A method according to

claim 4

, wherein said color patches outputted on said proof medium comprise color patches whose colorimetric values L*a*b* are varied in a CIELAB color space about the color of said standard print medium.

33. The method of

claim 4

, wherein a color of a central color patch is the same as a color of the standard print medium.

34. The method of

claim 33

, wherein the color patches comprise three-dimensional calorimetric values of L*a*b* and color patches are arranged as a*-b* planes in respective cross sections of different L*-axes values.

35. The method of

claim 34

, wherein each color patch is assigned an integer as a relative position from the central color patch according to each axis of L*a*b* for showing increment/decrement intervals of a colorimetric value and the color of the desired print medium is compared with the color patches, and wherein when no color patch is the same as the color of the desired print medium, a value between two closest color patches which is close to the color of the desired print medium is described as a real number to describe a calorimetric value of the desired print medium.

36. The method of

claim 35

, wherein a color difference Δ

E in adjacent color patches on each axis of L*a*b* has value between 1.5 and 2.0, inclusive.

7. An apparatus for correcting the color of a print medium, comprising:

color converting means given to a standard print medium, for converting device-dependent image data to first colorimetric data;

color correcting means for converting said first calorimetric data to second colorimetric data to correct the difference between the color of a desired print medium and the color of said standard print medium; and

an image output device for producing a proof on which the difference between the color of said desired print medium and the color of said standard print medium has been corrected, on a proof medium based on said second calorimetric data;

wherein said color correcting means comprises one-dimensional lookup tables for converting said first colorimetric data to said second colorimetric data.

9. An apparatus according to

claim 7

, wherein said color correcting means is generated by outputting color patches, whose colorimetric values are varied in a colorimetric color space about the color of the standard print medium, with said image output device, and comparing the color of the desired print medium with the colors of the color patches on the proof medium.

11. An apparatus according to

claim 9

, wherein said color patches outputted on said proof medium comprise color patches whose colorimetric values L*a*b* are varied in a CIELAB color space about the color of said standard print medium.

37. The method of

claim 9

, wherein a color of a central color patch is the same as a color of the standard print medium.

38. The method of

claim 37

, wherein the color patches comprise three-dimensional colorimetric values of L*a*b* and color patches are arranged as a*-b* planes in respective cross sections of different L*-axes values.

39. The method of

claim 38

, wherein each color patch is assigned an integer as a relative position from the central color patch according to each axis of L*a*b* for showing increment/decrement intervals of a calorimetric value and the color of the desired print medium is compared with the color patches, and wherein when no color patch is the same as the color of the desired print medium, a value between two closest color patches which is close to the color of the desired print medium is described as a real number to describe a colorimetric value of the desired print medium.

40. The method of

claim 39

, wherein a color difference Δ

E in adjacent color patches on each axis of L*a*b* has value between 1.5 and 2.0, inclusive.

8. An apparatus for correcting the color of a print medium, comprising:

gradation converting means for converting the gradation of device-dependent image data with respect to each color in order to match desired printing conditions;

color converting means corresponding to standard printing conditions given to a standard print medium, for converting the gradation-converted device-dependent image data to first colorimetric data;

color correcting means for converting said first calorimetric data to second colorimetric data to correct the difference between the color of a desired print medium and the color of said standard print medium; and

an image output device for producing a proof on which the difference between the color of said desired print medium and the color of said standard print medium has been corrected, on a proof medium based on said second calorimetric data.

10. An apparatus according to

claim 8

, wherein said color correcting means is generated by outputting color patches, whose calorimetric values are varied in a calorimetric color space about the color of the standard print medium, with said image output device, and comparing the color of the desired print medium with the colors of the color patches on the proof medium.

12. An apparatus according to

claim 10

, wherein said color patches outputted on said proof medium comprise color patches whose colorimetric values L*a*b* are varied in a CIELAB color space about the color of said standard print medium.

41. The method of

claim 10

, wherein a color of a central color patch is the same as a color of the standard print medium.

42. The method of

claim 41

, wherein the color patches comprise three-dimensional calorimetric values of L*a*b* and color patches are arranged as a*-b* planes in respective cross sections of different L*-axes values.

43. The method of

claim 42

, wherein each color patch is assigned an integer as a relative position from the central color patch according to each axis of L*a*b* for showing increment/decrement intervals of a calorimetric value and the color of the desired print medium is compared with the color patches, and wherein when no color patch is the same as the color of the desired print medium, a value between two closest color patches which is close to the color of the desired print medium is described as a real number to describe a calorimetric value of the desired print medium.

44. The method of

claim 43

, wherein a color difference Δ

E in adjacent color patches on each axis of L*a*b* has value between 1.5 and 2.0, inclusive.

13. A proofer for generating a color proof on a proof print medium having color different from the color of a desired print medium, wherein said proofer has a color adjusting function for adjusting the difference between the color of said desired print medium and the color of a standard print medium;

wherein said color adjusting function comprises one-dimensional lookup tables for converting the color of a standard print medium to the color of said desired print medium.

14. A proofer according to

claim 13

, wherein said proofer outputs said proof medium having color patches whose colors are varied, and said color adjusting function adjusts color by visually comparing the color of said desired print medium with the colors of said color patches on said proof medium.

15. A proofer according to

claim 13

, wherein said color adjusting function adjusts color by using a calorimetric data which is determined by calorimetrically measuring the color of said desired print medium with a calorimetric.

16. A proofer according to

claim 13

, further comprising a printing profile, wherein said color adjusting function adjusts color by a color converting means behind said printing profile.

17. A proofer according to

claim 13

, further comprising a synthetic color converting means at least combining a printing profile, a color converter for adjusting color, and a printer profile, for correcting color.

18. A method of correcting the color of a print medium, comprising the steps of:

converting device-dependent image data to first colorimetric data with color converting means given to a standard print medium;

thereafter, converting said first calorimetric data to second colorimetric data with color correcting means to correct the difference between the color of a desired print medium and the color of said standard print medium; and

producing a proof on which the difference between the color of said desired print medium and the color of said standard print medium has been corrected, on a proof medium with an image output device based on said second calorimetric data;

wherein the color correcting means corrects the data based on the ratios of Xα

/X0, Yα

/Y0 and Zα

/Z0, where Xα

, Yα and

Zα

are second calorimetric data values and X0, Y0 and Z0 are first colorimetric data values for which the difference between the color of a desired print medium and the color of said standard print medium has been corrected.

19. A method according to

claim 18

, wherein said color correcting means is generated by outputting color patches, whose colorimetric values are varied in a colorimetric color space about the color of the standard print medium, with said image output device, and comparing the color of the desired print medium with the colors of the color patches on the proof medium.

20. A method according to

claim 19

, wherein said color patches outputted on said proof medium comprise color patches whose colorimetric values L*a*b* are varied in a CIELAB color space about the color of said standard print medium.

21. An apparatus for correcting the color of a print medium, comprising:

color converting means given to a standard print medium, for converting device-dependent image data to first colorimetric data;

color correcting means for converting said first colorimetric data to second colorimetric data to correct the difference between the color of a desired print medium and the color of said standard print medium; and

an image output device for producing a proof on which the difference between the color of said desired print medium and the color of said standard print medium has been corrected, on a proof medium based on said second colorimetric data;

wherein the color correcting means corrects the data based on the ratios of Xα

/X0, Yα

/Y0 and Zα

/Z0, where Xα

, Yα and

Zα

are second calorimetric data values and X0, Y0 and Z0 are first colorimetric data values for which the difference between the color of a desired print medium and the color of said standard print medium has been corrected.

22. An apparatus according to

claim 21

, wherein said color correcting means is generated by outputting color patches, whose calorimetric values are varied in a colorimetric color space about the color of the standard print medium, with said image output device, and comparing the color of the desired print medium with the colors of the color patches on the proof medium.

23. An apparatus according to

claim 22

, wherein said color patches outputted on said proof medium comprise color patches whose calorimetric values L*a*b* are varied in a CIELAB color space about the color of said standard print medium.

24. A proofer for generating a color proof on a proof print medium having color different from the color of a desired print medium, wherein said proofer has a color adjusting function for adjusting the difference between the color of said desired print medium and the color of a standard print medium;

wherein the color adjusting function adjusts color proof data based on the ratios of Xα

/X0, Yα

/Y0 and Zα

/Z0, where Xα

, Yα and

Zα

are colorimetric data values for producing a proper color on said desired print medium and X0, Y0 and Z0 are colorimetric data values producing the proper color on said standard print medium.

25. A proofer according to

claim 24

, wherein said proofer outputs said proof medium having color patches whose colors are varied, and said color adjusting function adjusts color by visually comparing the color of said desired print medium with the colors of said color patches on said proof medium.

26. A proofer according to

claim 24

, wherein said color adjusting function adjusts color by using a colorimetric data which is determined by colorimetrically measuring the color of said desired print medium with a colorimeter.

27. A proofer according to

claim 24

, further comprising a printing profile, wherein said color adjusting function adjusts color by a color converting means behind said printing profile.

28. A proofer according to

claim 24

, further comprising a synthetic color converting means at least combining a printing profile, a color converter for adjusting color, and a printer profile, for correcting color.