Methods and apparatus for determining a total colorant limit for digital imaging devices
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
H04N-001/60
B41J-029/36
출원번호
UP-0836071
(2004-04-30)
등록번호
US-7742204
(2010-07-12)
발명자
/ 주소
Kühn, Mario
Mady, Samer
출원인 / 주소
Electronics For Imaging, Inc.
대리인 / 주소
Glenn, Michael A.
인용정보
피인용 횟수 :
3인용 특허 :
15
초록▼
Methods and apparatus are provided for calibrating a digital color imaging device to a printing press by determining a total colorant limit, per-channel colorant limits, and channel linearization tables using colorimetric and/or spectrophotometric techniques. In addition, for digital color imaging d
Methods and apparatus are provided for calibrating a digital color imaging device to a printing press by determining a total colorant limit, per-channel colorant limits, and channel linearization tables using colorimetric and/or spectrophotometric techniques. In addition, for digital color imaging devices that use multi-hue colorants, methods and apparatus are provided for determining distribution functions for the multi-hue colorants as a function of input values.
대표청구항▼
The invention claimed is: 1. A system for calibrating a digital color imaging device, the system comprising: a color output device for printing an image file including a test pattern, the test pattern comprising a plurality of strips, each strip comprising a plurality of test patches, the test patc
The invention claimed is: 1. A system for calibrating a digital color imaging device, the system comprising: a color output device for printing an image file including a test pattern, the test pattern comprising a plurality of strips, each strip comprising a plurality of test patches, the test patches for each strip comprising scales of percentages of a fixed number of at least two C, M, Y, and K colorants; a measurement device that measures each of the test patches for colorimetric data; a processor for calculating the total colorant limit by: receiving the colorimetric data from the measurement device based upon the colorimetric data; selecting one patch in each strip with a minimum lightness; determining, for each patch in each strip that was selected by the processor as having a minimum lightness, a total area coverage (TAC), the TAC comprising a sum of the percentages of colorants used to produce the patch; selecting a maximum TAC from the TAC determined for each patch in each strip that was selected by the processor as having the minimum lightness; and the processor setting the total colorant limit to the maximum TAC selected by the processor. 2. The system of claim 1 wherein the patches include at least one 100% single-colorant patch for each colorant and the processor generates a per-channel colorant limit by: determining a minimum limit for each colorant, determining a maximum limit for black by identifying a colorant value for a black patch with a minimum lightness, determining a maximum limit for a colorant other than black by identifying a colorant value of a printed patch having one of a maximum chroma and a colorant where oversaturation beings, and an optimal limit for each colorant. 3. The system of claim 2, wherein the minimum colorant limit for each colorant is based on a comparison between the measured colorimetric values of the single-colorant patch and a colorimetric value of a press profile. 4. The system of claim 1, wherein the colorants comprise multi-hue colorants. 5. The system of claim 2, wherein the processor generates an optimal limit for each colorant by determining the colorant values for interpolated patches between minimum and maximum colorants, calculating a chroma value for each interpolated patch, determining a deviation between calculated and measured chroma values, vector-correcting chroma values for interpolated patches, and identifying an interpolated patch having a minimum chroma. 6. The system of claim 1, wherein the instrument comprises a spectrophotometer. 7. The system of claim 1, wherein the instrument comprises a spectrocolorimeter. 8. The system of claim 1, wherein the colorimetric measurements comprise CIELAB data values. 9. The system of claim 1, wherein the colorimetric measurements comprise CIEXYZ data values. 10. The system of claim 1, wherein the processor generates a linearization table by calculating a plurality of tonal response values from the measured colorimetric values, retrieving colorimetric values from a press profile, calculating a plurality of midtone tonal response values from retrieved colorimetric values, calculating a tonal response of a press for a range of input values, and mapping the press input values to equivalent input values for the color output device using the tonal response values. 11. The system of claim 4, wherein the processor determines distribution functions for the multi-hue colorants. 12. The system of claim 11, wherein the processor determines a distribution function for each multi-hue colorant by calculating a tonal response from the measured colorimetric values, calculating a tonal response of a press for a range of input values, calculating a range of light distribution, and creating a table of light to normal tonal responses. 13. A computer-implemented method for calibrating a digital color imaging device, the method comprising: printing a test pattern, the test pattern comprising a plurality of strips, each strip comprising a plurality of test patches, the test patches for each strip comprising scales of percentages of a fixed number of at least two C, M, Y, and K colorants; measuring each of the test patches for colorimetric data; receiving the colorimetric data from the measurement device; selecting, with a processor, one patch in each strip with a minimum lightness; based on the patches selected in the previous step, determining, with the processor, a total area coverage (TAC), the TAC comprising a sum of the percentages of colorants used to produce the patch; based on the patches for which TAC was determined in the previous step, selecting, with the processor, the patch with a maximum TAC; and setting, with the processor, the total colorant limit to the maximum TAC that was determined in the previous step. 14. The method of claim 13, wherein the patches include at least one 100% single-colorant patch for each colorant and further comprising generating a per-channel colorant limit by: determining a minimum limit for each colorant, determining a maximum limit for black by identifying a colorant value for a black patch with a minimum lightness, determining a maximum limit for a colorant other than black by identifying a colorant value of a printed patch having one of a maximum chroma and a colorant where oversaturation begins, and an optimal limit for each colorant. 15. The method of claim 14, wherein the minimum colorant limit for each the minimum colorant limit for each colorant is based on a comparison between the measured colorimetric values of the single-colorant patch and a colorimetric value of a press profile. 16. The method of claim 13, wherein the colorants comprise multi-hue colorants. 17. The method of claim 14, further comprising the step of: generating an optimal limit for each colorant by determining the colorant values for interpolated patches between minimum and maximum colorants, calculating a chroma value for each interpolated patch, determining a deviation between calculated and measured chroma values, vector-correcting chroma values for interpolated patches, and identifying an interpolated patch having a minimum chroma. 18. The method of claim 13, wherein colorimetrically measuring comprises measuring the printed test pattern using a spectrophotometer. 19. The method of claim 13, wherein colorimetrically measuring comprises measuring the printed test pattern using a spectrocolorimeter. 20. The method of claim 13, wherein the colorimetric measurements comprise CIELAB data values. 21. The method of claim 13, wherein the colorimetric measurements comprise CIEXYZ data values. 22. The method of claim 13, further comprising generating a linearization table by calculating a plurality of tonal response values from the measured colorimetric values, retrieving colorimetric values from a press profile, calculating a tonal response of a press for a range of input values, and mapping the press input values to equivalent input values for the color output device using the tonal response values. 23. The method of claim 16, further comprising generating a distribution function for each multi-hue colorant. 24. The method of claim 23, wherein generating a distribution function for each multi-hue colorant comprises calculating a tonal response from the measured colorimetric values, calculating a tonal response of a press for a range of input values, calculating a range of light distribution, and creating a table of light to normal tonal responses.
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