Color control of a web printing press utilizing intra-image color measurements
First Claim
1. A method of intra-image color control in a web offset printing press, the method comprising:
- capturing spectral reflectance data from a measurement area within a printed image on a substrate moving on the printing press;
utilizing the captured spectral reflectance data to determine if the color of the printed image within the measurement area is within a predefined color tolerance;
in the event that the color of the printed image within the measurement area is not within the predefined color tolerance, calculating a color adjustment; and
applying the calculated color adjustment to the printing press for color control.
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Abstract
Accurate on-line color control for a printing press can be obtained using intra-image color control. A concurrent spectrophotometer and imaging system can capture spectral reflectance data from predetermined measurement areas for each ink key zone of the press. The spectral reflectance data can be compared to target reflectance values in the same standard color space, and a determination can be made as to whether the differences between the measured and target values exceed predetermined tolerances. If the differences exceed these tolerances, a necessary adjustment to the appropriate ink key can be calculated to bring the color differences back to within tolerance. This approach is particularly beneficial in web offset printing, where the printed image is constantly moving and the press conditions are particularly variable.
51 Citations
25 Claims
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1. A method of intra-image color control in a web offset printing press, the method comprising:
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capturing spectral reflectance data from a measurement area within a printed image on a substrate moving on the printing press;
utilizing the captured spectral reflectance data to determine if the color of the printed image within the measurement area is within a predefined color tolerance;
in the event that the color of the printed image within the measurement area is not within the predefined color tolerance, calculating a color adjustment; and
applying the calculated color adjustment to the printing press for color control. - View Dependent Claims (16)
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2. A method of intra-image color control in a web offset printing press, the method comprising:
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capturing spectral reflectance data from at least one measurement area within a printed image;
calculating a difference between the captured spectral reflectance data and target spectral reflectance data;
determining whether the difference exceeds a color tolerance;
calculating a color adjustment when the difference exceeds the color tolerance; and
applying the calculated color adjustment to the printing press for color control. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of intra-image color control in a web offset printing press, the method comprising:
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capturing spectral reflectance data from at least one measurement area in an ink key zone within a printed image;
converting the captured spectral reflectance values to colorimetric values;
comparing the colorimetric values to respective target colorimetric values to calculate a color difference value; and
calculating an inking correction using the captured spectral reflectance values when the color difference exceeds a color difference tolerance. - View Dependent Claims (12, 13, 14, 15)
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17. A system for intra-image color control in a web offset printing press, the system comprising:
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an imaging system operable to capture spectral reflectance data from a measurement area within a printed image on a substrate moving on the printing press;
a data process device that utilizes the captured spectral reflectance data to determine if the color of the printed image within the measurement area is within a predefined color tolerance and, in the event that the color of the printed image within the measurement area is not within the predefined color tolerance, calculates a color adjustment signal that is utilized to control color of images printed on the moving substrate.
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18. A system for intra-image color control in a web offset printing press, the system comprising:
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a spectrophotometric imaging system operable to capture spectral reflectance data from a measurement area of an image printed on a moving web, the measurement area being within an ink key zone of the printing press; and
a data processing device containing instructions to calculate a difference between the captured spectral reflectance data and target spectral reflectance data, and to determine whether the calculated difference exceeds a color tolerance, the data processing device further containing instructions to calculate a color adjustment when the calculated difference exceeds the color tolerance and to supply a color adjustment signal to the printing press in response thereto. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A method of intra-image color control in a web offset printing press, the method comprising:
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capturing spectral reflectance data from at least one measurement area within a printed image;
utilizing the captured spectral reflectance data to generate an ink density value representing the difference between an ink density value in the least one measurement area from which the spectral reflectance data was captured and a target ink density value for the at least one measurement area;
determining whether the ink density difference value exceeds a tolerance value; and
calculating a color adjustment when the ink density difference value exceeds the color tolerance; and
applying the calculated color adjustment to the printing press for color control.
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Specification