Patent EP0676892A2 successfully refreshed from Google Patents.
EP0676892A2
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EP
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Color printer calibration with improved color mapping linearity
Assignee: Xerox Corp
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Filing: 1995-03-31
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Granted: —
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Expires: 2015-03-31
Abstract
Abstract In a color printer calibration process, a color printer (30) is driven with a set of printer signals (C p ,M p ,Y p ,K p ) selected to print a set of color samples throughout a printer gamut. A color measuring device (70) measures the colorimetric response at each sample, to derive a mapping of printer signals to colorimetric responses (R p ,G p ,B p ) of the printer. From the colorimetric responses, a preprocessing step is used to increase the number of measurements, using linear interpolation between local responses whereby the number of colorimetric responses to be mapped is increased. Then, a lookup table (140) mapping colorimetric values to printer signals is generated, at regular intervals throughout the printer gamut, to produce a regular interval set of interpolated colorimetric values (C x ,M x ,Y x ), derived from the measured colorimetric values and the linearly interpolated values using a distance-weighted averaging method. The look up table is stored in a color conversion memory (150; Fig.3) for use in converting color definitions from a first color space to the printer color space.
Inventors
- 👤 Robert J. Rolleston
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 16:19
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/603; H04N1/6033
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
194 words
A method of calibrating a color printer, the color printer responsive to printer signals to deposit printer colorants on a medium in accordance with printer signals received, including the steps of: operating the color printer with printer signals selected to cause the printer to print color samples on the medium; measuring a colorimetric response at each color sample printed on the medium, and producing a colorimetric signal indicative thereof, mapped to a corresponding printer signal, said colorimetric signals dispersed through a gamut of the printer at irregular intervals; preprocessing the colorimetric signals to increase the number thereof with interpolated signals, generating each interpolated signal as an interpolated function of a plurality of spatially proximate colorimetic signals; mapping the increased number of colorimetric signals to printer signals, to produce a regular interval dispersal of calculated colorimetric signals through color space, each of the calculated colorimetric signals mapped to a corresponding printer signal and derived from the colorimetric signals and the interpolated signals; storing the mapping in a color conversion memory for use in converting color definitions from a first color space to the printer signals suitable for producing a corresponding response at the color printer.
Claim 2
Dependent Claim
18 words
The method as defined in claim 1, wherein the preprocessing step interpolated function is a linear interpolation method.
Claim 3
Dependent Claim
27 words
The method as defined in claim 2, wherein the linear interpolation method averages a plurality of signals local to the location at which a signal is desired.
Claim 4
Dependent Claim
33 words
The method as defined in claim 1, 2 or 3, wherein the method of mapping increased number of colorimetric signals to printer signals, produces colorimetic signals as a weighted function of printer signals.
Claim 5
Dependent Claim
22 words
The method as defined in claim 4, wherein the weighted function varies with the location of the printer signals in color space.
Claim 6
Independent Claim
29 words
The method as defined in any of claims 1 to 5, wherein the method of mapping increased number of colorimetric signals to printer signals includes an inverse tetrahedral transformation.
Claim 7
Dependent Claim
196 words
A color printer including a calibration system, the color printer responsive to printer signals to deposit printer colorants on a medium in accordance with printer signals received, including the steps of: means for operating the color printer with printer signals selected to cause the printer to print color samples on the medium; means for measuring a colorimetric response at each color sample printed on the medium, and producing a colorimetric signal indicative thereof, mapped to a corresponding printer signal, said colorimetric signals are dispersed through a gamut of the printer at irregular intervals; means for preprocessing the colorimetric signals to increase the number thereof with interpolated signals, using interpolation between spatially proximate responses; means for mapping the increased number of colorimetric signals to printer signals, to produce a regular interval dispersal of calculated colorimetric signals through color space, each of the calculated colorimetric signals mapped to a corresponding printer signal and derived from the measured colorimetric values and the interpolated values; means for storing the mapping in a color conversion memory for use in converting color definitions from a first color space to the printer signals suitable for producing a corresponding response at the color printer.
Claim 8
Dependent Claim
38 words
The device as defined in claim 7, wherein the preprocessing means interpolation is a linear interpolation function, preferably wherein the linear interpolation function averages a plurality of signals local to the location at which a signal is desired.
Claim 9
Dependent Claim
54 words
The device as defined in claim 7 or 8, wherein the means for mapping (1) produces calculated colorimetic signals as a weighted function of printer signals, wherein the weighted function preferably varies with the location of the printer signals in color space, and/or (2) includes an inverse tetrahedral transformation to calculated new colorimetic signals.
Claim 10
Dependent Claim
215 words
A color printer including a calibration system, the color printer responsive to printer signals to deposit printer colorants on a medium in accordance with printer signals received, including the steps of: a printer controller, controlling printer operation; a calibration memory, storing a set of printer signals suitable to drive the printer to print a test sheet; a printer, responsive to control signals from the printer controller and the calibration memory to print the test sheet; means for measuring the colorimetric response of the printer in printing the test sheet and producing as an output a set of measured colorimetric signals; means for mapping measured colorimetric signals to printer signals that caused the printer to print the colorimetric signals; a look up table processor, preprocessing the measured colorimetric signals to increase the number thereof with interpolated signals, using interpolation between spatially proximate responses; a colorimetic signal interpolation processor producing a regular interval dispersal of calculated colorimetric signals through color space, each of the calculated colorimetric signals mapped to a corresponding printer signal and derived from the measured colorimetric values and the interpolated values; a color space conversion memory, storing a lookup table, for use in converting colorimetic signals from a first color space to the printer signals suitable for producing a corresponding response at the printer.
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