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AssigneeX-Rite Europe GmbH
InventorsPeter Ehbets, Beat Frick, Mark Wegmüller, Adrian von Orelli
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For the color measurement of samples printed on a substrate including a brightener, a raw spectral reflection factor of the sample is measured in a first measurement by illumination of the sample with light without UV portion. In a second measurement, a fluorescence spectrum of the sample is measured by illumination of the sample with only UV light. The measured fluorescence spectrum is recalculated as a corrected fluorescence spectrum by weighting with spectrally dependent correction factors and, finally, the measured raw spectral reflection factor and the corrected fluorescence spectrum are added to form a corrected spectral reflection factor from which the values characterizing the color of the sample are then calculated. The spectral correction factors are determined during the device manufacture for a certain set of light types and stored in the device.
Process for the colour measurement of samples printed on substrates with brighteners, whereby a spectral reflection factor of a sample is determined and made available for the calculation of values characterizing the colour, characterized in that the spectral reflection factor of the sample is determined by way of a double measurement, whereby in a first measurement a raw spectral reflection factor of the sample is measured by illumination of the sample with light without UV portion, a fluorescence spectrum of the sample is measured in a second measurement by illumination of the sample with only UV light, the measured fluorescence spectrum is recalculated as a corrected fluorescence spectrum by way of a correction model in which the fluorescence spectrum is spectrally weighted with a set of spectrally dependent correction factors, and whereby the measured raw spectral reflection factor and the corrected fluorescence spectrum are added to form a corrected spectral reflection factor which corrected spectral reflection factor is used for the calculation of the values characterizing the colour of the sample.
Process for the colour measurement of samples (M) printed on substrates with brighteners, whereby a spectral reflection factor of a sample (M) is determined and made available for the calculation of values characterizing the colour, characterized in that the spectral reflection factor (53) of the sample (M) is determined by way of a double measurement, whereby in a first measurement (45) a raw spectral reflection factor (48) of the sample (M) is measured by illumination of the sample (M) with light without UV portion, a fluorescence spectrum (43) of the sample (M) is measured in a second measurement (41) by illumination of the sample (M) with only UV light, the measured fluorescence spectrum (43) is recalculated as a corrected fluorescence spectrum by way of a correction model (51) in which the fluorescence spectrum (43) is spectrally weighted with a set of spectrally dependent correction factors (50), and whereby the measured raw spectral reflection factor (48) and the corrected fluorescence spectra are added to form a corrected spectral reflection factor (53), whereby the corrected spectral reflection factor (53) is used for the calculation of the values characterizing the colour of the sample (M), whereby individual sets of correction factors (50) for the correction model (51) are used for different light types (49) and that respectively one corrected spectral reflection factor (53) is calculated for one more selected light types using the individual sets of correction parameters (50) associated with the respective light type, and whereby the correction factors (50) are determined from the correct spectral reflection factor (53) and a reference spectrum (33) of a calibration sample as a result of an equalization calculation (34) wherein the deviations between the corrected spectral reflection factor (53) and the reference spectrum (33) are minimized.
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