Method for determining the color stimulus specification of translucent objects and an apparatus for performing the method
First Claim
1. A method for determining the color stimulus specification of translucent objects, in which the surface of the object under test is partially illuminated and the light reflected by a selected portion of the surface of the object under test is measured and arithmetically evaluated, the method comprising the steps of:
- (i) in a first measurement, illuminating a first portion of said surface of the object under test, said first portion having a first area, and measuring the light reflected by a second portion of said surface of the object under test, said second portion having a second area, thus obtaining a first set of measurement values;
(ii) in a second measurement, illuminating a third portion of said surface of the object under test, said third portion having a third area, and measuring the light reflected by a fourth portion of said surface of the object under test, said fourth portion having a fourth area, thus obtaining a second set of measurement values;
(iii) providing a set of reference measurement values obtained from the measurement of a reference object and calculating first and second sets of compensated measurement values, said first and second sets of compensated measurement values being functions of said first and second sets of measurement values and said reference measurement values;
(iv) calculating an intermediate reflection value as a function of said first and second sets of compensated measurement values and a correction value which corresponds to the light loss caused by the translucency of the object under test; and
(v) calculating a final reflection value as a function of said intermediate reflection value and the known reflection values of said reference object to obtain from said final reflection value the color stimulus specification of said object under test;
said first area of said first portion and said third area of said third portion being equal in size, and said fourth area of said forth portion having a size which is different from the size of said second area of said second portion.
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Accused Products
Abstract
The apparatus for determining the color stimulus specification of translucent objects comprises two light sources to create on the surface of an object under test two light spots which have different size. The light is transmitted from the light sources to the object under test by means of an optically conducting fiber bundle. The light reflected by the object under test is received by a lens and led via an optically conducting fiber bundle to a spectrometer. Thereafter, the measurement signal is digitized and arithmetically evaluated in a microprocessor. Due to the fact that two differently sized light spots are used, the measurement error which results in determining the color specification value of a translucent object can be defined and corrected. For this purpose, use is made of reference measurement values which have been obtained by measuring opaque reference objects and which have been stored in a memory module of the apparatus. In order to eliminate the influence of the disturbing ambient light, a further measurement without any light spot can be performed.
105 Citations
22 Claims
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1. A method for determining the color stimulus specification of translucent objects, in which the surface of the object under test is partially illuminated and the light reflected by a selected portion of the surface of the object under test is measured and arithmetically evaluated, the method comprising the steps of:
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(i) in a first measurement, illuminating a first portion of said surface of the object under test, said first portion having a first area, and measuring the light reflected by a second portion of said surface of the object under test, said second portion having a second area, thus obtaining a first set of measurement values; (ii) in a second measurement, illuminating a third portion of said surface of the object under test, said third portion having a third area, and measuring the light reflected by a fourth portion of said surface of the object under test, said fourth portion having a fourth area, thus obtaining a second set of measurement values; (iii) providing a set of reference measurement values obtained from the measurement of a reference object and calculating first and second sets of compensated measurement values, said first and second sets of compensated measurement values being functions of said first and second sets of measurement values and said reference measurement values; (iv) calculating an intermediate reflection value as a function of said first and second sets of compensated measurement values and a correction value which corresponds to the light loss caused by the translucency of the object under test; and (v) calculating a final reflection value as a function of said intermediate reflection value and the known reflection values of said reference object to obtain from said final reflection value the color stimulus specification of said object under test; said first area of said first portion and said third area of said third portion being equal in size, and said fourth area of said forth portion having a size which is different from the size of said second area of said second portion. - View Dependent Claims (4, 5, 6, 8, 9, 10, 11)
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2. A method for determining the color stimulus specification of translucent objects, in which the surface of the object under test is partially illuminated and the light reflected by a selected portion of the surface of the object under test is measured and arithmetically evaluated, the method comprising the steps of:
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(i) in a first measurement, illuminating a first portion of said surface of the object under test, said first portion having a first area, and measuring the light reflected by a second portion of said surface of the object under test, said second portion having a second area, thus obtaining a first set of measurement values; (ii) in a second measurement, illuminating a third portion of said surface of the object under test, said third portion having a third area, and measuring the light reflected by a fourth portion of said surface of the object under test, said fourth portion having a fourth area, thus obtaining a second set of measurement values; (iii) providing a set of reference measurement values obtained from the measurement of a reference object and calculating first and second sets of compensated measurement values, said first and second sets of compensated measurement values being functions of said first and second sets of measurement values and said reference measurement values; (iv) calculating an intermediate reflection value as a function of said first and second sets of compensated measurement values and a correction value which corresponds to the light loss caused by the translucency of the object under test; and (v) calculating a final reflection value as a function of said intermediate reflection value and the known reflection values of said reference object to obtain from said final reflection value the color stimulus specification of said object under test; said third area of said third portion having a size which is different from the size of said first area of said first portion, and said second area of said second portion and said fourth area of said fourth portion being equal in size.
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3. A method for determining the color stimulus specification of translucent objects, in which the surface of the object under test is partially illuminated and the light reflected by a selected portion of the surface of the object under test is measured and arithmetically evaluated, the method comprising the steps of:
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(i) in a first measurement, illuminating a first portion of said surface of the object under test, said first portion having a first area, and measuring the light reflected by a second portion of said surface of the object under test, said second portion having a second area, thus obtaining a first set of measurement values; (ii) in a second measurement, illuminating a third portion of said surface of the object under test, said third portion having a third area, and measuring the light reflected by a fourth portion of said surface of the object under test, said fourth portion having a fourth area, thus obtaining a second set of measurement values; (iii) providing a set of reference measurement values obtained from the measurement of a reference object and calculating first and second sets of compensated measurement values, said first and second sets of compensated measurement values being functions of said first and second sets of measurement values and said reference measurement values; (iv) calculating an intermediate reflection value as a function of said first and second sets of compensated measurement values and a correction value which corresponds to the light loss caused by the translucency of the object under test; and (v) calculating a final reflection value as a function of said intermediate reflection value and the known reflection values of said reference object to obtain from said final reflection value the color stimulus specification of said object under test; said third area of said third portion having a size which is different from the size of said first area of said first portion, and said fourth area of said forth portion having a size which is different from the size of said second area of said second portion.
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7. A method for determining the color stimulus specification of translucent objects, in which the surface of the object under test is partially illuminated and the light reflected by a selected portion of the surface of the object under test is measured and arithmetically evaluated, the method comprising the steps of:
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in a first measurement, illuminating a first portion of the surface of an opaque reference object, measuring the amount of light reflected by said first portion of the surface of said reference object and storing the measurement result as a first reference value; in a second measurement, illuminating a second portion of the surface of said opaque reference object, said second portion of the surface of said reference object being bigger or smaller than said first portion of the surface of said reference object, measuring the amount of light reflected by said second portion of the surface of said reference object and storing the measurement result as a second reference value; in a third measurement, illuminating a first portion of the surface of an object under test, measuring the amount of light reflected by said first portion of the surface of said object under test and storing the measurement result as a first temporary measurement value; in a fourth measurement, illuminating a second portion of the surface of said object under test, said second portion of the surface of said object under test being bigger or smaller than said first portion of the surface of said object under test, measuring the amount of light reflected by said second portion of the surface of said object under test and storing the measurement result as a second temporary measurement value; in a fifth measurement, exposing said surface of said object under test to ambient light conditions and measuring the light reflected by a portion of said surface of said object under test, thus obtaining a third measurement value; arithmetically subtracting said third measurement value from said stored first temporary measurement value to obtain a first definitive measurement value, and arithmetically subtracting said third measurement value from said stored second temporary measurement value to obtain a second definitive measurement value; arithmetically dividing said first definitive measurement value by said stored first reference value to obtain a first compensated measurement value, and arithmetically dividing said second definitive measurement value by said stored second reference value to obtain a second compensated measurement value; calculating an intermediate reflection value as a function of said first and second compensated measurement values and a correction value which corresponds to the light loss caused by the translucency of said object under test; and calculating a final reflection value as a function of said intermediate reflection value and the known reflection values of said reference object to obtain from said final reflection value the color stimulus specification of said object under test.
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- 12. An apparatus for determining the color stimulus specification of translucent objects, comprising a light emitting means for illuminating the object under test, an optical means for receiving the light reflected by the object under test which is illuminated by said light emitting means, a sensor means for measuring the light received by said optical means, and a microprocessor means for evaluating the measurement data, said light emitting means comprising at least two light sources, a first light source of said at least two light sources illuminating a first portion of said object under test, and a second light source of said at least two light sources illuminating a second portion of said object under test, said first portion having a size which is different from the size of said second portion.
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13. An apparatus for determining the color stimulus specification of translucent objects, comprising a light emitting means for illuminating the object under test, an optical means for receiving the light reflected by the object under test which is illuminated by said light received by said optical means, and a microprocessor means for evaluating the measurement data, said optical means comprising at least two lenses, a first lens of said at least two lenses receiving the light reflected by a first portion of said object under test, and a second lens of said at least two lenses receiving the light reflected by a second portion of said object under test, said first portion having a size which is different from the size of said second portion.
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14. An apparatus for determining the color stimulus specification of translucent objects, comprising a light emitting means for illuminating the object under test, an optical means for receiving the light reflected by the object under test which is illuminated by said light emitting means, a sensor means for measuring the light received by said optical means, and a microprocessor means for evaluating the measurement data, said light emitting means comprising at least two light sources, a first light source of said at least two light sources illuminating a first portion of said object under test, and a second light source of said at l east two light sources illuminating a second portion of said object under test, said first portion having a size which is different from the size of said second portion, and said optical means comprising at least two lenses, a first lens of said at least two lenses receiving the light reflected by a third portion of said object under test, and a second lens of said at least two lenses receiving the light reflected by a fourth portion of said object under test, said third portion having a size which is different from the size of said fourth portion.
Specification