Essilor International (compagnie Generale D'optique)

Centre National De La Recherche Scientifique

Muséum National D'histoire Naturelle

Essilor International

Centre National De La Recherche Scientifique-cnrs

Françoise Vienot

Bernard Bourdoncle

Gilles Baillet

Margalith Harrar

Fatima Benhalima

Hans Brettel

A method of improving an initial color filter comprises a numerical generation of sinusoidal spectra. Two steps of selecting said spectra are then executed. The first selection is carried out according to a criterion of colorimetric similitude with respect to the initial filter. The second selection is carried out according to the capacity of dummy filters corresponding to each spectrum to restore hues in a natural manner. To do this, observations of samples of hues through each dummy filter are simulated numerically, using a color appearance model to take account of a visual perception of a human observer. In this way, an improved filter is determined, which has a color close to that of the initial filter and which affords a natural rendition of hues.

Method of improving a color filter

A quantitative evaluation of a color filter () in accordance with the capacity of said filter to restore hues comprises the use of a numerical color appearance model. Values of a perceptive attribute are calculated for hue samples (), by simulating the observation of each of the samples through the filter () and without a filter. The values of the perceptive attribute correspond to the visual perception of the samples by an observer (), and a deviation between the values with and without filter constitutes the result of the evaluation of the filter. Such a method makes it possible to quantitatively rank several color filters, and the ranking obtained corresponds to that which would be established by real observers evaluating the filters.

Quantitative evaluation of a color filter

A method of obtaining a range of colors includes the following steps: selecting a test color from a predetermined set of colors, selecting a test palette comprising a plurality of color samples, measuring the real color of each sample when illuminated by a white light source, measuring the apparent color of each sample when illuminated by a test source formed by the white light source filtered by the test color, measuring the chromatic error between the real color and the apparent color of each sample, taking account of chromatic adaptation, measuring the mean chromatic error for all the chromatic errors, comparing the mean chromatic error to a test value, and adding the test color to the range if the mean chromatic error is less than or equal to the test value.

Method of obtaining a range of colors

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Paris, France

Françoise Vienot