JPH0795426A - Device for color matching under different light sources - Google Patents

Abstract

PURPOSE:To accurately reproduce a color under an arbitrary light source by using the spectral distribution of illumination for observation and the color value corresponding to a prescribed light source to convert the color to the device value of a color output device. CONSTITUTION:A spectro photometric-colorimetric instrument 7 sends a spectral distribution signal 8 of the illuminating light source for observation to a color value calculating computer 1. The computer 1 sends a spectral distribution signal 2 of the illuminating light source for observation to a color conversion means 4. The computer 1 sends a color value signal 3, which is preliminarily registered and corresponds to a prescribed light source of color temperatures 4000 to 20000 [K], to the color conversion means 4. This means 4 consists of a feed forward neutral network with the learning function and uses the spectral distribution signal 2 and the color value signal 3 to correct a device value signal 6 of RGB or the like and sends it to a color output device 5. Thus, the color output device 5 reproduces the picture whose color under the illuminating light source for observation look to be equal to that under the prescribed light source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses the color conversion method to determine the difference in color appearance of reproduced colors of a color output device due to the influence of an illumination light source during observation, and XYZ, L * a * under a specific light source. b *, L * u * v *
From color values such as red (R), green (G), blue
(B) or Cyan (C), Magenta (M), Yellow
(Y) or cyan (C), magenta (M), yellow (Y),
When converting to a device value that depends on a color output device such as black (K), by performing color conversion to a device value that corresponds to the illumination light source at the time of observation, when reproducing colors are observed under different light sources The present invention relates to a color matching device under different light sources having a function of performing color correction so that the colors look the same.

[0002]

2. Description of the Related Art Conventionally, the color of printed matter is evaluated by a standard light source such as D50 or D65, and accurate color is reproduced under that light source. It was a general idea. Therefore, until now, there has been little need for color matching under an observation light source other than the standard light source. Therefore, almost no existing technology has been developed for a method and apparatus for color matching under such various light sources.

[0003]

However, with the recent development of simple color printing machines such as color DTPs and color printers, color printed matter has come to be used for various purposes, and the illumination conditions for observing the printed matter are various. It is miscellaneous. Therefore, it is necessary not only to match colors under a standard light source, but also to accurately reproduce colors under an arbitrary light source.

[0004]

According to the present invention, the above-mentioned problems include a conversion means for converting a color value into a device value and a spectroscopic measuring device, and a spectral distribution of a light source measured by the spectroscopic measuring device. And using the color value of the given light source, red
(R), Green (G), Blue (B), or Cyan (C)
, Magenta (M), or cyan (C), magenta (M),
By converting to a device value such as black (K) value, color correction is performed so that the reproduced color under the light source other than the predetermined light source looks the same as the color under the predetermined light source. Achieved by a color matching device.

As the converting means, one multi-layer feedforward type neural network is used. The predetermined light source is a standard light source of a D light source or a C light source having a color temperature of 4000 [K] to 20000 [K].

[0006]

[Function] Since color values such as XYZ, L * a * b *, and L * u * v * values depend on the illumination light at the time of measurement, the color values measured under different light sources are different. Has a value. for that reason,
Different light source pairs of color output device values such as R, G, B values, C, M, Y, (K) values and color values are obtained. The color conversion means in the present invention includes a predetermined light source such as a standard light source and spectral distributions of all light sources expected as illumination during observation such as A light source, B light source, C light source, F1 to F12 fluorescent lamp light source, and the like. When a set of color values under a light source is input, a conversion unit consisting of a feed-forward type neural network adjusted to accurately perform color conversion processing to device values, and the illumination light spectrum during observation By providing a measuring unit that measures the distribution and a transmitting unit that transmits the device values converted by the converting unit to the color output device, D50 and D6
A color matching device under different light sources is configured so that when a reproduced color is observed with a source other than the light source, the appearance is the same as the color observed with the specified light source.

A standard light source is preferable as the predetermined light source. FIG. 1 is a view showing that, according to the present invention, a difference in color appearance due to the influence of illumination light at the time of observation is corrected, and when a reproduced color is observed with a light source other than a predetermined light source such as D50 or D65, the appearance is reproduced with a light source other than the predetermined light source. FIG. 3 shows a schematic view of a color matching device under different light sources so that when a color is observed, its appearance is the same as that of a predetermined light source. In this case, FIG. 1 uses a multilayer feedforward neural network as the color conversion means. In FIG. 1, the neural network used as the color conversion unit indicated by reference numeral 1 is
As a color conversion method, it is an existing technology as described in Japanese Patent Laid-Open No. 04-261267. If there is a combination of a color value and a device value that depends on the characteristics of a color output device, a correct color can be obtained by the learning function of the neural network. The conversion can be performed. In the present invention, such a capability of the neural network is utilized to utilize as the color conversion means indicated by reference numeral 4.

The spectral distribution of the illumination light source at the time of observation is measured by the measuring means indicated by reference numeral 7, and the conversion from the set of the spectral distribution corresponding to the illumination light source at the time of observation and the color value of the predetermined light source to the device value is learned in advance. The neural network shown by the reference numeral 4 is a device such as RGB, CMY (K) in which the symmetric color under a predetermined light source such as D50 or D65 light source and the reproduced color under the light source during observation look the same. It is converted into a value and transmitted to the color output device as a device value signal 6 to reproduce the color.

[0009]

EXAMPLE As an example using such a color matching device under different light sources, a color temperature correcting device as described above is actually configured on a Sun workstation using a neural network as a color converting means, and As a color output device, we actually used a Canon Pixel Dio to find the device value corresponding to the light source of the color chart, and output it for the case of D65 and A light source. Then, the results are visually compared on different light booths of the D65 light source and the A light source, and it is confirmed that the reproduced color looks the same under both light sources.

[0010]

[Effect] According to the present invention, a device that corrects the reproduced color of the color output device so that the reproduced color always looks the same under different illumination according to the spectral distribution of the illumination at the time of observation is used. The color of the illumination light source during observation is converted by a pre-learned color conversion unit that converts the color value to the device value in order to obtain the device value that looks like the same color when the color is observed under different light sources. Spectral distribution and XYZ under a given light source
Values, L * a * b * values, and other color values are combined into red (R), green (G), blue (B), or cyan corresponding to various light sources.
(C), magenta (M), yellow (Y), or cyan
(C), magenta (M), yellow (Y), and black (K) by converting to device values of the color output device, the colors observed when different light sources are used are the same. It is possible to realize a color matching device under different light sources, which is capable of correcting reproduced colors so as to look like.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a color matching device under different light sources according to the present invention.

[Explanation of symbols]

 1 ... Calculator for color value calculation 2 ... Spectral distribution signal corresponding to observation light source 3 ... Color value signal corresponding to predetermined light source 4 ... Color conversion means 5 ... Color output device 6 ...・ Device value signal 7 ・ ・ ・ Spectrocolorimeter 8 ・ ・ ・ Spectral distribution signal

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Claims (3)

[Claims] Claim: What is claimed is: 1. A red (R) color filter comprising a conversion means for converting a color value into a device value and a spectroscopic measuring device, and using the spectral distribution of the light source and the color value of a predetermined light source measured by the spectroscopic measuring device. , Green (G), blue (B), or cyan
(C), magenta (M), yellow (Y) or cyan (C),
By converting to device values such as magenta (M), yellow (Y), and black (K) values, color correction is performed so that the reproduced color under a light source other than the predetermined light source looks the same as the color under the predetermined light source. A color matching device under different light sources. 2. The color matching apparatus under different light sources according to claim 1, wherein said conversion means is one multi-layered feedforward neural network having a learning function. 3. The predetermined light source according to claim 1 has a color temperature of 4000.
A color matching device under different light sources, which is a standard light source of D light source or C light source of [K] to 20000 [K].