JPH0795424A - 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 color value obtained from 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 calculates a color value signal 2 corresponding to the illuminating light source for observation and sends it 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 like a D light source, to the color conversion means 4. This means 4 consists of a feed forward neutral network with the learning function and used color value signals 2 and 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 looks 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 the 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 observing reproduced colors under different light sources. The present invention relates to a color matching device under a different light source having a function of performing color correction so that it looks the same.

[0002]

2. Description of the Related Art Conventionally, the color of printed matter is evaluated under a standard light source such as D50 or D65, and accurate color reproduction is possible 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 predetermined light source such as 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. Using the color values such as XYZ, L * a * b *, etc. and the color value of the predetermined light source obtained from, red (R), green (G), blue (B), or cyan (C), magenta (M )
Achieved by a color matching device under different light sources, characterized by converting to device values such as, yellow (Y) or cyan (C), magenta (M), yellow (Y), black (K) values . As the conversion means, one multi-layered feedforward type neural network is used.

The predetermined light source has a color temperature of 4000 [K].
The standard light source is a D light source or a C light source of from 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 has a predetermined light source such as a predetermined light source and A light source, B light source, C light source, F1 to F12 fluorescent lamp light source, etc. A conversion unit consisting of a feedforward type neural network adjusted to accurately perform color conversion processing when input, a measurement unit that measures the spectral distribution of illumination light during observation, a conversion unit By providing a transmission unit that transmits the device value converted in to the color output device, the appearance will be the same as the color observed with the predetermined light source when observing the reproduced color with a source other than the predetermined light source such as D50 and D65. A color matching device under different light sources is configured.

A standard light source is desirable 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 spectral distribution is used to derive the color value corresponding to each light source from the spectral reflectance data registered in advance. The neural network indicated by the reference numeral 4 which learned the conversion from the set of the color value corresponding to the illumination light source at the time of observation and the color value of the predetermined light source to the device value in advance is symmetric under the predetermined light source such as the D50 or D65 light source. Color and
RGB, CMY so that the reproduced color looks the same under the light source during observation
It is converted into a device value such as (K) and is transmitted to the color output device as a device value signal of reference numeral 6 for color reproduction.

[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 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 colors look the same under both light sources.

[0010]

[Effects] According to the present invention, therefore, a device for correcting the reproduced color of the color output device so that the reproduced color always looks the same under different illumination in accordance with the color temperature of the illumination during observation is used. , Observing under a predetermined light source by a pre-learned color conversion means for converting a color value to a device value in order to obtain a device value that looks like the same color when observing colors under different light sources Each of the illumination source of time
Red (R), green (G), blue (B) or cyan (C), magenta (M), yellow (Y) corresponding to various light sources are selected from a set of color values such as XYZ values and L * a * b * values. ) Or cyan (C)
, Magenta (M), yellow (Y), black (K) by converting to the device value of the color output device,
A color matching device under different light sources capable of correcting reproduced colors so that colors observed when different light sources are used during observation looks the same.

[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 ... Color value 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] 1. A conversion means for converting a color value to a device value and a spectroscopic measuring device are provided, and XYZ, L * a * b *, etc. obtained from the spectral distribution of a light source measured by the spectroscopic measuring device. Using the color value and the color value of the specified light source, red (R), green (G), blue (B), or cyan (C), magenta
(M), yellow (Y) or cyan (C), magenta (M),
Characterized by converting to device values such as yellow (Y) and black (K) values 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 for different light sources, which is a standard light source of D light source or C light source of [K] to 20000 [K].