JPH0795425A - 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 temperature 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 color temperature signal 8 obtained from the spectral distribution of an illuminating light source for observation to a color value calculating computer 1. The computer 1 sends a color temperature 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 color temperature 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 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 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]

SUMMARY OF THE INVENTION According to the present invention, the above-mentioned problems include a conversion means for converting a color value to a device value and a spectroscopic measuring device, and the color of the light source measured by the spectrocolorimeter. Using the temperature and XYZ, L * a * b *, and other color values of a given light source, red (R), green (G), blue (B), or cyan (C), magenta (M), yellow (Y ) Or cyan (C), magenta (M), yellow (Y), and black (K) values are converted into device values such that the reproduced color under a light source other than the predetermined light source becomes the color under the predetermined light source. This is achieved by a color matching device under different light sources, which is characterized in that the colors are corrected to look the same.

In this case, one multilayer feedforward type neural network is used as the conversion means. 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 pairs of device values of the color output device such as R, G, B values, C, M, Y, (K) values and light sources are obtained. The color conversion means in the present invention includes a predetermined light source such as a standard light source and
Accurately perform color conversion processing that converts to the device value when the color temperature 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 is input. A conversion unit consisting of a feedforward type neural network adjusted as described above, a measurement unit that measures the spectral distribution of the illumination light during observation, and a transmission unit that transmits the device value converted by the conversion unit to the color output device. By providing it, a color matching device under different light sources is configured so that when a reproduced color is observed with a source other than a predetermined light source such as D50 or D65, the appearance is the same as the color observed with the predetermined light source.

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 standard light source. In this case, FIG. 1 uses a multilayer feedforward neural network as the color conversion means. In FIG. 1, the neural network denoted by the reference numeral 1 is an existing technology as described in Japanese Patent Application Laid-Open No. 04-261267 as a color conversion method, and has a color value and a characteristic of a color output device. If there is a set of dependent device values, accurate color conversion can be performed by the learning function of the neural network. 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 color temperature of the illuminating light source at the time of observation is measured by the measuring means indicated by reference numeral 7, and the color temperature is used in advance from the set of the color temperature corresponding to the illuminating light source at the time of observation and the color value of the predetermined light source. The neural network shown by the reference numeral 4 which learned the conversion to the device value, RGB that the symmetric color under the predetermined light source such as D50 and D65 light source and the reproduced color under the light source at the time of observation look the same, It is converted into a device value such as CMY (K) and transmitted as a device value signal of reference numeral 6 to a color output device 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 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 colors look 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 color temperature of the illumination at the time of observation is used. By observing a color under different light sources, a color value is converted into a device value in order to obtain a device value that looks like the same color. Color temperature and XYZ value under a given light source,
Red corresponding to various light sources from a set of color values such as L * a * b * values
(R), green (G), blue (B) or cyan (C),
Different light sources during observation by converting to device values of color output device such as magenta (M), yellow (Y), or cyan (C), magenta (M), yellow (Y), black (K). It is possible to realize a color matching device under different light sources, which can correct reproduced colors so that the colors observed when used are 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 temperature signal of observation light source 3 ... Color temperature signal corresponding to a predetermined light source 4 ... Color conversion means 5 ... Color output device 6 ... Device Value signal 7 ... Spectral colorimeter 8 ... Color temperature signal

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Claims (3)

[Claims] 1. A color temperature of a light source measured by a spectrocolorimeter and XYZ, L * a * b *, of a predetermined light source, having a conversion means for converting a color value to a device value and a spectroscopic measurement device. Red (R), green (G), blue using color values such as L * u * v * values
(B) or Cyan (C), Magenta (M), Yellow
(Y) or cyan (C), magenta (M), yellow (Y),
Color matching under different light sources, which is characterized by converting the device value such as black (K) value so that the reproduced color under different light sources looks the same as the color under a predetermined light source. apparatus. 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].