JPH0786814B2 - Color hard copy forming method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for obtaining a color hard copy of a color image displayed on a display using emitted light or transmitted light, and in particular, observation on a display screen. The present invention relates to a color hard copy forming method including a signal processing step that makes it possible to form a color hard copy that gives an impression of a tint extremely close to the impression of the tint.

(Prior Art) Recently, with the rapid development of the information industry, various information processing systems have been developed, and recording methods and devices suitable for the respective information processing systems have also been developed. As one of such recording methods, it is displayed on a display that uses emitted light or transmitted light (for example, a color television that uses emitted light such as phosphor, plasma, electroluminescence, or a liquid crystal color television that uses transmitted light). There is a method of forming a hard copy of a color image on various color recording materials by using electric signals for displaying on these displays. This method is necessary for making a hard copy of a television image sent from a broadcasting station at home or making a hard copy of an image formed on a display by using a computer graphics technique.

However, there are the following two difficulties in converting a color image displayed on these displays into a hard copy. (1) The color (white) under the light source when observing a hard copy is considerably different from the white of the display. For example, the white color of a color television utilizing a phosphor is much more bluish than the white color under a light source when observing a hard copy. In this way, when the reference whites are different, it is not known at all what kind of relationship is required between the tristimulus values of both colors in order to make the impressions of appearance of both colors match.

(2) The display is in publish mode or transmissive mode, whereas when viewing a hard copy it is in reflective mode. Since there is no established theory about the appearance of colors when the modes are different, it is completely unknown how to handle the colors when setting the color target of a color hard copy.

Due to such difficulties, recording on a color recording material without changing the relationship of the red, green, and blue signals of the electric signals for displaying the image on the display, the color of the hard copy obtained However, there is an inconvenience that the color is far from the color of the image displayed on the display.

OBJECT OF THE INVENTION The first object of the present invention is to color tristimulus values of the color of the image on the display so as to give the same impression as the color of the image displayed on the display using emitted light or transmitted light. It is an object of the present invention to provide a method of converting a color of a copy image into tristimulus values and forming a color hard copy based on the tristimulus values thus converted.

Secondly, the object of the present invention is to provide a method for accurately realizing the target color on the color recording material based on the relationship of the tristimulus values of the colors of the color hard copy image thus converted. It is in.

(Structure of the Invention) An object of the present invention is to provide a method for forming a hard copy of an image on a display on a color recording material using emitted light or transmitted light, in which the tristimulus value of the color of the image on the display (X ^TV , Y ^TV , Z ^TV ) and the tristimulus value of the color (X ^OB , Y
^OB , Z ^OB ) and perform recording on the color recording material so as to realize the tristimulus values (X ^OB , Y ^OB , Z ^OB ), a method of forming a color hard copy, However, X ₀ ^TV , Y ₀ ^TV , and Z ₀ ^TV are the standard white tristimulus values of the display, and X ₀ ^OB , Y ₀ ^OB , and Z ₀ ^OB are white tristimulus under the observation light source of hard copy. And the recording energies determined on the basis of the monochromatic densities of the yellow, magenta, and cyan of the color recording material for realizing the above tristimulus values (X ^OB , Y ^OB , Z ^OB ) A color hard copy forming method according to claim 1, characterized in that the color recording material is recorded in an amount.

In the present invention, the CIE tristimulus values (X ^OB , X ^OB ,
Recording is performed on the color recording material so as to realize Y ^OB and Z ^OB . Even if the observation mode is different, 3
The ratio of the stimulus value to the tristimulus value of any color is based on the finding that the reference white is preserved even if it changes.

In the above formula, Y ₀ ^OB is 1.00. Since there is an acceptable range for the whiteness of color hardcopy, X ₀ ^OB and
Z ₀ ^OB is generally α ₁ X ₀ ≦ X ₀ ^OB ≦ α ₂ X ₀ β ₁ Z ₀ ≦ Z ₀ ^OB ≦ β ₂ Z ₀ .

X ₀ and Y ₀ are white under the observation light source, and in the case of the C light source described later, X ₀ = 0.9807, Y ₀ = 1.000, and Z ₀ = 1.1823. α ₁ , α ₂ , β ₁ , and β ₂ are parameters that determine the allowable range width of whiteness, and do not depend on the observation light source. According to our psychological experiments, α ₁ = 0.9797, α ₂ = 1.0084 β ₁ = 0.9490, β ₂ = 1.1485, preferably α ₁ = 0.9849, α ₂ = 1.0035 β ₁ = 0.9842, β ₂ = 1.1097, particularly preferably , Α ₁ = 0.9887, α ₂ = 0.9993 β ₁ = 1.0093, β ₂ = 1.0829, the object of the present invention is achieved.

The conversion of the tristimulus values according to the above equation ensures the visible identity of the colors on the display and in the hardcopy image.

This can be confirmed by the following experiment. That is, a color patch of a plurality of colors is generated on a color display, and tristimulus values (X ^TV , Y ^TV , Z ^TV ) of the color are obtained by using the above equation (X ^OB , Y ^OB , Z ^OB ) It is recorded on a hard copy and a psychological experiment is conducted to see how the two colors look different.

For example, a color TV monitor (product name CMM14-7HR / 1 type) manufactured by Shibasoku Co., Ltd. is used as a color display (the reference white tristimulus values of this color TV monitor are measured values X ^TV = 0.9498, Y ^TV = 1.0000, Z ^TV = 1.3946, color temperature is 9300K), and this color TV monitor inputs 8-bit R, G, B signals shown in Table-1 through an external interface (NEXUS6810 of Kashiwagi Laboratory). Then, 24 color patches were generated.

The tristimulus value of each color at this time is given by the following formula.

However, (X _R , y _R , z _R ), (x _G , y _G , z _G ), (x _B , y _B , z _B ) are the chromaticity coordinates of the red, green, and blue primaries of the display, respectively. , K _R ^TV , K _G ^TV , and K _B ^TV are constants for determining the reference white color of the display, and R *, G *, and B * are relative emission intensities or relative transmitted light intensities of 0 to 1.0. Takes a value. X ^TV , Y ^TV , Z ^TV and M vary depending on the display used and can be obtained by actual measurement.
For example, the value of M of the above-mentioned CMM14-7HR / 1 type color display manufactured by Shibasoku Co., Ltd. is as follows.

Also, the relationship between the 8-bit R, G, B signals in Table-1 and the R *, G *, B * in the formula is R * = (R / 255) ^r G * = (G / 255) ^r B * = (B / 255) ^r . In a properly adjusted television, r = 2.2.

On the other hand, JIS standard Z87 as an observation light source for color hard copy
Taking the 01 C light source (color temperature 6774 K) into consideration, the tristimulus value of each color under this C light source was obtained by the formula, and 24 color patches under the C light source were recorded on the color recording material.

This recording can be achieved in the simplest manner by changing the recording conditions and performing recording by the trial and error method until the above-mentioned tristimulus values are realized. For example, the tristimulus values X ^OB , Y ^OB , and Z ^OB at the C light source according to the formula are reproduced on a color paper by trial and error for the above 24 colors, and this color print is placed near the color monitor screen described above. It was observed under the room illumination level (close to the C light source). For comparison, when the television tristimulus value given by the formula was assumed to be the tristimulus value of the color of the color hard copy under the C light source as it was, a color print was also made in the same manner as above. It was found that the sample obtained by the conversion of the formula of the present invention gives the impression that the color of the television and the color of the color print match much more than the case of.

From the above, it was found that the target of the color for reproducing the image of the color display on the hard copy so that the impression of the tint is the same is given by the formula.

In the above, the means for achieving the target color by the trial and error method is used. Thus, it is a very difficult problem to accurately realize the target color on the color hard copy. This will be explained by taking a color paper as an example. (A) If the relationship between the tristimulus values of the target color and the analysis densities of yellow, magenta, and cyan to be realized on the color hard copy does not correspond exactly. (B) Even if this correspondence is correct, if the exposure amounts of blue, green, and red to obtain the analysis density are obtained from the look-up table and they are overprinted, the blue The main cause is that a predetermined concentration cannot be obtained due to leakage of spectral sensitivity of each of the green and red photosensitive layers and chemical interaction between the photosensitive layers (so-called multi-layer effect).

In the second embodiment of the present invention, in order to easily realize a target color on a color hard copy with high precision,
The monochromatic densities of yellow, magenta, and cyan of the color recording material for realizing the tristimulus value obtained by the formula are obtained, and recording is performed on the color recording material with the recording energy amount determined based on the monochromatic density.

That is, the case where a photosensitive material is used as a color recording material will be described as an example. First, yellow, magenta,
Blue that divides the density of cyan into n levels (for example, 30 levels),
Exposure amounts for green and red (different exposure colors may be combined, for example, yellow, red, infrared light, etc.) are set. The monochromatic exposure densities (hereinafter, referred to as monochromatic densities) formed by the monochromatic light of each exposure amount are different from the analysis densities, and, for example, in the case of yellow, it is the yellow density when the blue (or yellow) light is applied to the monochromatic light. However, in strong blue (or yellow) exposure, dyes in other photosensitive layers may develop due to leakage of spectral sensitivity, which means the density measured by a blue filter.

Next, a sample is prepared in which light of blue, green, and red (or other combination such as yellow, red, and infrared light) is mixed and applied. The mixed one gives a color patch with a combination of n ³ (27,000 in the case of n = 30) colors. This color patch is read by a scanner having a spectral sensitivity showing the same response as the color matching function. The output gives tristimulus values for each of the n ³ color patches.

In this way, the correspondence between the monochromatic exposure densities (yellow, magenta, cyan) and the tristimulus values (X, Y, Z) is obtained for each of the n ³ color patches. This correspondence is that there are tristimulus values (X, Y, Z) at n ³ grid points in a monochromatic density space (a space formed by three density axes of yellow, magenta, and cyan). This is converted so that monochromatic densities (yellow, magenta, cyan) exist in a tristimulus value space (a space formed by three axes of X, Y, and Z).

Therefore, the tristimulus values (Xi, Yi,
When Zi) is given by the method as described above, the corresponding monochromatic densities (yellow i, magenta i, cyan i) can be calculated by performing three-dimensional interpolation in the tristimulus space.

Also, the hard stimulus target color tristimulus values (Xi, Yi, Z
i), the corresponding monochromatic density (Yi, Mi, C
As another method of obtaining i) by using a calculation formula, it is useful to use the calculation formula shown below.

However, here, F and G are 3 × 3 matrices, and their elements Fi
jGij (i = 1 to 3, j = 1 to 3) is a nonlinear optimization calculation so that the correspondence between monochromatic density and tristimulus values obtained for the n ³ color patches described above can be explained most consistently. Can be determined by

Since each monochromatic exposure amount for giving this monochromatic density is known as described above, the color having the target tristimulus values (Xi, Yi, Zi) is reproduced as a hard copy if exposure is performed at that exposure amount. it can.

The exposure amount (recording energy amount) at the time of performing the above-mentioned exposure (image recording) varies depending on changes in the working environment (for example, temperature, humidity, etc.). Therefore, instead of directly associating the monochromatic density with the exposure amount, a lookup table (LUT) for associating the monochromatic density with the exposure signal (for example, 8-bit signal) may be provided and rewritable. . That is, prior to recording a color image, a test print is performed to correlate the monochromatic density with the exposure signal in response to changes in the work environment, changes in the recording material lot, etc. By recording, the desired color hard copy can always be obtained stably.

In the present invention, various color recording materials can be used. Examples thereof include normal color paper, reversal color paper, color diffusion transfer material, heat development color photosensitive material (for example, diffusion transfer type heat development color photosensitive material described in US Pat. No. 4,500,626), color electrophotography and the like. .

Also, when a recording material other than a photosensitive material is used as the color recording material, recording may be performed with the recording energy amount for giving a monochromatic density corresponding to the tristimulus value of the target color in the same manner as above. In addition to the light-sensitive material, various color recording materials to which the present invention can be applied include melt-type or sublimation-type color heat-sensitive recording materials and ink jet recording materials.

(Effect of the invention) Since the present invention obtains the target tristimulus value of the color to be formed on the hard copy by the conversion represented by the formula as described above, the color giving the same impression as the color of the image on the display is obtained. A color hard copy can be obtained.

Further, in order to determine the exposure amount by calculating the monochromatic exposure density corresponding to the target tristimulus value given by the formula,
It is possible to easily obtain a color hard copy having a color that gives the same impression as the color of the image on the display.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G03B 27/73 G03G 15/01 S G06F 3/153 340 A H04N 9/79 H04N 9/79 H

Claims (2)

[Claims] 1. A method for forming a hard copy of an image on a display on a color recording material using emitted light or transmitted light, the tristimulus value of the color of the image on the display (X ^TV , Y ^TV , Z ^TV ). From the following equation, the tristimulus value of color (X ^OB , X ^OB ,
Y ^OB , Z ^OB ) is obtained, and recording is performed on the color recording material so as to realize the tristimulus values (X ^OB , Y ^OB , Z ^OB ), and a color hard copy forming method. Here, X ₀ ^TV , Y ₀ ^TV , and Z ₀ ^TV are reference white tristimulus values of the display, and X ₀ ^OB , Y ₀ ^OB , and Z ₀ ^OB are white tristimulus under the observation light source of hard copy. It is a value. 2. A monochromatic density of yellow, magenta, and cyan of the color recording material for realizing the tristimulus values (X ^OB , Y ^OB , Z ^OB ) is obtained, and a recording energy amount determined based on the monochromatic density. The color hard copy forming method according to claim 1, wherein recording is performed on the color recording material.