JP2000121437A - Method and apparatus for predicting color - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and correctly estimate radiant intensity and spectral radiant intensity of a reflector from a small number of measurement values when reflectivity and spectral reflectivity of the reflector is known. SOLUTION: When radiant intensity (lightness) of photographic paper 1 of a monochrome silver salt photo whose reflectivity Ci by an observation optic system of 0 deg. incidence and 45 deg. observation is known is to be predicted, first, achromatic photographic paper 2 of a silver photo similar to the photographic paper 1 of interest with high lightness whose reflectivity (a) by the observation optic system of 0 deg. incidence and 45 deg. observation 1 is placed on a position for observing the photographic paper 1 of interest and illuminated by a predetermined light source 11 for illuminating the photographic paper 1 of interest. Radiant intensity of the illuminated photographic paper 2 is measured by a radiant intensity meter 12 placed at an observation point for observing the photographic paper 1 of interest. Next, a measurement value (b) of the radiant intensity is divided by the reflectivity (a) to predict illumination intensity by the light source 11. Then the predicted value b/a of the illumination intensity is multiplied by the reflectivity Ci of the photographic paper 1 of interest to predict radiant intensity from the photographic paper 1. Where the prediction value of the radiant intensity is di, di=(b/a)Ci.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for estimating the radiation intensity from a reflector having a known reflectance when the reflector is illuminated by a predetermined light source. More specifically, the present invention relates to a method and an apparatus for predicting a phenomenon in which the color of a reflector differs due to illumination having different spectral distributions, so-called metamerism, and the effect of the gloss of the reflector and the influence of observation conditions.

[0002]

2. Description of the Related Art A color management system (C) is used to match the appearance of colors in different devices and reflectors.
MS) has become widely used. In this color management system, conventionally, colors are evaluated under a standard light source such as a D50 light source or a D65 light source. For example, Japanese Unexamined Patent Publication No. 7-95425 discloses that a large number of color patches are illuminated by a plurality of light sources, and tristimulus values or 3
XYZ, L * a * b *, L * u * derived from the stimulus value
A method of actually measuring a v * value and performing color prediction using a neural network is shown.

[0003] Japanese Patent Application Laid-Open No. 9-214787 discloses that color correction is performed by performing a primary conversion in an XYZ color space based on a perceived reference white color. However, in this method, it is possible to match the perceived white color, but it is not possible to perform correction in consideration of metamerism.

Further, Japanese Patent Application Laid-Open No. 9-284581 discloses that
From the input image, estimate the spectral reflectance by a method using multivariate analysis, convert it to a color value signal based on the spectral information of the specified light source, consist of multiple neural networks, The color values for each of the light sources of the standard color samples whose color separation values are output in advance from the printer are given as input, and the color separation values of the standard color samples are given as the teacher signal, and the learning results are given to the light source. , And color separation is performed. However, there is no mention of a method of recognizing the color value of each light source of the standard color sample at that time.

The method of measuring gloss is defined in JIS, but the measurement of gloss is complicated and a large amount of data is recorded. Furthermore, considering the spectral distribution, it is considered that an extremely large amount of data and data processing are required.
However, no color prediction method has been considered based on such measured values in consideration of the illumination when actually observing, the observation position, and the observation viewpoint.

[0006]

Generally, the reflectance is zero.
The measurement is often performed using a 45 ° incidence / 45 ° observation optical system, a 45 ° incidence / 0 ° observation optical system, or an integrating sphere. However, the conditions for actually observing the color rarely match these measurement conditions. For this reason, conventionally, it has been difficult to accurately predict the radiation intensity from the reflector under the actual observation conditions. Also, it has been difficult to perform color prediction including metamerism under the conditions of actual observation.

[0007] In the case of actually installing and measuring a color chart without performing prediction as in the conventional method described above,
If the illumination, the observation position, and the observation viewpoint are different, all color chips need to be measured again.

[0008] Therefore, the present invention enables the radiation intensity and the spectral radiation intensity of a reflector to be easily and accurately estimated from a small number of measured values if the reflectance and the spectral reflectance of the reflector are known. It was made.

[0009]

According to the first aspect of the present invention, there is provided a method for predicting a radiation intensity from a reflection object to be predicted when the reflection object having a known reflectance is illuminated by a predetermined light source. Illuminating a first reflector having a known reflectance with the predetermined light source; recognizing a radiation intensity from the first reflector; and applying the recognized radiation intensity to the first reflector. Predicting the illumination intensity of the predetermined light source by dividing by the reflectance of the light source, and multiplying the predicted illumination intensity by the reflectance of the reflection object to predict the radiation intensity from the reflection object to be predicted. And a step of performing the following.

According to the second aspect of the present invention, as a method of estimating the radiation intensity from a reflection object to be predicted when the reflection object to be predicted having a known reflectance is illuminated by a predetermined light source, a method using a reflection object having a known reflectance is used. Illuminating the one reflector with the predetermined light source, recognizing the radiation intensity from the first reflector, and having a known reflectance and a reflectance of the first reflector. Illuminating a different second reflector with the predetermined light source; recognizing a radiation intensity from the second reflector; and recognizing a radiation intensity from the recognized first reflector with a second Estimating the illumination intensity by the predetermined light source by dividing the difference between the radiation intensity from the reflector and the difference between the reflectance of the first reflector and the reflectance of the second reflector. Multiplying the predicted illumination intensity by the reflectance of the reflection object to be predicted , Provided, a step of predicting a radiation intensity from the prediction target reflector.

[0011]

According to the present invention, at least one reflector having a known reflectance different from the reflection object to be predicted is illuminated by a predetermined light source illuminating the prediction object, and the radiation intensity from the reflection object is measured. And the like, and the correspondence between the reflectance and the radiation intensity is approximated by a continuous function represented by a linear function,
By applying the continuous function to the known reflectance of the reflection object to be predicted, the radiation intensity from the reflection object to be predicted when the reflection object to be predicted is illuminated by a predetermined light source is predicted.

Conceptually, the first-order gradient of the continuous function corresponds to the illumination intensity of the light source, and the intercept and the terms other than the first-order correspond to the surface reflection of the reflector.

When the continuous function is a linear function, it is sufficient that the gradient and intercept can be determined, so that it is sufficient to recognize the radiation intensity from at least two reflectors. As in the first aspect of the present invention, it is possible to use a single reflector and determine the coefficient on the assumption that the intercept is 0. In this case, since it is possible to predict the illumination intensity of the light source, as described in claim 12, a color having a high reflectance at any wavelength, which is less affected by surface reflection, that is, a color having a high brightness. It is desirable to use a colored reflector, for example, a white reflector.

In the case where a plurality of reflectors are used as in the second aspect of the present invention, it is desirable that the reflectances differ greatly from the viewpoint of accuracy. It is desirable to use an achromatic reflector having high lightness, for example, a white reflector, and a reflector having a lower reflectance at all wavelengths to be predicted than this reflector, for example, a black reflector.

As a method of recognizing the radiation intensity from the reflection object in the present invention, the intensity is measured by a radiation intensity meter or the like, or the intensity is visually compared with a light source having a known intensity, or recorded in advance. For example, a method of inputting a value of intensity or a name of a spectral distribution can be used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG.
Twelve embodiments of the invention will be described. In this example, the brightness of a photographic paper of a black-and-white silver halide photograph is predicted. The printing paper of the black and white silver halide photograph shows almost the same reflectance at any wavelength.

Specifically, a black-and-white silver halide photographic printing paper 1 having a known reflectance Ci (i = 1, 2,... 5) by a 0 ° incidence / 45 ° observation optical system is placed at a position to be observed, and Light source 1
1. In this example, when illuminated by three incandescent lamps installed at predetermined positions, the radiation intensity from the photographic printing paper 1 of each reflectance Ci at the observation viewpoint is predicted.

First, in a silver halide photograph similar to the photographic paper 1 to be predicted, an achromatic print of high brightness having a known reflectance (a, for example, 0.8) of 0 ° incidence / 45 ° observation optical system is used (for example, 0.8). Paper 2
Is placed at a position where the photographic paper 1 to be predicted is observed, and is illuminated by a light source 11 that illuminates the photographic paper 1 to be predicted, in this example, three incandescent lamps installed at predetermined positions.

The radiant intensity from the illuminated photographic paper 2 is recognized by measuring it with a radiant intensity meter 12 installed at a viewpoint for observing the photographic paper 1 to be predicted. The radiation intensity measured and recognized is defined as b (cd / m ² ). For example, b = 40 (cd / m ² ).

Next, in a calculation step 13, the radiation intensity measured by the light source 11 is predicted by dividing the measured radiation intensity b by the reflectance a. That is, the predicted illumination intensity b / a is obtained. The unit of the obtained result is cd / m ² , similarly to the radiation intensity measurement value b. For example, b / a = 40 (cd /
m ² ) ÷ 0.8 = 50 (cd / m ² ).

Next, in a calculation step 14, each of the illumination intensity prediction values b / a is multiplied by the respective reflectance Ci (i = 1, 2,. The radiation intensity from the photographic paper 1 is predicted. When the radiation intensity prediction value is di (i = 1, 2,..., 5), di = (b / a) Ci (1).

FIG. 2 shows the correspondence between the reflectance and the radiation intensity in this example. When the gloss of the surface is hardly affected by the recording color as in a silver halide photograph, it can be accurately approximated by a linear expression as in this example.

According to this example, even if the optical system for measuring the reflectance of the reflection object to be predicted and the optical system for actually observing the reflection object to be predicted are different, the reflection from the reflection object to be predicted is different. The radiation intensity can be predicted. In addition, if the gloss of the surface of the reflector that recognizes the radiation intensity matches the gloss of the surface of the reflector to be predicted, the illumination intensity of the light source is less likely to be affected by the gloss of the surface of the reflector.

The above example is for the case of estimating the brightness of photographic paper of a black-and-white silver halide photograph, but the invention of claim 1 can also be applied to the case of estimating the radiation intensity from other reflectors.

[Embodiment 2] An embodiment of the second aspect of the present invention will be described with reference to FIGS. In this example, similarly to the first embodiment, the brightness of a photographic paper of a black-and-white silver halide photograph is predicted.

First, in a silver halide photograph similar to that of the photographic paper 1 to be predicted, the reflectance a by the 0 ° incidence / 45 ° observation optical system is a1 (for example, 0.8) and a2 (for example,
0.1) as the photographic paper 2 respectively.
The photographic paper 1 to be predicted is placed at an observation position, and the light source 11 for illuminating the photographic paper 1 to be predicted is illuminated by three incandescent lamps installed at predetermined positions in this example.

The illuminated reflectances a1 and a2
Are recognized by measuring the radiation intensity from the photographic paper 2 by the radiation intensity meter 12 installed at the viewpoint for observing the photographic paper 1 to be predicted. The measured and recognized radiant intensities are represented by b1 (cd / m ² ) and b2 (cd / m ² ).
m ² ). For example, b1 = 40 (cd / m ² ), b
2 = 8 (cd / m ² ).

In this case, the two photographic papers are sequentially illuminated,
It may be measured or illuminated and measured simultaneously. In addition, the order of measurement may be reversed.

Next, in operation step 13, the difference (b1-b2) between the measured radiation intensities b1 and b2 is calculated using the reflectances a1 and a2.
The illumination intensity of the light source 11 is predicted by dividing the difference by the difference (a1-a2). That is, the illumination intensity predicted value (b1-b2)
/ (A1-a2). The unit of the obtained result is cd / m ² , similarly to the radiation intensity measurement values b1 and b2. For example, (b1-b2) / (a1-a2) = (40-8)
(Cd / m ² ) ÷ (0.8−0.1) = 45.7 (cd
/ M ² ).

Next, in the calculation step 14, the reflectance Ci (i = 1, 2,..., 5) of the photographic paper 1 to be predicted is added to the predicted illumination intensity (b1-b2) / (a1-a2). By multiplying, the radiation intensity from the photographic paper 1 of each reflectance Ci is predicted. The radiation intensity predicted value is represented by di (i = 1, 2).
.. 5), di = {(b1-b2) / (a1-a2)} Ci (2)

FIG. 3 shows the correspondence between the reflectance and the radiation intensity in this example. When the gloss of the surface is hardly affected by the recording color as in a silver halide photograph, it can be accurately approximated by a linear expression as in this example.

According to this example, even if the optical system that measures the reflectance of the reflection object to be predicted is different from the optical system that actually observes the reflection object to be predicted, the radiation from the reflection object to be predicted is different. The strength can be predicted. In addition, if the gloss of the surface of the reflector that recognizes the radiation intensity matches the gloss of the surface of the reflector to be predicted, the illumination intensity of the light source is less likely to be affected by the gloss of the surface of the reflector.

The above example is for the case of predicting the brightness of a photographic paper of a black-and-white silver halide photograph, but the invention of claim 2 can also be applied to the case of predicting the radiation intensity from other reflectors.

[Embodiment 3] An embodiment of the third aspect of the present invention will be described with reference to FIGS. This example is also described in the first and second embodiments.
In the same manner as above, the lightness of photographic paper for black-and-white silver halide photographs is predicted.

First, in the same manner as in Example 2, in the same silver halide photograph as the photographic paper 1 to be predicted, the reflectance a by the 0 ° incidence / 45 ° observation optical system is a1 (for example, 0.8) and a2 (for example, 0.1) two photographic papers are each placed as a photographic paper 2 at a position where the photographic paper 1 to be predicted is observed, and illuminated by the light source 11 illuminating the photographic paper 1 to be predicted; The radiation intensity from each of them is recognized by measuring the radiation intensity from the radiation intensity meter 12 installed at the viewpoint for observing the photographic paper 1 to be predicted.

Next, in the calculation step 13, a linear function is recognized as a continuous function for associating the radiation intensity with the reflectance from the radiation intensity measurement values b1, b2 and the reflectances a1, a2. As the simplest method, two measurement points P1 (a1, b) on the correspondence between the reflectance and the radiation intensity shown in FIG.
1) A straight line connecting P2 (a2, b2) can be a linear function. That is, the gradient k is k = (b1-b2) / (a1-a2) (3) and the intercept b0 is b0 = b1-a1 × k = b1-a1 × (b1-b2) / (a1- a2)... (4) can be recognized as a linear function. Further, it is also possible to determine the coefficient in consideration of the accuracy and the operation method.

The unit of the obtained result is the measured radiation intensity b
Cd / m ² as in 1 and b2. For example, the gradient k
Is k = (40−8) (cd / m ² ) ÷ (0.8−0.
1) = 45.7 (cd / m ² ), and the intercept b0 is b0 =
40 (cd / m ² ) −0.8 × 45.7 (cd / m ² )
= 3.4 (cd / m ² ).

Next, in the calculation step 14, the recognized continuous function is converted into the respective reflectances C of the photographic paper 1 to be predicted.
i (i = 1, 2,... 5) to obtain the respective reflectances Ci
The radiation intensity from the photographic paper 1 is predicted. Assuming that the radiation intensity prediction value is di (i = 1, 2,..., 5), di = Ci * k + b0 = Ci * k + (b1-a1 * k) = (Ci-a1) * k + b1 = (Ci-a1) * (B1-b2) / (a1-a2) + b1 (5)

FIG. 4 shows the correspondence between the reflectance and the radiation intensity in this example.

According to this example, even if the optical system for measuring the reflectance of the reflection object to be predicted is different from the optical system for actually observing the reflection object to be predicted, the radiation from the reflection object to be predicted is different. The strength can be predicted. In addition, if the gloss of the surface of the reflector that recognizes the radiation intensity matches the gloss of the surface of the reflector to be predicted, the illumination intensity of the light source is less likely to be affected by the gloss of the surface of the reflector.

In the 0 ° incidence / 45 ° observation optical system,
The reflectance due to the diffused light from the reflector is dominant in the measured value, and it is not easy to estimate the reflection due to the gloss of the surface of the reflector, but the measured reflectance and the gloss of the surface of the reflector are different. If it is almost irrelevant, the intercept b0 of the linear function recognized in this example is substantially equal to the component due to the gloss of the surface of the reflector or the optical system to be actually observed and 0 ° incidence.
It can be considered as a difference from the 5 ° observation optical system. Therefore, according to this example, since the influence of the gloss of the surface of the reflector is taken into account, the accuracy is improved as compared with the first and second embodiments.

The prediction may be performed based on the reflectance measured by an observation optical system different from the 0 ° incidence / 45 ° observation optical system.

Although the above example is for predicting the brightness of photographic paper for black and white silver halide photographs, the invention of claim 3 can also be applied to the case of predicting the radiation intensity from other reflectors.

In the third embodiment, a linear function is recognized using two reflectors having different reflectances from each other as an embodiment of the third aspect of the present invention. As an example, a plurality of reflectors whose respective reflectivities are known and the reflectivity of at least one reflector is different from the reflectivities of other reflectors are used, and a recognition value of the radiation intensity from the plurality of reflectors is used. And the reflectance of the plurality of reflectors, it is possible to recognize a linear function that associates the radiation intensity with the reflectance so that an error is reduced by the least square method or the like.

Furthermore, in the third embodiment,
As an embodiment of the invention of the present invention, if the surface gloss is the same as or similar to the surface gloss of the reflector to be predicted as the two reflectors for recognizing the radiation intensity, the surface of the reflector can be more accurately determined. A linear function reflecting the effect of the gloss of the image can be recognized.

Fourth Embodiment FIGS. 5 and 6 show a fourth embodiment of the present invention. This example predicts the spectral radiant intensity from a color gravure print. Specifically, a color gravure print 3 having a known spectral reflectance c (λ) by a 0 ° incidence / 45 ° observation optical system is placed at a position to be observed, and a predetermined light source, in this example, the sun from a predetermined direction. This is for predicting the spectral radiation intensity from the color gravure print 3 at the observation viewpoint when illuminated with the light 21. The spectral wavelength is, for example, in units of 1 nm.

First, the color gravure print 3 to be predicted
A color gravure print 4 printed in white so that no ink is recorded and having a known spectral reflectance a (λ) by a 0 ° incidence / 45 ° observation optical system in the same silver halide photograph as Place the print 3 at the position where you observe it,
The light source illuminates the color gravure print 3 to be predicted, in this example, sunlight 21 from a predetermined direction.

The spectral radiant intensity from the illuminated color gravure print 4 is recognized by measuring it with a spectral radiant intensity meter 22 installed at a viewpoint for observing the color gravure print 3 to be predicted. Let the spectral radiation intensity recognized and measured be b (λ). The unit is cd / m ² .

Next, in the calculation step 23, the illumination intensity of the sunlight 21 for each wavelength is predicted by dividing the measured radiation intensity b (λ) for each wavelength by the reflectance a (λ). That is, the illumination intensity predicted value b (λ) / a (λ) is obtained. Here, the reflectance a (λ) and the measured radiation intensity b
When the resolution of the measurement wavelength of (λ) is different, interpolation may be performed as necessary.

Next, in the calculation step 24, for each wavelength, the illumination intensity predicted value b (λ) / a (λ) is multiplied by the reflectance c (λ) of the color gravure print 3 to be predicted.
The radiation intensity from the color gravure print 3 is predicted. Assuming that the radiation intensity prediction value for each wavelength is d (λ), d (λ) = {b (λ) / a (λ)} c (λ) (6)

In the above example, the illumination intensity is predicted for each wavelength by the method according to the first aspect of the invention. The illumination intensity is predicted for each wavelength by the method according to the second, third, and fourth aspects. Or a continuous function may be recognized.

Also, instead of predicting the radiation intensity from the reflection object to be predicted for each wavelength as in the above example, the wavelength is divided into appropriate wavelength bands, for example, 380 nm to 400 n.
m, a wavelength of 400 nm to 420 nm, a wavelength of 760 nm to 780 nm,
The radiation intensity from the reflection object to be predicted may be predicted for each of m wavelength bands. In addition, prediction may be performed as a weighted band using a predetermined spectral sensitivity, for example, an XYZ color matching function of a CIE (1931) 2 ° visual field.

Further, XYZ tristimulus values and the like can be obtained by integrating the product of predetermined spectral sensitivity and radiation intensity by wavelength.

When estimating the sensitivity of a desired optical sensor, the spectral sensitivity of the optical sensor can be used instead of the color matching function.

[Embodiment 5] Referring to FIG.
3 shows an embodiment of the invention. This example predicts the XYZ tristimulus values of the radiation intensity from a color gravure print.

First, in a silver halide photograph similar to the color gravure print 3 to be predicted, an ink having a spectral reflectance a (λ) of a1 (λ) by the 0 ° incidence / 45 ° observation optical system is not recorded. A color gravure print printed white and a color gravure print printed black with a spectral reflectance a (λ) of a2 (λ) by a 0 ° incidence / 45 ° observation optical system, each of which is a prediction target. 3 is illuminated with a light source that illuminates the color gravure print 3 to be predicted, in this example, sunlight 21 from a predetermined direction.

In a general color gravure print, the reflectance of white is higher than that of black. That is, 380n
When m ≦ λ ≦ 780 nm, a1 (λ)> a2 (λ)
It is. This example is a case where such a general color gravure print is used.

The illuminated spectral reflectance a (λ) is a1
(Λ) and a2 (λ), the spectral radiant intensity from the color gravure print, and the spectral radiant intensity meter 22 installed at the viewpoint for observing the color gravure print 3 to be predicted.
Recognize by measuring with The respective measured and recognized spectral radiant intensities are represented by b1 (λ) and b2 (λ).
And

Next, let X (λ), y (λ), z (λ) be the color matching functions of the tristimulus values X, Y, Z, respectively,
A linear function for each wavelength is recognized for each of Y and Z as follows.

As for Y, first, for each wavelength, the difference between the radiation intensity measurement values b1 (λ) and b2 (λ) is divided by the difference between the reflectances a1 (λ) and a2 (λ). The gradient y1 (λ) for each wavelength is estimated by multiplying by the color matching function y (λ). That is, y1 (λ) = y (λ) × {b1 (λ) -b2 (λ)} / {a1 (λ) -a2 (λ)} (7) is obtained. Similarly, the intercept y2 (λ) for each wavelength is estimated. That is, y2 (λ) = y (λ) × {b1 (λ) -a1 (λ) × y1 (λ)} = y (λ) × [b1 (λ) -a1 (λ) × ｛b1 (λ) −b2 (λ)} / {a1 (λ) −a2 (λ)}] (8).

Here, at the wavelength where the color matching function y (λ) is defined, a1 (λ), a2 (λ), b1
Once (λ) and b2 (λ) are determined, the intercept y2 can be obtained in advance by the following equation: y2 = ∫λ _{= 380 ‥‥ 780} y2 (λ) dλ (9)

Using these predicted values, the spectral reflectance Ci
The Y stimulus value Y (di) of the radiation intensity from the color gravure print 3 of (λ) is as follows: Y (di) = ｛∫λ _{= 380 ‥‥ 780} Ci (λ) y1 (λ) dλ｝ + y2 (10) Can be predicted.

The X stimulus value X (di) and the Z stimulus value Z (di) of the radiation intensity from the color gravure print 3 having the spectral reflectance Ci (λ) can be similarly predicted. According to this example, the amount of calculation at the time of prediction can be reduced.

Although the above example uses a coefficient obtained a priori, the coefficient may be calculated by another method. In the above example, the color matching function is used.
A desired function such as the spectral sensitivity of the optical sensor can be used. In the above example, the integral is used.
The calculation may be performed using numerical integration or appropriate approximation instead of integration.

[Sixth Embodiment] As a sixth embodiment, the first embodiment will be described.
Examples of the invention of Examples 0 and 11 will be described. This example is a method for predicting the spectral reflectance of an electrophotograph by full-color xerography.

First, each of the four reflectors is 0 °.
The spectral reflectance a (λ) by the incident / 45 ° observation optical system is a
1 (λ), a2 (λ), a3 (λ), a4 (λ), full-color xerographic photographs recorded in white, black light black, black light gray, and process black, respectively, are used as reflectors to be predicted. At a position to be observed, and a light source for illuminating a reflection object to be predicted, in this example, 3800 ° from a predetermined position
Illuminate with a black body radiation intensity of K predetermined surface area.

Here, the four reflectors are 380 nm ≦ λ.
It is assumed that the gray density is set such that the reflectance of at least one reflector is different from the reflectance of the other reflectors in the range of ≦ 780 nm.

Recognition is performed by measuring the spectral radiant intensities from the four illuminated reflectors with a spectral radiant intensity meter installed at a viewpoint for observing the reflector to be predicted. Each measured and recognized spectral emission intensity is
Let b1 (λ), b2 (λ), b3 (λ) and b4 (λ).

Next, for each wavelength, a graph showing the correspondence between the reflectance and the radiation intensity as shown in FIG. 4 shows the reflectances a1 (λ), a2 (λ), a3 (λ), a4 (Λ) and
Radiation intensity measurement values b1 (λ), b2 (λ), b3 (λ),
The correspondence with b4 (λ) is plotted, and the correspondence is approximated by a straight line. Here, since the reflectance of at least one reflector is different from that of the other reflectors, the gradient e (λ) and intercept f (λ) of the linear function can be recognized from this straight line.

Next, when a full-color xerographic photograph having a spectral reflectance of c (λ) and a reflector having a reflectance of 1 at all wavelengths are placed at the observation position and illuminated by the above illumination, respectively. G1 (λ), g
2 (λ) is predicted by the linear function recognized above. That is, g1 (λ) = e (λ) × c (λ) + f (λ) (11) g2 (λ) = e (λ) + f (λ) (12)

The two spectral radiation intensities g1 (λ) and g2
From (λ), the spectral reflectance r (λ) of the full color xerographic photograph to be predicted can be predicted by r (λ) = g1 (λ) / g2 (λ) (13).

In general, the spectral reflectance of a full-color xerographic photograph, another printed matter, a photograph, or the like can be estimated from the density and area ratio of each color at the time of recording. This estimated value may be used as the spectral reflectance for estimating the radiation intensity.

In the above example, the actually measured spectral radiation intensity is used. However, when predicting the spectral reflectance, instead of the fire radiation intensity, a spectral distribution or a name that can specify the spectral distribution, for example, “A” Light source "or the like can be used. When predicting spectral reflectance by spectral distribution or its name,
By setting the gradient as a spectral distribution and setting the intercept due to surface reflection to 0, the spectral reflectance can be predicted.

In full-color xerography, surface reflection and recording color may not be independent. In this case, as described above, the graph of the correspondence between the reflectance and the radiation intensity can be approximated by, for example, a quadratic function, instead of being approximated by a straight line. It is also possible to change the function to be approximated for each wavelength.

[0075]

As described above, according to the present invention, if the reflectance and the spectral reflectance of a reflector are known, the radiation intensity and the spectral radiation intensity of the reflector can be easily and accurately determined from a small number of measured values. Can be estimated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment.

FIG. 2 is a diagram provided for explanation of a first embodiment;

FIG. 3 is a diagram provided for explanation of a second embodiment;

FIG. 4 is a diagram provided for explanation of a third embodiment;

FIG. 5 is a diagram showing a fourth embodiment;

FIG. 6 is a diagram provided for explanation of a fourth embodiment;

[Explanation of symbols]

 1.2 Printing paper 3, 4 Color gravure printed matter 11 Light source 12 Radiation intensity meter 13, 14 Operation step 21 Sunlight 22 Spectral radiation intensity meter 23, 24 Operation step

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Iwanaga 430 Border, Nakaicho, Ashigarakami-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd. F-term (reference) 2C061 BB10 KK25 KK28 2G020 AA04 DA04 DA05 DA06 DA12 DA43 DA66

Claims (16)

[Claims] 1. A method for predicting a radiation intensity from a reflection object to be predicted when the reflection object to be predicted having a known reflectance is illuminated by a predetermined light source, the first reflection having a known reflectance. Illuminating the object with the predetermined light source; recognizing the radiation intensity from the first reflector; dividing the recognized radiation intensity by the reflectance of the first reflector; Estimating the illumination intensity of the predetermined light source; and multiplying the estimated illumination intensity by the reflectance of the reflection object to predict the radiation intensity from the reflection object to be predicted. Color prediction method. 2. A method for predicting a radiation intensity from a reflection object to be predicted when the reflection object to be predicted having a known reflectance is illuminated by a predetermined light source, the first reflection having a known reflectance. Illuminating an object with the predetermined light source; recognizing a radiation intensity from the first reflector; a second reflector having a known reflectance and different from the reflectance of the first reflector; Illuminating the reflector with the predetermined light source; recognizing the radiation intensity from the second reflector; and determining the radiation intensity from the recognized first reflector and the second reflector. Estimating the illumination intensity of the predetermined light source by dividing a difference between the radiation intensity of the first reflector and the reflectance of the second reflector by dividing the difference between the reflectance of the first reflector and the reflectance of the second reflector; The estimated illumination intensity is multiplied by the reflectance of the reflection object to be predicted. Color prediction method characterized by comprising the steps of predicting a radiation intensity from the reflector, the. 3. A method for predicting a radiation intensity from a reflection object to be predicted when the reflection object to be predicted having a known reflectance is illuminated by a predetermined light source, the first reflection having a known reflectance. Illuminating an object with the predetermined light source; recognizing a radiation intensity from the first reflector; a second reflector having a known reflectance and different from the reflectance of the first reflector; Illuminating the reflector with the predetermined light source; recognizing the radiation intensity from the second reflector; radiating intensity from the recognized first and second reflectors; Recognizing a continuous function for associating the radiation intensity with the reflectance from the reflectances of the first and second reflectors; applying the recognized continuous function to the reflectance of the prediction target reflector; For predicting the radiation intensity from the target reflection object Color prediction method characterized by comprising Tsu and up, the. 4. A method for predicting a radiation intensity from a reflection object to be predicted when the reflection object to be predicted having a known reflectance is illuminated by a predetermined light source, wherein the respective reflection rates are known and Illuminating a plurality of reflectors, each having a reflectance of at least one reflector different from the reflectance of another reflector, with the predetermined light source, and recognizing radiation intensities from the plurality of reflectors, Recognizing a continuous function that associates the radiation intensity from the plurality of reflectors with the reflectance of the plurality of reflectors from the reflectance of the plurality of reflectors such that an error is reduced with respect to the reflectance. Applying the recognized continuous function to the reflectance of the reflection object to be predicted to predict the radiation intensity from the reflection object to be predicted. 5. The color predicting method according to claim 1, wherein the reflector for recognizing the radiation intensity has a surface gloss that is the same as or similar to the surface gloss of the reflector to be predicted. A color prediction method. 6. The color prediction method according to claim 1, wherein the radiation intensity predicted by said reflection object to be predicted is a spectral radiation intensity, and said reflection object recognizes said reflection object to be predicted and said radiation intensity. A color prediction method, wherein the reflectance of an object is a spectral reflectance, and the recognized radiation intensity is a spectral radiation intensity. 7. The color prediction method according to claim 6, wherein the predicted illumination intensity or the recognized continuous function is:
A color prediction method characterized in that prediction or recognition is performed for each predetermined wavelength band. 8. A method for recognizing a continuous function among the color prediction methods according to claim 1, wherein the radiation intensity predicted by the reflection object to be predicted is a predetermined color matching function or a predetermined spectral function. The product of the sensitivity and the spectral radiation intensity is the radiation intensity integrated by wavelength, the reflectance of the object to be predicted and the reflector that recognizes the radiation intensity is the spectral reflectance, and the radiation intensity to be recognized is the spectral reflectance. Radiation intensity,
The color prediction method, wherein the continuous function to be recognized has a constant term, and the constant term is recognized for each color matching function or each spectral sensitivity. 9. A method for recognizing a continuous function among the color prediction methods according to claim 3, wherein the continuous function is recognized as a linear function. 10. A radiation intensity obtained by integrating a predetermined color matching function or a product of a predetermined spectral sensitivity and a spectral radiation intensity by a wavelength when an object to be predicted having a known spectral reflectance is illuminated by a predetermined light source. 10. A method of predicting a reflectance based on: a method of predicting the radiation intensity of a predetermined reflection object by the method according to claim 1; and multiplying the predicted value by a predetermined color matching function or a predetermined spectral sensitivity. A value obtained by integrating the above values with the wavelength, or a predicted value, assuming a perfect diffuse reflector having a reflectivity of 1 at all wavelengths, and predicting the radiation intensity of a predetermined reflector by the method according to any one of claims 1 to 9. When the product of the predicted value and a predetermined color matching function or a predetermined spectral sensitivity is integrated by a wavelength, or a predicted value, the result is divided by the predetermined target light source to illuminate the target object. A color prediction method for predicting the reflectance. 11. The color prediction method according to claim 10, wherein a spectral radiation distribution is obtained instead of recognizing the spectral radiation intensity.
Alternatively, a color prediction method characterized by recognizing a name of a spectral radiation distribution or a color temperature. 12. The color prediction method according to claim 1, wherein the reflector for recognizing the radiation intensity includes at least an achromatic reflector having high brightness. 13. The color predicting method according to claim 2, wherein the reflector for recognizing the radiation intensity includes at least an achromatic reflector having a high brightness and all of the objects to be predicted than the reflector. A color prediction method, comprising: a reflector having a low reflectance at a wavelength. 14. A color prediction device comprising means for performing the color prediction method according to claim 1. 15. A recording medium on which a program for performing the color prediction method according to claim 1 is recorded. 16. A recording medium on which a prediction formula obtained by the color prediction method according to claim 1 is recorded.