JPH11311573A - Color reproducing method by using color image input apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reproducing colors by using of a color image input apparatus which can enhance color reproducibility simply with the use of an existing color image input apparatus. SOLUTION: A spectral reflectance ri (λ) (i=1, 2, 3,..., n) is measured for each representative ink used for a stencil paper in a spectral reflectance measurement process 50. The spectral reflectance ri (λ) measured in the process 50 is subjected to principal component analysis in a principal component analysis process 52. A transmittance characteristic X (λ) for an added filter is determined in an added filter transmittance characteristic determination process 54 on the basis of the principal component of each spectral reflectance obtained in the analysis process 52. An added filter of the transmittance characteristic X (λ) determined in the determination process 54 is set between the stencil paper and a color separation optical system unit in an added filter set process 56. An inverse problem can be solved simply with the use of added filters as small a count as possible, e.g. one filter, and calculations can be less complicated as much as possible, whereby the apparatus is made inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly accurate color matching between a display color input to a color image input device and a display color output from a color image output device with a simple structure. The present invention relates to a color reproduction method using a color image input device.

[0002]

2. Description of the Related Art As described in, for example, JP-A-5-244408, a color image input device for inputting a color image, such as a color scanner, generally has a color separation provided with a plurality of types of color filters. The display color of the base paper is detected through the optical system unit, and an image signal is output. This image signal is composed of color data representing the color of each pixel constituting a color image for color reproduction.
In an image output device such as a color liquid crystal, a color PDP, and a color printer, a color image is reproduced based on the color data. The color of each pixel represented by the above-described color data is obtained by, for example, a CCD (charge coupl) when light passing through a plurality of types of color filters provided in the color separation optical system unit of the color image input device.
It is expressed as a function of a plurality of light intensity values obtained for each of the color filters by being detected by a light detecting element such as an ed device. This light intensity value is a value obtained corresponding to the light transmittance of each of the plurality of types of color filters.

Usually, in the above color image output device, Y
(Yellow), M (magenta), C (cyan) or a mixture of four kinds of pigments (color materials) to which K (black) is added, and R (red), G (green), B (blue) Since various colors can be represented by mixing the emission colors of the three types of phosphors (coloring materials), the above color data is obtained from a plurality of existing primary colors (R, G, B or Y, M, C). , K) is generally expressed by a multi-primary color notation, for example, an RGB notation. For this reason, for example, three types of red filters, green filters, and blue filters are used as the plurality of types of color filters provided in the color separation optical system unit, and the red, green, and blue filters pass through the respective filters. The light intensity value at the time of
Assuming that the G value and the B value are used, color data R, G, and B configured as functions of the R value, the G value, and the B value are used.

[0004]

In the above-described color image input device, different colors x1 and x2 are used.
Are input, the output color data is the same r
(R, G, B). In such a case, CIE (Commission Intern Commission
ationale de l'Eclairage), the display color r = (X, X, Z) and the color data r = (R, G, B) specified by the tristimulus values X, Y, Z in the XYZ color system. ), The mutually different colors x1 (X1, Y1, Z1) and x2 (X) are obtained from the color data r (R, G, B).
2, Y2, Z2) cannot be reproduced, and it is considered that the color reproduction of the color image input apparatus is an inverse problem having inadequacy that does not satisfy the uniqueness of the solution.

On the other hand, in order to further increase the number of components of the color data, an additional filter having a light transmittance characteristic different from that of a plurality of types of color filters provided in the color separation optical system unit of the color image input device. May be provided in the optical path from the light source to the photodetector. However, as the number of additional filters having different light transmittance characteristics from the plurality of types of color filters provided in the color separation optical system unit is increased, the calculation for calculating the color data becomes complicated at an accelerated rate. Therefore, there is a disadvantage that the apparatus is complicated and expensive. In general, since the color separation optical system unit of a commercially available color image input device is integrally formed, the color separation optical system unit is installed in the color separation optical system unit in order to enhance the color reproducibility of an inexpensive commercially available color image input device. It has been practically difficult to provide an additional filter or to change to detect light transmitted through only the additional filter.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a color image input apparatus capable of easily improving the color reproducibility by using an existing color image input apparatus. An object of the present invention is to provide a color reproduction method using an apparatus.

[0007]

The present inventor has made various studies on the background described above, and as a result, has performed principal component analysis on the spectra r _i (λ) of the reflected light of various inks used for the base paper. Then, the first principal component R ₁ (λ),
While the second principal component R ₂ (λ), the third principal component R ₃ (λ), the fourth principal component R ₄ (λ), and the like are sequentially obtained, the principal components R ₁ (λ) and R ₂ ( λ), R ₃ (λ), R ₄ (λ)
Among them, a plurality of types of color filters provided in the color separation optical system unit, for example, an R filter, a G filter,
Each light transmittance spectrum R (λ), G of B filter
In the main components other than those corresponding to (λ) and B (λ), for example, the light transmittance R (λ) of the additional filter, that is, the combined filter of the X filter and the R filter having the light transmittance spectrum X (λ), is used. ) {X (λ)} ² , X above
Light transmittance G of the combined filter of the filter and the G filter
(Λ) ｛X (λ)｝ ² , the principal component of the minimum order among those corresponding to any of the light transmittances B (λ) ｛X (λ)｝ ² of the combined filter of the X filter and the B filter. When the additional filter, that is, the light transmittance spectrum X (λ) is determined so as to substantially match with the color x1 (X
1, Y1, Z1) and x2 (X2, Y2, Z2) are input, and color data r1 (R1, R1,
G1, B1, X1), r2 (R1, G1, B1, X2)
Are obtained, and the color data r1 (R1, G
1, B1, X1) and r2 (R1, G1, B1, X2) from the different colors x1 (X1, Y1, Z1), x2
(X2, Y2, Z2) can be reliably reproduced. In addition, it has been found that the additional filter can reproduce a color from color data obtained by overlapping with a plurality of types of color filters provided in the color separation optical system unit without detecting the single transmitted light. The present invention has been made based on such findings.

That is, the gist of the method of the present invention is that a plurality of types of primary colors are output from a color image input device which detects reflected light from a base paper on which a color image is displayed through a color separation optical system unit. A color reproduction method for reproducing the color of the base paper based on an image signal composed of color data composed of functions, wherein (a) the spectral reflectance of each representative ink among the inks used in the base paper. A spectral reflectance measurement step of measuring each, and (b) a principal component analysis step of obtaining a main component of the spectral reflectance by performing a principal component analysis of the spectral reflectance measured by the spectral reflectance measurement step, (c) an additional filter transmittance characteristic determining step of determining the transmittance characteristics of the additional filter based on the principal components of the respective spectral reflectances obtained in the principal component analysis step, and (d) the additional filter The additional filter with a transmittance characteristic determined by the transmittance characteristic determination step, and an additional filter provision step of providing between the base paper and the color separation optical system unit is to contain.

[0009]

In this manner, the spectral reflectance is measured for each representative ink among the inks used for the base paper in the spectral reflectance measuring step, and the spectral reflectance is measured in the principal component analysis step. The spectral reflectances measured in the reflectance measuring step are respectively analyzed for the principal components, and in the additional filter transmittance characteristic determining step, based on the main components of the spectral reflectances obtained in the principal component analyzing step, the additional filter The transmittance characteristic is determined, and an additional filter having the transmittance characteristic determined in the additional filter transmittance characteristic determining step is provided between the base paper and the color separation optical system unit by the additional filter setting step. . Therefore, according to the method of the present invention, the transmittance characteristic (light transmittance spectrum) of the additional filter is determined by using the principal component analysis. The inverse problem can be solved, and the computational complexity can be reduced as much as possible, and the apparatus can be inexpensive. In addition, since the additional filter is installed only between the base paper and the color separation optical system unit, not in the color separation optical system unit that is difficult to separate, the additional filter is integrally configured. Since a commercially available color image input device having a unit can be used, color reproduction can be performed at lower cost.

[0010]

In another preferred embodiment of the present invention, the step of determining the additional filter transmittance characteristic includes the step of determining a plurality of combined filters of one of the plurality of color filters in the color separation optical system unit and the additional filter. The light transmittance spectrum corresponds to the minimum order principal component of the multi-order principal components obtained by the principal component analysis step, excluding the principal component of the order corresponding to the color filter in the color separation optical system unit. like,
The light transmittance characteristic of the additional filter is determined. For example, a plurality of color filters in the color separation optical system unit are an R (red) filter having a light transmittance R (λ), a G (green) filter having a light transmittance G (λ),
A B (blue) filter having a light transmittance B (λ),
The additional filter is an X filter having a light transmittance X (λ), and the spectral reflectances r _i (λ) (i = 1, 2, 3,...) Of various inks used for base paper in the principal component analysis step. ...
, n) are the first principal component R ₁ (λ), the second principal component R ₂ (λ), the third principal component R ₃ (λ), and the fourth principal component R ₄ (λ), fifth principal component R
₅ (λ), the sixth principal component R ₆ (λ), etc.
Light transmittance R of the combined filter of the X filter and the R filter
(Λ) ｛X (λ)｝ ² , light transmittance G (λ) ｛X (λ)｝ ² of the combined filter of the X filter and the G filter, and light transmittance B of the combined filter of the X filter and the B filter (Λ)
Any of {X (λ)} ² is the main component R ₁ (λ),
R ₂ (λ), R ₃ (λ), R ₄ (λ), R ₅ (λ), R
₆ Among (λ), the light transmittances R (λ), G (λ), and B (λ) of the plurality of color filters in the color separation optical system unit
The light transmittance X () of the additional filter is set so as to correspond to the principal component of the smallest order (higher order) among those excluding those corresponding to the above, that is, so as to substantially match. λ) is determined.

In other words, in the additional filter transmittance characteristic determination step, a set of principal components Γ (= ｛R ₁ (λ), R ₂ (λ), R ₃ ) obtained in the principal component analysis step
(Λ), R ₄ (λ), R ₅ (λ), R ₆
(Λ),. . . From｝), the light transmittances R (λ), G (λ), B of the plurality of color filters in the color separation optical system unit
The set 除 い ′ (= Γ− ｛R (λ), G excluding (λ)
(Λ), B (λ)}), the light transmittance of the synthesis filter R (λ) ｛X (λ)｝ ² , G (λ) ｛X
An additional filter having a light transmittance X (λ) is determined so that one of (λ)｝ ² and B (λ) ｛X (λ)｝ ² is as close as possible. In this way, as few additional filters as possible to solve the inverse problem, that is, the light transmittance X (λ) thereof are determined efficiently.

[0012]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a color image processing apparatus to which a color reproduction method using a color image input apparatus according to the present invention is applied. In FIG. 1, a color scanner 10 functions as a color image input device as is known as a so-called image reader or the like, and optically reads a color image displayed on a base paper 12 to represent the color image. The image signal SG1 is output to an electronic control device 18 including a color display device 14, a keyboard 16, and the like.
The electronic control unit 18 includes a CPU, ROM, RA (not shown).
M, an interface and the like are provided therein, and the CPU processes the input signal according to a program stored in the ROM while utilizing the storage function of the RAM, and in the color matching preparation mode, the first color data conversion table and the second color data conversion table.
A color data conversion table is created in advance. In the normal mode, the image signal SG1 is converted into an image signal SG2 using a first color data conversion table stored in advance, and the image signal SG2 is output to the color display device 14. At the same time, the image signal SG2 is converted into an image signal SG3 by using a second color data conversion table stored in advance, and the image signal SG3 is output to the color image output device 20.

The color display device 14 functions as a color image output device by being constituted by a CRT or a liquid crystal plate capable of displaying a color image. The color image represented by the image signal SG2 is displayed on the screen based on the signal SG2. The color image output device 20 is constituted by a so-called color ink-jet printer or the like. Based on the image signal SG3 output from the electronic control device 18, the color image represented by the image signal SG3 is printed on the recording paper 22. To be displayed.

The image signals SG1, SG2, SG3 are
The color image is composed of a large number of color data representing the colors of the pixels constituting the color image, and the color data is represented by a multi-color notation (for example, a three-color notation) using an existing color as a reference color. For example, in the three-color notation, any of the existing colors, for example, R (red), G (green), B (blue), Y (yellow), M (magenta), and C (sian) may be the three primary colors. In general, a three-color notation (three-primary notation) based on the three primary colors R, G, and B is used. Since the color display device 14 represents various colors by additive color mixture, the color data according to the above-described three primary color notation can be used as it is. Is provided. Although the color image output device 20 represents various colors by subtractive color mixing, the color image output device 20 is designed to be able to input an image signal SG3 expressed by a three-color notation based on the three primary colors R, G, and B. In order to perform the conversion, the image signal SG3 represented by the three-color notation based on the R, G, and B is converted into the image signal represented by the three-color notation based on the three primary colors Y, M, and C. It has a signal conversion circuit.

The color data expressed by the three-color notation in which R, G, and B are three primary colors is, for example, R _n = (R _m , G
_m , B _m ), and the three primary color materials are R _m
Values, G _m values, by being mixed in the mixing ratio or the concentration corresponding to B _m values, the color of the color data R _n is represented.
Further, color data expressed by a three primary color system in which Y, M, and C are three primary colors is, for example, Y _n = (Y _m , M _m , C
_m ), and the color materials of the three primary colors are Y _m value and M
_m values, by being mixed in the mixing ratio or the concentration corresponding to C _m values, the color of the color data Y _n is expressed. In the electronic control unit 18, for example, the three primary colors of the color data R _n or Y _n are respectively from m = 0 to m = 255.
N = 256 ³
Street (kind) colors can be expressed.

FIG. 2 is a view for explaining a main part of the configuration of the color scanner 10. As shown in FIG. FIG. 2 shows a flat bed type, in which a transparent glass plate 30 on which the base paper 12 is placed and an additional filter 32 adhered to the transparent glass 30.
And a pair of rod-shaped light sources 3 constituted by a fluorescent lamp or the like
4, a mirror 36 for reflecting the reflected light from the base paper 12 in a direction parallel to the base paper 12, a lens device 40 for condensing the light from the mirror 36 on a CCD sensor 38, the CCD sensor 38 and the lens And a color filter device 42 provided between the device 40 and the device 40. The rod-shaped light source 34, the mirror 36, the CCD sensor 38, the lens device 4
0, the color filter device 42 is a color separation optical system unit 44 which is mechanically integrated by being attached to one case or frame, and is provided with respect to the transparent glass plate 30 on which the base paper 12 is placed. It is relatively movable in a parallel direction, that is, in the longitudinal direction of the base paper 12 (the left-right direction in FIG. 2).

The color filter device 42 includes, for example, an R (red) filter having a light transmittance R (λ), a light transmittance G
G (green) filter having (λ), light transmittance B (λ)
A plurality of color filters including a B (blue) filter having the following are provided on the outer periphery of a rotating plate (not shown). The CCD sensor 38 is connected to the base paper 12 by the lens device 40.
And a line-shaped light receiving surface on which reflected light reflected from a portion located on a line in the width direction is collected. As a result, a signal representing the intensity of light that has passed through the R filter, the G filter, and the B filter, that is, color data, is output from the CCD sensor 38 in pixel units.

Assuming that the transmittance characteristic of the additional filter 32, that is, the light transmittance is X (λ), the CCD sensor 38 has passed through the R filter and the additional filter 32 at the moment of switching to the R filter. The reflected light, that is, the reflected light that has passed through the synthesis filter having the light transmittance R (λ) {X (λ)} ² is detected, and at the moment when the light is switched to the G filter, the reflection that has passed through the G filter and the additional filter 32 is detected. Light, that is, light transmittance G (λ) {X (λ)} ²
The reflected light that has passed through the synthesis filter having the following formula is detected, and at the moment when the light is switched to the B filter, the reflected light that has passed through the B filter and the additional filter 32, that is, the light transmittance B
The reflected light that has passed through the synthesis filter having (λ) {X (λ)} ² is detected.

Here, the transmittance characteristic of the additional filter 32, that is, the light transmittance X (λ) is determined through the steps shown in the process diagram of FIG. 3, and the additional filter 32 has the light transmittance X (λ). Additional filter 3 manufactured or selected
2 is fixed to the transparent glass plate 30.
That is, the spectral reflectance r _i (λ) for each representative ink of the plurality of types of inks used for the base paper 12.
(i = 1, 2, 3,..., n) are measured using a well-known spectrophotometer or the like (spectral reflectance measurement step 5).
0). Next, the principal component analysis is performed for each of the above-mentioned spectral reflectances r _i (λ), whereby the spectral reflectances r _i (λ) of various inks (i = 1, 2, 3,. ) Is the first principal component R ₁ (λ),
Second principal component R ₂ (λ), third principal component R ₃ (λ), fourth principal component R ₄ (λ), fifth principal component R ₅ (λ), sixth principal component R
₆ (λ) etc. (principal component analysis step 5
2).

The above-mentioned principal component analysis generally serves to summarize information having various kinds of characteristic values that are mutually correlated in a multivariate analysis into a small number of uncorrelated total characteristic values. The following describes how to determine the transmittance characteristics of the additional filter 32 of the color scanner 10, that is, how to apply the additional filter 32 having what transmittance characteristics.

First, the wavelength (nm) of the spectral reflectance r _i (λ) (i = 1, 2, 3,..., N) is set to λ ₁ , λ ₂ , λ _{3 for} each of the representative inks. ,. . . , λ _p , the spectral reflectance r _i (λ _j ) of each ink becomes a discontinuous discrete value from a continuous spectrum as shown in Expression 1, and is expressed as r _ji. You.

[0023]

(1) r _i (λ _j ) = (r _1i , r _2i , r _3i ,..., R _pi ) (1)

Hereafter, considering that the spectral reflectance (1) sampled according to the principle of principal component analysis is represented by as few principal components as possible, the variance / covariance x _{ij of the} sampling value r _ji is expressed by the following equation (2). Once obtained, the vector S is obtained from Equation 3. Then, the eigenvalues lambda ₁ that eigenvalues of the vector S, is the eigenvector b satisfying Equation 4, lambda
₂ , λ ₃ ,. . . , λ _p (where λ ₁ ≧ λ ₂ ≧ λ ₃ ≧ ・ ・ ・
≧ λ _p ) and the corresponding eigenvectors b ₁ , b ₂ ,
b ₃ ,. . . , b _p (where the vector b ₁ = (b _1i ,
b _2i , b _3i,. . . , B _pi )) are determined respectively.

[0025]

[Number 2] covariance _{x ij = {1 / (n} -1)} Σ {(r il -r iav) (r jl -r jav)} ··· (2) where the sigma is l is It is the sum of products from 1 to n. Also,
r _iav = Σ r _li / p and r _jav = Σ r _li / p, where Σ is the sum of products from 1 to p.

[0026]

(Equation 3)

[0027]

## EQU4 ## Vector S · vector b = λ · vector b (4)

The eigenvectors obtained as described above
b₁ Is the first principal component, eigenvector b _Two Is the second principal component,
..Eigenvector b_pBecomes the p-th principal component, and in this order
Ink spectral reflectance r_i(Λ) will be mainly represented.
In general, in the principal component analysis, an integer p 'satisfying 1 ≦ p ′ ≦ p
On the other hand, the cumulative contribution ratio ε is defined by the following equation 5,
Normally ε has a value ε₀ (Usually a value of 0.8 or more)
So that the number of principal components p 'is determined. Eigenvector at this time
Torr b₁, b_Two, b_Three,. . . , b_{p '}Are added in this order.
The light transmittance becomes a candidate for the filter 32.

[0029]

(Equation 5)

Next, in the principal component analysis step 52, the spectral reflectances r _i (λ) (i = 1, 2,
3, . . . , n), the first principal component R ₁ (λ), the second principal component R
₂ (λ), third main component R ₃ (λ), fourth main component R ₄
(Λ), fifth main component R ₅ (λ), sixth main component R ₆ (λ)
Among the filters excluding those corresponding to the R filter, the G filter, and the B filter, the light transmittance R (λ) {X (λ)} of the combined filter of the additional filter 32 and the R filter.
² , light transmittance G (λ) ｛X (λ)｝ ² of the combined filter of the additional filter 32 and the G filter, and light transmittance B (λ) ｛X of the combined filter of the additional filter 32 and the B filter
The light transmittance X (λ) [= ｛R ₄ (λ) of the additional filter 32 so as to correspond to the main component of the smallest order (higher order) among those corresponding to (λ)｝ ^2. ) /
R ₄ (λ)｝ ^1/2 ] is determined (additional filter transmittance characteristic determining step 54).

For example, the main component R₁ (Λ)-R
₁₂Of (λ), R filter, G filter, B filter
The one corresponding to is R_Two (Λ), R_Five (Λ), R_Four 
(Λ), G (λ) {X (λ)}^Two , R (λ)
{X (λ)}^Two , B (λ) {X (λ)} ^Two Corresponding to
Is R_Two (Λ), R₆ (Λ), R₁₂(Λ)
Then, the main component R₆ (Λ) and R (λ) {X (λ)}^Two And
The light transmittance X (λ) of the additional filter 32 that substantially matches
Is determined.

That is, in the additional filter transmittance characteristic determining step 54, the set of principal components Γ (= ｛R ₁ (λ), R ₂ (λ), R
₃ (λ), R ₄ (λ), R ₅ (λ), R ₆
(Λ),. . . From｝), the light transmittances R (λ), G (λ), B of the plurality of color filters in the color separation optical system unit
The set 除 い ′ (= Γ− ｛R (λ), G excluding (λ)
(Λ), B (λ)}), the light transmittance of the synthesis filter R (λ) ｛X (λ)｝ ² , G (λ) ｛X
An additional filter 32 having a light transmittance X (λ) that makes one of (λ)｝ ² and B (λ) ｛X (λ)｝ ² as close as possible is determined.

Then, the additional filter 32 having the light transmittance X (λ) determined as described above is placed between the base paper 12 and the color separation optical system unit 44, for example, in a state of being in close contact with the transparent glass plate 30. It is fixed (additional filter installation step 56).

In the color image processing apparatus provided with the color scanner 10 having the additional filter 32 installed as described above, in synchronization with the switching of the color filters of the color filter device 42, that is, the switching of the R filter, the G filter, and the B filter. It enters the CCD sensor 38 of the color scanner 10 light _{I R (λ), I G} (λ), I B (λ) is equation 6,
7, 8 can be represented. Equations 6, 7, 8
, F (λ) is the reflected light intensity from the sample,
(Λ) is the spectral sensitivity E (λ) of the light source and the spectral sensitivity r of the sample.
(Λ), the spectral reflectance m (λ) of the mirror 36, and the spectral sensitivity s (λ) of the CCD sensor 38, where K (λ) = E
(Λ) r (λ) m (λ) s (λ).

[0035]

I _R (λ) = F (λ) K (λ) R (λ) ｛X (λ)｝ ² (6)

[0036]

_IG (λ) = F (λ) K (λ) G (λ) {X (λ)} ² (7)

[0037]

Equation 8] _{I B (λ) = F (} λ) K (λ) B (λ) {X (λ)} 2 ··· (8)

As is apparent from the above equations 6, 7, and 8, the color scanner 10 having the additional filter 32 is provided.
Is a first color filter having a light transmittance of R (λ) ｛X (λ)｝ ² , a second color filter having a light transmittance of G (λ) ｛X (λ) 、 ² , Light transmittance is B (λ) {X (λ)}
This is equivalent to a device having a color filter device having three combined color filters with a third color filter of ² .

By the way, in the conventional case where the additional filter 32 is not provided, two kinds of mutually different colors x1 (X
1, Y1, Z1) and x2 (X2, Y2, Z2) are input to the color scanner, respectively, as shown in FIGS. 4 and 5, the color data r = (R, G,
B,) may be one type in common. In such a case, the common color data r = (R, G, B,) is used to determine the two different colors x1 (X1, Y1). , Z
1), it was difficult to reproduce x2 (X2, Y2, Z2), that is, to perform inverse estimation. In other words, it is an inverse problem having inadequacy that cannot satisfy the uniqueness of the solution.

However, according to the color scanner 10 having the additional filter 32 whose light transmittance is determined as shown in FIG. 3, two different colors x1 (X
1, Y1, Z1) and x2 (X2, Y2, Z2) are input to the color scanner 10, respectively.
As shown in the figure, the color x1 (X1, Y1, Z
1) and two types of color data r1 corresponding to x2 (X2, Y2, Z2) = (R1, G1, B1, X1) and r
2 (R1, G1, B1, X2) so is output, the color display device 14 or the color image output device 20, for example, the relationship between the displayed color and the preset color data _{R n = f IMAG (X n} ) From the two types of color data r1 =
(R1, G1, B1, X1) and r2 (R1, G1,
B1, X2), the two types of mutually different colors x
1 (X1, Y1, Z1) and x2 (X2, Y2, Z2) are reproduced.

Here, the relationship R _n = f _IMAG (X _n ) between the color data and the display color is preferably obtained in advance by an inverse interpolation estimation method. This interpolation inverse estimation method is a method for solving an inverse problem of the input estimation type, and knows the relationship between outputs with respect to some inputs and obtains the maximum number that can be taken by the input side by interpolation calculation or a practically suitable interval. This is a method in which outputs are obtained for a number of combinations of a plurality of density values, and an input corresponding to an output value closest to a desired output value is obtained as a solution based on the results. In general, when solving the above-mentioned input estimation type inverse problem of estimating an input value from an output value in reverse, the uniqueness of the solution that one input value exists for one output value, It is necessary to avoid the existence of a solution where the input value surely exists with respect to the output value, and the inadequacy that the stability of the solution where the input value changes greatly with a small change in the output value is not guaranteed. However, in the interpolation inverse estimation method described above, output values (output side information) are finely formed at regular intervals by interpolation in order to determine a solution within an error distance, and input values are estimated from the output values. By doing so, a uniform and detailed relationship R _n = f _IMAG (X _n ) is created, so that the above inappropriateness is further avoided.

That is, regarding the color scanner 10,
Equal intervals on color matching base paper represented by tristimulus values X, Y, Z
Display color and the corresponding color data in advance
A predetermined number of display colors and
A corresponding relationship with a predetermined number of color data corresponding to this is obtained,
Exists between color data corresponding to the predetermined number of display colors.
Color data is created by interpolation at regular intervals,
Estimating the display color corresponding to the interpolated color data
Of multiple types of color data and the corresponding display colors
Relation R_n= F_IMAG(X_n) Is required in advance (complementary reverse guess)
Fixed process). For example, first, the color matching base paper
A colorimeter for measuring a specified number of displayed colors, for example, 125
(Spectrophotometer) to measure the 125 species
Colorimetric values of various kinds of colors, that is, CIE standard tristimulus values XYZ
Display color X represented_n(N = 125 types)
, 125 kinds of display colors X which are substantially equal color difference intervals_nIs drawn
The obtained color matching base paper is input to the color scanner 10.
The predetermined value output from the color scanner 10.
Number of color data R_n(N = 125 types) are obtained. This 12
Five types of color data R_nAnd the corresponding display color X_nWith
The relationship is based on the additive color mixing method (additive
Color mixing is performed, so it is non-linear
Becomes Next, the color scanner is
Various types of color data R for 10_nAnd the corresponding table
Color X_nAnd a detailed relationship is required. That is,
125 types of color data R_nAre equally spaced between
Data interpolation and the data interpolation
Many types of color data R at equal intervals _nCorresponding to them from
Various display colors X_nBy inversely estimating
Display colors X for color scanner 10_nAnd it
Corresponding color data R_nA detailed relationship between R_n= F_IMAG
(X_n) Is required.

As described above, in the spectral reflectance measuring step 50, the spectral reflectances r _i (λ) (i = 1, 2, 3,...) For each representative ink among the inks used for the base paper 12. ...,
n) is measured, and the principal component analysis process 52 performs a principal component analysis on the spectral reflectances r _i (λ) measured in the spectral reflectance measurement process 50, respectively. The principal component analysis step 52
The transmittance characteristic X (λ) of the additional filter 32 is determined on the basis of the main components of the respective spectral reflectances obtained by the above, and is determined by the additional filter setting step 56 and the additional filter transmittance characteristic determining step 54. Transmittance characteristic X
An additional filter 32 having (λ) is provided between the base paper 12 and the color separation optical system unit 44. Therefore,
According to the method of the present embodiment, the transmittance characteristic (light transmittance spectrum) of the additional filter 32 is determined by using the principal component analysis, so that only a small number, for example, one additional filter 32 is used. Thus, the inverse problem can be solved, and the complexity of the calculation can be reduced as much as possible. Further, since the additional filter 32 is installed only between the base paper 12 and the color separation optical system unit 44, not in the color separation optical system unit 44 where separation is difficult, the additional filter 32 is integrally formed. Since a commercially available color image input device including the color separation optical system unit 44 can be used, color reproduction can be performed at lower cost.

Further, according to the present embodiment, the additional filter
The excess ratio characteristic determination step 54 is performed in the color separation optical system unit 44.
Any of the plurality of color filters and the additional filter 32
The light transmittance spectra of multiple synthesis filters
From the multi-order main components obtained in the analysis step 52
Of the order corresponding to the color filter in the resolution optical system unit 44
So that it corresponds to the principal component of the minimum order excluding the principal component
Next, the transmittance characteristic X (λ) of the additional filter 32 is determined.
Things. For example, the color separation optical system unit 44
A plurality of color filters having a light transmittance R (λ)
(Red) filter, G (green) with light transmittance G (λ)
Color) filter, B (blue) filter having light transmittance B (λ)
And the additional filter 32 has a light transmittance X
(Λ), the principal component analysis step 52
Reflectance of various inks used for base paper 12
r_i(Λ) (i = 1,2,3, ..., n)
The main component of the spectrum of the emitted light is the first main component R₁ (Λ),
2 main components R_Two (Λ), third main component R_Three (Λ), 4th organization
Minute R_Four (Λ), fifth main component R_Five (Λ), sixth principal component R₆ 
(Λ), X filter and R filter
Light transmittance R (λ) {X (λ)} of the synthesis filter^Two , X
Light transmittance G of the combined filter of the filter and the G filter
(Λ) {X (λ)}^Two , X filter and B filter
Light transmittance B (λ) {X (λ)}^Two Any of
Is the main component R₁ (Λ), R_Two (Λ), R _Three 
(Λ), R_Four (Λ), R_Five (Λ), R₆ (Λ)
Plural color filters in the color separation optical system unit 44
Corresponding to the light transmittances R (λ), G (λ) and B (λ)
Of the lowest order (higher order) except for
So that they correspond to the main components, in other words, approximately match
The light transmission of the additional filter 32
The rate X (λ) is determined. In other words, the additional file
In the transmittance characteristic determining step 54, the main component analyzing step 52
Set 主 成分 (= よ り R₁ (Λ), R_Two 
(Λ), R_Three (Λ), R_Four (Λ), R_Five (Λ), R₆ 
(Λ),. . . ｝) From the color separation optical system unit 44
Light transmittance R (λ), G of a plurality of color filters in
(Λ), set Γ ′ (= Γ− ｛R excluding B (λ))
(Λ), G (λ), B (λ)｝)
Light transmittance of the filter R (λ) {X (λ)}^Two , G (λ)
{X (λ)}^Two , B (λ) {X (λ)}^Two Any of
Have light transmittance X (λ) to be as close as possible
Is determined. Therefore, the inverse problem
The solution is to have as few additional filters as possible
Is efficiently determined.

In the color scanner 10 of the present embodiment, the relation R _n = f _IMAG (X
_n ) is a predetermined number of display colors by inputting display colors at regular intervals on the color matching base paper represented by tristimulus values X, Y and Z and corresponding color data to the color scanner 10 in advance. And a corresponding relationship with a predetermined number of color data corresponding thereto, and color data existing between the color data corresponding to the predetermined number of display colors is created by interpolation at regular intervals, and the interpolation is performed. Since it is obtained in advance by estimating the display color corresponding to the color data (color scanner input / output relation interpolation inverse estimation step), the color reproducibility is further enhanced.

Although the embodiment of the present invention has been described with reference to the drawings, the present invention can be applied to other embodiments.

For example, the case where one type of additional filter 32 is mounted on the color scanner 10 of the above-described embodiment has been described. However, two or more types of additional filters may be mounted. In the additional filter transmittance characteristic determination step 54 in such a case, the spectral reflectances r _i (λ) of various inks in the principal component analysis step 52 are used.
(i = 1, 2, 3,..., n), the main components of the reflected light spectrum, that is, the first main component R ₁ (λ), the second main component R ₂ (λ), and the third main component Component R ₃ (λ), fourth main component R
₄ (λ), fifth main component R ₅ (λ), sixth main component R ₆
(Λ) and the like except for those corresponding to the R filter, the G filter, and the B filter, the light transmittance R (λ) ｛X of the combined filter of the additional filter 32 and the R filter.
(Λ) Y (λ)｝ ² , light transmittance of the combined filter of the additional filter 32 and the G filter G (λ) ｛X (λ) Y
(Λ)｝ ² , the smallest order (upper order) among those corresponding to the light transmittance B (λ) ｛X (λ) Y (λ)｝ ² of the combined filter of the additional filter 32 and the B filter The light transmittance X (λ) of the additional filter 32 so as to correspond to the main component and the main component of the next lower order.
And Y (λ) are determined.

Further, the color scanner 10 of the above-described embodiment is used.
Has been described with reference to a flatbed type, but a type in which the base paper 12 is placed on the outer peripheral surface of a transparent glass cylinder and moved relative to the color separation optical system unit 44 by rotation of the transparent glass cylinder. It can be a drum type.

Further, the additional filter 32 of the above-described embodiment is used.
Was adhered to the lower surface of the transparent glass plate 30,
It may be provided on the intermediate layer or the upper surface of the transparent glass plate 30, or may be provided at a position separated from the transparent glass plate 30 by a predetermined distance. In short, what is necessary is just to be provided between the base paper 12 and the color separation optical system unit 44.

Although not specifically exemplified, the present invention can be embodied with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a color image processing apparatus using a color scanner to which the method of the present invention is applied.

FIG. 2 is a cross-sectional view illustrating a main part of the color scanner of FIG. 1;

FIG. 3 is a diagram illustrating steps of a method for determining the light transmittance of an additional filter provided in the color scanner of FIG. 2;

FIG. 4 is a diagram showing an output signal γ when two different colors x1 and x2 are input to a conventional color scanner.

FIG. 5 is a diagram showing a mutual relationship between contents of input colors x1, x2 and an output signal γ in FIG. 4;

6 is a diagram showing output signals γ1 and γ2 when two different colors x1 and x2 are input to the color scanner of FIG. 2;

FIG. 7 shows input colors x1 and x2 and an output signal γ in FIG.
It is a figure which shows the mutual relationship of the content with 1 and (gamma) 2.

[Description of Signs] 10: Color scanner 12: Base paper 32: Additional filter 50: Spectral reflectance measurement step 52: Principal component analysis step 54: Additional filter transmittance characteristic determination step 56: Additional filter installation step

Claims (1)

[Claims] An image signal composed of color data composed of functions of a plurality of types of primary colors is output from a color image input device for detecting reflected light from a base paper on which a color image is displayed through a color separation optical system unit. A spectral reflectance measuring step of measuring a spectral reflectance of each representative ink among the inks used for the base paper based on the spectral reflectance. Performing a principal component analysis of the spectral reflectances measured in the reflectance measuring step, thereby obtaining a principal component of the spectral reflectance; and a principal component of each spectral reflectance obtained in the principal component analyzing step. An additional filter transmittance characteristic determining step of determining a transmittance characteristic of the additional filter based on the additional filter; and an additional filter having the transmittance characteristic determined by the additional filter transmittance characteristic determining step. Filter, said base paper and the additional filter provision step of providing between the color separation optical system unit, the color reproduction method using a color image input apparatus which comprises.