JP2012032340A - Color processing apparatus and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate a color in the presence of an arbitrary observation light source with high precision using a small amount of data while taking into consideration a case in which a material used for image formation includes a fluorescent material.SOLUTION: A fluorescence characteristic generation part 202 inputs a measured value obtained by irradiating a color chip formed on a predetermined recording medium with monochromatic light within a range from the ultraviolet range to the visible range and measuring a tristimulus value of radiation light from the color chip, and a measured value obtained by measuring radiance of the monochromatic light. Then a tristimulus value generation rate at the wavelength of the monochromatic light is calculated from the input tristimulus value and the radiance. A light source information input part 203 inputs spectral radiance of the observation light source for the image within a range from the ultraviolet range to the visible range. A colorimetric value calculation part 204 calculates colorimetric values when the color chip is observed in the presence of the observation light source from the tristimulus value generation rate and the spectral radiance at a plurality of wavelengths within the range from the ultraviolet range to the visible range.

Description

  The present invention relates to color processing in consideration of a fluorescent substance contained in a material amount for forming an image.

  When an image is output using an image output device such as a printer, the color of the image is mapped to a color that can be reproduced by the image output device based on the color reproduction characteristics of the image output device.

A method for measuring color reproduction characteristics will be described with reference to FIGS. A print output 22 in which the color chart 12 is printed on a predetermined medium 11 is formed by an image output device. Then, the colorimeter 12 emits light from the light source (colorimetric light source) 13 of the colorimeter, and the light reflected by the color chart 12 is received by the light receiver 15 through the spectroscope 14 so that the spectral radiance of the reflected light is reflected. Measure. By dividing the spectral radiance of the reflected light by the spectral radiance of the colorimetric light source 13, the spectral reflectance R (λ) of the color chart 12 is calculated (S23). Next, the spectral radiance S (λ) of the light source (observation light source) 24 in the environment for observing the output image is measured (S25). The tristimulus value XYZ27 is calculated from the spectral reflectance R (λ), the spectral radiance S (λ) of the observation light source 24, and the color matching function x (λ) y (λ) z (λ) by the following equation (S26). ).
X = k∫R (λ) S (λ) x (λ) dλ
Y = k∫R (λ) S (λ) y (λ) dλ (1)
Z = k∫R (λ) S (λ) z (λ) dλ
Where k = 100 / ∫S (λ) y (λ) dλ,
The integration range is 380-780nm.

  That is, if the color chart 12 of a large number of colors is printed on the medium 11 by the image output device and the colorimetric values (for example, tristimulus values XYZ27) of each color chart are obtained, the color output 12 can be printed when the color chart 12 is printed. The relationship between the input signal value (for example, RGB value) 21 and the colorimetric value is obtained. This correspondence represents the color reproduction characteristics of the image output device.

  However, when a material that emits fluorescence (such as a fluorescent whitening agent) is used for the amount of material used for image formation (such as recording paper), the spectral reflectance R (λ) measured by the above method is The spectral reflectance R (λ) under the observation light source may be different. The fluorescent material emits light in a wavelength range (fluorescence wavelength range) different from the excitation wavelength range included in the irradiation light. In general, the fluorescence wavelength is longer than the excitation wavelength.

  The schematic diagram of FIG. 3 shows the measured value of the emitted light from the color chart when the color chart containing the fluorescent material is irradiated with monochromatic light. FIG. 3 (a) shows the intensity of the emitted light when the color chart is irradiated with monochromatic light of 350 nm. The emitted light 1101 is reflected light with respect to the irradiated monochromatic light, and the emitted light 1102 is fluorescence excited by the irradiated monochromatic light. On the other hand, FIG. 3 (b) shows the intensity of the emitted light when the color chart is irradiated with monochromatic light of 440 nm. The emitted light 1103 is reflected light with respect to the irradiated monochromatic light.

  As shown in FIG. 3 (a), when the color chart includes a fluorescent material, when the excitation wavelength light is irradiated, the wavelength of the irradiation light is different from the reflected light 1101 of the irradiation light wavelength. Wavelength fluorescence 1102 is observed. On the other hand, as shown in FIG. 3B, when light that is not the excitation wavelength is irradiated, reflected light 1103 having the wavelength of the irradiated light is observed. Therefore, for example, under a light source including a 350 nm component and a 440 nm component, the 440 nm light observed as the emitted light of the color chart is the sum of the fluorescence 1102 and the reflected light 1103. Of course, since a general light source has many wavelength components, the sum of the reflected light of 440 nm and the fluorescence of 440 nm for each wavelength becomes the emitted light of 440 nm observed from the color chart under the light source.

  The spectral reflectance R (λ) of a sample containing a fluorescent material having an excitation wavelength in the ultraviolet region will be described with reference to FIG. Using the measurement system shown in Fig. 1, when measuring the emitted light of a sample containing a fluorescent substance, the fluorescent substance reacts with the light in the ultraviolet region (41 in Fig. 4 (a)) contained in the irradiated light, and the fluorescence Light in the wavelength region (42 in FIG. 4 (b)) is emitted. That is, the colorimeter receives, from the sample, radiated light to which fluorescence depending on the light energy in the ultraviolet region (excitation wavelength region) 41 of the colorimetric light source 13 is added. As a result, the spectral reflectance R (λ) also depends on the light energy in the ultraviolet region 41 of the colorimetric light source 13 (FIG. 4 (c)). When the colorimetric light source 13 and the observation light source 24 are the same, fluorescence corresponding to the light energy in the excitation wavelength region of the observation light source 24 is obtained in the measurement, so that a correct colorimetric value is calculated. On the other hand, if the colorimetric light source 13 and the observation light source 24 are different, the fluorescence that does not correspond to the light energy in the excitation wavelength region of the observation light source 24 is obtained in the measurement, so that the correct tristimulus value cannot be calculated.

  As described above, when the colorimetric light source 13 used for colorimetry of the sample containing the fluorescent substance and the observation light source 24 are different, there is a problem that the colorimetric value representing the color reproduction characteristic does not correspond to the actually visible color. As a method for solving this problem, a method for obtaining a colorimetric value using a light source corresponding to the observation environment (Patent Document 1), and an observation using color conversion characteristics determined based on the excitation characteristics of colors output from the output device A method for estimating a colorimetric value under the environment (Patent Document 2) has been proposed.

  The method disclosed in Patent Document 1 measures color reproduction characteristics by changing the light source for each observation environment. Therefore, in order to cope with many observation environments, a large amount of measurement is performed and a large amount of colorimetric values are managed. There is a need. Further, the method disclosed in Patent Document 2 needs to create excitation characteristic data indicating a combination of excitation light wavelength and fluorescence wavelength, and it is necessary to create and manage excitation characteristic data of many combinations thereof. For example, when the excitation wavelength is 300 nm to 780 nm and the fluorescence wavelength is 380 nm to 780 nm and the excitation characteristic data in increments of 10 nm is held, it becomes 41 × 49 two-dimensional matrix data (2009 data). Even if only the data of excitation wavelength <fluorescence wavelength is retained, it is necessary to retain 1189 data per color (one color chart).

  In this way, if the color reproduction characteristics when the media or color material contains a fluorescent substance are accurately acquired and mapping is performed in consideration of fluorescence, a large amount of colorimetric values are handled, so the man-hours and memory required for measurement Memory capacity and microprocessor (CPU) calculation load increase.

JP 2004-064112 A Japanese Patent Laid-Open No. 2003-110867

  An object of the present invention is to calculate a color under an arbitrary observation light source with high accuracy with a small amount of data in consideration of the case where the amount of material used for image formation includes a fluorescent substance.

  The present invention has the following configuration as one means for achieving the above object.

  The color processing according to the present invention is a measurement in which, in the range from the ultraviolet region to the visible region, monochromatic light is applied to a color chart formed on a predetermined recording medium, and tristimulus values of the emitted light from the color chart are measured. Value and a measurement value obtained by measuring the radiance of the monochromatic light are input, the tristimulus value generation rate at the wavelength of the monochromatic light is calculated from the input tristimulus value and radiance, and an image observation light source The spectral radiance in the range from the ultraviolet range to the visible range is input, and the color chart is observed from the tristimulus value generation rate and the spectral radiance at a plurality of wavelengths in the range from the ultraviolet range to the visible range. A colorimetric value for observing under a light source is calculated.

  According to the present invention, in consideration of the case where the amount of material used for image formation includes a fluorescent substance, it is possible to calculate the color under an arbitrary observation light source with high accuracy with a small amount of data.

FIG. 5 is a diagram for explaining a method for measuring color reproduction characteristics. FIG. 5 is a diagram for explaining a method for measuring color reproduction characteristics. The schematic diagram which shows the measured value of the radiated light from a color chart at the time of irradiating a monochromatic light to the color chart containing a fluorescent substance. The figure explaining the spectral reflectance R ((lambda)) of the sample containing the fluorescent material whose excitation wavelength exists in an ultraviolet region. FIG. 3 is a block diagram illustrating a configuration example of a color processing apparatus according to an embodiment. The block diagram explaining the functional structural example of the color processing part implement | achieved by the color processing program. The figure explaining an example of fluorescence characteristic data. FIG. 6 illustrates a configuration example of a color measurement device. 6 is a flowchart for explaining a processing example of a color processing unit. The flowchart explaining the production | generation of the fluorescence characteristic data by a fluorescence characteristic production | generation part. 7 is a flowchart for explaining calculation of colorimetric values by a colorimetric value calculation unit. The block diagram explaining the functional structural example of the color processing part of a modification.

  Hereinafter, color processing according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the color profile according to the present invention is referred to as a “fluorescence profile” in order to distinguish it from the color profile used for normal color conversion processing.

[Device configuration]
A configuration example of the color processing apparatus 100 of the embodiment will be described with reference to the block diagram of FIG. The microprocessor (CPU) 101 executes an operating system (OS) and various programs stored in the ROM of the main memory 102 and the hard disk drive (HDD) 103 using the RAM of the main memory 102 as a work memory. Then, the configuration described later is controlled via the system bus 105. The general-purpose interface (I / F) 104 is a serial bus interface such as USB or IEEE1394. The general-purpose I / F 104 is connected to an image output device (image forming device) 107 such as a printer, a color measurement device 108, a light source measurement device 109 that measures the spectral distribution of the light source in the observation environment, and the like.

  A monitor 106 is connected to the color processing apparatus 100 via a video I / F 110. The general-purpose I / F 104 is also connected with a keyboard and a pointing device (not shown). In accordance with a user instruction via the user interface displayed on the monitor 106, the CPU 101 loads the color processing program and data for realizing the color processing of the embodiment from the HDD 103 to the RAM, and executes the color processing program. Then, data indicating the color processing result is stored in the HDD 103 or the like.

Color Processing Unit A functional configuration example of the color processing unit 201 realized by the color processing program will be described with reference to the block diagram of FIG. The color processing unit 201 corresponds to a main part of functions realized by the CPU 101 by a color processing program.

  The color data output unit 205 outputs the color data read from the HDD 103 to the image output device 107. The fluorescence characteristic generation unit 202 generates fluorescence characteristic data, which will be described later, of the color chart formed by the image output device 107. The light source information input unit 203 inputs light source information, which will be described later, of the observation light source. The colorimetric value calculation unit 204 calculates colorimetric values (XYZ values, Lab values, etc.) when the color chart is observed under the observation light source from the fluorescence characteristic data and the light source information. The profile generation unit 206 generates a fluorescence profile indicating the correspondence between the color chart color data and the colorimetric values, and stores the generated fluorescence profile in the HDD 103.

The fluorescence profile is a table that describes the correspondence between the color data of the color chart and the colorimetric values calculated from the fluorescence characteristic data for each of a sufficient number of color charts to represent the color reproduction characteristics of the image output device 107. For example, assuming that the image output device 107 inputs 256-color RGB color signals, colorimetric values corresponding to 9-step color charts (9 ³ = 729), each of which is divided into 8 RGB gradations, are described. Has been. Also, for example, if the image output device 107 inputs color signals of 256 CMYK colors, the colorimetry corresponding to 9 steps of color charts (9 ⁴ = 6561) obtained by dividing the CMYK gradations into 8 parts. A value may be described. Of course, the number of gradation divisions is arbitrary, and it may be set to the number of divisions (number of color charts) according to the color reproduction accuracy. That is, the fluorescence profile is different from a normal color profile in that a colorimetric value calculated from fluorescence characteristic data is described.

  An example of fluorescence characteristic data will be described with reference to FIG. The fluorescence characteristic data is data obtained by combining the wavelength λi and the tristimulus value generation rates Rx (λi), Ry (λi), and Rz (λi) corresponding to the wavelength λi. The tristimulus value generation rate is a tristimulus value XYZ of radiated light including reflected light and fluorescence with respect to irradiation of monochromatic light with unit radiance.

  The range of the wavelength λi is the excitation wavelength range and the visible light wavelength range of the fluorescent material included in the color chart, and the sampling interval of the wavelength λi is determined according to the required color reproduction accuracy. If the sampling interval is narrowed, the color reproduction accuracy is improved, but the time required for measurement and the amount of fluorescence characteristic data increase. Conversely, if the sampling interval is widened, the color reproduction accuracy decreases, but the time required for measurement and the amount of fluorescence characteristic data decrease.

  In the following, assuming a fluorescent material having an excitation wavelength region in the ultraviolet region, for example, the range of wavelength λi is 300 nm to 780 nm, and the sampling interval is 10 nm. Accordingly, the wavelength λi of this example takes 49 values of 300, 310, 320,..., 780 nm (i = 0 to 48), and the fluorescence characteristic data of each color chart is shown in three rows as shown in FIG. It becomes a 49-column matrix. Therefore, there are 147 pieces of data per color (one color chart), which is about 1/8 of the data amount (1189 pieces of data) of Patent Document 2 described above.

[Color measuring device]
A configuration example of the color measuring apparatus 108 will be described with reference to FIG. As shown in FIG. 8 (a), the light source 401 outputs light P (λ) that irradiates the color chart 403. The light P (λ) desirably has a continuous spectrum in the visible light wavelength range (hereinafter, visible range) and the excitation wavelength range of the fluorescent substance. In this embodiment, a light source 401 having a continuous spectrum between 300 nm and 780 nm, which is the range of the wavelength λi, is used. The spectroscope 402 splits the light P (λ) and outputs monochromatic light P (λi) having a wavelength λi.

  The filter switching unit 404 switches between a state in which any of the XYZ filters is arranged on the optical path connecting the color chart 403 and the light receiver 405 and a state in which the XYZ filter is retracted from the optical path. As shown in FIG. 8 (b), the filter switching unit 404 is a turret having four windows 406 to 409, and X filters, Y filters, and Z filters are arranged in the windows 406, 407, and 408, respectively. Yes. Further, no filter is installed in the window 409, and the emitted light from the color chart 403 is passed through. The filter switching unit 404 can arrange any of the four windows on the optical path by rotating.

  The light receiver 405 measures the amount of radiated light Q (λ) from the color chart 403. The light receiver 405 has a viewing angle of 2 degrees and has a known spectral response sensitivity for all 49 measurement wavelengths λi. Further, the spectral transmittance of each XYZ filter and the spectral response sensitivity of the light receiver 405 are designed to have a spectral response sensitivity that approximates the color matching function of the double field of view when they are combined. In configuring the present invention, the viewing angle of the light receiver 405 is not limited to twice. For example, the configuration may be such that the viewing angle of the light receiver 405 is 10 degrees and approximates the color matching function of the 10-degree field of view when combined with XYZ filters.

  The color measuring device 108 irradiates the color chart 403 from the spectroscope 402 with monochromatic light P (λi) at an incident angle of 90 degrees, and measures the radiance of light from the color chart 403 in the 45-degree direction with the light receiver 405. When the window 406 (X filter) is arranged on the optical path, the light receiver 405 measures the radiated light x (λ) that has passed through the X filter, thereby obtaining a measured value of the amount of radiated light corresponding to the X value. Similarly, a window 407 (Y filter) and a window 408 (Z filter) are arranged on the optical path to obtain a measurement value of the amount of radiated light corresponding to the Y value and the Z value. By dividing these measured amounts by the response sensitivity of the light receiver 405 at the wavelength λi, the XYZ values of the color chart radiation when the monochromatic light P (λi) is irradiated can be obtained.

  Further, when measuring the radiance of the monochromatic light P (λi) that irradiates the color chart 403, a standard reflection sample is disposed instead of the color chart 403, and a window 409 (no filter) is disposed on the optical path. The standard reflection sample is a white plate that has a known reflectance for all 49 wavelengths λi under the incident angle and the reflection angle in the color measuring device 108, and has no fluorescence characteristic (does not emit fluorescence). By dividing the measured value of the wavelength λi by the reflectance of the standard reflection sample at the wavelength λi and the response sensitivity of the light receiver 405, the radiance of the monochromatic light λi can be obtained.

  Note that the calculation for converting the measured value of the amount of radiated light into an XYZ value or radiance may be performed by the color measurement device 108 or the fluorescence characteristic generation unit 202. In the following description, it is assumed that the color measurement device 108 performs the calculation and the fluorescence characteristic generation unit 202 inputs the calculation result as a measurement value. Further, the incident angle of light on the color chart 403 and the reflection angle of light to be measured are not limited to 90 degrees and 45 degrees, and may be any angles as long as measurement is possible. For example, the incident angle may be 45 degrees and the reflection angle may be 90 degrees, and the color chart 403 may be arranged on a movable table so that the incident angle and the reflection angle can be adjusted. Of course, in order to efficiently measure a plurality of color charts 403 and standard diffusion samples, it is also effective to prepare an XY stage and automatically switch the color chart 403 to be measured.

  The color measuring device 108 only needs to be able to measure the tristimulus values of the color chart 403 for incident light of a plurality of wavelengths. For example, instead of the light source 401 and the spectroscope 402, the laser light source of monochromatic light is switched. A configuration in which the color chart 403 is irradiated may be used.

  In addition, the color measuring device 108, instead of the XYZ filter, arranges a spectroscope equivalent to the spectroscope 402 on the optical path connecting the color chart 403 and the light receiver 405, so that the spectral radiance of the emitted light of the color chart 403 is increased. You may measure. In that case, a tristimulus value corresponding to the monochromatic light λi can be calculated by integrating the color matching function with the measured spectral radiance and integrating the wavelength. The color matching function may be input by an arbitrary method. For example, the color matching function may be stored in advance in the HDD 103 or may be input from an external storage device via the general-purpose I / F 104. However, since this method performs spectroscopy twice, ie, incident and measurement, the radiance of light reaching the light receiver is reduced, and the ratio of noise to the measured value is increased. Therefore, it is necessary to take another measure for noise reduction.

[Generate fluorescence profile]
A processing example of the color processing unit 201 will be described with reference to the flowchart of FIG. The color data output unit 205 outputs color data for forming a color chart to the image output apparatus 107, and causes the image output apparatus 107 to form a color chart based on the color data on a predetermined recording medium (S501).

  As will be described in detail later, the fluorescence characteristic generation unit 202 controls the color measurement device 108 to input measurement values, calculates tristimulus value generation rates, and generates fluorescence characteristic data (S502). That is, the fluorescence characteristic generation unit 202 functions as a first input unit that inputs a measurement value and a first calculation unit that calculates a tristimulus value generation rate. The fluorescence characteristic generation unit 202 can store the generated fluorescence characteristic data in a predetermined area of the HDD 103.

  The light source information input unit 203 controls the light source measurement device 109 to input the light source information of the observation light source (S503). That is, the light source information input unit 203 functions as a second input unit that inputs light source information.

  The colorimetric value calculation unit 204 calculates the colorimetric value of the color chart under the observation light source, as will be described in detail later, based on the fluorescence characteristic data and the light source information (S504). That is, the colorimetric value calculation unit 204 functions as a second calculation unit that calculates colorimetric values.

  The profile generation unit 206 generates a fluorescence profile that associates the color data output from the color data output unit 205 with the colorimetric values calculated by the colorimetric value calculation unit 204 (S505).

  The light source information is the spectral radiance of the observation light source in the wavelength range including the excitation wavelength range and the visible range of the fluorescent material included in the color chart. In the case of an observation light source that does not include light in the excitation wavelength region, the spectral radiance in the excitation wavelength region may be set to zero. In the following description, it is assumed that the light source information input unit 203 inputs a spectral radiance of 300 nm ≦ λ ≦ 780 nm. When the characteristics of the observation light source such as the observation environment defined by the standard and the standard observation environment are clear, the light source information input unit 203 is stored in a storage unit such as the HDD 103 without using the light source measurement device 109. The spectral radiance of the light source may be input.

Fluorescence characteristic generation unit Fluorescence characteristic data generation (S502) by the fluorescence characteristic generation unit 202 will be described with reference to the flowchart of FIG. FIG. 10 shows a process for measuring one color chart and acquiring fluorescence characteristic data, but the process shown in FIG. 10 is repeated for the number of color charts (for example, 729).

  The fluorescence characteristic generation unit 202 sets the index i to 0 (S601). Then, a measurement value obtained by irradiating the color chart 403 with the monochromatic light P (λi) having the wavelength λi and measuring the tristimulus values XYZ of the color chart 403 is input (S602). Subsequently, the measurement value obtained by irradiating the standard reflection sample with the monochromatic light P (λi) and measuring the radiance of the monochromatic light P (λi) is input (S603).

  Next, the fluorescence characteristic generation unit 202 calculates the tristimulus value generation rate of the color chart 403 at the wavelength λi from the radiance of the monochromatic light P (λi) and the tristimulus values XYZ of the color chart 403 for the monochromatic light P (λi). Rx (λi), Ry (λi), and Rz (λi) are calculated (S604). That is, the tristimulus value generation rate is calculated by dividing the tristimulus value XYZ by the radiance.

  Next, the fluorescence characteristic generation unit 202 increments the index i (S605), and compares the index i with the number n of wavelengths λi to be measured (S606). If i <n (i <49 in this example), the process returns to step S602, and steps S602 to S605 are repeated for all wavelengths λi (λ0 to λ49 in this example) to be measured.

  When the measurement is completed for all the wavelengths λi to be measured, the fluorescence characteristic generation unit 202 performs the wavelength (input wavelength) λi of the monochromatic light P (λi) and the tristimulus value generation rates Rx (λi), Ry (λi), Rz ( Fluorescence characteristic data indicating the correspondence relationship of λi) is generated (S607).

  The flowchart shown in FIG. 10 shows an example in which the tristimulus value XYZ is measured by switching the XYZ filter after setting the measurement wavelength. However, for example, the X filter is arranged on the optical path and the X value is measured for all the wavelengths λi to be measured. Subsequently, the filters are arranged in the order of the Y filter and the Z filter, and all the wavelengths λi to be measured are measured. Measurement may be performed. Alternatively, when the color measuring device 108 has a function of automatically switching the color chart to be measured, all color charts are measured for a combination of a certain wavelength λi and a certain filter, and then the combination of the wavelength λi and the filter is changed. Also good.

Colorimetric Value Calculation Unit Colorimetric value calculation (S504) by the colorimetric value calculation unit 204 will be described with reference to the flowchart of FIG. FIG. 11 shows the process of calculating the colorimetric value of one color chart, but the process shown in FIG. 11 is repeated for the number of color charts (for example, 729).

  The colorimetric value calculation unit 204 acquires the fluorescence characteristic data of the color chart for calculating the colorimetric value and the light source information (S701). For example, the fluorescence characteristic data is tristimulus value generation rates Rx (λi), Ry (λi), and Rz (λi) for input wavelengths λi = 300 nm to 780 nm shown in FIG. The light source information is the spectral radiance S (λ) (300 nm ≦ λ ≦ 780 nm) of the light source including the excitation wavelength range of the fluorescent substance.

Next, the colorimetric value calculation unit 204 sets the index i to 0 (S702). Then, the spectral radiance S (λi) of the wavelength λi is acquired (S703), and the tristimulus value generation rates Rx (λi), Ry (λi), and Rz (λi) for the input wavelength λi are acquired (S704). Then, from the obtained spectral radiance S (λi) and the obtained tristimulus value generation rates Rx (λi), Ry (λi), Rz (λi), the tristimulus values X _λi , Y _λi from the wavelength λi are obtained. , Z _λi is calculated (S705).
X _λi = S (λi) Rx (λi)
Y _λi = S (λi) Ry (λi) (2)
Z _λi = S (λi) Rz (λi)

  Next, the colorimetric value calculation unit 204 increments the index i (S706), and compares the index i with the number n of wavelengths λi to be measured (S707). If i <n (i <49 in this example), the process returns to step S703, and steps S703 to S706 are repeated for all wavelengths λi (λ0 to λ49 in this example) for which colorimetric values are to be calculated.

When the colorimetric values are calculated for all of the wavelengths λi, the colorimetric value calculation unit 204 integrates the tristimulus values X _λi , Y _λi , and Z _λi of each wavelength by the following formula, and the color chart 403 under the observation light source The tristimulus values XYZ are calculated (S708).
X = k∫X _λi dλ
Y = k∫Y _λi dλ (3)
Z = k∫Z _λi dλ
Here, the integration range is 300 to 780 nm.

In Expression (3), k is a constant. For example, when normalization is performed based on the spectral radiance S (λ) of the observation light source, it may be obtained by the following expression.
k = 100 / ∫S (λ) y (λ) dλ (4)
Here, the integration range is 380-780nm,
y (λ) is a function of Y in the color matching function.

  For example, the profile generation unit 206 determines the lower level of the observation light source from the correspondence between the colorimetric values of the color chart for 729 colors calculated in this way and the color data input to the image output apparatus when forming the color chart. A fluorescence profile can be generated. When using Lab values as colorimetric values, the XYZ values may be converted into Lab values using the XYZ → Lab conversion formula.

[Use fluorescence profile]
The fluorescence profile generated by the profile generation unit 206 can be used in a color management system (CMS). CMS is a system that realizes color reproduction that is as equal as possible between different devices by absorbing the difference in color reproduction range that varies from device to device. General CMS realizes color matching between different devices while mutually converting a device-dependent color space (RGB, CMYK, etc.) and a device-independent color space (CIEXYZ, CIELAB, etc.). For mutual conversion between the device-dependent color space and the device-independent color space, a color profile (such as an ICC profile) storing the color reproduction characteristics of the device is used. The color profile stores the color reproduction characteristics of the device as a conversion formula or conversion table (lookup table (LUT)), and the color space can be mutually converted by referring to the color profile.

  Therefore, based on the processing shown in FIG. 9, if the color profile of the color chart is obtained and a color profile is created in which the correspondence between the RGB values and the color measurement values of the color chart is described as an LUT, the fluorescence profile is generally It becomes possible to use with a typical CMS.

  In addition, a configuration in which the CMS acquires light source information of a fluorescence profile and an observation light source and performs color matching in an observation environment is possible. In that case, the CMS calculates colorimetric values under the observation light source for a color chart of a predetermined number of colors, and generates, for example, an LUT describing the correspondence between RGB values and colorimetric values. Alternatively, the fluorescence profile may be treated as an LUT describing the correspondence between, for example, RGB values of a predetermined number of color charts and fluorescence characteristic data. In that case, the CMS generates fluorescence characteristic data for an arbitrary RGB value by interpolation, and calculates a colorimetric value for the arbitrary RGB value under the observation light source. That is, CMS using these fluorescence profiles is also within the scope of the present invention.

  In this way, the relationship between the wavelength of monochromatic light (input wavelength) irradiated to the color chart and the tristimulus value generation rate of the color chart relative to the input wavelength is obtained, and the amount of material containing a fluorescent material is used with a small amount of data. The color of the printed material under an arbitrary observation light source can be calculated with high accuracy. Therefore, it is possible to accurately acquire color reproduction characteristics when media and color materials contain fluorescent materials, and to calculate the number of man-hours, memory storage capacity, and microprocessor (CPU) required for mapping when considering fluorescence. The load can be reduced.

[Modification]
In the above description, the example in which the colorimetric value is calculated based on the information input from the color measurement device 108 and the light source measurement device 109 connected to the outside of the color processing device 100 has been described. However, it is not always necessary to acquire information from the outside, and a configuration having a measurement function is also possible. A functional configuration example of the color processing unit 801 of the modification will be described with reference to the block diagram of FIG.

  The color processing unit 801 calculates a colorimetric value by measuring a color chart or an observation light source. The measurement unit 802 measures the fluorescence characteristic data of the color chart formed by the image output device 107 and the light source information of the observation light source by the same method as the color measurement device 108 and the light source measurement device 109 described in the first embodiment. The calculation unit 803 inputs the fluorescence characteristic data and the light source information measured by the measurement unit 802, and calculates the colorimetric value of the color chart under the observation light source by the same processing as the colorimetric value calculation unit 204. The storage unit 804 is a memory that stores data of measurement values (fluorescence characteristic data and light source information) of the measurement unit 802 and calculation results (fluorescence profile and the like) of the calculation unit 803.

[Other Examples]
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (7)

In the range from the ultraviolet region to the visible region, a measurement value obtained by irradiating a color chart formed on a predetermined recording medium to measure tristimulus values of emitted light from the color chart, and the monochromatic light A first input means for inputting a measurement value obtained by measuring radiance;
First calculation means for calculating a tristimulus value generation rate at the wavelength of the monochromatic light from the input tristimulus value and radiance;
A second input means for inputting a spectral radiance of an image observation light source in a range from the ultraviolet region to the visible region;
A colorimetric value of the color chart when the color chart is observed under the observation light source is calculated from the tristimulus value generation rate and the spectral radiance at a plurality of wavelengths in the ultraviolet to visible range. A color processing apparatus comprising: a second calculation unit. Furthermore, in order to form the color chart, output means for outputting the color chart color data to the image forming apparatus,
2. The color processing apparatus according to claim 1, further comprising a generating unit that generates a profile indicating a relationship between color data of the color chart and colorimetric values of the color chart.   3. The color processing apparatus according to claim 1, wherein the range from the ultraviolet region to the visible region includes an excitation wavelength region of a fluorescent material included in a material amount for forming the image.   4. The radiance of the monochromatic light is calculated from the amount of reflected light from the standard reflective sample when the standard reflective sample is irradiated with the monochromatic light. The described color processing apparatus.   5. The color processing apparatus according to claim 1, wherein the tristimulus value generation rate is a tristimulus value of radiated light with respect to irradiation of monochromatic light having unit radiance. A color processing method of a color processing apparatus having first and second input means and first and second calculation means,
Measurement in which the first input means measures a tristimulus value of emitted light from the color chart by irradiating a color chart formed on a predetermined recording medium with monochromatic light in a range from the ultraviolet range to the visible range. Value and a measured value obtained by measuring the radiance of the monochromatic light,
The first calculation means calculates a tristimulus value generation rate at the wavelength of the monochromatic light from the input tristimulus value and radiance,
The second input means inputs a spectral radiance of an image observation light source in a range from the ultraviolet region to the visible region,
Color measurement when the second calculation means observes the color chart under the observation light source from the tristimulus value generation rate and the spectral radiance at a plurality of wavelengths ranging from the ultraviolet region to the visible region. A color processing method characterized by calculating a value.   6. A program causing a computer device to function as each unit of the color processing device according to claim 1.

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