Color chart processing apparatus, color chart processing method, and color chart processing program

A color chart processing apparatus includes a spectrum calculating unit for receiving information regarding a spectral reflection factor of each color contained in a predetermined color chart and information regarding determination illumination light, and determining a spectrum of the color contained in the predetermined color chart under the determination illumination light by calculating the received information, and a determination information output unit for receiving a color signal of a subject, determining which color of the predetermined color chart closest matches the color signal of the subject by comparing the spectrum of each color determined by the spectrum calculating unit with the color signal of the subject, and outputting information identifying the resulting determination color.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color chart processing apparatus, a color chart processing method, and a color chart processing program for acquiring spectral image information of a subject, and determining correspondence between a color of the acquired image and a predetermined color chart.

2. Description of the Related Art

Color management has been conventionally performed in numerous fields. Colors of objects are typically determined based on sensory evaluation using a color chart. For example, in the dentistry field, a color chart called a shade guide is used to determine which grade an artificial denture is classified to when the artificial denture is produced. For example, a leaf color chart is used to determine an agricultural crop such as rice plant. By checking a crop against the leaf color chart, a current growing condition is known. Growth and development management is thus performed to adjust the amount of fertilizer. The application of color charts is not limited to the dentistry and agricultural fields. The color charts are used for diagnosis and examination in a variety of other fields, such as coating painting of cars, painting of buildings, foods, and clothes.

Each color is identified using a number in the color chart (color chart number). Experienced users and specialists visibly check an object to be examined against a color chart, thereby determining the color chart number. There occur variations inherent to a user himself, variations from user to user, and variations in illumination conditions under which a subject is placed. It is thus difficult to accurately identify the color chart number.

Japanese Unexamined Patent Application Publication No. 7-120324 (hereinafter referred to Document 1) discloses a technique of color classification using a camera system. In the disclosed technique, a multi-spectral camera is used to classify grade using a multi-spectral image captured by the camera. In comparison with an ordinary RGB camera, the multi-spectral camera substantially increases a color chart determination accuracy level.

SUMMARY OF THE INVENTION

A color chart processing apparatus of the present invention includes spectrum calculating means for receiving information regarding a spectral reflection factor of each color contained in a predetermined color chart and information regarding determination illumination light, and determining a spectrum of the color contained in the predetermined color chart under the determination illumination light by calculating the received information, and determination information output means for receiving a color signal of a subject, determining which color of the predetermined color chart closest matches the color signal of the subject by comparing the spectrum of each color determined by the spectrum calculating means with the color signal of the subject, and outputting information identifying the resulting determination color.

A color chart processing method of the present invention includes a spectrum calculating step of receiving information regarding a spectral reflection factor of each color contained in a predetermined color chart and information regarding determination illumination light, and determining a spectrum of the color contained in the predetermined color chart under the determination illumination light by calculating the received information, a determination step of determining which color of the predetermined color chart closest matches an input color signal of a subject by comparing the spectrum of each color determined in the spectrum calculating step with the color signal of the subject, and a step of outputting information identifying the resulting determination color in the determination step.

A color chart processing program of the present invention causes a computer to perform a spectrum calculating processing of receiving information regarding a spectral reflection factor of each color contained in a predetermined color chart and information regarding determination illumination light, and determining a spectrum of the color contained in the predetermined color chart under the determination illumination light by calculating the received information, a determination processing of determining which color of the predetermined color chart closest matches an input color signal of a subject by comparing the spectrum of each color determined in the spectrum calculating processing with the color signal of the subject, and a processing of outputting information identifying the resulting determination color in the determination processing.

A color chart processing program of the present invention causes a computer to perform a spectrum estimation calculating processing of determining a spectral reflection factor of a subject from a color signal of the subject and photographing illumination information obtained when the color signal of the subject is acquired, and reproducing the color signal of the subject using the determined spectral reflection factor and newly set subject rendering illumination information, a spectrum calculating step of receiving information regarding a spectral reflection factor of each color contained in a predetermined color chart and information regarding determination illumination light, and determining a spectrum of the color contained in the predetermined color chart under the determination illumination light by calculating the received information, a determination processing of determining which color of the predetermined color chart closest matches the reproduced color signal of the subject by comparing the color signal of the subject reproduced in the spectrum estimation calculating processing with the spectrum of each color determined in the spectrum calculating processing, and a processing of outputting information identifying the resulting determination color in the determination processing.

A color chart processing apparatus of the present invention includes mixing ratio database means for storing, by each color, information regarding a color contained in a predetermined color chart, information regarding a plurality of colors that are mixed to produce the color, and information regarding a mixing ratio, and mixing amount information output means for outputting information regarding a mixing amount by receiving information identifying the color contained in the predetermined color chart, and by reading information stored on the mixing ratio database means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The embodiments of the present invention are described below with reference to the drawings.FIG. 1is a block diagram illustrating a color chart processing apparatus in accordance with a first embodiment of the present invention.

The color chart processing apparatus ofFIG. 1determines which color of a predetermined color chart the color of a subject1corresponds to, and outputs a color chart ID such as a color chart number or a color chart symbol uniquely identifying a color of the color chart. A color detector2is arranged to face the subject1. The color detector2is composed of a multi-spectral camera, for example, and photographs the subject1, thereby acquiring a subject signal. The subject signal contains spectral information of the subject1. The subject signal may occasionally contain spectral information of illumination light at the photographing.

Meanwhile, a color chart spectrum database4stores spectrum information of each color contained in at least one color chart. In response to a color chart specified, the color chart spectrum database4outputs information of a spectrum of each color (hereinafter referred to as color chart spectral data).

A color chart determiner3receives the subject signal from the color detector2and the color chart spectral data from the color chart spectrum database4. The color chart determiner3also receives determination illumination light information as information of illumination light for use in color chart determination.

The color chart determiner3calculates spectrum information of each color in the specified color chart based on the determination illumination light information and the color chart spectral data. The color chart determiner3determines which color of the color chart the color of the subject1corresponds to by comparing the calculated spectral information of each color in the color chart with spectral information contained in the subject signal, and then outputs a color chart ID of the corresponding color.

In the embodiment thus constructed, the color detector2photographs the subject1illuminated by predetermined illumination light. The subject signal from the color detector2is supplied to the color chart determiner3. The color chart determiner3successively reads the color chart spectral data of each color in the predetermined color chart from the color chart spectrum database4, and obtains the spectral information of each color in the color chart under the predetermined illumination light based on the read color chart spectral data and the determination illumination light information. The color chart determiner3compares the calculated spectral information of each color with the spectral information in the subject signal, thereby determining which color of the color chart the color of the subject1corresponds to. The color chart determiner3then outputs the color chart ID of the determined color as the color of the subject1.

In accordance with the present embodiment, the spectral information of each color is calculated using the determination illumination light information. As in the visual color chart determination, the determination result of the color chart ID varies in response to the determination (observation) illumination light. For example, in the dentistry field, a photographing site of an object to be determined may be different from a determination site of a color chart. If the photographing site is remote from the determination site, information regarding photographing light may be unknown. Even if the photographing light is known, a user of a color chart may determine the color chart using preferred determination light based on experience without paying attention to the photographing light. The embodiment of the present invention is useful in such an occasion. The color chart determination is performed using information of the determination illumination light information, and useful and effective color chart ID is calculated.

In the present embodiment, the photographing illumination light information at the photographing of the object to be determined may be used. The color chart ID is thus calculated in a state in which the determination illumination light is equalized with the photographing illumination light.

In the present embodiment, the color chart spectrum database storing the spectral information of each color chart is arranged. The spectral information of each color in the color chart is calculated based on the spectral information from the color chart spectrum database and the information of the determination illumination light. The color chart ID indicating the color of the subject is obtained by comparing the calculated spectral information with the spectral information of the subject. Rather than using the degree of color unique to a color chart determination system, the color of the object is determined by applying a color in a color chart defined in each of a variety of fields. Since the color chart spectrum database storing the spectral information of the colors of a variety of color charts is used, it is not necessary to learn correspondence between a color unique to the system and the color in the color chart. Since the color chart ID is determined under any illumination light source, the color chart processing apparatus is extremely useful. For example, the color chart ID may be always determined under constant illumination conditions or may be determined under various illumination conditions.

FIG. 2is a block diagram of a color chart processing apparatus in accordance with a second embodiment of the present invention. A specific structure of the color chart processing apparatus shown herein calculates the color chart ID using only the information of the determination illumination light without using the information of the photographing illumination light.

The color chart processing apparatus of the present embodiment includes a color detection section8, a color chart spectrum database20, a color chart determination section13, and a color chart ID display19.

The color detection section8is a contact-type or non-contact-type spectrometer, and includes a spectral detector9and an illumination device10. The illumination device10directs photographing illumination light onto a subject. The illumination device10may be one of a variety of light sources including an xenon lamp, a fluorescent lamp, and a halogen lamp. The spectral detector9includes an optical system11and a spectral sensor12. The optical system11introduces the light reflected by the subject1to the spectral sensor12. The spectral sensor12spectroscopes incident light and obtains a spectral distribution of a light ray reflected from the subject. The spectral sensor12outputs the obtained spectral distribution as a determination subject spectrum to the color chart determination section13.

The color chart spectrum database20includes a color chart spectrum storage21. The color chart spectrum storage21includes a plurality of spectral data memories22storing spectral data of a plurality of color charts. As shown inFIG. 2, the color chart spectrum storage21includes the spectral data memories22storing the spectral data of a Munsell color chart, a crown color chart, a Macbeth color chart, a leaf color chart, a DIC color chart, an interior color chart, a skin tone color chart, and a frozen tuna color chart.

In the present embodiment, the spectral data to be stored on the spectral data memories22includes a spectral reflection factor of each color in each color chart. The following table 1 lists the spectral data stored on the spectral data memories22ofFIG. 2. The table 1 shows that the spectral data includes information of the spectral reflection factor of each of color chart ID.

The color chart spectrum database20receives a color chart selection signal for selecting a color chart. The color chart spectrum database20selects information of a spectral reflection factor stored on the spectral data memories22in response to the color chart selection signal and outputs the selected spectral reflection factor information to a color chart determiner14in the color chart determination section13.

The color chart determination section13includes the color chart determiner14, a color chart DB specifying device18and a determination illumination light specifying device17. The color chart DB specifying device18specifies the type of the color chart for use in the color chart determination. The color chart DB specifying device18generates a color chart selection signal responsive to the type of the color chart and outputs the generated color chart selection signal to the color chart spectrum database20. The color chart DB specifying device18not only generates the color chart selection signal representing the type of the predetermined color chart but also generates a color chart selection signal responsive to a designation of a user.

The determination illumination light specifying device17outputs to the color chart determiner14, for example, a determination illumination light spectrum as information identifying illumination light for use in the color chart determination. The determination illumination light specifying device17may be designed to output a predetermined determination illumination light spectrum or may be designed to output a determination illumination light spectrum responsive to a designation of the user. For example, the determination illumination light specifying device17, including a memory storing the spectral information of at least one light source such as D65 standard light source, outputs the spectral information of the predetermined light source in response to an instruction from the user.

The color chart determiner14includes a determination subject spectrum memory15and a pseudo spectrum calculator16forming spectrum calculation means. The determination subject spectrum memory15stores a subject spectrum from the color detection section8. The pseudo spectrum calculator16successively receives the spectral reflection factors of the color chart IDs from the color chart spectrum database20and obtains a spectrum (hereinafter referred to as a color chart spectrum) from a product of the spectral reflection factor of each color chart ID and the determination illumination light spectrum.

The pseudo spectrum calculator16reads the determination subject spectrum stored on the determination subject spectrum memory15, and determines a color chart spectrum closest matching the subject spectrum from among the color chart spectra of the determined color chart IDs. For example, the pseudo spectrum calculator16determines the color chart spectrum in accordance with the following equation (1).
φ(n)=|S(λ)−CN(n,λ)×JL(λ)|2(1)
where λ represents wavelength, n represents the color chart ID, S(λ) represents the subject spectrum, CN(n,λ) represents the color chart spectrum of the color chart IDn, and JL(λ) represents the determination illumination light spectra.

The pseudo spectrum calculator16determines the color chart spectrum minimizing φ(n) in equation (1), and outputs the color chart ID identifying the color chart spectrum.

The color chart ID is supplied from the color chart determiner14to a color chart ID display19. The color chart ID display19displays the input color chart ID on an unshown screen. The pseudo spectrum calculator16and the color chart ID display19form determination information output means.

Operation of the present embodiment thus constructed is described below.

A photographing area of the color detection section8is set to a predetermined location within the subject1that is undergoing the color chart ID determination. The illumination device10directs illumination light to the subject1and the color detection section8acquires the spectrum of the photographing area. The spectrum of the subject1is thus measured under the illumination light of the illumination device10. The measured determination subject spectrum is supplied to the determination subject spectrum memory15in the color chart determiner14.

In the color chart determination section13, the color chart DB specifying device18specifies the type of color chart to be determined. The color chart selection signal from the color chart DB specifying device18is supplied to the color chart spectrum database20. On a per color chart ID basis, the color chart spectrum database20reads the spectral data (spectral reflection factor) stored on the spectral data memories22and selected in response to the color chart selection signal and outputs the spectral data to the color chart determiner14.

Under the determination illumination light, the color chart determiner14determines the color chart spectrum based on the product of the spectral reflection factor and the determination illumination light spectrum, and then determines a color chart spectrum closest matching the subject spectrum by comparing the subject spectrum with the determined color chart spectrum. The color chart determiner14outputs the color chart ID of the determined color chart spectrum as a color chart ID of a color closest matching the color of the subject1.

The color chart ID is thus provided to the color chart ID display19. The color chart ID display19displays the input color chart ID on the unshown display screen.

The apparatus thus determines which color of the specified color chart closest matches the color of the subject under desired determination illumination light. The user then can verify on the display screen the determination results.

In accordance with the present embodiment, the user can obtain quickly and easily the color chart ID of the color closest matching the color of the subject. In this case, the color chart ID is easily obtained without the need for learning the correspondence between the color classification unique to the system and the color classification of the color chart. In a manner free from the photographing illumination light, the color chart ID is obtained under a desired determination illumination light source.

A color chart ID specifying device can easily update the type of the color chart for use in determination, thereby allowing the color chart determination to be used in a variety of applications.

The color chart ID display19not only displays the color chart ID but also displays the type of the color chart used in the color chart determination. The color chart determination may be performed using a plurality of types of the color charts on the same subject so that the determination results of the color chart IDs may be provided on a per color chart basis.

The information of the obtained color chart ID may be instantaneously transmitted to apparatuses at remote places or owned by a large number of members via an unshown network.FIG. 3is a block diagram of such a system.

The color chart ID is supplied from the color chart determiner14in the color chart determination section13to a color chart ID transmitter25. In response to the type of the input color chart, or in response to an operation of a user, the color chart ID transmitter25transmits the color chart ID to apparatuses of different operators on a per color chart ID basis.

A plurality of color chart IDs determined by the color chart determiner14can thus be used for a plurality of different applications. For example, the color chart DB specifying device18specifies an interior color chart and a DIC color chart for a color a building designer may wish to use, and the color chart determination is then performed. In this case, the color chart IDs are obtained from the interior color chart and the DIC color chart from the color chart determiner14. As shown inFIG. 3, the color chart ID transmitter25transmits the color chart ID of the interior color chart to a builder. The builder can then faithfully reproduce a color in accordance with the color specified by the building designer using the interior color chart. The color chart ID transmitter25transmits the color chart ID of the DIC color chart to a printer. For example, the printer prints catalogs in which the color specified by the building designer is faithfully reproduced using the DIC color chart. Since a plurality of color chart IDs are concurrently output in accordance with the present embodiment, the results are used in a plurality of applications.

FIG. 4is a block diagram illustrating a color chart processing apparatus of a third embodiment of the present invention. As shown inFIG. 4, elements identical to those ofFIG. 2are designated with the same reference numerals, and the description thereof is omitted herein.

The present embodiment is a specific configuration example of the color chart processing apparatus, and calculates the color chart ID using not only information regarding the determination illumination light but also information regarding the photographing illumination light. The third embodiment of the present invention is different from the second embodiment ofFIG. 2in that a color chart determination section30is employed instead of the color chart determination section13, and that the color chart determination section30receives from the color detection section8not only the subject spectrum but also a photographing illumination spectrum as the information of the photographing illumination light.

In the second embodiment, the subject is photographed under the photographing illumination light and the color chart determination is performed under illumination condition in which the color of the color chart is illuminated by a predetermined light source such as the D65standard light source. In contrast, in the third embodiment, effective color chart determination is performed under any illumination light illuminating the subject and the color chart.

The color chart determination section30includes a illumination sensor35and an illumination spectral data memory34for measuring an external spectrum. Since the illumination spectral data memory34stores spectra of a variety of illumination light sources. For example, the illumination spectral data memory34stores spectral data of artificial light sources including an xenon lamp, and a fluorescent lamp, a halogen lamp, and natural light sources including sunlight during day time, sunlight during evening time, sunlight during cloudy day, blue sky, etc.

During color chart determination, a determination illumination light specifying device33selects not only color chart illumination light corresponding to the determination illumination light of the second embodiment, but also illumination light assumed to be illumination light of the subject during the color chart determination (hereinafter referred to as subject rendering illumination light). The determination illumination light specifying device33selects as the subject rendering illumination light one of the illumination light of the illumination device10used in the actual photographing of the subject1, ambient light, and predetermined illumination prestored on the illumination spectral data memory34.

The determination illumination light specifying device33provides a spectrum estimating calculator32in a color chart determiner31with a subject rendering illumination light spectrum of the subject rendering illumination light, and provides the pseudo spectrum calculator16with a color chart illumination spectrum as a spectrum of the color chart illumination light.

The spectrum estimating calculator32calculates a spectrum of a subject to be determined (corresponding to the determination subject spectrum in the second embodiment) from the input photographing illumination spectrum, the input photographing rendering illumination light spectrum, and the input subject spectrum, and outputs the calculated spectrum of the subject to the determination subject spectrum memory15.

The operation of the present embodiment thus configured is described below.

As in the second embodiment, the color detection section8sets up a photographing area in a predetermined location in the subject1that is undergoing the color chart determination, and acquires a spectrum of that area. The color detection section8also acquires a photographing illumination spectrum as a spectrum of the illumination light of the illumination device10using a standard white board or the like. The color detection section8transmits to the color chart determination section30the acquired spectrum as a spectrum of the subject together with the acquired photographing illumination spectrum.

In the color chart determination section30, an illumination sensor35acquires a spectrum of external light (external light spectrum) and supplies the external light spectrum to the determination illumination light specifying device33. The determination illumination light specifying device33reads a predetermined illumination light spectrum stored on the illumination spectral data memory34. If the color detection section8and the color chart determination section30are arranged in a close range, the illumination sensor35may acquire the spectrum of the photographing illumination light (photographing illumination spectrum).

In the present embodiment, the color detection section8transmits the spectrum of the photographing illumination light used for photographing. During the color chart determination, the photographing illumination spectrum is equalized with the color chart illumination spectrum so the color chart determination is performed using the same determination illumination as the photographing illumination. In accordance with the present embodiment, color chart determination is possible using illumination different from the actual photographing illumination. Any determination illumination light spectrum (color chart illumination spectrum) can be used in the color chart determination. When any color chart illumination is used during the color chart determination, determination illumination identical to the photographing illumination can be used.

The spectrum estimating calculator32receives the photographing illumination spectrum, the subject spectrum, and the subject rendering illumination light selected by the determination illumination light specifying device33. The spectrum estimating calculator32calculates a subject determination spectrum S(λ) under the subject rendering illumination light in accordance with the following equation (2).
S(λ)={S′(λ)/L(λ)}×RL(λ)  (2)
where S′(λ): subject spectrum under the illumination light of the illumination device10,

L(λ): photographing illumination spectrum as the spectrum of the illumination light of the illumination device10, and

RL(λ): subject rendering illumination spectrum

Equation (2) is used to determine (reproduce) the subject spectrum when the subject1is photographed under the subject rendering illumination light. The subject spectrum S(λ) determined by the spectrum estimating calculator32is supplied to the determination subject spectrum memory15for storage.

Meanwhile, the determination illumination light specifying device33provides the pseudo spectrum calculator16with the color chart illumination spectrum JL(λ). In the same manner as in the second embodiment, the color chart determiner31determines the color chart ID that closest matches the color chart spectrum of any color in the specified color chart, in accordance with equation (1).

If the subject rendering illumination spectrum is equalized with the color chart illumination spectrum, the color chart determination is performed with the photographing illumination equalized with the determination illumination. Further, if the photographing illumination spectrum, the subject rendering illumination spectrum, and the color chart illumination spectrum are mutually equalized, the color chart determination can be performed with the actual photographing illumination equalized with the determination illumination.

In accordance with the present embodiment, any (separate) illumination light rays can be selected as illumination light illuminating the subject and the color chart. The color chart determination can be performed using not only the illumination light actually used to photograph the subject, but also using external light photographed with the illumination sensor, and stored illumination light of a light source used in a simulated photographing.

Thus, regardless of whether the color detector and the color chart determiner are remotely placed from each other or under the different illumination conditions, color chart determination can be performed at the same accuracy level as when the same light source is used for the subject and the color chart. Since the color chart illumination light illuminating the color chart is freely selected, color chart determination with illumination not identical in type to the illumination light of the subject can be performed. The light source in this case may be the one at the same location where the color chart determiner is placed, and the light source may be a predetermined light source. For example, even if the subject is in a variety of environments, the color chart determination can be performed under the constant illumination.

And now, in the color chart processing apparatus of each of the preceding embodiments, the color detector, the color chart determiner, the color chart spectrum database, and the color chart ID display can be in various configuration.

For example, as shown inFIG. 5, the color detector, the color chart determiner, the color chart spectrum database, and the color chart ID display are incorporated into a handy terminal, such as a PDA.

As shown inFIG. 5, the color detector is composed of a fiber41and an unshown diffraction grating. The diffraction grating is housed in a PDA42. A PDA monitor screen43serves as a color chart ID display. A card-type memory44is used as a memory in the color chart spectrum database. Since spectral data of the colors of the color chart is large, each card may store data of a particular color chart. The color chart spectral data may be compressed before storage.

FIG. 6illustrates a color chart spectrum database remotely located from a color chart determiner.

As shown inFIG. 6, a color chart spectrum database54is installed in a remote data center53. The color chart spectrum database54includes a transceiver55, a database server56, and a color chart spectrum storage device57. The color chart spectrum storage device57corresponds to the color chart spectrum storage in each of the preceding embodiments. The database server56transmits to a PDA51via the transceiver55the color chart spectral data of each color in the color chart stored on the color chart spectrum storage device57.

On the other hand, the PDA51stores an unshown color determiner. The PDA51also includes an unshown transceiver for receiving the color chart spectral data from the color chart spectrum database54, and performs the color chart determination with the color chart determiner using the color chart spectral data received via an antenna52.

Further,FIG. 7illustrates a data center which includes a color chart determining device calculating equations (1) and (2) other than a terminal including a color detector and a color chart determiner. As shown inFIG. 7, a terminal61includes the optical system11and the spectral sensor12out of the elements of the color detection section8ofFIG. 4. The terminal61photographs a subject, thereby obtaining a subject spectrum and a photographing illumination spectrum thereof. The terminal61includes the color chart DB specifying device18, the illumination sensor35, and the determination illumination light specifying device33out of the elements of the color chart determination section30ofFIG. 4. The terminal61further includes the color chart ID display19. Note that the determination illumination light specifying device33ofFIG. 7outputs information specifying an illumination spectrum (determination illumination light specifying information) rather than directly outputting an illumination spectrum for use in the color chart determination.

As described above, a portion corresponding to the color chart determiner31and a portion corresponding to the illumination spectral data memory34out of the elements of the color chart determination section30are arranged in a data center65. The data center65includes the illumination spectral data memory34and the color chart spectrum database20. Further, the data center65further includes a database server67and a calculation server68, having a function corresponding to the function of the color chart determiner31. The terminal61and the data center65exchange data with each other via a communication I/F62for the terminal61and a communication I/F66for the data center65.

In the color chart processing apparatus thus constructed, the subject spectrum of the subject1obtained by the terminal61, the photographing illumination spectrum, and information specifying the determination illumination light are transmitted to the data center65via the communication I/F62. The data center65receives a variety of information from the terminal61via the communication I/F66, and outputs the received information to the database server67and the calculation server68. The database server67and the calculation server68read from the illumination spectral data memory34the determination illumination light spectrum in response to the determination illumination light specifying information, and the color chart spectral data of each color in the color chart specified by the color chart selection signal from the terminal61, and then perform the calculation of equation (2). In this way, the database server67and the calculation server68determine the color chart ID as the color chart determination of the subject1.

The color chart ID determined by the database server67and the calculation server68is transmitted to the terminal61via the communication I/F66and the communication I/F62, and then displayed on the color chart ID display19.

Thus, the color chart spectral data and the illumination spectral data, each having a large data size, are prepared in the data center so that the color chart determination of the color chart ID can be performed within the data center. Thus, even if the terminal61has a relatively small memory size and a relatively low computation ability, the color chart ID is easily acquired. Updated data is constantly used, and data maintenance is easily performed.

The communication I/F62and the communication I/F66are connected via a cable. Alternatively, the communication I/F62and the communication I/F66can be radio linked to each other.

FIG. 8is a block diagram illustrating a color chart processing apparatus in accordance with the fourth embodiment of the present invention. As shown inFIG. 8, elements identical to those ofFIG. 4are designated with the same reference numerals and the description thereof is omitted herein.

In each of the preceding embodiments, the color detector obtains the subject signal by photographing a predetermined spot of the subject. In contrast, the present embodiment uses an electronic camera as a color detector, and obtains the subject signal from the image of the photographed subject.

As shown inFIG. 8, a color detection section71includes a multi-spectral camera72capable of capturing an image. The multispectral camera72captures spectral images in a frame sequential method using a band-pass filter disclosed in the previously mentioned Document 1. The number of bands of the spectral image is not limited to any particular one, and the number of bands is eight, for example. The multi-spectral camera72photographs the subject1, thereby outputting the subject image to a color chart determination section75. The color detection section71outputs a subject image per band, namely, a spectrum of the subject image (subject spectrum). The subject spectrum from the color detection section71is obtained on a per pixel basis of the subject image.

An illumination device74illuminates the subject1. An illumination sensor73detects the spectrum of the illumination light directed to the subject1, and outputs the spectrum as a photographing illumination spectrum.

The color detection section71is different from the color chart determination section30ofFIG. 4in that a determination image generator76is additionally attached. The determination image generator76is provided with the determination result of the color chart ID on a per pixel basis or on a per predetermined area basis of the captured image. The determination image generator76produces an image that maps the captured image to the color chart ID at each pixel or each predetermined area, and outputs the resulting image to the color chart ID display19. The color chart ID display19displays the image that maps the captured image to the color chart ID at each pixel or each predetermined area.

Next, the operation of the embodiment thus constructed is described with reference toFIGS. 9A and 9B.FIG. 9Aillustrates the subject image captured by the multi-spectral camera72andFIG. 9Billustrates a display example on a display screen of the color chart ID display19.

The multi-spectral camera72obtains a two-dimensional spectral image of eight bands.FIG. 9Aillustrates the subject image captured by the multi-spectral camera72. The subject image ofFIG. 9Ashows three upper teeth80through82.

At the same timing as the multi-spectral camera72photographs, the illumination sensor73detects the photographing illumination spectrum of the illumination light directed to the subject1. The image signal of the subject image obtained by the multi-spectral camera72and the photographing illumination spectrum are supplied to the color chart determination section75.

The color chart determination section75outputs the color chart ID on a per pixel basis of the subject image in accordance with equation (2). The calculation method of the color chart ID remains unchanged from that of each of the preceding embodiments. In this case, if the calculation process of the color chart ID is performed on the pixels on the whole area of the subject image, an extremely long period of process time is required. So, the color chart determiner31calculates the color chart ID of each pixel only in a color measurement area in the subject image. For example, if the color chart determination needs to be performed on a central tooth82out of the three teeth shown inFIG. 9A, a color measurement area83(seeFIG. 9B) containing the central tooth82is set up.

The color chart determiner31performs the color chart determination on each pixel of the color measurement area83of the subject currently being photographed. The color chart determiner31outputs the determined color chart ID to the determination image generator76. Based on the information of the input color chart ID on each pixel, the determination image generator76produces a determination image for displaying a distribution of the color chart ID. The determination image generator76supplies the produced determination image to the color chart ID display19, thereby displaying the image on the display screen thereof.

FIG. 9Billustrates one example of the determination image displayed on the display screen85. As shown inFIGS. 9A and 9B, a color is set for each color chart ID determined on a per pixel basis, and the color of each pixel in the subject image matches the color chart ID.FIG. 9Billustrates that color becomes different as shown in hatched portion, for example. An area of the same color chart ID is shown in the same color, and pixels of different color chart IDs are displayed by different colors. As shown inFIG. 9B, a crown color chart (shade guide) is used as a color chart. The pixels in the color measurement area have A3, A3.5, and A4 as values of the crown color chart. More specifically, of the tooth82measured, the crown color chart near the gum has A4, the crown color chart of a center portion of the tooth has A3.5, and the crown color chart of the end portion of the tooth has A3. The color distribution of the determination image is thus displayed.

Note that, the correspondence between the color of the determination image and the color chart ID is shown in a portion86of the display screen85.FIG. 9Billustrates the color chart ID in the determination image.

In accordance with the present embodiment, the color chart determination of the color chart ID of a plurality of regions is performed using the multi-spectral camera. In the present embodiment, the multi-spectral camera of eight bands is used. The present invention is not limited to eight band camera. More number of bands may be used. Depending on an object, three bands of RGB provide sufficient accuracy.

The illumination light spectrum for photographing is detected by the illumination sensor. Alternatively, the spectrum is pre-measured and stored as data on a memory or the like. Alternatively, as disclosed in Document 2 (Japanese Unexamined Patent Application Publication No. 11-096333), a special chart for detecting the illumination spectrum may be used.

Incidentally, an illumination-type multi-spectral camera may be used as disclosed in Japanese Patent Application No. 2002-218863 filed by the applicant of this patent application.

FIG. 10illustrates a configuration employing such an illumination-type multi-spectral camera.FIG. 11is a flowchart of a program process of a personal computer99ofFIG. 10.

As shown inFIG. 10, an illumination-type multi-spectral camera90is employed as the color detection section71. The functions of the color chart determination section75and the color chart spectrum database20ofFIG. 8are performed by the personal computer99. The function of the color chart ID display19ofFIG. 8is performed by a display100in the personal computer99.

The illumination-type multi-spectral camera90includes a body96and a handle97. The handle97is provided with a photograph button95. The body96includes at the front end portion thereof a focusing lens system92for focusing a light ray from the subject1into an image. A light receiving surface of a CCD93is arranged at a focusing position of the focusing lens system92. A multi-colored LED illumination device91for illuminating the subject1is arranged on the front side of the body96. A blocking member89for blocking external light from entering into the subject1is provided on the front end portion of the body96. The body96houses an illumination spectral data memory94. The illumination spectral data memory94stores illumination spectral data of the illumination light of the multi-colored LED illumination device91.

When photographing starts in response to an operation of the photograph button95, the multi-colored LED illumination device91directs LED illumination having a plurality of spectral characteristics to the subject1. A light beam reflected from the subject1is focused into an image on the CCD93via the focusing lens system92. The image is then converted into an image signal of the image of the subject. Meanwhile, the illumination spectral data based on the illumination light of the multi-colored LED illumination device91is read from the memory94. In this way, the illumination-type multi-spectral camera90provides the same output as the one provided by the color detection section71ofFIG. 8. The subject image and the illumination spectral data from the illumination-type multi-spectral camera90are transferred to the personal computer99via a cable98.

The personal computer99performs the functions of the color chart spectrum database20, the color chart determination section75and the color chart ID display19ofFIG. 8. More specifically, using unshown CPU and memory, the personal computer99calculates equation (2) on the supplied photographing illumination spectrum, subject spectrum, and subject rendering illumination spectrum, thereby calculating the subject determination spectrum S (λ) under the subject rendering illumination light (step S1inFIG. 11).

The personal computer99then reads the color chart spectral data (spectral reflection factor) stored on a recording medium such as an unshown hard disk (step S2), and calculates the subject spectrum with the supplied color chart illumination spectrum (step S3). The personal computer99compares the subject spectrum with the determination subject spectrum, thereby determining the color chart ID providing a color chart spectrum closest matching the color chart spectrum of any color in the specified color chart (step S4).

Thus, based on the subject image and the illumination spectral data input via the cable98, the personal computer99displays on the display100a determination image representing the color chart ID on a per pixel basis for the color measurement area of the subject image (step S5).

The present embodiment is thus configured using the illumination-type multi-spectral camera.

FIG. 12is a block diagram illustrating an application of the color chart processing apparatus. As shown in FIG.12, elements identical to those ofFIG. 1are designated with the same reference numerals, and the description thereof is omitted herein.

In a configuration ofFIG. 12, the color chart processing apparatus of the first embodiment is included. A color specified by the color chart ID is obtained by mixing a plurality of colors. No apparatuses that determine a mixing amount for producing a color of a predetermined color chart ID have been conventionally available.FIG. 12illustrates the configuration in which a determined color chart ID is used. The configuration applies to determine the mixing amount of a material for obtaining a color indicated in the color chart determination result of the color chart ID.

For example, in the dentistry field, an artificial tooth is produced based on the determined crown color chart (shade guide). In this case, a plurality of porcelains need to be mixed in the production of an artificial tooth. As shown inFIG. 12, the mixing amount of a porcelain is determined during the production of the artificial tooth.

A mixing ratio database111stores information of the mixing ratio on a per color chart ID basis to produce an intended color. For example, on a per color chart ID basis of the crown color chart, the mixing ratio database111stores information regarding a porcelain required to manufacture an artificial tooth. The information regarding the mixing ratio stored on the mixing ratio database111is supplied to a mixing ratio acquisition device112as mixing ratio data. The mixing ratio acquisition device112reads the mixing ratio data from the mixing ratio database111using the color chart ID supplied from the color chart determiner3, and outputs the mixing amount of each porcelain for obtaining the intended color.

In the present embodiment thus constructed, the color chart ID indicating which color of the specified color chart corresponds to the color of the subject is obtained from the color chart determiner3. The mixing ratio acquisition device112reads the mixing ratio data from the mixing ratio database111, and outputs the mixing ratio data as the mixing amount of each porcelain to obtain the resulting determination color.

Thus, in the example ofFIG. 12, the mixing amount of the porcelains for obtaining the same color as the resulting determination color for the object to be determined is automatically determined. In the example ofFIG. 12, the mixing amount of the porcelains is determined during the production of the artificial tooth. This embodiment is obviously applicable to any application where a plurality of materials are mixed to produce an desired color. For example, this embodiment is applicable to paint mixing operation.

FIG. 13illustrates a system in which the color chart processing apparatus ofFIG. 12is constructed using the illumination-type multi-spectral camera ofFIG. 10. As shown inFIG. 13, elements identical to those described with reference toFIG. 10are designated with the same reference numerals and the description thereof is omitted herein.

As shown inFIG. 13, the functions of the color detector2and the color chart determiner3ofFIG. 12are performed by a multi-spectral camera115, and the remaining functions are performed by the elements in a data center120. The multi-spectral camera115is different from the illumination-type multi-spectral camera90ofFIG. 10in that a color chart determination circuit116, a display117, and a transceiver circuit118are additionally included.

The data center120includes the color chart spectrum database4ofFIG. 13, a mixing ratio database111, and a database server121corresponding to the mixing ratio acquisition device112ofFIG. 12.

Note that, if the multi-spectral camera115can afford to house a memory of sufficient memory size and a calculation circuit, it is apparent that the structure of the data center120may be fully integrated into the multi-spectral camera115.

With such an arrangement, the database server121reads color chart spectral data stored on the color chart spectrum database4, and transfers the color chart spectral data to the multi-spectral camera115via a transceiver55. A transceiver circuit118of the multi-spectral camera115receives the color chart spectral data transmitted from the data center120, and outputs the received color chart spectral data to the color chart determination circuit116.

The color chart determination circuit116corresponds to the color chart determiner3ofFIG. 12, and calculates the color chart ID corresponding to the color of the subject1using the subject spectrum obtained by photographing the subject1, the photographing illumination spectrum from the memory94and the color chart spectral data from the data center120. The color chart ID determined by the color chart determination circuit116is transmitted to the data center120via the transceiver circuit118.

The database server121in the data center120determines the mixing amount for producing the color indicated by the color chart ID, based on the color chart ID from the multi-spectral camera115, and the mixing ratio data stored on the mixing ratio database111. The database server121transmits to the multi-spectral camera115the information regarding the determined mixing amount together with the information of the color chart ID.

The multi-spectral camera115transfers to the display117the color chart ID and the information of the mixing amount received by the transceiver circuit118to display these pieces of information on the screen of the display117.

Thus, in the example ofFIG. 13, the information of the mixing amount determined based on the information from the mixing ratio database111in a remote place is transmitted to the multi-spectral camera115via the radio link so that the information of the mixing amount is displayed together with the color chart ID.

FIG. 14is a block diagram illustrating a color chart processing apparatus in accordance with a fifth embodiment of the present invention. As shown inFIG. 14, elements identical to those ofFIG. 1are designated with the same reference numerals and the description thereof is omitted herein.

The present embodiment converts, for example, the color chart ID obtained by the color chart processing apparatus ofFIG. 1into a color chart ID of another color chart. For example, in the printing field, a color chart unique to printing applications (DIC color chart) is typically used different from a color chart of another field. The present embodiment is applicable to such an application.

A color chart determiner131receives determination illumination light information, and information regarding a color chart type and a color chart ID. The color chart determiner131determines a subject spectrum from these pieces of information. The color chart determiner131also receives conversion color chart type information, and reads from the color chart spectrum database4color chart spectral data of a color chart based on the conversion color chart type information. The color chart determiner131calculates the color chart ID of the color chart specified by the conversion color chart type information by calculating equation (1) based on the calculated subject spectrum, the read color chart spectral data, and conversion color chart illumination information for use in determination of a new color chart. The color chart determiner131then outputs the calculated color chart ID.

In the embodiment thus constructed, the color chart determiner131receives the color chart determination result that has used predetermined determination light for the color of a predetermined subject. The color chart determiner131determines an original subject spectrum from the input color chart ID. The color chart determiner131calculates equation (1) on the resulting determination subject spectrum, and outputs the color chart ID in which the color chart specified by the conversion color chart type information is used.

Thus, in accordance with the present embodiment, the color chart ID of a predetermined color chart can be converted into a color chart ID of another color chart.

FIG. 15is a block diagram of a color chart processing apparatus in accordance with a sixth embodiment of the present invention. As shown inFIG. 15, elements identical to those ofFIG. 4are designated with the same reference numerals and the description thereof is omitted herein.

In the present embodiment, the fifth embodiment is applied to the third embodiment. As shown inFIG. 15, the interior color chart is converted into the DIC color chart. Any color chart can be converted as long as the color chart is stored on a spectrum database.

The present embodiment is different from the third embodiment in that a color chart converter132is added to the structure ofFIG. 4. The function of an interior color chart spectrum database133or a DIC color chart spectrum database134are limited to only the function of outputting spectral data relating the interior color chart or spectral data relating to the DIC color chart from the color chart spectrum database20ofFIG. 4.

The color chart converter132receives a color chart ID from the color chart determiner31while also receiving information of the color chart illumination spectrum for use in the color chart determination of the color chart determiner31. The color chart converter132also receives information, regarding the DIC color chart, as the conversion color chart type information.

The color chart converter132calculates the following equation (3) based on the received color chart ID and color chart illumination spectrum, and the conversion color chart illumination spectrum and the spectral data of the DIC color chart. Here, n minimizing φ(n) in equation (3) is determined as a color chart ID of the DIC color chart. The color chart converter132outputs the determined color chart ID as a conversion color chart ID.
φ(n)=|CN1(N1,λ)×jL1(λ)−CN2(n,λ)×jL2(λ)|2(3)
where λ: wavelength

n: color chart ID

CN1(Nλ): color chart spectral data with interior color chart ID being N1

N1: interior color chart ID

CN2(n,λ): color chart spectral data with the DIC color chart ID being n

jL1(λ): determination illumination light spectrum of the interior color chart (color chart illumination spectrum)

jL2(λ): determination illumination light spectrum of D5C color chart (color chart illumination spectrum)

The conversion color chart ID and the color chart ID from the color chart determiner31are supplied to the color chart ID display19ofFIG. 4. The color chart ID is thus displayed for the color of the subject1when each of the interior color chart and the DIC color chart is used.

In accordance with the present embodiment, one determined color chart ID can be converted into the color chart ID of a completely different color chart. In this case, the color chart ID is converted based on the calculation of the spectral information of the color chart ID. The determination illumination light for acquiring the converted color chart ID is not necessarily the same as the determination illumination light used in the color chart determination prior to the conversion, and any determination illumination light can be set.

FIG. 16is a block diagram illustrating an application example of the color chart processing apparatus. As shown inFIG. 16, elements identical to those ofFIG. 4are designated with the same reference numerals and the description thereof is omitted herein.

As shown inFIG. 16, the color chart processing apparatus of the third embodiment is incorporated. Many color charts are present, and many colors are contained in each color chart. So, it is thus difficult to recognize quickly the color of a particular color chart ID in a desired color chart. Conventionally, no apparatuses that can easily recognize the color of any color chart ID have been available. The color chart processing apparatus ofFIG. 16enables the color of a specified color chart ID to be displayed under illumination light of on the location of operation or under any illumination light.

A display processor141includes a color chart ID specifying device142and a display color calculation section143instead of the color chart DB specifying device18and the color chart determiner31in the color chart determination section30ofFIG. 4. The display color calculation section143includes an observation spectrum calculator144and a chroma calculator145. The observation spectrum calculator144receives the determination illumination light spectrum from the determination illumination light specifying device33.

In response to a user operation, the color chart ID specifying device142specifies the color chart spectral data read from the color chart spectrum database20. The color chart ID specifying device142outputs a selection signal specifying a color chart and a color chart ID. The color chart spectrum database20outputs the color chart spectral data responsive to the input selection signal to the observation spectrum calculator144in the display color calculation section143.

The observation spectrum calculator144determines a spectrum of the color of the color chart ID specified by the color chart ID specifying device142under the determination illumination light, by multiplying the determination illumination light spectrum by the color chart spectral data. The observation spectrum calculator144outputs the determined spectrum to the chroma calculator145. The chroma calculator145converts the input spectrum into chroma information (XYZ, xy, L*a*b*, etc.) and outputs the chroma information to a color chart display146as chroma data.

FIG. 17is a block diagram specifically illustrating the configuration of the color chart display146ofFIG. 16.

As shown inFIG. 17, six LEDs displaying six primary colors are used for the color chart display146. As shown inFIG. 17, the color chart display146includes a multi-color converter147, LED150-1through LED150-6a projection optical system151, and a display152.

The multi-color converter147includes an LED characteristics data memory148, and a six-primary-color converter149. The chroma data from the chroma calculator145is input to the six-primary-color converter149. The LEDs150-1through150-6are different from each other in spectral characteristics, and emit different primary color light rays. The LED characteristics data memory148stores characteristics of LEDs150-1through150-6. The six-primary-color converter149converts the chroma data into signals (primary color signals) representing six primary colors in accordance with a conversion method disclosed in detail in Document 3 (Japanese Unexamined Patent Application Publication No. 2000-253264) and Document 4 (Japanese Unexamined Patent Application Publication No. 2000-338950). The six primary colors may be red, blue, green, cyan, yellow and magenta, for example,.

The six primary color signals from the six-primary-color converter149are supplied to the LEDS150-1through150-6emitting color light rays responsive to the six primary color signals. In response to the primary color signals, the LEDs150-1through150-6emit respective light rays. The light rays emitted from the LEDs150-1through150-6are projected to the display152through the projection optical system151.

FIG. 18is a sectional view illustrating a specific configuration of the display152. As shown inFIG. 18, the display152includes a lenticular lens153and a diffusion plate154. The primary color light rays from the LEDs150-1through150-6entering from the lenticular lens153become substantially parallel light rays and are then output from the diffusion plate154. By synthesizing the six primary color light rays on the display152, a uniform multi-color display is presented on the entire display screen of the display152. The display152may uses a screen (display screen) of the same size as the color chart.

As shown inFIG. 17, the display152is a rear-projection type, and subject to a directivity of the screen. For this reason, the display152includes the lenticular lens153and the diffusion plate154to correct directivity.

With this arrangement, a user specifies a color chart ID of the color to be checked on the color chart ID specifying device142. The selection signal from the color chart ID specifying device142is supplied to the color chart spectrum database20, and the color chart spectrum database20supplies the color chart spectral data (spectral reflection factor) of the specified color chart ID to the observation spectrum calculator144. For example, in response to the user operation, the determination illumination light specifying device33selects one of an external light spectrum of external light detected by the illumination sensor35and a spectrum stored on the illumination spectral data memory34, and supplies the selected spectrum to the observation spectrum calculator144as the determination illumination light spectrum. The observation spectrum calculator144determines the spectrum of the color of the specified color chart ID by multiplying the color chart spectral data and the determination illumination light spectrum, and then outputs the determined spectrum to the chroma calculator145.

The chroma calculator145converts the input spectrum into chroma information. The chroma calculator145outputs the determined chroma data to the color chart display146. The multi-color converter147in the color chart display146converts the chroma data into the six primary color signals. The six primary color signals are respectively supplied to the LEDs150-1through150-6. In response, the six primary color light rays are output, and then displayed on the display152via the projection optical system151.

The chroma data is converted into the six primary color signals. The output light rays from LEDs150-1through150-6for outputting the six primary color light rays are synthesized into a display color. A color range displayable is wide enough, and an accurate color reproduction based on the color chart ID is performed on the multi-color display screen.

As shown inFIG. 16, the color of the color chart is faithfully represented under the illumination of the external light. Since the color of the color chart ID responsive to the illumination spectrum of the external light is reproduced using the illumination sensor, the color chart is displayed on the screen as if the color chart is actually present there. Not only the spectral data from the illumination sensor but also the spectral data stored on the illumination spectral data memory is used as the determination illumination light spectrum. In such a case, the color of the color chart under any illumination light can be displayed.

By setting the screen of the color chart ID display displaying multi colors to be approximately identical in size to the actual color chart, more accurate determination is possible. A hologram screen or the like, may be used instead of the lenticular lens. The diffuse plate may be reinforced against external light by tinting the diffuse plate or by mirror finishing the surface of the diffuse plate. The display may be constructed of a device such as a self-emitting FED or an organic EL. Alternatively, the display may be constructed of an LCD, or a multi-color primary display such as the ones disclosed in Document 5 (Japanese Unexamined Patent Application Publication No. 2000-25326) and Document 4 (Japanese Unexamined Patent Application Publication No. 2000-338950).

By combining the fourth embodiment ofFIG. 8with the application example ofFIG. 16, the color of the determined color chart ID is displayed in response to the display of the image of the subject.

More specifically, an element similar to the display color calculation section143ofFIG. 16may be incorporated instead of the determination image generator76ofFIG. 8. The chroma data responsive to the color chart ID determined on a per pixel basis of the subject image is thus obtained. In such a case, a display161ofFIG. 19is used. As shown inFIG. 19, the display161displays the same image as shownFIG. 9B. In a way similar toFIGS. 9A and 9B, difference in color is represented in difference in hatching inFIG. 19.

The display161ofFIG. 19includes an image display area162for displaying the subject image in multi primary colors, and a color chart display area163for displaying each color example of the color chart. In a way similar toFIG. 9B, the image display area162displays a color corresponding to the color chart ID with the subject image overlapping thereon. In this case, as shown inFIG. 9B, a plurality of colors are used to simply distinguish between a plurality of color chart IDs. As shown inFIG. 19, however, displayed is the color that would be expected when the color specified by the color chart ID is seen under the determination illumination light or any illumination, as in the color chart display146ofFIG. 17.

Furthermore, the multi-spectral camera ofFIG. 10orFIG. 13may be used as a color chart display for displaying the color specified by the color chart ID.FIGS. 20 and 21illustrate such a case. Referring toFIGS. 20 and 21, elements identical to those ofFIG. 10are designated with the same reference numerals and the description thereof is omitted herein.

A multi-spectral camera171ofFIG. 20includes a lens system92for focusing light from the subject1, a CCD93for converting an optical image of the subject into an electrical signal, and a multi-color LED illumination device91for illuminating the subject. The multi-spectral camera171also includes an illumination sensor172for measuring an external light spectrum, and a viewfinder173as a display to be used to recognize a designation of the color chart ID. The multi-spectral camera171has on the front end thereof a blocking member89for preventing external light from entering the subject.

In accordance with the present embodiment, a screen174is arranged on the opening at the front end of the blocking member89. The screen174may have the same structure as the display152ofFIG. 18. For example, the screen174is mounted on the front end of the blocking member89with which the subject intended to be measured is to be in contact.

In accordance with such an arrangement, the primary color signal is supplied to the multi-colored LED illumination device91. The primary color light rays of the multi-colored LED illumination device91are synthesized on the screen174. In the same manner as the color chart display146ofFIG. 17, the screen174displays the same color as the one that is seen when the color specified by the color chart ID is seen under the determination illumination light.

FIG. 21illustrates another example of multi-spectral camera displaying a color specified by the color chart ID. Referring toFIG. 21, elements identical to those described with reference toFIG. 20are designated with the same reference numerals and the description thereof is omitted herein. As shown inFIG. 21, a multi-spectral camera175includes the blocking member89that places a screen176at a location spaced apart from the front end of the camera by a predetermined distance. The primary color light rays from the multi-colored LED illumination device91are projected onto the screen176. Standard white paper and the like, may be used for the screen176.

Referring toFIG. 20, the primary color light rays of the multi-colored LED illumination device91are projected from behind the screen174, and are synthesized on the screen174, and a color displayed on the front surface of the screen174is observed. In contrast, referring toFIG. 21, the primary color light rays of the multi-colored LED illumination device91are directed from the front of the screen176and synthesized on the screen176. A color displayed on the front surface of the screen176is observed. As shown inFIG. 21, the primary color light rays are projected onto the screen176from the multi-colored LED illumination device91. The primary color light rays may be projected onto the surface of a painted board or a printing sheet of paper to display the color of the specified color chart ID.