Color calibration system

A color calibration system in accordance with a preferred embodiment of the present invention comprises a display device provided with a color sensor for detecting a color temperature and illuminance of ambient light, a microcomputer, and a colorimeter for performing colorimetry on a display screen of the display device from the outside. The microcomputer calculates a target value by using a preset calculation equation and a detection result on the ambient light detected by the color sensor. Then, the microcomputer automatically performs color calibration of the display device so that a colorimetry result obtained by the colorimeter may agree with the target value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color calibration system for a display device.

2. Description of the Background Art

In order for color matching in a visual environment, conventionally, color calibration for a display device has been performed by using a colorimeter. In a background-art color calibration system, a user performs an adjustment operation using a preset white point (luminance, chromaticity) or a user-desired white point as a target value. In the color calibration system, it is necessary for the user to adjust in advance various conditions which cannot be managed by a display itself, such as a color temperature and illuminance of lighting and color of paper in the visual environment.

Illumination light and a display of the display device are different from each other in shape of spectral distribution of observed light. Therefore, even if use of a dedicated colorimeter causes respective colorimetry values in tristimulus values of the CIE XYZ color space and the like to agree with each other between the illumination light and the display of the display device, actual visuals do not necessarily coincide.

For this reason, the user repeats calibration several times with a target value set by using limited information and tools, to make color matching in the visual environment. In the above-discussed color calibration system, since an optimal adjustment target value in accordance with the environment is uncertain, it is difficult to make accurate color matching. In other words, in the above-discussed color calibration system, it is extremely complicated and difficult to make color matching. A solution for this problem is shown in, for example, Patent Document 1 (Japanese Patent Application Laid Open No. 2006-349835).

In the technique of Patent Document 1, colorimetry of a reference object having reference white, which is irradiated with ambient light, is performed by using a colorimeter. A colorimetry result obtained by the colorimeter is a target value for color calibration.

In the technique of Patent Document 1, depending on white reference objects, in some cases, there is a difference in reflectance and spectral distribution, and generally, the spectral distribution of the white reference object is greatly different in shape from that of a monitor. For this reason, even if color matching is performed by using a colorimetry result obtained by a dedicated colorimeter, accurate color matching can not be necessarily achieved.

Further, in order to continue stable color calibration, it is necessary to always control the reference object. Colorimeters capable of performing colorimetry on an object color are limited, and a cheap contact-type colorimeter cannot perform accurate colorimetry in some cases.

In other words, the technique of Patent Document 1 has a problem of precision of color calibration and that of difficulty in achieving the color calibration.

For stable calibration, it is important that the display state of luminance, tint, and the like of the display device of which the power supply is repeatedly turned on and off irregularly should be stable during the calibration. It is very difficult, however, for the user who is an operator of the color calibration to grasp a stable state of the display device.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a color calibration system capable of performing color calibration precisely and simply.

The present invention is intended for a color calibration system. According to a first aspect of the present invention, the color calibration system includes a display device, a microcomputer, and a colorimeter. The display device is provided with a color sensor for detecting a color temperature and illuminance of ambient light. The colorimeter performs colorimetry on a display screen of the display device from the outside. The microcomputer calculates a target value by using a preset calculation equation and a detection result on the ambient light detected by the color sensor. The microcomputer further automatically performs color calibration of the display device so that a colorimetry result obtained by the colorimeter agrees with the target value.

By the first aspect of the present invention, the color calibration of the display device can be automatically performed in such a manner that the colorimetry result obtained by the colorimeter agrees with the target value. It is therefore possible to perform the color calibration precisely and simply.

According to a second aspect of the present invention, the color calibration system includes a display device, a microcomputer, and a colorimeter. The colorimeter performs colorimetry on a display screen of said display device from the outside. The microcomputer includes a storage unit for storing target values corresponding to a combination of the type of lighting and the type of illuminance therein. The microcomputer displays the type of lighting and the type of illuminance as a selection menu in a selectable manner on a predetermined display unit. The microcomputer reads a predetermined target value out from the storage unit in accordance with a combination of the type of lighting and the type of illuminance which is selected from the selection menu. The microcomputer further automatically performs color calibration so that the predetermined target value which is read out agrees with a colorimetry result obtained by the colorimeter.

By the second aspect of the present invention, the color calibration can be automatically performed in such a manner that the predetermined target value agrees with the colorimetry result obtained by the colorimeter. It is therefore possible to perform the color calibration precisely and simply.

According to a third aspect of the present invention, the color calibration system includes a display device, a microcomputer, and a prism or a reflecting mirror. The display device is provided with a color sensor for detecting a color temperature and illuminance. The prism or the reflecting mirror is attachable to and detachable from the display device. The microcomputer calculates a target value by using a detection result on ambient light detected by the color sensor in a state where the prism or the reflecting mirror is not attached and a first calculation equation which is preset. The color sensor performs colorimetry on a display screen of the display device, which is inputted through the prism or the reflecting mirror in a state where the prism or the reflecting mirror is attached. The microcomputer automatically performs color calibration by using the result of the colorimetry obtained by the color sensor and the target value.

By the third aspect of the present invention, the color calibration can be automatically performed by using the result of colorimetry obtained by the color sensor and the target value. It is therefore possible to perform the color calibration precisely and simply.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be discussed specifically, with reference to figures showing the preferred embodiments.

FIG. 1shows a configuration of a color calibration system100for a display device for the purpose of color matching in accordance with the first preferred embodiment.

As shown inFIG. 1, the color calibration system100comprises a computer11, a display device12, a colorimeter13, and a communication means16. In the first preferred embodiment, a measurement result obtained by an RGB color sensor12cis referred to as a “detection result”. On the other hand, a measurement result obtained by the colorimeter13is referred to as a “colorimetry result”.

Application software11afor performing color calibration and making a color profile is installed in the computer11. The computer11comprises a communication interface11b.

The communication interface11bis connected to the colorimeter13in order to receive a colorimetry result obtained by the colorimeter13. The communication interface11bis further connected to a communication interface12don the side of the display device12in such a manner as to establish two-way communication.

To the computer11, a keyboard15(including a mouse) is connected for operating the computer11.

The display device12comprises an image display unit12a, a microcomputer12b, the RGB color sensor (RGB color filter sensor)12e, and the interface12d. The display device12can perform a white point adjustment through adjustment of emission balance of RGB primary colors to be subjected to color management.

On the image display unit12a, displayed is a display image (including white, color patch, and the like). The image display unit12acan also serve as a display unit of the computer11during the color calibration.

In accordance with the application software11a, the microcomputer12bcalculates a target value by using a preset calculation equation and a detection result obtained by the RGB color sensor12c. The microcomputer12bfurther automatically performs color calibration, in accordance with the application software11a, so that the colorimetry result obtained by the colorimeter13and transferred via the computer11may agree with the above target value.

Under the control of the microcomputer12bwhich operates in accordance with the application software11a, the RGB color sensor12cperforms a measurement. The RGB color sensor12ccan detect a color temperature and illuminance of indeterminate ambient light including lighting. The RGB color sensor12coutputs the measurement result obtained by itself as an RGB value. The RGB color sensor12cis disposed near the image display unit12ain the display device12.

The communication interface12dis connected to the communication interface11bon the side of the computer11through the communication means16in such a manner as to establish two-way communication.

The colorimeter13is disposed to face the image display unit12aduring the color calibration. The colorimeter13can perform colorimetry on the image displayed on the image display unit12afrom the outside.

Next, discussion will be made on an operation of the color calibration system100in accordance with the first preferred embodiment.

First, in accordance with the application software11ainstalled in the computer11, the microcomputer12bcontrols the RGB color sensor12c. Under the control, the RGB color sensor12cprovided in the display device12detects the color temperature and the illuminance of the ambient light14including lighting. The RGB color sensor12coutputs the detection result as an RGB value signal and transfers the detection result (RGB value) to the microcomputer12b.

Next, in accordance with the installed application software, the microcomputer12bcalculates the target value by using a present calculation equation (Eq. 1) and the received detection result (the detection result transferred from the RGB color sensor12c). The equation Eq. 1 is expressed as:

Herein, the left side of Eq. 1 represents the above target value calculated by the microcomputer12b. The target value is calculated as an XYZ tristimulus value matrix. The first term of the right side of Eq. 1 represents a matrix correction factor matrix. The second term of the right side of Eq. 1 represents an RGB value matrix which is the above detection result transferred from the RGB color sensor12c.

The matrix correction factor matrix is set in the microcomputer12bin advance. The matrix correction factor matrix is calculated by using a measurement result obtained by the RGB color sensor12con a predetermined color temperature sample and an XYZ measurement result obtained by a reference colorimeter (not shown) on the predetermined color temperature sample before performing the color calibration. The reference colorimeter can measure tristimulus values XYZ. A method of calculating the matrix correction factor matrix will be specifically discussed below.

First, as the color temperature samples (fluorescent lamp samples having different color temperatures), prepared are samples1,2, and3. The samples1,2, and3are measured by the RGB color sensor12c. On the other hand, the samples1,2, and3are measured by the reference colorimeter. The measurement result (RGB values) obtained by the RGB color sensor12cand the measurement result (XYZ tristimulus values) obtained by the reference colorimeter are shown inFIG. 2.

In the exemplary case ofFIG. 2, the measurement result obtained by the RGB color sensor12con the sample1indicates “R1, G1, B1”. The measurement result obtained by the RGB color sensor12con the sample2indicates “R2, G2, B2”. The measurement result obtained by the RGB color sensor12con the sample3indicates “R3, G3, B3”. On the other hand, the measurement result obtained by the reference colorimeter on the sample1indicates “X1, Y1, Z1”. The measurement result obtained by the reference colorimeter on the sample2indicates “X2, Y2, Z2”. The measurement result obtained by the reference colorimeter on the sample3indicates “X3, Y3, Z3”.

Next, matrix elements of the matrix correction factor matrix are obtained by using Eqs. 2, 3, and 4 shown below and the measurement results shown inFIG. 2.

The calculated matrix correction factor matrix is set in the microcomputer12bbefore performing the color calibration.

Returning to discussion on the operation of the first preferred embodiment, the microcomputer12bcalculates the target value from Eq. 1 by using the preset matrix correction factor and the above detection result transferred from the RGB color sensor12c.

The calculated target value is transferred from the microcomputer12bthrough the communication interface12dto the communication interface11b. The target value received by the communication interface11bis set to the application software installed in the computer11.

On the other hand, the colorimeter13performs colorimetry on the image displayed on the image display unit12aas occasion arises. The colorimetry result is transferred through the communication interface11b, the communication means16, and the communication interface12dto the microcomputer12bon the side of the display device12as occasion arises.

In accordance with the application software11ainstalled in the computer11, the microcomputer12bautomatically performs the color calibration so that the received colorimetry result obtained by the colorimeter13may agree with the calculated target value.

Since the color calibration system of the first preferred embodiment has the above configuration, the system does not need any special measurement device. Further, by using the RGB color sensor12cto detect the indeterminate ambient light14, it is possible for a user having no expert knowledge to easily determine the type of ambient light14and the color temperature thereof. The target value is calculated from the detection result and an automatic adjustment of the white point and luminance is performed so that the target value may agree with the colorimetry result obtained by the colorimeter13. It is therefore possible to perform the color calibration precisely and simply.

In the above discussion, the microcomputer12bperforms calculation of the target value, the color calibration, and so on. There may be a case, however, where the calculation of the target value is performed on the side of the computer11and the microcomputer12bperforms the color calibration.

Though the XYZ tristimulus value is obtained as the target value in the above discussion, a CIE chromaticity xy value may be adopted as the target value.

FIG. 3shows a configuration of a color calibration system200for a display device for the purpose of color matching in accordance with the second preferred embodiment.

As shown inFIG. 3, the color calibration system200comprises the computer11, the display device12, the colorimeter13, and the communication means16.

Application software11afor performing color calibration and making a color profile is installed in the computer11. The computer11comprises the communication interface11b.

The communication interface11bis connected to the colorimeter13in order to receive a colorimetry result obtained by the colorimeter13. The communication interface11bis further connected to the communication interface12don the side of the display device12in such a manner as to establish two-way communication.

To the computer11, the keyboard15(including the mouse) is connected for operating the computer11.

The display device12comprises the image display unit12a, the microcomputer12b, and the interface12d. The display device12can perform a white point adjustment through adjustment of emission balance of RGB primary colors to be subjected to color management.

On the image display unit12a, displayed is a display image (including white, color patch, and the like). The image display unit12acan also serve as the display unit of the computer11during the color calibration.

In accordance with the application software11ainstalled in the computer11, the microcomputer12boperates. The microcomputer12bstores target values corresponding to a combination of the type of lighting, the type of color temperature, and the type of illuminance as, e.g., a table therein.

Though, in the second preferred embodiment, discussion will be made on the configuration in which the table is stored and set in the microcomputer12b, a memory in which the table is stored and set may be additionally provided in the display device12. In the configuration including the memory, the microcomputer12bmakes reference to the table in the memory and performs an operation of reading necessary data out therefrom and so on.

As the type of lighting, for example, a fluorescent lamp, an incandescent lamp, an LED, an electric bulb, sunlight, or the like may be adopted. If the type of lighting is a fluorescent lamp, as the type of color temperature, for example, warm white, cool white, daylight color, neutral white, or the like may be adopted. As the type of illuminance, for example, dark, normal, bright, considerably bright, or the like may be adopted.

FIG. 4shows an exemplary table which is stored and set in the microcomputer12b. In the second preferred embodiment, as shown inFIG. 4, only if a fluorescent lamp is selected as the type of lighting, the type of color temperature can be selected. Specifically, in the second preferred embodiment, if a fluorescent lamp is selected as the type of lighting, target values T1to T16are determined in accordance with the combination of the type of lighting, the type of color temperature, and the type of illuminance. On the other hand, if any one other than the fluorescent lamp is selected as the type of lighting, target values T17to T32are determined in accordance with the combination of the type of lighting and the type of illuminance.

The microcomputer12bautomatically performs color calibration so that the colorimetry result obtained by the colorimeter13may agree with a target value.

The communication interface12dis connected to the communication interface11bon the side of the computer11through the communication means16in such a manner as to establish two-way communication.

The colorimeter13is disposed to face the image display unit12aduring the color calibration. The colorimeter13can perform colorimetry on the image displayed on the image display unit12afrom the outside.

Next, discussion will be made on an operation of the color calibration system200in accordance with the second preferred embodiment.

First, by using the keyboard15and the like, the user operates the computer11to start the color calibration. Then, the application software11ainstalled in the computer11is started.

In accordance with the application software, the microcomputer12bcauses the display unit of the computer11(the display device12in the second preferred embodiment) to display a selection menu shown inFIG. 5.

On the display unit, as shown inFIG. 5, the type of lighting, the type of color temperature, and the type of illuminance are displayed in a selectable manner. Herein, in the second preferred embodiment, as discussed above, the type of color temperature is displayed in a selectable manner only if the fluorescent lamp is selected as the type of lighting.

When the above selection menu is displayed on the display unit, the user selects the type of lighting, the type of color temperature, and the type of illuminance by using the keyboard15and the like.

Next, in accordance with the combination of the type of lighting, the type of color temperature, and the type of illuminance which are selected from the section menu, the microcomputer12breads a predetermined one of the target values T1to T32corresponding to the combination out from the predetermined table.

Referring toFIG. 4, considered is a case, for example, where “fluorescent lamp” is selected as the type of lighting, “cool white” is selected as the type of color temperature, and “normal” is selected as the type of illuminance from the selection menu. In this case, the target value T8is read out from the table shown inFIG. 4which is stored in the microcomputer12b.

Further, considered is a case where “incandescent lamp” is selected as the type of lighting and “dark” is selected as the type of illuminance from the selection menu. In this case, the target value T17is read out from the table shown inFIG. 4which is stored in the microcomputer12b.

The colorimeter13performs colorimetry on the image displayed on the image display unit12aas occasion arises while the microcomputer12breads a predetermined one of the target values T1to T32out from the table shown inFIG. 4. The colorimetry result is transferred through the communication interface11b, the communication means16, and the communication interface12dto the microcomputer12bon the side of the display device12as occasion arises.

In accordance with the application software11ainstalled in the computer11, the microcomputer12bautomatically performs the color calibration so that the received colorimetry result obtained by the colorimeter13may agree with the predetermined target value which is read out.

Thus, in the second preferred embodiment, the table shown inFIG. 4is stored in the microcomputer12band one target value is determined through selection made on the selection menu shown inFIG. 5. It is therefore possible for a user having no expert knowledge to perform the color calibration precisely and simply without any special equipment.

FIGS. 6 and 7show a configuration of a color calibration system300for a display device for the purpose of color matching in accordance with the third preferred embodiment.

FIG. 6shows a configuration in which a prism (or a reflecting mirror)6is attached to a display device61. On the other hand,FIG. 7shows a configuration in which the prism (or the reflecting mirror)6is detached from the display device61.

As shown inFIGS. 6 and 7, the color calibration system300comprises a computer62, the display device61, the prism (or the reflecting mirror)6, and the communication means16.

Hereinafter, the prism6or reflecting mirror6is referred to as a “prism6or the like”.

In the third preferred embodiment, as shown inFIG. 7, a result of measurement performed by an RUB color sensor61edirectly on the ambient light14, not through the prism6or the like, is referred to as a “detection result”. On the other hand, as shown inFIG. 6, a result of measurement performed by the RGB color sensor61eindirectly on light emitted from an image display unit6athrough the prism6or the like, is referred to as a “colorimetry result”.

Application software62afor performing color calibration and making a color profile is installed in the computer62. The computer62comprises a communication interface62b.

The communication interface62bis connected to a communication interface61don the side of the display device61in such a manner as to establish two-way communication.

Though not shown inFIG. 6or7, to the computer62, a keyboard (including a mouse) is connected for operating the computer62.

The display device61comprises an image display unit61a, a microcomputer61b, the interface61d, and the RGB color sensor (RGB color filter sensor)61e. The display device61can perform a white point adjustment through adjustment of emission balance of RGB primary colors to be subjected to color management.

As shown inFIGS. 6 and 7, the prism6or the like is attachable to and detachable from the display device61. In a state of attachment, the prism6or the like receives light from the image display unit61aand outputs the received light to the RGB color sensor61e. In a state where the prism6or the like is attached to the display device61, the prism6or the like blocks out the ambient light14so that the ambient light14cannot enter the RGB color sensor61e. In other words, in the state where the prism6or the like is attached to the display device61, only the light of an image displayed on the image display unit61a, going through the prism6or the like and being outputted from the prism6or the like, is inputted to the RGB color sensor61e.

On the image display unit61a, displayed is a display image (including white, color patch CP, and the like). The image display unit61acan also serve as a display unit of the computer62during the color calibration.

The RGB color sensor61eis disposed near the image display unit61ain the display device61. The RGB color sensor61ecan detect a color temperature and illuminance of indeterminate ambient light14including lighting. Further, the RGB color sensor61ecan perform indirect colorimetry on a color temperature and illuminance of light of the image displayed on the image display unit61a.

Specifically, in a state where the prism6or the like is not attached to the display device61, the RUB color sensor61edetects the ambient light14(a result of this detection corresponds to the above “detection result”). In the state where the prism6or the like is attached to the display device61, the RGB color sensor file performs colorimetry on the display image on the image display unit61a, which is inputted through the prism6or the like (a result of this colorimetry corresponds to the above “colorimetry result”). The RGB color sensor61eoutputs the measurement result obtained by itself as an RGB value.

In accordance with the application software62ainstalled in the computer62, the microcomputer61bcalculates a target value. The target value is calculated by using a first calculation equation preset in the microcomputer61band the detection result obtained by the RGB color sensor61eprovided in the display device61. The detection result refers to a detection result obtained by the RGB color sensor61eon the ambient light14in the state where the prism6or the like is not attached to the display device61.

In the microcomputer61b, besides the first calculation equation, a second calculation equation is also set. Herein, the second calculation equation refers to an equation for converting the RGB value which is the colorimetry result obtained by the RGB color sensor61einto an XYZ tristimulus value.

In accordance with the application software62ainstalled in the computer62, the microcomputer61bfurther automatically performs color calibration by using the colorimetry result obtained by the RGB color sensor61eand the target value. Specifically, the microcomputer61bconverts the colorimetry result obtained by the RGB color sensor61einto the XYZ tristimulus value by using the second calculation equation. Then, the microcomputer61bautomatically performs the color calibration so that the converted XYZ tristimulus value may agree with the target value.

The communication interface61dis connected to the communication interface62bon the side of the computer62through the communication means16in such a manner as to establish two-way communication.

Next, discussion will be made on an operation of the color calibration system300in accordance with the third preferred embodiment.

First, as shown inFIG. 7, the state in which the prism6or the like is not attached to the display device61is created. By using the keyboard and the like, the user performs an operation for causing the color calibration system300to recognize that the prism6or the like is not attached. There may be a case where a sensor (not shown) is additionally provided in the display device61and the sensor automatically detects whether the prism6or the like is attached or not.

Next, in accordance with the application software62ainstalled in the computer62, the microcomputer61bcontrols the RGB color sensor61e. Under the control, the RGB color sensor61eprovided in the display device61detects the color temperature and the illuminance of the ambient light14including lighting. Herein, as shown inFIG. 7, the ambient light14is detected directly, not through the prism6or the like. The RGB color sensor61eoutputs the detection result as an RGB value signal and transfers the detection result to the microcomputer61b.

In accordance with the application software62ainstalled in the computer62, the microcomputer61bcalculates the target value. The target value is calculated in the state where the microcomputer61brecognizes that the prism6or the like is not attached. The target value is calculated by using the first calculation equation (Eq. 11) preset in the microcomputer61band the received detection result (the detection result transferred from the RGB color sensor61e). The first calculation equation (Eq. 11) is expressed as:

Herein, the left side of Eq. 11 represents the above target value calculated by the microcomputer61b. The target value is calculated as an XYZ tristimulus value matrix. The first term of the right side of Eq. 11 represents a first matrix correction factor matrix. The second term of the right side of Eq. 11 represents an RGB value matrix which is the above detection result transferred from the RGB color sensor61e.

The first matrix correction factor matrix is set in the microcomputer61bin advance. The first matrix correction factor matrix is calculated by using a measurement result obtained by the RGB color sensor61eon a predetermined color temperature sample and an XYZ measurement result obtained by the reference colorimeter (not shown) on the predetermined color temperature sample before performing the color calibration. The reference colorimeter can measure tristimulus values XYZ. A method of calculating the first matrix correction factor matrix will be specifically discussed below.

First, as the color temperature samples (fluorescent lamp samples having different color temperatures), prepared are samples1,2, and3. The samples1,2, and3are measured directly by the RGB color sensor61e(in other words, not through the prism6or the like). On the other hand, the samples1,2, and3are measured directly by the reference colorimeter. The measurement result (RGB values) obtained by the RGB color sensor61eand the measurement result (XYZ tristimulus values) obtained by the reference colorimeter are shown inFIG. 2.

In the exemplary case ofFIG. 2, the measurement result obtained by the RGB color sensor61eon the sample1indicates “R1, G1, B1”. The measurement result obtained by the RGB color sensor61eon the sample2indicates “R2, G2, B2”. The measurement result obtained by the RGB color sensor61eon the sample3indicates “R3, G3, B3”. On the other hand, the measurement result obtained by the reference colorimeter on the sample1indicates “X1, Y1, Z1”. The measurement result obtained by the reference colorimeter on the sample2indicates “X2, Y2, Z2”. The measurement result obtained by the reference colorimeter on the sample3indicates “X3, Y3, Z3”.

Next, matrix elements of the first matrix correction factor matrix are obtained by using Eqs. 12, 13, and 14 shown below and the measurement results shown inFIG. 2.

The calculated first matrix correction factor matrix is set in the microcomputer61bbefore performing the color calibration.

Returning to discussion on the operation of the third preferred embodiment, the microcomputer61bcalculates the target value from Eq. 11 by using the preset first matrix correction factor and the above detection result transferred from the RGB color sensor61e.

Next, as shown inFIG. 6, the prism6or the like is attached to the display device61. By using the keyboard and the like, the user performs an operation for causing the color calibration system300to recognize that the prism6or the like is attached. As discussed above, there may be a case where a sensor (not shown) is additionally provided in the display device61and the sensor automatically detects whether the prism6or the like is attached or not.

Next, in accordance with the application software62ainstalled in the computer62, the microcomputer61bcontrols the RGB color sensor61e. Under the control, the RGB color sensor61erecognizes that the prism6or the like is attached to the display device61and then performs colorimetry on the image displayed on the image display unit61aas occasion arises. As shown inFIG. 6, the light of the image displayed on the image display device61enters the prism6or the like. Then, the incident light is reflected inside the prism6or the like. The reflected light is outputted from the prism6or the like and inputted to the RGB color sensor61e.

The colorimetry result (RGB values) obtained by the RGB color sensor61eis transferred to the microcomputer61b.

In accordance with the application software62ainstalled in the computer62, the microcomputer61bconverts the colorimetry result into the XYZ tristimulus value by using the preset second calculation equation (Eq. 15). The second calculation equation (Eq. 15) is expressed as:

Herein, the left side of Eq. 15 represents the converted. XYZ tristimulus value matrix. The first term of the right side of Eq. 15 represents a second matrix correction factor matrix. The second term of the right side of Eq. 15 represents an RGB value matrix which is the colorimetry result obtained by the RGB color sensor61e.

The second matrix correction factor matrix is set in the microcomputer61bin advance. The second matrix correction factor matrix is calculated by using a measurement result indirectly obtained by the RUB color sensor61eon the color patch CP displayed on the image display unit61aand an XYZ measurement result directly obtained by the reference colorimeter (not shown) on the color patch CP before performing the color calibration. The reference colorimeter can measure tristimulus values XYZ. A method of calculating the second matrix correction factor matrix will be specifically discussed below.

First, the color patch CP including the samples1,2, and3is displayed on the image display unit61a. The prism6or the like is attached to the display device61. The samples1to3are measured indirectly by the RGB color sensor61e(in other words, through the prism6or the like). On the other hand, the samples1to3are measured directly by the reference colorimeter (in other words, not through the prism6or the like). The measurement result (RGB values) obtained by the RGB color sensor61eand the measurement result (XYZ tristimulus values) obtained by the reference colorimeter are shown inFIG. 8.

In the exemplary case ofFIG. 8, the measurement result obtained by the RGB color sensor61eon the sample1indicates “R1′, G1′, Br′”. The measurement result obtained by the RUB color sensor61eon the sample2indicates “R2′, G2′, B2′”. The measurement result obtained by the RGB color sensor61eon the sample3indicates “R3′, G3′, B3′”. On the other hand, the measurement result obtained by the reference colorimeter on the sample1indicates “X1′, Y1′, Z1′”. The measurement result obtained by the reference colorimeter on the sample2indicates “X2′, Y2′, Z2′”. The measurement result obtained by the reference colorimeter on the sample3indicates “X3′, Y3′, Z3′”.

Next, matrix elements of the second matrix correction factor matrix are obtained by using Eqs. 16, 17, and 18 shown below and the measurement results shown inFIG. 8.

The calculated second matrix correction factor matrix is set in the microcomputer61bbefore performing the color calibration.

Returning to discussion on the operation of the third preferred embodiment, in accordance with the application software62ainstalled in the computer62, the microcomputer61bautomatically performs the color calibration so that the colorimetry result obtained by the RGB color sensor61e, which is converted into the XYZ tristimulus value by using Eq. 15, may agree with the above target value which is already calculated.

Since the color calibration system of the third preferred embodiment has the above configuration, the system does not need any special measurement device. Further, by using the RGB color sensor61eto detect the indeterminate ambient light14, it is possible for a user having no expert knowledge to easily determine the type of ambient light14and the color temperature thereof. The target value is calculated from the above detection result and an automatic adjustment of the white point and luminance is performed so that the target value may agree with the colorimetry result obtained by the RGB color sensor61e. It is therefore possible to perform the color calibration precisely and simply. Further, by attaching the attachable and detachable prism6or the like to the display device61, the colorimeter13of the first preferred embodiment can be omitted.

In the above discussion, the microcomputer61bperforms calculation of the target value, conversion of the colorimetry result obtained by the RGB color sensor61einto the XYZ tristimulus value, the color calibration, and so on. There may be a case, however, where the calculation of the target value is performed on the side of the computer62and the microcomputer61bperforms the conversion of the colorimetry result obtained by the RGB color sensor61einto the XYZ tristimulus value, and the color calibration.

Though the XYZ tristimulus value is obtained as the target value in the above discussion, a CIE chromaticity xy value may be adopted as the target value.

The color calibration discussed in the first to third preferred embodiments needs to be performed in a state where the luminance and the color temperature of the display device12or61are stable. In the fourth preferred embodiment, provided is a color calibration system capable of performing the color calibration in the state where the luminance and the color temperature of the display device12or61are stable.

In a color calibration system of the fourth preferred embodiment, the display device is additionally provided with two temperature sensors Ts1and Ts2besides the configuration of the display device12or61in accordance with the first to third preferred embodiments.

A control unit determines whether or not to perform the color calibration on the basis of respective measurement results of the temperature sensors Ts1and Ts2. In the fourth preferred embodiment, the display device is also provided with the control unit. In the fourth preferred embodiment, however, the microcomputer12bor61bin the first to third preferred embodiments serves also as the control unit.

FIG. 9shows a configuration in which the two temperature sensors Ts1and Ts2are provided in the display device12or61. In the fourth preferred embodiment, one of the temperature sensors, Ts1, is disposed at a first location in the display device12or61. On the other hand, the other temperature sensor Ts2is disposed at a second location in the display device12or61. Herein, during the operation of the display device12or61, at the second location, the temperature is higher than that at the first location.

The color calibration needs to be performed in the state where the luminance and the color temperature of the display device12or61are stable. Therefore, it is preferable that the difference in temperature between the first location and the second location is larger during the operation of the display device12or61.

InFIG. 10, the image display unit12aor61ain the display device12or61is a liquid crystal module unit. Further, inFIG. 10, the display device12or61is provided with a ventilation unit50through which air is taken from the outside of the display device to the inside thereof. As shown inFIG. 10, the first location at which the one temperature sensor Ts1is provided is a location near the ventilation unit50in the display device12or60where the temperature is lowest in the display device12or61during operation. The second location at which the temperature sensor Ts2is provided is a location at a center portion of the liquid crystal module unit12aor61ain a plan view of the display device12or61where the temperature is highest in the display device12or61during operation.

Next, discussion will be made on an operation of the fourth preferred embodiment.

The microcomputer12bor61bserving as the control unit acquires respective detection results of the temperature sensors Ts1and Ts2at certain time intervals (e.g., at intervals of 5 seconds).

The microcomputer12bor61breceives a command to start the color calibration from the side of the computer11or62. After receiving the command, the microcomputer12bor61bcalculates the difference between a sensed temperature acquired from the one temperature sensor Ts1and a sensed temperature acquired from the other temperature sensor Ts2. The difference between these sensed temperatures is calculated, naturally, by using the respective sensed temperatures that the microcomputer12bor61breceives from the temperature sensors Ts1and Ts2at the same time.

Herein, immediately after receiving the above command (at time t1), the microcomputer12bor61breceives a sensed temperature T1from the one temperature sensor Ts1and receives a sensed temperature T2from the other temperature sensor Ts2.

Then, the microcomputer12bor61bcalculates the difference (T2−T1) between the sensed temperature T2and the sensed temperature T1.

As discussed above, the microcomputer12bor61bacquires the respective sensed temperatures from the temperature sensors Ts1and Ts2at certain time intervals (e.g., at intervals of 5 seconds) as occasion arises. At time t2after e.g., 5 seconds elapsed from time t1, the microcomputer12bor61breceives a sensed temperature T11from the one temperature sensor Ts1and receives a sensed temperature T12from the other temperature sensor Ts2. Substantially, the microcomputer12bor61bcalculates the difference (T12−T11) between the sensed temperature T12and the sensed temperature T11.

Next, the microcomputer12bor61bdetermines whether or not to perform the color calibration on the basis of the time variation of the differential value between the detection result of the one temperature sensor Ts1and that of the other temperature sensor Ts2and a threshold value. The threshold value is set in the microcomputer12bor61bin advance.

Specifically, the microcomputer12bor61bcalculates an absolute value of the difference between the sensed temperature difference of this time and that of the last time. In the above case, the microcomputer12bor61bcalculates |(T12−T11)−(T2−T1)|(=time variation). Then, the microcomputer12bor61bjudges if the calculated result (time variation) is larger than the threshold value. In other expression using a numerical formula, the microcomputer12bor61bjudges if |(T12−T11)−(T2−T1)|>the threshold value. In other words, the microcomputer12bor61bdetermines whether the display device12or61is in a warm-up state or in a stable state after the warm-up state.

If the time variation is larger than the threshold value (the time variation>the threshold value, and in other words, in a case where the time variation in temperature between the first and second locations is large), the microcomputer12bor61bdetermines not to perform the color calibration.

On the other hand, if the time variation is not larger than the threshold value (the time variation≦the threshold value, and in other words, in a case where the time variation in temperature between the first and second locations is relatively small), the microcomputer12bor61bdetermines to perform the color calibration.

Next, discussion will be made on an operation after the microcomputer12bor61bdetermines not to perform the color calibration as discussed above.

When the microcomputer12bor61bdetermines not to perform the color calibration, the microcomputer12bor61btransfers the determination to the computer11or62through the communication means16.

Then, in accordance with the application software11aor62a, the computer11or62displays the following message on the display unit of the computer11or62(e.g., the display unit shared with the display device12or61). In other words, since the display device12or61is in the warm-up state, where it is inappropriate to perform the color calibration, the computer11or62does not perform the color calibration at the present time and displays the message indicating that the system is in a stand-by state on the display unit. It can be thought that the display unit serves as a notification means for notifying the outside of the result of determination not to perform the color calibration.

On the other hand, also after the above determination not to perform the color calibration, the microcomputer12bor61bsequentially acquires the respective sensed temperatures of the temperature sensors Ts1and Ts2at certain time intervals (e.g., at intervals of 5 seconds).

The microcomputer12bor61bcontinues to calculate the absolute value of the difference between the sensed temperature difference of the latest time between the temperature sensors Ts1and Ts2and that of the immediately previous time between the temperature sensors Ts1and Ts2until the time variation becomes not larger than the threshold value (the time variation≦the threshold value and the stable state of the display device12or61).

It is assumed that the microcomputer12bor61bdetects that the time variation is not larger than the threshold value (the time variation≦the threshold value) after a certain time period elapsed. Since the detection of that means that the display device12or61is in the stable state after completion of warm-up, the microcomputer12bor61bautomatically performs the color calibration after the detection (in other words, the microcomputer performs the color calibration discussed in the first to third preferred embodiments).

Thus, in the color calibration system of the fourth preferred embodiment, the microcomputer12bor61bserving as the control unit determines whether or not to perform the color calibration on the basis of the time variation of the differential value between the detection result of the one temperature sensor Ts1and that of the other temperature sensor Ts2and the threshold value.

Therefore, in the color calibration system of the fourth preferred embodiment, it is possible to detect whether the display device12or61is in the warm-up state or the stable state, and the color calibration for the display device12or61can be always performed in the stable state of the display device12or61.

Further, in the fourth preferred embodiment, as shown inFIG. 10, the one temperature sensor Ts1is disposed near the ventilation unit50where the temperature increases least in the display device12or61during operation. The other temperature sensor Ts2is disposed at the center portion of the liquid crystal module unit12aor61awhere the temperature increases most in the display device12or61during operation.

Therefore, it is possible to judge whether the display device12or61is in the warm-up state or the stable state with high accuracy. In other words, the precision of the color calibration increases.

As an application example of the present invention, the present invention can be applied to computer equipments including displays for home use. Further, the present invention can be used for adjustment of displays for some industries in determination of adjustment target point in a color adjustment apparatus using a colorimeter or the like, and so on.