JP2013228577A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently correct a change of image quality due to a secular change of gamma characteristics, and to suppress deterioration of the image quality until the correction is performed.SOLUTION: An image display device comprises: a measurement part 309 that measures actual gamma characteristics of a display element; a measurement data memory 409 that stores first measurement data to be obtained by the measurement part when a display element is driven on the basis of standard gamma characteristics before the actual gamma characteristics are changed by a use of the image display device; a control part 405 that causes a driver part to drive the display element on the basis of used gamma characteristics when the image display device is used; and a correction part 405 that obtains second measurement data to be obtained by the measurement part when the image display element is driven on the basis of the standard gamma characteristics or the used gamma characteristics after the actual gamma characteristics are changed by the use of the image display device and performs a correction to the used gamma characteristics in accordance with a difference between the first measurement data and the second measurement data.

Description

  The present invention relates to an image display device such as a liquid crystal projector that displays an image using a display element.

  In the image display apparatus as described above, there is a tendency that the gamma characteristic changes (changes with time) with long-term use. For example, in a liquid crystal projector using a liquid crystal display element, the liquid crystal layer is irradiated with strong light from a light source, heat is generated by the light irradiation, and moisture enters from the outside, thereby causing liquid crystal display. The gamma characteristic of the element varies. Then, due to the change with time of the gamma characteristic of the display element, the monitor gamma value, which is the color of the display image, deviates from a predetermined standard value (γ = 2.2 in the sRGB standard), and the image quality deteriorates.

  FIG. 11A shows an example of a change with time of the gamma characteristic. Reference numeral 101 denotes a gamma characteristic set to γ = 2.2 by gamma adjustment in the production process of the image display apparatus. On the other hand, reference numeral 102 denotes a gamma characteristic in which the halftone becomes brighter with time. The manner of occurrence of such a change with time of the gamma characteristic varies depending on the structure of the display element, and the gamma characteristic 101 may change to a gamma characteristic 103 having a dark intermediate length.

  Patent Document 1 discloses a technique in which a light amount sensor is provided in a liquid crystal projector and a change in color of a display image is corrected according to a detection result by the light amount sensor (a light amount of a light source for each color is controlled). .

  In Patent Document 2, a specific gamma characteristic of a liquid crystal display element is stored in a device-side memory, and the liquid crystal display element-side memory replaced with the gamma characteristic stored in the device-side memory when the liquid crystal display element is replaced. Discloses a liquid crystal display device that calculates a difference from the gamma characteristic stored in. In the liquid crystal display device, the gamma table for driving the replaced liquid crystal display element is corrected according to the difference.

JP 2007-122014 A JP 2011-081310 A

By combining the techniques disclosed in Patent Documents 1 and 2, the user can perform gamma adjustment again with an algorithm equivalent to the production process using the light amount sensor in the image display device in which the gamma characteristic has changed due to aging. Is also possible. However, until the gamma adjustment is performed again, the user continues to use the image display device in a state where the gamma value is deviated from the standard value in a direction in which the image quality is deteriorated.

  The present invention provides an image display apparatus that can satisfactorily correct a change in image quality due to a change in gamma characteristics with time and can suppress deterioration in image quality until correction.

  An image display apparatus according to an aspect of the present invention can drive a display element based on a display element that is driven to display an image, and a standard gamma characteristic and a use gamma characteristic that is different from the standard gamma characteristic. A drive unit, a measurement unit for measuring the actual gamma characteristic, which is a gamma characteristic actually obtained by driving the display element, and the display element is connected to the standard gamma before the actual gamma characteristic changes with use of the image display device. A measurement data memory for storing first measurement data acquired by the measurement unit when driven based on the characteristics, and a display element based on the used gamma characteristics when the image display device is used. And the display element was driven based on the standard gamma characteristic or the used gamma characteristic after the actual gamma characteristic changed with the use of the image display device Gamma used so that the actual gamma characteristic matches or approaches the standard gamma characteristic according to the difference between the first measurement data and the second measurement data. And a correction unit that corrects the characteristics.

  According to another aspect of the present invention, there is provided a control method for an image processing apparatus based on a display element driven to display an image, a standard gamma characteristic, and a use gamma characteristic different from the standard gamma characteristic. The present invention is applied to an image display apparatus having a drive unit that can drive a display element and a measurement unit that performs measurement on an actual gamma characteristic obtained by driving the display element. The control method includes a step of causing the drive unit to drive the display element based on the standard gamma characteristic to obtain first measurement data by the measurement unit before the actual gamma characteristic changes with use of the image display device. , When the image display device is used, the drive unit drives the display element based on the used gamma characteristic, and the real gamma characteristic is changed with the use of the image display device, and then displayed on the drive unit. The step of driving the element based on the standard gamma characteristic or the used gamma characteristic and acquiring the second measurement data by the measurement unit, and the actual gamma characteristic according to the difference between the first measurement data and the second measurement data Correcting the used gamma characteristic so as to match or approach the standard gamma characteristic.

In the present invention, when the display element is driven based on the used gamma characteristic that is appropriately shifted from the standard gamma characteristic in advance, and the actual gamma characteristic changes with time, the actual gamma characteristic matches or approaches the standard gamma characteristic. As shown in FIG. As a result, it is possible to satisfactorily correct a change in image quality due to a change with time, and it is also possible to suppress deterioration in image quality until correction.

1 is a diagram illustrating an example of use of a liquid crystal projector that is Embodiment 1 of the present invention. FIG. 1 is a diagram illustrating a configuration of an optical system of a liquid crystal projector of Example 1. FIG. FIG. 3 is a diagram illustrating a configuration of a signal processing circuit of the liquid crystal projector of Embodiment 1. FIG. 3 is a diagram illustrating gradation characteristics and a gamma table of a liquid crystal display element in the liquid crystal projector of the first embodiment. 5 is a flowchart showing a gamma adjustment process of the liquid crystal projector of Embodiment 1. 9 is a flowchart showing a gamma adjustment process of a liquid crystal projector that is Embodiment 2 of the present invention. 3 is a flowchart showing an initial gamma measurement process in the first embodiment. 5 is a flowchart illustrating gamma correction processing after a change with time in gamma characteristics according to the first exemplary embodiment. The figure which shows the conditions of the gamma table set in each said process. The figure which shows the fluctuation | variation of the luminance value of the intermediate gradation accompanying a time-dependent change. The figure which shows the change of a gamma characteristic.

  Embodiments of the present invention will be described below with reference to the drawings.

  In an image display apparatus such as a liquid crystal projector, the light amount from a display element such as a liquid crystal panel is measured using a photosensor in the production process, and gamma adjustment is performed based on the measurement result. If an optical sensor is built in the image display device, gamma adjustment can be performed with an algorithm equivalent to that in the production process even after the start of use of the image display device. However, in general, an optical sensor used for gamma adjustment in a production process is expensive because the linearity of the sensor output with respect to the amount of light is assured with high accuracy.

  In the embodiment of the present invention, it is possible to perform gamma adjustment after a change with time using a user by using an optical sensor whose linearity of sensor output with respect to the amount of light is coarser than that used in the production process. Further, by making the target value at the time of gamma adjustment in the production process different from the target value at the time of gamma adjustment after the change with time, deterioration of the image quality of the display image in the state of change with time is suppressed.

FIG. 1 shows an example of use of a liquid crystal projector as an image display apparatus that is Embodiment 1 of the present invention. The liquid crystal projector 201 forms an image (projected image) 205 by modulating light from a light source by a liquid crystal display element in accordance with an image signal (video signal) input from a video player 202 which is an image supply device. Then, the image 205 is projected onto a screen 204 that is a projection surface.

  FIG. 2 shows the configuration of the optical system of the liquid crystal projector 201. The light emitted from the light source 301 is converted into polarized light having a uniform polarization direction by the illumination optical system 302, and the intensity distribution is made uniform.

  Light emitted from the illumination optical system 302 is separated into G light and RB light by the dichroic mirror 303. The G light transmitted through the dichroic mirror 303 is reflected by a polarization beam splitter (PBS) 304 and enters a G liquid crystal display element (hereinafter referred to as a G liquid crystal panel) 307G. The G light modulated by the G liquid crystal panel 307G passes through the PBS 304, is reflected by the PBS 306, and travels toward the projection optical system 308.

  Of the RB light reflected by the dichroic mirror 303, the B light is rotated by 90 degrees in the polarization direction by a wavelength-selective polarizing plate (not shown), passes through the PBS 305, and passes through the B liquid crystal display element (hereinafter referred to as B light). 307B. The B light modulated by the B liquid crystal panel 307B is reflected by the PBS 305, passes through the PBS 306, and travels toward the projection optical system 308. On the other hand, of the RB light reflected by the dichroic mirror 303, the R light is reflected by the PBS 305 and enters an R liquid crystal display element (hereinafter referred to as an R liquid crystal panel) 307R. The R light modulated by the R liquid crystal panel 307R passes through the PBS 305, passes through the PBS 306, and travels toward the projection optical system 308.

  G light, B light, and R light that are combined by the PBS 306 and form a projection image (display image) 205 are projected onto the screen 204 shown in FIG. 1 by the projection optical system 308.

  An optical sensor 309 is disposed on the surface of the PBS 306 that does not transmit any of the G light, R light, and B light (hereinafter also referred to as display light) toward the projection optical system 308. The optical sensor 309 measures the light amount of the leaked light by using the characteristic that the PBS 306 generates a fixed ratio of leaked light with respect to the RGB display light. By measuring the amount of leaked light, the light intensity (luminance) of the projected image 205 can be indirectly measured.

  FIG. 3 shows the configuration of the optical system and the configuration of the electric circuit of the liquid crystal projector 201. In this figure, R, G, B liquid crystal panels 307R, 307G, 307B are collectively shown as a liquid crystal panel 307.

  The video signal input to the liquid crystal projector 201 via the video cable 203 is subjected to various video processing such as brightness correction, contrast correction, and color conversion processing in the video processing unit 401, and is suitable for driving each liquid crystal panel. Converted to video signal.

  The converted video signal is input to the gamma correction unit 402. When a liquid crystal driving voltage proportional to the gradation (input gradation) of the video signal is applied to the liquid crystal panel 307, as shown in FIG. 4 (a), display light having a light amount (luminance) in accordance with nonlinear luminance characteristics. Inject. The gamma correction unit 402 is configured so that the gamma characteristic indicating the relationship between the input gradation and the luminance (output gradation) has an appropriate gamma value (for example, γ = 2.2 in the sRGB standard) as shown in FIG. As shown in (2), gradation conversion processing is performed on the video signal using nonlinear gamma correction data. This gradation conversion process corresponds to gamma correction.

  The gamma correction data is stored in a ROM 406 as a gamma memory as a plurality of lookup tables (LUT) 1 (407), LUT 2 (408),. In the following description, the gamma correction data is referred to as a gamma table. A CPU 405 described below can drive the liquid crystal panel 307 by selecting one of these gamma tables together with the following liquid crystal driving unit 403.

  The video signal that has been gamma corrected by the gamma correction unit 402 is input to the liquid crystal driving unit 403. The liquid crystal driving unit 403 generates a liquid crystal driving voltage corresponding to the gradation (input gradation) of the video signal and applies it to the liquid crystal panel 307 to drive the liquid crystal panel 307.

  The optical sensor 309 photoelectrically converts the leakage light described above and outputs an electric signal having a value corresponding to the amount of the leakage light. An electrical signal as an analog signal output from the optical sensor 309 is converted into a digital signal by the AD converter 404 and input to the CPU 405.

  The CPU 405 controls each operation of the liquid crystal projector 201. The ROM 406 described above is configured by a nonvolatile memory, and has an area (gamma data memory) for storing the above-described gamma tables (LUT1, LUT2,...). Further, the ROM 406 includes an area for storing usage history (log) data of the liquid crystal panel 307 and an area for storing initial measurement luminance data (to be described later) by the optical sensor 309 (measurement data memory 409). Further, the CPU 405 constitutes a measurement unit together with the optical sensor 309, and the CPU 405 constitutes a control unit and a correction unit.

  Next, a process (control method) for correcting the gamma tables (LUT1, LUT2,...) With respect to the gamma characteristics that have changed with time in this embodiment, that is, a gamma table correction process will be described. Here, a case where the actual gamma characteristic actually obtained with the liquid crystal panel 307 (that is, a liquid crystal projector) is changed from a gamma characteristic before the start of user use of the projector to a brighter gamma characteristic due to a change with time with use. To do. However, even when the actual gamma characteristic changes from the gamma characteristic before the start of user use to a gamma characteristic that becomes darker, the following gamma table correction processing can be similarly applied.

  First, the flowchart of FIG. 5 shows a pre-processing procedure for gamma table correction performed in the production process of the liquid crystal projector of this embodiment. The gamma table correction process including this pre-processing is executed by the CPU 405 as a correction unit according to a computer program.

  In STEP601, the CPU 405 performs gamma adjustment. The target gamma characteristic in this gamma adjustment is a standard gamma characteristic in which the gamma value γ is 2.2, which is a standard value (hereinafter referred to as γ = 2.2).

  Next, in STEP 602, the CPU 405 writes a gamma table corresponding to the standard gamma characteristic (standard gamma data: hereinafter referred to as a standard gamma table) to the LUT 1 (407) in the ROM 406.

  Next, in STEP 603, the CPU 405 corresponds to a gamma characteristic in which the gamma value γ is 2.4 (hereinafter referred to as γ = 2.4), which is larger than the standard value, that is, a use gamma characteristic different from the standard gamma characteristic. The gamma table is written into LUT2 (408) in the ROM 406. The gamma table corresponding to the used gamma characteristic corresponds to used gamma data, and is hereinafter referred to as a used gamma table.

  Next, in STEP 604, the CPU 405 drives the liquid crystal panel 307 using the standard gamma table written in the LUT1 (407) (that is, based on the standard gamma characteristic). Then, using the optical sensor 309, initial measurement for obtaining measurement data (first measurement data) regarding the actual gamma characteristic at this time is performed. Details of the initial measurement will be described later.

  When the initial measurement is completed, the CPU 405 writes the measurement data acquired by the initial measurement in the measurement data memory 409 in STEP 605.

  Next, in STEP 606, the CPU 405 sets the use gamma table written in the LUT 2 (408) as the gamma table used for driving the liquid crystal panel 307 after the start of use by the user. Then, the preprocessing is completed.

  FIG. 9 shows a gamma table written in each LUT in this embodiment, a gamma table used for driving the liquid crystal panel 307 in the initial measurement, and a used gamma used for driving the liquid crystal panel 307 after the user starts use. Shows the table. In this embodiment, the use gamma table corresponding to γ = 2.4 is set as the user use gamma table (that is, the liquid crystal panel 307 is driven based on the use gamma characteristic). For this reason, at the beginning of user use, a darker projected image is displayed than when the standard gamma characteristic 101 with γ = 2.2 is used, as in the gamma characteristic 104 shown in FIG. 11B.

  The flowchart of FIG. 7 shows a specific procedure for the above-described initial measurement. In STEP 801, the CPU 405 sets a standard gamma table corresponding to the above-described standard gamma characteristic of γ = 2.2 as a gamma table for initial measurement.

  Next, in STEP802 to STEP804, the CPU 405 uses the optical sensor 309 to measure the luminance for a plurality of predetermined input gradations. In this embodiment, the luminance for seven input gradations is measured. Reference numeral 105 in FIG. 11B denotes seven measured luminances (hereinafter referred to as initial measured luminances) for the seven input gradations acquired in the initial measurement. The gamma characteristic obtained by connecting the measured luminances 105 with a curve substantially matches the standard gamma characteristic 101 with γ = 2.2. The seven initial measurement luminances 105 thus obtained are stored in the measurement data memory 409 as first measurement data.

  The flowchart of FIG. 8 shows the procedure of the gamma table correction process in the case where a change with time in the gamma characteristic caused by user use occurs in the projector of this embodiment.

  In STEP 901, the CPU 405 stores in a LUT 1 (407) as a correction measurement gamma table for obtaining second measurement data, which will be described later, used to calculate a correction amount in gamma table correction, as shown in FIG. Set standard gamma table.

  Next, in STEP902 to STEP904, the CPU 405 drives the liquid crystal panel 307 using the standard gamma table, and uses the optical sensor 309 to measure the luminance for the same seven predetermined input gradations as the initial measurement (FIG. 9). In other words, the measurement luminance is obtained as measurement data (second measurement data) related to the actual gamma characteristic after change with time. The measured luminances 106 and 107 shown in FIG. 11B are acquired here.

  Subsequently, in STEP 905, the CPU 405 calculates a difference for each input gradation between the seven measured luminances 106 and 107 obtained in STEP 902 to STEP 904 and the seven initial measured luminances 105 stored in the measurement data memory 409. This difference corresponds to the amount of deviation of the actual gamma characteristic after the change over time caused by driving the liquid crystal panel 307 for a long period of time with respect to the standard gamma characteristic.

  Then, the CPU 405 calculates a correction amount based on the standard gamma table stored in the LUT 1 (407). Various calculation methods can be used to calculate the correction amount. For example, a complementary calculation is performed using the measured luminances 106 and 107 after the change with time, and a gradation shift amount 108 (FIG. 11) for obtaining luminance equivalent to the initial measured luminance 105 (indicated by x in FIG. 11B). In (b), 21/255 gradations) may be calculated. The calculated correction amount is such that the actual gamma characteristic obtained when the liquid crystal panel 307 is driven using the used gamma table corrected with the correction amount matches the standard gamma characteristic or is used before correction. It is closer to the standard gamma characteristic than when using.

  After calculating the correction amount of the use gamma table in this way, the CPU 405 corrects the original use gamma table stored in the LUT 2 (408) using the correction amount in STEP906. In other words, correction for the used gamma characteristic is performed. Specifically, the corrected use gamma table is created by subtracting the gradation shift amount 108 which is the correction amount calculated in STEP 905 from the original use gamma table. Then, LUT2 (408) is rewritten with the corrected use gamma table. As a result, the corrected use gamma table is stored in LUT2 (408) (see FIG. 9).

  In STEP 907, the CPU 405 sets the corrected use gamma table stored in the LUT 2 (408) as a new use gamma table. Thus, the gamma table correction process is completed.

  Thereafter, the liquid crystal panel 307 is driven using the corrected use gamma table. As a result, a projected image is displayed with a standard gamma characteristic of γ = 2.2 or a gamma characteristic close to this, so that a change in image quality due to a change with time can be favorably corrected.

Here, the reason why the used gamma characteristic is set to the gamma characteristic of γ = 2.4 after the gamma adjustment in the production process will be described. FIG. 10 is a histogram showing the display luminance distribution of 128/255 gradations in a plurality of liquid crystal projectors after a plurality of liquid crystal projectors have been used for a long time after gamma adjustment. The horizontal axis in FIG. 10 indicates the display luminance value, and the vertical axis indicates the relative frequency. 1101 having the largest frequency indicates a luminance value when γ = 2.4 immediately after gamma adjustment is set, and 1102 is a luminance value when a gamma table with γ = 2.2 is set. The median value of the distribution after long-term use is standard gamma by incorporating in advance the characteristic that the display brightness of the projector changes gradually in the direction of increasing brightness and setting γ = 2.4 during gamma adjustment. It is distributed in the vicinity of γ = 2.2 corresponding to the characteristic. Then, by performing the gamma table correction process after the change with time, the luminance value 1102 corresponding to γ = 2.2 is obtained in all projectors.
As described above, in this embodiment, the gamma characteristic (used gamma characteristic) set at the start of user use is different from the target value (standard gamma characteristic) for gamma table correction. As a result, it is possible to provide an image display with a gamma characteristic that does not greatly deviate from γ = 2.2 for users who do not perform gamma table correction. Also, for users who place importance on gamma characteristics, image display at γ = 2.2 (or in the vicinity thereof) can be provided by performing gamma table correction. Therefore, a favorable image can be displayed for various users.

  In this embodiment, a liquid crystal panel having the characteristic that the luminance as the output gradation increases with time change (the gamma value of the actual gamma characteristic becomes small) is assumed, and the gamma value of the used gamma characteristic is changed to the standard gamma characteristic. The case of setting larger than the gamma value has been described. However, for liquid crystal panels that have a characteristic in which the brightness as the output gradation decreases with time (the gamma value of the actual gamma characteristic increases), the gamma value of the used gamma characteristic is greater than the gamma value of the standard gamma characteristic. A small value is set (for example, γ = 2.0). Thereby, an image can be provided satisfactorily. This is the same in the second embodiment described later.

  Next, a liquid crystal projector that is Embodiment 2 of the present invention will be described. The present embodiment is different from the first embodiment in the preprocessing procedure for gamma table correction in the production process, the gamma table held in the ROM 406, and the gamma table correction processing procedure. The configuration of the liquid crystal projector and the initial measurement procedure are the same as those in the first embodiment. In the present embodiment, components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  The flowchart of FIG. 6 shows the procedure of the preprocessing performed by the liquid crystal projector of this embodiment. As in the first embodiment, the gamma table correction process including this pre-process is executed by the CPU 405 as a correction unit according to a computer program.

  In STEP 701, the CPU 405 performs gamma adjustment. The target gamma characteristic in this gamma adjustment is a standard gamma characteristic.

  Next, in STEP 702, the CPU 405 writes a standard gamma table corresponding to the standard gamma characteristic into the LUT 1 (407) in the ROM 406.

  Next, in STEP 703, the CPU 405 drives the liquid crystal panel 307 using the standard gamma table written in the LUT 1 (407) (that is, based on the standard gamma characteristic). Then, using the optical sensor 309, initial measurement for obtaining measurement data (first measurement data) regarding the actual gamma characteristic at this time is performed. The procedure for the initial measurement is the same as in Example 1 (FIG. 7).

  When the initial measurement is completed, the CPU 405 writes the initial measurement brightness acquired by the initial measurement in the measurement data memory 409 as the first measurement data in STEP 704.

  Next, in STEP 705, the CPU 405 rewrites the standard gamma table written in the LUT 1 (407) with the use gamma table corresponding to the use gamma characteristic of γ = 2.4. That is, in this embodiment, the standard gamma table is not held in the ROM 406 after the initial measurement.

  Next, in STEP 706, the CPU 405 sets the use gamma table written in the LUT 1 (407) as a gamma table used for driving the liquid crystal panel 307 after the start of use by the user. Then, the gamma adjustment is completed.

  The procedure of the gamma table correction process of this embodiment will be described. The procedure of the gamma table correction process in this embodiment is basically the same as the procedure shown in FIG. However, in this embodiment, the standard gamma table is not held in the ROM 406 after the start of user use of the liquid crystal projector. For this reason, as shown in FIG. 9, the CPU 405 uses a correction gamma table stored in the LUT 1 (407) as a correction measurement gamma table for acquiring second measurement data, which will be described later. Is set (see STEP 901 in FIG. 8).

  Then, the CPU 405 drives the liquid crystal panel 307 using the used gamma table, and measures the luminance with respect to the seven predetermined input gradations as in the initial measurement using the optical sensor 309 (see STEP902 to STEP904 and FIG. 9). ). In other words, the measurement luminance is obtained as measurement data (second measurement data) related to the actual gamma characteristic after change with time.

  Subsequently, the CPU 405 calculates a difference for each input gradation between the above-described seven measured luminances and the seven initial measured luminances stored in the measurement data memory 409 (see STEP 905 in FIG. 8).

  Then, the CPU 405 calculates a correction amount for correcting the use gamma table stored in the LUT 1 (407) in the same manner as in the first embodiment. The calculated correction amount is such that the actual gamma characteristic obtained when the liquid crystal panel 307 is driven using the used gamma table corrected with the correction amount matches the standard gamma characteristic or is used before correction. It is closer to the standard gamma characteristic than when using.

  After calculating the correction amount of the use gamma table in this way, the CPU 405 uses the correction amount to newly generate the use gamma table stored in the LUT 1 (407) in the same manner as in the first embodiment. The gamma table is rewritten (see STEP 906 in FIG. 8). Then, the CPU 405 sets the corrected use gamma table that has been rewritten and stored in the LUT 1 (407) as a new use gamma table (see STEP 907 in FIG. 8). Thus, the gamma table correction process is completed.

  Thereafter, the liquid crystal panel 307 is driven using the corrected use gamma table. As a result, a projected image is displayed with a standard gamma characteristic of γ = 2.2 or a gamma characteristic close to this, so that a change in image quality due to a change with time can be favorably corrected.

  Also in this embodiment, image display is performed in accordance with the use gamma characteristic of γ = 2.4 from the start of user use until gamma table correction is performed (however, the actual gamma characteristic changes in a direction of becoming brighter due to a change with time). . After the gamma table correction, image display according to the standard gamma characteristic of γ = 2.2 is performed. As a result, it is possible to provide an image display with a gamma characteristic that does not greatly deviate from γ = 2.2 for users who do not perform gamma table correction. Also, for users who place importance on gamma characteristics, image display at γ = 2.2 (or in the vicinity thereof) can be provided by performing gamma table correction. Therefore, a favorable image can be displayed for various users.

  In this embodiment, an area for storing the standard gamma table in the ROM 406 is not required. For this reason, the capacity required for the ROM 406 as a memory can be reduced.

  As a modification of the present embodiment, instead of the procedure for obtaining the first measurement data as the initial measurement luminance using the standard gamma table of γ = 2.2, the use gamma table of γ = 2.4 is used. You may acquire the 1st measurement data equivalent to the case where a standard gamma table is used.

For example, the luminance of 128 (8-bit) gradation in the standard gamma table with γ = 2.2 is (128/255) ^2.2 = 21.8%, and 135 with the used gamma table with γ = 2.4. This is equivalent to (135/255) ^2.4 = 21.7%, which is the luminance of (8 bit) gradation. For this reason, the luminance of 135 (8 bit) gradation in the used gamma table can be handled as equivalent to the luminance of 128 (8 bit) gradation in the standard gamma table. The first measurement data obtained in this case can be regarded as measurement data obtained by the measurement unit when the liquid crystal panel is driven based on the standard gamma characteristic.

  In each of the above embodiments, a liquid crystal panel that uses a liquid crystal panel as a display element and projects a display image on the projection surface has been described. However, the present invention can be widely applied to image display devices that include display elements other than the liquid crystal panel and whose gamma characteristics change due to changes with use. The image display apparatus includes not only a projector but also an apparatus that directly displays an image on a display element such as a monitor.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  It is possible to provide an image display device such as a liquid crystal projector that can display an image with good image quality.

201 Liquid crystal projector 307 (R, G, B) Liquid crystal display element (liquid crystal panel)
309 Optical sensor 402 Gamma correction unit 403 Liquid crystal drive unit 405 CPU 405
406 ROM

Claims (5)

A display element driven to display an image;
A drive unit capable of driving the display element based on each of a standard gamma characteristic and a use gamma characteristic different from the standard gamma characteristic;
A measurement unit that performs measurement on an actual gamma characteristic that is a gamma characteristic actually obtained by driving the display element;
Measurement that stores first measurement data acquired by the measurement unit when the display element is driven based on the standard gamma characteristic before the actual gamma characteristic changes with use of the image display device Data memory,
A control unit that drives the display element based on the use gamma characteristic when the image display device is used;
Second measurement data obtained by the measurement unit when the display element is driven based on the standard gamma characteristic or the used gamma characteristic after the actual gamma characteristic is changed with the use of the image display device. A correction unit that acquires and corrects the used gamma characteristic so that the actual gamma characteristic matches or approaches the standard gamma characteristic according to a difference between the first measurement data and the second measurement data; An image display device comprising:   When the gamma value of the actual gamma characteristic becomes smaller as the image display device is used, the gamma value of the used gamma characteristic is set larger than the gamma value of the standard gamma characteristic, and the gamma value of the actual gamma characteristic is 2. The image display device according to claim 1, wherein the gamma value of the used gamma characteristic is set smaller than the gamma value of the standard gamma characteristic when the image display device becomes larger with use of the image display device. A gamma data memory storing standard gamma data for driving the display element based on the standard gamma characteristic and use gamma data for driving the display element based on the use gamma characteristic;
The correction unit newly creates the use gamma data stored in the gamma data memory using a difference between the first measurement data and the second measurement data acquired using the standard gamma data. The image display device according to claim 1, wherein the image display device is rewritten to use gamma data. A gamma data memory storing use gamma data for driving the display element based on the use gamma characteristics;
The correction unit creates the use gamma data stored in the gamma data memory using a difference between the first measurement data and the second measurement data acquired using the use gamma data. The image display device according to claim 1, wherein the image display device is rewritten to use gamma data. Obtained by driving a display element driven to display an image, a drive unit capable of driving the display element based on a standard gamma characteristic and a use gamma characteristic different from the standard gamma characteristic, and the display element A method of controlling an image display device having a measurement unit that performs measurement on real gamma characteristics,
Before the actual gamma characteristic changes with the use of the image display device, the driving unit drives the display element based on the standard gamma characteristic to acquire first measurement data by the measurement unit When,
When the image display device is used, causing the drive unit to drive the display element based on the use gamma characteristics;
After the actual gamma characteristic changes with use of the image display device, the display unit is driven based on the standard gamma characteristic or the used gamma characteristic by the driving unit, and second measurement data is obtained by the measuring unit. Step to get the
Correcting the used gamma characteristic so that the actual gamma characteristic matches or approaches the standard gamma characteristic according to a difference between the first measurement data and the second measurement data. A control method for an image display device.