JP2000066166A - Projection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the tints of projected images according to the brightness and tints of peripheral light and to well maintain color reproducibility by forming the luminance and color information on the peripheral of the device from the peripheral light and correcting the tints of the projected image in accordance with this information. SOLUTION: An external photometer 1 detects the peripheral light of a liquid crystal projector and forms the luminance and color information on the peripheral of the liquid crystal projector from the peripheral light. This photometric signals Rm, Gm, Bm are inputted via A/D converters 2 to 4 to an image quality improvement processing section 5. This image quality improvement processing section 5 discretely corrects the inputted digital video signals R, G, B in accordance with the photometric signals Rm, Gm, Bm and outputs the corrected video signals R', G', B' to D/A converters 6 to 8. The video signals R', G', B' are converted to analog signals which are respectively inputted to drive circuits 9 to 11. These drive circuits 9 to 11 convert the inputted video signals to the levels meeting the specifications of liquid crystal panels and respectively drive the liquid crystal panels 12 to 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display in which light emitted from a liquid crystal light source is made incident on a liquid crystal light valve and a projection image emitted from an image forming surface of the liquid crystal light valve is projected on a screen. It concerns the device.

[0002]

2. Description of the Related Art A conventional liquid crystal projector (projection type liquid crystal display device) is provided with an external photometer 19 for detecting ambient light, as shown in FIG. It has a function of changing the color temperature of a projected image when the surroundings are bright and dark based on the luminance information of the ambient light. This is because, as shown in FIG. 10, the relative luminous efficiency of a human is different between a bright place and a dark place.
In FIG. 10, the relative luminous efficiency in a bright place (the luminous efficiency of photopic vision) is equivalent to V (λ), and the luminous efficiency in a dark place (the relative luminous efficiency of scotopic vision) is V ′ (λ). ). FIG.
As is clear from the above, in dark places, human visual characteristics become sensitive at short wavelengths. Conversely, in bright places, human visual characteristics become sensitive at longer wavelengths. Therefore,
The color reproducibility of the projected image can be maintained by correcting so that the color temperature of the projected image becomes higher as the periphery becomes brighter.

[0003]

However, the above-mentioned conventional liquid crystal projector does not detect the difference in the color tone of the ambient light. It has not been possible to sufficiently correct the color of a projected image where light sources of various colors are used.

[0004] In the past, liquid crystal projectors have been used with the interior darkened because the brightness of the projected image was not sufficient. However, in recent years, the projected image of the liquid crystal projector is
It has become brighter than the previous one and has become sufficiently practical under normal lighting. In fact, it is necessary to take notes during use in presentations at conferences and conferences, so that illumination light with a certain level of brightness is desired during use of the liquid crystal projector. For this reason, the influence of the illumination light on the projected image, which previously did not need to be considered, has been increasing.

As illumination light, fluorescent lamps having a relatively high color temperature are preferred in Japan, while illuminations having a relatively low color temperature are preferred in Europe and the United States. Such color temperature of the illumination light also affects the color reproducibility of the projected image.

In addition, since the human eye usually has chromatic adaptation, light adaptation, and dark adaptation, a slight change in illumination light causes
Although the appearance of colors does not change, illuminations with colors different from those normally used are often used at exhibitions and concert venues where liquid crystal projectors will be used, which deviates from white light. Under an illuminating light having a different shade, the projection image is affected, and the color reproducibility is impaired.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to correct the hue of a projected image in accordance with the brightness and hue of the ambient light to maintain color reproducibility. It is an object of the present invention to provide a projection-type liquid crystal display device that can perform the above.

[0008]

According to a first aspect of the present invention, there is provided a projection type liquid crystal display device in which light emitted from a liquid crystal light source is incident on a liquid crystal light valve. In a projection type liquid crystal display device for projecting a projection image emitted from an image forming surface of the liquid crystal light valve on a screen, detecting ambient light of the projection type liquid crystal display device;
The apparatus includes external photometric means for outputting luminance and color information around the apparatus, and image quality improving means for correcting the hue of the projected image based on the luminance and color information.

According to a second aspect of the present invention, in the projection type liquid crystal display device according to the first aspect, the image quality improving means calculates a peripheral relative color temperature from the luminance and color information. The hue of the projected image is corrected based on the relative color temperature.

According to a third aspect of the present invention, in the projection type liquid crystal display device according to the first aspect, the external light metering means collects light around the apparatus at a wide angle to weaken the light directivity. It has.

According to a fourth aspect of the present invention, there is provided the projection type liquid crystal display device according to the first or second aspect.
The image quality improving means calculates a psychometric brightness in a uniform perceived color space from the luminance and color information, and changes a degree of color correction of the projection image based on the psychometric brightness.

According to a fifth aspect of the present invention, in the projection type liquid crystal display device according to the first aspect, the image quality improving means converts the brightness and color information into a psychometric brightness and color in a uniform perceived color space. The coordinates are converted into degree coordinates, and the hue of the projected image is corrected based on the psychometric lightness and chromaticity coordinates.

According to a sixth aspect of the present invention, there is provided the projection type liquid crystal display device according to the first aspect, wherein the external light metering means has dimming means for reducing the amount of incident ambient light. is there.

According to a seventh aspect of the present invention, in the projection type liquid crystal display device according to the first aspect, the external light measuring means outputs luminance and color information around the device at a specific time interval. If the difference between the luminance and color information inputted from the external photometric means and the luminance and color information inputted immediately before the luminance and color information is larger than a first specific value, the image quality improving means makes the inputted luminance and color information The hue correction value of the projection image is updated based on the correction value. If the hue correction value is smaller than the first specific value, the correction value is not updated. If the difference between the updated luminance and color information and the input luminance and color information is larger than the second specific value, the correction value is updated based on the input luminance and color information, Less than a specific value Those that do not update the correction value if Kere.

According to an eighth aspect of the present invention, in the projection type liquid crystal display device according to the first aspect, the image quality improving means measures an accumulated use time of the liquid crystal light source,
From the cumulative use time, the current luminance of the liquid crystal light source is obtained according to the cumulative use time-luminance characteristics of the representative liquid crystal light source, and the luminance around the device is obtained from the luminance and color information. The degree of hue correction is changed based on the brightness of the surroundings of the apparatus.

According to a ninth aspect of the present invention, in the projection type liquid crystal display device according to the first aspect, the external photometric means outputs luminance and color information around the device every specific time. A FIFO for sequentially recording the luminance and color information and erasing from the oldest recorded information
The image quality improvement means calculates an average value of the luminance and color information stored in the storage means, and corrects the hue of the projection image based on the average value.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block circuit diagram showing a liquid crystal projector according to Embodiment 1 of the present invention. 1, the liquid crystal projector according to the first embodiment includes an external photometer 1, A / D converters 2, 3, 4, an image quality improvement processing unit 5, D / A converters 6 to 8, a driving circuit, 9,
10 and 11, a liquid crystal panel 12 for red image, a liquid crystal panel 13 for green image, and a liquid crystal panel 14 for blue image. The liquid crystal panels 12 to 14 constitute a red image liquid crystal light valve, a green image liquid crystal light valve, and a blue image liquid crystal light valve, respectively. Although not shown, the liquid crystal projector according to the first embodiment includes a lamp such as a metal halide or xenon lamp serving as a liquid crystal light source.
It is provided with a spectral / projection optical unit, a video signal processing unit, and the like.

The spectral / projection optical means separates the light from the lamp into red light, green light, and blue light, makes them enter the liquid crystal panels 12 to 14, respectively.
The red image, the green image, and the blue image from the image forming surface are enlarged and superimposed on the screen as a color image. The video signal processing unit converts the video signal input from the external input signal source into an A / D conversion process, a liquid crystal panel 12 to 14.
Performs various signal processing such as pixel conversion processing, menu image superimposition processing, enlargement / reduction processing, etc. according to the number of pixels, and converts the above input video signals into digital red video signals R, green video signals G, and blue video signals B. Convert.

The external photometer 1 detects ambient light of the liquid crystal projector, and generates luminance and color information around the liquid crystal projector from the ambient light. The external photometer 1 is a dedicated device having a light receiving element that splits and receives the peripheral light into a plurality of color components and receives a photometric signal Rm corresponding to a red component of the received peripheral light and a photometric signal corresponding to a green component. Gm,
And a photometric signal Bm corresponding to the blue component. The photometric signals Rm, Gm, and Bm are signals serving as luminance and color information around the device, and are input to the image improving unit 5 via A / D converters 2 to 4.

The above-mentioned light receiving element has a configuration in which a color filter is attached to, for example, a MOS type imaging device or a CCD type imaging device. The light receiving element may have a low resolution (one having a small number of pixels). Also, the photometric signals Rm, Gm,
Bm may be a signal corresponding to light obtained by integrating the color components received by each pixel of the light receiving element. Note that the external photometer 1 is provided with photometric signals Y,
It may output photometric signals X, Y, and Z corresponding to RY, BY, and XYZ color spaces. Further, in the first embodiment, the photometric signals Rm, Gm, and Bm may be color information of the received ambient light, and may indicate the ratio of each of red, green, and blue components.

The image quality improvement processing unit 5 corrects the hue of the images projected by the liquid crystal panels 12 to 14 based on the peripheral brightness and hue information output from the external photometer 1.
That is, the image quality improvement processing unit 5 outputs the photometric signals Rm, Gm, B
m, based on the input digital video signals R, G,
The gains of B are individually corrected, and the corrected video signals (video signals R ', G', B ') are output to the D / A converters 6 to 8.

Next, the operation will be described. The digital video signals R, G,
B is input to the image quality improvement processing unit 5. Also, analog photometric signals Rm, Gm, B output from the external photometer 1
m is converted into digital data by A / D converters 2 to 4 and input to image quality improvement processing unit 5.

The video signals R ', G', and B 'corrected by the image quality improvement processing unit 5 are converted into analog signals by D / A converters 6 to 8, and the driving circuit 9 drives the liquid crystal panels 12 to 14. To 11 respectively. Drive circuit 9
11 to 11 convert the input video signal to a level suitable for the specification of the liquid crystal panel, and drive the liquid crystal panels 12 to 14 with the level-converted video signal.

The image quality improvement processing section 5 converts the photometric signals Rm, Gm, Bm from the external photometer 1 into chromaticity coordinates x, y, z (x + y + z = 1) in the XYZ color space, The correlated color temperature of the device ambient light is determined from y and z, and the correction values of the video signals R, G, and B are determined according to the correlated color temperature of the device ambient light. Hereinafter, an example of the color tone correction processing by the image quality improvement processing unit 5 will be described.

First, the photometric signals Rm, G of the NTSC system
The values of X, Y, and Z in the XYZ color space are obtained from the values of m and Bm by the operations of equations (1) to (3), and the chromaticity coordinates x, Find y and z. X = 0.6969R + 0.1739G + 0.109B (1) Y = 0.2991R + 0.5870G + 0.1139B (2) Z = 0.0000R + 0.0660G + 1.1169B (3) x = X / (X + Y + Z) (4) y = Y / (X + Y + Z) (5) z = Z / (X + Y + Z) (6)

Next, the correlated color temperature of the device ambient light is determined from the chromaticity coordinates x and y. FIG. 2 shows a black body radiation locus (thick line in the figure) and an isothermal line (thin line in the figure) on the xy chromaticity diagram. The correlated color temperature is a color temperature obtained from an isothermal line assumed to be the same as the color temperature on the blackbody radiation locus. Here, for example, x = 0.15 to 0.65, y =
A correlated color temperature in the range of 0.15 to 0.50 is stored in a table, and the correlated color temperature is obtained from the chromaticity coordinates x and y using the table.

Next, based on the correlated color temperature of the ambient light of the apparatus, the video signals R,
The correction coefficients RC, GC, and BC for G and B are determined. By multiplying the video signals R, G, B by these correction coefficients RC, GC, BC, respectively, the corrected video signals R ′, G ′, B ′ are obtained.
Get. The correction is performed, for example, using the correlated color temperature of the CIE standard light C (x = 0.3101, y = 0.3163, correlated color temperature 6770 [K]), which is the reference white of the NTSC system, as the reference color temperature, and the correlated color temperature of the peripheral light of the device. Is higher than the reference color temperature (the ambient light of the device is more bluish than the reference white), the video signals R and G are set so that the correlated color temperature of the projected image is lowered (so that the projected image is reddish). , B gain is increased or decreased. Conversely, when the correlated color temperature of the device ambient light is lower than the reference white (the device ambient light is redder than the reference white), the correlated color temperature of the projected image is increased (the projected image becomes bluish). ), The gains of the video signals R, G, B are increased or decreased. Here, the correlated color temperature of the CIE standard light C is used as the reference color temperature. However, the CIE standard light D65 (x = 0.3127, y = 0.3290, correlated color temperature 6500 [K]) adopted in the high-vision system is used. A correlated color temperature may be used.

As described above, according to the first embodiment, the external photometer 1 detects the ambient light of the liquid crystal projector,
The peripheral brightness and color information is generated, and the image quality improvement processing unit 5 corrects the hue of the projected image based on the peripheral brightness and color information output from the external photometer 1, thereby obtaining the brightness around the liquid crystal projector. Also, even if the color tone changes, it is possible to maintain good color reproducibility of the projected image.

Embodiment 2 The configuration of the liquid crystal projector according to Embodiment 2 of the present invention is the same as that of FIG. However, in the liquid crystal projector of the second embodiment, the internal configuration of the external photometer 1 is different from that of the first embodiment.

If the directing direction of the external photometer is strong, it is strongly affected by the peripheral light source in a specific direction. In the second embodiment, this problem is improved.

FIG. 3 is a configuration diagram of an external photometer in the liquid crystal projector according to the second embodiment of the present invention. 3, the external photometer 1 has a lens 15 and a light receiving element 16.

The lens 15 is a wide-angle lens such as a fish-eye lens for collecting ambient light at a wide angle and weakening the light-collecting directivity of the external photometer 1. The wide-angle lens 15 is not strongly affected by a peripheral light source such as fluorescent light located in a specific direction, so that a detection error due to a mounting position can be reduced. Further, the lens 15 does not need to focus the collected ambient light on the light receiving surface of the light receiving element 16. When the defocused peripheral light is incident on the light receiving surface of the light receiving element 16, the peripheral light source such as the fluorescent light does not form an image on a specific pixel of the light receiving element 16, so that the dynamic range of the light receiving element can be effectively used. The light receiving element 16 may be the same as the light receiving element used in the external photometer of the first embodiment. Also in the second embodiment, the photometric signals Rm, Gm, and Bm output from the external photometer 1 need only be color information of the received peripheral light, and indicate the ratios of the red, green, and blue components. It may be.

As described above, according to the second embodiment, the external photometer 1 is provided with the lens 15 for weakening the directivity, so that the external light meter 1 is not strongly affected by the peripheral light source located in a specific direction. Therefore, it is possible to reduce the detection error due to the mounting position of the external photometer 1.

Embodiment 3 The configuration of the liquid crystal projector according to Embodiment 3 of the present invention is the same as that of FIG. However,
In the liquid crystal projector according to the third embodiment, the signal processing in the image quality improvement processing unit 5 is different from that in the first embodiment.

When the periphery is sufficiently dark, the influence of the ambient light on the projected image can be ignored. As the periphery becomes brighter, the influence of the ambient light on the projected image becomes stronger. When the surroundings have a certain brightness or higher, the influence of the surrounding light on the projected image becomes too strong, and the hue of the projected image cannot be corrected. In order to improve this, in the third embodiment,
Within the range of the peripheral brightness where the hue correction of the projection image is effective, the degree of the hue correction of the projection image is increased as the periphery becomes brighter.

In addition, there is a non-linear relationship between the brightness that is perceived by the human eye and the actual increase in the amount of peripheral light. Therefore, in the third embodiment, the psychometric lightness L ^* indicating the brightness sensed by human eyes is used to determine the degree of color correction of the projected image. The psychometric lightness L ^* is one parameter of the L ^* a ^* b ^* uniform perceived color space recommended by the CIE (International Commission on Illumination) in 1976, and is proportional to the 1/3 power of the amount of light. That is, according to the psychometric brightness L ^* , the brightness sensed by the human eye is proportional to the 1/3 power of the peripheral light amount.

The image quality improvement processing unit 5 corrects the hue of the projected image based on the peripheral luminance and color information output from the external photometer 1, and also calculates the peripheral psychometric brightness L based on the brightness and hue information. ^* Is calculated, and the degree of color correction of the projected image is changed based on the psychological measurement lightness L ^* . That is, the image quality improvement processing unit 5 individually corrects the gains of the video signals R, G, and B based on the R, G, and B photometric signals in the same manner as in the first embodiment. The gains of the signals R, G, and B are commonly corrected based on the psychometric brightness L ^* , and the corrected video signals (video signals R ', G', and B ') are output to the D / A converters 6 to 8. I do.

The image quality improvement processing section 5 uses the Rm, Gm, and Bm values of the photometric signal from the external photometer 1 to determine the first embodiment.
Similarly, the individual correction coefficients RC, G of the video signals R, G, B
Decide C and BC. Further, the photometric signal R, G, converts the B value in the Y values of XYZ color space, seeking psychological measurement lightness L ^* from the Y value, the image signal R according to the psychological measurement lightness L ^*, G, A common correction coefficient for B is determined. Then, the video signals R, G, B are corrected by the individual correction coefficients RC, GC, BC and the common correction coefficient. Hereinafter, an example of the color tone correction processing by the image quality improvement processing unit 5 will be described.

First, the photometric signals Rm, G of the NTSC system
The psychometric lightness L ^* is obtained from m and Bm. The photometric signals Rm, Gm, Bm of the NTSC system are converted to CIE 1976 L ^*
a ^* b ^* Parameters L ^* , a ^* , b ^{* of} uniform perceived color space
Is converted to the X, Y, and Z values of the photometric signals Rm, Gm, and Bm according to the equations (1) to (3), and the tristimulus values X0 and Y0 of the CIE standard light source C, which is a reference white in the NTSC system. ,
Z0 is used. Tristimulus values X0, Y0, Z of the standard light source C
0 is used by standardizing Y0 to 100. The tristimulus values X0, Y0, Z0 when Y0 is normalized are (7) to
Equation (9) is obtained. X0 = 98.072 (7) Y0 = 100.000 (8) Z0 = 118.225 (9) Psychological measurement lightness L ^* is the above Y and Y0 (= 100)
Is obtained by the equations (10) and (11). L ^* = 116 × (Y / Y0) ^1/3 −16: Y / Y0> 0.008856 (10) L ^* = 903.29 × (Y / Y0): Y / Y0 ≦ 0.008856 (11) The psychometric lightness lightness L ^* Is input Rm, Gm, Bm
May be obtained by a three-dimensional table of the output L ^* with respect to and a linear approximation.

Next, a common correction coefficient VC is obtained using the psychometric lightness L ^* and specific values L1 and L2 (> L1) set in advance. Psychological measurement lightness L ^* is a specific value L
In the case between 1 and L2, the common correction coefficient VC is increased according to the magnitude of the psychological measurement L ^* . That is, VC = (L ^* -L1) / L1. When the psychological measurement lightness L ^* is smaller than the specific value L1, it is determined that the periphery is sufficiently dark, and the hue correction processing is not performed. That is, for the common correction coefficient VC and the individual correction coefficients RC, GC, and BC, VC = RC = GC = BC = 1. If the psychological measurement lightness L ^* is larger than the specific value L2, it is determined that the surroundings are too bright, and the common correction coefficient VC is determined using the peripheral psychometric lightness L ^* as the specific value L2. That is, VC = (L2−L1) / L1.

Next, the above-mentioned common coefficient VC and the individual correction coefficients RC, GC, B obtained in the same manner as in the first embodiment.
The video signals R, G, and B are corrected using C and C. The corrected video signals R ′, G ′, and B ′ are given by equations (12) to (14).
Is obtained. R ′ = R × RC × VC (12) G ′ = G × GC × VC (13) B ′ = B × BC × VC (14) As described above, according to the third embodiment, the image quality improvement processing unit 5 From the peripheral luminance and color information output from the external photometer 1, a psychometric brightness corresponding to the human visual characteristic is calculated, and the degree of color correction of the projection signal is changed based on the psychometric brightness. As a result, it is possible to realize color correction suitable for human visual characteristics.

Embodiment 4 The configuration of the liquid crystal projector according to Embodiment 4 of the present invention is the same as that of FIG. However, in the liquid crystal projector according to the fourth embodiment, the signal processing in the image quality improvement processing unit 5 is different from that in the first embodiment.

The generally used RGB color space and XYZ color space are non-linear color spaces for human visual characteristics, and the change amounts of R, G, B and the change amounts of X, Y, Z are as follows. Does not match the amount of change in human psychological brightness and hue. If the hue of the projected image is corrected in such a non-linear color space, the error increases. In order to improve this, in the fourth embodiment, the hue of the projected image is corrected in the uniform perceived color space indicating the brightness and hue perceived by human eyes. CIE1976 for the uniform perceived color space
L ^* a ^* b ^* uniform perceived color space and CIE 1976 L ^*
There is a u ^* v ^* uniform perceived color space, but here L ^* a ^*
b ^{* Use} uniform perceived color space.

The image quality improvement processing unit 5 converts the peripheral luminance and color information output from the external photometer 1 into L ^* a ^* b ^* psychological measurement lightness L ^* and color coordinates a ^* , b ^* in the uniform perceived color space. After the conversion, the hue of the projected image is corrected based on the L ^* , a ^* , and b ^* . In other words, the image quality improvement processing unit 5 determines the video signals R and R based on the color coordinates a ^* and b ^* in the uniform perceived color space.
The gains of G and B are individually corrected, and the gains of the video signals R, G and B whose gains have been individually corrected are used as the psychometric brightness L ^*.
, And outputs the corrected video signals (video signals R ′, G ′, B ′) to the D / A converters 6 to 8.

The image quality improvement processing unit 5 converts the photometric signals Rm, Gm, and Bm of the external photometer 1 into psychometric lightness L ^* and color coordinates a ^* , b ^* in a uniform perceived color space, and converts the color coordinates a ^*. , B ^* , the individual correction coefficients RC, GC, and BC are determined, and the psychometric brightness L ^* is determined in the same manner as in the third embodiment ^.
The common correction coefficient VC is determined according to Then, the video signals R, G, and B are corrected by the individual correction coefficients RC, GC, and BC and the common correction coefficient VC. Hereinafter, an example of the color tone correction processing by the image quality improvement processing unit 5 will be described.

First, the photometric signals Rm, G of the NTSC system
m and Bm are converted into a psychometric lightness L ^* and color coordinates a ^* and b ^* in a uniform perceived color space. As described in the third embodiment, the photometric signals Rm, Gm, and Bm of the NTSC system are used.
Is converted into L ^* , a ^* , b ^* of the uniform perceived color space by using the photometric signals Rm, Gm,
X, Y, and Z values of Bm, and N by the above equations (7) to (9)
The tristimulus values X0, Y0, and Z0 of the CIE standard light source C, which is the reference white color of the TSC system, are used. The psychometric lightness L ^* is
Calculated from the above equations (10) and (11), and a ^* , b
^* Is calculated from Expressions (15) to (22). a ^* = 500 × (X′−Y ′) (15) b ^* = 200 × (Y′−Z ′) (16) X ′ = (X / X0) ^1/3 : X / X0> 0.008856 (17) X ′ = 7.787 × (X / X0) +16/116: X / X0 ≦ 0.008856 (18) Y ′ = (Y / Y0) ^1/3 : Y / Y0> 0.008856 (19) Y ′ = 7.787 × (Y / Y0) +16/116: Y / Y0 ≦ 0.008856 (20) Z ′ = (Z / Z0) ^1/3 : Z / Z0> 0.008856 (21) Z ′ = 7.787 × (Z / Z0) +16/116: Z / Z0 ≤ 0.008856 (22)

Next, the color coordinates a ^* and b ^{* in the} uniform perceived color space
The individual correction coefficients RC, GC, and BC are determined based on FIG. 4 shows C in the CIE 1976 L ^* a ^* b ^* uniform perceived color space.
^* b ^* Isochromaticity and isochromaticity curves of the Munsell display system on the chromaticity diagram. In FIG. 4, a case where a ^* and b ^* = 0 is achromatic. In FIG. 4, Y is yellow, P is purple, and Munsell value (brightness) V is 5. Here, for example, a ^* = − 100 to 100, b ^* = − 100
By inputting a ^* and b ^* into a table with the range of ~ 100, the individual correction coefficients RC, GC,
Output BC.

Next, the individual correction coefficients RC, GC, B
The video signals R, G, and B are corrected by the equations (12) to (14) using C and the common correction coefficient VC obtained in the same manner as in the third embodiment based on the psychological measurement lightness L ^*. I do.

Here, the above equations (7) to (11), (1)
Since the calculations of 5) to (22) are not easy, when displaying a moving image in real time, the chromaticity coordinates a ^* and b ^* are calculated for each pixel, and the correction coefficients RC, GC, and BC are obtained. It is difficult. To achieve this, a high-speed arithmetic unit is required, which is not practical.

Therefore, the photometric signals Rm, Gm, B of the ambient light
The color correction is performed using a three-dimensional table that receives m as an input and outputs individual correction coefficients RC, GC, and BC. A method of using a three-dimensional table having outputs for all inputs and directly obtaining outputs for all inputs from the three-dimensional table is called a direct mapping method, which can realize high-precision correction at high speed, but has a large memory capacity. Requires
Not practical. Therefore, a three-dimensional table composed only of the upper signal of the input signal is used, and for the correction value that cannot be obtained directly from the three-dimensional table, several neighboring values are obtained by the direct mapping method using the upper signal of the input signal. In general, a method of interpolating (linearly approximating) an output signal from several neighboring values using a lower signal of an input signal is generally used. Processing for calculating RC, GC, and BC by the direct mapping method and the interpolation method of the neighboring values will be described below.

First, the direct mapping method of neighboring values will be described. As shown in FIG. 5, the input signals Ri, G
i and Bi are m-bit signals, respectively, and input signals Ri, Gi,
The upper n bits of Bi are Rn, Gn, and Bn, respectively.
Here, m> n. Input signal R from 3D table
A unit cubic lattice (Rn, Gn) of eight points near i, Gi, Bi
n, Bn), (Rn + Dn, Gn, Bn), (Rn + D
n, Gn, Bn + Dn), (Rn, Gn, Bn + D
n), (Rn, Gn + Dn, Bn), (Rn + Dn, G
n + Dn, Bn), (Rn + Dn, Gn + Dn, Bn +
Dn), output signals d0, d1, d2, d3, d4, d5, d6 located at (Rn, Gn + Dn, Bn + Dn).
d7 is obtained. Dn is 1 of the unit cubic lattice of the three-dimensional table
The side length is 2 ^mn .

Next, the interpolation method will be described. As shown in FIG. 6, the output signals located on the unit cubic lattice of eight points near the input signals Ri, Gi, Bi are d0, d1, d2, d.
3, d4, d5, d6, d7, input signals Ri, Gi, B
The lower mn bits of i are r, g, b, respectively, and the length of one side of the unit cubic lattice is Dn. Input signals Ri, Gi, B
d0, d1, d2, d3, d4, d around i
5, d6, d7, and R-axis direction, G-axis direction,
The volume of a rectangular parallelepiped divided into eight in three directions along the B axis is represented by w
0, w1, w2, w3, w4, w5, w6, w7. The output signal d for the input signals Ri, Gi, Bi is:
The interpolation is performed as in the equations (23) to (31). d = d0w0 + d1w1 + d2w2 + d3w3 + d4w4 + d5w5 + d6w6 + d7w7 (23) w0 = (Dn-r) (Dn-g) (Dn-b) (24) w1 = r (Dn-g) (Dn-b) (25) w2 = r (Dn-g) b (26) w3 = (Dn-r) (Dn-g) b (27) w4 = (Dn-r) g (Dn-b) (28) w5 = rg (Dn-b) (29) w6 = rgb (30) w7 = (Dn−r) gb (31) Here, the case where there is one output signal has been described. In the fourth embodiment, approximate values of RC, GC, and BC are simultaneously obtained from the three-dimensional table. And interpolate at the same time.

As described above, according to the fourth embodiment, the image quality improvement processing unit 5 converts the peripheral luminance and color information output from the external photometer 1 into a psychologically equivalent color space that matches human visual characteristics. Since the degree of color correction of the projection signal is changed based on the measured brightness and the color coordinates based on the psychometric brightness and the color coordinates, it is possible to realize color correction suitable for human visual characteristics. .

Embodiment 5 FIG. The configuration of the liquid crystal projector according to Embodiment 5 of the present invention is the same as that of FIG. However, in the liquid crystal projector of the fifth embodiment, the internal configuration of the external photometer 1 is different from that of the first embodiment.

When the periphery becomes darker than a certain extent, it is almost unnecessary to consider the influence of the ambient light on the projected image. For this reason, when the periphery is darker than a certain degree, it is not necessary to correct the color of the video signal based on the luminance and color information of the periphery from the external photometer 1, and therefore the luminance and color information from the external photometer 1 is unnecessary. Becomes In consideration of this, in the fifth embodiment, the dynamic range of the light receiving element constituting the external photometer can be effectively used.

FIG. 7 is a configuration diagram of an external photometer in the liquid crystal projector according to the fifth embodiment of the present invention. In FIG. 3, the external photometer 1 includes a lens 15, a light receiving element 16,
And an ND filter 17.

The ND filter 17 narrows down the amount of peripheral light collected by the lens 15 and causes the light to enter the light receiving element 16.
Thereby, when the periphery is sufficiently dark and color correction is unnecessary (for example, when the psychological measurement brightness L ^* is smaller than the specific value L1 in the third embodiment), almost all of the collected light is transmitted to the light receiving element 16. In the case where color correction is necessary for most of the dynamic range of the light receiving element 16 (for example, the psychological measurement lightness L ^* is set to the specific value L in the third embodiment).
(When it is larger than 1). In addition,
The lens 15 may be the same as the lens used in the external photometer of the second embodiment. Alternatively, the lens 15 need not be provided. Further, the light receiving element 16 may be the same as the light receiving element used in the external photometer of the first embodiment.

As described above, according to the fifth embodiment, the ND filter 17 for reducing the amount of incident light is provided in the external photometer 1, so that the light receiving element 1 constituting the external photometer 1 is provided.
6 can be effectively used.

Embodiment 6 FIG. The configuration of the liquid crystal projector according to Embodiment 6 of the present invention is the same as that of FIG. However, in the liquid crystal projector according to the sixth embodiment, the signal processing in the external photometer 1 and the image quality improvement processing unit 5 is different from that in the first embodiment.

When the hue correction value of the projected image fluctuates in response to a small fluctuation (flicker) of the surrounding illumination light,
The projected image flickers, making it difficult for the user to see. In the sixth embodiment, this problem is improved.

The external photometer 1 converts the photometric signal to a specific time Δt.
Output every time. If the difference between the photometric signal input at time t and the photometric signal input before Δt is greater than the specific value Dth, the image quality improvement processing unit 5 determines the difference based on the photometric signal input at time t. To update the correction coefficient, and
If it is smaller than th, the correction coefficient is not updated. Also,
The image quality improvement processing unit 5 determines that the color correction processing without updating the correction coefficient continues n (for example, n = 10) times or more.
If the difference between the photometric signal when the correction coefficient is finally updated and the photometric signal input at time t is greater than the specific value Dth ′, the correction coefficient is updated based on the photometric signal input at time t. , The correction coefficient is not updated.

The photometric signal R output from the external photometer 1
One of m, Gm, and Bm is defined as Dm. Time t
The photometric signals Rm, Gm, Bm, Dm output to
(T), Gm (t), Bm (t), and Dm (t).
The correction coefficients for the periods corresponding to the photometric signals Rm (t), Gm (t), and Bm (t) are RA (t), GA (t), and B (t).
Let A (t). Here, the correction coefficients RA, GA, BA
Are, for example, the correction coefficients RC, GC, and B of the first embodiment.
C or the correction coefficient RC × VC, G of the third embodiment.
C × VC and BC × VC. The correction coefficient RA
Video signals to be corrected in tone by (t), GA (t) and BA (t) are R (t), G (t) and B (t).

In the image quality improvement processing section 5, the photometric signal Rm (t
−Δt), Gm (t−Δt) and Bm (t−Δt) are stored, and the photometric signals Rm (t), Gm (t) and Bm
When (t) is input, first, the absolute value | Dm (t) -D of the difference between the photometric signal Dm (t) and the photometric signal Dm (t−Δt).
m (t−Δt) | is calculated.

Next, the above-mentioned | Dm (t) -Dm (t-Δ
t) | is compared with a specific value Dth, and | Dm (t) -Dm (t
−Δt) | satisfies | Dm (t) −Dm (t−Δt) |> Dth (32) (if any of the photometric signals Rm, Gm, and Bm satisfies the expression (32)), Correction coefficient RA (t), G
A (t) and BA (t) are converted to photometric signals Rm (t) and Gm
(T) and Bm (t).
Video signals R (t), G (t), and B (t) are obtained by using correction coefficients RA (t), GA (t), and BA (t) updated based on m (t), Gm (t), and Bm (t). t) is corrected for hue.

| Dm (t) −Dm (t−Δt) |
Does not satisfy the expression (32) (the photometric signals Rm, G
m and Bm do not satisfy the above equation (32)), the correction coefficients RA (t−Δt), GA (t−Δt), and the correction coefficients RA (t), GA (t) and BA (t). B
A (t−Δt) and the previous correction coefficient RA (t−Δt)
The video signals R (t), G (t), and B (t) are color-corrected by t), GA (t−Δt), and BA (t−Δt).

The image quality improvement processing unit 5 determines that the tone correction processing in which the correction coefficient is not updated is repeated n times (however, it is assumed that the processing at the time t has been completed up to the determination by the equation (32)). Finally, the updated correction coefficients are the photometric signals Rm (t−nΔt), Gm (t−nΔt), Bm
RA (t−nΔt) updated based on (t−nΔt)
If t), GA (t−nΔt), BA (t−nΔt), the processing described below is added to the processing at time t.

In the image quality improvement processing section 5, the photometric signal Rm (t
−nΔt), Gm (t−nΔt), Bm (t−nΔt)
Is stored, and when it is determined that the correction coefficient is not updated according to the equation (32), the absolute value | Dm (t) of the difference between the photometric signal Dm (t) and the photometric signal Dm (t−nΔt)
−Dm (t−nΔt) | is calculated.

Next, the above-mentioned | Dm (t) -Dm (t-n
Δt) | is compared with a specific value Dth ′, and | Dm (t) −Dm
If (t−nΔt) | satisfies | Dm (t) −Dm (t−nΔt) |> Dth ′ (33), (any one of the photometric signals Rm, Gm, and Bm satisfies the expression (33). B), correction coefficient RA (t), G
A (t) and BA (t) are converted to photometric signals Rm (t) and Gm
(T) and Bm (t).
Video signals R (t), G (t), and B (t) are obtained by using correction coefficients RA (t), GA (t), and BA (t) updated based on m (t), Gm (t), and Bm (t). t) is corrected for hue. If | Dm (t) −Dm (t−nΔt) | does not satisfy the above expression (33) (the photometric signals Rm, Gm, B
m does not satisfy the above equation (33)), the correction coefficients RA (t−nΔt), GA (t−nΔt), BA (t) as the correction coefficients RA (t), GA (t) and BA (t). t
−nΔt) and the last updated correction coefficient RA (t
− (N + 1) Δt), GA (t−nΔt), BA (t−
nΔt), video signals R (t), G (t), B (t)
Color correction.

Here, the correction coefficients RA (t), GA
When (t) and BA (t) are updated, the hue correction processing at the time t + Δt is processing of only the equation (32). Further, correction coefficients RA (t), GA (t), BA
If (t) is not updated, the processing of the above equation (33) is added also in the processing at time t + Δt.

As described above, according to the sixth embodiment, in the image quality improvement processing unit 5, the difference between the photometric signal input from the external photometer 1 and the photometric signal input immediately before it is smaller than the specific value Dth. If the correction coefficient is not small, the correction coefficient is not updated.
If the difference between the input photometric signal and the photometric signal when the correction coefficient was last updated is larger than the specific value Dth ', the correction coefficient is updated, so that a small fluctuation (flickering) of the surrounding illumination light is obtained. The correction value does not fluctuate in response to excessive sensitivity, and flickering of the projected image can be suppressed.

Embodiment 7 FIG. The configuration of the liquid crystal projector according to Embodiment 7 of the present invention is the same as that of FIG. However, in the liquid crystal projector according to the seventh embodiment, the signal processing in the image quality improvement processing unit 5 is different from that in the first embodiment.

The lamp which is the light source for the liquid crystal has a life.
Since the life of the components constituting the liquid crystal projector is short, the lamp is generally replaceable. Further, the brightness of the lamp changes remarkably with time, especially during a few hundred hours from the start of use, and then drops slowly.

The brightness of the projected image naturally depends on the brightness of the lamp which is the light source for the liquid crystal. As the brightness of the lamp becomes darker, the ratio of the brightness of the projected image to the brightness of the surroundings changes. In order to compensate for the high-precision color correction even for the change in the brightness of the projected image, it is necessary to detect the brightness of the lamp. Methods for detecting the brightness of the lamp include a method of adding a photometer and a method of causing an external photometer to detect the brightness of the lamp by some method. However, the former involves an increase in cost. In the latter case, it is impossible to detect the brightness of the surrounding area and the brightness of the lamp at the same time with one external photometer. If light is to be shielded, the user's hand will be bothered.

In the seventh embodiment, a high-precision color correction according to the brightness of the lamp is realized by obtaining the brightness of the lamp based on the cumulative use time of the lamp.

The image quality improvement processing unit 5 measures the cumulative use time of the lamp, obtains the current brightness of the lamp from the cumulative use time in accordance with the cumulative use time-luminance characteristic of the representative lamp, and furthermore, measures the photometric signal Rm, The peripheral brightness is obtained from Gm and Bm, and the degree of color correction is changed based on the brightness of the lamp and the peripheral brightness. In order to measure the cumulative use time of the lamp, for example, a clock or a counter that counts a clock used for other processing is used.

The image quality improvement processing unit 5 first obtains the current lamp brightness from the measured cumulative use time of the lamp.
Also, the photometric signals Rm, G input from the external photometer 1
The surrounding brightness is obtained from m and Bm. Here, the psychometric brightness is used for the brightness of the lamp and the brightness of the surroundings.
In addition, as the brightness of the lamp, the ratio k of the psychometric brightness of the current lamp to the psychometric brightness of the lamp at the start of use, k
Ask for. In addition, a table of the cumulative use time-psychological measurement lightness ratio characteristic of a representative lamp is used, and the psychological measurement lightness ratio k of the current lamp is obtained using this table. For example, if the psychometric brightness at the start of use of a typical lamp is 100% and the psychometric brightness after 100 hours of use is 90%, enter 100 hours as the cumulative use time in the above table. Then, the psychometric lightness ratio k
Is 0.9.

Next, the psychological measurement lightness ratio k and the individual correction coefficients RC, GC, and BC obtained in the same manner as in the third embodiment.
And the common correction coefficient VC calculated from the surrounding psychometric brightness in the same manner as in the third embodiment,
G and B are corrected. The corrected video signals R ', G', B '
Are as shown in equations (34) to (36). R '= R * RC * VC / k (34) G' = G * GC * VC / k (35) B '= B * BC * VC / k (36)

As described above, according to the seventh embodiment, the image quality improvement processing section 5 measures the cumulative use time of the lamp,
From this cumulative usage time, the cumulative usage time of a typical lamp-
The current luminance of the lamp is obtained according to the luminance characteristics, the peripheral luminance is obtained from the luminance and color information, and the degree of the tint correction is changed based on the luminance of the lamp and the peripheral luminance. Color correction with high accuracy.

Embodiment 8 FIG. FIG. 8 is a block circuit diagram showing a liquid crystal projector according to Embodiment 8 of the present invention. 8, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and reference numeral 18 denotes a memory.

When the color correction is performed in response to the instantaneous fluctuation of the surrounding illumination light, or when the light receiving section of the external photometer 1 is momentarily blocked by the movement of the listener or the performer. If the color correction is performed too sensitively, the projected image will flicker. In the eighth embodiment, these problems are improved.

The external photometer 1 converts the photometric signal to a specific time Δt
Output every time. The memory 18 has a FIFO (First In F
irst Out) type, in which the photometric signals Rm, Gm, Bm output from the external photometer 1 are sequentially stored, and sequentially deleted from the oldest recorded photometric signal. Image quality improvement processing unit 5
Calculates the average value of the photometric signals stored in the memory 18 and corrects the hue of the projected image based on the average value.

Assuming that the number of photometric signals that can be recorded in the memory 18 is 3N, the photometric signals Rm, Gm and Bm are N
Recorded individually. When the photometering signals Rm (t), Gm (t), and Bm (t) are output from the external photometer 1 at time t and transferred from the image quality improvement processing unit 5 to the memory 18, the memory 1
8 is a photometric signal Rm (t−NΔt) to Rm (t), Gm
(T−NΔt) to Gm (t), Bm (t−NΔt) to B
m (t) is stored.

The image quality improvement processing unit 5 sends all the photometric signals Rm (t−NΔt) to Rm (t), Gm (t
−NΔt) to Gm (t), Bm (t−NΔt) to Bm
(T) is read out, and as shown in equations (37) to (39), the average value R of the respective photometric signals Rm, Gm, and Bm is obtained.
AVE, GAVE, BAVE are calculated, and these RAVE, GAV
Perform color correction using E and BAVE. RAVE = ΣRi / N: (i = 1, 2,... N) (37) GAVE = ΣGi / N: (i = 1, 2,... N) (38) BAVE = ΣBi / N: (i = 1, 2,. (39) Note that, after the lamp is turned on, the memory 1 is used until NΔt elapses.
8 does not store the photometric signals Rm, Gm, and Bm, so that no color correction is performed. Generally, since it takes a little time for the lamp to become sufficiently bright from the start of lighting, there is no practical problem even if color correction is not performed during this time.

As described above, according to the eighth embodiment, the luminance and color information output from the external photometer 1 at specific time intervals are sequentially recorded in the FIFO type memory 18, and the image quality improvement processing unit 5 stores the luminance and color information in the memory 18. Calculates the average value of the luminance and color information stored in the memory and corrects the hue of the projected image based on this average value. The hue correction value does not fluctuate in response to the interruption of the incident light to the photometric means, and it is possible to suppress flickering of the projected image.

In the first to eighth embodiments, an example of a three-panel type using three liquid crystal panels 12 to 14 has been described, but a single-panel type with one liquid crystal panel may be used.

[0086]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, the external light meter detects the peripheral light of the projection type liquid crystal display device, and generates luminance and color information around the device. By correcting the hue of the projected image based on the output luminance and color information, it is possible to maintain good color reproducibility of the projected image even when the brightness and the hue around the device change. .

According to the second aspect of the present invention, the image quality improvement processing means calculates a relative color temperature from the luminance and color information around the device output from the external photometry means, and calculates the relative color temperature based on the relative color temperature. By correcting the hue, there is an effect that the color reproducibility of the projected image can be kept good even when the brightness and the hue around the device change.

According to the third aspect of the present invention, the external light metering means is provided with a light collecting means for collecting the peripheral light of the apparatus at a wide angle and weakening the light directivity, thereby increasing the influence of the peripheral light source located in a specific direction. So that you can
There is an effect that it is possible to reduce a detection error due to a mounting position of the external photometric means.

According to the fourth aspect of the present invention, the image quality improvement processing means calculates a psychometric brightness corresponding to human visual characteristics from luminance and color information around the device output from an external photometer, and calculates the psychometric brightness. By changing the degree of color correction of the projected image based on the measured lightness, there is an effect that it is possible to realize color correction suitable for human visual characteristics.

According to the fifth aspect of the present invention, in the image quality improvement processing means, the luminance and color information around the device output from the external photometer are converted into the psychometric lightness and brightness of a uniform perceived color space that matches the human visual characteristics. By converting to color coordinates and correcting the hue of the projected image based on the psychometric lightness and chromaticity coordinates, there is an effect that it is possible to realize color correction suitable for human visual characteristics.

According to the sixth aspect of the present invention, since the external photometric means is provided with the dimming means for reducing the amount of incident light, the dynamic range of the light receiving means constituting the external photometric means can be effectively used. There is a possible effect.

According to the seventh aspect of the present invention, in the image quality improving means, the difference between the luminance and color information inputted from the external photometric means and the luminance and color information inputted immediately before the first specific value. If the correction value is smaller, the correction value is not updated, and the correction value is not updated.If the hue correction is continued for a specific number of times or more, the input luminance and color information and the luminance and color information obtained when the correction value was last updated are compared. If the difference is smaller than the second specific value, the correction value is not updated, so that the color correction value does not fluctuate in response to a small change in the ambient light, thereby suppressing flickering of the projected image. This has the effect that it becomes possible.

According to the eighth aspect of the present invention, in the image quality improving means, the cumulative use time of the liquid crystal light source is measured, and based on the cumulative use time, the cumulative use time-luminance characteristic of the typical liquid crystal light source is used. Of the brightness of the liquid crystal light source by calculating the current brightness of the liquid crystal light source and the brightness around the device from the brightness and color information, and changing the degree of the tint correction based on the brightness of the liquid crystal light source and the brightness around the device. There is an effect that high-precision color correction for a change over time can be performed.

According to the ninth aspect of the present invention, the luminance and color information output from the external light
It is sequentially recorded in the O-type storage means, and in the image quality improvement means,
The average value of the luminance and color information stored in the storage means is calculated, and the hue of the projected image is corrected based on the average value. In addition, the hue correction value does not fluctuate in response to the interruption of the incident light with respect to the external photometric means, and the flickering of the projected image can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of a liquid crystal projector according to a first embodiment.

FIG. 2 is a diagram showing a black body radiation locus and isothermal lines on an xy chromaticity diagram.

FIG. 3 is a configuration diagram of an external photometer according to a second embodiment.

FIG. 4 is a diagram showing iso-hue and iso-saturation curves of the Munsell color system on the a ^* b ^* chromaticity diagram of the CIE 1976 L ^* a ^* b ^* uniform perceived color space.

FIG. 5 is a diagram showing an interpolation method using a three-dimensional table.

FIG. 6 is a diagram showing an interpolation method using a three-dimensional table.

FIG. 7 is a configuration diagram of an external photometer according to a fifth embodiment.

FIG. 8 is a block circuit diagram of a liquid crystal projector according to an eighth embodiment.

FIG. 9 is a perspective view of a conventional liquid crystal projector.

FIG. 10 is a view showing a standard relative luminous efficiency curve in photopic vision and scotopic vision.

[Explanation of symbols]

1 external photometer, 5 image quality improvement processing section, 9-11
Drive circuit, 12-14 liquid crystal panel, 15 lens, 16 light receiving element, 17 ND filter, 18
memory.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G020 AA08 DA02 DA04 DA05 DA13 DA35 DA65 2G066 AC07 BA11 BC02 BC07 BC09 BC11 BC21 CB01 2H088 EA14 EA15 HA06 HA24 MA05 5C006 AA01 AA16 AA22 AF13 AF46 AF51 AF53 AF63 AF11 AF83 AF85BB09 BF14 BF21 EA01 EC11 FA18 FA23 FA56

Claims (9)

[Claims] 1. A projection-type liquid crystal display device for causing light emitted from a liquid crystal light source to enter a liquid crystal light valve and projecting a projection image emitted from an image forming surface of the liquid crystal light valve onto a screen. An external photometric unit that detects ambient light of the display device and generates luminance and color information around the device from the ambient light; and an image quality improving unit that corrects the hue of the projected image based on the luminance and color information. A projection type liquid crystal display device. 2. The image quality improving unit calculates a peripheral relative color temperature from the luminance and color information, and corrects a color tone of the projection image based on the relative color temperature. Projection type liquid crystal display device. 3. The projection type liquid crystal display device according to claim 1, wherein said external light metering means has a light collecting means for collecting ambient light of the device at a wide angle and weakening the light directivity. 4. The image quality improving means calculates a psychometric brightness in a uniform perceived color space from the luminance and the color information, and changes a degree of hue correction of the projected image based on the psychometric brightness. The projection type liquid crystal display device according to claim 1 or 2, wherein 5. The image quality improving means converts the luminance and color information into psychometric lightness and chromaticity coordinates in a uniform perceived color space, and calculates the hue of the projected image based on the psychological lightness and chromaticity coordinates. 2. The projection type liquid crystal display device according to claim 1, wherein the correction is performed. 6. The projection type liquid crystal display device according to claim 1, wherein said external light metering means includes a light reducing means for reducing the amount of incident ambient light of the apparatus. 7. The external light metering means outputs luminance and color information around the apparatus at a specific time interval, and the image quality improving means receives the luminance and color information input from the external light metering means and immediately before the information. If the difference between the brightness and the color information is larger than the first specific value, the hue correction value of the projected image is updated based on the input brightness and color information, and if the difference is smaller than the first specific value, the correction is made. If the hue correction without updating the correction value and without updating the correction value continues more than a specified number of times, the difference between the luminance and color information when the correction value was last updated and the input luminance and color information ,
2. The projection type liquid crystal according to claim 1, wherein the correction value is updated based on the input luminance and color information if the value is larger than the second specific value, and the correction value is not updated if the value is smaller than the second specific value. Display device. 8. The image quality improving means measures the cumulative use time of the liquid crystal light source, and calculates the current luminance of the liquid crystal light source according to the cumulative use time-luminance characteristic of a representative liquid crystal light source from the cumulative use time. 2. The method according to claim 1, further comprising: obtaining a luminance around the device from the luminance and the color information; and changing a degree of tint correction based on the luminance of the liquid crystal light source and the luminance around the device. Projection type liquid crystal display device. 9. An FIFO type wherein said external photometric means outputs luminance and color information around the device at a specific time interval, and sequentially records said luminance and color information and deletes from the oldest recorded information. Wherein the image quality improving means calculates an average value of the luminance and color information stored in the storage means, and corrects the hue of the projected image based on the average value. The projection type liquid crystal display device according to claim 1.