JPH0950042A - Liquid crystal color display device and method for adjusting its gradation characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the variations in the light intensity of respective images of red light, green light and blue light in the color display images of a projection type liquid crystal color display device. SOLUTION: The driving frequencies of the driving voltages impressed on respective liquid crystal light valves 12r, 12g, 12b are respectively adjusted by variable frequency oscillation circuits 20r, 20g, 20b in accordance with the relations between the signal voltages inputted from respective image signal generating circuits 17r, 17g, 17b to respective liquid crystal panels 11r, 11g, 11b and the luminance of the respective images of the red light, green light and blue light measured by a luminance meter 25 and a luminance measuring instrument 26 in such a manner that the writing light intensity-output light intensity characteristics of the respective liquid crystal light valves 12r, 12g, 12b nearly coincide with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal color display device and a method of adjusting gradation characteristics thereof, and more particularly to a projection type liquid crystal color display device and a method of adjusting gradation characteristics thereof.

[0002]

2. Description of the Related Art Conventional projection liquid crystal color display devices include
Some have a transmissive liquid crystal light valve, and some have a reflective optical writing liquid crystal light valve.

FIG. 6 shows a transmissive liquid crystal light valve 42r.
It is a block diagram which shows schematically the conventional projection type liquid crystal color display device 49 provided with 42g * 42b.

Liquid crystal light valves 42r, 42g, 42
b modulates the emitted light and transmits it to form an image to be projected. Further, each of the liquid crystal light valves 42r, 42g, 42b is arranged in a matrix on a pair of transparent substrates enclosing a pair of transparent substrates that enclose a liquid crystal whose light transmittance changes according to the applied voltage. It has a pixel electrode for applying a voltage to the liquid crystal and a TFT (thin film transistor) as a switching element for switching a signal voltage applied to each of the pixel electrodes.

In addition to the liquid crystal light valves 42r, 42g and 42b, the projection type liquid crystal color display device 49 includes a light source 40.
And multiple dichroic mirrors 41r, 41g, 41
It is provided with b, 43r, 43g, 43b and a projection lens 44.

The light source 40 emits white light. The dichroic mirror 41g reflects red light (hereinafter abbreviated as “R”) and blue light (hereinafter abbreviated as “B”) of the white light emitted from the light source 40, and dichroic mirrors are respectively reflected. The light is guided to 41r and the dichroic mirror 41b, and at the same time, the green light (hereinafter abbreviated as “G”) is transmitted to irradiate the liquid crystal light valve 42g. The dichroic mirrors 41r and 41b respectively reflect R and B and irradiate the liquid crystal light valves 42r and 42b.

Liquid crystal light valves 42r, 42g, 42b
The respective R, G, and B radiated on the liquid crystal light are changed in accordance with the R, G, B image signals by changing the optical characteristics of the liquid crystal according to the signal voltage of the image signal applied to each pixel electrode. Permeate through the valves 42r, 42g, 42b. These transmitted lights are combined as R, G, B images by the dichroic mirrors 43r, 43g, 43b, enlarged by the projection lens 44, and projected on the screen 45. In this way, the projection liquid crystal color display device 49 performs color display.

By the way, in the projection type liquid crystal color display device having the transmissive liquid crystal light valve, the voltage-transmittance characteristics of the liquid crystal light valve are different for the R, G and B liquid crystal light valves, and as a result, in the display image. R ・ G ・ B
The light intensity can be uneven.

Therefore, for example, Japanese Patent Laid-Open No. 5-127620
As disclosed in the publication, white balance adjustment is performed by performing amplitude conversion of the R, G, and B image signals sent to each liquid crystal light valve and performing γ correction to improve image quality. .

In addition, as described above, the transmissive liquid crystal light valve has the switching element formed in each pixel, which restricts the high aperture ratio of the pixel.
There is a problem that the high brightness of the display image cannot be sufficiently achieved.

On the other hand, in the reflection type photo-writing type liquid crystal light valve, it is not necessary to provide a switching element in each pixel, so that it is possible to realize high brightness of a display image. Therefore, next, a conventional projection type liquid crystal display device including a reflection type optical writing type liquid crystal light valve will be described with reference to FIGS.

FIG. 7 is a sectional view schematically showing the structure of a liquid crystal light valve 51 of the optical writing type. The liquid crystal light valve 51 has a pair of translucent substrates 60a and 60b on both sides. A transparent electrode 61 is formed on one of the substrates 60a.
a is formed. A photoconductor layer 62, a light shielding layer 63, and a dielectric mirror 64 are sequentially stacked on the transparent electrode 61a, and an alignment film 65a is formed on the dielectric mirror 64. A transparent electrode 61b and an alignment film 65b are formed on the other substrate 60b. The liquid crystal light valve 51 is formed by adhering the two substrates 60a and 60b via the spacer 67 so that the alignment films 65a and 65b are inside, respectively. A liquid crystal layer 66 in which liquid crystal is filled is formed. An AC power supply 68 is connected to the transparent electrodes 61a and 61b, and both electrodes 6
It is configured such that a sinusoidal drive voltage can be applied between 1a and 61b. Further, the liquid crystal light valve 51 is provided with an image writing element to allow one of the substrates 60
Writing light 69a as image information is emitted from the a side, and reading light 69b is emitted from the other substrate 60b side.

FIG. 8 is an equivalent circuit for explaining the operation principle of the liquid crystal light valve 51. In the figure, the equivalent resistance of the liquid crystal layer 66, the intermediate layer, and the photoconductor layer 62 is
The equivalent capacitances of the liquid crystal layer 66, the intermediate layer, and the photoconductor layer 62 are denoted by a resistor 71, a resistor 72, and a resistor 73, respectively.
Indicated by Here, the intermediate layer is the alignment film 65a, the dielectric mirror 64, and the light shielding layer 63. The combined impedances of the liquid crystal layer 66, the intermediate layer, and the photoconductor layer 62 are the combined impedances Z1 and Z1, respectively.
Synthetic impedance Z2 and synthetic impedance Z
3 is indicated.

The liquid crystal light valve 5 is driven by the AC power source 68.
When the value of the drive voltage applied to the liquid crystal layer 1 is V, the liquid crystal layer 66
The voltage Vlc divided into two is Vlc = {Z1 / (Z1 +
Z2 + Z3)} × V.

In each region of the photoconductor layer 62, the resistor 73 of the photoconductor layer 62 is in a high resistance state when no image information is input to the photoconductor layer 62 by the writing light 69a (dark state). The combined impedance Z3 of the photoconductor layer 62 is high impedance. At this time, the voltage Vlc applied to the liquid crystal layer 66 does not exceed the threshold voltage.
On the other hand, in the state where the writing light 69a is irradiated and information is written in the photoconductor layer 62 (bright state), the photoconductor layer 6 is
The second resistor 73 is in a low resistance state, and the combined impedance Z3 of the photoconductor layer 62 is low impedance. At this time, the voltage Vlc applied to the liquid crystal layer 66 exceeds the threshold voltage, and the alignment state of the liquid crystal in the liquid crystal layer 66 changes. That is, in the bright state and the dark state, the photoconductor layer 62
The combined impedance Z3 of the liquid crystal is different, and thereby the voltage Vlc divided in the liquid crystal layer 66 changes, and the alignment state of the liquid crystal changes according to this change.

FIG. 9 is a schematic diagram showing a conventional projection type liquid crystal display device 59 having the liquid crystal light valve 51. The projection-type liquid crystal display device 59 includes a liquid crystal light valve 51, a CRT (cathode ray tube) 50, a reading light source 52, an optical lens 53, a polarization beam splitter 54, and a projection lens 55. The CRT 50 irradiates the liquid crystal light valve 51 with writing light 69a as image information from one substrate 60a side as an image writing element. In addition to the CRT, a light source and a liquid crystal panel may be used in combination as the image writing element. The reading light source 52 emits the reading light 69b. Read light 69b emitted from the read light source 52
Through the optical lens 53 and the polarization beam splitter 54 from the other substrate 60b side to the liquid crystal light valve 51.
Incident on. The read light 69b that has entered is reflected by the dielectric mirror 64 of the liquid crystal light valve 51 and is output. At this time, depending on the alignment state of the liquid crystal of the liquid crystal layer 66,
The light intensity of the output light will be modulated. The output light thus obtained is used as an image for the polarization beam splitter 54.
Through the projection lens 55 and is enlarged and projected on the screen 56.

In addition to the above basic structure, a CRT and a liquid crystal light valve are provided for R, G and B respectively, and further,
If the readout light is separated into R, G, and B by a dichroic mirror or dichroic prism, is irradiated to each liquid crystal light valve, and the reflected light is recombined and projected on the screen, color display is performed. You can

However, similarly to the projection type liquid crystal color display device having the transmissive liquid crystal light valve, the voltage-reflectance characteristic of the liquid crystal light valve is R even in the projection type liquid crystal color display device having the optical writing type liquid crystal light valve.
-The liquid crystal light valves for G and B are different from each other, and as a result, the R, G, and B light intensities in the displayed image are uneven.

Therefore, in a projection type liquid crystal color display device provided with an optical writing type liquid crystal light valve, R, G, B
Japanese Unexamined Patent Publication No. 3-259179 discloses a method of equalizing the retardation of the liquid crystal layer of each liquid crystal light valve in order to make the voltage-reflectance characteristics of each liquid crystal light valve for use in the same uniform. The retardation is the refractive index of the liquid crystal Δn
, The cell thickness of the liquid crystal layer is d, and the wavelength of the read light is λ.
Then, it is represented by Δnd / λ. According to the above method,
Three liquid crystal light valves for R, G and B are Δn _R d _R /
The liquid crystal layers of the liquid crystal light valves are formed so that the liquid crystal layers of the liquid crystal layers have different refractive indices Δn so as to satisfy the relationship of λ _R = Δn _G d _G / λ _G = Δn _B d _B / λ _B. Thereby, the retardation of the liquid crystal layers of the three liquid crystal light valves is made equal, and the voltage-reflectance characteristics are made uniform.

[0020]

However, in a projection type liquid crystal color display device provided with an optical writing type liquid crystal light valve, the liquid crystal layer of each liquid crystal light valve is formed by the method disclosed in Japanese Patent Laid-Open No. 3-259179. If the refractive indices Δn of the liquid crystals are formed to be different from each other, the dielectric constants of the respective liquid crystal layers will also be different from each other.
The impedance of each liquid crystal layer also differs from each other.

Therefore, according to the operation principle of the liquid crystal light valve described above, even if each of the R, G, and B liquid crystal light valves is irradiated with the same amount of writing light, the light intensity of the output light is different from each other. As a result, there is still a problem that the R, G, and B light intensities in the display image are uneven.

The present invention has been made to solve the above problems, and an object thereof is to make the gradation characteristics of each liquid crystal light valve the same so that red light, green light, and blue light in a display image are displayed. Another object of the present invention is to provide a liquid crystal color display device capable of high-quality color display in which the light intensity of each image is balanced and a method of adjusting the gradation characteristics thereof.

[0023]

In order to solve the above-mentioned problems, a liquid crystal color display device according to a first aspect of the present invention comprises three liquid crystals for forming red light, green light and blue light images, respectively. A light valve, in which the driving voltage applied to the liquid crystal is changed according to information obtained by irradiating the photoconductor layer with writing light from one side, and the alignment state of the liquid crystal is changed. The liquid crystal display device includes three liquid crystal light valves that modulate incident light and output the light as output light, and a driving unit that applies a driving voltage to each of the three liquid crystal light valves. The liquid crystal light valves are formed by the three liquid crystal light valves. In the liquid crystal color display device for displaying the combined red light, green light, and blue light images by combining, the driving means applies the liquid crystal light valves to the three liquid crystal light valves. The liquid crystal light valves are provided with variable means for varying the drive frequency of the drive voltage, and the intensity of the output light with respect to the intensity of the write light is equal or substantially equal to each other among the three liquid crystal light valves. The drive frequency of the drive voltage applied to the liquid crystal light valve is adjusted by the variable means.

With the above structure, the liquid crystal color display device according to the present invention can make the gradation characteristics of the three liquid crystal light valves equal, so that red light in the display image,
High-quality color display in which the light intensities of the green light image and the blue light image are well balanced can be performed.

That is, the driving frequency of the driving voltage applied to the three liquid crystal light valves is adjusted by the variable means, so that the impedance of the photoconductive layer and the impedance of the liquid crystal layer in each liquid crystal light valve are matched. Will be possible. Here, the general relationship among the impedance of the photoconductor layer, the impedance of the liquid crystal layer, and the driving frequency is represented by Expression (1), Expression (2), and Expression (3).
Shown in

Zpc = Rpc / {1+ (RpcωCpc) ² } ^1/2 (1) Zlc = 1 / ωClc (2) ω = 2πf (3) Zpc Impedance of photoconductor layer Zlc; impedance of liquid crystal layer f; drive frequency (Hz) Rpc; resistance of photoconductor layer (Ω) Cpc; capacity of photoconductor layer (F) Clc; capacity of liquid crystal (F) As shown in the above formulas (1), (2), and (3), the driving frequency is varied and adjusted to match the impedance of the photoconductor layer with the impedance of the liquid crystal layer. it can.

As a result, in order to equalize the retardations of the liquid crystal layers of the three liquid crystal light valves, Δnd / λ
By optimizing, the impedance of each photoconductor layer and the impedance of each liquid crystal layer in the three liquid crystal light valves can be matched even if the impedance of each liquid crystal layer is different from each other.

Further, Δnd / λ of each liquid crystal layer of the three liquid crystal light valves is not optimized, and the voltage of each liquid crystal layer −
Even when the reflectance characteristics are different from each other, similarly, 3
The impedance of each photoconductor layer and the impedance of each liquid crystal layer in one liquid crystal light valve can be matched.

Therefore, since the writing light intensity-output light intensity characteristics of the three liquid crystal light valves can be made uniform, it is not necessary to perform γ correction of the writing means, and the writing means has a special circuit for adjustment. It is possible to provide a high-quality liquid crystal color display device in which the light intensities of the red light, green light, and blue light images in the display image are well balanced without the need to provide the liquid crystal display device.

In order to solve the above-mentioned problems, a method for adjusting gradation characteristics of a liquid crystal color display device according to a second aspect of the present invention comprises three sheets for forming images of red light, green light and blue light, respectively. A liquid crystal light valve, wherein the driving voltage applied to the liquid crystal is changed according to information obtained by irradiating the photoconductor layer with writing light from one side, and the alignment state of the liquid crystal is changed. The three liquid crystal light valves each include three liquid crystal light valves that modulate light incident from the light source and output the light as output light, and driving means that applies a driving voltage to each of the three liquid crystal light valves. A method for adjusting gradation characteristics of a liquid crystal color display device for displaying a composite image of formed red light, green light, and blue light, wherein As the intensity of the output light coincides or substantially coincides with each other between said three liquid crystal light valves,
The driving frequency of the driving voltage applied to the three liquid crystal light valves by the driving unit is varied and adjusted.

In the liquid crystal color display device to which the adjusting method according to the present invention is applied by the above method, the gradation characteristics of the three liquid crystal light valves can be made equal, so that red light and green light in the display image can be obtained. , And high-quality color display in which the light intensity of each image of blue light is balanced can be performed.

That is, by varying and adjusting the drive frequency of the drive voltage applied to the three liquid crystal light valves, as described above, the impedance of the photoconductor layer and the liquid crystal layer of each liquid crystal light valve are adjusted. Matching with impedance becomes possible.

Accordingly, in order to make the retardations of the liquid crystal layers of the three liquid crystal light valves equal, Δnd / λ
By optimizing, the impedance of each photoconductor layer and the impedance of each liquid crystal layer in the three liquid crystal light valves can be matched even if the impedance of each liquid crystal layer is different from each other.

Further, Δnd / λ of each liquid crystal layer of the three liquid crystal light valves is not optimized, and the voltage of each liquid crystal layer −
Even when the reflectance characteristics are different from each other, similarly, 3
The impedance of each photoconductor layer and the impedance of each liquid crystal layer in one liquid crystal light valve can be matched.

Therefore, since the writing light intensity-output light intensity characteristics of the three liquid crystal light valves can be made uniform, it is not necessary to perform γ correction of the writing means, and a special circuit for adjusting the writing means. It is possible to provide a high-quality liquid crystal color display device in which the light intensities of the red light, green light, and blue light images in the display image are well balanced without the need to provide the liquid crystal display device.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic diagram showing a projection type liquid crystal color display device 1 of this embodiment. The projection liquid crystal color display device 1 includes red light (hereinafter abbreviated as “R”), green light (hereinafter abbreviated as “G”), and blue light (hereinafter, abbreviated as “G”).
Optical writing type liquid crystal light valves 12r, 12g, 12b for forming respective images (abbreviated as "B") are provided. In addition, each liquid crystal light valve 12r
A writing light source 10r, 10g, 10b serving as a writing means for writing image information in the 12g 12b, and a liquid crystal panel 11r comprising a TFT as a switching element.
11g and 11b, and image signal generation circuits 17r and 17
g ・ 17b is each liquid crystal light valve 12r ・ 12g ・ 1
2b is provided for each. A reading light source 19 is provided as a reading means for irradiating the liquid crystal light valves 12r, 12g, 12b with the reading light.
Three dichroic mirrors 13r, 13g, and 13b are provided. Furthermore, each liquid crystal light valve 12r
Three dichroic mirrors 14r, 14g, and 14b and a projection lens 15 are provided as a projection unit for combining reflected light from 12g and 12b, enlarging the light, and projecting it on the screen 16.

Further, the projection type liquid crystal color display device 1 serves as a driving means for driving the liquid crystal light valves 12r, 12g, 12b by applying an AC drive voltage to the liquid crystal light valves 12r, 12g, 12b. Drive circuits 18r, 18g, and 18b are provided, respectively. Further, each of the drive circuits 18r, 18g, and 18b is connected to a variable frequency oscillating circuit 20r, 20g, or 20b as a variable unit that changes the drive frequency of the AC drive voltage. Variable frequency oscillator circuit 20r / 20g / 2
The configuration of 0b is the same as that of a normal variable frequency oscillator, and FIG. 2 is a block diagram showing an example of the configuration.

Variable frequency oscillating circuit 20r / 20g / 20
As shown in FIG. 2, b is a voltage controlled oscillator 27 that oscillates a signal having a frequency corresponding to the level of the input error signal.
And the output from this voltage controlled oscillator 27
Of the frequency divider 28, a reference signal source 29 that oscillates at a predetermined frequency, an output from the frequency divider 28, and a reference signal from the reference signal source 29. A phase-locked loop including a phase comparator 30 that compares the phases and outputs an error signal corresponding to the phase difference between them, and a low-pass filter 31 that smoothes the output from the phase comparator 30 and supplies the smoothed output to the voltage controlled oscillator 27. Is formed in. With this configuration, the variable frequency oscillator circuit 20r.2
0g · 20b is the frequency division ratio N output from the control circuit 32.
The frequency of the oscillation signal can be varied according to the change in the value of and output to the drive circuits 18r, 18g and 18b, respectively.

FIG. 3 shows the liquid crystal light valves 12r and 12
It is sectional drawing which shows the structure of g * 12b roughly. The liquid crystal light valves 12r, 12g, 12b have a pair of translucent substrates 9a, 9b on both sides. The transparent electrode 1a is formed on one of the substrates 9a. A photoconductive layer 2, a light shielding layer 3, and a dielectric mirror 4 are sequentially stacked on the transparent electrode 1a, and an alignment film 5 is formed on the dielectric mirror 4.
a is formed. The transparent electrode 1b and the alignment film 5b are formed on the other substrate 9b. The liquid crystal light valves 12r, 12g, 12b are the two substrates 9a.
9b is formed by adhering the alignment films 5a and 5b to each other via a spacer 7, and a liquid crystal layer 6 in which a liquid crystal is sealed is formed in a gap provided by the spacer 7. Has been done. In addition, the transparent electrodes 1a and the transparent electrodes 1 of each of the liquid crystal light valves 12r, 12g, and 12b.
drive circuits 18r, 18g, and 18b, respectively.
Thus, an AC drive voltage can be applied.

Next, the display operation of the projection type liquid crystal color display device 1 having the above structure will be described.

The lights emitted from the writing light sources 10r, 10g, and 10b are respectively the liquid crystal panels 11r and 11g.
It is incident on 11b. Each liquid crystal panel 11r ・ 11g ・ 1
In 1b, the TFT switches the signal voltage applied to each pixel electrode in accordance with the image signal from the image signal generating circuits 17r, 17g, 17b, and the light transmittance of the liquid crystal changes accordingly. The light incident on each of the liquid crystal panels 11r, 11g, and 11b passes through the liquid crystal whose light transmittance changes according to the signal voltage, thereby forming writing light as each of R, G, and B image information. The respective writing lights for R, G, B are written in the photoconductor layer 2 of the liquid crystal light valves 12r, 12g, 12b to which the AC drive voltage is applied.

In each region of the photoconductor layer 2, the resistance of the photoconductor layer 2 is in a high resistance state in a region where no image information is input, and the combined impedance of the photoconductor layer 2 is high impedance. At this time, the voltage applied to the liquid crystal layer 6 does not exceed the threshold voltage. On the other hand, in the area where the image information is written, the resistance of the photoconductor layer 2 becomes a low resistance state,
The composite impedance of the photoconductor layer 2 becomes low impedance. At this time, the voltage applied to the liquid crystal layer 6 exceeds the threshold voltage, and the alignment state of the liquid crystal in the liquid crystal layer 6 changes. That is, the photoconductor layer 2 changes its impedance according to the image information to be written, and controls the voltage applied to the liquid crystal layer 6, which causes the liquid crystal layer 6 to change in the image in the form of a change in the alignment state of the liquid crystal. Information corresponding to the information is formed.

On the other hand, the light emitted from the reading light source 19 is
The three dichroic mirrors 13r, 13g, 13b separate them into R, G, B. These R, G, B are
The light enters the liquid crystal light valves 12r, 12g, and 12b, respectively. The incident R, G, and B are reflected by the dielectric mirrors 4 of the liquid crystal light valves 12r, 12g, and 12b and output, but at this time, depending on the alignment state of the liquid crystal of the liquid crystal layer 6, the output light is output. The light intensity will be modulated.
The output light thus obtained is converted into three R, G, and B images, and the three dichroic mirrors 14r, 14g, and 14 are used.
It is combined by b, is enlarged by the projection lens 15, and is projected on the screen 16. As a result, a color image is displayed on the screen 16.

Next, in order to display a high-quality color image in which the R, G, and B light intensities are balanced, the gradation characteristics of the three liquid crystal light valves 12r, 12g, and 12b are made equal. Liquid crystal light valve 12r / 12g / 12
A method of adjusting the drive frequency of the drive voltage applied to b will be described.

First, a luminance meter 25 is installed on the screen 16 and is connected to this luminance meter to measure R / G in the displayed image.
A brightness measuring instrument 26 for measuring each brightness of B is prepared.

Next, each liquid crystal panel 11r, 11g, 11
A plurality of signal voltages corresponding to the black level from the maximum transmittance are input to b from the image signal generation circuits 17r, 17g, and 17b, and writing light as image information is input to the liquid crystal light valves 12r, 12g, and 12b. At this time, the drive circuit 1 is attached to each of the liquid crystal light valves 12r, 12g, and 12b.
The AC voltage of the same drive frequency is applied by 8r, 18g, and 18b. In the present embodiment, the drive frequency of 560H is applied to each liquid crystal light valve 12r, 12g, and 12b.
The alternating voltage of z is applied.

Then, the R, G, and B luminances of the display image projected on the screen 16 from the liquid crystal light valves 12r, 12g, and 12b when a plurality of writing lights corresponding to the white level to the black level are input. Are individually measured using the luminance meter 25 and the luminance measuring device 26.

Table 1 shows the above measurement results, and Table 2 shows
It is the result of normalizing the respective luminances of R, G and B measured from the maximum transmittance to the signal voltage corresponding to the black level. The standardized value Larb. Of each measured value L _x is R · G · B
Let L _max be the maximum value measured at each luminance and L _min be the minimum value, then Larb. = (L _x −L _min ) / (L
It can be calculated by the formula of ( _max −L _min ) × 100.

[0050]

[Table 1]

[0051]

[Table 2]

FIG. 4 is a graph of Table 2.
It is a graph which shows the relationship between the signal voltage applied to each liquid crystal panel 11r * 11g * 11b, and each brightness | luminance of R * G * B in a display image. Here, each liquid crystal panel 11r · 11
The amount of writing light applied to each liquid crystal light valve 12r, 12g, 12b changes according to the signal voltage applied to g. 11b, while the brightness of each of R, G, B changes to each liquid crystal light valve 12r, 12g, 12b. Since it depends on the intensity of the output light from, the relationship between the signal voltage and the luminance can be read as the relationship between the intensity of the writing light and the intensity of the output light.

As shown in FIG. 4, the writing light intensity-output light intensity characteristic is the liquid crystal light valve 12r for R, G, and B.
-It can be seen that there is no match between 12g and 12b. Therefore, next, the variable frequency oscillating circuits 20r, 20g, and 20 are arranged so that the relationship between the writing light intensity and the output light intensity is the same among the liquid crystal light valves 12r, 12g, and 12b.
Depending on b, each liquid crystal light valve 12r, 12g, 12
The drive frequency of the drive voltage applied to b is varied and adjusted.

In the adjustment, the reference color is first determined. Usually, the standard color is one whose characteristics are in the center. In the present embodiment, the drive frequency of the drive voltage applied to the liquid crystal light valves 12r and 12g is changed so that the R and G signal voltage-luminance characteristics match the B signal voltage-luminance characteristic. I adjusted it. Usually, the adjustment is performed by lowering the drive frequency when increasing the brightness, and by increasing the drive frequency when decreasing the brightness. In this embodiment, the drive frequencies of the liquid crystal light valves 12r and 12g are increased to reduce the brightness of R and G for adjustment, and the drive voltage applied to the liquid crystal light valves 12r, 12g, and 12b is driven. Frequency of the liquid crystal light valve 12
1kHz for r ・ 12g, liquid crystal light valve 12b
Was set to 560 Hz. In this way, the variable frequency oscillator circuits 20r, 20g, and 20b respectively adjust the drive frequencies to adjust the drive frequencies, and then again adjust the luminances of R, G, and B from the maximum transmittance to the signal voltage corresponding to the black level. taking measurement.

Table 3 shows the above measurement results, and Table 4 shows
It is the result of standardizing each measured value. In addition, FIG. 5 is a graph of Table 4, showing R, G, and
The relationship between the signal voltage of B and the luminance is shown.

[0056]

[Table 3]

[0057]

[Table 4]

As shown in FIG. 5, each liquid crystal light valve 1
By varying and adjusting the drive frequencies of the drive voltages applied to 2r, 12g, and 12b, respectively, it can be seen that the relationship between the signal voltage and the luminance is substantially the same in R, G, and B.

As described above, in the projection type liquid crystal color display device 1 of this embodiment, the relationship between the signal voltage and the brightness is R, G, B.
Liquid crystal light valves 12r so that they substantially coincide with each other.
The gradation characteristics of the three liquid crystal light valves 12r, 12g, and 12b can be made equal by varying and adjusting the drive frequency of the drive voltage applied to 12g and 12b. It is possible to realize a high-quality projected display image with an excellent balance of G and B light intensities.

Further, the luminance meter 25 and the luminance measuring device 26 are provided integrally with the above-mentioned projection type liquid crystal color display device 1 so that each of the liquid crystal light valves 12r, 12g, 12 can be used during the display operation.
It is also possible to constantly adjust the drive frequency of the drive voltage applied to b by each variable frequency oscillation circuit 20r, 20g, 20b. In this case, for example, the brightness measuring device 2
6 shows the measurement results of the variable frequency oscillation circuits 20r and 20g.
Output to 20b, while each variable frequency oscillator circuit 20r, 20g, 20b compares the measured value of each luminance with each image signal, and how much the drive frequency value should be changed It may be configured such that an arithmetic circuit for arithmetically operating is connected. As a result, the arithmetic circuit calculates the variable amount of the driving frequency according to the measured value of each luminance, and the variable frequency oscillation circuits 20r, 20g, 20b are calculated according to the calculation result.
Can be adjusted by varying the drive frequency. In this way, if the drive frequency can be constantly adjusted during the display operation, the liquid crystal light valves 12r, 12g, 12c, 12c, 12g, 12c, 12c, 12c, 12c, 12d, 12c, 12c, 12d, 12c, 12c, 12d, 12g, 12c, 12d, 12c, 12c, 12d, 12c, 12d, 12c, 12d
The writing light intensity-output light intensity characteristics of b can be kept unchanged without changing.

Liquid crystal light valves 12r and 12g
The waveform of the AC voltage applied to 12b may be a square wave or a sine wave.

The variable frequency oscillator circuits 20r and 20g
The 20b is not limited to the circuit configuration shown in FIG. 2, and various circuit configurations for varying the drive frequency are possible.

Further, in the present embodiment, the liquid crystal light valves 12r and 12g are arranged so that the signal voltage-luminance characteristics of B and the signal voltage-luminance characteristics of R and G match.
The drive frequency of the drive voltage applied to the variable voltage is adjusted by adjusting the drive frequency, but the present invention is not limited to this.
Alternatively, the drive frequency may be varied and adjusted so that other characteristics match the G signal voltage-luminance characteristics.

Furthermore, in the present embodiment, the drive frequency of the drive voltage applied to each liquid crystal light valve 12r, 12g, 12b after adjustment is the liquid crystal light valve 12r, 12r.
Although it was 1 kHz for g and 560 Hz for the liquid crystal light valve 12b, the present invention is not limited to these numerical values. Each liquid crystal light valve 12r / 12g
According to the variation in the relationship between the signal voltage of 12b and the luminance, the variable amount of the drive frequency that compensates for the variation also changes.

Further, in the present embodiment, the projection means of the projection type liquid crystal color display device 1 is configured to project the combined R, G and B images on the screen 16 by one projection lens 15. But not limited to this, each RG
The image of B may be projected on the screen by each of the three projection lenses and combined on the screen.

Further, in the present embodiment, the liquid crystal panels 11r, 11g, 11b are used as the writing means, but the writing means is not limited to this, and a self-luminous device such as a CRT may be used as the writing means. Okay, L
It may be configured to scan and write a linear light emitting device such as an ED array by an optical means such as a galvanometer mirror.

[0067]

As described above, the liquid crystal color display device according to the first aspect of the present invention includes the variable means for varying the drive frequency of the drive voltage applied to the three liquid crystal light valves by the drive means. In addition, the intensity of the output light with respect to the intensity of the writing light is matched or substantially matched with each other among the three liquid crystal light valves.
The drive frequency of the drive voltage applied to the three liquid crystal light valves is adjusted by the variable means.

Accordingly, in order to equalize the retardations of the liquid crystal layers of the three liquid crystal light valves, Δnd / λ
By optimizing, the impedance of each photoconductor layer and the impedance of each liquid crystal layer in the three liquid crystal light valves can be matched even if the impedance of each liquid crystal layer is different from each other.

Further, Δnd / λ of each liquid crystal layer of the three liquid crystal light valves is not optimized, and the voltage of each liquid crystal layer −
Even when the reflectance characteristics are different from each other, similarly, 3
The impedance of each photoconductor layer and the impedance of each liquid crystal layer in one liquid crystal light valve can be matched.

Therefore, since the writing light intensity-output light intensity characteristics of the three liquid crystal light valves can be made uniform, it is not necessary to perform the γ correction of the writing means, and the writing means is specially adjusted. There is an effect that it is possible to provide a high-quality liquid crystal color display device in which the light intensity of each image of red light, green light, and blue light in a display image is balanced without providing a circuit.

In the method of adjusting the gradation characteristics of the liquid crystal color display device according to the second aspect of the present invention, as described above, the intensity of the output light with respect to the intensity of the writing light is the same between the three liquid crystal light valves. In this method, the drive frequency of the drive voltage applied to the three liquid crystal light valves by the drive means is adjusted so as to match or substantially match with.

As a result, Δnd / λ is set in order to equalize the retardations of the liquid crystal layers of the three liquid crystal light valves.
By optimizing, the impedance of each photoconductor layer and the impedance of each liquid crystal layer in the three liquid crystal light valves can be matched even if the impedance of each liquid crystal layer is different from each other.

Further, Δnd / λ of each liquid crystal layer of the three liquid crystal light valves is not optimized, and the voltage of each liquid crystal layer −
Even when the reflectance characteristics are different from each other, similarly, 3
The impedance of each photoconductor layer and the impedance of each liquid crystal layer in one liquid crystal light valve can be matched.

Therefore, since the writing light intensity-output light intensity characteristics of the three liquid crystal light valves can be made uniform, it is not necessary to perform the γ correction of the writing means, and the writing means is specially adjusted. There is an effect that it is possible to provide a high-quality liquid crystal color display device in which the light intensity of each image of red light, green light, and blue light in a display image is balanced without providing a circuit.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a projection type liquid crystal color display device according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a variable frequency oscillator circuit provided in the projection type liquid crystal color display device.

FIG. 3 is a cross-sectional view schematically showing a configuration of a liquid crystal light valve provided in the projection type liquid crystal color display device.

FIG. 4 is a graph showing a relationship between signal voltage and brightness before adjusting a drive frequency in the projection type liquid crystal color display device.

FIG. 5 is a graph showing the relationship between the signal voltage and the luminance after adjusting the drive frequency in the projection type liquid crystal color display device.

FIG. 6 is a configuration diagram schematically showing a conventional projection type liquid crystal color display device including a transmissive liquid crystal light valve.

FIG. 7 is a cross-sectional view schematically showing a configuration of an optical writing type liquid crystal light valve.

FIG. 8 is an equivalent circuit for explaining the operation principle of the liquid crystal light valve.

FIG. 9 is a schematic diagram showing a conventional projection type liquid crystal display device including an optical writing type liquid crystal light valve.

[Explanation of symbols]

 1 Projection Liquid Crystal Color Display Device 10r Writing Light Source 10g Writing Light Source 10b Writing Light Source 11r Liquid Crystal Panel 11g Liquid Crystal Panel 11b Liquid Crystal Panel 12r Liquid Crystal Light Valve 12g Liquid Crystal Light Valve 12b Liquid Crystal Light Valve 13r Dichroic Mirror 13g Dichroic Mirror 13b Dichroic Mirror 14r Dichroic mirror 14b Dichroic mirror 15 Projection lens 16 Screen 17r Image signal generating circuit 17g Image signal generating circuit 17b Image signal generating circuit 18r Driving circuit (driving means) 18g Driving circuit (driving means) 18b Driving circuit (driving means) 19 Read light source 20r Variable frequency oscillation circuit (variable means) 20g Variable frequency oscillation circuit (variable means) 20b Variable frequency oscillation Circuit (variable means) 25 Luminance meter 26 Luminance measuring instrument

Claims (2)

[Claims] 1. A liquid crystal light valve comprising three sheets for forming images of red light, green light and blue light, respectively, according to information obtained by irradiating a photoconductor layer with writing light from one side, Three liquid crystal light valves that modulate the light incident from the other and output it as output light when the driving voltage applied to the liquid crystal changes and the alignment state of the liquid crystal changes, and the three liquid crystal lights. A liquid crystal color display device that includes a driving unit that applies a driving voltage to each of the bulbs, and that displays by combining images of red light, green light, and blue light respectively formed by the three liquid crystal light valves, The liquid crystal display device further comprises variable means for varying the driving frequency of the driving voltage applied to the three liquid crystal light valves by the driving means, and the intensity of the writing light is increased. The drive frequency of the drive voltage applied to the three liquid crystal light valves is adjusted by the variable means so that the intensity of the output light with respect to the three liquid crystal light valves is substantially or substantially the same. A liquid crystal color display device characterized in that 2. A liquid crystal light valve comprising three sheets, each of which forms an image of red light, green light, and blue light, according to information obtained by irradiating the photoconductor layer with writing light from one side, Three liquid crystal light valves that modulate the light incident from the other and output it as output light when the drive voltage applied to the liquid crystal changes and the alignment state of the liquid crystal changes, and the three liquid crystal lights. A liquid crystal color display device including a driving means for applying a driving voltage to each of the bulbs, and performing display by synthesizing images of red light, green light, and blue light respectively formed by the three liquid crystal light valves. In the adjusting method of the adjustment characteristic, the driving hand is adjusted so that the intensity of the output light with respect to the intensity of the writing light is mutually matched or substantially matched between the three liquid crystal light valves. A method for adjusting gradation characteristics of a liquid crystal color display device, wherein the driving frequency of a driving voltage applied to the three liquid crystal light valves is varied and adjusted depending on the stage.