JP3071999B2 - Reflective LCD projector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal projector, and more particularly, to a photoconductor whose impedance is changed by writing light, and a nematic liquid crystal whose twisted structure is changed by the impedance change of the photoconductor. The present invention relates to a liquid crystal projector that includes an optical writing type spatial light modulation element having the following configuration, and displays information of writing light by reading light.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional liquid crystal projector, in which reference numerals 21a and 21b denote glass substrates and 22a and 22a.
22b is a transparent electrode, 23 is a photoconductor layer, 24 is a light shielding layer,
25 is a reflection mirror layer, 26 is a liquid crystal layer, 27 is a liquid crystal display device, 28 is a liquid crystal display device driving circuit, 29 is a video signal generator, 30 is an optical writing type spatial light modulator, 31 is a liquid crystal writing device, and 32 is a liquid crystal writing device. Input light, 33 is write information, 34 is read light, and 35 is output information.

The optical writing type spatial light modulator 30 comprises a photoconductor layer 23, a light shielding layer 24, a reflection mirror layer 25, and a liquid crystal layer 26.
Are sandwiched between transparent electrodes 22a and 22b, and the transparent electrodes 22a and 22b are
The structure is such that both sides of 22b are further sandwiched between glass substrates 21a and 21b. The input light that has passed through the liquid crystal display device 27 operating according to the video signal from the video signal generation unit 29 input to the liquid crystal display device driving circuit 28, when an AC bias voltage is applied to the transparent electrodes 22a and 22b,
This is an input to the optical writing type spatial light modulator 30 and is input as writing information 33. Then, the write information 33 causes an impedance change in the photoconductor layer 23, changes the twisted structure in the liquid crystal layer 26, changes the polarization state of the read light 34, and changes the output information 3
It becomes 5.

FIGS. 5 and 6 show that the ratio of the input light quantity from the write light incident side of the optical writing type spatial light modulator to the output light quantity on the read light incident side is not uniform in the read light irradiation surface. FIG. FIG.
FIG. 6 is a diagram showing the direction of liquid crystal molecules at each position divided into nine portions as shown in FIG. 5 in the read light irradiation surface of the optical writing type spatial light modulator 30. When an AC bias is applied to the transparent electrodes 22a and 22b, the twisted structure changes in the liquid crystal layer 26 and changes the polarization direction of the 45 ° readout light. When the optical writing type spatial light modulator 30 that operates as described above is applied to an actual reflection type liquid crystal projector, as shown in FIG. The incident path for each point is
Each is incident at a different angle.

More specifically, as shown in FIG. 7, an angle → light source → and → light source →, → light source → and → light source →
, → light source → and → light source →, → light source → and →
Light source →, each incident at the same spread angle,
Considering both the direction and the liquid crystal molecular axis in the incident readout light irradiation surface, the incident conditions are different at any point.

8 (a) to 8 (e) are graphs showing main characteristics of each part of a reflection type liquid crystal projector actually provided with an optical writing type spatial light modulator. FIG. 8 (a) shows an input image waveform, and FIG. 8 (b) is a γ correction characteristic waveform, FIG. 8 (c) is a voltage-transmittance (VT) characteristic waveform of the liquid crystal display device, and FIG. 8 (d) is an input / output characteristic of the optical writing type spatial light modulator. 8 (e) shows the output video waveform.

An input image waveform as shown in FIG. 8A is input to the image signal, and in the case of a projector, the images of the R, G, and B liquid crystal display devices 27 are synthesized and enlarged and projected on a screen. Because I get color images,
Three liquid crystal display devices 27 are required. Liquid crystal display device 27
Voltage-transmittance characteristics of the R, G, and B liquid crystal display devices 27 due to various factors, such as variations in liquid crystal materials and their manufacture, and variations in liquid crystal drivers, polarization plate adjustment errors, and differences in incident light wavelength characteristics. Therefore, in order to obtain a linear output video waveform as shown in FIG. 8 (e), γ correction is performed in the liquid crystal display device driving circuit 28, and further, chromaticity deviation in gradation is eliminated. I have to.

[0008] A completely linear input video waveform as shown in FIG. 8A is optically written through a γ correction characteristic waveform shown in FIG. 8B created based on the voltage-transmittance characteristic of the liquid crystal display device 27. When the light enters the spatial light modulator 30 of FIG.
It is output as the output video waveform shown in (e). The characteristics of the optical writing type spatial light modulator 30 include input-output characteristics, and through the curve a in the figure, the output image waveform becomes the curve a 'shown in FIG. .

As can be seen from the description of FIGS. 5 to 7, the input / output characteristics are not good because the incident angle from the light source to each point is different within the read light irradiation area of the optical writing type spatial light modulator 30. Become uniform. That is, if there are points corresponding to the b-curve and the c-curve on the readout light irradiation surface, the output video waveforms are output as b ′ curve and c ′ curve as shown in FIG. 8E, respectively.

[0010]

SUMMARY OF THE INVENTION In a system employing an optical writing type spatial light modulator for a reflection type liquid crystal projector which cannot supply readout light with perfect parallel light from a light source having a certain size, The ratio between the amount of input light from the light incident side and the amount of output light from the read light incident side has a characteristic that is not uniform in the read light irradiation surface, and the output video waveform is also not uniform in the read light irradiation surface due to the characteristic. There is a problem that a luminance difference occurs in a projected image on a screen.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has been developed in a reflection type liquid crystal projector which cannot supply readout light with perfect parallel light. It is an object of the present invention to provide a reflection type liquid crystal projector in which a measure against gradation unevenness caused by non-uniform internal input / output characteristics is corrected by changing a working voltage range (white / black voltage) of a liquid crystal display device. .

[0012]

The present invention SUMMARY OF], in order to solve the above problems, (1) a photoconductor whose impedance is changed by the writing beam, twisted structure is changed by the impedance change of the optical conductor Surune In a liquid crystal projector having an optical writing type spatial light modulator having a matte liquid crystal and displaying the information of the writing light by the reading light, the liquid crystal projector uses the reading light incident angle on the reading light irradiation surface.
Input-output characteristics of optical writing spatial light modulator
The output characteristics of the optical writing spatial light modulator
Control means for controlling the amount of writing light so that the characteristics become uniform in the plane . (2) In the above (1), the light irradiation surface of the optical writing type spatial light modulator has Is divided into an arbitrary number in a matrix, and control means for controlling the writing light amount for each of the divided blocks is further provided. (3) The control means performs display driving by applying a video signal to the information of the writing light. And controlling a video signal for driving the liquid crystal display device.

[0013]

The reading light irradiation surface of the optical writing type spatial light modulator is divided into a matrix, and in each block on the liquid crystal display device side corresponding to each of the divided blocks, the applied operating voltage (white) of the liquid crystal display device is applied. Changing the voltage, the black voltage) controls the writing light of the optical writing spatial light modulator, and the output information obtained by the reading light has a linear characteristic.

[0014]

Embodiments will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of a reflection type liquid crystal projector according to the present invention. The liquid crystal display device includes an optical writing type spatial light modulator and performs display driving of information of writing light with a video signal. FIG. 1 is a configuration diagram of a liquid crystal projector according to an embodiment. In the figure, 1a and 1b are glass substrates, 2a and 2
b is a transparent electrode, 3 is a photoconductor layer, 4 is a light shielding layer, 5 is a reflection mirror layer, 6 is a liquid crystal layer, 7 is a liquid crystal display device, 8 is a liquid crystal display device driving circuit, 9 is a video signal generation unit, Denotes an optical writing type spatial light modulator, 11 denotes a liquid crystal writing device, 12 denotes input light, 13 denotes writing information, 14 denotes reading light, 15 denotes output information, and 16 denotes a control unit.

Photoconductor layer 3, light-shielding layer 4, and reflection mirror layer 5
The liquid crystal layer 6 is sandwiched between transparent electrodes 2a and 2b, and furthermore, an AC bias voltage is applied to the transparent electrodes 2a and 2b in an optical writing type spatial light modulator having both sides sandwiched between glass substrates 1a and 1b. In this case, the input light transmitted through the liquid crystal display device 7 operating according to the video signal from the video signal generator 9 input to the liquid crystal display device driving circuit 8
It becomes an input to the optical writing type spatial light modulator 10,
The optically-written spatial light modulator 10 as the written information 13
Is input to Then, the impedance changes in the photoconductor layer 3 due to the write information 13, the twist structure changes in the liquid crystal layer 6, and the polarization state of the readout light 14 is changed to become the output information 15. The control unit 16 controls the liquid crystal display device 7
The write information 13 of the optical write-type spatial light modulator 10 is controlled by changing the applied operation voltage of.

FIG. 2 is a view for explaining that the ratio of the input light amount from the write incident light of the optical writing type spatial light modulator to the output light amount on the read light incident side becomes uniform in the read light irradiation surface. In the figure, reference numerals in the figure are the same as those in FIG. The inside of the reading light irradiation surface of the optical writing spatial light modulator 10 is divided into an arbitrary number by matrix (to 9 divisions), and the reading light source sends the light writing spatial light modulator 1
Since the input-output characteristic of the optical writing type spatial light modulator 10 changes depending on the angle of incidence of the 0 on the readout light irradiation surface, the readout light irradiation surface is subdivided and written into the subdivided blocks. The light amount is controlled by the control unit 16.

Therefore, the display surface of the liquid crystal display device 7 is also subdivided so as to correspond to each subdivided block in the readout light irradiation surface of the optical writing type spatial light modulator 10, and every nine subdivided blocks are provided. If the operating voltage range (white voltage, black voltage) of the liquid crystal display device 7 is made variable, the control unit 16 changes the amount of writing light in such a direction that the output of the optical writing type spatial light modulator 10 becomes constant. Can be controlled by

FIGS. 3A to 3E are graphs showing main characteristic graphs of respective parts of the reflection type liquid crystal projector of the present invention.
3A is an input video waveform, FIG. 3B is a gamma correction characteristic waveform, and FIG. 3C is a voltage-transmittance (V-
T) Characteristic waveforms, FIG. 3D shows input / output characteristics of the optical writing spatial modulator, and FIG. 3E shows output video waveforms.

As a means for inputting and writing data to the optical writing type spatial light modulator 10, in a liquid crystal writing device 11 comprising a liquid crystal display device 7, a liquid crystal display device driving circuit 8 and a video signal generator 9, FIG. After inputting a linear input video waveform as shown in FIG. 3) to the video signal and setting the working voltage range (white voltage, black voltage) of the liquid crystal display device 7, FIG.
The output image waveform of the final stage via the voltage-transmittance characteristic of the liquid crystal display device 7 as shown in FIG. 3C has a linear characteristic waveform as shown in FIG. In the drive circuit 8, the waveform shown in FIG. 3B is corrected (γ correction).

In the case of a reflection type liquid crystal projector, the input light 12 transmitted through the liquid crystal display device 7 becomes write information 13, is input to the optical write type spatial light modulator 10, is output by the read light 14, and becomes a final output image. However, considering the flow of the characteristic waveform, after passing through the voltage-transmittance characteristic of the liquid crystal display device 7 as shown in FIG.
Further, through the input-output characteristics of the optical writing type spatial light modulator 10 as shown in (1), the output characteristics of the optical writing type spatial light modulator 10 which becomes the final output image are arranged in a matrix on the reading light irradiation surface. Division (here 9 for explanation)
3), and the angle of incidence from the read light source to the read light irradiation surface of the optical write spatial light modulator 10 as shown in FIG. Since the input-output characteristics of the block change, the inside of the readout light irradiation surface is subdivided, and the following correction means is provided for each subdivided block.

The output of the optical writing type spatial light modulator 10 is
In order to make this constant, it is necessary to correct any one of the input sides. However, in the case of γ correction, the liquid crystal display device The liquid crystal display device 7 must also be subdivided so as to correspond to each subdivided block in the readout light irradiation surface of the write-type spatial light modulator 10, and all nine blocks must be individually gamma-corrected. Processing capacity, memory capacity, etc.
It is very huge and impractical.

Therefore, if the operating voltage range (white voltage, black voltage) of the liquid crystal display device 7 is varied for each subdivided block, as shown in FIG. Since the rate characteristic waveform changes, the control unit 16 can control the amount of writing light so that the output of the optical writing type spatial light modulator 10 becomes constant as shown in FIG. .

As described above, by changing the applied operating voltage (white voltage, black voltage) of the liquid crystal display device for each block in the read light irradiation surface divided into an arbitrary number of the optical writing type spatial light modulators. , The voltage-transmittance characteristic (V-
(T characteristic) The waveform changes, and as a result, the writing light amount incident on the optical writing type spatial light modulator is controlled, the output image in any divided block becomes uniform, and the luminance of the image projected on the screen becomes uniform.

[0024]

As is apparent from the above description, according to the present invention, there is provided a system in which an optical writing type spatial light modulator is used in a reflection type liquid crystal projector which cannot supply readout light with perfect parallel light. , Read light
Optical writing type that changes depending on the incident angle of readout light on the emitting surface
To correct the input-output characteristics of the spatial light modulator,
Output characteristics of buried spatial light modulator are uniform in the plane
Since the control means for controlling the writing light amount is provided so that the final output image projected on the screen does not have partial luminance unevenness or chromaticity unevenness, a uniform image can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of a reflection type liquid crystal projector according to the present invention.

FIG. 2 is a more specific explanatory diagram of the present invention.

FIG. 3 is a diagram showing a main characteristic graph of each part of the reflection type liquid crystal projector of the present invention.

FIG. 4 is a configuration diagram of a conventional liquid crystal projector.

FIG. 5 is a diagram for explaining a conventional example.

FIG. 6 is a diagram for explaining a conventional example.

FIG. 7 is a diagram for explaining a conventional example.

FIG. 8 is a diagram showing a main characteristic graph of each part of the conventional reflection type liquid crystal projector.

[Explanation of symbols]

1a, 1b: glass substrate, 2a, 2b: transparent electrode, 3 ...
Photoconductor layer, 4 light shielding layer, 5 reflection mirror layer, 6 liquid crystal layer, 7 liquid crystal display device, 8 liquid crystal display device driving circuit, 9
... video signal generator, 10 ... optical writing type spatial light modulator,
11: liquid crystal writing device, 12: input light, 13: write information, 14: read light, 15: output information, 16: control unit.

Claims (3)

(57) [Claims] 1. A comprising a photoconductor whose impedance is changed by the writing beam, a photo-writing type spatial light modulator twist structure by the impedance change of the optical conductor and a change Surune Matic liquid crystal, information of the writing light Changes with the read light incident angle on the read light irradiation surface in a liquid crystal projector that displays
The input-output characteristics of an optically written spatial light modulator
Output characteristics of the optical writing type spatial light modulator
A reflection type liquid crystal projector characterized by comprising control means for controlling a writing light amount so as to be uniform in a plane . 2. A control means for dividing an inside of a reading light irradiation surface of the optical writing type spatial light modulator into an arbitrary number of matrices and controlling a writing light amount for each of the divided blocks. The reflective liquid crystal projector according to claim 1. 3. The liquid crystal display device according to claim 1, wherein the control means controls a video signal for driving the liquid crystal display device by using a liquid crystal display device that performs display driving by using a video signal for writing light information. 2. The reflective liquid crystal projector according to 2.