JP3288236B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a display device ,
In particular, a table comprising: an optical modulator for modulating an optical state based on a signal containing gradation information; and a read light source for providing the optical modulator with read light for reading image information.
Display device .

[0002]

2. Description of the Related Art Optical modulation elements (optical modulation means) are used for various optical devices. For example, an optical modulation element of a display device. A liquid crystal display element will be described as the most familiar example. Conventionally, several methods have been proposed for performing gradation display using a liquid crystal element.

The first is a twisted nematic liquid crystal (T
N liquid crystal), and the voltage that changes according to the gradation information is expressed as T
In this method, the transmittance is applied to the N liquid crystal to modulate the transmittance of the entire pixel.

[0004] Second, one pixel is configured as an aggregate of a plurality of sub-pixels, and each sub-pixel is turned on / off by binary data, thereby modulating the area of the light-transmitting sub-pixel. It is a method.

[0005] This method is disclosed in, for example, Japanese Patent Application Laid-Open No. 56-88193.
And EP453033, EP361981
No. 6,009,036.

Third, by making the electric field strength or the inversion threshold value of the liquid crystal distributed in one pixel different, a part showing a bright state and a part showing a dark state coexist in one pixel. Is a method of modulating the area ratio of those portions.

[0007] This method is based on "Ferroelectric liquid crystal optical modulation means having a region where nucleation and inversion occur in a pixel" given to the inventor Kaneko et al.
ical modulation device with regions with in pixels
U.S. Pat. No. 4,796,980, U.S. Pat. No. 4,712,877, and U.S. Pat. No. 4,747,671 titled "To initiate uncleation and inversion".
And U.S. Pat. No. 4,763,994.

The fourth method is a method of modulating the length of a period during which one pixel is turned on to exhibit a bright state. This method was given to the inventors Kuribayashi et al. “Ferroelectric display panel and its gradation driving method (Ferroelectric display panel and driving method).
method therefor to activegray scale), which is disclosed in U.S. Pat. No. 4,709,995. Another example of digital duty modulation is
"Active" granted to inventor Nelson
Row backlight column shutter LSD with one shutter transition per row (Activerow backlight column shutter LCD wit
No. 5,311,206, entitled "h one shatter transition per row".

Here, the first method is called luminance modulation, the second method is called pixel division, the third method is called domain modulation, and the fourth method is called digital duty modulation.

[0010]

It is difficult to apply luminance modulation to an element using an optical modulation material having a characteristic in which transmittance changes sharply with applied voltage. Also, the brightness modulation is generally TN
Since the response speed of the liquid crystal is low, it is not suitable for a system in which information changes at a high speed.

Since pixel division is the same as arranging a large number of pixels with a small number of pixels, the spatial frequency is reduced and the resolution tends to be reduced. Further, the area of the light-shielding portion increases and the aperture ratio decreases.

In the domain modulation, the structure of a pixel for giving a distribution to the electric field strength or giving a distribution to the inversion threshold becomes complicated. Further, since the voltage margin for the halftone display is narrow, it is easily affected by the temperature.

In the digital duty modulation, since the ON / OFF time is modulated, and the unit time of the modulation is determined by the clock frequency and the gate switching time, it is difficult to perform highly accurate modulation. That is, the multi-tone display has a limit. In addition, since it is necessary to always convert analog data to analog / digital (A / D) to obtain digital gradation information, it is difficult to apply the method to a simple system.

The present invention has been made in view of the above technical problem, and has as its object to provide a display device having means for performing optical modulation based on analog data.

Another object of the present invention is to provide a display device having an optical modulation means which can be applied to an optical substance having a sharp applied voltage / transmittance characteristic.

Still another object of the present invention is to provide a display device having an optical modulation means capable of achieving high resolution with a high spatial frequency.

Another object of the present invention is to provide a display device having an inexpensive optical modulation means capable of reproducing gradation information by analog duty modulation with a relatively simple system.

Still another object of the present invention is to provide an image display device capable of displaying good halftones.

[0019]

According to the present invention, there is provided a display device comprising: a pair of electrodes for applying a voltage; and a photoconductive layer and a layer of an optical modulation material provided between the pair of electrodes. And a signal light source for providing optical information including gradation information to the photoconductive layer, and readout light irradiation means for providing readout light for reading out image information to the optical modulation material layer, The signal light source scans the optical information in one frame toward the photoconductive layer in a horizontal scanning direction in one direction and a vertical scanning direction in one direction, and in a frame close to the one frame, Means for scanning optical information toward the photoconductive layer along a horizontal scanning direction in the other direction and a vertical scanning direction in the other direction, wherein the optical information is scanned along the horizontal scanning direction in the one direction and the vertical scanning direction in the one direction. Previous A switching period between the optical information scanning and the optical information scanning along the other horizontal scanning direction and the other vertical scanning direction is set differently from a voltage inversion period of a voltage applied between the pair of electrodes. It is a thing.

(Operation) In the present invention, the scanning of the optical information is performed from different directions in adjacent frames, so that the luminance and brightness at the same gradation level can be obtained at any part (pixel) on the display surface. Becomes uniform. This eliminates the need to scan the reading light, so that the configuration of the reading light irradiation optical system is simplified, and the display device can be reduced in size and provided at low cost.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIGS. 30 to 33 which will be described later. Before that, the basic configuration will be described.

First, a basic modulation method of analog duty modulation will be described with reference to the drawings.

FIG. 1 is a diagram showing an example for realizing the present modulation system, 1 is an optical shutter for controlling the transmission of light as optical modulation means, 2 is a light source for generating light, DR
Reference numeral 1 denotes a driving unit for driving the optical shutter 1, DR2 denotes a driving unit for turning on the light source 2, and CONT denotes a control unit for controlling power supply and operation timing to the two driving units DR1 and DR2.

FIG. 2 is a graph showing an example of the characteristics of the optical modulation element (substance) of the optical shutter 1. For example, when the pulse width is constant and the applied voltage exceeds the threshold value _Vth , the transmittance sharply increases. The transmittance increases, and the transmittance becomes constant above the saturation value V _sat . If the optical modulator has a memory property, the optical state is kept constant even when the applied voltage is released.

FIG. 3 is a timing chart for explaining the basic operation of FIG. 1. In FIG. 3, reference numeral 10 denotes an optical transition of an optical shutter, reference numeral 20 denotes a lighting timing of a light source, and reference numeral 30 denotes a signal applied to an optical shutter. . The applied signal 30 is a signal in which the amplitude (peak value) V _op and the pulse width PW _op further change according to the gradation information.

The light source is turned on (ON) at time t ₁ ,
Light is emitted for a period t until the light is turned off (OFF) at ₃ .
This period t is a predetermined time so that halftones can be recognized. The signal modulated according to this timing is at time tt
_When the voltage is applied to the _ON state, the optical shutter is in the dark state (M
in) to the bright state (Max).

The rising timing t ₂ of this transition also depends on the amplitude V _op and the pulse width PW _op . Since the amplitude V _op is modulated by the gradation information, the timing t ₂ eventually changes within the range of the time width TM according to the gradation information. tt _off is the application timing of the signal for turning _off the optical shutter, and the time integral of the amount of light transmitted through the optical shutter 1 is the overlap time of the lighting time and the time when the optical shutter is in the ON state. Will change accordingly. Therefore, if the pulse width PW _op is fixed and the amount of the amplitude V _op is changed in an analog manner, the time integral of the transmitted light amount can be easily modulated.

All conventional digital duty modulations are
The pulse width PW _op and the amplitude V _op of the applied signal 30 are kept constant, and the application timing tt _ON of the applied signal 30 is digitally changed according to the clock.

On the other hand, the present modulation is novel in that the signal 30 is treated as an analog quantity, thereby enabling analog duty modulation.

FIG. 4 shows an example of a circuit for generating an analog signal 30.
The signal having the modulated amplitude and the predetermined pulse width required for driving the optical shutter can be obtained by amplifying the signal by the amplifier 1 and sampling by the switch including the transistor Tr2.

Next, another basic modulation method of the present modulation will be described with reference to FIG.

The difference from the system shown in FIG. 1 is that the optical modulating means is the light reflecting means 1A. A liquid crystal element or a mirror element is used as the light reflecting means 1A. In the case of a liquid crystal element, one of a pair of substrates enclosing liquid crystal is used as a transparent body and the other is used as a reflector, and light absorption or light reflection is selectively performed according to the alignment state of the liquid crystal. In the case of a mirror element, the angle of the reflection surface of the mirror is controlled by displacing the mirror, and whether the reflection surface is directed in a predetermined direction or in another direction is selected.

Then, the overlap time of the lighting time of the light source and the ON time of the reflection means is analog-modulated according to the gradation data.

Here, the ON time of the reflecting means is a time during which the liquid crystal element is in a light reflecting state or a time during which the reflecting surface of the mirror element is oriented in a predetermined direction.

(Drive Circuit) The drive circuit used in the present invention will be described.

FIG. 6 is a diagram showing a drive circuit of the optical modulation means used for the main modulation. Here, the optical modulation means is C
Shown by _LC .

The resistance R according to the gradation information_PCThe value of
First, the optical modulation means C _LCExceeded threshold
Apply sufficient voltage. This time R_PCIf the value of is high, C
_LCThe time at which the voltage applied to exceeds the threshold value is delayed. one
One, R_PCIf the value of is low, C_LCVoltage applied to
The time that exceeds the value is earlier. So, at these times,
Adjust the lighting timing and lighting time of the light source to transmit light
Alternatively, analog duty modulation of the reflected light becomes possible.

FIG. 7 is a diagram showing another driving circuit. FIG.
Differs in that connected in parallel to the optical modulation means C _LC resistor R _PC, with capacitive C _PC. In this case, a drive voltage Vd sufficient to exceed the threshold is applied for a predetermined time and _CLC
Is turned on, discharge development based on the time constant of the RC circuit is used. Time the voltage applied to C _LC is lower than the threshold and the value of the resistance R _PC is if slow discharge high slower.

On the other hand, the lower the value of R _PC discharge faster, the time at which the voltage applied to C _LC is lower than the threshold faster. If this time is set within the lighting time of the light source, the light transmission or reflection time is subjected to analog duty modulation due to the difference in timing.

FIG. 8 shows another example of a driving circuit. The value indicated by the variable voltage Vv is the gradation information. The difference from FIG. 7 is that the time constants of the RC circuits R _PC and C _PC are fixed.
_The timing at which the voltage applied to the _LC falls below the threshold is determined by the voltage Vv that is the gradation information. Accordingly, analog duty modulation can be performed by adjusting the timing with the lighting time in the same manner as in FIG.

(Light Source) The light source used in the present modulation will be described. The light emitted from this light source is selected from natural sunlight, white light, monochromatic light such as red (R), green (G), blue (B), and combinations thereof, as necessary.
Therefore, examples of the light source used in the present invention include a laser light source, a fluorescent lamp, a xenon lamp, a halogen lamp, a light emitting diode, and an electroluminescent element. ON / OFF of these lightings is controlled by the light source driving means according to the driving timing of the optical modulation means.
In particular, it is desired that the lighting time of the readout light source be not more than the reciprocal (1/60 second) of the flicker frequency (for example, 60 Hz) at which humans can recognize flicker. In the case of color display, it is desirable to turn on the R, G, and B light sources at different timings, and to perform optical modulation of R, G, and B in a time-division manner.

(Optical Modulation Means) Examples of the optical modulation means used in the present invention include a light shutter (light valve) for modulating the light transmittance and a reflection element as a light reflection means for modulating the light reflectance. .

The optical shutter used in the present modulation may be any shutter that can exhibit two states having different transmittances. A preferred example is one using liquid crystal as the optical modulation material.

As the optical modulation means using a liquid crystal, it is desirable to dispose a liquid crystal between a pair of electrodes and change the alignment state of liquid crystal molecules according to an applied electric field. Then, the light transmittance is controlled through the polarizing element according to the optical characteristics of the molecular orientation. Therefore, in the liquid crystal element, the transmittance, the reflectance,
The transmission state and the reflection state are caused by a combination with a polarizing element.

Specifically, it is preferable to use a liquid crystal cell in which liquid crystal is sealed between a pair of substrates. A transparent electrode and an alignment film are provided on at least one inner surface of the pair of substrates as needed.

As the substrate, translucent glass, plastic, quartz or the like is used. As the transparent electrode, a metal oxide conductor such as tin oxide, indium oxide, and ITO is preferably used.

As the alignment film, a polymer film that has been subjected to a uniaxial alignment treatment such as rubbing or an inorganic film formed by oblique deposition is preferable.

As the liquid crystal, a nematic liquid crystal exhibiting a nematic phase when operating as a cell and a smectic liquid crystal exhibiting a smectic phase when operating as a cell are preferably used.

As a reflection element used in the present modulation, a reflection surface of a metal film is moved by an electrostatic force by an applied voltage,
DM that modulates the direction of reflected light by changing the angle of the reflecting surface
An element called D (Digital Micromirror Device)
A liquid crystal element that reflects light when the liquid crystal is oriented in a transmissive state, with one surface of the liquid crystal cell as a reflector and the other surface as a transmissive body, may be mentioned.

FIG. 9 is a graph showing the applied voltage transmittance characteristics of the optical modulation element (substance) used for the main modulation. D
In the case of MD, it can be regarded as a graph showing the applied voltage dependence of the amount of reflected light reflected in a predetermined direction.

In FIG. 9, (a) shows a state transition with a positive threshold voltage as a boundary value, (b) shows a state with positive and negative thresholds and further has hysteresis, (C) shows a case where positive and negative threshold values are generated due to hysteresis, and (d) shows a case where voltage 0 is the threshold value. FIG. 9 shows ideal characteristics in order to simplify the description, and actually has a slight slope between the threshold value and the saturation value as shown in FIG.

Consider matching with the driving circuit. 9 (a) and 9 (b) are preferably combined with the parallel circuit shown in FIGS. 7 and 8, and FIGS. 9 (c) and 9 (d) are combined with the series circuit shown in FIG. Good to combine.

Examples 1 to 6 described below are reference examples to facilitate understanding of the present invention.

(Reference Example 1) FIG. 10 is a schematic diagram for explaining a method of driving the optical modulation means. In the figure, 10
Reference numeral 1 denotes a liquid crystal element in which a chiral smectic liquid crystal is arranged between a transparent substrate having a pair of electrodes; 103, a gradation information generating circuit for generating gradation information; 104, a light source; and 105, a viewer. The driving circuit is composed of the capacitor C _pc and the transistor 1
02, and the resistance between the source and the drain (or the emitter and the collector) changes according to the potential of the gate or the base of the transistor 102, so that the timing at which the voltage applied to the liquid crystal exceeds the inversion threshold of the liquid crystal is reached. Change. Vext is a voltage applying means for applying a voltage for resetting the liquid crystal element and a driving voltage. Cfl
c indicates the capacity of the liquid crystal.

The gradation information generating circuit 103 includes a light emitting diode PED and four variable resistors VRB, VRG, VRR, VR.
W and four transistors TB, TG,
TR, TW and power supply VCC. The diode PED and the transistor 102 constitute a photocoupler.

An electric signal as gradation information of each color given as a variable resistance value is converted into light information by the light emitting diode PED.

The light source 104 includes light emitting diodes EDR, EDG, and EDB for generating light of three colors RGB. BR
Is a variable resistor for white balance provided as needed.

FIG. 11 is a timing chart of the driving of FIG. 10. In FIG. 11, 103T indicates an output timing of optical information, Vflc indicates a voltage applied to the liquid crystal,
Tran indicates the transmittance of the liquid crystal element, 104T indicates the lighting timing of the light source, and 105T indicates the amount of transmitted light recognized by the observer.

First, a reset pulse is applied by the voltage applying means Vext at the same time that white light for reset is applied. Thus, the liquid crystal is once oriented to a dark state.

Next, at the same time that the light corresponding to the gradation information of R is output, the light emitting diode EDR of R lights up, and Ve
xt applies a voltage of the opposite polarity to the electrode of the liquid crystal element. Since the R light amount is extremely small during this period, the effective voltage applied to the liquid crystal does not exceed the threshold value _Vth , so that the liquid crystal element does not transmit the R light.

Thereafter, white light is again applied and V
ext increases, and the liquid crystal is inverted to a light transmitting state. However, at this time, since the light source is not turned on, the observer sees the dark state continuously.

Next, Vext becomes a negative voltage, but since the effective voltage applied to the liquid crystal does not exceed the threshold value, the liquid crystal element remains in the bright state. However, the light source is not turned on during this period.

Thus, the display period of R ends.

Next is a G display period in which the same driving as that of the R display period is performed. Here, since the light amount of the G information is larger than the case of R, the voltage applied to the liquid crystal exceeds the threshold value at time trv. Then, the liquid crystal element transmits the G light until the time t _off when the lighting of the light source ends, so that the observer recognizes the intermediate level G light.

Similarly, the next is a B display period in which the same driving as that of the R and G display periods is performed. Here, since the light amount of the B information is larger than the case of G, the voltage applied to the liquid crystal exceeds the threshold value at time trv2. Then, the liquid crystal element transmits B light until t _off 2 when the lighting of the light source is completed.
The observer recognizes the intermediate level B light closest to the maximum bright state.

As described above, in this embodiment, the timing at which Vflc exceeds the threshold is changed according to the gradation information. Then, when the gradation information corresponding to the minimum level transmission state is input, the transmission period (on period) of the liquid crystal element and the lighting period of the light source do not overlap with each other when the light source is on. , Set the light-off time.

Thus, in the present embodiment, a desired intermediate state can be obtained from the range from the minimum brightness level to the maximum brightness level. In addition, since the voltage applied to the liquid crystal is symmetrical, the DC component applied to the liquid crystal becomes substantially zero, and the deterioration of the liquid crystal element can be suppressed.

(Reference Example 2) FIG. 12 is a schematic diagram for explaining a driving method of the optical modulation means. 201 is a reflective liquid crystal element in which liquid crystal is arranged between substrates having a pair of electrodes,
204 is a light source driving circuit for driving the light source, C _pc is a capacitance element, R _pc is a resistance element, and Vd is a driving voltage source. This system is a circuit in which the resistance value changes when gradation information is input to the resistance element _Rpc .

The characteristics of the liquid crystal used are as shown in FIG.

FIG. 13 is a timing chart of the driving of FIG. 12, where Vs1 indicates the application timing of the power supply Vd,
1c indicates the voltage applied to the liquid crystal, Tran indicates the reflectance of the liquid crystal element, 204T indicates the lighting timing of the light source, and 205T indicates the amount of transmitted light recognized by the observer. l is for low values of R _pc , m is for intermediate values of R _pc , n is R
_This shows a case where the value of _pc is high, and each corresponds to analog gradation information.

First, when Vd is applied to the liquid crystal element at the time t _on , the voltage Vlc applied to the liquid crystal becomes the voltage V1 sufficiently exceeding the threshold value. At the same time, the liquid crystal element has a maximum reflectance.

At time t _off , the voltage Vd is released, so that the voltage Vlc applied to the liquid crystal gradually decreases in accordance with the resistance value _Rpc , and falls below the threshold at a certain timing. Since this timing depends on the gradation information, in the case of l, the time t
In _X1, the case of m at time t _X2, reflectance Tran is minimized at time t _X3 For n. Here, since the light source is set to start lighting at time t _X1 and turn off at time t _X3 , the reflected light amount corresponding to l, m, and n is as shown in 205T.

As described above, in this example, the timing at which V1c falls below the threshold is changed according to the gradation information. Then, when the gradation information corresponding to the minimum level of the reflection state is input, the reflection period (on period) of the liquid crystal element and the light emission period of the light source do not overlap each other when the light source is lit. , The lighting time of the light source is set.

Thus, in this example, the minimum brightness level l
, The desired intermediate reflection state can be obtained from the range of the maximum brightness level m.

(Embodiment 3) FIG. 14 is a schematic diagram for explaining a method of driving the optical modulation means. 301 is a reflective liquid crystal element in which liquid crystal is arranged between substrates having a pair of electrodes,
Reference numeral 304 denotes a light source driving circuit for driving the light source, C _pc denotes a capacitance element, R _pc denotes a resistance element, Vv denotes a driving voltage source, and Vs ₀ denotes a switch for turning on / off the supply of a voltage signal from the driving voltage source Vv. In this system, a supply voltage signal from a drive voltage source is analog gradation information.

The characteristics of the liquid crystal used are as shown in FIG.

FIG. 15 is a timing chart of the driving of FIG. 14, where Vs ₀ indicates the application timing of the gradation signal,
1c indicates the voltage applied to the liquid crystal, Tran indicates the reflectance of the liquid crystal element, 304T indicates the lighting timing of the light source, and 305T indicates the amount of transmitted light recognized by the observer. 1 indicates the case where the voltage value V1 of the gradation signal is low, m indicates the case where the voltage value Vm of the gradation signal is at an intermediate level, and n indicates the case where the voltage value Vn of the gradation signal is high.

First, when Vv is applied to the liquid crystal element at time t _on , the voltage Vlc applied to the liquid crystal becomes voltages V1, Vm, and Vn that sufficiently exceed the threshold. At the same time, the liquid crystal element has a maximum reflectance.

At time t _off , the voltage Vv is released, so that the voltage Vlc applied to the liquid crystal gradually decreases according to the voltage Vv, and falls below the threshold at a certain timing. Since this timing depends on the gradation information, in the case of 1, at time t _X1 ,
In the case of m, the reflectivity Tran of the liquid crystal element transitions to the minimum state at time t _X2 , and in the case of n at time t _X3 .
Here, since the light source is set to start lighting at time t _X1 and turn off at time t _X3 , the reflected light amount corresponding to l, m, and n is as shown in 305T.

As described above, in this example, the timing at which Vlc falls below the threshold is changed according to the gradation information. Then, when the gradation information corresponding to the minimum level of the reflection state is input, the reflection period (on period) of the liquid crystal element and the light emission period of the light source do not overlap each other when the light source is lit. , The lighting time of the light source is set.

Thus, in this example, the minimum brightness level 1
, The desired intermediate reflection state can be obtained from the range of the maximum brightness level m.

(Reference Example 4) FIG. 16 shows the driving of the optical modulation means.
It is a schematic diagram for demonstrating a method. 401 is a pair of electrodes
Antiferroelectric chiral smectic between substrates with
404 is a reflective liquid crystal element with a liquid crystal
Moving light source drive circuit, C_pcIs a capacitive element, R _pcIs a resistance element
Vv is a drive voltage source, Vs₀From the drive voltage source Vv
A switch for turning on / off the supply of the voltage signal. this
The system converts the supply voltage signal from the drive voltage source to the analog floor.
Key information. 405 indicates an observer.

The characteristics of the chiral smectic liquid crystal used are as shown in FIG.

FIG. 17 is a timing chart of the driving of FIG. 16, where Vs ₀ indicates the application timing of the gradation signal,
aflc is the voltage applied to the liquid crystal, Tran is the reflectance of the liquid crystal element, 404T is the lighting timing of the light source,
T indicates the transmitted light amount recognized by the observer. 1 indicates the case where the voltage value of the gradation signal is low, m indicates the case where the voltage value of the gradation signal is at the intermediate level, and n indicates the case where the voltage value of the gradation signal is high.

First, when Vv is applied to the liquid crystal element at time t _on , the voltage Vaflc applied to the liquid crystal becomes voltages V1, Vm, and Vn that sufficiently exceed the threshold. At the same time, the liquid crystal element has a maximum reflectance.

At time t _off , the voltage Vv is released, so that the voltage Vaflc applied to the liquid crystal gradually decreases according to the voltage Vv, and falls below the threshold at a certain timing. Since this timing depends on the gradation information, in the case of l, the time t _X1
In the case of m, the reflectance Tran of the liquid crystal element transitions to the minimum at time t _X2 , and in the case of n at time t _X3 . Here, since the light source is set to start lighting at time t _X1 and turn off at time t _X3 , the amount of reflected light corresponding to l, m, and n becomes as shown at 405T.

The present embodiment differs from the embodiments shown in FIGS. 14 and 15 in that a voltage Vv whose polarity is inverted from that of the previous period Prd1 is applied in the period Prd2 because the antiferroelectric liquid crystal is used. is there. Since the antiferroelectric liquid crystal is used, the threshold value becomes two of Vth1 and Vth2 due to the hysteresis. Even if the polarity of the voltage Vv is inverted, the alignment state of the liquid crystal is the same as shown in Tran. A chiral smectic liquid crystal has a high transition speed (switching speed) between two molecular alignment states, and is therefore most suitable as a liquid crystal used in the present invention.

As described above, in this example, the timing at which Vaflc falls below the threshold is changed according to the gradation information.
Then, when the gradation information corresponding to the minimum level of the reflection state is input, the reflection period (on period) of the liquid crystal element and the light emission period of the light source do not overlap each other when the light source is lit. , The lighting time of the light source is set.

The present invention employs a configuration in which a large number of optical modulation elements are arranged two-dimensionally, that is, the optical modulation means in each of the above-described examples, that is, the optical shutter and the light reflection means.

Specifically, it is a panel in which many pixels are arranged on a matrix or a DMD in which many micromirrors are arranged in a matrix.

Next, a driving method of the image display device according to the present invention will be described.

(Embodiment 5) FIG. 18 is a cross-sectional view of an optical modulation means for an image display device according to Embodiment 5 of the present invention. FIG.
FIG. 9 is a diagram showing the molecular orientation of the chiral smectic liquid crystal used in the device. FIG. 20 shows the electro-optical characteristics of the liquid crystal molecules. FIG. 21 is a timing chart showing the operation.

The element shown in FIG. 18 is a so-called reflection type liquid crystal panel, in which a transparent electrode 512 is formed on a transparent substrate 511, a photoconductive layer 513 as a photosensitive layer is provided thereon, and a reflection layer is provided thereon. A dielectric multilayer film 514 is provided as a layer. On the other transparent substrate 516, the transparent electrode 5
15 are provided. A chiral smectic liquid crystal 517 as an optical modulator is disposed between these two substrates. 522 is a polarizing element. Although not shown, an alignment film for aligning liquid crystal molecules is provided at a liquid crystal interface between the electrode 515 and the reflective layer 514. Vext is a voltage applying means for applying a voltage to the electrodes 512 and 515;
21 is a reset light, 518 is a write light including gradation information, and 519 is modulated gradation information, that is, read light for reading an image.

The equivalent circuit of this element is the same as that of FIG.

FIG. 19A shows a state where the liquid crystal molecules MOL are in the first alignment state, and FIG. 19B shows a state where the liquid crystal molecules MOL are in the second alignment state. When a voltage + Vu is applied to the liquid crystal in the first alignment state A, the liquid crystal transitions to the second alignment state. Thereafter, the liquid crystal remains in state B even when the voltage is set to 0, that is, when there is no electric field. Next, when a voltage -Vu is applied, the liquid crystal transits to state A and maintains state A even when the electric field is released. Such a transition is called liquid crystal inversion or switching.

Since these states A and B are optically different states, when appropriately combined with a polarizing element, one state is a state where the light transmittance is maximum and the other state is a state where the light transmittance is minimum. be able to. Here, Vu is set assuming that the saturation value of the applied voltage is substantially the same as the inversion threshold value of the liquid crystal.

The operation of this device will be described. To illustrate the nature of the operation, the capacitance C _pc equal volume capacity Cflc and the photoconductive layer of the liquid crystal layer, the resistance component of the liquid crystal layer is infinite, the impedance of the reflective layer to 0. 5 in FIG.
21T indicates the irradiation timing of the reset light applied to the photoconductive layer 513, and 518T indicates the irradiation timing of the writing light applied to the photoconductive layer 513 and the intensity of which changes according to the gradation information. Vext is the transparent electrode 51 at both ends of the device.
An alternating voltage Vflc applied between the terminals 2 and 515 indicates an effective voltage divided and applied to both ends of the liquid crystal layer 517. + Vu and -Vu are voltages at which the liquid crystal is inverted from the first to the second or from the second to the first alignment state as shown in FIG.
Tran indicates the orientation state of FLC.
It is assumed that the positional relationship of the polarizing elements composed of the polarizer analyzer is set such that the alignment state is a dark state where the transmittance is minimum and the second alignment state is a bright state where the transmittance is maximum. Reference numeral 504T denotes reading irradiation light for irradiating the liquid crystal layer 517, and reference numeral 505T denotes extraction light reflected and extracted by the reflection layer via the liquid crystal, the polarizer, and the analyzer.

First, t₅₀To t₅₁During the reset period
is there. The potential −V as Vext₁Given and reset
Light is applied to the photoconductive layer. Light guide by reset light
Photocarriers (electron-hole pairs) are generated in the photoconductive layer,
Electrons and holes are separated and reversed by the electric field that was applied with a partial pressure.
Direction, and face each other with the liquid crystal layer 517 in between.
Become. With this operation, Vflc is set to the potential −V₁Approaching
To go. Explaining with the equivalent circuit of FIG.
The self-discharge occurs due to the decrease in the resistance component in the photoconductive layer
As a result, the potential applied to the photoconductive layer by the partial pressure decreases, and Vfl
c is -V₁May be considered as approaching. Reset light
Has sufficient light intensity, regardless of the previous state, t
₅₁Vflc is -V₁Reset to
The first alignment state (dark) of the liquid crystal is ensured. t₅₁At
Turn off the set light and set Vext to + V _TwoTo Then Vf
The potential of lc is V_Three= -V₁
+ (V_Two-(-V₁)) / 2. 1st lap
If the writing light is not irradiated as in the period, t₅₂Up to Vf
lc is V_ThreeAnd V_Three<Vu, so the liquid crystal
It remains in the first alignment state (dark). t₅₂V after that
The polarity of ext is inverted so that t₅₀To t₅₂Same thing as
Again. As a result, Vflc is integrated within one cycle.
Then, 0, that is, the DC component becomes 0, and the stable FL
AC symmetry of the drive waveform required for C drive is guaranteed
You. t₅₂To t₅₃Vflc exceeds Vu and + V₁
And the liquid crystal is in the second alignment state (bright).

In the second period, the writing light is irradiated.
You. This writing light was not as strong as the reset light.
Time constant is slower, but Vflc approaches Vext
Go. If the writing light intensity is strong to some extent, t₅₁To t₅₂
Time T = t between_X1Vflc exceeds Vu
At this point, the liquid crystal changes from the first alignment state to the second alignment state.
Invert to the state (Ming). The writing light is updated as in the third cycle.
T becomes strong_X1Is t ₅₁Approaching the second time earlier
It turns into an alignment state. In both the second and third periods, t₅₃
To t₅₄Between t₅₁To t₅₂Equivalent to irradiation in between
Since the writing light is irradiated, t_X2Vflc is -Vu
Then, the liquid crystal returns to the first alignment state (dark). 1st, 1st
In both the second and third periods, the AC symmetry of Vflc is secured.
In each period, the liquid crystal is in the first alignment state and the second alignment state.
The orientation state is for 50% of the time. High writing light intensity
, The phase of the FLC in the second alignment state shifts forward.
To go. For such a liquid crystal operation, t
₅₁To t₅₂Irradiating the readout light during the period of
Irradiation time of read light and FLC second alignment state (bright)
Light will be observed only for the overlap time. In the first cycle
Light cannot be extracted, but as the writing light intensity increases,
As in the second and third periods, the overlap time increases, and the extracted light
The number of bundles also increases. Each cycle is below the flicker frequency of the human eye
Time (for example, 1 / 60th of a second)
To the eye, it will be observed as a change in light intensity.

[0100] Also, rather than between _{t 51 ~t 52, t 53 ~t} 54
If the reading light is irradiated during the period, as the writing light intensity is increased, the overlapping time is reduced, and the number of extracted light beams is reduced. That is, negative-positive conversion can be performed between the writing light and the extracted light. Since the writing light has a secondary planar spread, an in-plane potential distribution can be created by the writing light intensity, and a so-called optical writing type spatial optical modulation means capable of two-dimensional optical writing and reading can be constituted. it can. Using this, a monochrome film viewer can be configured.

FIG. 22 is a system configuration diagram of a full color film viewer as an image display device using the optical writing type spatial optical modulation means according to the present invention.

For the light source on the writing side, light-emitting diodes (LEDs) of three colors of R, G and B are prepared for each color.

Reference numeral 530R denotes an R writing light source LED, 5
30G is a G writing light source LED, 530B is a B writing light source LED, 535 is a reset light source, 53 is an R reflection surface, and B is a three-color mixing prism having a reflection surface. 536 is an optical modulation means, 532 and 534 are lenses,
533 is a film and 537 is a prism. 539R
Is an LED for reading light source of R, 539G is an LED for reading light source of G, 539B is an LED for reading light source of B,
Reference numeral 538 denotes a three-color mixing prism having an R reflection surface and a B reflection surface.

FIG. 23 is a timing chart showing the operation.

Each cycle described above is defined as 1 / (flicker frequency ×
3) = Set to about 5 ms or less, and set the writing light source to RGB1
The lights are turned on sequentially in cycles. RGB LEDs are also prepared for the light source on the reading side, and the same color as the writing side is sequentially turned on. The film 533 has video information, and here, gradation information having a transmittance of 0% for R, 50% for G, and 100% for B is included.

During the three cycles, the eyes are added and mixed, so that the eyes can be seen in full color.

As described above, the film 533 can be used for both a positive film and a negative film simply by switching the lighting timing of the reading light source.

If a transmissive liquid crystal TV with a color filter is arranged in place of the film 533, and a brighter halogen lamp + color rotating filter is used as a reading light source,
It can be a video projector.

In the case of monochromatic writing, the monochrome OH
In the case where the amount of light to be written in a specific pixel area does not change, such as when forming P, the reset light is not always necessary.

In the case where the reset light is used, it is sufficient that the intensity is equal to or higher than a certain value. Therefore, there is no problem even if writing is superimposed during the reset period.

Referring to FIGS. 24 and 25, another example of the optical writing type film viewer will be described.

The optical system configuration of the image display device is shown in FIG.
2 is the same as that shown in FIG.
8, the description is omitted.

FIG. 24 is a timing chart showing a method of driving an image display device using the optical modulation means according to this embodiment.

The basic operation is the same as that of the reference example shown in FIG.
However, the difference is that the writing light is shown at 518T.
T in each cycle₆₁~ T₆₂And t₆₄~ T₆₅Only during the period
It should be turned off during other periods. period
t₆₄~ T₆₅Is applied to the liquid crystal by the voltage A
This is for ensuring C symmetry. And t₆₂~
t₆₃During this period, uniform bias light is applied (550).
T). 1st cycle when writing light including gradation information is 0
The voltage applied to the liquid crystal is -V₆At t₆₁~ T ₆₂Period
It is constant throughout. Next, the bias light is t₆₂Irradiated at the time
Then, the voltage applied to the liquid crystal is square due to the lower resistance of the photoconductive layer.
It grows in the direction. Here, when the writing light has the minimum value,
Time t₆₃Exceeds the threshold (+ Vu) of the liquid crystal
R_pcOr C_pcAnd the time t₆₃of
Match the timing setting.

Therefore, in the first cycle, the write light is minimum, that is, 0, and the read light is also minimum, that is, 0 (50).
5T).

The period from t _{63 to} t _{60 of the} next cycle is an inversion operation. Therefore, since there is no irradiation of the reading light during this period, the reproduction of the image information is not performed.

[0117] Since the second periodic writing light is an intermediate level, t ₆₁ ~t reduces the resistance of the photoconductive layer during the _62, a high voltage in the positive direction according than -V ₆ in the liquid crystal.

[0118] When the bias light in a period t ₆₂ ~t ₆₃ is illuminated, in the second period different from the first period, since the initial value of the voltage applied to the liquid crystal at time t ₆₂ is higher than -V _6, reading light At time t _X1 in the middle of the irradiation period (t ₆₁ −t ₆₃ ), Vflc exceeds the threshold value + Vu. Therefore, t _X1
During the period from t to t ₆₃ , the liquid crystal is in the second alignment state (bright) (T
ran). Then, a period (t _{X1 to} t ₆₃ ) during which the reading light can be extracted is modulated according to the writing light amount.
t ₆₃ and later is the inversion operation.

In the third cycle, the writing light is at a maximum.
(518T). Therefore, the period during which the bias light is irradiated
(T₆₂~ T₆₃) First time t₆₂Voltage V applied to the liquid crystal
flc exceeds the threshold value + Vu. Therefore, the reading light
The entire period of irradiation (t₆₂-T ₆₃), The liquid crystal is in the second alignment
State (bright). So it can be taken out of the device
The time integration of the read light amount becomes maximum.

As described above, the time during which the reading light is extracted is determined according to the amount of the writing light.
If the writing light quantity changes in an analog manner, the read time also changes in an analog manner.

The period t _{63 to} t ₆₀ is an inversion operation. During this period, the polarity of the applied voltage Vext is inverted, and the same amount of the writing light bias light is irradiated again. This allows
Since the time integral per one cycle of the effective voltage applied to the liquid crystal is 0, deterioration of the liquid crystal can be suppressed.

[0122] In this example, the amount of bias light is appropriately determined in consideration of the length of the time constant and the time t ₆₂ -t ₆₃ of the photoconductive layer. The light source of the bias light may be the same as or different from the light source of the reset light. Preferably, both the light source of the bias light and the light source of the reset light have dimming means, respectively, so that the light amount can be set independently.

In this example, one cycle is 1/30.
Second, good halftone without being seen flicker When you set up t ₆₀ ~t ₆₃ to about 1 second of 60 minutes can be displayed.

FIG. 25 is a timing chart showing a driving method of an image display device using an optical modulation means according to still another example.

The basic operation is the same as the example shown in FIG. The difference is that instead of irradiating bias light,
The voltage Vext applied to the element is changed with time (t ₇₂ −t
₇₃ ) It is in operation.

During the period t ₇₀ -t ₇₁ , reset light is irradiated (721T). At this time, Vext is 0.

[0127] While the Vext at time t ₇₁ to the liquid crystal threshold voltage + Vu, the writing light to the photoconductive layer minimum (0)
Therefore, the voltage Vflc applied to the liquid crystal becomes + Vuu. If the capacity of the photoconductive layer is the same as the capacity of the liquid crystal, + Vuu is の of + Vu.

At time t ₇₂ , the write light is set to 0,
The voltage Vext applied to the element is gradually increased from + Vu to + Vem.
Up with time. In response, the voltage Vflc applied to the liquid crystal also increases with Vext.

If + Vem is set to be twice the value of + Vu, Vflc exceeds the threshold value + Vu at time t.
It becomes ₇₃ . Having thus the period t ₇₂ -t ₇₃ in the read light is on (704t), a liquid crystal for the liquid crystal alignment state is not a transition is not a alignment state exhibiting a maximum transmittance.

The inversion operation is performed during the remaining period from t ₇₃ to t ₇₀ . During this operation, there is no irradiation of the reading light, so that no image reproduction is performed.

The second cycle shows the case where irradiation of the intermediate level writing light (718T) is performed. Liquid crystal at time t ₇₀ is in the non-light-transmissive state by the reverse operation.
With Vext = 0, Vflc approaches voltage level 0.

[0132] At time t _71, Vext is the threshold + Vu
And the readout light starts to be turned on (704T). Ve
Although xfl increases Vflc, the threshold voltage + Vu
Does not reach.

[0133] At the time t _72, Vext begins to rise. Accordingly, Vflc also rises, so that Vflc exceeds threshold value + Vu at time t _X1 . Thus, the liquid crystal transitions to the alignment state exhibiting the maximum transmittance. Therefore, at this time _t72 , the lit readout light is reflected by the reflection layer through the liquid crystal layer, so that the image can be recognized. Then, the reflection time t _X1 -t _{73 of the} reading light is modulated according to the writing light amount. t ₇₃ and later is the inversion operation.

The third cycle shows a case where the light amount of the writing light is maximum. operation in the period of t ₇₀ -t ₇₁ is the same for each cycle.

[0135] By writing amount of light applied at time t _71, the time t ₇₂ V flc exceeds the threshold + Vu. Therefore, during the lighting period t ₇₂ -t _{73 of the} reading light, the liquid crystal transitions to the alignment state exhibiting the maximum transmittance. Therefore, the time during which the reading light is reflected by the element is maximum (705).
T).

As described above, since the time for which the reading light is reflected is determined according to the amount of the writing light, if the writing light amount changes in an analog manner, the reflection time also changes in an analogous manner.

The period t _{73 to} t ₇₀ is an inversion operation. In this period, the polarity of the applied voltage Vext is inverted, and the same amount of writing light bias light is applied again. This allows
Since the time integral per one cycle of the effective voltage applied to the liquid crystal is 0, deterioration of the liquid crystal can be suppressed.

In this embodiment, the time change rate of Vext is appropriately determined in consideration of the time constant of the photoconductive layer, the length of the period t ₇₁ -t _{73 and} the like.

In this embodiment, if one cycle is set to 1/30 second and from t _{70 to} t ₇₃ is set to 1/60 second, a good half tone can be displayed without flickering.

Reference Example 6 Next, Reference Example 6 of the present invention will be described. In the reference example described with reference to FIG. 22, a two-dimensional image having gradation information of a film or the like is written on the photoconductive layer of the liquid crystal element as an optical modulation means by one-time writing light irradiation. In this example, a two-dimensional image is written in a liquid crystal element in a time series by vertically and horizontally scanning. Then, in order to read out the gradation information, the readout light is similarly scanned at an appropriate timing.

FIG. 26 is a view for explaining the scanning method. Reference numeral 801 denotes a reflection type liquid crystal element having the same chiral smectic liquid crystal and photoconductive layer as that shown in FIG. The writing light 802 scans from the top to the bottom of the figure in a non-interlaced manner in the same manner as in normal CRT drawing.
That is, the operation of irradiating the photoconductive layer of the element with light with the writing light is performed in time series. On the other hand, the read light 80
Reference numeral 3 indicates that the liquid crystal portion corresponding to the position of the photoconductive layer in which the information has been written is irradiated, and this is also regarded as a predetermined period in order to reproduce the gradation information. Therefore, the operation of irradiating the element with the reading light is also performed in time series.
The scanning timing of the writing light 802 and the reading light 803 is such that the scanning of the reading light is performed after the scanning of the writing light.

FIG. 29 is a timing chart for explaining the operation of the reference example more specifically. In the example of FIG. 21, three periods are illustrated, but in FIG. 29, only one period is illustrated.

A reset light 821 is similar to the reset light 521 in FIG. 818T1, 820-1, Tran1, 50
4T1 indicates the operation of the first pixel to which the writing light 802 is first written in a non-interlace manner.

Reference numeral 818T1 denotes the timing of the writing light applied to the first pixel. At time t _{81 1} the writing light 80
When 2 is irradiated, an electron-hole pair having a charge amount ΔQ is generated in proportion to the writing light intensity, and a potential change of ΔV = ΔQ / C occurs. When a stronger writing light intensity is given, Vflc exceeds Vu earlier, and the FLC undergoes an orientation change, turning from dark to bright. That is, the writing light intensity-FLC phase conversion is performed.

In FIG. 29, the case where the writing light is applied with the maximum intensity to extract the maximum light amount, the case where the writing light is applied with the offset light intensity of a certain value for displaying black, and the intermediate light amount between the two. For three cases where writing light was given at the maximum intensity between the two to take out,
Illustrated.

When writing light is applied at the maximum intensity, FL
The time at which C changes to the second alignment state (bright) is t _X111 , and the time at which FLC changes to the second alignment state (bright) when the minimum write light is given at a certain offset light intensity is t _X113.
In this case, the change in the alignment state of the FLC is as shown in Tran1.

Reference numeral 504T1 denotes the timing of the readout light applied to the first pixel. When the first pixel is irradiated with the readout light during the period from _tX111 to _tX113, the observer observes the light for the overlap time between the irradiation time of the readout light and the second alignment state (bright) of the FLC. If writing and reading to and from the first pixel are repeated at a time equal to or lower than the flicker frequency, the light will be observed as a change in the light intensity of the first pixel to the observer's eyes.

Similarly, 818Tn, 820n, Tran
n and 504Tn indicate the operation of the n-th pixel which is located substantially at the center of the screen where the writing light 802 is written in a non-interlaced manner.

The 818TN, 820N, Tran
N and 504TN indicate the operation of the N-th pixel to which the writing light 802 is written last in a non-interlace manner.

The operation of each pixel is the same as that of the first pixel, except that
The pixel is written at time t _81n and the N-th pixel is written at time t _81N .

FIG. 27 is a diagram showing the configuration of an image display system according to this embodiment. Reference numeral 810 denotes a CR as a writing light source.
T, 811 is an imaging lens, 812 is a reset light source, 81
3 is a mirror, 814 is a polarization beam splitter, 815
Is a movable mirror, 816 is a filter for cutting infrared light or ultraviolet light, 817 is a reading light source, 818 is an illumination lens, and 819 is an image reproduction screen.

After the reset light irradiation, the writing light 8
02 is performed. Since a voltage is applied to the element 801, the effective voltage applied to the liquid crystal changes with time according to the amount of light due to light absorption in the photoconductive layer. The time during which the light can be reflected changes according to the gradation information. The reading light 803 is scanned in accordance with this timing.
Scanning is performed by movement of the movable mirror 815. That is, when the movable mirror 815 moves in the direction of the arrow AA, the element 80
The readout light 803 applied to 1 also moves in the direction of the arrow AA. Thus, the band-shaped readout light is vertically scanned.
Since the horizontal scanning time of the reading light 803 is set to 1/60 second or less, halftone can be recognized. The scanning between the movable mirror 815 and the CRT 810 is synchronized by a control circuit (not shown).

FIG. 28 is an example in which Example 6 described above is changed to support full color. As shown in FIG. 28, there are three writing light scanning means and three liquid crystal elements for each of R, G, and B.
R, 800G, and 800B.

By synchronizing the timing of writing light scanning for three colors, full-color display can be performed by additive color mixing. Since this display device is suitable for displaying full-color moving images, it is suitable as a large-screen television. Further, in the reference examples 5 and 6, the writing has been described in the non-interlaced manner by the spot light similar to the CRT, but it goes without saying that the writing may be line-sequential writing such as a line LED.

(Embodiment of the Present Invention) The reference example of the present invention has been described above. Next, an embodiment of the present invention will be described. In this embodiment, as in Reference Example 6, a two-dimensional image is vertically and horizontally scanned to write the liquid crystal elements in a time series. Then, the writing order of the two-dimensional image is changed in the adjacent frame.

FIGS. 30A and 30B are views for explaining the scanning method. Reference numeral 801 denotes the same as that shown in FIG.
This is a reflective liquid crystal device having a photoconductive layer having a chiral smectic liquid crystal having a memory property, a charge generation layer of an organic semiconductor, and a charge transport layer. The writing light 802 is a normal C
Similar to the RT drawing, scanning is performed from top to bottom in FIG. 30A, or from bottom to top in FIG. 30B by non-interlace. That is, the operation of irradiating the photoconductive layer of the element with light by the writing light 802 is performed in time series. The writing light 802 is performed such that the scanning directions are different from each other in adjacent frames (that is, two frames arranged in time series). Here, adjacent frames do not necessarily mean frames that are adjacent (continuous). That is, it is not necessary to switch the scanning direction for each frame, and after performing the scanning in the scanning direction shown in FIG. 30A a plurality of times, such as 2, 3,..., 10 times, the scanning direction shown in FIG. May be performed the same number of times. In this example, since the applied voltage is inverted for each frame, scanning in the same direction is repeated every even number of times to prevent image sticking of the liquid crystal and the photoconductive layer. It is also preferable not to make the switching period coincide with the switching period. 1st is black state
When an external electric field is applied with a polarity from the alignment state to the second alignment state, which is a bright state, readout light having a uniform surface distribution is irradiated.

FIGS. 33 and 34 are timing charts for more specifically explaining the operation of the embodiment. FIG.
When the writing light scanning shown in FIG.
FIG. 31 is a timing chart showing a case where the writing light scanning shown in FIG. 30B is performed. In the example of FIG.
Although the cycle is illustrated, FIGS. 33 and 34 illustrate only one cycle. Further, in FIGS. 33 and 34, the code indicating the time (for example, t ₈₀ ) uses the same code, but this does not indicate the same time but indicates the signal period in each frame.

A reset light 821 is similar to the reset light 521 in FIG. 818T1, 820-1, Tran1, 50
4T1 shows the operation of the pixel (first pixel) to which the writing light 802 is written first non-interlace in FIG. 33, and FIG. 34 shows the operation of the pixel (first pixel) to which writing light 802 is written last non-interlace. It shows the operation.

Reference numeral 818T1 denotes the timing of the writing light applied to the first pixel. At time t _{81 1} the writing light 80
When 2 is irradiated, an electron-hole pair having a charge amount ΔQ is generated in proportion to the writing light intensity, and a potential change of ΔV = ΔQ / C occurs. When a stronger writing light intensity is given, Vflc exceeds Vu earlier, and the FLC undergoes an orientation change, turning from dark to bright. That is, the writing light intensity-FLC phase conversion is performed.

In FIGS. 33 and 34, the case where the writing light is applied at the maximum intensity to extract the maximum light amount, the case where the writing light is applied at the offset light intensity of a certain value for displaying black, and the intermediate between the two cases. The drawing shows three cases in which the writing light was applied at the maximum intensity intermediate between the two in order to extract the amount of light.

When writing light is given at the maximum intensity, FL
The time at which C changes to the second alignment state (bright) is t _X111 , and the time at which FLC changes to the second alignment state (bright) when the minimum write light is given at a certain offset light intensity is t _X113.
In this case, the change in the alignment state of the FLC is as shown in Tran1.

Reference numeral 504T1 denotes the timing of the readout light applied to the first pixel. When the first pixel is irradiated with the readout light during the period from _tX111 to _tX113, the observer observes the light for the overlap time between the irradiation time of the readout light and the second alignment state (bright) of the FLC. If writing and reading to and from the first pixel are repeated at a time equal to or lower than the flicker frequency, the light will be observed as a change in the light intensity of the first pixel to the observer's eyes.

Further, 818TN, 820N, Tran
N and 504TN indicate the operation of the Nth pixel (Nth pixel) to be written last in FIG. 33 and the operation of the pixel to be written first (Nth pixel) in FIG. is there.

The operation of each pixel is the same as that of the first pixel, except that the Nth
The pixel is at time t_81NThen, writing is performed. In FIG.
The N-th pixel performs black phase conversion in a shorter time.
The offset light when it should be shown is also compared to the first pixel.
In FIG. 34, the first pixel is the Nth pixel
It is assumed that the offset light is stronger than that of. Nth
The time gradation width that can be taken out by the pixel is T_X1N3-T_X1N1,
T for one pixel_X113-T _X111It is.

Now, only in the scanning direction shown in FIG.
Assuming that scanning of writing light is performed, as shown in FIG.
The time gradation width that can be taken out is T_X113-T_X111> T
_X1N3-T_X1N1And a difference is produced. In the present invention, this difference is
To make up for this, close to the frame where scanning is performed as shown in FIG.
In the contacted frame, as shown in FIG.
Scanning in the direction opposite to the scanning direction of (A) can be performed and taken out
Time gradation width is T_X113-T _X111<T_X1N3-T_X1N1Will be
The average time gradation width that can be taken out is equal
(Or nearly equal). In addition, already
As described in, it is not always necessary to write in adjacent frames.
It is not necessary to reverse the scanning of the incident light,
Possible time gradation widths are equal (or almost equal) on average
The scanning of the writing light may be performed so as to be as follows.

FIG. 31 is a diagram showing the configuration of the image display system of the present embodiment. Reference numeral 810 denotes a C light source as a writing light source.
RT, 811 is an imaging lens, 812 is a reset light source, 8
13 is a mirror, 814 is a polarizing beam splitter, 81
Reference numeral 6 denotes a filter for cutting infrared light or ultraviolet light, 817 denotes a reading light source, 818 denotes an illumination lens, 819 denotes an image reproducing screen, and 820 denotes a mirror.

After irradiation with the reset light, the writing light 8
02 is performed. Since a voltage is applied to the element 801, the effective voltage applied to the liquid crystal changes with time according to the amount of light due to light absorption in the photoconductive layer. The time during which the light can be reflected changes according to the gradation information.

The second embodiment is an example in which the first embodiment described above is changed to a full color mode. As shown in FIG.
The scanning means of the writing light and the liquid crystal element are 3 for each of R, G and B.
800R, 800G, and 800B.

By synchronizing the timing of writing light scanning for the three colors, full-color display can be performed by additive color mixing. Since this display device is suitable for displaying full-color moving images, it is suitable as a large-screen television. Further, in this example, the writing has been described in the non-interlaced manner using the same spot light as the CRT, but it is needless to say that line sequential writing such as a line LED may be used.

In the analog duty modulation according to the present invention, the signal applied to the optical modulation means changes in an analog manner at a timing exceeding a threshold value for changing the optical state of the optical modulation means depending on the gradation information. This allows
Since the length of the on-time of the optical modulation means, for example, the time during which the optical shutter is open or the time when the mirror is displaced in a predetermined direction, and the light-up time of the light source are modulated in an analog manner, transmission or reflection is performed The time integrated value of the light amount corresponds to the gradation information. Therefore, the number of gradations is not limited to a digital amount such as a clock frequency, and A / D conversion of gradation information is not required. In addition, even if a digital (binary) display element having a sharp applied voltage and transmittance characteristics is used, an effect that can be performed by analog modulation, which has not been considered in the related art, can be obtained.

[0171]

According to the present invention, good gradation display can be performed. Further, according to the present invention, in the adjacent frame, the scanning of the optical information is performed from different directions, so that the luminance and brightness at the same gradation level are uniform in any part (pixel) on the display surface. become.
This eliminates the need to scan the reading light,
The configuration of the readout light irradiation optical system is simplified, and the display device can be reduced in size and provided at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram of a basic driving device of an optical modulation unit according to the present invention.

FIG. 2 is a diagram showing the dependence of the transmittance of an optical modulation substance used in the present invention on the applied voltage (pulse width).

FIG. 3 is a timing chart for explaining another example of the basic driving method of the optical modulation means of the present invention.

FIG. 4 is a diagram showing an example of a circuit for generating gradation information used in the present invention.

FIG. 5 is a diagram of another driving device of the optical modulation means of the present invention.

FIG. 6 is a diagram illustrating an example of a drive circuit of an optical modulation unit used in the present invention.

FIG. 7 is a diagram showing another example of the drive circuit of the optical modulation means used in the present invention.

FIG. 8 is a diagram showing still another example of the drive circuit of the optical modulation means used in the present invention.

FIG. 9 is a diagram showing the applied voltage dependence of the transmittance of the optical modulator used in the present invention.

FIG. 10 is a diagram showing an optical modulation unit.

FIG. 11 is a diagram showing a drive timing chart of an optical modulation unit.

FIG. 12 is a diagram for explaining a driving method of an optical modulation unit.

FIG. 13 is a diagram showing a drive timing chart of an optical modulation unit.

FIG. 14 is a diagram for explaining a driving method of the optical modulation unit.

FIG. 15 is a diagram showing a drive timing chart of an optical modulation unit.

FIG. 16 is a diagram for explaining a driving method of the optical modulation means.

FIG. 17 is a diagram showing a drive timing chart of an optical modulation unit.

FIG. 18 is a sectional view of an optical modulation unit for an image display device used in the present invention.

19 is a diagram showing the molecular orientation of a chiral smectic liquid crystal used in the device of FIG.

20 is a diagram showing the electro-optical characteristics of the liquid crystal molecules of FIG.

FIG. 21 is a timing chart showing the operation of the device of FIG.

FIG. 22 is a diagram illustrating an image display device used in a reference example of the present invention.

FIG. 23 is an operation timing chart of the image display device according to the reference example of the present invention.

FIG. 24 is an operation timing chart of the image display device according to the reference example of the present invention.

FIG. 25 is an operation timing chart of the image display device according to the reference example of the present invention.

FIG. 26 is a diagram for explaining scanning of writing light and reading light according to a reference example of the present invention.

FIG. 27 is a diagram illustrating an example of a display device according to a reference example of the present invention.

FIG. 28 is a diagram showing another example of the display device according to the reference example of the present invention.

FIG. 29 is an operation timing chart of the display device according to the reference example of the present invention.

FIG. 30 is a diagram for explaining a scanning method according to the embodiment of the present invention.

FIG. 31 is a diagram illustrating an example of a display device according to the embodiment of the present invention.

FIG. 32 is a diagram showing another example of the display device according to the embodiment of the present invention.

FIG. 33 is an operation timing chart of the display device according to the embodiment of the present invention.

FIG. 34 is an operation timing chart of the display device according to the embodiment of the present invention.

[Explanation of symbols]

 801 Reflective liquid crystal element 802 Writing light 803 Reading light 810 CRT 811 Imaging lens 812 Reset light source 813 Mirror 814 Polarization beam splitter 816 Filter for cutting infrared light or ultraviolet light 817 Reading light source 818 Illumination lens 819 Image reproduction screen 820 Mirror

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI G09G 3/36 G09G 3/36 H04N 5/66 102 H04N 5/66 102B (56) References JP-A-3-13513 (JP, A) JP-A-5-333364 (JP, A) JP-A-8-122812 (JP, A) JP-A-8-122810 (JP, A) JP-A-62-156624 (JP, A) -68984 (JP, A) JP-A-7-146462 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/133 575 G02F 1/133 560 G02F 1/13 505 G02F 1/135 G09G 3/20 G09G 3/36 H04N 5/66 102

Claims (4)

(57) [Claims] 1. An optical modulator comprising a pair of electrodes for applying a voltage, a photoconductive layer and a layer of an optical modulator provided between the pair of electrodes, and gradation information is applied to the photoconductive layer. A display device comprising: a signal light source that provides optical information including; and a reading light irradiation unit that provides reading light for reading image information to the layer of the optical modulation substance. Scans in the horizontal scanning direction in one direction and the vertical scanning direction in one direction toward the photoconductive layer, and in a frame close to the one frame, directs the optical information toward the photoconductive layer. Means for scanning along the horizontal scanning direction in the direction and the vertical scanning direction in the other direction, the optical information scanning along the one horizontal scanning direction and the one vertical scanning direction, and the horizontal direction in the other direction. Switching period of said optical information scanned along the vertical scanning direction of 査 direction and the other direction, the voltage inversion period which differ from the set display device of the voltage applied to between the pair of electrodes. 2. The display device according to claim 1, wherein the scanning of the optical information is a non-interlace scanning. 3. The display device according to claim 1, wherein the optical modulation material is a liquid crystal having a memory property. 4. The display device according to claim 1, wherein the photoconductive layer includes an organic semiconductor layer.