WO2018173813A1 - Liquid-crystal phase panel, and optical switch and optical shutter using same - Google Patents

Abstract

Using interdigitated electrodes to drive a polymer-stabilized blue-phase liquid crystal generates a large field distribution within the liquid crystal and also generates a large field in the vicinity of the electrodes, thereby risking a reduction in the switching speed of the polymer-stabilized blue-phase liquid crystal due to an electrostrictive effect.　The present invention uses parallel flat plates on which conventional film electrodes are formed. A polymer-stabilized blue-phase liquid crystal is inserted between said plates, and two silicon wedges having triangular cross sections and comprising silicon are placed on or adhered to both sides thereof so as to be rotationally symmetrical to one another.

Description

Liquid crystal phase panel and optical switch and optical shutter using the same

The present invention relates to a liquid crystal phase panel, an optical switch using the same, and an optical shutter.

FIG. 17 shows an example of a conventional liquid crystal phase panel (Non-Patent Document 1).
A nematic liquid crystal 12 is inserted between two parallel plate electrodes 11.

In the case of Zero-twisted ECB (electrically controlled birefringence), when no voltage is applied to the two parallel plate electrodes, the liquid crystal directors are arranged parallel to the plate electrodes, and the incident light is retarded. Get a foundation.
At this time, by setting the desired liquid crystal thickness, for example, it can be operated as a half-wave plate.

On the other hand, when a voltage is applied to the two parallel plate electrodes, the electric field becomes perpendicular to the plate electrodes, and the liquid crystal director also follows the electric field and becomes perpendicular. The two orthogonally polarized lights that are incident feel the refractive index of a circle formed by cutting the director refractive index ellipsoid, so that the incident light is not subjected to retardation and operates as an isotropic medium.

Conventional nematic liquid crystals are widely used in displays, but their switching speed is as slow as milliseconds, and cannot be used in applications that require a high switching speed.
Therefore, polymer-stabilized blue phase liquid crystals that can be switched at high speed have been studied.

This liquid crystal utilizes the Kerr effect and can be switched quickly, but it is necessary to generate an electric field parallel to the plate electrode.
In the parallel plate electrode described above, since the electric field is always perpendicular to the plate electrode, a comb-shaped electrode called IPS (In Plane Switching) shown in FIG. 1 has been studied.

This electrode applies a positive / negative or positive (negative) and zero voltage to the adjacent comb-shaped electrode 21 to generate a horizontal electric field.

However, a large electric field distribution is generated in the liquid crystal 22, particularly in the vicinity of the comb-shaped electrode 21, and the switching speed of the polymer-stabilized blue phase liquid crystal 22 is deteriorated due to the electrostrictive effect.

Further, at longer wavelengths, the required liquid crystal thickness increases, and a larger electric field distribution is generated in the liquid crystal.
The in-plane electric field distribution is large, leading to a phase distribution in the emitted light beam, and various performance degradations such as loss and crosstalk occur.

On the other hand, an embodiment has been reported in which a prism sheet is attached to a polymer-stabilized blue phase liquid crystal and is driven by a conventional vertical electric field to obtain gradation characteristics in which a hysteresis phenomenon is removed. (Patent Document 1, FIG. 1).

JP 2014-286045 A

Fundamentals of phase-only liquid crystal on silicon (LCOS) devices ”, Zichen Zhang et al (Light: Science & Applications (2014) P16)

The above problems are summarized as follows.
(1) In the comb-shaped electrode, a large electric field distribution is generated in the liquid crystal, and a large electric field is generated in the vicinity of the electrode, resulting in deterioration of the switching speed of the polymer-stabilized blue phase liquid crystal due to the electrostrictive effect.
(2) In particular, at a long wavelength, the required liquid crystal thickness increases, and a larger electric field distribution is generated in the liquid crystal.
(3) The in-plane electric field distribution is also large, causing a phase distribution in the emitted light beam and causing various performance degradations such as loss and crosstalk.
(4) In the structure of Patent Document 1, if the blue phase liquid crystal is obliquely incident at a large angle, the output light beam spreads and cannot be applied to a multistage optical switch which is one of the application fields of the present invention. In addition, when multiple stages are used to realize an optical switch, incident light is tilted after the second stage. In this case, the prior art leads to a large phase distribution in the emitted light beam. Therefore, the present invention solves the above-described problems and realizes a liquid crystal phase panel that generates a uniform electric field distribution in a polymer-stabilized blue phase liquid crystal and does not generate a deterioration in switching speed or a phase distribution of an emitted light beam. The goal is that.

In order to solve the above problems, the present invention is configured as follows with respect to a polymer-stabilized blue phase liquid crystal.
(1) Using a conventional parallel plate on which a thin film electrode is formed (FIG. 2), a polymer-stabilized blue phase liquid crystal is inserted between them, and two silicon wedges each having a triangular cross section made of silicon are connected to each other. They are arranged or pasted so as to be rotationally symmetric.
(2) Further, there are two sets of parallel flat liquid crystal panels to which the silicon substrate is attached, and they are arranged or attached so as to be symmetrical with each other (FIG. 6).

However, the wedge angle θa of the silicon wedge shall satisfy the following condition.

Here, θb = sin ⁻¹ (No × sin θo / N1), No is a surrounding refractive index (for example, air), N1 is a refractive index of silicon, and θo is an incident angle. N2 is the refractive index of the parallel plate (substrate 5) constituting the liquid crystal panel.

(Liquid crystal phase panel)
Specifically, the present invention can provide the following means.
(1) Using two substrates on which at least one surface of a transparent substrate in the light wavelength region of 1.6 μm band from ultraviolet rays is formed with a transparent thin film electrode in a desired light wavelength region, the thin film electrode has a desired gap Parallel plate liquid crystal panels that are opposed so as to be parallel electrodes and a polymer-stabilized blue phase liquid crystal is inserted between them and irradiated with light for stabilization,
Consists of a material having a higher refractive index than that of the substrate, and has two wedge-shaped substrates having a triangular cross section,
The parallel plate liquid crystal panels are laminated so as to be alternately sandwiched between the inclined surfaces of the two wedge-shaped substrates, and incident light incident from an end surface (referred to as an incident surface) of one wedge-shaped substrate is incident on the other wedge-shaped substrate. A liquid crystal phase panel capable of emitting light from an end face (referred to as an emission face) parallel to the end face.
(2) In the liquid crystal phase panel of (1), when light is incident from the end face of one wedge-shaped substrate, when no voltage is applied to the opposing thin film electrode, the liquid crystal phase panel operates as an almost isotropic medium and applies a voltage. A liquid crystal phase panel that operates as a half-wave plate at the operating wavelength.
(3) The liquid crystal phase panel according to any one of (1) and (2), wherein the substrate is glass mainly composed of SiO2.
(4) The liquid crystal phase panel according to any one of (1), (2), and (3), wherein the wedge-shaped substrate is made of silicon.
(5) In the liquid crystal phase panel according to any one of (1), (2), (3), and (4), the sloped surface of the wedge-shaped substrate and a material adjacent to the incident surface or the emission surface A liquid crystal phase panel, wherein an antireflective coating is formed so as to be nonreflective with respect to the refractive index of the liquid crystal.
(6) Using two liquid crystal phase panels according to any one of (1), (2), (3), (4), and (5), the exit surface of one liquid crystal phase panel and another liquid crystal phase panel A doubled liquid crystal phase panel characterized in that the incident surfaces of the liquid crystal panels are bonded to each other so as to have a line-symmetric structure.

(Optical switch)
(7) The birefringence axis of the birefringent medium having a thickness that becomes a half-wave plate at the used wavelength is rotated at a period Λ in the plane on the exit surface of the doubled liquid crystal phase panel of (6). An optical switch comprising: a polarizing grating plate bonded together, wherein the incident light can be deflected and emitted from the polarizing grating plate.
(8) In the optical switch according to (7), the parallel liquid crystal phase panel of the doubled liquid crystal phase panel is segmented into two or more regions, and the period Λ is different with respect to the segment. A multi-segmented optical switch characterized in that a polarizing grating plate composed of segments is bonded, and incident light incident on each segment can be independently deflected and emitted from the polarizing grating plate.
(9) Two or more sets of the optical switch according to any one of (7) and (8) are used, and the polarizing grating plate of one optical switch and the incident surface of another optical switch are arranged in tandem or bonded together. A multiplexed optical switch characterized by.
(10) An optical switch according to (9), wherein the periphery of the optical switch is controlled by a Peltier element to a desired temperature.
(11) The optical switch according to (10), wherein a cooling heat sink is connected in the vicinity of the Peltier element and is controlled to have a desired temperature.
(12) The optical switch according to (11), which is housed in a package and hermetically sealed.
(13) In the optical switch according to (9), an ultraviolet cut filter is disposed on or attached to at least one of the incident surface on which the incident light is incident or the polarization grating plate from which the incident light is emitted. .

(Driving method of optical switch)
(14) In the optical switch of (9), as a method of driving the thin film electrode of the parallel-plate liquid crystal panel, there is a set of rectangular waves whose absolute values are V inverted, and the time width of the set is T A method of driving an optical switch, wherein the optical switch is driven in a desired arrangement of a state “1” and a state “0” having a time width T in which no voltage is applied.
(15) In the method for driving an optical switch according to (14), states “0” and “1” are used as a method for driving the thin film electrode of the segment in the thickness direction (stacking direction) of the stacked optical switches. A driving method of an optical switch, characterized in that the window of time T is driven substantially synchronously between the segments.
(16) The optical switch driving method according to any one of (14) and (15), characterized in that the time width T is 1 msec or less and the voltage absolute value for driving inversion is 5 V or more. To drive the optical switch.
(17) In the method for driving an optical switch according to any one of (14) and (15), a so-called overdrive in which the voltage of the first rising edge of the rectangular wave from 0 V to + V is increased as compared with other portions. A method for driving an optical switch, characterized by comprising:

(Optical shutter)
(18) The liquid crystal phase panel according to any one of (1), (2), (3), (4), (5), and (6) is sandwiched between two deflectors whose optical axes are orthogonal or parallel. An optical shutter characterized by its structure.

The present invention has the following effects.
(1) It is possible to realize a liquid crystal phase panel that generates a uniform electric field distribution in a polymer-stabilized blue phase liquid crystal, which has been difficult with the prior art, and does not cause deterioration in switching speed and phase distribution of an emitted light beam.
(2) It is possible to realize a high-speed and highly reliable optical switch module that operates stably even at various environmental temperatures.
(3) It is possible to realize a high-speed optical shutter that has been difficult with the prior art.

It is explanatory drawing of the comb-shaped electrode called IPS (In * Plane * Switching) of the polymer stabilized blue phase liquid crystal which is a prior art. It is explanatory drawing of the parallel electrode of the polymer stabilization blue phase liquid crystal which is a prior art. (A) is a refractive index ellipsoid representing the isotropic characteristics of the polymer-stabilized blue phase liquid crystal part when no voltage is applied, and (B) is the refractive index of the polymer-stabilized blue phase liquid crystal part when voltage is applied. It is a figure showing an ellipsoid. It is one Example of this invention liquid crystal phase panel. In the liquid crystal phase panel of the present invention, it is an explanatory diagram when light is incident at an angle of θo. In the liquid crystal phase panel of the present invention, it is an explanatory diagram in the worst case where no retardation occurs. This is an example of a liquid crystal phase panel in which two sets of the liquid crystal phase panel 1 are used and they are bonded to each other so as to be symmetrical with each other. This is a calculation example of the refractive index angles θ ′ and θ ″ to two liquid crystal layers when incident at θo. It is another Example of this invention. 1 is a block diagram of a 1 × 2 optical switch using an inventive liquid crystal phase panel and a deflection grating. FIG. It is explanatory drawing of a deflection | deviation grating. It is another Example of the optical switch using this invention liquid crystal phase panel. It is explanatory drawing of the segmented deflection | deviation grating. It is an Example of 1 * 8 optical switch using the liquid crystal phase panel of this invention. It is one Example of the optical switch module using the liquid crystal phase panel of this invention. An example of a method for driving electrodes in the thickness direction (stacking direction) of stacked optical switches is shown. It is one Example of the optical shutter using this invention liquid crystal phase panel. It is an example of the conventional liquid crystal phase panel.

The following are some examples of the present invention.

FIG. 3 shows an embodiment of a liquid crystal phase panel according to the present invention.
First, the polymer-stabilized blue phase liquid crystal used in the liquid crystal phase panel 1 of the present invention will be described.
The blue phase liquid crystal is a frustration system, and the local stability to remove the double twist of the liquid crystal exceeds the global stability to connect the space without defects. Present at a narrow temperature.
By adding a polymer to this, defects in the space are filled and thermally stabilized, and the operating range is expanded to several tens of degrees Celsius.

As shown in FIG. 2A, the polymer-stabilized blue phase liquid crystal becomes a circular refractive index ellipsoid when an electric field is not applied, and operates as an optically isotropic medium.
On the other hand, as shown in FIG. 2B, when an electric field is applied, a birefringence is generated by the square of the electric field, resulting in an elliptical refractive index ellipsoid.

In this case, when light is incident from the major axis direction (vertical direction) of the refractive index ellipsoid, two orthogonal polarizations of light (which exist perpendicular to the light traveling vector) have a circular refractive index (refracted). No retardation is generated, and it is necessary to enter obliquely as shown in FIG. 3.
In this case, the refractive index ellipsoid cut into a circle is an ellipse, and the two polarizations of light have different refractive indexes and cause retardation.

3A is a perspective view, FIG. 3B is a cross-sectional view, and FIG. 3C is an enlarged view of a polymer-stabilized blue phase liquid crystal portion when a voltage is applied.
The liquid crystal phase panel 1 of the present invention comprises a parallel plate liquid crystal panel 2 and two silicon wedges 3 having a triangular cross section.

The parallel plate liquid crystal panel 2 is obtained by inserting a polymer-stabilized blue phase liquid crystal 6 between two substrates 5 each having a thin film electrode 4 formed on one surface and stabilizing the light by irradiation with light.
Two silicon wedges 3 having a triangular cross section are used on both sides of the surface, and the parallel flat liquid crystal panel 2 is attached to the surface of the hypotenuse.
The two silicon wedges 3 are attached so as to be rotationally symmetric about the parallel flat liquid crystal panel 2.

The surface of the oblique side of the silicon wedge 3 is provided with a non-reflective coating as a non-reflective condition for the substrate 5 constituting the parallel flat liquid crystal panel 2.
The substrate 5, the thin film electrode 4 and the polymer stabilized blue phase liquid crystal 6 constituting the parallel flat liquid crystal panel 2 are formed so as to have substantially the same refractive index.

Now, as shown in FIG. 3A, when light is incident at a vertical angle from above, the light is refracted at the boundary between the silicon wedge 3 and the parallel plate liquid crystal panel 2 according to Snell's law shown in the equation (2). It propagates obliquely at an angle θ ′ with respect to the layer of the polymer-stabilized blue phase liquid crystal 6.

Here, the condition for the angle θa of the silicon wedge 3 is that the expression (3) must be satisfied.

The reason is that if the expression (3) is not satisfied, the light is totally reflected and the light is not output from the lower surface.

Here, θa is the wedge angle of the silicon wedge 3, N1 is the refractive index of silicon, and N2 is the refractive index of the substrate 5.

It is assumed that the refractive indexes of the thin film electrode 4 and the substrate 5 and the polymer-stabilized blue phase liquid crystal constituting the parallel plate liquid crystal panel 2 are almost the same.

Next, as shown in FIG. 4A, when light is incident at an angle of θo from above, the refractive index angle θb to the silicon wedge 3 is given by the equation (4).

Further, at the boundary between the silicon wedge 3 and the parallel flat liquid crystal panel 2, as shown in the equation (5), the refractive index angle θb depending on the incident angle is added (or subtracted) in addition to the wedge angle θa of the silicon wedge 3 in the equation (2). The light enters at the angle.

According to Snell's law, light propagates obliquely at an angle of θ ′ with respect to each layer of the parallel plate liquid crystal panel 2 (including the polymer-stabilized blue phase liquid crystal 6) as shown in the equation (5).
In this case, the condition with respect to the angle of the silicon wedge 3 through which light is transmitted without being totally reflected is expressed by equation (6).

Here, No is the refractive index of the surroundings, N1 is the refractive index of silicon, N2 is the refraction of the parallel plate liquid crystal panel 2 (including the thin film electrode 4 and the polymer-stabilized blue phase liquid crystal 6 having the same refractive index N2 as the substrate 5). Rate.

When the silicon wedge 3 satisfying the equations (3) and (6) is used, as shown in FIG. (C), the refractive index ellipsoid 7 of the polymer-stabilized blue phase liquid crystal ellipsized by the electric field is oblique. Retardation can be generated because light propagates through the substrate.

An arbitrary liquid crystal phase panel 1 such as a half-wave plate can be realized by appropriately setting the film thickness of the liquid crystal.

However, when used in an optical switch, in this structure, as shown in equations (2) and (5), the liquid crystal layer propagates at a different angle θ ′ depending on the incident angle. It becomes a problem because the foundation changes.

In particular, when the light is incident at an angle as shown in FIG. 5, the light propagates vertically through the liquid crystal layer, so that the worst state in which no retardation occurs is obtained.
In this case, the incident angle θo is given by equation (7).

Therefore, as shown in FIG. 6, two sets of the above-described liquid crystal phase panel 1 were used, and they were laminated so as to be line-symmetric with each other.

FIG. 7 shows refractive index angles θ ′ and θ ″ to the two liquid crystal layers when incident at θo. It can be seen that θ ′ and θ ″ cancel each other, and in total, θ ′ + θ ″ is substantially constant.

By adopting such a structure, light incident obliquely propagates through the liquid crystal layer with almost the same optical path length in total, and uniform retardation can be obtained with respect to the incident angle.

FIG. 8 is another embodiment of the present invention.
The case where the trapezoidal silicon wedge 3 is used instead of the triangular cross section is shown.
The principle of operation is the same as when the cross-sectional shape is a triangle.

FIG. 9 shows a 1 × 2 optical switch 90 formed by attaching a deflection grating 92 to one surface of the liquid crystal phase panel 91 of the present invention.

The deflection grating 92 is composed of an element having birefringence (for example, a director of liquid crystal) as shown in FIG. 10, and the thickness thereof is locally such that every part is a half-wave plate.

The birefringence axis of each element having birefringence rotates with a certain period Λ, and the light can be deflected left and right in accordance with the rotation direction of the input circularly polarized light.

Here, the light can be deflected left and right by rotating the input circularly polarized light in the forward and reverse directions with the liquid crystal phase panel 91 of the present invention.

The deflection angle is determined by the input light wavelength and the period Λ, and a larger deflection angle can be obtained with a smaller period Λ.

FIG. 11 shows the electrode 4 of the liquid crystal phase panel 91 of the present invention divided into two segments, and the deflection grating 93 is also segmented as shown in FIG.

In this way, two light beams can be switched independently at different angles at the same time. Two or more segments are possible.

FIG. 13 shows a case where the 1 × 2 optical switch 90 of FIG. 9 is connected in multiple stages, and operates as a 1 × 8 optical switch.
By increasing the number of stages to be connected, the number N of outputs of 1 × optical switch can be increased.

FIG. 14 shows an embodiment of the optical switch module. The periphery of the optical switch is controlled using the Peltier element 100 so as to reach a desired temperature.

Heat is dissipated using a heat sink 101 outside the Peltier element 100. A glass window 102 coated with an ultraviolet cut filter is attached to the input and output to form a hermetic structure.

FIG. 15 shows an example of a method of driving the electrodes in the thickness direction (stacking direction) of the stacked optical switches.

As a method of driving the electrodes, the windows of the time “T” in the state “0” and the state “1” are driven almost synchronously between the electrodes.

The time width T is 1 ms or less, and the absolute value of the driving voltage that is inverted between positive and negative is 100V.

Also, (2) and (3) are so-called overdrive in which the drive voltage increases the voltage rising from the first 0V to + V and the voltage falling from 0V to -V of the rectangular wave as compared with other parts. In this case, the rise time of the optical switch can be reduced.

FIG. 16 shows a configuration in which an optical shutter is configured by arranging a deflector 93 on the input / output surface of the liquid crystal phase panel 91 of the present invention so as to be orthogonal or parallel.

Light that oscillates at 45 ° with respect to the X axis (or Y axis) is incident.
At this time, when the optical axis of the deflector 93 on the input side is set to be 45 °, the light passes through the deflector 93 and enters the liquid crystal phase panel 91 of the present invention.

When a voltage is applied to the liquid crystal phase panel 91 (ON), it operates as a half-wave plate, so that the polarization rotates by 90 °.

When no voltage is applied (OFF), the liquid crystal phase panel 91 operates in an isotropic manner, so that the polarization state is preserved.

When the output-side deflector 93 is orthogonal to the input-side deflector 93, light is transmitted when ON and light is blocked when OFF.

On the other hand, in the case of parallel Nicols, light is blocked when ON, and light is transmitted when OFF.
As described above, it operates as an optical shutter.

The 1 × N switch according to the present invention can be applied to an optical steering device.

1 Liquid crystal phase panel
2 Parallel flat panel
3 Silicon wedge
4 Thin film electrodes
5 Substrate
6 Polymer Stabilized Blue Phase Liquid Crystal
7 Refractive index ellipsoid
11 Parallel plate electrode
12 Nematic liquid crystal
21 Comb-shaped electrode
22 Polymer Stabilized Blue Phase Liquid Crystal
90 1 × 2 optical switch
91 Liquid crystal phase panel arranged in line symmetry
92 Deflection grating
93 Deflector

Claims (18)

Using two substrates on which at least one surface of a transparent substrate in the light wavelength region of 1.6 μm band from ultraviolet rays is formed with a transparent thin film electrode in a desired light wavelength region, the thin film electrode and a parallel electrode are formed at a desired gap. A parallel-plate liquid crystal panel that is opposed so as to face each other, and a polymer-stabilized blue phase liquid crystal is inserted between them and irradiated with light for stabilization,
Consists of a material having a higher refractive index than that of the substrate, and has two wedge-shaped substrates having a triangular cross section,
The parallel plate liquid crystal panels are laminated so as to be alternately sandwiched between the inclined surfaces of the two wedge-shaped substrates, and incident light incident from an end surface (referred to as an incident surface) of one wedge-shaped substrate is incident on the other wedge-shaped substrate. A liquid crystal phase panel capable of emitting light from an end face (referred to as an emission face) parallel to the end face. 2. The liquid crystal phase panel according to claim 1, wherein when light is incident from the end face of one wedge-shaped substrate, it operates as a substantially isotropic medium when no voltage is applied to the opposing thin film electrodes, and when a voltage is applied. A liquid crystal phase panel that operates as a half-wave plate at a wavelength used. _3. The liquid crystal phase panel according to claim 1, wherein the substrate is made of glass containing SiO ₂ as a main component. 4. The liquid crystal phase panel according to claim 1, wherein the wedge-shaped substrate is made of silicon. 5. The liquid crystal phase panel according to claim 1, wherein the refractive index of the material adjacent to the inclined surface of the wedge-shaped substrate and the entrance surface or the exit surface is not present. A liquid crystal phase panel, characterized in that a non-reflective coating that is reflective is formed. Two liquid crystal phase panels according to any one of claims 1, 2, 3, 4, and 5 are used, and an emission surface of one liquid crystal phase panel and an incident surface of another liquid crystal phase panel are line-symmetric structures, respectively. A doubled liquid crystal phase panel characterized by being attached to each other. 7. A polarization grating plate in which the birefringence axis of a birefringent medium having a thickness that becomes a half-wave plate at the used wavelength is rotated at a period Λ in-plane on the exit surface of the doubled liquid crystal phase panel according to claim 6 And the incident light can be deflected and emitted from the polarization grating plate. 8. The optical switch according to claim 7, wherein the parallel liquid crystal phase panel of the doubled liquid crystal phase panel is segmented into two or more regions, and is composed of segments having different periods Λ with respect to the segment. A multi-segmented optical switch, characterized in that a polarizing grating plate is laminated, and incident light incident on each segment can be independently deflected and emitted from the polarizing grating plate. The optical switch according to any one of claims 7 and 8, wherein two or more sets of optical switches are used, and the polarizing grating plate of one optical switch and the incident surface of another optical switch are arranged in tandem or bonded together. Multiplexed optical switch to do. 10. The optical switch according to claim 9, wherein the periphery of the optical switch is controlled by a Peltier element to a desired temperature. 11. The optical switch according to claim 10, wherein a cooling heat sink is connected in the vicinity of the Peltier element, and is controlled to have a desired temperature. 12. The optical switch according to claim 11, wherein the optical switch is housed in a package and hermetically sealed. 10. The optical switch according to claim 9, wherein an ultraviolet cut filter is disposed on or attached to at least one of the incident surface on which the incident light is incident or the polarization grating plate from which the incident light is emitted. 10. The optical switch according to claim 9, wherein the thin film electrode of the parallel-plate liquid crystal panel is driven by a set of rectangular waves having an absolute value of V and inverted, and the time width of the set is T. A method of driving an optical switch, wherein the optical switch is driven in a desired arrangement of “1” and a state “0” of a time width T in which no voltage is applied. 15. The method of driving an optical switch according to claim 14, wherein the thin film electrodes of the segments in the thickness direction (stacking direction) of the stacked optical switches are driven by a time T between the state “0” and the state “1”. The optical switch is driven substantially synchronously between the segments. 16. The optical switch driving method according to claim 14, wherein the time width T is 1 msec or less, and the voltage absolute value for driving inversion between positive and negative is 5 V or more. Driving method. 16. The method of driving an optical switch according to claim 14, wherein the optical switch is driven by so-called overdrive in which a voltage rising from the first 0V to + V of the rectangular wave is increased as compared with other portions. An optical switch driving method characterized by the above. 7. An optical shutter having a structure in which the liquid crystal phase panel according to claim 1 is sandwiched between two deflectors whose optical axes are orthogonal or parallel to each other. .

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