CN107741667B - Liquid crystal spatial light modulator - Google Patents

Liquid crystal spatial light modulator Download PDF

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CN107741667B
CN107741667B CN201711064463.4A CN201711064463A CN107741667B CN 107741667 B CN107741667 B CN 107741667B CN 201711064463 A CN201711064463 A CN 201711064463A CN 107741667 B CN107741667 B CN 107741667B
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liquid crystal
layer
light
spatial light
light modulator
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CN107741667A (en
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蒋向东
高升旭
王继岷
明洋舟
董湘
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University of Electronic Science and Technology of China
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133509—Filters, e.g. light shielding masks
    • G02F1/133512—Light shielding layers, e.g. black matrix
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133553—Reflecting elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
    • G02F1/1396—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell
    • G02F1/1397—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2203/00—Function characteristic
    • G02F2203/12—Function characteristic spatial light modulator

Abstract

The invention provides a liquid crystal spatial light modulator, and belongs to the technical field of liquid crystal devices. The liquid crystal display comprises a first transparent electrode and a second transparent electrode which are oppositely arranged in parallel, a first orientation layer, an STN type super-twisted nematic liquid crystal layer, a second orientation layer, a high-resistance isolation layer, an isolation grid, a reflecting layer and a photosensitive layer. According to the invention, the STN type super-twisted nematic liquid crystal is adopted to replace the traditional TN type liquid crystal, so that the visual angle can be widened, the good contrast can be kept, and the advantage of low power consumption can be achieved; in addition, the novel combined structure formed by the reflecting layer and the isolation grids is adopted to replace a light-blocking film and a medium reflector which are arranged in a traditional device in a stacking mode, and the novel combined structure has the advantages of improving the photosensitive sensitivity of the light-addressing liquid crystal spatial light modulator, improving the imaging effect of the light-addressing liquid crystal spatial light modulator, enabling the resolution of reading light to be higher and reducing the driving voltage of the light-addressing liquid crystal spatial light modulator.

Description

Liquid crystal spatial light modulator
Technical Field
The invention belongs to the technical field of liquid crystal devices, and particularly relates to a liquid crystal spatial light modulator.
Background
A Spatial Light Modulator (SLM) is an active control device that can modulate a parameter of an optical field through liquid crystal molecules, such as modulating a phase through a refractive index, modulating a polarization state through rotation of a polarization plane, or realizing conversion from incoherent Light to coherent Light, so as to write certain information into an optical wave, thereby achieving the purpose of optical wave modulation.
The spatial light modulator is generally classified into a reflective type and a transmissive type according to a reading mode of a reading light; and may be divided into optical addressing (OA-SLM) and electrical addressing (EA-SLM) according to the manner of inputting the control signal. When the light is addressed, the addressing of all the pixels is completed simultaneously, and the method is a parallel addressing mode and is characterized by high speed. The spatial light modulator is a key device in modern optical fields such as real-time optical information processing, adaptive optics, optical calculation and the like. To a large extent, the performance of spatial light modulators determines the practical value and the development prospects of the application field.
At present, most of liquid crystal light valves of spatial light modulators using optical addressing are multi-film systems, and chinese patent CN98114542 discloses a liquid crystal light valve, which sequentially comprises from top to bottom: an upper glass layer, an upper conductive layer, a liquid crystal layer, a dielectric reflector, a light blocking layer, a photosensitive layer, a lower conductive layer, and a lower glass layer. Wherein: the light barrier layer is a composite multilayer absorption film formed by cadmium telluride (CdTe) and vanadium-oxygen phthalocyanine (VOPc), and the CdTe polycrystalline material has a resistivity of 108And omega cm, the composite dielectric reflector can only absorb blue light and green light strongly, a composite multilayer structure formed by magnesium fluoride and zinc sulfide is used as a dielectric reflector, and semiconductor silicon (Si) is used as a photosensitive layer. The liquid crystal light valve can be used for optical interconnection of real-time change, parallel optical logic operation, optical digital operation, optical matrix operation, edge enhancement in image processing, image addition and subtraction and the like. However, the spatial resolution of the liquid crystal light valve is not high enough, the viewing angle is limited, the liquid crystal light valve is only suitable for general image processing, and the manufacturing process is complex, easy to suffer from environmental pollution, unstable in quality and poor in repeatability.
In the prior art, because the carriers are mainly generated in the surface area, the part of the carriers form a conductive charge layer on the surface of the photoconductive layer, and after part of reading light is transmitted through the dielectric mirror and the absorption layer to be irradiated on the photoconductive layer, the charge layer formed on the surface of the photoconductive layer can smoothly write a charge latent image generated by the light, so that the resolution and the contrast of an output image are reduced. At present, most of liquid crystal light valve liquid crystal boxes adopt a traditional TN vertical electric field mode, liquid crystal is in a rotating vertical type, the change of optical characteristics along with visual angles is very small, generally, the upper visual angle is about 10 degrees, the lower visual angle is about 40 degrees, the left visual angle and the right visual angle are about 30 degrees, and the visual angle is narrow. The liquid crystal molecules are converted from the horizontal panel arrangement to the vertical panel arrangement by using voltage, and the light rays which are transmitted by the liquid crystal are directional due to the relationship of the rotation angle, so that the light rays seen by naked eyes can be deviated under different angles, namely, the gray scale inversion is realized; meanwhile, during the rotation, the liquid crystal near the glass side is not straight affected by the alignment film (PI), resulting in a non-uniform phenomenon. Especially, the liquid crystal light valve with high light shielding requirement is realized by adopting a twisted nematic mode, the light valve adopts a double-sided planar electrode, a 90-degree twisted angle arrangement structure and a nematic phase material added with a chiral agent, and a polarizer is orthogonally attached along a friction direction, however, the liquid crystal light valve has the following defects:
(1) the viewing angle is narrow; when linearly polarized light with the same intensity is incident at different angles, the linearly polarized light becomes elliptically polarized light due to the change of the effective refractive index, and after passing through the second polaroid, the emergent light intensities with different incident angles are not equal any more, so that the problem of visual angle is formed, and the visual angle is less than 40 degrees.
(2) The response speed is slower; the twisted nematic mode liquid crystal light valve works in a natural falling mode, and the response speed of the twisted nematic mode liquid crystal light valve exceeds 40ms because no other external force acts on the twisted nematic mode liquid crystal light valve.
(3) The contrast is low; twisted nematic liquid crystal light valves use the optical rotation properties of liquid crystals and have a low contrast, especially a dark state that is not dark enough.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: a liquid crystal spatial light modulator having a high response speed, a high contrast ratio and a wide viewing angle is provided.
The invention provides the following technical scheme for solving the technical problems:
a liquid crystal spatial light modulator comprising: the liquid crystal display panel comprises a first transparent substrate and a second transparent substrate which are oppositely arranged in parallel, wherein the opposite sides of the first transparent substrate and the second transparent substrate are respectively provided with a first transparent electric conduction layer and a second transparent electric conduction layer so as to form a first transparent electrode and a second transparent electrode; the reflecting layer comprises pixel units distributed in an array manner and photosensitive areas connected with the pixel units, wherein light absorbing materials are arranged in the pixel units to form light blocking areas; the isolation grid is a metal reflection array formed by metal reflection units distributed on the partial surface of the light blocking area in a one-to-one correspondence manner; the high-resistance isolation layer completely covers the isolation grid and the reflection layer.
Furthermore, the material of the photosensitive region in the invention is Ag.
Furthermore, the material of the isolation grid is Al.
Further, the material of the light blocking region in the present invention is an insulating material.
Further, the high resistance isolation layer 10 of the present invention15～1016Ω。
Further, the relative dielectric constant of the high-resistance isolation layer in the invention is 3.9.
As a preferred embodiment, the material of the high-resistance isolation layer in the present invention is SiO2。
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the STN type super twisted nematic liquid crystal is adopted to replace the traditional TN type liquid crystal, the liquid crystal director can jump in a narrower voltage range, and the incident light can rotate 180-270 degrees based on the STN type super twisted nematic effect, so that the visual angle can be widened and the good contrast ratio can be maintained; in addition, the invention adopts a novel combined structure of the light-blocking layer and the isolation grid to replace a light-blocking film and a medium reflector which are arranged in a traditional device in a stacking way, and has the advantages of improving the photosensitive sensitivity of the light-addressing liquid crystal spatial light modulator, improving the imaging effect of the light-addressing liquid crystal spatial light modulator, enabling the resolution of reading light to be higher and reducing the driving voltage of the reading light.
Drawings
FIG. 1 is a schematic diagram of a liquid crystal spatial light modulator according to the present invention;
FIG. 2 is a schematic diagram showing twisted states of liquid crystal molecules under an applied voltage of a conventional TN type liquid crystal molecule and an STN type liquid crystal molecule of the present invention, wherein 1 is a TN type liquid crystal molecule and 2 is a STN type liquid crystal molecule;
FIG. 3 is a schematic top view of an isolation grid and a light blocking layer in an LC spatial light modulator according to the present invention;
in the figure: 1 is an upper glass substrate, 2 is an ITO conductive layer, 3 is a first orientation layer, 4 is a liquid crystal box, 401 is liquid crystal molecules, 5 is a second orientation layer, 6 is an isolation layer, 7 is an isolation grid, 8 is a light-blocking area, 9 is a metal Ag film, 10 is a photosensitive layer, and 11 is a lower glass substrate.
Detailed Description
The principles and features of this invention are explained in detail below in conjunction with the detailed description and the drawings attached hereto:
example (b):
the embodiment provides a method for preparing a liquid crystal spatial light modulator, which comprises the following steps:
step A: preparing a photosensitive layer 10;
in the embodiment, two glass substrates are respectively selected as an upper glass substrate 1 and a lower glass substrate 11, and ITO conductive layers 2 are completely deposited on single surfaces of the upper glass substrate 1 and the lower glass substrate 11 to form a first transparent electrode and a second transparent electrode respectively; then, depositing a trace amount of doped amorphous silicon thin film with the thickness of 3-8 microns on one side of the lower glass substrate 11 by adopting a PECVD method to serve as the photosensitive layer 10, wherein the material of the photosensitive layer 10 is not limited to a hydrogenated amorphous silicon thin film in the embodiment, and the material of the photosensitive layer 10 can be any suitable material according to common general knowledge in the art;
and B: preparing a reflecting layer;
firstly, depositing a layer of metal Ag film 9 with the thickness of 1-2 microns on the photosensitive layer 10 prepared in the step A by adopting an electron beam evaporation method, wherein the process parameters are specifically as follows, the background vacuum degree is 9 × 10-4Pa～2×10-3Pa, evaporation current of 150A, sputtering time of 0.5 h, working pressure of 5 × 10-3Pa; the deposition mode is as follows: thermal evaporation; substrate temperature: 75 ℃; target material: pure silver;
then, a photoetching process is adopted to etch the metal Ag film 9 to form a grid-shaped area so as to expose the photosensitive material below, thereby forming pixel units (namely photosensitive areas) distributed in an array manner, wherein the pixel units are imaging units with the size of micron level; the voltage of each pixel unit can be independently controlled, and the pixel units are regularly distributed to form a pixel array; the pixel unit (photosensitive region) is filled with a light absorption material to form a light blocking region 8, the light absorption material is preferably black negative glue, which will be described in detail below; the light-blocking regions 8 distributed in an array form and the metal Ag film 9 which is connected with each light-blocking region 8 and is used as a photosensitive region jointly form a reflecting layer of the device;
and C: preparing an isolation grid 7:
respectively depositing a layer of metal Al film on part of the upper surface of each light-blocking area 8 prepared in the step B, wherein a plurality of metal Al films are mutually independent and are distributed in an array manner to form an isolation grating 7; the shape of a single metal Al film is not limited, and can be circular, triangular, quadrilateral, pentagonal, hexagonal or any suitable shape; the metal reflective films distributed in an array manner are arranged on the reflective layer of the device, so that the metal reflective films have the function of shielding reading light, the influence of the reading light on the structure below the metal reflective layer is reduced, the device can work under the condition of reading light with higher intensity, and the application range of the device is further expanded;
step D: preparing an isolation layer 6:
a layer of SiO is deposited on the surfaces of the isolation grid 7 prepared in the step C and the light-blocking layer prepared in the step B2A thin film forming spacer layer 6; the isolating layer 6 is preferably a high-resistance isolating layer for preventing the free diffusion of metal ions in the metal reflecting layer from reducing the resistivity of the liquid crystal layer;
step E: preparing a liquid crystal box;
taking the glass substrate 1, preparing a first orientation layer 3 on one surface of the glass substrate plated with the ITO conductive layer 2, and preparing a second orientation layer 5 on the surface of the isolation layer 6, wherein the mode of preparing the orientation layer is not limited in the invention, and the preparation of the orientation layer is usually carried out by adopting a mode of obliquely evaporating a silicon dioxide film or coating polyimide, wherein: when the silicon dioxide film is obliquely evaporated to prepare the orientation layer, the obliquely evaporated orientation layer with different pretilt angles can be obtained by adjusting different evaporation angles; when the polyimide is coated to prepare the orientation layer, the orientation layer is prepared by spin coating of an orientation agent, baking and rubbing;
then, an STN type liquid crystal material is filled between the first orientation layer 3 and the second orientation layer 5 to form a liquid crystal box 4, when the liquid crystal material is filled, the liquid crystal material is prepared by adopting processes of spraying spacers, sealing the box with UV glue, performing ultraviolet curing and the like, and dust is prevented from entering when the liquid crystal box is sealed and filled; the first alignment layer 3, the second alignment layer 5 and the liquid crystal box 4 between the two layers form an STN type super-twisted nematic liquid crystal box; the fabrication of the liquid crystal spatial light modulator shown in fig. 1 is completed.
The working principle of the device is shown in fig. 1, wherein the photoelectric signal of the control pixel is called writing light, the photoelectric signal emitted by the spatial modulator is called reading light, a two-dimensional light intensity distribution (such as an image) is usually adopted as the writing light, the embodiment adopts an incoherent image to be processed as the writing light, the image is formed on the photosensitive layer 10 from the bottom side of the device, the reading light enters from the top, and the polarization direction of the reading light is consistent with the director of the liquid crystal molecule through the polarizer. The readout light passes through the ITO conductive layer 2 close to the side and the liquid crystal box 4, then is reflected by the separation grid 7, passes through the liquid crystal box 4 again, passes through the polarization beam splitter plate, and then passes through an analyzer with the light transmission axis direction perpendicular to the polarization direction of the polarizer to form an output light beam. For dark areas on the written optical image, the light impinging on the photosensitive layer 10 is low, the resistance of the photosensitive material is high, and the applied voltage is mainly distributed to the photosensitive layer. The voltage distributed across the liquid crystal layer is low enough to produce an effective electro-optic effect and still maintain the twisted alignment. The readout light is not substantially modulated at the corresponding dark area pixels and the output beam still remains small. On the contrary, for the pixel area with high illumination degree on the writing light image, the illumination irradiated to the photosensitive layer 10 is large, the photosensitive layer 10 generates photo-generated electron hole pairs after being irradiated, the bright resistivity of the photosensitive material is reduced due to the generation of a large number of carriers, the impedance of the photosensitive material is small, most of the applied voltage falls on the corresponding pixel area of the liquid crystal layer, and the output light in the area reaches the maximum output due to the mixed field effect. For other illumination areas on the written light image, the output intensity of the corresponding pixel in the output beam is also between the maximum and minimum values. The liquid crystal molecules 401 are rotated by the electric field to control whether the readout light passes through or not. When writing light with different intensities and different frequencies is irradiated on the photosensitive layer 10, resistance values of regions of the photosensitive layer 10 are different, and thus generated modulation electric fields are different, and rotation angles of liquid crystal molecules in the regions are different when the modulation electric fields are different, so that spatial distribution of light intensity of an output light beam is modulated according to spatial distribution of a writing light image.
Compared with the prior art, the invention has the remarkable improvement points that:
the liquid crystal spatial light modulator adopts STN type super twisted nematic liquid crystal, can widen the dynamic range of voltage regulation, thereby widening the display gray scale, and has the advantages of low power consumption, high contrast and wide visual angle. The following is a detailed description of the specific structure of the device of the present invention:
as shown in fig. 2, the conventional liquid crystal spatial light modulator that generally uses TN twisted nematic liquid crystal can rotate incident light to 90 ° at maximum in a pressurized state, while the STN super twisted nematic liquid crystal used in the present invention can rotate incident light by 180 ° to 270 ° based on the STN super twisted effect, thereby widening the visual angle by this characteristic;
on the other hand, when a liquid crystal spatial light modulator (i.e., a large display screen) with a larger area is prepared, the device prepared by using the TN liquid crystal has a poor contrast, and the device prepared by using the STN liquid crystal still can keep a high contrast, because the electro-optical characteristic curve of the device prepared by using the STN liquid crystal is steeper, and the sharp electro-optical characteristic curve can enable the liquid crystal director to jump within a narrow voltage range. In addition, the device using the STN type liquid crystal belongs to a passive matrix type device, so that the power consumption is low and the power is saved. Therefore, the improvement of STN type liquid crystal has the advantages of large display capacity, high contrast ratio and energy saving.
Compared with the prior art, the liquid crystal spatial light modulator has the advantages that the photosensitivity of the light addressing liquid crystal spatial light modulator is improved, the imaging effect of the light addressing liquid crystal spatial light modulator is improved, the resolution of reading light is higher, and the driving voltage of the reading light is reduced; meanwhile, the device is simple and convenient to prepare and low in production cost. This is described in detail below with specific reference to the device structure:
as shown in fig. 3, in the present invention, through reasonable structure design and material selection, the light sensing region formed by the metal Ag film 9 and the light blocking region 8 formed by the light absorbing material filled in the pixel units distributed in an array form a reflective layer structure, since the metal Ag film 9 is a low resistivity thin film, it also has high reflectivity, it can enhance the reflection of the writing light to the light sensing layer 10, and at the same time, it also reduces the light read by the device entering the device, and the metal Ag film 9 is divided into small reflective planes, which can form two-dimensional modulated charge distribution, and thus it is ideal in the electrical matching of the spatial light modulator, and it is beneficial to improve various performances of the spatial light modulator. The material of the light blocking region 8 of this embodiment is preferably a photosensitive Resin black matrix material (Resin-BM), which is a green environment-friendly light blocking material having an Optical Density (OD) higher than 3.5, excellent light blocking performance, good uniformity, good adhesion, high resolution, low reflectance (< 4%, λ 550nm), and excellent chemical resistance and heat resistance. The existence of the light blocking area 8 enables each pixel unit to be insulated, and the problem that reading light is not clear due to the fact that device resolution and contrast are reduced caused by light crosstalk between the pixel units is effectively solved. Therefore, the reflecting layer structure provided by the invention can solve the problems of poor adhesion and insufficient contrast of the existing light absorption layer material. The isolation grid 7 is composed of metal reflecting units distributed on the upper surfaces of parts of the light blocking areas 8, and the material of the metal reflecting units is preferably Al; the isolation grid 7 can effectively enhance the reflection of the readout light, and prevent the readout light from entering the device, so that the device can modulate the readout light with higher intensity.
Further, according to theoretical analysis of liquid crystal materials, the response time of the liquid crystal materials satisfies the following relationship:
Figure GDA0002536613490000061
wherein gamma is1Refers to the viscosity coefficient of the liquid crystal material, d refers to the gap of the liquid crystal cell, V refers to the drive voltage, and Δ refers to the dielectric coefficient of the liquid crystal material. The viscosity coefficient and the dielectric coefficient are directly related to the characteristics of the liquid crystal material, and the formula shows that the increase of the driving voltage of the liquid crystal cell is beneficial to improving the response speed. The novel structure provided by the invention adopts metal with lower resistivityCompared with the traditional dielectric reflector, the silver and aluminum metal provided by the invention has small voltage drop on the silver and aluminum metal, namely more effective voltage is used for driving the liquid crystal box, thereby being beneficial to improving the response speed of the device.
As is known in the art, the liquid crystal layer satisfies the liquid crystal dynamic equation:
Figure GDA0002536613490000062
from the above equation, it can be deduced that the response time of the liquid crystal layer depends on the cell thickness z and the twist elastic constant K22Coefficient of rotational viscosity gamma, applied electric field intensity E and friction angle
Figure GDA0002536613490000063
(angle between initial alignment direction of liquid crystal and electrode direction). In addition, an electrode structure having a narrow electrode width and a wide electrode gap can provide a higher transmittance, and a problem to be noted is that the narrower the electrode width, the larger the driving voltage is required for the wider the electrode gap. Under the condition of the same electrode width, the larger the electrode gap, the higher the contrast viewing angle, the same electrode gap, and the narrower the electrode width, the higher the contrast viewing angle. But overall the electrode width, the electrode gap variation does not have much impact on the contrast viewing angle. The small rubbing angle can not only achieve higher transmittance, but also the driving voltage required by the liquid crystal box is smaller, but the threshold voltage is larger, which is also a factor influencing the response speed of the liquid crystal box. The friction angle is increased, and the response speed is accelerated.
Through experimental tests, the liquid crystal spatial light modulator shown in the figure 1 detects the change of reading light along with the change of writing light under the condition of illumination, and the experimental test device has the response rise time of 3.6ms and the response fall time of 2.3 ms. The response time is measured by using a model DMS 505 display measurement system, and the test conditions are as follows:
environmental conditions: relative humidity is 60%, and air pressure is standard atmospheric pressure; the driving signal source selects a square wave driving signal source with the frequency of 100Hz, the receiving angle theta of the optical signal is 15 degrees, the testing range of the threshold voltage is 0-5.0V, and the stepping precision is 0.2V. The waiting time is the time from the application of the drive signal to the liquid crystal light valve to the start of the test, which is greater than the response time of the light valve.
When the liquid crystal light valve is 3 ', the projection screen is 200', the projection screen has a luminance of 80cd/m2Writing light threshold sensitivity P of liquid crystal light valveminIs 20 mu m/cm2. The average response time can reach 3.0ms, the maximum contrast can reach 1500: 1, the area with the contrast of more than 1000 exceeds 15 degrees in the horizontal direction and the vertical direction, and the area with the contrast of more than 100 approaches 60 degrees in the horizontal direction and the vertical direction.
While the present invention has been described with reference to the embodiments illustrated in the drawings, the present invention is not limited to the embodiments, which are illustrative rather than restrictive, and it will be apparent to those skilled in the art that many more modifications and variations can be made without departing from the spirit of the invention and the scope of the appended claims.

Claims (7)

1. A liquid crystal spatial light modulator comprising: first transparent substrate and the second transparent substrate of parallel relative setting, first transparent substrate and second transparent substrate incline in opposite directions has first transparent electric conduction layer and the transparent electric conduction layer of second respectively and then forms first transparent electrode and second transparent electrode, its characterized in that:
the liquid crystal display device sequentially comprises a first orientation layer, an STN type super twisted nematic liquid crystal layer, a second orientation layer, a high-resistance isolation layer, an isolation grid, a reflecting layer and a photosensitive layer from a first transparent electrode to a second transparent electrode; the reflecting layer comprises pixel units distributed in an array manner and photosensitive areas connected with the pixel units, wherein light absorption materials are arranged in the pixel units to form light blocking areas; the isolation grid is a metal reflection array formed by metal reflection units distributed on the partial surface of the light blocking area in a one-to-one correspondence manner; the high-resistance isolation layer completely covers the isolation grid and the reflection layer.
2. The liquid crystal spatial light modulator of claim 1, wherein the material of the photosensitive region is Ag.
3. The liquid crystal spatial light modulator of claim 1, wherein the material of the isolation grid is Al.
4. The liquid crystal spatial light modulator of claim 1, wherein the material of the light blocking region is an insulating material.
5. The liquid crystal spatial light modulator of claim 1, wherein the resistance of the high resistance spacer layer is 1015～1016Ω。
6. The liquid crystal spatial light modulator of claim 1, wherein the high-resistance spacer layer has a relative permittivity of 3.9.
7. The liquid crystal spatial light modulator according to claim 5 or 6, wherein the material of the high-resistance isolation layer is silicon dioxide.
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