CN112817158A - Large-breadth controllable polarization pattern generation device and method - Google Patents

Large-breadth controllable polarization pattern generation device and method Download PDF

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CN112817158A
CN112817158A CN201911124170.XA CN201911124170A CN112817158A CN 112817158 A CN112817158 A CN 112817158A CN 201911124170 A CN201911124170 A CN 201911124170A CN 112817158 A CN112817158 A CN 112817158A
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polarization
light
phase modulator
polarization pattern
component
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郑致刚
黄文彬
张新君
王骁乾
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East China University of Science and Technology
Suzhou University
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East China University of Science and Technology
Suzhou University
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
    • 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
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G02F1/13378—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation
    • G02F1/133788—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation by light irradiation, e.g. linearly polarised light photo-polymerisation

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Abstract

The invention discloses a large-breadth controllable polarization pattern generating device, which comprises a polarization pattern generating component, a polarization pattern generating component and a polarization pattern generating component, wherein the polarization pattern generating component is used for outputting a pixilated programmable polarization pattern to a workpiece; the polarization pattern generating component comprises a phase modulator, and the phase modulator obtains polarization distribution information of the required light orientation on the workpiece according to the received signals; the light field distribution projected on the surface of the phase modulator by the illumination component is modulated by the phase modulator, and the modulated light beam denatures the light polarization sensitive material on the worktable. The invention realizes single-frame polarization pattern recording based on single or multiple pulses by utilizing the characteristics of large pulse laser energy, short pulse width and high repetition frequency, and has the advantages of large area, high efficiency and good reliability.

Description

Large-breadth controllable polarization pattern generation device and method
Technical Field
The invention relates to the field of liquid crystal orientation arrangement control, in particular to a large-breadth controllable polarization pattern generation device.
Background
Liquid crystals have wide applications in the fields of information display, optics, photonics devices and the like; the liquid crystal can further realize the modulation of amplitude, phase and polarization of light according to the designed orientation arrangement, and plays an important role in the applications, so the orientation arrangement control mode of the liquid crystal becomes a research hotspot of academic and industrial production, and the prior art disclosed at present mainly comprises a rubbing orientation technology and a photo-orientation technology:
photoalignment is a non-contact liquid crystal aligning method which is newly developed, and the photoalignment technology is divided into four types at present, wherein the photoalignment technology utilizes photosensitive materials to perform oriented photocrosslinking, isomerization or photocracking reaction under the irradiation of ultraviolet or blue light polarized light to obtain the required arrangement: mask overlay polarization patterning techniques, periodic liquid crystal alignment techniques obtained by holographic interference methods, dynamic mask photo-alignment techniques based on DMDs, and also polarization alignment techniques based on spatial modulators.
The polarization orientation technology based on the liquid crystal spatial modulator is a programmable control device capable of modulating the phase and amplitude of incident light, and pattern recording of different orientation arrangements of liquid crystals in different selected areas can be realized by single projection orientation.
Patent application No. CN201820881217.1 discloses a photo-alignment apparatus for realizing arbitrary distribution by one exposure, which introduces a photo-alignment method for single exposure using a pixelated electrically controlled phase delay device, wherein the phase delay of each pixel of the pixelated electrically controlled phase delay device is controlled by a corresponding voltage respectively for generating the phase delay of arbitrary pattern distribution, but the problem of generating a phase pattern by one exposure is that the data size is proportional to the format size, which limits the format size of the prepared device, and also considers that a high-precision high-resolution photo-alignment pattern cannot be generated.
Foreign beam corporation has provided an apparatus and method for photoalignment using continuous laser irradiation on LCOS phase modulators (De SiOL, Roberts D E, Liao z, et al, digital polarization adaptive geometric phase Optics [ J ]. Optics express, 2016, 24 (16): 18297 18306.), they have used low energy continuous laser for exposure, taking into account the information amount of the image and the exposure uniformity and properties of material heat capacity, thermal diffusion, etc., tens of seconds to tens of minutes are required for exposure to a single field of view, and the exposure breadth is limited by the image information and cannot photoalign large area breadth.
Therefore, a new apparatus and method for outputting polarization patterns using pulsed laser illumination in the field of liquid crystal display is desired.
Disclosure of Invention
To solve the problems of the prior art, in one aspect, the present invention provides a large-format controllable polarization pattern generation apparatus, comprising a polarization pattern generation component for outputting a pixelated programmable polarization pattern onto a workpiece; the polarization pattern generation component comprises a phase modulator, and the phase modulator obtains polarization distribution information of the required light orientation on the workpiece according to the received signals;
the large-breadth controllable polarization pattern generation device further comprises an illumination component, the light field distribution projected on the surface of the phase modulator by the illumination component is modulated by the phase modulator, and the modulated light beam denatures the light polarization sensitive material on the workbench.
As a further improvement of the embodiment of the present invention, the polarization pattern generation means includes a quarter-wave plate and a phase modulator connected in series for outputting a pixelated programmable polarization pattern onto the workpiece; the phase modulator is connected with the imaging detection component; the phase modulator is a liquid crystal phase modulator and is used for loading different phases to each pixel and regulating and controlling a polarized surface light source into light spots containing different polarization information to be transmitted to the imaging detection assembly.
As a further improvement of the embodiment of the present invention, the phase modulator is a pixel-type phase retarder whose phase difference δ is adjustable; the polarization rotation direction is δ/2; the incident light polarization direction, the crystal axis direction of the phase modulator and the crystal axis direction of the quarter-wave plate form included angles of 0 degree, 45 degrees and 90 degrees.
As a further improvement of the embodiment of the present invention, the polarization pattern generation means includes a first quarter-wave plate, a phase modulator, a second quarter-wave plate, which are connected in this order;
the long axis direction of the first quarter-wave plate, the crystal axis direction of the phase modulator and the crystal axis direction of the second quarter-wave plate form included angles of 0 degree, 45 degrees and 90 degrees.
As a further improvement of the embodiment of the present invention, the operating wavelength of the phase modulator is between the ultraviolet band and the visible light band;
the pulse width of the pulse laser generated by the lighting component is in the picosecond to second level, and the wavelength of the pulse laser is 340nm to 600 nm;
after the pulse laser, single or multiple pulses are subjected to beam expanding, collimating and beam splitting steps, the accumulated energy density is lower than the damage threshold of a phase modulator at the position of the phase modulator; after the subsequent imaging step, the accumulated energy density on the surface of the sample is higher than the threshold energy of the light polarization sensitive material.
As a further improvement of the embodiment of the present invention, the resolution of the pattern received by the light polarization sensitive material is related to the resolution and the scaling factor of the phase modulator as follows:
Figure BDA0002275210510000031
wherein n is the pixel size of the phase modulator, and m is the reduction factor.
Image writing rate of the exposure device: 2mm2/min～100mm2And/min, depending on the complexity of the image and the splicing step distance, the positioning precision is +/-20 nm.
As a further improvement of the embodiment of the present invention, the phase delay modulation of the pulsed light source by the phase modulator is greater than 2 pi;
the single gray level controlled by a computer program has the phase modulation precision superior to 0.01 pi so as to realize random phase delay modulation in one period; the phase modulator has a phase delay amount drift of less than 0.005 pi.
The invention relates to a large-breadth controllable polarization pattern generation device which is applied to a high-speed exposure patterning liquid crystal photo-alignment device, wherein the high-speed exposure patterning liquid crystal photo-alignment device comprises an illumination component, a polarization pattern generation component, an imaging detection component, a focal length servo system and a motion control component which are sequentially connected;
the illumination component is used for providing a light source for continuous stroboscopic exposure and realizing single-polarization collimation uniform surface light spots;
the imaging detection component is used for detecting the generated pattern imaging; the focal length servo system comprises a normally open light source insensitive to light polarization sensitive materials and a vertical direction correction assembly, and is used for correcting the defocusing phenomenon generated by movement;
the motion control component is used for adjusting the spatial position of the platform carrying the light polarization sensitive material so as to realize light field splicing.
As a further development of an embodiment of the invention, the illumination means is a pulsed light source or a continuous light source with a controllable light barrier system.
As a further improvement of the embodiment of the present invention, the pulse width of the pulse laser is less than or equal to the image maintaining time of the phase modulator, and when an image of the phase modulator is maintained, at least one pulse laser peak is irradiated onto the phase modulator.
As a further improvement of the embodiments of the present invention, the illumination member includes a collimating assembly and a polarizer;
the collimation assembly is used for adjusting the linear light source or the point light source into a parallel surface light source and outputting the parallel surface light source to the polarization image generation component;
the polarizer is connected with the collimation assembly and is used for controlling the initial polarization direction of light and generating a surface light source with any polarization direction within the range of 0-179 degrees.
As a further improvement of the embodiment of the present invention, the imaging detection assembly further comprises a miniature imaging component;
the miniature imaging component is used for miniature the polarization pattern output by the polarization pattern generating component and writing the polarization pattern into the light polarization sensitive material;
the miniature imaging component comprises an imaging objective lens group, the main shaft direction of the light path of the imaging objective lens group is perpendicular to the platform, and the motor drives the imaging objective lens group to vertically move up and down to form a focusing surface on the platform.
As a further improvement of the embodiment of the present invention, the platform is disposed below the imaging objective lens group and has a two-dimensional motion track, which is used for bearing the light polarization sensitive material and driving the light polarization sensitive material to move in a two-dimensional plane under the driving of the motion control component, so that the surface of the light polarization sensitive material is always kept at the focal plane of the imaging objective lens group;
and the motion control component is connected with the miniature imaging component and is used for splicing the miniature polarization pattern light field.
As a further improvement of the embodiment of the present invention, the imaging detection assembly includes a first light splitter, a tube lens, an imaging objective lens group, a polarizer, a first lens, and a first imaging CCD, which are connected in sequence;
the front focal plane of the imaging objective group is positioned near the rear focal plane of the tube mirror; the imaging surface of the first imaging CCD is positioned on the front focal plane of the first lens; the back focal plane of the first lens is positioned on the front focal plane of the tube mirror.
As a further improvement of the embodiment of the present invention, the focal length servo system includes a detection light source, a second lens, a second light splitting plate, an imaging objective lens group, a second imaging CCD, and a motor, which are connected in sequence;
the detection light source is positioned on the front focal plane of the second lens; the second light splitter is positioned on the back focal plane of the second lens; the imaging surface of the second imaging CCD is positioned on the front focal plane of the second lens; the motor drives the imaging objective lens group;
the first imaging CCD receives a reflection image projected to the light polarization sensitive material surface, and the first imaging CCD and the phase modulator form a conjugate image.
As a further improvement of the embodiment of the present invention, the motion control component further includes a controller and a motor driving device, wherein the controller is configured to convert the collected light path data into a control signal and send the control signal to each execution component;
the controller comprises a motion control module comprising a platform motion control unit;
the motor driving device is used for driving a motor to drive the focusing platform and the platform to move, and the detection device is used for monitoring the movement of the motor in real time and sending the movement position and the movement speed of the motor to the movement control module;
and the platform motion control unit is used for controlling the light polarization sensitive material to move in a two-dimensional plane so as to realize the splicing of polarized light fields or the interconnection of different polarized light fields through the pattern splicing assembly.
On the other hand, the invention discloses a large-breadth controllable polarization pattern generation method, which comprises the following steps:
s1, adjusting the linear light source or point light source emitted by the light source into a collimated polarized light source through a polarizing collimator;
s2, loading corresponding phases by a phase modulator of the polarization pattern generating component according to the pattern information, and regulating and controlling the polarization surface light source into light spots containing different polarization information to be transmitted to the light splitting component;
s3, the light splitting component transmits the light with polarization information to the imaging detection assembly;
s4, recording the single light control orientation on the light polarization sensitive material;
and S5, moving the platform carrying the light polarization sensitive material to the next designated position for the next pattern light field recording.
As a further improvement of the embodiment of the present invention, after the step S5, S6 is further included, and each alignment unit is spliced together to form an optical alignment structure with a large area polarization light pattern on the light polarization sensitive material.
As a further improvement of the embodiment of the present invention, in step S2, the polarization information of each pixel point in each sub-graph is adjusted through a gray scale image, specifically, the method includes that the phase modulator adjusts the polarization level of each pixel point through voltage, and each pixel point determines the magnitude of the voltage through different gray scale information, so as to adjust and control the polarization information through the gray scale image;
the gray-scale image is written in real time or pre-loaded;
the phase modulator is a high-speed liquid crystal phase modulator and is used as a real-time programmable phase plate to perform wavefront correction on linearly polarized light, so that pixelation control on a polarization pattern is realized.
As a further improvement of the embodiment of the present invention, after the step S3, the method further includes:
the miniature imaging component forms a fixed miniature multiplying power through the ratio of focal lengths of the cylindrical lens and the imaging objective lens group, and miniature the polarization pattern output by the phase modulator so as to output a polarization pattern light field;
the servo focusing system adjusts the distance between the imaging objective lens group and the light polarization sensitive material surface, so that the focal plane of the imaging objective lens group is always kept at the light polarization sensitive material surface;
as a further improvement of the embodiment of the present invention, the step S4 specifically includes:
detecting any value between 550nm and 650nm of wavelength of light emitted by a light source;
the second lens reflects the light spots projected to the light polarization sensitive material surface to the second imaging CCD, the Z-axis servo focusing position is mapped through the light spot diameter, the vertical height of the Z-axis lens is adjusted, the light spot diameter in the second imaging CCD can be always kept to be R, and whether the light polarization sensitive material surface is on the focusing surface of the objective lens or not is judged by detecting the size of the light spots projected to the light polarization sensitive material surface through the second imaging CCD.
As a further improvement of the embodiment of the present invention, after the step S5 of recording the single polarization pattern on the light polarization sensitive material, the platform carrying the light polarization sensitive material is moved to the next designated position for the next orientation, which is implemented by the following steps:
the controller transmits the position data to the motion control module, the motion control module converts the received data into a control signal and transmits the control signal to the motor driver, the motor driver controls the motion of the motor according to the received control signal, and the detection device is responsible for monitoring the motion of the motor in real time and transmitting the motion position and the motion speed of the motor to the motion control module; and then the motion control module feeds back the current position and the speed of the platform to the controller.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention can control the phase change of a single exposure area in real time by utilizing the high-speed exposure patterning liquid crystal photo-orientation method of pulse laser illumination, thereby realizing high-precision high-resolution exposure, simultaneously utilizing the characteristics of large pulse laser energy, short pulse width and high repetition frequency, realizing single-frame polarization pattern recording based on single or multiple pulses, and having the advantages of large area, high efficiency and good reliability;
2. the light source adopts ultraviolet or blue light after beam expansion collimation, the light field is adjusted by the phase modulator, different polarization phases can be generated, and then the light field is combined with an imaging system for micro-shrinkage, so that polarization modulation in any direction in unit pixels is finally realized, and the problems of single polarization orientation, low flexibility and low processing efficiency are effectively solved;
3. the invention adopts the assistance of a focusing servo system to control the objective lens to move up and down, focus in real time and improve the resolution;
4. the invention adopts the high-precision platform to accurately control the sample to do two-dimensional plane movement, thereby providing favorable conditions for realizing large-format writing;
5. because the light energy is not concentrated, the invention proposes that the abutted seams between each light-operated orientation view field are eliminated and the resolution is improved by controlling the relation between the size of a single view field and the single translation distance;
6. the invention has the advantages of high precision, arbitrary controllability, large-area writing and high efficiency of single-exposure polarization patterns, and has important significance for designing and manufacturing large-size, high-precision and multifunctional liquid crystal optical devices.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a high-speed exposure patterned liquid crystal photo-alignment device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram showing the selection of the pulse laser frequency and the refresh frequency of the phase modulator of the high-speed exposure patterned liquid crystal photo-alignment device according to the embodiment of the present invention;
fig. 3 is a schematic representation of the peak absorption characteristics of a light polarization sensitive material used in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a large-breadth controllable polarization pattern generating device, which comprises a polarization pattern generating component, a polarization pattern generating component and a polarization pattern generating component, wherein the polarization pattern generating component is used for outputting a pixilated programmable polarization pattern to a workpiece; the polarization pattern generating component comprises a phase modulator, and the phase modulator obtains polarization distribution information of the required light orientation on the workpiece according to the received signals;
in an embodiment of the present invention, the large-format controllable polarization pattern generating apparatus further includes an illumination component, an optical field distribution projected by the illumination component on the surface of the phase modulator is modulated by the phase modulator, and the modulated light beam denatures the light polarization sensitive material on the worktable.
The polarization pattern generating component comprises a quarter-wave plate and a phase modulator which are sequentially connected and is used for outputting a pixilated programmable polarization pattern to a workpiece; the phase modulator is connected with the imaging detection component; the phase modulator is a liquid crystal phase modulator and is used for loading different phases to each pixel and regulating and controlling the polarized surface light source to be light spots containing different polarization information and transmitting the light spots to the imaging detection assembly.
Specifically, the phase modulator is a pixel-type phase retarder whose phase difference δ is adjustable; the polarization rotation direction is delta/2; the polarization direction of incident light, the crystal axis direction of the phase modulator and the crystal axis direction of the quarter-wave plate form included angles of 0 degree, 45 degrees and 90 degrees.
In an embodiment of the present invention, specifically, the polarization pattern generation component includes a first quarter-wave plate, a phase modulator, and a second quarter-wave plate connected in sequence;
wherein the long axis direction of the first quarter-wave plate, the crystal axis direction of the phase modulator and the crystal axis direction of the second quarter-wave plate form included angles of 0, 45 and 90 degrees.
In particular, the operating wavelength of the phase modulator is between the ultraviolet band and the visible band;
in the embodiment of the invention, the pulse width of the pulse laser generated by the lighting component is in the range of picoseconds to seconds, and the wavelength of the pulse laser is 340nm to 600 nm;
after single or multiple pulses are subjected to beam expanding, collimating and beam splitting, the accumulated energy density is lower than the damage threshold of a phase modulator at the position of the phase modulator; after the subsequent imaging step, the accumulated energy density on the surface of the sample is higher than the threshold energy of the light polarization sensitive material.
In particular, the resolution of the pattern received by the light polarization sensitive material is related to the resolution and the scale factor of the phase modulator as follows:
Figure BDA0002275210510000091
wherein n is the pixel size of the phase modulator, and m is the reduction factor.
Exposure device image writing rate: 2mm2/min～100mm2And/min, depending on the complexity of the image and the splicing step distance, the positioning precision is +/-20 nm.
In the embodiment of the invention, the phase delay modulation of the phase modulator on the pulse light source is more than 2 pi;
the single gray level controlled by a computer program has the phase modulation precision superior to 0.01 pi so as to realize random phase delay modulation in one period; the phase modulator has a phase delay amount drift of less than 0.005 pi.
The large-breadth controllable polarization pattern generation device is applied to a high-speed exposure patterning liquid crystal photo-alignment device, and the high-speed exposure patterning liquid crystal photo-alignment device comprises an illumination component, a polarization pattern generation component, an imaging detection component, a focal length servo system and a motion control component which are sequentially connected as shown in figure 1;
the illumination component is used for providing a light source for continuous stroboscopic exposure and realizing single-polarization collimation uniform surface light spots;
the polarization pattern generating component comprises a quarter-wave plate and a phase modulator which are connected in sequence and is used for outputting a pixilated programmable polarization pattern to a workpiece; the phase modulator is connected with the imaging detection component; the phase modulator is a liquid crystal phase modulator and is used for loading different phases to each pixel;
an imaging detection component for detecting the generated pattern imaging; the focal length servo system comprises a normally open light source insensitive to the light polarization sensitive material and a vertical direction correction assembly, and is used for correcting the defocusing phenomenon generated by movement;
and the motion control component is used for adjusting the spatial position of the platform carrying the light polarization sensitive material so as to realize light field splicing.
In an embodiment of the present invention, the illumination member is a pulsed light source, specifically, a pulsed laser; in other alternative embodiments the illumination means may also be a continuous light source with a controllable barrier system; the illumination unit generates a pulse width of a pulsed laser light of picosecond to second order and a wavelength of the pulsed laser light is 340nm to 600 nm.
In other alternative embodiments, the pulsed light source may also be generated by a continuous laser plus mechanical or electro-optical barrier, or by a pulsed LED or continuous LED plus controllable barrier system.
Preferably, the pulse width of the pulsed laser is less than or equal to the image hold time of the phase modulator, and at least one peak of the pulsed laser is impinging on the phase modulator while an image of the phase modulator is being held.
In the embodiment of the invention, the wavelength of light emitted by the laser is 442nm, the single pulse energy is 0.2mJ, the pulse width is 10ns, the light is pulse light and S polarization, the light is collimated and adjusted by the beam expanding system, and after the light passes through the polarizer, a collimated uniform light spot with the light spot diameter of 2cm, the divergence angle of less than 10mrad, the S polarization and the light intensity uniformity of better than 80 percent is formed.
Specifically, in an embodiment of the present invention, the illumination component comprises a collimating assembly and a polarizer; the collimating component and the polarizing plate form a collimating polarizing component.
The collimation assembly is used for adjusting the linear light source or the point light source into a parallel surface light source and outputting the parallel surface light source to the polarization image generation component;
the polarizer is connected with the collimation assembly and is used for controlling the initial polarization direction of light and generating a surface light source with any polarization direction within the range of 0-179 degrees.
Further, the imaging detection assembly further comprises a miniature imaging component;
the miniature imaging component is used for carrying out miniature on the polarization pattern output by the polarization pattern generating component and writing the polarization pattern into the light polarization sensitive material;
the miniature imaging component comprises an imaging objective lens group, the main shaft direction of the optical path of the imaging objective lens group is vertical to the platform, and the motor drives the imaging objective lens group to vertically move up and down to form a focusing surface on the platform.
In the embodiment of the invention, the platform is arranged below the imaging objective lens group and is provided with a two-dimensional motion track which is used for bearing the light polarization sensitive material and driving the light polarization sensitive material to move on a two-dimensional plane under the drive of the motion control component, so that the surface of the light polarization sensitive material is always kept on the focal plane of the imaging objective lens group;
the motion control component is connected with the miniature imaging component and is used for splicing the miniature polarization pattern light field.
The imaging detection assembly comprises a first light splitter, a tube lens, an imaging objective lens group, a polarizing film, a first lens and a first imaging CCD which are sequentially connected;
the front focal plane of the imaging objective group is positioned on the back focal plane of the cylindrical mirror; the imaging surface of the first imaging CCD is positioned on the front focal surface of the first lens; the back focal plane of the first lens is positioned on the front focal plane of the tube mirror.
As a further improvement of the embodiment of the present invention, the focal length servo system includes a detection light source, a second lens, a second light splitting plate, an imaging objective lens group, a second imaging CCD, and a motor, which are connected in sequence;
the detection light source is positioned on the front focal plane of the second lens; the second light splitting sheet is positioned on the back focal plane of the second lens; the imaging surface of the second imaging CCD is positioned on the front focal plane of the second lens; a motor-driven imaging objective lens group;
the first imaging CCD receives the reflected image projected to the light polarization sensitive material surface, and the first imaging CCD and the phase modulator form conjugate images.
In the embodiment of the invention, the motion control part further comprises a controller, a motor driving device and a motor detection device, wherein the controller is used for converting the acquired light path data into control signals and sending the control signals to each execution part;
the controller comprises a motion control module, and the motion control module comprises a platform motion control unit;
the motor detection device is used for monitoring the motion of the motor in real time and sending the motion position and the motion speed of the motor to the motion control module;
and the platform motion control unit is used for controlling the light polarization sensitive material to move in a two-dimensional plane so as to realize the splicing of the polarized light fields or the interconnection of different polarized light fields through the pattern splicing assembly.
In some embodiments, to address the problem of generating arbitrary polarization orientations, a polarization pattern generation component, comprising a quarter-wave plate and a phase modulator connected in series, is used to generate a pattern of arbitrary polarization distribution; the phase modulator regulates and controls the polarization level of each pixel point through voltage, and each pixel point determines the magnitude of the voltage through different gray scale information, so that the polarization information is regulated and controlled through the gray scale image. The gray scale map can be written in real time or pre-loaded; the phase modulator can be but is not limited to an ultra-high speed liquid crystal spatial light modulator, and can be used as a real-time programmable phase plate to perform wavefront correction on linearly polarized light, so that pixelation control on a polarization pattern is realized. The resolution of the original polarized light field is determined by the pixel size of the liquid crystal spatial light modulator.
The specific process of forming the polarization pattern based on the phase modulator is as follows: the fast axis directions of the first quarter-wave plate and the second quarter-wave plate are orthogonal and form 45-degree angles with the main axis direction of the liquid crystal arrangement of the phase modulator respectively. After the collimated light spot passes through the first quarter-wave plate, the collimated light spot is incident at an included angle of 3 degrees with the normal line of the phase modulator, the phase modulator is uniformly irradiated, the phase modulator adopted in the embodiment is an LCOS device, the working frequency is 50Hz to 400Hz, and the damage threshold of the pulse laser is more than 300mJ/cm210ns, 1920 × 1080 pixels, 8 micrometers of single pixel size, 1.54cm × 0.86cm of size of the whole phase modulator 22, and the phase modulation precision is better than 0.03 pi for a phase modulation amount greater than 2 pi at 442 nm.
The light splitting component is respectively connected with the miniature imaging component and the imaging detection component and is used for filtering light with specified wave bands to respectively enter the miniature imaging component and the imaging detection component;
the motion control part also comprises a pattern splicing assembly, and the pattern splicing assembly is used for splicing the miniature polarization pattern light field.
The control logic in the embodiment of the invention is specifically as follows: the control software in the industrial personal computer transmits the position data to the motion control module, the motion control module converts the received data into a control signal and transmits the control signal to the motor driver, and the motor driver controls the motion of the motor according to the received control signal; the detection device is responsible for monitoring the motion of the motor in real time and sending the motion position and the motion speed of the motor to the motion control module; and the motion control module feeds back the current position and speed of the platform to the software.
The phase modulator LCOS in the optical system is connected with the industrial personal computer through a data transmission line, so that the control software can transmit phase diagram data to the LCOS. The motion control card is connected with the laser through a trigger line and controls the light emission of the laser by sending a pulse signal.
On the other hand, the embodiment of the invention discloses a large-breadth controllable polarization pattern generation method, which comprises the following steps:
s1, adjusting the linear light source or point light source emitted by the light source into a collimated polarized light source through a polarizing collimator;
s2, loading corresponding phases by a phase modulator of the polarization pattern generating component according to the pattern information, and regulating and controlling the polarization surface light source into light spots containing different polarization information to be transmitted to the light splitting component;
s3, the light splitting component transmits the light with polarization information to the imaging detection assembly;
s4, recording the single light control orientation on the light polarization sensitive material;
and S5, moving the platform carrying the light polarization sensitive material to the next designated position for the next pattern light field recording.
Step S6, which is further included after step S5, splices each alignment unit together to form a light alignment structure with a large area-polarized light pattern on the light polarization sensitive material.
Specifically, step S2 adjusts the polarization information of each pixel point in each sub-image through a gray scale image, specifically including that the phase modulator adjusts the polarization level of each pixel point through voltage, and each pixel point determines the magnitude of the voltage through different gray scale information, thereby implementing the adjustment and control of the polarization information by the gray scale image;
the gray scale image is written in real time or pre-loaded;
the phase modulator is a high-speed liquid crystal phase modulator and is used as a real-time programmable phase plate to perform wavefront correction on linearly polarized light, so that pixelation control on a polarization pattern is realized.
Further, after step S3, the method further includes forming a fixed micro-magnification by the micro-imaging component according to the focal length ratio of the barrel lens to the imaging objective lens set, and micro-shrinking the polarization pattern output by the phase modulator to output a polarization pattern light field;
the servo focusing system adjusts the distance between the imaging objective lens group and the light polarization sensitive material surface, so that the focal plane of the imaging objective lens group is always kept at the light polarization sensitive material surface.
Further, the high-speed exposure patterned liquid crystal photoalignment method further includes, after the step S5:
and S6, splicing each orientation unit together to form the optical orientation structure with large-area polarization light pattern on the optical polarization sensitive material.
Step S2 is to adjust the polarization information of each pixel in each sub-image by using a gray scale image, and specifically includes that the phase modulator adjusts the polarization level of each pixel by using voltage, and each pixel determines the magnitude of the voltage by using different gray scale information, so as to adjust and control the polarization information by using the gray scale image;
the gray scale image is written in real time or pre-loaded;
the phase modulator is a high-speed liquid crystal phase modulator and is used as a real-time programmable phase plate to perform wavefront correction on linearly polarized light, so that pixelation control on a polarization pattern is realized.
Preferably, the wavelength of the light emitted from the light source in step S4 is any value between 550nm and 650 nm;
the second lens reflects the light spots projected to the light polarization sensitive material surface to the second imaging CCD, the Z-axis servo focusing position is mapped through the light spot diameter, the vertical height of the Z-axis lens is adjusted, the light spot diameter in the second imaging CCD can be always kept to be R, and whether the light polarization sensitive material surface is on the focusing surface of the objective lens or not is judged by detecting the size of the light spots projected to the light polarization sensitive material surface through the second imaging CCD.
In the embodiment of the present invention, after the single polarization pattern is recorded on the light polarization sensitive material, the stage carrying the light polarization sensitive material is moved to the next designated position for the next orientation in step S6, which is implemented by the following steps:
the controller transmits the position data to the motion control module, the motion control module converts the received data into a control signal and transmits the control signal to the motor driver, the motor driver controls the motion of the motor according to the received control signal, and the detection device is responsible for monitoring the motion of the motor in real time and transmitting the motion position and the motion speed of the motor to the motion control module; and then the motion control module feeds back the current position and the speed of the platform to the controller.
After the single light-operated orientation is recorded on the light polarization sensitive material, the moving distance of the platform carrying the light polarization sensitive material to the next specified position is the size of a single orientation unit through the motion control module, and the moving mode is that the platform is moved and scanned line by line in sequence; specifically, the time of each moving step is integral multiple of the pulse width of the pulse laser, and the same pattern light field can be exposed by using multiple laser pulses.
The relationship between the pulse laser frequency and the refreshing frequency of the phase modulator is shown in fig. 2, the pulse laser frequency corresponds to the frequency of the phase modulator, and the pulse width is less than or equal to the image maintaining time of the phase modulator, that is, when an image of the phase modulator is maintained, a pulse laser peak irradiates the phase modulator.
In the image holding time of the phase modulator, several pulse laser peaks may be irradiated onto the receiving window of the phase modulator to strengthen the single exposure energy.
The wavelength absorption characteristics of the photoalignment material used in this example are shown in fig. 3; the adopted material is an azo photo-alignment material, corresponding to the material 3 in fig. 3, a better photo-alignment effect can be obtained when laser with the wavelength of 442nm is used for illumination, pulse laser light sources with different wavelengths can be selected according to the photo-alignment material, or corresponding photo-alignment materials can be selected according to the pulse laser light sources with different wavelengths, a miniature part adopts a miniature objective lens with the power of 20 times, namely, the area of a light spot is reduced by 400 times, the energy density is improved by 400 times, the size of a single pixel after the miniature is only 0.4 micron, and the exposure direct writing of high-precision pattern information can be realized. At this time, the photosensitive amount of the photo-alignment material was 50mJ/cm2Above the photoalignment energy threshold and below the damage threshold.
It should be noted that the "strobe" defined in the present invention is to emit light and/or quench light at a predetermined frequency.
Compared with the prior art, the invention has the following beneficial effects:
1. the light source adopts ultraviolet or blue light after beam expansion collimation, the light field is adjusted by the phase modulator, different polarization phases can be generated, and then the light field is combined with an imaging system for micro-shrinkage, so that polarization modulation in any direction in unit pixels is finally realized, and the problems of single polarization orientation, low flexibility and low processing efficiency are effectively solved;
2. the invention can control the phase change of a single exposure area in real time by utilizing the high-speed exposure patterning liquid crystal photo-orientation method of pulse laser illumination, thereby realizing high-precision high-resolution exposure, simultaneously utilizing the characteristics of large pulse laser energy, short pulse width and high repetition frequency, realizing single-frame polarization pattern recording based on single or multiple pulses, and having the advantages of large area, high efficiency and good reliability;
3. the invention adopts the assistance of a focusing servo system to control the objective lens to move up and down, focus in real time and improve the resolution;
4. the invention adopts the high-precision platform to accurately control the sample to do two-dimensional plane movement, thereby providing favorable conditions for realizing large-format writing;
5. because the light energy is not concentrated, the invention proposes that the abutted seams between each light-operated orientation view field are eliminated and the resolution is improved by controlling the relation between the size of a single view field and the single translation distance;
6. the invention has the advantages of high precision, arbitrary controllability, large-area writing and high efficiency of single-exposure polarization patterns, and has important significance for designing and manufacturing large-size, high-precision and multifunctional liquid crystal optical devices.
All the above-mentioned optional technical solutions can be combined arbitrarily to form the optional embodiments of the present invention, and are not described herein again.
It should be noted that: in the embodiment, when the large-format controllable polarization pattern generating apparatus executes a large-format controllable polarization pattern generating method, only the division of the functional modules is taken as an example, and in practical applications, the function distribution may be completed by different functional modules according to needs, that is, the internal structure of the system is divided into different functional modules to complete all or part of the functions described above. In addition, the embodiments of the large-format controllable polarization pattern generation device and the large-format controllable polarization pattern generation method provided by the embodiments described above belong to the same concept, and specific implementation processes thereof are described in the embodiments of the methods and are not described herein again.
Those skilled in the art will appreciate that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. A large-breadth controllable polarization pattern generation device is characterized by comprising a polarization pattern generation component, a polarization pattern generation component and a polarization pattern generation component, wherein the polarization pattern generation component is used for outputting a pixilated programmable polarization pattern to a workpiece; the polarization pattern generation component comprises a phase modulator, and the phase modulator obtains polarization distribution information of the required light orientation on the workpiece according to the received signals;
the large-breadth controllable polarization pattern generation device further comprises an illumination component, the light field distribution projected on the surface of the phase modulator by the illumination component is modulated by the phase modulator, and the modulated light beam denatures the light polarization sensitive material on the workbench.
2. The large format controllable polarization pattern generating apparatus of claim 1 wherein the polarization pattern generating means comprises a quarter wave plate and a phase modulator connected in series for outputting a pixelated programmable polarization pattern onto a workpiece; the phase modulator is connected with the imaging detection component; the phase modulator is a liquid crystal phase modulator and is used for loading different phases to each pixel and regulating and controlling a polarized surface light source into light spots containing different polarization information to be transmitted to the imaging detection assembly.
3. The large format controllable polarization pattern generation apparatus of claim 2, wherein the phase modulator is a phase retarder of the pixel type with adjustable phase difference δ; the polarization rotation direction is δ/2; the incident light polarization direction, the crystal axis direction of the phase modulator and the crystal axis direction of the quarter-wave plate form included angles of 0 degree, 45 degrees and 90 degrees.
4. The large format controllable polarization pattern generating apparatus of claim 2, wherein the polarization pattern generating means comprises a first quarter wave plate, a phase modulator, a second quarter wave plate connected in sequence;
the long axis direction of the first quarter-wave plate, the crystal axis direction of the phase modulator and the crystal axis direction of the second quarter-wave plate form included angles of 0 degree, 45 degrees and 90 degrees.
5. The large format controllable polarization pattern generating apparatus of claim 2, wherein the operating wavelength of the phase modulator is between ultraviolet to visible light;
the pulse width of the pulse laser generated by the lighting component is in the picosecond to second level, and the wavelength of the pulse laser is 340nm to 600 nm;
after the pulse laser, single or multiple pulses are subjected to beam expanding, collimating and beam splitting steps, the accumulated energy density is lower than the damage threshold of a phase modulator at the position of the phase modulator; after the subsequent imaging step, the accumulated energy density on the surface of the sample is higher than the threshold energy of the light polarization sensitive material.
6. The large format controllable polarization pattern generating apparatus of claim 1, wherein the resolution of the pattern received by the light polarization sensitive material is related to the resolution and the scaling factor of the phase modulator as follows:
Figure FDA0002275210500000021
wherein n is the pixel size of the phase modulator, and m is the reduction factor.
Image writing rate of the exposure device: 2mm2/min～100mm2And/min, depending on the complexity of the image and the splicing step distance, the positioning precision is +/-20 nm.
7. The large format controllable polarization pattern generating apparatus of claim 5 wherein the phase modulator modulates the phase retardation of the pulsed light source by more than 2 π;
the single gray level controlled by a computer program has the phase modulation precision superior to 0.01 pi so as to realize random phase delay modulation in one period; the phase modulator has a phase delay amount drift of less than 0.005 pi.
8. A method for generating a large-breadth controllable polarization pattern is characterized by comprising the following steps:
s1, adjusting the linear light source or point light source emitted by the light source into a collimated polarized light source through a polarizing collimator;
s2, loading corresponding phases by a phase modulator of the polarization pattern generating component according to the pattern information, and regulating and controlling the polarization surface light source into light spots containing different polarization information to be transmitted to the light splitting component;
s3, the light splitting component transmits the light with polarization information to the imaging detection assembly;
s4, recording the single light control orientation on the light polarization sensitive material;
and S5, moving the platform carrying the light polarization sensitive material to the next designated position for the next pattern light field recording.
9. The method as claimed in claim 8, further comprising step S6 after step S5, splicing each of the orientation units together to form a light orientation structure of the large-breadth controllable polarization pattern on the light polarization sensitive material.
10. The large-format controllable polarization pattern generation method according to claim 8, wherein the step S2 adjusts the polarization information of each pixel point in each sub-graph through a gray scale image, specifically includes that the phase modulator regulates and controls the polarization level of each pixel point through voltage, and each pixel point determines the magnitude of the voltage through different gray scale information, so as to regulate and control the polarization information through the gray scale image;
the gray-scale image is written in real time or pre-loaded;
the phase modulator is a high-speed liquid crystal phase modulator and is used as a real-time programmable phase plate to perform wavefront correction on linearly polarized light, so that pixelation control on a polarization pattern is realized.
CN201911124170.XA 2019-11-15 2019-11-15 Large-breadth controllable polarization pattern generation device and method Pending CN112817158A (en)

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