CN112817185A - Illumination system applied to high-speed exposure patterning liquid crystal photo-alignment device - Google Patents
Illumination system applied to high-speed exposure patterning liquid crystal photo-alignment device Download PDFInfo
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- CN112817185A CN112817185A CN201911125169.9A CN201911125169A CN112817185A CN 112817185 A CN112817185 A CN 112817185A CN 201911125169 A CN201911125169 A CN 201911125169A CN 112817185 A CN112817185 A CN 112817185A
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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
- G02F1/1337—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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- 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
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Abstract
The invention discloses an illumination system applied to a high-speed exposure patterning liquid crystal photo-alignment device, which comprises a pulse light source and a collimation polarizing component, wherein the collimation polarizing component is used for providing a light source for continuous stroboscopic exposure and realizing single polarization collimation uniform surface light spots; the illumination system is connected to a polarization pattern generation component, which comprises a phase modulation device; the energy per unit area of the pulse light source is higher than the threshold energy of the optical polarization sensitive material on the liquid crystal substrate and lower than the damage threshold of the phase modulation device. 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
Technical Field
The invention relates to the field of liquid crystal display, in particular to an illumination system applied to a high-speed exposure patterning liquid crystal photo-alignment 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 by irradiating LCOS phase modulation devices with continuous laser light (De Sio L, Roberts D E, Liao Z, et al, digital polarization altering geographic phase Optics [ J ] Optics express, 2016, 24 (16): 18297 18306.), they have adopted low-energy continuous laser light to expose, considering the information amount of the image and the properties of exposure uniformity, 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 a large area breadth.
Therefore, a new illumination system for outputting a polarization pattern by using pulsed laser illumination in the field of liquid crystal display is desired.
Disclosure of Invention
In order to solve the problems of the prior art, the invention discloses an illumination system applied to a high-speed exposure patterning liquid crystal photo-alignment device, which comprises a pulse light source and a collimation polarizing component, wherein the pulse light source and the collimation polarizing component are used for providing a light source for continuous stroboscopic exposure and realizing single-polarization collimation uniform surface light spots;
the high-speed exposure patterning liquid crystal photo-alignment device further comprises a polarization pattern generation component, and the illumination system is connected with the polarization pattern generation component; the polarization pattern generation means includes a phase modulation device;
after the single or multiple pulse light beams generated by the pulse light source are subjected to beam expanding, collimating and beam splitting, the accumulated energy density is lower than the damage threshold of a phase modulation device at the position of a phase modulator; after the subsequent imaging step, the accumulated energy density is higher than the threshold energy of the light polarization sensitive material on the surface of the sample.
The energy per unit area of the pulse light source is higher than the threshold energy of the optical polarization sensitive material on the liquid crystal substrate and lower than the damage threshold of the phase modulation device.
As a further improvement of the embodiment of the invention, the pulse light source is generated by a pulse laser or a continuous laser plus a mechanical or photoelectric light barrier, or a pulse LED or a continuous LED plus a controllable light barrier system is adopted.
As a further improvement of the embodiment of the invention, the pulse light emitted by the pulse light source forms a collimated uniform light spot with a divergence angle less than 10mrad and light intensity uniformity better than 80% after passing through the collimating and polarizing component.
As a further improvement of the embodiment of the present invention, the repetition frequency of the pulsed light source is 1Hz to 10 kHz;
the pulse width of the pulse light source is in the range of picoseconds to seconds, and the energy of a single pulse is in the range of nano-focus to millifocus.
As a further improvement of the embodiment of the present invention, the wavelength of the pulsed light source is between 340nm and 600nm, and the half width of the pulsed light source is less than 5 nm;
in a constant temperature and humidity environment, the drift amplitude of the central wavelength of the pulse light source is less than 3 nm; the half-wave width of the light source is less than 5nm, and the energy of the pulse light source is more than eighty percent and is concentrated in the half-width of the central wavelength.
As a further improvement of the embodiment of the present invention, an influence of the pulsed light source on the phase delay of the polarization pattern generation means output pattern satisfies the following formula:
wherein δ is the polarization angle of a single pixel set by the phase adjusting device;
As a further improvement of the embodiment of the present invention, the phase error of the central wavelength shift and half width, temperature, and wave plate error of the pulsed light source to the polarization degree of the polarization pattern generation means output pattern is less than 1%.
As a further improvement of the embodiment of the present invention, after the incident light of the pulsed light source is phase-modulated by the polarization pattern generating means, the intensity ratio between the polarization direction and the direction perpendicular to the polarization direction is greater than 10: 1.
As a further improvement of the embodiment of the present invention, the pulse light source is a pulse laser, a pulse width of the pulse laser is less than or equal to an image maintaining time of the phase modulation device, and when one image of the phase modulation device is maintained, at least one pulse laser peak is irradiated onto the phase modulation device.
As a further improvement of the embodiment of the present invention, the illumination system further comprises a collimating polarizing component, the collimating polarizing component comprises a collimating assembly and a polarizing plate;
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.
In the embodiment of the invention, the high-speed exposure patterning liquid crystal photo-alignment device applying the illumination system further comprises a polarization pattern generation component, an imaging detection component, a focal length servo system and a motion control component which are sequentially connected with the illumination system;
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 modulation device is a liquid crystal phase modulation device and is used for loading different phases to each pixel;
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 improvement of the embodiment of the present invention, the phase modulation device is a pixel type phase retarder whose phase difference is adjustable; reflecting the polarized surface light source into light spots containing different polarization information and transmitting the light spots to the light splitting component;
the phase delay modulation of the phase modulation device 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 delay amount drift of the phase modulation device is less than 0.005 pi.
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 embodiments of the present invention, the quarter-wave plate is disposed between the phase modulator and the imaging detection assembly;
the phase modulator is a liquid crystal spatial light modulator and is a pixel type phase delayer with adjustable phase difference delta; the polarization rotation direction is δ/2; the polarization direction of incident light, the crystal axis direction of the phase modulation device 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 modulation device, and 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 modulation device and the crystal axis direction of the first 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 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.
As a further improvement of the embodiment of the present invention, the wavelength of light emitted from the detection light source is any value between 550nm and 700 nm;
the specified waveband reflecting flat sheet is a reflecting flat sheet plated with a wavelength reflecting film of a detection light source.
In the embodiment of the invention, a linear light source or a point light source emitted from a laser is adjusted into a collimated polarized surface light source; the illumination light source is uniformly irradiated on the phase modulator at a preset angle, and a pattern with any polarization distribution is generated by the quarter-wave plate and the phase modulator; further, a fixed micro-magnification ratio is formed by the focal length ratio of the cylindrical lens and the micro objective lens, the polarization pattern output by the phase modulator is micro-shrunk, and then a polarization pattern light field is output; detecting and adjusting the distance between the miniature objective lens and the light polarization sensitive material surface to ensure that the focal plane of the miniature objective lens is always kept at the light polarization sensitive material surface; detecting the size of the light spot projected on the light polarization sensitive material surface, and judging whether the light polarization sensitive material surface is on the focus surface of the objective lens; then recording the single light-controlled orientation on the light polarization sensitive material; moving the platform carrying the light polarization sensitive material to the next designated position for the next pattern light field recording; and splicing each orientation unit together to form randomly distributed light orientation structures on the light polarization sensitive material.
The image reflected from the surface of the light polarization sensitive material sequentially passes through a miniature objective lens, a cylindrical lens, a specified waveband reflection flat sheet and a first light splitter, then enters a first imaging CCD through a first lens, a phase modulator and the first imaging CCD are positioned on the front focal plane of the cylindrical lens to form a conjugate relation, the definition of the image of the first imaging CCD is adjusted by controlling the up-and-down movement of a lens of the miniature objective lens, whether the focal plane of the miniature objective lens is on the surface of the light polarization sensitive material is judged, the size of a laser spot in a second imaging CCD is calibrated, and the subsequent splicing is focused and monitored; and judging whether the focal plane of the objective lens is on the surface of the light polarization sensitive material or not through the contrast of the outline of the imaging light spot projected to the light polarization sensitive material.
In the embodiment of the invention, the wavelength of light emitted by the detection light source 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.
WhileMoving the platform carrying the light polarization sensitive material to the next designated position for the next orientation is realized 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 positions and the current speeds of the focusing platform and the sample carrying platform to the controller.
Specifically, after a single photo-alignment is recorded on the light polarization sensitive material, the platform carrying the light polarization sensitive material is moved to the next designated position by the motion control module by the size of the single alignment unit, and the moving mode is line-by-line sequential moving scanning.
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 when the pulse type illumination system is applied to high-speed exposure patterning liquid crystal photo-orientation, thereby realizing high-precision high-resolution exposure;
2. the single-frame polarization pattern recording is realized based on single or multiple pulses by utilizing the characteristics of large pulse laser energy, short pulse width and high repetition frequency, and the single-frame polarization pattern recording device has the advantages of large area, high efficiency and good reliability;
3. 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;
4. 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;
5. 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;
6. 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;
7. 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 modulation device 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 invention discloses an illumination system applied to a high-speed exposure patterning liquid crystal photo-alignment device, which comprises a pulse light source and a collimation polarizing component, wherein the collimation polarizing component is used for providing a light source for continuous stroboscopic exposure and realizing single polarization collimation uniform surface light spots;
the high-speed exposure patterning liquid crystal photo-alignment device also comprises a polarization pattern generation component, and the illumination system is connected with the polarization pattern generation component; the polarization pattern generating part includes a phase modulation device;
after single or multiple pulses generated by the pulse light source 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 is higher than the threshold energy of the light polarization sensitive material on the surface of the sample.
In the embodiment of the present invention, the pulsed light source is a pulsed laser, and in other alternative embodiments, the pulsed light source may also be generated by a continuous laser plus a mechanical or photoelectric barrier, or by a pulsed LED or a continuous LED plus a controllable barrier system.
Furthermore, the pulse light emitted by the pulse light source forms a collimated uniform light spot with a divergence angle less than 10mrad and light intensity uniformity better than 80% after passing through the collimating and polarizing component.
Wherein, the repetition frequency of the pulse light source 11 is 1Hz to 10 kHz;
in the embodiment of the invention, the pulse width of the pulse light source is in the range of picoseconds to seconds, and the single pulse energy is in the range of nano-focus to milli-focus; specifically, the wavelength of the pulse light source is between 340nm and 600nm, and the half width of the pulse light source is less than 5 nm;
in a constant temperature and humidity environment, the drift amplitude of the central wavelength of the pulse light source is less than 3 nm; the half-wave width of the light source is less than 5nm, and the energy of the pulse light source is more than eighty percent and is concentrated in the half-width of the central wavelength.
Wherein, the influence of the pulsed light source on the phase delay of the output pattern of the polarization pattern generation part 2 satisfies the following formula:
wherein δ is the polarization angle of a single pixel set by the phase adjusting device;
The phase error of the central wavelength drift, the half width, the temperature and the wave plate error of the pulse light source to the polarization degree of the output pattern of the polarization pattern generation component is less than 1 percent.
After the incident light of the pulse light source is subjected to phase modulation by the polarization pattern generation component, the intensity ratio of the incident light in the polarization direction to the incident light in the direction perpendicular to the polarization direction is larger than 10: 1.
In the embodiment of the invention, the pulse light source is pulse laser, the pulse width of the pulse laser is less than or equal to the image maintaining time of the phase modulation device, and when one image of the phase modulation device is maintained, at least one pulse laser peak irradiates the phase modulation device.
The collimation polarization part of the illumination system comprises a collimation assembly and a polarization piece;
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.
In the embodiment of the present invention, as shown in fig. 1, the high-speed exposure patterned liquid crystal photo-alignment apparatus using the illumination system further includes a polarization pattern generation component, an imaging detection component, a focal length servo system and a motion control component, which are sequentially connected to the illumination system;
the polarization pattern generating component comprises a quarter-wave plate and a phase modulation device 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 modulation device is a liquid crystal phase modulation device and is used for loading different phases to each pixel; specifically, the phase modulation device is a pixel type phase retarder whose phase difference is adjustable; reflecting the polarized surface light source into light spots containing different polarization information and transmitting the light spots to the light splitting component;
the phase delay modulation of the phase modulation device on the pulse light source is larger 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 delay amount drift of the phase modulation device is less than 0.005 pi.
An imaging detection component 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 imaging detection assembly also comprises a miniature imaging component which is used for miniature the polarization pattern output by the polarization pattern generation 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 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 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. The platform is arranged below the imaging objective lens group and is provided with a two-dimensional motion track which is used for bearing a light polarization sensitive material and driving the light polarization sensitive material to move on 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 on a focus 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.
In the embodiment of the invention, 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 connected in sequence;
wherein, the front focal plane of the imaging objective group is positioned near the back focal plane of the tube lens; 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.
The focal length servo system comprises a detection light source, a second lens, a second light splitter, an imaging objective lens group, a second imaging CCD and a motor which are connected in sequence;
wherein 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.
The quarter-wave plate is arranged between the phase modulator and the imaging detection assembly;
the phase modulator is a liquid crystal spatial light modulator and is a pixel type phase delayer with adjustable phase difference delta; the polarization rotation direction is δ/2; the polarization direction of incident light, the crystal axis direction of the phase modulation device and the crystal axis direction of the quarter-wave plate form included angles of 0 degree, 45 degrees and 90 degrees.
In the embodiment of the present invention, the number of the quarter-wave plates is two, and the polarization pattern generation component 2 includes a first quarter-wave plate, a phase modulation device, and a second quarter-wave plate which are connected in sequence;
the long axis direction of the first quarter-wave plate, the crystal axis direction of the phase modulation device and the crystal axis direction of the first quarter-wave plate form included angles of 0 degree, 45 degrees and 90 degrees.
Furthermore, the motion control component also comprises a controller and a motor driving device, wherein the controller is used for converting the acquired light path data into control signals and sending the control signals to each execution component;
the controller comprises a motion control module, and the motion control module comprises a platform motion control unit;
the motor driving device is used for driving the 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.
In the embodiment of the invention, the wavelength of light emitted by the detection light source is any value between 550nm and 700 nm;
the specified waveband reflecting flat sheet is a reflecting flat sheet plated with a wavelength reflecting film of a detection light source.
In the embodiment of the invention, a linear light source or a point light source emitted from a laser is adjusted into a collimated polarized surface light source; the illumination light source is uniformly irradiated on the phase modulator at a preset angle, and a pattern with any polarization distribution is generated by the quarter-wave plate and the phase modulator; further, a fixed micro-magnification ratio is formed by the focal length ratio of the cylindrical lens and the micro objective lens, the polarization pattern output by the phase modulator is micro-shrunk, and then a polarization pattern light field is output; detecting and adjusting the distance between the miniature objective lens and the light polarization sensitive material surface to ensure that the focal plane of the miniature objective lens is always kept at the light polarization sensitive material surface; detecting the size of the light spot projected on the light polarization sensitive material surface, and judging whether the light polarization sensitive material surface is on the focus surface of the objective lens; then recording the single light-controlled orientation on the light polarization sensitive material; moving the platform carrying the light polarization sensitive material to the next designated position for the next pattern light field recording; and splicing each orientation unit together to form randomly distributed light orientation structures on the light polarization sensitive material.
The image reflected from the surface of the light polarization sensitive material sequentially passes through a miniature objective lens, a cylindrical lens, a specified waveband reflection flat sheet and a first light splitter, then enters a first imaging CCD through a first lens, a phase modulator and the first imaging CCD are positioned on the front focal plane of the cylindrical lens to form a conjugate relation, the definition of the image of the first imaging CCD is adjusted by controlling the up-and-down movement of a lens of the miniature objective lens, whether the focal plane of the miniature objective lens is on the surface of the light polarization sensitive material is judged, the size of a laser spot in a second imaging CCD is calibrated, and the subsequent splicing is focused and monitored; and judging whether the focal plane of the objective lens is on the surface of the light polarization sensitive material or not through the contrast of the outline of the imaging light spot projected to the light polarization sensitive material.
In the embodiment of the invention, the wavelength of light emitted by the detection light source 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.
WhileMoving the platform carrying the light polarization sensitive material to the next designated position for the next orientation is realized 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 positions and the current speeds of the focusing platform and the sample carrying platform to the controller.
Specifically, after a single photo-alignment is recorded on the light polarization sensitive material, the platform carrying the light polarization sensitive material is moved to the next designated position by the motion control module by the size of the single alignment unit, and the moving mode is line-by-line sequential moving scanning. The moving manner is not limited in the present invention.
The relationship between the pulse laser frequency and the phase modulation device refresh frequency is shown in fig. 2, the pulse laser frequency corresponds to the phase modulation device frequency, and the pulse width is less than or equal to the image maintaining time of the phase modulation device, that is, when one image of the phase modulation device is maintained, one pulse laser peak irradiates the phase modulation device.
In the image maintaining time of the phase modulation device, a plurality of pulse laser peaks can be irradiated on the receiving window of the phase modulation device, so that the single exposure energy can be enhanced.
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 invention can control the phase change of a single exposure area in real time when the pulse type illumination system is applied to high-speed exposure patterning liquid crystal photo-orientation, thereby realizing high-precision high-resolution exposure;
2. the invention utilizes the characteristics of large pulse laser energy, short pulse width and high repetition frequency, realizes single-frame polarization pattern recording based on single or multiple pulses, and has the advantages of large area, high efficiency and good reliability;
3. 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;
4. 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;
5. 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;
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: the illumination system applied to the high-speed exposure patterning liquid crystal photo-alignment device provided by the above embodiments is only illustrated by dividing the above functional modules when executing the illumination mode, and in practical applications, the above functions may be distributed by different functional modules according to needs, that is, the internal structure of the system may be divided into different functional modules to complete all or part of the above described functions.
Those skilled in the art will appreciate that all or part of the steps for implementing the above embodiments may be performed by 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. An illumination system applied to a high-speed exposure patterning liquid crystal photo-alignment device is characterized by comprising a pulse light source and a collimation polarization component, wherein the pulse light source and the collimation polarization component are used for providing a light source for continuous stroboscopic exposure and realizing single-polarization collimation uniform surface light spots;
the high-speed exposure patterning liquid crystal photo-alignment device further comprises a polarization pattern generation component, the illumination system is connected with the polarization pattern generation component, and the polarization pattern generation component comprises a phase modulation device;
after the single or multiple pulse light beams generated by the pulse light source are subjected to beam expanding, collimating and beam splitting, the accumulated energy density is lower than the damage threshold of a phase modulation device at the position of a phase modulator; after the subsequent imaging step, the accumulated energy density is higher than the threshold energy of the light polarization sensitive material on the surface of the sample.
2. The illumination system of claim 1, wherein the pulsed light source is a pulsed laser or a continuous laser plus mechanical or electro-optical barrier, or a pulsed LED or a continuous LED plus controllable barrier system.
3. The illumination system of claim 1, wherein the pulsed light from the pulsed light source passes through the collimating and polarizing component to form a collimated uniform spot having a divergence angle of less than 10mrad and a uniformity of intensity of better than 80%.
4. The illumination system of claim 1, wherein the pulsed light source has a repetition frequency of 1Hz to 10 kHz;
the pulse width of the pulse light source is in the range of picoseconds to seconds, and the energy of a single pulse is in the range of nano-focus to millifocus.
5. The illumination system of claim 1, wherein the wavelength of the pulsed light source is between 340nm and 600nm, and the half width of the pulsed light source is less than 5 nm;
in a constant temperature and humidity environment, the drift amplitude of the central wavelength of the pulse light source is less than 3 nm; the half-wave width of the light source is less than 5nm, and the energy of the pulse light source is more than eighty percent and is concentrated in the half-width of the central wavelength.
6. The illumination system applied to the high-speed exposure patterning liquid crystal photo-alignment device according to claim 1, wherein the influence of the pulsed light source on the phase delay of the polarization pattern generation part output pattern satisfies the following formula:
wherein δ is the polarization angle of a single pixel set by the phase adjusting device;
7. The illumination system for high-speed exposure patterned liquid crystal photo-alignment device according to claim 6,
the phase error of the central wavelength drift, the half width, the temperature and the wave plate error of the pulse light source to the polarization degree of the output pattern of the polarization pattern generation component is less than 1 percent.
8. The illumination system of claim 1, wherein the incident light from the pulsed light source is phase modulated by the polarization pattern generator, and the intensity ratio between the polarized light and the light perpendicular to the polarized light is greater than 10: 1.
9. The illumination system of claim 1, wherein the pulsed light source is a pulsed laser having a pulse width less than or equal to the image-sustaining time of the phase modulation device, and at least one pulse laser peak is irradiated onto the phase modulation device when one image of the phase modulation device is maintained.
10. The illumination system of claim 1, further comprising a collimating polarizing component comprising a collimating assembly and a polarizing plate;
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.
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