CN116841077B - A depth-adjustable waveguide display method based on a rotating zoom liquid crystal lens - Google Patents
A depth-adjustable waveguide display method based on a rotating zoom liquid crystal lens Download PDFInfo
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- CN116841077B CN116841077B CN202310689589.XA CN202310689589A CN116841077B CN 116841077 B CN116841077 B CN 116841077B CN 202310689589 A CN202310689589 A CN 202310689589A CN 116841077 B CN116841077 B CN 116841077B
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133526—Lenses, e.g. microlenses or Fresnel lenses
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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
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
- G02B6/0015—Means for improving the coupling-in of light from the light source into the light guide provided on the surface of the light guide or in the bulk of it
- G02B6/0016—Grooves, prisms, gratings, scattering particles or rough surfaces
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
- G02B6/0023—Means for improving the coupling-in of light from the light source into the light guide provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
- G02B6/0026—Wavelength selective element, sheet or layer, e.g. filter or grating
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
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- Optics & Photonics (AREA)
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- Crystallography & Structural Chemistry (AREA)
- Liquid Crystal (AREA)
Abstract
The invention discloses a depth-adjustable waveguide display method based on a rotary zoom liquid crystal lens, which comprises the steps that light emitted by an image source is collimated by a collimator, the light enters a coupling grating to couple the collimated light into an optical waveguide plate, the light is diffracted and coupled out of the optical waveguide plate to serve as coupled out light after being transmitted by total reflection in the optical waveguide plate and encounters the coupling grating, the coupled out light enters human eyes after passing through the zoom Moire lens, and ambient light enters human eyes after sequentially passing through a compensating Moire lens and the zoom Moire lens, wherein the focal lengths of the two Moire lenses are synchronously adjusted by controlling rotation of an element PBOE in the zoom Moire lens close to the human eyes and an element PBOE in the compensating Moire lens far away from the human eyes, so that an image transmitted by the waveguide is imaged at a required depth, and the real environment seen by the human eyes is not influenced. The method solves the problem that the traditional waveguide display system can only image the virtual image at an infinite distance.
Description
Technical Field
The invention relates to the technical field of near-to-eye waveguide display, in particular to a depth-adjustable waveguide display method based on a rotary zoom liquid crystal lens.
Background
In recent years, augmented Reality (AR) technology develops a heat, which has a great application potential in various fields of medical treatment, education, military, etc., and by superimposing a virtual image generated by a computer into a real scene, AR is expected to thoroughly change the interactive experience of a user, thereby becoming a mainstream display device of the next generation.
Recently, patterned liquid crystal optical elements are increasingly used in the AR field. Using the photo-alignment technique we can transfer any pattern recorded on the photo-alignment layer into the liquid crystal layer, thus obtaining a liquid crystal planar element with the designed phase modulation function, by using nematic liquid crystal and cholesteric liquid crystal, transmissive and reflective elements can be prepared, respectively. The optical elements are simple to prepare, small in thickness and light in weight, are very suitable for being applied to an AR system, and meanwhile, the angle response range and the wavelength response range of a liquid crystal device are better than those of a traditional holographic device due to the fact that the ordinary light refractive index n o and the extraordinary light refractive index n e of a liquid crystal material are large in difference, and in addition, the patterned liquid crystal element has unique polarization response characteristics, so that a new design dimension is provided for the design of the optical system. The chinese patent publication No. CN112147786a discloses an augmented reality display system, which includes a waveguide display system and a myopia-adjusting optical element, the waveguide display system includes a display image source and a waveguide substrate, and a waveguide internal reflection surface and a waveguide reflection exit surface disposed in the waveguide substrate, the myopia-adjusting optical element has a first side surface and a second side surface opposite to each other, the first side surface is used for being opposite to a human eye, the second side surface is completely attached to an outer surface of the waveguide substrate, the waveguide substrate makes a light beam from the display image source propagate in a waveguide in a total reflection manner and is conducted onto the waveguide internal reflection surface, the waveguide internal reflection surface is used for reflecting the light beam onto the waveguide reflection exit surface, the waveguide reflection exit surface is used for transmitting the light beam through the myopia-adjusting optical element and reflecting the light beam to the human eye, and the myopia-adjusting optical element may be a liquid crystal lens. Chinese patent publication No. CN114089531a discloses a binocular waveguide display method based on a reflective polarization multiplexing liquid crystal lens, which is based on a waveguide display device, and includes an optical waveguide plate, on the same side of which an in-coupling liquid crystal lens, a right-handed out-coupling grating, and a left-handed out-coupling grating are disposed, and the in-coupling liquid crystal lens is located between the right-handed out-coupling grating and the left-handed out-coupling grating.
Waveguides have been shown to have potential and advantages in terms of volume, weight, field of view, and exit pupil size as a widely accepted AR solution. In conventional waveguide display technology, however, collimated light is extracted to the eyes of the user through an optical coupler of the output section. In this case, the virtual image is imaged at infinity, and the observer's eye is forced to focus at infinity by the accommodation reaction. When a real object is located near a user, the displayed image may become blurred due to the difference in adjustment depth between the real object and the virtual image. This problem may affect the user's augmented reality experience and cause visual fatigue due to mismatch between the accommodation and vergence distance, which is referred to as Vergence Accommodation Conflict (VAC). How to solve this problem is a research hotspot in the field at present.
Disclosure of Invention
The invention aims to provide a depth-adjustable waveguide display method based on a rotary zoom liquid crystal lens, which can solve the problem that a traditional waveguide display system can only image a virtual image at an infinite distance.
The invention provides the following technical scheme:
the depth-adjustable waveguide display device comprises an image source, a collimator, an optical waveguide plate provided with an in-coupling grating and an out-coupling grating on the same side and liquid crystal Moire lenses respectively positioned on two sides of an out-coupling area of the optical waveguide plate, wherein the liquid crystal Moire lenses comprise a compensating Moire lens and a zooming Moire lens;
The depth-adjustable waveguide display method comprises the following steps:
light emitted by the image source is collimated by the collimator, and the in-coupling grating couples the collimated light into the optical waveguide plate;
light propagates in the optical waveguide plate by means of total reflection, and is diffracted out of the optical waveguide plate as out-coupled light after impinging on the out-coupling grating;
the coupled light enters human eyes after passing through the zoom Moire lens;
the ambient light enters human eyes after sequentially passing through the compensating Moire lens and the zooming Moire lens;
Wherein the focal lengths of the two moire lenses are adjusted synchronously by controlling the rotation of the element PBOE of the zoom moire lens close to the human eye and the rotation of the element PBOE of the compensation moire lens far from the human eye, so that the image propagated by the waveguide is imaged at a required depth, and the real environment seen by the human eye is not affected.
The image source may be OLED, microLED, DLP, LCOS or other types of light engines.
The collimator may be any type of lens or lens system used to collimate light emitted by an image source.
And a circular polarizer is added behind the image source and is used for converting light emitted by the image source into circular polarized light with the corresponding chirality of the waveguide coupling grating, so that the system efficiency is improved. .
The in-coupling grating and the out-coupling grating on the optical waveguide plate are liquid crystal polarizer grating PVG, the chirality of the in-coupling grating and the out-coupling grating is the same, and the in-coupling grating and the out-coupling grating are symmetrically arranged on the optical waveguide plate. For example, two gratings are prepared from cholesteric liquid crystals (for example, right-handed liquid crystals) with the same chirality, and can diffract circular polarized light (right-handed circular polarized light) with the corresponding handedness.
The zoom Moir lens and the compensation Moir lens are each composed of two liquid crystal Pancharaam-Berry phase optical elements PBOE, the PBOE having the same phase distribution. I.e. four identical PBOE groups of two groups of components form a zoom moire lens and a compensation moire lens, which are symmetrically arranged on both sides of the coupling-out region of the waveguide plate, wherein PBOE of the zoom moire lens close to the human eye and PBOE of the compensation moire lens far from the human eye are manipulated by a rotation control device, and can synchronously rotate by the same angle.
The phase distribution of PBOE satisfies the condition that the combined phase distribution of two PBOE of the incident circularly polarized zoom or compensation moir lenses approximates one zoom lens by rotating one of the zoom or compensation moir lenses PBOE.
The phase distribution of PBOE may be as long as the above condition is satisfied, for example:
the PBOE has a function of one-handed circularly polarized light (e.g., right-handed circularly polarized light) (Typical Moire lens sub-element phase distribution, other similar phase distributions may be used) phase distribution/modulation, due to PBOE's characteristics, with respect to another-handed circular polarization (e.g., left-handed circular polarization)Where (r, θ 0) is the polar diameter and polar angle in the polar coordinate system, λ is the operating wavelength, F 0 is the reference focal length, and round () is a function of the rounding up.
When waveguide coupled-out light (right-handed circularly polarized light) passes through two such PBOE (constituting a zoom Moire lens) in succession, the first PBOE produces a phase modulation of phi (r, theta 0) and reverses the circular polarization direction of rotation, the second PBOE produces a phase modulation of-phi (r, theta 0), since the circular polarization direction of PBOE diffracted light reverses with respect to incident light, when two such PBOE are combined, when the second PBOE is rotated by an angle theta about the center with respect to the first PBOE, the total phase modulation received by the right-handed circularly polarized light incident on this combined element isThis corresponds to a focal length ofWherein the adjustable range of θ is-pi to +pi.
The focal length of the zoom moire lens varies continuously between [ - ≡f 0 ] depending on the angle of rotation (only negative focal length is considered, positive focal length lens images the virtual image behind the human eye, no meaning), where F 0 is a designed reference value. The light coupled out of the waveguide enters human eyes after passing through the zoom Moire lens, so that the virtual image can be imaged at the required depth by adjusting the rotation angle of the Moire lens.
The above phase distribution is only a common arrangement, and the PBOE may also have other phase distributions, for exampleOr other forms.
The PBOE of the zoom Moir lens close to the human eye and the PBOE of the compensation Moir lens far from the human eye are operated by a rotation control device to synchronously rotate by the same angle.
In PBOE synchronous rotation, for incident circular polarized light of the same rotation direction, the zoom moire lens and the compensation moire lens always have focal lengths with the same size and opposite signs.
In the invention, the compensating Moire lens is arranged for compensating the influence of the zoom Moire lens on the ambient light, and in the process of operating the zoom Moire lens and synchronously rotating the compensating Moire lens by the rotation control device, the two lenses always have focal lengths with the same size and opposite signs for the incident circular polarized light with the same rotation direction, and meanwhile, the optical waveguide plate is very thin, so that a lens group formed by the compensating Moire lens and the zoom Moire lens has no optical power under the condition of neglecting the distance between the two lenses, and the ambient light cannot be influenced (the ambient light can be regarded as superposition of the left-handed circular polarized light and the right-handed circular polarized light). In addition, since the coupling-out grating is a liquid crystal polarizer grating (reflective element), it does not affect the transmitted ambient light and the ambient transmittance is high. In combination with the above analysis, the real environment seen by the human eye does not change in the present invention.
PVG is prepared using cholesteric liquid crystal based on photo-alignment technology and PBOE is prepared using nematic liquid crystal based on photo-alignment technology. Specifically:
the preparation method of the liquid crystal polarizer grating on the waveguide plate comprises the steps of preparing a photo-alignment layer on the waveguide plate by spin coating, carrying out in-coupling grating exposure and out-coupling grating exposure, spin coating a reactive liquid crystal solution containing a chiral agent and a photoinitiator, and ultraviolet curing the liquid crystal layer, wherein spin coating and curing of the liquid crystal layer can be repeated for a plurality of times to increase the thickness of the liquid crystal layer and improve diffraction efficiency.
The preparation method of PBOE comprises the steps of preparing a photo-alignment layer on a substrate in a spin coating mode, exposing to record required phase distribution, spin-coating a reactive liquid crystal solution containing a photoinitiator, ultraviolet curing the liquid crystal layer, and repeating the spin coating and curing of the liquid crystal layer to enable the thickness of the liquid crystal layer to meet half-wave conditions so as to obtain maximum element efficiency.
The depth-adjustable waveguide display method provided by the invention can continuously and widely regulate and control the focusing position of the coupled light of the waveguide by utilizing the rotary zoom liquid crystal lens (Moire lens), so that the image propagated by the waveguide can be imaged at a desired depth, and the problems of imaging blur, visual fatigue and the like caused by that a virtual image can only be imaged at infinity in the traditional waveguide display are solved. Meanwhile, focusing is performed by rotation in the invention, instead of focusing by changing the axial distance of the element in the conventional zoom system, so that the system is lighter, thinner and more compact. And through the use of the compensating moire lens, the method provided by the invention can not influence the observation of a user on a real scene, so that a good AR display effect is ensured.
The method provided by the invention utilizes the characteristics of liquid crystal PBOE for generating opposite phase modulation on different circular polarized lights and reversing the rotation direction of incident light, uses two identical PBOE combinations to form a Moire lens, uses a liquid crystal polarizer grating as a coupler in a waveguide, and utilizes the polarization selectivity of the liquid crystal polarizer grating to meet the circular polarized light incidence requirement of the Moire lens. PBOE and the liquid crystal polarizer grating have similar and simple preparation processes, so that the method provided by the invention is convenient to realize.
Drawings
FIG. 1 is a schematic diagram of the overall system architecture of a depth-adjustable waveguide display device provided by the present invention;
FIG. 2 is a schematic view of waveguide imaging with moire lens focusing to different focal lengths;
FIG. 3 is a schematic diagram of the structure of a liquid crystal polarizer grating;
FIG. 4 is a schematic diagram of the structure of a liquid crystal Pancharaam-Berry phase optical element;
FIG. 5 is an exposure light path of a liquid crystal polarizer grating;
FIG. 6 is an exposure light path of a liquid crystal Pancharaam-Berry phase optical element;
Wherein In-PVG and Out-PVG In FIGS. 1 and 2 represent In-coupling liquid crystal polarizer gratings and Out-coupling liquid crystal polarizer gratings, PBOE represents liquid crystal Panchara-Berry phase optical elements, T-PBOE represents rotatable PBOE, LCP and RCP In FIG. 3 represent left-hand circular polarization and right-hand circular polarization, respectively, Λ x、Λy、ΛB represents a transverse period, a longitudinal period and a Bragg period of PVG, respectively, α represents a grating tilt angle, d In FIG. 4 represents a thickness of a liquid crystal layer of PBOE, P In FIG. 5 represents a linear polarizer, QWP is a quarter wave plate, BS is a beam splitter, M1 and M2 are mirrors, S is an exposed sample substrate, PBS In FIG. 6 is a polarizing beam splitter, and SLM is a spatial light modulator.
Detailed Description
The present invention will be described in detail with reference to the drawings and examples for a clearer understanding of technical features, objects and effects of the present invention.
As shown in fig. 1, the overall system structure of the depth-adjustable waveguide display device provided by the invention is schematically shown, and the structure comprises an image source 1, a collimator 2, an optical waveguide plate 3, an in-coupling PVG 4, an out-coupling PVG 5, a zoom moire lens 6, a compensation moire lens 7 and a rotation controller 8 (which may also be referred to as a rotation control device). The image source 1 is placed in the focal plane of the collimator 2, so that the collimator 2 converts the light emitted by the image source 1 into parallel light. The in-coupling PVG 4 and the out-coupling PVG 5 are responsive to circularly polarized light of the same handedness (in the example assumed to be right-handed circularly polarized light) and are arranged on the same side symmetrically on the optical waveguide plate 3, a right-handed circular polarizer may be added behind the image source 1 to increase the overall efficiency of the system. The right-hand circularly polarized light is diffracted by the in-coupling PVG 4, and the propagation angle of the diffracted light is larger than the total internal reflection angle of the optical waveguide plate 3, and is thus coupled into the optical waveguide plate 3, and propagates continuously by means of total reflection until the out-coupling PVG 5 is diffracted again, the total reflection condition is broken, the light coupled out of the optical waveguide plate 3, and the light not diffracted by the out-coupling PVG 5 continues to propagate in the optical waveguide plate 3 until the out-coupling PVG 5 is encountered next time, which is called exit pupil expansion of the waveguide. Two moire lenses (a zoom moire lens 6 and a compensation moire lens 7) in the system are respectively composed of two PBOE, one PBOE is connected with a rotary controller 8, coupled light enters human eyes after passing through the zoom moire lens 6, and the zoom moire lens 6 can continuously focus through the control of the rotary controller 8, so that an image propagated by a waveguide can be imaged at a certain depth position at infinity or near. Ambient light enters human eyes after passing through the compensating moire lens 7 and the zooming moire lens 6, the compensating moire lens 7 and the zooming moire lens 6 are symmetrically arranged on two sides of the optical waveguide plate 3 and are controlled by the rotary controller 8 to rotate synchronously at the same angle, and the ambient light has focal lengths with the same size and opposite signs at the moment, so that the ambient light entering the human eyes is not affected.
As shown in fig. 2, which is a schematic view of waveguide imaging when the moire lens focuses to different focal lengths, the imaging results under two focal lengths are shown, and the imaging results respectively correspond to the angle of T-PBOE rotation θ 1 and θ 2 controlled by the rotation controller 8, at this time, the zoom moire lens 6 has focal lengths of-F 1 and-F 2 for right-handed circular polarized light, and-F 1＜-F2 <0. Thus when the waveguide outcoupling light passes through the zoom moire lens 6, the virtual image when rotated by θ 1 is imaged at a depth position farther from the human eye, and the virtual image when rotated by θ 2 is imaged at a depth position closer. This example demonstrates the feasibility of the depth-tunable waveguide display method proposed by the present invention.
As shown in fig. 3, a schematic diagram of the structure of the liquid crystal polarizer grating is shown. PVG is a bragg grating with a two-dimensional periodic structure, the cholesteric liquid crystal in the PVG structure tends to form an inclined helical structure due to the tendency of the lowest volume free energy, the transverse period Λx is determined by the orientation of the photo-alignment layer, the bragg period Λ B is equal to half of the cholesteric liquid crystal pitch, the liquid crystal pitch (p) is determined by the helical twist constant (HTP) and doping concentration (c) of the chiral dopant in the reactive liquid crystal, p= (htp·c) -1, and the grating tilt angle is determined by α= ±arcsin (Λ B/Λx), where the sign depends on the handedness of the cholesteric liquid crystal. The bragg condition of PVG for normal incidence light is expressed as:
2neffΛBcosα＝λB
Where lambda B is the Bragg wavelength in vacuum and n eff is the effective refractive index of the liquid crystal. In addition, the polarization selectivity of PVG is also shown in FIG. 4, PVG formed by right-handed chiral cholesteric liquid crystal only diffracts right-handed circular polarized light, and left-handed circular polarized light directly penetrates PVG.
As shown in fig. 4, a schematic structural diagram of a panchornam-Berry phase optical element is shown, PBOE is a transmissive phase modulation element based on panchornam-Berry phase (geometric phase), and is prepared from nematic liquid crystal, the molecular direction of the nematic liquid crystal is kept consistent in the longitudinal direction (y direction), and the liquid crystal molecules with the same (x, z) coordinates have the same orientation angle. Arrangement of liquid crystal molecules in xz planeDepending on the photo-alignment layer, elements with such an arrangement of liquid crystal molecules will produce left-and right-handed circular polarization respectivelyAnd reverse the circular polarization direction of the incident light (left-handed rotation to right-handed rotation, right-handed rotation to left-handed rotation). The diffraction efficiency of PBOE is related to the thickness of the element, and is maximum when Δn·d=λ/2, where Δn=n e-no denotes the anisotropy of the liquid crystal, n o is the ordinary refractive index, n e is the extraordinary refractive index, d is the thickness of the liquid crystal layer, λ is the application wavelength, λ is set to be consistent with the bragg wavelength of PVG in the present invention, and the thickness of PBOE liquid crystal layer to be prepared is calculated to obtain the maximum diffraction efficiency.
As shown in fig. 5, the exposure light path of the liquid crystal polarizer grating is shown, the two exposure light beams are orthogonal circular polarized light with equal light intensity, when the two light beams are symmetrically incident on the exposure surface at an included angle of 2θ, the interference light field is linearly polarized light with uniform light intensity distribution and a polarization direction linearly changed along the x-axis period, and the period is Λ=λ e/2sin θ, wherein λ e is the exposure wavelength. The substrate with the photo-alignment layer is placed on the exposure plane and the direction of this periodic polarization can be recorded and after spin-coating the liquid crystal the photo-alignment layer orients the liquid crystal, resulting in a lateral period ax in PVG.
As shown in FIG. 6, the exposure light path of the liquid crystal Pancaratnam-Berry phase optical element, used for exposing PBOE of the constituent Moire lens, in the embodiment PBOE, produces incident right-hand circular polarizationThus, the two interference light paths also need to generate a phase difference distribution of phi (r, theta 0) in the exposure plane during exposure. The exposure light path shown in fig. 6 firstly uses a PBS to split laser beams, two beams of light are respectively expanded and then combined by a second PBS, one beam of light passes through an SLM (spatial light modulator) before being combined, the SLM modulates the phase distribution of the one beam of light, and then a 4f system is used to image the SLM on an exposure plane, so that the interference light phase difference of the exposure plane is directly determined by the SLM, after the beam combination, the interference light passes through a quarter wave plate, the two beams of interference light are respectively converted into left-hand circular polarized light and right-hand circular polarized light, and therefore, the phase difference distribution generated by the SLM is converted into the polarization direction distribution of linear polarized light after interference, and finally recorded by a light orientation layer.
By loading the phase distribution of phi (r, theta 0) on the SLM, the invention can produce the desired PBOE, concatenate two such PBOE, and control the second PBOE to rotate by an angle theta, the total phase modulation experienced by the right-hand circular polarization incident on this combined element isThis constitutes a zoom Moir lens (focal length)) The compensating Moire lens is also composed of two identical PBOE, the first PBOE is controlled to synchronously rotate a theta angle, and the right-hand circular polarized light incident on the compensating Moire lens is subjected to phase modulation as followsThe focal length is the same as the size of the varifocal moire lens, and the signs are opposite.
Fig. 5 and 6 show an interference exposure method, a non-interference exposure method can also be used to prepare PVG and PBOE, such as a laser direct writing method, placing the exposed sample on a two-dimensional displacement table, exposing the sample point by controlling the displacement table, and generating the desired linear polarization direction by polarization control at each position exposure, thereby generating the designed molecular arrangement pattern on the photo-alignment layer.
In the preparation of PVG and PBOE, RM257 which is widely used and has good optical performance is selected as a reactive liquid crystal material. Whereas for chiral dopants, the present invention selects R5011 (HTP. Apprxeq.108/. Mu.m) with a large twisting power.
The specific preparation flow of PVG and PBOE is as follows:
(1) Cleaning a substrate;
(2) Preparing and spin-coating a photo-alignment layer solution;
(3) Drying the photo-alignment layer;
(4) Exposing;
(5) Preparing a liquid crystal mixture solution (chiral dopant is added in PVG preparation, and no chiral dopant is added in PBOE preparation);
(6) Spin-coating liquid crystal;
(7) Ultraviolet curing;
(8) Repeating steps 6 and 7 until a sufficient thickness of the liquid crystal layer is formed;
When the light guide plate provided with PVG is prepared, the light guide plate is directly used as a preparation substrate, the in-coupling PVG and the out-coupling PVG are sequentially exposed in different areas during exposure, and the same exposure light path is used for the two exposures, but after the in-coupling exposure is completed, the substrate is required to be rotated for 180 degrees and then the out-coupling exposure is performed, so that the symmetrical setting requirement of the two gratings is met.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
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| CN211979331U (en) * | 2020-03-05 | 2020-11-20 | 深圳奥比中光科技有限公司 | Near-to-eye display system and electronic equipment |
| CN113189783A (en) * | 2021-04-14 | 2021-07-30 | 深圳市麓邦技术有限公司 | Optical system and liquid crystal moire lens |
| CN115220235A (en) * | 2022-08-17 | 2022-10-21 | 谷东科技有限公司 | Binocular waveguide near-to-eye display device and augmented reality display equipment |
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| US11822079B2 (en) * | 2018-08-10 | 2023-11-21 | Apple Inc. | Waveguided display system with adjustable lenses |
| CN109212741B (en) * | 2018-10-31 | 2021-08-03 | 武汉邮电科学研究院有限公司 | Continuous zoom lens and optical system |
| CN111142255A (en) * | 2018-11-02 | 2020-05-12 | 成都理想境界科技有限公司 | AR optical display module and display device |
| US20200301239A1 (en) * | 2019-03-18 | 2020-09-24 | Microsoft Technology Licensing, Llc | Varifocal display with fixed-focus lens |
| CN113589528B (en) * | 2021-07-21 | 2022-11-01 | 浙江大学 | Two-dimensional pupil expanding method based on liquid crystal polarizer grating |
| US11768375B2 (en) * | 2021-09-03 | 2023-09-26 | Microsoft Technology Licensing, Llc | Control of variable-focus lenses in a mixed-reality device for presbyopes |
| CN114089531B (en) * | 2021-11-16 | 2022-08-09 | 浙江大学 | Binocular waveguide display method based on reflective polarization multiplexing liquid crystal lens |
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| CN211979331U (en) * | 2020-03-05 | 2020-11-20 | 深圳奥比中光科技有限公司 | Near-to-eye display system and electronic equipment |
| CN113189783A (en) * | 2021-04-14 | 2021-07-30 | 深圳市麓邦技术有限公司 | Optical system and liquid crystal moire lens |
| CN115220235A (en) * | 2022-08-17 | 2022-10-21 | 谷东科技有限公司 | Binocular waveguide near-to-eye display device and augmented reality display equipment |
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