Liquid crystal vector holographic generating element, preparation method and application

Abstract

The present invention relates to a liquid crystal vector holographic generating element, a preparation method, and applications thereof. The element comprises: a first substrate and a second substrate; a first alignment film formed on the first substrate near the second substrate; a second alignment film formed on the second substrate near the first substrate; a vector holographic phase control pattern disposed on the first and second alignment films; first and second spacer particles disposed between the first and second alignment films; and a liquid crystal layer disposed within the internal space formed by the first and second alignment films, the first and second alignment films, and the first and second spacer particles. The liquid crystal vector holographic element produced by the present invention can reconstruct arbitrary holographic patterns and vector distributions, is inexpensive to manufacture, and is easy to prepare. It can be widely used in fields such as multi-channel optical communications, optical information storage, and enhanced optical encryption.

Description

Technical Field

[0001] The present invention relates to the fields of liquid crystal photoelectric elements, vector light fields and holographic imaging technology, and in particular to a liquid crystal vector holographic generating element, a preparation method and an application thereof. Background Art

[0002] As a technology for controlling optical waveforms, holography has become a powerful tool for a variety of applications, from augmented reality (AR) and virtual reality (VR) to data storage and optical encryption. Vector holography can simultaneously manipulate the spatial vector distribution of light based on the manipulation of the light amplitude distribution. This gives vector holography a larger information capacity and the ability to transmit multi-dimensional information in parallel, and has great potential in multi-channel optical communications and enhanced optical encryption. Researchers have made some progress in vector holography, but this is basically achieved through metasurfaces composed of subwavelength structural units, which have complex manufacturing processes and relatively high manufacturing costs. The current vector holographic technology route has problems such as high preparation costs that need to be solved, which also makes the application and promotion of vector holographic technology very difficult. Therefore, in this technical field, there is a great need for an intelligent response vector optical platform that is easy to manufacture and low in cost.

[0003] Liquid crystals are soft materials with birefringent properties, inherently possessing the anisotropy of crystals and the fluidity of liquids. They have become a dominant force in the display market and have also found widespread application in various non-display applications. In particular, liquid crystal devices, with their advantages of photolithography-free manufacturing, tunability under external field stimulation, high efficiency, low cost, and wide bandwidth, have attracted widespread attention in optical waveform control. These characteristics of liquid crystals make the technical approach of vector holography based on liquid crystals a solution to the current challenges of complex manufacturing processes and high costs, thus possessing significant value and significance. However, to date, vector holography based on liquid crystals has remained unrealized due to various technical limitations. Summary of the Invention

[0004] The present invention aims to solve the problems of complex production process and high production cost of current vector holographic technology. It proposes a liquid crystal vector holographic generating element, preparation method and application. The prepared liquid crystal vector holographic element can realize the reconstruction of arbitrary holographic patterns and vector distributions. It has low production cost and is easy to prepare. It can be widely used in multi-channel optical communication, optical information storage and enhanced optical encryption and other fields.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A liquid crystal vector hologram generating element comprises: a first substrate and a second substrate; a first alignment film formed on the first substrate on a side close to the second substrate; a second alignment film formed on the second substrate on a side close to the first substrate; vector hologram phase control patterns are provided on the first alignment film and the second alignment film; first spacer particles and second spacer particles are provided between the first alignment film and the second alignment film; and a liquid crystal layer is provided in an internal space formed by the first alignment film, the second alignment film, the first spacer particles, and the second spacer particles.

[0007] To achieve the above object, the present invention further provides a method for preparing a liquid crystal vector holographic generating element, comprising:

[0008] Obtaining a first substrate and a second substrate, ultrasonically cleaning the first substrate and the second substrate with anhydrous ethanol and ultrapure water in sequence, drying the first substrate and the second substrate after ultrasonic cleaning, and performing ultraviolet ozone cleaning on the dried first substrate and the second substrate;

[0009] A photo-controlled alignment film is spin-coated on the first and second substrates after ozone cleaning, and then heated and cured to form a first and second alignment films on the cured first and second substrates, and a vector holographic phase control pattern is provided on the first and second alignment films;

[0010] Obtain first spacer particles and second spacer particles, shake and mix the first spacer particles and the second spacer particles with ultraviolet curing glue, apply them on both sides of the first orientation film after mixing evenly, encapsulate the applied first spacer particles and the second spacer particles based on the second orientation film, then cure the ultraviolet glue by ultraviolet light irradiation, and pour liquid crystal material into the internal space formed by the first orientation film, the second orientation film, the first spacer particles and the second spacer particles, and form a liquid crystal layer after cooling, thereby obtaining a liquid crystal vector holographic generating element.

[0011] To achieve the above-mentioned object, the present invention further provides an application method of a liquid crystal vector holographic generating element, comprising:

[0012] Acquire a liquid crystal vector hologram generating element, illuminate the liquid crystal vector hologram generating element based on linearly polarized light, and simultaneously acquire partially overlapping right-handed circularly polarized target images and left-handed circularly polarized target images, i.e., vector hologram images set by the liquid crystal vector hologram generating element;

[0013] The position of the rotary analyzer is set, the rotary analyzer is placed according to the position of the rotary analyzer, and the rotary analyzer is rotated by a preset angle to decrypt the vector holographic image to obtain a decrypted image.

[0014] Optionally, obtaining the phase distribution of the vector holographic phase control pattern includes:

[0015] Obtaining a randomly generated first phase distribution and a first standard amplitude distribution, performing a fast Fourier transform on the first phase distribution and the first standard amplitude distribution, and obtaining a first complex amplitude distribution in the far field;

[0016] Acquire a randomly generated second phase distribution and a second standard amplitude distribution, perform a fast Fourier transform on the second phase distribution and the second standard amplitude distribution, and acquire a second complex amplitude distribution in the far field;

[0017] Calculating the first complex amplitude distribution and the second complex amplitude distribution to obtain a first phase distribution of the first sub-control pattern and a second phase distribution of the second sub-control pattern, iterating the first phase distribution and the second phase distribution to obtain a third phase distribution of the first sub-control pattern and a fourth phase distribution of the second sub-control pattern;

[0018] The third phase distribution of the first sub-control pattern and the fourth phase distribution of the second sub-control pattern are spatially multiplexed to form a transformation, so as to obtain the phase distribution of the vector holographic phase control pattern.

[0019] Optionally, acquiring a first phase distribution of the first sub-control pattern and a second phase distribution of the second sub-control pattern includes:

[0020] Adding the first complex amplitude distribution and the second complex amplitude distribution to obtain a common phase term, setting a target phase distribution, and adding the common phase term and the target phase distribution to obtain a phase distribution of left-handed circularly polarized light and a phase distribution of right-handed circularly polarized light;

[0021] Inputting the designed first target amplitude distribution and second target amplitude distribution, calculating the phase distribution of the left-handed circularly polarized light, the phase distribution of the right-handed circularly polarized light, the first target amplitude distribution, and the second target amplitude distribution to obtain the first amplitude distribution and the second amplitude distribution;

[0022] Perform an inverse fast Fourier transform on the first amplitude distribution and the phase distribution of the left-handed circularly polarized light to obtain a first complex amplitude distribution, and take the phase angle to obtain a first phase distribution of the first sub-control pattern. Perform an inverse fast Fourier transform on the second amplitude distribution and the phase distribution of the right-handed circularly polarized light to obtain a second complex amplitude distribution, and take the phase angle to obtain a second phase distribution of the second sub-control pattern.

[0023] Optionally, acquiring the third phase distribution of the first sub-control pattern and the fourth phase distribution of the second sub-control pattern includes:

[0024] A fast Fourier transform is performed based on the first phase distribution and the standard amplitude distribution of the first sub-control pattern to obtain a third complex amplitude distribution. A fast Fourier transform is performed based on the second phase distribution and the standard amplitude distribution of the second sub-control pattern to obtain a fourth complex amplitude distribution. Multiple iterative calculations are performed based on the third complex amplitude distribution and the fourth complex amplitude distribution to obtain a third phase distribution of the first sub-control pattern and a fourth phase distribution of the second sub-control pattern.

[0025] Optionally, the method for obtaining the phase distribution of the vector holographic phase control pattern is:

[0026]

[0027] Wherein, x and y are the coordinates of a corresponding pixel in the vector holographic phase control pattern on a two-dimensional plane parallel to the first substrate and the second substrate, is the third phase distribution, is the fourth phase distribution, is the phase distribution of the vector holographic phase control pattern in the liquid crystal vector holographic generating element, m is the total number of pixels in the x direction, and n is the total number of pixels in the y direction.

[0028] Optionally, acquiring partially overlapping right-handed circularly polarized target images and left-handed circularly polarized target images includes:

[0029] Based on irradiating the liquid crystal vector holographic generating element with left-handed circularly polarized light and right-handed circularly polarized light in different polarization states, reconstructing a right-handed circularly polarized target image and a left-handed circularly polarized target image on a specific plane P in the far field, and based on the incidence of linearly polarized light, simultaneously acquiring partially overlapping right-handed circularly polarized target images and left-handed circularly polarized target images;

[0030] The specific plane P is an arbitrary plane in the far field, and the electric field vector distribution on the specific plane P in the far field is:

[0031]

[0032] in, is the phase distribution of the target amplitude image of right-handed circularly polarized light on a specific plane P in the far field, is the phase difference distribution between the first target amplitude image with left-handed circularly polarized light and the second target amplitude image with right-handed circularly polarized light on a specific plane P in the far field, E is the electric field vector distribution on the specific plane P in the far field, |L> represents the left-handed circular basis vector, |R> represents the right-handed circular basis vector, e is a natural constant, and i is an imaginary unit.

[0033] Optionally, the director misdistribution of some liquid crystal molecules belonging to the third phase distribution of the first sub-control pattern is:

[0034]

[0035] Among them, α L The third phase distribution of the first sub-control pattern is part of the liquid crystal molecules with misdirection distribution. A third phase distribution of the first sub-control pattern;

[0036] The distribution of the director misalignment of some liquid crystal molecules belonging to the fourth phase distribution of the second sub-control pattern is:

[0037]

[0038] Among them, α R is the misdirection distribution of some liquid crystal molecules belonging to the fourth phase distribution of the second sub-control pattern, is the fourth phase distribution of the second sub-control pattern.

[0039] The beneficial effects of the present invention are:

[0040] The liquid crystal vector holographic generating element provided by the present invention comprises a first substrate, a second substrate, a first alignment film, a second alignment film, a liquid crystal layer, and spacer particles; the first alignment film is arranged on a side of the first substrate close to the second substrate, and the second alignment film is arranged on a side of the second substrate close to the first substrate; the spacer particles are placed between the first alignment film and the second alignment film to support the liquid crystal layer; a vector holographic phase control pattern is arranged in the alignment film, and the molecules in the alignment film are controlled to follow the vector holographic phase control pattern, and the molecules in the alignment film induce the liquid crystal molecules to arrange according to the vector holographic phase control pattern; the vector holographic control pattern is provided by the vector holographic control pattern disclosed by the present invention. Information algorithm is used for generation; when left-handed circularly polarized light illuminates the liquid crystal vector holographic generating element, the set right-handed circularly polarized target image is reconstructed in the far field; when right-handed circularly polarized light illuminates the liquid crystal vector holographic generating element, the set left-handed circularly polarized target image is reconstructed in the far field; when linearly polarized light illuminates the liquid crystal vector holographic generating element, the two are simultaneously reconstructed and superimposed to generate the set vector holographic image; the set right-handed circularly polarized target image, left-handed circularly polarized target image and vector holographic image can all be customized to any design; by changing the polarization state of the incident light, polarization multiplexing can be achieved, and in combination with a polarizer, the encrypted information in the vector holographic image can be decrypted. The liquid crystal vector holographic generating element provided by the present invention can realize the reconstruction of any holographic pattern and vector distribution, has low production cost and is easy to prepare, and can be widely used in the fields of multi-channel optical communication, optical information storage, and enhanced optical encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is a schematic structural diagram of a liquid crystal vector holographic generating element according to an embodiment of the present invention;

[0043] Figure 2 This is a flow chart for preparing a liquid crystal vector holographic generating element according to an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the flow of the liquid crystal vector holographic iterative algorithm according to an embodiment of the present invention;

[0045] Figure 4 Schematic diagram of a vector holographic image according to an embodiment of the present invention;

[0046] Figure 5 A schematic diagram of liquid crystal misdirection distribution according to an embodiment of the present invention;

[0047] Figure 6 This is a microtexture image of a liquid crystal vector holographic generating element prepared in an embodiment of the present invention under a polarizing microscope;

[0048] Figure 7 A diagram of a device for generating vector holograms according to an embodiment of the present invention;

[0049] Figure 8 This is a vector holographic image captured experimentally when linearly polarized light is incident on an embodiment of the present invention;

[0050] Figure 9 A schematic diagram of a vector holographic image designed according to an embodiment of the present invention;

[0051] Figure 10 This is a microtexture image of a liquid crystal vector holographic generating element prepared in an embodiment of the present invention under a polarizing microscope;

[0052] Figure 11 A diagram of an experimental setup for polarization multiplexing and encryption according to an embodiment of the present invention;

[0053] Figure 12 Polarization multiplexing and encrypted vector holographic images taken for experiments according to an embodiment of the present invention;

[0054] Among them, 1-1, first substrate; 1-2, first orientation film; 1-3, first spacer particles; 1-4, liquid crystal layer; 1-5, second spacer particles; 1-6, second orientation film; 1-7, second substrate; 7-1, laser; 7-2, polarizer; 7-3, liquid crystal vector hologram generating element; 7-4, analyzer; 7-5, diffraction screen; 7-6, camera; 11-1, laser; 11-2, polarizer; 11-3, quarter-wave plate; 11-4, liquid crystal vector hologram generating element; 11-5, analyzer; 11-6, diffraction screen; 11-7, camera. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] Example 1: The present invention discloses a liquid crystal vector holographic generating element, comprising: a first substrate and a second substrate; a first alignment film formed on the first substrate on a side close to the second substrate; a second alignment film formed on the second substrate on a side close to the first substrate; vector holographic phase control patterns provided on the first and second alignment films; first and second spacer particles provided between the first and second alignment films; and a liquid crystal layer provided in an internal space formed by the first and second alignment films, the first and second alignment films, the first and second spacer particles, and the second alignment films. Specifically,

[0058] Prepare liquid crystal vector holographic generating element and generate vector holographic pattern, such as Figure 1 FIG. 1 is a schematic diagram showing the structure of the liquid crystal vector holographic generating element in this embodiment. Figure 1 A first alignment film 1-2 is formed on the side of the first substrate 1-1 closest to the second substrate 1-7, and a second alignment film 1-6 is formed on the side of the second substrate 1-7 closest to the first substrate 1-1. First and second spacer particles 1-3 and 1-5 are placed between the first and second alignment films 1-2 and 1-6, and a liquid crystal layer 1-4 is provided between the first and second spacer particles 1-3 and 1-5.

[0059] The present invention also discloses a method for preparing a liquid crystal vector holographic generating element, comprising: obtaining a first substrate and a second substrate, ultrasonically cleaning the first substrate and the second substrate with anhydrous ethanol and ultrapure water in sequence, drying the ultrasonically cleaned first and second substrates, and performing ultraviolet ozone cleaning on the dried first and second substrates; spin-coating a photo-controlled alignment film on the ozone-cleaned first and second substrates, and heat-curing the film to form a first alignment film and a second alignment film on the cured first and second substrates, and providing a vector holographic phase control pattern on the first and second alignment films; obtaining first and second spacer particles, mixing the first and second spacer particles with ultraviolet curing adhesive by oscillation, and applying the mixed adhesive to both sides of the first alignment film after uniform mixing, encapsulating the applied first and second spacer particles with the second alignment film, then curing the ultraviolet adhesive by ultraviolet light irradiation, and pouring a liquid crystal material into the internal space formed by the first and second alignment films, forming a liquid crystal layer after cooling, thereby obtaining a liquid crystal vector holographic generating element, specifically:

[0060] like Figure 2 As shown, the specific preparation process is as follows:

[0061] First, a first substrate and a second substrate are obtained, a first alignment film is formed on a side of the first substrate close to the second substrate, and a second alignment film is formed on a side of the second substrate close to the first substrate.

[0062] The first and second substrates may be rigid or flexible substrates with high transmittance and a relatively flat surface, specifically quartz glass with high transmittance and a relatively flat surface. The first and second alignment films may be photo-controlled alignment films, which may be made of azo materials, specifically SD1 material.

[0063] To improve the adhesion and wettability between the photo-controlled alignment film and the substrate, the following steps can be performed: Anhydrous ethanol and ultrapure water can be used to ultrasonically clean the substrates in sequence. Specifically, the first and second substrates are first immersed in anhydrous ethanol and ultrasonically cleaned for 20 minutes. After removal, the first and second substrates are ultrasonically cleaned in ultrapure water for 10 minutes. After removal, the first and second substrates are ultrasonically cleaned in ultrapure water for another 10 minutes. The first and second substrates are then removed and immediately placed in an oven set to 120 degrees Celsius for 40 minutes. After drying, the first and second substrates are removed and cleaned with UV ozone for 30 minutes.

[0064] The prepared substrates were then placed on a spin coater for spin coating. The spin coating parameters were as follows: the spin coating was performed in two steps. The first step was performed at a speed of 3000 rpm for 40 seconds. The second step was performed at a speed of 300 rpm for 10 seconds. After the photo-controlled alignment film made of the selected SD1 material was spin-coated on the first and second substrates, the first and second substrates were placed on a hot plate at 100 degrees Celsius to cure the photo-controlled alignment film for 12 minutes. After curing, a first alignment film was formed on the first substrate, and a second alignment film was formed on the second substrate.

[0065] First and second spacer particles are placed on either side of the first alignment film formed on the first substrate. Specifically, the spacer particles can be silicon or silicon dioxide spheres with a diameter of 1-15 μm. The spacer particles are placed by mixing the spacer particles with UV-curable adhesive by oscillation. After the mixture is evenly mixed, the spacer particles are applied to both sides of the first alignment film. The second substrate, with the side of the second alignment film facing the spacer particles, is then placed on the substrate for encapsulation. UV light is then applied to cure the UV-curable adhesive, placing the spacer particles between the two substrates.

[0066] When the liquid crystal material is in an isotropic state, the liquid crystal material is poured between the first alignment layer and the second alignment layer on the first substrate, and a liquid crystal layer is formed after cooling, specifically:

[0067] The liquid crystal material is heated to an isotropic state. The packaged liquid crystal substrate is then placed on a hot plate and heated until the substrate's temperature stabilizes at a temperature that maintains the liquid crystal's isotropic state. While the liquid crystal material is isotropic, it is drawn into a capillary glass tube and poured between the first alignment film on the first substrate and the second alignment film on the second substrate. Once the liquid crystal material has completely filled the gap between the first and second alignment films, the hot plate is turned off. After cooling to room temperature, a liquid crystal layer is formed. The molecules within the liquid crystal layer are arranged according to the generated vector holographic phase control pattern.

[0068] By exposing the alignment film, the molecules in the alignment film are arranged according to the set vector holographic phase control pattern.

[0069] The liquid crystal layer is composed of liquid crystal molecules with different orientations. The liquid crystal molecules in the liquid crystal layer are arranged parallel to the first substrate and the second substrate under the guidance of the first alignment film and the second alignment film.

[0070] The first orientation film and the second orientation film are provided with vector holographic phase control patterns arranged in the same plane. The vector holographic phase control patterns control the molecular pointing loss in the orientation films to be arranged according to the vector holographic phase control images. The molecular pointing loss in the orientation films induces the pointing loss of the liquid crystal molecules in a two-dimensional plane parallel to the first substrate and the second substrate to be distributed according to the designed vector holographic phase control patterns.

[0071] The vector holographic phase control pattern is pixelated and consists of many small pixel areas. The directions of the orientation film molecules are consistent within a single pixel area of ​​the vector holographic phase control pattern.

[0072] The present invention also discloses an application method of a liquid crystal vector hologram generating element, comprising: obtaining a liquid crystal vector hologram generating element, irradiating the liquid crystal vector hologram generating element with linearly polarized light, and simultaneously obtaining partially overlapping right-handed circularly polarized target images and left-handed circularly polarized target images, that is, vector holographic images set by the liquid crystal vector hologram generating element; setting a rotary analyzer position, placing a rotary analyzer according to the rotary analyzer position, rotating the rotary analyzer by a preset angle to decrypt the encrypted image, and obtaining a decrypted image.

[0073] Obtaining the phase distribution of the vector holographic phase control pattern includes: obtaining a randomly generated first phase distribution and a first standard amplitude distribution, performing fast Fourier transform on the first phase distribution and the first standard amplitude distribution, and obtaining a first complex amplitude distribution in the far field; obtaining a randomly generated second phase distribution and a second standard amplitude distribution, performing fast Fourier transform on the second phase distribution and the second standard amplitude distribution, and obtaining a second complex amplitude distribution in the far field; calculating the first complex amplitude distribution and the second complex amplitude distribution to obtain a first phase distribution of a first sub-control pattern and a second phase distribution of a second sub-control pattern, iterating the first phase distribution and the second phase distribution to obtain a third phase distribution of the first sub-control pattern and a fourth phase distribution of the second sub-control pattern; performing spatial multiplexing transformation on the third phase distribution of the first sub-control pattern and the fourth phase distribution of the second sub-control pattern to obtain the phase distribution of the vector holographic phase control pattern.

[0074] Obtaining the first phase distribution of the first sub-control pattern and the second phase distribution of the second sub-control pattern includes: adding the first complex amplitude distribution and the second complex amplitude distribution to obtain a common phase item, setting a target phase distribution, adding the common phase item and the target phase distribution to obtain the phase distribution of left-handed circularly polarized light and the phase distribution of right-handed circularly polarized light; inputting the designed first target amplitude distribution and second target amplitude distribution, calculating the phase distribution of the left-handed circularly polarized light, the phase distribution of the right-handed circularly polarized light, the first target amplitude distribution and the second target amplitude distribution to obtain the first amplitude distribution and the second amplitude distribution; performing an inverse fast Fourier transform on the first amplitude distribution and the phase distribution of the left-handed circularly polarized light to obtain a first complex amplitude distribution, and taking an amplitude angle to obtain the first phase distribution of the first sub-control pattern, performing an inverse fast Fourier transform on the second amplitude distribution and the phase distribution of the right-handed circularly polarized light to obtain a second complex amplitude distribution, and taking an amplitude angle to obtain the second phase distribution of the second sub-control pattern.

[0075] Obtaining the third phase distribution of the first sub-control graph and the fourth phase distribution of the second sub-control graph includes: performing a fast Fourier transform based on the first phase distribution of the first sub-control graph and the standard amplitude distribution to obtain a third complex amplitude distribution, performing a fast Fourier transform based on the second phase distribution of the second sub-control graph and the standard amplitude distribution to obtain a fourth complex amplitude distribution, and performing multiple iterative calculations based on the third complex amplitude distribution and the fourth complex amplitude distribution to obtain the third phase distribution of the first sub-control graph and the fourth phase distribution of the second sub-control graph.

[0076] like Figure 3 As shown, the phase distribution of the vector holographic phase control pattern Generated by the liquid crystal vector holographic algorithm disclosed in the present invention, the specific algorithm steps are as follows:

[0077] Unlike the classic Gerchberg–Saxton (GS) algorithm widely used in pure phase holography, this paper proposes a dual-loop iterative modified Gerchberg–Saxton algorithm for spiral multiplexed LC vector holography. The basic principle is to perform two synchronized and separate loops on the target holographic images corresponding to the LCP and RCP, similar to the traditional loops of the GS algorithm. Specifically, the present invention establishes a link between the two phase holograms through several intermediate steps.

[0078] First, input an arbitrary phase distribution and the standard amplitude distribution |E g The complex amplitude distribution E in the far field is calculated using the fast Fourier transform (FFT). L1 . The same input with an arbitrary phase distribution and the standard amplitude distribution |E g The complex amplitude distribution E in the far field is calculated using the fast Fourier transform (FFT). R1 The far field here refers to the Fraunhofer diffraction region;

[0079] The standard amplitude distribution is selected based on the amplitude distribution of the light beam used in the actual experiment. The embodiment of the present invention uses laser Gaussian light, so the embodiment adopts the Gaussian distribution. The arbitrary phase distribution input here is a randomly set phase distribution required to start the algorithm in the embodiment of the present invention and does not correspond to any actual experimental meaning. L1 Corresponding to the complex amplitude distribution of left-handed LCP, E R1 Corresponding to the complex amplitude distribution of right-handed light RCP.

[0080] The standard amplitude distribution selected in the embodiment of the present invention is Gaussian distribution. Then, E L1 and E R1 Add and take the phase to get the common phase term The common phase term The target phase distribution of the present invention is respectively and Add together to get and Obtain the phase distribution of left-handed light LCP and right-handed light RCP respectively and Amplitude distribution |E L1 | and |E R1 | and target amplitude distribution |E A | and |E B | is used to calculate the new amplitude distribution |E L |=|E A |+Rand(k)*(|E A |-||E L1 | / max(||E L1 |)) and |E R |=|E B |+Rand(k)*(|E B |-|E R1 | / max(|E R1 |)). Wherein Rand(k) is a random number. Wherein the target amplitude distribution |E A | and |E B | is the phase distribution of the first sub-control pattern and the phase distribution of the second sub-control pattern The corresponding far-field designed amplitude distribution is target amplitude image A and target amplitude image B. Figure 4As shown, the spacer A selected in Example 1 of the present invention is the letter "NATURE", and the target amplitude image B selected in Example 1 of the present invention is also the letter "NATURE". The two overlap in space and have the same relative amplitude. In the area where the overlapping letter is "NA", In the area where the letters "TURE" overlap

[0081] Input the amplitude distribution |E calculated by the above process L | and phase distribution And perform inverse fast Fourier transform (IFFT) to obtain the complex amplitude distribution E RL , and take the phase angle to get the phase distribution of the first sub-control pattern Input the amplitude distribution |E calculated by the above process R | and phase distribution And perform inverse fast Fourier transform (IFFT) to obtain the complex amplitude distribution E in the near field LR , and take the phase angle to get the phase distribution of the second sub-control pattern Then, using the phase distribution The complex amplitude distribution E in the far field of the new iteration is calculated by using the fast Fourier transform (FFT) and the standard amplitude distribution |Eg| L1 Using phase distribution The complex amplitude distribution E in the far field of the new iteration is calculated by using the fast Fourier transform (FFT) and the standard amplitude distribution |Eg| R1 .

[0082] After multiple iterations, the phase distribution of the final first sub-control pattern for reconstructing the target amplitude image A and the target amplitude image B is obtained. and the phase distribution of the second sub-control pattern Here, the number of iterations can be selected to be greater than or equal to 300 times, and the phase distribution of the vector holographic phase control pattern The phase distribution of the first sub-control pattern and the phase distribution of the second sub-control pattern Spatial multiplexing is formed.

[0083] Phase distribution of vector holographic phase control patterns The phase distribution of the first sub-control pattern and the phase distribution of the second sub-control pattern Spatial multiplexing is formed. Spatial multiplexing methods include but are not limited to:

[0084]

[0085]

[0086]

[0087] Where x and y represent the coordinates of a corresponding pixel in the vector holographic phase control pattern on the two-dimensional plane parallel to the first substrate and the second substrate. Figure 3 The multiplexing mode selected in the embodiment 1 of the present invention is as follows:

[0088]

[0089] Wherein, x and y are the coordinates of a corresponding pixel in the vector holographic phase control pattern on the two-dimensional plane parallel to the first substrate and the second substrate, is the phase distribution of the first sub-control pattern, is the phase distribution of the second sub-control pattern, is the phase distribution of the vector holographic phase control pattern in the liquid crystal vector holographic generating element, m is the total number of pixels in the x direction, and n is the total number of pixels in the y direction.

[0090] The liquid crystal material of the liquid crystal layers 1-4 can be any one of nematic liquid crystal, twisted nematic liquid crystal, dual-band liquid crystal, smectic liquid crystal and ferroelectric nematic liquid crystal, and the selected liquid crystal material is nematic liquid crystal.

[0091] Under the induction of the molecular pointing misdistribution of the alignment film, the molecular pointing misdistribution of the liquid crystal is consistent within a single pixel area of ​​the vector holographic phase control pattern.

[0092] The vector holographic phase control pattern controls the two-dimensional misorientation of the liquid crystal molecules in the liquid crystal layer to be α, wherein the misorientation of the liquid crystal molecules in the pixel area of ​​the first sub-control pattern is induced to be α L , wherein the liquid crystal molecule director misdistribution in the pixel area belonging to the second sub-control pattern is induced to be α R .

[0093] The distribution of the director mismatch of some liquid crystal molecules in the pixel area belonging to the first sub-control pattern is α L satisfy:

[0094]

[0095] Among them, α L The third phase distribution of the first sub-control pattern is part of the liquid crystal molecules with misdirection distribution. A third phase distribution of the first sub-control pattern;

[0096] The distribution of the misdirection of some liquid crystal molecules in the pixel area belonging to the second sub-control pattern is α R satisfy:

[0097]

[0098] Among them, α R is the misdirection distribution of some liquid crystal molecules belonging to the fourth phase distribution of the second sub-control pattern, is the fourth phase distribution of the second sub-control pattern.

[0099] Liquid crystal director distribution Figure 5 As shown, since the liquid crystal molecules of the nematic liquid crystal material are symmetrical head to tail, the orientation angle range of the director is 0-pi.

[0100] Figure 6 This is the microtexture image of the prepared liquid crystal vector holographic generating element under a polarizing microscope.

[0101] Figure 7 The diagram of the device for vector holography produced by the present invention includes a laser 7-1, a polarizer 7-2, a liquid crystal vector holography generating element 7-3, an analyzer 7-4, a diffraction screen 7-5, and a camera 7-6. The laser can be a semiconductor laser, a helium-neon laser, or a supercontinuum laser. The laser used in Example 1 is a semiconductor laser with a wavelength of 632.8 nm. Specifically, the polarizer can be a Glan Taylor crystal polarizing prism, which can output high extinction ratio linear polarized light with an extinction ratio of 100,000:1. Specifically, the analyzer can be a nanoparticle thin film linear polarizer with an extinction ratio of 100,000:1. Specifically, the diffraction screen can be a black diffraction screen, which can better capture the holographic image.

[0102] When linearly polarized light is incident on the liquid crystal vector holographic generating element in Example 1, the target amplitude image A and the target amplitude image B will be reconstructed simultaneously in the far field. The polarization state of the target amplitude image A is left-handed circularly polarized light, and the polarization state of the target amplitude image B is right-handed circularly polarized light. The phase difference distribution between the two on a specific plane P in the far field is θ in The polarization angle of the incident linearly polarized light. is the designed phase difference distribution.

[0103] When linearly polarized light is incident on the liquid crystal vector holographic generating element designed in Example 1, the electric field vector distribution E on a specific plane P in the far field is:

[0104]

[0105] in, is the phase distribution of the target amplitude image of right-handed circularly polarized light on a specific plane P in the far field, is the phase difference distribution of the first target amplitude image with left-handed circular polarization and the second target amplitude image with right-handed circular polarization on a specific plane P in the far field, E is the electric field vector distribution on the specific plane P in the far field, |L> represents the left-handed circular basis vector, |R> represents the right-handed circular basis vector, e is a natural constant, i is an imaginary unit, and it is expressed as Jones vector:

[0106] The specific plane P is an arbitrary plane in the far field.

[0107] Since the target amplitude image A selected in Example 1 of the present invention is the letters "NATURE", the target amplitude image B selected in Example 1 of the present invention is also the letters "NATURE", and the two overlap in space and have the same relative amplitude.

[0108] When the incident light is linearly polarized light with a polarization direction angle of 0°, the area with the overlapping letters "NA" A R =A L , the polarization state is linearly polarized light with a polarization angle of 16°.

[0109] When the incident light is linearly polarized light with a polarization angle of 0°, the area where the overlapping letters are “TURE” A R =A L , the polarization state is linearly polarized light with a polarization angle of -74°.

[0110] When the polarization direction of the analyzer is perpendicular to the direction of linearly polarized light, the transmitted linearly polarized light will be extinct.

[0111] like Figure 8 As shown, the liquid crystal vector holographic generating element prepared in this embodiment 1 reconstructs a vector holographic image "NATURE" under the incidence of linearly polarized light. Specifically, the transmission axis angle of the polarizer here is 0°, and the letters "TURE" and "NA" can be seen to be extinct by rotating the analyzer to 16° and 74°, which indicates that the polarization states of "NA" and "TURE" in the vector holographic image are linearly polarized light with polarization angles of 16° and -74°, respectively.

[0112] Example 2: Polarization multiplexing and encryption application based on liquid crystal vector holographic generating elements.

[0113] The liquid crystal vector hologram generating element of Example 2 was prepared according to the liquid crystal vector hologram preparation method disclosed in the present invention.

[0114] Phase distribution of the vector holographic phase control pattern in the liquid crystal vector holographic generating element in Example 2 The phase distribution of the first sub-control pattern and the phase distribution of the second sub-control pattern Spatial multiplexing is formed. Spatial multiplexing methods include but are not limited to: and Where x and y represent the coordinates of a corresponding pixel in the vector holographic phase control pattern on the two-dimensional plane parallel to the first substrate and the second substrate. The multiplexing method selected by the present invention is:

[0115] The vector holographic phase control pattern of the liquid crystal vector holographic generating element in Example 2 controls the two-dimensional misalignment distribution of the liquid crystal molecules in the liquid crystal layer to be α, wherein the misalignment distribution of the liquid crystal molecules in the pixel area belonging to the first sub-control pattern is induced to be α L , wherein the liquid crystal molecule director misdistribution in the pixel area belonging to the second sub-control pattern is induced to be α R .

[0116] The part of the liquid crystal molecules in the pixel area belonging to the first sub-control pattern has a misdirection distribution α L satisfy:

[0117]

[0118] The part of the liquid crystal molecules in the pixel area belonging to the first sub-control pattern has a misdirection distribution α R satisfy:

[0119]

[0120] The directivity distribution of the liquid crystal molecules of the liquid crystal vector holographic element of the second embodiment determines the phase distribution of the modulated output light field. The specific directivity distribution is α L The liquid crystal molecules in the first sub-control area convert the incident right circularly polarized light into left circularly polarized light and carry the phase And reconstruct the target amplitude image A in the far field; the specific pointing error distribution is α R The liquid crystal molecules in the second sub-control area convert the incident left-handed circularly polarized light into outgoing right-handed circularly polarized light and carry the phase And reconstruct the target amplitude image B in the far field. Specifically, the incident linearly polarized light is converted into a phase-carrying Left-handed circularly polarized light and carrying phase The target amplitude image A and target amplitude image B will be reconstructed simultaneously in the far field by using right-handed circularly polarized light. By selecting different polarization states for the incident light, different holographic images can be generated, thereby achieving polarization multiplexing.

[0121] When linearly polarized light is incident on the liquid crystal vector holographic generating element in this embodiment 2, the target amplitude image A and the target amplitude image B will be reconstructed simultaneously in the far field. The polarization state of the target amplitude image A is left-handed circularly polarized light, and the polarization state of the target amplitude image B is right-handed circularly polarized light. The phase difference distribution between the two on a specific plane P in the far field is θ in The polarization angle of the incident linearly polarized light. is the designed phase difference distribution.

[0122] When linearly polarized light is incident on the liquid crystal vector hologram generating element in this embodiment 2, the electric field vector distribution E on a specific plane P in the far field is:

[0123]

[0124] The phase distribution of the target amplitude image B with the polarization state of right circularly polarized light on a specific plane P in the far field. The specific plane P is an arbitrary plane in the far field.

[0125] like Figure 9 The figure shows a schematic diagram of the vector holographic image designed in Example 2. Specifically, the target amplitude image A selected in Example 2 is the "hour hand", and the target amplitude image B selected in Example 2 is the "minute hand". The relative amplitudes of the areas where the two overlap in space are the same. In the overlapping part, the area with the number "3" is The area with the number "5" in the overlapping part

[0126] When the incident light is linearly polarized light with a polarization angle of 0°, the area with the overlapping number "3" is A R =A L , the polarization state is linearly polarized light with a polarization angle of 45°.

[0127] When the incident light is linearly polarized light with a polarization direction angle of 0°, the area with the overlapping number "5" is A R =A L , the polarization state is linearly polarized light with a polarization angle of -45°.

[0128] When the polarization direction of the analyzer is perpendicular to the direction of the linearly polarized light, the transmitted linearly polarized light will be extinguished, so that the vector encrypted information in the vector holographic image can be decrypted by the analyzer.

[0129] Figure 10This is a microtexture image of the liquid crystal vector hologram generating element of Example 2 prepared according to the liquid crystal vector hologram preparation method disclosed in the present invention, taken under a polarizing microscope;

[0130] Figure 11 This is a diagram of a device for vector holography constructed according to the present invention. The device includes a laser 11-1, a polarizer 11-2, a quarter-wave plate 11-3, a liquid crystal vector holography generating element 11-4, an analyzer 11-5, a diffraction screen 11-6, and a camera 11-7. The laser can be a semiconductor laser, a helium-neon laser, or a supercontinuum laser. The laser used in Example 1 is a semiconductor laser with a wavelength of 632.8 nm. Specifically, the polarizer can be a Glan Taylor crystal polarizing prism, which can output high extinction ratio linear polarized light with an extinction ratio of 100,000:1. Specifically, the analyzer can be a nanoparticle thin film linear polarizer with an extinction ratio of 100,000:1. Specifically, the diffraction screen can be a black diffraction screen to better capture the holographic image. Specifically, the quarter-wave plate can be a quartz true zero-order quarter-wave plate, which is used to switch the polarization state of the incident light.

[0131] like Figure 12 The figure shows the polarization multiplexing and encrypted vector holographic image captured experimentally in Example 2. Specifically, the angle of the polarizer transmission axis is set to 0°, and the angle between the fast axis of the quarter wave plate and the transmission axis of the polarizer is rotated to -45° to generate right-handed circularly polarized light incident, and reconstruct the left-handed circularly polarized holographic image "hour hand". Specifically, the angle of the polarizer transmission axis is set to 0°, and the angle between the fast axis of the quarter wave plate and the transmission axis of the polarizer is rotated to 45° to generate left-handed circularly polarized light incident, and reconstruct the right-handed circularly polarized holographic image "minute hand". Specifically, the angle of the polarizer transmission axis is set to 0°, and the angle between the fast axis of the quarter wave plate and the transmission axis of the polarizer is rotated to 0° to generate linearly polarized light incident with a polarization direction of 0°, and simultaneously reconstruct the circularly polarized holographic image "hour hand" and the right-handed circularly polarized holographic image "minute hand", thereby realizing polarization multiplexing.

[0132] Specifically, when linearly polarized light with a polarization direction of 0° is incident, by rotating the polarizer to -45° and 45°, the letters "3" and "5" can be seen to be extinct, and the second information "35" can be decrypted, realizing the encryption and decryption of vector information.

[0133] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. An application method of a liquid crystal vector holographic generating element, characterized in that: include: Get the liquid crystal vector holographic generating element: Obtaining a first substrate and a second substrate, ultrasonically cleaning the first substrate and the second substrate with anhydrous ethanol and ultrapure water in sequence, drying the first substrate and the second substrate after ultrasonic cleaning, and performing ultraviolet ozone cleaning on the dried first substrate and the second substrate; A photo-controlled alignment film is spin-coated on the first and second substrates after ozone cleaning, and then heated and cured to form a first and second alignment films on the cured first and second substrates, and a vector holographic phase control pattern is provided on the first and second alignment films; Acquiring the phase distribution of the vector holographic phase control pattern includes: Obtaining a randomly generated first phase distribution and a first standard amplitude distribution, performing a fast Fourier transform on the first phase distribution and the first standard amplitude distribution, and obtaining a first complex amplitude distribution in the far field; Acquire a randomly generated second phase distribution and a second standard amplitude distribution, perform a fast Fourier transform on the second phase distribution and the second standard amplitude distribution, and acquire a second complex amplitude distribution in the far field; Calculating the first complex amplitude distribution and the second complex amplitude distribution to obtain a first phase distribution of the first sub-control pattern and a second phase distribution of the second sub-control pattern, iterating the first phase distribution and the second phase distribution to obtain a third phase distribution of the first sub-control pattern and a fourth phase distribution of the second sub-control pattern; performing spatial multiplexing transformation on the third phase distribution of the first sub-control pattern and the fourth phase distribution of the second sub-control pattern to obtain the phase distribution of the vector holographic phase control pattern; Obtaining first spacer particles and second spacer particles, mixing the first spacer particles and the second spacer particles with ultraviolet curing adhesive by oscillation, and applying the mixed particles to both sides of a first alignment film after uniformity, encapsulating the applied first spacer particles and the second spacer particles based on the second alignment film, then curing the ultraviolet adhesive by ultraviolet light irradiation, and pouring liquid crystal material into the internal space formed by the first alignment film, the second alignment film, the first spacer particles, and the second spacer particles, and forming a liquid crystal layer after cooling, thereby obtaining the liquid crystal vector hologram generating element; Irradiating the liquid crystal vector hologram generating element with linearly polarized light, and simultaneously acquiring partially overlapping right-handed circularly polarized target images and left-handed circularly polarized target images, i.e., vector hologram images set by the liquid crystal vector hologram generating element; The position of the rotary analyzer is set, the rotary analyzer is placed according to the position of the rotary analyzer, and the rotary analyzer is rotated by a preset angle to decrypt the vector holographic image to obtain a decrypted image.

2. The application method according to claim 1, characterized in that: Acquiring a first phase distribution of the first sub-control pattern and a second phase distribution of the second sub-control pattern includes: Adding the first complex amplitude distribution and the second complex amplitude distribution to obtain a common phase term, setting a target phase distribution, and adding the common phase term and the target phase distribution to obtain a phase distribution of left-handed circularly polarized light and a phase distribution of right-handed circularly polarized light; Inputting the designed first target amplitude distribution and second target amplitude distribution, calculating the phase distribution of the left-handed circularly polarized light, the phase distribution of the right-handed circularly polarized light, the first target amplitude distribution, and the second target amplitude distribution to obtain the first amplitude distribution and the second amplitude distribution; Perform an inverse fast Fourier transform on the first amplitude distribution and the phase distribution of the left-handed circularly polarized light to obtain a first complex amplitude distribution, and take the phase angle to obtain a first phase distribution of the first sub-control pattern. Perform an inverse fast Fourier transform on the second amplitude distribution and the phase distribution of the right-handed circularly polarized light to obtain a second complex amplitude distribution, and take the phase angle to obtain a second phase distribution of the second sub-control pattern.

3. The application method according to claim 2, characterized in that: Acquiring a third phase distribution of the first sub-control pattern and a fourth phase distribution of the second sub-control pattern includes: A fast Fourier transform is performed based on the first phase distribution and the standard amplitude distribution of the first sub-control pattern to obtain a third complex amplitude distribution. A fast Fourier transform is performed based on the second phase distribution and the standard amplitude distribution of the second sub-control pattern to obtain a fourth complex amplitude distribution. Multiple iterative calculations are performed based on the third complex amplitude distribution and the fourth complex amplitude distribution to obtain a third phase distribution of the first sub-control pattern and a fourth phase distribution of the second sub-control pattern.

4. The application method according to claim 1, characterized in that: The method for obtaining the phase distribution of the vector holographic phase control pattern is: Wherein, x and y are the coordinates of a corresponding pixel in the vector holographic phase control pattern on a two-dimensional plane parallel to the first substrate and the second substrate, is the third phase distribution, is the fourth phase distribution, is the phase distribution of the vector holographic phase control pattern in the liquid crystal vector holographic generating element, m is the total number of pixels in the x direction, and n is the total number of pixels in the y direction.

5. The application method according to claim 1, characterized in that: Acquiring partially overlapping right-handed circularly polarized target images and left-handed circularly polarized target images includes: Based on irradiating the liquid crystal vector holographic generating element with left-handed circularly polarized light and right-handed circularly polarized light in different polarization states, reconstructing a right-handed circularly polarized target image and a left-handed circularly polarized target image on a specific plane P in the far field, and based on the incidence of linearly polarized light, simultaneously acquiring partially overlapping right-handed circularly polarized target images and left-handed circularly polarized target images; The specific plane P is an arbitrary plane in the far field, and the electric field vector distribution on the specific plane P in the far field is: in, is the phase distribution of the target amplitude image of right-handed circularly polarized light on a specific plane P in the far field, is the phase difference distribution between the first target amplitude image with left-handed circularly polarized light and the second target amplitude image with right-handed circularly polarized light on a specific plane P in the far field, E is the electric field vector distribution on the specific plane P in the far field, |L> represents the left-handed circular basis vector, |R> represents the right-handed circular basis vector, e is a natural constant, and i is an imaginary unit.

6. The application method according to claim 1, characterized in that: The distribution of the director misalignment of some liquid crystal molecules belonging to the third phase distribution of the first sub-control pattern is: Among them, α L The third phase distribution of the first sub-control pattern is part of the liquid crystal molecules with misdirection distribution. A third phase distribution of the first sub-control pattern; The distribution of the director misalignment of some liquid crystal molecules belonging to the fourth phase distribution of the second sub-control pattern is: Among them, α R is the misdirection distribution of some liquid crystal molecules belonging to the fourth phase distribution of the second sub-control pattern, is the fourth phase distribution of the second sub-control pattern.

7. The application method according to claim 1, characterized in that: The liquid crystal vector hologram generating element includes: a first substrate and a second substrate, a first orientation film is formed on the first substrate and on a side close to the second substrate, a second orientation film is formed on the second substrate and on a side close to the first substrate, vector holographic phase control patterns are arranged on the first orientation film and the second orientation film, first spacer particles and second spacer particles are arranged between the first orientation film and the second orientation film, and a liquid crystal layer is arranged in the internal space formed by the first orientation film, the second orientation film, the first spacer particles and the second spacer particles.

Images