An apparatus for generating annular structured light and a method of manufacturing the same

Abstract

The application discloses a device for generating annular structured light and a preparation method thereof, and the device comprises a helium-neon laser, a polarizer, a liquid crystal cell, an LED ultraviolet light source and a CCD which are sequentially arranged; the liquid crystal cell comprises two layers of substrates which are coated with orientation films, spacer particles and a liquid crystal layer, the spacer particles are arranged between the two layers of the orientation films of the substrates which are opposite to each other, and a filling space is formed for injecting the liquid crystal layer; the method for generating the annular structured light comprises three parts of preparation of a reconfigurable liquid crystal superstructure system, light path building and annular structured light acquisition. The application realizes the generation of the annular structured light by using the liquid crystal material, and the method for generating the amplitude type structured light by using the reconfigurable liquid crystal superstructure system has the advantages of simplicity, quickness, flexibility, reliability, low cost, reconfigurability and integration.

Description

TECHNICAL FIELD

[0001] The present application relates to a device for generating structured light and a preparation method thereof, in particular to a device for generating annular structured light and a preparation method thereof. BACKGROUND

[0002] Structured light has been widely studied in the field of optics. Different structured light fields can be generated by adjusting the phase, amplitude or polarization of Gaussian beams. Structured light fields have great potential in the fields of optical imaging, optical communication, optical computing, microscopic detection, material processing and microparticle manipulation due to their unique optical properties.

[0003] Currently, the general method for generating structured light is to use a combination of lenses, wave plates, super-structured surfaces and other optical devices. However, the structures of these optical components are fixed and cannot be adjusted. Moreover, the method for generating structured light relies on a complex and large optical system, making it difficult to generate specific structured light. SUMMARY

[0004] The present application aims to provide a device for generating annular structured light, which uses a reconfigurable chiral liquid crystal super-structure system to generate amplitude-type structured light to achieve the acquisition of annular structured light. Another object of the present application is to provide a preparation method for generating annular structured light using the device.

[0005] The device for generating annular structured light comprises a helium-neon laser, a polarizer, a liquid crystal cell, an LED ultraviolet light source and a CCD arranged in sequence. The liquid crystal cell comprises two layers of substrates coated with an orientation film, spacer particles and a liquid crystal layer. The spacer particles are placed between the two layers of orientation films on the opposite substrates to form a filling space for injecting the liquid crystal layer.

[0006] Preferably, the device further comprises a 1 / 4 wave plate arranged between the polarizer and the liquid crystal cell.

[0007] Preferably, one of the two layers of substrates has liquid crystal molecules on the surface of the orientation film side arranged in a periodic pattern, with the director of the molecules gradually changing from 0° to 180° in a unit period, and the distribution of the director of the molecules satisfying wherein α(x) represents the molecular orientation at different positions on the x-axis, and A is the period; the other of the two layers of substrates has liquid crystal molecules on the surface of the orientation film side arranged perpendicular to the substrate.

[0008] Preferably, the material of the orientation film is selected from one of a surfactant, a rubbing orientation agent, a photo-crosslinking material, a photo-degradation material or a photo-induced cis-trans isomerization material.

[0009] Preferably, the material of the two layers of orientation films is respectively azo photo-controlled orientation material 4,4'-bis(4-hydroxy-3-carboxy-azophenyl) benzidine-2,2'-disulfonic acid sodium (biphenylamine) and N,N-dimethyl-N-[3-(trimethoxysilane) propyl] octadecyl ammonium chloride (DMOAP).

[0010] Preferably, the spacer particles are spherical microparticles.

[0011] Preferably, the orientation film comprises a first orientation film and a second orientation film.

[0012] The preparation method of the first orientation film is as follows:

[0013] The orientation film material is uniformly spin-coated on a substrate, annealed, and then the orientation film is subjected to orientation treatment, so that the molecules in the orientation film are arranged along a direction perpendicular to the direction of linearly polarized light by controlling the polarization direction when the linearly polarized light is exposed to the molecules in the orientation film.

[0014] The preparation method of the second orientation film is as follows:

[0015] The second substrate is soaked in an orientation agent solution, rinsed, and annealed to form a second orientation film on the second substrate which has a vertical orientation effect on liquid crystal molecules.

[0016] Preferably, the power of the helium-neon laser is 0.3-0.5 mw, and the power of the LED ultraviolet light source is 50-100 muw.

[0017] The method for generating a ring-shaped structured light using the device is as follows: the helium-neon laser and the LED ultraviolet light source are turned on at the same time, the helium-neon laser and the LED ultraviolet light are simultaneously irradiated on the liquid crystal cell, and a ring-shaped structured light pattern is obtained by CCD shooting.

[0018] Under the joint action of the two side orientation films, the molecules of the liquid crystal layer will self-assemble to form a multi-level helical superstructure with broken symmetry. The helical superstructure is formed by helical arrangement of liquid crystal molecules in a direction perpendicular to the substrate, and near the vertical orientation film, the helical column is deformed to form a periodic modulated microstructure in a direction parallel to the substrate, the periodic direction is inconsistent, and the helical period and the deformation period are often not equal, which has optical properties that ordinary cholesteric liquid crystals do not have. At the same time, the pitch of the liquid crystal molecules in the liquid crystal layer of the application tends to positive infinity from several microns under the irradiation of the 365 nm ultraviolet light source.

[0019] Beneficial effects: compared with the prior art, the present application has the following remarkable advantages: the present application realizes the generation of structured light by using liquid crystal materials, and the method for generating amplitude-type structured light by using a reconfigurable liquid crystal superstructure system has the advantages of simplicity, quickness, flexibility, reliability, low cost, reconfigurability and integration. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A liquid crystal cell structure diagram prepared by the present application;

[0021] Figure 2 A liquid crystal molecule director overhead view near the first alignment film of the present application;

[0022] Figure 3 A liquid crystal molecule director front view near the second alignment film of the present application;

[0023] Figure 4 A device diagram built by the present application;

[0024] Figure 5 A texture diagram of the liquid crystal sample under the polarizing microscope before light of the present application;

[0025] Figure 6 A light spot diagram generated by the present application, the right ring-shaped light spot is a ring-shaped structured light;

[0026] Figure 7 A texture diagram of the liquid crystal sample under the polarizing microscope after light of the present application;

[0027] Figure 8 A method flow diagram for generating ring-shaped structured light provided by the present application. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be further described below in combination with the drawings and examples.

[0029] Figure 4 A device diagram built by the present application, the device includes a helium-neon laser 1, a polarizer 2, a 1 / 4 wave plate 6 (632.8 nanometers), a liquid crystal cell 3, an LED ultraviolet light source 4 and a CCD 5 arranged in sequence. The power of the helium-neon laser 1 is 0.3mw-0.5mw, the wavelength of the LED ultraviolet light source 4 is 365 nanometers, and the power is 50-100 microwatts.

[0030] The liquid crystal cell 3 includes two layers of substrates coated with an alignment film, spacer particles and a liquid crystal layer. The spacer particles are placed between the two layers of alignment films on the opposite substrates to form a filling space for injecting the liquid crystal layer. The structure diagram of the liquid crystal cell 3 is shown in Figure 1 The preparation method of the liquid crystal cell is as follows:

[0031] A first alignment film is formed on the side of the first substrate close to the second substrate, and a second alignment film is formed on the side of the second substrate close to the first substrate.

[0032] In order to make the alignment film and the substrate have strong adhesion and infiltration, the substrate is ultrasonically cleaned by using an ITO cleaning solution, and the cleaning time is 30 minutes. Then the substrate is ultrasonically cleaned twice with ultrapure water, and each cleaning time is 10 minutes. The cleaned substrate is placed in an oven, the oven temperature is adjusted to 120 DEG C, and the drying time is 40 minutes. Finally, the substrate is subjected to UVO (ultraviolet ozone cleaning) for 30 minutes.

[0033] The preparation method of the first alignment film and the second alignment film is as follows:

[0034] The first alignment film is prepared as follows: an azo photoalignment material SD1 is uniformly spin-coated on the side of the first substrate close to the second substrate, and the spin-coating mode is as follows: first, a low speed of 800 rpm is set, and the substrate is spin-coated at this speed for 5 seconds, and then a high speed of 3000 rpm is set, and the substrate is spin-coated at this speed for 40 seconds; after spin-coating the alignment agent, the first substrate on which the photoalignment agent SD1 is spin-coated is annealed, the annealing temperature is 100 DEG C, and the annealing time is 10 minutes, and finally a photoalignment film is formed on the side of the first substrate close to the second substrate; the SD1 has anisotropy of liquid crystal and unique photoresponse characteristics of azobenzene. Under the irradiation of linearly polarized light, the SD1 molecules are arranged in a direction perpendicular to the direction of the linearly polarized light, and the liquid crystal molecules are ordered and aligned through the interaction between the molecules, so that the alignment of the liquid crystal molecules is controlled.

[0035] After the photoalignment film is formed on the side of the first substrate close to the second substrate, the photoalignment film needs to be subjected to alignment treatment.

[0036] The present application adopts a multi-step overlapping photoalignment technology, and uses a specific direction of induced polarized light to perform multi-step exposure on the photoalignment film in a specific exposure pattern. The method comprises the following steps: setting a partial overlap of exposure patterns of adjacent steps, and setting a polarization direction of the induced polarized light to monotonously increase or monotonously decrease with the exposure order, so as to form an alignment pattern with a continuous and gradual distribution of molecular director.

[0037] After exposure, the molecular director in the first alignment film is periodically arranged. In a unit period, the molecular director gradually changes from 0 DEG to 180 DEG. Figure 2 The liquid crystal molecular director in the vicinity of the first alignment film of the present application is shown in the top view. The distribution of the molecular director in the first alignment film satisfies Wherein, alpha (x) represents the molecular director at different positions on the x-axis, and A is the period.

[0038] The liquid crystal molecular director under the second alignment film is vertically aligned.Figure 3 The second orientation film is a vertical alignment agent N, N-dimethyl-N-[3- (trimethoxysil) propyl] octadecyl ammonium chloride (DMOAP), and the preparation process is as follows: a 0.5% volume concentration of DMOAP solution is configured, the second substrate is soaked in the solution for 1.5 hours, the excess silane molecules are washed away by using ultrapure water, and then the second substrate is placed on a hot stage for baking at 100 degrees Celsius for one hour, so that the second orientation film with a vertical alignment effect is formed on the second substrate. The silane molecules of the alignment agent can vertically anchor the liquid crystal molecules, so that the liquid crystal molecules are arranged vertically to the substrate.

[0039] Then, SiO2 particles with a diameter of 9 microns are selected and mixed with the frame sealant, and uniformly coated on the edge of the first substrate. The upper and lower substrates are bonded with a positional error, and placed under ultraviolet light until the frame sealant is cured.

[0040] The liquid crystal material is injected into the liquid crystal cell, and the preparation of the reconfigurable chiral liquid crystal helix superstructure system device is completed.

[0041] The polarizer 2, the 1 / 4 wave plate 6 (632.8 nanometers), the liquid crystal cell 3, and the CCD 5 are placed in sequence behind the helium-neon laser 1, so that the helium-neon laser passes through the liquid crystal cell 3 and irradiates the CCD 5. In the present application, circularly polarized light is selected to be incident on the sample, and therefore the angle between the transmission vibration axis of the polarizer and the optical axis direction of the 1 / 4 wave plate (632.8 nanometers) is set to 45° to generate incident circularly polarized light. The LED ultraviolet light source 4 is fixed obliquely above the liquid crystal cell 3, so that the LED ultraviolet light 4 irradiates the liquid crystal cell 3.

[0042] Before the helium-neon laser 1 and the LED ultraviolet light source 4 are turned on, the liquid crystal sample is observed using a polarizing microscope, Figure 5 The texture diagram of the liquid crystal sample under the polarizing microscope before light irradiation in the present application.

[0043] The helium-neon laser 1 and the LED ultraviolet light source 4 are turned on at the same time, so that the helium-neon laser and the LED ultraviolet light source irradiate the liquid crystal cell at the same time. After the liquid crystal cell 1 is irradiated for one minute, the generated annular structure light is photographed using the CCD, Figure 6 The typical light spot diagram generated in the present application, the first positive order is annular structure light, and different annular light beams can be obtained by accurately controlling the irradiation time. The liquid crystal cell is removed, and the liquid crystal sample is observed again using a polarizing microscope, Figure 7 The texture diagram of the liquid crystal sample under the polarizing microscope after light irradiation in the present application. Figure 8 The method flow chart for generating annular structure light in the present application.

Claims

1. A device for generating ring-shaped structured light, characterized in that, The device comprises a helium-neon laser (1), a polarizer (2), a liquid crystal cell (3), an LED ultraviolet light source (4) and a CCD (5) arranged in sequence; the liquid crystal cell (3) comprises two layers of substrates coated with orientation films, spacer particles and a liquid crystal layer, the spacer particles are placed between the two layers of orientation films on the opposite substrates to form a filling space for injecting the liquid crystal layer; One of the two substrates has liquid crystal molecules on the side of the surface alignment film arranged periodically, and the director of the liquid crystal molecules gradually changes from 0° to 180° in a unit period, and the distribution of the director satisfies wherein α(x) represents the director of the liquid crystal molecules at different positions on the x-axis, and A is the period; the other of the two substrates has liquid crystal molecules on the side of the surface alignment film arranged perpendicularly to the substrate; The liquid crystal layer is filled with chiral liquid crystal; Under the joint action of the two orientation films, the molecules of the liquid crystal layer self-assemble to form a multi-level helical superstructure with broken symmetry.

2. The apparatus of claim 1, wherein The device further comprises a 1 / 4 wave plate (6) arranged between the polarizer (2) and the liquid crystal cell (3).

3. The apparatus of claim 1, wherein The material of the orientation film is selected from one of surfactants, rubbing orientation agents, photo-crosslinking materials, photo-degradation materials or photo-induced cis-trans isomerization materials.

4. The apparatus of claim 1 or 3, wherein The materials of the two layers of orientation films are azo photo-controlled orientation materials SD1 and N, N-dimethyl-N-[3-(trimethoxysilane) propyl] octadecyl ammonium chloride DMOAP, respectively.

5. The apparatus of claim 1, wherein The spacer particles are spherical microparticles.

6. The apparatus of claim 1, wherein The orientation film comprises a first orientation film and a second orientation film. The preparation method of the first orientation film is: The orientation film material is uniformly spin-coated on the substrate, annealed, then the orientation film is subjected to orientation treatment, the molecules in the orientation film are irradiated by controlling the polarization direction of linearly polarized light exposure, so that the molecules in the orientation film are arranged along the direction perpendicular to the direction of linearly polarized light; The preparation method of the second orientation film is: The second substrate is soaked in an orientation agent solution, rinsed and annealed to form a second orientation film on the second substrate which has a vertical orientation effect on liquid crystal molecules.

7. The apparatus of claim 1, wherein The power of the helium-neon laser (1) is 0.3-0.5 mw, and the power of the LED ultraviolet light source (4) is 50-100 μw.

8. A method for producing a ring-shaped structured light using the apparatus of claim 1, wherein, The method is to turn on the helium-neon laser (1) and the LED ultraviolet light source (4) at the same time, so that the helium-neon laser and the LED ultraviolet light irradiate the liquid crystal cell at the same time, and the ring-shaped structure light pattern is obtained by shooting with the CCD (5).

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