A teaching experiment platform based on liquid crystal devices

Abstract

The application relates to a liquid crystal device-based teaching experiment platform, which comprises an optical breadboard and a laser emission unit, an interference unit, a first experiment unit for adjusting and detecting the polarization state of light, a second experiment unit for characterizing the far-field diffraction light intensity distribution of a liquid crystal device and testing the parameters of the liquid crystal device, and a third experiment unit for characterizing the spectral characteristics of a reflective liquid crystal device on the optical breadboard. The laser emission unit comprises a multi-channel voltage signal generator and a laser, a first beam expander and an electrically-controlled liquid crystal polarization grating arranged in sequence, and the electrically-controlled liquid crystal polarization grating is electrically connected with the multi-channel voltage signal generator. Compared with the prior art, the application integrates the functions of interference, diffraction, reflection, characterization and test of the polarization state of a liquid crystal device, has strong operability, is miniaturized and portable, and is very suitable for physical experiment teaching of students of various ages.

Description

Technical Field

[0001] This invention relates to the field of optical devices, and in particular to a teaching experimental platform based on liquid crystal devices. Background Technology

[0002] Currently, experiments on the properties of light in physics education still tend to follow relatively traditional approaches. For example, experiments using two polarizers to perform Malus's law experiment to verify the polarization characteristics of light, holographic experiments using the interference of reference light and object light, or direct interference experiments using various interferometers (such as Mach-Zehnder, Michelson, etc.). The experimental principles are either too simple or too complex, resulting in very little room for students to operate hands-on in the experiments. Therefore, it is difficult to arouse students' interest in optical experiments. At the same time, the experimental devices are large and inconvenient to carry. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a teaching experiment platform based on liquid crystal devices. It integrates the characterization and testing functions of interference, diffraction, reflection, and polarization state of liquid crystal devices, is highly operable, miniaturized, and portable, and is very suitable for physics experiment teaching for students of all ages.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A teaching experimental platform based on liquid crystal devices includes an optical breadboard and a laser emitting unit, an interference unit, a first experimental unit for adjusting and detecting the polarization state of light, a second experimental unit for characterizing the far-field diffraction intensity distribution of the liquid crystal device and testing the parameters of the liquid crystal device, and a third experimental unit for characterizing the spectral characteristics of a reflective liquid crystal device. The laser emitting unit includes a multi-channel voltage signal generator and a laser, a first beam expander, and an electrically controlled liquid crystal polarization grating arranged sequentially. The electrically controlled liquid crystal polarization grating is electrically connected to the multi-channel voltage signal generator.

[0006] Furthermore, the interference unit includes a first patterned alignment liquid crystal device, a first reflector, a third reflector, a first beam splitter, a second beam expander, and a first receiver. The first reflector and the third reflector are symmetrically arranged. The first patterned alignment liquid crystal device is located between the first reflector and the first beam splitter, and the second beam expander is located between the first beam splitter and the first receiver.

[0007] Furthermore, the teaching experimental platform also includes a second reflector and a second beam splitter, the second beam splitter being located between the first experimental unit and the second experimental unit.

[0008] Furthermore, the first experimental unit includes a first optical component and a second receiver, wherein the first optical component is located between the second beam splitter and the second receiver.

[0009] Furthermore, the first optical component is a transmissive or reflective optical component, including a second patterned liquid crystal device, a first polarizer, a first quarter-wave plate, and a first lens.

[0010] Furthermore, the teaching experimental platform also includes a fourth reflecting mirror, and the second beam splitter is located between the fourth reflecting mirror and the second reflecting mirror.

[0011] Furthermore, the second experimental unit includes a second optical component and a third receiver, wherein the second optical component is located between the fourth reflector and the third receiver;

[0012] The second optical component includes an electronically controlled liquid crystal cell, a second quarter-wave plate, and a second polarizer.

[0013] Furthermore, the third experimental unit includes a third optical component and a fourth receiver, wherein the third optical component is located between the fourth receiver and the second beam splitter.

[0014] The third optical component includes a third polarizer, a third quarter-wave plate, and a second lens.

[0015] Furthermore, the teaching experimental platform also includes a polarization microscope module for presenting the microstructure of liquid crystal devices. The polarization microscope module is located on an optical breadboard and includes a recorder, a microscope, a fourth polarizer, a rotatable stage, a fifth polarizer, and a light source arranged in sequence.

[0016] Furthermore, the teaching experiment platform also includes a computer terminal or mobile device for data visualization.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) When the electrically controlled liquid crystal polarization grating of the present invention is in the absence of voltage, or when a voltage is applied that allows the electrically controlled liquid crystal polarization grating to be tuned to the half-wave condition, the two arms of the interference optical path are left / right circularly polarized ±1st order diffracted light generated by the liquid crystal polarization grating. The circular polarization chirality of one of the light paths is flipped by a patterned liquid crystal device that satisfies the half-wave condition, ultimately making the circular polarization chirality of the two arm optical paths the same. Due to the symmetry of the two arms, the optical path is approximately the same, and the interference optical path is in working state. When the liquid crystal polarization grating is subjected to a saturation voltage, the interference optical path does not work and is switched to the zero-order light working mode. The zero-order light is led out to the other three working optical paths (diffracted light from the transmissive liquid crystal device) through a reflector placed between the two arm optical paths. The method of integrating the characterization and testing of the interference, diffraction, reflection, and polarization states of liquid crystal devices into the same optical experimental platform is simple, efficient, and innovative. It increases the interest of students' experiments, motivates students to conduct experiments, and effectively improves students' hands-on experimental skills and their ability to explore unknown knowledge. Of course, when the liquid crystal polarization grating is in an intermediate state of non-zero wave, non-half wave, or non-full wave under a certain voltage, the interference optical path and the other three working optical paths led out by the mirror between the two arm optical paths can work simultaneously, and the light energy distribution ratio between these optical paths is controlled by the liquid crystal polarization grating.

[0019] (2) The interference optical path formed by the interference unit of the present invention is different from the common Mach-Zehnder and Michelson interference optical paths. It makes full use of the low voltage adjustable characteristics of liquid crystal devices and belongs to the high-efficiency electrically switched interference optical path.

[0020] (3) This invention utilizes the characteristic that the liquid crystal layer of the liquid crystal device is relatively thin, and the optical state of the liquid crystal device can be controlled by low voltage. The low voltage can be less than 3 volts / micrometer, and the liquid crystal layer is equivalent to a capacitor. The required energy consumption is relatively small, and no large power supply device is required. Therefore, the integrated optical experimental platform is miniaturized and portable, and is suitable for large-scale experimental teaching and demonstration experimental teaching for students of all ages.

[0021] (4) The present invention can present the microstructure of liquid crystal devices through a polarization microscope module;

[0022] (5) The computer terminal or mobile terminal of this invention is matched with the relevant experiments of the teaching experimental platform to calculate and process experimental data, reflect the optical characteristics corresponding to the device parameters, and can visualize the optical characteristics and test parameters in the relevant experiments, which greatly improves the user experience of the optical experimental platform and allows students to have a more intuitive understanding and deeper learning of optical knowledge. Attached Figure Description

[0023] Figure 1This is a schematic diagram of the structure of the present invention when the ±1st order diffraction light deflection angle is relatively small.

[0024] Figure 2 A schematic diagram of the present invention when the ±1st order diffraction light deflection angle is relatively large;

[0025] Figure 3 This is a schematic diagram of the polarization microscope module.

[0026] Explanation of the labels in the diagram:

[0027] 1. Optical breadboard, 2. Laser, 21. Probe laser, 31. First beam expander, 32. Second beam expander, 4. Electro-controlled liquid crystal polarization grating, 41. First circularly polarized light, 42. Second circularly polarized light, 43. Zero-order light, 51. First mirror, 52. Second mirror, 53. Third mirror, 54. Fourth mirror, 61. First beam splitter, 62. Second beam splitter, 7. First patterned alignment liquid crystal device, 10. Multiplexed voltage signal generator, 80. First optical component, 81. Second optical component, 82. Third optical component, 90. First receiver, 91. Second receiver, 92. Third receiver, 93. Fourth receiver, 94. Polarization microscope module, 311. Beam expander laser, 941. Recorder, 942. Microscope, 943. Fourth polarizer, 944. Rotatable stage, 945. Fifth polarizer, 946. Light source. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0029] A teaching experiment platform based on liquid crystal devices, such as Figure 1 The system includes an optical breadboard 1 and a laser emitting unit, an interference unit, a first experimental unit for adjusting and detecting the polarization state of light, a second experimental unit for characterizing the far-field diffraction intensity distribution of the liquid crystal device and testing the parameters of the liquid crystal device, and a third experimental unit for characterizing the spectral characteristics of the reflective liquid crystal device. The laser emitting unit includes a multi-channel voltage signal generator 10 and a laser 2, a first beam expander 31, and an electrically controlled liquid crystal polarization grating 4 arranged sequentially. The electrically controlled liquid crystal polarization grating 4 is electrically connected to the multi-channel voltage signal generator 10.

[0030] The interference unit includes a first patterned liquid crystal device 7, a first reflector 51, a third reflector 53, a first beam splitter 61, a second beam expander 32, and a first receiver 90. The first reflector 51 and the third reflector 53 are symmetrically arranged. The first patterned liquid crystal device 7 is located between the first reflector 51 and the first beam splitter 61, and the second beam expander 32 is located between the first beam splitter 61 and the first receiver 90.

[0031] Laser 2 generates a linearly polarized probe laser 21 of a specific wavelength. After the probe laser 21 passes through the first beam expander 31, it becomes a beam expander laser 311. Then, the beam expander laser 311 passes through an electrically controlled liquid crystal polarization grating 4. Applying a suitable voltage can switch it between two modes: ±1st order diffraction light and zeroth order light 43. The positive and negative first order diffraction lights include first circularly polarized light 41 and second circularly polarized light 42 with opposite rotation directions.

[0032] The orientation angle α of the liquid crystal layer of the electronically controlled liquid crystal polarization grating 4 satisfies:

[0033]

[0034] Where x is the laboratory coordinate position, and Λ is the period constant of the liquid crystal polarization grating;

[0035] The thickness of the liquid crystal layer satisfies the half-wave condition. In the absence of voltage, the diffraction efficiency of its positive and negative first-order diffracted light is close to the theoretical maximum value of 100%, and the intensity of the intermediate zero-order light is almost 0. When a saturation voltage is applied, the diffraction efficiency of its positive and negative first-order diffracted light tends to 0, and the intensity of the intermediate zero-order light becomes the maximum. The diffraction efficiency can be continuously modulated by voltage, thereby controlling the light energy distribution ratio between the positive and negative first-order diffracted light and the zero-order light.

[0036] The optical experimental platform disclosed in this embodiment differs from the working principle of traditional interferometers (Mach-Zehnder, Michelson, etc.). Based on the principle of light diffraction, it utilizes an electrically controlled liquid crystal polarization grating 4 to propagate the probe laser 21 in different directions according to the different chiralities of circularly polarized light, generating a first circularly polarized light 41 and a second circularly polarized light 42. A first reflecting mirror 51 and a third reflecting mirror 53 adjust the first and second circularly polarized lights 41 and 42 to an orthogonal positional relationship. A first patterned alignment liquid crystal device 7 satisfying the half-wave condition is placed in the optical path of the first circularly polarized light 41, causing the first circularly polarized light 41 to propagate in different directions according to the different chiralities of circularly polarized light 42. The circularly polarized light 41 and the second circularly polarized light 42 have the same circular polarization chirality. The two beams are combined by the first beam-splitting element 61 (beam splitter or beam-splitting prism) to form coaxial interference. A second beam-expanding element 32 (beam expander) is placed in the coaxial interference unit to magnify the interference pattern. A first receiver 90 (receiving screen or photosensitive electronic device) is placed at a specific distance to receive the interference signal. The positions of the first reflecting mirror 51, the third reflecting mirror 53, and the first beam-splitting element 61 can be appropriately adjusted according to different deflection angles of the electronically controlled liquid crystal polarization grating 4. For large deflection angles, such as... Figure 1 Settings, for small deflection angles, such as... Figure 2 set up.

[0037] The teaching experimental platform also includes a second reflector 52, a fourth reflector 54, and a second beam splitter 62. The second beam splitter 62 is located between the first experimental unit and the second experimental unit, and between the fourth reflector 54 and the second reflector 52.

[0038] The first experimental unit includes a first optical component 80 and a second receiver 91. The first optical component 80 is located between the second beam splitter 62 and the second receiver 91. The first optical component 80 is a transmissive optical component or a reflective optical component. When the first optical component 80 is a transmissive optical component, it includes a second patterned liquid crystal device and several first polarizers, first quarter-wave plates and first lenses for generating or filtering specific circularly polarized light. The number of second patterned liquid crystal devices is one or several.

[0039] The second experimental unit includes a second optical component 81 and a third receiver 92. The second optical component 81 is located between the fourth reflector 54 and the third receiver 92. The second optical component 81 includes an electro-controlled liquid crystal cell and several second quarter-wave plates and second polarizers for detecting polarization state. There are one or more electro-controlled liquid crystal cells. The multiple electro-controlled liquid crystal cells are uniformly oriented, and their orientation axes are arranged at specific angles. These angles can be any angles such as 30°, 45°, and 60°. Different angles will cause different changes in the polarization state of the emitted light.

[0040] The electronically controlled liquid crystal cell includes two substrates, which are glass substrates or flexible thin film substrates. Each substrate has a transparent conductive electrode coated on one side surface. An alignment layer is coated on the transparent conductive layer with a uniform alignment direction. The alignment layers of the two substrates are stacked inward and separated by a spacer at a specific distance, with liquid crystal material filled in between.

[0041] A light alignment layer, a rubbing alignment layer, or a vertical alignment layer oriented parallel to the plane of the substrate is provided on the surface of the substrate;

[0042] When a friction alignment layer is provided on the substrate surface, a groove structure generated by friction is provided on the friction alignment layer, and the groove direction is the easy alignment direction of the electronically controlled liquid crystal cell;

[0043] The vertical alignment layer is used to align the liquid crystal molecules perpendicular to the plane of the substrate.

[0044] The third experimental unit includes a third optical component 82 and a fourth receiver 93. The third optical component 82 is located between the fourth receiver 93 and the second beam splitter 62. The third optical component 82 includes a number of third polarizers, third quarter-wave plates and second lenses for filtering specific circularly polarized light.

[0045] Due to the switchable characteristics of the electronically controlled liquid crystal polarization grating 4, when switching to the zero-order light working mode, a saturation voltage needs to be applied to the liquid crystal polarization grating. At this time, all the energy is concentrated in the zero-order light 43, which serves as the light source for the subsequent three sets of working optical paths, greatly improving the energy utilization rate, which is something that traditional interference units cannot achieve.

[0046] When a saturation voltage is applied, the ±1 diffraction order light of the electro-liquid polarization grating 4 disappears, and all the energy is concentrated in the zero-order light 43. It is deflected to one side of the electro-liquid polarization grating 4 by the second reflecting mirror 52, and then a portion of the light is deflected by the second beam splitter 62 (beam splitter prism) to form the first experimental optical path, while the remaining portion forms the second experimental optical path. The first optical component 80 is located in the first experimental optical path, and the second receiver 91 (receiving screen or photosensitive electronic device) is placed at a specific distance. The first optical component 80 is a reflective or transmissive optical component. When the first optical component 80 is reflective, the zero-order light 43 is reflected back by the first optical component 80, passes through the second beam splitter 62, and forms the third experimental optical path. The third experimental optical path passes through the third optical component 82 and is then received by the fourth receiver 93 (receiving screen, spectrometer, or chromatograph, etc., photosensitive electronic device).

[0047] The second experimental optical path is used to tune and detect the polarization state of light (Stokes parameters). The second experimental optical path is reflected by the fourth reflector 54 and passes through the second optical component 81. The third receiver 92 (receiving screen or light intensity detector) is placed at a specific distance.

[0048] The polarization state of light can be tuned by an electro-controlled liquid crystal cell causing the polarization plane of the emitted light to rotate. This requires a uniformly oriented electro-controlled liquid crystal cell and a non-tunable second quarter-wave plate of a specific wavelength with an orientation axis angle of 45°. Alternatively, the polarization state of light can be tuned by an electro-controlled liquid crystal cell causing the polarization state of the emitted light to change between elliptic polarization, circular polarization, and linear polarization. This requires placing several uniformly oriented electro-controlled liquid crystal cells and a non-tunable second quarter-wave plate of a specific wavelength in the optical path, with their orientation axes set at a specific angle.

[0049] The orientation patterns of the first patterned liquid crystal device 7 and the second patterned liquid crystal device can be arbitrarily customized, such as: patterns similar to polarizing gratings, patterns of geometric phase lenses, patterns of Q-wave plate spiral phase, etc. The liquid crystal layer of the first patterned liquid crystal device 7 and the second patterned liquid crystal device contains photosensitive materials or magnetic sensitive materials, and the liquid crystal layer can be regulated by one or more means of electricity, light, heat or magnetic field.

[0050] The teaching experiment platform also includes a set of computer terminals or mobile devices that are designed to be used with related experiments. These terminals are designed to be visual and interactive, allowing for the calculation and processing of experimental data and the visualization of the optical characteristics corresponding to the device parameters. The optical characteristics and test parameters in the related experiments can be displayed visually, which greatly improves the user experience of the optical experiment platform and allows students to have a more intuitive understanding and deeper learning of optical knowledge.

[0051] Example 2

[0052] In this embodiment, the teaching experimental platform also includes a polarization microscope module 94 for presenting the microstructure of liquid crystal devices, such as... Figure 1 and Figure 3 The polarization microscope module 94 is located on the optical breadboard 1 and includes a recorder 941, a microscope 942 for magnifying the texture of a liquid crystal device, a fourth polarizer 943, a rotatable stage 944, a fifth polarizer 945, and a light source 946 arranged in sequence. The recorder 941 is a CCD or CMOS camera, and the fourth polarizer 943 and the fifth polarizer 945 are rotatable.

[0053] Everything else is the same as in Example 1.

[0054] Examples 1 and 2 propose a teaching experimental platform based on liquid crystal devices. The design method of integrating the characterization and testing of interference, diffraction, reflection, and polarization state of liquid crystal devices into the same optical experimental platform is simple, efficient, and innovative. It increases the interest of students' experiments, motivates students to conduct experiments, and effectively improves students' hands-on experimental skills and their ability to explore unknown knowledge.

[0055] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A liquid crystal device-based teaching experiment platform, characterized in that, The application relates to a teaching experiment platform, which comprises an optical breadboard (1) and a laser emission unit, an interference unit, a first experimental unit for adjusting and detecting the polarization state of light, a second experimental unit for characterizing the far-field diffraction light intensity distribution of a liquid crystal device and testing the parameters of the liquid crystal device and a third experimental unit for characterizing the spectral characteristics of a reflective liquid crystal device on the optical breadboard (1), wherein the laser emission unit comprises a multi-channel voltage signal generator (10) and a laser (2), a first beam expanding element (31) and an electrically-controlled liquid crystal polarization grating (4) which are sequentially arranged, the electrically-controlled liquid crystal polarization grating (4) is electrically connected with the multi-channel voltage signal generator (10), the interference unit comprises a first patterned alignment liquid crystal device (7), a first mirror (51), a third mirror (53), a first light splitting element (61), a second beam expanding element (32) and a first receiver (90), the first mirror (51) and the third mirror (53) are symmetrically arranged, the first patterned alignment liquid crystal device (7) is located between the first mirror (51) and the first light splitting element (61), the second beam expanding element (32) is located between the first light splitting element (61) and the first receiver (90), and the teaching experiment platform is based on the diffraction principle of light, the electrically-controlled liquid crystal polarization grating (4) is used to make the probe laser (21) propagate in different directions according to the different chirality of circularly polarized light, first circularly polarized light (41) and second circularly polarized light (42) are generated, the first mirror (51) and the third mirror (53) are used to adjust the first circularly polarized light (41) and the second circularly polarized light (42) into a position relationship, the first patterned alignment liquid crystal device (7) satisfying the half-wave condition is arranged in the light path of the first circularly polarized light (41), the chirality of the first circularly polarized light (41) and the second circularly polarized light (42) is the same, the two-arm light rays are combined by the first light splitting element (61), and coaxial interference is formed. The teaching experiment platform further comprises a second reflector (52), a fourth reflector (54) and a second light splitting element (62), the second light splitting element (62) is located between the first experiment unit and the second experiment unit, the first experiment unit comprises a first optical assembly (80) and a second receiver (91), the first optical assembly (80) is located between the second light splitting element (62) and the second receiver (91), the second light splitting element (62) is located between the fourth reflector (54) and the second reflector (52), the second experiment unit comprises a second optical assembly (81) and a third receiver (92), the second optical assembly (81) is located between the fourth reflector (54) and the third receiver (92), the third experiment unit comprises a third optical assembly (82) and a fourth receiver (93), the third optical assembly (82) is located between the fourth receiver (93) and the second light splitting element (62), under the condition of applying a saturation voltage, the ±1 diffraction order light of the electrically controlled liquid crystal polarization grating (4) disappears, all the energy is concentrated into the zero-order light (43), which is deflected to one side of the electrically controlled liquid crystal polarization grating (4) through the second reflector (52), and then a part of the light is deflected to form a first experiment light path through the second light splitting element (62), the rest of the light forms a second experiment light path, the first optical assembly (80) is located in the first experiment light path, the second receiver (91) is placed at a specific distance, the first optical assembly (80) is a reflective or transmissive optical assembly, when the first optical assembly 80 is reflective, the zero-order light (43) is reflected back by the first optical assembly (80) and passes through the second light splitting element (62) again to form a third experiment light path, the third experiment light path passes through the third optical assembly (82) and is then received by the fourth receiver (93).

2. The liquid crystal device based teaching experiment platform according to claim 1, wherein, The first optical assembly (80) is a transmissive or reflective optical assembly, comprising a second patterned alignment liquid crystal device, a first polarizer, a first quarter wave plate and a first lens.

3. The liquid crystal device based teaching experiment platform according to claim 1, wherein, The second optical assembly (81) comprises an electrically controlled liquid crystal cell, a second quarter wave plate and a second polarizer.

4. The liquid crystal device based teaching experiment platform according to claim 1, wherein, The third optical assembly (82) comprises a third polarizer, a third quarter wave plate and a second lens.

5. The liquid crystal device based teaching experiment platform according to claim 1, wherein, The teaching experiment platform further comprises a polarization microscope module (94) for presenting the microstructure of the liquid crystal device, the polarization microscope module (94) is located on the optical breadboard (1) and comprises a recorder (941), a microscope (942), a fourth polarizer (943), a rotatable stage (944), a fifth polarizer (945) and a light source (946) arranged in sequence.

6. The liquid crystal device based teaching experiment platform according to claim 1, wherein, The teaching experiment platform further comprises a computer terminal or a mobile terminal for data visualization.

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