Structure and control method of an air-spaced programmable time-delay half-wave plate
By designing a space-division programmable half-delay waveplate structure and control method, the problem of beam abruptness caused by the inconsistency in response time in the cascaded system of liquid crystal optical phased array and liquid crystal polarization grating was solved, realizing the synchronous response of liquid crystal optical phased array and liquid crystal polarization grating, and ensuring stable beam pointing in laser communication.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2023-06-29
- Publication Date
- 2026-06-26
AI Technical Summary
In existing cascaded systems of liquid crystal optical phased arrays and liquid crystal polarization gratings, the response times of the half-wave plate in front of the liquid crystal optical phased array and the liquid crystal polarization grating are inconsistent, causing the beam to jump during scanning, which cannot meet the requirement of stable and continuous beam pointing in laser communication.
A space-division programmable time-delay half-wave plate structure is designed, including an upper glass substrate, an ITO array grating electrode, upper and lower substrate alignment layers, a liquid crystal layer, and an ITO common electrode. By configuring a wave controller circuit module and a wave controller algorithm, the response time delay of the half-wave plate can be arbitrarily controllable, synchronously responding to the liquid crystal optical phased array and the liquid crystal polarization grating, thus solving the beam jump problem.
Synchronous response of the cascaded system of liquid crystal optical phased array and liquid crystal polarization grating is achieved, ensuring the stability of the beam during continuous angle scanning, avoiding beam jumps, and meeting the stable beam pointing requirements of laser communication.
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Figure CN116794901B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of liquid crystal optical phased array technology, specifically relating to the structure and control method of a space-division programmable time-delay half-wave plate. Background Technology
[0002] With the development of laser and optical communication technologies, application scenarios are placing increasingly higher demands on the performance of beam pointing and control devices. Existing mechanical and semi-mechanical control methods, due to their high power consumption, large size, and large rotational inertia, can no longer meet these technical requirements. Non-mechanical laser beam scanning schemes, with their advantages of small size, low inertia, high scanning response speed, and high reliability, have become one of the most popular and practical research directions in this field.
[0003] Liquid crystal optical phased arrays based on liquid crystal materials are an important branch of non-mechanical optical scanning schemes. They have advantages such as mature manufacturing technology, low driving voltage, small size, low power consumption, no inertia and programmability, and have broad application prospects in fields such as laser communication and lidar.
[0004] To address the issue of small deflection angles in single liquid crystal optical phased arrays (LCDs), a relatively mature solution is to cascade an LCD with a liquid crystal polarization grating. The polarization grating enables large-angle discrete deflection, while the LCD LCD achieves continuous scanning between discrete angles. However, due to the inconsistent response times between the LCD LCD and the half-wave plate in front of the polarization grating in the cascaded deflection system, beam abrupt changes occur during continuous beam pointing, which is unacceptable in laser communication applications. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention proposes a structure and control method for a space-division programmable time-delay half-wave plate, enabling arbitrary and controllable response delay of the half-wave plate. This is applied to a cascaded system of a liquid crystal optical phased array and a liquid crystal polarization grating, resolving the problem of beam abrupt changes during scanning caused by asynchronous responses of different devices, and achieving stable and continuous beam pointing in laser communication.
[0006] The technical solution adopted in this invention is: a structure of a space-division programmable time delay half-wave plate, comprising: an upper glass substrate 11, an ITO array grating electrode 12, an upper substrate alignment layer 13, a liquid crystal layer 14, a lower substrate alignment layer 15, an ITO common electrode 16, and a lower glass substrate 17.
[0007] The upper glass substrate 11 and the lower glass substrate 17 are placed in parallel opposite each other; a liquid crystal layer 14 is placed between the upper glass substrate 11 and the lower glass substrate 17; the upper glass substrate 11 contains an upper substrate alignment layer 13 and a transparent conductive ITO array grating electrode 12; the lower glass substrate 17 contains a lower substrate alignment layer 15 and an ITO common electrode 16.
[0008] The number of grating electrodes in the ITO array grating electrode 12 of the upper glass substrate 11 is N, and N≥2, the spacing between adjacent electrodes is d, and the effective aperture size formed by the grating electrodes of the ITO array grating electrode 12 is D.
[0009] Furthermore, the space-division programmable time-delay half-wave plate is externally configured with a wave controller circuit module 18, which includes a wave controller algorithm module.
[0010] Furthermore, the orientation directions of the upper substrate alignment layer 13 and the lower substrate alignment layer 15 are consistent with those of the ITO array grating electrode 12.
[0011] This invention also provides a control method for a space-division programmable time-delay half-wave plate, the specific steps of which are as follows:
[0012] S1. Construct a quarter-wave plate optical path to test the voltage phase relationship of the space-division programmable time delay half-wave plate and test the response time of the device;
[0013] The voltage with an additional phase of π is set as V1, the voltage with an additional phase of 2π is set as V2, the response time of the device is set as t1, and the response time of the liquid crystal optical phased array is tested as t2.
[0014] When the space-division programmable time delay half-wave plate is in operation, all N grating electrodes in the ITO array grating electrode 12 are under voltage V1 or V2.
[0015] S2. Set the difference between the response time of the liquid crystal optical phased array and the response time of the space-division programmable delay half-wave plate to Δt, set the required delay, and achieve synchronous response between the two.
[0016] Where Δt = t2 - t1, t represents the response time.
[0017] In the initial state, the first to Nth grating electrodes in the ITO array grating electrode 12 are all under voltage V2.
[0018] When t = 0, voltage V1 is applied to the first to Nth grating electrodes in the ITO array grating electrode 12. According to the test results, the device response is completed when t = t1. If a time delay of Δt is required, the response time is changed to t2 = t1 + Δt. The step-by-step control of the first to Nth grating electrodes is completed within the time period from t = 0 to Δt, thereby realizing the synchronous response of the liquid crystal polarization grating and the space-division programmable half-wave plate.
[0019] S3. Based on the number N of grating electrodes in the ITO array grating electrode 12, analyze how to achieve step-by-step control of N electrodes in the time period from t=0 to Δt.
[0020]
[0021] Where t∈(0,Δt), This indicates the number of grating electrodes in the ITO array grating electrode 12 with applied voltage V1 when t = t0, i.e., for the first to... The grating electrode is loaded with voltage V1.
[0022] because If the calculation result contains a decimal, further processing is required:
[0023]
[0024] in, Indicates to Rounding down, Y(t0) represents the number of grating electrodes in the ITO array grating electrode 12 with voltage V1 applied when t = t0, that is, the voltage V1 applied to the grating electrodes from the first to the Y(t0).
[0025] S4. Apply voltage modulation signal;
[0026] When t = 0, the electrodes on the space-division programmable time-delay half-wave plate are all under voltage V2, meaning the device adds a phase shift of 2π to the incident light without changing its polarization state. When t = t i At that time, for the first Y(t) in the ITO array grating electrode 12 i A voltage V1 is applied to each of the grating electrodes. When t = Δt, all electrodes on the space-division programmable time-delay half-wave plate are at voltage V1.
[0027] Among them, t i ∈(0, Δt).
[0028] S5. Load the wave control algorithm module to control the space-division programmable time delay half-wave plate. The obtained voltage signal enables arbitrary time delay control of the liquid crystal polarization grating, thereby achieving synchronous response with the liquid crystal optical phased array and solving the problem of beam jump during angle switching.
[0029] The beneficial effects of this invention are as follows: The structure of this invention includes: an upper glass substrate 11, an ITO array grating electrode 12, an upper substrate alignment layer 13, a liquid crystal layer 14, a lower substrate alignment layer 15, an ITO common electrode 16, and a lower glass substrate 17. The space-division programmable time-delay half-wave plate described in this invention, compared to the fixed response time of existing half-wave plates, achieves arbitrary controllability of the half-wave plate time delay by controlling the time-space partitioning of the voltage on the array electrode. This can be used to achieve synchronous response in a cascaded system of liquid crystal optical phased arrays and liquid crystal polarization gratings, and to achieve synchronous response of the system by coordinating different devices in the cascaded system. This solves the problem of beam jump when cascading liquid crystal polarization gratings and liquid crystal optical phased arrays to achieve continuous angle scanning. Attached Figure Description
[0030] Figure 1 This is a schematic diagram of the structure of a space-division programmable time-delay half-wave plate according to the present invention.
[0031] Figure 2 This is a schematic diagram illustrating the beam skipping problem caused by the mismatch in response time between devices in an embodiment of the present invention.
[0032] Figure 3 A schematic diagram illustrating how a beam jump causes two light spots to appear simultaneously in an embodiment of the present invention.
[0033] Figure 4 The system structure diagram of cascaded synchronous response using a space-division programmable time delay half-wave plate in this embodiment of the invention is shown.
[0034] Figure 5 This is a schematic diagram of waveplate region control in an embodiment of the present invention. Detailed Implementation
[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0036] like Figure 1 As shown, a schematic diagram of the structure of a space-division programmable time-delay half-wave plate of the present invention includes: an upper glass substrate 11, an ITO array grating electrode 12, an upper substrate alignment layer 13, a liquid crystal layer 14, a lower substrate alignment layer 15, an ITO common electrode 16, and a lower glass substrate 17.
[0037] The upper glass substrate 11 and the lower glass substrate 17 are placed in parallel opposite each other; a liquid crystal layer 14 is placed between the upper glass substrate 11 and the lower glass substrate 17; the upper glass substrate 11 contains an upper substrate alignment layer 13 and a transparent conductive ITO array grating electrode 12; the lower glass substrate 17 contains a lower substrate alignment layer 15 and an ITO common electrode 16.
[0038] The number of grating electrodes in the ITO array grating electrode 12 of the upper glass substrate 11 is N, and N≥2, the spacing between adjacent electrodes is d, and the effective aperture size formed by the grating electrodes of the ITO array grating electrode 12 is D.
[0039] In this embodiment, a wave controller circuit module 18 is configured outside the space-division programmable time delay half-wave plate, and the wave controller circuit module 18 includes a wave control algorithm module.
[0040] In this embodiment, the orientation directions of the upper substrate alignment layer 13 and the lower substrate alignment layer 15 are consistent with those of the ITO array grating electrode 12.
[0041] In this embodiment, the present invention also provides a control method for a space-division programmable time-delay half-wave plate, the specific steps of which are as follows:
[0042] S1. Construct a quarter-wave plate optical path to test the voltage phase relationship of the space-division programmable time delay half-wave plate and test the response time of the device;
[0043] The voltage with an additional phase of π is set as V1, the voltage with an additional phase of 2π is set as V2, the response time of the device is set as t1, and the response time of the liquid crystal optical phased array is tested as t2.
[0044] When the space-division programmable time delay half-wave plate is in operation, all N grating electrodes in the ITO array grating electrode 12 are under voltage V1 or V2.
[0045] S2. Set the difference between the response time of the liquid crystal optical phased array and the response time of the space-division programmable delay half-wave plate to Δt, set the required delay, and achieve synchronous response between the two.
[0046] Where Δt = t2 - t1, and r represents the response time.
[0047] In the initial state, the first to Nth grating electrodes in the ITO array grating electrode 12 are all under voltage V2.
[0048] When t = 0, a voltage V1 is applied to the first to Nth grating electrodes in the ITO array grating electrode 12. According to the test results, the device response is completed when t = t1. If a time delay of Δt is required, the response time is changed to t2 = t1 + Δt. The step-by-step control of the first to Nth grating electrodes is completed within the time period from t = 0 to Δt, realizing the synchronous response of the liquid crystal polarization grating and the space-division programmable half-wave plate.
[0049] S3. Based on the number N of grating electrodes in the ITO array grating electrode 12, analyze how to achieve step-by-step control of N electrodes in the time period from t=0 to Δt.
[0050]
[0051] Where t∈(0,Δt), This indicates the number of grating electrodes in the ITO array grating electrode 12 with applied voltage V1 when t = t0, i.e., for the first to... The grating electrode is loaded with voltage V1.
[0052] because If the calculation result contains a decimal, further processing is required:
[0053]
[0054] in, Indicates to Rounding down, Y(t0) represents the number of grating electrodes in the ITO array grating electrode 12 with voltage V1 applied when t = t0, that is, the voltage V1 applied to the grating electrodes from the first to the Y(t0).
[0055] S4. Apply voltage modulation signal;
[0056] When t = 0, all electrodes on the space-division programmable time-delay half-wave plate are under voltage V2, meaning the device adds a 2π phase shift to the incident light without changing its polarization state. When t = ti, the first (t)th phase shift of the ITO array grating electrode 12 is... i A voltage V1 is applied to each of the grating electrodes. When t = Δt, all electrodes on the space-division programmable time-delay half-wave plate are at voltage V1.
[0057] Among them, t i ∈(0, Δt).
[0058] S5. Load the wave control algorithm module to control the space-division programmable time delay half-wave plate. The obtained voltage signal enables arbitrary time delay control of the liquid crystal polarization grating, thereby achieving synchronous response with the liquid crystal optical phased array and solving the problem of beam jump during angle switching.
[0059] The method of the present invention also provides an embodiment 2, such as... Figure 2 The diagram shows a beam skipping problem caused by the mismatch in response time between devices.
[0060] Figure 2 (a) Curves showing the change of beam energy over time in the +0.3° and -0.3° regions when the beam is deflected from -0.3° to +0.3° using a combination of a half-wave plate and a liquid crystal polarizing grating; Figure 2(b) Curves showing the change of beam energy over time in the +0.3° and -0.3° regions when the beam is deflected from -0.3° to +0.3° for a liquid crystal phased array. Figure 2 (c) Figure 2 (d) is a cascade of liquid crystal phased array, liquid crystal phase shifter and liquid crystal polarization grating (cascade structure as follows) Figure 5 As shown, a combination of a half-wave plate and a liquid crystal polarization grating achieves beam deflection from -0.3° to +0.3°, while a liquid crystal phased array achieves beam deflection from +0.3° to -0.3°. When the beam deflection switches from -0° to +0°, the beam energy at the 0° position jumps to 0.3° due to the different response times of the devices.
[0061] The above-mentioned beam jump problem is illustrated in the following diagram. Figure 3 As shown; the system structure of the cascaded liquid crystal phased array, liquid crystal phase shifter, and liquid crystal polarization grating, with the space-division programmable time delay half-wave plate achieving cascaded synchronous response is as follows. Figure 4 As shown.
[0062] In this embodiment 2, based on the aforementioned beam jump problem, the time delay and time delay curve of the space-division programmable half-wave plate are set as follows: Δt = t2 - t1
[0063] After discretization:
[0064]
[0065]
[0066] At t = t i At that time, for the first Y(t) in the ITO array grating electrode 12 i A voltage V1 is applied to the Y(t)th grating electrode in the ITO array grating electrode 12. i -N grating electrodes are loaded with voltage V2.
[0067] A schematic diagram of the specific control method is shown below. Figure 5 As shown: When t = 0, all N grating electrodes in the ITO array grating electrode 12 are under voltage V2. When t = 0 to Δt, for the 1st-Y(t)th grating electrode in the ITO array grating electrode 12... i A voltage V1 is applied to each of the N grating electrodes in the ITO array grating electrode 12. When t = Δt = t2 - t1, a voltage V1 is applied to all N grating electrodes. This achieves the matching of the response time of the space-division programmable time-delay half-waveplate with the response of the liquid crystal polarization grating, thereby solving the problem of beam abrupt changes.
[0068] In summary, the space-division programmable time-delay half-wave plate described in the method of the present invention has a fixed response time compared to existing half-wave plates. By controlling the time-space partitioning of the voltage on the array electrodes, the time delay of the half-wave plate can be arbitrarily controllable. It can be used to realize the synchronous response of a cascaded system of liquid crystal optical phased array and liquid crystal polarization grating. It can also be used to achieve the synchronous response of the system by cooperating with different devices in the cascaded system, thus solving the problem of beam jump when cascading liquid crystal polarization grating and liquid crystal optical phased array to achieve continuous angle scanning.
[0069] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.
Claims
1. A control method for a space-division programmable time-delay half-wave plate, the wave plate comprising: The upper glass substrate comprises an upper substrate alignment layer and a transparent conductive ITO array grating electrode, and the lower glass substrate comprises a lower substrate alignment layer and an ITO common electrode. The number of grating electrodes in the ITO array grating electrode in the upper glass substrate is N, and... The spacing between adjacent electrodes is d, the effective aperture size formed by the grating electrodes of the ITO array grating electrode is D, and a wave controller circuit module is configured outside the waveplate, which includes a wave control algorithm module. The specific steps are as follows: S1. Construct a quarter-wave plate optical path to test the voltage phase relationship of the space-division programmable time delay half-wave plate and test the response time of the device; Set the additional phase as The voltage at that time is Additional phase is The voltage at that time is The response time of the device is The response time of the liquid crystal optical phased array was tested to be ; When the space-division programmable time-delay half-wave plate is in operation, the ITO array grating electrodes... Each grating electrode is in or Under voltage; S2. Set the difference between the response time of the liquid crystal optical phased array and the response time of the space-division programmable delay half-wave plate to be... Set the required delay to achieve synchronous response between the two; in, t represents the response time; In the initial state, the first-th electrode in the ITO array grating... Each grating electrode is under voltage Down; When t=0, for the first-th grating electrode in the ITO array... Voltage is applied to each grating electrode According to the test results, when t= When the device response is complete, the device can be adjusted to a time limit. The delay, turning its response time into , at t=0~ Within a certain time period, the step-by-step control of the first to Nth grating electrodes is completed, realizing the synchronous response of the liquid crystal polarization grating and the space-division programmable half-wave plate; S3. Based on the number of grating electrodes in the ITO array grating electrode Analysis at t=0~ The time period enables step-by-step control of N electrodes; ； in, , Indicates when At that time, a voltage is applied to the ITO array grating electrode. The number of grating electrodes, i.e., for the first to the last... grating electrode loading voltage ; because If the calculation result contains a decimal, further processing is required: ； in, Indicates to Round down. Indicates when At that time, a voltage is applied to the ITO array grating electrode. The number of grating electrodes, i.e., for the first to the last... grating electrode loading voltage ; S4. Apply voltage modulation signal; when At that time, the electrodes on the space-division programmable time-delay half-wave plate are all in the state of Under voltage, that is, the device adds voltage to the incident light. The phase shift does not change the polarization state of the incident light, when At that time, for the ITO array grating electrode Loading voltage ;when At that time, the electrodes on the space-division programmable time-delay half-wave plate are all in the state of Voltage; in, ; S5. Load the wave control algorithm module to control the space-division programmable time delay half-wave plate. The obtained voltage signal enables arbitrary time delay control of the liquid crystal polarization grating, thereby achieving synchronous response with the liquid crystal optical phased array and solving the problem of beam jump during angle switching.
2. The control method for a space-division programmable time-delay half-wave plate according to claim 1, characterized in that, The orientation direction of the upper substrate alignment layer is consistent with that of the lower substrate alignment layer and is also consistent with the orientation direction of the ITO array grating electrode.
3. The control method for a space-division programmable time-delay half-wave plate according to claim 1, characterized in that, The upper glass substrate and the lower glass substrate are placed parallel to each other; the liquid crystal layer is located between the upper glass substrate and the lower glass substrate.