A non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system and method

Abstract

This invention discloses a non-mechanical liquid crystal optical phased array (U-PHI) high-speed measurement system and method. The system includes: a laser, a polarizer, a liquid crystal optical phased array under test, a quarter-wave plate, a first depolarizing beam splitter, a second depolarizing beam splitter, a 135° polarization direction analyzer, a 45° polarization direction analyzer, a polarizing beam splitter, four photodetectors, a DSP signal processing module, and a main control terminal. The method of this invention, based on a small number of waveplates, optical crystals, and unit photodetectors, realizes a simple, low-cost, and highly controllable non-mechanical liquid crystal optical phased array (U-PHI) high-speed measurement system. It also achieves one-click U-PHI testing of liquid crystal devices, completing one test in 1ms, improving testing time and accuracy, greatly reducing human error caused by individual differences, and facilitating system integration, miniaturization, lightweighting, and low power consumption. This accelerates batch testing and quality assurance of mass-produced products in the liquid crystal device industry and is suitable for mass production equipment.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal optical phased array technology, specifically relating to a non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system and method. Background Technology

[0002] Beamforming technology is widely used in wireless communication, detection, and power transfer. As a prime example, Multiple-Input Multiple-Output (MIMO) has been used in 5G communication system base stations. Beamforming technology supports dynamic and flexible configuration of multiple user numbers, coverage areas, and communication bandwidth. In optical spectroscopy, to realize one-to-many free-space laser networks, flexible laser beamforming is required to generate and reconfigure multiple beams with high pointing accuracy and output power accuracy. Conversely, traditional laser pointing systems using mechanical gimbals and solid-state optical antennas cannot flexibly deflect a single laser beam or arbitrarily generate multiple beams. Furthermore, these characteristics of multi-beam generation and reconfiguration can be introduced into other free-space optics fields, including lidar detectors and laser guidance seekers. Liquid crystal optical phased arrays (LCOPA) have also been studied at the physical level of free-space laser networks for over 40 years, with liquid crystal (LC) as the core material or platform. Reconfigurable optical multi-beams are achieved based on novel liquid crystal phased array devices: they support user-defined dynamic beam arrangements, including arbitrary number of beams, arbitrary angles, and arbitrary power occupancy rates, greatly meeting the needs of various communication, radar detection, and other applications.

[0003] Currently, driving liquid crystal optical phased array devices requires clarifying the correspondence between their phase and voltage. This correspondence is generally measured by manually rotating the analyzer, which is often time-consuming and labor-intensive, greatly limiting the number of test points and thus affecting the accuracy of the test results. At the same time, manual testing introduces a large amount of random error, which also greatly affects the phase modulation accuracy of the phased array devices. Manual measurement, data processing, and U-PHI (voltage-phase relationship) table fabrication are inefficient, seriously affecting the rapid batch measurement and data management of mass-produced devices. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system and method, which can transform manual measurement into fully automatic measurement, achieving higher accuracy while significantly improving efficiency. Furthermore, after measurement, the experimental data can be automatically organized into a truth table for use by driving devices.

[0005] The technical solution adopted in this invention is as follows: a non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system, comprising: a laser 1, a polarizer 2, a liquid crystal optical phased array under test 3, a quarter-wave plate 4, a first depolarizing beam splitter 5, a second depolarizing beam splitter 6, a 135° polarization direction analyzer 7, a 45° polarization direction analyzer 8, a polarizing beam splitter 9, photodetectors 10-1, 10-2, 10-3, and 10-4, a DSP signal processing module 11, and a main control terminal 12.

[0006] The laser beam emitted from laser 1 passes sequentially through polarizer 2, the liquid crystal optical phased array under test 3, a quarter-wave plate 4, and the first depolarizing beam splitter 5. After passing through the first depolarizing beam splitter 5, the laser beam is split into two beams, B1 and B2. Beam B1 is then split into two beams, B11 and B12, by polarizing beam splitter 9. Beam B11 exits to photodetector 10-2, which generates an electrical signal that is transmitted to DSP signal processing module 11. Beam B12 exits to photodetector 10-1, which generates an electrical signal that is transmitted to DSP signal processing module 11. SP signal processing module 11: After beam B2 passes through the second depolarizing beam splitter 6, it is split into two beams B21 and B22. Beam B21 passes through the 135° polarization direction analyzer 7 and the photodetector 10-4 in sequence. The photodetector 10-4 generates an electrical signal that is transmitted to the DSP signal processing module 11. Beam B22 passes through the 45° polarization direction analyzer 8 and the photodetector 10-3 in sequence. The photodetector 10-3 generates an electrical signal that is transmitted to the DSP signal processing module 11. After the DSP signal processing module 11 processes the signal, it is transmitted to the main control terminal 12.

[0007] Furthermore, the DSP signal processing module 11 includes: a comparator 11-1, an operational amplifier 11-2, an operational amplifier 11-3, an analog-to-digital converter 11-4, a current-limiting diode 11-5, and a digital signal processing unit 11-6.

[0008] Photodetector 10-4 generates an electrical signal that is input to the non-inverting input of comparator 11-1, and photodetector 10-3 generates an electrical signal that is input to the inverting input of comparator 11-1. The output of comparator 11-1 is connected to the input of current-limiting diode 11-5, and the output of current-limiting diode 11-5 is connected to one end of digital signal processing unit 11-6. Photodetector 10-2 generates an electrical signal that is input to one end of operational amplifier 11-2, and the other end of operational amplifier 11-2 is connected to one end of analog-to-digital converter 11-4. Photodetector 10-1 generates an electrical signal that is input to one end of operational amplifier 11-3, and the other end of operational amplifier 11-3 is connected to one end of analog-to-digital converter 11-4. The other end of analog-to-digital converter 11-4 is connected to one end of digital signal processing unit 11-6. The other end of digital signal processing unit 11-6 is connected to main control terminal 12 and the liquid crystal optical phased array 3 under test.

[0009] The digital signal processing unit 11-6 includes: FPGA and STM32.

[0010] Furthermore, the polarization direction of the polarizer 2 is at 45° to the anchoring orientation direction of the liquid crystal optical phased array 3 under test, and the fast axis direction of the quarter wave plate 4 is parallel to the transmission axis of the polarizer 2. The polarizer 2, the liquid crystal optical phased array 3 under test, and the quarter wave plate 4 form a liquid crystal-based electrically controlled polarization rotator.

[0011] This invention also provides a non-mechanical liquid crystal optical phased array U-PHI high-speed measurement method, the specific steps of which are as follows:

[0012] S1. Determine system parameters;

[0013] The parameters include: the operating wavelength of the liquid crystal phased array device under test and the laser operating wavelength, the operational amplifier model and parameters, the analog-to-digital converter model, the comparator model, the digital signal processing unit chip model, the inter-chip communication protocol, and the communication protocol between the upper and lower level computers.

[0014] S2. Set up the measurement system and calibrate it;

[0015] The non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system was constructed. The photodetector unit and DSP signal processing module 11 were initialized. It was checked whether the photodetector unit was in place and working normally. It was checked whether the DSP signal processing module 11 was correctly programmed and whether it was working normally by running a running light. The optical path was calibrated to be coaxial and the beam was correctly illuminated to the correct position of the liquid crystal optical phased array 3 under test. All photodetectors were made to work in sequence. Under different temperatures and in different temperature scenarios, the photoelectric response gain and curve of different batches of photodetectors were tested. The time delay from the photodetector to the DSP signal processing module 11 was measured. The photodetector time delay table, gain difference table, gain compensation table and temperature compensation table were tested and calibrated.

[0016] The photoelectric detection unit includes: photodetector 10-1, photodetector 10-2, photodetector 10-3, and photodetector 10-4.

[0017] S3. Configure system parameters;

[0018] Configure the local photodetector delay table T1;

[0019] Configure local photodetector gain normalization parameters: The photodetector units of the same photodetector module are subjected to gain normalization processing and a unified gain standard value is calibrated.

[0020] Configure the local photodetector gain difference table G1: Based on the normalized standard value, configure the gain value of different detectors in the photodetector under different power beam illumination and the difference between the gain value and the normalized standard value, generate the gain difference table and configure it to the information processing unit.

[0021] Configure the local photodetector gain batch table G2;

[0022] Configure the local photodetector gain temperature compensation meter G3;

[0023] Generate the total supplementary table Gtotal = G1 + G2 + G3 for the local photodetector.

[0024] S4. Calculate the phase difference of the electric field vectors corresponding to the two outgoing beams B11 and B12 of the polarization beam splitter 9;

[0025] The two outgoing beams B11 and B12 from the polarizing beam splitter 9 are horizontally polarized (P-beam) and vertically polarized (S-beam), respectively, and correspond to the electric field vectors. and and The first Cartesian right-hand coordinate system that makes up the system After the two beams of light are collected by two corresponding photodetectors, they are sent to the DSP signal processing module 11 to calculate the relative phase modulation amount of the liquid crystal phased array 3 under test at this time.

[0026] The main control terminal 12 sequentially drives the liquid crystal optical phased array 3 under test with voltage code 0, and outputs the P-component of the beam emitted from the liquid crystal optical phased array 3 under test. With S-ray component After being acquired by the corresponding photodetector, the signal is amplified and sent to the analog-to-digital converter 11-4, where it is converted into a digital signal and then sent to the digital signal processing unit 11-6. The digital signal processing unit 11-6 calculates the following algorithm... and Phase difference:

[0027] The x-axis and y-axis are selected to be along the fast and slow axes of the quarter-wave plate 4, respectively, and the fast and slow axis directions of the liquid crystal optical phased array 3 under test are made at an angle of ±45° with the transmission axis of the polarizer 2.

[0028] The Jones vector of the linearly polarized light transmitted through polarizer 2 is In this coordinate system, the Jones matrix of the 1 / 4 wave plate 4 is Since the fast and slow axes of the liquid crystal optical phased array 3 under test form a 45° angle with the x-axis, the Jones matrix of the liquid crystal optical phased array 3 under test is: The polarization state E of the linearly polarized light after passing through the device under test and the quarter-wave plate 4 is:

[0029]

[0030] Where i represents the imaginary unit, and δ represents the phase difference between the fast and slow axes of the liquid crystal optical phased array 3 under test. After normalization, we get... It can be seen that the emitted light at this time is linearly polarized light. This can be determined through calculation. Simplification yields Therefore Then the phase difference between the P and S beams is calculated.

[0031] Where γ represents the angle between the polarized light vector and the four fast axes of the quarter-wave plate; Ex and Ey represent the magnitudes of the electric fields of the P and S rays, respectively.

[0032] S5. Determine the π phase compensation;

[0033] The second depolarizing beam splitter 6 maintains polarization and equally splits two beams. One beam, B22, after passing through the 45° polarization analyzer 8, emits an electric field vector of... The beam is collected by photodetector 10-3; the output electric field vector of another beam B21 after passing through the 135° polarization analyzer 7 is... The data was collected by a photodetector 10⁻⁴, resulting in the original coordinate system. A second Cartesian right-hand coordinate system rotated by 45°

[0034] The and The included angle is 45°. and The included angle is 135°, in the second Cartesian right-hand coordinate system. With the first Cartesian right-hand coordinate system The included angle is 45°, which is compared with the second Cartesian right-hand coordinate system. In and The magnitude of this value resolves the π-phase ambiguity problem and distinguishes the quadrant in which the polarization direction of the light emitted from the quarter-wave plate 4 lies. That is, in the coordinate system described above... The polarization state of the original beam can pass through the new coordinate system. Down and The length of the vector modulus distinguishes the quadrant in which its polarization direction lies, as follows:

[0035] 1) If the current-limiting diode 11-5 outputs a high level 1, then the polarization direction can be obtained in the first quadrant;

[0036] 2) If the current limiting diode 11-5 outputs a low level of 0, then the polarization direction can be obtained in the second quadrant.

[0037] S6. Enables high-speed measurement of U-PHI;

[0038] The phase difference information obtained based on steps S1 to S5 is temporarily stored in the RAM of the digital signal processing unit 11-6. During this period, the main control terminal 12 increments the voltage V each time. step The transmission control of the liquid crystal optical phased array 3 under test is performed once for each transmission, and steps S1 to S5 are performed once after each transmission. After one transmission is completed, the flag bit is pulled high to inform the digital signal processing unit 11-6 of the buffer result and to notify the main control terminal 12 to start the next transmission cycle.

[0039] After all N executions are completed, the flag is raised to notify the main control terminal 12. The DSP signal processing module 11 can also receive the main control command from the main control terminal 12 to continuously complete the phase-controlled voltage generation and signal processing in one go, realizing high-speed U-PHI measurement. The digital signal processing unit 11-6 sends the cached phase difference data to the main control terminal 12 through the communication protocol and interface between the upper and lower computers determined in step S1 for further data processing. It then lists the voltage and phase difference in parallel to obtain the complete voltage-phase relationship (U-PHI) truth table of the liquid crystal optical phased array 3 under test, and uploads it to the main control terminal 12.

[0040] Furthermore, in the DSP signal processing module 12, the analog signals of the two orthogonal components of the light beam obtained by the two photodetectors (10-1, 10-2) are converted into digital signals by the analog-to-digital converter 11-4 and then sent to the digital signal processing unit 11-6 to calculate the phase information of the light beam through the method in step S4; the signals collected by the other two photodetectors (10-3, 10-4) are compared by a comparator 11-1, and after passing through the current limiting diode 11-5, the output square wave is sent to the digital signal processing unit 11-6 to determine the quadrant in which the polarization direction of the light beam is located, thus solving the π phase ambiguity problem.

[0041] The beneficial effects of this invention are as follows: The system of this invention includes: a laser, a polarizer, a liquid crystal optical phased array under test, a quarter-wave plate, a first depolarizing beam splitter, a second depolarizing beam splitter, a 135° polarization direction analyzer, a 45° polarization direction analyzer, a polarizing beam splitter, four photodetectors, a DSP signal processing module, and a main control terminal. The method of this invention, based on a small number of waveplates, optical crystals, and unit photodetectors, realizes a simple, low-cost, and highly controllable non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system. It also achieves one-click U-PHI testing of liquid crystal devices, completing one test in 1ms, improving testing time and accuracy, greatly reducing human error caused by individual differences, and facilitating system integration, miniaturization, lightweighting, and low power consumption. This accelerates batch testing and quality assurance of mass-produced products in the liquid crystal device industry and is suitable for mass production equipment.

[0042] The system described in this invention is based on a liquid crystal optical phased array spatial light modulator. It can not only realize the entire static and non-mechanical process of U-PHI testing of liquid crystal phased arrays, but also complete ultra-large-scale and ultra-fine U-PHI testing in a very short time, greatly improving the efficiency and accuracy of U-PHI testing of liquid crystal devices such as liquid crystal optical phased arrays and liquid crystal cells. The method of this invention realizes one-click measurement and one-click generation of truth table for U-PHI testing. Combined with optimization algorithms, it can also realize one-click fitting and U-PHI data optimization, and supports multiple modes such as single-step measurement and batch measurement. Attached Figure Description

[0043] Figure 1 This is a structural diagram of a non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system according to the present invention.

[0044] Figure 2 This is a structural diagram of the DSP signal processing module in an embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the components of polarized light in a dual coordinate system in an embodiment of the present invention.

[0046] Figure 4 This is a schematic diagram of the components of polarized light in a dual coordinate system in the second phenomenon embodiment of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] like Figure 1 As shown, the present invention discloses a non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system, comprising: a laser 1, a polarizer 2, a liquid crystal optical phased array under test 3, a quarter-wave plate 4, a first depolarizing beam splitter 5, a second depolarizing beam splitter 6, a 135° polarization direction analyzer 7, a 45° polarization direction analyzer 8, a polarizing beam splitter 9, photodetectors 10-1, 10-2, 10-3, and 10-4, a DSP signal processing module 11, and a main control terminal 12.

[0049] The laser beam emitted from laser 1 passes sequentially through polarizer 2, the liquid crystal optical phased array under test 3, a quarter-wave plate 4, and the first depolarizing beam splitter 5. After passing through the first depolarizing beam splitter 5, the laser beam is split into two beams, B1 and B2. Beam B1 is then split into two beams, B11 and B12, by polarizing beam splitter 9. Beam B11 exits to photodetector 10-2, which generates an electrical signal that is transmitted to DSP signal processing module 11. Beam B12 exits to photodetector 10-1, which generates an electrical signal that is transmitted to DSP signal processing module 11. SP signal processing module 11: After beam B2 passes through the second depolarizing beam splitter 6, it is split into two beams B21 and B22. Beam B21 passes through the 135° polarization direction analyzer 7 and the photodetector 10-4 in sequence. The photodetector 10-4 generates an electrical signal that is transmitted to the DSP signal processing module 11. Beam B22 passes through the 45° polarization direction analyzer 8 and the photodetector 10-3 in sequence. The photodetector 10-3 generates an electrical signal that is transmitted to the DSP signal processing module 11. After the DSP signal processing module 11 processes the signal, it is transmitted to the main control terminal 12.

[0050] like Figure 2 As shown, in this embodiment, the DSP signal processing module 11 includes: a comparator 11-1, an operational amplifier 11-2, an operational amplifier 11-3, an analog-to-digital converter 11-4, a current-limiting diode 11-5, and a digital signal processing unit 11-6.

[0051] The digital signal processing unit 11-6 includes either an FPGA or an STM32. Various types of digital signal processing units can be used, with FPGA and STM32 being two of the more common ones.

[0052] Photodetector 10-4 generates an electrical signal that is input to the non-inverting input of comparator 11-1, and photodetector 10-3 generates an electrical signal that is input to the inverting input of comparator 11-1. The output of comparator 11-1 is connected to the input of current-limiting diode 11-5, and the output of current-limiting diode 11-5 is connected to one end of digital signal processing unit 11-6. Photodetector 10-2 generates an electrical signal that is input to one end of operational amplifier 11-2, and the other end of operational amplifier 11-2 is connected to one end of analog-to-digital converter 11-4. Photodetector 10-1 generates an electrical signal that is input to one end of operational amplifier 11-3, and the other end of operational amplifier 11-3 is connected to one end of analog-to-digital converter 11-4. The other end of analog-to-digital converter 11-4 is connected to one end of digital signal processing unit 11-6. The other end of digital signal processing unit 11-6 is connected to main control terminal 12 and the liquid crystal optical phased array 3 under test.

[0053] In this embodiment, the polarization direction of the polarizer 2 is at 45° to the anchoring orientation direction of the liquid crystal optical phased array 3 under test, and the fast axis direction of the quarter wave plate 4 is parallel to the transmission axis of the polarizer 2. The polarizer 2, the liquid crystal optical phased array 3 under test, and the quarter wave plate 4 form a liquid crystal-based electrically controlled polarization rotator.

[0054] In this embodiment, the present invention also provides a non-mechanical liquid crystal optical phased array U-PHI high-speed measurement method, the specific steps of which are as follows:

[0055] S1. Determine system parameters;

[0056] The parameters include: the operating wavelength of the liquid crystal phased array device under test and the laser operating wavelength, the operational amplifier model and parameters, the analog-to-digital converter model, the comparator model, the digital signal processing unit chip model, the inter-chip communication protocol, and the communication protocol between the upper and lower level machines. The system parameters in this embodiment are shown in Table 1.

[0057] Table 1

[0058] Analog-to-digital converter AD7606 Host computer protocol USB 2.0 Inter-chip communication protocol SPI comparator TLV3501 operational amplifier OPA277P Operating wavelength 1550nm Laser diameter 2mm

[0059] S2. Set up the measurement system and calibrate it;

[0060] The non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system was constructed. The photodetector unit and DSP signal processing module 11 were initialized. It was checked whether the photodetector unit was in place and working normally. It was checked whether the DSP signal processing module 11 was correctly programmed and whether it was working normally by running a running light. The optical path was calibrated to be coaxial and the beam was correctly illuminated to the correct position of the liquid crystal optical phased array 3 under test. All photodetectors were made to work in sequence. Under different temperatures and in different temperature scenarios, the photoelectric response gain and curve of different batches of photodetectors were tested. The time delay from the photodetector to the DSP signal processing module 11 was measured. The photodetector time delay table, gain difference table, gain compensation table and temperature compensation table were tested and calibrated.

[0061] The photoelectric detection unit includes: photodetector 10-1, photodetector 10-2, photodetector 10-3, and photodetector 10-4.

[0062] S3. Configure system parameters;

[0063] Configure the local photodetector delay table T1;

[0064] Configure local photodetector gain normalization parameters: The photodetector units of the same photodetector module are subjected to gain normalization processing and a unified gain standard value is calibrated.

[0065] Configure the local photodetector gain difference table G1: Based on the normalized standard value, configure the gain value of different detectors in the photodetector under different power beam illumination and the difference between the gain value and the normalized standard value, generate the gain difference table and configure it to the information processing unit.

[0066] Configure the local photodetector gain batch table G2;

[0067] Configure the local photodetector gain temperature compensation meter G3;

[0068] Generate the total supplementary table Gtotal = G1 + G2 + G3 for the local photodetector.

[0069] S4. Calculate the phase difference of the electric field vectors corresponding to the two outgoing beams B11 and B12 of the polarization beam splitter 9;

[0070] The two outgoing beams B11 and B12 from the polarizing beam splitter 9 are horizontally polarized (P-beam) and vertically polarized (S-beam), respectively, and correspond to the electric field vectors. and and The first Cartesian right-hand coordinate system that makes up the system After the two beams of light are collected by two corresponding photodetectors, they are sent to the DSP signal processing module 11 to calculate the relative phase modulation amount of the liquid crystal phased array 3 under test at this time.

[0071] The main control terminal 12 sequentially drives the liquid crystal optical phased array 3 under test with voltage code 0, and outputs the P-component of the beam emitted from the liquid crystal optical phased array 3 under test. With S-ray component After being acquired by the corresponding photodetector, the signal is amplified and sent to the analog-to-digital converter 11-4, where it is converted into a digital signal and then sent to the digital signal processing unit 11-6. The digital signal processing unit 11-6 calculates the following algorithm... and Phase difference:

[0072] The x-axis and y-axis are selected to be along the fast and slow axes of the quarter-wave plate 4, respectively, and the fast and slow axis directions of the liquid crystal optical phased array 3 under test are made at an angle of ±45° with the transmission axis of the polarizer 2.

[0073] The Jones vector of the linearly polarized light transmitted through polarizer 2 is In this coordinate system, the Jones matrix of the 1 / 4 wave plate 4 is Since the fast and slow axes of the liquid crystal optical phased array 3 under test form a 45° angle with the x-axis, the Jones matrix of the liquid crystal optical phased array 3 under test is: The polarization state E of the linearly polarized light after passing through the device under test and the quarter-wave plate 4 is:

[0074]

[0075] Where i represents the imaginary unit, and δ represents the phase difference between the fast and slow axes of the liquid crystal optical phased array 3 under test. After normalization, we get... It can be seen that the emitted light at this time is linearly polarized light. This can be determined through calculation. Simplification yields Therefore Then the phase difference between the P and S beams is calculated.

[0076] Where γ represents the angle between the polarized light vector and the four fast axes of the quarter-wave plate; Ex and Fy represent the magnitudes of the electric fields of the P and S rays, respectively.

[0077] S5. Determine the π phase compensation;

[0078] The phase obtained in step S4 may have ambiguity within the π period. This is because the photoelectric sensor can only collect beam amplitude information, which is equivalent to taking the absolute value of the variable for the algorithm. This leads to ambiguity in π-phase complementary phases such as tan45° and tan135°. To overcome the above problem, two optical paths are added. Since the beam was previously split into two beams by the depolarizing beam splitter, the beams entering the photodetectors (10-1, 10-2) and the beams entering the photodetectors (10-3, 10-4) have the same properties after splitting. This is equivalent to the beam passing through the 1 / 4 wave plate 4 being copied into two copies for parallel analysis. The analysis results of the two sides can be fused.

[0079] The depolarization beam splitter includes: a first depolarization beam splitter 5 and a second depolarization beam splitter 6.

[0080] The second depolarizing beam splitter 6 maintains polarization and equally divides the two beams. One beam, B22, after passing through the 45° polarization analyzer 8, emits an electric field vector of... The beam is collected by photodetector 10-3; the output electric field vector of another beam B21 after passing through the 135° polarization analyzer 7 is... The data was collected by a photodetector 10⁻⁴, resulting in the original coordinate system. A second Cartesian right-hand coordinate system rotated by 45°

[0081] The and The included angle is 45°. and The included angle is 135°, in the second Cartesian right-hand coordinate system. With the first Cartesian right-hand coordinate system The included angle is 45°, which is compared with the second Cartesian right-hand coordinate system. In and The magnitude of this value resolves the π-phase ambiguity problem and distinguishes the quadrant in which the polarization direction of the light emitted from the quarter-wave plate 4 lies. That is, in the coordinate system described above... The polarization state of the original beam can pass through the new coordinate system. Down and The length of the vector modulus distinguishes the quadrant in which its polarization direction lies, as follows:

[0082] 1) such as Figure 3 As shown, if Vector magnitude greater than If the vector magnitude is known, then the current-limiting diode 11-5 outputs a high level 1, and the polarization direction can be obtained in the first quadrant.

[0083] 2) such as Figure 4 As shown, if Vector magnitude is less than If the vector magnitude is determined, then the current-limiting diode 11-5 outputs a low level of 0, indicating that the polarization direction is in the second quadrant.

[0084] S6. Enables high-speed measurement of U-PHI;

[0085] In this embodiment, the phase difference information obtained based on steps S1 to S5 is temporarily stored in the RAM of the digital signal processing unit 11-6. During this period, the main control terminal 12 sends control of the liquid crystal optical phased array 3 under test by stepping from 0 to 255 voltage in increments of 1. Steps S1 to S5 are performed once for each transmission. After one transmission is completed, the flag bit is pulled high to inform the digital signal processing unit 11-6 of the cached result and to notify the main control terminal 12 to start the next transmission cycle.

[0086] After all 256 operations are completed, the flag is raised to notify the main control terminal 12. The DSP signal processing module 11 can also receive the main control command from the main control terminal 12 and continuously complete the phase-controlled voltage generation and signal processing in one go to achieve high-speed U-PHI measurement. The digital signal processing unit 11-6 sends the cached phase difference data to the main control terminal 12 through the communication protocol and interface between the upper and lower computers determined in step S1 for further data processing. It then lists the voltage and phase difference in parallel to obtain the complete voltage-phase relationship (U-PHI) truth table of the liquid crystal optical phased array 3 under test and uploads it to the main control terminal 12.

[0087] In this embodiment, the analog signals of the two orthogonal components of the light beam obtained by the two photodetectors (10-1, 10-2) in the DSP signal processing module 12 are converted into digital signals by the analog-to-digital converter 11-4 and then sent to the digital signal processing unit 11-6 to calculate the phase information of the light beam through the method in step S4. The signals collected by the other two photodetectors (10-3, 10-4) are compared by a comparator 11-1, and after passing through the current limiting diode 11-5, the output square wave is sent to the digital signal processing unit 11-6 to determine the quadrant in which the polarization direction of the light beam is located, thus solving the π phase ambiguity problem.

[0088] In this embodiment, the non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system uses the first depolarizing beam splitter 5 to maintain the polarization of the incident beam and split it into two paths with equal energy. One path is used to calculate the phase modulation magnitude of the liquid crystal phased array, and the other path is used to determine the phase ambiguity of the electric field vector π.

[0089] In this embodiment, all four photodetectors are initially calibrated using the built-in calibration table of the DSP signal processing module 12 to minimize system errors caused by the detectors.

[0090] In summary, the method of this invention, based on a small number of waveplates, optical crystals, and unit photodetectors, realizes a simple, low-cost, and highly controllable non-mechanical U-PHI high-speed measurement system for liquid crystal optical phased arrays. It also achieves one-click U-PHI testing of liquid crystal devices, completing one test in 1ms, improving testing time and accuracy, and greatly reducing human error caused by individual differences. This facilitates system integration, miniaturization, lightweighting, and low power consumption, accelerating batch testing and quality assurance of mass-produced products in the liquid crystal device industry, and is suitable for mass production equipment. The system described in this invention, based on a liquid crystal optical phased array spatial light modulator, can not only realize the entire static and non-mechanical process of U-PHI testing for liquid crystal phased arrays, but also complete ultra-large-scale and ultra-fine U-PHI testing in a very short time, greatly improving the efficiency and accuracy of U-PHI testing for liquid crystal devices such as liquid crystal optical phased arrays and liquid crystal cells. The method of this invention achieves one-click measurement and one-click generation of truth tables for U-PHI testing. Combined with optimization algorithms, it can also achieve one-click fitting and U-PHI data optimization, supporting multiple modes such as single-step measurement and batch measurement.

[0091] 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. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of the claims of the invention.

Claims

1. A non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system, comprising: Laser (1), polarizer (2), liquid crystal optical phased array under test (3), quarter wave plate (4), first depolarizing beam splitter (5), second depolarizing beam splitter (6), 135° polarization direction analyzer (7), 45° polarization direction analyzer (8), polarizing beam splitter (9), first photodetector (10-1), second photodetector (10-2), third photodetector (10-3), fourth photodetector (10-4), DSP signal processing module (11), main control terminal (12); The laser beam emitted from the laser (1) passes sequentially through the polarizer (2), the liquid crystal optical phased array under test (3), the quarter-wave plate (4), and the first depolarizing beam splitter (5). After passing through the first depolarizing beam splitter (5), the laser beam emitted from the laser (1) is split into two beams, B1 and B2. After passing through the polarizing beam splitter (9), beam B1 is split into two beams, B11 and B12. Beam B11 is emitted to the second photodetector (10-2), and the second photodetector (10-2) generates an electrical signal that is transmitted to the DSP signal processing module (11). Beam B12 is emitted to the first photodetector (10-1), and the first photodetector (10-1) generates an electrical signal that is transmitted to the DSP signal processing module (11). DSP signal processing module (11); After beam B2 passes through the second depolarization beam splitter (6), it is split into two beams B21 and B22. Beam B21 passes through the 135° polarization direction analyzer (7) and the fourth photodetector (10-4) in sequence. The fourth photodetector (10-4) generates an electrical signal that is transmitted to the DSP signal processing module (11). Beam B22 passes through the 45° polarization direction analyzer (8) and the third photodetector (10-3) in sequence. The third photodetector (10-3) generates an electrical signal that is transmitted to the DSP signal processing module (11). After the DSP signal processing module (11) processes the signal, it transmits it to the main control terminal (12).

2. The non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system according to claim 1, characterized in that, The DSP signal processing module (11) includes: a comparator (11-1), a first operational amplifier (11-2), a second operational amplifier (11-3), an analog-to-digital converter (11-4), a current-limiting diode (11-5), and a digital signal processing unit (11-6). The fourth photodetector (10-4) generates an electrical signal that is input to the non-inverting input of the comparator (11-1); the third photodetector (10-3) generates an electrical signal that is input to the inverting input of the comparator (11-1); the output of the comparator (11-1) is connected to the input of the current-limiting diode (11-5), and the output of the current-limiting diode (11-5) is connected to one end of the digital signal processing unit (11-6); the second photodetector (10-2) generates an electrical signal that is input to one end of the first operational amplifier (11-2), and the first operational amplifier... The other end of the amplifier (11-2) is connected to one end of the analog-to-digital converter (11-4); the first photodetector (10-1) generates an electrical signal that is transmitted to one end of the second operational amplifier (11-3), and the other end of the second operational amplifier (11-3) is connected to one end of the analog-to-digital converter (11-4); the other end of the analog-to-digital converter (11-4) is connected to one end of the digital signal processing unit (11-6); the other end of the digital signal processing unit (11-6) is connected to the main control terminal (12) and the liquid crystal optical phased array (3) under test respectively. The digital signal processing unit (11-6) includes: FPGA and STM32.

3. The non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system according to claim 1, characterized in that, The polarizer (2) has a polarization direction at 45° to the anchoring orientation of the liquid crystal optical phased array (3) under test, and the fast axis of the quarter wave plate (4) is parallel to the transmission axis of the polarizer (2). The polarizer (2), the liquid crystal optical phased array (3) under test and the quarter wave plate (4) together form an electronically controlled polarization rotator based on liquid crystal.

4. A non-mechanical liquid crystal optical phased array U-PHI high-speed measurement method applied to the measurement system of claim 1, comprising the following specific steps: S1. Determine system parameters; The parameters include: The operating wavelength of the liquid crystal phased array device under test is the same as that of the laser, the operational amplifier model and parameters, the analog-to-digital converter model, the comparator model, the digital signal processing unit chip model, the inter-chip communication protocol, and the communication protocol between the upper and lower computer. S2. Set up the measurement system and calibrate it; The non-mechanical liquid crystal optical phased array U-PHI high-speed measurement system was built, the photoelectric detection unit and DSP signal processing module (11) were initialized, and the photoelectric detection unit was checked to see if it was in place and working normally. The DSP signal processing module (11) was checked to see if it was correctly programmed and to see if it was working normally by running a running light. The optical path was corrected to be coaxial and the beam was correctly illuminated to the correct position of the liquid crystal optical phased array (3) under test. All photoelectric detectors were made to work in sequence. The photoelectric response gain and curve of different batches of photoelectric detectors were tested under different temperature scenarios. The time delay from the photoelectric detector to the DSP signal processing module (11) was measured. Complete the testing and calibration of the photodetector time delay table, gain difference table, gain compensation table, and temperature compensation table; The photoelectric detection unit includes: a first photodetector (10-1), a second photodetector (10-2), a third photodetector (10-3), and a fourth photodetector (10-4). S3. Configure system parameters; Configure the local photodetector delay table T1; Configure local photodetector gain normalization parameters: The photodetector units of the same photodetector module are subjected to gain normalization processing and a unified gain standard value is calibrated. Configure the local photodetector gain difference table G1: Based on the normalized standard value, configure the gain value of different detectors in the photodetector under different power beam illumination and the difference between the gain value and the normalized standard value, generate the gain difference table and configure it to the information processing unit. Configure the local photodetector gain batch table G2; Configure the local photodetector gain temperature compensation meter G3; Generate the total supplementary table for the local photodetector, Gtotal = G1 + G2 + G3; S4. Calculate the phase difference of the electric field vectors corresponding to the two outgoing beams B11 and B12 of the polarization beam splitter (9); The two outgoing beams B11 and B12 of the polarizing beam splitter (9) are horizontally polarized P-beam and vertically polarized S-beam, respectively, which correspond to the electric field vectors. and , and The first Cartesian right-hand coordinate system that makes up the system After the two beams of light are collected by two corresponding photodetectors, they are sent to the DSP signal processing module (11) to calculate the relative phase modulation amount of the liquid crystal phased array (3) under test at this time. The main control terminal (12) sequentially drives the liquid crystal optical phased array (3) under test with voltage code 0, and outputs the P-component of the beam of light emitted from the liquid crystal optical phased array (3) under test. With S-ray component After being acquired by the corresponding photodetector, the signal is amplified and sent to the analog-to-digital converter (11-4), converted into a digital signal, and then sent to the digital signal processing unit (11-6). The digital signal processing unit (11-6) calculates the signal using the following algorithm. and Phase difference: choose axis, The axes are respectively along the fast and slow axes of the 1 / 4 wave plate (4), and the fast and slow axis directions of the liquid crystal optical phased array (3) under test are at an angle of ±45° to the transmission axis of the polarizer (2); The Jones vector of the linearly polarized light transmitted through polarizer (2) is [ In this coordinate system, the Jones matrix of the 1 / 4 wave plate (4) is ; Due to the fast and slow axes of the liquid crystal optical phased array (3) under test being parallel to... The axis is at a 45° angle, and the Jones matrix of the liquid crystal optical phased array (3) under test is: The polarization state of linearly polarized light after passing through the device under test and the 1 / 4 wave plate (4) can be obtained. for: ； in, Represents the imaginary unit. This represents the phase difference between the fast axis and the slow axis of the liquid crystal optical phased array (3) under test; After normalization, we get It can be seen that the emitted light at this time is linearly polarized light. This can be determined through calculation. Simplification yields Therefore Then, the phase difference between the P and S beams is calculated; in, The angle between the polarized light vector and the fast axis of the quarter-wave plate (4) is shown. , The electric fields of P and S light are of appropriate magnitude; S5. Determine the π phase compensation; The second depolarizing beam splitter (6) maintains polarization and splits two beams equally. The output electric field vector of one beam, B22, after passing through the 45° polarization analyzer (8) is: The light is collected by the third photodetector (10-3); the output electric field vector of the other beam B21 after passing through the 135° polarization analyzer (7) is... The data was collected by the fourth photodetector (10-4), resulting in the original coordinate system. A second Cartesian right-hand coordinate system rotated by 45° ; The and The included angle is 45°. and The included angle is 135°, in the second Cartesian right-hand coordinate system. With the first Cartesian right-hand coordinate system The included angle is 45°, which is compared with the second Cartesian right-hand coordinate system. In and The size of the waveplate (4) is used to solve the problem of π phase ambiguity and to distinguish the quadrant in which the polarization direction of the emitted light is located; that is, in the coordinate system The polarization state of the original beam can pass through the new coordinate system. Down and The length of the vector modulus distinguishes the quadrant in which its polarization direction lies, as follows: 1) If the current-limiting diode (11-5) outputs a high level 1, then the polarization direction can be obtained in the first quadrant; 2) If the current-limiting diode (11-5) outputs a low level of 0, then the polarization direction can be determined to be in the second quadrant; S6. Enables high-speed measurement of U-PHI; The phase difference information obtained in steps S1-S5 is temporarily stored in the RAM of the digital signal processing unit (11-6). During this period, the main control terminal (12) increments the voltage step by step. Send control to the liquid crystal optical phased array under test (3). Each time it is sent, steps S1~S5 are performed. After one execution is completed, the flag bit is pulled up to inform the digital signal processing unit (11-6) to cache the result and notify the main control terminal (12) to start the next transmission cycle. After all N voltage transmissions have been completed, the flag bit is pulled high to inform the main control terminal (12), or the DSP signal processing module (11) receives the main control instruction from the main control terminal (12) and completes the phase control voltage generation and signal processing in one continuous operation to achieve high-speed measurement of U-PHI. The digital signal processing unit (11-6) sends the cached phase difference data to the main control terminal (12) through the communication protocol and interface between the upper and lower computers determined in step S1 for further data processing. The voltage and phase difference are listed in parallel to obtain the complete voltage-phase relationship U-PHI truth table of the liquid crystal optical phased array (3) under test, and then uploaded to the main control terminal (12).

5. The high-speed measurement method for non-mechanical liquid crystal optical phased array U-PHI according to claim 4, characterized in that, The analog signals of the two orthogonal components of the light beam obtained by the first and second photodetectors (10-1, 10-2) in the DSP signal processing module (12) are converted into digital signals by the analog-to-digital converter (11-4) and then sent to the digital signal processing unit (11-6) to calculate the phase information of the light beam through the method in step S4. The signals collected by the third and fourth photodetectors (10-3, 10-4) are compared by a comparator (11-1), and after passing through the current limiting diode (11-5), the output square wave is sent to the digital signal processing unit (11-6) to determine the quadrant in which the polarization direction of the light beam is located, thus solving the π phase ambiguity problem.

Images