Angle resolving method based on liquid crystal polarization grating-liquid crystal optical phased array cascade system

Abstract

The invention discloses an angle resolving method based on a liquid crystal polarization grating-liquid crystal optical phased array cascade system, and the method comprises the steps: obtaining the total angle information of the cascade system and the deflection angle information of N levels of liquid crystal polarization gratings, the N levels of angle information forming an initial set, and N being a natural number; performing angle calculation by using a depth-first backtracking algorithm, and searching an optimal combination through recursive search; and after all the recursive search paths are explored, obtaining a finally stored optimal combination, and generating a corresponding control signal sequence based on positive and negative values in the optimal combination. Through parameterized configuration and constraint pruning, adaptive angle decomposition is carried out on a cascade system with any series and any angle configuration, the curing defect of a traditional FPGA hard coding table look-up scheme is avoided, and the method has the advantages of being high in resolving efficiency, high in adaptability, easy to achieve in engineering and the like.

Description

Technical Field

[0001] This application belongs to the field of optical phased array technology, and in particular relates to an angle calculation method based on a liquid crystal polarization grating-liquid crystal optical phased array cascade system. Background Technology

[0002] Traditional mechanical beam deflection systems (such as gimbals and fast-reflecting mirrors) suffer from drawbacks such as large size, high inertia, and slow response (milliseconds), making it difficult to meet the high-precision dynamic tracking requirements of modern space communication, lidar, and other scenarios. Non-mechanical beam deflection technologies have thus emerged, including: Liquid crystal optical phased array (LC-OPA): It modulates the phase of the light beam by arranging liquid crystal molecules in an electronically controlled manner, achieving continuous deflection with micro-radian precision. However, the deflection angle of a single stage is usually limited to within ±5°, making it difficult to cover a large angle range.

[0003] Liquid crystal polarization grating (LCPG): Based on the principle of geometric phase, it can efficiently diffract circularly polarized light (>99.5%) to a fixed angle (such as ±50°), but it only supports discrete deflection and cannot be continuously controlled.

[0004] To address the limitations of single devices, cascading LCPGs and LC-OPAs has emerged as a new solution: LCPG cascade: By stacking N LCPGs with half-wave plate switches, 2^N discrete large-angle deflections (such as ±50°) in one or two dimensions can be achieved, supporting non-mechanical and inertial scanning.

[0005] LC-OPA fine control: Based on the coarse deflection of LCPG, micro-radius level continuous correction is achieved through liquid crystal phase shifter array, improving pointing accuracy to 10 urad.

[0006] Cascaded systems, which use traditional FPGA hard-coding to solve angles, suffer from poor versatility due to the binding of logic to the system, difficulty in modifying logic development, and high development difficulty. Summary of the Invention

[0007] The purpose of this application is to overcome the shortcomings of the prior art and provide an angle calculation method based on a cascaded system of liquid crystal polarization grating-liquid crystal optical phased array. By applying it to the cascaded system of liquid crystal optical phased array-liquid crystal polarization grating, the angle calculation of the cascaded system with adaptive order and hardware polarization grating angle is realized.

[0008] The objective of this application is achieved through the following technical solution: An angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system, the method comprising: Obtain the total angle information of the cascaded system and the deflection angle information of the N-level liquid crystal polarization gratings. The N-level angle information forms an initial set, where N is a natural number. An angle calculation is performed using a depth-first backtracking algorithm, and the optimal combination is found through recursive search. After all recursive search paths have been explored, the final optimal combination is obtained and saved. Based on the positive or negative value in the optimal combination, the corresponding control signal sequence is generated.

[0009] Furthermore, the angle calculation using a depth-first backtracking algorithm, and the search for the optimal combination through recursive search, includes: Traverse the initial set, filter out the series that participate in angle decomposition according to the current system configuration, select the base deflection angle of the series from the initial set as the effective value, form an effective set, and form a candidate set with each value and corresponding negative value in the effective set. Using an initially empty combination and an initial index position as input, a recursive search is performed. A candidate value is selected from the candidate set in sequence and added to the combination. The updated combination and the next index position are used to enter the next level of search until the size of the combination reaches the level. Once all candidate values ​​in a recursive layer have been tried, remove the values ​​added in this layer from the current combination, and then return to the previous recursive layer.

[0010] Furthermore, the method also includes a mutual exclusion constraint check when performing a recursive search, the mutual exclusion constraint check including: Check if the absolute value of the candidate value is the same as the absolute value of any existing value in the current combination. If they are the same, it is determined that the constraint is violated, the candidate value is abandoned, and the next candidate value is tried.

[0011] Furthermore, the method also includes a uniqueness constraint check when performing a recursive search, the uniqueness constraint check including: Check if the number of times the absolute value of the candidate value appears in the current combination exceeds the number of times the absolute value of the candidate value appears in the initial set. If it exceeds, it is determined to be a violation of the constraint, the candidate value is abandoned, and the next candidate value is tried.

[0012] Furthermore, the method also includes: Calculate the residual error between the algebraic sum of the optimal combination and the target value to determine whether the angle solution meets the error constraint.

[0013] Furthermore, the method also includes: A preset tolerance parameter is used to calculate the allowable error range at a limited angle. When the residual error is less than or equal to the tolerance parameter, it is determined that the error constraint is met.

[0014] Furthermore, the method also includes: When it is necessary to improve the solution accuracy, decrease the tolerance parameter; when it is necessary to speed up the solution, increase the tolerance parameter.

[0015] The beneficial effects of this application are as follows: This invention first obtains the total control angle of the cascaded system. Then, based on the cascaded system hierarchy, the deflection angles of each liquid crystal polarization grating, and the deflection angle range of the liquid crystal optical phased array, a depth-first search backtracking algorithm is used to calculate the control angles of each level of the cascaded system from the total angle. The method of this invention, through an improved backtracking algorithm applied to a liquid crystal optical phased array-liquid crystal polarization grating cascaded system, achieves adaptive hierarchy cascaded system angle calculation, providing a highly efficient and versatile angle calculation method for liquid crystal optical phased array-liquid crystal polarization grating cascaded systems. Attached Figure Description

[0016] Figure 1 This is a flowchart of the angle calculation method based on the cascaded liquid crystal polarization grating-liquid crystal optical phased array system of the present invention; Figure 2 This is a flowchart of the recursive search process of this invention. Detailed Implementation

[0017] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0018] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Cascaded systems, which use traditional FPGA hard-coding to solve angles, suffer from poor versatility due to the binding of logic to the system, difficulty in modifying logic development, and high development difficulty.

[0020] To address the aforementioned technical problems, the following embodiments of an angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system are proposed in this application.

[0021] Reference Figure 1 ,like Figure 1 The diagram shown is a flowchart of an angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system provided in this embodiment. The method includes the following steps: S1: Obtain the total angle information and liquid crystal polarization grating deflection angle information of the cascaded system.

[0022] In this embodiment, based on the Xilinx ZYNQ xc7z020clg400-1 chip, a serial communication module is implemented using the FPGA resources on the PL side to communicate with the host computer to obtain the target total deflection angle. There are N levels of liquid crystal polarization gratings, each corresponding to an angle information level. These N levels of angle information form an initial set, describing the angle information of each level of the liquid crystal polarization grating in the cascaded system, obtained from a configuration table embedded in the BRAM resources on the PL side. After clarifying the data source and considering the data routing path, the target total deflection angle and the liquid crystal polarization grating levels and angle information are connected to the AXI-HP interface of the ARM on the PS side via the AXI bus interface module on the PL side. This interface is connected to the chip's internal memory management module, which automatically pushes data to a specific address memory cell in the on-board SDRAM chip, waiting for the PS side ARM's calculation algorithm to retrieve it.

[0023] S2: Use a depth-first backtracking algorithm to calculate the angle and find the optimal combination through recursive search.

[0024] In this embodiment, firstly, valid values ​​are filtered out. The initial set is traversed, and the level K that participates in the angle decomposition is determined according to the current system configuration. The basic deflection angle of the specified level K is selected from the initial set as valid values, forming an effective set containing M valid values, where M≤N.

[0025] Then, a candidate set is constructed based on the valid set. For each value v in the valid set, its own value v and its negative value -v are added to the candidate set. Therefore, the size of the candidate set is 2*M.

[0026] Then, a recursive search is initiated, taking an empty current combination and an initial index position (usually 0) as input.

[0027] Note the iterative selection and constraint checks. In each level of recursion, select a candidate value from the candidate set sequentially and attempt to add it to the current combination. Before adding, perform the following constraint checks: 1. Mutual Exclusion Constraint: Check if the absolute value of the candidate value is the same as the absolute value of any existing value in the current combination. If they are the same, it is considered a violation of the constraint, the candidate value is abandoned, and the next candidate value is tried. This step ensures that only one of the two states (positive or negative) of each basic value is selected.

[0028] 2. Uniqueness Constraint: Check if the absolute value of the candidate value appears more times in the current combination than it appears more times in the initial set. If it does, the constraint is violated. This step handles the case of duplicate values ​​that may exist in the initial set.

[0029] Then, the recursion continues. If a candidate value passes all constraint checks, it is formally added to the current combination. The search function is then recursively called with the updated current combination and the next index position as parameters to enter the next level of search.

[0030] Determine and evaluate the termination condition. The termination condition for recursion is defined as the size of the current combination reaching a preset level K. When the termination condition is met: 1. Calculate the algebraic sum (Sum) of all values ​​in the current combination.

[0031] 2. Calculate the absolute error between this algebraic sum and the total deflection angle of the target (Error = |Target Value - Sum|).

[0032] 3. Compare this absolute error with the minimum error of a globally recorded set. If the current error is smaller, update the minimum error to this current error and save the current combination as the new optimal combination.

[0033] Among them, the preset error tolerance parameter Used to limit the allowable error range for angle calculation. The preset error threshold is used; when the condition is met... When the current combination is determined to satisfy the error constraint, it can be saved as a candidate optimal combination or the search can be terminated early. The error tolerance parameter... The value of affects the pruning strength and the number of iterations in the backtracking search. A larger value makes it easier to meet error constraints and reduces the number of iterations. Smaller values ​​result in higher solution accuracy but increase the number of iterations.

[0034] Finally, backtracking is performed. Once all candidate values ​​in a given recursive level have been tried, the value added in this level is removed from the current combination, and the function returns to the previous recursive level. This "backtracking" step allows the algorithm to explore all possible combination paths.

[0035] S3: After all recursive search paths have been explored, the final optimal combination is obtained and the corresponding control signal sequence is generated based on the positive or negative value of the optimal combination.

[0036] For example, when the cascaded system has a series K=3 in the angular decomposition, the corresponding basic deflection angles are respectively The optimal combination was obtained through backtracking. When the polarity control signal sequence is +1, -1, +1, the first bit (+1) indicates that the first-stage liquid crystal polarization grating is selected for positive deflection, the second bit (-1) indicates that the second stage is selected for negative deflection, and the third bit (+1) indicates that the third stage is selected for positive deflection. This control signal sequence is output to the downstream drive module to realize the corresponding cascaded deflection direction configuration.

[0037] In this embodiment, the setting of the system cascade layer number and tolerance parameter affects the number of iterations of the backtracking algorithm. By changing the system cascade layer number and tolerance parameter and comparing the results, it can be seen that under different parameter conditions, the backtracking algorithm of the present invention can obtain angle calculation results that satisfy the error constraints.

[0038] In summary, the method of this invention achieves adaptive angle calculation for arbitrary cascades by applying an improved backtracking algorithm to a cascaded liquid crystal optical phased array-liquid crystal polarization grating system. Based on a depth-first search algorithm without changing the program, this technical solution embodies the core technical features of this invention.

[0039] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system, characterized in that, The method includes: Obtain the total angle information of the cascaded system and the deflection angle information of the N-level liquid crystal polarization gratings. The N-level angle information forms an initial set, where N is a natural number. An angle calculation is performed using a depth-first backtracking algorithm, and the optimal combination is found through recursive search. After all recursive search paths have been explored, the final optimal combination is obtained and saved. Based on the positive or negative value in the optimal combination, the corresponding control signal sequence is generated.

2. The angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system as described in claim 1, characterized in that, The angle calculation using a depth-first backtracking algorithm, and the search for the optimal combination through recursive search, includes: Traverse the initial set, filter out the series that participate in angle decomposition according to the current system configuration, select the base deflection angle of the series from the initial set as the effective value, form an effective set, and form a candidate set with each value and corresponding negative value in the effective set. Using an initially empty combination and an initial index position as input, a recursive search is performed. A candidate value is selected from the candidate set in sequence and added to the combination. The updated combination and the next index position are used to enter the next level of search until the size of the combination reaches the level. Once all candidate values ​​in a recursive layer have been tried, remove the values ​​added in this layer from the current combination, and then return to the previous recursive layer.

3. The angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system as described in claim 2, characterized in that, The method also includes mutual exclusion constraint checking when performing recursive search, and the mutual exclusion constraint checking includes: Check if the absolute value of the candidate value is the same as the absolute value of any existing value in the current combination. If they are the same, it is determined that the constraint is violated, the candidate value is abandoned, and the next candidate value is tried.

4. The angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system as described in claim 2, characterized in that, The method also includes a uniqueness constraint check when performing a recursive search. The uniqueness constraint check includes: Check if the number of times the absolute value of the candidate value appears in the current combination exceeds the number of times the absolute value of the candidate value appears in the initial set. If it exceeds, it is determined to be a violation of the constraint, the candidate value is abandoned, and the next candidate value is tried.

5. The angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system as described in claim 1, characterized in that, The method further includes: Calculate the residual error between the algebraic sum of the optimal combination and the target value to determine whether the angle solution meets the error constraint.

6. The angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system as described in claim 5, characterized in that, The method further includes: A preset tolerance parameter is used to calculate the allowable error range at a limited angle. When the residual error is less than or equal to the tolerance parameter, it is determined that the error constraint is met.

7. The angle calculation method based on a cascaded liquid crystal polarization grating-liquid crystal optical phased array system as described in claim 6, characterized in that, The method further includes: When it is necessary to improve the solution accuracy, decrease the tolerance parameter; when it is necessary to speed up the solution, increase the tolerance parameter.

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