A phase control system and method for common aperture coherent synthesis
By using neural networks to predict phase and adjust laser delay in common aperture coherent synthesis systems, the problem that traditional phase control methods are difficult to compensate in complex noise environments is solved, and efficient and stable coherent synthesis laser output and system bandwidth improvement are achieved.
Patent Information
- Application Number
- CN202411244188.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-06
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2044-09-06
AI Technical Summary
In common aperture coherence synthesis, traditional active phase control methods have problems such as poor path expansion and high system complexity, making it difficult to quickly and accurately perform dynamic compensation of phase noise in complex noise environments, especially deep learning algorithms based on images Inversion phase is difficult to apply to co-aperture coherence synthesis of completely overlapping far and near field spots.
Provide a phase control system including a laser module, a synthesis module, a detection module, a phase control model and a delay controller. The phase control model obtained by neural network training predicts the phase of each beam of laser, and uses a delay controller to adjust the laser through liquid crystal. The delay enables phase adjustment and improves the beam intensity of the synthetic laser.
The phase adjustment of each beam split laser is realized, the power of the synthetic laser is increased, the control bandwidth and intelligence level of the system are improved, and the phase compensation can be performed quickly and accurately in complex environments, which is suitable for coherent synthesis of common apertures.
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Figure CN118763492B_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of coherent synthesis, and in particular to a phase control system and method for common-aperture coherent synthesis. Background Art
[0002] Coherent synthesis technology can maintain beam quality while increasing laser power, and is an effective technical path to break through the single-aperture output power limit of high-energy lasers. Due to the influence of various factors such as thermal effects, mechanical vibrations, airflow disturbances, and power supply noise, the phase of the laser is constantly changing, and active phase-locking methods are usually required to control the phase synchronization of each laser to obtain efficient and stable synthetic lasers. Therefore, active phase control is the key technology of coherent synthesis, and the complex noise environment puts forward high-bandwidth requirements for the control system, and phase noise needs to be dynamically compensated quickly and accurately.
[0003] Traditional active phase methods include stochastic parallel gradient descent (SPGD) algorithm, multi-jitter method, heterodyne detection method, interference fringe measurement method, etc. These methods have problems such as poor path scalability or high system complexity. Deep learning algorithms are expected to solve the above difficulties and have been verified in simulation and experiments. However, deep learning algorithms are based on image inversion phase and are usually used for aperture coherent synthesis. They are difficult to apply to common aperture coherent synthesis where far and near field spots completely overlap. Summary of the invention
[0004] The purpose of the present application is to provide a phase control system and method for common-aperture coherent synthesis, which can improve the power of the synthesized laser.
[0005] To achieve the above objectives, this application provides the following solutions:
[0006] In a first aspect, the present application provides a phase control system for common aperture coherent synthesis, comprising: a laser module, a synthesis module, a detection module, a phase control model, a delay controller, a liquid crystal and a phase modulator;
[0007] The laser module is used to split the seed laser, each split laser passes through one of the phase modulators, and the laser module is also used to amplify and collimate the laser after passing through the phase modulator and then output it;
[0008] The synthesis module is used to perform common aperture synthesis on each laser beam output by the laser module and then output it;
[0009] The detection module is used to sample each laser beam output by the laser module, each sampled laser beam is focused after passing through the liquid crystal, and a sub-aperture synthetic spot image is generated according to the focused laser beam; the number of the liquid crystals is the same as the number of the phase modulators, and each sampled laser beam corresponds to one liquid crystal;
[0010] The detection module is also used to sample the synthetic laser output by the synthesis module and collect the beam intensity of the sampled synthetic laser;
[0011] The delay controller is used to adjust the delay of each laser beam by adjusting each liquid crystal according to the intensity of the light beam, so as to maximize the intensity of the light beam collected by the detection module;
[0012] The phase control model is used to output the predicted phase of each laser beam according to the aperture-divided synthetic spot image; the phase control model is obtained by training a neural network;
[0013] Each of the phase modulators is used to adjust the phase of the corresponding split laser beam to the corresponding predicted phase.
[0014] Optionally, the laser module includes a beam splitter, N laser amplifiers and N collimators, N is the number of paths in which the beam splitter splits the seed laser, and each split laser beam passes through a phase modulator, a laser amplifier and a collimator in sequence.
[0015] Optionally, the N collimators are arranged in a preset array, and the preset array arrangement includes a one-dimensional array arrangement and a two-dimensional array arrangement.
[0016] Optionally, the synthesis module includes a common-aperture beam combiner, and the common-aperture beam combiner is used to perform common-aperture synthesis on each laser beam output by the laser module.
[0017] Optionally, the detection module includes a first sampling mirror and a second sampling mirror;
[0018] The first sampling mirror is used to sample each laser beam output by the laser module;
[0019] The second sampling mirror is used to sample the synthetic laser output by the synthesis module.
[0020] Optionally, the detection module includes a focusing lens and a photodetector;
[0021] The focusing lens is used to focus the laser output by each liquid crystal;
[0022] The photoelectric detector is used to collect the beam intensity of the sampled synthetic laser.
[0023] Optionally, the detection module includes a camera, and the camera is used to generate a sub-aperture synthetic spot image according to the focused laser.
[0024] Optionally, in terms of adjusting the delay of each laser beam by adjusting each liquid crystal according to the intensity of the light beam to maximize the intensity of the light beam collected by the detection module, the delay controller is specifically used to:
[0025] A random parallel gradient descent algorithm is used to adjust the delay of each laser beam by adjusting each liquid crystal according to the intensity of the light beam, so as to maximize the intensity of the light beam collected by the detection module.
[0026] Optionally, the execution rate of the phase control model is 10 times the execution rate of the delay controller.
[0027] In a second aspect, the present application provides a phase control method for co-aperture coherent synthesis, wherein the phase control method for co-aperture coherent synthesis applies the phase control system for co-aperture coherent synthesis, and the phase control method for co-aperture coherent synthesis includes:
[0028] Enable the phase control model and delay controller;
[0029] When the intensity of the light beam collected by the detection module changes from small to large and maintains the maximum value setting time in the process of changing from small to large, the phase adjustment is completed and the delay controller is turned off.
[0030] According to the specific embodiments provided in this application, this application discloses the following technical effects:
[0031] The present application provides a phase control system and method for common-aperture coherent synthesis, which outputs the predicted phase of each laser beam according to the aperture-synthesized spot image; the phase control model is obtained by training the neural network; each phase modulator is used to adjust the phase of the corresponding split laser to the corresponding predicted phase, and the delay controller adjusts the delay of each laser beam by adjusting each liquid crystal according to the beam intensity, so as to maximize the beam intensity collected by the detection module, thereby realizing phase adjustment of each split laser beam, thereby obtaining a synthetic laser with maximized beam intensity and improving the power of the synthetic laser. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0033] Figure 1A schematic diagram of the structure of a phase control system for common aperture coherent synthesis provided in one embodiment of the present application;
[0034] Figure 2 A schematic diagram of the simulation effect of coherent synthesis of light beams provided in an embodiment of the present application, wherein (a) is a schematic diagram of the simulation effect of coherent synthesis of 4 light beams with separate apertures, (b) is a schematic diagram of the simulation effect of coherent synthesis of 4 light beams with a common aperture, (c) is a schematic diagram of the simulation effect of coherent synthesis of 16 light beams with separate apertures, and (d) is a schematic diagram of the simulation effect of coherent synthesis of 16 light beams with a common aperture.
[0035] Reference numerals:
[0036] 1-seed laser, 2-beam splitter, 3-phase modulator, 4-laser amplifier, 5-collimator, 6-first sampling mirror, 7-common aperture beam combiner, 8-second sampling mirror, 9-photodetector, 10-delay controller, 11-liquid crystal, 12-focusing lens, 13-camera, 14-phase control model, P1-one-dimensional array arrangement, P2-common aperture synthetic image, P3-spot image. DETAILED DESCRIPTION
[0037] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0038] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0039] The present application provides a phase control system for common aperture coherent synthesis, such as Figure 1 As shown, the phase control system for common aperture coherent synthesis includes: a laser module, a synthesis module, a detection module, a phase control model 14, a delay controller 10, a liquid crystal 11 and a phase modulator 3.
[0040] The laser module is used to split the seed laser 1, and each split laser beam passes through one of the phase modulators 3. The laser beam passing through the phase modulator 3 is amplified and collimated before being output.
[0041] The synthesis module is used to perform common aperture synthesis on each laser beam output by the laser module and then output it.
[0042] The detection module is used to sample each laser beam output by the laser module. Each sampled laser is focused after passing through the liquid crystal 11, and a synthetic spot image with a sub-aperture is generated according to the focused laser. The number of the liquid crystals 11 is the same as the number of the phase modulators 3, and each laser beam after sampling corresponds to one liquid crystal 11.
[0043] The detection module is also used to sample the synthetic laser output by the synthesis module and collect the beam intensity of the sampled synthetic laser.
[0044] The delay controller 10 is used to adjust the delay of each laser beam by adjusting each liquid crystal 11 according to the intensity of the beam, so as to maximize the intensity of the beam collected by the detection module. The delay controller 10 outputs an electrical signal.
[0045] The phase control model 14 is used to output the predicted phase of each laser beam according to the aperture-divided synthetic spot image; the phase control model 14 is obtained by training a neural network.
[0046] Each of the phase modulators 3 is used to adjust the phase of the corresponding split laser beam to the corresponding predicted phase.
[0047] The purpose of phase control in this application is to keep the phase of each light beam consistent, and the phase control model 14 can obtain the phase value of each light beam according to the aperture synthetic spot image, so as to calculate how the phase of each light beam should be compensated according to the phase output by the phase control model 14. For example, if there are two light beams with actual phases of φ10 and φ20 respectively, and the phase control model 14 predicts the phases to be φ1 and φ2, then the phases after compensation will be φ10-φ1 and φ20-φ2. If the prediction result is accurate, there will be no phase difference between the two light beams after compensation, and phase synchronization is completed.
[0048] The present application mainly relates to active phase control of common-aperture coherent synthesis. After the array is collimated and emitted and before entering the common-aperture combiner 7, the light beam is sampled to obtain a synthetic light spot with a divided aperture, so that the image processing neural network can be applied to the phase control technology of common-aperture synthesis. The bandwidth depends on the phase-locking time of the system, that is, the shorter the time required for phase locking, the higher the control bandwidth. Since the neural network can realize one-step phase prediction and compensation, the number of control steps is greatly reduced compared to other iterative control algorithms, so the present application improves the control bandwidth of the phase-locked system.
[0049] The phase modulators described in the present application are used to adjust the phase of the corresponding split laser to the corresponding predicted phase. The delay controller adjusts the delay of each laser beam by adjusting each liquid crystal according to the beam intensity, so as to maximize the beam intensity collected by the detection module, thereby achieving the phase condition of each split laser beam, thereby obtaining a synthetic laser with maximized beam intensity, improving the power of the synthetic laser, and by adjusting the phase of each split laser beam, an efficient and stable synthetic laser can be obtained.
[0050] The laser module includes a beam splitter 2, N laser amplifiers 4 and N collimators 5, where N is the number of split laser beams after the beam splitter 2 splits the seed laser 1, and each split laser beam passes through a phase modulator 3, a laser amplifier 4 and a collimator 5 in sequence.
[0051] In the present application, the phase control model 14, the delay controller 10, N phase modulators 3, and N liquid crystals 11 constitute a control module.
[0052] The N collimators 5 are arranged in a preset array, and the preset array includes a one-dimensional array P1 and a two-dimensional array.
[0053] The synthesis module includes a common aperture beam combiner 7, which performs common aperture synthesis on the laser beams output by the laser module. The common aperture synthesized image P2 is as follows: Figure 1 shown.
[0054] The detection module includes a first sampling mirror 6 and a second sampling mirror 8 .
[0055] The first sampling mirror 6 is used to sample each laser beam output by the laser module.
[0056] The second sampling mirror 8 is used to sample the synthetic laser output by the synthesis module.
[0057] The detection module includes a focusing lens 12 and a photodetector 9 .
[0058] The focusing lens 12 is used to focus the laser light output by each liquid crystal 11 .
[0059] The photoelectric detector 9 is used to collect the intensity of the sampled synthetic laser beam.
[0060] The detection module includes a camera 13, and the camera 13 is used to generate a sub-aperture synthetic spot image P3 according to the focused laser.
[0061] In the present application, the role of the liquid crystal 11 is essentially to adjust the phase, because different delays are ultimately manifested in different phases, and synchronization needs to be adjusted. The liquid crystal 11 is equivalent to a slow phase modulator 3, but can conveniently regulate spatial light.
[0062] Specifically, the seed laser 1 is divided into N paths after passing through the beam splitter 2, and each path of laser light passes through the phase modulator 3 and the laser amplifier 4 respectively, and is finally emitted and output by the collimator 5. The collimator 5 is arranged in a certain array manner, and the array beam is incident on the common aperture synthesizer. After a certain beam combining structure, each beam overlaps in the near field and is combined into a laser beam for output. Before entering the common aperture synthesizer, a first sampling mirror 6 is placed to sample all the array beams. After the sampled beam passes through the liquid crystal 11 and the focusing lens 12, the camera 13 records the aperture synthesis spot image P3 for input into the phase control model 14 for phase control. After the common aperture synthesizer, a second sampling mirror 8 is provided. The photodetector 9 obtains the sampling beam intensity and inputs it into the delay controller 10, driving each liquid crystal 11 to adjust the delay of each optical path. The delay controller 10 is electrically connected to the photodetector 9 and each liquid crystal 11, and the phase control model 14 is electrically connected to the camera 13 and the phase modulator 3, and the rest is an optical path.
[0063] In this optical system, due to the structure of the common aperture beam combiner 7, the optical path of each light beam from the spatial emission position to the combined laser beam is different. The sub-aperture composite beam at the camera 13 and the common aperture composite beam at the photodetector 9 have different delay distributions (resulting in different phase distributions). The delay needs to be regulated so that when the light spot at the camera 13 is phase synchronized, the light spot at the photodetector 9 is also phase synchronized. Usually, the optical path delay does not change with time. It only needs to be adjusted at the system startup stage, and the voltage signal on each liquid crystal 11 is solidified, and the delay control can be turned off later.
[0064] In terms of adjusting the delay of each laser beam by adjusting each liquid crystal 11 according to the intensity of the light beam to maximize the intensity of the light beam collected by the detection module, the delay controller 10 is specifically used to: adopt a random parallel gradient descent algorithm to adjust the delay of each laser beam by adjusting each liquid crystal 11 according to the intensity of the light beam to maximize the intensity of the light beam collected by the detection module, specifically including:
[0065] (1) A random small disturbance is applied to each liquid crystal 11, and the phase-locked loop will quickly adjust the voltage of the phase modulator 3 to compensate for the phase change caused by the small disturbance, so that the light spot at the camera 13 is always in the best synthesis state. The voltage of the photodetector 9 changes due to the change of the voltage of the phase modulator 3.
[0066] (2) According to the voltage change of the photodetector 9, the electrical signal on each liquid crystal 11 is updated to adjust the delay.
[0067] (3) Repeat the above steps (1) to (2).
[0068] After several iterative steps, the voltage signal on the photodetector 9 reaches the maximum, the delay adjustment is completed, and the coherent synthesis system of the present application can operate normally. When the camera 13 is phase-locked, the spot at the photodetector 9 also reaches a phase-locked state, so that the phase control of the common aperture synthesis can be performed by detecting and sampling the aperture spot image. The voltage signal on the photodetector 9 reaches the maximum, which means that the voltage signal changes from small to large. When the voltage signal value does not change after a set time, it is considered that the voltage signal has reached the maximum.
[0069] The phase control of this application adopts a deep learning algorithm. By building a neural network, the mapping relationship between image and phase is learned. After training convergence, fast and accurate phase compensation can be achieved, and phase-locked control can be completed in a very small number of steps. The neural network used in the phase control model is VGG, ResNet or UNet, etc., in which the number of network layers and the number of nodes need to be reasonably selected and appropriately modified for coherent synthesis applications. Each sample in the training set of the neural network training includes input data and label data. The input data is the spot image, and the label data is the phase of each light beam. The phase output by the specific phase control model is based on a fixed light beam as a reference, and the phase difference of the other beams relative to this beam, that is, the spot image synthesized by N beams, outputs N-1 predicted phases.
[0070] The execution rate of the phase control model 14 is 10 times the execution rate of the delay controller 10 .
[0071] In an exemplary embodiment, 4-way and 16-way coherent beam combination are simulated. Figure 2 (a) and (b) are 4-way coherent beam synthesis, (c) and (d) are 16-way coherent beam synthesis, (a) and (c) are sub-aperture coherent synthesis, (b) and (d) are common aperture coherent synthesis, the execution rate of phase control model 14 is set to 600Hz, and the delay control adopts SPGD algorithm with an execution rate of 60Hz. The difference between the two is 10 times to ensure that each time the delay control is performed, the sub-aperture synthesis spot at the camera 13 has completed phase locking. Phase control model 14 can compensate the phase in a single step and has a high control bandwidth. Figure 2 The moment when the efficiency drops in (a) and (b) corresponds to the moment when the delay controller 10 changes the control signal on each liquid crystal 11. After multiple iterative controls, both 4-way and 16-way coherent synthesis can achieve maximum efficiency, indicating the effectiveness of the delay adjustment and phase control algorithms. The simulation verifies that the present application can use the deep learning algorithm in the common aperture coherent synthesis system.
[0072] Compared with the traditional deep learning coherent synthesis algorithm, the solution proposed in this application expands the scope of application of the algorithm and can be used for common-aperture coherent synthesis systems with completely overlapping light spots, thereby improving the control bandwidth of common-aperture synthesis and the intelligence level of the system.
[0073] In an exemplary embodiment, the present application provides a phase control method for co-aperture coherent synthesis, the phase control method for co-aperture coherent synthesis applies the phase control system for co-aperture coherent synthesis, and the phase control method for co-aperture coherent synthesis includes:
[0074] Step 101: Start the phase control model and the delay controller.
[0075] Turn on the phase control of the phase control model and keep it. The purpose of this step is to keep the light beam at the camera in a phase-locked state at all times. The execution rate of the phase control model should be much higher than the execution rate of the delay controller to ensure that the light spot at the camera is in a phase-locked state every time the delay is adjusted.
[0076] The delay controller is turned on to iteratively adjust the control voltage of each liquid crystal to compensate for the optical path delay. The signal intensity of the photodetector represents the efficiency of the common aperture synthesis and is used as the input of the delay controller.
[0077] Step 102: When the intensity of the light beam collected by the detection module increases from small to large and maintains the maximum value setting time during the process of increasing from small to large, the phase adjustment is completed and the delay controller is turned off.
[0078] When the beam intensity is maximum, the light spots at the camera and the photodetector have the same phase relationship.
[0079] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0080] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.
Claims
1. A phase control system for common aperture coherent synthesis, characterized in that: The phase control system for common aperture coherent synthesis comprises: a laser module, a synthesis module, a detection module, a phase control model, a delay controller, a liquid crystal and a phase modulator; The laser module is used to split the seed laser, each split laser passes through one of the phase modulators, and the laser module is also used to amplify and collimate the laser after passing through the phase modulator and then output it; The synthesis module is used to perform common aperture synthesis on each laser beam output by the laser module and then output it; The detection module is used to sample each laser beam output by the laser module, each sampled laser beam is focused after passing through the liquid crystal, and a sub-aperture synthetic spot image is generated according to the focused laser beam; the number of the liquid crystals is the same as the number of the phase modulators, and each sampled laser beam corresponds to one liquid crystal; The detection module is also used to sample the synthetic laser output by the synthesis module and collect the beam intensity of the sampled synthetic laser; The delay controller is used to adjust the delay of each laser beam by adjusting each liquid crystal according to the intensity of the light beam, so as to maximize the intensity of the light beam collected by the detection module; The phase control model is used to output the predicted phase of each laser beam according to the aperture-divided synthetic spot image; the phase control model is obtained by training a neural network; Each of the phase modulators is used to adjust the phase of the corresponding split laser beam to the corresponding predicted phase.
2. The phase control system for common aperture coherent synthesis according to claim 1, characterized in that: The laser module includes a beam splitter, N laser amplifiers and N collimators, where N is the number of paths for the beam splitter to split the seed laser, and each split laser path passes through a phase modulator, a laser amplifier and a collimator in sequence.
3. The phase control system for common aperture coherent synthesis according to claim 2, characterized in that: The N collimators are arranged in a preset array, and the preset array includes a one-dimensional array and a two-dimensional array.
4. The phase control system for common aperture coherent synthesis according to claim 1, characterized in that: The synthesis module comprises a common aperture beam combiner, and the common aperture beam combiner is used to perform common aperture synthesis on each laser beam output by the laser module.
5. The phase control system for common aperture coherent synthesis according to claim 1, characterized in that: The detection module includes a first sampling mirror and a second sampling mirror; The first sampling mirror is used to sample each laser beam output by the laser module; The second sampling mirror is used to sample the synthetic laser output by the synthesis module.
6. The phase control system for common aperture coherent synthesis according to claim 1, characterized in that: The detection module includes a focusing lens and a photodetector; The focusing lens is used to focus the laser output by each liquid crystal; The photoelectric detector is used to collect the beam intensity of the sampled synthetic laser.
7. The phase control system for common aperture coherent synthesis according to claim 1, characterized in that: The detection module comprises a camera, and the camera is used to generate a synthetic spot image with different apertures according to the focused laser.
8. The phase control system for common aperture coherent synthesis according to claim 1, characterized in that: In terms of adjusting the delay of each laser beam by adjusting each liquid crystal according to the intensity of the beam to maximize the intensity of the beam collected by the detection module, the delay controller is specifically used for: A random parallel gradient descent algorithm is used to adjust the delay of each laser beam by adjusting each liquid crystal according to the intensity of the light beam, so as to maximize the intensity of the light beam collected by the detection module.
9. The phase control system for common aperture coherent synthesis according to claim 1, characterized in that: The execution rate of the phase control model is 10 times the execution rate of the delay controller.
10. A phase control method for common aperture coherent synthesis, characterized in that: The phase control method for common aperture coherent synthesis applies the phase control system for common aperture coherent synthesis described in any one of claims 1 to 9, and the phase control method for common aperture coherent synthesis includes: Enable the phase control model and delay controller; When the intensity of the light beam collected by the detection module changes from small to large and maintains the maximum value setting time in the process of changing from small to large, the phase adjustment is completed and the delay controller is turned off.