Multi-received SLM partition-controlled adaptive optics alignment system and method

Abstract

This invention provides a multi-channel receiving SLM partition-controlled adaptive optics alignment system and method. The method includes: a beam to be aligned in a perturbed channel is decomposed into a target beam and a reference beam after passing through a beam splitter; a wavefront sensor receives the reference beam, acquires the intensity distribution and phase distribution of the reference beam, and inputs them into a processor; the processor uses a preset SLM multi-zone control algorithm to partition the liquid crystal of the phase-type SLM, and matches each selected zone with each optical receiver one by one, generating a phase hologram for each selected zone and inputting it into the liquid crystal controller; each selected zone of the SLM liquid crystal performs partition alignment and outputs the received target beam; this invention can achieve multi-point focusing, dynamic alignment, and power allocation of the received beam through a single SLM, supports multi-point simultaneous alignment and arbitrary power allocation of a multi-channel receiving UOWC system under dynamic conditions, and has outstanding advantages such as high flexibility, good real-time performance, and strong scalability.

Description

Technical Field

[0001] This invention relates to the field of underwater wireless optical communication technology, and more specifically, to a multi-received spatial light modulator (SLM) partitioned adaptive optics alignment system and method. Background Technology

[0002] Underwater wireless communication technologies mainly include underwater acoustic communication, underwater radio electromagnetic wave communication, and underwater optical wireless communication (UOWC). Unlike underwater acoustic and electromagnetic wave communication technologies, UOWC technology uses light waves as carriers to transmit information. Therefore, UOWC technology has outstanding advantages such as large bandwidth, low transmission delay, and good security, making it an excellent solution for short-range, high-capacity underwater communication.

[0003] In Unseen Light Coherence (UOWC) scenarios, besides absorption and scattering by water, water turbulence is also a significant factor hindering the long-distance propagation of light waves in the underwater medium. These obstacles can significantly reduce the link transmission performance of UOWC signals. To reduce the impact of turbulence on UOWC system performance, researchers have proposed many techniques to mitigate disturbances, such as aperture averaging, spatial diversity, beam shaping, and adaptive optics. Unlike the passive, static compensation methods of the first three techniques, adaptive optics is an active compensation technique. It can actively compensate for phase differences based on changes in turbulence and is currently one of the most mainstream light intensity scintillation compensation techniques.

[0004] Adaptive optics systems consist of wavefront detection devices and compensation devices. By employing appropriate compensation devices and algorithms, they compensate for and correct incident wavefront aberrations, thereby reducing the impact of optical scintillation. Compensation devices in adaptive optics systems include deformable mirrors (DM), digital micromirror devices (DMD), and scintillation mirrors (SLM). Compared to DM and DMD, SLM offers finer phase and / or intensity modulation accuracy, while maintaining a modulation rate up to 1 kHz. It is a high-speed, high-precision device with multi-dimensional modulation capabilities and has been widely used in adaptive optics systems. Currently, several studies have discussed underwater adaptive optics technology based on SLM, which can be tested under single-link conditions or, depending on the communication service requirements, can use single-input multiple-output (SIMO) or multiple-input multiple-output (MIMO) system architectures.

[0005] In multi-input UOWC systems, multiple signal receivers may exist simultaneously at the receiving end. Utilizing multiple receivers can improve the system's receive diversity gain and may also yield other additional benefits. For example, in multi-wavelength UOWC communication systems, to achieve better system performance, multiple receivers can be used to match the received optical power with the responsivity of different photoelectric detectors (PDs). When multiple receivers are enabled, traditional adaptive compensation schemes for single-link UOWC systems are no longer applicable, and corresponding adaptive compensation schemes need to be developed for UOWC systems with multiple receivers.

[0006] Currently, there are relatively few adaptive compensation schemes for multi-user UOWC systems based on SLM, indicating a significant research gap. (See the literature "H. Wang, Z. Zhang, J. Dang & L. Wu, 'Optical adaptive antenna array for multiuser mobile optical communication,' IEEE Access, vol. 7, pp. 65444-65449, May..."). In 2019, the authors proposed embedding a coherent signal source into a spherical optical phased array with an outer spherical lens system, predicting the signal power at the receiving end based on the channel transmission matrix, and performing power compensation during signal transmission. In the existing patent literature "A Large-Angle Beam Control System Based on Optical Phased Array", the liquid crystal optical phased array is divided into multiple consecutive sub-regions, and these sub-regions are controlled in a partitioned manner to achieve continuous beam scanning and ensure the stability of the laser communication link power during the fine tracking stage. Although most existing technologies have achieved multiple reception on SLM using coherent light and phased array technology, there are two drawbacks: First, the power distribution of the system requires the support of a feedback link to achieve power compensation at the transmitting end, but for the harsh underwater communication environment, the reliability and time delay of the feedback link make actual deployment difficult. Second, the multi-receiver alignment scheme implemented on SLM using phased array technology requires the received signal to have strong coherent light characteristics, but under time-varying underwater turbulence, the coherence of the beam at the receiving end is difficult to guarantee, which has a significant impact on the actual performance of the system. Summary of the Invention

[0007] To overcome the difficulties and stringent requirements of deployment in existing SLM-based multi-receiver alignment schemes, this invention provides a multi-receiver SLM-based zone-controlled adaptive optics alignment system and method. This system enables multi-point focusing, dynamic alignment, and power allocation of the received beam using a single SLM, supporting simultaneous multi-point alignment and arbitrary power allocation in multi-receiver UOWC systems under dynamic conditions. This scheme can be applied to common multi-receiver optical communication systems, such as SIMO optical communication systems with multi-receiver capabilities, MIMO optical communication systems, and optical communication systems equipped with array receivers.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0009] A multi-channel receiving SLM partition-controlled adaptive optics alignment system is used to partition and align a beam to be aligned in a disturbed channel. The beam to be aligned is coupled with a signal emitted by at least one signal source. The system includes: a beam splitter, a wavefront sensor, a processor, a phase-type SLM, and at least one optical receiver. The phase-type SLM includes a liquid crystal and a liquid crystal controller. The wavefront sensor, processor, and liquid crystal controller are connected in sequence.

[0010] The beam splitter is used to receive the beam to be aligned and to decompose the beam into a target beam and a reference beam.

[0011] The wavefront sensor is used to receive reference light, acquire the intensity distribution and phase distribution of the reference light, and input them into the processor.

[0012] The processor is used to partition the liquid crystal of the phase-type SLM according to the intensity and phase distribution of the reference light, the number of light receivers, and the parameters of the system, using a preset SLM multi-zone control algorithm, to obtain the same number of selected areas on the liquid crystal of the phase-type SLM as the light receivers, and to match each selected area with each light receiver one by one to obtain the selected area matching result of the phase-type SLM liquid crystal; to generate a phase hologram of each selected area according to the selected area matching result of the phase-type SLM liquid crystal, and to input all phase holograms into the liquid crystal controller;

[0013] The liquid crystal of the phase-type SLM is used to receive target light, and the liquid crystal controller is used to convert the phase hologram of each selected area into a control voltage and control each selected area on the liquid crystal to perform partition alignment output of the target light. The target light after alignment output of each selected area is focused on the corresponding light receiving end.

[0014] Each of the aforementioned light receivers is used to receive the target light after alignment output from the corresponding selected area of ​​the phase-type SLM liquid crystal, and to perform photoelectric conversion and post-processing.

[0015] Preferably, the wavefront sensor includes a camera and a microlens array disposed in front of the camera lens, and the camera is connected to a processor.

[0016] Preferably, the camera is a CMOS camera.

[0017] Preferably, the disturbance channel is a UOWC channel, and the disturbance includes any one or more of the following: turbulence, bubbles, salinity gradient, temperature gradient, ocean current, ocean waves, and sea breeze.

[0018] This invention also provides a multi-received SLM partition-controlled adaptive optics alignment method, based on the above-described multi-received SLM partition-controlled adaptive optics alignment system, comprising the following steps:

[0019] The beam to be aligned in the perturbation channel is split into target light and reference light after passing through the beam splitter;

[0020] The wavefront sensor receives reference light, acquires the intensity distribution and phase distribution of the reference light, and inputs them into the processor.

[0021] The processor, based on the intensity and phase distribution of the reference light, the number of light receivers, and the system parameters, uses a preset SLM multi-zone control algorithm to partition the liquid crystal of the phase-type SLM, obtaining the same number of selected areas on the liquid crystal as the light receivers, and matching each selected area with each light receiver one by one to obtain the selected area matching result of the phase-type SLM liquid crystal; it generates a phase hologram for each selected area based on the selected area matching result of the phase-type SLM liquid crystal, and inputs all phase holograms into the liquid crystal controller;

[0022] The phase-type SLM receives the target light in its liquid crystal, and the liquid crystal controller converts the phase hologram of each selected area into a control voltage and controls each selected area on the liquid crystal to perform partitioned alignment and output of the target light. The target light after alignment and output of each selected area is focused on the corresponding light receiving end.

[0023] After each of the aforementioned light receivers receives the target light after it has been aligned and output from the corresponding selected area of ​​the phase-type SLM liquid crystal, it performs photoelectric conversion and post-processing.

[0024] Preferably, the preset SLM multi-zone control algorithm is as follows:

[0025] S1: Based on the number of optical receivers In the intensity distribution diagram of the reference light Perform a traversal search on the top and retrieve the previous results. The light spot with the largest average light intensity ,in, and They are the first and second positive integers, respectively. ;

[0026] Each of the light spots Size 1 pixel, It is the third positive integer, and satisfies: , and This indicates the horizontal and vertical resolution of the image obtained by the wavefront sensor. This indicates a rounding down operation; the average light intensity is the corresponding light spot. The average light intensity of all pixels within the range;

[0027] S2: Light intensity distribution diagram of the reference light In, from each light spot Starting from the center coordinates, perform a region expansion operation with a preset shape and size to obtain... One light spot expansion area;

[0028] S3: Based on the size of the image obtained by the wavefront sensor and the size of the phase-type SLM liquid crystal, Each light spot extension region is mapped onto the liquid crystal of a phase-type SLM, and the light on the phase-type SLM liquid crystal is obtained. Each constituency;

[0029] When the size of the image obtained by the phase-type SLM liquid crystal is the same as that of the wavefront sensor, Each light spot extension region is mapped one-to-one onto the liquid crystal of the phase-type SLM; when both the horizontal and vertical dimensions of the phase-type SLM liquid crystal are larger than the size of the image obtained by the wavefront sensor, the intensity distribution map of the reference light is used. After establishing a mapping relationship between the center point and the center point of the phase-type SLM liquid crystal, then... Each light spot extension region is mapped one-to-one onto the liquid crystal of the phase-type SLM; when at least one of the horizontal or vertical dimensions of the phase-type SLM liquid crystal is smaller than the corresponding size of the image obtained by the wavefront sensor, the intensity distribution map of the reference light... After trimming the excess area according to the size of the phase-type SLM liquid crystal, repeat steps S1~S3 to reselect the area;

[0030] S4: The phase-type SLM liquid crystal... individual constituencies and Each optical receiver performs a one-to-one matching based on the minimum total Euclidean distance constraint to obtain the selected area matching result of the phase-type SLM liquid crystal.

[0031] Preferably, the traversal search in step S1 includes:

[0032] S1.1: Set the position of each of the light spots Sliding windows of the same size ;

[0033] S1.2: Move the sliding window Starting from the preset starting position, Each pixel represents the intensity distribution of the reference light at a step size. Slide on top, It is the fourth positive integer;

[0034] S1.3: Calculate the sliding window value for each slide. The average light intensity of all pixels within the range;

[0035] S1.4: Intensity distribution diagram of the entire reference light After the sliding is complete, obtain the sliding window with the largest average light intensity. The intensity distribution of the reference light. The corresponding area is used as the first light spot. And in the intensity distribution diagram of the reference light. Remove this region from the middle;

[0036] S1.5: Repeat steps S1.1 to S1.4 to obtain average light intensity that decreases sequentially. A light spot, denoted as: Complete the traversal search.

[0037] Preferably, in step S2, the preset shape includes: a preset regular shape and a preset irregular shape;

[0038] When the number of optical receivers Greater than the preset threshold At that time, the shape of each light spot expansion area is a preset regular shape; when the number of light receivers Less than or equal to the preset threshold At that time, the shape of each light spot expansion area is a preset irregular shape. It is the fifth positive integer;

[0039] The preset size is specifically:

[0040] According to the preset The power control ratio requirements for each optical receiver are based on the intensity distribution diagram of the reference light. In this process, the size of the expansion area of ​​each light spot is determined proportionally.

[0041] Preferably, when the number of optical receivers Greater than the preset threshold At this time, the shape of each light spot expansion area is a preset regular shape, and the intensity distribution of the reference light is shown in the diagram. All areas on the surface are divided into One light spot expansion area;

[0042] When the number of optical receivers Less than or equal to the preset threshold At this time, the shape of each light spot expansion area is a preset irregular shape, and the intensity distribution of the reference light is shown in the diagram. The above includes Each spot expansion area, and a power redundancy backup area in addition to all spot expansion areas.

[0043] Preferably, the step of generating a phase hologram for each selected region based on the selected region matching result of the phase-type SLM liquid crystal specifically involves:

[0044] Based on the selected area matching results of the phase-type SLM liquid crystal and the position coordinates of each light receiver, a phase hologram corresponding to each selected area is generated using an optical field control algorithm;

[0045] The light field control algorithm includes any one of the following: the Gerchberg-Saxton phase retrieval algorithm, the Zernike coefficient correction algorithm, and the stochastic parallel gradient descent algorithm.

[0046] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0047] This invention provides a multi-channel receiving SLM zone-controlled adaptive optical alignment system and method. First, the beam to be aligned in the perturbation channel is decomposed into target light and reference light by a beam splitter. A wavefront sensor receives the reference light, acquires its intensity and phase distributions, and inputs them into a processor. Based on the intensity and phase distributions of the reference light, the number of optical receivers, and the system parameters, the processor uses a preset SLM multi-zone control algorithm to partition the liquid crystal of the phase-type SLM, acquiring the same number of selected zones on the liquid crystal as the optical receivers, and then matching each selected zone with each optical receiver one-to-one. The process involves: acquiring the area matching results of the phase-type SLM liquid crystal; generating a phase hologram for each selected area based on the area matching results of the phase-type SLM liquid crystal, and inputting all phase holograms into the liquid crystal controller; the phase-type SLM liquid crystal receiving the target light; the liquid crystal controller converting the phase hologram of each selected area into a control voltage, and controlling each selected area on the liquid crystal to perform partitioned alignment and output of the target light; the target light after alignment output of each selected area is focused onto the corresponding light receiving end; each light receiving end receiving the target light after alignment output of the corresponding selected area of ​​the phase-type SLM liquid crystal performs photoelectric conversion and post-processing.

[0048] This invention achieves multi-point focusing, dynamic alignment, and power allocation of the received beam using a single SLM (Single-Lens Array), supporting simultaneous multi-point alignment and arbitrary power allocation in multi-channel receiving systems under dynamic conditions. It can be applied to common multi-channel receiving optical communication systems, such as SIMO (Single-Lens Oscillator), MIMO (Multi-Lens Oscillator), and optical communication systems equipped with array receivers. This invention utilizes closed-loop correction logic under an adaptive mechanism to achieve multi-point adaptive optical path alignment in multi-channel receiving systems. The main advantages of this invention are as follows:

[0049] 1) Power control and optical field modulation of the PD in the receiver can be achieved without the participation of the transmitter, avoiding the reliability and effectiveness issues of dynamic and real-time information feedback in harsh underwater environments, making the system more flexible in actual deployment;

[0050] 2) A partitioning design method for SLM based on an arbitrary number of PDs and arbitrary shapes is proposed. A single SLM can support multiple independent control areas and independently control multiple PDs, and has good scalability.

[0051] 3) An SLM partition control algorithm was designed, which calculates the partition size and completes PD matching in real time according to the power constraint conditions, and has outstanding advantages such as high flexibility and good real-time performance;

[0052] 4) By using adaptive optics technology to control the closed-loop drive partitioning algorithm to achieve dynamic partitioning, it is possible to ensure that each PD can still obtain stable receiving power even when light intensity fluctuates due to factors such as water turbulence. This is of great significance for communication scenarios where signal power stability is sensitive. Attached Figure Description

[0053] Figure 1 This is a diagram of an adaptive compensation alignment system architecture for a multi-channel receiver UOWC system provided in Example 1.

[0054] Figure 2 This is a schematic diagram of the SLM liquid crystal panel and the light field intensity distribution after turbulence disturbance provided in Example 2.

[0055] Figure 3 This is a schematic diagram of the SLM rule partitioning scheme for the dual-PD UOWC system provided in Example 2.

[0056] Figure 4 This is a schematic diagram of the SLM rule partitioning scheme for the three-PD and four-PD UOWC system provided in Example 2.

[0057] Figure 5 This is a schematic diagram of the SLM irregular partition control scheme for the dual-PD UOWC system provided in Example 2.

[0058] Figure 6This is a diagram showing the results of the partitioning and modulation of the actual light field in the verification experiment provided in Example 2. Detailed Implementation

[0059] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0060] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions.

[0061] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0062] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0063] Example 1

[0064] This embodiment provides a multi-channel receiving SLM partition control adaptive optical alignment system for partition control and alignment of a beam to be aligned in a disturbed channel. The beam to be aligned is coupled with a signal emitted by at least one signal source, and includes: a beam splitter, a wavefront sensor, a processor, a phase-type SLM, and at least one optical receiver; the phase-type SLM includes a liquid crystal and a liquid crystal controller; the wavefront sensor, processor, and liquid crystal controller are connected in sequence.

[0065] The beam splitter is used to receive the beam to be aligned and to decompose the beam into a target beam and a reference beam.

[0066] The wavefront sensor is used to receive reference light, acquire the intensity distribution and phase distribution of the reference light, and input them into the processor.

[0067] The processor is used to partition the liquid crystal of the phase-type SLM according to the intensity and phase distribution of the reference light, the number of light receivers, and the parameters of the system, using a preset SLM multi-zone control algorithm, to obtain the same number of selected areas on the liquid crystal of the phase-type SLM as the light receivers, and to match each selected area with each light receiver one by one to obtain the selected area matching result of the phase-type SLM liquid crystal; to generate a phase hologram of each selected area according to the selected area matching result of the phase-type SLM liquid crystal, and to input all phase holograms into the liquid crystal controller;

[0068] The liquid crystal of the phase-type SLM is used to receive target light, and the liquid crystal controller is used to convert the phase hologram of each selected area into a control voltage and control each selected area on the liquid crystal to perform partition alignment output of the target light. The target light after alignment output of each selected area is focused on the corresponding light receiving end.

[0069] Each of the aforementioned light receivers is used to receive the target light after alignment output from the corresponding selected area of ​​the phase-type SLM liquid crystal, and to perform photoelectric conversion and post-processing;

[0070] The wavefront sensor includes a camera and a microlens array disposed in front of the camera lens. The camera is connected to a processor, and the camera is specifically a CMOS camera.

[0071] In this embodiment, the disturbance channel is specifically a UOWC channel, and the disturbance includes any one or more of the following: turbulence, bubbles, salinity gradient, temperature gradient, ocean current, ocean waves, and sea breeze.

[0072] In the specific implementation process, such as Figure 1 As shown, this embodiment proposes an adaptive compensation alignment system for a multi-channel receiver UOWC system. The transmitter of this system consists of... One signal source and It consists of several light sources, when When it is a single-input UOWC system, In a multi-input UOWC system, specifically, the information bits are first coupled to the light source driving circuit via a T-type biaser, converting the electrical signal into an optical signal. This optical signal is then combined into a single beam by the reflector and beam splitter at the transmitting end, and then enters the underwater channel via a collimating lens group. The beam passing through the underwater turbulence channel is collected at the receiving end, and the beam width is adjusted by the collimating lens group at the receiving end. It then enters the adaptive compensation unit (i.e., the adaptive optical alignment system in this embodiment). In the adaptive compensation unit, the beam is split by the beam splitter into a lower-energy beam 1 (reference light) and a higher-energy beam 2 (target light). Beam 1 is detected by a Shack-Hartmann wavefront sensor, which consists of a microlens array in front of the lens and a camera. The camera can be, but is not limited to, a complementary metal-oxide-semiconductor (CMOS) camera. The light intensity and phase information measured by the wavefront sensor are transmitted back to the processor, which then determines the light intensity and phase distribution based on the number of photodiodes (PDs). 、 Parameters such as power distribution ratio are used to divide the incident light field into different regions on the liquid crystal surface and adjust it to align with different PDs.

[0073] As can be seen, the adaptive compensation alignment system for multi-channel receiving UOWC systems in this embodiment does not require control of the transmitting power through a feedback link. Power allocation and control can be achieved only at the receiver end, which can avoid problems such as signal transmission errors, delays, and quantization accuracy loss caused by the feedback link, and has higher flexibility and reliability in practical applications. In addition, general multi-channel receiving optical communication systems require multiple independent optical systems at the receiver end to provide focusing or alignment solutions for each PD, while this system only needs to perform partitioned control of the liquid crystal plane of a single SLM to achieve independent focusing and alignment of multiple PDs, reducing the synchronization requirements of multi-channel received signals and having better scalability.

[0074] Example 2

[0075] This embodiment provides a multi-channel receiving SLM partition-controlled adaptive optics alignment method, based on the multi-channel receiving SLM partition-controlled adaptive optics alignment system described in Embodiment 1, and includes the following steps:

[0076] The beam to be aligned in the perturbation channel is split into target light and reference light after passing through the beam splitter;

[0077] The wavefront sensor receives reference light, acquires the intensity distribution and phase distribution of the reference light, and inputs them into the processor.

[0078] The processor partitions the liquid crystal of the phase-type SLM using a preset SLM multi-zone control algorithm based on the intensity and phase distribution of the reference light, the number of light receivers, and the parameters of the system. It obtains the same number of selected areas on the liquid crystal of the phase-type SLM as the number of light receivers, and matches each selected area with each light receiver one by one to obtain the selected area matching result of the phase-type SLM liquid crystal.

[0079] Based on the selected area matching results of the phase-type SLM liquid crystal and the position coordinates of each light receiver, a phase hologram corresponding to each selected area is generated using an optical field control algorithm, and all phase holograms are input into the liquid crystal controller; the optical field control algorithm includes any one of the following: Gerchberg-Saxton phase retrieval algorithm, Zernike coefficient correction algorithm, stochastic parallel gradient descent algorithm, and other optical field modulation algorithms;

[0080] The phase-type SLM receives the target light in its liquid crystal, and the liquid crystal controller converts the phase hologram of each selected area into a control voltage and controls each selected area on the liquid crystal to perform partitioned alignment and output of the target light. The target light after alignment and output of each selected area is focused on the corresponding light receiving end.

[0081] After each of the aforementioned light receivers receives the target light after it has been aligned and output from the corresponding selected area of ​​the phase-type SLM liquid crystal, it performs photoelectric conversion and post-processing.

[0082] The preset SLM multi-zone control algorithm is specifically as follows:

[0083] S1: Based on the number of optical receivers In the intensity distribution diagram of the reference light Perform a traversal search on the top and retrieve the previous results. The light spot with the largest average light intensity ,in, and They are the first and second positive integers, respectively. ;

[0084] Each of the light spots Size 1 pixel, It is the third positive integer, and satisfies: , and This indicates the horizontal and vertical resolution of the image obtained by the wavefront sensor. This indicates a rounding down operation; the average light intensity is the corresponding light spot. The average light intensity of all pixels within the range;

[0085] S2: Light intensity distribution diagram of the reference light In, from each light spot Starting from the center coordinates, perform a region expansion operation with a preset shape and size to obtain... One light spot expansion area;

[0086] S3: Based on the size of the image obtained by the wavefront sensor and the size of the phase-type SLM liquid crystal, Each light spot extension region is mapped onto the liquid crystal of a phase-type SLM, and the light on the phase-type SLM liquid crystal is obtained. Each constituency;

[0087] When the size of the image obtained by the phase-type SLM liquid crystal is the same as that of the wavefront sensor, Each light spot extension region is mapped one-to-one onto the liquid crystal of the phase-type SLM; when both the horizontal and vertical dimensions of the phase-type SLM liquid crystal are larger than the size of the image obtained by the wavefront sensor, the intensity distribution map of the reference light is used. After establishing a mapping relationship between the center point and the center point of the phase-type SLM liquid crystal, then... Each light spot extension region is mapped one-to-one onto the liquid crystal of the phase-type SLM; when at least one of the horizontal or vertical dimensions of the phase-type SLM liquid crystal is smaller than the corresponding size of the image obtained by the wavefront sensor, the intensity distribution map of the reference light... After trimming the excess area according to the size of the phase-type SLM liquid crystal, repeat steps S1~S3 to reselect the area;

[0088] S4: The phase-type SLM liquid crystal... individual constituencies and Each optical receiver performs a one-to-one matching based on the minimum total Euclidean distance constraint to obtain the selected area matching result of the phase-type SLM liquid crystal;

[0089] The traversal search in step S1 includes:

[0090] S1.1: Set the position of each of the light spots Sliding windows of the same size ;

[0091] S1.2: Move the sliding window Starting from the preset starting position, Each pixel represents the intensity distribution of the reference light at a step size. Slide on top, It is the fourth positive integer;

[0092] S1.3: Calculate the sliding window value for each slide. The average light intensity of all pixels within the range;

[0093] S1.4: Intensity distribution diagram of the entire reference light After the sliding is complete, obtain the sliding window with the largest average light intensity. The intensity distribution of the reference light. The corresponding area is used as the first light spot. And in the intensity distribution diagram of the reference light. Remove this region from the middle;

[0094] S1.5: Repeat steps S1.1 to S1.4 to obtain average light intensity that decreases sequentially. A light spot, denoted as: Complete the traversal search;

[0095] In step S2, the preset shapes include: preset regular shapes and preset irregular shapes;

[0096] When the number of optical receivers Greater than the preset threshold At that time, the shape of each light spot expansion area is a preset regular shape; when the number of light receivers Less than or equal to the preset threshold At that time, the shape of each light spot expansion area is a preset irregular shape. It is the fifth positive integer;

[0097] The preset size is specifically:

[0098] According to the preset The power control ratio requirements for each optical receiver are based on the intensity distribution diagram of the reference light. In this process, the size of the expansion area of ​​each light spot is determined proportionally;

[0099] When the number of optical receivers Greater than the preset threshold At this time, the shape of each light spot expansion area is a preset regular shape, and the intensity distribution of the reference light is shown in the diagram. All areas on the surface are divided into One light spot expansion area;

[0100] When the number of optical receivers Less than or equal to the preset threshold At this time, the shape of each light spot expansion area is a preset irregular shape, and the intensity distribution of the reference light is shown in the diagram. The above includes Each spot expansion area, and a power redundancy backup area in addition to all spot expansion areas.

[0101] In the specific implementation process, in the control closed-loop processing flow of the above system, the wavefront sensor first analyzes the detected reference light, and then delineates the corresponding number of control areas and their sizes according to the number of PDs in the UOWC system receiver. The key point of this method is to collect light intensity and phase information by the wavefront sensor, and then partition and regulate the SLM liquid crystal through the SLM multi-zone control algorithm. This multi-zone control scheme involves two key technical points: first, how to divide the area; and second, how to control each zone to maintain the tracking alignment effect of multiple PDs in a dynamic underwater channel environment.

[0102] like Figure 2 Image (a) shows an SLM liquid crystal plane, as shown in Figure 1. Figure 2 (b) shows an example of beam intensity distribution after strong turbulence. The key point of this method is how to allocate irregular distorted light intensity to the corresponding PD according to the required power ratio or specific intensity. Specifically, when arranging the SLM position, it is necessary to ensure that the SLM panel and the CMOS camera of the wavefront sensor are in an optical conjugate relationship. Then, the light intensity distribution is detected by the camera and divided into multiple regions according to the energy ratio. Each region is partitioned and controlled on the SLM so that the beam of the corresponding region points to the designated PD. This scheme realizes the change of the number of partitions and the change of the number of focusable PDs through a preset algorithm. It has the advantages of flexible application and support for various scenarios.

[0103] The received beam, disturbed by turbulence in the underwater channel, is split into beam 1 (reference beam) and beam 2 (target beam) by a beam splitter. The wavefront sensor's camera detects the current light field intensity and phase distribution based on the distribution of beam 1; where the intensity distribution matrix of beam 1... It can be represented as:

[0104]

[0105] in, and This indicates the horizontal and vertical resolution of the camera image. This represents the intensity value of each pixel. Based on the intensity distribution of beam 1 detected by the camera, the energy distribution of beam 2 reaching the SLM surface can be obtained. Specifically, if the ratio of the transmittance to the reflectance of the beam splitter is... k Then the intensity distribution matrix of beam 2 It can be represented as:

[0106]

[0107] The partitioning operation is then performed using the SLM-based Multi-region Control (SLM-MRC) algorithm, as follows:

[0108] Step 1: Based on the number of PDs ,exist Perform a traversal search on the top to find the previous The light spot with the largest average light intensity ;

[0109] Light spot Defined as by ( A region consisting of ) pixels, where: This is the round-down operator; the shape of the light spot can be any planar geometric shape such as rectangle, circle, triangle, hexagon; the center coordinates are... The average intensity is the average of the intensities of all pixels within the light spot.

[0110] The basic steps of traversal search are as follows:

[0111] 1) Let To and An area of ​​the same size, and let lie in The specified starting position, for example, The bottom left corner or other edge position;

[0112] 2) As a sliding window, with a size of pixel plane Slide on top, with a sliding step size of 1 pixel;

[0113] 3) Each time you slide, [the following text is incomplete and likely refers to a separate action:] Calculate the average light intensity value once;

[0114] 4) When for the whole After sliding, find the one with the highest average light intensity value. Record its in The position in the middle, making Then remove that area, specifically by selecting the region with the highest average light intensity value. The light intensity values ​​of all pixels within the corresponding area are set to the theoretical minimum value;

[0115] 5) Repeat steps 1) through 4) until the average light intensity value decreases sequentially. A spot of light up to and its location;

[0116] Step 2: For each light spot center coordinates Expand the selection area outwards; the shape of the expanded selection area includes regular and irregular shapes, and regular shapes include, but are not limited to, rectangles, circles, polygons, etc.; the expansion operation continues until the power control ratio requirement is met, that is, the power control ratio of multiple PDs is: And the power of each PD does not exceed the preset power threshold. ;

[0117] Since the computational complexity of irregular partitioning schemes increases exponentially with the number of partitioning points (PDs), and the more PDs there are, the more likely it is to find the correct partitioning scheme. The probability of selecting a region that meets the conditions will decrease rapidly. Therefore, this method sets a maximum threshold for the number of partitioning zones (PDs) that can be supported during the execution of irregular partitioning schemes. The threshold The settings can be adjusted based on factors such as system computing power, SLM area, and incident light field energy distribution: when At that time, a rule-based partitioning scheme is used for partitioned control based on the number of PDs; when In such cases, adjustments will be made according to the irregular partitioning scheme, specifically following the rules below:

[0118] 1) Sequentially using the center coordinates of the light spot Centered on the predefined partition shape, the selection area is expanded outwards, with the expansion step value being one column, one row, multiple columns, or multiple rows of pixels;

[0119] 2) Each time the expansion is performed, the average light intensity of the expanded area must be calculated to determine whether the power requirement is met or the maximum power limit has been reached. ;

[0120] 3) If the two selection areas collide at the edges after expansion, the selection areas are expanded in the opposite or predefined direction until the power control ratio requirement is met;

[0121] In this embodiment, an example of a regular-shaped partitioning scheme is as follows: When the UOWC system is a dual PD receiver, one example of its partitioning scheme is as follows: Figure 3 As shown, where, Figure 3 (a) in the diagram represents a horizontal partitioning scheme. This scheme calculates the appropriate partitioning line position based on the light field intensity distribution measured by the wavefront sensor and the PD power allocation requirements, supporting separate control of the left and right regions. Simultaneously, combined with the real-time detection and control mechanism of the adaptive optics system, the partitioning line position can be dynamically set throughout the communication process, achieving dynamic allocation of the left and right regions. Regions A and B, divided by the partitioning line, will generate phase holograms based on the target PD's coordinates using corresponding light field modulation algorithms, and the SLM will be controlled accordingly. Figure 3 Similar to scheme (a) in the text, based on vertical partitioning Figure 3 Scheme (b) is another dual-PD partitioning scheme;

[0122] Based on this, we can use this approach to design corresponding rule-based partitioning schemes for three-PD and four-PD UOWC systems, for example... Figure 4 (a) and Figure 4 (b) in the figure presents a three-partition scheme and a four-partition scheme respectively. Their working principle is similar to that of the two-partition scheme. Based on the above multi-partition control idea, under the premise that hardware resources allow, a partitioning strategy with any number of PDs can be further implemented on the basis of this method.

[0123] In addition to the regular partitioning scheme based on the full-area utilization strategy mentioned above, this method can also adopt an irregular partitioning scheme: according to the number of PDs and power control requirements at the receiving end, the location of the controlled area can be freely selected within the SLM area. Taking a dual-PD UOWC system as an example, an example of an irregular partitioning scheme is as follows: Figure 5As shown, the size, position, and shape of regions A and B can be adjusted in real time according to the dynamic changes in received light intensity. To ensure that the beams in regions A and B have a stable light intensity, region C can be set as a power redundancy backup area for regions A and B. When the optical power of one or both regions A and B decreases due to external conditions, they can expand into region C to ensure that the PD corresponding to the power decrease area can receive more light intensity compensation, thereby maintaining the stability of the received light intensity of the PD. The unused light intensity in region C will be adjusted to a position relatively far away from regions A and B to reduce the impact on the target region PD. Similarly, when the power of region A or B increases due to changes in external conditions, the area of ​​region A or B can be reduced, which is equivalent to expanding region C. By setting up a "power redundancy backup area" and using adaptive optics technology to control the closed-loop drive partitioning algorithm to achieve dynamic partitioning, it can be ensured that each PD can still obtain stable received power even when light intensity fluctuates due to factors such as water turbulence. This is of great significance for communication scenarios where signal power stability is sensitive.

[0124] In both the regular and irregular partitioning schemes described above, the specific number of partitions can be set according to the number of receiver PDs in the UOWC system to adapt to different application scenarios.

[0125] Step 3: After the selection area is automatically expanded, map the selection area position according to the dimensions of the camera sensor plane and the SLM LCD plane; when the SLM LCD and camera sensor plane dimensions are the same, perform a one-to-one mapping; when both the horizontal and vertical dimensions of the SLM LCD are larger than the camera sensor size, maintain the correspondence between the camera center and the SLM LCD center, and perform direct mapping according to the physical dimensions; when at least one of the horizontal or vertical dimensions of the SLM LCD is smaller than the camera sensor size, it is necessary to... After cutting off the excess area according to the actual size of the SLM, the selection is performed; after mapping, the first... Center coordinates of individual selection area The corresponding mapping to the SLM liquid crystal is the first point coordinate ;

[0126] Step 4: After the selection area is mapped, ... individual constituencies and Each PD performs relation matching based on the principle of minimizing the total Euclidean distance. Specifically, firstly, we define... The coordinates of the center point of each PD are ,and and They belong to the same coordinate system; then PD and Distance of each constituency It can be represented as:

[0127]

[0128] By iterating through all combinations of PD and selection area using the above formula, we find the minimum... The combination of the value's PD and the selected area is denoted as:

[0129]

[0130] Step 5: After determining the mapping relationship between the selected area and the PD, a holographic phase map is generated in the corresponding selected area based on the PD coordinates using the light field control algorithm. The light field control algorithm can be any one of the following: Gerchberg-Saxton phase retrieval algorithm, Zernike coefficient correction algorithm, stochastic parallel gradient descent algorithm, or other light field modulation algorithm. Then, the holographic phase map is loaded onto the SLM's liquid crystal controller, which enables the control of the light field alignment of different zones with the corresponding PD.

[0131] In addition, this embodiment also provides a verification experiment to verify the effectiveness of the proposed multi-path receiving SLM partitioned adaptive optics alignment method; the following uses the construction of an actual light field as an example to illustrate the use of a CMOS camera and dual PDs, i.e. The area selection and SLM area matching process under the following conditions; assuming that the required received power ratio of the two PDs is 1:1, and each PD has the same maximum power. limit;

[0132] Figure 6 (a) in the image is the light intensity distribution map acquired by the CMOS camera. According to the SLM-MRC algorithm, firstly in... Figure 6 In the CMOS intensity map (a), the two strongest light spots are found, and the selection area is expanded outward around these two strongest light spots. This method selects to expand the selection area outward in a rectangular shape, and finally obtains regions A and B under the maximum power limit. These two regions have the characteristics of equal power and both equal to the maximum threshold. Since the CMOS camera is spatially conjugate with the SLM in the actual deployment process, regions A and B in the CMOS intensity map correspond to... Figure 6 (b) Regions A and B on the SLM are used to obtain the specific control positions on the SLM; then, based on the coordinates of the PD corresponding to regions A and B, the corresponding phase holograms are generated using the optical field control algorithm and loaded onto the SLM, while the phase hologram of the non-PD location is loaded onto region C; finally, the 1:1 power allocation and optical path alignment control of the two PDs are completed; thus, it can be seen that, with the support of the adaptive optics system, this method can perform dynamic partition control and realize power control and continuous alignment of the target PD;

[0133] In summary, by combining the SLM-MRC scheme with the control closed-loop process of the adaptive optics system, the controlled area can be updated in real time according to the changes in incident light intensity, and a holographic phase map can be generated in real time, so as to achieve the purpose of focusing the beam onto multiple receivers or PD arrays in the underwater channel.

[0134] The same or similar labels correspond to the same or similar parts;

[0135] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0136] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A multi-channel receiving SLM partitioned adaptive optical alignment system for partitioned control and alignment of a beam to be aligned in a perturbed channel, wherein the beam to be aligned is coupled with a signal emitted by at least one signal source, characterized in that, include: The system comprises a beam splitter, a wavefront sensor, a processor, a phase-type SLM, and more than one optical receiver; the phase-type SLM includes a liquid crystal and a liquid crystal controller; the wavefront sensor, the processor, and the liquid crystal controller are connected in sequence. The beam splitter is used to receive the beam to be aligned and to decompose the beam into a target beam and a reference beam. The wavefront sensor is used to receive reference light, acquire the intensity distribution and phase distribution of the reference light, and input them into the processor. The processor is used to partition the liquid crystal of the phase-type SLM according to the intensity and phase distribution of the reference light, the number of light receivers, and the parameters of the system, using a preset SLM multi-zone control algorithm. This partitions the liquid crystal of the phase-type SLM to obtain the same number of selected areas on the liquid crystal as the light receivers, and matches each selected area with each light receiver to obtain the selected area matching result of the phase-type SLM liquid crystal. Based on the selected area matching result of the phase-type SLM liquid crystal, a phase hologram of each selected area is generated, and all phase holograms are input into the liquid crystal controller. The preset SLM multi-zone control algorithm is specifically as follows: S1: Based on the number of optical receivers In the intensity distribution diagram of the reference light Perform a traversal search on top and retrieve the previous results. The light spot with the largest average light intensity ,in, and They are the first and second positive integers, respectively. ; Each of the light spots Size T 1 pixel, It is the third positive integer, and satisfies: , and This indicates the horizontal and vertical resolution of the image obtained by the wavefront sensor. This indicates a rounding down operation; the average light intensity is the corresponding light spot. The average light intensity of all pixels within the range; S2: Light intensity distribution diagram of the reference light In, from each light spot Starting from the center coordinates, perform a region expansion operation with a preset shape and size to obtain... One light spot expansion area; S3: Based on the size of the image obtained by the wavefront sensor and the size of the phase-type SLM liquid crystal, Each light spot extension region is mapped onto the liquid crystal of a phase-type SLM, and the light on the phase-type SLM liquid crystal is obtained. Each constituency; When the size of the image obtained by the phase-type SLM liquid crystal is the same as that of the wavefront sensor, Each light spot extension region is mapped one-to-one onto the liquid crystal of the phase-type SLM; when both the horizontal and vertical dimensions of the phase-type SLM liquid crystal are larger than the size of the image obtained by the wavefront sensor, the intensity distribution map of the reference light is used. After establishing a mapping relationship between the center point and the center point of the phase-type SLM liquid crystal, then... Each light spot extension region is mapped one-to-one onto the liquid crystal of the phase-type SLM; when at least one of the horizontal or vertical dimensions of the phase-type SLM liquid crystal is smaller than the corresponding size of the image obtained by the wavefront sensor, the intensity distribution map of the reference light... After trimming the excess area according to the size of the phase-type SLM liquid crystal, repeat steps S1~S3 to reselect the area; S4: The phase-type SLM liquid crystal... individual constituencies and Each optical receiver performs a one-to-one matching based on the minimum total Euclidean distance constraint to obtain the selected area matching result of the phase-type SLM liquid crystal; The liquid crystal of the phase-type SLM is used to receive target light, and the liquid crystal controller is used to convert the phase hologram of each selected area into a control voltage and control each selected area on the liquid crystal to perform partition alignment output of the target light. The target light after alignment output of each selected area is focused on the corresponding light receiving end. Each of the aforementioned light receivers is used to receive the target light after alignment output from the corresponding selected area of ​​the phase-type SLM liquid crystal, and to perform photoelectric conversion and post-processing.

2. The SLM partition-controlled adaptive optics alignment system with multiple receivers according to claim 1, characterized in that, The wavefront sensor includes a camera and a microlens array positioned in front of the camera lens, with the camera connected to a processor.

3. The SLM partition-controlled adaptive optical alignment system with multiple receivers according to claim 2, characterized in that, The camera in question is specifically a CMOS camera.

4. A multi-channel receiving SLM partition-controlled adaptive optics alignment system according to any one of claims 1 to 3, characterized in that, The disturbance channel is specifically an underwater wireless optical communication channel, and the disturbance includes any one or more of the following: turbulence, bubbles, salinity gradient, temperature gradient, ocean current, waves, and sea breeze.

5. A multi-channel receiving SLM partition-controlled adaptive optics alignment method, based on the multi-channel receiving SLM partition-controlled adaptive optics alignment system described in any one of claims 1 to 4, characterized in that, Includes the following steps: The beam to be aligned in the perturbation channel is split into target light and reference light after passing through the beam splitter; The wavefront sensor receives reference light, acquires the intensity distribution and phase distribution of the reference light, and inputs them into the processor. The processor, based on the intensity and phase distribution of the reference light, the number of light receivers, and the system parameters, uses a preset SLM multi-zone control algorithm to partition the liquid crystal of the phase-type SLM, obtaining the same number of selected areas on the liquid crystal as the light receivers, and matching each selected area with each light receiver one by one to obtain the selected area matching result of the phase-type SLM liquid crystal; it generates a phase hologram for each selected area based on the selected area matching result of the phase-type SLM liquid crystal, and inputs all phase holograms into the liquid crystal controller; The phase-type SLM receives the target light in its liquid crystal, and the liquid crystal controller converts the phase hologram of each selected area into a control voltage and controls each selected area on the liquid crystal to perform partitioned alignment and output of the target light. The target light after alignment and output of each selected area is focused on the corresponding light receiving end. After each of the aforementioned light receivers receives the target light after it has been aligned and output from the corresponding selected area of ​​the phase-type SLM liquid crystal, it performs photoelectric conversion and post-processing.

6. The SLM partition-controlled adaptive optical alignment method with multiple receivers according to claim 5, characterized in that, The traversal search in step S1 includes: S1.1: Set the position of each of the light spots Sliding windows of the same size ; S1.2: Move the sliding window Starting from the preset starting position, Each pixel represents the intensity distribution of the reference light at a step size. Slide on top, It is the fourth positive integer; S1.3: Calculate the sliding window value for each slide. The average light intensity of all pixels within the range; S1.4: Intensity distribution diagram of the entire reference light After the sliding is complete, obtain the sliding window with the largest average light intensity. The intensity distribution of the reference light. The corresponding area is used as the first light spot. And in the intensity distribution diagram of the reference light. Remove this region from the middle; S1.5: Repeat steps S1.1 to S1.4 to obtain average light intensity that decreases sequentially. A light spot, denoted as: Complete the traversal search.

7. The SLM partition-controlled adaptive optical alignment method with multiple receivers according to claim 5, characterized in that, In step S2, the preset shapes include: preset regular shapes and preset irregular shapes; When the number of optical receivers Greater than the preset threshold At that time, the shape of each light spot expansion area is a preset regular shape; when the number of light receivers Less than or equal to the preset threshold At that time, the shape of each light spot expansion area is a preset irregular shape. It is the fifth positive integer; The preset size is specifically: According to the preset The power control ratio requirements for each optical receiver are based on the intensity distribution diagram of the reference light. In this process, the size of the expansion area of ​​each light spot is determined proportionally.

8. The SLM partition-controlled adaptive optical alignment method with multiple receivers according to claim 7, characterized in that, When the number of optical receivers Greater than the preset threshold At this time, the shape of each light spot expansion area is a preset regular shape, and the intensity distribution of the reference light is shown in the diagram. All areas on the surface are divided into One light spot expansion area; When the number of optical receivers Less than or equal to the preset threshold At this time, the shape of each light spot expansion area is a preset irregular shape, and the intensity distribution of the reference light is shown in the diagram. The above includes Each spot expansion area, and a power redundancy backup area in addition to all spot expansion areas.

9. The SLM partition-controlled adaptive optical alignment method for multi-channel reception according to claim 5, characterized in that, The process of generating a phase hologram for each selected region based on the selected region matching results of the phase-type SLM liquid crystal is as follows: Based on the selected area matching results of the phase-type SLM liquid crystal and the position coordinates of each light receiver, a phase hologram corresponding to each selected area is generated using an optical field control algorithm; The light field control algorithm includes any one of the following: the Gerchberg-Saxton phase retrieval algorithm, the Zernike coefficient correction algorithm, and the stochastic parallel gradient descent algorithm.

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