Laser modulation method and system

Abstract

The application belongs to the technical field of adaptive optics, and specifically discloses a laser modulation method, which comprises the following steps: determining a block division rule; dividing a modulation module into blocks according to the block division rule; selecting a plurality of blocks meeting a specific condition from the divided blocks; and performing the following operations on the plurality of blocks meeting the specific condition one by one: applying a modulation parameter to a current block to modulate laser; obtaining an optical intensity distribution image of the modulated laser affected by atmospheric turbulence; calculating an evaluation value; if the difference between the current calculated evaluation value and the previous calculated evaluation value is greater than an evaluation threshold, calculating the modulation parameter according to the current calculated evaluation value and the previous calculated evaluation value; then, using the calculated modulation parameter to adjust the current block for the next time; and until the adjustment of the modulation parameter for each block meeting the specific condition is completed. The method can make the laser spot stable, bright and convergent under the action of strong atmospheric turbulence.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of adaptive optics, in particular to a laser modulation method and system. BACKGROUND

[0002] Laser is easily affected by atmospheric turbulence in the transmission process, resulting in random drift, expansion, distortion, scintillation and other turbulence effects of the transmitted light wave, which greatly reduces the energy transmission effect of the optical system and is the main factor affecting the performance of astronomical imaging, laser communication and other systems.

[0003] Adaptive optics technology can be used to modulate laser to reduce the influence of atmospheric turbulence on laser transmission. The development of adaptive optics technology originated in the United States. Astronomer H. W. Babcock proposed a correction scheme for atmospheric turbulence-induced wavefront aberration of astronomical telescopes. In 1972, the United States successfully built the first experimental system for atmospheric turbulence distortion compensation imaging, which realized the correction of wavefront aberration caused by atmospheric turbulence on a horizontal light path with a distance of 300m. Due to the high cost and complex system of traditional adaptive optics system, its use field is limited, and more and more scientific researchers begin to explore the means to reduce the cost of adaptive optics system.

[0004] Compared with conventional adaptive optics technology, wavefront detection-free technology does not need to detect wavefront and calculate wavefront reconstruction. The control signal required by the wavefront corrector is used as an optimization parameter, and the system performance indicators such as imaging clarity function, Strehl ratio and received light energy that people are interested in are used as target functions. The optimization is carried out in an iterative manner to obtain an ideal correction effect.

[0005] When the existing adaptive optics technology modulates laser, it takes a long time. Under the action of medium-strong atmospheric turbulence, the stability and convergence of the received laser beam are not good. SUMMARY

[0006] The embodiments of the present application provide a laser modulation method and a laser modulation device, which aim to solve the technical problems of long time consumption and poor stability and convergence of laser beam when laser is modulated in the prior art.

[0007] In one aspect, the laser modulation method provided by the embodiments of the present application comprises the following steps,

[0008] S1, determining a block division rule according to a first light intensity distribution image and a second light intensity distribution image of laser, the first light intensity distribution image being a light intensity distribution image of laser which is not modulated and not affected by atmospheric turbulence, and the second light intensity distribution image being a light intensity distribution image of laser which is not modulated and affected by atmospheric turbulence;

[0009] S2, calculating an evaluation value according to the first light intensity distribution image and the second light intensity distribution image;

[0010] S3, performing block division on the modulation region of the modulation module according to a block division rule; selecting a plurality of blocks meeting a specific condition from the divided blocks; the modulation module comprises a plurality of modulation units;

[0011] S4, selecting one block from the plurality of blocks meeting the specific condition according to a specific rule, and performing the following operations on the currently selected block:

[0012] S41, applying a modulation parameter to the currently selected block of the modulation module to modulate the laser; obtaining a third light intensity distribution image of the modulated laser affected by the atmospheric turbulence;

[0013] S42, calculating an evaluation value according to the first light intensity distribution image and the third light intensity distribution image; if the difference between the currently calculated evaluation value and the previously calculated evaluation value is greater than a preset evaluation threshold, performing step S43;

[0014] S43, calculating the modulation parameter according to the currently calculated evaluation value and the previously calculated evaluation value, and jumping to perform step S41.

[0015] According to the embodiments of the present application, step S43 further comprises:

[0016] If the difference between the currently calculated evaluation value and the previously calculated evaluation value is less than or equal to the evaluation threshold, or the number of repetitions of step S41 or step S42 or step S43 is greater than or equal to a preset iteration threshold, step S4 is performed.

[0017] According to any one of the preceding embodiments of the first aspect of the present application, the block division rule comprises

[0018] The modulation region of the modulation module is divided into multiple blocks, and the number of modulation units in each block after each division is the same,

[0019] The number of blocks after the last division is greater than the number of blocks after the previous division,

[0020] The number of modulation units in each block after the last division is less than the number of modulation units in each block after the previous division.

[0021] According to any one of the preceding embodiments of the first aspect of the present application, the modulation region of the modulation module is divided into multiple blocks, comprising determining the ROI region of the first light intensity distribution image,

[0022] determining the modulation region corresponding to the ROI region of the first light intensity distribution image,

[0023] The modulation region is divided into multiple blocks, and each time a specific modulation region in the modulation region is selected for block division.

[0024] According to any one of the preceding embodiments of the first aspect of the present application, in the multiple block divisions of the modulation region, the area of the specific modulation region selected in the later block division is greater than the area of the specific modulation region selected in the previous block division.

[0025] According to any one of the preceding embodiments of the first aspect of the present application, the specific modulation region selected in the later block division covers the specific modulation region selected in the previous block division.

[0026] According to any one of the preceding embodiments of the first aspect of the present application, at least part of the blocks formed after the previous block division partially overlap with the blocks formed after the later block division.

[0027] According to any one of the preceding embodiments of the first aspect of the present application, the ROI region of the first light intensity distribution image is a region in the first light intensity distribution image centered on the point of maximum light intensity.

[0028] According to any one of the preceding embodiments of the first aspect of the present application, selecting the multiple blocks meeting the specific condition from the divided blocks includes

[0029] Among the multiple blocks obtained after each block division, multiple blocks capable of covering the center region of the specific modulation region are selected.

[0030] According to any one of the preceding embodiments of the first aspect of the present application, the specific rule includes

[0031] The order of block division is adopted between each block division, and the selection of blocks according to the spiral path is adopted for different blocks within the same block division.

[0032] According to any one of the preceding embodiments of the first aspect of the present application, the starting point of the spiral path is located at the center of the specific modulation region, and the ending point is located at the midpoint of the boundary of the specific modulation region; or

[0033] The starting point of the spiral path is located at the midpoint of the boundary of the specific modulation region, and the ending point is located at the center of the specific modulation region.

[0034] According to any one of the preceding embodiments of the first aspect of the present application, the calculation formula of the evaluation value is as follows

[0035]

[0036] Wherein, R is the evaluation value, β and α are gain coefficients, Mask(i, j) represents the weight value of the pixel point (i, j) in the ROI region of the first light intensity distribution image, I(i, j) represents the light intensity of the pixel point (i, j) in the ROI region of the second light intensity distribution image or the ROI region of the third light intensity distribution image, and r represents the size of the ROI region.

[0037] According to any one of the preceding embodiments of the first aspect of the present application, if the light intensity of the pixel point (i, j) in the ROI region of the first light intensity distribution image is greater than the light intensity threshold, the value of Mask(i, j) is 1.

[0038] If the light intensity of the pixel point (i, j) in the ROI region of the first light intensity distribution image is less than or equal to the light intensity threshold, the value of Mask(i, j) is 0.

[0039] According to any one of the preceding embodiments of the first aspect of the present application, the modulation parameter includes a voltage value, and the current voltage value is calculated by the following formula

[0040] U n+1 =U n +sign*(R n+1 -R n ) γ

[0041] Wherein, U n+1 represents the current calculated voltage value, U n represents the previous calculated voltage value, R n+1 represents the current calculated evaluation value, R n represents the previous calculated evaluation value, the value of sign is 1 or -1, and γ represents a gain coefficient.

[0042] According to any one of the preceding embodiments of the first aspect of the present application, when the difference between the current calculated evaluation value and the previous calculated evaluation value is less than or equal to the evaluation threshold, and the modulation parameter applied to the current selected block of the modulation module is the initial modulation parameter, the value of the next modulation sign is -1.

[0043] According to any one of the preceding embodiments of the first aspect of the present application, the specific modulation region is a square, and the blocks covered by the spiral path include at least one block on the boundary of the specific modulation region.

[0044] In a second aspect, the laser modulation system provided by the embodiments of the present application includes a transmitting module, a receiving module, a modulation module, and a control module. The transmitting module is configured to emit laser light. The receiving module is configured to receive laser light. The modulation module is configured to modulate the laser light emitted by the transmitting module. The control module is configured to:

[0045] The control receiving module receives the unmodulated laser emitted by the control transmitting module in a state without or with weak atmospheric turbulence and generates a first light intensity distribution image;

[0046] The control receiving module receives the unmodulated laser emitted by the control transmitting module in a state with atmospheric turbulence and generates a second light intensity distribution image;

[0047] The first light intensity distribution image and the second light intensity distribution image are used to determine a block division rule for the modulation module;

[0048] The modulation module is divided into blocks according to the block division rule, and the modulation parameters of the divided blocks are adjusted in a specific order. After each adjustment of the modulation parameters, the control receiving module receives the laser emitted by the control transmitting module in a state with atmospheric turbulence and generates a latest light intensity distribution image. The latest light intensity distribution image and the first light intensity distribution image are used to determine whether the modulation parameters of the current block need to be adjusted.

[0049] If the modulation parameters need to be adjusted, the modulation parameters of the current block are continuously adjusted. If the modulation parameters do not need to be adjusted, the modulation parameters of the next block are adjusted.

[0050] According to the second aspect of the present application, the modulation module is divided into blocks according to the block division rule, which includes

[0051] The modulation region of the modulation module is divided into blocks according to the block division rule, and the modulation region is selected according to the first light intensity distribution image.

[0052] According to any one of the preceding embodiments of the second aspect of the present application, the modulation region of the modulation module is divided into blocks according to the block division rule, which includes

[0053] The first specific modulation region of the modulation region is selected for the first division,

[0054] The second specific modulation region of the modulation region is selected for the second division,

[0055] The area of the second specific modulation region is greater than the area of the first specific modulation region, and the area of each block after the second division is smaller than the area of each block after the first division.

[0056] The laser modulation method of the embodiment of the present application selects the modulation region of the modulation module to adjust the modulation parameter, and the other regions outside the modulation region do not need to be adjusted, which can save the calculation amount. Secondly, the modulation region is divided into blocks, and the modulation parameter is adjusted in block units. Compared with adjusting a modulation unit alone, the calculation amount is further reduced. Thirdly, for the blocks in the modulation region, only the multiple blocks meeting the specific conditions are selected to adjust the modulation parameter, which further reduces the calculation amount, improves the operation speed, and further improves the modulation efficiency of the modulation module. The system can still receive a laser beam with stable and bright spot and convergence effect under the action of strong atmospheric turbulence. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1a is a schematic diagram of the ROI region of the first light intensity distribution image under the condition of strong atmospheric turbulence;

[0058] Figure 1b is a schematic diagram of the ROI region of the second light intensity distribution image under the condition of weak atmospheric turbulence;

[0059] Figure 2 is a top view of the pixel array of the spatial light modulator of the embodiment of the present application;

[0060] Figure 3 is a schematic diagram of the structure of the laser modulation system of the embodiment of the present application;

[0061] Figure 4 is a flowchart of the laser modulation method of the embodiment of the present application;

[0062] Figure 5 is a schematic diagram of the ROI region of the first light intensity distribution image under the condition of strong atmospheric turbulence;

[0063] Figure 6 is a schematic diagram of the modulation unit array of the spatial light modulator of the embodiment of the present application;

[0064] Figure 7 is a schematic diagram of the modulation region of the embodiment of the present application. DETAILED DESCRIPTION

[0065] The features and exemplary embodiments of various aspects of the present application will be described in detail below, in order to make the purposes, technical solutions and advantages of the present application more clear and apparent, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, but not to limit the present application. The present application can be implemented without some of these specific details by those skilled in the art. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0066] As shown in Figure 1a and Figure 1b , after the laser propagates in the atmosphere, it is affected by the atmospheric turbulence, and finally the convergence degree of the light spot in the light intensity distribution image of the imaging is low, and the energy is not concentrated. Figure 1a The light intensity distribution image of the laser under the condition of strong atmospheric turbulence is shown in Figure 1b The light intensity distribution image of the laser under the condition of weak atmospheric turbulence is shown. The laser modulation method and the laser modulation system 100 of the embodiment of the application use a spatial light modulator, a deformable mirror and the like to adaptively modulate the laser, so as to achieve the effect that the laser can still be stable, bright and convergent after propagating in the atmosphere. The laser modulation method and the laser modulation system 100 of the embodiment of the application will be described below by taking the use of the spatial light modulator to modulate the laser as an example.

[0067] Spatial light modulator: a device for modulating the spatial distribution of light waves, which changes the amplitude or intensity, phase, polarization state and the like of the spatial light distribution under the control of the electrical driving signal. The spatial light modulator is a key device in the fields of real-time optical information processing, adaptive optics and optical computing and the like of modern optics. As shown in Figure 2 , the spatial light modulator includes a two-dimensional array liquid crystal panel composed of many basic independent modulation units MU (pixel units, which are composed of liquid crystal molecules); a control voltage signal (modulation parameter) can be independently sent to each modulation unit MU, and after loading the electric field, the arrangement direction and angle of the liquid crystal molecules change, and the birefringence also changes, thereby changing the phase and the like of the laser passing through the modulation unit MU.

[0068] The structure of the laser modulation system 100 disclosed by the embodiment of the application is shown in Figure 3 , which includes a transmitting module 1, a receiving module 2, a modulation module 3 and a control module 4. Among them, the transmitting module 1 is used for transmitting laser to the atmosphere, the transmitted laser passes through the atmosphere to reach the receiving module 2, the receiving module 2 images the received laser to generate a light intensity distribution image; the modulation module 3 is arranged on the light path between the transmitting module 1 and the receiving module 2, and is used for modulating the laser emitted by the transmitting module 1; the control module 4 is communicatively connected with the receiving module 2 and the modulation module 3, and adjusts the modulation parameter of the modulation module 3 by acquiring the light intensity distribution image of the laser from the receiving module 2, so that the modulation module 3 modulates the laser according to the modulation parameter sent by the control module 4, and the cycle is repeated, so that the laser received by the receiving module 2 is finally stable, bright and convergent. Of course, the control module 4 can also be communicatively connected with the transmitting module 1 to control the transmitting module 1. As described above, in the embodiment, the modulation module 3 is a spatial light modulator.

[0069] Please refer toFigure 4 The laser modulation method disclosed in the embodiments of the present application comprises the following steps,

[0070] S1, determining a block division rule according to a first light intensity distribution image and a second light intensity distribution image of the laser, wherein the first light intensity distribution image is a light intensity distribution image of the laser that is not modulated and is not affected by atmospheric turbulence, and the second light intensity distribution image is a light intensity distribution image of the laser that is not modulated and is affected by atmospheric turbulence;

[0071] The block division rule is used for block division of a plurality of modulation units MU of the spatial light modulator; after the blocks are divided, the modulation parameters are adjusted in units of the blocks.

[0072] The first light intensity distribution image of the laser can be obtained in the case of no turbulence or extremely weak turbulence interference by building a wavefront-free detection adaptive optical system; or the corresponding first light intensity distribution image can be obtained by optical simulation according to the parameters of the wavefront-free detection adaptive optical system. As shown in FIG. 1, a part of the first light intensity distribution image (this area is the ROI area of the first light intensity distribution image described below) is in the case of no turbulence or extremely weak turbulence interference, and the convergence degree of the laser is high, which is the state to be achieved. Figure 5

[0073] Similarly, the second light intensity distribution image of the laser under the action of atmospheric turbulence and without modulation can be obtained by building a wavefront-free detection adaptive optical system. In a laboratory scenario, a turbulence sheet can be used to simulate an atmospheric turbulence environment. As shown in FIG. 2, a part of the second light intensity distribution image (this area is the ROI area of the second light intensity distribution image described below) is under the action of atmospheric turbulence and without modulation. Figure 1a Figure 1b

[0074] S2, calculating an evaluation value according to the first light intensity distribution image and the second light intensity distribution image; the evaluation value is used for representing the convergence degree of the second light intensity distribution image.

[0075] S3, performing block division on a modulation region A2 of a modulation module 3 (spatial light modulator) according to the block division rule; selecting a plurality of blocks meeting a specific condition from the divided blocks B; the modulation module 3 comprises a plurality of modulation units MU; since the area of the modulation unit array A1 of the spatial light modulator is large, and the laser is emitted to the spatial light modulator and only acts on part of the modulation unit array A1, when the modulation parameters of the spatial light modulator are adjusted, all the modulation units MU do not need to be adjusted, but the target region (i.e., the modulation region A2) of the modulation unit array A1 is selected for modulation parameter adjustment; thus, only the modulation region A2 needs to be divided into blocks.

[0076] ​​​S4, selecting one block from the plurality of blocks meeting the specific condition according to a specific rule; the specific rule can be a certain order or path, and the selected block is different each time, i.e., the plurality of blocks meeting the specific condition are selected according to a certain order to adjust the modulation parameter until all the blocks meeting the specific condition are traversed; the specific condition can be a region of the modulation region A2 meeting a certain condition;

[0077] The following operations are performed on the currently selected block:

[0078] S41, applying the modulation parameter to the currently selected block of the modulation module 3 to modulate the laser; obtaining a third light intensity distribution image of the modulated laser affected by the atmospheric turbulence; this step only adjusts the modulation parameter of the currently selected block B, which can improve the adjustment efficiency;

[0079] S42, calculating the evaluation value according to the first light intensity distribution image and the third light intensity distribution image; the evaluation value can represent the convergence degree of the currently obtained third light intensity distribution image; if the difference between the currently calculated evaluation value R n+1 and the evaluation value R n calculated last time is greater than a preset evaluation threshold T r , step S43 is performed; R n+1 - R n > T r , which indicates that the convergence degree of the modulated laser is greatly improved after one parameter adjustment, indicating that the current adjustment direction is correct, and the adjustment can continue in the current adjustment direction.

[0080] S43, calculating the modulation parameter according to the currently calculated evaluation value and the evaluation value calculated last time, and jumping to step S41; the modulation parameter applied to the currently selected block B next time can be estimated by the currently calculated evaluation value and the evaluation value calculated last time.

[0081] Please refer to Figure 6 In the above method, first, the modulation region A2 in the modulation unit array A1 of the spatial light modulator is selected for modulation parameter adjustment, and other regions other than the modulation region A2 do not need to be adjusted, which can save calculation amount; second, the modulation region A2 is divided into blocks, and the modulation parameter is adjusted in units of block B, and each block B contains multiple modulation units MU, which further reduces the calculation amount compared with adjusting one modulation unit MU; third, for the blocks B in the modulation region A2, only the plurality of blocks B Figure 6 meeting the specific condition (gray blocks) are selected for modulation parameter adjustment, which further reduces the calculation amount, improves the operation speed, and further improves the modulation efficiency of the spatial light modulator.

[0082] In some embodiments, step S43 further comprises:

[0083] If the current calculated evaluation value R n+1 is less than or equal to the evaluation threshold T n , the difference between the current calculated evaluation value R r and the previous calculated evaluation value R n+1 , the iteration threshold T is greater than or equal to the preset iteration threshold T, then jump to execute step S4; R n ≤ T r , it indicates that the degree of improvement of the convergence of the modulated laser after the adjustment of the modulation parameters is not large, and the adjustment of the current block B can be ended, and the next block B is selected for the adjustment of the modulation parameters; the iteration threshold T is greater than or equal to the preset iteration threshold T, which indicates that the adjustment of the current block B has met the requirements after T times of adjustment, and the adjustment of the currently selected block B is forcibly ended, and the next block B is selected for the adjustment of the modulation parameters, thereby saving the modulation time.

[0084] The above steps end until all blocks B meeting the specific conditions are traversed.

[0085] Referring to Figure 7 , in some embodiments, the block division rule comprises

[0086] The modulation region A2 of the modulation module 3 is divided into multiple blocks each time, and the number of modulation units MU in each block B after each division is the same. It can be understood that each division is uniform division, and this division method can make the calculation more simple and improve the calculation efficiency. The number of blocks after the last division is greater than the number of blocks after the previous division. The number of modulation units MU in each block B after the last division is less than the number of modulation units MU in each block B after the previous division.

[0087] It can be understood that after the above multiple divisions, the number of blocks B increases and the number of modulation units MU included in each block B decreases each time, which is beneficial to realize the smooth transition of the laser phase, effectively save the running time, and achieve the effect of stable, bright and convergent spot.

[0088] Specifically, as shown in Figure 7 , the modulation region A2 is divided into three blocks, the first division line L1 represents the first division, and the divided block is the first block B1; the second division line L2 represents the second division, and the divided block is the second block B2; the third division line L3 represents the third division, and the divided block is the third block B3. From Figure 7As can be seen, the area of the first block B1 is greater than the area of the second block B2, and the area of the second block B2 is greater than the area of the third block B3. The greater the area, the greater the number of modulation units MU contained; the number of the first block B1 is less than the number of the second block B2, and the number of the second block B2 is less than the number of the third block B3.

[0089] In some embodiments, the above-mentioned multiple blockings of the modulation region A2 of the modulation module 3 include:

[0090] The ROI region (i.e., the region of interest) of the first light intensity distribution image is determined; the ROI region can be determined by locating the position of the light intensity maximum point of the first light intensity distribution image, and the region with a radius or side length of r centered on the point is the ROI region; the embodiments of the present application take a square as an example for illustration, i.e., the ROI region is a square containing r*r pixel points; as Figure 5 indicated, the ROI region of the first light intensity distribution image is

[0091] The modulation region A2 corresponding to the ROI region of the first light intensity distribution image is determined; it can be understood that each region in the first light intensity distribution image corresponds to a region of the modulation unit array A1 of the spatial light modulator, and after the ROI region of the first light intensity distribution image is determined, the modulation region A2 on the modulation unit array A1 can be determined;

[0092] In the above-mentioned multiple blockings of the modulation region A2, a specific modulation region A3 in the modulation region A2 is selected for each blocking; as Figure 7 indicated, the region surrounded by the first blocking line L1, the second blocking line L2, and the third blocking line L3 of the outermost circle is the specific modulation region A3; only the specific modulation region A3 is blocked, and the modulation parameter adjustment on the blocks B contained in the specific modulation region A3 can reduce the calculation amount and improve the operation speed;

[0093] In the above-mentioned multiple blockings of the modulation region A2, the area of the specific modulation region A3 selected in the later blocking is greater than the area of the specific modulation region A3 selected in the previous blocking; as Figure 7As shown, the area of the region surrounded by the third sub-block line L3 of the outermost circle (the third specific modulation region A33) is greater than the area of the region surrounded by the second sub-block line L2 of the outermost circle (the second specific modulation region A32), and the area of the region surrounded by the second sub-block line L2 of the outermost circle is greater than the area of the region surrounded by the first sub-block line L1 of the outermost circle (the first specific modulation region A31); it can be understood that the number of total modulation units MU that need to be adjusted after each sub-block is more and more, and the modulation units MU of the key region can be adjusted for multiple times of modulation parameter adjustment, and the modulation units MU of the less important region can be adjusted for a small number of times of modulation parameter adjustment, which can also reduce the calculation amount and improve the modulation efficiency;

[0094] In the multiple sub-blocks of the modulation region A2, the specific modulation region A3 selected in the later sub-block covers the specific modulation region A3 selected in the previous sub-block; for example Figure 7 As shown, the third specific modulation region A33 covers the second specific modulation region A32, and the second specific modulation region A32 covers the first specific modulation region A31; it can be understood that the region covered multiple times will be adjusted for multiple times of modulation parameter adjustment, so that the region covered multiple times can be selected as the key region and adjusted for multiple times of modulation parameter adjustment.

[0095] At least part of the blocks formed after the previous sub-block partially overlaps with the blocks formed after the later sub-block; for example Figure 7 As shown, each first block B1 partially overlaps with multiple second blocks B2; each second block B2 partially overlaps with multiple third blocks B3; it can be understood that this overlapping mode can realize smooth transition of laser phase.

[0096] It can be understood that the above sub-block mode, from the first sub-block to the third sub-block, the number of total modulation units MU that need to be adjusted after each sub-block is more and more, after each sub-block, the number of blocks B is more and more, nested expansion from the center to the periphery, the number of modulation units MU contained in each block B is less and less, at least part of the blocks formed after the previous sub-block partially overlaps with the blocks formed after the later sub-block, which is conducive to realizing smooth transition of laser phase and effectively saving running time, and achieving the effect of stable and bright and convergent spot.

[0097] Please continue to refer to Figure 6 and Figure 7 The above selecting multiple blocks meeting specific conditions from the divided blocks includes:

[0098] In the multiple blocks B obtained after each sub-block, multiple blocks B capable of covering the center region of the specific modulation region A3 are selected.

[0099] In some embodiments, a specific condition is that the selected block B can cover the central region of a specific modulation region A3. Figure 6 The area containing the gray block), blocks that meet specific conditions are as follows: Figure 6 The block shown can cover the central area of ​​a specific modulation region A3. Figure 6 (The gray areas in the image). It's understandable that these areas were chosen because laser spots are generally circular, and the modulation units MU at the four corners of the specific modulation region A3 have little effect on improving the laser modulation effect. Therefore, they can be ignored when adjusting modulation parameters. Figure 6 Blocks other than the gray areas shown are not included in the adjustment range to reduce the amount of computation.

[0100] Please continue reading. Figure 6 and Figure 7 The specific rules mentioned above include: the order in which blocks are divided between different divisions, and the selection of different blocks within the same division using a spiral path L. For example... Figure 7 As shown, when selecting blocks, the first block B1 formed after the first block division is selected first. For multiple first blocks that meet specific conditions, the selection is performed as follows: Figure 6 The spiral path L shown is used to select one by one. After the first block B1 that meets the specific conditions has been selected (after debugging), the second block B2 formed after the second division is selected. Similarly, the second block B2 that meets the specific conditions is selected one by one according to the spiral path L, and so on.

[0101] Of course, the modulation parameters can also be adjusted after each block division. That is, after the first block division, the first block B1 that meets the specific conditions is selected one by one, and the modulation parameters are adjusted one by one; then the second block division is performed, and the second block B2 that meets the specific conditions is selected one by one, and the modulation parameters are adjusted one by one; and so on.

[0102] It is understandable that by calculating each block sequentially according to the spiral path L and adjusting the modulation parameters, relative phase compensation can be achieved, and the oscillation of the compensation phase is less likely to occur when multiple blocks are modulated.

[0103] Please continue reading. Figure 6 In some embodiments, the starting point of the spiral path L is located at the center of the specific modulation region A3, and the ending point is located at the midpoint of the boundary of the specific modulation region A3; of course, the starting point of the spiral path L can also be located at the midpoint of the boundary of the specific modulation region A3, and the ending point is located at the center of the specific modulation region A3. In this way, the largest possible modulation range can be obtained.

[0104] In some embodiments, the starting point of the spiral path L is calculated from the midpoint of the left boundary of the specific modulation region A3 (the midpoint of the right boundary, the midpoint of the upper boundary or the midpoint of the lower boundary of the specific modulation region A3 can also be used), and the moving step size is calculated according to the size of the block B each time until the centermost block is reached, and the iteration ends. This design can better compensate for the atmospheric turbulence disturbance suffered by the unfocused light beam and the insufficient convergence of the light beam energy caused by the inaccurate focusing position, because the focusing phase tends to be a continuous annular distribution; and reduces the redundant calculation of the boundary part region of the spatial light modulator, because the boundary part region of the spatial light modulator has weak influence on the laser phase compensation.

[0105] In some embodiments, the specific modulation region A3 is square, and the blocks B covered by the spiral path L include at least one block B on the boundary of the specific modulation region A3. It can be understood that in this way, the modulation range of the specific modulation region A3 can be larger.

[0106] In some embodiments, the calculation formula of the evaluation value is as follows

[0107]

[0108] wherein R is the evaluation value; β and α are gain coefficients, the values of which are selected according to experience; Mask(i,j) represents the weight value of the pixel point (i,j) in the ROI region of the first light intensity distribution image, I(i,j) represents the light intensity of the pixel point (i,j) in the ROI region of the second light intensity distribution image or the ROI region of the third light intensity distribution image, and r represents the boundary size of the ROI region of the corresponding light intensity distribution image, that is, the boundary of the ROI region contains r pixel points, and the entire ROI region includes r*r pixel points.

[0109] The ROI region of the second light intensity distribution image and the ROI region of the third light intensity distribution image can be determined in the same way as the ROI region of the first light intensity distribution image. That is, the position of the light intensity maximum value point of the second light intensity distribution image and the third light intensity distribution image is located first, and the region with a radius or a side length of r centered on the light intensity maximum value point is the ROI region; the embodiments of the present application take a square ROI region as an example, that is, the ROI region is square and contains r*r pixel points.

[0110] In some embodiments, if the light intensity of the pixel point (i,j) in the ROI region of the first light intensity distribution image is greater than the light intensity threshold, the value of Mask(i,j) is 1; if the light intensity of the pixel point (i,j) in the ROI region of the first light intensity distribution image is less than or equal to the light intensity threshold, the value of Mask(i,j) is 0. In this way, the laser under the condition of no turbulence or extremely weak turbulence can be used as the modulation target, and the effect of stable and bright and convergent laser spots can be achieved.

[0111] In some embodiments, the modulation parameter comprises a voltage value, the current voltage value is calculated by the following formula

[0112] U n+1 = U n + sign * (R n+1 - R n ) γ

[0113] wherein U n+1 represents the current calculated voltage value, U n represents the previous calculated voltage value, R n+1 represents the current calculated evaluation value, R n represents the previous calculated evaluation value, the value of sign is 1 or -1, and γ represents a gain coefficient, the value of which is selected according to experience. When modulating for the first time, an initial voltage value U0 is attached to the first adjusted block B, and the initial voltage value U0 can be selected according to experience.

[0114] In some embodiments, when the difference between the current calculated evaluation value and the previous calculated evaluation value is less than or equal to an evaluation threshold, and the modulation parameter applied to the current selected block B of the modulation module 3 is an initial modulation parameter, the value of sign in the next modulation is -1. Assigning the value -1 to sign indicates that the direction of the previous adjustment is incorrect, and the adjustment direction needs to be changed. For example, the previous modulation parameter is to increase the voltage value U0 to obtain a new voltage value U1, and after modulating the laser, it is found that the result is not good, then the adjustment direction can be changed to decrease the voltage value on the basis of U0, and each subsequent adjustment is to decrease the voltage value. In this way, it is not necessary to perform positive adjustment (increase the voltage value) and negative adjustment (decrease the voltage value) every time, but to determine the appropriate adjustment direction in time according to the initial adjustment effect, thereby reducing the calculation amount.

[0115] Please continue to refer to Figure 3 As described above, the laser modulation system 100 disclosed in the embodiments of the present application comprises a transmitting module 1, a receiving module 2, a modulation module 3 and a control module 4; wherein the transmitting module 1 is used for emitting laser, for example, the transmitting module 1 can be a laser, the receiving module 2 is used for receiving laser, for example, the receiving module 2 can comprise a camera; the modulation module 3 is used for modulating the laser emitted by the transmitting module 1, and the modulation module 3 can be a spatial light modulator; the control module 4 can be a computer; the control module 4 is used for:

[0116] controlling the receiving module 2 to receive the unmodulated laser emitted by the transmitting module 1 in a state without or with weak atmospheric turbulence and generate a first light intensity distribution image;

[0117] The control receiving module 2 receives the unmodulated laser emitted by the transmitting module 1 in the state of atmospheric turbulence and generates a second light intensity distribution image;

[0118] The first light intensity distribution image and the second light intensity distribution image are used to determine a block division rule for the modulation module 3;

[0119] The modulation module 3 is divided into blocks according to the block division rule, and the modulation parameters of the divided blocks are adjusted in a specific order. After each adjustment of the modulation parameters, the control receiving module 2 obtains the laser emitted by the transmitting module 1 in the state of atmospheric turbulence and generates a latest light intensity distribution image. The latest light intensity distribution image and the first light intensity distribution image are used to determine whether the modulation parameters of the current selected block need to be adjusted.

[0120] If the modulation parameters need to be adjusted, the modulation parameters of the current selected block are continuously adjusted. If the modulation parameters do not need to be adjusted, the modulation parameters of the next block are adjusted. The specific judgment rule can refer to the judgment rule in the above laser modulation method, and will not be repeated here.

[0121] Compared with adjusting the modulation parameters of each modulation unit MU of the modulation module 3 one by one, this way of adjusting the modulation parameters of the modulation module 3 in blocks reduces the calculation amount and improves the laser modulation efficiency. Moreover, through the specific block division rule, the smooth transition of the laser phase is realized, and the running time is effectively saved.

[0122] In some embodiments, the modulation module 3 is divided into blocks according to the block division rule, including:

[0123] The modulation region A2 of the modulation module 3 is divided into blocks according to the block division rule, and the modulation region A2 is selected according to the first light intensity distribution image. In this embodiment, the modulation region A2 in the modulation unit array A1 of the spatial light modulator is selected for modulation parameter adjustment, and other regions outside the modulation region A2 do not need to be adjusted, which can save calculation amount.

[0124] In some embodiments, the modulation region A2 of the modulation module 3 is divided into blocks according to the block division rule, including:

[0125] The first specific modulation region A31 of the modulation region A2 is selected for the first block division,

[0126] The second specific modulation region A32 of the modulation region A2 is selected for the second block division,

[0127] The area of the second specific modulation region A32 is larger than the area of the first specific modulation region A31, and the area of each block B after the second partitioning is smaller than the area of each block B after the first partitioning. The beneficial effects of this partitioning method have been described in detail in the foregoing introduction of the laser modulation method, and will not be described here again.

[0128] In some embodiments, the specific modulation region A3 selected in the later time covers the specific modulation region A3 selected in the former time. The beneficial effects of this selection method of the specific modulation region have been described in detail in the foregoing introduction of the laser modulation method, and will not be described here again.

Claims

1. A method of laser modulation, characterized by, The method comprises the following steps of: S1, determining a block division rule according to a first light intensity distribution image and a second light intensity distribution image of the laser, the first light intensity distribution image being a light intensity distribution image of the laser without modulation and without influence of atmospheric turbulence, and the second light intensity distribution image being a light intensity distribution image of the laser without modulation and with influence of atmospheric turbulence; S2, calculating an evaluation value according to the first light intensity distribution image and the second light intensity distribution image; S3, performing block division on a modulation region of the modulation module according to the block division rule; The block division step comprises performing multiple block divisions on the modulation region of the modulation module, The multiple block division steps comprise: determining an ROI region of the first light intensity distribution image, determining a modulation region corresponding to the ROI region of the first light intensity distribution image, and performing multiple block divisions on the modulation region, each time selecting a specific modulation region in the modulation region for block division; The number of modulation units in each block after each block division is the same, the number of blocks after the latter block division is greater than the number of blocks after the former block division, the number of modulation units of each block after the latter block division is less than the number of modulation units of each block after the former block division, and the area of the specific modulation region selected in the latter block division is greater than the area of the specific modulation region selected in the former block division; A plurality of blocks meeting a specific condition are selected from the divided blocks; the modulation module comprises a plurality of modulation units; S4, selecting one block from the plurality of blocks meeting the specific condition according to a specific rule, and performing the following operations on the currently selected block: S41, applying a modulation parameter to the currently selected block of the modulation module to modulate the laser; and obtaining a third light intensity distribution image of the laser after modulation and with influence of atmospheric turbulence; S42, calculating an evaluation value according to the first light intensity distribution image and the third light intensity distribution image; if the difference between the currently calculated evaluation value and the evaluation value calculated last time is greater than a preset evaluation threshold, step S43 is performed; S43, calculating the modulation parameter according to the currently calculated evaluation value and the evaluation value calculated last time, and jumping to step S41; if the difference between the currently calculated evaluation value and the evaluation value calculated last time is less than or equal to the evaluation threshold, or the number of repetitions of step S41 or step S42 or step S43 is greater than or equal to a preset iteration threshold, step S4 is performed.

2. The method of claim 1, wherein: The specific modulation region selected in the latter block division covers the specific modulation region selected in the former block division.

3. The method of claim 2, wherein: At least part of the blocks formed after the former block division partially overlap with the blocks formed after the latter block division.

4. The method of claim 3, wherein: The ROI region of the first light intensity distribution image is a region centered on a point of maximum light intensity in the first light intensity distribution image.

5. The method of claim 4, wherein: The selecting of the plurality of blocks meeting the specific condition from the divided blocks comprises Among the plurality of blocks obtained after each block division, a plurality of blocks capable of covering a central region of the specific modulation region are selected.

6. The method of claim 4, wherein: The specific rule comprises The order of the block division between each block division, and the selection of the blocks according to a spiral path within the same block division are adopted.

7. The method of claim 6, wherein: The starting point of the spiral path is located at the center of the specific modulation region, and the ending point is located at the midpoint of the boundary of the specific modulation region; or The starting point of the spiral path is located at the midpoint of the boundary of the specific modulation region, and the ending point is located at the center of the specific modulation region.

8. The method of claim 7, wherein: The calculation formula of the evaluation value is as follows ； Where R is the evaluation value, and This is the gain coefficient. Represents the pixels in the ROI region of the first light intensity distribution image. The weight value, This represents the pixels in the ROI region of the second light intensity distribution image or the ROI region of the third light intensity distribution image. light intensity, This indicates the size of the ROI region.

9. The method of claim 8, wherein: If the pixels in the ROI region of the first light intensity distribution image If the light intensity is greater than the light intensity threshold, then The value is 1; If the pixels in the ROI region of the first light intensity distribution image If the light intensity is less than or equal to the light intensity threshold, then The value is 0.

10. The method of claim 1, wherein: The modulation parameter includes a voltage value, and the current voltage value is calculated by the following formula ； wherein, represents the voltage value of the current calculation, represents the voltage value of the previous calculation, represents the evaluation value of the current calculation, represents the evaluation value of the previous calculation, the value of is 1 or -1, represents the gain coefficient.

11. The method of claim 10, wherein: When the difference between the current calculated evaluation value and the previous calculated evaluation value is less than or equal to the evaluation threshold and the modulation parameter applied to the currently selected block of the modulation module is the initial modulation parameter, the next modulation is -1.

12. The method of claim 7, wherein: The specific modulation region is a square, and the block covered by the spiral path includes at least one block on the boundary of the specific modulation region.

13. A laser modulation system based on the laser modulation method of any one of claims 1-12, comprising a transmitting module, a receiving module, a modulation module and a control module, the transmitting module is used to emit laser, the receiving module is used to receive laser, the modulation module is used to modulate the laser emitted by the transmitting module, characterized in that, The control module is used to: Control the receiving module to receive the unmodulated laser emitted by the transmitting module in the state without or with weak atmospheric turbulence and generate a first light intensity distribution image; Control the receiving module to receive the unmodulated laser emitted by the transmitting module in the state with atmospheric turbulence and generate a second light intensity distribution image; Determine the block division rule of the modulation module according to the first light intensity distribution image and the second light intensity distribution image; According to the block division rule, the modulation module is divided into blocks, and the modulation parameters of the divided blocks are adjusted in a specific order. After each adjustment of the modulation parameters, the receiving module acquires the laser emitted by the transmitting module in the state with atmospheric turbulence and generates a latest light intensity distribution image. According to the latest light intensity distribution image and the first light intensity distribution image, it is determined whether the modulation parameters of the currently selected block need to be adjusted. If the modulation parameters need to be adjusted, the modulation parameters of the currently selected block are continuously adjusted. If the modulation parameters do not need to be continuously adjusted, the modulation parameters of the next block are adjusted.

14. The laser modulation system of claim 13, wherein: The block division rule of the modulation module includes The modulation region of the modulation module is divided into blocks according to the block division rule, and the modulation region is selected according to the first light intensity distribution image.

15. The laser modulation system of claim 14, wherein: The block division rule of the modulation region of the modulation module includes The first specific modulation region of the modulation region is selected for the first block division, The second specific modulation region of the modulation region is selected for the second block division, The area of the second specific modulation region is greater than the area of the first specific modulation region, and the area of each block after the second block division is smaller than the area of each block after the first block division.

Images