Method and device for measuring target rotation speed based on polarization-assisted phase compensation

Abstract

A method and device for measuring the rotational speed of a target based on phase compensation with polarization assistance belongs to the field of laser rotational speed measurement technology. The present invention aims to solve the existing problem of being unable to accurately measure the rotational speed of a moving target in atmospheric turbulence. The present invention's solution: a laser is compositely modulated by polarization and orbital angular momentum through a set of spatial light modulators to generate a polarized vortex beam. After being emitted by a transmitting system, the laser passes through atmospheric turbulence and irradiates a rotating target object to generate an echo signal. The Stokes polarization information of the polarized vortex beam before and after distortion is extracted as input information for the GS algorithm. After processing by a distortion correction module, a compensation phase screen is output, and phase correction is performed on the left-hand and right-hand polarization components of the polarized vortex beam. A detection and processing module detects the polarization components of the vortex beam and obtains the Doppler frequency shift. The rotational speed of the moving target is calculated by a rotation speed calculation module.

Description

Technical Field

[0001] The present invention relates to a method and device for improving target rotation speed measurement based on a phase compensation algorithm optimized by polarization assistance and particle swarm algorithm, and belongs to the technical field of laser rotation speed measurement. Background Art

[0002] Rotational velocity measurement can be used to measure the rotational speed of a target and has broad application potential in industrial control, military, aerospace, and other fields. However, in actual velocity measurement, atmospheric turbulence can severely interfere with the transmission of the light beam, making it currently impossible to precisely measure the rotational speed of a moving target in this turbulent atmosphere. Summary of the Invention

[0003] In order to solve the problem that it is currently impossible to accurately measure the rotation speed of a moving target in atmospheric turbulence, the present invention provides a method and device for measuring the rotation speed of a target based on polarization-assisted phase compensation.

[0004] In one aspect of the present invention, a method for measuring target rotation speed based on polarization-assisted phase compensation is provided, the method comprising the following steps:

[0005] Step 1: a target light beam is emitted from a transmitting system and hits a moving target in a turbulent environment to generate an echo signal, wherein the target light beam includes left-handed circularly polarized vortex light and right-handed circularly polarized vortex light;

[0006] Step 2: Monitor the polarization Stokes information before and after turbulence distortion; the polarization Stokes information includes the phase distribution and intensity distribution of four parameters S0, S1, S2 and S3;

[0007] The phase information of the parameters S1 and S2 before distortion and the light intensity information of the parameters S0 and S3 are used as the input light field information, and the phase information of the parameters S1 and S2 after distortion and the light intensity information of the parameters S0 and S3 are used as the output light field information. The input and output light field information are input into the GS algorithm to obtain the distorted polarization vortex beam S1 component φ GS,S1 , S2 component of distorted polarized vortex beam φ GS,S2 ;

[0008] Step 3: Use the wavefront sensor to monitor the left-handed component and the right-handed component of the echo signal, and use the distortion phase of the left-handed component and the right-handed component as the output light field information. Use the phase of the left-handed circularly polarized vortex light and the right-handed circularly polarized vortex light before distortion as the input light field information. The input light field information and the output light field information are input into the GS algorithm to obtain the distorted polarized left-handed vortex beam component. and the distorted polarized right-handed vortex beam component

[0009] Step 4: Calculate the S1 component pre-correction phase screen C1, S2 component pre-correction phase screen C2, and pre-correction phase screen left-handed component H according to the results of steps 2 and 3. L0 and the right-handed component H of the pre-corrected phase screen R0 :

[0010] C1=angle(S1)-φ GS,S1

[0011] C2=angle(S2)-φ GS,S2

[0012]

[0013]

[0014] Where, angle(S1) and angle(S2) represent the phases of the polarization Stokes parameters S1 and S2 before distortion, and angle(E R )、angle(E L ) represents the phase of the right-handed and left-handed optical fields before distortion;

[0015] Step 5: Obtain the left-handed component H of the correction phase screen L and the right-handed component H of the corrected phase screen R :

[0016] H R =T(H R0 +δ L (Γ*C1+C2))

[0017] H L =T(H L0 +δ R (Γ*C1+C2))

[0018] Where Γ is the relative coefficient matrix of fitness optimization, T is the turbulence fluctuation adjustment coefficient matrix, δ R is the evaluation factor of the anti-turbulence ability of the right-handed light field, δ L is the evaluation factor of the anti-turbulence ability of the left-handed light field;

[0019] Step 6. Use the correction phase screen obtained in step 5 to perform phase correction on the left-handed and right-handed polarization components of the vortex beam of the echo signal. The detection and processing module detects the polarization component of the vortex beam and obtains the Doppler frequency shift; the rotation speed of the moving target is calculated by the rotation speed calculation module.

[0020] Preferably, the fitness optimization relative coefficient matrix Γ and the turbulence fluctuation degree adjustment coefficient matrix T are both optimized by the particle swarm algorithm, wherein the fitness optimization relative coefficient matrix Γ is optimized with the highest or average velocity measurement accuracy. As the fitness function, the optimization goal is to minimize the speed measurement error of the speed measurement system.

[0021] Where τ is the integration time of the detector, SNR is the spectral signal-to-noise ratio of the left-handed or right-handed circularly polarized component, and l is the order of the left-handed circularly polarized vortex light and the right-handed circularly polarized vortex light;

[0022] The turbulence fluctuation adjustment coefficient matrix T is optimized with purity as the fitness function.

[0023] Preferably, the fitness optimization relative coefficient matrix Γ and the turbulence fluctuation adjustment coefficient matrix T are cross-fixed to complete the optimization process, specifically:

[0024] Examples of turbulence fluctuation adjustment coefficient matrices T corresponding to high, medium and low turbulence fluctuation degrees are given. In each example, the fitness optimization relative coefficient matrix Γ is optimized using the particle swarm algorithm to obtain the final fitness optimization relative coefficient matrix Γ.

[0025] After determining the fitness optimization relative coefficient matrix Γ, the turbulence fluctuation degree adjustment coefficient matrix T is optimized by the particle swarm algorithm to obtain the final turbulence fluctuation degree adjustment coefficient matrix T, and then the optimal correction phase screen left and right components are obtained.

[0026] Preferably, the right-handed light field anti-turbulence ability evaluation factor δ R and the left-handed light field anti-turbulence ability evaluation factor δ L According to the following equations:

[0027]

[0028] Among them, β S0 is the S0 auxiliary evaluation factor, Where, SNR S0 is the spectrum signal-to-noise ratio of the S0 parameter of the light field when there is no turbulence, is the blaze index within the effective area of ​​the beam receiving area, P S0 is the received optical power of S0 parameter when there is no turbulence, is the received optical power of S0 parameter when there is turbulence;

[0029] β S3 is the S3 auxiliary evaluation factor, Where, SNR S3 is the spectrum signal-to-noise ratio of the S3 parameter of the light field in the absence of turbulence, is the blaze index within the effective area of ​​the beam receiving area, P S3 is the received optical power of the S3 parameter when there is no turbulence, is the received optical power of the S3 parameter when there is turbulence.

[0030] Another aspect of the present invention provides a target rotation speed measurement device based on polarization-assisted phase compensation, which is used to implement the above method. The target rotation speed measurement device includes a target beam generation module, a first beam splitter 7, a first polarization information acquisition module 8, an atmospheric turbulence simulator 9, a second beam splitter 10, a second polarization information acquisition module 11, a transmitting system 12, a left / right optical component selection system 14, a receiving system 15, a distortion correction module 16, a detection processing module 17 and a rotation speed solution module 18;

[0031] The light beam emitted by the modulated beam generation module includes left-handed circularly polarized vortex light and right-handed circularly polarized vortex light, which is divided into two paths by the first beam splitter 7. One path is used by the first polarization information acquisition module 8 to collect the pre-distortion polarization Stokes information. The other path passes through the atmospheric turbulence simulator 9 and is then divided into two paths by the second beam splitter 10. One path is used by the second polarization information acquisition module 11 to collect the post-distortion polarization Stokes information. The other path passes through the transmitting system 12 to irradiate the moving object 13 to generate an echo signal.

[0032] After passing through the left / right optical component selection system 14, the receiving system 15 receives the echo signal, corrects the distortion through the distortion correction module 16, detects the light spot signal through the detection and processing module 17, and obtains the time series signal of the light intensity through the oscilloscope, performs Fourier transform on it, and calculates the rotation speed of the moving target through the rotation speed calculation module 18.

[0033] Preferably, the target beam generating module includes a laser 1, a first lens group 2, a first spatial light modulator 3, a second spatial light modulator 5, a half-wave plate, a second lens group 4 and a quarter-wave plate 6; the laser light emitted by the laser 1 reaches the first lens group 2, the first lens group 2 expands, collimates and polarizes the light beam to form a beam of 45-degree linearly polarized light, the first spatial light modulator 3 performs orbital angular momentum quantum control on the horizontal polarization direction of the light beam to generate a -5-order vortex beam signal, passes through the half-wave plate and the second lens group 4, adjusts the vertical polarization direction of the light beam to the horizontal direction, the second spatial light modulator 5 performs orbital angular momentum quantum control on the vertical polarization direction of the light beam to generate a 5-order vortex beam signal, passes through the quarter-wave plate 6 to convert it into left-handed and right-handed circularly polarized vortex light, and the target beam can be obtained by superposition;

[0034] The first spatial light modulator 3 and the second spatial light modulator 5 are polarization-dependent liquid crystal reflective phase modulators that can modulate the light field in the horizontal X direction. The modulation process of the Gaussian mode laser signal requires loading the phase map of the vortex light onto the two spatial light modulators, and the vortex beam can be generated by laser incidence.

[0035] The function of the half-wave plate and the half-wave plate in the second lens group 4 is to rotate the polarization component direction of the light beam, which can cause the linear polarized light to produce a phase delay of π / 2 and convert the vertical polarization direction into the horizontal direction; the second lens group uses a 4F lens system to expand the light beam;

[0036] The 1 / 4 wave plate 6 converts the polarization components of the polarized vortex beam in the X and Y directions into left-handed and right-handed polarized light components.

[0037] Preferably, the first polarization information acquisition module 8 and the second polarization information acquisition module 11 have the same structure, including a 1 / 4 wave plate, a polarizer and a charge-coupled device. The polarization direction of the light beam is adjusted by adjusting the 1 / 4 wave plate and the polarizer to obtain the Stokes polarization information of S0, S1, S2, and S3.

[0038] Preferably, the left-handed / right-handed component selection system 14 includes a quarter-wave plate and a linear polarizer, and the left-handed and right-handed components of the polarized vortex beam are obtained by adjusting the rotation angles of the two optical elements;

[0039] Adjust the fast axis direction of the quarter-wave plate to vertical and the transmission direction of the linear polarizer to 45° to obtain the right-handed component of the polarized vortex beam;

[0040] Keeping the quarter-wave plate unchanged, the transmission direction of the linear polarizer is adjusted to 135° to obtain the left-handed component of the polarized vortex beam.

[0041] Preferably, the distortion correction module 16 includes a third spatial light modulator 16 - 1 , a third beam splitter 16 - 2 , a wavefront sensor 16 - 3 and a feedback signal controller 16 - 4 ;

[0042] The third spatial light modulator 16 - 1 is a wavefront corrector, and the feedback signal controller 16 - 4 transmits the obtained correction phase to it, thereby correcting the polarization component of the vortex light beam.

[0043] The wavefront sensor 16 - 3 obtains the distortion phase of the light field and sends it to the feedback signal controller 16 - 4 ;

[0044] The input and output light field information obtained by the first polarization information obtaining module 8 and the second polarization information obtaining module 11 are synchronously sent to the feedback signal controller 16 - 4 ;

[0045] The feedback signal controller 16-4 uses the GS algorithm and the particle swarm optimization algorithm to obtain the corrected phase screen left-handed component H L and the right-handed component H of the corrected phase screen R Perform phase correction.

[0046] Preferably, the detection and processing module 17 includes an avalanche photodiode detector and an oscilloscope. The avalanche photodiode detector detects the light beam output by the left / right-hand component selection system 14, obtains a time series signal of light intensity, performs Fourier transform on it, obtains Doppler frequency shift, and the rotation speed calculation module 18 calculates the rotation speed of the moving target.

[0047] The beneficial effects of the present invention are as follows: the present invention introduces compensation information of the new polarization Stokes dimension of the polarized vortex light beam, uses it as a new input information of the phase recovery algorithm, improves the GS algorithm, can better realize the recovery and correction of the phase of the vortex light beam, and enhances the precision measurement capability of the rotation speed of the moving target by the vortex light beam transmitted in the atmospheric turbulence. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a system block diagram of the target rotation speed measurement device based on polarization-assisted phase compensation according to the present invention;

[0049] Figure 2 It is a structural diagram of the distortion correction module;

[0050] Figure 3 It is the atmospheric turbulence phase screen loaded by the atmospheric turbulence simulator;

[0051] Figure 4 This is a flow chart of the target rotation speed measurement method based on polarization-assisted phase compensation according to the present invention. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0054] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0055] Specific implementation method 1: Figures 1 to 4 This embodiment describes a method for measuring target rotation speed based on polarization-assisted phase compensation, which includes the following steps:

[0056] Step 1: a target light beam is emitted from a transmitting system and hits a moving target in a turbulent environment to generate an echo signal, wherein the target light beam includes left-handed circularly polarized vortex light and right-handed circularly polarized vortex light;

[0057] Step 2: Monitor the polarization Stokes information before and after turbulence distortion; the polarization Stokes information includes the phase distribution and intensity distribution of four parameters S0, S1, S2 and S3;

[0058] The phase information of the parameters S1 and S2 before distortion and the light intensity information of the parameters S0 and S3 are used as the input light field information, and the phase information of the parameters S1 and S2 after distortion and the light intensity information of the parameters S0 and S3 are used as the output light field information. The input and output light field information are input into the GS algorithm to obtain the distorted polarization vortex beam S1 component φ GS,S1 , S2 component of distorted polarized vortex beam φ GS,S2 ; S1 and S2 have the same interphase region and have richer phase information. The light intensity information of S0 and S3 has the relationship: S0=I0=I R +I L , S3=I R -I L , I R is the intensity of the right-handed circularly polarized vortex beam, I L The formula is the intensity of the left-handed circularly polarized vortex beam, and I0 is the total light intensity. Therefore, the phase information of S1 and S2 and the intensity information of S0 and S3 are selected as the input information of the GS algorithm. The GS algorithm uses a known input and output light field and performs multiple iterations on the light field intensity information. The algorithm calculates a compensating phase screen, which is used to correct the phase of the distorted light field.

[0059] Step 3: Use the wavefront sensor to monitor the left-handed component and the right-handed component of the echo signal, and use the distortion phase of the left-handed component and the right-handed component as the output light field information. Use the phase of the left-handed circularly polarized vortex light and the right-handed circularly polarized vortex light before distortion as the input light field information. The input light field information and the output light field information are input into the GS algorithm to obtain the distorted polarized left-handed vortex beam component. and the distorted polarized right-handed vortex beam component

[0060] Step 4: Calculate the S1 component pre-correction phase screen C1, S2 component pre-correction phase screen C2, and pre-correction phase screen left-handed component H according to the results of steps 2 and 3. L0 and the right-handed component H of the pre-corrected phase screen R0 :

[0061] C1=angle(S1)-φ GS,S1

[0062] C2=angle(S2)-φGS,S2

[0063]

[0064]

[0065] Where, angle(S1) and angle(S2) represent the phases of the polarization Stokes parameters S1 and S2 before distortion, and angle(E R )、angle(E L ) represents the phase of the right-handed and left-handed optical fields before distortion;

[0066] Step 5: Obtain the left-handed component H of the correction phase screen L and the right-handed component H of the corrected phase screen R :

[0067] H R =T(H R0 +δ L (Γ*C1+C2))

[0068] H L =T(H L0 +δ R (Γ*C1+C2))

[0069] Where Γ is the relative coefficient matrix of fitness optimization, T is the turbulence fluctuation adjustment coefficient matrix, δ R is the evaluation factor of the anti-turbulence ability of the right-handed light field, δ L is the evaluation factor of the anti-turbulence ability of the left-handed light field;

[0070] Step 6. Use the correction phase screen obtained in step 5 to perform phase correction on the left-handed and right-handed polarization components of the vortex beam of the echo signal. The detection and processing module detects the polarization component of the vortex beam and obtains the Doppler frequency shift; the rotation speed of the moving target is calculated by the rotation speed calculation module.

[0071] The fitness optimization relative coefficient matrix Γ and the turbulence fluctuation adjustment coefficient matrix T are both optimized by the particle swarm optimization algorithm. The particle swarm optimization algorithm is a parallel intelligent evolutionary algorithm that starts from random particles (random solutions), evaluates the quality of the solution through the fitness function, iteratively updates its own speed and position by tracking individuals and the current global optimal value, and searches for the global optimal value. It has the advantages of easy implementation, high accuracy, and fast convergence. Among them, the fitness optimization relative coefficient matrix Γ is based on the maximum or average speed measurement accuracy. As the fitness function, the optimization goal is to minimize the speed measurement error of the speed measurement system.

[0072] Where τ is the detector's integration time, SNR is the spectral signal-to-noise ratio of the left-handed or right-handed circularly polarized component, and l is the order of the left-handed and right-handed circularly polarized vortex light; in this case, l = 5. Iterative updates maximize the beam's velocity measurement accuracy, ultimately yielding the optimal velocity measurement accuracy and its corresponding Γ matrix.

[0073] The turbulence fluctuation adjustment coefficient matrix T is optimized with purity as the fitness function. T is the adjustment coefficient matrix obtained by the particle swarm algorithm, which can adjust the fluctuation degree of the compensation phase screen according to the turbulence intensity. For the turbulence fluctuation adjustment coefficient matrix T. The population set by the algorithm has a wider turbulence distortion range, and uses purity as the fitness function, so that it can adapt to different degrees of distortion phase. When the turbulence intensity is high, the phase distortion is large, and the adjustment coefficient matrix can increase the fluctuation degree of the compensation phase screen, thereby better reducing and compensating the distortion. When the turbulence intensity is low, the fluctuation degree of the compensation phase screen decreases. The above method further improves the compensation ability of the algorithm.

[0074] The fitness optimization relative coefficient matrix Γ and the turbulence fluctuation adjustment coefficient matrix T are cross-fixed to complete the optimization process, specifically:

[0075] Give examples of the turbulence fluctuation adjustment coefficient matrix T corresponding to high, medium and low turbulence fluctuation degrees, that is, give at least three examples of the turbulence fluctuation adjustment coefficient matrix T, that is, first assume that the turbulence fluctuation adjustment coefficient matrix T is known, in each example, optimize the fitness optimization relative coefficient matrix Γ by using the particle swarm algorithm to obtain the final fitness optimization relative coefficient matrix Γ;

[0076] After determining the fitness optimization relative coefficient matrix Γ, the turbulence fluctuation degree adjustment coefficient matrix T is optimized by the particle swarm algorithm to obtain the final turbulence fluctuation degree adjustment coefficient matrix T, and then the optimal correction phase screen left and right components are obtained.

[0077] Evaluation factor δ of right-handed light field's anti-turbulence capability R and the left-handed light field anti-turbulence ability evaluation factor δ L According to the following equations:

[0078]

[0079] Among them, β S0 is the S0 auxiliary evaluation factor, Where, SNR S0 is the spectrum signal-to-noise ratio of the S0 parameter of the light field when there is no turbulence, is the blaze index within the effective area of ​​the beam receiving area, P S0 is the received optical power of S0 parameter when there is no turbulence, is the received optical power of S0 parameter when there is turbulence;

[0080] β S3 is the S3 auxiliary evaluation factor, Where, SNR S3 is the spectrum signal-to-noise ratio of the S3 parameter of the light field in the absence of turbulence, is the blaze index within the effective area of ​​the beam receiving area, P S3 is the received optical power of the S3 parameter when there is no turbulence, is the received optical power of the S3 parameter when there is turbulence.

[0081] Specific implementation method 2: The following is combined Figures 1 to 4 This embodiment is described. The target rotation speed measurement method based on polarization-assisted phase compensation described in this embodiment is used to implement the target rotation speed measurement method based on polarization-assisted phase compensation described in Embodiment 1. The target rotation speed measurement device includes a target beam generating module, a first beam splitter 7, a first polarization information acquisition module 8, an atmospheric turbulence simulator 9, a second beam splitter 10, a second polarization information acquisition module 11, a transmitting system 12, a left / right optical component selection system 14, a receiving system 15, a distortion correction module 16, a detection processing module 17, and a rotation speed calculation module 18.

[0082] The light beam emitted by the modulated beam generation module includes left-handed circularly polarized vortex light and right-handed circularly polarized vortex light, which is divided into two paths by the first beam splitter 7. One path is used by the first polarization information acquisition module 8 to collect the pre-distortion polarization Stokes information. The other path passes through the atmospheric turbulence simulator 9 and is then divided into two paths by the second beam splitter 10. One path is used by the second polarization information acquisition module 11 to collect the post-distortion polarization Stokes information. The other path passes through the transmitting system 12 to irradiate the moving object 13 to generate an echo signal.

[0083] After passing through the left / right rotation component selection system 14, the receiving system 15 receives the echo signal, corrects the distortion through the distortion correction module 16, detects the light spot signal through the detection processing module 17, and obtains the time series signal of the light intensity through the oscilloscope, performs Fourier transform on it, and calculates the rotation speed of the moving target through the rotation speed calculation module 18.

[0084] The target beam generation module includes a laser 1, a first lens group 2, a first spatial light modulator 3, a second spatial light modulator 5, a half-wave plate, a second lens group 4 and a quarter-wave plate 6; the laser light emitted by the laser 1 reaches the first lens group 2, the first lens group 2 expands, collimates and polarizes the light beam to form a beam of 45-degree linearly polarized light, the first spatial light modulator 3 performs orbital angular momentum quantum control on the horizontal polarization direction of the light beam to generate a -5-order vortex beam signal, passes through the half-wave plate and the second lens group 4, adjusts the vertical polarization direction of the light beam to the horizontal direction, the second spatial light modulator 5 performs orbital angular momentum quantum control on the vertical polarization direction of the light beam to generate a 5-order vortex beam signal, passes through the quarter-wave plate 6 to convert it into left-handed and right-handed circularly polarized vortex light, and the target beam can be obtained by superposition;

[0085] The first spatial light modulator 3 and the second spatial light modulator 5 are polarization-dependent liquid crystal reflective phase modulators that can modulate the light field in the horizontal X direction. The modulation process of the Gaussian mode laser signal requires loading the phase map of the vortex light onto the two spatial light modulators, and the vortex beam can be generated by laser incidence.

[0086] The function of the half-wave plate and the half-wave plate in the second lens group 4 is to rotate the polarization component direction of the light beam, which can cause the linear polarized light to produce a phase delay of π / 2 and convert the vertical polarization direction into the horizontal direction; the second lens group uses a 4F lens system to expand the light beam;

[0087] The 1 / 4 wave plate 6 converts the polarization components of the polarized vortex beam in the X and Y directions into left-handed and right-handed polarized light components.

[0088] The first polarization information acquisition module 8 and the second polarization information acquisition module 11 have the same structure, including a quarter wave plate, a polarizer and a charge coupled device. By adjusting the quarter wave plate and the polarizer, the polarization direction of the light beam is adjusted to obtain the Stokes polarization information of S0, S1, S2, and S3. Among them, S0 = I0, S1 = I H -I V , S2=I +45° -I -45° , S3=I R -I L ,I0,I H ,I V ,I +45° ,I -45° ,I R ,I L Represent the total light intensity, horizontal, vertical, diagonal, anti-diagonal, right-handed and left-handed circular polarization directions of light intensity respectively.

[0089] The atmospheric turbulence simulator 9 is a transmissive spatial light modulator loaded with a random phase screen simulated by a power spectrum inversion method to replace the atmospheric turbulence process, and the light beam is distorted when passing through the transmissive spatial light modulator.

[0090] The left / right-hand component selection system 14 includes a quarter-wave plate and a linear polarizer, and by adjusting the rotation angle of the two optical elements, the left and right-hand components of the polarized vortex beam can be obtained;

[0091] Adjust the fast axis direction of the quarter-wave plate to vertical and the transmission direction of the linear polarizer to 45° to obtain the right-handed component of the polarized vortex beam;

[0092] Keeping the quarter-wave plate unchanged, the transmission direction of the linear polarizer is adjusted to 135° to obtain the left-handed component of the polarized vortex beam.

[0093] See also Figure 2 The distortion correction module 16 includes a third spatial light modulator 16-1, a third beam splitter 16-2, a wavefront sensor 16-3 and a feedback signal controller 16-4; the wavefront sensor 16-3 is implemented by CCD.

[0094] The third spatial light modulator 16 - 1 is a wavefront corrector, and the feedback signal controller 16 - 4 transmits the obtained correction phase to it, thereby correcting the polarization component of the vortex light beam.

[0095] The wavefront sensor 16 - 3 obtains the distortion phase of the light field and sends it to the feedback signal controller 16 - 4 ;

[0096] The input and output light field information obtained by the first polarization information obtaining module 8 and the second polarization information obtaining module 11 are synchronously sent to the feedback signal controller 16 - 4 ;

[0097] The feedback signal controller 16-4 uses the GS algorithm and the particle swarm optimization algorithm to obtain the corrected phase screen left-handed component H L and the right-handed component H of the corrected phase screen R Perform phase correction.

[0098] The detection and processing module 17 includes an avalanche photodiode detector and an oscilloscope. The avalanche photodiode detector detects the light beam output by the left / right rotation component selection system 14 to obtain a time series signal of light intensity, performs Fourier transform on it, obtains the Doppler frequency shift, and the rotation speed calculation module 18 calculates the rotation speed of the moving target.

[0099] The avalanche photodiode detector performs Fourier transform on the time series signal of the total light intensity of the received signal at each moment, and extracts the Doppler frequency shift Δf i , and the rotation speed is obtained by the following formula:

[0100] Δf=mΩ / 2π

[0101] Where m is the orbital angular momentum order of the corresponding spot area, and Ω is the rotation speed of the target.

[0102] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A method for measuring target rotation speed based on polarization-assisted phase compensation, characterized in that: The method comprises the following steps: Step 1: a target light beam is emitted from a transmitting system and hits a moving target in a turbulent environment to generate an echo signal, wherein the target light beam includes left-handed circularly polarized vortex light and right-handed circularly polarized vortex light; Step 2: Monitor the polarization Stokes information before and after turbulence distortion; the polarization Stokes information includes the phase distribution and intensity distribution of four parameters S0, S1, S2 and S3; The phase information of the parameters S1 and S2 before distortion and the light intensity information of the parameters S0 and S3 are used as the input light field information, and the phase information of the parameters S1 and S2 after distortion and the light intensity information of the parameters S0 and S3 are used as the output light field information. The input and output light field information are input into the GS algorithm to obtain the distorted polarization vortex beam S1 component φ GS,S1 , S2 component of distorted polarized vortex beam φ GS,S2 ; Step 3: Use the wavefront sensor to monitor the left-handed component and the right-handed component of the echo signal, and use the obtained distortion phase of the left-handed component and the right-handed component as the output light field information. The phase of the left-handed circularly polarized vortex light and the right-handed circularly polarized vortex light before distortion is used as the input light field information. The input light field information and the output light field information are input into the GS algorithm to obtain the distorted polarized left-handed vortex beam component φ GS,EL and the distorted polarized right-handed vortex beam component φ GS,ER ; Step 4: Calculate the S1 component pre-correction phase screen C1, S2 component pre-correction phase screen C2, and pre-correction phase screen left-handed component H according to the results of steps 2 and 3. L0 and the right-handed component H of the pre-corrected phase screen R0 : C1=angle(S1)-φ GS,S1 C2=angle(S2)-φ GS,S2 H R0 =angle(E R )-φ GS,ER H L0 =angle(E L )-φ GS,EL Where, angle(S1) and angle(S2) represent the phases of the polarization Stokes parameters S1 and S2 before distortion, and angle(E R )、angle(E L ) represents the phase of the right-handed and left-handed optical fields before distortion; Step 5: Obtain the left-handed component H of the correction phase screen L and the right-handed component H of the corrected phase screen R : H R =T(H R0 +δ L (Γ*C1+C2)) H L =T(H L0 +δ R (Γ*C1+C2)) Where Γ is the relative coefficient matrix of fitness optimization, T is the turbulence fluctuation adjustment coefficient matrix, δ R is the evaluation factor of the anti-turbulence ability of the right-handed light field, δ L is the evaluation factor of the anti-turbulence ability of the left-handed light field; Step 6. Use the correction phase screen obtained in step 5 to perform phase correction on the left-handed and right-handed polarization components of the vortex beam of the echo signal. The detection and processing module detects the polarization component of the vortex beam and obtains the Doppler frequency shift; the rotation speed of the moving target is calculated by the rotation speed calculation module.

2. The target rotation speed measurement method based on polarization-assisted phase compensation according to claim 1, characterized in that: The fitness optimization relative coefficient matrix Γ and the turbulence fluctuation adjustment coefficient matrix T are both optimized by the particle swarm algorithm, among which the fitness optimization relative coefficient matrix Γ is optimized with the highest or average velocity measurement accuracy. As the fitness function, the optimization goal is to minimize the speed measurement error of the speed measurement system. Where τ is the integration time of the detector, SNR is the spectral signal-to-noise ratio of the left-handed or right-handed circularly polarized component, and l is the order of the left-handed circularly polarized vortex light and the right-handed circularly polarized vortex light; The turbulence fluctuation adjustment coefficient matrix T is optimized with purity as the fitness function.

3. The target rotation speed measurement method based on polarization-assisted phase compensation according to claim 2, characterized in that: The fitness optimization relative coefficient matrix Γ and the turbulence fluctuation adjustment coefficient matrix T are cross-fixed to complete the optimization process, specifically: Examples of turbulence fluctuation adjustment coefficient matrices T corresponding to high, medium and low turbulence fluctuation degrees are given. In each example, the fitness optimization relative coefficient matrix Γ is optimized using the particle swarm algorithm to obtain the final fitness optimization relative coefficient matrix Γ. After determining the fitness optimization relative coefficient matrix Γ, the turbulence fluctuation degree adjustment coefficient matrix T is optimized by the particle swarm algorithm to obtain the final turbulence fluctuation degree adjustment coefficient matrix T, and then the optimal correction phase screen left and right components are obtained.

4. The target rotation speed measurement method based on polarization-assisted phase compensation according to claim 1, characterized in that: Evaluation factor δ of right-handed light field's anti-turbulence capability R and the left-handed light field anti-turbulence ability evaluation factor δ L According to the following equations: Among them, β S0 is the S0 auxiliary evaluation factor, Where, SNR S0 is the spectrum signal-to-noise ratio of the S0 parameter of the light field when there is no turbulence, is the blaze index within the effective area of ​​the beam receiving area, P S0 is the received optical power of S0 parameter when there is no turbulence, is the received optical power of S0 parameter when there is turbulence; β S3 is the S3 auxiliary evaluation factor, Where, SNR S3 is the spectrum signal-to-noise ratio of the S3 parameter of the light field in the absence of turbulence, is the blaze index within the effective area of ​​the beam receiving area, P S3 is the received optical power of the S3 parameter when there is no turbulence, is the received optical power of the S3 parameter when there is turbulence.

5. A target rotation speed measurement device based on polarization-assisted phase compensation, the device being used to implement the method according to any one of claims 1 to 4, characterized in that: The target rotation speed measuring device comprises a target light beam generating module, a first beam splitter (7), a first polarization information acquiring module (8), an atmospheric turbulence simulator (9), a second beam splitter (10), a second polarization information acquiring module (11), a transmitting system (12), a left / right optical component selecting system (14), a receiving system (15), a distortion correction module (16), a detection processing module (17), and a rotation speed calculating module (18); The light beam emitted by the modulated light beam generating module includes left-handed circularly polarized vortex light and right-handed circularly polarized vortex light, which is divided into two paths by a first beam splitter (7), one of which is used by a first polarization information acquisition module (8) to collect the pre-distortion polarization Stokes information, and the other is divided into two paths by a second beam splitter (10) after passing through an atmospheric turbulence simulator (9), one of which is used by a second polarization information acquisition module (11) to collect the post-distortion polarization Stokes information, and the other is used by a transmitting system (12) to illuminate a moving object (13) to generate an echo signal; After passing through the left / right optical component selection system (14), the receiving system (15) receives the echo signal, corrects the distortion through the distortion correction module (16), detects the light spot signal through the detection processing module (17), and obtains the time series signal of the light intensity through the oscilloscope, performs Fourier transform on it, and calculates the rotation speed of the moving target through the rotation speed calculation module (18).

6. The target rotation speed measurement device based on polarization-assisted phase compensation according to claim 5, characterized in that: The target beam generation module comprises a laser (1), a first lens group (2), a first spatial light modulator (3), a second spatial light modulator (5), a half-wave plate, a second lens group (4) and a quarter-wave plate (6); the laser light emitted by the laser (1) is sent to the first lens group (2); the first lens group (2) expands, collimates and polarizes the light beam to form a beam of 45-degree linearly polarized light; the first spatial light modulator (3) performs orbital angular momentum quantum control on the horizontal polarization direction of the light beam to generate a -5th order vortex beam signal; the vertical polarization direction of the light beam is adjusted to the horizontal direction through the half-wave plate and the second lens group (4); the second spatial light modulator (5) performs orbital angular momentum quantum control on the vertical polarization direction of the light beam to generate a fifth order vortex beam signal; the light beam is converted into left-handed and right-handed circularly polarized vortex light through the quarter-wave plate (6); and the target beam can be obtained by superposition; The first spatial light modulator (3) and the second spatial light modulator (5) are polarization-dependent liquid crystal reflective phase modulators, which can modulate the horizontal X direction of the light field; the modulation process of the Gaussian mode laser signal requires loading the phase diagram of the vortex light onto the two spatial light modulators, and the vortex light beam can be generated by the laser incident; The half-wave plate and the half-wave plate in the second lens group (4) are used to rotate the polarization component direction of the light beam, so as to cause the linear polarized light to produce a phase delay of π / 2 and convert the vertical polarization direction into a horizontal direction; the second lens group uses a 4F lens system to expand the light beam; The 1 / 4 wave plate (6) converts the polarization components of the polarized vortex light beams in the X and Y directions into left-handed and right-handed polarized light components.

7. The target rotation speed measurement device based on polarization-assisted phase compensation according to claim 5, characterized in that: The first polarization information acquisition module (8) and the second polarization information acquisition module (11) have the same structure, including a quarter wave plate, a polarizer and a charge coupled device. The polarization direction of the light beam is adjusted by adjusting the quarter wave plate and the polarizer, thereby obtaining Stokes polarization information of S0, S1, S2 and S3.

8. The target rotation speed measurement device based on polarization-assisted phase compensation according to claim 5, characterized in that: The left / right rotating light component selection system (14) includes a quarter wave plate and a linear polarizer, and the left and right rotating components of the polarized vortex light beam are obtained by adjusting the rotation angle of the two optical elements; Adjust the fast axis direction of the quarter-wave plate to vertical and the transmission direction of the linear polarizer to 45° to obtain the right-handed component of the polarized vortex beam; Keeping the quarter-wave plate unchanged, the transmission direction of the linear polarizer is adjusted to 135° to obtain the left-handed component of the polarized vortex beam.

9. The target rotation speed measurement device based on polarization-assisted phase compensation according to claim 5, characterized in that: The distortion correction module (16) includes a third spatial light modulator (16-1), a third beam splitter (16-2), a wavefront sensor (16-3) and a feedback signal controller (16-4); The third spatial light modulator (16-1) is a wavefront corrector, and the feedback signal controller (16-4) transmits the obtained correction phase to it, thereby correcting the polarization component of the vortex light beam. The wavefront sensor (16-3) obtains the distortion phase of the light field and sends it to the feedback signal controller (16-4); The input and output light field information acquired by the first polarization information acquisition module (8) and the second polarization information acquisition module (11) are synchronously sent to the feedback signal controller (16-4); The feedback signal controller (16-4) uses the GS algorithm and the particle swarm optimization algorithm to obtain the corrected phase screen left-handed component H L and the right-handed component H of the corrected phase screen R Perform phase correction.

10. The target rotation speed measurement device based on polarization-assisted phase compensation according to claim 5, characterized in that: The detection processing module (17) includes an avalanche photodiode detector and an oscilloscope. The avalanche photodiode detector detects the light beam output by the left / right rotation component selection system (14) to obtain a time series signal of light intensity, performs Fourier transform on the light intensity, obtains Doppler frequency shift, and calculates the rotation speed of the moving target by the rotation speed calculation module (18).

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