A photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation

Abstract

The application provides a photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation. In view of the scattering effect and attenuation of a strong scattering medium on a light signal, a point-to-point scanning imaging mechanism is adopted to avoid image blurring caused by the scattering effect, and a single-pixel photon counter is used to capture weak ballistic photon signals. The time of flight of the ballistic photon signal is calculated by a polarization modulation ranging method, and the depth blurring problem introduced by the asynchronous polarization modulation is corrected by a time reshaping method, and finally the relative depth image of the target object is reconstructed. The method can realize three-dimensional imaging of the target object through the strong scattering medium, the imaging effect is clear, and the method has robustness to different strong scattering media, and provides convenience for three-dimensional photon counting imaging in a scattering environment.

Description

Technical Field

[0001] This invention belongs to the field of photon counting three-dimensional imaging and relates to a photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation, which is applicable to various photon counting three-dimensional imaging application scenarios through strong scattering media. Background Technology

[0002] Compared with traditional photon counting 3D imaging, photon counting 3D penetration imaging technology can be applied to the detection and analysis of targets through complex and unknown scattering media, and has been applied in fields such as biomedicine and remote sensing.

[0003] In traditional 3D photon counting imaging techniques, distance calculation methods using time-of-flight technology can be divided into two types: direct and indirect methods. The direct method uses a timing circuit to obtain the flight time of the target's echo signal and then calculates a 3D point cloud image. In 3D penetration imaging based on the direct method, it is necessary to model and inversely derive the scattering process, and then reconstruct the 3D image using deconvolution of the spatiotemporal probe data. However, this method requires pre-calibration of the scattering medium, and its spatial resolution is limited by scattering effects. Indirect methods can be mainly divided into three types: time-gated methods, intensity-correlated methods, and gain modulation methods. Among these, only the time-gated method has been studied for 3D penetration imaging, which filters out backscattering noise by setting a specific gating time for the echo information. However, this method is still affected by scattering effects, and the 3D reconstruction quality of the target is poor in strong scattering environments. To solve these problems, a photon counting 3D penetration imaging technique suitable for strong scattering environments is needed.

[0004] The asynchronous polarization modulation-based photon counting scanning 3D penetration imaging method utilizes a point-to-point scanning imaging mechanism to avoid image blurring caused by scattering effects. By effectively detecting and time-correlatedly modulating the scattered ballistic photon signals, the relationship between photon count and target distance can be established, thereby achieving 3D penetration imaging of targets in strongly scattering environments. The key challenges of this method are accurately modeling the detected ballistic photon signals and resolving the signal periodic aliasing problem caused by asynchronous modulation. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by utilizing a point-to-point scanning imaging mechanism to perform photon counting three-dimensional imaging of targets in strong scattering environments, thereby directly avoiding imaging blurring caused by scattering effects. It provides a three-dimensional penetration imaging method based on asynchronous polarization modulation for strong scattering environments.

[0006] The technical solution adopted in this invention is as follows: Based on a point-to-point scanning imaging mechanism, a single-pixel photon counter is used to enhance the detection capability of weak ballistic photon signals, thereby adapting to three-dimensional penetration imaging in strong scattering environments and obtaining a polarization-modulated photon count image of the target. Furthermore, a gamma pulse model is used to effectively describe the asymmetry of echo signals in different scattering environments, enhancing the generalization of the model representation. Simultaneously, a relationship between signal flight time and the number of detected photons is established, and the signal flight time is calculated. Then, a time reshaping method is used to solve the depth ambiguity problem caused by the asynchronous control of the pulsed laser and the polarization modulator, further correcting the signal flight time. Finally, the relative depth of the target is obtained through the calculated signal flight time, thus achieving three-dimensional penetration imaging of the target. A schematic diagram of the imaging system is attached. Figure 1 As shown, the method includes the following steps:

[0007] Step 1: Establish the optical path of the imaging system. The laser beam from the pulsed laser scans the target surface point by point through a two-dimensional scanning galvanometer. The signal period of the pulsed laser is T. R The reflected signal from the target surface is partially captured by the receiving system after passing through the scattering medium. The captured echo photons pass through the polarization modulation module in the receiving system, which includes a polarizer LP1, an electro-optic phase modulator EOM, and an analyzer LP2, and are then received by a single-pixel photon counter.

[0008] Step 2: Adjust the probe optical path to acquire a polarization-modulated image. First, adjust the polarization angles of polarizer LP1 and analyzer LP2 to the vertical direction, then rotate analyzer LP2 45° clockwise. Set the voltage signal of EOM to V. t1 =V π / 2, acquire the first polarization modulation image k1, where V π This is the half-wave voltage of EOM. Then set the voltage signal of EOM to V. t2 =[1+cos(πt / (2 G ))] / 2, acquire the second polarization modulation image k2, where T G The modulation period of EOM is T. G =T r Finally, the voltage signal of EOM will be set to V. t3 =[1-sin(πt / (2T)] G ))] / 2, acquire the third polarization modulation image k3;

[0009] Step 3: Based on the gamma pulse model, model the ballistic photon signal after passing through the scattering medium, derive the relationship between the number of photons in the received polarization-modulated image and the signal flight time, and thus calculate the initial flight time T of the ballistic photon signal reflected from the target based on the three detected polarization-modulated images. m ;

[0010] Step 4: Since the pulsed laser and EOM are located on opposite sides of the scattering medium, the signal period T of the pulsed laser... r Modulation period T with EOM G The inability to perform synchronous control means that ballistic photon signals reflected from different spatial points of the target may have different modulation periods T. G The modulation introduces errors into the calculated initial flight time, resulting in depth blurring in the reconstructed 3D image of the target. Therefore, a time-reconstruction method is employed to address this issue. This method determines the polarization modulation of the ballistic photon signals reflected from different spatial points of the target, thereby correcting the flight time and obtaining a corrected ballistic photon signal flight time map. Finally, based on the corrected ballistic photon signal flight time diagram The relative depth map D of the target is calculated. R ;

[0011] Furthermore, the specific implementation of step 3 includes the following sub-steps:

[0012] Step 3.1, using the time-varying rate The non-uniform Poisson process is used to describe the detection process of ballistic photons by a photon counter, where t is time and η is the quantum efficiency of the photon counter. Let be the photon transmittance of the polarization modulation module, s(t) represent the waveform of the ballistic photon signal after passing through the scattering medium, and d be the dark counting noise of the photon counter. Therefore, in a single modulation period (0, T) G In the diagram, the photon counting rate m of the photon counter can be expressed as:

[0013]

[0014] Step 3.2, for a single spatial scanning point, the waveform s(t) of the ballistic photon signal after passing through the scattering medium can be expressed as:

[0015]

[0016] Where, N s T represents the average number of photons in a single signal pulse. sLet f(t) represent the flight time of the initial echo photon, and f(t) represent the pulse function. Considering that a strong scattering medium will cause the waveform of the pulse signal to broaden non-uniformly in the time domain, the gamma pulse function is used to describe the waveform of the echo photon signal. Therefore, the pulse function f(t) can be expressed as:

[0017]

[0018] Where a and b are the shape and size parameters of the gamma distribution, respectively, and Γ(·) is the gamma function. Equation (3) satisfies

[0019] Statistical analysis shows that for most scattering media, the transmitted signal waveform can be described by the gamma pulse function when a=2. Therefore, we use a=2, while treating b as a variable to adapt to different scattering media. Thus, the waveform s(t) of the ballistic photon signal after scattering through the scattering medium can be further expressed as...

[0020]

[0021] Step 3.3, the function of the EOM in the polarization modulation module can be regarded as introducing a phase shift α = πV to the photon signal. t / V π V t This is the voltage signal of the EOM. The photon transmittance of the polarization module is...

[0022]

[0023] Where θ is the angle between polarizer LP1 and analyzer LP2, i.e., θ = 45°.

[0024] Based on formulas (1), (4) and (5), the relationship between the photon counting rate m of the photon counter and the flight time of the initial echo photon can be obtained:

[0025]

[0026] Among them, T m =T d +T s T represents the polarization modulation time. d This is the time interval between the signal period of the pulsed laser and the modulation period of the EOM.

[0027] Step 3.4, based on the negative logarithmic maximum likelihood function under low light conditions, using the three polarization modulation images k1, k2, and k3 obtained in step 2, according to... Three photon count rate images, m1, m2, and m3, can be obtained, where N is the number of laser pulses and l = 1, 2, 3.

[0028] Then, according to formula (6), the following three equations can be obtained:

[0029]

[0030]

[0031]

[0032] Based on formula (7-9), N s and T m It can be calculated as follows:

[0033]

[0034]

[0035] in, Initial flight time diagram T m T obtained from all spatial scan points m composition.

[0036] Furthermore, the specific implementation of step 4 includes the following sub-steps:

[0037] Step 4.1, when the ballistic photon signals reflected from all spatial points of the target are not in the same modulation period T G When modulated, the echo signals at some spatial points no longer satisfy formula (1), but instead satisfy the following formula.

[0038]

[0039] Based on formulas (1) and (12), T in formula (6) s and T m The relationship can be summarized as follows:

[0040]

[0041] T described in formula (13) s and T m The uncertainty of the relationship can lead to ambiguity in the calculated 3D depth of the target. Therefore, a time-reconstruction method is needed to solve this problem. A schematic diagram of the time-reconstruction method is attached. Figure 2 As shown.

[0042] Assuming the actual flight time of the ballistic photon signal does not exceed half of the polarization modulation period, i.e., T s ≤T G / 2, when max(T) m )-min(T m )≤T GAt / 2, it is determined that the ballistic photon signals reflected from all spatial points of the target are in the same modulation period T. G Modulated, no correction is needed for the initial flight time calculated in step 3.4, i.e. When max(T) m )-min(T m )≤T G At / 2, it is determined that the ballistic photon signals reflected from all spatial points of the target are not in the same modulation period T. G Modulated, at this time the initial flight time map T calculated in step 3.4 is... m After correction, the corrected ballistic photon signal flight time map is obtained.

[0043]

[0044] Among them, T m (i,j) is T m The value of the target point (i,j) in the target space. for The value of the target space point (i,j).

[0045] Step 4.2, base The relative depth map of the target can be calculated:

[0046]

[0047] Compared with existing technologies, the advantages and beneficial effects of this invention are as follows: This invention utilizes a point-to-point scanning imaging mechanism to perform photon counting 3D imaging of targets in strong scattering environments, directly avoiding imaging blurring caused by scattering effects. Furthermore, it effectively describes the asymmetry of echo signals in different scattering environments using a gamma pulse model, enhancing the generalization of the model representation. Simultaneously, it employs a time reshaping method to address the depth blurring problem caused by the asynchronous control of the pulsed laser and polarization modulator, further correcting the signal's time of flight. This invention can be applied to 3D imaging in various strong scattering environments, resulting in clear spatial information, accurate depth information, and high depth resolution in the final imaging results. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a photon counting scanning three-dimensional penetration imaging system based on asynchronous polarization modulation.

[0049] Figure 2 This is a schematic diagram of the time reshaping method.

[0050] Figure 3 This is a schematic diagram of the imaging environment of an embodiment.

[0051] Figure 4 This is an intensity image of an embodiment.

[0052] Figure 5 This is a real photograph of the light transmission from both sides of the scattering medium used in the imaging process of the embodiment.

[0053] Figure 6 This is a surface reflectance reconstruction diagram of an embodiment.

[0054] Figure 7 This is a relative depth reconstruction map of an embodiment. Detailed Implementation

[0055] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0056] This invention primarily addresses the application requirement of three-dimensional imaging of targets through strongly scattering media. Based on polarization modulation ranging theory, we propose a photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation. A point-to-point scanning imaging mechanism is used to avoid image blurring caused by scattering effects. Furthermore, by capturing three polarization-modulated images, the flight time of the ballistic photon signals reflected from the target is calculated and corrected, ultimately reconstructing the relative depth image of the target.

[0057] Appendix Figure 3 This is a schematic diagram of the imaging environment in an embodiment. In room 1, a pulsed laser scans a target object—a paper cup—using a two-dimensional galvanometer. The intensity image is shown in the attached diagram. Figure 4 As shown. The reflected light from the target object's surface reaches room 2 after passing through a strong scattering medium. The strong scattering medium used is frosted glass, and actual photos of its light transmission on both sides are attached. Figure 5 As shown, the polarization modulation module and single-pixel photon counter of the imaging system are located in room 2 to capture ballistic photon signals reflected from the target surface.

[0058] This embodiment provides a photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation to perform three-dimensional imaging of a target through a strongly scattering medium, specifically including the following steps:

[0059] Step 1: Establish the optical path of the imaging system. The laser beam from the pulsed laser scans the target surface point by point through a two-dimensional scanning galvanometer. The signal period of the pulsed laser is T. r =100ns. The reflected signal from the target surface is partially captured by the receiving system after passing through the scattering medium. The captured echo photons pass through the polarization modulation module in the receiving system, which includes a polarizer LP1, an electro-optic phase modulator EOM, and an analyzer LP2, and are then received by a single-pixel photon counter;

[0060] Step 2: Adjust the probe optical path to acquire a polarization-modulated image. First, adjust the polarization angles of polarizer LP1 and analyzer LP2 to the vertical direction, then rotate analyzer LP2 45° clockwise. Set the voltage signal of EOM to... The first polarization-modulated image k1 is acquired, where V π -10V is the half-wave voltage of EOM. Then set the voltage signal of EOM to V. t2 =[1+cos(πt / (2T)] G ))] / 2, acquire the second polarization modulation image k2, where T G The modulation period of EOM is T. G =T r =100ns. Finally, the voltage signal of EOM will be set to V. t3 =[1-sin(πt / (2T)] G ))] / 2, acquire the third polarization modulation image k3;

[0061] Step 3: Based on the gamma pulse model, model the ballistic photon signal after passing through the scattering medium, derive the relationship between the number of photons in the received polarization-modulated image and the signal flight time, and thus calculate the initial flight time T of the ballistic photon signal reflected from the target based on the three detected polarization-modulated images. m The specific implementation includes the following sub-steps:

[0062] Step 3.1: Utilize the time-varying rate The non-uniform Poisson process is used to describe the detection process of ballistic photons by a photon counter, where η = 0.3 is the quantum efficiency of the photon counter. Let d = 0.25, where s(t) represents the photon transmittance of the polarization modulation module, s(t) represents the waveform of the ballistic photon signal after passing through the scattering medium, and d = 0.25. -1 Let m be the dark counting noise of the photon counter. Therefore, in a single modulation period (0, 100], the photon counting rate m of the photon counter can be expressed as:

[0063]

[0064] Step 3.2, for a single spatial scanning point, the waveform s(t) of the ballistic photon signal after passing through the scattering medium can be expressed as:

[0065]

[0066] Where, N s T represents the average number of photons in a single signal pulse. sLet f(t) represent the flight time of the initial echo photon, and f(t) represent the pulse function. Considering that a strong scattering medium will cause the waveform of the pulse signal to broaden non-uniformly in the time domain, the gamma pulse function is used to describe the waveform of the echo photon signal. Therefore, the pulse function f(t) can be expressed as:

[0067]

[0068] Where a and b are the shape and size parameters of the gamma distribution, respectively, and Γ(·) is the gamma function. The above equation satisfies...

[0069] By using a = 2 and treating b as a variable to adapt to different scattering media, the waveform s(t) of the ballistic photon signal after scattering through the scattering medium can be further expressed as:

[0070]

[0071] Step 3.3, the function of the EOM in the polarization modulation module can be regarded as introducing a phase shift α = πV to the photon signal. t / 10, where V t This is the voltage signal of the EOM. The photon transmittance of the polarization module is...

[0072]

[0073] Where θ is the angle between polarizer LP1 and analyzer LP2, i.e., θ = 45°.

[0074] Then we can obtain the relationship between the photon counting rate m of the photon counter and the flight time of the initial echo photon:

[0075]

[0076] Among them, T m =T d +T s T represents the polarization modulation time. d This is the time interval between the signal period of the pulsed laser and the modulation period of the EOM.

[0077] Step 3.4, based on the negative logarithmic maximum likelihood function under low light conditions, using the three polarization modulation images k1, k2, and k3 obtained in step 2, according to... Three photon count rate images, m1, m2, and m3, can be obtained, where N is the number of laser pulses and l = 1, 2, 3.

[0078] Then, we can obtain the following three equations:

[0079] m1 = 0.25T G +0.15N s

[0080]

[0081]

[0082] Solve the system of equations consisting of the three equations above, N s and T m We can obtain:

[0083]

[0084]

[0085] in, Initial flight time diagram T m T obtained from all spatial scan points m composition.

[0086] Step 4: Since the pulsed laser and EOM are located on opposite sides of the scattering medium, the signal period T of the pulsed laser... r Modulation period T with EOM G The inability to perform synchronous control means that ballistic photon signals reflected from different spatial points of the target may have different modulation periods T. G The modulation introduces errors into the calculated initial flight time, resulting in depth blurring in the reconstructed 3D image of the target. Therefore, a time-reconstruction method is employed to address this issue. This method determines the polarization modulation of the ballistic photon signals reflected from different spatial points of the target, thereby correcting the flight time and obtaining a corrected ballistic photon signal flight time map. Finally, based on the corrected ballistic photon signal flight time diagram The relative depth map D of the target is calculated. R The specific implementation includes the following sub-steps:

[0087] Step 4.1: Determine whether the ballistic photon signals reflected from all spatial points of the target are modulated within the same modulation period. Since this embodiment has max(T)... m )-min(T m )≤T G / 2, therefore, it is determined that the ballistic photon signals reflected from all spatial points of the target are not in the same modulation period T. G Modulated, at this time the initial flight time map T calculated in step 3.4 is... m After correction, the corrected ballistic photon signal flight time map is obtained.

[0088]

[0089] Among them, T m(i,j) is T m The value of the target point (i,j) in the target space. for The value of the target space point (i,j).

[0090] Step 4.2, based on The relative depth map of the target can be calculated:

[0091]

[0092] Based on the above steps, the surface reflectance reconstruction map and relative depth reconstruction map of the target object are obtained as shown in the appendix. Figure 6 and attached Figure 7 As shown, the method proposed in this invention is based on a point-to-point scanning imaging mechanism and a polarization modulation ranging principle. It uses a single-pixel photon counter to acquire the weak ballistic photon signal after passing through a strongly scattering medium, and further reconstructs the relative depth image of the target, thus enabling three-dimensional imaging of the target through a strongly scattering medium.

[0093] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0094] It should be understood that the above description of the embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art can make substitutions or modifications under the guidance of this invention without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A three-dimensional penetration imaging method based on photon counting scanning using asynchronous polarization modulation, characterized in that, Includes the following steps: Step 1: Set up the imaging system; The imaging system includes a pulsed laser, a two-dimensional scanning galvanometer, a target object, a scattering medium, and a receiving system. The receiving system includes a polarization modulation module and a single-pixel photon counter. The polarization modulation module includes a polarizer LP1, an electro-optic phase modulator EOM, and an analyzer LP2. Step 2: Adjust the detection optical path to obtain polarization modulation images, that is, adjust the polarization angle of polarizer LP1 and analyzer LP2 to obtain multiple polarization modulation images; Step 3: Based on the gamma pulse model, the ballistic photon signal after passing through the scattering medium is modeled, and the relationship between the number of photons in the received polarization-modulated image and the signal flight time is derived. Therefore, based on the detected multiple polarization-modulated images, the initial flight time map of the ballistic photon signal reflected from the target is calculated. ; Step 4: Determine the polarization modulation of the ballistic photon signals reflected from different spatial points of the target, thereby correcting the flight time and obtaining the corrected ballistic photon signal flight time map. Finally, based on the corrected ballistic photon signal flight time diagram The relative depth map of the target is calculated. .

2. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 1, characterized in that: The specific implementation method of step 1 is as follows; The laser beam from the pulsed laser scans the target surface point by point using a two-dimensional scanning galvanometer. The signal period of the pulsed laser is... The reflected signal from the target surface is partially captured by the receiving system after passing through the scattering medium. The captured echo signal photons pass through the polarization modulation module in the receiving system, which includes a polarizer LP1, an electro-optic phase modulator EOM, and an analyzer LP2, and are then received by a single-pixel photon counter.

3. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 1, characterized in that: Three polarization modulation images were obtained in step 2.

4. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 2, characterized in that: The specific implementation method of step 2 is as follows; First, adjust the polarization angles of polarizer LP1 and analyzer LP2 to the vertical direction. Then, rotate analyzer LP2 45° clockwise. Set the voltage signal of EOM to... Acquire the first polarization-modulated image ,in It is the half-wave voltage of EOM, and then the voltage signal of EOM is set to... Acquire the second polarization-modulated image. where t is time, The modulation period of EOM is, and Finally, the voltage signal of EOM will be set to... Acquire the third polarization-modulated image. .

5. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 1, characterized in that: Step 3 includes the following sub-steps: Step 3.1, using the time-varying rate The non-uniform Poisson process is used to describe the detection process of ballistic photons by a photon counter, where... The quantum efficiency of the photon counter. Photon transmittance of the polarization modulation module This represents the waveform of the ballistic photon signal after passing through the scattering medium. This is the dark counting noise of the photon counter; therefore, in a single modulation cycle middle, The modulation period of EOM, and the photon counting rate of the photon counter. It is represented as: (1) Step 3.2, for a single spatial scanning point, the waveform of the ballistic photon signal after passing through the scattering medium. It is represented as: (2) in, This represents the average number of photons in a single signal pulse. Indicates the flight time of the initial echo photon. The pulse function is used to describe the waveform of the echo photon signal, considering that a strong scattering medium will cause the waveform of the pulse signal to broaden non-uniformly in the time domain. Therefore, the pulse function is... Represented as: (3) in, and These are the shape and size parameters of the gamma distribution, respectively. For the gamma function, formula (3) satisfies ; Statistical analysis reveals that for most scattering media, the transmitted signal waveform is... The time-varying gamma pulse function is used to describe this, therefore, the following is adopted. At the same time As a variable to adapt to different scattering media; therefore, the waveform of the ballistic photon signal after scattering the medium. It is further represented as: (4) Step 3.3, the EOM in the polarization modulation module is regarded as introducing a phase shift to the photon signal. ,in This is the voltage signal of the EOM. The photon transmittance of the polarization module is: (5) in, The angle between polarizer LP1 and analyzer LP2 is... ; Based on formulas (1), (4) and (5), the photon counting rate of the photon counter is obtained. The relationship with the flight time of the initial echo photon is as follows: (6) in, Indicates the polarization modulation time. This is the time interval between the signal period of the pulsed laser and the modulation period of the EOM; Step 3.4: Based on the negative logarithmic maximum likelihood function under low light conditions, the three polarization modulation images obtained in Step 2 are used... , and ,according to Obtain three photon count rate images , and ,in The number of laser pulses. ; Then, according to formula (6), the following three equations are obtained: (7) (8) (9) Based on formula (7-9), and The result is: (10) (11) in, Initial flight time map Determined from all spatial scan points composition.

6. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 5, characterized in that: Step 4 includes the following sub-steps: Step 4.1, when the ballistic photon signals reflected from all spatial points of the target are not in the same modulation period When modulated, the echo signals at some spatial points no longer satisfy formula (1), but instead satisfy the following formula: (12) Based on formulas (1) and (12), in formula (6) and The relationship can be summarized as follows: (13) The formula described in formula (13) and The uncertainty of the relationship can lead to ambiguity in the calculated 3D depth of the target. Therefore, it is necessary to use the time reshaping method to solve the above problem. The specific implementation method is as follows: Assuming the actual flight time of the ballistic photon signal does not exceed half of the polarization modulation period, i.e. ,when At that time, it is determined that the ballistic photon signals reflected from all spatial points of the target are in the same modulation period. Modulated, no correction is needed for the initial flight time calculated in step 3.4, i.e. ;when At that time, it is determined that the ballistic photon signals reflected from all spatial points of the target are not in the same modulation period. Modulated, at this point, the initial flight time map calculated in step 3.4 is... After correction, the corrected ballistic photon signal flight time map is obtained. : (14) in, for Target Space Point The value, for Target Space Point The value; Step 4.2, based on Calculate the relative depth map of the target: (15)。 7. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 5, characterized in that: The strong scattering medium is frosted glass.

8. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 2, characterized in that: The signal period of the pulsed laser is .

9. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 4, characterized in that: ， 。 10. The photon counting scanning three-dimensional penetration imaging method based on asynchronous polarization modulation as described in claim 5, characterized in that: ， 。

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