A method and device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system

Abstract

The application provides a polarization state transmission characteristic acquisition method and device of a non-visual imaging system, and aims to solve the technical problem that, in the current non-visual imaging technology based on time of flight, the polarization characteristic transmission of three times of reflection light is not studied enough, so that a polarization state with higher light energy utilization rate cannot be selected to enhance the echo signal and improve the target detection quality. The method is as follows: making polarized light of a preset polarization state incident to an interface at a certain azimuthal incidence angle; adjusting the pitch angle of the interface and the azimuthal angle of the imaging target in sequence to obtain the polarization state of the reflected light of the interface at each pitch angle and the polarization state of the reflected light of the imaging target at each azimuthal angle under the azimuthal incidence angle; and repeating the adjustment until the polarization state transmission characteristics of the reflected light of the interface at each pitch angle and the polarization state transmission characteristics of the reflected light of the imaging target at each azimuthal angle under the azimuthal incidence angle of the polarized light of all corresponding preset polarization states are obtained.

Description

Technical Field

[0001] This invention relates to non-line-of-sight imaging technology, and more particularly to a method and apparatus for obtaining polarization state transmission characteristics of a non-line-of-sight imaging system. Background Technology

[0002] Non-line-of-sight (NLOS) imaging technology can break through the field of view of traditional optical imaging, detecting targets obscured by corners. Based on whether or not illumination light is actively emitted, it is divided into active detection NLOS imaging technology and passive detection NLOS imaging technology. Active detection NLOS imaging technology is currently the mainstream imaging technology. Its specific principle is as follows: the light beam passes through the mid-interface near the corner, and after reflection from the mid-interface, a very small portion of the light reaches the target. After reflection from the target, it is reflected a second time through the mid-interface and finally received by the detector. The received data is then processed to reconstruct information such as the target's shape and reflectivity. This technology breaks through the field of view of traditional optical imaging systems, enabling imaging of targets outside the field of view, and has extremely important application value in fields such as emergency rescue and autonomous driving.

[0003] Currently, the most commonly used non-line-of-sight (NFS) imaging technology is time-of-flight (TOF) NFS. It uses ultrafast pulsed lasers as the light source and high-temporal-resolution streak cameras as detectors, employing the photon's time of flight as the core of the reconstruction algorithm to decode the target's depth information and reflectivity distribution. In TOF NFS, the light wave undergoes three reflections, resulting in weak echo signals and significant detection challenges. Although this technology is widely used, insufficient research on the polarization characteristics of the three reflected light streams remains a gap in understanding. This prevents the selection of polarization states with higher light energy utilization to enhance the echo signal and improve target detection quality. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem in current time-of-flight-based non-line-of-sight imaging technology that, due to insufficient research on the polarization characteristics of the three reflected light, it is impossible to select a polarization state with higher light energy utilization to enhance the echo signal and improve the target detection quality. The invention provides a method and apparatus for obtaining the polarization state transmission characteristics of a non-line-of-sight imaging system.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for obtaining polarization state transmission characteristics of a non-line-of-sight imaging system, characterized by the following steps:

[0007] 1. Adjust the polarization state of the emitted laser to obtain polarized light with a preset polarization state;

[0008] 2】The current polarized light is incident on the middle interface at an incident angle of a certain direction. The elevation angle of the middle interface is adjusted to obtain the reflected light at each elevation angle. At the same time, the polarization intensity of the reflected light at each elevation angle of the middle interface at the incident angle of that direction is detected to obtain the polarization state of the reflected light at each elevation angle of the middle interface at the incident angle of that direction.

[0009] 3】Adjust the azimuth angle of the imaging target to obtain incident light at different azimuth angles, and at the same time detect the polarization intensity of the reflected light of the imaging target at each azimuth angle under the incident angle, so as to obtain the polarization state of the reflected light of the imaging target at each azimuth angle under the incident angle.

[0010] 4. Adjust the azimuth angle of the current polarized light incident on the mid-interface;

[0011] 5】Return to step 2】, until the polarization state of the light reflected from the interface at various pitch angles and the polarization state of the light reflected from the imaging target at various azimuth angles are obtained under multiple preset incident angles of different polarization.

[0012] 6. Adjust the polarization state of the emitted laser to obtain polarized light with another preset polarization state;

[0013] 7】Return to step 2】, until all preset polarized light is obtained at multiple preset different incident angles, the polarization state of the light reflected by the interface at each pitch angle and the polarization state of the light reflected by the imaging target at each azimuth angle.

[0014] 8】Based on the polarization state of the polarized light of all preset polarization states at multiple preset incident angles, the polarization state of the light reflected by the middle interface at each pitch angle and the polarization state of the light reflected by the imaging target at each azimuth angle, the polarization state transmission characteristics of the polarization state of the light reflected by the middle interface at each pitch angle and the polarization state transmission characteristics of the light reflected by the imaging target at each azimuth angle are obtained.

[0015] Steps 1 through 7 are all performed in a dark room.

[0016] Furthermore, in step 2], the pitch angle adjustment range of the interface is 0° to 90°;

[0017] In step 3, the azimuth angle of the imaging target is adjusted within the range of -180° to 180°;

[0018] In step 4, the azimuth incident angle of the polarized light is adjusted within the range of 0° to 90°.

[0019] In step 7, all preset polarized light includes polarized light with polarization angles of 0°, 45° and 90°.

[0020] Further, in step 8], the polarization state transmission characteristics of the reflected light from the mid-interface at various pitch angles and the polarization state transmission characteristics of the reflected light from the imaging target at various azimuth angles under multiple different incident angles of the corresponding preset polarization state are obtained by the following formulas:

[0021]

[0022]

[0023] Where M1 represents the Mueller matrix of the light reflected from the interface, and M2 represents the Mueller matrix of the light reflected from the imaging target. Indicates the polarization state of the emitted laser. This indicates the polarization state of the light reflected from the interface. This indicates the polarization state of the light reflected from the imaging target.

[0024] The present invention also provides a device for obtaining polarization state transmission characteristics of a non-view imaging system, which is used to realize the above-mentioned method for obtaining polarization state transmission characteristics of a non-view imaging system. Its special feature is that it includes a light source module, a first slide rail, a mid-interface target stage, a mid-interface polarization detection module, a beam splitter, a reflective target stage, a second slide rail, and a target polarization detection module.

[0025] The light source module includes a first substrate, and a laser and a polarization module disposed on the first substrate;

[0026] Both the first and second slide rails are semi-circular tracks; the first slide rail includes a left slide rail and a right slide rail symmetrically arranged on both sides of the obstacle; the second slide rail is arranged in the opposite direction to the first slide rail and is located on the side of the obstacle closer to the right slide rail.

[0027] The first substrate is slidably connected to the track of the left slide rail, the beam splitter is disposed on the mid-interface polarization detection module, and the mid-interface polarization detection module is slidably connected to the track of the right slide rail, and the target polarization detection module is slidably connected to the track of the second slide rail.

[0028] The intermediate interface target platform is located at the center of the first slide rail, and its pitch angle can be adjusted from 0° to 90°; the intermediate interface is set on the side wall of the intermediate interface target platform facing the first slide rail.

[0029] The reflective target stage is located at the center of the second slide rail, and its azimuth angle can be adjusted from -180° to 180°; the imaging target is set on the side wall of the reflective target stage facing the second slide rail.

[0030] The polarization module and the intermediate interface are located sequentially on the output light path of the laser. The output laser light is polarized and then incident on the surface of the intermediate interface after being adjusted by the polarization module. After being reflected by the intermediate interface, it forms the reflected light of the intermediate interface. The beam splitter is located on the light path of the reflected light of the intermediate interface. The reflected light of the intermediate interface is split by the beam splitter to form a reflected light and a transmitted light.

[0031] The mid-interface polarization detection module is located on the optical path of the beam splitter's reflected light and is used to detect the polarization of the mid-interface reflected light to obtain its polarization state. The imaging target is located on the optical path of the beam splitter's transmitted light. The transmitted light from the beam splitter is reflected by the imaging target to form the imaging target's reflected light. The target polarization detection module is located on the optical path of the imaging target's reflected light and is used to detect the polarization of the imaging target's reflected light to obtain its polarization state.

[0032] Furthermore, the mid-interface polarization detection module includes a second substrate, and a first polarizer and a first light intensity detector disposed on the second substrate;

[0033] The first polarizer and the first light intensity detector are located sequentially on the optical path of the beam splitter's reflected light, and are used to perform polarization detection on the reflected light at the mid-interface.

[0034] Furthermore, the polarization detection module includes a third substrate, and a second polarizer and a second light intensity detector disposed on the third substrate;

[0035] The second polarizer and the second light intensity detector are located sequentially in the optical path of the reflected light from the imaging target, and are used to perform polarization detection on the reflected light from the imaging target.

[0036] Furthermore, the polarization module includes a first 0° linear polarizer, a first 45° linear polarizer, a first 90° linear polarizer, a first left-handed circular polarizer, and a right-handed circular polarizer, which are used to adjust the polarization state of the emitted laser according to the detection requirements.

[0037] Furthermore, the first analyzer includes a second 0° linear polarizer, a second 45° linear polarizer, a second 90° linear polarizer, and a second left-handed circular polarizer, used to select the polarization state of the reflected light from the interface.

[0038] Furthermore, the second analyzer includes a third 0° linear polarizer, a third 45° linear polarizer, a third 90° linear polarizer, and a third left-handed circular polarizer, used to select the polarization state of the reflected light from the imaging target.

[0039] Furthermore, the beam splitter is a 50:50 beam splitter.

[0040] The beneficial effects of this invention are as follows:

[0041] 1. This invention innovatively provides a method for obtaining the polarization state transmission characteristics of a non-line-of-sight imaging system. First, polarized light of a predetermined polarization state is incident on a mid-interface at a predetermined azimuth angle. Then, the elevation angle of the mid-interface and the azimuth angle of the imaging target are sequentially adjusted to obtain the polarization states of the light reflected from the mid-interface at various elevation angles and the polarization states of the light reflected from the imaging target at various azimuth angles at the predetermined elevation angles. This adjustment is repeated until the polarization state transmission characteristics of the light reflected from the mid-interface at various elevation angles and the polarization state transmission characteristics of the light reflected from the imaging target at various azimuth angles for all corresponding predetermined polarization states are obtained. This method provides theoretical support for the all-optical link of non-line-of-sight imaging technology. By obtaining the polarization state transmission characteristics of the light reflected from the mid-interface at various elevation angles and the polarization state transmission characteristics of the light reflected from the imaging target at various azimuth angles for different polarization states, a polarization state with higher light energy utilization can be selected to enhance the echo signal, improve target detection quality, and further improve the detection accuracy and detection speed of non-line-of-sight imaging technology.

[0042] 2. The present invention provides a method for obtaining polarization state transmission characteristics of a non-line-of-sight imaging system. It takes into account the target position of non-line-of-sight imaging. By adjusting the pitch angle of the centering interface from 0° to 90° and the azimuth angle of the imaging target from -180° to 180°, the reflection characteristics of the entire space can be detected, meeting the measurement requirements in non-line-of-sight situations. Compared with traditional one-dimensional detection, the detection method of the present invention can provide data for the subsequent polarization state bidirectional reflection distribution model, making the model more accurate.

[0043] 3. The present invention provides a method for obtaining polarization state transmission characteristics of a non-view imaging system, which combines polarization imaging technology with non-view imaging technology, providing a research basis for rapid imaging and improving the accuracy of restored images using non-view imaging technology.

[0044] 4. The present invention provides a device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system. It has a simple structure and is easy to operate. It can quickly obtain the polarization state of the reflected light from the interface at various pitch angles and the polarization state of the reflected light from the imaging target at various azimuth angles under multiple preset incident angles with polarized light of all preset polarization states. This provides a basis for selecting polarization states with higher light energy utilization to enhance echo signals, improve target detection quality and image restoration quality, and greatly improves the detection accuracy and detection speed of non-line-of-sight imaging technology. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a device for acquiring polarization state transmission characteristics of a non-view imaging system according to the present invention.

[0046] The specific labeling in the attached diagram is as follows:

[0047] 11-Laser, 12-Polarization module, 13-First substrate;

[0048] 2-Target platform in the middle interface; 3-Obstacles;

[0049] 4-Interface polarization detection module; 41-First polarizer; 42-First light intensity detector; 43-Second substrate; 5-Reflection target stage; 6-First slide rail; 61-Left slide rail; 62-Right slide rail;

[0050] 7-Target polarization detection module, 71-Second polarizer, 72-Second light intensity detector, 73-Third substrate;

[0051] 8-Second slide rail; 9-Bundle splitter. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0053] A method for obtaining polarization state transmission characteristics of a non-line-of-sight imaging system specifically includes the following steps:

[0054] 1. Adjust the polarization state of the emitted laser to obtain polarized light with a preset polarization state.

[0055] 2】The current polarized light is incident on the middle interface at a certain azimuth angle, and the pitch angle of the middle interface is adjusted to obtain the reflected light at each pitch angle. In this embodiment, the pitch angle adjustment range of the middle interface is 0° to 90°; at the same time, the polarization intensity of the reflected light at each pitch angle of the middle interface at the azimuth angle is detected to obtain the polarization state of the reflected light at each pitch angle of the middle interface at the azimuth angle.

[0056] 3. Adjust the azimuth angle of the imaging target to obtain incident light at different azimuth angles. In this embodiment, the azimuth angle of the imaging target can be adjusted from -180° to 180°. At the same time, the polarization intensity of the reflected light from the imaging target at each azimuth angle is detected to obtain the polarization state of the reflected light from the imaging target at each azimuth angle.

[0057] 4. Adjust the azimuth angle of the polarized light incident on the mid-interface. In this embodiment, the azimuth angle of polarized light can be adjusted from 0° to 90°.

[0058] 5】Return to step 2】, until the polarization state of the light reflected from the interface at various pitch angles and the polarization state of the light reflected from the imaging target at various azimuth angles are obtained under multiple preset incident angles of different polarization.

[0059] 6. Adjust the polarization state of the emitted laser to obtain polarized light with another preset polarization state.

[0060] 7】Return to step 2】, until all preset polarized light is obtained at multiple preset different incident angles, the polarization state of the light reflected by the interface at each pitch angle and the polarization state of the light reflected by the imaging target at each azimuth angle; in this embodiment, all preset polarized light includes polarized light with polarization angles of 0°, 45° and 90°.

[0061] 8】Based on the polarization state of the polarized light of all preset polarization states at multiple preset incident angles, the polarization state of the light reflected by the middle interface at each pitch angle and the polarization state of the light reflected by the imaging target at each azimuth angle, the polarization state transmission characteristics of the polarization state of the light reflected by the middle interface at each pitch angle and the polarization state transmission characteristics of the light reflected by the imaging target at each azimuth angle are obtained.

[0062] Specifically, the polarization state transmission characteristics of the light reflected from the mid-interface at various elevation angles and the polarization state transmission characteristics of the light reflected from the imaging target at various azimuth angles are obtained by the following formula:

[0063]

[0064]

[0065] Where M1 represents the Mueller matrix of the light reflected from the interface, and M2 represents the Mueller matrix of the light reflected from the imaging target. Indicates the polarization state of the emitted laser. This indicates the polarization state of the light reflected from the interface. This indicates the polarization state of the light reflected from the imaging target.

[0066] The two formulas mentioned above are polarization transmission equations, which respectively reflect the polarization transmission variations of the reflected light from the interface at various elevation angles and the polarization transmission variations of the reflected light from the reflective target at various azimuth angles under multiple incident angles with different polarization states. By analyzing these two polarization transmission equations, we can obtain the polarization transmission characteristics of the reflected light from the interface at various elevation angles and the polarization transmission characteristics of the reflected light from the imaging target at various azimuth angles under multiple preset incident angles with different polarization states. This provides a foundation for selecting polarization states with higher light energy utilization to enhance echo signals, improve target detection quality and image restoration quality, and greatly improves the detection accuracy and speed of non-line-of-sight imaging technology.

[0067] In this invention, steps 1 through 7 are all performed in a dark room.

[0068] To achieve the aforementioned method for obtaining the polarization state transmission characteristics of a non-view imaging system, this invention also provides a device for obtaining the polarization state transmission characteristics of a non-view imaging system, such as... Figure 1 As shown, it includes a light source module, a first slide rail 6, a mid-interface target stage 2, a mid-interface polarization detection module 4, a beam splitter 9, a reflective target stage 5, a second slide rail 8, and a target polarization detection module 7.

[0069] The light source module includes a first substrate 13, a laser 11, and a polarization module 12 disposed on the first substrate 13. In this invention, the laser 11 is a non-polarized picosecond pulse laser, which emits pulsed laser light at a repetition frequency in the megahertz range. The polarization module 12 is located in the output light path of the laser 11 and is used to adjust the polarization state of the laser according to the detection requirements to form polarized light. Specifically, in this embodiment, the polarization module 12 includes a first 0° linear polarizer, a first 45° linear polarizer, a first 90° linear polarizer, a first left-handed circular polarizer, and a right-handed circular polarizer; wherein the first 0° linear polarizer, the first 45° linear polarizer, and the first 90° linear polarizer are used to realize the various linear polarization states of the incident light, and the first left-handed circular polarizer and the right-handed circular polarizer are used to realize the circular polarization state of the incident light. The laser light, after passing through the first 0° linear polarizer, the first 45° linear polarizer, the first 90° linear polarizer, the first left-handed circular polarizer, and the right-handed circular polarizer, can output polarized light in different states. ,Right now This is a commonly used expression for polarization:

[0070] , , , ,in This represents the intensity of light polarized at 0°. This represents the intensity of light polarized at 90°. This indicates the intensity of light polarized at 45°. This represents the light intensity of light polarized at 135°. This indicates the intensity of left-handed polarized light. This indicates the intensity of right-handed polarized light. This represents the total light intensity of the target. This represents the difference in intensity between horizontally polarized light and vertically polarized light. This represents the difference in light intensity between 45° and 135° polarized light. This represents the difference in light intensity between left-handed and right-handed polarized light.

[0071] Obstacle 3, such as walls and cement, is the reason why the imaging target cannot be directly illuminated by laser, resulting in non-line-of-sight imaging. In order to match the non-line-of-sight imaging system, the polarized light is not expanded here.

[0072] In this invention, both the first slide rail 6 and the second slide rail 8 are configured as semi-circular tracks. The first slide rail 6 includes a left slide rail 61 and a right slide rail 62 symmetrically arranged on both sides of the obstacle 3. The second slide rail 8 is arranged in the opposite direction to the first slide rail 6 and is located on the side of the obstacle 3 closer to the right slide rail 62. The first substrate 13 is slidably connected to the track of the left slide rail 61, and is used to obtain different incident angles of the laser by sliding the first substrate 13 along the left slide rail 61.

[0073] The intermediate interface target stage 2 is located at the center of the first slide rail 6, and the intermediate interface is set on the side wall of the intermediate interface target stage 2 facing the track of the first slide rail 6. In this invention, the intermediate interface target stage 2 should be able to receive emitted lasers from different incident angles, and the reflected light from emitted lasers from different incident angles can be received by the beam splitter 9, that is, the intermediate interface along... Figure 1 The xoz plane of the mid-coordinate system is used. The reflective target stage 5 is located at the center of the second slide rail 8, and the imaging target is set on the side wall of the reflective target stage 5 facing the track of the second slide rail 8. In this invention, the imaging target is a typical non-line-of-sight imaging target, which generally has a strong reflectivity. Since it is difficult to construct a spatial three-dimensional polarization state bidirectional reflection distribution model with one-dimensional detection, the elevation angle of the mid-interface target stage 2 should be adjustable from 0° to 90°, and the azimuth angle of the reflective target stage 5 should be adjustable from -180° to 180°. This allows for the detection of reflection characteristics throughout the entire space, meeting the measurement requirements under non-line-of-sight conditions. This design considers the target position for non-line-of-sight imaging and can provide data for the subsequent polarization state bidirectional reflection distribution model, making the model more accurate.

[0074] The mid-interface polarization detection module 4 includes a second substrate 43, a first analyzer 41, and a first light intensity detector 42 disposed on the second substrate 43. The second substrate 43 is slidably connected to the right slide rail 62, and the reflected light from the mid-interface at various pitch angles is obtained by sliding the second substrate 43 along the right slide rail 62. The beam splitter 9 is disposed on the second substrate 43. The polarization module 12 and the mid-interface are located sequentially on the output light path of the laser 11. The output laser is polarized and then incident on the surface of the mid-interface after being polarized by the polarization module 12. After being reflected by the mid-interface, it forms the mid-interface reflected light. The beam splitter 9 is located on the optical path of the mid-interface reflected light, and the mid-interface reflected light is split by the beam splitter 9 to form a reflected light beam and a transmitted light beam. In this embodiment, the beam splitter 9 is preferably a 50:50 beam splitter, that is, half of the mid-interface reflected light is reflected and half is transmitted through the beam splitter 9. The reflected light from the beam splitter 9 enters the first analyzer 41, and the transmitted light from the beam splitter 9 continues to propagate to the imaging target surface. The first polarizer 41 and the first intensity detector 42 are located sequentially on the optical path of the reflected light from the beam splitter 9. The polarization state is selected by the first polarizer 41, and the polarization intensity of the reflected light from the mid-interface at various pitch angles is measured by the first intensity detector 42 at a preset incident angle. In this embodiment, the first polarizer 41 includes a second 0° linear polarizer, a second 45° linear polarizer, a second 90° linear polarizer, and a second left-handed circular polarizer, used to achieve full polarization state detection of the reflected light from the mid-interface at various pitch angles. Specifically, the Mueller matrix M1 of the reflected light from the mid-interface at various pitch angles is obtained using the following formula:

[0075]

[0076] The target polarization detection module 7 includes a third substrate 73, and a second polarizer 71 and a second light intensity detector 72 disposed on the third substrate 73. In this embodiment, the first substrate 13, the second substrate 43, and the third substrate 73 are all optical breadboards. The third substrate 73 is slidably connected to the track of the second slide rail 8, and is used to obtain the reflected light of the imaging target at various azimuth angles by sliding the third substrate 73 along the second slide rail 8. The imaging target is located in the optical path of the transmitted light of the beam splitter 9, and the transmitted light of the beam splitter 9 is reflected by the imaging target to form the reflected light of the imaging target. The second polarizer 71 and the second light intensity detector 72 are sequentially located in the optical path of the reflected light of the imaging target. The second polarizer 71 performs polarization state selection, and the second light intensity detector 72 measures the polarization intensity of the reflected light of the imaging target at various azimuth angles under a preset incident angle. In this embodiment, the second polarizer 71 includes a third 0° linear polarizer, a third 45° linear polarizer, a third 90° linear polarizer, and a third left-handed circular polarizer, used to achieve full polarization state detection of the reflected light from the imaging target at various azimuth angles. Specifically, the Mueller matrix M2 of the reflected light from the imaging target at various azimuth angles is obtained by the following formula:

[0077]

[0078] The two formulas mentioned above are polarization transmission equations, which respectively reflect the polarization transmission changes of the reflected light from the mid-interface at various elevation angles and the polarization transmission changes of the reflected light from the reflective target at various azimuth angles under multiple incident angles with different polarization states. By analyzing these two polarization transmission equations, we can obtain the polarization transmission characteristics of the reflected light from the mid-interface at various elevation angles and the polarization transmission characteristics of the reflected light from the imaging target at various azimuth angles under multiple preset incident angles with different polarization states. This provides a foundation for selecting polarization states with higher light energy utilization to enhance echo signals, improve target detection quality and image restoration quality, and greatly improves the detection accuracy and speed of non-line-of-sight imaging technology.

[0079] The specific method for acquiring polarization state transmission characteristics using the polarization state transmission characteristic acquisition device of a non-view imaging system provided by the present invention is as follows:

[0080] 1) The polarization module 12 is adjusted to 0° linear polarization by the first 0° linear polarizer, so that the emitted laser of the laser 11 is polarized light with 0° polarization.

[0081] 2】Move the first substrate 13 along the left slide rail 61 so that the current polarized light is incident on the middle interface at a certain angle of incidence; adjust the pitch angle of the target stage 2 at the middle interface, and adjust the pitch angle of the middle interface from 0° to 90° to obtain the reflected light at each pitch angle of the middle interface.

[0082] Simultaneously, the second substrate 43 moves along the right slide rail 62, causing the beam splitter 9 on the second substrate 43 to receive the reflected light from the mid-interface at various pitch angles; the polarization intensity of the reflected light from the mid-interface at each pitch angle under this incident angle is detected by the first polarizer 41 and the first light intensity detector 42. The polarization state of the reflected light from the middle interface at various pitch angles under the incident angle at that azimuth is obtained.

[0083] 3. Adjust the azimuth angle of the reflecting target stage 5 to move the azimuth angle of the imaging target from -180° to 180° to obtain incident light at different azimuth angles, and reflect the incident light to form reflected light from the imaging target at each azimuth angle; simultaneously, move the third substrate 73 along the second slide rail 8 so that the second analyzer 71 on the third substrate 73 receives the reflected light from the imaging target at each azimuth angle, and detect the polarization intensity of the reflected light from the imaging target at each azimuth angle through the second analyzer 71 and the second light intensity detector 72. This allows us to obtain the polarization state of the reflected light from the imaging target at various azimuth angles under the incident angle at that azimuth.

[0084] 4】Move the first substrate 13 along the left slide rail 61 and adjust the azimuth angle of the polarized light of the current preset polarization state incident on the middle interface within the range of 0° to 90°.

[0085] 5】Return to step 2】, until the polarization state of the light reflected from the interface at various pitch angles and the polarization state of the light reflected from the imaging target at various azimuth angles are obtained under multiple preset incident angles of different polarization.

[0086] 6】The polarization state of the emitted laser is adjusted by the polarization module 12 to obtain polarized light with another preset polarization state. In this embodiment, each time the polarization state of the emitted laser is adjusted, it is adjusted to 45° linear polarization, 90° linear polarization, left-hand circular polarization, or right-hand circular polarization by the first 45° linear polarizer, the first 90° linear polarizer, the first left-hand circular polarizer, and the right-hand circular polarizer, so that the emitted laser of the laser 11 is polarized light with the corresponding polarization state.

[0087] 7】Return to step 2】, until all preset polarized light is obtained at multiple preset different incident angles, the polarization state of the light reflected from the interface at each pitch angle and the polarization state of the light reflected from the imaging target at each azimuth angle.

[0088] 8】Based on the polarization state of the light reflected from the mid-interface at various pitch angles and the polarization state of the light reflected from the imaging target at various azimuth angles under multiple preset incident angles, the polarization state transmission characteristics of the light reflected from the mid-interface at various pitch angles and the polarization state transmission characteristics of the light reflected from the imaging target at various azimuth angles under multiple preset incident angles are obtained.

[0089] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for obtaining polarization state transmission characteristics of a non-line-of-sight imaging system, characterized in that, Includes the following steps:

1. Adjust the polarization state of the emitted laser to obtain polarized light with a preset polarization state; 2】The current polarized light is incident on the middle interface at an incident angle of a certain direction. The elevation angle of the middle interface is adjusted to obtain the reflected light at each elevation angle. At the same time, the polarization intensity of the reflected light at each elevation angle of the middle interface at the incident angle of that direction is detected to obtain the polarization state of the reflected light at each elevation angle of the middle interface at the incident angle of that direction. 3】Adjust the azimuth angle of the imaging target to obtain incident light at different azimuth angles, and at the same time detect the polarization intensity of the reflected light of the imaging target at each azimuth angle under the incident angle, so as to obtain the polarization state of the reflected light of the imaging target at each azimuth angle under the incident angle.

4. Adjust the azimuth angle of the current polarized light incident on the mid-interface; 5】Return to step 2】, until the polarization state of the light reflected from the interface at various pitch angles and the polarization state of the light reflected from the imaging target at various azimuth angles are obtained under multiple preset incident angles of different polarization.

6. Adjust the polarization state of the emitted laser to obtain polarized light with another preset polarization state; 7】Return to step 2】, until all preset polarized light is obtained at multiple preset different incident angles, the polarization state of the light reflected by the interface at each pitch angle and the polarization state of the light reflected by the imaging target at each azimuth angle. 8】Based on the polarization state of the polarized light of all preset polarization states at multiple preset incident angles, the polarization state of the light reflected by the middle interface at each pitch angle and the polarization state of the light reflected by the imaging target at each azimuth angle, the polarization state transmission characteristics of the polarization state of the light reflected by the middle interface at each pitch angle and the polarization state transmission characteristics of the light reflected by the imaging target at each azimuth angle are obtained. Steps 1 through 7 are all performed in a dark room.

2. The method for obtaining polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 1, characterized in that: In step 2, the pitch angle adjustment range of the interface is 0° to 90°; In step 3, the azimuth angle of the imaging target is adjusted within the range of -180° to 180°; In step 4, the azimuth incident angle of the polarized light is adjusted within the range of 0° to 90°. In step 7, all preset polarized light includes polarized light with polarization angles of 0°, 45° and 90°.

3. A method for obtaining polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 1 or 2, characterized in that: In step 8), the polarization state transmission characteristics of the reflected light from the mid-interface at various elevation angles and the polarization state transmission characteristics of the reflected light from the imaging target at various azimuth angles under multiple different incident angles with the corresponding preset polarization state are obtained by the following formulas: ； ； Where M1 represents the Mueller matrix of the light reflected from the interface, and M2 represents the Mueller matrix of the light reflected from the imaging target. Indicates the polarization state of the emitted laser. This indicates the polarization state of the light reflected from the interface. This indicates the polarization state of the light reflected from the imaging target.

4. A device for acquiring polarization state transmission characteristics of a non-view imaging system, used to implement the method for acquiring polarization state transmission characteristics of a non-view imaging system as described in any one of claims 1-3, characterized in that: It includes a light source module, a first slide rail (6), a mid-interface target stage (2), a mid-interface polarization detection module (4), a beam splitter (9), a reflective target stage (5), a second slide rail (8), and a target polarization detection module (7); The light source module includes a first substrate (13), and a laser (11) and a polarization module (12) disposed on the first substrate (13). The first slide rail (6) and the second slide rail (8) are both semi-circular tracks; the first slide rail (6) includes a left slide rail (61) and a right slide rail (62) symmetrically arranged on both sides of the obstacle (3); the second slide rail (8) is arranged in the opposite direction to the first slide rail (6) and is located on the side of the obstacle (3) closer to the right slide rail (62); The first substrate (13) is slidably connected to the track of the left slide rail (61), the beam splitter (9) is disposed on the mid-interface polarization detection module (4), and the mid-interface polarization detection module (4) is slidably connected to the track of the right slide rail (62), and the target polarization detection module (7) is slidably connected to the track of the second slide rail (8). The intermediate interface target platform (2) is located at the center of the first slide rail (6), and its pitch angle can be adjusted from 0° to 90°; the intermediate interface is set on the side wall of the intermediate interface target platform (2) facing the first slide rail (6); The reflective target stage (5) is located at the center of the second slide rail (8), and its azimuth angle can be adjusted from -180° to 180°; the imaging target is set on the side wall of the reflective target stage (5) facing the track of the second slide rail (8); The polarization module (12) and the middle interface are located sequentially on the output light path of the laser (11). The output laser of the laser (11) is polarized and then incident on the surface of the middle interface after being adjusted by the polarization module (12). After being reflected by the middle interface, it forms the middle interface reflected light. The beam splitter (9) is located on the light path of the middle interface reflected light. The middle interface reflected light is split by the beam splitter (9) to form a reflected light and a transmitted light. The mid-interface polarization detection module (4) is located on the optical path of the reflected light from the beam splitter (9) and is used to perform polarization detection on the mid-interface reflected light to obtain the polarization state of the mid-interface reflected light. The imaging target is located on the optical path of the transmitted light from the beam splitter (9). The transmitted light from the beam splitter (9) is reflected by the imaging target to form the imaging target reflected light. The target polarization detection module (7) is located on the optical path of the imaging target reflected light and is used to perform polarization detection on the imaging target reflected light to obtain the polarization state of the imaging target reflected light.

5. The device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 4, characterized in that: The mid-interface polarization detection module (4) includes a second substrate (43), and a first polarizer (41) and a first light intensity detector (42) disposed on the second substrate (43). The first polarizer (41) and the first light intensity detector (42) are located sequentially on the optical path of the reflected light from the beam splitter (9) and are used to perform polarization detection on the reflected light from the mid-interface.

6. The device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 5, characterized in that: The target polarization detection module (7) includes a third substrate (73), a second polarizer (71) and a second light intensity detector (72) disposed on the third substrate (73). The second polarizer (71) and the second light intensity detector (72) are located sequentially on the optical path of the reflected light from the imaging target, and are used to perform polarization detection on the reflected light from the imaging target.

7. The device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 6, characterized in that: The polarization module (12) includes a first 0° linear polarizer, a first 45° linear polarizer, a first 90° linear polarizer, a first left-handed circular polarizer, and a right-handed circular polarizer, which are used to adjust the polarization state of the emitted laser according to the detection requirements.

8. The device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 7, characterized in that: The first analyzer (41) includes a second 0° linear polarizer, a second 45° linear polarizer, a second 90° linear polarizer and a second left-handed circular polarizer, used to select the polarization state of the reflected light from the interface.

9. The device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 8, characterized in that: The second analyzer (71) includes a third 0° linear polarizer, a third 45° linear polarizer, a third 90° linear polarizer and a third left-hand circular polarizer, used to select the polarization state of the reflected light from the imaging target.

10. The device for acquiring polarization state transmission characteristics of a non-line-of-sight imaging system according to claim 9, characterized in that: The beam splitter (9) is a 50:50 beam splitter.

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