Detection Systems and Terminal Devices

Abstract

An embodiment of the present application discloses a detection system and a terminal device. The detection system includes a beam splitting module, a polarization module, and a frequency mixer. The beam splitting module is configured to perform a beam splitting process on the input signal light to obtain a first signal light and a second signal light. The polarization module is configured to output a transmission signal light obtained after at least a first polarization process is performed on the first signal light, and is configured to obtain a reflected signal light of the transmission signal light and output a third signal light obtained after at least a second polarization process is performed on the reflected signal light. The frequency mixer is configured to perform a frequency mixing process on the second signal light and the third signal light, or to perform a frequency mixing process on the third signal light and a fourth signal light obtained after at least a third polarization process is performed on the second signal light. In this way, the effect of crosstalk can be effectively reduced. In addition, the polarization module itself is a factor in reducing crosstalk.

Description

[Technical Field]

[0001] The present application relates to the field of laser detection, and in particular to detection systems and terminal devices. [Background technology]

[0002] Lidar can be classified into direct detection and coherent detection according to different detection methods. Direct detection Lidar is Lidar that uses the direct detection method. Coherent detection Lidar is Lidar that uses the coherent detection method. Direct detection Lidar obtains distance information by multiplying the measured time delay difference between the reflection and reception of a light pulse by the speed of light. However, direct detection Lidar requires a highly sensitive detector and a high-peak power transmitted pulse signal, and is significantly affected by noise. In contrast, coherent Lidar uses continuous light as the detection signal and obtains signal frequency, magnitude, and phase information by mixing local oscillator light and signal light. This has advantages such as high detection efficiency, resistance to ambient light interference, and the ability to obtain speed information in real time.

[0003] For coherent detection systems (e.g., coherent lidar), crosstalk has a greater impact on coherent detection systems than direct detection lidar due to its detection advantages for weak signals. In coherent detection systems, the level of crosstalk control directly affects their detection capabilities and accuracy. Therefore, it is necessary to consider how to reduce the impact of crosstalk in coherent detection. Summary of the Invention [Means for solving the problem]

[0004] The present application discloses a detection system and a terminal device for effectively reducing the effects of crosstalk in the detection system.

[0005] According to a first aspect, an embodiment of the present application provides a detection system including a beam splitting module, a polarization module, and a frequency mixer. The beam splitting module is configured to perform beam splitting processing on input signal light to obtain first signal light and second signal light. The polarization module is configured to output transmission signal light obtained after at least a first polarization processing is performed on the first signal light, and is configured to obtain reflected signal light of the transmission signal light and output third signal light obtained after at least a second polarization processing is performed on the reflected signal light. The frequency mixer is configured to perform frequency mixing processing on the second signal light and the third signal light, or to perform frequency mixing processing on the third signal light and fourth signal light obtained after at least a third polarization processing is performed on the second signal light.

[0006] In this embodiment of the present application, the polarization module is configured to output a transmission signal light obtained after at least a first polarization process is performed on the first signal light, and to output a third signal light obtained after at least a second polarization process is performed on the reflected signal light. The third signal light may be understood as the signal light obtained after at least a first polarization process and at least a second polarization process are performed on the first signal light. The third signal light and only crosstalk light, whose polarization state is the same as that of the third signal light, can be output to the frequency mixer. Since the crosstalk light whose polarization state is different from that of the third signal light cannot be output to the frequency mixer, the effect of crosstalk can be effectively reduced. Furthermore, the polarization module itself is a factor in reducing crosstalk.

[0007] In a possible implementation, the frequency mixer is a polarized frequency mixer, and the polarization state of the second signal light and the polarization state of the third signal light are orthogonal, or the frequency mixer is a non-polarized frequency mixer, and the polarization state of the fourth signal light and the polarization state of the third signal light are the same.

[0008] In this implementation, the polarization module reduces crosstalk caused by reflected light, i.e., the crosstalk light does not enter the frequency mixer. Therefore, the frequency mixer performs frequency mixing on the second signal light and the third signal light, or on the third signal light and the fourth signal light, thereby improving frequency mixing efficiency and reducing the influence of non-ideal factors such as depolarization.

[0009] In one possible implementation, the polarization module includes a polarization conversion module and a unidirectional transmission component configured to output the first signal light to the polarization conversion module and the third signal light to the frequency mixer, and the polarization conversion module configured to perform a first polarization process on the first signal light and a second polarization process on the reflected signal light.

[0010] In this implementation, the unidirectional conductive component is configured to output the first signal light to the polarization conversion module to the frequency mixer and output the third signal light to avoid some of the signal light leaking to the frequency mixer.

[0011] In a possible implementation, the unidirectionally conducting component is further configured to reflect, filter, or absorb signal light of a first polarization state incident from a first direction, the first direction being an input direction of the third signal light, and the first polarization state being different from the polarization state of the third signal light.

[0012] In this implementation, the unidirectionally conducting component is further configured to reflect, filter, or absorb the signal light of the first polarization state incident from the first direction, so that most of the crosstalk light does not enter the frequency mixer, and the effect of crosstalk can be effectively reduced.

[0013] In possible implementations, the unidirectional conducting component is configured to reflect the third signal light from a first reflecting surface to the frequency mixer and / or the unidirectional conducting component is configured to reflect the signal light of a first polarization state incident from a first direction from a second reflecting surface, the first reflecting surface being different from the second reflecting surface and the first polarization state being different from the polarization state of the third signal.

[0014] In this implementation, the unidirectional conductive component is configured to reflect the third signal light from the first reflecting surface to the frequency mixer, and / or the unidirectional conductive component is configured to reflect the signal light of the first polarization state incident from the first direction from the second reflecting surface, thereby preventing the signal light of the first polarization state from entering the frequency mixer, and the structure is simple.

[0015] In a possible implementation, the polarization conversion module includes an optical antenna and a first polarization conversion component. The optical antenna is configured to output the signal light obtained after at least collimation processing of the first signal light to the first polarization conversion component and to output the third signal light to the unidirectional conductive component. The first polarization conversion component is configured to perform a first polarization processing on the first signal light obtained after collimation processing and to output the third signal light obtained after second polarization processing on the reflected signal light. Alternatively, the first polarization conversion component is configured to output the fifth signal light obtained after the first polarization processing of the first signal light to the optical antenna and to perform a second polarization processing on the reflected signal light. The optical antenna is configured to output the transmission signal light obtained after at least collimation processing of the fifth signal light.

[0016] In this implementation, the optical antenna performs a collimation process on the signal light so that the signal light can be coupled to the first polarization conversion component with maximum efficiency, or the signal light can be coupled and transmitted with maximum efficiency.

[0017] In one possible implementation, the beam splitting module includes a beam splitter and a second polarization conversion component. The beam splitter is configured to perform beam splitting on the input signal light to obtain a first signal light and a second signal light. The second polarization conversion component is configured to output a fourth signal light obtained after performing at least a third polarization process on the second signal light to the frequency mixer. For example, the polarization state of the fourth signal light is orthogonal to the polarization state of the second signal light.

[0018] In this implementation, the second polarization conversion component is configured to output a fourth signal light obtained after at least a third polarization process is performed on the second signal light to the frequency mixer, so that the signal light of the required polarization state can be output to the frequency mixer.

[0019] In a possible implementation, the polarization state of the first signal light and the polarization state of the second signal light are the same.

[0020] In a possible implementation, the beam splitting module is a polarizing beam splitter, and the polarization states of the first and second signal lights are orthogonal, and the polarization state of the signal light input by the beam splitting module is neither orthogonal nor parallel to the polarization state of the first signal light.

[0021] In this implementation, the beam splitting module performs beam splitting on the input signal light to obtain first and second signal lights with orthogonal polarization states. In this way, the polarization states of the local oscillator light and the signal light input by the frequency mixer can be made the same, thereby improving frequency mixing efficiency. The structure is simple, and no additional polarization conversion components are required.

[0022] In a possible implementation, the beam splitter is a polarizing beam splitter. The beam splitter is specifically configured to perform beam splitting and polarization state adjustment on the input signal light to obtain a first signal light and a second signal light. The polarization state of the first signal light and the polarization state of the second signal light are orthogonal, and the polarization state of the signal light input by the beam splitter and the polarization state of the first signal light are neither orthogonal nor parallel.

[0023] In this implementation, the beam splitting module performs beam splitting and polarization state adjustment on the input signal light to obtain first and second signal lights with orthogonal polarization states. In this way, to implement frequency mixing using a polarization frequency mixer, it can be ensured that the polarization states of the local oscillator light and the signal light input by the frequency mixer are orthogonal.

[0024] In a possible implementation, the transmit and receive optical paths in the detection system are arranged coaxially.

[0025] According to a second aspect, an embodiment of the present application provides a Lidar system including a detection system according to the first aspect or any one of the possible implementations of the first aspect.

[0026] According to a third aspect, an embodiment of the present application provides a terminal device, including a detection system according to the first aspect or any one of the possible implementations of the first aspect.

[0027] According to a fourth aspect, an embodiment of the present application provides a detection apparatus comprising at least one laser, at least one detector, and a detection system according to the first aspect or any one of the possible implementations of the first aspect. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of the structure of a detection system according to an embodiment of the present application; [Figure 2A]3 illustrates an example of a polarization state of a first signal light, a polarization state of a second signal light, and a polarization state of a third signal light according to an embodiment of the present application. [Figure 2B] 3 illustrates an example of a polarization state of a first signal light, a polarization state of a second signal light, and a polarization state of a third signal light according to an embodiment of the present application. [Figure 2C] 3 illustrates an example of a polarization state of a first signal light, a polarization state of a second signal light, and a polarization state of a third signal light according to an embodiment of the present application. [Figure 3A] 3A and 3B are diagrams illustrating examples of a polarization state of a first signal light, a polarization state of a second signal light, a polarization state of a third signal light, and a polarization state of a fourth signal light according to an embodiment of the present application. [Figure 3B] 3A and 3B are diagrams illustrating examples of a polarization state of a first signal light, a polarization state of a second signal light, a polarization state of a third signal light, and a polarization state of a fourth signal light according to an embodiment of the present application. [Figure 3C] 3A and 3B are diagrams illustrating examples of a polarization state of a first signal light, a polarization state of a second signal light, a polarization state of a third signal light, and a polarization state of a fourth signal light according to an embodiment of the present application. [Figure 3D] 3A and 3B are diagrams illustrating examples of a polarization state of a first signal light, a polarization state of a second signal light, a polarization state of a third signal light, and a polarization state of a fourth signal light according to an embodiment of the present application. [Figure 4A] 1 illustrates an example of the polarization state of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, and the polarization state of the third signal light according to an embodiment of the present application. [Figure 4B] 1 illustrates an example of the polarization state of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, and the polarization state of the third signal light according to an embodiment of the present application. [Figure 4C] 1 illustrates an example of the polarization state of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, and the polarization state of the third signal light according to an embodiment of the present application. [Figure 5A]1 illustrates an example of the polarization state of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, and the polarization state of the third signal light according to an embodiment of the present application. [Figure 5B] 1 illustrates an example of the polarization state of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, and the polarization state of the third signal light according to an embodiment of the present application. [Figure 5C] 1 illustrates an example of the polarization state of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, and the polarization state of the third signal light according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of a structure of a polarization module according to an embodiment of the present application; [Figure 7] FIG. 10 illustrates an example in which a unidirectional conducting component processes a third signal light incident from a first direction and a signal light of a first polarization state according to an embodiment of the present application. [Figure 8A] FIG. 6 is a schematic diagram of the structure of a polarization conversion module 602 according to an embodiment of the present application. [Figure 8B] FIG. 6 is a schematic diagram of the structure of a polarization conversion module 602 according to an embodiment of the present application. [Figure 9] 1 is a schematic diagram of the structure of a beam splitting module 10 according to an embodiment of the present application. [Figure 10] FIG. 1 illustrates an example in which the transmit and receive optical paths can be coaxially arranged, according to an embodiment of the present application. [Figure 11] FIG. 2 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. [Figure 12] FIG. 2 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. [Figure 13] FIG. 2 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. [Figure 14] FIG. 2 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. [Figure 15A]Example test results of a coaxial transceiver detection system using a non-polarizing component (circulator) as the non-reciprocal component are shown. [Figure 15B] Example test results of a coaxial transceiver detection system using a non-polarizing component (circulator) as the non-reciprocal component are shown. [Figure 16A] 10 shows example test results for a coaxial transceiver detection system using a polarized component as the non-reciprocal component. [Figure 16B] 10 shows example test results for a coaxial transceiver detection system using a polarized component as the non-reciprocal component. DETAILED DESCRIPTION OF THE INVENTION

[0029] As described in the background art, there is currently a need to consider how to reduce the influence of crosstalk in a detection system. The present application provides a detection system that can effectively reduce the influence of crosstalk. In addition, the detection system provided in the present application can further reduce crosstalk caused by components included in the detection system.

[0030] In order to better understand the Lidar provided in this application, some knowledge related to Lidar will be explained below.

[0031] Coaxial and side-axis optical systems Based on the different layouts of the transmission and receiving optical paths in lidar, there are two basic optical systems: coaxial optical systems and side-axis optical systems. In coaxial optical systems, the axis of the transmission light beam and the axis of the receiving light path are aligned or partially aligned on the same optical axis. Coaxial optical systems have a simple structure and high transmission and reception efficiency, but are susceptible to near-field backscattering. In side-axis (also called dual-axis) optical systems, the laser beam is separated from the receiver optical axis, and the transmission light beam can only overlap the receiving field of view within a certain range. Side-axis systems are less susceptible to near-field backscattering, but have a close-range blind spot.

[0032] Simple coaxial transceiver optical systems often introduce various crosstalks, some of which are caused by components such as circulators, and some of which are caused by stray light in the environment. The majority of crosstalk is introduced by the components themselves.

[0033] In a coherent detection system using a coaxial optical system, the reflected light picks up a much larger signal than the target reflected light (i.e., the desired signal light) through the components. After the reflected light mixes with the local oscillator light, the detection of the near-field signal is significantly affected, and the noise level at long distances increases. In other words, the impact of crosstalk is more severe in a coherent detection system using a coaxial optical system.

[0034] An example of a detection system provided in the present application will now be described with reference to the accompanying drawings.

[0035] 1 is a schematic diagram of the structure of a detection system according to one embodiment of the present application. As shown in FIG. 1, the detection system includes a beam splitting module 10, a polarization module 20, and a frequency mixer 40. In some embodiments, the functions of the beam splitting module 10, the polarization module 20, and the frequency mixer 40 are as follows.

[0036] The beam splitting module 10 is configured to perform beam splitting on an input signal light to obtain a first signal light and a second signal light.

[0037] The polarization module 20 is configured to output a transmission signal light obtained after at least a first polarization process is performed on the first signal light, and is configured to obtain (or receive) a reflected signal light of the transmission signal light, and to output to the frequency mixer 40 a third signal light obtained after at least a second polarization process is performed on the reflected signal light.

[0038] The frequency mixer 40 is configured to perform a frequency mixing process on the second signal light and the third signal light, or to perform a frequency mixing process on the third signal light and a fourth signal light obtained after at least a third polarization process is performed on the second signal light.

[0039] In some embodiments, the beam splitting module 10 is further configured to output the first signal light to the polarization module 20 and the second signal light to the frequency mixer 40. The polarization state of the third signal light and the polarization state of the second signal light are orthogonal, and the frequency mixer 40 is a polarization frequency mixer. In a possible implementation, the polarization state of the second signal light and the polarization state of the first signal light are the same, for example, both are horizontally polarized or vertically polarized. The polarization state of the third signal light and the polarization state of the first signal light are orthogonal.

[0040] 2A to 2C show examples of the polarization states of a first signal light, a second signal light, and a third signal light according to an embodiment of the present application. In FIG. 2A, 201 indicates the polarization state of the first signal light, 202 indicates the polarization state of the second signal light, and 203 indicates the polarization state of the third signal light. The polarization states of the second signal light and the first signal light are the same (both are horizontally polarized). The polarization states of the third signal light and the first signal light are orthogonal. The polarization states of the third signal light and the second signal light are orthogonal. In FIG. 2B, 204 indicates the polarization state of the first signal light, 205 indicates the polarization state of the second signal light, and 206 indicates the polarization state of the third signal light. The polarization states of the second signal light and the first signal light are the same (both are vertically polarized). The polarization states of the third signal light and the first signal light are orthogonal. The polarization state of the third signal light and the polarization state of the second signal light are orthogonal. In FIG. 2C, 207 indicates the polarization state of the first signal light, 208 indicates the polarization state of the second signal light, and 209 indicates the polarization state of the third signal light. The polarization state of the second signal light and the polarization state of the first signal light are the same (both are vertically polarized). The polarization state of the third signal light and the polarization state of the first signal light are orthogonal. The polarization state of the third signal light and the polarization state of the second signal light are orthogonal.

[0041] In some embodiments, the beam splitting module 10 is further configured to output the first signal light to the polarization module 20 and output a fourth signal light obtained after at least a third polarization process is performed on the second signal light to the frequency mixer 40. The polarization state of the fourth signal light is the same as the polarization state of the third signal light, and the frequency mixer 40 is a non-polarizing frequency mixer. In a possible implementation, the polarization state of the first signal light is the same as the polarization state of the second signal light, for example, both are horizontally polarized or vertically polarized. The polarization state of the third signal light is orthogonal to the polarization state of the first signal light. The polarization state of the third signal light is orthogonal to the polarization state of the second signal light. The polarization state of the second signal light is orthogonal to the polarization state of the fourth signal light. Performing at least a third polarization process on the second signal light by the beam splitting module 10 may be polarization conversion of the second signal light, for example, converting the second signal light from polarization state 1 to polarization state 2, where polarization state 1 and polarization state 2 are orthogonal. For example, the beam splitting module 10 converts the second signal light from horizontal polarization to vertical polarization to obtain the fourth signal light. In possible implementations, the polarization states of the first signal light and the second signal light may be the same or different. The polarization states of the second signal light and the fourth signal light may be neither orthogonal nor parallel. The polarization states of the third signal light and the first signal light may be neither orthogonal nor parallel. In these embodiments, the polarization states of the first signal light, the second signal light, and the third signal light may not be limited as long as the polarization states of the third signal light and the fourth signal light are guaranteed to be orthogonal. For example, the polarization state of the first signal light and the polarization state of the second signal light are the same, the angle between the polarization state of the second signal light and the polarization state of the fourth signal light is 45 degrees, the angle between the polarization state of the third signal light and the polarization state of the first signal light is 45 degrees, and the polarization state of the fourth signal light and the polarization state of the third signal light are the same.In another example, the included angle between the polarization state of the first signal light and the polarization state of the second signal light is 90 degrees, the included angle between the polarization state of the second signal light and the polarization state of the fourth signal light is 45 degrees, the included angle between the polarization state of the third signal light and the polarization state of the first signal light is 45 degrees, and the polarization state of the fourth signal light and the polarization state of the third signal light are the same.

[0042] 3A to 3D show examples of the polarization states of the first, second, third, and fourth signal lights according to an embodiment of the present application. In FIG. 3A, 301 indicates the polarization state of the first signal light, 302 indicates the polarization state of the second signal light, 303 indicates the polarization state of the third signal light, and 304 indicates the polarization state of the fourth signal light. The polarization states of the first and second signal lights are the same (both are horizontally polarized). The polarization states of the third and first signal lights are orthogonal. The polarization states of the fourth and second signal lights are orthogonal. The polarization states of the fourth and third signal lights are the same. In FIG. 3B, 305 indicates the polarization state of the first signal light, 306 indicates the polarization state of the second signal light, 307 indicates the polarization state of the third signal light, and 308 indicates the polarization state of the fourth signal light. The polarization state of the first signal light and the polarization state of the second signal light are the same (both are vertically polarized). The polarization state of the third signal light and the polarization state of the first signal light are orthogonal. The polarization state of the fourth signal light and the polarization state of the second signal light are orthogonal. The polarization state of the fourth signal light and the polarization state of the third signal light are the same. In FIG. 3C, 309 indicates the polarization state of the first signal light, 310 indicates the polarization state of the second signal light, 311 indicates the polarization state of the third signal light, and 312 indicates the polarization state of the fourth signal light. The polarization state of the first signal light and the polarization state of the second signal light are the same (vertically polarized). The included angle between the polarization state of the third signal light and the polarization state of the first signal light is 45 degrees (although other angles may be used). The included angle between the polarization state of the fourth signal light and the polarization state of the second signal light is 45 degrees (although other angles may be used). The polarization state of the fourth signal light and the polarization state of the third signal light are the same. In Figure 3D, 313 indicates the polarization state of the first signal light, 314 indicates the polarization state of the second signal light, 315 indicates the polarization state of the third signal light, and 316 indicates the polarization state of the fourth signal light. The polarization state of the first signal light and the polarization state of the second signal light are the same (non-vertical polarization or non-horizontal polarization). The polarization state of the third signal light and the polarization state of the first signal light are orthogonal. The polarization state of the fourth signal light and the polarization state of the second signal light are orthogonal. The polarization state of the fourth signal light and the polarization state of the third signal light are the same.

[0043] In some embodiments, the beam splitting module 10 is further configured to output the first signal light to the polarization module 20 and the second signal light to the frequency mixer 40. The polarization state of the first signal light and the polarization state of the second signal light are orthogonal. The polarization state of the signal light input by the beam splitting module 10 and the polarization state of the first signal light (or the second signal light) are neither orthogonal nor parallel. The polarization state of the second signal light and the polarization state of the third signal light are the same. The frequency mixer 40 is a non-polarized frequency mixer. In a possible implementation, the polarization state of the third signal light and the polarization state of the first signal light are orthogonal, for example, both are horizontally polarized or vertically polarized.

[0044] 4A to 4C show examples of the polarization states of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, and the polarization state of the third signal light according to one embodiment of the present application. In FIG. 4A, 401 indicates the polarization state of the signal light input by the beam splitting module 10 (i.e., the input signal light of the beam splitting module), 402 indicates the polarization state of the first signal light (vertical polarization), 403 indicates the polarization state of the second signal light (horizontal polarization), and 404 indicates the polarization state of the third signal light. The polarization states of the first signal light and the second signal light are orthogonal. The polarization states of the third signal light and the first signal light are orthogonal. The polarization states of the second signal light and the third signal light are the same. In FIG. 4B, 405 denotes the polarization state of the signal light input by the beam splitting module 10 (i.e., the input signal light of the beam splitting module), 406 denotes the polarization state of the first signal light (horizontal polarization), 407 denotes the polarization state of the second signal light (vertical polarization), and 408 denotes the polarization state of the third signal light. The polarization states of the first signal light and the second signal light are orthogonal. The polarization states of the third signal light and the first signal light are orthogonal. The polarization states of the second signal light and the third signal light are the same. In FIG. 4C, 409 denotes the polarization state (e.g., horizontal polarization) of the signal light input by the beam splitting module 10 (i.e., the input signal light of the beam splitting module), 410 denotes the polarization state (non-vertical polarization or non-horizontal polarization) of the first signal light, 411 denotes the polarization state of the second signal light, and 412 denotes the polarization state of the third signal light. The polarization state of the first signal light is orthogonal to the polarization state of the second signal light. The polarization state of the third signal light is orthogonal to the polarization state of the first signal light. The polarization state of the second signal light is the same as the polarization state of the third signal light. The polarization angle between the input signal light and the first signal light of the beam splitting module may be 45 degrees or other angles, but this is not limited in this embodiment of the present application.

[0045] In some embodiments, the beam splitting module 10 is further configured to output the first signal light to the polarization module 20 and to output a fourth signal light, obtained after at least a third polarization process is performed on the second signal light, to the frequency mixer 40. The polarization state of the fourth signal light and the polarization state of the third signal light are orthogonal, and the frequency mixer 40 is a polarization frequency mixer. In these embodiments, the polarization state of the first signal light and the polarization state of the second signal light are orthogonal. The polarization state of the signal light input by the beam splitting module 10 and the polarization state of the first signal light (or the second signal light) are neither orthogonal nor parallel. The polarization state of the second signal light and the polarization state of the fourth signal light are orthogonal. The polarization state of the third signal light and the polarization state of the first signal light are orthogonal.

[0046] 5A to 5C show examples of the polarization states of the signal light input by the beam splitting module 10, the polarization state of the first signal light, the polarization state of the second signal light, the polarization state of the third signal light, and the polarization state of the fourth signal light according to one embodiment of the present application. In FIG. 5A, 501 indicates the polarization state of the signal light input by the beam splitting module 10 (i.e., the input signal light of the beam splitting module), 502 indicates the polarization state of the first signal light (vertical polarization), 503 indicates the polarization state of the second signal light (horizontal polarization), 504 indicates the polarization state of the third signal light, and 505 indicates the polarization state of the fourth signal light. The polarization states of the first signal light and the second signal light are orthogonal. The polarization states of the third signal light and the first signal light are orthogonal. The polarization states of the fourth signal light and the second signal light are orthogonal. In FIG. 5B, 506 indicates the polarization state of the signal light input by the beam splitting module 10 (i.e., the input signal light of the beam splitting module), 507 indicates the polarization state of the first signal light (horizontal polarization), 508 indicates the polarization state of the second signal light (vertical polarization), 509 indicates the polarization state of the third signal light, and 510 indicates the polarization state of the fourth signal light. The polarization state of the first signal light and the polarization state of the second signal light are orthogonal. The polarization state of the third signal light and the polarization state of the first signal light are orthogonal. The polarization state of the fourth signal light and the polarization state of the second signal light are orthogonal. In FIG. 5C , 511 indicates the polarization state (e.g., horizontal polarization) of the signal light input by the beam splitting module 10 (i.e., the input signal light of the beam splitting module), 512 indicates the polarization state (non-vertical polarization or non-horizontal polarization) of the first signal light, 513 indicates the polarization state of the second signal light, 514 indicates the polarization state of the third signal light, and 515 indicates the polarization state of the fourth signal light. The polarization states of the first signal light and the second signal light are orthogonal. The polarization states of the third signal light and the first signal light are orthogonal. The polarization states of the fourth signal light and the second signal light are orthogonal.

[0047] In some embodiments, both the first signal light and the third signal light are linearly polarized, and both the transmission signal light and the reflected signal light of the transmission signal light obtained after at least the first polarization process is performed on the first signal light are circularly polarized or elliptically polarized. The fourth signal light may be linearly polarized. In some embodiments, the polarization module has a polarization selection function, i.e., a function of outputting only signal light of a specific polarization state (e.g., the third signal light) to the frequency mixer and not outputting signal light of other polarization states to the frequency mixer.

[0048] In the detection system provided in the present application, the polarization module is configured to output a transmission signal light obtained after at least a first polarization process is performed on the first signal light, and to obtain (or receive) a reflected signal light of the transmission signal light, and to output a third signal light obtained after at least a second polarization process is performed on the reflected signal light to the frequency mixer 40. Since crosstalk light of a polarization state different from that of the third signal light cannot be output to the frequency mixer, the influence of crosstalk of the reflected light can be effectively reduced. Specifically, only the third signal light and crosstalk light whose polarization state is the same as that of the third signal light are output to the frequency mixer by the polarization module (i.e., the polarization module outputs only signal light of a specific polarization state to the frequency mixer), and crosstalk light of other polarization states cannot enter the frequency mixer. In other words, most crosstalk light cannot enter the frequency mixer. Therefore, the influence of crosstalk can be effectively reduced.

[0049] Possible structures of the polarization module 20 will now be described with reference to the accompanying drawings.

[0050] 6 is a schematic diagram of the structure of a polarization module according to an embodiment of the present application. As shown in FIG. 6, the polarization module 20 includes a unidirectional transmission component 601 and a polarization conversion module 602. The functions of the unidirectional transmission component 601 and the polarization conversion module 602 are as follows.

[0051] The unidirectionally conducting component 601 is configured to output the first signal light to the polarization conversion module and the third signal light to the frequency mixer 40 .

[0052] The polarization conversion module 602 is configured to perform a first polarization process on the first signal light and a second polarization process on the reflected signal light. The polarization conversion module 602 is further configured to output a transmission signal light obtained after the first polarization process is performed on the first signal light and output a third signal light obtained after the second polarization process is performed on the reflected signal light to the unidirectional conductive component 601. The polarization conversion module 602 is further configured to receive the reflected signal light.

[0053] The unidirectionally conducting component 601 may be a unidirectionally conducting non-reciprocal component. Signal light incident on the unidirectionally conducting component 601 from a first direction is transmitted, filtered, or absorbed, i.e., cannot pass through the unidirectionally conducting component 601. Signal light incident on the unidirectionally conducting component 601 from a second direction can pass through the unidirectionally conducting component 601. For example, the unidirectionally conducting component 601 includes two input ends. Signal light input from one input end (corresponding to the first direction) is transmitted, filtered, or absorbed, while signal light input from the other input end (corresponding to the second direction) passes through the unidirectionally conducting component 601 and is output from the output end of the unidirectionally conducting component 601. In some embodiments, a first signal light enters the unidirectionally conducting component 601 from a second direction, and the unidirectionally conducting component 601 outputs the first signal light to the polarization conversion module 602. The third signal light enters the unidirectional conductive component 601 from a first direction, and the unidirectional conductive component 601 inputs the third signal light to the frequency mixer 40. The unidirectional conductive component 601 is further configured to reflect, filter, or absorb the signal light of the first polarization state incident from the first direction. The first direction is the input direction of the third signal light, and the first polarization state is different from the polarization state of the third signal light. In other words, the signal light of the first polarization state incident on the unidirectional conductive component 601 from the first direction is reflected, filtered, or absorbed by the unidirectional conductive component 601. That is, the signal light of the first polarization state is not output to the frequency mixer. It should be understood that the unidirectionally conducting component 601 has the function of selecting polarization, i.e., outputting a signal light of a second polarization state (e.g., a third signal light) incident from a first direction to the frequency mixer, and the function of reflecting, filtering, or absorbing a signal light of a first polarization state incident from the first direction. The first polarization state is any polarization state different from the second polarization state.In other words, the unidirectional transmission component 601 outputs only the signal light of the second polarization state (e.g., the third signal light) incident from the first direction to the frequency mixer, and does not output the signal light of other polarization states (any polarization state different from the second polarization state) incident from the first direction to the frequency mixer. For example, the unidirectional transmission component 601 is configured to reflect the third signal light from the first reflecting surface to the frequency mixer and reflect the signal light of the first polarization state incident from the first direction from the second reflecting surface. The first reflecting surface is different from the second reflecting surface, and the first polarization state is different from the polarization state of the third signal. The unidirectional transmission component 601 may be a polarization optical splitter or a polarization light selection component, such as a polarization beam splitter (PBS). FIG. 7 illustrates an example in which the unidirectional transmission component processes the third signal light incident from the first direction and the signal light of the first polarization state according to an embodiment of the present application. 7, the third signal light incident on the unidirectional conductive component 601 from a first direction is reflected from the first reflecting surface (the upper reflecting surface in the figure) to the frequency mixer. The signal light of the first polarization state incident on the unidirectional conductive component 601 from the first direction is reflected from the second reflecting surface.

[0054] The polarization conversion module 602 is configured to output a transmission signal light obtained after at least a first polarization process is performed on the first signal light, receive a reflected signal light of the transmission signal light, and output a third signal light obtained after at least a second polarization process is performed on the reflected signal light. It can be seen that the polarization conversion module 602 performs at least a first polarization process on the first signal light and at least a second polarization process on the reflected signal light to obtain the third signal light that can be output from the frequency mixer by the unidirectional transmission component 601. The unidirectional transmission component 601 has a polarization selection function, i.e., it outputs the third signal light incident from a first direction to the frequency mixer and reflects, filters, or absorbs the signal light of the first polarization state incident from a second direction. In this way, only the third signal light (the desired target transmission light) is output by the unidirectional transmission component 601 to the frequency mixer, and crosstalk light is not output to the frequency mixer. Therefore, the influence of crosstalk can be effectively reduced.

[0055] Possible structures of the polarization conversion module 602 will now be described with reference to the accompanying drawings.

[0056] 8A and 8B are schematic diagrams of the structure of a polarization conversion module 602 according to an embodiment of the present application. As shown in Fig. 8A, the polarization conversion module 602 includes an optical antenna 6021 and a first polarization conversion component 6022. The first signal light output by the unidirectional conductive component 601 is incident on the optical antenna.

[0057] In some embodiments, the functions of the optical antenna 6021 and the first polarization conversion component 6022 are as follows.

[0058] The optical antenna 6021 is configured to output the signal light obtained after at least collimation processing is performed on the first signal light to the first polarization conversion component, and is configured to output the third signal light to the unidirectional conductive component.

[0059] The first polarization conversion component 6022 is configured to perform a first polarization process on the first signal light obtained after the collimation process, and is configured to output a third signal light obtained after the reflected signal light is subjected to a second polarization process.

[0060] The first polarization conversion component 6022 may be further configured to receive the reflected signal light and output a third signal light to the optical antenna 6021. The first polarization conversion component 6022 may be further configured to output a transmission signal light obtained after a first polarization process is performed on the first signal light obtained after the collimation process. The optical antenna 6021 may include a collimator. For example, the optical antenna 6021 includes a camera lens including one or more lenses. The optical antenna 6021 can collimate the first signal light, i.e., collimate the input light. The first polarization conversion component 6022 may be a quarter-wave plate or others. In some embodiments, the first polarization conversion component 6022 has the following characteristics: an optical beam (any linear polarization) may be converted from linear polarization (e.g., the first signal light) to circular polarization or elliptical polarization after passing through the first polarization conversion component 6022 once (or once), and may be converted from a polarization state to another polarization state orthogonal to the polarization state (output light and return light) after passing through the first polarization conversion component 6022 twice. The third signal light can be considered as the signal light obtained after the first signal light passes through the first polarization conversion component 6022 twice, i.e., the first polarization conversion component 6022 performs a first polarization process on the first signal light obtained after the collimation process to output the transmitted signal light, and then performs a second polarization process on the reflected signal light to output the third signal light. The polarization state of the transmitted signal light and the polarization state of the reflected signal light are the same.

[0061] 8B, the polarization conversion module 602 includes a first polarization conversion component 6023 and an optical antenna 6024. The first signal light output by the unidirectional conductive component 601 enters the first polarization conversion component 6023.

[0062] In some embodiments, the functions of the first polarization conversion component 6023 and the optical antenna 6024 are as follows.

[0063] The first polarization conversion component 6023 is configured to output a fifth signal light obtained after the first polarization process is performed on the first signal light to the optical antenna 6024, and is configured to perform a second polarization process on the reflected signal light.

[0064] The optical antenna 6024 is configured to output a transmission signal light obtained after at least a collimation process is performed on the fifth signal light.

[0065] The optical antenna 6024 may be further configured to receive the reflected signal light and output the reflected signal light to the first polarization conversion component 6023. The first polarization conversion component 6023 may be configured to output a third signal light, obtained after a second polarization process is performed on the reflected signal light, to the unidirectional conducting component 601.

[0066] The optical antenna 6024 may include a collimator. For example, the optical antenna 6024 is a camera lens including one or more lenses. The optical antenna 6024 can collimate the fifth signal light, i.e., collimate the input light. The first polarization conversion component 6023 may be a quarter-wave plate or others. In some embodiments, the first polarization conversion component 6023 has the following characteristics: a light beam (any linear polarization) may be converted from linear polarization (e.g., the first signal light) to circular polarization or elliptical polarization after passing through the first polarization conversion component 6023 once (or once), and may be converted from a polarization state to another polarization state orthogonal to the polarization state (output light and return light) after passing through the first polarization conversion component 6023 twice. The third signal light can be considered as the signal light obtained after the first signal light passes through the first polarization conversion component 6023 twice, that is, the first polarization conversion component 6023 performs a first polarization process on the first signal light to output a fifth signal light, and then performs a second polarization process on the reflected signal light to output a third signal light. The polarization state of the transmitted signal light and the polarization state of the reflected signal light are the same.

[0067] The function of the optical antenna in the polarization conversion module 602 is to allow the signal light to be coupled to the required components with maximum efficiency. In this embodiment of the present application, the optical antenna 6024 performs a collimation process on the signal light so that the signal light can be coupled to the first polarization conversion component 6023 with maximum efficiency, or the signal light can be coupled and transmitted from the detection system with maximum efficiency.

[0068] Possible constructions of the beam splitting module 10 will now be described with reference to the accompanying drawings.

[0069] 9 is a schematic diagram of the structure of a beam splitting module 10 according to an embodiment of the present application. As shown in FIG. 9, the beam splitting module 10 includes a beam splitter 101 and a second polarization conversion component 102.

[0070] The beam splitter 101 is configured to perform beam splitting processing on the input signal light to obtain a first signal light and a second signal light.

[0071] The second polarization conversion component 102 is configured to output a fourth signal light, which is obtained after at least a third polarization process is performed on the second signal light, to the frequency mixer.

[0072] In some embodiments, the polarization state of the first signal light and the polarization state of the second signal light are the same, and the polarization state of the fourth signal light and the polarization state of the second signal light are orthogonal. The beam splitter 101 is specifically configured to perform beam splitting on the input signal light to obtain the first signal light and the second signal light, outputting the first signal light to the polarization module 20 and outputting the second signal light to the second polarization conversion component 102. It should be understood that the beam splitter 101 performs beam splitting according to a specific ratio of the light incident on the beam splitter 101. One light enters the polarization module 20 as the signal light, and the other light enters the second polarization conversion component 102 as the local oscillator light. In practical applications, the ratio of the beam splitting performed by the beam splitter 101 may be configured according to actual requirements, i.e., the ratio of the signal light and the ratio of the local oscillator light. The function of the second polarization conversion component 102 is to perform polarization conversion on the signal light (e.g., second signal light) input by the second polarization conversion component 102. In other words, the second polarization conversion component 102 is configured to convert the polarization state of the second signal light (local oscillator light), for example, to convert the polarization state of the second signal light (i.e., local oscillator light) by 90 degrees. For example, the second polarization conversion component 102 converts the second signal light from horizontal polarization to vertical polarization to obtain a fourth signal light. The second polarization conversion component 102 may be a half-wave plate or others. In these embodiments, the second polarization conversion component 102 is configured to output the fourth signal light obtained after at least a third polarization process is performed on the second signal light to the frequency mixer, so that the frequency mixer performs frequency mixing on the local oscillator light (i.e., fourth signal light) and the third signal light.

[0073] In some embodiments, the beam splitter 101 is a polarizing beam splitter. The polarization state of the first signal light and the polarization state of the second signal light are orthogonal, and the polarization state of the signal light input by the beam splitter 101 and the polarization state of the first signal light are neither orthogonal nor parallel. The beam splitter 101 may be configured to perform beam splitting and polarization state adjustment (e.g., adjusting the polarization state of the signal light) on the input signal light to obtain the first signal light and the second signal light, and output the first signal light to the polarization module 20 and the second signal light to the second polarization conversion component 102. Assuming that light propagates toward paper, vertical polarization may be defined as polarization state 1 and horizontal polarization may be defined as polarization state 2. The polarization state of the optical signal input to the beam splitter 101 is polarization state 3, which forms a specific angle (e.g., 1° to 89°) with each of polarization state 1 and polarization state 2. Based on the characteristics of the polarizing beam splitter, the beam splitter 101 can adjust the splitting ratio between the signal path (corresponding to the signal light) and the local oscillator path (corresponding to the local oscillator light) based on the specific angles formed between the polarization state 3 and the polarization state 1 and between the polarization state 3 and the polarization state 2 to implement the function of the beam splitter. For example, the beam splitter 101 adjusts a specific angle of the polarization state 3 (i.e., a polarization state adjustment process) so that most of the light is used as the signal light and enters the polarization module 20 with the polarization state 1 (corresponding to the first signal light). The beam splitter 101 adjusts a specific angle of the polarization state 3 so that a small portion of the light is used as the local oscillator light and enters the second polarization conversion component 102 with the polarization state 2 (corresponding to the second signal light). The second polarization conversion component 102 is configured to output a fourth signal light obtained after at least a third polarization process is performed on the second signal light to the frequency mixer.In these embodiments, the beam splitter 101 performs beam splitting and polarization state adjustment on the input signal light to obtain first and second signal lights with orthogonal polarization states, and the second polarization conversion component 102 outputs the fourth signal light obtained after performing at least a third polarization process on the second signal light to the frequency mixer, so that the polarization states of the local oscillator light and the signal light input by the frequency mixer are orthogonal. It should be understood that when the frequency mixer 40 is a polarization frequency mixer, the beam splitter 101 in the beam splitting module 10 is a polarization beam splitter. In this way, the polarization states of the local oscillator light and the signal light input by the frequency mixer can be orthogonal.

[0074] In some embodiments, the beam splitting module 10 is a beam splitter, and the polarization state of the first signal light is the same as that of the second signal light. The beam splitting module 10 is specifically configured to perform beam splitting on the input signal light to obtain the first signal light and the second signal light, output the first signal light to the polarization module 20, and output the second signal light to the frequency mixer 40. The beam splitter 101 can perform beam splitting according to a specific ratio of the light incident on the beam splitter 101. One light enters the polarization module 20 as the signal light, and the other light enters the frequency mixer as the local oscillator light. In practical applications, the ratio of the beam splitting performed by the beam splitting module 10 can be configured according to actual requirements, i.e., the ratio of the signal light and the ratio of the local oscillator light. In these embodiments, the beam splitting module 10 only needs to perform beam splitting on the input signal light to obtain the first signal light and the second signal light. This has a simple structure and low cost.

[0075] In some embodiments, the beam splitting module 10 is a polarizing beam splitter. The polarization state of the first signal light and the polarization state of the second signal light are orthogonal, and the polarization state of the signal light input by the beam splitting module 10 and the polarization state of the first signal light are neither orthogonal nor parallel. Assuming that light propagates toward paper, vertical polarization may be defined as polarization state 1 and horizontal polarization may be defined as polarization state 2. The polarization state of the optical signal input to the beam splitting module 10 is polarization state 3, which forms a specific angle (e.g., 1° to 89°) with each of polarization state 1 and polarization state 2. Based on the characteristics of the polarizing beam splitter, the beam splitting module 10 can adjust the splitting ratio between the signal path (corresponding to the signal light) and the local oscillator path (corresponding to the local oscillator light) based on the specific angles formed between polarization state 3 and polarization state 1 and between polarization state 3 and polarization state 2 to implement the function of a beam splitter. For example, the beam splitting module 10 adjusts a specific angle of polarization state 3 so that most of the light is used as signal light and enters the polarization module 20 in polarization state 1. The beam splitting module 10 adjusts a specific angle of polarization state 3 so that a small portion of the light is used as local oscillator light and enters the frequency mixer 40 in polarization state 2. In this embodiment of the present application, a large percentage may be a splitting ratio greater than 90%, and a small percentage may be a splitting ratio less than 10%. It should be understood that an optical signal with polarization state 3 enters the beam splitting module 10, and most of the signal light split by the beam splitting module 10 is in polarization state 1, and a small portion of the local oscillator light is in polarization state 2. In this embodiment of the present application, the beam splitting module 10 performs beam splitting on the input signal light to obtain first and second signal lights with orthogonal polarization states. In this way, the polarization states of the local oscillator light and the signal light input by the frequency mixer can be made the same, and the frequency mixing efficiency can be improved.

[0076] In some embodiments, the transmission and reception optical paths in the detection system provided herein may be arranged coaxially. The transmission and reception optical paths are arranged coaxially, which is called a coaxial optical system. A coaxial optical system has the advantages of a simple structure and high transmission and reception efficiency, but is susceptible to crosstalk and stray light. The detection system in these embodiments has a simple structure, high transmission and reception efficiency, and is less susceptible to crosstalk and stray light. FIG. 10 shows an example of a detection system in which the transmission and reception optical paths are arranged coaxially, according to an embodiment of the present application. As shown in FIG. 10, 1001 denotes an output light source, 1002 denotes a collimation optical path, 1003 denotes an optical splitter, 1004 denotes a scanning mechanism, 1005 denotes an object, 1006 denotes a focusing lens, and 1007 denotes a detector. As shown in FIG. 10 , signal light transmitted by an output light source passes through a collimation light path 1002 (also called a collimator), an optical splitter 1003, and a scanning mechanism 1004 in sequence to reach the target. The signal light reflected by the target passes through a scanning mechanism 1004, an optical splitter 1003, and a focusing lens 1006 in sequence to reach a detector 1007. In this embodiment of the present application, the transmission light path is the optical path from the generation of the transmission light (i.e., the signal light transmitted by the output light source) to the transmission of the transmission light by the optical splitter 1003, and the reception light path is the optical path from the reception of the reflected light by the scanning mechanism 1004 to the transmission of the reflected light to the detector 1007. In FIG. 10 , solid arrows indicate the transmission light paths, and dashed arrows indicate the reception light paths. It can be seen from FIG. 10 that the transmission light paths and the reception light paths may be arranged coaxially. In FIG. 10, the detection system may be a Lidar system, the transmission light source 1001 may be a laser, and the detector 1007 may be a PIN detector, an APD detector, a balanced detector, or the like.

[0077] We have described above possible configurations of the beam splitting module 10 and possible configurations of the polarization module 20. In the following, some possible examples of the detection system of Figure 1 will be described with reference to the accompanying drawings.

[0078] FIG. 11 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. The detection system of FIG. 11 is a possible implementation of the detection system of FIG. 1. As shown in FIG. 11, the detection system includes a signal generator 1101, a laser 1102, an amplifier 1103, a beam splitter 101, a second polarization conversion component 102, a unidirectional conducting component 601, an optical antenna 6021, a first polarization conversion component 6022, a frequency mixer 40, a detector 1104, an analog-to-digital converter (ADC) 1105, and a processing unit 1106. It should be understood that the beam splitter 101 and the second polarization conversion component 102 correspond to the beam splitting module 10. In other words, a possible structure of the beam splitting module 10 includes the beam splitter 101 and the second polarization conversion component 102. The unidirectional conductive component 601, the optical antenna 6021, and the first polarization conversion component 6022 correspond to the polarization module 20. In other words, a possible structure of the polarization module 20 includes the unidirectional conductive component 601, the optical antenna 6021, and the first polarization conversion component 6022. It should be noted that in a particular design and implementation of the detection system, any one or more components in FIG. 11 may be reduced or replaced. It should also be understood that in a particular implementation, the detection system may include one or more of all the components shown in FIG. 11. The structure of the detection system is not particularly limited in this application. An example of the functions of all the components in FIG. 11 will be described below.

[0079] The signal generator 1101 is configured to modulate the laser 1102. The modulation method of the laser 1102 may be direct modulation or external modulation performed using a modulator, and the modulation method may be frequency-modulated continuous wave, phase-encoded, etc. In some embodiments, the structure of the signal generator 1101 for modulating the laser 1102 may also have the following alternative: the laser signal output by the laser 1102 is incident on a modulator, the modulator modulates the input laser signal, and outputs the modulated laser signal to the amplifier 1103. For example, the modulator modulates the laser signal output by the laser 1102 based on the modulation signal input by the signal generator. That is, in some scenarios, the signal generator is optional.

[0080] Laser 1102 is configured to output a laser signal to amplifier 1103. Laser 1102 may be a narrow linewidth laser, such as a semiconductor laser, a fiber laser, or other type of laser.

[0081] Amplifier 1103 is configured to amplify the input laser signal and output the amplified input laser signal to beam splitter 101. Amplifier 1103 may be an optical amplifier, such as an erbium doped fiber amplifier (EDFA), a semiconductor optical amplifier (SOA), or other type of optical amplifier.

[0082] The beam splitter 101 is configured to perform beam splitting processing on the amplified laser signal (hereinafter referred to as signal light) to obtain a first signal light and a second signal light, and is configured to output the first signal light to the unidirectional conductive component 601 and output the second signal light to the second polarization conversion component 102. In other words, the amplified signal light is split into two by the beam splitter 101. One part is incident on the unidirectional conductive component 601 and the other part is incident on the second polarization conversion component 102 as local oscillator light.

[0083] The second polarization conversion component 102 is configured to output a fourth signal light obtained after at least a third polarization process is performed on the second signal light to the frequency mixer 40. For example, in some scenarios, the second polarization conversion component is optional. For details, see the description of FIG. 13.

[0084] The unidirectional conducting component 601 is configured to output the first signal light from the beam splitter 101 to the optical antenna 6021 .

[0085] The optical antenna 6021 is configured to output, to the first polarization conversion component 6022, the signal light obtained after at least collimation processing is performed on the first signal light.

[0086] The first polarization conversion component 6022 is configured to perform a first polarization process on the first signal light obtained after the collimation process, output a transmission signal light obtained after the first polarization process on the first signal light obtained after the collimation process, receive a reflected signal light, and output a third signal light obtained after the reflected signal light is subjected to a second polarization process to the optical antenna 6021. In other words, the first polarization conversion component 6022 is configured to perform a first polarization process on the first signal light obtained after the collimation process, and perform a second polarization process on the reflected signal light. The reflected signal light is a signal light that is transmitted to an arbitrary object and returned. After passing through the optical antenna 6021, the first signal light passes through the first polarization conversion component 6022 to become circularly polarized or elliptically polarized light (i.e., a transmission signal light) and is transmitted to an arbitrary object to generate a reflected signal light. The reflected signal light returned by any object passes through the first polarization conversion component 6022 again to become a third signal light, which is incident on the optical antenna 6021 .

[0087] The optical antenna 6021 is configured to output the third signal light to the unidirectional conducting component 601. After receiving the third signal light, the optical antenna 6021 sends the third signal light back to the unidirectional conducting component 601.

[0088] The unidirectional conductive component 601 is configured to output the third signal light to the frequency mixer 40. Because the polarization state of the first signal light has changed from polarization state 1 to polarization state 2, when the third signal light returns to the unidirectional conductive component 601, the third signal light does not return along the original path but is reflected by the frequency mixer 40. Polarization state 1 is the polarization state of the first signal light, for example, vertical polarization. Polarization state 2 is the polarization state of the third signal light, for example, horizontal polarization.

[0089] The frequency mixer 40 is configured to perform frequency mixing on a fourth signal light (local oscillator light) and a third signal light to obtain a mixed signal. The polarization state of the second signal light and the polarization state of the third signal light are the same. The frequency mixer 40 is a non-polarized frequency mixer component. Regardless of the depolarization effect of signal lights reflected by any object, the polarization directions of the two lights incident on the frequency mixer 40, i.e., the third signal light and the fourth signal light, are the same. In this application, the polarization states of the two signal lights being the same means that the polarization directions of the two signal lights are the same, and the polarization states of the two signal lights being orthogonal means that the polarization directions of the two signal lights are orthogonal.

[0090] The detector 1104 is configured to detect a mixed signal obtained after the frequency mixer 40 performs the frequency mixing process. The detector 1104 may be a PIN detector, an avalanche photon diode (APD) detector, a single-photon avalanche diode (SPAD) balanced detector, or other detectors.

[0091] The ADC 1105 is configured to sample the mixed signal detected by the detector 1104 and send the sampled signal to the processing unit 1106. In other words, after being sampled by the ADC 1105, the mixed signal detected by the detector 1104 is sent to the processing unit 1106 for subsequent signal processing.

[0092] The processing unit 1106 is configured to perform subsequent signal processing on the sampled signals to obtain information such as the position and velocity of the detected object.

[0093] In a coaxial transceiver detection system (i.e., a detection system using a coaxial optical system), various kinds of crosstalk are inevitably introduced. In a practical detection system, due to optical lenses, etc., reflected light returns to the frequency mixer with a small loss and adds to the frequency beat, causing a near-field peak. Also, due to component crosstalk, some signal light leaks directly into the frequency mixer due to coherence, disrupting near-field signal detection.

[0094] In the detection system provided in this embodiment of the present application, a polarizing component (i.e., a polarizing module) is used to effectively reduce the crosstalk problem caused by reflected light and the characteristics of the component. The detection system provided in this embodiment of the present application is applicable to "line transmission and line reception" lidar systems, "area transmission and area reception" lidar systems, "spot transmission and spot reception" lidar systems, etc.

[0095] FIG. 12 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. The detection system of FIG. 12 is a possible implementation of the detection system of FIG. 1. As shown in FIG. 12, the detection system includes a signal generator 1101, a laser 1102, an amplifier 1103, a beam splitter 101, a second polarization conversion component 102, a unidirectional transmission component 601, a first polarization conversion component 6023, an optical antenna 6024, a frequency mixer 40, a detector 1104, an ADC 1105, and a processing unit 1106. It should be understood that the beam splitter 101 and the second polarization conversion component 102 correspond to the beam splitting module 10. In other words, a possible structure of the beam splitting module 10 includes the beam splitter 101 and the second polarization conversion component 102. The unidirectional transmission component 601, the optical antenna 6021, and the first polarization conversion component 6022 correspond to the polarization module 20. In other words, a possible structure of the polarization module 20 includes a unidirectionally conducting component 601, a first polarization conversion component 6023, and an optical antenna 6024. It should be noted that in a particular design and implementation of the detection system, any one or more components in FIG. 12 may be reduced or replaced. It should also be understood that in a particular implementation, the detection system may include one or more of all of the components shown in FIG. 12. The structure of the detection system is not particularly limited in this application. An example of the functions of all the components in FIG. 12 will be described below.

[0096] The signal generator 1101 is configured to modulate the laser 1102. The modulation method of the laser 1102 may be direct modulation or external modulation performed using a modulator, and the modulation method may be frequency-modulated continuous wave, phase-encoded, etc. In some embodiments, the structure of the signal generator 1101 for modulating the laser 1102 may also be as follows: the laser signal output by the laser 1102 is incident on the modulator, the modulator modulates the input laser signal, and outputs the modulated laser signal to the amplifier 1103. For example, the modulator modulates the laser signal output by the laser 1102 based on the modulation signal input by the signal generator.

[0097] Laser 1102 is configured to output a laser signal to amplifier 1103. Laser 1102 may be a narrow linewidth laser, such as a semiconductor laser, a fiber laser, or other type of laser.

[0098] Amplifier 1103 is configured to amplify the input laser signal and output the amplified input laser signal to beam splitter 101. Amplifier 1103 may be an optical amplifier, such as an erbium doped fiber amplifier (EDFA), a semiconductor optical amplifier (SOA), or other type of optical amplifier.

[0099] The beam splitter 101 is configured to perform beam splitting processing on the amplified laser signal (hereinafter referred to as signal light) to obtain a first signal light and a second signal light, and is configured to output the first signal light to the unidirectional conductive component 601 and output the second signal light to the second polarization conversion component 102. In other words, the amplified signal light is split into two by the beam splitter 101. One part is incident on the unidirectional conductive component 601 and the other part is incident on the second polarization conversion component 102 as local oscillator light.

[0100] The second polarization conversion component 102 is configured to output to the frequency mixer 40 a fourth signal light obtained after at least a third polarization process is performed on the second signal light.

[0101] The unidirectionally conducting component 601 is configured to output the first signal light from the beam splitter 101 to the first polarization conversion component 6023 .

[0102] The first polarization conversion component 6023 is configured to output a fifth signal light, which is obtained after the first polarization process is performed on the first signal light, to the optical antenna 6024.

[0103] The optical antenna 6024 is configured to output a transmission signal light obtained after at least a collimation process is performed on the fifth signal light, and is configured to receive a reflected signal light and output the reflected signal light to the first polarization conversion component 6023.

[0104] The first polarization conversion component 6023 is configured to perform a second polarization process on the reflected signal light, and is configured to output a third signal light obtained after the second polarization process is performed on the reflected signal light to the unidirectional transmission component 601.

[0105] The unidirectional conductive component 601 is configured to output the third signal light to the frequency mixer 40. Because the polarization state of the first signal light has changed from polarization state 1 to polarization state 2, when the third signal light returns to the unidirectional conductive component 601, the third signal light does not return along the original path but is reflected by the frequency mixer 40. Polarization state 1 is the polarization state of the first signal light, for example, vertical polarization. Polarization state 2 is the polarization state of the third signal light, for example, horizontal polarization.

[0106] The frequency mixer 40 is configured to perform frequency mixing on the fourth signal light (local oscillator light) and the third signal light to obtain a mixed signal. The polarization state of the second signal light and the polarization state of the third signal light are the same. The frequency mixer 40 is a non-polarized frequency mixer component. Regardless of the depolarization effect of the signal light reflected by any object, the polarization directions of the two lights incident on the frequency mixer 40, i.e., the third signal light and the fourth signal light, are the same.

[0107] The detector 1104 is configured to detect a mixed signal obtained after the frequency mixer 40 performs the frequency mixing process. The detector 1104 may be a PIN detector, an avalanche photon diode (APD) detector, a balanced detector, etc.

[0108] The ADC 1105 is configured to sample the mixed signal detected by the detector 1104 and send the sampled signal to the processing unit 1106. In other words, after being sampled by the ADC 1105, the mixed signal detected by the detector 1104 is sent to the processing unit 1106 for subsequent signal processing.

[0109] The processing unit 1106 is configured to perform subsequent signal processing on the sampled signals to obtain information such as the position and velocity of the detected object.

[0110] Comparing the detection system of Figure 12 with the detection system of Figure 11, it can be seen that the optical antenna of Figure 11 performs at least a collimation process on the first signal light output by the unidirectional conductive component 601 and transmits the collimated signal light to the first polarization conversion component 6022, and the first polarization conversion component 6023 of Figure 12 performs a first polarization process on the first signal light output by the unidirectional conductive component 601 and outputs a fifth signal light obtained after the first polarization process is performed on the first signal light to the optical antenna 6024.

[0111] FIG. 13 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. The detection system of FIG. 13 is a possible implementation of the detection system of FIG. 1. As shown in FIG. 13, the detection system includes a signal generator 1101, a laser 1102, an amplifier 1103, a beam splitting module 10, a unidirectional conductive component 601, an optical antenna 6021, a first polarization conversion component 6022, a frequency mixer 40, a detector 1104, an ADC 1105, and a processing unit 1106. The beam splitting module 10 may be a beam splitter. The unidirectional conductive component 601, the optical antenna 6021, and the first polarization conversion component 6022 correspond to the polarization module 20. In other words, a possible structure of the polarization module 20 includes the unidirectional conductive component 601, the optical antenna 6021, and the first polarization conversion component 6022. In Fig. 13, 1301 indicates the polarization direction of the signal light input by the beam splitting module 10, 1302 indicates the polarization direction of the first signal light, 1303 indicates the polarization direction of the second signal light, and 1304 indicates the polarization direction of the third signal light. The functions of all the components in Fig. 13 are as follows:

[0112] The signal generator 1101 is configured to modulate the laser 1102. The modulation method of the laser 1102 may be direct modulation or external modulation performed using a modulator, and the modulation method may be frequency-modulated continuous wave, phase-encoded, etc. In some embodiments, the structure of the signal generator 1101 for modulating the laser 1102 may also be as follows: the laser signal output by the laser 1102 is incident on the modulator, the modulator modulates the input laser signal, and outputs the modulated laser signal to the amplifier 1103. For example, the modulator modulates the laser signal output by the laser 1102 based on the modulation signal input by the signal generator.

[0113] Laser 1102 is configured to output a laser signal to amplifier 1103. Laser 1102 may be a narrow linewidth laser, such as a semiconductor laser, a fiber laser, or other type of laser.

[0114] Amplifier 1103 is configured to amplify the input laser signal and output the amplified input laser signal to beam splitter 101. Amplifier 1103 may be an optical amplifier, such as, for example, an EDFA, SOA, or other type of optical amplifier.

[0115] The beam splitting module 10 is configured to perform beam splitting processing on the amplified laser signal (hereinafter referred to as signal light) to obtain a first signal light and a second signal light, and is configured to output the first signal light to the unidirectional conductive component 601 and output the second signal light to the frequency mixer 40. In other words, the amplified signal light is split into two by the beam splitting module 10. One is incident on the unidirectional conductive component 601 and the other is incident on the frequency mixer 40 as local oscillator light. In this embodiment of the present application, the polarization state of the first signal light and the polarization state of the second signal light are the same.

[0116] The unidirectional conducting component 601 is configured to output the first signal light from the beam splitting module 10 to the optical antenna 6021 .

[0117] The optical antenna 6021 is configured to output, to the first polarization conversion component 6022, the signal light obtained after at least collimation processing is performed on the first signal light.

[0118] The first polarization conversion component 6022 is configured to perform a first polarization process on the first signal light obtained after the collimation process, output a transmission signal light obtained after the first polarization process on the first signal light obtained after the collimation process, receive a reflected signal light, and output a third signal light obtained after the reflected signal light is subjected to a second polarization process to the optical antenna 6021. In other words, the first polarization conversion component 6022 is configured to perform a first polarization process on the first signal light obtained after the collimation process, and perform a second polarization process on the reflected signal light. The reflected signal light is a signal light that is transmitted to an arbitrary object and returned. After passing through the optical antenna 6021, the first signal light passes through the first polarization conversion component 6022 to become circularly polarized or elliptically polarized light (i.e., a transmission signal light) and is transmitted to an arbitrary object to generate a reflected signal light. The reflected signal light returned by any object passes through the first polarization conversion component 6022 again to become a third signal light, which is incident on the optical antenna 6021 .

[0119] The optical antenna 6021 is configured to output the third signal light to the unidirectional conductive component 601. In other words, the optical antenna 6021 receives the third signal light and then sends the third signal light back to the unidirectional conductive component 601.

[0120] The unidirectional conductive component 601 is configured to output the third signal light to the frequency mixer 40. Because the polarization state of the first signal light has changed from polarization state 1 to polarization state 2, when the third signal light returns to the unidirectional conductive component 601, the third signal light does not return along the original path but is reflected by the frequency mixer 40. Polarization state 1 is the polarization state of the first signal light, for example, vertical polarization. Polarization state 2 is the polarization state of the third signal light, for example, horizontal polarization.

[0121] The frequency mixer 40 is configured to frequency-mix the second signal light (local oscillator light) and the third signal light to obtain a mixed signal. The polarization state of the second signal light and the polarization state of the third signal light are orthogonal. The frequency mixer 40 is a polarized frequency mixing component. Regardless of the depolarization effect of the signal light reflected by any object, the polarization directions of the two lights incident on the frequency mixer 40, i.e., the third signal light and the second signal light, are orthogonal.

[0122] The detector 1104 is configured to detect a mixed signal obtained after the frequency mixer 40 performs the frequency mixing process. The detector 1104 may be a PIN detector, an avalanche photon diode (APD) detector, a balanced detector, etc.

[0123] The ADC 1105 is configured to sample the mixed signal detected by the detector 1104 and send the sampled signal to the processing unit 1106. In other words, after being sampled by the ADC 1105, the mixed signal detected by the detector 1104 is sent to the processing unit 1106 for subsequent signal processing.

[0124] The processing unit 1106 is configured to perform subsequent signal processing on the sampled signals to obtain information such as the position and velocity of the detected object.

[0125] 13 and 11, it can be seen that the structure of the beam splitting module 10 in FIG. 13 is different from the structure of the beam splitting module in FIG.

[0126] In some embodiments, the structure of the polarization module 20 of FIG. 13 may be substituted for the structure of the polarization module 20 of FIG.

[0127] FIG. 14 is a schematic diagram of the structure of another detection system according to an embodiment of the present application. The detection system of FIG. 14 is a possible implementation of the detection system of FIG. 1. As shown in FIG. 14, the detection system includes a signal generator 1101, a laser 1102, an amplifier 1103, a beam splitting module 10, a unidirectional conductive component 601, an optical antenna 6021, a first polarization conversion component 6022, a frequency mixer 40, a detector 1104, an ADC 1105, and a processing unit 1106. The beam splitting module 10 may be a polarizing beam splitter. The unidirectional conductive component 601, the optical antenna 6021, and the first polarization conversion component 6022 correspond to the polarization module 20. In other words, a possible structure of the polarization module 20 includes the unidirectional conductive component 601, the optical antenna 6021, and the first polarization conversion component 6022. In Fig. 14, 1401 indicates the polarization direction of the signal light input by the beam splitting module 10, 1402 indicates the polarization direction of the first signal light, 1403 indicates the polarization direction of the second signal light, and 1404 indicates the polarization direction of the third signal light. The functions of all the components in Fig. 14 are as follows:

[0128] The signal generator 1101 is configured to modulate the laser 1102. The modulation method of the laser 1102 may be direct modulation or external modulation performed using a modulator, and the modulation method may be frequency-modulated continuous wave, phase-encoded, etc. In some embodiments, the structure of the signal generator 1101 for modulating the laser 1102 may also be as follows: the laser signal output by the laser 1102 is incident on the modulator, the modulator modulates the input laser signal, and outputs the modulated laser signal to the amplifier 1103. For example, the modulator modulates the laser signal output by the laser 1102 based on the modulation signal input by the signal generator.

[0129] Laser 1102 is configured to output a laser signal to amplifier 1103. Laser 1102 may be a narrow linewidth laser, such as a semiconductor laser, a fiber laser, or other type of laser.

[0130] Amplifier 1103 is configured to amplify the input laser signal and output the amplified input laser signal to beam splitter 101. Amplifier 1103 may be an optical amplifier, such as an erbium doped fiber amplifier (EDFA), a semiconductor optical amplifier (SOA), or other type of optical amplifier.

[0131] The beam splitting module 10 is configured to perform beam splitting on the input signal light to obtain a first signal light and a second signal light, and output the first signal light to the unidirectional conducting component 601 and the second signal light to the frequency mixer 40. In this embodiment of the present application, the polarization states of the first signal light and the second signal light are orthogonal.

[0132] The unidirectional conducting component 601 is configured to output the first signal light from the beam splitting module 10 to the optical antenna 6021 .

[0133] The optical antenna 6021 is configured to output, to the first polarization conversion component 6022, the signal light obtained after at least collimation processing is performed on the first signal light.

[0134] The first polarization conversion component 6022 is configured to perform a first polarization process on the first signal light obtained after the collimation process, output a transmission signal light obtained after the first polarization process on the first signal light obtained after the collimation process, receive a reflected signal light, and output a third signal light obtained after the reflected signal light is subjected to a second polarization process to the optical antenna 6021. In other words, the first polarization conversion component 6022 is configured to perform a first polarization process on the first signal light obtained after the collimation process, and perform a second polarization process on the reflected signal light. The reflected signal light is a signal light that is transmitted to an arbitrary object and returned. After passing through the optical antenna 6021, the first signal light passes through the first polarization conversion component 6022 to become circularly polarized or elliptically polarized light (i.e., a transmission signal light) and is transmitted to an arbitrary object to generate a reflected signal light. The reflected signal light returned by any object passes through the first polarization conversion component 6022 again to become a third signal light, which is incident on the optical antenna 6021 .

[0135] The optical antenna 6021 is configured to output the third signal light to the unidirectional conducting component 601. After receiving the third signal light, the optical antenna 6021 sends the third signal light back to the unidirectional conducting component 601.

[0136] The unidirectional conductive component 601 is configured to output the third signal light to the frequency mixer 40. Because the polarization state of the first signal light has changed from polarization state 1 to polarization state 2, when the third signal light returns to the unidirectional conductive component 601, the third signal light does not return along the original path but is reflected by the frequency mixer 40. Polarization state 1 is the polarization state of the first signal light, for example, vertical polarization. Polarization state 2 is the polarization state of the third signal light, for example, horizontal polarization.

[0137] The frequency mixer 40 is configured to frequency-mix the second signal light (local oscillator light) and the third signal light to obtain a mixed signal. The polarization state of the second signal light is the same as that of the third signal light. The frequency mixer 40 is a non-polarized frequency mixer component. Regardless of the depolarization effect of the signal light reflected by any object, the polarization directions of the two lights incident on the frequency mixer 40, i.e., the third signal light and the second signal light, are the same.

[0138] The detector 1104 is configured to detect a mixed signal obtained after the frequency mixer 40 performs the frequency mixing process. The detector 1104 may be a PIN detector, an avalanche photon diode (APD) detector, a balanced detector, etc.

[0139] The ADC 1105 is configured to sample the mixed signal detected by the detector 1104 and send the sampled signal to the processing unit 1106. In other words, after being sampled by the ADC 1105, the mixed signal detected by the detector 1104 is sent to the processing unit 1106 for subsequent signal processing.

[0140] The processing unit 1106 is configured to perform subsequent signal processing on the sampled signals to obtain information such as the position and velocity of the detected object.

[0141] In some embodiments, the structure of the polarization module 20 in Figure 14 may be replaced with the structure of the polarization module 20 in Figure 12. In some embodiments, the beam splitting module 10 in Figure 14 can output the second signal light to the second polarization conversion component 102. The second polarization conversion component 102 outputs a fourth signal light, which is obtained after at least a third polarization process is performed on the second signal light, to the frequency mixer 40.

[0142] Figures 15A and 15B show example test results for a coaxial transceiver detection system using a non-polarizing component (circulator) as a non-reciprocal component. Figure 15A shows the signal and noise levels measured multiple times by a coaxial transceiver detection system using a non-polarizing component, and Figure 15B shows the spectrum obtained after fast Fourier transform (FFT). It can be seen that at low frequencies (near distance), there is a crosstalk signal of approximately -40 dBm, which is much larger than the target echo signal level at 200 MHz to 300 MHz. The crosstalk signal not only makes near-distance signal detection very difficult, but also raises the noise floor level across the entire frequency range, from low to mid-frequency. Figures 16A and 16B show example test results for a coaxial transceiver detection system using a polarizing component as a non-reciprocal component. Under the same parameters and conditions, a polarizing component is substituted for the non-reciprocal component used in the coaxial transceiver detection system (i.e., the detection system provided in this application is used). The test results are shown in Figures 15A and 15B. From Figure 16A, we can see that after accurate adjustment, the level of the crosstalk signal in the signal spectrum decreases from -40 dBm to -50 dBm, a decrease of about 10 dB. Since the polarized component effectively reduces the crosstalk caused by reflected light, the level of the crosstalk signal is significantly reduced, which brings several advantages to both the detection of near-field signals and the reduction of noise levels in the low- to mid-frequency range.

[0143] In addition, because the crosstalk signal is much larger than the signal level, the magnitude of the time-domain signal depends more on the magnitude of the crosstalk signal. However, reducing the level of the frequency-domain crosstalk signal means that the magnitude of the time-domain signal is also reduced accordingly. In this way, the back-end processed ADC can reduce the quantization range by a fixed number of bits (least significant bit, LSB), thereby reducing the quantization noise. Please note that the above results are only a rough representation of the effects under the test conditions. Although the trends are similar, the results may be slightly different under other conditions.

[0144] In summary, the detection system provided in this embodiment effectively reduces the crosstalk problem caused by reflected light and the characteristics of the components by using polarized components.

[0145] The present application provides a lidar system. The lidar system includes any of the detection systems provided herein. The detection systems provided herein may be applicable to "line transmit and line receive" lidar systems, "area transmit and area receive" lidar systems, or "spot transmit and spot receive" lidar systems, etc. Figure 10 may be considered an example of a lidar system according to the present application.

[0146] The present application provides a terminal device, which includes a detection system provided in the present application. For example, the terminal device is an intelligent vehicle (or an autonomous driving device), and one or more detection systems provided in the present application are deployed in the intelligent vehicle.

[0147] The present application provides a detection apparatus that includes at least one laser, at least one detector, and any of the detection systems provided herein.

[0148] The above description is merely a specific implementation of the present invention and is not intended to limit the protection scope of the present invention. Any modifications or replacements that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims. [Explanation of symbols]

[0149] 10 beam splitting module, 20 polarization module, 40 frequency mixer, 101 beam splitter, 102 second polarization conversion component, 201 polarization state of first signal light, 202 polarization state of second signal light, 203 polarization state of third signal light, 204 polarization state of first signal light, 205 polarization state of second signal light, 206 polarization state of third signal light, 207 polarization state of first signal light, 208 polarization state of second signal light, 209 polarization state of third signal light, 301 polarization state of first signal light, 302 polarization state of second signal light, 303 polarization state of third signal light, 304 polarization state of fourth signal light, 305 polarization state of first signal light, 306 polarization state of second signal light, 307 polarization state of third signal light, 308 polarization state of fourth signal light, 309 polarization state of first signal light, 310 Polarization state of second signal light, 311 Polarization state of third signal light, 312 Polarization state of fourth signal light, 313 Polarization state of first signal light, 314 Polarization state of second signal light, 315 Polarization state of third signal light, 316 Polarization state of fourth signal light, 401 Polarization state of signal light input by beam splitting module 10, 402 Polarization state of first signal light, 403 Polarization state of second signal light, 404 Polarization state of third signal light, 405 Polarization state of signal light input by beam splitting module 10, 406 Polarization state of first signal light, 407 Polarization state of second signal light, 408 Polarization state of third signal light, 409 Polarization state of signal light input by beam splitting module 10, 410 Polarization state of first signal light, 411 Polarization state of second signal light, 412 Polarization state of third signal light, 501 Polarization state of signal light input by beam splitting module 10, 502 Polarization state of first signal light, 503 Polarization state of second signal light, 504 Polarization state of third signal light, 505 Polarization state of fourth signal light, 506 Polarization state of signal light input by beam splitting module 10, 507 Polarization state of first signal light, 508 Polarization state of second signal light, 509 Polarization state of third signal light, 510 Polarization state of fourth signal light, 511 Polarization state of signal light input by beam splitting module 10, 512 Polarization state of first signal light, 513 Polarization state of second signal light, 514 Polarization state of third signal light, 515Polarization state of fourth signal light, 601 unidirectional transmission component, 602 polarization conversion module, 1001 transmission light source, 1002 collimation light path, 1003 optical splitter, 1004 scanning mechanism, 1005 object, 1006 focusing lens, 1007 detector, 1101 signal generator, 1102 laser, 1103 amplifier, 1104 detector, 1105 ADC, 1106 processing unit, 1301 polarization direction of signal light input by beam splitting module 10, 1302 polarization direction of first signal light, 1303 polarization direction of second signal light, 1304 polarization direction of third signal light, 1401 polarization direction of signal light input by beam splitting module 10, 1402 polarization direction of first signal light, 1403 polarization direction of second signal light, 1404 polarization direction of third signal light, 6021 Optical antenna, 6022 first polarization conversion component, 6023 first polarization conversion component, 6024 optical antenna

Claims

1. a beam splitting module, a polarization module, and a frequency mixer; the beam splitting module (10) is configured to perform beam splitting on an input signal light to obtain a first signal light and a second signal light; the polarization module (20) is configured to output a transmission signal light obtained after at least a first polarization process is performed on the first signal light, obtain a reflected signal light of the transmission signal light, and output a third signal light obtained after at least a second polarization process is performed on the reflected signal light; the frequency mixer (40) is configured to perform frequency mixing processing on the third signal light and fourth signal light obtained after at least a third polarization processing is performed on the second signal light; Detection system.

2. A detection system as described in claim 1, wherein the frequency mixer (40) is a non-polarized frequency mixer, and the polarization state of the fourth signal light is the same as the polarization state of the third signal light.

3. The polarization module comprises a polarization conversion module (602) and a unidirectionally transmitting component (601); the unidirectionally conducting component (601) is configured to output the first signal light to the polarization conversion module and the third signal light to the frequency mixer (40); the polarization conversion module (602) is configured to perform the first polarization processing on the first signal light and the second polarization processing on the reflected signal light; The detection system of claim 1 .

4. the unidirectionally conducting component (601) is further configured to reflect, filter, or absorb signal light of a first polarization state incident from a first direction, the first direction being an input direction of the third signal light, and the first polarization state being different from the polarization state of the third signal light; The detection system of claim 3 .

5. The unidirectionally conductive component (601) comprises at least one reflective surface; the unidirectionally conducting component (601) is configured to reflect the third signal light from a first reflecting surface to the frequency mixer; and / or the unidirectionally transmitting component (601) is configured to reflect, from a second reflecting surface, signal light of a first polarization state incident from a first direction, the first direction being an input direction of the third signal light, the first reflecting surface being different from the second reflecting surface, and the first polarization state being different from the polarization state of the third signal light; The detection system of claim 3 .

6. The polarization conversion module (602) comprises an optical antenna (6021, 6024) and a first polarization conversion component (6022, 6023); the optical antennas (6021, 6024) are configured to output signal light obtained after at least collimation processing of the first signal light to the first polarization conversion component (6022, 6023), and are configured to output the third signal light to the unidirectional transmission component (601); the first polarization conversion component (6022, 6023) is configured to perform the first polarization process on the first signal light obtained after the collimation process, and to output the third signal light obtained after the reflected signal light is subjected to the second polarization process; or the first polarization conversion component (6022, 6023) is configured to output a fifth signal light obtained after the first polarization processing is performed on the first signal light to the optical antenna (6021, 6024), and is configured to perform the second polarization processing on the reflected signal light; The optical antennas (6021, 6024) are configured to output the transmission signal light obtained after at least collimation processing is performed on the fifth signal light. The detection system of claim 3 .

7. The beam splitting module (10) comprises a beam splitter (101) and a second polarization conversion component (102); the beam splitter (101) is configured to perform beam splitting processing on an input signal light to obtain the first signal light and the second signal light; the second polarization conversion component (102) is configured to output the fourth signal light obtained after at least the third polarization processing is performed on the second signal light to the frequency mixer (40). The detection system of claim 1 .

8. The detection system of claim 1 , wherein the polarization state of the first signal light and the polarization state of the second signal light are the same.

9. the beam splitting module (10) is a polarizing beam splitter; the polarization state of the first signal light and the polarization state of the second signal light are orthogonal to each other, and the polarization state of the input signal light and the polarization state of the first signal light are neither orthogonal nor parallel to each other; The detection system of claim 1 .

10. The detection system of claim 1 , wherein the detection system includes a transmit optical path and a receive optical path, the transmit optical path and the receive optical path being coaxially arranged.

11. A terminal device comprising a detection system according to any one of claims 1 to 10.

12. A detection device comprising at least one laser, at least one detector, and a detection system according to any one of claims 1 to 10.

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