FMCW lidar system

Abstract

An FMCW lidar system, the FMCW lidar system comprising: a laser light source configured to emit a swept laser light; the light engine comprises a light emitting / receiving device, the light engine is configured to receive the sweep frequency laser and emit at least one part of the sweep frequency laser as a detection light beam from the light emitting / receiving device, the detection light beam is incident to an obstacle and then generates a reflection light beam, and the light emitting / receiving device is further configured to receive the reflection light beam; the scanning assembly is arranged on one side of the light transmitter / receiver and is configured to deflect the detection light beam to realize detection light beam scanning; and the birefringence component is configured to compensate a transmitting and receiving deviation angle caused by the movement of the scanning component, so that the detection light beam and the reflection light beam are transmitted and received by the same port of the light transmitter / receiver.

Description

Technical Field

[0001] The present disclosure relates to the field of laser radar technology, and in particular to a FMCW laser radar system. Background Art

[0002] LiDAR is a radar system that emits laser beams to detect the position, speed and other characteristic quantities of a target. Its working principle is to transmit a detection signal to the target, and then compare the received signal reflected from the target with the transmitted signal. After appropriate processing, relevant information about the target can be obtained, such as target distance, direction, height, speed, attitude, and even shape parameters, so as to detect, track and identify targets such as aircraft and missiles. LiDAR is now widely deployed in different scenarios including automatic vehicles. LiDAR can actively estimate the distance and speed to environmental features when scanning the scene, and generate a point position cloud indicating the three-dimensional shape of the environmental scene. Summary of the invention

[0003] Some embodiments of the present disclosure provide a FMCW laser radar system, the FMCW laser radar system comprising:

[0004] a laser light source configured to emit a swept-frequency laser;

[0005] A light engine, comprising a light emitter / receiver, wherein the light engine is configured to receive the frequency-sweeping laser and emit at least a portion of the frequency-sweeping laser from the light emitter / receiver as a detection beam, wherein the detection beam generates a reflected beam after being incident on an obstacle, and the light emitter / receiver is further configured to receive the reflected beam;

[0006] a scanning component, disposed on one side of the light transmitter / receiver, configured to deflect the detection beam to achieve detection beam scanning; and

[0007] The birefringence component is configured to compensate for the transceiver offset angle caused by the movement of the scanning component, so that the detection light beam and the reflected light beam are transmitted and received by the same port of the optical transmitter / receiver.

[0008] In some embodiments, the FMCW laser radar system further includes:

[0009] a lens assembly disposed between the light emitter / receiver and the scanning assembly, configured to collimate the detection beam and couple the reflected beam into the light emitter / receiver,

[0010] The detection beam is a first polarization mode beam with a first polarization direction, and the reflected beam is a second polarization mode beam with a second polarization direction. The first polarization direction and the second polarization direction are perpendicular to each other, and the first polarization mode beam and the second polarization mode beam have different refractive indices in the birefringence component.

[0011] In some embodiments, the birefringent component has a compensation deviation angle α for the reflected light beam, and the compensation deviation angle α is determined by the following formula:

[0012] 0<α≤θ m

[0013] Among them, θ m is the maximum value of the transmit and receive offset angle, θ m Determined by the following formula:

[0014]

[0015] Where, ω is the scanning angular velocity of the scanning component, L m is the maximum detection distance of the FMCW laser radar system, and c is the speed of light.

[0016] In some embodiments, the birefringent component includes an optical wedge, the optical wedge is disposed between the lens component and the scanning component, the inclined surface of the optical wedge is away from the lens component relative to its plane, the optical axis of the optical wedge is perpendicular to the optical axis of the lens component, and the compensation offset angle α satisfies the following formula:

[0017] α=arctan(n2sinβ)-arctan(n1sinβ)

[0018] Wherein, n1 is the refractive index of the first polarization mode light beam in the optical wedge, n2 is the refractive index of the second polarization mode light beam in the optical wedge, and β is the wedge angle of the optical wedge.

[0019] In some embodiments, the birefringent component includes a polarization beam splitter prism group, the polarization beam splitter prism group is arranged between the lens assembly and the scanning assembly, the polarization beam splitter prism group includes a first right-angle prism and a second right-angle prism with bevels attached, the optical axis of the first right-angle prism is parallel to the optical axis of the lens assembly, and the second right-angle prism is arranged on the side of the first right-angle prism away from the lens assembly, the optical axis of the second right-angle prism is perpendicular to the optical axis of the lens assembly, and the compensation offset angle α satisfies the following formula:

[0020] α=arctan(0.7n4)-arctan(0.7n3)

[0021] Among them, n3 is the refractive index of the first polarization mode light beam in the polarization beam splitter prism group, and n4 is the refractive index of the second polarization mode light beam in the polarization beam splitter prism group.

[0022] In some embodiments, the birefringent assembly includes a birefringent flat lens, the birefringent flat lens is disposed between the lens assembly and the light transmitter / receiver, the birefringent flat lens is disposed parallel to the lens assembly, the optical axis of the birefringent flat lens intersects the optical axis of the lens assembly, and the compensation offset angle α satisfies the following formula:

[0023]

[0024]

[0025] Among them, n5 is the refractive index of the first polarization mode light beam in the birefringent flat lens, n6 is the refractive index of the second polarization mode light beam in the birefringent flat lens, γ is the angle between the optical axis of the birefringent flat lens and its plane, d is the thickness of the birefringent flat lens, and f is the focal length of the lens assembly.

[0026] In some embodiments, the optical engine includes a laser radar chip, and the laser radar chip includes:

[0027] A frequency-sweeping laser receiving end, configured to receive the frequency-sweeping laser;

[0028] A beam splitter connected to the laser receiving end and configured to split the frequency-sweeping laser into a detection beam and a local oscillator beam;

[0029] a mixer configured to receive the local oscillator light beam and the reflected light beam, and mix the local oscillator light beam and the reflected light beam to obtain a mixed laser; and

[0030] a balanced detector, receiving the frequency-mixed laser and outputting a detection electrical signal based on the frequency-mixed laser;

[0031] The FMCW laser radar system also includes:

[0032] The acquisition and processing device is electrically connected to the balanced detector, receives the detection electrical signal from the balanced detector, and processes the detection electrical signal to determine the distance and / or speed of the obstacle relative to the FMCW laser radar system.

[0033] In some embodiments, the laser radar chip further includes:

[0034] a polarization rotating beam splitter, as the optical transmitter / receiver, configured to receive the detection beam and output it, and to receive the reflected beam and change the polarization direction of the reflected beam,

[0035] The mixer receives the local oscillator beam from the beam splitter and the reflected beam from the polarization rotating beam splitter.

[0036] In some embodiments, the laser radar chip further includes:

[0037] a detection beam output end, configured to receive and output the detection beam from the beam splitter; and

[0038] a reflected light beam receiving end, configured to receive the reflected light beam,

[0039] The optical transmitter / receiver includes a circulator, which includes a first port, a second port and a third port. The first port is connected to the detection beam output end, receives the detection beam emitted from the detection beam output end and transmits it to the second port, the detection beam is emitted from the second port, the second port also receives the reflected beam and transmits it to the third port, the third port is connected to the reflected beam receiving end, and transmits the reflected beam to the reflected beam receiving end.

[0040] Some embodiments of the present disclosure provide a mobile device, comprising the FMCW laser radar system as described in the aforementioned embodiments.

[0041] Compared with the related art, the above solution of the embodiment of the present disclosure has at least the following beneficial effects:

[0042] The FMCW (Frequency-Modulated Continuous Wave) laser radar system disclosed in the present invention can supplement the receiving and transmitting offset angle caused by the rotation of the scanning component by adding a birefringence component, so that the detection beam and the reflected beam in each channel of the FMCW laser radar system can be received and transmitted by the same port, thereby minimizing the size of the FMCW laser radar system while ensuring the detection performance of the FMCW laser radar system. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0044] Figure 1 A schematic diagram of the structure of an FMCW laser radar system provided in some embodiments of the present disclosure;

[0045] Figure 2for Figure 1 Schematic diagram of the deviation angle of transmission and reception caused by the scanning component in the process of movement;

[0046] Figure 3 It is a curve relationship diagram between the reflected beam intensity and obstacle distance of the FMCW laser radar system;

[0047] Figure 4 It is a curve relationship diagram between the reflected beam coupling efficiency of the FMCW laser radar system and the obstacle distance of the transmitting and receiving offset angle;

[0048] Figure 5 for Figure 1 Schematic diagram of the optical path of the middle lens assembly and the birefringent assembly;

[0049] Figure 6 A schematic diagram of the structure of a FMCW laser radar system provided in some embodiments of the present disclosure;

[0050] Figure 7 for Figure 6 Schematic diagram of the optical path of the middle lens assembly and the polarization beam splitter prism group;

[0051] Figure 8 A schematic diagram of the structure of a FMCW laser radar system provided in some embodiments of the present disclosure;

[0052] Fig. 9 for Figure 8 Schematic diagram of the optical path of the middle lens assembly and the birefringent flat lens;

[0053] Fig.10 A schematic diagram of the structure of a light engine provided for some embodiments of the present disclosure; and

[0054] Fig.11 A schematic diagram of the structure of a light engine provided in some embodiments of the present disclosure. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0056] The terms used in the embodiments of the present disclosure are only for the purpose of describing specific embodiments, and are not intended to limit the present disclosure. The singular forms "a", "said" and "the" used in the embodiments of the present disclosure and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0057] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0058] It should be understood that although the terms first, second, third, etc. may be used to describe in the present disclosure, these should not be limited to these terms. These terms are only used to distinguish. For example, without departing from the scope of the present disclosure, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0059] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or device. In the absence of more restrictions, the elements defined by the sentence "comprises a" do not exclude the presence of other identical elements in the product or device including the elements.

[0060] In the related technologies, the existing laser radars are based on the ranging method and mainly include the following two technical routes: ToF (Time of Flight) and FMCW (Frequency-Modulated Continuous Wave).

[0061] The principle of ToF distance measurement is to measure the distance by multiplying the flight time of the light pulse between the target and the laser radar by the speed of light. ToF laser radar uses pulse amplitude modulation technology. Unlike the ToF route, FMCW mainly sends and receives continuous laser beams, interferes with the return light and local light, and uses mixing detection technology to measure the frequency difference between sending and receiving, and then converts the frequency difference into the distance of the target. In short, ToF uses time to measure distance, while FMCW uses frequency to measure distance.

[0062] FMCW has the following advantages over ToF: ToF's light waves are easily interfered by ambient light, while FMCW's light waves have strong anti-interference capabilities; ToF's signal-to-noise ratio is too low, while FMCW's signal-to-noise ratio is very high; ToF's speed dimension data quality is low, while FMCW can obtain speed dimension data for each pixel.

[0063] The FMCW laser radar has great technical advantages, but there are the following problems in its practical application:

[0064] For traditional FMCW laser radar systems, in order to reduce the size of the FMCW laser radar system, each detection channel is usually used to correspond to an optical transmitter / receiver. The detection beam and the reflected beam of each detection channel are transmitted and received by the same port of the corresponding optical transmitter / receiver, and the detection beam is collimated by a lens and the reflected beam is coupled to the same port, which is also referred to as the transceiver port. The detection channel where the transceiver port is located has an instantaneous field of view (iFOV), and its value is given by the formula The calculation shows that MFD is the mode field diameter of the transceiver port, and F is the effective focal length of the lens. The size of the instantaneous field angle determines the angle range of the beam that can be transmitted / received by the same port at a certain moment.

[0065] Traditional FMCW laser radar systems also usually use scanning components, such as rotating mirrors, to scan the detection beam. In order to achieve the frame rate requirements of the laser radar point cloud, it is necessary to ensure that the rotating mirror reaches a certain rotation angular velocity. Considering that during the ranging process, the beam will fly in the air for a period of time, including the time for the detection beam to be transmitted to the obstacle and the time for the reflected beam to return from the obstacle. During this period of time, the rotation of the scanning component did not stop, which is equivalent to a certain deviation between the transmission and reception pointing angles of the above-mentioned transceiver port, that is, the deviation between the pointing angle of the detection beam and the pointing angle of the receiving beam is called the transceiver offset angle. The transceiver offset angle can be described by the formula θ=ω*Δt. When θ=0, the optical axes of the detection beam and the reflected beam completely coincide. At this time, the detection capability of the FMCW laser radar system is the strongest. When 0<θ≤iFOV, the detection capability of the FMCW laser radar system will decrease accordingly. When Δθ>iFOV, the transceiver port will be unable to measure the reflected beam.

[0066] The present disclosure provides an FMCW laser radar system, which includes: a laser light source, configured to emit a swept-frequency laser; an optical engine, including an optical transmitter / receiver, the optical engine is configured to receive the swept-frequency laser, and emit at least a portion of the swept-frequency laser from the optical transmitter / receiver as a detection beam, the detection beam generates a reflected beam after being incident on an obstacle, and the optical transmitter / receiver is also configured to receive the reflected beam; a scanning component, arranged on one side of the optical transmitter / receiver, configured to deflect the detection beam to achieve detection beam scanning; and a birefringence component, configured to compensate for the transmission and reception offset angle caused by the rotation of the scanning component, so that the reflected beam can be received by the same optical transmitter / receiver that transmits the corresponding detection beam to the greatest extent, and the detection beam and the reflected beam are transmitted and received by the same port of the optical transmitter / receiver.

[0067] The FMCW laser radar system disclosed in the present invention can compensate for the receiving and transmitting offset angle caused by the rotation of the scanning component by adding a birefringence component, so that in each channel of the FMCW laser radar system, the reflected light beam can be received by the same light transmitter / receiver that transmits the corresponding detection light beam to the greatest extent, and the detection light beam and the reflected light beam can be sent and received by the same port, thereby minimizing the size of the FMCW laser radar system while ensuring the detection performance of the FMCW laser radar system.

[0068] The optional embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0069] Figure 1 FIG. 1 is a schematic diagram of the structure of the FMCW laser radar system provided in some embodiments of the present disclosure. Figure 1 As shown, the present disclosure provides a FMCW laser radar system 100 , which includes a laser light source 10 , a light engine 20 , a lens assembly 30 , a scanning assembly 40 , and a birefringence assembly 50 .

[0070] The laser light source 10 is configured to emit a frequency-sweeping laser, the frequency of which varies with time, such as a periodic triangular wave, and the laser light source 10 can be directly modulated by an electrical signal. That is, the electrical signal driving the laser light source 10 can vary with time, so that the laser light source 10 generates and outputs a frequency-sweeping laser, i.e., a light beam whose frequency varies within a predetermined range. In some embodiments, the laser light source 10 can also use a modulator to frequency-modulate the output constant-frequency laser to output a frequency-sweeping laser. Specifically, the frequency of the laser light beam output by the laser light source 10 is substantially constant, referred to as the frequency of the unmodulated light beam, such as 100 to 300 THz. The modulator receives a laser light beam with a substantially constant frequency and receives a modulation signal. Under the action of the modulation signal, the modulator modulates the laser light beam with a substantially constant frequency into a frequency-sweeping light beam with a frequency that varies with time and outputs it.

[0071] The light engine 20 includes a light transmitter / receiver 21, which is configured to receive the swept laser emitted by the laser light source 10, and emit at least a portion of the swept laser as a detection beam from the light transmitter / receiver 21. The detection beam generates a reflected beam after being incident on the obstacle T, and the light transmitter / receiver 21 is also configured to receive the reflected beam. The FMCW laser radar system 100 measures the distance and / or speed of the test point on the obstacle based on the reflected beam, which can be understood as the distance between the test point on the obstacle and the FMCW laser radar system 100.

[0072] The lens assembly 30 is disposed on one side of the optical transmitter / receiver 21, and is configured to collimate the detection beam and couple the reflected beam into the optical transmitter / receiver 21. The lens assembly 30 may be a lens or a lens group, and has the functions of focusing and collimating. Specifically, the lens assembly 30 collimates the detection beam emitted by the optical transmitter / receiver 21 to ensure its propagation distance. After the detection beam reaches the obstacle, a reflected beam is generated, and the reflected beam is focused and coupled into the optical transmitter / receiver 21 after passing through the lens assembly 30, so as to facilitate the subsequent detection of the FMCW laser radar system.

[0073] The scanning component 40 is arranged on the side of the lens component 30 away from the optical transmitter / receiver 21, and is configured to deflect the detection beam passing through the lens component to achieve detection beam scanning. The scanning component 40 is, for example, a rotating mirror, a rotating prism, a rotating optical wedge, a galvanometer, MEMS, etc., which can achieve detection beam scanning of the detection beam passing through the lens component through its own regular movement, thereby, a line laser radar can be used for surface detection. Then, the test information of each test point on the obstacle surface is obtained to form a laser point cloud, thereby determining the three-dimensional structure of the obstacle T. Taking the rotating mirror as an example, the rotating mirror needs to rotate within a preset angle range at a predetermined rotational angular velocity to achieve deflection of the detection beam passing through the lens component 30 to achieve detection beam scanning.

[0074] Figure 2 for Figure 1 Schematic diagram of the receiving and transmitting deviation angle caused by the scanning component in the movement process, such as Figure 2 As shown, when the scanning component 40 is in the state shown by the dotted line, the detection light beam is incident on the scanning component 40 and is reflected by it to be incident on the obstacle T. After the detection light beam reaches the obstacle, a reflected light beam is generated. When the reflected light beam returns to the scanning component 40, the scanning component 40 is in the state shown by the solid line due to its movement, and has a predetermined angle of deflection relative to the state shown by the dotted line. After being reflected by the scanning component 40, there is a deviation between the path of the reflected light beam and the detection light beam, that is, the transmitting and receiving offset angle θ.

[0075] The birefringent component 50 and the lens component 30 are arranged at a predetermined interval, and are configured to compensate for the transceiver deviation angle θ caused by the movement of the scanning component 40, so that the reflected light beam can be received by the same optical transmitter / receiver that transmits the corresponding detection light beam to the greatest extent, and the detection light beam and the reflected light beam are transmitted and received by the same port of the optical transmitter / receiver. The compensated transceiver deviation angle is made smaller than the instantaneous field of view (iFOV) of the same port of the optical transmitter / receiver, and as close to 0 as possible. The optical axes of the detection light beam and the reflected light beam transmitted and received by the same port of the optical transmitter / receiver are made to coincide as much as possible, so as to ensure the detection capability of the FMCW laser radar system.

[0076] The FMCW laser radar system in the present disclosure can compensate for the receiving and transmitting offset angle caused by the rotation of the scanning component by adding a birefringence component, so that the detection beam and the reflected beam in each channel of the FMCW laser radar system can be transmitted and received by the same port, that is, the transmitting and receiving port, thereby minimizing the size of the FMCW laser radar system while ensuring the detection performance of the FMCW laser radar system.

[0077] In some embodiments, the detection beam is a first polarization mode beam with a first polarization direction, and the reflected beam is a second polarization mode beam with a second polarization direction, the first polarization direction is perpendicular to the second polarization direction, and the first polarization mode beam and the second polarization mode beam have different refractive indices in the birefringence component 50, so that the first polarization mode beam as the detection beam and the second polarization mode beam as the reflected beam have different transmission paths in the birefringence component 50. By using the above properties, the transceiver offset angle caused by the rotation of the scanning component can be supplemented, so that in each channel of the FMCW laser radar system, the reflected beam can be received by the same optical transmitter / receiver that transmits the corresponding detection beam to the greatest extent, and the detection beam and the reflected beam can be transmitted and received by the same port. In some embodiments, the first polarization mode beam is, for example, a TE mode polarization beam, and the second polarization mode beam is, for example, a TM mode polarization beam. The detection beam is a TE mode polarization beam, which is output from the optical transmitter / receiver 21 of the light engine 20, and then incident on the obstacle T after passing through the lens component 30, the birefringence component 50, and the scanning component 40. The light beam after the TE mode polarized light beam is reflected by the obstacle T includes both the TE mode polarized light beam and the TM mode polarized light beam. In some embodiments, only the TM mode polarized light beam is used as the reflected light beam for detection.

[0078] Figure 3 The curve relationship between the reflected beam intensity and obstacle distance of the FMCW laser radar system is shown in Figure 2. In the FMCW laser radar detection scenario, the reflected beam intensity is positively correlated with the intensity of the swept laser emitted by the laser light source. The greater the reflected beam intensity, the stronger the detection capability of the FMCW laser radar system. Figure 3 As shown, when other conditions (including the intensity of the swept laser, the optical components of the FMCW lidar system and their relative positions) remain unchanged, the change in the intensity of the reflected light beam, i.e., the intensity of the diffusely reflected light, decreases with increasing obstacle distance, and there is a quadratic attenuation relationship between the two. In this application, the obstacle distance refers to the distance between the obstacle and the lidar system.

[0079] Figure 4The figure is a curve relationship diagram between the reflected beam coupling efficiency of the FMCW laser radar system and the transceiver offset angle and the obstacle distance. The vertical axis represents the reflected beam coupling efficiency, and the horizontal axis represents the transceiver offset angle or the obstacle distance. The transceiver offset angle is proportional to the obstacle distance. When the optical transmitter / receiver uses an optical fiber / waveguide device with a lens assembly, it is necessary to consider the coupling efficiency of the reflected beam coupled into the optical transmitter / receiver under the action of the lens assembly. According to the fiber coupling theory, the coupling efficiency depends on the matching degree between the lens convergent light spot mode field and the fiber mode field. When there is a transceiver offset angle, that is, the transceiver light axis has an angle, the spot position of the reflected light beam converged by the lens assembly is displaced accordingly with the center position of the optical fiber, so that the relationship between the reflected light beam coupling efficiency and the transceiver offset angle is Gaussian distribution, and the transceiver offset angle is proportional to the light beam flight time, that is, proportional to the obstacle distance.

[0080] When the FMCW lidar system is working, the energy of the reflected light beam received by the optical transmitter / receiver is Figure 3 and Figure 4 The product of the two curves in .

[0081] In some embodiments, the birefringent component has a compensation deviation angle α for the reflected light beam, and the compensation deviation angle α is determined by the following formula:

[0082] 0<α≤θ m …………Formula (1)

[0083] Among them, θ m is the maximum value of the transmit and receive offset angle, θ m Determined by the following formula:

[0084]

[0085] Where ω is the scanning angular velocity of the scanning component, and Δt is the flight time of the light beam between the FMCW lidar system and the obstacle. m is the maximum detection distance of the FMCW laser radar system, which is preset when the FMCW laser radar system is designed, and c is the speed of light.

[0086] In this embodiment, the FMCW laser radar system can compensate for the transceiver deviation angle caused by the rotation of the scanning component by adding a birefringent component 50, so that in each channel of the FMCW laser radar system, the reflected light beam can be received by the same light transmitter / receiver that transmits the corresponding detection light beam to the greatest extent, and the detection light beam and the reflected light beam can be transmitted and received by the same port. For example, the compensation deviation angle α is equal to the maximum value θ of the transceiver deviation angle. m When the maximum detection distance L mWhen detecting obstacles at a certain distance, the reflected light beam can be received by the same optical transmitter / receiver that transmits the corresponding detection light beam to the greatest extent. The detection light beam and the reflected light beam are sent and received by the same port of the optical transmitter / receiver, thereby ensuring the coupling efficiency of the reflected light beam and the detection performance of the FMCW lidar system.

[0087] Figure 5 for Figure 1 Schematic diagram of the optical path of the lens assembly and the birefringent assembly. Figure 1 and Figure 5 As shown, the birefringent assembly 50 includes an optical wedge 51, which is arranged on the side of the lens assembly away from the optical transmitter / receiver 21. The inclined surface of the optical wedge 51 is away from the lens assembly 30 relative to its plane, and the optical axis 511 of the optical wedge 51 is perpendicular to the optical axis of the lens assembly 30. The detection light beam emitted from the transceiver port 211 of the optical transmitter / receiver 21 toward the lens assembly 30 is, for example, a first polarization mode light beam, specifically a TE mode polarization light beam, and has a certain divergence angle, for example, represented by three rays (represented by lines with solid arrows). The lens assembly 30 performs a collimation operation on the detection light beam, so that the detection light beam after passing through the lens assembly 30 is emitted as a parallel light beam. After the detection light beam passes through the optical wedge 51, it is deflected by the rotating assembly 40 and encounters an obstacle to generate a reflected light beam, for example, a second polarization mode light beam, specifically a TM mode polarization light beam, and the reflected light beam is also represented by three rays (represented by lines with line arrows). Due to the movement of the scanning assembly, such as the rotation of the rotating mirror, the reflected light beam does not return along the emission path of the detection light beam, but has a certain transmission and reception deviation angle. The characteristics of the optical wedge 51 can be used to compensate for the transmission and reception deviation angle. Figure 5 , an example of the optical wedge 51 completely compensating the transceiver offset angle is shown. At this time, the compensation offset angle α is equal to the transceiver offset angle. After the reflected light beam is compensated by the optical wedge 51, its return light path is the same as the light output path of the detection light beam. The reflected light beam is coupled into the transceiver port 211 of the optical transmitter / receiver 21 through the lens assembly 30, realizing the coaxial transceiver of the detection light beam and the reflected light beam, so as to ensure the coupling efficiency of the reflected light beam and improve the detection performance of the FMCW laser radar system.

[0088] The compensation offset angle α satisfies the following formula:

[0089] α=arctan(n2sinβ)-arctan(n1sinβ)…………Equation (3)

[0090] Wherein, n1 is the first polarization mode light beam, for example, the refractive index of the TE mode polarized light beam in the optical wedge, n2 is the second polarization mode light beam, for example, the refractive index of the TM mode polarized light beam in the optical wedge, and β is the wedge angle of the optical wedge.

[0091] As described above, the compensation offset angle α can be calculated by the maximum value θ of the transmit / receive offset angle to be compensated. m Determine the maximum value of the transmit and receive offset angle θ m The scanning angular velocity ω of the scanning component in the FMCW laser radar system and the maximum detection distance L of the FMCW laser radar system are m After the compensation offset angle α is determined, the specification of the optical wedge 51 can be selected according to equation (3).

[0092] Figure 6 A schematic diagram of the structure of an FMCW lidar system provided in some embodiments of the present disclosure. Figure 6 In the embodiment shown, the FMCW laser radar system and Figure 1 The FMCW laser radar system structures in the illustrated embodiments are substantially the same, and the similarities between the two are not repeated here, and the following mainly describes the differences between the two.

[0093] exist Figure 6 In the FMCW laser radar system 100 shown, the birefringence component 50 does not include an optical wedge 51 , but includes a polarization beam splitting prism group 52 . Figure 7 for Figure 6 Schematic diagram of the optical path of the lens assembly and the polarization beam splitter prism assembly. Figure 6 and Figure 7 As shown, the birefringent assembly 50 includes a polarization beam splitting prism group 52, and the polarization beam splitting prism group 52 is arranged on the side of the lens assembly away from the light transmitter / receiver 21. The polarization beam splitting prism group 52 includes a first right angle prism 521 and a second right angle prism 522 with inclined surfaces attached. A right angle plane of the first right angle prism 521 faces the lens assembly 30, an optical axis 5211 of the first right angle prism 521 is parallel to the optical axis 31 of the lens assembly 30, and the second right angle prism 522 is arranged on the side of the first right angle prism 521 away from the lens assembly, and an optical axis 5221 of the second right angle prism 522 is perpendicular to the optical axis 31 of the lens assembly 30.

[0094] The detection light beam emitted from the transceiver port 211 of the optical transmitter / receiver 21 toward the lens assembly 30 is, for example, a first polarization mode light beam, specifically a TE mode polarization light beam, having a certain divergence angle, for example, represented by three light rays (represented by a line with a solid arrow). The lens assembly 30 performs a collimation operation on the detection light beam, so that the detection light beam after passing through the lens assembly 30 is emitted as a parallel light beam. After the detection light beam passes through the polarization beam splitting prism group 52, it is deflected by the rotating assembly 40 and then encounters an obstacle to generate a reflected light beam, for example, a second polarization mode light beam, specifically a TM mode polarization light beam, and the reflected light beam is also represented by three light rays (represented by a line with a line arrow). Due to the movement of the scanning assembly, such as the rotation of the rotating mirror, the reflected light beam does not return along the emission path of the detection light beam, but has a certain transceiver deviation angle. The transceiver deviation angle can be compensated by utilizing the characteristics of the polarization beam splitting prism group 52. Figure 7 , an example of the polarization beam splitter prism group 52 completely compensating the transmit-receive offset angle is shown. At this time, the compensation offset angle α is equal to the transmit-receive offset angle. After the reflected light beam is compensated by the polarization beam splitter prism group 52, its return light path is the same as the light output path of the detection light beam. The reflected light beam is coupled into the transmit-receive port 211 of the optical transmitter / receiver 21 through the lens assembly 30, realizing the coaxial transmission and reception of the detection light beam and the reflected light beam, so as to ensure the coupling efficiency of the reflected light beam and improve the detection performance of the FMCW laser radar system.

[0095] The compensation offset angle α satisfies the following formula:

[0096] α=arctan(0.7n4)-arctan(0.7n3)…………Equation (4)

[0097] Among them, n3 is the refractive index of the first polarization mode light beam, for example, the TE mode polarized light beam in the polarization beam splitting prism group, and n4 is the refractive index of the second polarization mode light beam, for example, the TM mode polarized light beam in the polarization beam splitting prism group.

[0098] As described above, the compensation offset angle α can be calculated by the maximum value θ of the transmit / receive offset angle to be compensated. m Determine the maximum value of the transmit and receive offset angle θ m The scanning angular velocity ω of the scanning component in the FMCW laser radar system and the maximum detection distance L of the FMCW laser radar system are m After the compensation offset angle α is determined, the specification of the polarization beam splitting prism assembly 52 can be selected according to formula (4).

[0099] Figure 8 A schematic diagram of the structure of an FMCW lidar system provided in some embodiments of the present disclosure. Figure 8 In the embodiment shown, the FMCW laser radar system and Figure 1The FMCW laser radar system structures in the illustrated embodiments are substantially the same, and the similarities between the two are not repeated here, and the following mainly describes the differences between the two.

[0100] exist Figure 8 In the FMCW laser radar system 100 shown, the birefringent component 50 is disposed between the lens component 30 and the optical transmitter / receiver 21 , and does not include an optical wedge 51 , but includes a birefringent flat lens 53 . Fig. 9 for Figure 8 Schematic diagram of the optical path of the lens assembly and the birefringent flat lens. Figure 8 and Fig. 9 As shown, the birefringent plate lens 53 is disposed between the lens assembly 30 and the light transmitter / receiver 21 , the birefringent plate lens 53 is disposed parallel to the lens assembly 30 , and the optical axis of the birefringent plate lens 30 intersects with the optical axis of the lens assembly 30 .

[0101] The detection light beam emitted from the transceiver port 211 of the optical transmitter / receiver 21 toward the polarization beam splitter prism group 52 is, for example, a first polarization mode light beam, specifically a TE mode polarization light beam, having a certain divergence angle, for example, represented by three light rays (represented by a line with a solid arrow). The detection light beam passing through the birefringent flat lens 53 is collimated by the lens assembly 30, so that the detection light beam after passing through the lens assembly 30 is emitted as a parallel light beam. After the detection light beam is deflected by the rotating assembly 40 and encounters an obstacle, a reflected light beam is generated, for example, a second polarization mode light beam, specifically a TM mode polarization light beam, and the reflected light beam is also represented by three light rays (represented by a line with a line arrow). Due to the movement of the scanning assembly, such as the rotation of the rotating mirror, the reflected light beam does not return along the emission path of the detection light beam, but has a certain transceiver deviation angle. The transceiver deviation angle can be compensated by utilizing the characteristics of the birefringent flat lens 53. Fig. 9 , an example of the birefringent flat lens 53 completely compensating the transceiver offset angle is shown. At this time, the compensation offset angle α is equal to the transceiver offset angle. After the reflected light beam is compensated by the birefringent flat lens 53, its return light path is the same as the light output path of the detection light beam. The reflected light beam can be coupled into the transceiver port 211 of the optical transmitter / receiver 21 to achieve coaxial transceiver of the detection light beam and the reflected light beam, so as to ensure the coupling efficiency of the reflected light beam and improve the detection performance of the FMCW laser radar system.

[0102] The compensation offset angle α satisfies the following formula:

[0103]

[0104]

[0105] Among them, n5 is the first polarization mode light beam, for example, the refractive index of the TE mode polarized light beam in the birefringent flat lens, n6 is the second polarization mode light beam, for example, the refractive index of the TM mode polarized light beam in the birefringent flat lens, γ is the angle between the optical axis of the birefringent flat lens and its plane, d is the thickness of the birefringent flat lens, and f is the focal length of the lens assembly.

[0106] As described above, the compensation offset angle α can be the maximum value θ of the transmit / receive offset angle to be compensated. m Determine the maximum value of the transmit and receive offset angle θ m The scanning angular velocity ω of the scanning component in the FMCW laser radar system and the maximum detection distance L of the FMCW laser radar system are m After the compensation deviation angle α is determined, the specification of the birefringent flat lens 53 can be selected according to equations (5) and (6).

[0107] Fig.10 This is a schematic diagram of the structure of the light engine provided by some embodiments of the present disclosure. Fig.10 As shown, the optical engine 20 includes a laser radar chip 22, and the laser radar chip 22 includes a swept-frequency laser receiving end 221, a beam splitter 222, a mixer 223, and a balanced detector 224. The use of the laser radar chip can miniaturize the overall structure of the FMCW laser radar system.

[0108] The swept-frequency laser receiving end 221 is configured to receive the swept-frequency laser emitted by the laser light source 10 , and introduces the swept-frequency laser, for example, a TE mode polarized light beam, into the laser radar chip 22 .

[0109] The beam splitter 222 is connected to the laser receiving end 221, and is configured to split the swept-frequency laser into a detection beam and a local oscillator beam. The beam splitter 222 is, for example, a 1×2 beam splitter, which splits the swept-frequency detection laser into two completely identical laser beams, that is, the wavelength, phase, and frequency modulation of the detection beam and the local oscillator beam are completely identical.

[0110] The mixer 223 is connected to the spectrometer 222 and configured to receive the local oscillator laser from the spectrometer 222. The mixer 223 is also configured to receive the local oscillator beam and the reflected beam, and mix the local oscillator beam and the reflected beam to obtain a mixed laser, that is, to detect the beat frequency beam.

[0111] The balanced detector 224 is connected to the mixer 223, receives the mixed laser from the mixer 223 and outputs a detection electrical signal based on the mixed laser. The FMCW laser radar system 100 determines the distance of the obstacle based on the detection optical signal.

[0112] In some embodiments, Fig.10As shown, the laser radar chip 22 also includes a polarization rotation beam splitter 225. The polarization rotation beam splitter 225 serves as the light transmitter / receiver, and is configured to receive the detection beam and output it, as well as receive the reflected beam and change the polarization direction of the reflected beam. Integrating the polarization rotation beam splitter 225 as a light transmitter / receiver on the laser radar chip 22 can further reduce the size of the light engine 20, thereby reducing the size of the FMCW laser radar system.

[0113] Specifically, the polarization rotation beam splitter 225 is connected to the beam splitter 222, receives the detection beam output by the beam splitter 222, for example, a TE mode polarized beam, and outputs it from the transceiver port of the polarization rotation beam splitter 225. At this time, the TE mode polarized beam outputs the laser radar chip 22, propagates in space, for example, passes through the lens module 30, the birefringence component 50 and the scanning component 40 to reach the obstacle T. The TE mode detection beam is reflected on the surface of the obstacle T to generate a reflected beam, for example, a TM mode polarized beam, which is coupled into the transceiver port of the polarization rotation beam splitter 225, forms a TM mode polarized beam after passing through the polarization rotation beam splitter 225, and is input to the mixer 223. The mixer 223 receives the local oscillator beam from the beam splitter 222, for example, a TE mode polarized beam and the reflected beam from the polarization rotation beam splitter.

[0114] Fig.11 A schematic diagram of the structure of a light engine provided in some embodiments of the present disclosure. In some embodiments, as Fig.11 As shown, Fig.10 Compared with the embodiment described in the embodiment, the laser radar chip 22 includes the aforementioned swept-frequency laser receiving end 221, the beam splitter 222, the mixer 223 and the balanced detector 224, but does not include the polarization rotation beam splitter 225.

[0115] The laser radar chip 22 also includes a detection beam output end 226 and a reflected beam receiving end 227. The detection beam output end 226 is connected to the beam splitter 222 and is configured to receive and output the detection beam from the beam splitter 222. The reflected beam receiving end 227 is configured to receive the reflected beam and is connected to the mixer 223 and is configured to transmit the received reflected beam to the mixer 223.

[0116] The optical transmitter / receiver 21, for example, includes a circulator 23, which includes a first port 231, a second port 232 and a third port 233. The first port 231 is connected to the detection beam output end 226 of the laser radar chip 22, receives the detection beam emitted from the detection beam output end 226 and transmits it to the second port 232. The second port 232 of the circulator 23 is the transceiver port 211 of the optical transmitter / receiver 21, which coaxially transmits and receives the detection beam and the reflected beam. Specifically, after the detection beam is emitted from the second port, it propagates in space, for example, after passing through the lens module 30, the birefringence component 50 and the scanning component 40, it reaches the obstacle T, generating a reflected beam. The reflected beam is coupled into the second port 232 of the circulator 23 after passing through the scanning component 40, the birefringence component 50 and the lens module 30, and is coupled into the second port 232 of the circulator 23 by the second port 231. The reflected beam can only be transmitted to the second port 231 of the circulator 23. The second port also receives the reflected beam and transmits it to the third port 233. The third port 233 is connected to the reflected beam receiving end 227 of the laser radar chip 22, and transmits the reflected beam to the reflected beam receiving end 227.

[0117] In some embodiments, the FMCW laser radar system further includes: an acquisition and processing device, which is not shown in the figure. The acquisition and processing device is electrically connected to the balanced detector 224, receives the detection electrical signal from the balanced detector 224, and processes the detection point electrical signal to determine the distance and / or speed of the obstacle. In some embodiments, the acquisition and processing device includes an analog-to-digital conversion module and a signal processing module. The analog-to-digital conversion module is, for example, an analog-to-digital converter, which receives the detection electrical signal from the balanced detector 224, and the detection electrical signal is an analog signal. The analog-to-digital conversion module converts the detection electrical signal, which is an analog signal, into a digital signal. The signal processing module is connected to the analog-to-digital conversion module, receives the digital signal from the analog-to-digital conversion module, and processes the digital signal to determine the distance and / or speed of the detected target. In some embodiments, the signal processing module is, for example, a field programmable gate array (FPGA), a digital signal processor (DSP), etc.

[0118] In the above-mentioned embodiment, a laser transmission channel is used as an example to illustrate that by adding a birefringent component, the receiving and transmitting offset angle caused by the rotation of the scanning component can be supplemented, so that the detection beam and the reflected beam in the laser transmission channel in the FMCW laser radar system can be transmitted and received by the same port, while minimizing the size of the FMCW laser radar system and ensuring the detection performance of the FMCW laser radar system. It can be understood by those skilled in the art that the FMCW laser radar system can include 2 or more laser transmission channels, and the detection beam and the reflected beam transmitted in each laser transmission channel can be transmitted and received by the same port. Multiple laser transmission channels can share lens components, scanning components and birefringent components.

[0119] Some embodiments of the present disclosure provide a mobile device, the mobile device comprising the FMCW laser radar system as described in the above embodiments. The mobile device may be a vehicle, such as an unmanned cleaning vehicle, an unmanned logistics vehicle, an unmanned car, etc.

[0120] The various parts in this manual are described in a combination of parallel and progressive ways. Each part focuses on the differences from other parts, and the same or similar parts between the various parts can be referenced to each other.

[0121] With respect to the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other, so that professionals in the field can implement or use the present application. Various modifications to these embodiments will be apparent to professionals in the field, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

[0122] Finally, it should be noted that: each embodiment in this specification is described by way of example, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0123] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A FMCW laser radar system, characterized in that: The FMCW laser radar system includes: a laser light source configured to emit a swept-frequency laser; A light engine, comprising a light emitter / receiver, wherein the light engine is configured to receive the frequency-sweeping laser and emit at least a portion of the frequency-sweeping laser from the light emitter / receiver as a detection beam, wherein the detection beam generates a reflected beam after being incident on an obstacle, and the light emitter / receiver is further configured to receive the reflected beam; a scanning component, disposed on one side of the light transmitter / receiver, configured to deflect the detection beam to achieve detection beam scanning; and The birefringence component is configured to compensate for the transceiver offset angle caused by the movement of the scanning component, so that the detection light beam and the reflected light beam are transmitted and received by the same port of the optical transmitter / receiver.

2. The FMCW laser radar system according to claim 1, wherein: The FMCW laser radar system also includes: a lens assembly disposed between the light emitter / receiver and the scanning assembly, configured to collimate the detection beam and couple the reflected beam into the light emitter / receiver, The detection beam is a first polarization mode beam with a first polarization direction, and the reflected beam is a second polarization mode beam with a second polarization direction. The first polarization direction and the second polarization direction are perpendicular to each other, and the first polarization mode beam and the second polarization mode beam have different refractive indices in the birefringence component.

3. The FMCW laser radar system according to claim 2, wherein: The birefringent component has a compensation deviation angle α for the reflected light beam, and the compensation deviation angle α is determined by the following formula: 0<α≤θ m Among them, θ m is the maximum value of the transmit and receive offset angle, θ m Determined by the following formula: Where, ω is the scanning angular velocity of the scanning component, L m is the maximum detection distance of the FMCW laser radar system, and c is the speed of light.

4. The FMCW laser radar system according to claim 3, wherein: The birefringent assembly comprises an optical wedge, which is arranged between the lens assembly and the scanning assembly. The inclined surface of the optical wedge is away from the lens assembly relative to its plane. The optical axis of the optical wedge is perpendicular to the optical axis of the lens assembly. The compensation offset angle α satisfies the following formula: α=arctan(n2sinβ)-arctan(n1sinβ) Wherein, n1 is the refractive index of the first polarization mode light beam in the optical wedge, n2 is the refractive index of the second polarization mode light beam in the optical wedge, and β is the wedge angle of the optical wedge.

5. The FMCW laser radar system according to claim 3, wherein: The birefringent assembly includes a polarization beam splitting prism group, which is arranged between the lens assembly and the scanning assembly. The polarization beam splitting prism group includes a first right-angle prism and a second right-angle prism with bevels attached. The optical axis of the first right-angle prism is parallel to the optical axis of the lens assembly, and the second right-angle prism is arranged on the side of the first right-angle prism away from the lens assembly. The optical axis of the second right-angle prism is perpendicular to the optical axis of the lens assembly. The compensation offset angle α satisfies the following formula: α=arctan(0.7n4)-arctan(0.7n3) Among them, n3 is the refractive index of the first polarization mode light beam in the polarization beam splitter prism group, and n4 is the refractive index of the second polarization mode light beam in the polarization beam splitter prism group.

6. The FMCW laser radar system according to claim 3, wherein: The birefringent assembly includes a birefringent flat lens, which is disposed between the lens assembly and the light transmitter / receiver, and is disposed parallel to the lens assembly. The optical axis of the birefringent flat lens intersects the optical axis of the lens assembly, and the compensation deviation angle α satisfies the following formula: Among them, n5 is the refractive index of the first polarization mode light beam in the birefringent flat lens, n6 is the refractive index of the second polarization mode light beam in the birefringent flat lens, γ is the angle between the optical axis of the birefringent flat lens and its plane, d is the thickness of the birefringent flat lens, and f is the focal length of the lens assembly.

7. The FMCW laser radar system according to any one of claims 1 to 6, wherein: The optical engine includes a laser radar chip, and the laser radar chip includes: A frequency-sweeping laser receiving end, configured to receive the frequency-sweeping laser; A beam splitter connected to the laser receiving end and configured to split the frequency-sweeping laser into a detection beam and a local oscillator beam; a mixer configured to receive the local oscillator light beam and the reflected light beam, and mix the local oscillator light beam and the reflected light beam to obtain a mixed laser; and a balanced detector, receiving the frequency-mixed laser and outputting a detection electrical signal based on the frequency-mixed laser; The FMCW laser radar system also includes: The acquisition and processing device is electrically connected to the balanced detector, receives the detection electrical signal from the balanced detector, and processes the detection electrical signal to determine the distance and / or speed of the obstacle relative to the FMCW laser radar system.

8. The FMCW laser radar system according to claim 7, wherein: The laser radar chip also includes: a polarization rotating beam splitter, as the optical transmitter / receiver, configured to receive the detection beam and output it, and to receive the reflected beam and change the polarization direction of the reflected beam, The mixer receives the local oscillator beam from the beam splitter and the reflected beam from the polarization rotating beam splitter.

9. The FMCW laser radar system according to claim 7, wherein: The laser radar chip also includes: a detection beam output end, configured to receive and output the detection beam from the beam splitter; and a reflected light beam receiving end, configured to receive the reflected light beam, The optical transmitter / receiver includes a circulator, which includes a first port, a second port and a third port. The first port is connected to the detection beam output end, receives the detection beam emitted from the detection beam output end and transmits it to the second port, the detection beam is emitted from the second port, the second port also receives the reflected beam and transmits it to the third port, the third port is connected to the reflected beam receiving end, and transmits the reflected beam to the reflected beam receiving end.

10. A mobile device, characterized in that: The mobile device comprises the FMCW lidar system as described in any one of claims 1-9.

Images