CN116338635A

CN116338635A - Laser radar

Info

Publication number: CN116338635A
Application number: CN202111604396.7A
Authority: CN
Inventors: 颜世佳; 汪敬
Original assignee: Suteng Innovation Technology Co Ltd
Current assignee: Suteng Innovation Technology Co Ltd
Priority date: 2021-12-24
Filing date: 2021-12-24
Publication date: 2023-06-27

Abstract

The embodiment of the application discloses a laser radar, include: the optical system comprises an optical source, a first tunable filter, an optical circulator, an optical window, a dispersive element, a demultiplexer and n first detectors; wherein n is an integer greater than or equal to 2; the light source, the tunable filter, the optical circulator, the optical window and the dispersive element are sequentially connected, and the n first detectors are connected with the optical circulator through the demultiplexer. By adopting the embodiment of the application, the laser ranging can be realized as an all-solid-state laser radar, and the dependence of a mechanical scanning element is eliminated.

Description

Laser radar

Technical Field

The application relates to the technical field of laser detection, in particular to a laser radar.

Background

A LiDAR (light detection and ranging, liDAR) is a radar system that transmits a laser beam to detect a characteristic amount such as a position, a speed, or the like of a target. The laser radar works on the principle that a detection signal (laser beam) is sent to a target object (such as a vehicle, an airplane or a missile), and then a received signal (echo signal) reflected from the target object is compared with the sent signal and processed, so that relevant information of the target object, such as parameters of target distance, azimuth, altitude, speed, gesture, even shape and the like, can be obtained, and the target object can be detected, tracked and identified.

Currently, commonly used vehicle-mounted lidars include pulse-of-flight (TOF) based range lidar and frequency modulated continuous wave (frequency modulated continuous waveform, FMCW) coherent range lidar. Because the FMCW laser radar adopts a coherent detection technology, interference light of an external environment is difficult to generate a beat signal by coherent mixing with local reference, so that the anti-interference performance of the FMCW laser radar is relatively good. The FMCW radar transmits laser beams which are frequency modulated continuous lasers, the laser beams are divided into two parts, one part is used as local oscillation light, the other part is used as detection light to be transmitted to a detection area, after the detection light encounters a target object in the detection area, echo signals are reflected, and the detector calculates the distance of the object through the echo signals and the local oscillation light.

Lidars are generally divided into two main categories: mechanical lidar and solid-state lidar. The mechanical laser radar can realize large-angle rotation scanning through the mechanical scanning element, but has the defects of difficult precise assembly, low scanning frequency, huge system and the like. The solid-state lidar has no mechanical scanning components inside, but rather implements beam deflection in other ways, such as optical parametric methods (Optical parametric amplification, OPA), to accomplish large angle scanning. The solid-state laser radar which gets rid of the mechanical moving parts has the advantages of high scanning speed, high precision, small volume and the like, is regarded as the development trend of the laser radar in the future, but the technology of the solid-state laser radar is not completely mature and is still in the exploration stage. Therefore, the semi-solid state laser radar provided with the micro-electro-mechanical system (MEMS) galvanometer appears as a transition scheme of a mechanical laser radar and a solid state laser radar, and the semi-solid state laser radar has a certain integration level and high response speed, but still has the problems of mechanical rotation and smaller deflection angle range.

Disclosure of Invention

The embodiment of the application provides a laser radar which can be used as an all-solid-state laser radar to realize laser ranging and is free from the dependence of a mechanical scanning element. The technical scheme is as follows:

in a first aspect, embodiments of the present application provide a lidar, the lidar comprising:

the optical system comprises an optical source, a first tunable filter, an optical circulator, an optical window, a dispersive element, a demultiplexer and n first detectors; wherein n is an integer greater than or equal to 2;

the light source, the tunable filter, the optical circulator, the optical window and the dispersive element are sequentially connected, and the n first detectors are connected with the optical circulator through the demultiplexer;

the light source is used for transmitting a multi-wavelength light beam to the first tunable filter;

the first tunable filter is configured to filter the multi-wavelength light beam to obtain a first filtered light beam, and send the first filtered light beam to the optical circulator; the first filtered light beam comprises n different wavelengths of light, and the wavelength of the n different wavelengths of light comprised by the first filtered light beam is periodically changed;

the optical circulator is configured to send the first filtered light beam to the optical window, receive a reflected light beam corresponding to the first filtered light beam and an echo light beam corresponding to the first filtered light beam from the optical window, and send the reflected light beam and the echo light beam to the demultiplexer;

The dispersion element is used for dispersing the emergent light rays corresponding to each wavelength in the emergent light beams corresponding to the first filtering light beams to the outside of the laser radar according to different emergent angles and receiving the echo light beams corresponding to the emergent light beams;

the n first detectors and the demultiplexer are configured to process the echo beam and the reflected beam.

In a second aspect, embodiments of the present application provide another lidar, the lidar comprising:

the device comprises a light source, a tunable filter, an optical circulator, an optical window, a dispersion element, a scanning element, a demultiplexer and n first detectors; wherein n is an integer greater than or equal to 2;

the light source, the tunable filter, the optical circulator, the optical window, the scanning element and the dispersive element are sequentially connected, and the n first detectors are connected with the optical circulator through the demultiplexer;

the light source is used for transmitting the multi-wavelength light beam to the tunable filter;

the tunable filter is configured to perform frequency modulation on the multi-wavelength light beam, obtain a frequency modulated light beam including a target waveform, and send the frequency modulated light beam including the target waveform to the optical circulator; wherein the target waveform includes at least one of: triangular, saw tooth and sinusoidal waves;

the scanning element is used for adjusting the emergent angle of the emergent beam corresponding to the first filtering beam passing through the optical window;

the dispersion element is used for dispersing the emergent light rays corresponding to each wavelength in the emergent light beam to the outside of the laser radar according to different emergent angles and receiving the echo light beam corresponding to the emergent light beam;

The technical scheme provided by some embodiments of the present application has the beneficial effects that at least includes:

the laser radar comprises a first tunable filter, an optical circulator, an optical window, a dispersive element and other components, and the wavelength of a multi-wavelength light beam emitted by a light source is changed by periodically changing the working voltage or current of the first tunable filter, so that the angle of the emitted light beam of the laser radar is changed by utilizing the dispersion principle and the dispersive element, the requirement of large-angle scanning of the laser radar is met, the dependence on mechanical elements in the mechanical laser radar and the semisolid laser radar is eliminated, and the problems of difficult assembly, low radar integration, small rotation angle range, slower rotation response speed and the like of the mechanical laser radar are solved; and compared with the prior art adopting a plurality of light sources, the method greatly reduces the radar cost, saves the space of the radar system, and is favorable for the miniaturization and high integration development of the radar.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a lidar according to an embodiment of the present application;

FIG. 2 is a spectral diagram of a spectral range provided by an embodiment of the present application;

fig. 3 is a schematic structural diagram of a lidar according to an embodiment of the present application;

fig. 4A is a schematic structural diagram of a lidar according to an embodiment of the present application;

fig. 4B is a schematic structural diagram of a lidar according to an embodiment of the present application;

fig. 4C is a schematic structural diagram of a lidar according to an embodiment of the present application;

fig. 5 is a schematic structural diagram of a lidar according to an embodiment of the present application;

fig. 6 is a schematic structural diagram of a lidar according to an embodiment of the present application;

fig. 7 is a schematic structural diagram of a lidar according to an embodiment of the present application;

Fig. 8 is a schematic structural diagram of a lidar according to an embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

In the description of the present application, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present application, it is to be understood that the terms "comprise" and "have," and any variations thereof, are intended to cover non-exclusive inclusions, unless otherwise specifically defined and defined. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art in a specific context. Furthermore, in the description of the present application, unless otherwise indicated, "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a exists alone, A and B exist together, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship.

In order to solve the defects of difficult precision assembly, low scanning frequency, huge system and the like of the mechanical laser radar, and thoroughly transition from the semi-solid laser radar, the problems of slow mechanical rotation response, small deflection angle range and the like caused by mechanical moving parts are solved, and the solid-state laser radar shown in the figure 1 is provided.

As shown in fig. 1, a schematic structural diagram of a lidar according to an embodiment of the present application is provided, where the lidar includes: light source 101, first tunable filter 102, optical circulator 103, optical window 104, dispersive element 105, demultiplexer 106, and n first detectors comprising: the

detectors

1071, 1072, 1073, 107n, n are integers greater than or equal to 2. The light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104 and the dispersive element 105 are connected in sequence, and the n first detectors are connected to the optical circulator 103 through the demultiplexer 106.

It is understood that in the embodiments of the present application, the elements are connected by optical fiber paths or spatial light, or the like.

A light source 101 for emitting a multi-wavelength light beam to a first tunable filter 102. In the embodiment of the application, a spontaneous amplified radiation (amplified spontaneous emission, ASE) broad spectrum light source, an FP (Fabry-perot) laser and other multi-longitudinal mode lasers can be used as the light source, for example, an ASE broad spectrum light source based on an erbium-doped fiber, and the light source has the advantages of high stability, high power density, small volume and the like.

The wavelength range corresponding to the multi-wavelength light beam emitted from the light source 101 is affected by the transmission window of the transmission medium in the measurement environment and the scattering characteristics of the object to be measured. In other words, the multi-wavelength light beam emitted from the light source 101 includes a plurality of wavelength values. For example, in urban mapping, the laser transmission medium is the atmosphere, and the measured object is a building, a lawn and a road surface, so that a wavelength with a wavelength value of 1064nm can be selected, and a wavelength range corresponding to the multi-wavelength light beam of the light source 101 includes the wavelength value; for example, in marine measurement, the transmission medium of the laser is water, so that a wavelength with a wavelength value of 532nm can be selected, and the wavelength range corresponding to the multi-wavelength beam of the light source 101 includes the wavelength value; in the field of autopilot and robotics, the wavelength range corresponding to the multi-wavelength light beam of the light source 101 should include wavelength values of 905nm and 1550 nm.

A first tunable filter 102 for filtering the multi-wavelength light beam to obtain a first filtered light beam, and transmitting the first filtered light beam to an optical circulator 103. The first tunable filter includes at least one of: liquid crystal etalons, fiber FP etalons, multilayer film FP etalons, micro-ring etalons, mach-zehnder MZ interference etalons, and the like.

The first filtered beam includes n different wavelengths of light, the first filtered beam includes n different wavelengths of lightLong periodic variations. For example, as shown in fig. 2, a spectrum diagram of an initial spectrum range provided in the embodiment of the present application is shown, the first tunable filter 102 is a tunable FP etalon, and the light source 101 emits multi-wavelength light at least including a wavelength λ ₁ 、λ ₂ 、λ ₃ 、λ ₄ 、λ ₅ 、......、λ _n 、λ’ ₁ 、λ’ ₂ 、λ’ ₃ 、λ’ ₄ 、λ’ ₅ 、......、λ’ _n Etc.; lambda (lambda) ₁ 、λ ₂ 、λ ₃ 、λ ₄ 、λ ₅ 、......、λ _n The initial spectral range FSR1 (Free Spectral Range) for the tunable FP etalon comprises wavelength values as shown in the left diagram of fig. 2; lambda's' ₁ 、λ’ ₂ 、λ’ ₃ 、λ’ ₄ 、λ’ ₅ 、......、λ’ _n For the corresponding variable spectral range FSR2 of the tunable FP etalon to include wavelength values over 1/M cycles, each cycle includes M spectral range changes, M being a positive integer greater than 1, as shown in the right hand graph of fig. 2. In the embodiment of the present application, the spectral range corresponding to the first filtered light beam emitted by the first tunable filter 102 is periodically changed by periodically changing the operating voltage or the operating current of the first tunable filter 102.

An optical circulator 103 for transmitting the first filtered beam to the optical window 104, and receiving a reflected beam corresponding to the first filtered beam and an echo beam corresponding to the first filtered beam from the optical window 104, and transmitting the reflected beam and the echo beam to the demultiplexer 106.

The optical circulator 103 may be understood as a multiport optical device having non-reciprocal characteristics. In the present embodiment, the optical circulator 103 includes at least three ports, a first port connected to the first tunable filter 102, a second port connected to the optical window 104, and a third port connected to the demultiplexer 106. The first filtered beam is incident from a first port of the optical circulator 103 and exits from a second port towards the optical window 104.

The light window 104 is provided with a partially reflective film for dividing the first filtered light beam into a reflected light beam and an outgoing light beam when the first filtered light beam reaches the light window 104. The reflected beam enters the second port of the optical circulator 103 and exits the third port toward the demultiplexer 106. Whereas the outgoing light beam corresponding to the first filtered light beam passes through the optical window 104 to the dispersive element 105. In the present application, the optical window 104 may be a reflective sheet of a partially reflective film, a fiber grating of a partially reflective film, or the like, wherein the partially reflective film refers to a reflective film having a reflectance of less than 100%, for example, the partially reflective film has a reflectance of 1% or 5%.

And a dispersive element 105 for scattering the outgoing beam corresponding to the first filtered beam passing through the optical window 104 to the outside of the laser radar and receiving the echo beam corresponding to the outgoing beam. Since the wavelength of the outgoing light beam sent to the dispersive element 105 is periodically changed, the outgoing angle of the outgoing light beam outgoing from the lidar is periodically changed accordingly, thereby realizing a spatial scanning function. For example, as can be seen from the grating equation d× (sin i±sin θ) =m×λ, where d is a grating constant, i is an incident angle, θ is an exit angle, λ is a wavelength, m is a grating order, and the wavelength of the incident light to the grating periodically changes, so that the exit angle of the exit light periodically changes, thereby realizing the spatial scanning function. In the embodiment of the present application, the dispersive element 105 includes a reflective dispersive element, which has the characteristics of small volume and high reflectivity. In another embodiment, the dispersive element 105 may also be a transmission grating.

The echo beam corresponding to the first filtered beam is reflected to the optical window 104 by the dispersive element 105, and further passes through the second port and the third port of the optical ring 103, and is emitted to the demultiplexer 106.

n first detectors 107 and demultiplexers 106 for processing the echo beams and the reflected beams. Specifically, the demultiplexer 106 divides an echo light beam and a reflected light beam including a plurality of wavelengths into n echo light rays and reflected light rays by wavelength, and further transmits the echo light rays and the reflected light rays having the same wavelength range to the target first detector of the n first detectors 107. For example, the echo beam and the reflected beam include wavelengths lambda, respectively ₁ 、λ ₂ 、λ ₃ 、λ ₄ 、λ ₅ 、......、λ _n The demultiplexer 106 will include the wavelength lambda and the reflected light ₁ Transmits the echo light and the reflected light of (a) to the first detector 1071, and includes a wavelength lambda ₂ Transmits the echo light and the reflected light of (a) to the first detector 1072, and includes a wavelength lambda ₃ Is sent to a first detector 1073, etc.

As shown in fig. 3, a schematic structural diagram of a lidar according to an embodiment of the present application is provided, and the working voltage or the working current of the first tunable filter 102 is periodically adjusted based on the lidar structure provided by the embodiment of the present application. The laser radar includes: the second control module 108, the second power supply 109, the light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104, the dispersive element 105, the demultiplexer 106 and n first detectors, the n first detectors comprising: the

detectors

1071, 1072, 1073, 107n, n are integers greater than or equal to 2. The light source 101, the tunable filter 102, the optical circulator 103, the optical window 104 and the dispersive element 105 are sequentially connected, n first detectors are connected to the optical circulator 103 through the demultiplexer 106, and the second control module 108 is connected to the first tunable filter 102 through the second power supply 109.

A second control module 108 for indicating the periodic variation of the operating voltage and operating current of the second power supply 109 applied to the first tunable filter 102, for example, the period is T, when the first voltage E is applied to the first tunable filter 102 ₁ Or a first current I ₁ The first filtered beam exiting the first tunable filter 102 corresponds to an initial spectral range FSR1; when the first voltage E is applied to the first tunable filter 102 ₂ Or a first current I ₂ The first filtered beam exiting the first tunable filter 102 corresponds to the initial spectral range FSR2.

The structure and function of the light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104, the dispersive element 105, the demultiplexer 106 and the n first detectors 107 are shown in fig. 1, and will not be described here again.

In order to make the waveform of the laser signal emitted by the solid-state laser radar be a target waveform, the requirement of the complex use scene of the solid-state laser radar is met, and the target waveform at least comprises one of the following: triangular, saw tooth and sine waves, the application proposes a solid-state lidar as shown in fig. 4A, 4B, 4C.

As shown in fig. 4A, a schematic structural diagram of a lidar according to an embodiment of the present application is provided, where the lidar includes: modulator 401, light source 101, first tunable filter 102, optical circulator 103, optical window 104, dispersive element 105, demultiplexer 106, and n first detectors, the n first detectors comprising: the

detectors

1071, 1072, 1073, 107n, n are integers greater than or equal to 2. The light source 101, the first tunable filter 102, the modulator 401, the optical circulator 103, the optical window 104 are connected in sequence with the dispersive element 105, and n first detectors are connected with the optical circulator 103 through the demultiplexer 106.

The first tunable filter 102 is specifically configured to filter the multi-wavelength light beam sent by the light source 101, obtain a first filtered light beam, and send the first filtered light beam to the modulator 401.

A modulator 401 for frequency modulating or amplitude modulating the first filtered light beam to obtain a frequency modulated light beam comprising a target waveform, and transmitting the frequency modulated light beam comprising the target waveform to an optical circulator. Wherein the target waveform comprises at least one of: triangular, saw tooth and sinusoidal. The modulator 401 comprises a frequency modulator (light frequency modulator, LFM) and an amplitude modulator, the principle of operation being understood to be that upon application of an electric field to a material having an electro-optical effect, the refractive index of the material is further changed, resulting in a change in the light intensity or phase of the light passing through the modulator 401, thereby effecting frequency or amplitude modulation. For example, the modulator 401 is an optical amplitude modulator made of LiTaO3 material implemented based on mach-zehnder interference principle, or a voltage-controlled oscillator (VCO), or the like.

As shown in fig. 4B, a schematic structural diagram of a lidar according to an embodiment of the present application is provided, where the lidar includes: the second tunable filter 402, the light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104, the dispersive element 105, the demultiplexer 106 and n first detectors, the n first detectors comprising: the

detectors

1071, 1072, 1073, 107n, n are integers greater than or equal to 2. The light source 101, the first tunable filter 102, the second tunable filter 402, the optical circulator 103, the optical window 104 and the dispersive element 105 are sequentially connected, and n first detectors are connected to the optical circulator 103 through the demultiplexer 106.

The first tunable filter 102 is specifically configured to filter the multi-wavelength light beam sent by the light source 101, obtain a first filtered light beam, and send the first filtered light beam to the second tunable filter 402.

A second tunable filter 402 for frequency modulating the first filtered beam to obtain a frequency modulated beam comprising the target waveform, and transmitting the frequency modulated beam comprising the target waveform to the optical circulator 103.

In the present embodiment, the first tunable filter 102 performs the functions of beam scanning and wavelength division multiplexing, while frequency modulation is performed by adjusting the operating voltage or operating current of the second tunable filter 402. Specifically, the first filtered light beam transmitted by the light source 101 is filtered by the first tunable filter 102 to obtain a first filtered light beam, and the first filtered light beam is transmitted to the second tunable filter 402; by varying the operating voltage or operating current of the second tunable filter 402, the free spectral range FSR' of the second tunable filter 402 is periodically adjusted to achieve frequency modulation of the first filtered beam, resulting in a frequency modulated beam comprising the target waveform.

In the embodiment of the present application, the FSR fineness of the second tunable filter 402 is higher than that of the first tunable filter 102, and the frequency modulation range of the second tunable filter 402 may be enough to satisfy the frequency modulation bandwidth of the signal.

As shown in fig. 4C, a schematic structural diagram of a lidar according to an embodiment of the present application is provided, where the lidar includes: the first control module 403, the first power supply 404, the light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104, the dispersive element 105, the demultiplexer 106 and n first detectors, the n first detectors comprising: the

detectors

1071, 1072, 1073, 107n, n are integers greater than or equal to 2. The light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104 and the dispersive element 105 are sequentially connected, n first detectors are connected with the optical circulator 103 through the demultiplexer 106, and the first control module 403 is connected with the light source 101 through the first power supply 404;

the first control module 403 is configured to periodically change an operating voltage or an operating current of the light source 101 by using the first power supply 404, and perform amplitude modulation on the multi-wavelength light beam sent by the light source 101, so as to obtain a multi-wavelength light beam including a target waveform.

The lidar having the amplitude modulation or frequency modulation function of the first filtered beam shown in fig. 4A and 4B can be understood as an indirect modulation realized by using the principle that the transmission characteristic of the crystal varies with the voltage. The lidar shown in fig. 4C, which includes the first control module 403 and the first power supply 404, can be understood as a direct modulation in which a current is periodically injected to the semiconductor laser as the light source 101 to thereby realize amplitude modulation. It is understood that the present application also includes lidar of other structures that directly modulate or indirectly modulate a multi-wavelength beam.

The structure and function of the light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104, the dispersive element 105, the demultiplexer 106 and the n first detectors 107 are shown in fig. 1 to 3, and will not be described here again.

According to the method, frequency modulation and/or amplitude modulation of the multi-wavelength light beams generated by the light source are realized through the modulator, the second tunable filter or the first control module and the first power supply, so that the emergent light beams corresponding to the multi-wavelength light beams comprise target waveforms, information is better transmitted by the emergent light beams based on the target waveforms, and the adaptability and the practicability of the laser radar to complex use scenes are improved; the laser radar further comprises a first tunable filter, an optical circulator, an optical window, a dispersive element and other components, the working voltage or current of the first tunable filter is periodically changed to change the wavelength of the multi-wavelength light beam emitted by the light source, so that the dispersion principle and the dispersive element are utilized to change the angle of the emitted light beam of the laser radar, the requirement of large-angle scanning of the laser radar is met, the dependence on mechanical elements in the mechanical laser radar and the semisolid laser radar is eliminated, and the problems of difficult assembly, low radar integration level, small rotation angle range, slower rotation response speed and the like of the mechanical laser radar are solved; and compared with the prior art adopting a plurality of light sources, the method greatly reduces the radar cost, saves the space of the radar system, and is favorable for the miniaturization and high integration development of the radar.

Fig. 5 is a schematic structural diagram of a lidar according to an embodiment of the present application, where the lidar includes: filter 501, light source 101, first tunable filter 102, optical circulator 103, optical window 104, dispersive element 105, demultiplexer 106, and n first detectors including: the

detectors

1071, 1072, 1073, 107n, n are integers greater than or equal to 2. The light source 101, the filter 501, the first tunable filter 102, the modulator 401, the optical circulator 103, the optical window 104 and the dispersive element 105 are sequentially connected, and n first detectors are connected to the optical circulator 103 through the demultiplexer 106.

The light source 101 is specifically configured to send a multi-wavelength light beam to the filter 501.

The filter 501 is configured to filter the multi-wavelength light beam to obtain a second filtered light beam, and send the second filtered light beam to the first tunable filter 102. Specifically, the filter 501 screens the wavelength band of the multi-wavelength light beam to a wavelength band including the system application wavelength band, for example, the filter 501 is a band-pass filter, and the light source 101 emits the multi-wavelength light including wavelength λ _m 、λ _p 、λ ₁ 、λ ₂ 、λ ₃ 、λ ₄ 、λ ₅ 、......、λ _n 、λ’ ₁ 、λ’ ₂ 、λ’ ₃ 、λ’ ₄ 、λ’ ₅ 、......、λ’ _n Etc., wherein the wavelength is lambda _m 、λ _p Is not in the beam range corresponding to the system application band, and when the multi-wavelength beam passes through the filter 501, the filter 501 will have a wavelength lambda _m 、λ _p Is filtered out. It will be appreciated that the filter may be wholly or partially filtered out of the non-applied bands included in the multi-wavelength beam.

The first tunable filter 102 is specifically configured to filter the second filtered light beam, obtain a first filtered light beam, and send the first filtered light beam to the modulator 401.

A modulator 401 for frequency modulating or amplitude modulating the first filtered light beam to obtain a frequency modulated light beam comprising a target waveform, and transmitting the frequency modulated light beam comprising the target waveform to the optical circulator 103.

The structure and function of the modulator 401, the light source 101, the first tunable filter 102, the optical circulator 103, the optical window 104, the dispersive element 105, the demultiplexer 106 and the n first detectors 107 are shown in fig. 1 to 3, and will not be described here again.

In the embodiment of the application, the filter is used for carrying out primary filtering on the multi-wavelength light beam emitted by the light source, so that the noise in the second filtered light beam sent to the first tunable filter is reduced, and the working accuracy and reliability of the laser radar are improved.

In another embodiment, another lidar provided herein includes: filter, light source, first tunable filter, second tunable filter, optical circulator, optical window, dispersive element, demultiplexer and n first detectors, n first detectors include: a detector 1, a detector 2, a detector 3 once again the detector n, n is an integer greater than or equal to 2. The light source, the filter, the first tunable filter, the second tunable filter, the optical circulator, the optical window and the dispersive element are sequentially connected, and the n first detectors are connected with the optical circulator through the demultiplexer.

In the embodiment of the application, the multi-wavelength light beam provided by the light source is emitted to the filter; the filter plate filters the multi-wavelength light beam to obtain a second filtered light beam, and sends the second filtered light beam to the first tunable filter; the first tunable filter filters the second filtered light beam to obtain a first filtered light beam, and sends the first filtered light beam to the second tunable filter; the second tunable filter performs frequency modulation on the first filtering light beam to obtain a frequency modulation light beam comprising a target waveform, and sends the frequency modulation light beam comprising the target waveform to the optical circulator; the working principles of the optical circulator, the optical window, the dispersive element, the demultiplexer and the n first detectors are shown in fig. 4B, and are not described here again.

In one embodiment, the present application also provides a lidar comprising: filter, light source, first tunable filter, first control module, first power, optical circulator, optical window, dispersive element, demultiplexer and n first detectors, n first detectors include: a detector 1, a detector 2, a detector 3 once again the detector n, n is an integer greater than or equal to 2. The light source, the filter, the first tunable filter, the optical circulator, the optical window and the dispersive element are sequentially connected, n first detectors are connected with the optical circulator through the demultiplexer, and the first control module is connected with the light source through a first power supply.

In the embodiment of the application, a first control module periodically changes the working voltage or the working current of a light source through a first power supply, and amplitude modulation is carried out on a multi-wavelength light beam sent by the light source to obtain the multi-wavelength light beam comprising a target waveform; the multi-wavelength light beam provided by the light source and comprising the target waveform is emitted to the filter; the filter plate filters the multi-wavelength light beam to obtain a second filtered light beam, and sends the second filtered light beam to the first tunable filter; the first tunable filter filters the second filtered light beam to obtain a first filtered light beam, and sends the first filtered light beam to the optical circulator; the working principles of the optical circulator, the optical window, the dispersive element, the demultiplexer and the n first detectors are shown in fig. 4C, and are not described here again.

The frequency modulation and/or the amplitude modulation of the multi-wavelength light beam generated by the light source are realized through the modulator, the second tunable filter or the first control module and the first power supply, so that the emergent light beam corresponding to the multi-wavelength light beam comprises a target waveform, the emergent light beam can better transmit information based on the target waveform, and the adaptability and the practicability of the laser radar to complex use scenes are improved; the laser radar further comprises a first tunable filter, an optical circulator, an optical window, a dispersive element and other components, the working voltage or current of the first tunable filter is periodically changed to change the wavelength of the multi-wavelength light beam emitted by the light source, so that the dispersion principle and the dispersive element are utilized to change the angle of the emitted light beam of the laser radar, the requirement of large-angle scanning of the laser radar is met, the dependence on mechanical elements in the mechanical laser radar and the semisolid laser radar is eliminated, and the problems of difficult assembly, low radar integration level, small rotation angle range, slower rotation response speed and the like of the mechanical laser radar are solved; and compared with the prior art adopting a plurality of light sources, the method greatly reduces the radar cost, saves the space of the radar system, and is favorable for the miniaturization and high integration development of the radar.

In a coherent detection system, when the polarization states of two beams of light which interfere are inconsistent, the amplitude of an interference signal is faded. In the extreme, when the polarization directions of the two light beams are orthogonal, there is no coherence. For the emergent beam of the laser radar, through the processes of reflection, scattering, transmission and the like of an obstacle, the polarization conversion or depolarization effect of the echo beam of the system relative to the emergent beam occurs. This process is not entirely predictable due to obstructions and environmental uncertainties. In order to improve the utilization rate of the echo light beam and improve the amplitude fading condition of the coherent signal, a dual-polarization diversity system can be adopted to divide the echo light beam into two linearly polarized light beams with orthogonal polarization directions, and the linearly polarized light beams are respectively coherent with the reflected light beams corresponding to the emergent light beams with the same polarization.

Fig. 6 is a schematic structural diagram of a lidar according to an embodiment of the present application, where the lidar includes: a gyratory mirror 601, n polarizing beam splitters 602, n second detectors 603, a filter 501, a light source 101, a first tunable filter 102, an optical circulator 103, a gyratory mirror 601, an optical window 104, a dispersive element 105, a demultiplexer 106, and n first detectors, the n first detectors comprising: the

detector

1071, 1072, 1073, and the detector 107n, n polarizing beam splitters 602 include: polarizing beam splitter 6021, polarizing beam splitter 6022, polarizing beam splitter 6023, and the.i., polarizing beam splitter 602n, n second detectors include: the second detector 6031, the second detector 6032, the second detector 6033, the second detector 603, and the second detector 603n, n is an integer of 2 or more.

The light source 101, the filter 501, the first tunable filter 102, the modulator 401, the optical circulator 103, the optical window 104 and the dispersive element 105 are sequentially connected, n first detectors are connected with the optical circulator 103 through the demultiplexer 106, n polarization beam splitters 602 are respectively connected with the demultiplexer 106, and each first detector 106 and each second detector 603 are connected with one polarization beam splitter; the first detector 107 and the second detector 603 corresponding to each polarizing beam splitter 602 are a set of detectors.

For example, as shown in fig. 6, a polarization beam splitter 6021 is connected to the first detector 1071 and the second detector 6031, respectively, a polarization beam splitter 6022 is connected to the first detector 1072 and the second detector 6032, respectively, and a polarization beam splitter 6023 is connected to the first detector 1073 and the second detector 6033, respectively.

The optical circulator 103 is specifically configured to transmit the frequency modulated light beam including the target waveform transmitted by the modulator 401 to the optical window 104 through the optical rotation sheet 601, receive the reflected light beam corresponding to the frequency modulated light beam and the echo light beam corresponding to the frequency modulated light beam transmitted by the optical window 104 through the optical rotation sheet 601, and transmit the reflected light beam and the echo light beam to the demultiplexer 106.

The optical rotator 601 is used for rotating the polarization directions of the reflected light beam and the echo light beam by a preset angle. For example, the optical rotation plate 601 is a 22.5 ° optical rotation plate, that is, the polarization direction of the light beam passing through the optical rotation plate will generate 45 ° rotation each time; when the polarization direction of the multi-wavelength beam is parallel to the x-axis, the polarization direction of the reflected beam sent to the demultiplexer 106 is tilted 45 degrees based on the x-axis.

The demultiplexer 106 is configured to split the reflected light beam and the echo light beam into n light beams, respectively, send n reflected light beams corresponding to the reflected light beam to n polarization beam splitters 602, and send n echo light beams corresponding to the echo light beam to n polarization beam splitters 602, respectively; the wavelengths of the n light rays corresponding to the reflected light beams are in one-to-one correspondence with those of the n light rays corresponding to the echo light beams.

A polarizing beam splitter 602 for splitting the reflected light into a reflected light in a first polarization direction and a reflected light in a second polarization direction, splitting the echo light into an echo light in the first polarization direction and an echo light in the second polarization direction, and transmitting the reflected light in the first polarization direction and the echo light in the first polarization direction to the first detector 107, and transmitting the reflected light in the second polarization direction and the echo light in the second polarization direction to the second detector; the wavelengths of the reflected light and the echo light detected by the first detector 107 and the second detector 603 in the same group of detectors are equal.

For example, in an amplitude modulation system, the reflected beam and the echo beam include the same wavelength, and the reflected beam sent to the demultiplexer has a polarization direction of The wavelengths of the echo beams of the reflected beams are respectively lambda based on the inclination of the x-axis by 45 degrees ₁ 、λ ₂ 、λ ₃ 、λ ₄ 、λ ₅ 、......、λ _n The method comprises the steps of carrying out a first treatment on the surface of the The demultiplexer 106 will include a wavelength lambda ₁ Transmits the reflected light and the echo light of the (a) to a polarization beam splitter 6021, and has a wavelength lambda ₂ Transmits the reflected light and the echo light of the (a) to a polarization beam splitter 6022, and has a wavelength lambda ₃ Is sent to a polarization beam splitter 6023. It will be appreciated that in a frequency modulation system, the wavelengths of the reflected and echo beams are not exactly the same, but the frequency difference is within the coherence range, so the above described workflow still applies.

Polarizing beam splitter 6021 will include wavelength λ ₁ Is split into reflected light of a first polarization direction, e.g. parallel to the x-axis, and reflected light of a second polarization direction, e.g. parallel to the y-axis, which will include the wavelength lambda ₁ Is divided into echo light of a first polarization direction and echo light of a second polarization direction, further comprising a wavelength lambda ₁ And the reflected light and the echo light, which are of the first polarization direction, are sent to a first detector 1071, which will include a wavelength λ ₁ And the reflected light and the echo light in the second polarization direction are sent to a second detector 6031; polarizing beam splitter 6022 will include wavelength λ ₂ Is divided into a first polarized reflected light and a second polarized reflected light, and will include a wavelength lambda ₂ Is divided into echo light of a first polarization direction and echo light of a second polarization direction, further comprising a wavelength lambda ₂ And the reflected light and the echo light, which are of the first polarization direction, are sent to a first detector 1072, which will include a wavelength lambda ₂ And the reflected light and the echo light in the second polarization direction are sent to a second detector 6032.

It is understood that the rotation angle of the light rotator in the present application includes, but is not limited to, 22.5 °, and the relationship between the first polarization direction and the second polarization direction corresponding to the polarizing beam splitter includes, but is not limited to, orthogonality.

The working principles of the light source, the first tunable filter, the modulator, the optical circulator, the optical window and the dispersive element are shown in fig. 4A, and are not described here again.

According to the method, the rotating light sheet, the polarizing beam splitter and the n second detectors are arranged, so that the polarization conversion or depolarization effect of the echo light beam relative to the emergent light beam is weakened, the utilization rate of the echo light beam is improved, and the amplitude fading condition of coherent signals is improved.

Fig. 7 is a schematic structural diagram of a laser radar according to an embodiment of the present application, where the laser radar is a semi-solid laser radar, and the semi-solid laser radar includes: the optical source 701, the tunable filter 702, the optical circulator 703, the optical window 704, the dispersive element 705, the mechanical scanning element 708, the demultiplexer 706 and the n first detectors 707, the n first detectors comprising: the first detector 7071, the first detector 7072, the first detector 7073, and the first detector 107n, n is an integer of 2 or more. It will be appreciated that the following embodiments are exemplified by n=3, and as shown in fig. 8, the present application also includes any case where n is a value.

The light source 701, the tunable filter 702, the optical circulator 703, the optical window 704, the mechanical scanning element 708, and the dispersive element 705 are connected in sequence, and n first detectors 707 are connected to the optical circulator 703 through a demultiplexer 706.

A light source 701 for emitting a multi-wavelength light beam to a tunable filter 702.

A tunable filter 702 for frequency modulating the multi-wavelength light beam, obtaining a first filtered light beam including a target waveform, and transmitting the first filtered light beam including the target waveform to an optical circulator; wherein the target waveform comprises at least one of: triangular, saw tooth and sinusoidal.

By varying the operating voltage or current of the tunable filter 702, the free spectral range FSR' of the tunable filter 702 is periodically adjusted to achieve frequency modulation of the first filtered beam, resulting in a first filtered beam comprising the target waveform. In this embodiment of the present application, the system further includes a third control module and a third power supply, where the third control module is connected to the tunable filter 702 through the third power supply, and the third control module is configured to instruct the third power supply to periodically change an operating voltage or an operating current of the tunable filter 702.

An optical circulator 703 for transmitting the first filtered beam to the optical window 704 and receiving a reflected beam corresponding to the first filtered beam and an echo beam corresponding to the first filtered beam from the optical window 704 and transmitting the reflected beam and the echo beam to the demultiplexer 706.

A scanning element 708 for adjusting an exit angle of an exit beam corresponding to the first filtered beam passing through the optical window. In this application, the scanning element 708 may be a scanning element or a microelectromechanical system (MEMS) galvanometer.

The dispersive element 705 is configured to scatter the outgoing beam corresponding to the first filtered beam passing through the optical window 704 and the light exit port to the outside of the laser radar, and to receive the echo beam corresponding to the outgoing beam.

n first detectors 701 and demultiplexers 706 for processing the echo beams and the reflected beams.

Specifically, light source 701 transmits a signal including wavelength λ to tunable filter 702 ₁ 、λ ₂ 、λ ₃ 、λ ₄ 、λ ₅ 、......、λ _n Is a multi-wavelength beam of (a) light; the tunable filter 702 frequency-modulates the multi-wavelength light beam, acquires a first filtered light beam including a target waveform, and sends the first filtered light beam including the target waveform to the optical circulator 703; the optical circulator 703 transmits the first filtered beam to the optical window 704, the scanning element 705 rotates a light exit of the laser radar to change an exit angle of an exit beam passing through the optical window 704, to realize omnidirectional scanning of the laser radar, to receive a reflected beam corresponding to the first filtered beam from the optical window 704 and an echo beam corresponding to the first filtered beam, and to transmit the reflected beam and the echo beam to the demultiplexer 706; n first detectors 701 and demultiplexers 706 for processing the echo beams and the reflected beams.

The light source adopts a broadband light source or a multi-wavelength light source, is matched with a tunable filter to carry out frequency modulation, and can realize a wavelength division multiplexing system by only one laser, so that the cost is reduced compared with a plurality of lasers adopted by the traditional wavelength division multiplexing system; the tunable filter realizes two functions of wavelength division multiplexing and frequency modulation, omits a modulator for the system or directly carries out amplitude modulation on a control module and a power supply of the light source, further reduces the cost, saves the space and is beneficial to realizing the cost reduction and miniaturization of the laser radar system.

Fig. 8 is a schematic structural diagram of a lidar according to an embodiment of the present application, where the lidar includes: a spinning light sheet 801, n polarizing beam splitters 802, n second detectors 803, a light source 701, a tunable filter 702, an optical circulator 703, an optical window 704, a dispersive element 705, a mechanical scanning element 708, a demultiplexer 706, and n first detectors 707, the n first detectors comprising: first detector 7071, first detector 7072, first detector 7073, first detector 707n, n polarizing beam splitters 802 include: polarizing beamsplitter 8021, polarizing beamsplitter 8022, polarizing beamsplitter 8023, and the.i., polarizing beamsplitter 802n, n second detectors comprise: the second detector 8031, the second detector 8032, the second detector 8033, and the second detector 803nn is an integer greater than or equal to 2.

The light source 701, the tunable filter 702, the optical circulator 703, the light rotating sheet 801, the optical window 704, the mechanical scanning element 708 and the dispersion element 705 are sequentially connected, n first detectors 707 are connected with the optical circulator 703 through a demultiplexer 706, n polarization beam splitters 802 are respectively connected with the demultiplexer 706, and each first detector 706 and each second detector 803 are connected with one polarization beam splitter; the first detector 707 and the second detector 803 corresponding to each polarizing beam splitter 802 are a set of detectors.

For example, as shown in fig. 8, a polarizing beam splitter 8021 is connected to the first detector 7071 and the second detector 8031, a polarizing beam splitter 8022 is connected to the first detector 7072 and the second detector 8032, and a polarizing beam splitter 8023 is connected to the first detector 7073 and the second detector 8033, respectively.

The optical circulator 703 is specifically configured to send the frequency modulated light beam including the target waveform sent by the modulator 401 to the optical window 704 through the optical rotation sheet 801, receive the reflected light beam corresponding to the frequency modulated light beam and the echo light beam corresponding to the frequency modulated light beam sent by the optical window 704 through the optical rotation sheet 801, and send the reflected light beam and the echo light beam to the demultiplexer 706.

The optical rotating sheet 801 is used for rotating the polarization directions of the reflected light beam and the echo light beam by a preset angle. For example, a 22.5 ° rotation of rotation plate 801, i.e., a 45 degree rotation of the polarization direction of the light beam passing through the rotation plate each time; when the polarization directions of the multi-wavelength light beams are parallel to the x-axis, the polarization directions of the reflected light beams and the echo light beams transmitted to the demultiplexer 706 are inclined at 45 degrees based on the x-axis.

A demultiplexer 706, configured to split the reflected light beam and the echo light beam into n light beams, respectively, send n reflected light beams corresponding to the reflected light beam to n polarization beam splitters 802, and send n echo light beams corresponding to the echo light beam to n polarization beam splitters 802, respectively; the wavelengths of the n light rays corresponding to the reflected light beams are in one-to-one correspondence with those of the n light rays corresponding to the echo light beams.

A polarization beam splitter 802 for splitting the reflected light into a reflected light in a first polarization direction and a reflected light in a second polarization direction, splitting the echo light into an echo light in the first polarization direction and an echo light in the second polarization direction, and transmitting the reflected light in the first polarization direction and the echo light in the first polarization direction to a first detector 707, and transmitting the reflected light in the second polarization direction and the echo light in the second polarization direction to a second detector; the wavelengths of the reflected light and the echo light detected by the first detector 707 and the second detector 803 in the same group of detectors are equal.

For example, the polarization directions of the reflected beam and the echo beam sent to the demultiplexer are inclined by 45 degrees based on the x-axis, and the wavelengths of the reflected beam and the echo beam are respectively lambda ₁ 、λ ₂ 、λ ₃ 、λ ₄ 、λ ₅ 、......、λ _n The method comprises the steps of carrying out a first treatment on the surface of the Demultiplexer 706 will have a wavelength lambda ₁ Is transmitted to the biasA beam splitter 8021 for splitting the wavelength lambda ₂ Is sent to a polarizing beam splitter 8022, which transmits the reflected beam and the echo beam with a wavelength lambda ₃ The reflected beam and the echo beam of (c) are sent to the polarization beam splitter 8023.

Polarizing beam splitter 8021 will include a wavelength λ ₁ Is split into reflected light of a first polarization direction, e.g. parallel to the x-axis, and reflected light of a second polarization direction, e.g. parallel to the y-axis, which will include the wavelength lambda ₁ Is divided into echo light of a first polarization direction and echo light of a second polarization direction, further comprising a wavelength lambda ₁ And the reflected light and the echo light, which are of the first polarization direction, are sent to a first detector 7071, which will include a wavelength lambda ₁ And the reflected light and the echo light in the second polarization direction are sent to a second detector 8031; polarizing beam splitter 8022 will include a wavelength λ ₂ Is divided into a first polarized reflected light and a second polarized reflected light, and will include a wavelength lambda ₂ Is divided into echo light of a first polarization direction and echo light of a second polarization direction, further comprising a wavelength lambda ₂ And the reflected light and the echo light, which are of a first polarization direction, are sent to a first detector 7072, which will include a wavelength λ ₂ And the reflected light and the echo light in the second polarization direction are sent to a second detector 8032.

The foregoing disclosure is only illustrative of the preferred embodiments of the present application and is not intended to limit the scope of the claims herein, as the equivalent of the claims herein shall be construed to fall within the scope of the claims herein.

Claims

1. A lidar, the lidar comprising:

2. The lidar of claim 1, further comprising: a modulator;

the first tunable filter is connected with the optical circulator through the modulator;

the first tunable filter is specifically configured to filter the multi-wavelength light beam to obtain a first filtered light beam, and send the first filtered light beam to the modulator;

the modulator is configured to perform frequency modulation or amplitude modulation on the first filtered light beam to obtain a frequency modulated light beam including a target waveform, and send the frequency modulated light beam including the target waveform to the optical circulator; wherein the target waveform includes at least one of: triangular, saw tooth and sinusoidal.

3. The lidar of claim 1, further comprising: the first power supply and the first control module;

The first control module is connected with the light source through the first power supply;

the first control module is used for periodically changing the working voltage or the working current of the light source through the first power supply, and carrying out amplitude modulation on the multi-wavelength light beam of the light source to obtain a multi-wavelength light beam comprising a target waveform; wherein the target waveform includes at least one of: triangular, saw tooth and sinusoidal.

4. The lidar of claim 1, further comprising: a second tunable filter;

the first tunable filter is connected with the optical circulator through the second tunable filter;

the first tunable filter is specifically configured to filter the multi-wavelength light beam to obtain the first filtered light beam, and send the first filtered light beam to the second tunable filter;

the second tunable filter is configured to frequency-modulate the first filtered light beam to obtain a frequency-modulated light beam including a target waveform, and send the frequency-modulated light beam including the target waveform to the optical circulator; wherein the target waveform includes at least one of: triangular, saw tooth and sinusoidal.

5. The lidar according to any of claims 1 to 4, further comprising: a filter;

the light source is connected with the first tunable filter through the filter sheet;

the light source is specifically configured to send the multi-wavelength light beam to the filter;

the filter is used for filtering the multi-wavelength light beam to obtain a second filtered light beam, and sending the second filtered light beam to the first tunable filter;

the first tunable filter is specifically configured to filter the second filtered light beam to obtain a first filtered light beam, and send the first filtered light beam to the optical circulator.

6. The lidar according to any of claims 1 to 4, further comprising: the optical rotating sheet, n polarization beam splitters and n second detectors;

the optical circulator is connected with the optical window through the optical rotation sheet, the n polarization beam splitters are respectively connected with the demultiplexer, and each first detector and each second detector are connected with one polarization beam splitter; the first detector and the second detector corresponding to each of the polarizing beam splitters are a set of detectors;

The optical circulator is specifically configured to send the first filtered light beam to the optical window through the optical rotation sheet, receive a reflected light beam corresponding to the first filtered light beam and an echo light beam corresponding to the first filtered light beam sent from the optical window through the optical rotation sheet, and send the reflected light beam and the echo light beam to the demultiplexer;

the optical rotation sheet is used for rotating the polarization directions of the reflected light beam and the echo light beam by a preset angle;

the demultiplexer is configured to decompose the reflected light beam and the echo light beam into n light beams, send n reflected light beams corresponding to the reflected light beam to the n polarization beam splitters, and send n echo light beams corresponding to the echo light beam to the n polarization beam splitters, respectively; the wavelength ranges of the n reflected light rays corresponding to the reflected light beams are in one-to-one correspondence with the wavelength ranges of the n echo light rays corresponding to the echo light beams;

the polarization beam splitter is configured to split each reflected light into a reflected light in a first polarization direction and a reflected light in a second polarization direction, split each echo light into an echo light in the first polarization direction and an echo light in the second polarization direction, send the reflected light in the first polarization direction and the echo light in the first polarization direction to the first detector, and send the reflected light in the second polarization direction and the echo light in the second polarization direction to the second detector; the wavelength ranges of the reflected light rays and the echo light rays detected by the first detector and the second detector in the same group of detectors are equal.

7. The lidar according to any of claims 1 to 4, further comprising: a second power supply and a second control module;

the second control module is connected with the first tunable filter through the second power supply;

the second control module is used for periodically changing the working voltage or the working current of the first tunable filter through the second power supply.

8. The lidar according to any of claims 1 to 4, wherein the first tunable filter comprises at least one of: liquid crystal etalons, fiber FP etalons, multilayer film FP etalons, micro-ring etalons, and MZ interference etalons.

9. The lidar according to any of claims 1 to 4, wherein the dispersive element comprises at least a reflective dispersive element.

10. A lidar, the lidar comprising:

the tunable filter is configured to perform frequency modulation on the multi-wavelength light beam, obtain a first filtered light beam including a target waveform, and send the first filtered light beam including the target waveform to the optical circulator; wherein the target waveform includes at least one of: triangular, saw tooth and sinusoidal waves;

11. The lidar of claim 10, further comprising: the optical rotating sheet, n polarization beam splitters and n second detectors;