CN116679310A - FMCW laser measuring device - Google Patents
FMCW laser measuring device Download PDFInfo
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- CN116679310A CN116679310A CN202310898176.2A CN202310898176A CN116679310A CN 116679310 A CN116679310 A CN 116679310A CN 202310898176 A CN202310898176 A CN 202310898176A CN 116679310 A CN116679310 A CN 116679310A
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- 238000001514 detection method Methods 0.000 claims abstract description 88
- 230000035559 beat frequency Effects 0.000 claims abstract description 43
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- 238000006243 chemical reaction Methods 0.000 claims description 17
- 239000000523 sample Substances 0.000 claims description 16
- 230000005540 biological transmission Effects 0.000 claims description 14
- 238000005259 measurement Methods 0.000 claims description 12
- 230000010355 oscillation Effects 0.000 claims description 11
- 239000013307 optical fiber Substances 0.000 claims description 7
- 230000003111 delayed effect Effects 0.000 claims description 5
- 239000000835 fiber Substances 0.000 claims description 5
- 238000010408 sweeping Methods 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 2
- 238000012545 processing Methods 0.000 description 13
- 238000010586 diagram Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
- G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/66—Tracking systems using electromagnetic waves other than radio waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/491—Details of non-pulse systems
- G01S7/4911—Transmitters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/491—Details of non-pulse systems
- G01S7/4912—Receivers
- G01S7/4915—Time delay measurement, e.g. operational details for pixel components; Phase measurement
Abstract
The present application provides an FMCW laser measuring device comprising: a laser light source configured to emit a linear swept laser; the beam splitter receives the linear sweep laser and splits the linear sweep laser into detection sweep laser and reference sweep laser, wherein the detection sweep laser and the reference sweep laser are respectively used for detecting a target object and controlling the laser source in a feedback manner; a reference light path channel, which is used for executing delay beat frequency operation on the reference sweep frequency laser to output beat frequency signals; and the feedback circuit is used for receiving the beat frequency signal and outputting a feedback signal, and the feedback signal is configured to adjust the output of the laser light source in real time so as to ensure the frequency modulation linearity of the linear sweep frequency of the laser light source and the beat frequency stability of the FMCW laser measuring device.
Description
Technical Field
The application relates to the technical field of laser radars, in particular to an FMCW laser measuring device.
Background
A laser measuring device, such as a laser radar, is a radar system that detects a characteristic quantity such as a position, a speed, or the like of a target with a laser beam emitted. The working principle is that a detection beam is emitted to a target, then the received beam reflected from the target is compared with the emitted beam, and after proper processing, the related information of the target, such as parameters of the distance, azimuth, altitude, speed, gesture, even shape and the like of the target, can be obtained, so that the targets of an airplane, a missile and the like are detected, tracked and identified. Lidar is now widely deployed in different scenarios including automotive vehicles. The lidar may actively estimate distance and speed to environmental features as the scene is scanned and generate a point cloud indicative of the three-dimensional shape of the environmental scene. Lidar is one of the core sensors widely used in autopilot scenarios and can be used to collect three-dimensional information of the external environment. Lidars can be largely classified into two types of lidars, time of Flight (ToF) and frequency modulated continuous wave (Frequency Modulated Continuous Wave, FMCW), according to the detection mechanism.
Disclosure of Invention
Some embodiments of the present application provide an FMCW laser measuring device including:
a laser light source configured to emit a linear swept laser;
the beam splitter receives the linear sweep laser and splits the linear sweep laser into detection sweep laser and reference sweep laser, wherein the detection sweep laser and the reference sweep laser are respectively used for detecting a target object and monitoring the sweep state of the laser source;
a reference light path channel for delaying the reference sweep frequency laser and outputting beat frequency signals,
and the feedback circuit is used for receiving the beat frequency signal and outputting a feedback signal, and the feedback signal is configured to adjust the output of the laser light source in real time so as to ensure the frequency modulation linearity of the linear sweep frequency of the laser light source and the beat frequency stability of the FMCW laser measuring device.
In some embodiments, the reference optical path channel comprises:
the first beam splitter is configured to split the reference sweep frequency laser into a first reference sweep frequency laser and a second reference sweep frequency laser;
a delay device for receiving the first reference sweep laser so that the first reference sweep laser is transmitted for a certain length to delay a predetermined time;
a first mixer for mixing the delayed first and second reference sweep lasers and outputting a reference mixed beam; and
and the first detection device receives the reference mixed light beam and outputs the beat frequency signal.
In some embodiments, the feedback circuit comprises:
a reference frequency source configured to output a reference frequency signal;
a phase discriminator configured to receive the reference frequency signal and the beat frequency signal and perform a phase discriminating operation on the reference frequency signal and the beat frequency signal to output a signal indicative of a phase difference;
and the negative feedback unit is configured to output the feedback signal according to the phase difference signal.
In some embodiments, the reference frequency signal has a stable frequency f r ，
The delay means comprises an optical fiber or waveguide having a predetermined length, the stable frequency f r
The following formula is satisfied:
wherein t is c F is one half of the sweep measurement period c For swept bandwidth, L represents a predetermined length of the fiber or waveguide, C 0 Indicating the speed of light and n indicating the refractive index of the fiber or waveguide.
In some embodiments, the FMCW laser measuring device further includes:
the driving device is electrically connected with the laser light source and the feedback circuit, and is configured to receive the feedback signal and output a feedback driving signal to the laser light source, so that the frequency modulation linearity of the linear sweep of the laser light source and the beat frequency stability of the FMCW laser measuring device are ensured.
In some embodiments, the driving means comprises:
a driving unit for generating a frequency modulation driving signal; and
the superposition unit is used for receiving the frequency modulation driving signal and the feedback signal and transmitting a detection channel, the detection channel is configured to receive the detection sweep laser, the transmission detection channel is provided with a light emitting/receiving unit, the light emitting/receiving unit is configured to emit a detection light beam, the detection light beam is reflected after encountering a target object to generate a reflected light beam, the light emitting/receiving unit is further configured to receive the reflected light beam, the detection light beam is at least one part of the detection sweep laser, and the feedback driving signal is output.
In some embodiments, the FMCW laser measuring device further includes:
a transmission detection channel configured to receive the detection swept laser light, the transmission detection channel having a light emitting/receiving unit configured to emit a detection beam that is reflected upon encountering a target to produce a reflected beam, the light emitting/receiving unit further configured to receive the reflected beam, the detection beam being at least a portion of the detection swept laser light,
the FMCW laser measuring device is used for measuring the target object according to the reflected light beam.
In some embodiments, the transmission probe channel further comprises:
the second beam splitter is configured to split the detection sweep frequency laser into the detection beam and the local oscillation beam;
the second mixer is configured to receive the local oscillation light beam and the reflected light beam, and mix the local oscillation light beam and the reflected light beam to obtain a detection mixed light beam; and
and the second detection device is used for receiving and detecting the detection mixed light beam and outputting a detection signal.
In some embodiments, the distance R and the velocity v of the target measured by the FMCW laser measuring device satisfy the following relationships:
wherein t is c F is one half of the sweep measurement period c For sweeping the bandwidth, f b1 For the up-beat frequency of the up-beat stage, f b2 For the down-conversion beat frequency of the down-conversion stage, C 0 Is the speed of light, f 0 Is the frequency of the light source.
In some embodiments, the FMCW laser measuring device further includes:
and a lens assembly disposed between the light emitting/receiving unit and the target object, configured to perform collimation of a probe beam emitted from the light emitting/receiving unit, and perform focusing of the reflected beam to couple into the light emitting/receiving unit.
Compared with the related art, the scheme provided by the embodiment of the application has at least the following beneficial effects:
the linear sweep frequency laser output by the laser light source is monitored in real time through the reference light path channel, a feedback signal for adjusting the laser light source in real time is determined through the feedback circuit, and the feedback signal is configured to adjust the output of the laser light source in real time, so that the frequency modulation linearity of the linear sweep frequency of the laser light source and the beat frequency stability of the FMCW laser measuring device are ensured.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application. It is evident that the drawings in the following description are only some embodiments of the present application and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art. In the drawings:
fig. 1 is a schematic structural diagram of an FMCW laser measuring device according to some embodiments of the present application;
fig. 2 is a waveform diagram of a probe beam and a reflected beam of an FMCW laser measuring device according to some embodiments of the present application;
fig. 3 is a schematic structural diagram of an FMCW laser measuring device according to some embodiments of the application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described in further detail below with reference to the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, the "plurality" generally includes at least two.
It should be understood that the term "and/or" as used herein is merely one relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.
It should be understood that although the terms first, second, third, etc. may be used in embodiments of the present application, these should not be limited to these terms. These terms are only used to distinguish one from another. For example, a first may also be referred to as a second, and similarly, a second may also be referred to as a first, without departing from the scope of embodiments of the application.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a product or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such product or apparatus. Without further limitation, an element defined by the phrase "comprising" does not exclude the presence of other like elements in a commodity or device comprising such element.
In the art, the laser radar mainly comprises the following two technical routes based on a ranging mode: toF (Time of Flight) and FMCW (Frequency-Modulated Continuous Wave, frequency modulated continuous wave). The distance measurement principle of the ToF is that the distance is measured by multiplying the time of flight of a light pulse between a target object and a laser radar by the speed of light, and the ToF laser radar adopts a pulse amplitude modulation technology. Unlike the ToF route, FMCW mainly interferes return light and local light by transmitting and receiving a continuous laser beam, measures the frequency difference between transmission and reception by using a mixing detection technique, and converts the distance of a target object by the frequency difference. Briefly, toF uses time to measure distance, while FMCW uses frequency to measure distance. FMCW has the following advantages over ToF: light waves of ToF are easy to be interfered by ambient light, and light waves of FMCW have strong interference resistance; the signal-to-noise ratio of ToF is too low, while the signal-to-noise ratio of FMCW is high, the speed dimension data of ToF is low in quality, and FMCW can acquire the speed dimension data of each pixel point.
In the related art, the accuracy of the detection distance and the detection speed of the FMCW laser measuring device is related to the linearity of the linear sweep laser output by the FMCW laser measuring device, and the linear sweep laser output by the FMCW laser measuring device is required to have good frequency modulation linearity and beat frequency stability of the FMCW laser measuring device. However, the laser light source directly carries out frequency modulation processing, and linear sweep frequency laser obtained without feedback control has flaws, and the frequency modulation linearity of the linear sweep frequency laser has larger errors, so that the beat frequency stability of the FMCW laser measuring device is poor, and the detection distance and the detection speed result are inaccurate.
The present application provides an FMCW laser measuring device comprising: a laser light source configured to emit a linear swept laser; the beam splitter receives the linear sweep laser and splits the linear sweep laser into detection sweep laser and reference sweep laser, wherein the detection sweep laser and the reference sweep laser are respectively used for detecting a target object and controlling the laser source in a feedback manner; the reference light path channel is used for performing delay beat frequency operation on the reference sweep frequency laser to output beat frequency signals, and the feedback circuit is used for receiving the beat frequency signals and outputting feedback signals, wherein the feedback signals are configured to adjust the output of the laser light source in real time so as to ensure the frequency modulation linearity of the linear sweep frequency of the laser light source and the beat frequency stability of the FMCW laser measuring device.
According to the scheme, the linear sweep frequency laser output by the laser light source is monitored in real time through the reference light path channel, the feedback signal for adjusting the laser light source in real time is determined through the feedback circuit, the feedback signal is configured to adjust the output of the laser light source in real time, and the frequency modulation linearity of the linear sweep frequency of the laser light source and the beat frequency stability of the FMCW laser measuring device are guaranteed.
Alternative embodiments of the present application will be described in detail below with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of an FMCW laser measuring device according to some embodiments of the application.
As shown in fig. 1, some embodiments of the present application provide an FMCW laser measuring device 100, the FMCW laser measuring device 100 including: a laser source 10, a beam splitter 20, a reference optical path channel 30, and a feedback circuit 50.
The laser light source 10 is configured to emit a linearly swept laser, which is driven, for example, with a drive circuit that outputs a frequency modulated drive signal, which the laser light source 10 receives to emit the linearly swept laser. The laser light source 10 is, for example, a solid-state laser, a semiconductor laser, or the like, and specifically may be a distributed feedback laser (DFB), a Vertical Cavity Surface Emitting Laser (VCSEL), an external cavity laser, or the like. The beam splitter 20 receives the linear sweep laser and splits the linear sweep laser into a detection sweep laser and a reference sweep laser, which are used to detect the target T and monitor the sweep state of the laser source, respectively. The beam splitter 20 is, for example, a 1×2 beam splitter, and splits the linear sweep laser into two identical beams of laser light, that is, the wavelength, phase, and frequency modulation of the detection sweep laser light and the reference sweep laser light are identical.
The reference optical path channel 30 receives the reference swept laser, delays the reference swept laser, and outputs a beat signal, such as a voltage signal of a certain frequency. The feedback circuit 50 receives the beat signal and outputs a feedback signal configured to adjust the output of the laser source 10 in real time, ensuring the frequency modulation linearity of the laser source linear sweep and the beat stability of the FMCW laser measurement device.
The linear sweep frequency laser output by the laser light source is monitored in real time through the reference light path channel, a feedback signal for adjusting the laser light source in real time is determined through the feedback circuit, and the feedback signal is configured to adjust the output of the laser light source in real time, so that the frequency modulation linearity of the linear sweep frequency of the laser light source and the beat frequency stability of the FMCW laser measuring device are ensured.
In some embodiments, as shown in fig. 1, the reference optical path 30 includes a first beam splitter 31, a delay device 32, a first mixer 33, and a first detection device 34. The first beam splitter 31 receives the reference sweep laser light and splits it into a first reference sweep laser light and a second reference sweep laser light. The first beam splitter 31 is, for example, a 1×2 beam splitter, and splits the reference swept laser beam into two identical laser beams, that is, the first reference swept laser beam and the second reference swept laser beam have identical wavelength, phase, and frequency modulation.
The delay device 32 receives the first reference sweep laser such that the first reference sweep laser is transmitted a length such that the first reference sweep laser is delayed for a predetermined time. The first mixer 33 receives the delayed first reference sweep laser and the second reference sweep laser, and mixes the delayed first reference sweep laser and the second reference sweep laser to output a reference mixed beam, i.e., a reference beat beam. The first detecting device 34 receives and detects the reference mixed light beam, obtains a beat signal and outputs the beat signal, and the beat signal output by the first detecting device 34 is an electrical signal. The beat frequency signal is, for example, a frequency signal, and because the frequency modulation linearity of the linear sweep frequency laser output by the FMCW laser measuring device has deviation, noise exists in the actually obtained beat frequency signal compared with an ideal beat frequency signal, and the beat frequency stability of the FMCW laser measuring device is affected. In some embodiments, the first mixer 33 is, for example, a 2x2 coupler, a 90 degree mixer, and the first detection device 34 is, for example, a photodetector, a balanced detector, or the like.
In some embodiments, as shown in fig. 1, the feedback circuit 50 includes: a reference frequency source 51, a phase detector 52 and a negative feedback unit 53. The reference frequency source 51 is configured to output a reference frequency signal, and the reference frequency source 51 adopts a circuit structure, and the generated reference frequency signal may be a specific frequency signal which is accurate and constant, and the reference frequency signal is, for example, the ideal beat frequency signal, and has specific frequency and amplitude characteristics which are accurate and constant. The phase detector 52 receives the reference frequency signal and the beat frequency signal, performs a phase discrimination operation on the reference frequency signal and the beat frequency signal, outputs a signal indicating a phase difference, and the negative feedback unit is configured to output the feedback signal according to the phase difference signal. The phase discrimination operation can extract noise existing in the beat frequency signal obtained in practice, and further obtain a feedback signal according to the phase difference signal to regulate the output of the laser light source 10 in real time.
In some embodiments, the reference frequency signal has a stable frequencyI.e. the ideal frequency. The delay means 32 comprises an optical fiber or waveguide having a predetermined length L, where "/" indicates and/or, i.e. the delay means 32 may employ both an optical fiber and a waveguide, and may employ both an optical fiber and a waveguide, the stable frequency f r The following formula is satisfied:
wherein t is c F is one half of the sweep measurement period c L table for sweep frequency bandwidthShowing a predetermined length of the optical fiber or waveguide, C 0 Indicating the speed of light and n indicating the refractive index of the fiber or waveguide.
That is, after the length L of the optical fiber or waveguide serving as the delay means is determined, the frequency f is stabilized r I.e. to correspondingly determine, based on which reference frequency source 51 is designed to output a stable frequency f that is stable r 。
In some embodiments, as shown in fig. 1, the FMCW laser measuring device further includes a driving device 60. The driving device 60 is electrically connected to the laser light source 10 and the feedback circuit 50, and is configured to receive the feedback signal and output a feedback driving signal to the laser light source 10, so as to ensure the frequency modulation linearity of the linear sweep of the laser light source and the beat frequency stability of the FMCW laser measuring device.
In some embodiments, the driving device 60 includes a driving unit 61 and a superimposing unit 62, where the driving unit 61 generates a frequency modulation driving signal based on the frequency modulation amplitude and slope. The superimposing unit 62 receives the frequency modulation driving signal and the feedback signal, and superimposes the two signals to generate and output the feedback driving signal.
The device is arranged in such a way, the laser source is driven to output linear sweep frequency laser through the frequency modulation driving signal, the linear sweep frequency laser output by the laser source is monitored in real time through the reference light path channel, the feedback signal for adjusting the laser source in real time is determined through the feedback circuit, the feedback signal is overlapped with the frequency modulation driving signal to generate the feedback driving signal, the feedback driving signal is used for adjusting the output of the laser source in real time, and the frequency modulation linearity of the linear sweep frequency of the laser source and the beat frequency stability of the FMCW laser measuring device are guaranteed.
In some embodiments, as shown in fig. 1, the FMCW laser measuring device further includes a transmission probe channel 40.
The transmission detection channel 40 receives the detection swept laser light, the transmission detection channel having a light emitting/receiving unit configured to emit a detection beam that is reflected upon encountering a target object T to produce a reflected beam, the light emitting/receiving unit further configured to receive the reflected beam, the detection beam being at least a portion of the detection swept laser light, the laser radar 100 determining the target object from the reflected beam.
In some embodiments, the transmission detection channel 40 includes a second beam splitter 41, a second mixer 43, and a second detection device 44. The second beam splitter 41 is configured to split the detection swept laser into the detection beam and the local oscillation beam, and the second beam splitter 41 is, for example, a 1×2 beam splitter, and splits the detection swept laser into two identical beams of laser light, that is, the wavelength, phase, and frequency modulation of the detection beam and the local oscillation beam are identical.
The second mixer 43 is configured to receive the local oscillation beam and the reflected beam and to mix the local oscillation beam and the reflected beam to obtain a detection mixed beam, i.e. a detection beat frequency beam. The second detection means 44 receives and detects the detection mixed beam and outputs the detection signal. In some embodiments, the second mixer 43 is, for example, a 2x2 coupler, a 90 degree mixer, and the second detection device 44 is, for example, a photodetector, a balanced detector, or the like.
In some embodiments, the transmission detection channel 40 further includes an optical multiplexer 42, which is disposed after the second beam splitter 41 and may serve as an optical transmitting/receiving unit, and the optical multiplexer 42 is used to transmit the detection beam and the reflected beam. Specifically, the optical multiplexer 42 receives the probe beam from the second beam splitter 41, and emits the probe beam, so as to emit the probe beam, the probe beam is reflected respectively after encountering the object to generate reflected beams, the reflected beams are received by the optical multiplexer 42, and the optical multiplexer 42 transmits the reflected beams to the second mixer 43 to mix with the local oscillation beam. In some embodiments, optical multiplexer 42 is, for example, a Polarizing Beam Splitter (PBS), a coupler, a beam splitter, a circulator, and the like.
In some embodiments, as shown in fig. 1, the FMCW laser measuring device further includes an acquisition processing device 80, and the acquisition processing device 80 receives the detection signal from the second detection device 44, acquires and processes the detection signal, and determines the distance and speed of the detected object.
In some embodiments, as shown in fig. 1, the acquisition processing device 80 includes an analog-to-digital conversion module 81 and a signal processing module 82, where the analog-to-digital conversion module 81 is, for example, an analog-to-digital converter, which receives the detection signal from the second detection device 44, and the detection signal is an analog signal, the analog-to-digital conversion module 81 converts the detection signal that is the analog signal into a digital signal, and the signal processing module 82 is connected to the analog-to-digital conversion module 81, receives the digital signal from the analog-to-digital conversion module 81, and processes the digital signal to determine the distance and the speed of the detected object. In some embodiments, the signal processing module 82 is, for example, a Field Programmable Gate Array (FPGA), digital Signal Processing (DSP), or the like.
Fig. 2 is a waveform diagram of a probe beam and a reflected beam of an FMCW laser measuring device according to some embodiments of the application. As shown in fig. 2, the swept optical signal of the probe beam emitted by the FMCW laser measuring device is represented by a solid line, which represents a curve of the frequency of the outgoing beam over time, and the swept optical signal is, for example, a periodic triangular wave signal. The reflected light signal of the reflected light beam received by the FMCW laser measuring device is represented by a dashed line, the dashed line represents a curve of the frequency of the received reflected light beam changing with time, and the reflected light signal is also, for example, a periodic triangular wave signal, and there is a time delay between the periodic triangular wave signal and the sweep light signal.
The waveforms of the probe beam and the reflected beam shown in fig. 2 are ideal linear sweep waves, whereas in the embodiment of the application, the linear sweep laser output by the laser source is monitored in real time through the reference light path channel, and the feedback signal for adjusting the laser source in real time is determined through the feedback circuit, and the feedback signal is configured to adjust the output of the laser source in real time, so that the frequency modulation linearity of the linear sweep of the laser source and the beat frequency stability of the FMCW laser measuring device can be ensured, and the probe beam output by the FMCW laser measuring device adopting the embodiment of the application can be very close to the ideal state shown in fig. 2. Only three sweep measurement periods are shown in fig. 2, in each of which the swept optical signal includes an up-conversion stage and a down-conversion stage, and correspondingly, the corresponding reflected optical signal also includes an up-conversion stage and a down-conversion stage. And one measuring point corresponds to each sweep frequency measuring period.
As shown in fig. 2, the abscissa indicates time in μs and the ordinate indicates frequency in GHz, and the frequency of the probe beam increases from 0 to 4GHz and then decreases from 4GHz to 0, for example, over time, so as to periodically vary, and correspondingly, the frequency of the received reflected beam also increases from 0 to 4GHz and then decreases from 4GHz to 0, for example, over time.
For any one measurement point, the distance R of the target object measured by the FMCW laser measuring device satisfies the following relationship:wherein t is c F is one half of the sweep measurement period c For sweeping the bandwidth, f b1 For the up-beat frequency of the up-beat stage, f b2 For the down-conversion beat frequency of the down-conversion stage, C 0 Is the speed of light.
For any one measurement point, the velocity v of the target object measured by the FMCW laser measuring device satisfies the following relationship:wherein C is 0 Is the speed of light, f b1 For the up-beat frequency of the up-beat stage, f b2 For the down-conversion beat frequency of the down-conversion stage, f 0 Is the frequency of the light source.
In some embodiments, as shown in fig. 1, the lidar 100 further comprises: and a lens assembly L. A lens assembly L is disposed between the light emitting/receiving unit and the target T, and is configured to collimate the probe beam emitted from the light emitting/receiving unit and focus the reflected beam to couple into the light emitting/receiving unit. The lens assembly L may be a lens or a lens group.
In some embodiments, components within the wire-pitch spacer frame in fig. 1 may be integrated on a silicon optical chip, for example, the beam splitter 20, the first beam splitter 31, the delay device 32, the first mixer 33, the second beam splitter 41, the optical path multiplexer 42, and the second mixer 43 may be formed on the silicon optical chip, and the detection channel and the reference optical path channel are implemented by means of chips, so that the size of the FMCW laser measuring device as a whole is reduced. In other embodiments, at least one of the first detection device 34, the second detection device 44, and the laser light source 10 may also be integrated on a silicon photo chip.
Fig. 3 is a schematic structural diagram of an FMCW laser measuring device according to some embodiments of the application. The embodiment shown in fig. 3 is substantially the same as the embodiment shown in fig. 1, and the same points are not described herein, and only the differences between the two are described below.
In some embodiments, as shown in fig. 3, the lidar 100 further includes a first amplifier 71 disposed between the reference light path 30 and the feedback circuit 50, and configured to amplify the beat signal output by the first detection device 34, and input the amplified signal to the feedback circuit 50 for processing, so as to avoid feedback errors caused by weak beat signals.
In some embodiments, as shown in fig. 3, the lidar 100 further includes a second amplifier 72 disposed between the transmission detection channel 40 and the acquisition processing device 80, and configured to amplify the detection signal output by the second detection device 44, and input the amplified signal to the acquisition processing device 80 for processing, so as to avoid measurement errors caused by weak detection signals.
In the description, each part is described in a parallel and progressive mode, and each part is mainly described as a difference with other parts, and all parts are identical and similar to each other.
The features described in the various embodiments of the present disclosure may be interchanged or combined with one another in the description to enable those skilled in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Finally, it should be noted that: in the present specification, each embodiment is described by way of example, and each embodiment is mainly described in a different manner from other embodiments, so that identical and similar parts between the embodiments are all mutually referred to. The system or the device disclosed in the embodiments are relatively simple in description, and the relevant points refer to the description of the method section because the system or the device corresponds to the method disclosed in the embodiments.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (10)
1. An FMCW laser measuring device, comprising:
a laser light source configured to emit a linear swept laser;
the beam splitter receives the linear sweep laser and splits the linear sweep laser into detection sweep laser and reference sweep laser, wherein the detection sweep laser and the reference sweep laser are respectively used for detecting a target object and monitoring the sweep state of the laser source;
a reference light path channel for delaying the reference sweep frequency laser and outputting beat frequency signals,
and the feedback circuit is used for receiving the beat frequency signal and outputting a feedback signal, and the feedback signal is configured to adjust the output of the laser light source in real time so as to ensure the frequency modulation linearity of the linear sweep frequency of the laser light source and the beat frequency stability of the FMCW laser measuring device.
2. The FMCW laser measuring device of claim 1, wherein the reference optical path channel includes:
the first beam splitter is configured to split the reference sweep frequency laser into a first reference sweep frequency laser and a second reference sweep frequency laser;
a delay device for receiving the first reference sweep laser so that the first reference sweep laser is transmitted for a certain length to delay a predetermined time;
a first mixer for mixing the delayed first and second reference sweep lasers and outputting a reference mixed beam; and
and the first detection device receives the reference mixed light beam and outputs the beat frequency signal.
3. The FMCW laser measuring device of claim 2, wherein the feedback circuit includes:
a reference frequency source configured to output a reference frequency signal;
a phase discriminator configured to receive the reference frequency signal and the beat frequency signal and perform a phase discriminating operation on the reference frequency signal and the beat frequency signal to output a signal indicative of a phase difference;
and the negative feedback unit is configured to output the feedback signal according to the phase difference signal.
4. A FMCW laser measuring device according to claim 3, wherein the reference frequency signal has a stable frequency f r ，
The delay means comprises an optical fiber or waveguide having a predetermined length, the stable frequency f r
The following formula is satisfied:wherein t is c F is one half of the sweep measurement period c For swept bandwidth, L represents a predetermined length of the fiber or waveguide, C 0 Indicating the speed of light and n indicating the refractive index of the fiber or waveguide.
5. The FMCW laser measuring device according to any one of claims 1 to 4, wherein the FMCW laser measuring device further includes:
the driving device is electrically connected with the laser light source and the feedback circuit, and is configured to receive the feedback signal and output a feedback driving signal to the laser light source, so that the frequency modulation linearity of the linear sweep of the laser light source and the beat frequency stability of the FMCW laser measuring device are ensured.
6. The FMCW laser measuring device of claim 5, wherein the driving device includes:
a driving unit for generating a frequency modulation driving signal; and
and the superposition unit is used for receiving the frequency modulation driving signal and the feedback signal and outputting the feedback driving signal.
7. The FMCW laser measuring device according to any one of claims 1 to 4, wherein the FMCW laser measuring device further includes:
a transmission detection channel configured to receive the detection swept laser light, the transmission detection channel having a light emitting/receiving unit configured to emit a detection beam that is reflected upon encountering a target to produce a reflected beam, the light emitting/receiving unit further configured to receive the reflected beam, the detection beam being at least a portion of the detection swept laser light,
the FMCW laser measuring device is used for measuring the target object according to the reflected light beam.
8. The FMCW laser measuring device of claim 7, wherein the transmission probe channel further includes:
the second beam splitter is configured to split the detection sweep frequency laser into the detection beam and the local oscillation beam;
the second mixer is configured to receive the local oscillation light beam and the reflected light beam, and mix the local oscillation light beam and the reflected light beam to obtain a detection mixed light beam; and
and the second detection device is used for receiving and detecting the detection mixed light beam and outputting a detection signal.
9. The FMCW laser measuring device according to claim 8, wherein a distance R and a velocity v of the target object measured by the FMCW laser measuring device satisfy the following relations, respectively:wherein t is c F is one half of the sweep measurement period c For sweeping the bandwidth, f b1 For the up-beat frequency of the up-beat stage, f b2 For the down-conversion beat frequency of the down-conversion stage, C 0 Is the speed of light, f 0 Is the frequency of the light source.
10. The FMCW laser measuring device of claim 7, wherein the FMCW laser measuring device further includes:
and a lens assembly disposed between the light emitting/receiving unit and the target object, configured to perform collimation of a probe beam emitted from the light emitting/receiving unit, and perform focusing of the reflected beam to couple into the light emitting/receiving unit.
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