CN115469324A - Laser radar and laser ranging method - Google Patents
Laser radar and laser ranging method Download PDFInfo
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- CN115469324A CN115469324A CN202211246722.6A CN202211246722A CN115469324A CN 115469324 A CN115469324 A CN 115469324A CN 202211246722 A CN202211246722 A CN 202211246722A CN 115469324 A CN115469324 A CN 115469324A
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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
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The embodiment of the invention provides a laser radar and a laser ranging method, which relate to the technical field of laser radars, wherein the laser radar is applied to target detection in a fog environment and comprises the following steps: a laser module and a distance measuring module; the laser module generates and emits a picosecond level Gaussian pulse sequence and a nanosecond level Gaussian pulse sequence, wherein the wavelength of the picosecond level Gaussian pulse sequence is different from that of the nanosecond level Gaussian pulse sequence; and the distance measurement module filters the received reflection signal based on the wavelength of the nanosecond high-speed Gaussian pulse sequence to obtain a target reflection signal of the nanosecond high-speed Gaussian pulse sequence, and measures distance according to the target reflection signal. The invention prolongs the detection distance of the laser radar in the fog.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a laser radar and a laser ranging method.
Background
The laser radar is a radar system for detecting characteristic quantities such as position, speed and the like of a target by emitting a laser beam, and the working principle of the radar system is to emit a detection signal (laser beam) to the target, then compare and process a received signal (target echo) reflected from the target with the emission signal to obtain relevant information of the target, such as parameters of distance, direction, height, speed, attitude, even shape and the like of the target, so as to realize detection, tracking, identification and the like of the target. LiDAR (Light Detection and Ranging) is a short name of a laser Detection and Ranging system, and is a laser radar system integrating three technologies of laser, a global positioning system and an inertial navigation system.
The propagation distance of the Laser light pulse in the air is related to water drops absorbed and scattered by the Laser light pulse in the air, so that the Laser light pulse generated from a VCSEL (Vertical-Cavity Surface-Emitting Laser) unit and an array on the LiDAR system is obviously attenuated under severe weather conditions such as fog, snow and rain, the detection range of the LiDAR system under severe weather conditions such as fog, snow and rain is greatly reduced, and the ideal detection distance cannot be reached.
Therefore, there is a need for a method that can extend the detection range of a LiDAR system in harsh weather conditions, such as fog, snow, and rain.
Disclosure of Invention
The embodiment of the invention aims to provide a laser radar and a laser ranging method, so as to prolong the detection distance of the laser radar in fog. The specific technical scheme is as follows:
in a first aspect, an embodiment of the present invention provides a lidar, where the lidar is applied to target detection in a fog environment, and includes: a laser module and a distance measuring module;
the laser module is used for generating and emitting a picosecond level Gaussian pulse sequence and a nanosecond level Gaussian pulse sequence, wherein the wavelength of the picosecond level Gaussian pulse sequence is different from that of the nanosecond level Gaussian pulse sequence;
and the distance measurement module is used for filtering the received reflection signal based on the wavelength of the nanosecond level Gaussian pulse sequence to obtain a target reflection signal of the nanosecond level Gaussian pulse sequence and measuring distance according to the target reflection signal.
In one possible embodiment, the laser module includes a controlled sub-module, a first pulse sequence generation and control circuit, a first laser firing unit and array, a second pulse sequence generation and control circuit, and a second laser firing unit and array;
the controlled submodule is used for triggering and controlling the first pulse sequence generating and controlling circuit and the second pulse sequence generating and controlling circuit in each control cycle, and sequentially outputting the picosecond-level Gaussian pulse sequence and the nanosecond-level Gaussian pulse sequence;
the first pulse sequence generating and controlling circuit is used for generating a picosecond-level Gaussian pulse sequence, triggering the first laser emitting unit and the array and outputting the picosecond-level Gaussian pulse sequence;
the first laser emission unit and the array are used for outputting the picosecond-level Gaussian pulse sequence;
the second pulse sequence generation and control circuit is used for generating a nanosecond Gaussian pulse sequence, triggering the second laser emission unit and the array and outputting the nanosecond Gaussian pulse sequence;
and the second laser emission unit and the array are used for outputting the nanosecond Gaussian pulse sequence.
In a possible implementation, the first pulse sequence generating and controlling circuit is specifically configured to: generating a picosecond-level Gaussian pulse sequence at a preset frequency, triggering the first laser emission unit and the array, and outputting a Gaussian pulse sequence with a wavelength of 1030 nanometers;
the second pulse sequence generation and control circuit is specifically configured to: and generating a nanosecond Gaussian pulse sequence, triggering the second laser emission unit and the array, and outputting a 905/940 nanometer wavelength Gaussian pulse sequence.
In one possible embodiment, the time interval between the end of the picosecond Gaussian pulse sequence and the start of the nanosecond Gaussian pulse sequence is determined by the distance per second at which water droplets or water molecules are blown out of the air and the wind speed in the air.
In one possible embodiment, the width of a single picosecond gaussian laser light pulse in the picosecond gaussian pulse sequence is 1-1.2 picoseconds, and the width of a single nanosecond gaussian laser light pulse in the nanosecond gaussian pulse sequence is 10 nanoseconds.
In a possible embodiment, the laser module is specifically configured to:
generating and emitting a picosecond Gaussian pulse sequence and a nanosecond Gaussian pulse sequence in a foggy day mode;
in the normal mode, nanosecond-level gaussian pulse sequences are generated and transmitted.
In one possible embodiment, the ranging module comprises: the optical filter, the photoelectric detector and the signal processing submodule;
the optical filter is used for filtering out all visible light and picosecond Gaussian laser light pulses in the reflected signals transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence to obtain target reflected signals of the nanosecond Gaussian pulse sequence;
the photoelectric detector is used for receiving the target reflection signal, converting photons of the target reflection signal into an electric signal and transmitting the electric signal to the signal processing submodule;
and the signal processing submodule is used for receiving and processing the electric signal and determining the distance between the laser radar and the target object.
In one possible implementation, the optical filter includes: a first optical filter and a second optical filter;
the first optical filter is used for filtering out all visible light transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence;
and the second optical filter is used for filtering out all picosecond Gaussian laser light pulses transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence.
In a second aspect, an embodiment of the present invention provides a laser ranging method, where the method is applied to a laser radar, where the laser radar is applied to target detection in a fog environment, and the laser radar includes: a laser module and a ranging module, the method comprising:
the laser module generates and emits a picosecond-level Gaussian pulse sequence and a nanosecond-level Gaussian pulse sequence, wherein the wavelength of the picosecond-level Gaussian pulse sequence is different from that of the nanosecond-level Gaussian pulse sequence;
and the distance measurement module filters the received reflection signal based on the wavelength of the nanosecond high-speed Gaussian pulse sequence to obtain a target reflection signal of the nanosecond high-speed Gaussian pulse sequence, and measures distance according to the target reflection signal.
In one possible embodiment, the laser module includes a controlled sub-module, a first pulse sequence generation and control circuit, a first laser emission unit and array, a second pulse sequence generation and control circuit, and a second laser emission unit and array; the ranging module includes: the system comprises an optical filter, a photoelectric detector and a signal processing submodule;
the laser module generates and emits picosecond stage Gaussian pulse sequence and nanosecond stage Gaussian pulse sequence, and comprises:
the controlled submodule triggers and controls the first pulse sequence generation and control circuit and the second pulse sequence generation and control circuit in each control cycle, and the picosecond-level Gaussian pulse sequence and the nanosecond-level Gaussian pulse sequence are sequentially output;
the first pulse sequence generation and control circuit generates a picosecond-level Gaussian pulse sequence, triggers the first laser emission unit and the array and outputs the picosecond-level Gaussian pulse sequence;
the first laser emission unit and the array output the picosecond-level Gaussian pulse sequence;
the second pulse sequence generation and control circuit generates a nanosecond Gaussian pulse sequence, triggers the second laser emission unit and the second laser emission array and outputs the nanosecond Gaussian pulse sequence;
the second laser emission unit and the array output the nanosecond Gaussian pulse sequence;
the distance measurement module filters the received reflected signal based on the wavelength of the nanosecond level Gaussian pulse sequence to obtain a target reflected signal of the nanosecond level Gaussian pulse sequence, and measures distance according to the target reflected signal, and the distance measurement module comprises:
the optical filter filters out all visible light and picosecond Gaussian laser light pulses in a reflected signal transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence to obtain a target reflected signal of the nanosecond Gaussian pulse sequence;
the photoelectric detector receives the target reflection signal, converts photons of the target reflection signal into an electric signal and transmits the electric signal to the signal processing submodule;
and the signal processing submodule receives and processes the electric signal and determines the distance between the laser radar and the target object.
The embodiment of the invention has the following beneficial effects:
according to the laser radar and the laser ranging method provided by the embodiment of the invention, the laser module generates and transmits the picosecond level Gaussian pulse sequence and the nanosecond level Gaussian pulse sequence, the wavelength of the picosecond level Gaussian pulse sequence is different from that of the nanosecond level Gaussian pulse sequence, the ranging module filters the received reflection signal based on the wavelength of the nanosecond level Gaussian pulse sequence to obtain a target reflection signal of the nanosecond level Gaussian pulse sequence, and ranging is carried out according to the target reflection signal. The picosecond Gaussian pulse sequence and the nanosecond Gaussian pulse sequence are generated and emitted by the laser module, and the picosecond Gaussian pulse can generate shock waves for the near-infrared Gaussian pulse to remove fog drops in air, so that water drops around the propagation direction are scattered, a path for the nanosecond Gaussian pulse to propagate to an object to be detected is formed, the nanosecond Gaussian pulse sequence can be further propagated, and the detection distance of the laser radar in fog is further prolonged.
Of course, not all of the advantages described above need to be achieved at the same time in the practice of any one product or method of the invention.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other embodiments can be obtained by those skilled in the art according to the drawings.
Fig. 1 is a schematic structural diagram of a laser radar according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of another lidar according to an embodiment of the present invention;
FIG. 3a is a schematic diagram of a laser pulse sequence according to an embodiment of the present invention;
FIG. 3b is a schematic diagram of another laser pulse sequence provided by an embodiment of the present invention;
fig. 4 is a schematic flowchart of a laser ranging method according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived from the embodiments given herein by one of ordinary skill in the art, are within the scope of the invention.
The distance traveled by a laser light pulse in air, in relation to water droplets absorbed and scattered by the laser light pulse in air, is statistically significantly attenuated by laser light pulses generated from VCSEL units and arrays on a LiDAR system under inclement weather conditions such as fog, snow, and rain, and is statistically detected to be less than 50% in fog than in non-fog. Therefore, under severe weather conditions such as fog, snow, and rain, a large number of laser light pulses cannot reach an ideal detection distance, and only a very small number of laser light pulses can reach a predetermined destination. Because of the existence of a large amount of water molecules under the severe weather conditions of fog, snow, rain and the like, when the water molecules enter the material pores of the detection object/barrier, the surface emissivity of the material of the detection object/barrier changes, so that when a small part of laser light pulse reaches the detection object/barrier and is reflected back to the laser radar, the reflected signal is further reduced, and the detection distance of the laser radar is further influenced.
In the related art, a 1550 nm wavelength laser light pulse is used in place of a 905 nm wavelength laser light pulse as a laser light pulse signal generated by transmitting LiDAR in fog. However, experiments have shown that while the 1550 nm wavelength laser light pulse has a propagation distance on a clear day that is about 120% longer than the 905 nm wavelength laser light pulse, the 1550 nm wavelength laser light pulse and the 905 nm wavelength laser light pulse both have propagation distances that decrease to a similar range in fog. Therefore, the 1550 nm laser source is used to replace the 905 nm laser source, which cannot effectively extend the detection distance of the LiDAR in the fog.
In addition, the location of the inspected object around the LiDAR can be calculated using FMCW (Frequency Modulated Continuous Wave) techniques by modulating the Frequency of the transmitted light Wave, estimating the reflected signal of the transmitted light Wave mixed with a local oscillator, and calculating the location of the inspected object. In this approach, although the distance of objects around the LiDAR can be detected, FMCW technology requires expensive and bulky lasers, which are costly.
In order to solve at least one of the above problems, embodiments of the present invention provide a laser radar and a laser ranging method, so as to extend a detection distance of the laser radar in a fog. The laser radar provided by the embodiment of the invention is applied to target detection in a fog environment, and comprises the following components: a laser module and a ranging module; the laser module is used for generating and emitting a picosecond-level Gaussian pulse sequence and a nanosecond-level Gaussian pulse sequence, the wavelengths of the picosecond-level Gaussian pulse sequence and the nanosecond-level Gaussian pulse sequence are different, and the ranging module is used for filtering received reflection signals based on the wavelength of the nanosecond-level Gaussian pulse sequence to obtain target reflection signals of the nanosecond-level Gaussian pulse sequence and ranging according to the target reflection signals.
According to the laser radar provided by the embodiment of the invention, the picosecond Gaussian pulse sequence and the nanosecond Gaussian pulse sequence are generated and emitted by the laser module, and the picosecond Gaussian pulse is a near-infrared Gaussian pulse and can generate shock waves to remove fog drops in air, so that water drops around the propagation direction are scattered, a path for the nanosecond Gaussian pulse to propagate to an object to be detected is formed, the attenuation rate of the nanosecond Gaussian pulse is reduced, the nanosecond Gaussian pulse sequence can be further propagated, the detection distance of the laser radar in fog is further prolonged, and expensive semiconductor elements are not required to be designed and integrated.
In an embodiment of the present invention, a laser radar is provided, where an application scenario of the laser radar is a foggy day mode, and the laser radar is applied to target detection in a foggy environment, as shown in fig. 1, a laser radar 100 includes: a laser module 110 and a ranging module 120.
The laser module 110 is configured to generate and emit a picosecond stage Gaussian pulse sequence and a nanosecond stage Gaussian pulse sequence, where the wavelengths of the picosecond stage Gaussian pulse sequence and the nanosecond stage Gaussian pulse sequence are different;
and the distance measurement module 120 is configured to filter the received reflection signal based on the wavelength of the nanosecond gaussian pulse sequence to obtain a target reflection signal of the nanosecond gaussian pulse sequence, and perform distance measurement according to the target reflection signal.
The LiDAR system of embodiments of the present invention may be a LiDAR system, the laser module 110 is a laser in the LiDAR system, and the ranging module 120 is a receiving system in the LiDAR system.
In one example, the laser module 110 sequentially generates and emits a picosecond Gaussian pulse sequence and a nanosecond Gaussian pulse sequence, wherein the picosecond Gaussian pulse sequence comprises at least one picosecond Gaussian laser light pulse, and the nanosecond Gaussian pulse sequence comprises at least one nanosecond Gaussian laser light pulse.
The picosecond Gaussian pulse sequence and the nanosecond Gaussian pulse sequence have different wavelengths, specifically, the wavelength of the picosecond Gaussian laser light pulse in the picosecond Gaussian pulse sequence is different from that of the nanosecond Gaussian laser light pulse in the nanosecond Gaussian pulse sequence, and preferably, the width of a single picosecond Gaussian laser light pulse in the picosecond Gaussian pulse sequence is different from that of a single nanosecond Gaussian laser light pulse in the nanosecond Gaussian pulse sequence.
The picosecond gaussian pulse sequence and the nanosecond gaussian pulse sequence emitted by the laser module 110 are reflected by the target object, which may be a detected object/obstacle, and the reflected signal is a reflected signal. The distance measurement module 120 receives the transmission signal, and filters the received reflection signal according to the wavelength of the nanosecond gaussian laser light pulse in the nanosecond gaussian pulse sequence to obtain a target reflection signal of the nanosecond gaussian pulse sequence, where the wavelength of the target reflection signal is the same as the wavelength of the nanosecond gaussian laser light pulse, and further, performs distance measurement on the target object according to the target reflection signal.
In one example, the distance measurement of the target object according to the target reflection signal may be performed by comparing the target reflection signal with the picosecond-level gaussian pulse sequence emitted by the laser module 110 and the nanosecond-level gaussian pulse sequence (i.e. the emission signal) in the nanosecond-level gaussian pulse sequence, determining a time increment between the emission signal and the target reflection signal, and calculating a half of a product of the time increment and the speed of light, so as to calculate the distance between the laser radar and the target object.
According to the laser radar provided by the embodiment of the invention, the picosecond Gaussian pulse sequence and the nanosecond Gaussian pulse sequence are generated and emitted by the laser module, and the picosecond Gaussian pulse is a near-infrared Gaussian pulse and can generate shock waves to remove fog drops in air, so that water drops around the propagation direction are scattered, a path for the nanosecond Gaussian pulse to propagate to an object to be detected is formed, the attenuation rate of the nanosecond Gaussian pulse is reduced, the nanosecond Gaussian pulse sequence can be further propagated, and the detection distance of a LiDAR system in fog is further prolonged.
In a possible embodiment, the laser module 110 is specifically configured to: generating and emitting a picosecond Gaussian pulse sequence and a nanosecond Gaussian pulse sequence in a foggy day mode; in the normal mode, nanosecond-level gaussian pulse sequences are generated and transmitted.
The laser module 110 generates and emits a picosecond-level Gaussian pulse sequence and a nanosecond-level Gaussian pulse sequence in a foggy day mode, wherein the picosecond-level Gaussian pulse can generate shock waves for near-infrared Gaussian pulses to remove fog drops in air, so that water drops around the propagation direction are scattered, and a path for the nanosecond-level Gaussian pulses to propagate to an object to be detected is formed, so that the attenuation rate of the nanosecond-level Gaussian pulses is reduced, the nanosecond-level Gaussian pulse sequence can be further propagated, and the detection distance of the laser radar in the foggy day is prolonged. In the normal mode, the blocking of fog is reduced, and the laser module 110 generates and emits a nanosecond gaussian pulse sequence to perform long-distance detection.
In another embodiment of the present invention, a lidar is provided, as shown in fig. 2, with a laser module 110 including a controlled sub-module 111, a first pulse sequence generation and control circuit 112, a first lasing element and array 113, a second pulse sequence generation and control circuit 114, and a second lasing element and array 115.
The controlled submodule 111 is configured to trigger and control the first pulse sequence generating and controlling circuit 112 and the second pulse sequence generating and controlling circuit 114 in each control cycle, and sequentially output a picosecond-level gaussian pulse sequence and a nanosecond-level gaussian pulse sequence;
the first pulse sequence generating and controlling circuit 112 is used for generating a picosecond-level Gaussian pulse sequence, triggering the first laser emitting unit and the array 113 and outputting the picosecond-level Gaussian pulse sequence;
a first laser emitting unit and array 113 for outputting a picosecond Gaussian pulse sequence;
the second pulse sequence generating and controlling circuit 114 is used for generating a nanosecond Gaussian pulse sequence, triggering the second laser emitting unit and the array 115 and outputting the nanosecond Gaussian pulse sequence;
and a second laser emitting unit and an array 115 for outputting nanosecond-level Gaussian pulse sequences.
In one example, the chip of the laser module 110 may be a programmable, digitally controlled driver IC (Integrated Circuit) chip capable of continuously outputting picosecond gaussian laser pulses and nanosecond gaussian laser pulses in sequence. The chip contains a controlled sub-module 111, a first pulse sequence generation and control circuit 112, and a second pulse sequence generation and control circuit 114, and also integrates a laser emission unit and an array of two optical pulses with independent wavelengths: a first laser emission unit and array 113, and a second laser emission unit and array 115. The first pulse train generation and control circuit 112 and the second pulse train generation and control circuit 114 are each composed of an integrated circuit. The laser emitting unit and the array which integrate two light pulses with independent wavelengths eliminate the design of a complex integrated circuit for distinguishing picosecond laser light pulses from nanosecond laser light pulses at the same time.
The controlled sub-module 111 triggers and controls the first pulse sequence generating and controlling circuit 112 in each control cycle, so that the first pulse sequence generating and controlling circuit 112 generates a picosecond-level gaussian pulse sequence, triggers the first laser emitting unit and the array 113, and outputs the picosecond-level gaussian pulse sequence; and the controlled sub-module 111 triggers and controls the second pulse sequence generation and control circuit 114 in each control cycle, so that the second pulse sequence generation and control circuit 114 generates a nanosecond gaussian pulse sequence and triggers the second laser emission unit and the array 115 to output the nanosecond gaussian pulse sequence.
Preferably, the picosecond Gaussian pulse sequence is arranged in front of the nanosecond Gaussian pulse sequence, and the nanosecond Gaussian pulse sequence is arranged behind the nanosecond Gaussian pulse sequence, so that the picosecond Gaussian laser pulse generates shock waves to remove fog drops in the air, water drops around the propagation direction are scattered, a path for the nanosecond Gaussian laser pulse to propagate to the detected object is formed, the nanosecond Gaussian pulse sequence can propagate farther, and the detection distance of the laser radar in the fog is further prolonged.
In one possible embodiment, the first Laser Emitting unit and array 113 is a YAG VCSEL (Y3 Al5O12Vertical-Cavity Surface-Emitting Laser, YAG crystal-Vertical Cavity Surface-Emitting Laser) unit and array, and the second Laser Emitting unit and array 115 is a GaAs/InGaAs VCSEL (GaAs/InGaAs Vertical-Cavity Surface-Emitting Laser) unit and array.
In a possible implementation, the first pulse sequence generating and controlling circuit 112 is specifically configured to: generating a picosecond-level Gaussian pulse sequence at a preset frequency, triggering the first laser emission unit and the array 113, and outputting a Gaussian pulse sequence with a wavelength of 1030 nanometers;
the second pulse sequence generation and control circuit 114 is specifically configured to: and generating a nanosecond Gaussian pulse sequence, triggering a second laser emission unit and the array, and outputting a 905/940 nanometer wavelength Gaussian pulse sequence.
Preferably, the preset frequency is a repetition rate of 1000 hertz. Illustratively, the first pulse train generation and control circuitry 112 generates picosecond gaussian pulse trains at a repetition rate of 1000 hertz and triggers the YAG VCSEL unit and array to output a gaussian pulse train at a wavelength of 1030 nanometers, the YAG VCSEL unit and array being a discrete VCSEL that outputs pulses of light at a wavelength of 1030 nanometers. The second pulse train generation and control circuit 114 generates a nanosecond gaussian pulse train and triggers GaAs/InGaAs VCSEL cells and arrays to output a gaussian pulse train at 905/940 nm wavelength.
In one possible embodiment, the time interval between the end of the picosecond Gaussian pulse sequence and the start of the nanosecond Gaussian pulse sequence is determined by the distance per second at which water droplets or water molecules are blown out of the air and the wind speed in the air.
In order to enable shock waves generated by picosecond Gaussian laser light pulses of a picosecond Gaussian pulse sequence to clear fog drops in air, the time interval between the end of the picosecond Gaussian pulse sequence and the beginning of the nanosecond Gaussian pulse sequence needs to be less than the time for the water drops to diffuse back to a physical position before being blown away in fog.
Taking the example that the laser light pulse is transmitted in the fog, the average diffusion speed of water drops/water molecules in the fog is related to the wind speed in the fog, and the time interval between the end of the picosecond Gaussian pulse sequence and the start of the nanosecond Gaussian pulse sequence can be estimated by calculating the distance of the water drops or water molecules in the fog blown out per second and the ratio of the distance to the highest wind speed in the fog. One way, the average wind speed in the fog can be determined based on local historical data, depending on the geographic location and season of the year in which the fog is present, assuming that the fastest speed of the wind in the fog is about 4.89 meters per second (m/sec) in some common situation, experiments have shown that a 5 micron (um) radius water droplet is blown away from the original physical location an average distance of about 10 millimeters (mm) per second. Exemplary time intervals between the end of the picosecond Gaussian pulse sequence and the beginning of the nanosecond Gaussian pulse sequence are: Δ t1< = distance water droplets or water molecules are blown out per second in the mist/maximum wind speed in the mist, expressed as: Δ t1< =10 mm/(4.89 m/sec) =2msec (msec).
In other embodiments, the wind speed can also be detected in real time according to a preset sensor, so that the detection pulse is dynamically adjusted during the driving process.
Preferably, the time interval between the end of the nanosecond gaussian pulse sequence and the start of the picosecond gaussian pulse sequence may be the same as the time interval between the end of the picosecond gaussian pulse sequence and the start of the nanosecond gaussian pulse sequence.
In one possible embodiment, the width of a single picosecond gaussian laser light pulse in the picosecond gaussian pulse sequence is 1-1.2 picoseconds (1.2 psec), and the width of a single nanosecond gaussian laser light pulse in the nanosecond gaussian pulse sequence is 10 nanoseconds. The average energy per picosecond gaussian laser light pulse (1.2 psec) was about 100 megajoules.
In one possible embodiment, the time interval between two consecutive picosecond gaussian laser light pulses in a set of picosecond gaussian pulse sequences is determined according to the total time of the set of picosecond gaussian pulse sequences, the width of a single picosecond gaussian laser light pulse, and the number of picosecond gaussian laser light pulses in the set of picosecond gaussian pulse sequences.
In one example, the time interval Δ t2 between two consecutive picosecond gaussian laser light pulses in a set of picosecond gaussian pulse sequences can be expressed as: (total time of the set of picosecond gaussian pulse sequences-number of picosecond gaussian laser light pulses in the set of picosecond gaussian pulse sequences-width of a single picosecond gaussian laser light pulse)/(number of picosecond gaussian laser light pulses in the set of picosecond gaussian pulse sequences-1). For example, the total time of a set of picosecond gaussian pulse sequences is 30 milliseconds, the width of a single picosecond gaussian laser light pulse is 1.2 picoseconds, the number of picosecond gaussian laser light pulses in the set of picosecond gaussian pulse sequences is 30, and the time interval between two adjacent picosecond gaussian laser light pulses in the set of picosecond gaussian pulse sequences can be expressed as: Δ t2= (30 ms-30 x 1.2 ps)/(30-1).
Illustratively, the laser module 110 emits picosecond Gaussian pulse trains and portions of nanosecond Gaussian pulse trains as shown in FIG. 3 a. As shown in fig. 3b, the time interval between the end of the nanosecond gaussian pulse sequence and the start of the picosecond gaussian pulse sequence is Δ t1, the time interval between two adjacent picosecond gaussian laser light pulses in a set of picosecond gaussian pulse sequences is Δ t2, the width of a single nanosecond gaussian laser light pulse is w1, and the width of a single picosecond gaussian laser light pulse is w2.
After the first set of 30 consecutive picosecond gaussian laser light pulse transmissions, the scattering and interaction of the second set of nanosecond gaussian laser light pulses will be minimized, and therefore the nanosecond gaussian laser light pulses may propagate a longer distance in the fog.
In one possible implementation, as shown in fig. 2, the ranging module 120 includes: an optical filter 121, a photodetector 122, and a signal processing sub-module 123;
the optical filter 121 is configured to filter out all visible light and picosecond gaussian laser light pulses in a reflected signal transmitted to the photodetector 122 based on the wavelength of the nanosecond level gaussian pulse sequence to obtain a target reflected signal of the nanosecond level gaussian pulse sequence;
the photodetector 122 is configured to receive the target reflection signal, convert photons of the target reflection signal into an electrical signal, and transmit the electrical signal to the signal processing sub-module 123;
and the signal processing sub-module 123 is configured to receive and process the electrical signal, and determine a distance between the laser radar and the target object.
The optical filter 121 filters all visible light and picosecond gaussian laser light pulses in the reflected signal propagated to the photodetector 122 according to the wavelength of the nanosecond gaussian pulse sequence to obtain a target reflected signal of the nanosecond gaussian pulse sequence, so that the reflected signal propagated to the photodetector 122 is only the target reflected signal.
The photodetector 122 receives and detects the incoming target reflection signal, converts the photons of the target reflection signal with the wavelength of 905/940 nm into an electrical signal, and further transmits the converted electrical signal to the signal processing sub-module 123, so that the signal processing sub-module 123 can acquire the electrical signal corresponding to the photons of the wavelength of 905/940 nm of the laser module 110. Illustratively, the photodetector 122 may be a two-dimensional SPAD (Single Photon Avalanche photodiode) array, which is a photodetector Avalanche Diode with Single Photon detection capability, and is capable of detecting photons with wavelength of 905/940 nm of the target reflection signal and converting the photons with wavelength of 905/940 nm of the target reflection signal into an electrical signal.
Further, the signal processing sub-module 123 receives and processes the electrical signal to determine the distance between the lidar and the target object. For example, the signal processing sub-module 123 determines a time increment between the transmitted signal and the target reflected signal according to the receiving time of the target reflected signal in the electrical signal and the transmitting time of the picosecond-level gaussian pulse sequence transmitted by the laser module 110 and the nanosecond-level gaussian pulse sequence (i.e., the transmitted signal) in the nanosecond-level gaussian pulse sequence, and calculates a half of a product of the time increment and the speed of light, so as to calculate the distance between the laser radar and the target object.
In one possible implementation, the optical filter 121 includes: a first optical filter and a second optical filter;
a first optical filter for filtering out all visible light propagating towards the photodetector 122 based on the wavelength of the nanosecond-level gaussian pulse sequence;
a second optical filter for filtering out all picosecond gaussian laser light pulses propagating towards the photodetector 122 based on the wavelength of the nanosecond gaussian pulse train.
Illustratively, the first optical filter filters all visible light propagating towards the two-dimensional SPAD array according to the wavelength of the nanosecond gaussian pulse sequence, and the second optical filter filters all picosecond gaussian laser light pulses propagating towards the two-dimensional SPAD array according to the wavelength of the nanosecond gaussian pulse sequence to filter out all visible light and picosecond gaussian laser light pulses in the reflected signal propagating towards the two-dimensional SPAD array, so that only the 905/940 nanometer wavelength nanosecond gaussian laser light pulses pass through and propagate to the two-dimensional SPAD array.
According to the laser radar provided by the embodiment of the invention, the laser module can continuously generate and emit the picosecond-level Gaussian pulse sequence and the nanosecond-level Gaussian pulse sequence, the picosecond-level Gaussian pulse can generate shock waves for the near-infrared Gaussian pulse, fog drops in air are removed, water drops around the propagation direction are scattered, and a path for the nanosecond-level Gaussian pulse to propagate to the detected object is formed, so that the attenuation rate of the nanosecond-level Gaussian pulse is reduced, the nanosecond-level Gaussian pulse sequence can be further propagated, and the detection distance of the laser radar in fog is further prolonged.
The embodiment of the invention also provides a laser ranging method, which can be applied to the laser radar applied to target detection in a fog environment and comprises the following steps: laser module and range finding module. Referring to fig. 4, the method includes:
s401, a laser module generates and emits a picosecond stage Gaussian pulse sequence and a nanosecond stage Gaussian pulse sequence, wherein the wavelength of the picosecond stage Gaussian pulse sequence is different from that of the nanosecond stage Gaussian pulse sequence;
s402, the distance measurement module filters the received reflection signal based on the wavelength of the nanosecond Gaussian pulse sequence to obtain a target reflection signal of the nanosecond Gaussian pulse sequence, and measures distance according to the target reflection signal.
According to the laser ranging method provided by the embodiment of the invention, the laser module can continuously generate and emit the picosecond-level Gaussian pulse sequence and the nanosecond-level Gaussian pulse sequence, the picosecond-level Gaussian pulse is a near-infrared Gaussian pulse and can generate shock waves, fog drops in air are removed, water drops around the propagation direction are scattered, a path for the nanosecond-level Gaussian pulse to propagate to the detected object is formed, the attenuation rate of the nanosecond-level Gaussian pulse is reduced, the nanosecond-level Gaussian pulse sequence can be further propagated, and the detection distance of the laser radar in fog is further prolonged.
In one possible embodiment, the laser module comprises a controlled sub-module, a first pulse sequence generation and control circuit, a first laser emission unit and array, a second pulse sequence generation and control circuit, and a second laser emission unit and array; the ranging module includes: the system comprises an optical filter, a photoelectric detector and a signal processing submodule;
the laser module generates and emits a picosecond-level Gaussian pulse sequence and a nanosecond-level Gaussian pulse sequence, and comprises the following components:
the controlled submodule triggers and controls the first pulse sequence generation and control circuit and the second pulse sequence generation and control circuit in each control cycle, and outputs a picosecond stage Gaussian pulse sequence and a nanosecond stage Gaussian pulse sequence in sequence;
the first pulse sequence generation and control circuit generates a picosecond-level Gaussian pulse sequence, triggers the first laser emission unit and the array and outputs the picosecond-level Gaussian pulse sequence;
the first laser emission unit and the array output picosecond-level Gaussian pulse sequences;
the second pulse sequence generation and control circuit generates a nanosecond Gaussian pulse sequence, triggers the second laser emission unit and the second laser emission array and outputs the nanosecond Gaussian pulse sequence;
the second laser emission unit and the array output nanosecond Gaussian pulse sequences;
the above-mentioned range finding module filters the reflection signal received based on nanosecond level gaussian pulse sequence's wavelength, obtains nanosecond level gaussian pulse sequence's target reflection signal to carry out the range finding according to target reflection signal, include:
the optical filter filters out all visible light and picosecond Gaussian laser light pulses in the reflected signal transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence to obtain a target reflected signal of the nanosecond Gaussian pulse sequence;
the photoelectric detector receives the target reflection signal, converts photons of the target reflection signal into an electric signal and transmits the electric signal to the signal processing submodule;
and the signal processing sub-module receives and processes the electric signal to determine the distance between the laser radar and the target object.
In a possible embodiment, the first pulse sequence generating and controlling circuit generates a picosecond gaussian pulse sequence and triggers the first laser emitting unit and the array to output the picosecond gaussian pulse sequence, and the method includes:
the first pulse sequence generating and controlling circuit generates a picosecond-level Gaussian pulse sequence at a preset frequency, triggers the first laser emitting unit and the first laser emitting array and outputs a Gaussian pulse sequence with a wavelength of 1030 nanometers;
the second pulse sequence generation and control circuit generates a nanosecond Gaussian pulse sequence, triggers the second laser emission unit and the second laser emission array, and outputs the nanosecond Gaussian pulse sequence, and the nanosecond Gaussian pulse sequence generation and control circuit comprises:
the second pulse sequence generation and control circuit generates a nanosecond Gaussian pulse sequence, triggers the second laser emission unit and the second laser emission array and outputs a Gaussian pulse sequence with the wavelength of 905/940 nanometers.
In one possible embodiment, the time interval between the end of the picosecond Gaussian pulse sequence and the start of the nanosecond Gaussian pulse sequence is determined by the distance per second at which water droplets or water molecules are blown out of the air and the wind speed in the air.
In one possible embodiment, the width of a single picosecond gaussian laser light pulse in the picosecond gaussian pulse sequence is 1-1.2 picoseconds, and the width of a single nanosecond gaussian laser light pulse in the nanosecond gaussian pulse sequence is 10 nanoseconds.
In a possible embodiment, the laser module generates and emits picosecond and nanosecond high gaussian pulse sequences, and comprises:
the laser module generates and emits a picosecond stage Gaussian pulse sequence and a nanosecond stage Gaussian pulse sequence in a foggy day mode;
the laser module generates and emits nanosecond-level Gaussian pulse sequences in a normal mode.
In one possible embodiment, the optical filter includes: a first optical filter and a second optical filter;
the optical filter filters out all visible light and picosecond Gaussian laser light pulses in a reflected signal transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence, and comprises the following components:
the first optical filter filters out all visible light transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence;
the second optical filter filters out all picosecond Gaussian laser light pulses propagating towards the photodetector based on the wavelength of the nanosecond Gaussian pulse sequence.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, 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 process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, as for the method embodiment, since it is basically similar to the method embodiment, the description is simple, and the relevant points can be referred to the partial description of the method embodiment.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.
Claims (10)
1. A lidar for use in target detection in a foggy environment, comprising: a laser module and a ranging module;
the laser module is used for generating and emitting a picosecond level Gaussian pulse sequence and a nanosecond level Gaussian pulse sequence, wherein the wavelength of the picosecond level Gaussian pulse sequence is different from that of the nanosecond level Gaussian pulse sequence;
and the distance measurement module is used for filtering the received reflection signal based on the wavelength of the nanosecond level Gaussian pulse sequence to obtain a target reflection signal of the nanosecond level Gaussian pulse sequence and measuring distance according to the target reflection signal.
2. The lidar of claim 1, wherein the laser module comprises a controlled sub-module, a first pulse sequence generation and control circuit, a first lasing unit and array, a second pulse sequence generation and control circuit, and a second lasing unit and array;
the controlled submodule is used for triggering and controlling the first pulse sequence generating and controlling circuit and the second pulse sequence generating and controlling circuit in each control cycle, and sequentially outputting the picosecond-level Gaussian pulse sequence and the nanosecond-level Gaussian pulse sequence;
the first pulse sequence generating and controlling circuit is used for generating a picosecond Gaussian pulse sequence, triggering the first laser emitting unit and the array and outputting the picosecond Gaussian pulse sequence;
the first laser emission unit and the array are used for outputting the picosecond-level Gaussian pulse sequence;
the second pulse sequence generation and control circuit is used for generating a nanosecond Gaussian pulse sequence, triggering the second laser emission unit and the array and outputting the nanosecond Gaussian pulse sequence;
and the second laser emission unit and the array are used for outputting the nanosecond Gaussian pulse sequence.
3. Lidar according to claim 2,
the first pulse sequence generation and control circuit is specifically configured to: generating a picosecond-level Gaussian pulse sequence at a preset frequency, triggering the first laser emission unit and the array, and outputting a Gaussian pulse sequence with a wavelength of 1030 nanometers;
the second pulse sequence generation and control circuit is specifically configured to: and generating a nanosecond Gaussian pulse sequence, triggering the second laser emission unit and the array, and outputting a 905/940 nanometer wavelength Gaussian pulse sequence.
4. Lidar according to claim 2, wherein the time interval between the end of the picosecond gaussian pulse sequence and the start of the nanosecond gaussian pulse sequence is determined by the distance per second at which water droplets or water molecules are blown out of the air and the wind speed in the air.
5. The lidar of claim 2, wherein a width of a single picosecond gaussian laser light pulse in the picosecond gaussian pulse sequence is between 1 and 1.2 picoseconds, and wherein a width of a single nanosecond gaussian laser light pulse in the nanosecond gaussian pulse sequence is 10 nanoseconds.
6. Lidar according to claim 1, wherein the laser module is in particular configured for:
generating and emitting a picosecond Gaussian pulse sequence and a nanosecond Gaussian pulse sequence in a foggy day mode;
in the normal mode, nanosecond-level gaussian pulse sequences are generated and transmitted.
7. The lidar of claim 1, wherein the ranging module comprises: the optical filter, the photoelectric detector and the signal processing submodule;
the optical filter is used for filtering out all visible light and picosecond Gaussian laser light pulses in the reflected signals transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence to obtain target reflected signals of the nanosecond Gaussian pulse sequence;
the photoelectric detector is used for receiving the target reflection signal, converting photons of the target reflection signal into an electric signal and transmitting the electric signal to the signal processing submodule;
and the signal processing submodule is used for receiving and processing the electric signal and determining the distance between the laser radar and the target object.
8. The lidar of claim 7, wherein the optical filter comprises: a first optical filter and a second optical filter;
the first optical filter is used for filtering out all visible light transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence;
and the second optical filter is used for filtering out all picosecond Gaussian laser light pulses transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence.
9. A laser ranging method is characterized in that the method is applied to a laser radar, the laser radar is applied to target detection in a fog environment, and the laser radar comprises: a laser module and a ranging module, the method comprising:
the laser module generates and emits a picosecond-level Gaussian pulse sequence and a nanosecond-level Gaussian pulse sequence, wherein the wavelength of the picosecond-level Gaussian pulse sequence is different from that of the nanosecond-level Gaussian pulse sequence;
and the distance measurement module filters the received reflection signal based on the wavelength of the nanosecond high-speed Gaussian pulse sequence to obtain a target reflection signal of the nanosecond high-speed Gaussian pulse sequence, and measures distance according to the target reflection signal.
10. The method of claim 9, wherein the laser module comprises a controlled sub-module, a first pulse sequence generation and control circuit, a first laser firing unit and array, a second pulse sequence generation and control circuit, and a second laser firing unit and array; the ranging module includes: the system comprises an optical filter, a photoelectric detector and a signal processing submodule;
the laser module generates and emits a picosecond-level Gaussian pulse sequence and a nanosecond-level Gaussian pulse sequence, and comprises the following components:
the controlled submodule triggers and controls the first pulse sequence generating and controlling circuit and the second pulse sequence generating and controlling circuit in each control cycle, and the picosecond-level Gaussian pulse sequence and the nanosecond-level Gaussian pulse sequence are sequentially output;
the first pulse sequence generating and controlling circuit generates a picosecond-level Gaussian pulse sequence, triggers the first laser emitting unit and the first laser emitting array and outputs the picosecond-level Gaussian pulse sequence;
the first laser emission unit and the array output the picosecond Gaussian pulse sequence;
the second pulse sequence generating and controlling circuit generates a nanosecond Gaussian pulse sequence, triggers the second laser emitting unit and the second laser emitting array and outputs the nanosecond Gaussian pulse sequence;
the second laser emission unit and the array output the nanosecond Gaussian pulse sequence;
the distance measurement module filters the received reflection signal based on the wavelength of the nanosecond level Gaussian pulse sequence to obtain a target reflection signal of the nanosecond level Gaussian pulse sequence, and measures distance according to the target reflection signal, and the distance measurement module comprises:
the optical filter filters out all visible light and picosecond Gaussian laser light pulses in the reflected signal transmitted to the photoelectric detector based on the wavelength of the nanosecond Gaussian pulse sequence to obtain a target reflected signal of the nanosecond Gaussian pulse sequence;
the photoelectric detector receives the target reflection signal, converts photons of the target reflection signal into an electric signal and transmits the electric signal to the signal processing submodule;
and the signal processing submodule receives and processes the electric signal and determines the distance between the laser radar and the target object.
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