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Joking about lidar, is the useless theory true?

2022-01-26 23:24:46 EV horizon

【EV Horizon technology analysis 】“ Fools use lidar ! It's as useless as a pile of appendixes on a person !”

one day ,“ Iron man ” Musk said something like this :

When he said this publicly , What we know The field of automatic driving is divided into visual camera school and lidar school . Of course , Not to mention whether Musk's lidar uselessness theory is accurate , However, lidar has indeed become the focus of the development of various car enterprises , Not long ago 2021 Guangzhou auto show is a good example , A large number of lidars are installed on some new cars . So it seems , Lidar has become an important link for major car enterprises to realize advanced automatic driving . that , It's like musk said “ It's useless ” Do you ?

First acquaintance with lidar

Lidar English is Lidar(Light Detection and Ranging), It is a sensor with laser as the carrier for ranging and detection . And it also belongs to a kind of radar , But it is different from our common millimeter wave radar and ultrasonic radar , Lidar uses laser beam to detect .

Good morning! Before the launch of lidar , Mainstream car companies have adopted the sensing mechanism with millimeter wave radar and camera as the core . First , Millimeter wave radar is a kind of radar sensor that uses antenna to transmit millimeter wave as radiation wave , The relative distance between the car and other objects is obtained by processing the reflected signal of the target 、 relative velocity 、 Physical environment information such as angle and motion direction . however , Millimeter wave radar can only simply obtain whether there are obstacles ahead , However, it is impossible to accurately identify the category of obstacles , And this will cause “ Ghost brake ” The phenomenon of .

Generally speaking , The traditional millimeter wave radar will be due to the problem of system algorithm , Automatically filter out stationary objects , But different hardware and system solutions , The degree of filtering is different , This is also “ Ghost brake ” The source of the . such as , Filter too little for non dangerous obstacles , When some metal fragments on the road reflect , There will be similar emergency braking , So the signs on the road 、 Gantry for high-speed camera 、 Guardrails on both sides 、 Even a metal bottle on the road and so on , Such objects that can reflect echoes will be recognized as obstacles by millimeter wave radar , Therefore, when the vehicle turns on automatic driving , The system automatically decelerates the vehicle 、 The phenomenon of false braking .

Mistaking road signs for vehicles “ Ghost brake ”( Pictures from the Internet )

The vehicle camera is one of the necessary sensors to assist driving , It can sense the situation around the vehicle and realize forward collision warning 、 Lane departure warning 、 Pedestrian detection 、 Automatic parking and other automatic driving functions , Improve driving safety . in addition , The car camera will also be set in different positions , Have certain requirements, characteristics and application scenarios , Is a very systematic existence . among , For look around and look back , It is generally used 135 Wide angle lens above degrees , The detection range is 10 Within meters , The front camera requires greater sight distance , It is generally used 40-70 The viewing range of degrees , Sight distance requirements are generally in 120 Meters above , The sight distance of binocular camera is generally less than that of monocular camera .

however , As a vehicle sensor, the camera also has some shortcomings , Including low recognition accuracy , Vulnerable to strong light 、 curtain of rain 、 Heavy fog and other bad weather influence . At this stage, we rely solely on the camera to identify , Unable to meet the environmental awareness requirements of automatic driving . So the advantages of lidar , It is reflected in the low error of object recognition .

Groundbreaking lidar

laser , Its original Chinese name was “ laser ”、“ Lesser ”, Is its English name LASER transliteration , It's from English Light Amplification by Stimulated Emission of Radiation An abbreviation consisting of the first letter of each word . intend “ Light is amplified by stimulated radiation ”. after , Academician Qian Xuesen, the founder of China's two bombs and one satellite, changed it to what we now call laser ( Light stimulated radiation ).

In fact as early as 1916 year , Einstein discovered the principle of laser , but 44 Years later, 1960 year 7 month , Theodore of Hughes laboratory in the United States ・ Meiman , Invented the first laser in human history . In order to achieve “ burning ” The conditions required , He used a high-strength flash tube to excite the ruby , Eventually led to the real sense of laser . And in it “ career ” The second year of , That is to say 1961 year , Scientists put forward the idea of lidar .

t-bag ・ Meiman

Because the directivity of laser is very strong , And it integrates the physical characteristics of light vertical , So as a ranging tool, it can't be better .1967 year 7 month , Americans made their first manned flight to the moon , A launcher was installed on the moon to measure the distance between the earth and the moon .

A laser mirror pressed on the moon

1969 year 7 month 21 Japan , ride “ Apollo 11 Number ” Astronaut Neil who landed on the moon ・ Armstrong and buzz ・ Aldrin's on the moon “ Ningjinghai ” After landing , Left the lunar laser mirror on the moon , And in the 20 century 60 End of the decade 70 s , Man sent to the moon “ Corner mirror ”( Lunar laser reflector ) share 5 Noodles . Its function allows astronomers on earth to emit lasers to it , And capture the reflected beam .

however , Laser radar is really used as a civilian mass production sensor , It's on top of a sweeping robot .

2002 year , American military robot company iRobot Try to combine robot technology with sweeping function , Its first mass production sweeping robot Roomba 400 That's what happened . Once put into the market, it is very popular , It was sold for nearly 10 Ten thousand units . however , At that time, robots were not perfect because of their sensing equipment , So in the working state, it produces “ Don't move ” The phenomenon of . therefore , stay 2010 year , The other is called Neato Our company installed lidar on the floor sweeping robot , Launched Neato XV-11.

It can 360 Degree rotation laser emitting device , The ground modeling is completed by ranging the ground obstacles in real time , After that, I cooperated with SLAM(simultaneous localization and mapping, Synchronous positioning and mapping ) Algorithm , It can realize the protection of the ground “ Global planning ” Clean . It can be said that this revolutionary equipment , The popularity of sweeping robots has been officially opened .

In fact, people with a clear eye can see at once , This sweeping robot is a low configuration version of automatic driving , Now that the sweeping robot has eaten “ Crab ”, Can the autopilot also be equipped with a lidar? ?20 century 80 End of the decade , Carnegie Mellon University (Carnegie Mellon University) Transformed from a Chevrolet van into the world's first self driving vehicle Navlab 1, It is equipped with lidar and GPS Receiver . The interior of the truck looks like a TV surveillance car , Filled with computers that monitor road conditions and control air conditioning units , It includes a Warp supercomputer 、3 individual SUN Workstation and video hardware .

Navlab 1

However, due to the limitation of technology at that time , The equipment that governs the automatic driving of this car is very huge , Including cameras 、 Laser range finder ,20 KW vehicle power supply ,Wrap Supercomputers and a few Sun 3 and 4 The workstation , gyroscope , Inertial navigation system and satellite positioning system , And also equipped with several intel 386 Real time processors , It is used to process sensor information and generate vehicle motion instructions . It can be said that this car has one “ Computer Room ” Participation in the work , It almost takes up the space of the carriage .

Navlab 1 Inside

Over the next decade or so , With the continuous development of Technology , Some more practical self driving vehicles have been introduced accordingly , until 2014 year , Autonomous vehicles are beginning to get on track , And lidar has gradually ushered in a new round of development .

Cognitive lidar

that , What exactly is lidar ? Let's start with its principle .

Usually when the family is decorated , When the designer wants to measure the size and area of the house , Often take a laser rangefinder to detect , Like this :

In fact, the principle of lidar is similar , It can be seen as working with multiple laser rangefinders , Another example is this :

In detail , Lidar determines the distance by measuring the time difference and phase difference of the laser signal , And use Doppler imaging technology to draw a clear image of the target 3D Images . Lidar emits and receives laser beams , Analyze the reentry time after the laser meets the target object , Calculate the relative distance to the target object , And use the 3D coordinates of a large number of dense points on the surface of the target object collected in this process 、 Reflectivity and texture information , Quickly get the 3D model and line of the measured object 、 Noodles 、 Volume and other related data , Create a three-dimensional point cloud image , Map the environment , In order to achieve the purpose of environmental perception .

Because light travels very fast , The flight time can be very short , Therefore, the measurement equipment is required to have very high accuracy . In terms of effect , Lidar dimensions ( Wire harness ) The more , The higher the accuracy of measurement , The more secure it is .

Using an ultra-high speed camera that can detect single photons , For the first time, scientists have captured the picture of laser flying in the air ( Pictures from the Internet )

In terms of system structure , Laser radar = Laser emission + Laser reception + Information processing + scanning system . These institutions perform their respective functions , Work together to complete the whole exploration .

The specific term , First, the laser is driven periodically by the excitation source in the laser emission system , Emit laser pulses , The laser modulator controls the direction and the number of laser lines through the beam controller , Finally, through the transmitting optical system , Shoot the laser at the target object . And this requires the support of the scanning system , Rotate at a steady speed to scan the plane , And generate real-time plan information .

after , The photodetector of the laser receiving system receives the laser reflected from the target object , The received signal will be generated and transmitted to the information processing system to amplify and process the signal and digital to analog conversion , Calculated by the information processing module , Get the surface shape of the target 、 Physical properties, etc , Finally, the object model is built .

As “ Non professional Xiaobai ” In the us , In the face of a wide range of lidar products in the market , How to recognize the quality of performance ? In general , Lidar pays attention to many parameters , Including the wavelength of the laser 、 Detection distance 、FOV( vertical + level )、 Ranging accuracy 、 Angular resolution 、 Count 、 Wire harness 、 Safety level 、 Output parameters 、IP Protection level 、 power 、 Supply voltage 、 Laser emission mode ( mechanical / solid state )、 Service life, etc .

But as we , Just focus on counting . Then what are they ? Let's say one by one .

Laser wavelength

Wavelength refers to the distance that a wave travels in a vibration period , The larger the wavelength of the laser , The stronger its diffraction ability , The clearer the recognition of distant irregular objects . At present, the wavelength of lidar on the market is divided into 905nm and 1550 nm Two kinds of . among , The wavelength is 905nm The lidar uses silicon-based photodetector as the emission source , And it has the advantages of low cost and mature technology . But it also has disadvantages , Namely 905nm The laser source is harmful to human eyes . Although it belongs to invisible light source , But with a certain amount of energy , When a laser of this wavelength irradiates the human eye , Will burn the retina , Therefore, when it is used as a lidar transmitting source, the power should be reduced , Therefore, its anti weather interference ability is weak , Insufficient penetration of rain and fog .

and 1550 nm The lidar uses indium gallium arsenic (InGaAs) The near infrared detector is the emission source , Its laser is far away from the visible spectrum absorbed by the human eye , Compared with 905 nm laser , Of equal power 1550 nm The safety of laser human eyes is improved 40 times , High security . Therefore, it can operate at full power , It has high penetration in extreme weather environment (1550nm The transmittance is 0.65,905nm The transmittance is only about 0.51). however , Its disadvantages are also obvious , The overall price is higher than 905nm Laser radar , And the volume size of the system is also higher than the former , Therefore, it cannot be installed in the front position , It can only be installed on the roof .

Detection distance

The ranging of lidar is related to the reflectivity of the target , Reflectivity is the rate at which the laser that hits the target can be reflected back , The higher the reflectivity of the target , The more effective echoes the radar can detect , So the farther you can measure . Therefore, in the parameter table of lidar products ,[email protected]% Reflectivity means that the laser beam is 200m The lowest distance can be identified 10% An object that reflects light ( White paper ), So if a lidar manufacturer releases its products , Only the farthest detection distance is mentioned, not less than 10% The reflectivity of , That's absolutely irresponsible behavior .

Ranging accuracy

This refers to the accuracy of detection distance , Usually measured in centimeters , The higher the detection accuracy ,3D The more accurate the depth of field is .

Generally speaking , There are two range detection principles of lidar , One is triangulation ranging , The other is TOF Ranging method .

First , The principle of triangulation is : When the laser signal emitted by the laser source irradiates an object surface at a certain incident angle , There is a reflection phenomenon . The reflected light spot passes through an optical lens and is imaged in CCD On the sensor . When the object to be measured moves in the direction of the laser ,CCD The spot on the will move , The distance between the measured object and the baseline is calculated by the moving distance of the light spot . therefore , The overall measurement needs to be made by the incident light 、 The reflected light forms a triangle to calculate the distance between the target object and the radar 、 Relative azimuth angle value .

and TOF Ranging method is that the laser emits a laser pulse at the same time , The time of sending is recorded by a timer , The return light is received by the receiver and the distance down time , Subtract two times , obtain “ Flight time ”, Then calculate the distance from the speed of light .

Although both determine the distance of the target according to the propagation of light , However, triangular radar has the highest accuracy only at close range , If you detect a long-range target , As the detection distance gets farther , The target image is CCD The position difference and angle on the sensor are getting smaller and smaller , When the measured value exceeds a certain distance ,CCD Almost indistinguishable , Therefore, it is not suitable for remote measurement . and TOF Pulse laser sampling is used , Dependent on flight time , Time accuracy does not change with length , meanwhile TOF Can strictly control the field of view to reduce the influence of ambient light . Compared with triangulation ,TOF Radar can measure more distance , And it can maintain high accuracy over a long distance .

Laser harness

When we go to learn about lidar , The most frequently heard parameter is the number of wire harnesses of this lidar , So what is the relationship between the number of wire harnesses and them ?

Generally speaking , Lidar is divided into single line and multi line , And multiline can continue to subdivide 4 Line 、8 Line 、16 Line 、32 Line 、64 Line 、128 Line . Actually , The harness here refers to the laser signal emitted by the lidar , Single line lidar can only conduct parallel scanning exploration, but not vertical scanning exploration , Therefore, although it has a good performance in scanning speed and separation rate , But because the height of the object cannot be measured , Therefore, it has great limitations in use , Therefore, it can only be used on servo robots , That is, the best sweeping robot .

Between several brands 50 Comparison of human body harness irradiated outside meters ( Pictures from the Internet )

Multi line lidar , seeing the name of a thing one thinks of its function , It can emit multiple laser signals , It can effectively measure the height and contour of the object , And the more harnesses , The higher the accuracy of the measured contour , Of course , The more data you process , The higher the hardware requirements , Naturally, the more expensive the price is .

FOV( vertical + level )

This indicator, if used in vernacular, is the exploration field size of lidar , The one we often see on top of the vehicle 360 Degree rotation lidar , Its level FOV yes 360 degree . And the level of solid-state lidar FOV It will be smaller , among 120 Degree is already a big perspective , So the level FOV The bigger it is , The wider the range that can be detected . And vertical FOV Generally, it can be reflected on multi line radar , It refers to the angle between the top laser beam and the bottom laser beam . And most of the lidar's vertical FOV Will lower the field of vision to the ground , The passing level is 0 degree , So go on 15 degree , Down 25 degree , So vertical FOV Namely 40 degree . The biggest reason for this is that the radar can detect more ground vehicles and pedestrian targets , To ensure the accuracy of scanning during driving .

Angular resolution

The image output by lidar is also called “ Point cloud ” Images , The angle between two adjacent points is the angular resolution , Generally speaking, there are two kinds of angular resolution , One is vertical resolution , The other is horizontal resolution . among , It's not difficult to achieve high resolution in the horizontal direction , Because it is driven by the motor in the horizontal direction , So the horizontal resolution can be very high . Generally, it can be done 0.01 Degree level . The vertical resolution is related to the geometric size of the emitter , It also has something to do with its layout , The smaller the distance between two adjacent transmitters , The smaller the vertical resolution , The vertical resolution is 0.1~1 Degree level . in addition , Because the sampling rate of lidar is certain , So the higher the frame rate , The lower the angular resolution ; The lower the frame rate , The higher the angular resolution .

For example, the minimum angular resolution of this lidar in the figure above 0.08° Corresponding to the frame rate 10Hz Under the condition of , When the frame rate is set to 20Hz when , The angular resolution automatically becomes 0.16°. The sampling rate represents the number of effective acquisition times per second by the lidar , It can be intuitively understood as the number of point clouds generated in one second . The sampling rate can be calculated by angular resolution and frame rate : Angular resolution 0.08° when , Number of point clouds per frame :360°/0.08°= 4500; Per second 10 frame , Then the number of point clouds per second :4500×10=45000; therefore PAVO The sampling rate of is 45kHz.

Count

This is easy to understand , It is the number of laser points emitted by the lidar per second . The number of lidar points generally ranges from tens of thousands to hundreds of thousands of points per second . such as , One performance is 64 Line , level FOV yes 120°, The horizontal resolution is 10Hz The scanning frequency is 0.2° Under the circumstances , Its conversion is equal to : The laser can shoot... In a single shot 64 spot , Scan once 120° Can play 64x120/0.2=38400,1 Second scan 10 Time , Altogether 384000 pts/s. So the more points , The better the scan .

In addition to the above , Lidar should also pay attention to , It is the detection rate of dark objects and the anti-interference ability to ambient light .

Detection rate of dark objects

In the world we live in , The colors of all things are colorful , But the dark ones absorb most of the light energy ( Such as : Blackened homemade solar water heater ), Therefore, the detection rate of laser signal of lidar hitting white objects and dark objects is very different , Besides, most objects in life are mainly dark , Therefore, the detection rate of dark objects by lidar is very important .

at present , The lidar sold on the market is based on 90% Reflective white paper ( Diffuse objects ) As a test reference , But the effective detection of dark data is also an important performance index . At least under normal circumstances, one claims to have 10 Lidar over meters , At least 6 Only the effective detection of dark objects more than meters can .

Anti interference ability of ambient light

In addition to the detection of dark objects , Ambient light will also affect the detection of lidar , This includes sunlight or indoor lights , They will affect the radar sensor and produce noise , And it will also cause the effective measurement distance of the radar to become shorter or completely unable to measure the distance . So can you distinguish ambient light , This has high requirements for the tuning, system and algorithm of lidar .

Find out the category of lidar

That's just how lidar works , If the scanning method is different , It can also be divided into rotating mechanical lidar 、 Hybrid semi-solid radar and all solid radar .

Mechanical lidar

Mechanical lidar generally adopts 360 Degree rotary scanning mode , It can physically rotate the surrounding environment 3D scanning , So as to form a comprehensive coverage and form a point cloud .

But it also has disadvantages , First of all, the high-frequency rotation and complex mechanical structure make the average failure time only 1000-3000 Hours , It is difficult to reach the lowest level of vehicle specification equipment 13000 Hours of demand . And the mechanical lidar should be placed at the highest point of the vehicle , So not only does it occupy too much land , The top of the vehicle also needs to be reinforced , It has an impact on the center of gravity safety of the vehicle , In addition, the most important thing that restricts it is ―― your ! 80000 cases , It must also be a beautiful knife .

Pure solid state lidar

Compared with the mechanical structure radar mentioned above, the pure solid-state lidar , Because there is no complex rotating mechanism , Therefore, the durability of products has been greatly improved , And the volume of the whole equipment is effectively compressed . At present, the common Solid-state Radar on the market is divided into OPA Optical phased array and Flash There are two kinds of flash .

OPA(Optical Phased Array) Optical phased array lidar

Before mentioning this form of lidar , Let's first understand what phase array control is .

The most common example in our life is water waves . such as : In a square pool , Two water waves generated by two vibrations will overlap each other at the intersection . If the two waves in some directions reinforce each other , Some directions just offset , You can easily control the direction of water waves .

So if based on this phenomenon , Multiple light sources will be used to form an array , By controlling the emission time difference of each light source , You can synthesize angles flexibly , Precise and controllable main beam , This is the principle of phased array . In reality , The common equipment using this principle is the phase array radar commonly used in military . By controlling the current phase of each array element of phased array radar plane array , Using the phase difference, the wave sources at different positions can interfere , To point in a particular direction . The effect of scanning can be realized by controlling the phase difference back and forth .

Common military phased array radars, such as those placed in the United States “ arley ・ Burke class ” On the destroyer AN/SPY-1D“ Aegis ” Phased array radar and China 052C The missile destroyer is equipped with 346“ Star of the sea ” Phased array radar .

“ arley ・ Burke class ” On the destroyer AN/SPY-1D“ Aegis ” Phased array radar

In our country 052C The missile destroyer is equipped with 346“ Star of the sea ” Phased array radar

On lidar , The phase difference is also used to control the interference to make the laser “ to turn to ” A specific angle , Reciprocating control to achieve scanning effect , This is called an optical waveguide array .

The optical waveguide array realizes beam scanning by power on , Using the electro-optic effect of optical waveguide , Apply voltage to the waveguide core , Each waveguide core has a different additional refractive index , The beam can have different additional phase differences in the light field of the output section of the waveguide array element , The phase difference is distributed according to a certain law, which can cause the deflection of the output light speed . The output is distributed according to a certain law through the phase difference , So as to realize the scanning of light beam .

however , Although this radar is good in data , But there are very high requirements in technology . First , The size of the array unit must not be greater than half a wavelength , Therefore, the size of each device is only 500nm about , The requirements for materials and processes are extremely harsh , Therefore, the cost is correspondingly high , Therefore, the application of RE market is not very high .

Flash Flash lidar

Flash The principle of flash lidar is to emit a large area of laser to the front in a short time , It's like a continuously turned on flashlight , The image around the environment is drawn through a highly sensitive receiver .Flash The principle of lidar is similar to photographing , But the final generated data includes depth and so on 3D data , At present, it is also the most mainstream technical scheme of pure solid-state lidar .

however , Because it emits a large area of laser in a short time , Therefore, there are certain restrictions on the detection distance , Basically, it should be on the low-speed unmanned vehicle .

Hybrid solid-state radar

If the characteristics of mechanical radar and solid-state radar are slightly combined , Hybrid solid-state radar is a good choice . Because the radar costs 、 Volume and other aspects are easier to control . At present, the common hybrid solid-state radar on the market is MEMS Galvanometer 、 Rotating mirror 、 Prism mode .

MEMS(Micro-Electro-Mechanical System) Galvanometer lidar

MEMS Galvanometer lidar is used to control a small mirror torsion angle to realize scanning , And the laser transmitter won't move , What is its specific principle ?

MEMS Refers to micro electromechanical system (Micro-Electro-Mechanical System), It can be seen as a reduced mechanical rotating mirror . According to the drive classification , It can be divided into electrothermal drive 、 Electrostatic drive 、 Electromagnetic drive And piezoelectric drive . And can translate and twist (x、y Two directions ) Two mechanical motion modes are used for scanning , Very high scanning frequency can be achieved . Now used for laser scanning projection MEMS The chip scanning frequency can reach 40kHz, Equivalent to scanning in one second 4 Ten thousand times . in addition , Due to the cancellation of the motor 、 Heavy mechanical motion equipment such as multi prism , Millimeter size micro galvanometer greatly reduces the size of lidar .

however , although MEMS Galvanometer lidar has the advantages of high durability and low cost , But the galvanometer will be affected by the external temperature 、 The influence of vibration environment leads to the change of resonance frequency and the disorder of harness , Eventually lead to imaging distortion and other problems , also MEMS Galvanometer lidar also has low signal-to-noise ratio , Problems such as short effective distance . Although increasing the mirror size can effectively increase MEMS The accuracy of lidar , But the maximum deflection angle will also be limited ,FOV The field of view angle will be more limited , This has high requirements for the manufacturer's process and design ability .

Rotating mirror lidar

The rotating mirror lidar relies on a mirror rotating around the center to scan the light refraction , It's power consumption 、 Heat dissipation and other aspects have good advantages .

Its disadvantages are also related to MEMS Like a galvanometer , The signal-to-noise ratio is low , And short effective distance ,FOV Problems such as limited field of view angle .

Prism lidar

The interior of this lidar generally adopts double wedge prism structure , The laser deflects once after passing through the second wedge prism , Then it deflects again after passing through the second wedge prism . As long as the relative rotation speed of the two prisms is controlled, the scanning shape of the laser beam can be controlled .

It is worth noting that , The scanning track of prism lidar is petal shaped , Not our common parallel scanning trajectory . This advantage is that as long as the scanning speed is properly controlled , How to cover the whole area by scanning several levels in the same position for a long time , And unlike the traditional rotary lidar, it makes the transceiver module rotate , Thus, the multiple calibration similar to the traditional rotating lidar is avoided .

But the biggest disadvantage of prism lidar is its FOV( Field angle ) smaller , Therefore, it is necessary to match multiple prism lidar to cover the field of view and supplement the blind .

Lidar in other fields

Lidar has a high recognition rate , Resolution accuracy and other advantages , Therefore, in addition to the ranging function , Laser tracking has also been developed 、 Laser velocimetry 、 Laser scanning imaging and other technologies , And it is widely used in the surrounding facilities of our life .

such as , What we often see is 3D Print inside , It includes lidar , It is mainly used to measure and monitor printed matter , In order to reduce the manufacturing error . And in the city where we live , Lidar will be used to measure speed , Its detection distance is longer and more accurate than the traditional velocity radar .

In marine exploration and fishery resources , Lidar is mainly used in fishery resources investigation and marine ecological environment monitoring . among , The blue-green pulsed light is used as the excitation light source in the survey of industrial resources , Through the recognition and extraction of laser echo signal, the distribution area and density information of fish are obtained , Combined with polarization feature analysis, fish species can be identified . Marine laser fluorescence radar is often used in marine ecological environment monitoring , Through the detection and analysis of the fluorescence and other spectral signals emitted by the laser-induced target, the species and concentration distribution information of marine plankton, chlorophyll and other substances can be obtained .

besides , Lidar can also be used in danger prediction 、 Medical scanning 、 Military detection, etc , Very extensive .

Editor's summary :

Although the above is just some basic science popularization , But in my opinion , Vehicle lidar is in the field of automatic driving , It's an addition to improving perception , To make up for millimeter wave radar 、 Due to the deficiency of automatic driving perception systems such as visual camera and ultrasonic radar , So it shouldn't be myth . In terms of existing technology , With the blessing of lidar , It can really greatly improve the perception of automatic driving , It also plays a vital role in the higher-level automatic driving function .

at present , The new four modernizations of cars , namely :“ electric 、 Intelligent 、 Networking 、 Sharing ” The development trend has become the consensus of the industry . And intelligent vehicles with automatic driving function must have “ Security 、 Efficient 、 comfortable 、 Energy saving ” travel , And finally realize a new generation of cars that can be operated instead of people . Therefore, the addition of lidar is essential , And according to 《 Development report of automatic driving in China 2020》 Statement of the ,2025 In years, the application of lidar will accelerate , Then the policy 、 technology 、 The infrastructure is relatively complete , and L3 Class models will also be launched on a large scale , With the price of lidar will be greatly reduced due to the maturity of Technology , Models equipped with lidar will no longer be limited to high-end models , But down to the middle and high-end models . therefore “ The swallows visited great mansions , Now fly into the nobodies' homestalls. ” The era of will come , We'll see .

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