Laser sensor must determine accurately transmission time, because velocity of light is too fast. Want resolution to give the time of 3ps, this is the exorbitant requirement that raises to electronic technology, implementation rises cost is too high. But the laser sensor nowadays kept away from ably this one obstacle, use a kind of simple statistical principle, namely the resolution that mean law implemented 1mm, and can assure answer speed.

 

Remote laser range finder shoots a bundle of very fine laser to the target when the job, receive target catoptric to stimulate beam of light by photoelectricity component, clock determines stimulate beam of light from the time that shoots to receive, computation goes out to arrive from the observer the distance;LED Bai Guang of the target measures fast appearance to become resemble be on CCD of chip of appearance interior integrated circuit, CCD chip performance is steady, working life is long, and the effect that does not suffer working environment and temperature basically. Accordingly, LED Bai Guang measures fast appearance to measure precision to have assure, function is stable and reliable.

 

 

The application of sensor of laser range finding

 

The car prevents bump into detector: Generally speaking, the sensor of laser range finding of system of precaution of collision of most existing car uses the space between the target car of the situation after laser light beam is used at identifying a car to perhaps be in afore with contacting means, be less than when car span when booking safe distance, the car prevents collision system to undertake scram to the car, perhaps give out to the driver call the police, speed of car of integrated perhaps target, car is apart from, distance of car apply the brake, answer time to wait to undertake judge and be responsed immediately to car travel, can reduce train operation accident in great quantities. Use on the freeway, its advantage is more clear.

 

Wagon flow measures monitoring: It is important perhaps that use means secures high speed commonly on the dragon mast of crossing, laser blasts off and receive vertically face to be down, aim the intermediate place of a driveway, when car passes through, the opposite change that sensor of laser range finding can output the interval that measures to be worth in real time is worth, depict an outline that measures a vehicle then. This kind measures means to use range finding limits to be less than 30 meters commonly can, and rate of requirement laser range finding is higher, it is OK that general requirement can achieve 100 hertzs. Monitoring of this main to be in a section of a highway can achieve very good result, can distinguish all sorts of models, the sampling rate that scans to automobile body height can achieve 10 centimeters one is nodded (when 40Km/h, sampling rate is 11 centimeters a dot) . Be restricted to wagon flow tall, be restricted to grow, car cent wait to be able to differentiate in real time, can output a result quickly.

 

 

Without man-machine: Move robot (Robot) , unmanned aircraft (Drone) , unmanned carry drive car, automatically those who wait for new idea system is arisen, implicative and exciting range finding and avoid barrier (demand of Obstacle Avoidance) technology. Among them range finding is avoid the foundation of barrier, a variety of technologies can realize range finding, include wireless radio frequency (Radio Frequency;RF) , supersonic wave (Ultrasonic) , infrared ray (Infrared) and laser / Lei She (Laser) . These technologies have its actor drawback each, and cost also has otherness.

 

Among them, infrared ray and laser belong to photoelectricity semiconductor technology, apply infrared diode respectively (Infrared Light-Emitting Diode;IR LED) and laser diode (the hair wave of Laser Diode;LD) , receive echo to differentiate after that the distance of the object, infrared technology suits stone’s throw to apply, laser technology fits Sunday run category. Additional, avoid barrier technology still has technology of wireless radio frequency, supersonic wave to wait commonly, they are common apply at car domain.

 

Lidar sensor

 

Lidar is car domain relative to newer applied system, dan Zhengyu will cause the attention of people more. System and semiconductor supplier people dedicated mix at research and development improve new solution, plan 2020/2021 year appearance application rises.

 

What is LIDAR(lidar) ? Accordingly, it is to use laser to undertake exploration the abbreviation with range finding technology. Besides need laser emitter, this one system still needs to have the receiver of a high accuracy. As a result of what can offer object be explorationed through distinctive method three-dimensional and video, lidar basically is used at measuring with the distance between fixed or mobile object.

 

Nowadays, any people that bought laser range finder are using this kind of method to be in the place such as a shop of medium, housing materials to measure an interval, the interval that its can measure can amount to several meters. And to driver support system, crucial challenge depends on making sure the system is below any environmental states (illuminate of temperature change, sunshine, dark medium or pluvial Xue Tian is angry) can work normally, and even can make out 300 meters of objects beyond. Of course, still need can volume is the minorrest, mass production can leave in lowermost cost.

 

Lidar system is not burgeoning thing, also had applied a lot of years in industry and martial side. But, what what say here is complex rigid lens system, contain 360 degrees not to have blind angle line of sight even, the space that can take an object is three-dimensional and video. If still resemble industry and military affairs going up in that way price by tens of thousands dollar, so will impossible by large-scale apply in car domain.

 

Nowadays, lidar system has way of 2 main development, infra-red lidar system adds system of electrical micro-machine weapon (MEMS Micro-Electro-Mechanical System) (deserve to go up rotational laser emitter) , perhaps use the lidar system of fixed condition.

 

Before the distinction that is discussing these techniques briefly, need explains to receiving a system.

 

The main function that receives a system is to identify what give out from emitter to mix from beam of light of the catoptric on the object. Because this detector needs special delicacy, down to can explore individual photon. Nowadays, newest relevant equipment used diode of avalanche of odd photon of SPAD(Single-Photon Avalanche Diode) technology.

 

Graph: The principle of SPAD sensor unit

 

The principle of this technology is very simple, if pursue,11 are shown. This diode has structure of special deflection PN knot, so individual photon can cause avalanche electric current inside diode (a large number of electric current that cause by small electric current, similar avalanche phenomenon, friend name) . The diode electric current that increases quickly can be explored by corresponding circuit, generate digital signal next, use at later period processing.

 

Graph: Principle of lidar range finding

 

Graph 12 those who show is the working principle that uses SPAD sensor to measure an interval. When time is X, laser emitter issues smooth signal of a pulse, this one signal can be reflexed to come back by the object, after passing Y time (or more) photon arrives at sensor, to the time length that the distance between this object can transmit from the light computation comes out.

 

If a bundle or many bundles of light blasts off in the lens face from roll or system of micro computer weapon come out, and the array that one is comprised by several sensor component, so three-dimensional and stereo object also can be explored to come out. Graph 13 with the 14 measurement that revealed two kinds of basic laser to explore a system process.

 

Graph: Principle of range finding of solid state lidar

 

Graph: Be based on the principle of lidar range finding of MEMS

 

When using the system of miniature lens face that is based on MEMS technology, onefold bundle laser signal is met be come back by disperse the internal heat with sudorifics and reflex with line form form, catoptric photon is detected by the photosensitive sensor in corresponding SPAD component. This is life, adjustable to accuracy of lens face system, job spend and dependability has very high demand. After all this is the system that an interior contains movable part.

 

At first sight goes up, a system that does not have movable spare parts comes true more easily it seems that. But in this one system, need several (more than 100) laser diode and relative to bigger receiver array. Laser diode must can give out pulse width to go up in nanosecond class, electric current amounts to several ampere signal ability, manufacturer of this half-and-half conductor is very big challenge.

 

Two kinds of systems still are in development. Will look from the angle of manufacturer of a semiconductor, the semiconductor element that systematic place requires is feasible on the technology, but the dimensional area that SPAD array place requires is bad to come true. Want to activation and control laser diode array, realize the target cost of about 100 dollars, need new method. System of corresponding electrical micro-machine weapon also is among research and development.