Why do we need a LiDAR calibration plate?

The core features of LiDAR in autonomous driving can be summarized as three-dimensional environmental perception, high resolution, and anti-interference ability. In terms of three-dimensional environmental perception, 3D LiDAR can emit a large number of laser beams to the surrounding environment in a short period of time, with a detection distance of 200-300m and a maximum field of view of 90°*30°; the angular resolution can reach up to 0.05°*0.05°, ensuring that it can still accurately detect and track multiple targets at a long distance, with a distance resolution of 0.1mard and a speed resolution of less than 10m/s.

LiDAR determines the distance of an object by measuring the time difference of laser signals, and obtains accurate three-dimensional information of the measured object by horizontal rotation scanning or scanning angles in the air, and obtaining signals at different pitch angles. The performance redundancy and extremely high reliability meet the different needs of rail transportation, shipping, airport aviation, urban transportation, industrial inspection and other fields. Due to the high frequency and short wavelength of laser, extremely high angle, distance and speed resolution can be obtained. Such high speed and distance resolution means that LiDAR can use range Doppler imaging technology to obtain very clear images.

In terms of anti-interference capability, unlike microwave and millimeter-wave radars, which are easily affected by electromagnetic waves widely present in nature, there are not many signal sources in nature that can interfere with laser radars. Therefore, laser radars have strong anti-active interference capabilities and can work around the clock. Since the emission frequency of the laser beam in laser radars is generally more than tens of thousands of pulses per second, which is much higher than that of traditional microwave radars, they have the advantages of high resolution, high accuracy (centimeter level), and long detection distance. In addition, the anti-interference capability is stronger than that of electromagnetic waves. Since multi-dimensional head portraits of the target are generated, the amount of information obtained is richer and is not affected by the motion state of the target object. However, most laser radars will be affected by rain, snow, fog and haze, and their penetration will deteriorate, the measurement accuracy will decrease, and it is difficult to distinguish between traffic signs and traffic lights. The high cost has also become a key factor restricting the large-scale mass production of laser radars.

Of course, since the principles and functions of different sensors carried by sensor devices with various ranging principles are different, they play their respective advantages in different scenarios and in the data field. At present, the characteristics of a single sensor have made rapid progress, and none of them can form complete information coverage. Future development must be multi-sensor fusion, and the integration of multiple technologies and multiple platforms is an inevitable trend for future development. The smart cars of the future can be regarded as "mobile sensor platforms" and will be equipped with a large number of sensors. And as intelligent driving continues to advance from L2 to L3 and above, LiDAR has become increasingly important due to its high precision, long detection distance, and 3D environment modeling.

From the function of radar, laser radar is mainly composed of laser emitting device, laser receiving end, information processing unit, and beam signal scanning system: 1) Laser emission: by converting electricity into light, the excitation source drives the laser to emit laser pulse beam, the laser modulator controls the direction and number of laser beams through the beam controller, and finally transmits the laser to the target object through the transmitting optical system; 2) Laser reception: through the reflection of the object, the photoelectric detector in the laser receiving unit receives the laser beam reflected back by the target object and receives the reflected signal of the obstacle; 3) Laser information processing: after the received signal is amplified and processed by the integrated module and the digital-to-analog converter, it is calculated by the information processing module to obtain the shape, physical properties and other characteristics of the target obstacle. The control module establishes the object model and distance measurement based on the collected information. 4) Beam signal scanning: Generally speaking, laser radar rotates at a stable speed to send a laser beam to scan the plane where it is located, generate real-time plane map information in real time, and perform data calculation and update.

At present, the technical route of mainstream automotive laser radar is mechanical → semi-solid → pure solid according to the scanning method. Smart sensors are the "eyes" of smart driving vehicles. The mainstream sensor products currently used for environmental perception mainly include four categories: cameras, millimeter wave radars, ultrasonic radars and laser radars.