How does lidar achieve environmental perception?
In simple terms, a laser ranging module consists of a laser, a receiver and a processor.
We all know that light is reflected when it hits the surface of an object.
The same is true for lasers. When the laser emits light and irradiates the surface of an object in space, it will instantly reflect, and there must be a beam of echoes that will be received by the receiver.
Since the speed of light is known, at this time, the processor can obtain the precise distance of this point by calculating the round-trip time of the beam of light.
The three-dimensional positioning of this point can be obtained by assigning angle information to this beam of light in the space coordinate system.
This is ToF, time-of-flight ranging.
Coherent methods
Ranging also uses coherent methods, that is, frequency-modulated continuous wave (FMCW) lidars emit a continuous beam of light whose frequency changes stably over time. Since the frequency of the source beam is constantly changing, the difference in the transmission distance of the beam will cause the difference in frequency. After mixing the echo signal with the local oscillator signal and low-pass filtering, the obtained beat frequency signal is a function of the beam round-trip time. FM continuous wave lidar is not interfered by other lidars or sunlight and has no blind spot for ranging; it can also measure the speed and distance of objects using Doppler frequency shift. The FM continuation wave LiDAR concept is not new, but it faces many technical challenges, such as the linewidth limitation of the emitted laser, the frequency range of the chirp, the linearity of the linear pulse frequency variation, and the replicability of a single LFM pulse.
the 3D vision of lidar
Just imagine, when we have an infinite number of rays, we can use an infinite number of such points to outline the details of all objects in the three-dimensional space.
This is the point cloud - the 3D vision of lidar.
Take a look at a point cloud image of a lidar. If you look closely, it is not difficult to find that the point cloud image is composed of points one by one.
The collection of these points clearly shows the details of pedestrians, zebra crossings, vehicles, distant street signs, trees and other objects, and even the slender high-voltage wires in the air can be captured.
Uniform and regular point clouds like this can completely and clearly restore the three-dimensional world, and become the real "eyes" of intelligent vehicles.
what benefits can lidar bring to smart cars?
When people start to see more and more smart cars equipped with lidar on the road, they may not help thinking: what benefits can lidar bring to smart cars?
