Lidar Detailed Interpretation

For automotive manufacturers, of course, the more durable the better, so with a variety of moving parts of the laser radar certainly can not be done in the reliability and price perfect, for this reason, many experts believe that the laser radar want to enter The mainstream market must switch to a solid-state design, but this requires new devices that fire lasers in different directions to cover the vehicle’s surroundings. Right now, the researchers come up with three main solutions for solid-state lidar:

The first is based on microelectromechanical systems (MEMS). The entire system requires only a small reflector to guide the fixed green laser light beam in different directions. Since the mirror is small, its moment of inertia is not large enough to move fast enough to track 2D scanning in less than a second. A big advantage of MEMS LIDARs is that the sensors can dynamically adjust their scanning modes to focus on specific objects, capture and recognize the details of the finer and smaller objects, which traditional laser lidar could not.

The second laser radar phased array design, it is equipped with a row of launchers can adjust the relative phase of the signal to change the laser beam emission direction. If the transmitter emits the laser simultaneously, the laser will fire in the same direction. However, if the left transmitter phase is on the right side, the laser will fire to the left and fire to the right. Although the principle is straightforward, most phased array lidars are still in the lab. Phased-array laser radar belongs to the future, and now still stays in the era of rotary or MEMS laser radar, the former is even more dominant.

The third is Flash LiDAR, which runs more like a camera. The blue laser beam is diffused directly in all directions, so the entire scene can be illuminated with just one flash. The system then uses a miniature sensor array to pick up laser beams reflected in different directions. One of the great advantages of Flash LiDAR is its ability to quickly document the entire scene without the hassle of moving targets or Lidar during scanning. However, this approach also has its own flaws. The bigger the pixel, the more signal you have to process. The massive pixels into the photodetector, will inevitably bring a variety of interference, the result is the decline in accuracy.

green laser light

For any Lidar system, it is not easy to fire a laser at 300 meters and probe its reflected signal. Major manufacturers are also trying their best to find some ways to increase the detection range of laser radar. Today, most laser radar sensors are in the near-infrared laser range, the average manufacturer will choose this wavelength of 905 nm. However, it is closer to the wavelength of visible light (red wavelength is about 780 nm), while the laser will damage the human eye and burn the photosensitive detection cells on the retina, so the power of 905 nm laser is severely restricted.

In order to avoid harming the human eye, developers decided to switch to another wavelength laser. Developed a laser radar using a 1550 nm high powered laser, which is much safer for the human eye because it goes well beyond the visible range. Solve the security issue, the power of 1550 nm laser radar can be greatly improved. Relevant data show that researchers have increased the lidar power 40 times, it is much more difficult to detect remote laser signals. However, there are bound to be lost, 1550 nm lasers and detectors are expensive because they require more specialized materials. In addition to boosting laser power, we can extend the lidar detection range by enhancing the detector’s sensitivity. This detector is quite sensitive, suitable for a photon in the frequency can be activated.

In the development of a new generation of lidar, manufacturers are also faced with a third design new choice, that is, how to measure the time and distance. Most LIDARs use straightforward time-of-flight methods. It emits a very short pulse and then uses super-precise timers to figure out how long it takes for the pulse to go back and forth. In addition to measuring distance by flight time, some vendors have developed more sophisticated methods and named it CW Wave Frequency Modulation (CWFM). As the name suggests, this method emits a continuous laser beam to the target that splits into two beams, one that fly toward the target and reflect back and the other reconstruct the beam during the flight. The laser beam emitted from the laser pen radar will steadily increase in frequency, while the two beams separated by it will fly a different distance and will have different frequencies after recombination. This creates an interferogram with a beat frequency, from which researchers can derive the flight distance of the first beam.

Lectures on how to design laser radar in the end, I am afraid that various companies have tried various possible solutions, but even experts are not assertive in the end what kind of design can be the last laugh. However, everyone is confident that the next few years, laser radar will usher in a big price reduction.

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