A group of physicists from Switzerland have created a prototype lidar based on the number of parallel coherent wave. The presented device works faster modern lidar and is more resistant to external noises. The work presented in the journal Nature.
Lidar (LiDAR) is used to measure distances and velocities of objects using a laser. The basic principle of these devices is based on the analysis of the time delay between the transmitted and received signals. In recent years, interest in lidar is heated by the development of unmanned vehicles, where it is necessary to quickly recognize and categorize objects in conditions not the best visibility compared to conventional cameras, lidar can effectively recognize objects in poor weather conditions or poor lighting. Lidars are also widely used in augmented reality devices.
There are two basic types of lidar: working on the principle of time-of-flight and using the coherent properties of the laser. Most modern devices rely on measuring the time-of-flight, where the distance to the object is determined by direct measuring the time delay between transmitted and received laser pulses. This method often uses several pulses in parallel to a voluminous reader, and the information about the speed of the object can be obtained only through sequential processes of transmission-reflection measurement signal. Because of the many successive measurements determination of speed becomes a difficult task, because in each iteration there is noise that reduces the effectiveness of the device.
Another type of measure for distance and speed, coherent lidar, sends a frequency-modulated continuous wave for the object and the reflected signal is determined by homogeniously. Coherent lidars have many advantages such as higher resolution on the determination of the velocity with effect of Doppler (which can be done in one iteration) and the resistance to noise, such as sunlight, noise and signals from other lidars. However, the main technical difficulty lies in the parallelization of lidar signal based on continuous waves.
A group of physicists from the Federal Polytechnic school of Lausanne under the supervision of Professor Tobias Kippenberg (Tobias J. Kippenberg) presented a new implementation of a parallel lidar using nonlinear photonic systems — high-q resonator, silicon nitride, in which the laser beam is converted into a stable optical pulse sequence.