Three Technical Paths of Solid-State Lidar Sensor

Solid-state LiDAR is a radar that has no moving parts at all,after years of development, solid-state LiDAR has three main technology paths.


1. Micro Electro Mechanical System (MEMS) technology
MEMS technology miniaturizes and digitizes mechanical structures, integrating previously larger mechanical structures onto silicon-based chips through microelectronic processes. The LiDAR uses MEMS micro mirrors to achieve scanning of the vertical plane, while the entire machine rotates 360 degrees horizontally to complete horizontal scanning.

Strictly speaking, MEMS is not considered a pure solidstate LiDAR, because in the MEMS scheme, the mechanical aspect is not completely eliminated,but rather miniaturized and the scanning unit becomes a MEMS micro mirror.

2. OPA (optical phased array) technology

Compared with other technical solutions, the OPA solution describes the promising prospects of a laser radar chip-level solution, which uses multiple light sources to form an array and synthesizes a main beam with a specific direction by controlling the time difference of each light source's emission. Also,the main beam can scan in different directions. Radar accuracy can get the millimeter level and is in line with the trend of miniaturizationand low-cost in the future. However, the difficulty is how to improve the point cloud data per unit time and also the huge investment cost.

3.Flashtechnology
The principle of Flash LiDAR is fast flashing, not scanning. It directly emits a large area of laser covering the detection area in a short period of time, and then uses a highly sensitive receiver to complete the drawing of the surrounding environment.
Meanwhile, solid-state LiDAR also has some disadvantages, such as:
① The scanning angle is limited, and solid-state means that the LiDAR cannot rotate 360 degrees and can only detect the front. Therefore, to achieve omnidirectional scanning, multiple solid-state LiDARs need to be arranged in different directions.

② Sidelobe problem, grating diffraction can form other bright patterns in addition to the central bright pattern, which can cause the laser to form sidelobes outside the maximum power direction and disperse the laser energy.

③ The higher processing difficulty, and the optical phased array requires that the size of the array unit must not exceed half a wavelength. Currently, the working wavelength of LiDAR is generally around 1 micrometer, so the size of the array unit must not exceed 500nm. Moreover, the higher the array density, the more concentrated the energy, which increases the requirements for machining accuracy and requires new technological breakthroughs.
④ Large receiving surface and poor signal-to-noise ratio: Traditional mechanical radars only require a small receiving window, but solid-state laser radars require the entire receiving surface, which introduces more ambient light noise and increases the difficulty of scanning and analysis.

Overall, it is currently difficult for solid-state LiDAR to simultaneously meet its inherent characteristics, which also makes it difficult for solid-state LiDAR to be commercialized in a short period of time.

At present, mechanical LiDAR is still the mainstream.

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