Mechanical vs. Solid State LiDAR: Pros, Cons & Comparison

Introduction : To map a 3D environment, a LiDAR system cannot just fire in one direction; it must sweep its laser across a scene. The engineering method used to steer this light defines the two most common categories of LiDAR: Mechanical Scanning and Solid State.

Mechanical Scanning LiDAR

The system uses a high grade motor to physically rotate the entire laser emitter and receiver assembly 360 degrees. High precision mirrors are often used to tilt the beam up and down as it spins, creating a complete “sphere” of data points. This classic LiDAR design is used in spinning cylinder mounted on top of early autonomous test vehicles. The goal of the design is to provide a panoramic view of the vehicle’s surroundings using a single, powerful sensor unit.

Pros of mechanical scanning LiDAR

Following are benefits or advantages of mechanical scanning LiDAR type.

1. It offers 360 degree field of view. A single unit can monitor an entire perimeter, which is ideal for complex urban navigation.
2. Because the hardware is physically moving at a set speed, the resolution remains uniform across the entire field of view.
3. It is proven technology.

Cons of mechanical scanning LiDAR

Following are drawbacks or disadvantages of mechanical scanning LiDAR type.

1. Due to mechanical wear, moving parts eventually fail. Bearings wear out, and the motor requires regular maintenance.
2. These units are bulky and heavy, making them difficult to integrate into sleek consumer car designs or small drones.
3. These systems are significantly more expensive due to use of precision motors.

Solid State LiDAR

This LiDAR type does not have moving parts unlike mechanical type. They are designed based on silicon chips. Instead of spinning a motor, these systems steer light electronically or through micro-scale components as follows.

• MEMS : Uses microscopic mirrors that tilt rapidly to steer the beam.
• Optical Phased Array : Steers light by changing the phase of light through a series of emitters with no moving parts at all.
• Flash LiDAR : Acts like a standard camera; it illuminates the entire scene with one large “flash” and captures the return on a grid of sensors simultaneously.

Pros of Solid state LiDAR

Following are benefits or advantages of solid state LiDAR type.

1. With no macro-scale moving parts, these LiDAR sensors are highly resistant to the vibrations and shocks common in automotive and industrial settings.
2. They can be small enough to fit behind a rearview mirror or inside a smartphone.
3. They can be mass produced using CMOS technology, which drastically lowers the price for high volume manufacturing.

Cons of Solid state LiDAR

Following are drawbacks or disadvantages of solid state LiDAR type.

1. Most solid state units have a “forward facing” view (typically 60° to 120°). To get a 360° view, a vehicle needs multiple sensors.
2. Flash LiDAR, in particular, spreads its energy over a wide area, which often limits its effective range compared to a concentrated scanning beam.

Comparison between Mechanical and Solid State LiDAR Types

Summary

The choice between the two is based on performance vs. practicality. Mechanical LiDAR is the powerhouse for high end mapping where you need to see everything at once, regardless of cost or size. Solid State LiDAR is the future of the mass market; it is the invisible sensor that will eventually be standard on every consumer car and delivery drone due to its low cost, small footprint and long-term reliability.