905 nm vs. 1550 nm LiDAR: Pros, Cons and Comparison

Introduction : In LiDAR engineering, industry is currently split between two primary wavelength viz. 905 nm (Near Infrared) and 1550 nm (Short Wave Infrared). Let us compare these two approaches with respect to SNR, safety and manufacturing costs and explore differences between them.

905 nm LiDAR

It is the most common wavelength used in LiDAR today, found in everything from warehouse robots to many automotive sensors.

Pros of 905 nm LiDAR

Following are benefits or advantages of 905 nm LiDAR type.

• 905 nm light can be detected using Silicon based sensors such as SiPMs or SPADs. Silicon is the foundation of the entire semiconductor industry, making these detectors extremely cheap to mass produce.

Cons of 905 nm LiDAR

Following are drawbacks or disadvantages of 905 nm LiDAR type.

• The human eye is transparent to 905 nm light, meaning the lens focuses this light directly onto the retina. To prevent permanent eye damage, the laser power must be kept very low. This low power limits the effective range of the sensor.
• At 905 nm, there is significant solar noise. To distinguish the laser’s reflection from sunlight, engineers must use complex filtering or multi shot pulsing techniques.

1550 nm LiDAR

This wavelength based LiDAR is often considered the premium choice. It is used by companies focused on long range and high speed autonomous driving.

Pros of 1550 nm LiDAR

Following are benefits or advantages of 1550 nm LiDAR type.

• The sun emits very little energy at the 1550 nm wavelength. This means there is almost no background noise to compete with the laser signal.
• 1550 nm light is absorbed by the moisture in the human eye before it reaches the retina, it is considered “eye safe.”
• Due to above, engineers can design LiDAR which can fire the laser at significantly higher power levels which results in massive boost to SNR and range.

Cons of 1550 nm LiDAR

Following are disadvantages of 1550 nm LiDAR type.

• The cost is the major drawback. Silicon is blind to 1550 nm light. To detect these photons, manufacturers must use specialized materials like Indium Gallium Arsenide (e.g. InGaAs). These materials are much more expensive to produce and harder to integrate onto standard silicon chips, leading to a significantly higher price tag per sensor.

Comparison between 905 nm Vs. 1550 nm LiDAR

Summary

The choice between the two is based on SNR vs. Cost considerations. Choose 905 nm if your primary goal is affordability and mass market integration. Choose 1550 nm if your primary goal is ultimate performance and safety at high speeds.