Choosing the Right Filter for a 905nm Laser Ranging System

Laser ranging technology has become essential in both military and civilian uses, especially with the rise of autonomous vehicles. This technology often uses either phase shift or pulse methods for measuring distances, with pulse ranging being popular for its cost-effectiveness and simplicity.

For effective laser ranging, especially in systems like autonomous vehicles, selecting the right filter is crucial. Here’s what to consider for a 905nm laser:

1. Laser Wavelength Variability: Lasers come with a specific wavelength range, often with a tolerance of about ±5nm.
2. Temperature Effects: The laser’s wavelength can change with temperature. For a 905nm semiconductor laser, the wavelength extends by about 1nm for every 10°C increase in temperature.
3. Measurement Angles: The angle at which measurements are taken can affect the filter choice. Larger angles require filters with a broader bandwidth and a slight adjustment in the center wavelength towards longer wavelengths.
4. Manufacturing Tolerances: When filters are made, their central wavelength and bandwidth can vary slightly.

Considering these points, for autonomous driving where the measurement angle is about 20° using a 905nm laser, the typical filter specifications would be:

• Center wavelength: 922 ± 3nm
• Bandwidth: 66 ± 6nm
• Peak Transmission: >95%
• Block Efficiency: >OD4 for wavelengths from 200 to 1100nm.