Collection: 905nm Bandpass Filter

Context: A LIDAR instrument designed for autonomous vehicles or mapping systems that must operate effectively in high-solar-radiation environments (daylight).

Usage of Filter: The filter is configured as a "matching filter" with a narrow passband (5 nm or less) placed immediately before the detector.

Function: It is specifically tuned to a "solar blind" or atmospheric absorption window where solar radiation is naturally attenuated by water vapor in the atmosphere, while passing the specific 905 nm laser wavelength.

Result: This achieves a high Signal-to-Noise Ratio (SNR) by exploiting both the filter's rejection of broadband sunlight and the atmosphere's natural attenuation of background noise at that specific wavelength band.

Context: A pulsed-laser beam detector used in laser rangefinders, speed detectors, and LIDAR jammers that require high sensitivity to weak return pulses.

Usage of Filter: The filter is used at the optical input aperture to strictly limit the spectral bandwidth of light reaching the photodiode array.

Function: It acts as a spectral gate that blocks "foreign" laser sources (e.g., 1550 nm or 1064 nm) and significantly reduces the total optical power from ambient sunlight and heat sources entering the receiver.

Result: Prevents receiver saturation and allows the system's "Automatic Threshold Circuit" (ATC) and variable gain amplifiers to focus amplification solely on the 905 nm signal, improving detection range and accuracy.

Context: Advanced wide-angle LiDAR and 3D sensing systems requiring optical filters that maintain performance even when light enters at steep angles (High Angle of Incidence).

Usage of Filter: The 905nm filter is constructed using alternating layers of Hydrogenated Silicon Carbide (SiC:H) (high refractive index) and Silicon Oxide (low refractive index).

Function: The SiC:H material provides a high refractive index (approx. 3.46), which minimizes the "blue shift" (spectral shift toward shorter wavelengths) that typically occurs when interference filters are tilted or receive light from wide angles.

Result: Ensures the filter maintains high transmittance of the 905 nm signal across a wide Field of View (FOV), preventing the signal loss at the edges of the image that occurs with standard filter materials.