Arguably the most versatile active remote sensing technique, LIDAR (Light Detection and Ranging) is used across platforms and across disciplines. Long known to be one of the most important technologies in Earth and atmospheric sciences, LIDAR is now being utilized for obstacle avoidance in autonomous vehicles, urban planning, security, infrastructure development, and many other applications. This surge of novel uses recently forced an influx of technological advancements and a renewed interest in LIDAR sensors that is driving down the cost and making the technology more accessible.
In order to keep up with the technology, LIDAR interference filters must be designed to maximize signal-to-noise ratios by reliably isolating the target LIDAR return signal. Recent advancements in thin-film, ultra-narrow bandpass interference filters have allowed for >95% transmission, less than 0.1 nm bandwidths, steep edges, a square spectral shape, wide range blocking measured at > OD 8 (-80 dB), uniform coatings, and minimal thermal dependence. High performance LIDAR interference filters have greatly improved signal-to-noise ratios and reduced the need for multiple filtering techniques.
Thin-film interference filters are made by depositing alternating layers of materials with contrasting indices of refraction onto a substrate. As light makes its way through the filter, part of the light reflects at each layer, resulting in internal interference. Depending on the thicknesses and configuration of the layers, the net result is that certain wavelengths of light are transmitted through the filter, while others are either absorbed by it or reflected off of it.
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