White Paper: Photonics/Optics

Thin-Film Interference Filters for LIDAR

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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.

LIDAR is becoming more efficient, affordable, and accessible than ever. Recent technological advancements have seen dramatically increased accuracy and resolution, even in systems that are small enough to be discretely hidden within the side mirrors of self-driving cars. Thin-film interference filters have kept up with the technology through state-of-the-art design and coating techniques, advanced measurement systems, tight uniformity control, and minimal thermal dependence.

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.

This white paper highlights how high-performance LIDAR interference filters have greatly improved signal-to-noise ratios and reduced the need for multiple filtering techniques. The basics of LIDAR and LIDAR interference filters are presented, followed by specific applications and additional filter considerations.

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