NIR LIDAR for Hazard Mitigation

We have investigated the feasibility of employing a hazard detection and mitigation system based upon a polarization discriminating range-gated Lidar system. This dual use system will be capable of both imaging targets in low visibility scenarios, such as smoke, fog, haze, light rain, and low light levels, and providing an early warning of in-flight hazards, primarily icing conditions in clouds. The polarization discriminating optical system and accompanying image processing software are capable of differentiating highly depolarizing surfaces from those that contribute little to depolarization. Examples of this type of differentiation include water and ice phases in clouds and hard-target surfaces surrounded by an aerosol particulate media. The NIR Lidar system is designed to operate around 1.5 m for maximum eye-safety, even when used from the ground. Major components of the Lidar unit include a laser transmitter, a fast gated detector, and polarization switching components. The performance of this type of system has been demonstrated in the Phase I project in laboratory experiments using custom built rain and fog generating chambers. Both image enhancement of a hard target and detection differing depolarization ratios were demonstrated. Backscattered noise from obscurants is greatly reduced by the fast-gated camera system, and a narrowband optical filter provides additional noise rejection. The NIR Lidar system can be easily integrated with a database of common object types for identification of hard targets, such as obstacles on a runway. Illuminated NIR imagery is ideal for providing images of hard targets, as object detail is very near that seen with a visible camera, unlike FLIR (forward-looking infrared) imagery, and the performance is equivalent in day or night conditions.