Advanced LIDAR In Development

A new near-infrared Light Detection and Ranging (LIDAR) system being developed by RL Associates, Chester, PA, could provide pilots with advanced warning of potentially hazardous atmospheric conditions, such as icing. The system, now in prototype testing, may also provide better images in fog, rain and extremely hazy ground conditions. LIDAR works like radar but uses light waves instead of radio waves. Lasers use light at wavelengths much smaller than radio waves, so they are much better at detecting very small objects. LIDAR is used in atmospheric research, but not on commercial planes to measure the densities of various particles in the middle and upper atmospheres. RL Associates says the system uses a laser light beam that is polarized, or has its electric field pointing in a specific direction. The system beams the polarized infrared light out, and then records the amount of polarization that returns to the sensors. Rain and fog return a less polarized signal, and metal and people return a more polarized signal. The data is processed to form an image of the ground, or could be translated into verbal commands, if needed. The system can better detect different types of particles in the atmosphere, such as ice, super cooled liquid or just regular water vapor. It can also identify the difference between water vapor and other kinds of substances. The company says the system is the first of its kind to use near-infrared. The system also employs a "range-gated detector" that is only turned on for very short periods of time when the return signal is expected. This leads to a vastly improved signal-to-noise ratio, resulting in better images, particularly in obscuring conditions such as fog or haze.