Eye-safe lidar at 2.09 μm

Abstract

A 2.09 μm eye-safe laser radar is being built that will have a coherent and an incoherent mode of operation. The trade-offs between coherent and incoherent detection methods will be investigated. In coherent detection a single pulse can be used for both velocity and range measurements. The problem that arises in coherent detection is that accurate velocity measurements require a long pulse and the longer the pulse the worse the range resolution. Another problem that exists in coherent detection is the longer the coherence length of the pulse the more degradation in the signal at the receiver caused by speckle. In an incoherent system velocity measurements can be made with two successive range measurements. The pulse length used can be shortened, increasing the range resolution and decreasing the degradation caused by speckle. This system will be used to compare the theoretical predictions with actual measurements as well as to examine the practical implementation of the different detection techniques.