The Practicalities of a Spatial Coherence Filter in free-space LIDAR Environments

A scanning LIDAR system that uses a single pixel detector can be highly attractive, with simple data processing coupled with low cost and complexity. However, the impact of ambient light noise is much greater than with a multiple pixel system. A potential means of overcoming this is to filter for transverse spatial coherence. Such filters have been discussed and evaluated in the literature, typically based on an axicon or a spiral phase plate that creates a ring with coherent light. Incoherent light, in contrast, smears the light out diffusely, allowing for spatial separation and thus, filtering. The focus of the existing literature tends to be in optical communication or underwater ranging, whereas a free-space LIDAR environment has distinct issues that inhibit the practicality of the filter if a direct replication is performed. This work thus focusses on exploring the practical implementation of these filters in a free-space LIDAR environment.