Long distance high accuracy 3-D laser radar and person identification

Results from our fast and high accuracy 3-D laser radar are given at distances up to 500 m. The system is based on gated viewing with range accuracy below 1 mm under optimal circumstances. It consists of a high sensitivity, fast, intensified CCD camera, and an Nd:YAG passively Q-switched 32.4 kHz pulsed green laser at 532 nm. The CCD has 752×582 pixels. Camera shutter and delay steps are controlled in steps of 100 ps. Each laser pulse triggers the camera delay and shutter. A 3-D image is constructed from a sequence of 50-100 2-D reflectivity images, where each frame integrates ~700 laser pulses on the CCD. In 50 Hz video mode we record a 2-D sequence in a second and process a 3-D image in a few seconds. We compare 3-D images at short to long distances and quantify the degree of person identification in 3-D. Turbulence, vibrations and system errors are found to limit a successful PID to distances shorter than ~500m for our prototype system.