Time-of-Flight Analysis of Three-Dimensional Imaging Laser Radar Using A Geiger-Mode Avalanche Photodiode

A laser radar system, direct-detection three-dimensional imaging laser radar using a Geiger-mode avalanche photodiode (APD) is introduced in this paper. The system consists of a passively Q-switched microchip laser as a light source, a Geiger-mode APD as a detector, a time-to-digital converter (TDC) as a signal processor, and a customized algorithm for three-dimensional visualization. Due to the extremely high sensitivity of the detector, the system has the ability to detect a target that is obstructed by a sparse obstacle. The combination of both the detector having short dead time and the TDC having a multi-stop function enables the system to operate in a single-or a multi-hit mode during the acquisition of time-of-flight data. It has been shown experimentally that the multi-hit mode is more efficient in detecting the objects behind a sparse obstacle than the single-hit mode. (C) 2010 The Japan Society of Applied Physics