US Patent 7301608 Photon-counting, non-imaging, direct-detect LADAR

A light wave rangefinder includes a light transmitting optical system for directing a laser pulse at a target, and a light receiving optical system for receiving reflected light from the target, including a Geiger-mode avalanche photodiode (APD) array and a non-imaging optical device. The non-imaging optical device is positioned between the received reflected light and the APD array, and is configured to uniformly distribute the received reflected light across the APD array. The APD array is uniformly illuminated by a single received reflected laser pulse, producing a plurality of Geiger-mode avalanche events.