Demonstration of Range Doppler Compensated Holographic Ladar

摘要

Holographic ladar systems rely on the capture of temporally stable optical fringe patterns resulting from interference between the local oscillator (LO) beam and signal light imaged from a target. For pulsed systems, fringe visibility is maximized when the LO is temporally matched with the arrival time and duration of the signal, and when there is no gross relative motion between the sensor and target. In this demonstration, both range and velocity of a moving target were measured with a co-aligned high pulse rate laser range finder. Temporal matching was achieved by pulsing the LO to overlap the range-dependent signal arrival. Gross Doppler was compensated by using an acousto-optic modulator to impose a frequency shift onto the LO and transmitter (TX) that corresponded to the measured velocity. Range offset was compensated from ～200 m to ＞700 m and Doppler compensation was demonstrated from stand-still to full speed of the test vehicle (～24 m/s).