The final design and testing of a filter for the Australian Navy's Las
er Airborne Depth Sounder is reported. This filter is a six-stage, act
ively tuned, Lyot birefringent filter with approximately 10 times bett
er signal-to-noise performance than the narrow-band filter currently i
n use. It is expected that this filter will improve the available flyi
ng time by up to 6 h/day. (C) 1997 Society of Photo-Optical Instrument
ation Engineers.