Underwater laser imaging system (ULIS)

This paper describes design and characteristics of an Underwater Laser Imaging System (ULIS) developed for detection of underwater mines and mine-like targets. The ULIS uses a diode pumped Nd:YLF laser, frequency doubled to 523.5 nm as a transmitter and an Image Intensifier Tube ((IT)-T-2) Its a receiver. The transmitter uses an innovative technique of frequency stabilization to reduce laser line-width so that the receiver can use a less than 1 nm Narrow Band Pass Filter (NBPF). This results in a significant reduction of the back-ground noise in the receiver. Also, the (IT)-T-2 based receiver is range gated to reduce back-scatter noise, A polygon scanner is used in the ULIS with the transmitter and the receiver to obtained range resolved imagery. Description of the system components and performance characteristics of the system as ladar are provided.