Development of a novel low-cost NIR gated-viewing sensor for maritime search and rescue applications

A novel gated-viewing instrument is presented for vision enhancement in maritime search and rescue applications predominantly under limited visibility conditions at night. The compact device consists of a camera and an eye-safe NIR (near-infrared) illuminator and has a field of view of approximate to 7 degrees x 6 degrees, which is similar to field glasses. The detection range is 250 m for Lambertian reflectors, but is much larger if clothes with retro-reflectors are worn. A key challenge is the cost effectiveness of the instrument as potential users in the field of maritime search and rescue applications usually suffer from financial limitations. As a result, no image intensifier, but an off-the-shelf CMOS camera in accumulation mode with a reasonable quantum efficiency in the NIR region is used. The active illumination is based on a self-developed illuminator consisting of 7 pulsed vertical-cavity surface-emitting laser (VCSEL) arrays. The mean optical power is 7 W, the center wavelength is lambda approximate to 804 nm, and the light pulse width is approximate to 100 ns at a repetition rate of 345 kHz. Detailed simulations leading to the system design are presented together with respective characterization measurements of the camera and illuminator as well as first test measurements of the complete system.