Development and testing of a synchronous-scanning underwater imaging system capable of rapid two-dimensional frame imaging

The design and construction of a synchronous-scanning underwater imaging system capable of rapid two-dimensional scanning are described. The imager employs a 7-W, all-lines, argon-ion laser in onjunction with a galvanometrically driven raster scanner and an image-dissector tube receiver. The imager is capable of directly generating real-time RS-170 video imagery. The results of an in-water test of the imaging system, in which a high-contrast imaging test pattern was imaged, demonstrate operating anges of up to 4 attenuation lengths (AL) when the test was run at real-time frame rates, ranges of 5.1-5.5 AL when the system operated with an eight-frame running average, and ranges of 6.3 AL when a 128-frame running average was used. The system performance was compared with that of several floodlight/silicon-intensified-target TV camera configurations, which produced a maximum imaging range of ∼2.6 AL. Also, an imaging configuration that used the raster-scanned beam of the laser as an illumination source for the sil n-intensified-target camera was tested. That system had an ultimate range of ∼ 4 AL.