Subsea sonar unit with two oil-water interfaces to avoid sonar deterioration with depth and temperature variation

摘要

Underwater sonar unit comprising oil-filled housing 4 positioned in propagation path of acoustic beam transmitted from acoustic transducer 6, and corrective lens 2 mounted in propagation path 1a between transducer and housing, wherein corrective lens surface has shape relative to cross-section of acoustic beam that has same shape as housing surface relative to cross-section of acoustic beam at housing surface. The corrective lens may be water 5 enclosed in polyurethane body with sound speed close to water at room temperature and moulded with one concave end with similar curvature to housing 1 and other edge 3 glued to transducer. The lens may be moulded with proper width according to transducer beam width to give equal incidence angles at front face. The lens material may have sound speed close to water and free of air bubbles to avoid deformation at depth. The lens may be filled with water, including anti-freezing agent, and assembled with transducer in oil-filled spherical dome shell. The ultrasonic beam does not suffer performance deterioration in extreme conditions as temperature and pressure varies because of sonar beam deflection passing through two oil-water fluid interfaces with sound variation effects cancelled because of similarly shaped interface surfaces.