Abstract: A compact apparatus for transmitting and receiving multiple sonar beams utilizes an acoustic lens to direct plane waves incident in desired directions to collimating lenses for presentation in phase to electroacoustic transducers having planar surfaces. The electroacoustic transducers emit sound waves which are transformed by the lenses into plane waves emergent in the desired directions.

Abstract: A compact apparatus for transmitting and receiving multiple sonar beams utilizes an acoustic lens to direct plane waves incident in desired directions to electroacoustic transducers positioned on spherical shell segments centered in the focal regions of the lens associated with the incident beams. The electroacoustic transducers transmit spherical waves that are transformed by the acoustic lens to plane waves emergent in the desired directions.

Abstract: Parametric array Doppler sonar apparatus includes an acoustic lens containing a flat disk-like central portion and an annular outer portion serving as a convergent lens. Multiple transducers are positioned between the lens and the focal plane so as to launch collimated acoustic beams in specified directions through the central portion of the lens and to receive reflected energy propagating principally through the annular portion of the lens.

Abstract: An acoustic lens for marine doppler sonar apparatus of the type in which acoustic energy is radiated and received along a beam directed at an angle with respect to a ship's axis is fabricated so as to have an external surface substantially flush with the ship's hull and an internal surface angularly disposed with respect to the external surface. Electro-acoustic transformation elements are mounted on the internal surface. The lens material is selected to have an acoustic propagation velocity greater than that of water so that acoustic signals are refracted in passing across the lens-water interface. The lens prevents spurious acoustic signals that would ordinarily be reflected from the aerated water close to the ship's hull from reaching the electro-acoustic transformation elements.