Theory and technical approach in the feasibility design of a conical acoustic lens

The opto-acoustic design of a liquid-filled conical acoustic lens is discussed. An approximate model of stacked cylindrical elements is used to estimate the focal line. Final optimization is to be achieved experimentally. Diffraction is to be utilized to cover 60° vertical range by point hydrophones. An iterative optimization procedure yields cone angle and window aperture size that give diffraction patterns to accomplish this with 3 db maximum loss at the extreme elevations. Baffles were positioned to suppress internal acoustic reflections by a ray-tracing analysis. Reflection losses <1 db are predicted above the critical angle for total internal reflection at the water-window boundary.