Opto-acoustic 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 enables point hydrophones to cover a vertical range of60deg. 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 are positioned by a ray-tracing analysis to minimize internal acoustic reflections. Reflection losses <1 dB are predicted above the critical angle (for total internal reflection) at the water-window boundary.