Dual Beam Doppler Shift Hydrophone.
Patent, Filed 10 Dec 79, patented 5 Mar 91,
DEPARTMENT OF THE NAVY WASHINGTON DC
Pagination or Media Count:
A dual beam hydrophone wherein a reference later beam and a signal laser beam are both modulated simultaneously by the movement of reflecting surfaces responding to pressure variations due to an impinging acoustic wave. Each beam, travels the same path length within the hydrophone before being detected, thus eliminating any otherwise needed signal compensation. The reference beam and signal beam are acoustically modulated 180 degrees out of phase which reduces by one half the number of reflections normally required to produce the same sensitivity.