Patent ID: 6731570
Filing Date: 2004-05-04
Classification: G01H,G01S

Abstract:
A remote sound detector for detecting a hidden source of acoustic signals, comprising:a) a transmitter including a laser source operably arranged for producing a laser beam, and a modulator for modulating the laser beam to produce a train of pulse to pulse coherent signals, and the transmitter being operable for transmitting the signals as a beam into a region of atmosphere which is located above the hidden source of the acoustic signals; b) a receiver operably arranged for receiving resultant signals from an intersection of the beam with the acoustic signals in the region of atmosphere; c) an interferometer operably arranged for providing an interference pattern between the laser beam and each resultant signal; d) a detector including a photoreceiver operably arranged for detecting and producing an output signal corresponding to changes in each interference pattern, and operably connected to the receiver and arranged for determining a presence of the hidden source of the acoustic signals from a phase difference between successive resultant signals; and e) a sampler operably arranged for sampling the output signals from the photoreceiver, and a comparator operably arranged for comparing the output signals from immediate successive pairs of outputs from the photoreceiver to produce a result.