Remote sensing using coherent sonic wave photoacoustic detection and methods

摘要

A method and system for detecting composition of a physical space comprising: a laser beam source; an acoustic sensor; a beam focusing mechanism for focusing the laser beam at predetermined points in the physical space to generate a thermal inhomogeneity which results in the propagation of a pressure wave that propagates outward from the predetermined excitation point at a propagation velocity approximating the speed of sound for the particular composition of the media; at least one processor for controlling the timing for the laser beam focusing to generate thermal inhomogeneities; whereby the laser focal point is moved sequentially along the light-of-sight at various excitation points by the beam focusing mechanism approximately at the phase front velocity to define a series of predetermined excitation points and pressure wave propagations such that the series of pressure wave propagations combine to produce a coherent pressure wave detectable by the acoustic sensor.

主权项

1. A method for detecting the composition of a physical space comprising;
at a first predetermined time focusing a laser at a first predetermined excitation point along the line of sight of the laser to create rapid localized heating of the gases to produce a thermal inhomogeneity which results in the propagation of a first pressure wave; the first pressure-wave propagating outward from the predetermined excitation point at a propagation velocity approximating the speed of sound that is defined for the particular composition of the media; at a second predetermine time focusing a laser to a second predetermined excitation point along the line of sight of the laser to produce a second pressure wave; the velocity from the first predetermined excitation point to the second predetermined excitation point being selected to approximate the propagation velocity of the pressure wave which creates an effective superposition of the first and second pressure-waves at the second predetermined excitation point; and moving the laser focal point sequentially along the light-of-sight at various excitation points approximately at the phase front velocity to define a series of predetermined excitation points and pressure wave propagations; whereby the series of pressure wave propagations combine to produce a coherent pressure wave that can be detected at a predetermined distance by an appropriate acoustic sensor.