Patent ID: 6327896
Filing Date: 2001-12-11
Classification: G01M,G02F

Abstract:
A photo-acoustic leak detection system for determining whether a gas is leaking from a component, comprising:(a) an acousto-optic cell capable of operating at a range of frequencies and diffracting a plurality of beams incident upon said acousto-optic cell at a common entry location and common angle, wherein a first of said beams has a first wavelength that is substantially incapable of being absorbed by the gas, wherein a second of said beams has a second wavelength that is capable of being absorbed by the gas;(b) a signal controlling apparatus comprising:(1) a first signal controller producing a first frequency selected such that when said acousto-optic cell operates at said first frequency, said acousto-optic cell diffracts said first beam at a predetermined angle;(2) a second signal controller producing a second frequency selected such that when said acousto-optic cell operates at said second frequency, said acousto-optic cell diffracts said second beam at said predetermined angle; and(3) a switch receiving said first signal and said second signal, said switch having a first position and a second position such that when said switch is in said first position said switch emits said first signal to said acousto-optic cell, which operates at said first frequency and diffracts said first beam at said predetermined angle, and when said switch is in said second position, said switch emits said second signal to said acousto-optic cell, which operates at said second frequency and diffracts said second beam at said predetermined angle;(c) an acoustic sensor which receives a first acoustic signal and a second acoustic signal, said first acoustic signal emitted by the gas and/or the component upon the gas substantially failing to absorb said first beam, said second acoustic signal emitted by the gas and/or the component upon the gas absorbing said second beam, said acoustic sensor providing a first and second sensor signal indicative of said first and second acoustic signals, respectively; and(d) a signal processor which receives said first and second sensor signals, said signal processor using said first sensor signal as a non-leak baseline measurement and providing an output signal, which is the difference between said first and second signals and indicative of whether a leak exists.