Patent ID: 7075653
Filing Date: 2006-07-11
Classification: G01F,G01M,G01N

Abstract:
1. A method of detecting the presence of a gas comprising the steps of, illuminating a target with a light beam from a laser having a wavelength generally corresponding to an absorption band of said gas, receiving at a detector a received portion of said light beam which is reflected from said target, sampling said received portion of said light beam to produce a series of measurements which are indicative of a concentration length product of said gas through which said received portion of said light beam has traveled, periodically determining a detection threshold from a statistical analysis of said series of measurements which estimates a threshold level above which a current measurement of said series of measurements is significant, comparing said current measurement of said series of measurements with a recent determination of said detection threshold, and producing a signal which indicates the presence of said gas at a level greater than said threshold level when said current measurement exceeds the recent determination of said detection threshold.