Patent ID: 6664533
Filing Date: 2003-12-16
Classification: G01J,G01N

Abstract:
A method of remotely detecting a particular gas dispersed in the atmosphere, the dispersed gas being of the type that absorbs light at frequencies within an absorption line range for the dispersed gas in the atmosphere, the method comprising the steps of:driving a source of generally monochromatic light by a laser drive to provide a carrier output at a predetermined frequency; frequency modulating the laser drive with a modulation frequency to generate at least one frequency modulated sideband signal in the output of the light source; and adding to the laser drive a ramp frequency to scan the light source and the sideband signal across a scan range including at least a portion of the absorption line range; directing at least a test portion of the ramped and modulated light toward an uncooperative target; collecting light reflected from the uncooperative target and directing it toward a first detector to generate at least one test signal based on the degree of attenuation of the sideband signal by the dispersed gas; and generating an output indicative of an amount of the dispersed gas in the atmosphere, if any, based on the at least one test signal.