Patent ID: 7541586
Filing Date: 2009-06-02
Classification: G01N

Abstract:
1. A compact cavity ring down spectroscopy apparatus for detection and measurement of trace species in a sample gas, which comprises: a housing for said apparatus; a tunable solid-state continuous-wave mid-infrared PPLN OPO laser within said housing; an acousto-optic modulator in fiber optical communication with said laser for steering a first order diffraction beam of said laser and for interrupting said beam when resonance is achieved; a ring down resonant cavity within the housing for holding a sample gas, said cavity cell receiving said first order diffraction beam of said laser and comprising at least two high-reflectivity mirrors, wherein said mirrors define an intracavity light path and one of said mirrors is a movable tuning mirror, wherein the cavity has 4 mirrors in a bowtie configuration; a piezo transducer drive attached to the tuning mirror for modulating cavity length to maintain resonance between the laser frequency and cavity modes; and a photo-detector within said housing, for receiving said beam from the cavity and for generating a resonance signal and a voltage decay (ring down) signal, thereby measuring an interaction of said sample with said intracavity beam; and, a microprocessor for reducing the periodic noise in the voltage decay signal by recording the cw-CRD voltage decay signals as data and subjecting the data to a cluster analysis or averaging the interquartile range of the data; wherein the trace species of the sample gas is selected from the group consisting of: HCHO, H2S, methyl mercaptan, CO2, CO, HCN, HCl, NH3, C2H2, sarin, VX, mustard gas, arsine, phosgene, tear gas, pepper gas, nitro-based explosive, and B2; and, wherein the apparatus is configured as a desktop apparatus wherein the foot print is between about 6″ to about 12″ wide, by about 5″ to about 8″ deep, by about 5″ to about 8″ tall.