Patent ID: 7259856
Filing Date: 2007-08-21
Classification: G01N

Abstract:
1. A process for measuring the absorption spectrum of a target analyte using a cavity ring down spectrometer comprising a tunable laser light source, a wavelength monitor which measures the wavelength of the light emitted by said laser and provides an output signal based on said measurement, and a resonant optical cavity, said process comprising the steps of: i) tuning said laser such that the light transmitted from said laser into said cavity is varied over a wavelength interval λ ii) shutting off the transmission of light into said cavity to thereby trigger a ringdown event; ili) repeating steps i) and ii) a plurality of times; iv) for each said ringdown event, recording the decay time constant τ, the wavelength of the light transmitted into the cavity immediately prior to shutting off transmission, and the trigger time at which the light is shut off; v) organizing the decay time constants, light wavelength and trigger times recorded in step (iv) as a function of trigger time; vi) ordering said light wavelengths by increasing value and placing groups of wavelengths into individual bins, said groups being defined by discontinuities in the wavelength monitor signal; vii) computing the average wavelength of each bin group; viii) grouping the decay time constants and trigger times into bins that parallel said wavelength bins, with the decay time constants in each of said parallel bin being arranged by increasing trigger time; ix) computing the average decay time for each decay time bin identified in step (viii) and using this decay time average, together with the average wavelength from the parallel wavelength bin, to compute the optical loss for the target analyte at said average wavelength; x) providing said computed optical loss as an output.