Method and System for Correcting Incident Light Fluctuations in Absorption Spectroscopy

摘要

A method and system for correcting the effect of intensity fluctuations of the transmitted light in an absorption spectroscopy system used for the detection or measurement of chemical species in a medium, whereby one or more modulation bursts are imposed onto a light beam that passes through the medium. This burst signal may be obtained by modulating the bias current of a tunable diode laser, and the modulation burst signal may be optimally at the second harmonic of the modulation frequency of a wavelength modulated beam to allow usage of the same signal path processing used for the spectroscopic detection of the measurand for a second harmonic detection system. The burst signal can be controlled using a smooth window function to minimise the effects of non-linear perturbations that are inherent in tunable diode laser wavelength modulation spectroscopy systems, of optical interference fringes (etalons) and of the residual light absorption by background chemical species or the measurand at the wavelength coinciding with the modulation burst.

主权项

1. A method of correcting for the effects of intensity fluctuations of incident light within an absorption spectroscopy system, comprising the steps of:
controlling a light source to emit a wavelength modulated beam of light; applying at least one modulation burst signal to perform one or more of modulating the wavelength modulated beam or modulating a separate beam synchronised with the wavelength modulated beam, which at least one modulation burst signal is a tapering signal modulation; detecting the modulated beam(s) of light after transmission through a sample medium; and processing the detected beam(s) to obtain at least one detected burst signal and to measure absorption effects of one or more measurands, wherein the processing includes comparing the at least one detected burst signal with the applied at least one modulation burst signal to determine intensity fluctuations of the incident light that are separate from absorption effects of the measurand(s), and correcting for the effects of the determined intensity fluctuations for increased accuracy of measurement of the absorption effects of the measurand(s).