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Proceedings Paper

Spectral correlation as a tool for automated operation of tunable diode laser gas analyzers
Author(s): Raimund Brunner; Roland Grisar; Maurus Tacke
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Paper Abstract

We report on an experimental investigation of the possibility to correlate diode laser gas transmission spectra to computed or previously measured spectra. Spectral correlation of this kind could profitably be applied in automated gas analyzers in order to retrieve optimum laser emission characteristics after laser degradation. The full procedure reported here includes experimental gas transmission spectroscopy by lead-chalcogenide lasers recorded simultaneously with the transmission of a Mach- Zehnder interferometer within a reference channel. The interferometer fringes are used for identification of a single-mode laser operating range and for wavenumber linearization and background intensity correction of the gas transmission spectra within this range. Direct correlation of these corrected spectra turns out to be inadequate for spectra with strong quasi-periodic absorption lines as is the case for carbon dioxide. In particular in the presence of noise, a number of nearly indistinguishable correlation factor maxima are found. Better results were obtained by generating a barcode pattern from the corrected transmission before performing the numerical correlation with one unambiguous correlation factor maximum. This barcode technique was also verified to be more reliable for irregular spectra as for methane, and to be less sensitive to noise and background intensity variations.

Paper Details

Date Published: 21 October 1996
PDF: 12 pages
Proc. SPIE 2834, Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring, (21 October 1996); doi: 10.1117/12.255313
Show Author Affiliations
Raimund Brunner, Fraunhofer-Institut fuer Physikalische Messtechnik (Germany)
Roland Grisar, Fraunhofer-Institut fuer Physikalische Messtechnik (Germany)
Maurus Tacke, Fraunhofer-Institut fuer Physikalische Messtechnik (Germany)

Published in SPIE Proceedings Vol. 2834:
Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring
Alan Fried, Editor(s)

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