Spectral correlation as a tool for automated operation of tunable diode laser gas analyzers

Raimund Brunner; Roland Grisar; Maurus Tacke

doi:10.1117/12.255313

21 October 1996 Spectral correlation as a tool for automated operation of tunable diode laser gas analyzers

Raimund Brunner, Roland Grisar, Maurus Tacke

Proceedings Volume 2834, Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring; (1996) https://doi.org/10.1117/12.255313
Event: SPIE's 1996 International Symposium on Optical Science, Engineering, and Instrumentation, 1996, Denver, CO, United States

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.

Citation Download Citation

Raimund Brunner, Roland Grisar, and Maurus Tacke "Spectral correlation as a tool for automated operation of tunable diode laser gas analyzers", Proc. SPIE 2834, Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring, (21 October 1996); https://doi.org/10.1117/12.255313

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