Digital signal processor-based high-precision on-line Voigt lineshape fitting for direct absorption spectroscopy

Area of Science:

• Spectroscopy
• Physical Chemistry
• Optical Engineering

Background:

• Accurate on-line measurement in direct absorption spectroscopy (DAS) is crucial for real-time monitoring.
• Voigt lineshape fitting is essential for analyzing spectral data, but computationally intensive.
• Existing methods may lack the precision or speed required for real-time applications.

Purpose of the Study:

• To develop and implement a system-on-chip, high-precision digital signal processor (DSP)-based on-line Voigt lineshape fitting method for DAS.
• To improve the accuracy and efficiency of spectral analysis in real-time DAS measurements.
• To enable accurate recovery of physical parameters like temperature and concentration from spectral data.

Main Methods:

• A look-up table was created for rapid and accurate calculation of Voigt lineshapes based on Gauss and Lorentz full width at half maximum (FWHM).
• A Gauss-Newton nonlinear fitting module was implemented using the look-up table and raw absorbance data to determine spectral parameters.
• A digital signal processor (DSP) was utilized to perform real-time Voigt lineshape fitting within a DAS measurement system.

Main Results:

• The DSP-based on-line Voigt lineshape fitting successfully fitted spectral data in real-time.
• Temperature and H2O concentration were accurately recovered from flame transitions using the developed method.
• The proposed method demonstrated improved measurement accuracy compared to direct integration of raw absorbance data.

Conclusions:

• The implemented DSP-based on-line Voigt lineshape fitting provides a robust solution for high-accuracy measurements in DAS.
• This approach enhances real-time spectral analysis capabilities, enabling precise determination of gas properties.
• The method offers a significant improvement over traditional spectral analysis techniques for on-line applications.