Zero-crossing sampling of Fourier-transform interferograms and spectrum reconstruction using the real-zero...

Area of Science:

• Spectroscopy
• Analytical Chemistry
• Signal Processing

Background:

• Fourier-transformed infrared (FT-IR) spectroscopy is a powerful analytical technique.
• Traditional FT-IR interferogram acquisition requires high-resolution analog-to-digital converters (ADCs) to capture wide dynamic ranges.
• The need for high-resolution ADCs can increase instrument cost and complexity.

Purpose of the Study:

• To introduce and evaluate the real-zero interpolation method for FT-IR interferogram reconstruction.
• To demonstrate the feasibility of reconstructing FT-IR spectra from binary interferograms.
• To assess the impact of oversampling on the dynamic range of reconstructed interferograms.

Main Methods:

• Applied the real-zero interpolation method to FT-IR interferograms.
• Integrated a phase-locked loop circuit into an FT-IR spectrometer for interferogram oversampling.
• Acquired binary interferograms of polystyrene and Mylar films.
• Performed computer simulations to evaluate the oversampling ratio's effect on dynamic range.

Main Results:

• Successfully reconstructed Fourier spectra from binary interferograms of polystyrene and Mylar films.
• Demonstrated that the real-zero interpolation method can reconstruct interferograms from zero-crossing information alone.
• Quantified the relationship between the oversampling ratio and the dynamic range of the reconstructed interferogram via simulations.

Conclusions:

• The real-zero interpolation method offers a viable alternative for FT-IR interferogram acquisition, potentially reducing hardware requirements.
• The method's practical applicability and limitations for real-world FT-IR analysis require further investigation.
• Oversampling is a critical parameter influencing the dynamic range achievable with this reconstruction technique.