SUPER-DYNAMIC-RANGE MEASUREMENT OF FT-IR SPECTRA BY DELTA-SIGMA MODULATION

An innovative quantization technique, delta-sigma (Δ∑) modulation, is applied to high dynamic range measurement of FT-IR spectra. An FT-IR interferogram is quantized into only one bit by a comparator in the nonlinear feedback loop system after sampled at a rate higher than the Nyquist rate. The FT-IR spectrum is calculated by the simple DFT (discrete Fourier transform) algorithm directly from the one-bit binary data. A modulator was implemented to an commercial FT-IR spectrometer and a single-beam spectrum of a nichrome source was measured for demonstrating its potential.