Allan Variance Characterization of Compact Fourier Transform Infrared Spectrometers

Abstract

Handheld Fourier transform infrared (FT-IR) spectrometers are very promising candidates for several applications where accurate real-time material detection and quantification are needed. Due to their compact size, their mode of operation which does not allow for long warm-up time, and changing environmental conditions, these spectrometers suffer from short-term noise and long-term instabilities which affect their performance. In this work, the effect of long-term multiplicative instabilities on the signal-to-noise ratio (S/N), measured using the 100% line-method, is studied. An expression for the variance, in this case, is deduced. The Allan variance technique is used to identify and quantify the presence of the different types of noises. The methodology is applied to a commercial NeoSpectra scanner module from Si-Ware Systems, Inc.

Measurements and analysis of spectrally resolved spot profile of diffuse reflection micro spectrometers using knife-edge white reference

“…Additionally, the optical head includes optical mirrors and lenses to collect light from the target area on the sample and direct it to the spectral sensor [5] [6]. Illustrative schematic of the whole system is shown in Figure 1 Characterizing the MEMS spectrometer involves evaluating an essential parameters such as the signal to noise ratio [7], the spectral resolution [8] and the spot profile of the light interacting with the sample and finally collected by the spectrometer. This profile serves to quantify the quantity of light that can be effectively coupled from the sample to the spectrometer.…”