Miniature FT-IR spectrometer for passive and active sensing

A novel handheld Fourier-transform infrared spectrometer (FTS) system, currently in development, is described. Estimated and measured performance data presented here are based on modeling and preliminary testing. The basic instrument will be useful for a variety of sensing applications, including chemical agent detection. One novel aspect is a refractively-scanned, field-widened interferometer, providing, in a miniature footprint, energy equal to a laboratory spectrometer. A second novel aspect is the use of solid-phase extraction to concentrate airborne chemicals for infrared detection. FTS instruments provide a powerful approach to identification of chemical and biological substances. The specificity is very high, while the sensitivity varies with sampling interfaces and detection methods. Cost, size, sensitivity and weight have impeded the widespread deployment of FTS systems. Cost can be reduced by a variety of means, including improved designs, mass production, and the on-going electronics and manufacturing revolutions. Size can be addressed by the use of field widening, which has been known for many years, though seldom used. Photoacoustic detection provides a very low-cost and relatively sensitive sampling interface. Modeling indicates that the sensitivity can reach part per billion to part per trillion levels.