Chemical analysis and imaging by discrete fourier transform spectroscopy

Abstract

An instrument for chemical spectroscopy with imaging capabilities. A lightsource produces an array of light beams, each of which is made up of a plurality of discrete wavelengths. The array of light beams are modulated by an interferometer, then directed through a sample to an array of detectors. The sample may be a chemical mixture (e.g. a fuel stream in a manufacturing facility) or a body part (e.g. breast, limb, or head). An array of laser or light-emitting diodes provides light at the desired wavelengths and high intensity. The set of wavelengths is selected for a particular kind of analysis, and a specific set of possible absorbing species to be detected. The different wavelengths are guided optically (using fiber optics, lenses, and/or mirrors) into a single lightbeam, or an array of lightbeams. This light is then directed through the sample and onto a detector. The lightsource and detector, or lightsource alone, may be rastered if necessary to form an image. Individual lightbeams in an array may be modulated, polarized, or both so as to improve resolution. The signal from the detector undergoes a Fast Fourier Transform to produce a near-infrared absorption spectrum as a function of wavelength. The absorption spectra can be used to produce an image of the spacial distribution of detected species within the sample. Either the lightsource or detectors can be placed on the end of a probe or catheter for imaging through the wall of a hollow sample.