SI-AS FOCAL-PLANE ARRAY DETECTION FOR FOURIER-TRANSFORM SPECTROSCOPICIMAGING IN THE INFRARED FINGERPRINT REGION

An instrument is described that simultaneously records images and spec tra of materials in the infrared fingerprint region using a long-wavel ength infrared focal-plane array detector, a step-scan Michelson inter ferometer, and an infrared microscope. With the combination of step-sc an Fourier transform (FT) Michelson interferometry and arsenic-doped s ilicon (Si:As) focal-plane array image detection, an infrared spectros copic imaging system has been constructed that maintains both an instr umental multiplex: and multichannel advantage and operates from approx imately 4000 to 400 cm(-1). With this method of mid-infrared spectrosc opic imaging, the fidelity of the generated spectral images recorded t hrough the microscope is solely determined by the number of pixels on the focal-plane array detector, and only a few seconds of data acquisi tion time are required for spectral image acquisition, This seamless c ombination of spectroscopy for molecular analysis and the power of vis ualization represents the future of infrared microscopy. Step-scan ima ging principles, the operation and characteristics of long-wavelength array detectors, and instrument design details are outlined, and infra red chemical imaging results are presented. The results are discussed with respect to their implications for the chemical analysis of a vari ety of solid-state materials.