Advances in Infrared Instrumentation

Abstract : The goal of this project is to develop an IR spectrometer concept for spectral measurement of randomly occurring optical events for differentiation of man-made versus naturally occurring phenomenon such as lightning. Pulsewidth as short as 10 microseconds makes standard Michelson interferometer unsuitable. SSG investigated optical concepts with no moving parts by detection of a spatially extended optical fringe pattern with a linear detector array. Visible breadboard interferometer of Tilted Michelson and Common Path Triangle configurations were assembled and demonstrated successfully. We learned that although the randomly occurring test sources were detected, the SNR sensitivity was lower than expected comparable to a single slit spectrometer using the same FPA. For increase of SNR, a novel photodiode array spectrometer concept using many entrance slots and encode them with a pattern in accordance with a Hadamard derived coding scheme was invented by VanTassel and Wong (U.S. Patent No. 5050989). A visible breadboard Hadamard Transform Spectrometer was also built to validate the sensitivity advantage over the single slit spectrometer.