A HIGH RESOLUTION HADAMARD TRANSFORM SPECTROMETER
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Date
1971
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Ohio State University
Abstract
A high resolution ($0.1 cm^{-1}$) Hadamard Transform Spectrometer for the infrared is described. The instrument employs an echclle grating and alkaline halide lenses, instead of mirrors. A helium-cooled germanium bolometer (1.9$^{\circ} K$ ) is used as a detector. Multiplexing is accomplished by stepping a 253 slot coded mask at the exit focal plane 126 times, thus generating a 127 square cyclic Hadamard matrix. The radiation is then returned, chopped, through a corner reflector for de-dispersion to the detector. The multiplexing procedure results in a theoretical S/N gain of 5.6 in the encoded spectrum. Since the 127 square matrix is inverted only once, and then stored, a small digital computer is sufficient for encoding the spectra. Sample spectra are given, including comparisons of single and multiplex slit scans.
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Author Institution: Astronomy Research Facility, University of Massachusetts