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Proceedings Paper

Realization of the van Cittert monochromator system for high-accuracy mid-IR spectrophotometry and spectroradiometry
Author(s): Janos P. Makai; Janos Balazs; Laszlo Dobrentei; Jozef J. Makai; Istvan Reti
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Paper Abstract

Classical dispersive double monochromator systems generally provide high stray light rejection but the energy throughput is very low at higher wavelengths. The low throughput disables the characterization of high optical density samples. Spectral multiplexing, like in Fourier transform or array spectrometers, increases the throughput and improves the signal-to-noise ratio of the spectroradiometer/spectrophotometer but they show other shortcomings. To correct these shortcomings a new system based on a van Cittert monochromator is under construction. The van Cittert system consists of two identical monochromators coupled together as a subtractive system. The usual narrow slit, between the two monochromators, is replaced by a wide one and a part of this wide slit is covered by a lamella, mounted on a fine resolution translation stage. The wide slit transmits a wide spectral range but the lamella filters out a narrow range, it operates like a notch filter. The second monochromator collects and recombines the transmitted radiation at its exit slit. The sample can be positioned behind the exit slit and the beam forming elements in a spectrophotometer system. By the translation of the lamella the center wavelength of the notch can be shifted over the whole spectral range covered by the wide slit. Carrying out spectroradiometric/spectrophotometric measurements the total transmitted power is measured at every stop of the lamella. From this array of measurement results the transmittance, reflectance, emittance or absorptance of the sample can be calculated as a function of the wavelength. The theoretical basics and the first results will be shown.

Paper Details

Date Published: 18 November 1998
PDF: 7 pages
Proc. SPIE 3437, Infrared Spaceborne Remote Sensing VI, (18 November 1998); doi: 10.1117/12.331305
Show Author Affiliations
Janos P. Makai, Research Institute for Technical Physics and Material Science (Austria)
Janos Balazs, Research Institute for Technical Physics and Material Science (Hungary)
Laszlo Dobrentei, Research Institute for Technical Physics and Material Science (Hungary)
Jozef J. Makai, Siemens Telefongyar Ltd. (Hungary)
Istvan Reti, Research Institute for Technical Physics and Material Science (Hungary)

Published in SPIE Proceedings Vol. 3437:
Infrared Spaceborne Remote Sensing VI
Marija Strojnik; Bjorn F. Andresen, Editor(s)

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