18 November 1998 Realization of the van Cittert monochromator system for high-accuracy mid-IR spectrophotometry and spectroradiometry
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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.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Janos P. Makai, Janos P. Makai, Janos Balazs, Janos Balazs, Laszlo Dobrentei, Laszlo Dobrentei, Jozef J. Makai, Jozef J. Makai, Istvan Reti, Istvan Reti, } "Realization of the van Cittert monochromator system for high-accuracy mid-IR spectrophotometry and spectroradiometry", Proc. SPIE 3437, Infrared Spaceborne Remote Sensing VI, (18 November 1998); doi: 10.1117/12.331305; https://doi.org/10.1117/12.331305
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