Scientific Results

ELOIS: An innovative spectrometer design using a free-form grating

Year: 2015

Authors: De Clercq C., Moreau V., Jamoye J.-F., Zuccaro Marchi A., Gloesener P.

Autors Affiliation: AMOS, Liege Science Park, 2 Rue des Chasseurs Ardennais, Angleur, B-4031, Belgium; ESTEC – European Space Research and Technology Centre, Keperlaan 1, Noordwijk, AZ 2201, Netherlands

Abstract: For spaceborne hyperspectral applications1, grating-based spectrometers are of special interest due to the high spectral resolution and optical throughput that can be achieved. The classical spectrometer designs are 1:1 systems. For these systems the achievable signal to noise ratio is limited by the slit width/pixel pitch combination. One way to increase the signal to noise ratio of a spectrometer without increasing the global instrument size is to design an instrument with a magnification power of less than one. With a smaller magnification, the entrance slit is wider and a larger amount of light is collected while the image is smaller and compatible with typical detector size and pixel pitch. We presents an innovative spectrometer design with 2:1 magnification and high image quality and radiometric performances. This spectrometer called ELOIS (for Enhanced Light Offner Imaging Spectrometer) is designed with a grating atop a free-form surface. The use non-rotationally symmetric surfaces offer additional freedom for designing compact and well-corrected instruments. Nevertheless, most of the available manufacturing techniques, such as direct ruling, holography, lithography or e-beam writing, are typically applicable on simple shape of the grating surface, such as flat or spherical surface. AMOS demonstrated the feasibility of the Free Form Grating (FFG), i.e. A ruled grating on a surface without any rotational symmetry, using cost-effective approach for manufacturing blazed grating by Single Point Diamond Turning (SPDT).

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KeyWords: Cost effectiveness; Design; Light; Manufacture; Optical design; Optical engineering; Spectral resolution; Spectrometers; Spectroscopy; Systems analysis, Cost-effective approach; Freeform optics; High spectral resolution; Hyperspectral Imaging; Imaging spectrometers; Manufacturing techniques; Radiometric performance; Single point diamond turning, Signal to noise ratio
DOI: 10.1117/12.2191345

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