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23 September 2015 ELOIS: an innovative spectrometer design using a free-form grating
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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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Coralie De Clercq, Vincent Moreau, Jean-François Jamoye, Alessandro Zuccaro Marchi, and Pierre Gloesener "ELOIS: an innovative spectrometer design using a free-form grating", Proc. SPIE 9626, Optical Systems Design 2015: Optical Design and Engineering VI, 96261O (23 September 2015);

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