Design and Modelization of Aconvex Grating for an Hyperspectral Imager of the Chandrayaan 2 Instrument for the Moon Probe in the Infrared (original) (raw)

For hyperspectral imaging, diffraction grat ings based spectrometers exhibit high spectral reso lution and optical performance. Among those spectrometers, the Offner type (which consists of an entrance slit, two concave mirrors and convex grating) offers a lot of advantages. In this paper, we propose the design and modelization of a convex grating which covers a spectral band ranging from 0.7 μm to 5 μm with a minimum diffraction efficiency of 20% at 800 nm, 50% at 3000 nm and 25% at 5000 nm. For a so wide band, a grating with a single blaze cannot satisfy these requirements. We will therefore propose an approach of multi-blaze gr ating which is subdivided into different sections each with its own blaze angle. Mea nwhile, we perform the diffraction efficiency predict ion using the scalar and rigorous theories to prove the compliance of this design with the technical specifications. The rigorous theory will also allow us to study the polarization sensitivity of this grating and the c...