Patent ID: 8520204

Claim:
A Dyson imaging spectrometer comprising: an entry port ( 1 ) extending in a direction X in an object plane of the spectrometer, said entry port being adapted to emit an incident light beam; a diffraction grating ( 4 ) comprising a set of lines on a concave support; an optical system comprising a hemispherical lens ( 2 ), said lens comprising a plane first face ( 8 ) and a convex second face ( 3 ), the convex face ( 3 ) of the lens and the concave face of the diffraction grating ( 4 ) being concentric, said optical system being adapted to receive the incident light beam and to direct it toward the diffraction grating ( 4 ), to receive a beam diffracted by the diffraction grating, and to form a spectral image of said diffracted beam, said spectral image lying in an image field in an image plane of the spectrometer; and an exit port in the image plane ( 7 ) of the spectrometer adapted to receive an image of the entry port spatially resolved in a first direction and spectrally resolved in a second direction; characterized in that: said diffraction grating comprises a set of non-parallel and non-equidistant lines and/or the support of the diffraction grating is aspherical in order to improve the image quality of the spectral image in the image field at the same time as minimizing spectral and field distortion, and in that the optical system comprises a plate ( 13 ) with plane and parallel faces, said plate ( 13 ) lying against the plane face ( 8 ) of the lens ( 2 ) and being disposed on the optical path of the incident beam between the entry port and the diffraction grating, the object plane of the spectrometer being situated on one face of the plate ( 13 ) and the image plane of the spectrometer being separated from the lens ( 2 ) by a gap.