Optical system design of grating-based imaging spectrometer

Imaging spectrometer is a kind of optical remote sensing instruments which combining image with spectrum. Grating-based imaging spectrometer has a wide range of applications because of concise principle, stable performance, and nature of the technology. This article designs a kind of grating-based imaging spectrometer optical system using ZEMAX. The fore optic adopts reflection structure, aiming at the issue that the traditional Cassegrain structure has limited ability of aberration correction and makes system processing complex when both the primary and secondary mirror all use aspheric surface, this design adopts the improved Cassegrain structure for aberration correction. The transfer function of final fore optic is 0.5 at 50 lp/mm, the field curvature is less than 0.078 and there is no distortion .The Czerny-Turner structure based on plane grating that the spectral imaging system usually adopts has low spectral resolution, and the image quality is so bad as not to meet the requirement of the instrument. So the spectral imaging system based on convex grating is used, it has compact structure, strong ability to correct aberrations and high spectral resolution. The final spectral resolution is less than 5 nm, MTF is 0.75 at 50 lp/mm.According to the principle of matching, the grating-based imaging spectrometer is achieved by combinatorial optimization of the fore optic and spectral imaging system. The RMS radius of spot diagram of the spectrometer is always less than 0.2 with the change of wavelength, 80% of the wavelength energy concentrates in 6 m and the MTF is greater than 0.5 at 50 lp/mm over the whole FOV.The entire optical system is characterized by simple structure ,good capability of aberration correction and small size.