Design of a fast dual band hyper-spectral imager with wide field of view for airborne application

We present a new fast dual band hyperspectral imager with wide field of view to be used in airborne remote sensing. To satisfy the requirement for high SNR, we have analyzed system, detector and optics. We have established wavefront error (WFE) budget to get high spectral resolution with a good MTF, and we designed the optics which has high optical efficiency with fast f-number and wide field of view. As a result, an f-2.7 hyperspectral imager with field of view (FOV) 14.5 degree was designed. The hyperspectral imager consisted of three sub-systems, common fore-optics and two imaging spectrometers. All of the optics was composed of mirrors only, and the mirrors are made of AlSi (RSA 443) material which covers a high temperature range. Of them, the fore-optics is an off-axis three mirror system (TMS) with image-space telecentricity. Each spectrometer is based on Offner configuration which has the advantages such as low smile and keystone. Convex gratings have blaze to get relative diffraction efficiency over 60%. The assembled system working in wavelengths of 400-1700 nm shows excellent performance of MTFs over 0.31/0.21 (VNIR/SWIR) at the Nyquist frequency. Spectral resolutions of the hyperspectral imager are better than full width half maximum (FWHM) 3.8 nm in VNIR, and 7.2 nm in SWIR.