| In order to improve the quality and efficiency of hyperspectral remote sensing images,the hyperspectral imager should have light weight,small size,wide swath width and high spectral and spatial resolution working on Unmanned Aerial Vehicle platform.In addition to high-performance imaging spectrometer,miniature fore-optics with wide field of view and large relative aperture need to be designed and developed.In this paper,two fore-optics working in VNIR waveband(0.4?m-1.0?m)and SWIR(1.0?m-2.5?m)imaging spectrometer are studied and designed.It focuses on the correction of secondary spectrum and color distortion caused by the wide waveband.First of all,this paper analyzes design requirements of imaging spectrometer fore-optics,and identifies the key parameters.Then,an apochromatic design idea for fore-optics is expounded,and the method of selecting and solving the initial structure of high-performance objective is given.Based on the theory of Gaussian Optics and Seidel third-order aberration theory,the paper derives apochromatic formula and calculates initial structure of apochromatic optical systems.According to the requirement of the index,complex double Gaussian system fore-optics with F number of 2.8 and full field of view angle of 40° are obtained,which works in VNIR waveband(0.4?m-10?m)and SWIR(1.0?m-2.5?m).It also gives an image quality evaluation and residual aberration analysis.The system consisting of only three optical glass materials and spherical surfaces is a coaxial structure,can automatically eliminate vertical axis aberrations,which has a low processing and manufacturing costs as well as greatly reduces the difficulty of detection.It also has small second spectrum,imagery telecentricity,uniform illumination and compact structure.In addition,the paper analyzes and formulates tolerance,eliminates thermal changes and stray light.Finally,processing and assembly method is given,and its imaging performance is tested. |
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