用于高光谱成像仪的大视场离轴三反系统设计

Design of wide field of view off-axis three-mirror system for hyperspectral imager

大视场、高分辨力星载高光谱成像仪已成为空间遥感的迫切需求,要求其望远系统在宽视场内具有高空间分辨力。在共轴三反系统的几何光学成像理论基础上,研究了用于高光谱成像仪的大视场离轴三反消像散(TMA)望远系统的设计问题,编制了初始结构计算程序,采用视场离轴方式,设计了一个波段范围0.4～2.5μm、焦距360 mm、相对孔径1:4、线视场11.42°的离轴三反望远系统,其主镜为6次非球面,次镜和三镜为二次曲面,考虑到市售探测器的限制,提出了视场分离的分光方法,在离轴三反系统的焦平面附近加一个刀口反射镜实现视场分离。在奈奎斯特空间频率28 lp/mm处,调制传递函数大于0.75,成像质量接近衍射极限。

Wide angle and high resolution spaceborne hyperspectral imager are urgently required in space remote sensing system,of which the telescope system requires high spatial resolution in wide field of view.Based on the theory about geometry optics of common-axis three-mirror systems,the design problem of wide-field of view,off-axis three-mirror anastigmatic（TMA） telescope systems of hyperspectral imager were studied.By means of field of view off-axis,an off-axis three-mirror telescope system was designed.The spectral range was 0.4-2.5 μm,and the focal length was 360 mm,the relative aperture wais 1：4,and the field of view was 11.42°.The primary mirror was six order aspheric surface,and the second mirror and third mirror were quadratic surface.Considering the restriction of detectors,a method of split field of view was developed.Split field of view was achieved by means of putting a edge mirror near the focal plane of the telescope.The MTF is more than 0.75 at Nyquist spatial frequency 28 lp/mm,and the image quality approaches to the diffraction limit.