含有自由曲面的大视场低畸变同轴三反射光学系统设计

Optical Design of Large Field and Low Distortion Coaxial Three Mirror System with Free-Form Surface

遥感测绘应用要求光学系统焦距长、幅宽大、畸变低、体积小,并且可以实现与卫星平台的一体化设计。经过结构优选,采用改进型同轴三反结构,同时实现了长焦距、大幅宽和低畸变。由于二次遮拦和大视场的影响,一般的非球面优化设计成像质量不能满足要求。自由曲面的加入有效地增加了光学系统优化的自由度,经过优化设计后,光学系统设计传递函数大于0.418(72lp/mm),最大相对畸变小于0.00145%,光学系统成像质量明显提高。利用计算全息(CGH)技术实现了自由曲面的检测与精磨加工,设计残余波像差均方根(RMS)值为0.007λ,峰谷(PV)值为0.027λ,满足自由曲面的面形公差要求。加工、装调后实测光学系统的实验室静态传递函数,弧矢方向最低静态传递函数为0.225(72lp/mm),满足系统技术指标要求。

Remote sensing mapping applications need optical system with long focal length, wide width, low distortion, small volume, and the optical system can be designed for integration on satellite platform. Through the structure selection, modified coaxial three mirror system is adopted to realize long focal length, wide width and low distortion at the same time. Because of the influence of the second obscuration and large field, the image quality of general aspheric optimization design cannot meet the requirements. Degrees of freedom are increased efficiently by the introduction of free-form surface. After optimization design, the optical design modulation transfer function （MTF） is greater than 0. 418 at 72 lp/mm, and the maximum relative distortion is less than 0. 00145%. Imaging quality is improved significantly. The free-form surface is tested and fine grinded by the application of computer- generated holography （CGH） technology, the root mean square （RMS） of remnant wavefront error is 0. 007~., and the peak to valley （PV） value is 0. 0272, remnant wavefront error meet the requirements of free-form surface irregularity tolerance. Laboratory static MTF is tested after processing and adjustment, the minimum static MTF is 0. 225 at 72 lp/mm, the image quality meet the requirements of technical indicators.