空间同轴三反相机Φ520 mm次镜的加工与检测

Fabrication and test for Φ520 mm secondary mirror of on-axis three mirror space camera

为了满足空间同轴三反相机对大口径凸非球面高精度的面形质量和精确的几何参数控制要求,提出以计算机控制确定性研抛工艺为核心的多工序组合加工及检测技术。在加工阶段,首先利用超声振动磨削技术对非球面进行面形铣磨,其次应用机器人对非球面面形进行快速研磨和粗抛,最后采用离子束修形技术实现非球面的高精度加工;在检测阶段,首先利用三坐标测量机对铣磨和研磨过程中非球面的面形及几何参数进行控制,进入干涉仪测量范围后,再采用Hindle球法对非球面光学参数进行干涉检测。结合工程实例,对一口径520 mm的凸双曲面次镜进行了加工及检测,其面形精度RMS为0.015λ(λ=632.8 nm),几何参数控制精度ΔR误差为0.1 mm、ΔK优于0.1%,满足光学设计技术指标要求。

In order to satisfy the requirements of high-precision surface figure error quality and geometry parameters controlling in the on-axis three mirror space camera of large-aperture convex aspheric, multiply process combination and test technique based on the foundation of deterministic lapping and polishing were proposed. In the process stage, ultrasonic milling was firstly introduced to form the aspherical surface form, then robot lapping and polishing were used to rapidly grind and polish, at last, ion beam figuring was used to finish the aspheric fabrication. In the test stage, the geometry parameters and surface figure error of aspheric were firstly controlled by using the coordinate measuring machine （CMM） and then tested by using Hindle sphere testing after the aspheric surface accuracy in interferometric test range. An example for fabricating and testing a convex hyperbolic secondary mirror with diameter of 520 mm was given, the surface figure error of mirror was 0.015λ（λ=632.8 nm）, the geometry parameters control accuracy of △R and △K are 0.1 mm and 0.1%, respectively, all the fabrication results of aspheric satisfy the specifications requirements of the optical design.