介绍了采用薄镜面主动支撑技术来加工大口径天文薄镜面的试验情况。试验镜为一弯月型球面反射镜,直径为1035 mm,镜面曲率半径为3220 mm,径厚比约为40∶1。在磨制过程中,有55个分离支撑点支撑在镜子背面。支撑点的位置与支撑力的大小通过有限元分析计算确定,其中3个为固定支撑点,另外52个为主动支撑点。每个支撑点位置设置了力促动器,调节力促动器加力的大小,可以主动改正镜面的低频误差。加工后最后达到的面形精度:λ=632.8 nm,面形误差(RMS)小于等于λ/21.5,局部高频误差(RMS)小于等于λ/23。试验证明所采用的方法适合于大口径天文薄镜面的加工。

A tentative fabrication test for thin astronomical mirror has been done. In the test, the active support system is used. The mirror is a meniscus spherical mirror and its parameters are as follows: the diameter is 1035 mm, radius of curvature is 3220 mm, and aspect ratio is close to 40. During the processing, the mirror was supported by 55 supporting points in its back surface. The positions of supporting points and the magnitude of supporting force supplied by force actuators were analyzed by using finite element analysis software. In all of 55 supporting points, 3 points are fixed and the rest are active support which is linked with force actuator. The low-frequency error on the mirror can be corrected when the forces of actuators were adjusted. Finally root mean square (RMS) of surface accuracy error is less than 0.0465λ, RMS of high-frequency error is less than 0.0435λ. It is demonstrated that the technique is suited for fabrication of astronomical thin mirror.