光学拼接镜面微位移主动调节机构的设计和实测

设计和制造了一套微位移主动调节机构和支撑系统,用以实现拼接镜面天文光学望远镜的每块平面子镜精密地调节倾斜和轴向平移,并在典型的仰角工况下对该机构进行了实测。设计技术要求子镜主动调节行程须达±1 mm,同时分辨率须达50 nm以下。选用了工作行程为6 mm和分辨率为50 nm的位移促动器,并引入杠杆机构提高位移分辨率和抑制误差;采用平衡配重和预拉弹簧机构使工作中位移促动器上保持恒定负载,以保护位移促动器和保证其输出位移精度。依据拼接镜面的工作原理,建立了子镜微位移调节系统性能测试的数学模型,并在实验室内采用分辨率为5 nm的位移传感器进行了实测。结果表明其位移分辨率可达12 nm,线性良好,与理论值相对误差为5.6%,验证了该机构设计的合理性和在不同工作位置良好的灵敏度。

Design and test of the active micro-motion mechanism for optical mirror segement

Active micro-motion mechanism is fundamental for astronomical telescope using segmented mirror to form and maintain required figure by active tip-tilt and/or piston. Mechanical design and laboratory test of such an active mechanism for a mirror segment prototype are described. Technical requirement specifies that active motion range covers up to 2 mm with resolution down to 50 nm. Three displacement actuators with 6 mm working travel and 50 nm motion resolution are adopted with three sets of lever mechanism introduced to increase the resolution of displacement and to abate error in the system. Also, three sets of lever-weight-balance mechanism together with three pairs of tensional spring are integrated to ensure, despite of variable elevation angles of the telescope in operation, constant load on the displacement actuators, whereby the actuators are safely protected with stabler output displacement accuracy, which is undesirably load-dependent. Based on working philosophy of segmented mirrors, mathematical model and experimental method were established for the active micro-motion system to be tested in laboratory, for which displacement sensors of 5 nm output resolution are used. Measurement results have confirmed the feasible design of the active micro-motion mechanism with output displacement resolution as fine as 12 nm and transmission ratio error no greater than (5.6%), besides its execellent linearity and sensitivity.