摘要
对口径620mm、厚18mm的弯月形薄反射镜进行了面形误差的主动校正实验,通过浮动支撑方式保证了在校正过程中镜面空间位置不变。实验主镜的支撑结构由轴向36个主动支撑点和侧向6个被动支撑点组成,在轴向支撑点中对称选择中圈3个点作为虚拟硬点,通过调整其他促动器的支撑力保证虚拟硬点受力始终为零来实现浮动支撑。系统采用哈特曼波前传感器作为面形检测设备,采用最小二乘法计算校正力。实验中测出系统的像差校正能力,选择中低频的Zernike像差参与校正,并进行了不同俯仰角下面形的闭环与开环校正,实验结果表明通过浮动支撑方式有效地控制了校正过程中镜面的平移和倾斜。在不同俯仰角下通过闭环校正,均可将镜面面形误差均方根(RMS)的初始值(约0.6λ,λ=632.8nm)校正到约λ/15,开环面形校正精度的RMS达到λ/10～λ/14。通过实验研究了俯仰角变化时的面形校正过程和校正力计算方法,并验证了采用浮动支撑方式控制镜面空间位置的可行性。
For a meniscus mirror with 620 mm diameter and 18 mm thickness, active correction of surface-profile error is carried out. Through flotation support, the spatial position of the mirror is fixed. The support system of the mirror consists of 36 axial active supports and 6 lateral passive supports. Three points in the middle circle of axial supports are chosen symmetrically as dummy hard points, and the flotation support is achieved through adjusting the support forces of other actuators to null the dummy hard point forces at all times. The Hartmann wavefront sensor is used as testing equipment and the least square method is used to calculate the active corrective forces. In the experiment, the correction ability of the active supports is analyzed first and low-frequency Zernike terms are selected for correction finally. Then the close-loop and open-loop correction at different elevations is carried out, and the results show that through flotation support, the surface-profile error can be corrected effectively without piston and tilt. More than 0.6 （λ = 632.8 nm） root-mean-square （RMS） of surface-profile error of the initial state can be corrected to it/15 at any elevation angles, and the RMS of correction precision of open-loop reaches A/10 /14 . Through the experiment the feasibility of correction process with varying elevation angle and the arithmetic of correction forces are discussed, and the control of mirror position through flotation support is approved.
出处
《光学学报》
EI
CAS
CSCD
北大核心
2013年第5期79-87,共9页
Acta Optica Sinica
基金
中国科学院第三期创新工程资助课题
关键词
光学设计
主动光学
面形误差校正
薄反射镜
浮动支撑
最小二乘法
optical design active optics surface-profile error correction thin mirror flotation support leastsquare method
