薄镜面面形主动校正技术研究

采用12个主动支撑点对口径400 mm薄实验镜进行面形主动校正,使用Zygo干涉仪测量面形误差,主动支撑点的力促动器由位移促动器和力传感器组成。分别测量单个促动器的响应函数,由各促动器的响应函数组成刚度矩阵,然后用阻尼最小二乘法计算各支撑点的校正力。实验中分析主动支撑结构对各项Zernike形式像差的校正能力,并选择了7项像差进行校正。经过5次校正,使初始状态下1.16λ(λ=0.632 8μm)RMS面形精度达到0.13 RMS,接近镜面抛光后的精度。

Active correction technology for thin-mirror surface

The surface of a 400 mm diameter experiment mirror was corrected by 12 active supports.In the experiment,the surface error was tested by Zygo interferometer.The force actuator of the active support is composed of displacement actuator and load cell.The response functions of each actuator are tested first,the response functions of all the actuators compose the stiffness matrix,and then the active correcting force is calculated through damp least square method.In the experiment,the ability of the active supports for correcting each aberration was analyzed,the mirror surface was corrected to generate a single Zernike polynomial wavefront of 1λ (λ=0.632 8 μm),and seven terms was selected for the correction finally.After 5 times correction,the 1.16λ RMS surface shape error of the initial state was corrected to 0.13λ RMS,near the surface quality after polishing.