气囊抛光过程的运动精度控制

Motion-precision control in bonnet-polishing

针对用于球面、非球面光学元件超精密光学加工的气囊抛光技术,提出了一套控制抛光过程中气囊运动精度的方法。该方法通过控制加工单元的温度,保证抛光过程中设备运动精度达到50μm;使用坐标传递法,使检测数据二维方向对准不确定度达到0.30-0.70mm。另外,基于磨头去除量估计与反馈修正法,提高精抛过程面形误差收敛效率。最后,通过磨头探测校准法,将磨头与加工工件法向位置精度提高至10μm。实际抛光实验显示：使用运动精度控制法在280mm口径的平面精密抛光中获得的面形加工精度为0.8nm（RMS）,在160mm口径的凹球面精密抛光中获得的面形加工结果为1.1nm（RMS）,实现了超高精度面形修正的目的,为超高精度球面、非球面光学元件加工提供了一套行之有效的方法。该方法同样适用于其他接触式小磨头数控抛光方法。

To meet the ultra-high precision manufacture demands of spherical surfaces and aspherical surfaces in an optical system of Deep Ultra Violet（DUV）and Extreme Ultra Violet（EUV）,a series of motion-precision control methods in bonnet-polishing were proposed.Firstly,the temperatures of main operation units were finely controlled to allow the motion-precision of polishing to be to 50μm.Then,the coordinates transmitting method was used to guarantee the two-dimension unity between measured data and operating data to be 0.30-0.70 mm.Furthermore,the convergence efficiency of surface-error in fine polishing was improved by bonnet removal estimation method and feedback correction method.Finally,the vertical position accuracy between bonnet and work piece was improved to 10μm by probing-correction method.The experiment results on a actual polishing by using motionprecision control methods indicate that the surface machining accuracy is 0.8nm（RMS）in polishingaflat with a diameter of 280 mm,and that is 1.1nm（RMS）in polishing a concave with a diameter of160 mm.The proposed methods realize ultra-high precision polishing for spherical surfaces and aspherical surfaces,and they are also suitable for other contact small tool computer controlled polishing.