气囊抛光过程的运动精度控制

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。

Motion-precision control in bonnet-polishing

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 50 μm. 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 10 μm by probing-correction method. The experiment results on a actual polishing by using motion-precision control methods indicate that the surface machining accuracy is 0.8 nm(RMS) in polishing a flat with a diameter of 280 mm, and that is 1.1 nm(RMS) in polishing a concave with a diameter of 160 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.