大口径导光板抛光及其功率谱密度分析

Polishing of large-aperture mirror and analysis of power spectral density

光学技术对于现代科学尤其是航天科学的发展起着越来越重要的作用。而具有高精度大口径光学元器件的跨尺度加工一直是现代光学技术的难点。超精密气囊抛光技术是基于计算机控制光学表面成形技术。其采用充气的柔性抛光气囊作为抛光工具,解决了传统数控抛光方法中抛光头不能很好地和工件吻合的缺点。以Preston方程为基础,研究了超精密气囊抛光的理论材料去除特性,建立了气囊抛光中"进动"运动方式下的材料去除模型,并针对气囊抛光工具的物理特性,按照Hertz接触理论对去除模型进行了修正。在理论分析的基础上完成了一块口径为570 mm的平面楔形工件的抛光,使得工件的面形精度P-V值达到了1/8λ,RMS值达到1/75λ。并分析了该元件的功率谱密度(PSD)曲线,窄带噪声及其产生原因。

As the development of modem optical technology, especially space optical science, more high precision mirrors with large apertures are needed. But it is difficult to manufacture high precision large aperture optical components of multi-scale processing. The method of optical polishing using an ultra- precise bonnet was based upon the technology of computer controlled optical surfacing. A bonnet filled with air was applied as a precise polishing tool which was flexible and able to adapt itself well to the shape of the part, which was superior than other polishing methods. A material removing model of bonnet processed polishing was established according to kinematic principle based on the Preston equation. The model was modified in terms of Hertz contact theory using the physical characteristics of polishing bonnet tools. A satisfactory result was obtained for one of the surfaces of a wedge mirror with a diameter of 570mm. The result of P-V and RMS parameters are 1/8 r and 1/75 ）t respectively. The PSD curves of the part and the noise of the narrow band are analyzed, as well as the reasons.