Maskless fluid jet polishing of optical structured surfaces

Various kinds of optical structured surface have been widely used in different fields, such as imaging and illumination. However, the machining process of the optical structured surface usually leaves tool marks, burs, debris and defects on the structured surface. Currently, it is still a challenging problem to remove these kinds of defects and further improve the surface quality effectively, to obtain better functional performance. In this paper, maskless fluid jet polishing (MFJP) is innovatively presented which is an attempt to solve this problem. In MFJP, low pressure micro abrasive water jet slurry is impinged on the structured surface to implement tiny material removal without using a mask. Experimental investigations on the polishing of sinusoidal structured surface and V-groove structured surface were performed to realize the technical feasibility of MFJP on structured surface, based on the analysis of surface roughness, form maintainability, and surface smoothness. A computational fluid dynamics (CFD) model was also developed to simulate the MFJP process on V-groove surface to demonstrate the fluid flow movement and material removal characteristics. In addition, the effect of the key polishing parameters was also studied and discussed. The results indicate that MFJP can significantly improve the surface quality of optical structured surface, while possessing high form maintainability under certain conditions. It may become a competitive method for the precision polishing of optical structured surfaces. And this study also sheds some light on the application of MFJP for the polishing of other kinds of surfaces with small or micrometer scale cavities or channels, such as microfluidic chips, etc.