With the development of optical systems towards miniaturization, integration and intelligence, micro-structured array optical elements with the advantages of small size, high integration and good optical performance have become the key components in optical systems. The micro-structure array mold has the characteristics of hard and brittle materials and complex geometric shapes. It is still difficult to achieve high surface shape accuracy and high surface quality processing, which limits its application. In order to solve the above problems, a non-contact shape profiling polishing method for micro-structured array molds is proposed. According to the depth of the micro-structured array, a shape profiling polishing tool was designed. Based on the material properties of nickel-phosphorus alloy, a non-Newtonian fluid polishing fluid suitable for high surface quality polishing of nickel-phosphorus alloy was prepared. Combined with the proposed conformal polishing method, a precision five-axis motion platform is built, which can accurately adjust the position angle relationship between the profiling tool and the mold in multiple dimensions. At the same time, a set of non-Newtonian fluid polishing fluid circulation device is designed to realize the reuse of non-Newtonian fluid polishing fluid, avoid the matrix corrosion caused by the long time of the mold in the polishing fluid, and avoid the settlement of the abrasive particles in the polishing process, so as to achieve more efficient material removal. The finite element simulation model of shear thickening polishing is established by ANSYS software, and the distribution of stress and slip velocity on the surface of the mold under different process parameters is analyzed. The simulation results show that the polishing gap and the rotation speed of the polishing tool have a great influence on the stress and slip velocity on the surface of the mold. With the increase of the polishing gap, the stress value and slip velocity on the surface of the mold decrease at the same time. On the contrary, the greater the speed of the polishing tool, the greater the stress value and slip velocity. The optimum processing parameters of polishing gap of 0.2 mm and polishing tool speed of 600rpm were determined by process experiment. The experimental results show the surface roughness of  micro-structured array surface is reduced from the initial Ra 1.22 nm to 1.18 nm, less than 0.2 μm shape accuracy are achieved, while the tool marks  are effectively removed. At the same time, through the lighting test, it was found that the rainbow pattern on the surface of the mold was completely removed.

 

Micro-structured array,Non-contact polishing,Tool mark removal,Shape retention