Research Ring-shaped Surface Polishing Line Monitoring Technology

Phase-shifting technique is one of the most precise methods in the field of optical measurement. With complicated environment, it is extremely hard to on-line test the optical elements in the workshop. The application of the dynamic phase-shifting interferometry resolves this problem directly. This technique achieves synchronous phase-shifting, which is possible for removing most of the error caused by the vibration in the room.SGIII is a major project on laser-based nuclear fusion in our country. Neodymium glass is widely used in SGIII main system, hence processing neodymium glass is an urgent and difficult task. However, it is hard to control the surface figure of neodymium glass during continuous polishing. Iterative polishing and off-line testing make great trouble in improving the productivity of the neodymium glass. This thesis mainly researches on real-time monitoring the shape of the polished surface of neodymium glass in the workshop, aiming to obtain the variation of the polished surface figure and improving the productivity of the neodymium glass. Firstly, this thesis offers a summary on modern optical processing technology for neodymium glass processing, and analyzes the difficulty of polishing neodymium glass, i.e. it is hard to control the surface figure. By comparing different phase-shifting techniques and algorithms, a scheme for on-line testing the surface figure of neodymium glass using dynamic phase-shifting interferometry is proposed. In addition, a system based on4D dynamic interferometer is established for on-line testing. A method for real-time monitoring the variation of the product surface figure during the neodymium glass polishing is introduced. The variation of the product surface figure is obtained by the variation of the surface figure of a small flat called accompany polished flat, while the surface figure of the small flat is acquired by the interference between its two surfaces. Fringes and surface figure data of the interference between the two surfaces of the small flat are collected, which are compared with surface figure data of the product by off-line testing. Then reasonable processing condition as well as the relation between the surface figure variation of the small flat and the product is found.