Simulation Analysis And Experimental Study On Glass Molding Of Infrared Chalcogenide Glass Diffractive Surface

Precision glass molding(PGM)is an important technology for mass-producing high surface quality optical components.Chalcogenide glass diffraction optical elements are widely used in military,medical,and inspection fields due to their small size and low weight.Therefore,it is worthwhile to study the production of chalcogenide glass diffraction optical elements using glass molding technology.For diffraction optical molding,the filling of the diffraction structure and the stress of the molded lens will affect the surface precision deviation of the element.In order to improve the diffraction efficiency of diffraction optical elements and reduce the surface precision deviation of chalcogenide glass diffraction optical elements in glass molding technology,this paper studies the influence of the filling of the diffraction structure and the maximum stress of the molded lens on the surface precision deviation.The special research contents are as follows:Firstly,the materials that can be used as molds and cores,and the types of glass that can be molded are analyzed in detail,and the material properties of optical glass and their influence on the molding process are introduced.The basic theory of glass molding is described and the viscoelastic theory is discussed,analyzing the advantages and disadvantages of each model,and establishing 5 pairs of generalized Maxwell model as theoretical guidance for the simulation stage.Secondly,the chalcogenide glass diffraction optical element molding process is simulated and analyzed.In order to determine the filling effect and stress of the diffraction structure,a local diffraction structure simulation model is established with microcrystalline aluminum RSA905 as the core and chalcogenide glass IG6 as the preform,and the effects of molding temperature,pressing velocity,and friction coefficient on the filling of the molded lens diffraction structure and the maximum stress are analyzed.The research shows that with the increase of molding temperature,the filling of the diffraction structure does not change significantly,and the maximum stress of the molded lens first decreases and then increases;the smaller the pressing velocity,the more complete the filling of the diffraction structure and the smaller the maximum stress of the molded lens;the larger the friction coefficient,the more complete the filling of the diffraction structure and the larger the maximum stress of the molded lens.And this is used as the process parameter guidance for the experimental stage.Finally,the chalcogenide glass diffraction optical element molding experiment is carried out to obtain the best process parameters that meet the surface shape deviation of the molded lens less than 0.5μm.The molding process experiment results of infrared chalcogenide glass IG6 as the preform and microcrystalline aluminum RSA905 as the core show that when the molding temperature is constant,the smaller the pressing velocity,the smaller the diffraction surface precision deviation of the molded lens;when the pressing velocity is constant,the molding temperature is 230℃,and the surface shape deviation of the molded lens is the smallest.The best process parameters are molding temperature of230℃ and pressing velocity of 0.01mm/s.Under this process parameter,the surface precision deviation is 0.3053μm,and the surface roughness Ra is 2.92 nm.And under this process parameter,continuous molding experiments are carried out for 7 groups,and the molded lens is randomly sampled,and the surface precision deviation meets the requirements,verifying the stability of the process parameters.