Simulation And Experiment Research On Aspheric Lens Molding Of Chalcogenide Glass

With the higher and higher requirement of image quality and imaging resolution of the infrared optical system,the infrared aspheric lens gradually replace the traditional infrared optical elements,such as infrared spherical lens,infrared plane lens and infrared prism etc.,because the infrared aspheric lens can significantly improve image quality,improve the infrared optical properties,reduce the number of infrared optical elements,simplify the system structure,and reduce the volume of the system.Therefore,there is no delay in the research on the mass and precision molding technology of the infrared aspheric lens.In this paper,the thermo-mechanical properties of chalcogenide glass Ge22Se58As20 above its softening temperature are studied,and a new elastic-viscoplasticity model is established to describe its thermo-mechanical behavior.The thermo-mechanical parameters in the molding of chalcogenide glass are determined by the cylinder molding test.According to the thermos-mechanical behavior,the parameter fitting of the elastic-viscoplasticity constitutive model is carried out by the Taylor formula expansion and the nonlinear least square curve fitting.Then,the four order Runge-Kutta numerical integration method is used to optimize the parameters of the elastic-viscoplasticity constitutive model,which verifies the accuracy and applicability of the elastic-viscoplasticity constitutive model.Then,based on the existing molding defects of chalcogenide glass,the molding experiment of chalcogenide glass is carried out,and the surface defects of chalcogenide glass are observed.Then through the finite element simulation of cylinder molding of chalcogenide glass,verify the elastic-viscoplasticity constitutive model in the application of chalcogenide glass cylinder molding.And through temperature-displacement field coupling simulation analysis of stress and strain distribution,research the influence of molding temperature on shape defects.In addition,the influence of molding conditions on the surface defects is also studied through the study of the effect of molding temperature on surface scratches on temperature-displacement field coupling simulation results.Based on the molded chalcogenide glass composition and energy spectrum analysis,study the causes of formation of microdimples.And then research the effects of temperature,molding force,interfacial roughness and curvature radius of chalcogenide glass and molds on the surface microdimples.Finally,based on the above background,this paper is devoted to studying the molding technology of chalcogenide glass aspheric lens,and validates the applicability and effectiveness of chalcogenide glass elastic-viscoplasticity constitutive model in aspherical lens molding.There are forming errors in chalcogenide glass molding because of the difference between the mold material’s and chalcogenide glass’ s thermal expansion coefficient,and the stress field,temperature field and flow field and other factors.These forming errors may cause that the aspheric optical lens can not meet the high shape precision requirements(λ/2～λ/10,λ is this glass wavelength)of infrared optical components.In this paper,the surface morphology,the reproduction quality and the infrared transmission characteristics of the formed aspheric lens of the chalcogenide glass are evaluated.The surface roughness of the aspheric lens is Ra = 8 nm,without shape and surface defect,and it is confirmed that the chalcogenide glass molding process does not affect the infrared transmission characteristics of infrared lens.