Viscoelastic Stress Analysis of Precision Aspherical Glass Lens Forming Process using Finite Element Method

The conventional production of lenses is a rather complicated process. Glass raw material which has been pressed to a rough form has to be processed on both sides in order to obtain a finished precision optical component. There have been recent advances in the optical fabrication techniques such as magnetorheological polishing (MRF), ion beam polishing and single point diamond turning (SPDT), but the overall complexity and cost involved in these processes are very high for medium to high volume production of aspherical glass optics. The conventional fabrication methods are more suitable for manufacturing spherical glass lenses. Aspherical lenses on the other hand have one or both surfaces that do not conform to a sphere and provide greater advantage over spherical lenses due to reduced light losses and aberrations, better image quality, and compact lens assemblies. In order to fulfill the high demands on refractive and reflective optical components, it is necessary to develop accurate fabrication techniques that generate aspherical optical surfaces in glass with a figure accuracy of λ/10 (λ = 633 nm), and a surface roughness of 1-5 nm rms.