Numerical design tools for thermal replication of optical-quality surfaces

The slumping of molten glass under gravity into a mould, so as to replicate the mould surface on the upper free surface of the glass, is used in the m anufacture of some optical components for which the curvature of the upper free surface is critical. A finite-element simulation of the process based on the creeping-flow equations is described. In addition a method is given for computing surface curvature from the non-exact discrete data produced b y the finite-element computations. These methods are illustrated for a part icular case of a circular glass disc slumping into a spherical mould. (C) 2 000 Elsevier Science Ltd. All rights reserved.