Optimal Mould Design for the Manufacture of High-Precision Lenses

The increasing need for low-cost, high-precision optical devices requires innovative manufacturing techniques or the optimization of existing ones. The present study focuses on the latter alternative and proposes a computer-aided, mould optimization algorithm for the manufacturing of high-precision glass lenses by compression moulding. The intuitive, yet very efficient, algorithm computes at each optimization loop the mismatch between the desired and deformed glass shapes and uses this information to update the mould design. To solve this optimal shape design problem, a finite element model representative of the real industrial process is developed and solved in the commercial package ABAQUS. This model solves the several stages involved in the process and includes the thermo-mechanical coupling, the varying mechanical contact between the glass and the mould, and the stress and structure relaxation in the glass. The algorithm is successfully tested for the mould design for a plano-concave and a bi-concave lens as the residual error between the deformed and desired glass profiles is decreased to a value of the order of one micron