Correction of temperature influences on plastic lenses for applications in laser material processing

Abstract

Today, the use of plastic lenses in processing optics for laser material processing is fundamentally limited to laser powers lower than 1 W. This is due to thermo-optical effects in the plastic material which primarily lead to a shift in the focus position. To overcome this laser power limitation, a design routine was developed for injection molded lenses, which simulates the optical properties of the lens in thermal equilibrium state during laser irradiation and which iteratively adapts the lens design for the manufacturing process in this way that the lens is compensated for thermal effects and manufacturing errors like shrinkage. The approach is demonstrated for an injection molded focusing lens used at an average laser power of 15 W. The focusing properties of the compensated manufactured lens are compared with the underlying simulations as well as with an uncompensated lens geometry used at the same laser power.