Using the 3D-SMS for finding starting configurations in imaging systems with freeform surfaces

Abstract

As the scientific field of the freeform optics is newly developing, there is only a small number of approved starting systems for the imaging lens design. We investigate the possibility to generate starting configurations of freeform lenses with the Simultaneous Multiple Surface (SMS) method. Surface fit and transfer to the ray tracing program are discussed in detail. Based on specific examples without rotational symmetry, we analyze the potential of such starting systems. The tested systems evolve from Scheimpflug configurations or have arbitrarily tilted image planes. The optimization behavior of the starting systems retrieved from the 3D-SMS is compared to classical starting configurations, like an aspheric lens. Therefore we evaluate the root mean square (RMS) spot radius before and after the optimization as well as the speed of convergence. In result the performance of the starting configurations is superior. The mean RMS spot diameter is reduced about up to 17.6 % in comparison to an aspheric starting configuration and about up to 28 % for a simple plane plate.