It was previously demonstrated by Bauerle et al. [Opt. Express 20, 14477 (2012)] that the computation of ray paths through the optical system (ray mapping) can be used to design multisurface freeform optical elements creating a prescribed irradiance pattern for a zero-etendue source. The procedure outlined there uses the heuristic step of reducing the ray mapping's curl to improve adherence to surface integrability criteria. This Letter formally derives a quantitative estimate for the limitations of this approach in the collimated case and shows the key factors influencing the quality of the final optics.
展开▼
