These slides were presented at the Zemax Envision 2020 web conference on October 7th, 2020.
Rev. 1 was presented at Zemax Envision 2020.
Rev. 2 includes an additional citation for work done by G. Gao, L. Li, and Y. Huang, where the authors applied an analysis of the spherical aberration in a spherical singlet to bend the singlet's surfaces to produce improved uniform illumination from a small (point-like source) LED.