Optimization of high-numerical-aperture objectives by splitting a singlet with control of higher-order aberration

A scheme is proposed for the automatic control of higher-order aberrations during the course of lens optimization, as well as third-order aberrations. First, the singlet with the larger paraxial marginal ray slope difference is modified into a doublet. The doublet is combined with two elements, for which their refractive index difference is selected to be small, instead of the traditional combination with the crown and flint glasses. And the middle surface in the doublet will give a variably controllable higher-order aberration contribution to the image quality, whereas the third-order aberration is comparably fixed, so that the "system aberration balance" would be achieved in the optimization run. The optimization of a photographic objective is investigated using this method. The design result can provide good image quality. Results of manufacturing simulations are also given for the systems, which show that the optical system optimized with our scheme can be successfully fabricated.