Rigorous electromagnetic analysis of a microcylindrical axilens with long focal depth and high transverse resolution

We first present nonparaxial designs for a microcylindrical axilens with di fferent long focal depths and rigorously analyze electromagnetic field dist ributions of the axilens using integral equations and the boundary-element method. Numerical results show that the designed axilenses indeed have the special feature of attaining a long focal depth while keeping high transver se resolution for numerical apertures of 2.4, 2.0, and 1.0. The ratio betwe en the extended focal depth of the designed axilens and the focal depth of the conventional focal lens is 1.41, the corresponding maximal extended foc al depth of the axilens can reach 28 mum, and the spot size of the focal be am is similar to 10 mum over the focal range. (C) 2001 Optical Society of A merica.