A method for effective focal length measurement using imaging conjugates is discussed and demonstrated. This method is used to determine the effective focal length of an objective lens with precision and without the need to know the exact position of the principal planes by measuring relative distances of imaging conjugates. Focal length determination was done with the aid of an interferometer and with a precision of ±0.054%. A discussion of the method is presented and an error analysis discussed. This method can be used for characterizing optical systems with a wide range of focal lengths because of its simple experimental configuration.
A Multi-Objective approach for lens design optimization was verified. The optimization problem was approached by
addressing simultaneously, but separately, image quality and system tolerancing. In contrast to other previous published
methods, the error functions were not combined into a single merit function. As a result the method returns a set of nondominated
solutions that generates a Pareto Front. Our method resulted in alternate and useful insights about the trade off
solutions for a lens design problem. This Multi-objective optimization can conveniently be implemented with
evolutionary methods of optimization that have established success in lens design. We provided an example of the
insights and usefulness of our approach in the design of a Telephoto lens system using NSGA-II, a popular multiobjective
evolutionary optimization algorithm.