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.
High image quality and complex, refractive optical systems, as those used in remote sensing applications, are, in general, very difficult to be manufactured with the required performance. This can be charged to the high sensitivity of such systems to the fabrication tolerances, mainly concerning the relative alignment of the optical components with respect to each other. When the system does not achieve the expected quality, the puzzle is to identify where the problems lies. This is even worsened when the number of optical elements becomes high. Due to these facts, some misalignment characterization and estimation techniques based on Bayesian estimators and wavefront measurements have been proposed in the literature. This paper is the result of a deep study and investigation of these techniques, with emphasis on an application to an intentionally simple system for the sake of illustration that highlights conceptual issues that could be extended to more realistic, complex optical systems. With this purpose, the sensitivity of the wavefront Zernike coefficients to the misalignment parameters, its use in a parameter estimator design that includes nonlinear terms, the study of the system observability, and a statistical analysis of the estimator performance considering the observation noise are addressed in details. Numerical simulation results for the simple system are shown. We also present insights on how to apply the technique to the alignment of a 11-lens optical system used in the Brazilian remote sensing camera MUX, that will fly on-board the upcoming Sino-Brazilian satellites CBERS 3&4.