Imaging systems based on four-spherical-mirror design

Optical designs free of obscuration can be derived of coaxial central obscuring systems. By lateral pupil shifting, basic aberration terms can be controlled and a variety of off-axis optical design are based on this approach. Different approaches are based on the “generalized Schwarzschild theorem” or “Fermat´s theorem” and the satisfaction of the sine condition. Based on the definition of the configuration space by Howard and Stone we investigate several imaging systems and compare their optical performance and practicability for the integration in optical measurement systems. Therefore several samples will be optimized in fifteen parameter that describe distances, chief ray angle and radius of curvature of each individual mirror used in the system. Related to the application, restrictions especially in size and estimated costs will cause unusual design changes compared to classical approaches.