Microscope illumination optical system

摘要

An illumination optical system for a microscope is provided wherein the illumination state can be successively changed between Koehler illumination and critical illumination while ensuring one or more conditions are satisfied so that the image of the light source illuminates an appropriately large region of the field of view of the microscope during critical illumination. Preferably, no cemented lens elements are used so that degradation of the cement caused by ultraviolet light sources is avoided, thereby enabling an appropriate illumination type to be provided at will and without degradation of the optical components of the illumination optical system over time.