Illumination system for microscopes

An illumination system for microscopes comprising a light source, a collector lens, an aperture stop arranged in the vicinity of an image of said light source formed by said collector lens, a field stop arranged on the object side of said collector lens between said light source and aperture stop, condenser lens, and relay lens system for high magnification level to be arranged between said aperture stop and said condenser lens so as to form an image of said light source image in the vicinity of the front focal point of said condenser lens for illumination for microscopy at the high magnification level, said illumination system being so adapted as to remove said relay lens system for high magnification level and said condenser lens out of the optical path and arrange a relay lens system for low magnification level so as to locate the front focal point thereof in the vicinity of said light source image for microscopy at a low magnification level, an image of said field stop being formed on an object to be observed by said condenser lens and relay lens system for high magnification level, and said image of said field stop being formed on the object to be observed by said relay lens for low magnification level at the low magnification level.