Transmitted illumination device for microscopes

A transmitted illumination device for a microscope comprising from a light source to a test piece, a collector lens, a front detachably mounted additional system, a field stop, a rear lens system, an aperture stop and a condenser lens, said front detachably mounted additional system consisting of two air spaced front and rear components, said front component being a convex lens convex toward the front and said rear component being a convex lens system adjoining said field stop and having conjugate positions located at said field stop and at a position between said front and rear components, respectively, said rear lens system consisting of a front component composed of a fixed convex lens adjoining said field stop and a rear component air-spaced from said fixed convex lens and composed of a detachably mounted convex lens, said front additional lens system being removed from the illumination device and said rear component of said rear lens system being inserted thereinto when operated at low magnification, both said front additional lens system and said rear component of said rear lens system being inserted thereinto when operated at high magnification, the image of said light source projected onto said aperture stop with sizes corresponding to desired magnifications and the image of said field stop being projected onto an object surface by means of said rear lens system.