Apparatus And Method For Transmitted Light Illumination For Light Microscopes And Microscope System

The invention relates to an apparatus for transmitted light illumination for light microscopes having changing effective entrance pupil of an objective. The apparatus has a light source for emitting an illuminating light beam, and a holding device for holding a sample to be examined, and at least one diaphragm edge for trimming the illuminating light beam bundle, wherein the diaphragm edge is arranged between the holding device and the light source and extends transversely to an optical axis, wherein a beam path of the illuminating light between the diaphragm edge and a sample held by the holding device is free from adjustable beam focussing components. The apparatus is characterized in that in order to adapt the beam path of the illuminating light to the effective entrance pupil of the objective, means are provided for variable positioning of the diaphragm edge in the direction of the optical axis, wherein a position of the diaphragm edge in the direction of the optical axis can be varied irrespectively of a position of the diaphragm edge transversely to the optical axis. The invention also relates to a method for transmitted light illumination for a light microscope and a microscope system.