Koehler illumination

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Koehler illumination

(Science: microscopy) mode of microscope illumination in which the light Source is imaged onto the condenser iris diaphragm and the field diaphragm (in front of the lamp collector lens) is imaged by the condenser onto the plane of focus of the specimen. With koehler illumination, the aperture and field can be regulated independently to provide maximum resolution and optimum contrast. Also, a field with uniform illumination is obtained, circumscribed by the image of the field diaphragm.