Köhler illumination

A method for even illumination of the object plane in an optical microscope that is applicable to both transmitted and reflected light configurations. Using Köhler illumination, the image of the light source (located in an aperture plane) is perfectly defocused in the object plane (located in a field plane).

Related MicroscopyU Article

Microscope Alignment for Köhler Illumination

Perhaps one of the most misunderstood and often neglected concepts in optical microscopy is proper configuration of the microscope with regards to illumination, which is a critical parameter that must be fulfilled in order to achieve optimum performance. The intensity and wavelength spectrum of light emitted by the illumination source is of significant importance, but even more essential is that light emitted from various locations on the lamp filament be collected and focused at the plane of the condenser aperture diaphragm. This interactive tutorial reviews both the filament and condenser alignment procedures necessary to achieve Köhler illumination.