Köhler Illumination

Köhler illumination eliminates uneven illumination in the field of view so that all parts of the light source contribute to specimen illumination. There are two types of Koehler illumination, one method in which light is transmitted through the specimen (transmitted) and one method where it is reflected from the specimen (incident). Transmitted Koehler illumination is used for transparent or semi-transparent specimens, while incident Koehler illumination is useful for objects such as metal, which do not transmit light.