Microscope Maintenance Part 2: Köhler Illumination

March 21, 2016 ZEISS Microscopy

Make it even more visible: Help maintaining the optical brilliance of your ZEISS microscope with our guides

August Karl Johann Valentin Köhler (March 4, 1866 – March 12, 1948) was a German professor and early staff member of the Carl Zeiss workshop in Jena, Germany. He is best known for his development of the microscopy technique of Köhler illumination, an important principle in optimizing microscopic resolution power by evenly illuminating the field of view. This invention revolutionized light microscope design and is widely used in traditional as well as modern digital imaging techniques today.

What is Köhler illumination?

Before discussing this technique, let us go back to the late 19th Century and the origins of the procedure. The main sources of illumination for microscopy at this time were not only inconsistent, but also had the tendency to produce unwanted glare. Illumination commonly relied on the heating of the element zirconium which produced an intensely bright chemical light known as ‘zirconia light’, or the ‘Auer gas light’ (named after the scientist Baron Carl Auer von Welsbach). Although the Auer light was described as being suitable for microscopy, it had the undesirable side effects of producing carbonic acid and relatively large amounts of heat.

Köhler illumination is named after the inventor of the technique, August Köhler (1866-1948). At the time of invention, he was working on photomicroscopy that required long-term exposure of emulsion plates and not helped by the unreliable light sources. In 1893, Köhler published a paper which set out a method to overcome these problems and explained his technique for correct alignment of the microscope to provide a homogenous illumination of the specimen of interest. Following the publication, Köhler was invited to join the Carl Zeiss Company in 1900 where he worked for the next 45 years.

ZEISS: Service you can count on.
ZEISS: Service you can count on.

Köhler illumination is one of the most important specimen lighting techniques to date. The correct set up produces an evenly illuminated field of view, ensures that you have optimal contrast in your specimens, will increase the overall resolution of the microscope, and provides more imaging data from your experiments. Although the method can be overlooked by microscopists and perceived as somewhat time-consuming, once you are familiar with it, this technique can easily be applied each time you start an imaging session.

With proper tutorials and training, setting up Köhler illumination on your upright or inverted ZEISS microscope quickly becomes routine. Our partner site BitesizeBio in a recent article covers this part, including video tutorials by our ZEISS service experts.

Don’t miss the first part in our series of microscope maintenance articles: Routine Care and Replacing Bulbs

Tailored support for your needs: Get in contact with your ZEISS Microscopy service partner!

The post Microscope Maintenance Part 2: Köhler Illumination appeared first on Microscopy News Blog.


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