In the world of microscopy – the field on the use of microscopes to view specimens and objects – lighting is of utmost importance. Whatever the kind of microscope you use – a metallurgical microscope or a fluorescent microscope – you need to have the correct illumination. You need to have the ideal light not only to see the specimen in question but to see it on its “natural state” as well. You need to get an image without the unnecessary glare or “ghost images.”

In the earlier times, there were a lot of issues on sample illumination. As a result, the images seen under microscope come out as problematic, uneven, hazy, and to some extent, incorrect. All these problems are due to incorrect or poor lighting.

It was in 1893 when almost all issues of illumination were addressed. Thank goodness for the Kohler illumination! This technique was designed by August Karl Johann Valentin K”hler, a German professor. He was also an employee of the world famous Carl Zeiss Company, the leader in optical systems and engineering.

The Kohler Illumination is known for optimizing microscopic resolution simply by illuminating the field of view in an even manner. In simple terms, this means that you will get the ideal illumination if all the elements and parts of the microscope are properly aligned.

The Kohler Illumination therefore revolutionized the design of the light microscope – the type that involves diffraction, refraction and reflection. It somehow perfects the use of light in examining specimens.

Here are some of the most important “light hurdles” that the Kohler Illumination overcame:

The Filament Image

Years before the invention of the Kohler Illumination, the filament of the bulb used in lighting up the sample being examined is visible in the sample plane. Now, if you were a scientist, or a student, you wouldn’t want a distraction in your sample plane. If this was a test, and you didn’t realize that it was the filament showing up in your sample plane, you’d answer the question incorrectly.

Numerous attempts were undertaken to get rid of that filament image. First, people started using an opal bulb. Then they also tried lowering the power of the light source. This way, the image reflected by the light is not sharp enough to register itself in the sample plane as well. Of course, there’s that opal glass diffuser – to cause a certain amount of light scattering.

Still, these attempts were not perfect in eliminating the filament image. In addition, they cause even more problems. For instance, if you reduce power of the light source, you could have reduced quality of light as well. As a result, you might not be able to clearly see the specimen in your sample plate. Then there’s that question on uniformity of light.

With the Kohler Illumination, however, the light microscope saw a different kind of “light.” It was able to produce light at optimum levels. It was able to answer lighting issues – that of the filament image, most especially.

Indeed, thank goodness for the Kohler Illumination!

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