There are many important parts of a microscope, and while the purpose of some of them is obvious, many budding scientists ask themselves “What is a Microscope Condenser?” or “What is a Microscope Condenser Used For?”

In this short article, we’ll give a brief and accurate overview of what a microscope condenser is, and why this microscope piece is critical to the performance of your microscope.

What is a Microscope Condenser?
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A microscope condenser, also called a substage condenser when it's not above the stage (as in an inverted microscope), is defined as an optical lens which renders a divergent beam from a point source into a parallel or converging beam to illuminate an object.

Maybe not the clearest definition! That’s a fancy way of saying the microscope condenser is a microscope part located between the light source and the sample you’re examining, which works to concentrate the light onto the object you’re examining, illuminating it so you can get a clear view of it when you look through your microscope’s eyepiece.

How has the Microscope Condenser Evolved over Time?

The earliest microscope condensers were used during the 17th century. Robert Hooke used a combination of salt water and a plano convex lens.
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Today microscope condensers usually consist of a variable-aperture diaphragm and one (sometimes more) lenses. Whether you have an electric microscope which uses 110v or battery power to illuminate your specimen, or your microscope uses ambient light with a mirror, a modern microscope condenser focuses available light through its lenses and onto the specimen, illuminating it from below for study.

When the light passes through the specimen you’re observing, the light diverges into an inverted cone, filling the front lens of the objective to display your specimen properly.

What is the Abbe Condenser?

The Abbe condenser is a microscope condenser that was developed in 1870 and named for Ernst Abbe, its inventor. This specialized condenser uses an iris diaphragm to control the diameter of the beam of light, allowing scientists to accurately focus their light source to properly view specimens with their microscope.

While the Abbe Condenser is not practical for magnification levels above 400x, this type of condenser can be found on many modern microscopes.

What Condenser Numerical Aperture is Proper for Oil Immersion?

Just like objective lenses, your microscope condenser will vary in its NA (Numerical Aperture – a fancy way of assigning a number to determine optical resolution). If your microscope uses oil immersion (or even water immersion), then the maximum numerical aperture for your microscope condenser should be 0.95.

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