Microscope Eyepieces

Written by Patricia Skinner
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Microscope eyepieces, as the name suggests, are the parts of the microscope against which you place your eyes. Sometimes they are referred to as oculars, but most people are more familiar with the term "microscope eyepieces." They work in conjunction with the objectives, or the cylindrical protrusions beneath microscope eyepieces.

The eyepieces serve a number of purposes. They assist in magnification, and in most microscopes, they allow for the difference in distance between the eyes of microscope users. The illustration on this page shows the basic parts of a typical eyepiece for a modern microscope. In the world of microscopes, microscope eyepieces vary in their design and function according to the function of the microscope.

To Fit the Viewer

Some microscope eyepieces, for example, have what's known as an ultra wide viewfield. Others will have a specially designed high focal plane, so that if you wear eye glasses your eyes will be the right distance from the eyepiece to focus. Compensating eyepieces, as we have already mentioned, are specially for making allowances for the varying distances between people's eyes. This is usually achieved by adjusting a thumbscrew until clear focus is achieved.

Another design of eyepiece is called the Ramsden eyepiece. This is a positive eyepiece which has a diaphragm below its lenses. Yet another classification of microscope eyepieces are called Kellner eyepieces. Basically, they are similar to the Ramsden eyepiece but they have double eye lens pieces which are cemented together.

Compensating eyepieces play a crucial role in the accuracy of microscopy. It is important to read the instructions for the adjustment of your compensating eyepiece, as they vary from one manufacturer to another. The adjustment of the compensating eyepiece often depends on the degree of "highly corrected" objectives--yet another characteristic of modern microscopes.


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