Stereo Microscopes

Microscopes are used to see things that cannot be seen by the unaided eye. But what if you wanted to study the surface of a leaf or a piece of wood?

A stereo microscope is used in this situation. It is similar to a compound light microscope in some respects but differs in others. Primarily, a stereomicroscope operates on the optical theory of light absorption. Light absorption is simply using a light source, like a small bulb, to illuminate a sample or specimen from below. The specimen absorbs the light and the image is directed through a series of lenses to an eyepiece as a magnified view.

Whereas a compound microscope uses a single light source and produces a two-dimensional image, the stereo microscope uses two light sources to produce a 3D image of the sample. It also has two eyepieces that work in conjunction to bring height, width and depth to the image.

Typically, stereo microscopes are used for lower magnification on larger specimens. The stereo microscope has a limited magnification range of 10X to 200X.

Stereo microscopes are usually used to view the surfaces of solid specimens like wood or plastic. Common uses for this type of microscope are microsurgery, dissection and sorting. They are also widely used in watch making and production of electronic circuit boards as well as inspection of the same. In this respect, stereo microscopes can be likened to a glorified pair of glasses.

Some compound microscopes use two eyepieces for viewing comfort. This should not be confused with a stereo microscope. In the compound scope, both eyes are seeing the same image. A stereo microscope differentiates the image from the left and right, combining them to create a three dimensional image of the specimen.

The basic operation is the same as in compound scopes. A light source is situated below the stage. The stage is where the specimen slide is mounted with two small wire or metal clips with the specimen over a small hole, or aperture. The specimen is applied to a small glass slide and placed on the stage, over the aperture. 

The optical lenses are directly above the stage so that the specimen is between the light source and the lenses. The lenses are mounted on the nosepiece. The nosepiece can contain three or more of these lenses with different magnification powers. You can choose which one you want to use by rotating the nosepiece accordingly. The lenses direct the light through a tube called the body and into the eyepieces, where you see the image.

The total magnification you are using can be determined by simple multiplication. For instance, the eyepieces usually have a standard magnifying power of 10X. The lenses range from 2X to 20X. If you choose the 20X lens, you will see the image magnified 200X (10X x 20X=200X).

One real common educational use for the stereo microscope is in biology classes. Students can actually watch the process of photosynthesis (process by which plants produce their own food).

Some of these stereo microscopes can be purchased at hobby shops and toy stores, but I wouldn’t expect too much from these. If you really want a quality item, look at a professional equipment warehouse.