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Compound vs. Stereo Microscopes: What’s the Difference?

Different microscopes have different uses, and being familiar with any given instrument’s specifications can help you choose the right tool for the job. Whether you're trying to get into a new hobby, a seasoned technician inspecting a part you made in a machine shop, or buying a gift for the gemologist or coin collector in your life, it is highly beneficial to know what microscope is best for your desired purpose and why. UNITRON makes specialized microscopes for a full range of applications ranging from forensics to metallurgy,  but most of these scopes fall into two main categories: stereo and compound (“upright” or “inverted”). Both types have their benefits and are the perfect solution for certain tasks, but neither is a universal solution to all microscopy needs. Depending on what you plan on using your scope for, a stereo or compound microscope could be better suited for your needs. As such, understanding their differences is key to making the right decision. 


Sometimes referred to as "dissecting microscopes" in the biology world, stereo microscopes utilize dual eyepieces to create a sense of depth when viewing three-dimensional objects. Although they typically have a lower magnification level and lower optical resolution than compound microscopes, they are ideally suited to observe and simultaneously manipulate the sample. This perception of depth, created by dual optical paths and dual eyepieces, makes stereo microscopes perfect for viewing larger three-dimensional objects (items you can hold in your hands). They also have a long working distance, allowing the user to easily manipulate objects while they're on the stand, stage or bench. Stereo microscopes are perfect for hobbyists trying to examine coins, stamps, and mineral samples. Their working distance makes them well-suited for professionals repairing small instruments like watches or quality inspection, or for students performing dissections. Most stereo microscopes fall into two main categories: fixed power and zoom power. Zoom stereo microscopes allow you to smoothly zoom in or out on the sample to the exact amount that you need. Fixed power stereo microscopes have only a couple available magnifications, but these microscopes also tend to be smaller and more portable and, therefore, may be a good option for fieldwork and classroom settings.


Compound microscopes offer much higher magnification than stereo, with total magnifications for some reaching 1000x or more. The term “compound” refers to the optical design and includes both upright microscopes (the objectives are above the stage) and inverted microscopes (the objectives are below the stage). The high magnification capability makes compound microscopes perfect for viewing small samples and features like microstructures and defects in metals, impurities in pharmaceutical agents, or fiber structure in forensic samples. As a result, compound scopes are a mainstay in both industrial, forensics and biological research labs. Compound microscopes tend to have a much smaller working distance (typically 2-10 millimeters) than stereo microscopes (typically >40 millimeters), making them more suitable for observing flat samples such as polished sections of rock or metal, or samples placed on slides. Contrast methods may vary by the type of compound microscope, and the choice of contrast depends on the sample. Brightfield scopes illuminate the sample with white light and, as the name implies, the sample may appear darker than an area without the specimen. Darkfield is a method that illuminates the specimen with light from a high angle, and you will only see light that is reflected or diffracted back into the objective. The result is a brighter appearing sample on a dark background.  Other contrast methods are also possible including polarized light and differential interference contrast, and these are topics for another article.  Microscopes are highly useful instruments with applications across many disciplines, scientific fields, and hobby areas, and it's important to understand each microscope type's strengths when deciding which is best for your application. Visit UNITRON today to learn more about our full range of professional-grade microscopes and microscope accessories.
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