A stereo microscope, also referred to as a dissecting microscope, is distinct from other types of microscopes for three main reasons:
- It utilizes incident light illumination, that is, the light reflected off the surface of the specimen is observed as opposed to light passing straight through the sample, which is called transmitted light illumination.
- It’s used for low magnification only.
- It provides three-dimensional visualization.
How Does a Stereo Microscope Work?
Like all light microscopes, stereo microscopes utilize photons of light to illuminate the specimen, however it has other distinct differences.
The main defining feature of a stereo microscope is that it uses two objective lenses and two eyepieces built as independent optical paths for each eye at slightly different angles to each other. This enables both depth perception and three-dimensional views.
The lighting is reflected from a source or incident (top lighting), resulting in light being reflected off the surface of the specimen as opposed to being passed through the sample, providing great visualization of the sample surface.
Some stereo microscopes have fixed magnification and some have zoom magnification.
As stereo microscopes only provide a low magnification yet yield a 3D image it makes them great for certain activities. For example, they are commonly used for dissecting, hence the name ‘dissecting microscope’.
They are also used to work with other intricate structures that do not require significant magnification, for instance watch making and repair, jewelry, circuit repair, biological research and microsurgery, and industrial quality control.
There is a common misconception that this type of microscope is a binocular compound microscope, but it is not.
Choosing a Stereo Microscope
There are a lot of stereo microscopes to choose from and exactly which one you select is usually determined by your requirements and budget. However there are some key features you should familiarize yourself with so you understand exactly what’s on offer.
Magnification – Stereo microscopes with fixed magnification are the most basic type and as a result are the least expensive. Fixed magnification describes microscopes that have one or two pairs of fixed objective lenses and therefore only one or two levels of magnification. That is, they don’t have the capacity to zoom in on specimens. These microscopes are still very useful, yet for a little more you can easily secure one with the ability to conveniently zoom in on specimens.
Stereo microscopes with zoom magnification have minimum and maximum magnification levels and by turning a zoom knob you can view any magnification within these levels.
Optimal Illumination – Lighting does not only need to be bright enough, but be adjustable so that any small raised surfaces on the subject does not cast shadows onto itself.
Having an adjustable light intensity also helps as the heat and light can affect certain specimens, especially live ones. This is especially important because your observations with a stereo microscope rely on incident light illumination as described above.
Greenough Principle – Microscopes based on the original Greenough principle are thought to be the best available. Greenough specified that the optimal stereo effect occurs when each light path is at 15 degrees. These microscopes have all of the most desired features including the ability to zoom, as well as high magnification and superb stereo imaging. The first true Greenough microscope was created by Zeiss, and other manufacturers now also produce microscopes using this principle.
These microscopes are typically preferred by professionals carrying out frequent and demanding activities, such as dissecting biological specimens. Compared to many microscopes, these are relatively inexpensive and simple to use.
Cycloptic®, the first modern stereo microscope based on the telescope principle. The Cycloptic feature was later renamed Common Main Objective (CMO).
Two basic stereo microscope principles:
a) the telescope or CMO principle
b) the Greenough principle
What is the Difference Between a Compound Microscope and a Stereo Microscope?
Compound and Stereo microscopes are probably the two most common types of light microscopes used today. They are often referred to as high powered and low powered respectively.
A compound microscope is typically used for analysing specimens that require a greater magnification, for example, for looking at the cell structure of plants and animals. Stereo microscopes are usually used to examine larger samples that require less magnification including insects, bugs and rocks.
Compound Microscopes
- Optical Path: The major difference between compound and stereo microscopes is the optical path. Compound microscopes have a single optical path, which is split in two so that the same image is viewed through the ocular lens regardless of whether there are one or two eyepieces.
- Magnification: A compound microscope usually has between 3 and 5 objective lenses that may go from a magnification of 4x to 100x. If you have a 10x eyepiece, you can multiply this by the objective lens magnifications to see the magnification range of the microscope ie 40x to 1000x.
- Illumination of the object: Compound microscopes utilize transmitted light illumination where light is passed through the sample.
- Mainly used to see what our eyes can’t see in detail, such as the structure of living cells. for examining microbes such as bacteria and viruses.
Stereo Microscopes
- Optical Path: Stereo microscopes have two independent light paths going through the objective lenses and the ocular eyepieces. These paths are at slightly different angles providing a slightly different view of the object. This stereo view enables objects to be seen in three dimensions providing a perception of depth.
- Magnification: Stereo microscopes are typically regarded as low powered and go from magnifications of 6.5x to 50x.
- Illumination of the object: Stereo microscopes utilize incident light illumination where light is reflected off the surface of the object.
- Mainly used for viewing opaque objects such as insects, feathers, minerals, jewelry, coins, watches, hardware, and other large specimens.
The major difference between compound and stereo microscopes is the optical path. Compound microscopes utilize transmitted light illumination (light is passed through the sample).
Compound microscopes provide a single optical path, meaning the same image can be viewed through the eyepiece using either the left or right eye. Unlike stereo microscopes, compound scopes are used to observe objects under a very high magnification – which can range from 40x to 1000x or more.
On the other hand, stereo microscopes, also referred to as dissecting or zoom stereo microscopes are used to observe objects at a lower magnification. Stereo microscopes also rely on incident light illumination (light is reflected off the surface of the object).
As mentioned, stereo microscopes are typically lower power than compound models, with magnification ranging from 0.6x to 4.5x.
These differences also make them both useful for two very different kinds of observation. For instance, compound microscopes are typically used to view specimens such as bacteria and plant cells, while stereo microscopes are typically used to analyze larger objects such as electronic components, coins and jewelry.
Check out these Stereo Microscopes
AmScope Professional Binocular Stereo Zoom Microscope
- Magnification: 7x-45x
- Light: 64 Bulb LED Ring
- Package Size: 16.9" x 14.6" x 13.0"
Pros:
The SM-1BSX-64S Professional Binocular Stereo Zoom Microscope by AmScope is a great microscope for students, hobbyists, and those who work with large objects such as electronic or mechanical gadgets, or dental appliances.
The microscope is attached to a robust 12″ pillar stand which enables a large adjustable working distance between the microscope lenses and the object.
The 0.7x-4.5x zoom objective lenses on this AmScope microscope, together with the 10x superwidefield eyepieces, provide a magnification of 7x-45x.
The addition of a 0.5x Barlow lens helps to increase the focal length and provides clear images over the larger working distance.
The pillar also enables 360 degree rotation of the binocular viewing head, which allows others to view the same object without having to move the whole microscope.
Some other great features include:
- a Greenough stereoscopic system
- a 64 bulb LED light ring gives you the ability to precisely control the intensity of the light and switch to a cool light mode for subjects which are light or temperature sensitive. The LED light ring is detachable if required.
- the stage plate can be reversed which allows you to switch between a white or black background. This can help provide contrast and a better perspective on certain samples.
- the stage clips are large, easy to manoeuvre and don’t bend easily.
Cons:
There is no port for a camera on this microscope, but this product is really great value for the price.
In Summary:
The Amscope Professional Binocular Stereo Zoom Microscope is a robust, well constructed tool providing high quality optics for a very reasonable price.
Swift S41-20 Professional Dissecting Binocular Stereo Microscope
- Magnification: 10x and 20x
- Light: Dual Goose Neck LEDs
- Size: 15" x 18" x 16"
Pros:
The Swift Professional Dissecting Binocular Stereo Microscope comes with a binocular viewing head with interchangeable pairs of 10x and 20x widefield eyepieces as well as a 1x objective which provides low magnification and longer focal length.
This microscope is great for inspecting large-scale specimens that need to be handled while being viewed, such as soldering electronic circuit boards or working with dental appliances.
When viewing objects with this microscope, having 2 flexible gooseneck LED lights which can be directed where you want them provides a clear image with no shadows.
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Some other great features include:
- the base is heavy providing stability for most viewing.
- a sturdy pillar with adjustable boom-arm enables a good size working space.
Cons:
The 10x and 20x eyepieces allow for great magnification of the object, but this can be too high for some work. The option of a 5x eyepiece would be beneficial, though this can be purchased separately if required.
There is no intensity adjustment on the gooseneck LED lights, but this would add to the price of this microscope.
In Summary:
The Swift Professional Dissecting Binocular Stereo Microscope is a well built tool with a sturdy base providing stability, quality lenses providing excellent viewing and LED lighting enabling clear images.
This microscope provides excellent value for money.