Stereo microscopes, sometimes still referred to as dissecting microscopes, give an erect, three dimensional perspective.
This microscope has a low magnification power and uses two separate eyepieces with two objectives, which creates the visual effect of depth perception.
The primary use of a dissecting microscope is for viewing relatively large and solid surfaces or specimens.
It earned this name because it proved a very useful tool due to the observer's ability to manipulate the specimen that is being viewed with an important degree of precision.
This microscope allows for detailed work such as microsurgery, watch making and circuit board inspection and manufacturing.
As you will read below, stereo microscopes are designed based on two basic groups - Greenough and Common Main Objective and two basic configurations - Fixed magnification or a continuously variable zoom
The Greenough stereo microscope is the oldest of the two and is a wonderful tool used in production processes for soldering on a miniature scale and dissecting specimens in biology. It is easy to maintain and simple to use.
Horatio S. Greenough is credited with designing the use of two angled objectives, thus producing a slightly different view and creating the three dimensional effect. These twin body tubes each have their own objective and ocular lens.
The advantage of the Greenough design is the similarity to a compound microscope since it allows selection of high apertures.
The disadvantage is what's known as the keystone effect. This is a slight tilt in the focal plane due to the two lenses viewing the same image at slight angles.
As the lenses are not exactly parallel, this results in the outside of the image in the field of view to be slightly over focused or under focused. Therefore, only the central regions of the image are correctly focused at identical magnifications.
The common main objective design, or CMO, is the usual stereo microscope used in research and development because of its high resolution and the optical and illumination accessories available.
The CMO uses a large, single objective lens, which is shared by a pair of ocular channels and lens assembly.
This design virtually eliminates any image tilt in the focal plane. However, it creates an optical anomaly that makes the viewed object appear to elevate in the center, also referred to as “perspective distortion”.
This is more of a problem in the less expensive CMO stereo microscopes so those used in top research, being more expensive and made by a major manufacturer, should not have this distortion.
Both the Greenough design and CMO are available in the fixed and zoom variety, with zoom being a more versatile option in stereo microscopy. Of course your choice is dependent on the task to be achieved.
The term “fixed" refers to one of the microscopes used in stereo microscopy.
The fixed magnification uses two objective lenses, which refer to the optical element gathering and focusing the light rays on the image.
The magnification has a fixed degree and is limited to the capability of the lens. Changing to a stronger eyepiece increases the magnification.
This can be useful as you cannot change to a higher or lower magnification while viewing a specimen, therefore it keeps a stable focus.
These types of microscopes come in a variety of mountings, one of which is a turret style.
Objective turret is another term for this type of mounting and indicates that an additional objective lens can be rotated into viewing position.
This easily allows the viewer to change magnifications by simply rotating the turret mounting.
Stereo turret microscopes are less flexible than the zoom type but are a more economical choice.
The stereo zoom microscope behaves much as its name implies and is very popular. This microscope can zoom in or out to increase or decrease the desired magnification. The available range can also be altered by changing to a stronger eyepiece.
The stereo zoom microscope comes with a choice of stands:
Stereo zoom microscopes are available with either binocular or trinocular heads. The “binocular” indicates that there are two eyepieces mounted to the zoom microscope. Changing the focus requires turning a knob, which slides the microscope up and down.
A “trinocular” head means that a third eyepiece, or “phototube”, can be added without affecting the microscope operation.
This third eyepiece allows the attachment of a camera that can be used to take still or video pictures.
The trinocular option added to the stereo zoom capability is a popular choice due to this feature.
There are a selection of stereo microscopes available today and the right one for you is dependent on your needs. This particular light microscope has added greatly to the field of microscopy due to its real 'hands-on' capabilities.
Prices vary, feel free to browse below:
Stereo Zoom Microscope - read about the zoom variety that is now ergonomically designed, with boom adjustable frames and many digital options.
Digital Stereo Microscope - read about the invaluable ability to send digital images to a wide variety of electronic components.
Nikon - read about Nikon's stereo models with a wide-range of capabilities that can accommodate a variety of research fields.
Leica - check out the series of stereo models Leica has to offer. Great ergonomics and serious innovation.
Zeiss - here you can learn about a high quality instrument capable of many tasks, that can be customized to suit any manufacturing, research or medical need.
Wild - if you want a tried but true work-horse then you need to check out Wild's great range of stereos. These have a serious reputation and are still loved.
Bausch and Lomb - renowned for their clarity and image quality, Bausch and Lomb Stereo Microscopes are just one part of a large portfolio of products that the Bausch and Lomb company has produced over its 150 year history.
AO Stereo - A must see for the serious collector! These were an important step in the evolution of the microscope. When you combine that with good build quality and long service history many enjoyed, you can see where they have become as collectable as they are now.