Product Intelligence Stereomicroscope Technology
by Katriona Scoffin S
tereomicroscopes are optical microscopes that give a three- dimensional (3-D) view of a sample and generally operate at low magnification. The 3-D image allows solid surfaces to be examined
with greater clarity and permits the precise manipulation of samples during magnification.
A stereomicroscope effectively consists of two compound microscopes, each viewing the sample from a different angle. The stereoscopic image is achieved by maintaining two optical pathways through separate eye- pieces focusing on the same point. This produces two separate images at a slightly differing angle to each other, one for each eye, enabling stereoscopic depth perception.
Stereomicroscopes are used in food science, marine biology, embryol- ogy, environmental science, and forensic science. In pharmaceutical and biotechnology labs, stereomicroscopes are commonly used for magnify- ing biological samples such as plant tissues and organ samples. Wider industry applications include microsurgery, geology, and microelectron- ics, including the examination of circuit boards and microchips.
Considerations for purchasing a stereomicroscope Stereomicroscopes, in common with all lab microscopes, have a wide
range of functionality. At the most basic, a fixed magnification instrument with simple brightfield illumination is a good choice for the manipulation of large biological samples. At the other extreme, automated stereo zoom fluorescent microscopes with digital imaging allow for the time-elapsed recording of cell division and come with a wide range of accessories for other varied applications.
Stereomicroscopes are of the following main types: • Common main objective (CMO) or Greenough design • Fixed or zoom magnification. Other specifications can be categorized by: • Optics • Illumination • Ergonomics • Stands • Imaging
Types of stereomicroscopes
CMO or Greenough Stereomicroscopes have two main optical designs: CMO, also known as the Galilean or telescope design, and Greenough (see Figure 1).
Figure 1 – The two main optical designs for stereomicroscopes: a) CMO design. b) Greenough design. (Image courtesy of Leica Science Lab by Leica Microsystems, Buffalo Grove, IL;
www.leica-microsystems.com.)
AMERICAN LABORATORY • 28 • JUNE/JULY 2013
Common main objective microscopes have a single objective with two ocular channels and eyepieces. CMO microscopes can cost several times as much as Greenough microscopes, but they have superior light-gathering capabilities and higher resolution. Their modular design allows for the addition of a wide choice of accessories.
The Greenough design produces the stereo effect through the use of two angled objectives mounted side by side. Greenough microscopes are inexpensive and are ideal for everyday laboratory work.
Fixed or zoom magnification Fixed magnification: The magnification is changed by swapping the eyepiece, either through replacement or by rotating a turret. Fixed magnification microscopes are the basic option. Lenses can be swapped to change magnification, for example, from 20× to 40×. When choosing a microscope, be realistic about the magnification level and range you require. For whole biological samples, the requirement may be as low as 10× or 20×. A typical working magnification range for a stereomicro- scope is 10× to 100×.
Zoom magnification: The magnification can be altered on a continual basis. In zoom designs, the eyepieces can also be switched to change the range of magnification. For example, the M80 from Leica Microsystems has an 8:1
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