Modern stereomicroscopes are built according to either of two design concepts - the Greenough Concept or the Telescope Concept.  Both are briefly described below:

      THE GREENOUGH CONCEPT

Two identical objectives, arranged with their optical axes including a small angle generate two separate images.  Observed through separate eyepieces, they combine to form a three-dimensional image.  Advantages of this concept are:

• Low cost
• Compact design
• Basic Instruments with high optical performance

    THE TELESCOPE (CMO = CENTER MOUNTED OBJECTIVE) CONCEPT

Two microscope systems arranged in parallel share a common objective; the stereo angle is formed by the extra-axial pairs of rays.

• Upgradeable
• Modular design
• Attachment of as many accessories possible