What do I need to know about microscope stages?
November 25, 2008
Your microscope’s stage holds specimens and slides for examination.
Plain stages are usually fixed platforms with a circular hole above the illuminator and below the objective lens position. Filter and diaphragm wheels may be mounted to the underside of the stage to modify the illuminator’s light.
Mechanical stages have slide holders that have precisely controllable positions in two axes. This is critical for magnifications of 400x and above, since slight motions can move the specimen far out of the field of view. These stages have X-Y vernier scales and knobs for accurately placing the specimen under the objective.
Some stages move up and down to focus the microscope while the microscope tube and attached objective turret (nosepiece) remain fixed.
A stage plate is used with stereo microscopes. It uses a circular hole in the scope’s base to hold either a frosted glass plate for transmitted light from below or a dual-sided (black and white) plastic disk for improved contrast lighting with top (reflected) lighting of specimens.
The stage working distance is the vertical distance that is available for focusing by moving the stage, arm or tube, either separately or together. When combined with the objective’s working distance, it determines how big or thick a specimen can be and still be viewable. Low-power microscopes will have more generous stage working distances than high-power microscopes.