Dissecting microscopes are used for viewing live specimens or three-dimensional objects too large or thick to be accommodated by compound microscopes. Specimens can be physically manipulated under magnification, since they do not have to be mounted onto a slide for observation under a dissecting microscope. These microscopes are not as powerful as compound microscopes; rather, objects are viewed under low magnification, ranging from about 10x to 80x magnification, the range depending on the make and model.
Most dissecting microscopes have a moveable top portion with two adjustable eyepieces, similar to binoculars.
These are the eyepieces, where the viewer looks through. Usually, a dissecting microscope has a stereo head with two eyepieces, each set at 10x magnification, though it is possible to upgrade to higher power magnification levels.
Since no two eyes are exactly alike, slight adjustments can be made to the ocular lens to compensate for the differences, using the rotating diopter ring found on one or both of the ocular lenses, allowing both eyes to focus on a single image clearly.
The objective lens extends down from the head of the microscope, toward the stage. The microscope's magnification is determined by the eyepiece and objective lenses collectively. Often, stereo microscopes have two separate objectives, each one connecting to one of the eyepieces.
Rotating Objective Turret
Some microscopes allow the magnification of the objective to be altered by this zoom control knob for viewing different specimens.
The head of the microscope can be moved up and down with the focus knob, allowing the observer to view the image sharply; this is called rack and pinion focusing.
The specimen is placed on the stage plate for viewing. This plate is mounted on the base of the microscope, directly under the objective lens. Often, metal stage clips lie to either side of the stage, which can be used to hold a glass slide in place, if necessary. The background color of the stage can be alternated for optimal contrast with the specimen, usually, with either white or black stage inserts.
Many microscopes have both top and bottom lighting. Top lighting shines down on the stage to light up solid specimens with direct illumination, and bottom lighting is transmitted up through the stage to highlight translucent objects.
Usually the light switch or switches can be found on the top or back of the microscope base. A light source should be turned on before making any adjustments to the lenses or observing specimen. Often it is equipped with a dimmer, which allows the user to set the desired level of illumination.
- microscope image by guy from Fotolia.com