What are Compound Microscopes?
Most of the microscopes used today are compound. A compound
microscope features two or more lenses. A hollow cylinder called
the tube connects the two lenses. The top lens, the one people
look through, is called the eyepiece. The bottom lens is known
as the objective lens. Below the two lenses is the stage, with
the illuminator below that.
Compound microscopes were among the first magnifying instruments
invented. Two Dutch eyeglass makers named Zaccharias and Hans
Janssen are credited with making the first compound microscope
in 1590 by putting one lens at the top of a tube and another at
the bottom of the tube. Their idea was fleshed out by others
scientists over the next several centuries, but the basic design
remained very similar.
The eyepiece, also known as the ocular lens, is at the top of
the compound microscope. It is not adjustable, that is, it only
has one strength. Most ocular lenses are 10x, meaning that they
magnify objects to ten times their normal size. People look in
through the eyepiece through the tube and out through the
objective lens.
A compound microscope normally contains several objective
lenses. The objective lenses are different lengths, with the
longer ones being the strongest. The lenses are situated on a
round disk below the tube. Viewers choose which strength lens
they want and place it below the tube by turning the disk until
the desired lens is in place.
The stage and illuminator are below the objective lens.
Specimens are placed over a translucent part of the stage. Light
provided by the illuminator shines through the clear part of the
stage, making it easier for the viewer to see the magnified
details of the specimen. Two adjustment knobs help focus the
object on the stage by bringing the lenses and the stage closer
together.
Compound microscopes have been around for hundreds of years and
are still very useful. A number of scientific disciplines use
compound microscopes to discover the wonders of the microscopic
world.