Microscope Glossary of Terms
Below you will find
definitions of terms used in
this site, and in microscopy in general.
an advanced illumination system which uses a
lens under the stage that would typically move in the
vertical direction. It would usually also have an adjustable
iris to control the beam diameter of the light prior to
entering the lens. By adjusting the iris opening and the
lens distance from the target, the user has very good
control over the amount of light and its focal point.
Usually found on the more advanced microscope systems and
very useful at higher magnifications (400X and above).
a lens specially designed and coated to correct
for the tendency of light to separate into colors when
passing through glass. An achromatic lens corrects this such
that colors are more accurate after being magnified.
A compound microscope with two eyepieces
viewing down a single optical channel and objective. This is
different than a stereo microscope,
which has a separate optical channel for each eye.
Click here for an example.
C-mount & CS-mount:
a.k.a. C/CS-mount, is a threaded standard developed for mounting
a lens to a camera. Most commonly used for video cameras
(i.e., CCTV cameras, not camcorders), and is used to mount
cameras to microscopes. The mechanical definition of both
standards is 1" diameter, 32 TPI (threads per inch),
male on the lens (or microscope) side and female on the
camera side. The optical definition of the C-mount is that
the image reaches the focal plane, or camera's detector, at 17.5mm past the edge of
the lens' (or microscope's) mounting threads. The CS-mount is identical in all
respects except the focal plane is 12.5mm past the mounting
threads. A CS-mount camera can be mounted on a C-mount lens
or microscope by using a 5mm extension ring. See also: T-mount.
A configuration where one knob is
centered on top of another. For example, coarse and fine
focus may have a larger coarse focus knob with a fine focus
knob on top of it (so the center of both knobs is on the
Also commonly used for Mechanical
Stage X/Y movement knobs.
Literally a microscope with multiple lenses,
however that describes virtually all modern microscopes. It
has come to refer to the high-powered microscope such as that pictured at
the top of this page used for viewing cells, bacteria, etc. It would typically include
multiple user-selectable objective lenses of varying magnifications and present a
two-dimensional view. See also: stereo
A microscope with cordless illumination. Typically a L.E.D. system using
batteries and can be either 'rechargeable' or
'battery powered'. 'Rechargeable' will include
rechargeable batteries (e.g. NiMH) in the microscope's base
and an AC battery charger. 'Battery powered' uses
standard batteries (e.g. alkaline) and will therefore not
include a charger (of course rechargeable batteries can
still be used with an optional external charger). Cordless
microscopes are great for field work, classrooms where the
power is not conveniently distributed, areas where AC power
is not reliable, etc. Battery powered microscopes
coupled with a solar powered battery charger can be used
indefinitely in areas with no AC power. L.E.D.
microscopes also typically have a much longer bulb life than
other styles of illumination.
(angled) illumination technique used to improve contrast in
specimen which are typically transparent. The light is
angled such that if it is uninterrupted by the specimen,
will continue past the objective lens. Therefore the
specimen appears dark when viewed through that objective.
However if a feature of the specimen were to divert the
light up into the objective, then that feature will appear
bright. Low power (stereo microscope) darkfield is
often used for illuminating inclusions in gemology. High
power (compound microscope) darkfield applications include
viewing live blood cells. A technical description of
this technique can be found here
A microscope and video camera combination
with a digital output such as USB or firewire. Often
includes software to display the image on a PC.
DIN Standard Objectives:
(Deutsches Institut fuer Normung)
An international standard which dictates the design compatibility
of the objective lens. Therefore DIN standard objectives
from one manufacturer can be used in another manufacturer's
DIN standard compatible microscope.
a lens design that is actually two different
lenses cemented together (usually one positive magnifier and
one negative). This design is used in widefield
eyepieces to obtain significantly better color
performance than single lens designs.
A monocular microscope with a second, vertical viewing port. The
vertical port can be used with an eyepiece for a second
person, such as an instructor, to view the specimen, or it
can be used with an adapter and a video or still camera.
Click here for an example.
See also: trinocular microscope.
Eyepiece or Ocular:
The lens closest to your eye when looking through a microscope. A binocular or stereo microscope will have two,
a monocular microscope will have one. It also plays a
critical role in the total system magnification. See also widefield
Eyepiece Tube or Eyetube:
The tube into which the eyepiece lens (ocular) is set. This
is typically presented at an angle for comfortable viewing
such as in the picture at the top of this page. However it may also
be mounted in a vertical position such as on a trinocular or
dual-view microscope for either a second viewer,
or for a camera designed to fit inside an eyetube.
FPS: frames per second:
Used to indicate the speed in
which a video image is refreshed and displayed on a monitor.
In video microscopy this is usually controlled by the
camera. The faster the refresh rate (number is larger), the
"smoother" any movement of the specimen will appear.
Distance between the two eyepieces. Typically
it is adjustable to accommodate different users. Some
microscopes also have graduated scales to indicate the
actual distance between the eyepieces, allowing a user to
determine the optimum number and then quickly set
it before each use.
A highly effective illumination design.
Please click here for a more detailed definition.
A mechanism mounted on top, or as part, of the stage that
allows the operator to move the specimen slide in the X or Y
direction by turning a knob. Very useful at higher
magnifications as it can be difficult to move the slide by
hand otherwise since it must be moved such a small amount.
Also, moving by hand can be difficult since you must move it in
the opposite direction. Most mechanical stages come with a graduated scale so you can
see how far the slide has been moved or keep track of the
position of various objects on the slide. Please click here for more information.
compound, high power microscope with an illumination system
designed to shine light down on the top of the specimen
(a.k.a. incident or reflected light). This is unlike a
typical biological compound microscope which is designed to
illuminate from underneath and up through the specimen
(transmitted light). Some metallurgical microscopes will
include both types of lighting systems. Reflected
lighting is necessary to view opaque specimen such as metal,
ceramics, integrated circuits, etc., or any application that
requires high magnification of opaque substances. If the
application does not require high magnification, then a
stereo microscope may be more appropriate.
A compound microscope with one eyepiece such as that pictured at the top of this
The most important lens in a microscope and the
one closest to the specimen.
In a compound microscope there are usually 3, 4 or 5 objective
lenses allowing a selection of magnification levels. For a
picture, see "OBJECTIVES" in the illustration at the top of
Oil Immersion lens:
A lens designed to be immersed in oil.
A drop of immersion oil is placed on top of the cover glass
and the lens is slowly lowered until it rests in the oil.
This allows the light to pass through oil rather than air,
and at higher magnifications results in a crisper, higher
A lens design such that specimens that appear centered in
the field of view at one magnification level will also
appear centered when the magnification level is changed. See
A lens design such that specimens that appear in focus at
one magnification will also appear focused when the
magnification level is changed. Keep in mind, however,
that depth of field (how much of a specimen's height will
appear in focus at one time) changes significantly when
magnification is changed. The higher the magnification,
the shallower the depth of field. See also: parcentered
A technique using
special objectives and condenser system to enhance the contrast of
unstained, relatively transparent specimens such as blood and
other tissue cells, thereby allowing microscopic viewing of living
tissue. It is a sophisticated technique that shifts the light
"phase" 1/4 wavelength, causing any light deviated by the specimen to
appear dark on a light background. Development of this technique
by inventor Frits Zernike earned him a Nobel prize in physics in
1953. An excellent, more detailed discussion of this process can be found on the
Molecular Expressions web-site here.
Plan or Planachromat Objective Lens:
An objective lens with a flatter design than a standard achromat resulting in
improved focus around the outside of the field-of-view as
well as better resolution and contrast. Typically the best
lens design available on a microscope.
Polarized Light Microscopy:
used to enhance the contrast and image quality on specimen
where other techniques such as phase contrast or darkfield
are not as effective. Two polarizing filters are used called
the 'polarizer' and 'analyzer' filters. The polarizer is
placed in the path of the light source, and the analyzer in
the optical pathway. A more accurate and detailed
description of this process can be found on the
Molecular Expressions web-site here.
A safety feature
consisting of a mechanical stop, usually adjustable, which
prevents the objective lens from
hitting the microscope stage.
A head design where the interpupillary adjustment
(increasing or decreasing the distance between the
eyepieces) is achieved by twisting the
eyepieces in an up and down arc motion like binoculars.
A safety device usually located on the focus
knob allowing the knob to "slip" and continue turning
when it reaches the end of its travel, or if it runs into
the stage. Due to the gear ratios involved, without this it
may be possible to damage the mechanism by applying too much
force to the knob after it has reached the end.
A target with a
highly accurate scale or other geometry on it used most
often for calibrating microscope eyepiece reticles..
Typically a 1" x 3" transparent glass slide with a chrome
scale printed on it. It is placed on the microscope 'stage'
and viewed just like a specimen. Its scale can then be
aligned with the scale on the eyepiece reticle which results
in a precise measurement of the microscope's magnification.
This then allows the use of the reticle to make accurate
dimensional measurements of other specimen. More details on
the calibration procedure can be found here. Typically
available for use with transmitted light (chrome scale on
transparent background) or reflected light (transparent
scale on solid background). Also available with
N.I.S.T. traceability, meaning the dimensions on the stage
micrometer have themselves been calibrated with certified
equipment by a certified calibration laboratory. More
details on N.I.S.T. traceability can be found here.
Stereo microscope a.k.a. dissecting microscope:
with a separate optical channel for each eye (eyepieces and
objectives) which allows viewing in three dimensions. Also
called a low-power microscope and is used to view larger
specimen such as insects, minerals, plants, larger
biologicals, etc. See
also: compound microscope.
Super High Contrast Objective Lens:
An achromatic objective lens that has contrast-enhancing
coatings applied resulting in a more detailed, clearer image.
Turret or Objective Turret:
The rotatable metal piece into
which the microscope's objective lenses are attached. A "turret" style stereo
microscope refers to the type that has more than one
objective lens which can then be rotated into position. On a compound microscope the turret is
the ring holding the objective lenses allowing the operator
to rotate them into position as needed. See the picture at
the top of this page.
A photographic mechanical
mounting standard developed in 1957 originally intended as a
universal lens mount for 35mm cameras. There are now
T-mounts available for a large variety of digital and film
cameras making it a good method for mounting cameras to
microscopes. The thread (a.k.a. T-thread) is specified as
42mm diameter and 0.75mm pitch, or M42-.75. See also: C-mount
A binocular microscope with a third, vertical viewing port. The vertical
port can be used with an eyepiece for a second person, such
as an instructor, to view the specimen, or it can be used
with an adapter and a video or still camera. Click here for an example. See also: dual-view
Widefield eyepiece (WF):
an eyepiece with an achromatic doublet lens designed in such a way
that it does not have to be limited to viewing only in its
center, and the portion of the lens that allows
non-distorted viewing is larger than a normal lens. This
appears to the user as a bigger aperture or "hole"
to look through. It therefore has the advantage of being
easier to use and more forgiving of a user's head movements.
An eyepiece listed as WF10X/18mm would indicate
it has a widefield achromatic doublet lens, 10X
magnification and has an 18mm diameter aperture.