- term referring to the lens. A lens which brings in light
from two parts of the spectrum (red and blue wavelengths) to the same focus,
reducing Chromatic Aberration. This is the most common lens on a microscope.
Color fringes may appear when viewing under bright white light because not all
wave lengths are brought within an acceptable focus range. If you use filtered
light (monochromatic) as in phase contrast the image will be sharper.
- the distance between the objective and the top of the body tube,
usually 160mm. Objectives are designed for a specific length, if mis-matched,
spherical aberration will occur.
- provides an even cone of light that illuminates the specimen. Light from
the condenser converges on the specimen, passes through it, and diverges to
from an inverted illumination cone that is captured by the objective lens.
The Abbe condenser is the most common. The condenser numerical aperture (NA)
should be equal to or greater than the highest objective NA., usually 1.25
to 1.32 for a 100x oil objective. The resolving power of the optical system
composed of condenser, objective ocular lens is limited to the lowest NA of
its individual components.
- the distance along the optical axis throughout which the
object can be located and yet be imaged with satisfactory clarity. This is used
in stereo microscopy.
- a circular disc, located under the stage platform
containing five or six apertures of various sizes which controls the size of
illumination cone converging on the specimen.
- also known as ocular, it produces the second stage of
magnification enlarging the image magnified by the objective lens. Eyepieces
vary in magnification from 5x to 30x. The standard is 10x.
- These are placed at a focal plane of the eyepiece
coincident with the primary image plane of the objective. When the microscope is
focused the image of the specimen and graticule will be seen together.
- most common is the 100x oil objective. Oil is placed on the
cover glass of the slide which (and sometimes on the top element of the
condenser) to produce a high magnification and high resolving power of the
objective when immersed in the oil. This produces the full NA of objective lens.
- magnification, which is the ability of the lens to make an
object appear larger. It is the number of times the image is seen through the
microscope is larger than the item appears to the unaided eye.
- (N.A.) a term representative of the angle included by a
cone of light accepted by the objective of a microscope. The higher the N.A.,
the greater the resolving power.
- forms the primary image of the microscope which is seen
through the eyepiece. The markings on the objective lens are the magnifying
power (such as 10x), followed by the NA (0.25) and the tube length. Other
numbers which appear on the objective lens may refer to the manufactures catalog
number of the particular item.
- the optical system of the microscope near the specimen. The
objective projects the specimen image into the intermediate image plane of the
microscope tube.
- a term used describing the property of a microscope where
the subject stays in focus when the objective lenses are changed. Less then 1/2
of a revolution from the fine adjustment is usually acceptable.
- a two sided mirror 50mm in diam., with one side flat (plano)
and the other curved, (concave). The concave side is used for low NA when no
condenser is used, the plano surface is used with a substage condenser.
- the optical technique used to view the structure of
transparent objects whose varying but invisible differences in thickness result
in differences in the phase of transmitted light. This is done when the
transmitted light changes its optical path by about 1/3 wavelength.
- term used to describe the gear system for lowering and
raising the stage or barrel when focusing. The coarse adjustment control (knob),
usually moves the barrel or stage.
- usually on the 40x and 100x objectives, a spring is loaded
inside the objective so that minimal damage is done to the slide and the top
element of the lens should it be racked down beyond its normal stop.
- the connection between objective and eyepiece. According to
DIN the mechanical tube lenght is 160mm. Meiji objectives are computed for this
tube lenght.
- is given if its value is other than 1.0 and must be added
to the eyepiece magnification. It is due to optical systems between objective
and eyepiece or to a change in the tube lenght.
- the distance between the cover glass or object and the tip
of the objective. This governs the allowable movement of the objective in
obtaining critical focus of the specimen.
