Leica DVM6, User Manual

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Leica DVM6 User Manual Terms Used 74
Terms Used (Continued)
Numerical aperture
The numerical aperture, abbreviated nA,
describes the half-angle of the light cone
received by the microscope from each sample
point.
A high nA means high luminous intensity and
high resolution but also low depth of field at the
same time. The actual nA depends on the zoom
position, the position of the iris diaphragm and
the selected objective.
Planapochromatic (PlanAPO)
This specifies that the objective, in addition to
apochromatic correction, also features an even
image field up to the border area.
Polarized light
Polarized light only vibrates in a single plane.
Light emitted normally is a mix of light waves
that vibrate in all directions and can be polar-
ized through reflection, birefringence, selective
absorption or scattering.
Polarization can be used to differentiate
changes in the structure and the composition
of the material that cannot be detected with
ordinary light.
Reflection
Light returns from an optical surface to the
same medium it came from.
Depth of field (DOF)
The depth of field is a measure of the extent of
the focal range in an microscope's object space.
The higher the magnification is, the lower the
depth of field.
Field of view, object field (FOV)
This is the area shown by the microscope if the
sample is in focus. It is normally expressed in
mm as a visible diagonal measurement. It can
be determined very easily by focusing on the
image of a scale (mm scale).
The field of view has an inverse relationship
with the magnification level. The higher the
magnification, the smaller the visible field of
view.
Side light adapter
The side light adapter illuminates the sample at
a shallow angle. This emphasizes surface errors.