OPERATION
Axio Lab.A1
Lighting and contrasting method in reflected light
Carl Zeiss
04/2013 430037-7144-001
101
4.2
Lighting and contrasting method in reflected light
4.2.1
Adjusting the reflected light brightfield according to KÖHLER
(1) Application
Reflected light brightfield microscopy is the simplest and most common optical microscopy method for
examining opaque samples or specimens, e.g. material sections or wafers.
For a true-to-object imaging, indirect ray bundles, i.e. ray bundles diffracted and scattered on the
specimen details, are of major importance in addition to the so-called direct ray bundles. The higher the
portion of indirect bundles of rays (aperture), the more realistic the microscopic image according to ABBE
will be.
The bundled light emitted by the reflected light unit is reflected on a color-neutral beam splitter and then
passes through the objective which focuses the beam on the surface of the sample (so-called condenser
function). The objective collects the light reflected by the specimen and together with the tube lens it
generates the microscopic intermediate image which can then be visually observed or objectively
documented.
(2) Instrumentation
Reflected light brightfield viewing is only possible with the stand for reflected light.
Reflector module brightfield ACR P&C for reflected light in the reflector turret
(3) Setting the reflected light brightfield
The microscope has been started up correctly as described in Section 3.
The microscope is switched on.
x
Adjust the light intensity by turning the regulator (Fig. 4-19/
4
).
x
Position a high-contrast reflected light specimen on the microscope stage.
x
Swivel in the 10x objective on the nosepiece (Fig. 4-19/
3
).
x
On the nosepiece (Fig. 4-19/
6
) swivel in the position with the reflector module brightfield.
x
Bring the specimen into focus with the focusing drive (Fig. 4-19/
5
). If possible, always focus away from
the specimen in order to avoid a collision between the objective and the specimen.
x
Set the knurled wheel of aperture diaphragm
A
(Fig. 4-19/
1
) in the middle position (about half
open/closed).
x
Adjust (reduce) the knurled wheel of luminous-field aperture
F
(Fig. 4-19/
2
) until the luminous-field
aperture is visible in the field of vision.
x
Use the focusing drive to adjust the focus on the edge of the luminous-field aperture.
x
Now open the luminous-field aperture until the latter just disappears behind the edge of the field of
view.
x
For aperture diaphragm adjustment (image contrast) remove an eyepiece from the tube socket and
look into the socket with the naked eye, or use the auxiliary microscope instead of the eyepiece.
This functions only with sufficiently reflecting specimens.