http://odge.de/deutsch-englisch/Metallmikroskop+%7Bn%7D.html

http://www.britannica.com/eb/article-8867/microscope
Optical microscopes > Specialized types of microscopes > Metallographic microscopes
Metallographic microscopes are used to identify defects in metal surfaces and to determine the crystal grain boundaries in metal alloys. This type of microscope employs a type of illumination, called vertical illumination, in which the light source is inserted into the microscope tube below the eyepiece by means of a beam splitter. Light progresses through…

http://www.materials.ox.ac.uk/teaching/practicals/1P1bmicroscopy.pdf
The metallographic microscope
All the samples you will see this afternoon are metals; they are opaque and
therefore must be viewed in reflected light. To achieve this light from a
source at the rear of the microscope is reflected by a half-silvered mirror
down through the objective to the sample and then back through the
objective to the eyepiece. To do this the sample must be flat with its surface
normal to the incident light beam. Typically samples are examined as
polished and also after etching to reveal different aspects of their structure.
The samples you will look at this afternoon are pre-prepared and the first
will be set up on the microscope for you. The demonstrators will show you
how to level subsequent samples.