3 Product and Functional Description | 3.4 Microscopy and Contrast Methods
ZEISS
For a thickness measurement (step height), half the difference of the phase jump at the respective
interface must be considered:
Example: extreme case of copper on glass
,
,
consequently, for the additional thickness due to the phase jump we obtain
or
Without consideration of the phase jump at the respective interfaces, the thickness value would
be too large by 30 nm.
3.4.11 Reflected Light Polarization Microscopy
Reflected light polarization is a contrasting method suited for cut, polished surfaces of mineral
ore, coal, ceramics, special metals and alloys. Depending on the orientation of the crystals and the
sample details, the cut surfaces often react differently when reflected in linearly polarized light.
The illumination light is polarized by the polarizer before passing through the objective onto the
sample surface where it is reflected. Then the beam parts experience path differences depending
on the structure and polarization of optical rotations which, when passing through the analyzer,
are represented by different shades of gray. With the aid of a compensator with a λ-plate the gray
contrast can be converted into a color contrast.
Even when examining "dark" sample surfaces, a rotatable λ/4 plate in front of the objective (an-
tireflective cap) helps eliminate the reflections which are inevitable when working with objectives
with very low magnification.
A sample is bireflectant when the sample details show differences in brightness and color which
change when the direction of vibration of the polarizer or the stage is rotated. For samples with
low bireflectance using the analyzer with a rotatable lambda plate is recommended.
3.4.12 Reflected Light Fluorescence Microscopy
The reflected light fluorescence method is used to show fluorescent substances in typical fluores-
cent colors in high contrast. The light originating from a high-performance light source in a re-
flected light fluorescence microscope passes through a heat protection filter onto an excitation fil-
ter (bandpass). The filtered short-wave excitation radiation is reflected by a Dichroic Beam splitter
and is focused on the sample through the objective. The sample absorbs the short-wave radiation
before emitting longer-wave fluorescence radiation (Stokes’ Law). This radiation is then captured
from the image side by the objective and passes through the Dichroic Beam splitter. Last, the
beams pass through a emission filter (longpass/bandpass) and only the long-wave radiation emit-
ted by the sample passes.
The spectra of the excitation and the emission filter must match very closely. They must be in-
serted in a FL P&C reflector module together with the according Dichroic Beam splitter.
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Instruction Manual ZEISS Axioscope 5, Axioscope 5/7 MAT | en-US | Rev. 13 | 430035-7344-001
