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Technology Features |
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Optical method: non-contact,
non-destructive and no Beta radiation |
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Fast measurement and film thickness
evaluation - within milliseconds! |
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Wide thickness measurement range:
~ 0.1
to 150 micrometer ( 0.004 to 6 mil ) |
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High accuracy: typically
better ± 0.005 micrometer over the entire range |
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Simultaneous determination of
double-layers
possible |
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Motion bridge controlled measurement on
web coaters possible |
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Measurement on very small spots using our
FTM-Micro film thickness microscope |
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Application Note |
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Measurement Method
Principles |
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A
commonly well-known effect, which occurs for example with soap bubbles or on a thin oil
film on water, is used for the determination of the film thickness. You can see many
colors which change according to the layer thickness, e.g. when the soap bubble is blown up.
Also check out this Soap Bubble Web site for some
nice pictures and more detailed explanation of this effect!
These
"colors at thin layers" are based on the interference phenomenon, i.e. on the
superposition of light waves, which have been reflected at the front and back side of the
layer (at two boundaries with different optical densities). |
The interference model |
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The undisturbed
superposition of the two reflected light rays 1 and 2 leads to periodical amplifications
and extinction in the spectrum of a white continuum light source (such as a halogen
spectral lamp as a pseudo white-light source).
Since the superposition of the two light rays is not purely additive, a so-called
interference occurs. The figure at the right shows the interference spectrum of a 1 µm
layer (chart on top) and 2 µm layer (chart at bottom).
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Examples of interference spectra |
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