Confocal Raman refers to the ability to spatially filter
and to control the volume of the sample that is analysed. The principal
is used generally with a microscope system.
Just adding a microscope to a Raman spectrometer does not give a controlled
sampling volume - for this a spatial filter is required.
There are several methods in use today, some confocal, some pseudo confocal
and some are better than others - but it is well established that by using
a true confocal Raman microscope, it will enable Raman analysis of individual
particles or layers on the micron scale or lower to be detected.
For a True confocal design, the limits of spatial resolution are
defined principally by the laser wavelength and quality of the laser
beam that is used and the type of microscope objective selected and so
on.
For the highest spatial resolution, a correctly matched 100x objective
and visible laser excitation will often produce the optimum results.
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True confocal - best image resolution
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Video Image
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Pseudo confocal - blurred image - less separation between small and
physical features
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