Confocal Raman imaging opened the door for many applications in Raman spectroscopy and imaging that were previously unavailable
for measurement with conventional (non-confocal) Raman methods. However, high confocality always results in a high focus sensitivity
and this can make measurements difficult with rough or inclined samples. The TrueSurface imaging extension resolves these
problems and extends Raman imaging to large scale (> 1×1 mm2) samples without extensive tilt alignment or sample preparation and without comprising the advantages of confocal imaging.
For the characterization of the inner properties of a sample with Raman Spectroscopy an ultrasensitive confocal Raman microscope
allows the acquisition of a Raman image stack revealing 3D information on the distribution of the chemical compounds.
TrueSurface Microscopy for Topographic Raman Imaging
Figure 1: Topographic Raman image of an aspirin tablet obtained with the TrueSurface Microscopy Mode.
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WITec's exclusive True Surface Microscopy mode makes it possible to perform confocal imaging measurements parallel with and
guided by large area topographic scans (> 1×1 mm2). To achieve this unique capability, the WITec microscope series can be equipped with a highly precise sensor for optical
profilometry. The large area topographic coordinates from the profilometer measurement are used to perfectly trace the samples
surface in either confocal or confocal Raman imaging mode. Sample preparation is reduced to a minimum without having to compromise
the confocality of the system. The TrueSurface Microscopy mode is beneficial for many applications, including the characterization
of micromechanical, medical, or semiconductor devices, the mapping of functionalized surfaces, or the imaging of bio-medical
or pharmaceutical material surface properties. Figure 1 shows a height profile of a pharmaceutical tablet (aspirin) with the
confocal Raman measurement overlaid. The drugs are labeled red and blue respectively, while the excipient is shown in green.
Topographic variation was more than 300 µm.
