Large Area Profilometry for Confocal Microscopy
WITec´s award winning TrueSurface Microscopy allows confocal Raman imaging along heavily inclined or very rough samples with the surface held in constant focus while maintaining the highest confocality. It is thereby possible to perform confocal imaging measurements parallel with and guided by a large area topographic scan.
The core element of this revolutionary imaging mode is an integrated sensor for optical profilometry. It is directly installed at the microscope turret which facilitates user-friendly and convenient handling.
The sensor operates according to the confocal chromatic sensor principle: a white-light point source is focused onto the sample with a lens system that has a good point mapping capability, but a strong linear chromatic error (hyperchromatic lens system). Every color has therefore a different focal distance. The light reflected from the sample is focused through a pinhole onto a spectrometer. As only one specific color is in focus at the sample surface, only this light can pass through the confocal pinhole. The detected wavelength is therefore related to the surface topography.
The profilometric capabilities of the True Surface Imaging mode allows scan ranges of up to 50x100 mm with a spatial resolution on the order of 40-120 nm vertically and 10-25 µm laterally. The large-area topographic coordinates from the profilometer measurement can be precisely correlated with the large-area confocal Raman imaging data. In combination with AFM, the True Surface profilometer can be used as a pre-inspection tool to determine topographic features of interest for high-resolution AFM investigations on large samples.
TrueSurface Microscopy is beneficial for a large variety of applications, including the characterization of micromechanical, medical, or semiconductor devices, the mapping of functionalized surfaces, or the imaging of biomedical or pharmaceutical material surface properties.
Inclined geological sample analyzed by TrueSurface Topography. The red arrow marks the area of interest. The same area was measured using TrueSurface imaging option (above) and in confocal Raman imaging mode (below; scan range: 2x2mm2; topography range: >1.7mm).
A height profile of a pharmaceutical tablet was scanned with TrueSurface and overlaid with the confocal Raman image. The drugs are labeled red and blue, while the excipient is shown in green. Topographic variation was more than 300µm.