In addition to the standard visual or directly Raman automatic focusing automatically available with all VistaControl software versions (including the fast mapping/imaging function), the Adaptive automatic focus control (AdFoCon) function is newly available as an option.
This option adds high precision and stability to Raman/PL auto-focusing and multi-folds the sample focusing speed to a few milliseconds for all types of objectives. An additional very low power laser system scans the surface of the samples to continuously adjust the focus position of the objectives. The AdFoCon system works reliably under white light conditions to track specimen focus during all normal microscopy imaging applications. During Raman/PL spectral or mapping measurements, this special laser will be blocked during the actual spectral acquisition and then restarted for further focusing operations. This process only takes a few milliseconds each time.
Additionally, because it is a true laser-driven surface focusing system, AdFoCon will allow the user to automatically implement a surface offset to their measurements, to compensate for the potential difference between the position of the sample surface at a given position and the maximum of the Raman signal. This is often the case for crystalline structures, where the Raman signal is amplified by penetrating deeper into the lattice structure with the excitation laser, and thus no measurement from the lattice surface occurs.