Adaptive Focus Control (AdFoCon)

Aside from the standard Raman autofocus automatically available with all VistaControl versions including the stage-mapping function (at least a motorized z-stage will be required), the optionally available “Adaptive Focus Control” will add a high precision and fast white-light and Raman/PL autofocus system, that will reduce the refocussing of the objective to a few milliseconds per position.

An additional low power laser system scans the samples surface to adjust the focus position continuously with almost no additional overhead.
The system works reliably under white-light conditions, to track the samples focus during normal microscope imaging applications.
During Raman/PL spectral or image acquisitions, the focussing laser will be blocked during the actual spectral acquisition and then reinitiated for the next focussing operation. This process only takes a few milliseconds each time.

In addition, as it is a true surface based focussing system, AdFoCon will allow the user to implement a surface offset on their measurements, to compensate for potential offsets in surface position and best possible Raman signal. This is often the case in crystalline structures, as the Raman signal is intensified by penetrating deeper into the lattice structure with the excitation laser.

Adaptive Focus Control (AdFoCon) main features

  • provides continuous closed-loop feedback of the focus position for white light mappings
  • provides continuous closed-loop feedback of the focus position for Raman mappings
  • “Fast Raman Mapping” and “Adaptive Focus Control” are two independent but simultaneously running processes
  • The “Adaptive Focus Control” produces almost no time overhead, if the differences in sample height are small. For large changes in sample height the speed is limited by the moving speed of the focusing stage of course.
  • a time-consuming pre-scan, while possible is not needed
  • height information gathered can be displayed as a height map after the measurement