The Phase Focus Virtual Lens® can operate in principle using any wavelength in the electromagnetic spectrum, as well as with electron and other particle waves. In addition (and where appropriate) it may also be implemented in both transmission and reflection modes. Great flexibility is therefore available for a wide variety of metrology applications:
- Measurement of reflected or transmitted phase changes with very high sensitivity and high lateral resolution, for applications from surface topography and tribology to film thickness measurement.
For example, in the visible light regime the typical phase change sensitivity of 0.02 radians (1°) enables mapping of depths, heights and thicknesses with sub-nanometre accuracy, over arbitrarily wide fields of view. Lateral resolution of 0.9µm is typical for scan areas of approximately 200 mm2.
- High resolution wide-area metrology without need for stitching of adjacent sections.
An arbitrarily large region of interest within the specimen may be selected by the user. Multiple diffraction patterns from within this selected area are acquired and processed together, to produce a single amplitude and phase image pair covering the whole region.
- Quantitative data with high accuracy, reproducibility and reliability, independent of illumination non-uniformities and other imperfections in the illumination beam optics.
As well as reconstructing an amplitude and image pair from the specimen, the phase and amplitude distribution of the illuminating beam (probe) that impinges on the specimen is also computed. This provides automatic elimination of a major source of errors and artefacts that might otherwise arise from flaws in the optical system. The Virtual Lens also has a high tolerance to significant inaccuracies in probe and/or stage positioning, and to vertical specimen vibration.
- High contrast imaging and quantitative characterisation of transparent specimens including hydrogels, multi-phase systems, biological cell constructs and optical lenses .
- Characterisation of material type via dielectric constant, independent of surface topography.