spiral staircase
EPSI (Extended Phase Shift Interferometry) combines the advantages from VSI (Vertical Scanning Interferometry) - unlimited z range but lower height resolution – and PSI (Phase Shift Interferometry) extreme height resolution but to λ/2 half limited z range.
Measurement results as this spiral staircase demonstrate the unlimited z-rage… |
… combined with the sub nanometer height resolution. |
Step heights near λ/2 would make the use of unwrapping algorithms impossible. |
