Dual-wavelength vertical scanning low-coherence interferometric microscope.

White-light interferometry has turned into a standard tool in the field of high-accuracy topography measurements. Nevertheless, surfaces with relatively large local surface tilts or height steps often give rise to systematic measuring errors. The reasons are diffraction and dispersion effects, which cause deviations between height values obtained from the envelope maximum of the white-light interference signal and those obtained from the signal's phase.