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White Light Interferometry (WLI)

White Light Interferometry (WLI) Testing Technique

White Light Interferometry (WLI) provides quantitative surface topography information from all solid materials.

The resolution of the measurements are ~0.5µm in the lateral (X, Y) plane and ~1nm in the height (Z) plane.  This allows microfeatures and large scale topographic variations to be monitored in detail.

Surface metrology data is presented in the form of pseudo-colour height maps, 3D images, line profiles and surface roughness parameters (e.g. Ra, Rz).

  • Height maps, 3D images and movies to illustrate the surface topography
  • Profilometry - Measurement of feature heights / depths on the nm - mm scale using line profiles
  • Surface roughness parameters -  including Sa - mean surface roughness; Sp - highest peak of the surface; Sv - deepest valley; Sy - total height between highest peak and deepest hole; Sz - mean of distance between the five highest peaks and five deepest holes
  • Measurement of transparent film thickness in the 0.2µm - 50µm range.

Typical applications

  • Characterization of surface defects, stains and residues on metals, glasses and polymers
  • Measurement of coating film thickness and uniformity on arterial stents
  • Monitoring the effect of acid erosion on human tooth enamel
  • Measurement of wear scars in tribological studies.

Typical industries using White Light Interferometry



WLI - At a Glance

  • Information: Quantitative surface topography and roughness parameters
  • Area Analysed: From ~100mm x 100mm to ~60µm x 80µm
  • Film Thickness: transparent films from ~200nm - ~50µm thick
  • Imaging: Yes
  • Image Resolution: ~0.5µm in X,Y; 1nm in Z
  • Data Output: Height maps, line profiles, 3D images and movies


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