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FRT WLI - White Light Interferometer

White light interferometry (WLI) is a fast method to perform 3D topographical measurements. It utilizes a light source with very low temporal coherence. By means of a beam splitter this light is separated into a reference beam (reflected to a reference mirror) and an object beam that strikes the surface to be measured.The light reflected from both, the reference mirror and the measured object, is overlayed. This interference pattern is captured by a camera.

Whilst performing the topography measurement, the objective is gradually moved in small steps into z-direction. At each position the camera takes a single image. Then, all images are compiled into an image stack, which is used to render the 3D topography.

Due to the low temporal coherence of the white-light the WLI characterizes reflective and rough surfaces as well as step heights with very good height resolution, which is  typical for interferometric measurement approaches.


 White Light Interferometer 
Measuring Principle
 
  • non-contact topography measurement
  • sub-nanometer height resolution
  • very fast 3D measurements
  • measurement of highly reflective, rough or structured surfaces
         Download Options
Typical Applications
 
  • roughness measurement in nm-range, e.g. on optical
    components such as mirrors or lenses
  • evaluation of micro structures (e.g. MEMS, microfluidics, microoptics)
  • measurement of step-height in the field of semiconductors
  • measurement on different materials (e.g. metal, semiconductors, glass,
    plastics, paper, lacquers, and coatings)
  • measurement on liquids
Technical Specifications
   
 lens (mirau)
10x
 20x
 50x 1
 measuring range z 2 100 µm   100 µm 100 µm
 measuring range x, y
1.6 mm x 1.2 mm
0.8 mm x 0,6 mm
0.32 mm x 0.24 mm
 working distance
3.6 mm
3.6 mm
1.7 mm
 sampling intervall (x, y)
2.5 µm
1.25 µm
0.5 µm
 resolution z
0.1 nm
0.1 nm
0.1 nm
 working temperature 3  20°C ± 2°C*3  20°C ± 2°C*3  20°C ± 2°C*3

1  50x lens optional
2  optional up to 400 µm
3  operating temperature: 5°C - 40°C

Technical specifications and content are subject to change.