Influence of the wavelengths of the light source on the polychromatic roughness measurement

Surface roughness is one of the characteristics used to evaluate the quality of manufactured components. At present, optical methods are being researched which are non-contact and areal compared to tactile methods and allow a higher measuring frequency.

The polychromatic illumination of the component surface produces elongated speckle patterns. The degree of elongation correlates with the surface roughness.

Due to their scattering behavior, the wavelengths used for illumination have a direct influence on the elongation of the speckle and thus on the measuring range as well as the measuring distance. Currently, the influence of the type of light source (wavelength range, number of wavelengths, distance between wavelengths) on the limits of the measurement method is of great importance for the application.


  • Planning, implementation & evaluation of measurement series
  • Evaluation of the measuring principle as a function of the number and size of the wavelengths

Your Profile:

  • Pleasure in experimental or analytical work
  • Interest in laser measurement technology
  • Self-reliant working style
  • Desirable: knowledge of MATLAB

Contact Details

Johannes Stempin
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Phone:+49 (0)421 218 646 22

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