Measuring surfaces with the scattered light method means speed, high accuracy and a laminar evaluation of functionally-important components.

In this process the sensor illuminates the surface, depending on the application and sensor type with a measuring spot between 0.03 to 1.8 mm diameter. The light rays deflected with varying intensity according to the surface roughness, so that so that scattered light distributions that vary in width occur. In this process this distribution curve is the basic information for roughness, form and gloss.

The scattered light sensor detects roughness with the characteristic value Aq, which is calculated from the distribution curve with the aid of variance. For the prescribed manufacturing method, Aq correlates with the peak-to-valley height Ra or Rz.

The Aq value takes on a new and interesting significance when, after an initial production step (e.g. grinding or turning), surfaces are subjected to an additional smoothing procedure (finishing or spinning). Here the scattered light characteristic value Aq is even superior to the traditional percentage contact area characteristic variables (Rmr, Rk). The characteristic value M, the focal position of the scattered light distribution, is used for form measurement.

The scattered light characteristic values can be entered into design drawings in accordance with a VDA guideline (VDA 2009).