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Definition and application

For the detection of surface damage, shape deviations or topographies, the so-called shape-from-shading method is used in automated quality control. This is a tilt-measuring 3D shape detection method that uses the relationships between tilt angle, light incidence and observation direction to record surface properties on a camera basis.
With this method, test objects such as components or semi-finished products are usually exposed one after the other from four different directions. In each case, gray-scale images are recorded and information on the component topography is determined on the basis of the resulting surface shading.
Common applications include the detection of defects on surfaces, the detection of desired structures (e.g. Braille) or the detection of coding. With this method, codes such as data matrix codes can be recognized and read even on highly reflective surfaces.
As long as the applied codes lead to topographical changes compared to the base surface (e.g. by imprinted or lasered codes), they can also be reliably read again after lamination steps such as lacquering or chrome plating by means of shape-from-shading.