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Selection of the suitable mv system

Shape from Shading

Shape from Shading is an innovative method of image processing that reconstructs the shape of objects from the shading in an image. This technique offers many advantages and is particularly effective for surface inspection and analysis.

The process is particularly suitable for quality control, as it can detect small deviations and defects on surfaces that are difficult to see with the naked eye. Scratches, flaking, chipped edges or clear impact marks that can be felt with the finger are easily detected.

Working principle
"Shape from Shading"

The component is illuminated from different directions and the resulting shadow images are recorded. The images are usually taken sequentially. Typically, a lighting controller and four-segment lighting are used.

A special algorithm then computes the four individual images into one resulting image. The image processing software analyses shadows and reflections to calculate the inclination and curvature of the surface. With most area scan camera-based systems, the object should not be moving during the image acquisition.

Benefits of "shape from shading" technology

1. Efficient detection with shiny objects

One of the key benefits of Shape from Shading is its ability to accurately detect and analyse shiny objects. The method uses reflections and shadows to obtain detailed information about the object's surface.

2. Visibility of finest scratches

The Shape from Shading method reveals even the finest scratches on an object's surface. By accurately analysing the shading, the smallest surface defects can be identified and documented.

3. Grey tone-independent algorithms

Thanks to greyscale independent algorithms, Shape from Shading works equally well with light and dark objects. This flexibility makes it ideal for use in different environments and with different types of materials.

4. Cost-efficient components

Another advantage is the use of low-cost components. The method requires only 4-segment lighting and a 4-channel strobe controller, eliminating the need for expensive specialist camera equipment.

Potential disadvantages

1. No real 3D data generation

A major counterargument is that the method does not provide true 3D information. Instead, it only provides information about the degree of surface curvature and deformation.

2. Inspection at standstill

The Shape from Shading method usually requires the inspection object to remain stationary. This can make it difficult to inspect moving objects or dynamic production lines.

3. Longer acquisition time per inspection

Four images are required per inspection, requiring more acquisition time. This additional time can affect efficiency in time-critical applications.

4. Processing time for high resolutions

At higher resolutions, the algorithm can be time consuming, taking several hundred milliseconds. This can increase overall processing time and limit real-time capability.

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Bild Übersicht BV-Systeme / industrielle Bildverarbeitung