Once all the common techniques and combinations have been exhausted without success often even experienced machine vision engineers may conclude an application is just too difficult to recreate repeatable high quality images of the object or defect. As the machine vision market has matured, research has been undertaken to create reliable inspection solutions for some of these critical but difficult inspection tasks. Some of these advanced approaches have now been packaged and are available as system solutions.
These solutions often require specialist illuminators, the capture of multiple images with different lighting geometries and then software processing to extract synthetic images from the combination of illumination images.
One of these difficult applications is the reliable surface inspection of shiny surfaces such as polished metal. Shape from shading combines a specialist dome light illumination with inbuilt directional illumination control which captures four directional images which are processed in software to create both a surface topology image and a texture image along with x and y slope images.