Accurate laser triangulation using a perpendicular camera setup to assess the height profile of PCBs

Recycling of printed circuit boards (PCBs) is still subject to current research. For identifying valuable materials in electronical components on the PCBs the height profile of PCBs is a important feature. Laser triangulation with a perpendicular laser is a classical approach to generate height profiles. However, in such a setup it is not possible to acquire different modalities such as panorama images and the height profile simultaneously. The solution is to use a setup in which the laser is slanted and the camera is perpendicular to the PCBs. A new triangulation approach employing raycasting and intersecting a laser plane and a ray of sight is needed to retain accuracy of the height profile generation. Evaluation results show that the accuracy of height measurement with an average error of 0.077 mm is still sufficient for detecting small surface mounted devices on PCBs with a minimal height of about 0.2 mm.