Rectification for fronto-parallel camera movement in 3D reconstruction of printed circuit boards

摘要

Recycling of printed circuit boards (PCBs) is one of the open challenges in research. For recycling, the identification of the components on PCBs is of great importance. For PCB component classification the height profile of a PCB is one of the important features. One approach to obtain this profile is photogrammetry employing different views of the PCB's surface. Thereby, rectification of the images is essential for highly accurate, dense 3D reconstruction employing block matchers. However, commonly utilized rectification approaches rely on the fundamental matrix which deteriorates in scenes with low depth structure. Thus, a new rectification approach is needed for the case of PCBs. We propose a homography-based approach employing salient image features which are tracked in the images of a camera moved fronto-parallel above the PCB. It can be shown that the accuracy of the 3D reconstruction after applying the proposed rectification allows reconstructing structures at 0.1mm accuracy. This is sufficient for detecting small surface mounted devices with a minimal height of 0.2 mm.