Rigid and flexible endoscopes for three dimensional measurement of inside machine parts using fringe projection

Routine maintenance is mandatory for safe and efficient operation of complex machines, such as airplane turbines. Occasional special events, like bird strike, entail extraordinary inspection works. Hereby, inside machine parts are hard to reach, oftentimes occluded by other parts and not directly accessible for visual inspection. Disassembly of machine parts is time-consuming and expensive and, therefore undesired. This leaves distal imaging, i.e. endoscopy, to be the only practical option for defect detection. Ordinary endoscopes, which provide two dimensional intensity image data, are insufficient to fully assess the risks caused by small three dimensional defects. As a solution to this issue, we have developed and implemented two different systems for three dimensional endoscopic measurement based on structured light projection which are capable of recording high resolution and high accuracy point cloud data. A measurement standard deviation of roughly 20 μm is achieved within a field of measurement of 20×30×30mm3.