Measuring Method of Micro Cone Hole Based on Depth from Focus

In the aero engine, the nozzle is one of the most important parts. Nozzles are very small and difficult to be measured. The cone hole in the nozzle is hard to be machined, the quality of the cone hole seriously affects the atomization performance of the nozzle. Different from conventional measuring methods, this paper uses image processing to measure the angle of the cone hole. A method based on Depth From Focus was proposed, which makes use of a series of images to reconstruct the 3D model of the nozzle. This paper uses telecentric lenses and CCD to get images from different distance, then some experiments were made to prove this method can goodly measure the angle of the cone hole. Also this paper finds out that the smaller the moving interval is, the more accuracy there will be, but the more time will be cost.