Study on Inner Hole Testing of Nozzle with Small Size and Complex Contour

Testing of small size and complex contour of Nozzle, an important component affecting the engine performance, is very difficult, particularly for the inner hole. Due to difficulty in holding, it is easy to scrap the surface of the inner hole by the traditional contact-type detection methods. In this paper testing method of the hole is researched in details with image stitching technology. In the testing, a serial of focused images in different depths of inner hole of nozzle are collected by CCD camera, and compared by image focusing evaluation function, thus depth information in various locations of the inner hole images is obtained. A full depth image, the panorama of the inner hole, is rebuilt by multi-focus image fusion algorithm, for the image pixels corresponding to the focus altitudes are segmented. To achieve 3D reconstruction of the inner hole, the depth information by linear interpolation is fitted to restore a precise inner hole depth information. The results show that the inner hole of nozzle can be tested precisely with high precision which can meet the design requirements, and the entire contour can be reconstructed by the testing method.