Inverse projected-fringe technique for measurement of dimensions and surface profile of axisymmetric objects

An inverse projected-fringe technique based on simulating the system of a projector-partcamera is proposed for an on-machine inspection of axisymmetric parts. The parts considered for this study are relatively large, have high specular surfaces and have sharp slopes. A computer simulation-based method and the CAD model of the part was used to produce the inverse fringes as well as to find an appropriate trace passing through the symmetrical axis of the part that offers the best signal to noise ratio (SNR). This technique measures the deviation from a master-part and provides an accuracy of better than 10 microns for the part with a radial dimension of about 10 cm. It is shown that the proposed technique improves the SNR and the repeatability of the system compared to the standard fringe projection technique, in particular for the areas with a steep slope.