Using a projected fringe pattern to identify the focused image and its application to 3D shape measurements

In this paper, we present a scanning approach to retrieve the 3D shape of the object with large depth discontinuities. A fringe pattern is projected onto the inspected object. A CCD camera is used to observe the projected fringes. The depth-of-field of the camera lens is so short that only fringes within the focused area can be clearly observed. By moving the inspected object around the focused area along the depth direction, a set of images, which addresses the contour of the object with its corresponding depth, is obtained. The 3D shape of the object is then retrieved by assembling the image contours with their corresponding depths.