Spy quantitative inspection with a machine vision light sectioning method

Machine vision light sectioning sensing is developed and expanded to the range of spy quantitative inspection for hole-like work pieces in this paper. A light beam from a semiconductor laser diode is converged into a line-shape by a cylindrical lens. A special compact reflecting-refracting prism group is designed to ensure that such a sectioning light is projected axially onto the inner surface, and to make the deformed line be imaged onto a CCD sensitive area. The image is digitized and captured into a computer by a 512×512 pixel card, and machine vision image processing methods such as thresholding, line centre detect and the least-squares method are developed for contour feature extraction and description. Two other important problems in such an inspection system are how to orientate the deep-going optical probe and how to bring the projected line into focus. A focusing criterion based on image position deviation and a four-step orientating procedure are put forward, and analysed to be feasible respectively. The experimental results show that the principle is correct and the techniques are realizable, and a good future for application in industry is possible.