3-D shape measurement using a focused-section method

Presents a method for measuring a 3-D shape based on a scheme of shape-from-focus. The method includes the practical object-scanning mechanism of a light-section (or light stripe sectioning) method and the versatility of a conventional shape-from-focus method. A focused plane is inclined typically at 45° to an optical axis of an image-taking lens in order to sweep an object in the same way that a fan-shaped light does in the light-section method. The focused-section method (FSM) processes a focused section image in order to detect an object contour which is an intersection curve of a focused section and an object surface. The contour was obtained by calculating a centroid of a spatial distribution for focus measure on each video raster. A ridge with a height of 200 μm could be measured by the FSM at a precision of 20 μm using a 1/3" CCD camera with a 60- mm f/2.8 macro lens. A linearity of 3 mm high×2 mm wide×2 mm depth was experimentally confirmed