LIGHT SECTIONING WITH LARGE DEPTH OF FOCUS BY MEANS OF FRESNEL DIFFRACTION OF AN EDGE

We propose the use of Fresnel diffraction from an edge to produce a fr inge pattern illumination with large depth of focus. The line separati ng dark and bright areas of the fringe pattern is used for light secti oning of the object, and the height profile is obtained through triang ulation. The properties and advantages of this illumination approach a re discussed. Experimental 3-D measurements are shown for various obje cts having large depth variations and are obtained with a height resol ution of 1 mm at a distance of 500 mm, within a field of view of 25 de g.