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 fringe pattern illumination with large depth of focus. The line separating dark and bright areas of the fringe pattern is used for light sectioning of the object, and the height profile is obtained through triangulation. The properties and advantages of this illumination approach are discussed. Experimental 3-D measurements are shown for various objects having large depth variations and are obtained with a height resolution of 1 mm at a distance of 500 mm, within a field of view of 25 deg.