Applied multifocus 3D microscopy

The depth from focus measurement principle relies on the detection of the optimal focusing distance for measuring the depth map of an object and finding its 3D shape. The principle is most effective at microscopic ranges where it is usually found implemented around a z-controlled microscope and sometimes named multifocus 3D microscopy. Assuch, the method competes with many other 3D measurement methods showing both advantages and disadvantages. Multifocus 3D microscopy is presented and compared to chromatic aberation, confocal microscopy, white light interferometry. Then, this paper discusses two applications of multifocus 3D microscopy for measuring woodrespectively metallic parts in the sub-millimeter range. The first application aims at measuring the topography of wood samples for surface quality control. The wood samples surface topography is evaluated with data obtained from both confocal microscopy and multifocus 3D microscopy. The profiles and a standard roughness factor are compared. The second application concerns the measurement of burrs on metallic parts. Possibilities and limits of multifocus 3Dmicroscopy are presented and discussed.