Miniaturized 3D surface profilometer using digital fringe projection

Three-dimensional measurement systems of high precision have been widely applied in high-technology industries and bio-medical areas, especially for microscale accuracy measurement. However, due to their bulky volume, most of the current surface profilometers cannot perform 3D measurement within a space-restricted inspection environment. To overcome this drawback, a novel 3D surface profilometer with a miniaturized probe was developed according to the digital fringe projection (DFP) principle. Measurement of small objects within a limited space can be made by the profilometer which comprises a digital fringe projection system, coherent image fibres and optical lenses. Using phase shifting and an accurate calibration method, the proposed system can analyse the phase fringe and reconstruct clouds of surface points accurately. An example of 3D intra-oral dental measurement was provided to verify the feasibility and performance of the developed system and techniques. The experimental results indicate that the spatial and vertical measurement resolution can reach 25 µm and 5 µm, respectively, and the accuracy can be controlled within 25 µm, less than 1% of full measurement range.