Research On Three-dimensional Topography Measurement Using Structured Light

On the basis of rapid development of measurement, three-dimensional topographymeasurement of objects has become a hot research area. With laser technology, computertechnology, such as image processing and high-tech development, optical non-contacttopography measurement technique is widely used, especially the three-dimensionaltopography measurement technology has progressed greatly, which is represented by fringeprojection and regarded as the most promising of three-dimensional topography measurementmethod. This method has got most attention in industrial environment in recent yearsdepending on the advantages of high accuracy, easy extraction of optical fringe informationand strong real time, which can not be act for in three-dimensional auto-measurement andobject identification.In structured light, the three-dimensional topography measurement method based onphase has been the focus due to the simple structure, low cost and strong environmental anti-interference capability. This paper probes into two typical three-dimensional topographymeasurement methods based on phase named Fourier transform method and phase-shiftingmethod. Projecting grating fringes on object surface, these two methods generates shapedeformation to grating fringes since the object surfaces are full of bumps and holes. Thendatum of three-dimensional topography measurement can be extracted from the deformationfringes.The specific contents and works are as follows:Firstly, on the base of three-dimensional topography measurement theory analysis,Fourier transform method and phase-shifting method as two typical three-dimensionaltopography measurement methods are described. The phase measurement expression of thetwo methods are also deduced. The principle of phase unwrapping is also studied.Secondly, the structure of the measurement system is analyzed. The calibration methodsare also discussed, and a novel rapid calibration method is introduced.Thirdly, to solve the disadvantages of conventional phase unwrapping methods, quality-guide algorithm is introduced. After that, a comparision of two phase unwrapping algorithmsis made by simulations. Further more, simulations are carried out to verify the validities ofFourier transform method and phase-shifting method for three-dimensional topography measurement. The simulation results indicate that phase-shifting method can make a higheraccuracy than Fourier transform method.Finally, the system platform of three-dimensional topography measurement based onphase-shifting methods constructed. The experiment process is described and the impactfactors related to experimental conditions are also researched. The experimental height error,diameter error, and length error of cylinder are respectively8.2%,1.8%,3.3%. Resultsindicate that a union of phase-shifting method, system calibration method and phaseunwrapping method in this paper can make more precise measurement on three-dimensionaltopography of object.