Research On Technologies Of Structured Light3D Profilometry Based On Fiber Optic Interference Fringe Projection

This dissertation is supported by the National Nature Science Foundation ofChina (NSFC) and State Key Laboratory of Precision Measurement Technology andInstrument Explore Fund, researching on the dynamic measurement technology forthe small-size object surface3D shape, developing a new3D shape measurementmethod based on the optical-fiber interference fringes structured light projection,which utilizes the Mach-Zehnder fiber interferometer structure and the theory ofYoung’s two-hole interference, to realize the projection of interference fringes whichhave high-density and cosine distribution, therefore acquiring the interference fringesimages modulated by the measured object through array camera, using FourierTransform Profilometry and combining with the mathematic model of measurementsystem, finally realizing the3D morphology reconstruction and measurement of thetest object.The main research contents are shown as follows:1、This dissertation takes a further study on the program which projectinghigh-density fringes structured light in the small field of view based on Mach-Zehnderfiber interferometer structure and Young’s two-hole interference theory, and constitutethe mathematical model of optical fiber interferometer fringes projection system, thendiscusses the characteristics of projection fringes influenced by system structureparameters through modeling and simulation, building the double-fiber interferometerfringes projection system, acquiring and analyzing the interference fringe images inthe projection light field through array camera, which confirmed the feasibility of theprogram.2、With the target of compensating random phase fluctuation of the interferencefringes, designing a closed-loop phase stabilizing system through Fresnel reflectionsignal from the optical fiber output end, utilizing the methods of DC phase tracking(PTDC) and AC phase tracking (PTAC) phase control process, to drive thepiezoelectric ceramics transducer (PZT) for changing the length of optical fiberinterference arms, then controlling the interferometer phase difference, ensuring thephase of the interference fringes were not drifted by the temperature fluctuation in theexperimental environment. 3、In order to extract the phase information from the interference fringe imagesaccurately, proposing Gauss transformation function algorithm to make compensationof the actual interference fringes images, realizing the uniform distribution of theimages back-ground intensity; Using Fringe Equivalence Line Filter (FELF) methodto filter out the noise and retain the cosine distribution feature of the fringe patterns.Studying the background light intensity, spatial frequency and noise in theinterference fringes images, which make influence on the spectrum aliasing and phaseunwrapping result in the process of fringes phase extraction, provide the basis for theselection of the band-pass filter window, error elimination of phase unwrapping, andachieving the phase information of the interference fringes images precisely; studyingthe dual-frequency phase unwrapping algorithm and taking the simulation experiment,to provide the algorithm basis for the high precision3D morphology measurementbased on the dual-wavelength optical fiber interference fringe projection.4、 Building the mathematical model between interference fringes phaseinformation and the actual3D coordinate in the non-parallel condition of fiber outputend and camera lens connecting line with the measured object reference plane,according to the linear relationship between the phase difference of the fringes andheight information of the tested object, using the implicit calibration method forgaining the structure parameters of measuring system, and taking the error analysis toget the optimization of system structure parameters.5、Establishing the measurement experimental platform of3D shape based on thedual-fiber interference fringes projection, and utilizing the platform to measure thesurface morphology of small size object and3D defects of the simulation products,then realizing the3D stereo recovery of dynamic deformation process of rubbermembrane by the high-frame-rates array camera.