Shape and displacement measurement of discontinuous surfaces by combining fringe projection and digital image correlation

Abstract

We describe how a shape-measurement system (SMS) based on fringe projection can be combined with a two-dimensional digital image correlation (DIC) technique to accurately measure both surface profile and displacement fields at the same time. Whereas the measurement of all three displacement components by traditional DIC requires the use of at least two cameras, the approach presented here provides the full three-dimensional (3-D) displacement field from a single-camera, singleprojector SMS with no additional hardware requirements. Furthermore, the single-pixel spatial resolution of the fringe projection technique can be exploited to prevent the correlation peak-splitting phenomenon that occurs when a DIC subimage straddles a global geometrical discontinuity. Thus, unlike traditional 3-D DIC techniques, the proposed method can measure displacement fields on discontinuous surfaces as easily as on smooth ones. Details of the algorithm are given together with experimental results of a rigid-body translation test. Measurements made during a routine fatigue test on a part of a wing panel are also presented. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Digital Speckle Photography with Correlation Processing of Spatial Spectrum of Specklegram for Determination of Micro Displacement of Scattering Object

“…Прямое определение смещения спекл-структуры реализуется корреляционным спосо-бом [9,10], но этот метод не даёт субпиксельной точности измерений и не действует в диапазоне субпиксельной величины смещений.…”

“…Непосредственное определение вектора по-перечного смещения спекл-структуры возможно методом взаимной корреляции смещенной и несмещенной спекл-структур [9][10][11]. Использо-вание корреляционного метода для определения взаимного смещения спекл-структур имеет много преимуществ, таких как простота реализации, возможность автоматизации процессов измере-ния, прямое получение информации о смещении спекл-структуры без преобразования в частотную область.…”

Multiple‐view Shape and Deformation Measurement by Combining Fringe Projection and Digital Image Correlation

“…For dealing with discontinuous surfaces, we also introduced a new correlation strategy [20] that exploits the single‐pixel spatial resolution of the estimated point cloud to prevent the correlation peak splitting phenomenon that occurs when a subset straddles a global geometrical discontinuity. In this strategy, continuous regions of a speckle image are identified and segmented based on the measured point cloud.…”

“…In this paper, we present a method that combines fringe projection with the DIC technique on a single hardware platform to measure simultaneously both shape and deformation. The work described here can be considered a natural extension of a recently described single‐camera single‐projector system [20] to multiple cameras and projectors, which provides a route to complete 360° coverage of the sample surface. In particular, view alignment is not required as each sensor is automatically defined in a unified global coordinate system by an initial calibration procedure.…”

“…The paper starts with a summary of the basic technique, recently proposed in [20], to measure both shape and deformation fields with one camera and one projector. This provides the starting point for the extension to multiple sensors, which, together with the validation experiments and modelling, provides the focus of the current paper.…”