The combination of DIC and FPP can overcome the disadvantages of their respective methods.
#COMPLEX STEREOGRAM WINDOWS#
Furthermore, the filtering effects of subset windows will lower the accuracy of non-uniform deformation fields. Three-dimensional DIC (3D-DIC) can measure the 3D deformation of objects with high accuracy, but it requires synchronous triggering of multiple cameras. Two-dimensional DIC (2D-DIC) adopts a single camera to capture images, making it is easy to operate, but it can only measure in-plane deformation. It cannot achieve the tracking of object points.ĭIC employs a speckle texture on the surface of the measured object as the deformation information carrier. However, it is only sensitive to the out-of-plane displacement of the measured object in deformation measurements. The phase information can be solved from the deformed fringe images, and the three-dimensional (3D) shape of the object can be reconstructed by the phase. Fringe projection profilometry (FPP) and digital image correlation (DIC) are two common non-interference measurement methods.įPP uses a projector to project fringes onto the measured object. We suggest that continuing to model the geometrical shape of many natural folds as conical, based upon stereogram patterns that define small circles, is pointless as natural folded rocks are more likely to have the form of periclines"-Abstract, page iii.Optical metrology is widely used in biomedicine, reverse engineering, bridge monitoring and other fields, because of its non-contact, speed and high-accuracy advantages. In comparison to conical folds, natural pericline folds are common, and their formation is readily reproduced by dynamic modelling without requiring highly non-uniform stress-fields or special mechanical behavior.
Additionally, SCAT and differential geometry analyses are used to mathematically demonstrate the difference between periclines and conical folds.
Reverse engineering to produce three-dimensional shapes from the synthetic stereogram defines cones as this is a permissible solution to this stereogram pattern however, the shape and orientation of these cones are shown to be poor representations of the shape of the pericline.
Stereograms from natural periclines near Licking, Missouri mimic those of the synthetic stereogram patterns. Utilizing similar two-dimensional geometrical analysis of orientation data extracted from various transects across virtual pericline folds produces high spatial resolution synthetic stereograms with patterns that reproduce those of cylindrical and non-cylindrical conical folds as well as "fish-hook" patterns. Stereograms for which orientation data define small circles are classified as non-cylindrical regular folds and are interpreted as "conical folds," where the shape of the fold is represented by a cone that terminates at a point. Geometrical analysis of folds commonly relies upon analyzing patterns defined by the variation in the orientation of poles to planar surfaces deformed by a shortening event when plotted using graphical calculators (e.g., stereogram, polar tangent diagrams) to interpret the shape of folds. "Accurate representation of the 3D shapes of natural folds is essential to characterization of the dynamic models for fold formation.
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