Accuracy of Sampling Moire Method and the Application to Deflection Measurement of Large-scale Structures

Recently, a simple and accurate phase measurement technique called sampling moire method is developed for accurate small displacement distribution measurement by one of the authors. In this method, the phase distribution of moire fringes can be analyzed from a single grating image by performing image processing of down-sampling and image interpolation to generate multiple phase-shifted moire fringe images. In this work, measurement accuracy of the sampling moire method is investigated both by a computer simulation and a displacement measurement experiment. Three factors of sampling pitch, order of image interpolation and waveform of grating are analyzed. In addition, an application of the sampling moire method applied to deflection measurement of a long crane with 10 meter is presented. Experimental results show that sub-millimeter deflection of the crane can be detected successfully. Sampling moire method is a promising technique for various research field in experimental mechanics such as evaluation of materials property, structural health monitoring of a large-scale structures, etc.