Study on automatic measurement of deformation and application by digital single-beam speckle interferometry

Abstract

The purpose of the digital single-beam speckle interferometry is to extract displacement information from gray images of the specimen surface before and after deformation, which is derived primarily from the single-beam speckle interferometry. Single-beam speckle interferometry uses optical Fourier transform to extract displacement information in the frequency domain. While digital single-beam speckle interferometry uses a computer to implement optical Fourier transform after digitizing an image to extract displacement information in the frequency domain. Four phase shift images are generated by a computer and the phase shift technology is used to obtain wrapped and unwrapped fringe patterns. Furthermore, based on the fringe patterns, the direction and magnitude of the displacement can be determined automatically. The factors that may influence measurement accuracy are investigated. To validate the reliability of this method, it is used to measure displacement near the crack tip of the cracked concrete beam.