High-precision digital speckle related measurement method

Abstract

A high-precision digital speckle related measurement method adopts a measuring device consisting of a CW (continuous wave) laser, a collimated beam expander, a converging lens, a CCD (charge coupled device) camera and a computer for measurement, and is realized through adopting the following steps: filtering speckle images arranged in a generation plane of a to-be-tested object before and after the displacement and recorded by the CCD camera, so as to obtain the complex signal distribution of light intensity; performing interpolation after analyzing the phase position distribution, so as to obtain the phase position distribution matrix with the sub-pixel accuracy; utilizing the phase position vortex topological charge numbers plus 1 and minus 1 to replace the original phase position values, and replacing other points with 0, so as to build two sparse matrixes; and finally performing related operation to the two sparse matrixes so as to obtain the in-plane displacement information of the to-be-tested object. The method can realize the high computational efficiency and high measuring accuracy at the same time, has the characteristics of compactness in optical path, simplicity and feasibility, and is suitable for the real-time and on-line detection in the field of photoelectric nondestructive detection.

Description

technical field [0001] The invention relates to a digital speckle correlation measurement method for measuring in-plane displacement of an object, which is applied in the field of photoelectric non-destructive testing and the like, in particular to a high-precision digital speckle correlation measurement method. Background technique [0002] Laser speckle refers to the bright and dark spots formed after the diffuse reflection light interferes with each other in the reflection space when the laser is irradiated on the surface of a rough object. Speckle carries the information of the measured object, and the change information of the measured object can be obtained by analyzing the speckle field. The digital speckle correlation measurement method was developed gradually after the 1980s, and it is a non-contact optical measurement method used to measure the in-plane displacement of objects. It has the advantages of simple optical path, full-field measurement, non-contact and l...

AI Technical Summary

Problems solved by technology

But even after finding the optimal correlation search sub-area size, the number of calculation points is still very high at large displacements, and the calculation efficiency cannot meet the requirements of real-time measurement in many projects

In the study of measurement accuracy of digital speckle correlation measurement methods, there are mainly interpolation methods, surface fitting methods, and gradient algorithms. These traditional digital speckle correlation measurement methods are all based on speckle field gray correlation calculations. Although its accuracy can reach sub-pixel, the computational efficiency also becomes low

[0005] In terms of patent literature on digital speckle correlation measurement, the patent "extraction of bone trabecula and measurement method of mechanical The method and device for measuring the mechanical properties of bone trabecular by speckle correlation method, this patent is a new application of digital speckle correlation measurement method, without paying attention to the measurement accuracy and calculation efficiency of the method itself; the patent "a multi-functional Thin film mechanical properties detection device" (publication number CN101788427A, public date is 2010.07.28), the device uses the digital speckle correlation method to measure the deformation of the film, combined with the bubbling method and the improved layer transfer method, the mechanical properties of the film and the coating can be obtained. performance; this device also uses the speckle intensity map to directly perform correlation search, and its measurement accuracy and calculation efficiency have not been analyzed in detail

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