Phase vortex based digital speckle correlation measurement method

Abstract

The invention discloses a phase vortex based digital speckle correlation measurement method. The method comprises the following steps of: acquiring speckle light intensity images of two states before and after movement of a measured object by using a digital speckle correlation measurement light path; filtering the two images by using a Laguerre-Gaussian complex filter to acquire light intensity complex signals; extracting cross points of real part zero lines and imaginary part zero lines of the signals to acquire phase vortex distribution of the two states before and after the movement of the measured object respectively; calculating corresponding topological charge distribution data matrixes; and finally performing correlation operation on the two data matrixes to acquire displacement information of the measured object. By adopting the method, the influence of background noise and high frequency noise on reliability of correlation measurement can be effectively eliminated, the measurement accuracy can reach a subpixel level; and the method is simple, practicable, quick and accurate and can be widely applied to the fields of nondestructive examination and the like.

Description

technical field [0001] The invention relates to a digital speckle correlation measurement method for measuring tiny displacements. Specifically, it relates to a digital speckle correlation measurement based on phase vortex characteristic parameters to realize the tiny displacement of the measured object. Background technique [0002] Laser speckle refers to the light and dark spots that appear to be chaotic and statistically consistent with the reflection field or transmission field 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 proposed by I.Yamaguchi in Japan and W.H.Peters and W.F.Ranson in the United States in the early 1980s. It is a non-contact optical measurement method for measuring the in-plane displacement of objects; it has an optical path S...

AI Technical Summary

Problems solved by technology

After literature search, the patent "A device and method for measuring micro-displacement by femtosecond laser speckle correlation method" (authorization number is ZL200610026621, authorization date is 2008.04.02), through the correlation calculation of two speckle intensity maps before and after object deformation It can realize the precision measurement of sub-pixel displacement, but the disadvantage is that this method requires a femtosecond laser system. Because the system is expensive and difficult to maintain, its practical application scope is limited; Its Measuring Device" (publication number CN101158679, publication date is 2008.04.09), discloses a method and device for measuring the mechanical properties of trabecular bone using digital speckle correlation method, the patent is digital speckle correlation measurement The new application of the method, without paying attention to the measurement accuracy and precision of the method itself; the patent "a multifunctional film mechanical property detection device" (publication number is CN101788427A, public date is 2010.07.28), the device uses digital speckle The correlation method measures the deformation of the film, combined with the bubbling method and the improved layer transfer method, to obtain the mechanical properties of the film and coating; this device also uses the speckle intensity map to directly perform correlation searches without considering the influence factors such as image pollution

[0003] According to the analysis, in the existing public literature, in the aspect of digital speckle correlation measurement method and its application research, most of them use the speckle light intensity image obtained by experiment to conduct direct correlation search for measurement, while the actual measurement of speckle The presence of background noise and high-frequency noise in the figure reduces the accuracy and reliability of the digital speckle correlation measurement method

Images