Polarization four-step phase shifting method for digital speckle interferometry

Abstract

The invention discloses a polarization four-step phase shifting method for digital speckle interferometry. According to the polarization four-step phase shifting method for digital speckle interferometry, polarization beam splitting prisms, a beam expander, quarter wave plates and polarizers are adopted to establish a polarization four-step phase shifting optical path; in a phase shifting process,two polarizers are rotated, so that 0-degree, 90-degree, 180-degree and 270-degree four-step phase shifting can be realized, and corresponding speckle images are acquired; and a random phase field atan initial moment is restored through a four-step phase shifting algorithm. Compared with a traditional time phase shifting method, the method replaces piezoelectric ceramics with two rotatable polarizers, and therefore, the hysteresis, nonlinearity and creep interference of the piezoelectric ceramics can be avoided, stable speckle images can be acquired, and accurate random phase extraction canbe realized.

Description

technical field [0001] The invention relates to the technical field of digital speckle interference, in particular to a polarization phase shift method for digital speckle interference technology. Background technique [0002] The digital speckle interferometry technology utilizes the mutual interference between the reference light and the light diffusely reflected on the surface of the object to generate a speckle image, and realizes the deformation measurement of the object surface by measuring the interferometric phase change before and after the object is loaded and deformed. It has non-contact, large measurement range and sensitivity It has a wide range of applications in three-dimensional deformation of materials and structures, stress-strain measurement and vibration analysis. In order to measure object deformation, how to extract random phase from speckle image is one of the key technologies of digital speckle interferometry. At present, the commonly used phase extr...

AI Technical Summary

Problems solved by technology

The space phase shift method and the space carrier method can realize dynamic deformation measurement, but the images collected at different positions of the former need to be strictly calibrated, and the separation of high and low frequency spectrum in the latter is difficult to achieve accurate automation. Therefore, the time phase shift method is currently widely used phase extraction method

In actual engineering, the time phase shift method generally generates a fixed phase difference through the movement of piezoelectric ceramics, but due to the hysteresis, nonlinearity and creep characteristics of piezoelectric ceramics, the collected speckle images are unstable.

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