Out-of-plane displacement measurement system and method based on projected moiré method

Abstract

The invention relates to a projection moire fringe method-based out-of plane displacement measurement system and method. Light emitted by a light source is projected onto the surface of a measured object through a projection grating and a projection lens, so that grid lines can be formed on the surface of the measured object; the grid lines are subjected to out-of plane displacement modulation of the surface, and as a result, the grid lines are distorted; the distorted grid lines are imaged on a reference grating through an imaging lens, so that moire fringes can be formed; the moire fringes are recorded by a CCD camera; and out-of plane displacement can be calculated through analyzing the phase variation of a moire fringe image. According to the measurement system and method of the invention, the measurement area, resolution and measurement range of the system can be flexibly adjusted according to test requirements; and even a large-area object is tested, high resolution and high precision can be still realized. The automation degree of the measurement system of the invention is high, after acquired images are subjected to later-stage processing of a computer, quick batched measurement can be realized; and the whole system has high anti-external environmental interference performance and is suitable for on-site testing.

Description

technical field [0001] The invention relates to a technology in the field of optical measurement, in particular to a system and method for measuring out-of-plane displacement based on a projection moiré method. Background technique [0002] At present, it is mainly various optical testing technologies that can realize full-field out-of-plane displacement measurement. Among them, several mature methods include electronic speckle interferometry technology, photogrammetry technology, digital image correlation technology, and projection fringe method. Each of these methods has its specific application scope and environment, and the measurement range, measurement area and resolution are also different. For example, the theoretical resolution of electronic speckle interferometry can reach the sub-wavelength level, but its measurement range is difficult to reach more than a millimeter, mainly because the off-plane displacement of the millimeter level will cause the speckle field to...

AI Technical Summary

Problems solved by technology

However, this technology cannot change the measurement area of ​​the system according to the test requirements, and can only realize the measurement of tiny objects; due to the use of a projector for sinusoidal fringe projection, the nonlinearity of the projector makes the projected fringes not satisfy the sinusoidal law. Using the phase shift algorithm to calculate the phase will produce a large error; the measurement resolution of the projected fringe method is much lower than that of the projected moiré method under the same test environment

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