An In-plane Displacement Algorithm of Speckle Photography Based on Fourier Transform Phase

A Fourier transform and displacement technology, applied in the field of optical detection, can solve the problems of inability to determine the direction of speckle displacement, inability to realize sub-pixel detection, etc., and achieve the effect of easy implementation and simple algorithm

Active Publication Date: 2018-11-27
KUNMING UNIV OF SCI & TECH
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Problems solved by technology

[0002] The in-plane displacement of an object can be obtained by using digital speckle. As a means of optical measurement, it has been widely used in many fields because of its advantages of non-contact and high sensitivity. , The final digital speckle image is added or subtracted in the spatial domain to obtain a synthetic speckle image, and then the synthetic speckle image is Fourier transformed, and then the obtained image (power spectrum of the Fourier transform) Perform filtering and denoising, image enhancement, binarization and fringe thinning processing, and finally extract the fringe spacing to obtain the movement amount. The traditional algorithm directly uses the light intensity information (the power spectrum of the Fourier transform), and only the speckle that can be detected The minimum field movement is required to be greater than (at least equal to) the average diameter of speckle particles, and sub-pixel detection cannot be achieved, and the direction of speckle displacement cannot be determined

Method used

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  • An In-plane Displacement Algorithm of Speckle Photography Based on Fourier Transform Phase
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  • An In-plane Displacement Algorithm of Speckle Photography Based on Fourier Transform Phase

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Embodiment 1

[0035] The in-plane displacement algorithm of speckle photography based on the Fourier transform phase described in this embodiment is used to calculate the in-plane displacement of sandpaper. The optical path and related experimental equipment are as follows: figure 2 , laser 1 (YAG laser, wavelength lambda =533nm), the laser beam emitted by the beam splitter 3 is directly irradiated on the sandpaper 4, and the reflected light is reflected by the beam splitter 3 to the CMOS camera 5 (with a resolution of 1744×1308 pixels and a pixel pitch of 3.2μm×3.2μm) Speckle is formed on the surface, and the light intensity is converted into an electrical signal, which is transmitted to the computer 2 and saved to obtain a digital speckle image. Due to the sandpaper and the Michelson interferometer 6 (the illumination light is He-Ne laser, the wavelength lambda 0 =633nm) connected, so the in-plane displacement of the sandpaper 4 can be accurately measured, and a CCD camera can be used...

Embodiment 2

[0048] The in-plane displacement algorithm of speckle photography based on the Fourier transform phase described in this embodiment is used to measure the in-plane displacement (deformation) of an object after being stressed. The optical path and related experimental equipment such as Figure 9 , the touch rod 7 of the afterburner is in contact with the sponge 8, the object under force, and white speckles are sprayed on the sponge 8. When the force on the afterburner is changed, the object under force is deformed, and the deformation process is recorded by a digital camera 9, and the obtained For the white light digital speckle pattern, two speckle patterns are input into the computer, and the in-plane displacement of each point on the sponge can be obtained by processing according to the algorithm of the present invention, so as to obtain the deformation situation, and proceed according to the following steps:

[0049] (1) Use the above-mentioned experimental device to record ...

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Abstract

The invention discloses a speckle photography surface displacement algorithm based on Fourier transform phases. Fourier transform of digital speckle patterns of an object before and after displacement is respectively carried out, Fourier transform results are divided to acquire a two-dimensional complex number, a phase angle of the two-dimensional complex number is calculated, cosine operation of the phase angle is carried out to acquire an equivalent young's interference pattern, Fourier transform of the young's interference pattern is carried out, coordinates of maximum values of a Fourier transform power spectrum except zero frequency are queried, surface displacement can be acquired, a displacement direction of the object can be determined according to plus or minus of a phase angle gradient, and a derivative algorithm of the algorithm can be utilized to realize sub-pixel displacement calculation. The algorithm solves problems of tedious steps, heavy computation and inconvenient operation and especially solves problems that only speckle fields of which minimum movement amount is greater than or equal to an average diameter of speckle particles can be detected, sub-pixel detection can not be realized, and an object displacement direction can not be determined.

Description

technical field [0001] The invention relates to an algorithm for measuring the in-plane displacement of an object by digital speckle photography, in particular to a speckle photography in-plane displacement algorithm based on Fourier transform phase, which belongs to the field of optical detection. Background technique [0002] The in-plane displacement of an object can be obtained by using digital speckle. As a means of optical measurement, it has been widely used in many fields because of its advantages of non-contact and high sensitivity. , The final digital speckle image is added or subtracted in the spatial domain to obtain a synthetic speckle image, and then the synthetic speckle image is Fourier transformed, and then the obtained image (power spectrum of the Fourier transform) Perform filtering and denoising, image enhancement, binarization and fringe thinning processing, and finally extract the fringe spacing to obtain the movement amount. The traditional algorithm d...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01B11/02
CPCG01B11/02
Inventor 钱晓凡荣文秀
Owner KUNMING UNIV OF SCI & TECH
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