CN111964601B - Speckle interference multi-parameter measuring system and method based on Taffy optical path - Google Patents

Abstract

The invention relates to a speckle interference multi-parameter measurement system and measurement method based on Duffy optical path. After referring to the surface, a beam of reference light waves is formed in the second reflector; the reflected light waves are irradiated to the surface of the object to be measured along the direction of the optical axis and are divided into the first object light wave and the second object light wave, the first object light wave and the second object light wave. Displacement occurs and two shearing object light waves are respectively formed. These four shearing object light waves and a reference light wave pass through the second beam splitting prism at the same time and are jointly imaged on the target surface of the monochromatic CCD camera to form a coupled speckle interference image; The invention can realize the synchronous dynamic measurement of the deformation, strain and other multi-parameter information of the measured object, not only the structure of the measurement system is simple, but also the measurement method is easy.

Description

Speckle interference multi-parameter measurement system and measurement method based on Duffy optical path

technical field

The invention relates to a speckle interference multi-parameter measurement system and a measurement method based on the Duffy optical path, belonging to the technical field of optical measurement.

Background technique

Speckle interferometry is a modern optical measurement method with the advantages of high sensitivity, high precision, real-time, full-field non-contact measurement. In recent years, it has been widely used in advanced material testing and analysis in aerospace, mechanical manufacturing, automotive engineering and other fields. middle. The speckle interferometry system can directly measure the structural deformation information, but cannot directly measure the first derivative of the deformation, that is, the strain information. According to different deformation measurement requirements, speckle interferometry systems can generally be divided into in-plane deformation measurement systems and out-of-plane deformation measurement systems. Usually, strain information can be obtained by numerical differentiation of deformation information by speckle interferometry, or by shear speckle interferometry; however, shear speckle interferometry cannot directly measure deformation, and numerical differential calculation often causes random errors Diffusion transmission. In practical engineering applications, the quality safety assessment and service life prediction of load-bearing structures are inseparable from the simultaneous acquisition of deformation and strain information. Therefore, a speckle interferometry system that can measure deformation and multiple strain information at the same time is designed and developed to meet practical applications. The need for simultaneous multi-parameter measurement is crucial.

Existing speckle interferometry systems that can measure deformation and strain can generally be divided into two categories: the first type is to simply combine the speckle interferometry system and the shear speckle interferometry system to form an overall system to measure deformation and strain information respectively. The combined system can achieve independent measurement of deformation and strain information by switching different optical paths in turn, but it cannot achieve simultaneous measurement, and the combined system has a complex structure, the measurement process is extremely inconvenient, and it is not suitable for dynamic measurement; the second type is based on Michelson (Michelson) ) type shear speckle interferometry system is introduced into the reference light wave to realize the simultaneous measurement of deformation and strain. This system is currently the most common deformation and strain synchronous measurement system. Using the spatial phase shift technology, the deformation and strain information can be synchronously demodulated only in a coupled speckle interferogram, and the system has a simple spatial structure and convenient measurement methods. , suitable for dynamic measurement. However, the field of view of this system is limited by the Michelson shear device, which usually needs to be improved by adding an optical 4f system. Moreover, the spatial carrier frequency modulation and the shear amount control are not independent of each other, so it is difficult to completely separate the useful spectral information; Either the combined measurement system or the Michelson-type system can only measure deformation and a single strain component.

SUMMARY OF THE INVENTION

The invention provides a speckle interference multi-parameter measurement system and measurement method based on Duffy optical path, which can realize synchronous dynamic measurement of deformation and strain information of a measured object, not only the measurement system has a simple structure, but also the measurement method is easy.

The technical scheme adopted by the present invention to solve its technical problems is:

A speckle interference multi-parameter measurement system based on the Duffy optical path, using a laser as an illumination light source, the emitted laser beam is divided into transmitted light waves and reflected light waves according to 5:5 in a first beam splitting prism through a first reflecting mirror;

The aforementioned transmitted light waves pass through the optically rough reference surface to form spatial diffuse reflection light waves, and the spatial diffuse reflection light waves pass through the first aperture diaphragm and the second reflector in sequence to form a beam of reference light waves;

The aforementioned reflected light wave is irradiated to the surface of the object to be measured along the direction of the optical axis, and is divided into a first object light wave and a second object light wave. The object light wave passes through the second aperture diaphragm, the third mirror, the all-inverse right-angle prism, and the Wollaston shearing device in sequence to form two sheared object light waves, and the second object light wave passes through the third aperture diaphragm, Four reflection mirrors, all-inverting right-angle prisms, and Wollaston shearing device form two beams of shearing object light waves;

Four shearing object light waves and one reference light wave pass through the second beam splitting prism at the same time and are imaged together on the target surface of the monochromatic CCD camera;

Among them, the second aperture diaphragm and the third aperture diaphragm are symmetrically arranged relative to the optical axis, the third reflecting mirror and the fourth reflecting mirror are symmetrically arranged relative to the optical axis, the object to be measured, the first beam splitting prism, the all-inverse right-angle prism, the Wola The ston shearing device, the second beam splitting prism and the monochromatic CCD camera are all distributed on the optical axis in turn, and an all-reverse right-angle prism is arranged at the center position of the third reflecting mirror and the fourth reflecting mirror perpendicular to the center line of the optical axis;

The connecting line formed by the first reflecting mirror, the first beam splitting prism and the optical rough reference surface is perpendicular to the optical axis;

As a further preference of the present invention, two shearing object light waves after the first object light wave is displaced by the Wollaston shearing device interfere with each other to form a first shearing speckle interference image, and the second object light wave passes through the Wollaston shearing device. The two shearing object light waves after the dislocation of the cutting device interfere with each other to form a second shearing speckle interference image;

The reference light wave and the shearing object light wave interfere with each other to form a mixed speckle interference image. The mixed speckle interference image interferes with the first shearing speckle interference image and the second shearing speckle interference image respectively on the target surface of the monochromatic CCD camera. form a coupled speckle interference image;

A measurement method based on any of the above-mentioned Duffy optical path-based speckle interference multi-parameter measurement systems,

Step 1: Before the measured object is loaded and deformed, the laser light source is provided by the laser, and the monochromatic CCD camera collects the first sheared speckle interference image before the deformation;

Step 2: Fourier transform is performed on the first sheared speckle interference image before deformation, and the spatial spectrum of the first sheared speckle interference image before deformation is obtained;

The third step: extracting high-frequency terms containing phase information by setting a filter window for the obtained spatial spectrum of the first sheared speckle interference image before deformation;

The fourth step: extracting the phase of the high frequency term of the obtained first sheared speckle interference image before deformation, to obtain phase information containing deformation and strain information in the first sheared speckle interference image before deformation;

Step 5: The loading device loads and deforms the measured object, and obtains the phase information of the deformation and strain information in the first sheared speckle interference image after deformation according to the steps from the first to the fourth step;

Step 6: Subtract the phase information of the first sheared speckle interference image before and after the deformation of the measured object in real time to obtain the phase difference related to deformation and strain in the first sheared speckle interference image;

Step 7: Obtain the phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference related to deformation and strain in the hybrid speckle interference image respectively according to the methods of the first step to the sixth step;

Step 8: Compare the phase difference related to deformation and strain in the first shearing speckle interference image obtained above, the phase difference related to deformation and strain in the second shearing speckle interference image, and the mixed speckle interference image. The phase difference distribution images related to deformation and strain are filtered respectively, and the filtered phase difference distribution image is unwrapped to obtain a smooth and continuous phase distribution; the measured object is obtained by calculating the obtained smooth and continuous phase difference distribution. deformation and strain;

As a further preference of the present invention,

In the first step, the first object light wave passes through the two shearing object light waves after the dislocation of the Wollaston shearing device, and the measured object before deformation interferes with each other on the target surface of the monochromatic CCD camera to form the first shearing speckle interference. image, whose light intensity is expressed as

I ₁ (x,y)＝[u ₁₁ (x,y)+u ₁₂ (x+△x,y)]·[u ₁₁ (x,y)+u ₁₂ (x+△x,y)] ^* (1 )

为u₁₁(x,y)的复共轭，

为u₁₂(x+△x,y)的复共轭，Δx为被测物体经过渥拉斯顿剪切装置后沿x方向物面剪切量；Among them, u ₁₁ (x, y) is the complex amplitude of a beam of shearing object light waves after the first object light wave is dislocated, and u ₁₂ (x+△x, y) is another beam of shearing objects after the first object light wave is dislocated the complex amplitude of a light wave,

is the complex conjugate of u ₁₁ (x,y),

is the complex conjugate of u ₁₂ (x+△x,y), and Δx is the shearing amount of the measured object along the x-direction after passing through the Wollaston shearing device;

As a further preference of the present invention, in the second step, Fourier transform is performed on the first sheared speckle interference image before deformation, and the spatial spectrum of the obtained first sheared speckle interference image before deformation is expressed as:

代表空间频谱中含有背景光的低频项频谱，

表示频域中卷积运算符，C^*(f_x-f₀,f_y)和C(f_x+f₀,f_y)是互为共轭的高频项频谱，其含有x方向剪切的相位信息；f_x为空间频谱的横坐标，f_y为空间频谱的纵坐标，f₀是由孔径光阑引入的载波频率；in,

represents the spectrum of the low-frequency term containing the background light in the spatial spectrum,

Represents the convolution operator in the frequency domain, C ^* (f _x -f ₀ , f _y ) and C(f _x +f ₀ , f _y ) are mutually conjugated high-frequency term spectra, which contain x-direction clipping The phase information of ; f _x is the abscissa of the spatial spectrum, f _y is the ordinate of the spatial spectrum, and f ₀ is the carrier frequency introduced by the aperture diaphragm;

In the third step, select the cutoff frequency, set the filter window to extract high-frequency terms containing phase information, specifically, use the set (f ₀ , 0) as the center, and the cut-off frequency _{fr (f r <} f ₀ ) as The circular filter window of the radius extracts the spectrum as the spectrum containing the phase information clipped in the x-direction, and performs center-shift processing and inverse Fourier transform on it;

As a further preference of the present invention, in the fourth step, the first sheared speckle interference image obtained before the deformation of the measured object contains phase information of deformation and strain information, which is expressed as

为u₁₂(x+△x,y)的复共轭；Among them, Im is the operator for taking the imaginary part, Re is the operator for taking the real part, u ₁₁ (x, y) is the complex amplitude of a shearing object light wave after the first object light wave is dislocated, u ₁₂ (x+△x, y) is the complex amplitude of another shearing object light wave after the dislocation of the first object light wave,

is the complex conjugate of u ₁₂ (x+△x,y);

In the fifth step, the first sheared speckle interference image after deformation is obtained according to the steps from the first step to the fourth step and contains the phase information of the deformation and strain information, specifically φ _1a (x+Δx,y);

In the sixth step, the phase information of the first sheared speckle interference image before and after the deformation of the measured object is subtracted in real time to obtain the phase difference related to deformation and strain in the first sheared speckle interference image.

为第一剪切散斑干涉图像中与变形、应变有关的相位差，φ_1a(x+△x,y)为变形后第一剪切散斑干涉图像含有变形、应变信息的相位信息，

为变形前第一剪切散斑干涉图像含有变形、应变信息的相位信息；in,

is the phase difference related to deformation and strain in the first shearing speckle interference image, φ _1a (x+△x,y) is the phase information that contains deformation and strain information in the first shearing speckle interference image after deformation,

is the phase information containing deformation and strain information for the first sheared speckle interference image before deformation;

As a further preference of the present invention, in the seventh step, the phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference related to deformation and strain in the hybrid speckle interference image are obtained as:

为第二剪切散斑干涉图像中与变形、应变有关的相位差，

为混合散斑干涉图像中与变形、应变有关的相位差，

为变形后第二剪切散斑干涉图像含有变形、应变信息的相位信息，

为变形前第二剪切散斑干涉图像含有变形、应变信息的相位信息，

为变形后混合散斑干涉图像含有变形、应变信息的相位信息，

为变形前混合散斑干涉图像含有变形、应变信息的相位信息；in,

is the phase difference related to deformation and strain in the second sheared speckle interference image,

is the phase difference related to deformation and strain in the mixed speckle interference image,

is the phase information of the deformation and strain information of the second sheared speckle interference image after deformation,

is the phase information containing the deformation and strain information of the second sheared speckle interference image before deformation,

is the phase information of the deformed mixed speckle interference image containing deformation and strain information,

Phase information containing deformation and strain information for the mixed speckle interference image before deformation;

As a further preference of the present invention, the obtained smooth and continuous phase difference distribution is used to calculate the deformation and strain of the measured object, which are expressed as

为被测物体的面内应变分量，

分别为被测物体的离面应变分量，△x为被测物体经过渥拉斯顿剪切装置后沿x方向物面剪切量，λ为系统所用激光光源波长，θ为系统观察方向与法线方向夹角，

为第一剪切散斑干涉图像中与变形、应变有关的相位差，

为第二剪切散斑干涉图像中与变形、应变有关的相位差，

为混合散斑干涉图像中与变形、应变有关的相位差。Among them, w is the out-of-plane deformation of the measured object,

is the in-plane strain component of the measured object,

are the out-of-plane strain components of the measured object, respectively, △x is the shearing amount of the measured object along the x-direction after passing through the Wollaston shearing device, λ is the wavelength of the laser light source used by the system, and θ is the observation direction and method of the system. Line direction angle,

is the phase difference related to deformation and strain in the first sheared speckle interference image,

is the phase difference related to deformation and strain in the second sheared speckle interference image,

is the phase difference related to deformation and strain in the mixed speckle interference image.

Through the above technical solutions, with respect to the prior art, the present invention has the following beneficial effects:

1. The present invention only needs to use one laser as the illumination light source and one monochromatic CCD camera to record the image, including multiple independent coexisting optical paths, which simplifies the structure of the measurement system and reduces the measurement cost;

2. In the measurement system provided by the present invention, a plurality of adjustable aperture diaphragms are set to realize the space carrier, the single coupled speckle interference image is processed in the frequency domain by the Fourier transform, and the corresponding deformation is directly extracted by the frequency domain filtering. and the phase information of multiple strain components, realizing multi-parameter dynamic simultaneous measurement;

3. The present invention uses the Wollaston shearing device to realize two independent common optical path shearing paths at the same time, so that the system has strong anti-interference ability and good stability.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

FIG. 1 is a schematic diagram of the structure of a speckle interference multi-parameter measurement system based on the Duffy optical path provided by the present invention.

In the figure: 1 is the laser, 2 is the object to be measured, 3 is the first mirror, 4 is the first beam splitting prism, 5 is the optical rough reference surface, 6 is the first aperture diaphragm, 7 is the second mirror, 8 is the second beam splitting prism, 9 is the second aperture diaphragm, 10 is the third reflecting mirror, 11 is the third aperture diaphragm, 12 is the fourth reflecting mirror, 13 is an all-inversion right angle prism, and 14 is the Wollaston scissors Cut device, 15 monochrome CCD cameras.

Detailed ways

The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are all simplified schematic diagrams, and only illustrate the basic structure of the present invention in a schematic manner, so they only show the structures related to the present invention.

In order to realize the synchronous dynamic measurement of the deformation and strain information of the measured object 2, the present invention provides a speckle interference multi-parameter measurement system based on the Duffy optical path. As shown in FIG. 1, the system includes a laser 1, a first reflection Mirror 3, second reflector 7, third reflector 10, fourth reflector 12, first beam splitter prism 4, second beam splitter prism 8, Wollaston shearing device 14, all-inversion right angle prism 13, first Aperture diaphragm 6, second aperture diaphragm 9, third aperture diaphragm 11 and monochromatic CCD camera 15, in the figure, measured object 2, first beam splitting prism 4, all-inverting right angle prism 13, Wollaston shear The cutting device 14, the second beam splitting prism 8 and the monochromatic CCD camera 15 are all distributed on the optical axis in turn, and an all-inversion right angle prism is arranged at the center position of the third reflecting mirror 10 and the fourth reflecting mirror 12 perpendicular to the center line of the optical axis. 13. The connecting line formed by the first reflecting mirror 3 and the optical rough reference surface 5 is perpendicular to the optical axis, while the first beam splitting prism 4 is located on this connecting line, and the second aperture stop 9 and the third aperture stop 11 are relative to the optical axis. Symmetrically arranged, the third reflecting mirror 10 and the fourth reflecting mirror 12 are symmetrically arranged relative to the optical axis;

In this measurement system, the laser 1 is used as the illumination light source, and the laser light emitted by it passes through the first reflecting mirror 3 and is split into the transmitted light wave and the reflected light wave according to 5:5 in the first beam splitting prism 4; the transmitted light wave passes through the optical rough reference surface 5 Then a spatial diffuse reflection light wave is formed, and the spatial diffuse reflection light wave passes through the first aperture diaphragm 6 and the second mirror 7 in sequence to form a beam of reference light waves; The first object light wave and the second object light wave, the first object light wave and the second object light wave are respectively at the same angle with the optical axis, wherein the first object light wave passes through the second aperture diaphragm 9 and the third mirror 10 in sequence , the all-reverse right-angle prism 13, and the Wollaston shearing device 14 form two beams of shearing object light waves, and the second object light wave passes through the third aperture diaphragm 11, the fourth mirror 12, the all-reverse right-angle prism 13, and the second object light wave in sequence. The Ruston shearing device 14 forms two sheared object light waves;

That is to say, when the first object light wave and the second object light wave pass through the Wollaston shearing device 14, they are respectively dislocated and form two shearing object light waves respectively, and these four shearing object light waves and one reference light wave pass through at the same time The second beam splitting prism 8 is then jointly imaged on the target surface of the monochromatic CCD camera 15 to form a coupled speckle interference image, wherein the first image is the two beams of the first object light wave after being displaced by the Wollaston shearing device 14 The shearing speckle interference image formed by the mutual interference of the shearing object light waves, the second image is the shearing speckle interference image formed by the mutual interference of the other two shearing object light waves after the second object light wave is displaced by the Wollaston shearing device 14 Speckle interference images; the two sheared speckle interference images are imaged on both sides of the target surface of the monochromatic CCD camera 15 respectively, and there is no overlapping interference with each other; the third image is formed by the mutual interference of the reference light wave and the sheared object light wave Mixed speckle interference image; on the target surface of the monochromatic CCD camera 15, the mixed speckle interference image and the first two sheared speckle interference images respectively interfere again to form a coupled speckle interference image, which can finally achieve deformation and multiple Simultaneous measurement of strain components.

Next, based on the above measurement system, the present application provides a measurement method, the principle of which is mainly to use a loading device to load the measured object 2 to deform it, and to collect the measured object 2 on the target surface of the monochrome CCD camera 15 respectively. For the coupled speckle interference images before and after deformation, Fourier transform is performed on the two collected coupled speckle interference images to obtain the spectrum of the multi-parameter speckle interference image (that is, the mixed spectrum of the measured object 2 before and after deformation), and the settings are appropriate. The frequency range is to set filter windows for the spectral regions containing deformation and strain information in the mixed spectrum, respectively, to obtain the spectral parts of the complex amplitude of the light wave containing deformation and multi-strain information, and perform inverse Fourier transform on them to obtain the spectral regions containing deformation and multi-strain information. The optical wave complex amplitude of deformation and multi-strain information, through the complex amplitude phase extraction, the phase distribution corresponding to the deformation and multi-strain information are obtained respectively; the phase information related to the deformation of the measured object 2 before and after the deformation is subtracted in real time to obtain the characterization The phase difference of the surface deformation of the measured object 2 (including the out-of-plane deformation phase information of the measured object 2 and the mixed phase information containing the strain information), and the mixed phase information containing the strain information is subjected to geometric operations, thereby further obtaining the deformation measurement results; According to the method of subtracting the single phase information, the multiple strain phase information of the measured object 2 before and after the deformation is subtracted in real time, and the phase difference characterizing the multiple strains on the surface of the measured object 2 is obtained, and the mixed phase related to the strain is obtained. The information is subjected to geometric operations to obtain independent strain phase information, thereby obtaining measurement results of multiple strains on the surface of the object to be measured 2 .

According to the measurement system provided in FIG. 1, the measurement method of the speckle interference multi-parameter measurement system based on the Duffy optical path proposed in this application specifically includes the following steps:

Step 1: Before the measured object 2 is loaded and deformed, the laser light source is provided by the laser 1, and the monochromatic CCD camera 15 collects the first sheared speckle interference image before the deformation; that is, the first object light wave passes through the Wollaston shearing device 14 The two shearing object light waves after dislocation and the measured object 2 before deformation interfere with each other on the target surface of the monochromatic CCD camera 15 to form the first shearing speckle interference image, and its light intensity is expressed as

I ₁ (x,y)＝[u ₁₁ (x,y)+u ₁₂ (x+△x,y)]·[u ₁₁ (x,y)+u ₁₂ (x+△x,y)] ^* (1 )

为u₁₁(x,y)的复共轭，

为u₁₂(x+△x,y)的复共轭，Δx为被测物体2经过渥拉斯顿剪切装置14后沿x方向物面剪切量。Among them, u ₁₁ (x, y) is the complex amplitude of a beam of shearing object light waves after the first object light wave is dislocated, and u ₁₂ (x+△x, y) is another beam of shearing objects after the first object light wave is dislocated the complex amplitude of a light wave,

is the complex conjugate of u ₁₁ (x,y),

is the complex conjugate of u ₁₂ (x+Δx, y), and Δx is the shearing amount of the measured object 2 along the x-direction after passing through the Wollaston shearing device 14 .

Step 2: Fourier transform is performed on the first sheared speckle interference image before deformation, and the spatial spectrum of the first sheared speckle interference image before deformation is obtained; the obtained first sheared speckle interference before deformation is obtained The spatial spectrum of the image is expressed as

代表空间频谱中含有背景光的低频项频谱，

表示频域中卷积运算符，C^*(f_x-f₀,f_y)和C(f_x+f₀,f_y)是互为共轭的高频项频谱，其含有x方向剪切的相位信息；f_x为空间频谱的横坐标，f_y为空间频谱的纵坐标，f₀是由孔径光阑引入的载波频率。in,

represents the spectrum of the low-frequency term containing the background light in the spatial spectrum,

Represents the convolution operator in the frequency domain, C ^* (f _x -f ₀ , f _y ) and C(f _x +f ₀ , f _y ) are mutually conjugated high-frequency term spectra, which contain x-direction clipping The phase information of ; f _x is the abscissa of the spatial spectrum, f _y is the ordinate of the spatial spectrum, and f ₀ is the carrier frequency introduced by the aperture diaphragm.

Step 3: Extract high-frequency terms containing phase information from the obtained spatial spectrum of the first sheared speckle interference image before deformation by setting a filter window; specifically, select a cutoff frequency, set a filter window to extract high-frequency terms containing phase information Frequency term, using the set circular filter window with (f ₀ , 0) as the center and the cutoff frequency _{fr (f r <} f ₀ ) as the radius to extract the spectrum as the spectrum containing the phase information clipped in the x direction, for It is center-shifted and inverse Fourier transformed.

The fourth step: extract the phase of the high frequency term of the obtained first sheared speckle interference image before deformation, and obtain the phase information of the first sheared speckle interference image before deformation containing deformation and strain information, which is expressed as:

为u₁₂(x+△x,y)的复共轭。Among them, Im is the operator for taking the imaginary part, Re is the operator for taking the real part, u ₁₁ (x, y) is the complex amplitude of a shearing object light wave after the first object light wave is dislocated, u ₁₂ (x+△x, y) is the complex amplitude of another shearing object light wave after the dislocation of the first object light wave,

is the complex conjugate of u ₁₂ (x+Δx,y).

Step 5: The loading device loads and deforms the measured object 2, and obtains the phase information of the deformation and strain information in the first sheared speckle interference image after deformation according to the steps from the first to the fourth step, specifically φ _1a (x+ Δx,y).

Step 6: Subtract the phase information of the first sheared speckle interference image before and after the deformation of the measured object 2 in real time to obtain the phase difference related to deformation and strain in the first sheared speckle interference image

为第一剪切散斑干涉图像中与变形、应变有关的相位差，φ_1a(x+△x,y)为变形后第一剪切散斑干涉图像含有变形、应变信息的相位信息，

为变形前第一剪切散斑干涉图像含有变形、应变信息的相位信息。in,

is the phase difference related to deformation and strain in the first shearing speckle interference image, φ _1a (x+△x,y) is the phase information that contains deformation and strain information in the first shearing speckle interference image after deformation,

Phase information containing deformation and strain information for the first sheared speckle interference image before deformation.

Step 7: Obtain the phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference related to deformation and strain in the hybrid speckle interference image respectively according to the methods of the first step to the sixth step;

The phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference related to deformation and strain in the hybrid speckle interference image are obtained as

为第二剪切散斑干涉图像中与变形、应变有关的相位差，

为混合散斑干涉图像中与变形、应变有关的相位差，

为变形后第二剪切散斑干涉图像含有变形、应变信息的相位信息，

为变形前第二剪切散斑干涉图像含有变形、应变信息的相位信息，

为变形后混合散斑干涉图像含有变形、应变信息的相位信息，

为变形前混合散斑干涉图像含有变形、应变信息的相位信息。in,

is the phase difference related to deformation and strain in the second sheared speckle interference image,

is the phase difference related to deformation and strain in the mixed speckle interference image,

is the phase information of the deformation and strain information of the second sheared speckle interference image after deformation,

is the phase information containing the deformation and strain information of the second sheared speckle interference image before deformation,

is the phase information of the deformed mixed speckle interference image containing deformation and strain information,

Phase information containing deformation and strain information for mixed speckle interference images before deformation.

Step 8: Since the phase difference distribution images obtained by formulas (4) and (5) contain a large amount of random noise, which will affect the subsequent deformation and strain calculations, an appropriate filtering algorithm is selected for this purpose. The phase difference related to deformation and strain in the speckle interference image, the phase difference related to deformation and strain in the second shearing speckle interference image, and the phase difference distribution image related to deformation and strain in the hybrid speckle interference image are filtered respectively. processing, the filtered phase difference distribution image is unwrapped to obtain a smooth and continuous phase distribution; the deformation and strain of the measured object 2 are obtained by calculating the obtained smooth and continuous phase difference distribution, which can be expressed as

为被测物体2的面内应变分量，

分别为被测物体2的离面应变分量，△x为被测物体2经过渥拉斯顿剪切装置14后沿x方向物面剪切量，λ为系统所用激光光源波长，θ为系统观察方向与法线方向夹角，

为第一剪切散斑干涉图像中与变形、应变有关的相位差，

为第二剪切散斑干涉图像中与变形、应变有关的相位差，

为混合散斑干涉图像中与变形、应变有关的相位差。Among them, w is the out-of-plane deformation of the measured object 2,

is the in-plane strain component of the measured object 2,

are the out-of-plane strain components of the measured object 2, respectively, Δx is the shearing amount of the measured object 2 along the x direction after passing through the Wollaston shearing device 14, λ is the wavelength of the laser light source used by the system, and θ is the system observation the angle between the direction and the normal direction,

is the phase difference related to deformation and strain in the first sheared speckle interference image,

is the phase difference related to deformation and strain in the second sheared speckle interference image,

is the phase difference related to deformation and strain in the mixed speckle interference image.

In the embodiments provided in this application, other required strain components can also be obtained by adjusting the observation direction of the measurement system and the shearing direction of the Wollaston shearing device.

It will be understood by one of ordinary skill in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as herein, are not to be taken in an idealized or overly formal sense. explain.

The meaning of "and/or" described in this application means that each of them exists alone or both are included.

The meaning of "connection" described in this application may be a direct connection between components or an indirect connection between components through other components.

Taking the above ideal embodiments according to the present invention as inspiration, and through the above description, relevant personnel can make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the contents in the specification, and the technical scope must be determined according to the scope of the claims.

Claims (7)

1. A speckle interference multi-parameter measurement system based on a Taffy optical path is characterized in that: the laser is used as an irradiation light source, and laser emitted by the laser is split into transmission light waves and reflection light waves in a first light splitting prism according to the ratio of 5:5 through a first reflector;

the transmitted light waves form spatial diffuse reflection light waves after passing through the optical rough reference surface, and the spatial diffuse reflection light waves form a beam of reference light waves after sequentially passing through the first aperture diaphragm and the second reflector;

the reflected light waves are irradiated to the surface of a measured object along the direction of an optical axis and then are divided into first object light waves and second object light waves, included angles between the first object light waves and the optical axis are the same as included angles between the second object light waves and the optical axis, the first object light waves sequentially pass through a second aperture diaphragm, a third reflector, a full-inverse right-angle prism and a Wollaston shearing device to form two shear object light waves, and the second object light waves sequentially pass through the third aperture diaphragm, a fourth reflector, the full-inverse right-angle prism and the Wollaston shearing device to form two shear object light waves;

the four beams of shear light waves and one beam of reference light waves simultaneously pass through a second light splitting prism and then are imaged on a target surface of a monochromatic CCD camera;

the device comprises a first aperture diaphragm, a second aperture diaphragm, a third reflector, a fourth reflector, a measured object, a first spectroscope, a full-reflection right-angle prism, a Wollaston shearing device, a second spectroscope and a monochromatic CCD camera, wherein the second aperture diaphragm and the third aperture diaphragm are symmetrically arranged relative to an optical axis;

a connecting line formed by the first reflector, the first beam splitter prism and the optical rough reference surface is vertical to the optical axis;

two shear object light waves of the first object light wave after dislocation of the Wollaston shearing device are mutually interfered to form a first shear speckle interference image, and two shear object light waves of the second object light wave after dislocation of the Wollaston shearing device are mutually interfered to form a second shear speckle interference image;

the reference light waves and the shearing object light waves are mutually interfered to form a mixed speckle interference image, and the mixed speckle interference image respectively interferes with the first shearing speckle interference image and the second shearing speckle interference image again to form a coupling speckle interference image on the target surface of the monochromatic CCD camera;

filtering the phase difference related to deformation and strain in the obtained first shearing speckle interference image, the phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference distribution image related to deformation and strain in the mixed speckle interference image respectively through a filtering algorithm, and unwrapping the phase difference distribution image after filtering to obtain smooth and continuous phase distribution; and calculating to obtain the deformation and the strain of the measured object through the obtained smooth and continuous phase difference distribution.

2. A measuring method of the speckle interference multi-parameter measuring system based on the Taffy optical path is characterized in that:

the first step is as follows: before a measured object is loaded and deformed, a laser source is provided through a laser, and a monochromatic CCD camera collects a first shearing speckle interference image before deformation;

the second step is that: fourier transformation is carried out on the first shearing speckle interference image before deformation, and a spatial frequency spectrum of the first shearing speckle interference image before deformation is obtained;

the third step: extracting a high-frequency item containing phase information from the acquired space frequency spectrum of the first shearing speckle interference image before deformation by setting a filter window;

the fourth step: performing phase extraction on the high-frequency item of the acquired first shearing speckle interference image before deformation to obtain phase information of the first shearing speckle interference image before deformation, wherein the phase information contains deformation and strain information;

the fifth step: the loading device loads deformation on the measured object, and phase information containing deformation and strain information of the deformed first shearing speckle interference image is obtained according to the steps from the first step to the fourth step;

and a sixth step: subtracting phase information of the first shearing speckle interference image before and after the measured object is deformed in real time to obtain a phase difference related to deformation and strain in the first shearing speckle interference image;

the seventh step: respectively acquiring the phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference related to deformation and strain in the mixed speckle interference image according to the modes from the first step to the sixth step;

eighth step: filtering the phase difference related to deformation and strain in the obtained first shearing speckle interference image, the phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference distribution image related to deformation and strain in the mixed speckle interference image respectively, and unwrapping the phase difference distribution image after filtering to obtain smooth and continuous phase distribution; and calculating and obtaining the deformation and the strain of the measured object through the obtained smooth and continuous phase difference distribution.

3. The measuring method of the speckle interference multi-parameter measuring system based on the duffy optical path as claimed in claim 2, wherein:

in the first step, the two shear object light waves after the first object light wave passes through the Wollaston shearing device and is staggered, a measured object before deformation interferes with each other on a target surface of a monochromatic CCD camera to form a first shear speckle interference image, and the light intensity of the first shear speckle interference image is expressed as

I₁(x,y)＝[u₁₁(x,y)+u₁₂(x+Δx,y)]·[u₁₁(x,y)+u₁₂(x+Δx,y)]^* (1)

Wherein u is₁₁(x, y) is the complex amplitude of a shearer wave after dislocation of the first object wave, u₁₂(x + Deltax, y) is the complex amplitude of another shear object wave after the dislocation of the first object wave,

is u₁₁(x, y) in the presence of a complex conjugate,

is u₁₂And (x + Deltax, y) complex conjugation, wherein Deltax is the object surface shearing quantity of the object to be measured along the x direction after the object passes through the Wollaston shearing device.

4. The measuring method of the speckle interference multi-parameter measuring system based on the duffy optical path as claimed in claim 3, wherein:

in the second step, Fourier transform is carried out on the first shearing speckle interference image before deformation, and the space frequency spectrum of the first shearing speckle interference image before deformation is obtained and expressed as

Wherein,

representing the spectrum of low frequency terms in the spatial spectrum with background light,

representing convolution operators in the frequency domain, C^*(f_x-f₀,f_y) And C (f)_x+f₀,f_y) Is a mutually conjugated high-frequency term spectrum containing phase information sheared in the x direction; f. of_xIs the abscissa, f, of the spatial frequency spectrum_yIs the ordinate, f, of the spatial frequency spectrum₀Is the carrier frequency introduced by the aperture stop;

in a third step, the cut-off frequency is selected, the filtering window is set to extract the high frequency term containing the phase information, in particular by setting (f)₀0) centered on the cut-off frequency f_r(f_r＜f₀) The spectrum is extracted for a circular filter window of radius as the spectrum containing phase information clipped in the x-direction, shifted and inverse fourier transformed.

5. The measuring method of the speckle interference multi-parameter measuring system based on the Taffy optical path as claimed in claim 4, wherein:

in the fourth step, phase information containing deformation and strain information of the first shearing speckle interference image before the measured object is deformed is obtained and expressed as

Wherein Im is an operator of taking an imaginary part, Re is an operator of taking a real part, and u₁₁(x, y) is the complex amplitude of a shearer wave after dislocation of the first object wave, u₁₂(x + Deltax, y) is the complex amplitude of another shear object wave after the dislocation of the first object wave,

is u₁₂(x + Δ x, y) complex conjugation;

in the fifth step, phase information containing deformation and strain information of the deformed first shearing speckle interference image is obtained according to the steps from the first step to the fourth step, and the phase information is phi_1a(x+Δx,y)；

In the sixth step, the phase information of the first shearing speckle interference image before and after the measured object is deformed is subtracted in real time to obtain the phase difference related to deformation and strain in the first shearing speckle interference image

Wherein,

is the phase difference related to deformation and strain in the first shearing speckle interference image, phi_1a(x + Deltax, y) is the phase information of the deformed and strain information contained in the deformed first shearing speckle interference image,

the first shearing speckle interference image before deformation contains phase information of deformation and strain information.

6. The measuring method of the speckle interference multi-parameter measuring system based on the duffy optical path as claimed in claim 5, wherein:

in the seventh step, the phase difference related to deformation and strain in the second shearing speckle interference image and the phase difference related to deformation and strain in the mixed speckle interference image are respectively obtained

Wherein,

the phase difference related to deformation and strain in the second shearing speckle interference image,

in order to mix the phase difference related to deformation and strain in the speckle interference image,

the deformed second shearing speckle interference image contains phase information of deformation and strain information,

the second shearing speckle interference image before deformation contains phase information of deformation and strain information,

the deformed mixed speckle interference image contains phase information of deformation and strain information,

the mixed speckle interference image before deformation contains phase information of deformation and strain information.

7. The measuring method of the speckle interference multi-parameter measuring system based on the duffy optical path as claimed in claim 6, wherein: calculating the deformation and strain of the measured object by the obtained smooth and continuous phase difference distribution, and expressing as

Wherein w is the out-of-plane deformation of the object to be measured,

is the in-plane strain component of the object to be measured,

respectively is an out-of-plane strain component of a measured object, deltax is the object plane shearing quantity of the measured object along the x direction after passing through the Wollaston shearing device, lambda is the wavelength of a laser light source used by the system, theta is the included angle between the observation direction of the system and the normal direction,

the phase difference related to deformation and strain in the first shearing speckle interference image,

the phase difference related to deformation and strain in the second shearing speckle interference image,

the phase difference related to deformation and strain in the speckle interference image is mixed.

Images