CN111964601B - Speckle interference multi-parameter measuring system and method based on Taffy optical path - Google Patents
Speckle interference multi-parameter measuring system and method based on Taffy optical path Download PDFInfo
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Abstract
The invention relates to a speckle interference multi-parameter measuring system and a measuring method based on a Taffy optical path.A laser emitted by a laser is split into a transmission light wave and a reflection light wave in a first beam splitter prism through a first reflector, and the transmission light wave forms a beam of reference light wave in a second reflector after passing through an optical rough reference surface; 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, the first object light waves and the second object light waves are respectively staggered and form two shear object light waves respectively, the four shear object light waves and one reference light wave simultaneously pass through a second light splitting prism and then are imaged on a target surface of a monochrome CCD camera together, and a coupling speckle interference image is formed; the invention can realize synchronous dynamic measurement of multi-parameter information such as deformation, strain and the like of the measured object, and has simple structure of the measurement system and easy measurement method.
Description
Technical Field
The invention relates to a speckle interference multi-parameter measuring system and a speckle interference multi-parameter measuring method based on a Taffy optical path, and belongs to the technical field of optical measurement.
Background
Speckle interference is a modern optical measurement method with the advantages of high sensitivity, high precision, real-time, full-field non-contact measurement and the like, and has been widely applied to advanced material testing and analysis in the fields of aerospace, mechanical manufacturing, automobile engineering and the like in recent years. The speckle interference system can directly measure structural deformation information, but cannot directly measure deformation first-order derivative, namely strain information. According to different deformation measurement requirements, speckle interference systems can be generally divided into in-plane deformation measurement systems and out-of-plane deformation measurement systems. Generally, strain information can be obtained by numerical differentiation of speckle interferometry deformation information, or by shearing speckle interferometry system measurements; however, the shearing speckle interference cannot directly measure deformation, and the numerical differential calculation often causes random error diffusion transmission. In practical engineering application, the quality safety evaluation and the service life prediction of the bearing structure can not be obtained at the same time of deformation and strain information, so that the design and development of a speckle interference system capable of simultaneously measuring deformation and a plurality of strain information are of great importance to meet the requirement of multi-parameter synchronous measurement in practical application.
Existing speckle interferometry systems capable of performing deformation and strain measurements can generally be divided into two categories: the first type is that the speckle interference system and the shearing speckle interference system are simply combined to form an integral system for respectively measuring deformation and strain information. The combined system can realize independent measurement of deformation and strain information by sequentially switching different light paths, but cannot realize simultaneous measurement, has a complex structure, is inconvenient in the measurement process and is not suitable for dynamic measurement; the second type is to introduce a reference optical wave into a shearing speckle interference system based on Michelson (Michelson) type so as to realize simultaneous measurement of deformation and strain. The system is the most common deformation and strain synchronous measurement system at present, deformation and strain information can be synchronously demodulated in one coupling speckle interference pattern by utilizing a spatial phase shift technology, and the system is simple in spatial structure, convenient and fast in measurement method and suitable for dynamic measurement. However, the field of view of the system is limited by the michelson shearing device, an optical 4f system is generally required to be added for improvement, and spatial carrier frequency modulation and shearing amount control are not independent from each other, so that useful spectrum information is difficult to be completely separated; furthermore, both the combined measurement system and the michelson system can only measure deformation and a single strain component.
Disclosure of Invention
The invention provides a speckle interference multi-parameter measuring system and a speckle interference multi-parameter measuring method based on a Taffy optical path, which can realize synchronous dynamic measurement of deformation and strain information of a measured object, and have the advantages of simple structure and easy measuring method.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a speckle interference multi-parameter measuring system based on a Taffy optical path takes a laser as an irradiation light source, and laser emitted by the laser is split into transmission light waves and reflection light waves in a first beam splitter 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;
as a further preferable mode of the invention, the two shear light waves of the first object light wave after being staggered by the wollaston shearing device interfere with each other to form a first shear speckle interference image, and the two shear light waves of the second object light wave after being staggered by the wollaston shearing device interfere with each other 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;
a measuring method based on the speckle interference multi-parameter measuring system based on the Taffy optical path,
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; calculating and obtaining the deformation and the strain of the measured object through the obtained smooth and continuous phase difference distribution;
as a further preferred aspect of the present invention,
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+△x,y)]·[u11(x,y)+u12(x+△x,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 the other shear object wave after the dislocation of the first object wave,
is u11(x, y) in the presence of a complex conjugate,
is u12Complex conjugation of (x + Deltax, y), wherein Deltax is the object surface shearing quantity of the object to be measured along the x direction after passing through the Wollaston shearing device;
as a further preferred embodiment of the present invention, in the second step, fourier transform is performed on the first sheared speckle interference image before deformation, and the spatial frequency spectrum of the first sheared 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*(fx-f0,fy) And C (f)x+f0,fy) Is a mutually conjugated high-frequency term spectrum containing phase information sheared in the x direction; f. ofxIs the abscissa, f, of the spatial frequency spectrumyIs the ordinate, f, of the spatial frequency spectrum0Is the carrier frequency introduced by the aperture stop;
in the third step, the cut-off frequency is selected, and the filtering window is set to extract the high-frequency item containing the phase informationSpecifically, using a setting of (f)00) centered on the cut-off frequency fr(fr<f0) Extracting a frequency spectrum for a circular filtering window with a radius as a frequency spectrum containing phase information sheared in the x direction, performing shift processing on the frequency spectrum and performing inverse Fourier transform on the frequency spectrum;
as a further preferable aspect of the present invention, in the fourth step, phase information including deformation and strain information of the first sheared speckle interference image before the deformation of the object to be measured is acquired, and the phase information is 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 the other shear object wave after the dislocation of the first object wave,
is u12(x +. DELTA.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 phi1a(x+△x,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, phi1a(x + delta x, y) is the deformed first shearing speckle interferenceThe image contains phase information of deformation and strain information,
phase information of deformation and strain information is contained in the first shearing speckle interference image before deformation;
as a further preferred aspect of the present invention, in the seventh step, the phase difference related to the distortion and strain in the second cutout speckle interference image and the phase difference related to the distortion and strain in the mixed speckle interference image are acquired as
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;
as a further preferred aspect of the present invention, the deformation and strain of the measured object are calculated from the obtained smooth continuous phase difference distribution, expressed 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 an 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.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, only one laser is used as an irradiation light source, one monochromatic CCD camera is used for recording images, and the system comprises a plurality of independent coexisting light paths, so that the structure of the measurement system is simplified, and the measurement cost is reduced;
2. in the measuring system provided by the invention, a plurality of adjustable aperture diaphragms are arranged to realize space carrier waves, the single coupling speckle interference image is subjected to frequency domain processing by utilizing Fourier transform, phase information corresponding to deformation and a plurality of strain components is directly extracted by using frequency domain filtering, and multi-parameter dynamic simultaneous measurement is realized;
3. the Wollaston shearing device is used for simultaneously realizing two independent common-light-path shearing paths, so that the system has strong anti-interference capability and good stability.
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The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic diagram of the speckle interference multi-parameter measurement system based on the Duffy optical path.
In the figure: 1 is the laser instrument, 2 is the testee, 3 is first speculum, 4 is first beam splitter prism, 5 is the coarse reference surface of optics, 6 is first aperture diaphragm, 7 is the second speculum, 8 is second beam splitter prism, 9 is the second aperture diaphragm, 10 is the third speculum, 11 is the third aperture diaphragm, 12 is the fourth speculum, 13 is the total reflection right angle prism, 14 is Wollaston shearing mechanism, 15 monochromatic CCD cameras.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic views illustrating only the basic structure of the present invention in a schematic manner, and thus show only the constitution related to the present invention.
In order to realize synchronous dynamic measurement of deformation and strain information of a measured object 2, the invention provides a speckle interference multi-parameter measurement system based on a Taffy optical path, which comprises a laser 1, a first reflector 3, a second reflector 7, a third reflector 10, a fourth reflector 12, a first beam splitter 4, a second beam splitter 8, a Wollaston shearing device 14, a total-reflection right-angle prism 13, a first aperture diaphragm 6, a second aperture diaphragm 9, a third aperture diaphragm 11 and a monochromatic CCD camera 15, as shown in figure 1, in the figure, the measured object 2, the first beam splitter 4, the total-reflection right-angle prism 13, the Wollaston shearing device 14, the second beam splitter 8 and the monochromatic CCD camera 15 are sequentially distributed on an optical axis, the total-reflection right-angle prism 13 is distributed on a central position of a central line of the third reflector 10 and the fourth reflector 12, which are vertical to the optical axis, a connecting line formed by the first reflector 3 and the optical rough reference surface 5 is vertical to the optical axis, meanwhile, the first beam splitter prism 4 is positioned on the connecting line, the second aperture diaphragm 9 and the third aperture diaphragm 11 are symmetrically arranged relative to the optical axis, and the third reflector 10 and the fourth reflector 12 are symmetrically arranged relative to the optical axis;
in the measuring system, a laser 1 is used as an irradiation light source, and laser emitted by the laser is split into a transmission light wave and a reflection light wave in a first beam splitter prism 4 according to a ratio of 5:5 through a first reflector 3; the transmitted light waves form spatial diffuse reflection light waves after passing through the optical rough reference surface 5, and the spatial diffuse reflection light waves form a beam of reference light waves after sequentially passing through a first aperture diaphragm 6 and a second reflector 7; the reflected light wave is irradiated to the surface of a measured object 2 along the optical axis direction and then is divided into a first object light wave and a second object light wave, included angles between the first object light wave and the optical axis are the same as included angles between the second object light wave and the optical axis, wherein the first object light wave sequentially passes through a second aperture diaphragm 9, a third reflector 10, a full-inverse right-angle prism 13 and a Wollaston shearing device 14 to form two shear object light waves, and the second object light wave sequentially passes through a third aperture diaphragm 11, a fourth reflector 12, a full-inverse right-angle prism 13 and a Wollaston shearing device 14 to form two shear object light waves;
that is to say, the first object light wave and the second object light wave respectively generate dislocation through the wollaston shearing device 14 and respectively form two bundles of sheared object light waves, the four bundles of sheared object light waves and one bundle of reference light waves simultaneously pass through the second beam splitter 8 and then are imaged on the target surface of the monochromatic CCD camera 15 together to form a coupled speckle interference image, wherein the first image is a sheared speckle interference image formed by mutual interference of two bundles of sheared object light waves after the first object light wave is dislocated through the wollaston shearing device 14, and the second image is a sheared speckle interference image formed by mutual interference of the other two bundles of sheared object light waves after the second object light wave is dislocated through the wollaston shearing device 14; the two shearing speckle interference images are respectively imaged at two sides of the target surface of the monochromatic CCD camera 15, and no overlapping interference occurs between the two shearing speckle interference images; the third image is a mixed speckle interference image formed by mutual interference of the reference light wave and the shear light wave; on the target surface of the monochromatic CCD camera 15, the mixed speckle interference image and the first two shearing speckle interference images are interfered again to form a coupling speckle interference image, and finally, deformation and simultaneous measurement of a plurality of strain components can be realized.
Then, based on the above-mentioned measuring system, the present application provides a measuring method, whose principle is mainly to use a loading device to load the measured object 2 to deform it, to collect the coupled speckle interference images before and after the measured object 2 is deformed on the target surface of the monochrome CCD camera 15, fourier transform is carried out on the two collected coupling speckle interference images to obtain frequency spectrums of the multi-parameter speckle interference images (namely mixed frequency spectrums before and after deformation of the object to be measured 2), a proper frequency range is set to set filtering windows respectively for extracting frequency spectrum regions containing deformation and strain information in the mixed frequency spectrums to respectively obtain optical wave complex amplitude frequency spectrum parts containing the deformation and multi-strain information, and respectively carrying out inverse Fourier transform to obtain optical complex amplitudes containing deformation and multi-strain information, respectively obtaining phase distribution of corresponding deformation and multi-strain information through complex amplitude phase extraction; subtracting phase information related to deformation of the object to be measured 2 before and after deformation in real time to obtain a phase difference (including out-of-plane deformation phase information of the object to be measured 2 and mixed phase information containing strain information) representing surface deformation of the object to be measured 2, and performing geometric operation on the mixed phase information containing the strain information to further obtain a deformation measurement result; according to the method of subtracting single phase information, the phase difference of multiple strains of the measured object 2 before and after deformation is subtracted in real time to obtain the phase difference representing the multiple strains on the surface of the measured object 2, and the mixed phase information related to the strains is geometrically calculated to obtain independent strain phase information, so that the measurement results of the multiple strains on the surface of the measured object 2 are obtained.
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 provided in the present application specifically includes the following steps,
the first step is as follows: before the object to be measured 2 is loaded and deformed, a laser source is provided through a laser 1, and a monochromatic CCD camera 15 collects a first shearing speckle interference image before deformation; namely, the two shear object light waves after the first object light wave passes through the Wollaston shearing device 14 and is dislocated, the object 2 to be measured before deformation interferes with each other on the target surface of the monochromatic CCD camera 15 to form a first shear speckle interference image, and the light intensity is expressed as
I1(x,y)＝[u11(x,y)+u12(x+△x,y)]·[u11(x,y)+u12(x+△x,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 the other 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 +. DELTA.x, y) complex conjugation, wherein the DELTA.x is the object plane shearing quantity of the object 2 to be measured along the x direction after passing through the Wollaston shearing device 14.
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 spatial frequency spectrum of the acquired first shearing speckle interference image before deformation is represented as
Wherein,
representing the spectrum of low frequency terms in the spatial spectrum with background light,
representing convolution operators in the frequency domain, C*(fx-f0,fy) And C (f)x+f0,fy) Is a spectrum of high frequency terms conjugated to each other, containing the x-directionPhase information of the clip; f. ofxIs the abscissa, f, of the spatial frequency spectrumyIs the ordinate, f, of the spatial frequency spectrum0Is the carrier frequency introduced by the aperture stop.
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; specifically, the cutoff frequency is selected, the filter window is set to extract the high frequency term containing the phase information, and the set value is used as (f)00) centered on the cut-off frequency fr(fr<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.
The fourth step: performing phase extraction on the high-frequency term of the acquired first shearing speckle interference image before deformation to obtain phase information containing deformation and strain information of the first shearing speckle interference image before deformation, wherein the phase information is 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 the other shear object wave after the dislocation of the first object wave,
is u12Complex conjugation of (x +. DELTA.x, y).
The fifth step: the loading device loads deformation on the measured object 2, and phase information, specifically phi, 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 step1a(x+△x,y)。
And a sixth step: subtracting phase information of the first shearing speckle interference image before and after the measured object 2 is deformed in real time to obtain a 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, phi1a(x + delta x, y) is phase information of the deformed first shearing speckle interference image containing deformation and strain information,
the first shearing speckle interference image before deformation contains phase information of deformation and strain information.
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;
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 phase information of the deformed and strained information is contained in the deformed second shearing speckle interference imageIn the form of a capsule, the particles,
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.
Eighth step: because the phase difference distribution images obtained by the formulas (4) and (5) contain a large amount of random noise, subsequent deformation and strain calculation can be influenced, a proper filtering algorithm is selected for 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 the phase difference distribution images after filtering are subjected to unwrapping processing to obtain smooth and continuous phase distribution; the deformation and strain of the measured object 2 are obtained through the obtained smooth and continuous phase difference distribution calculation and can be expressed as
Wherein w is the out-of-plane deformation of the object 2 to be measured,
is the in-plane strain component of the object 2 to be measured,
respectively, the out-of-plane strain component of the measured object 2, delta x is the object plane shearing quantity of the measured object 2 along the x direction after passing through the Wollaston shearing device 14, and lambda is used by the systemThe wavelength of the laser light source, theta is the included angle between the system observation direction 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.
In the embodiments provided in the present application, other desired strain components can also be obtained by adjusting the viewing direction of the measurement system and the shearing direction of the wollaston shearing device.
It will be understood by those skilled 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 will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The meaning of "and/or" as used herein is intended to include both the individual components or both.
The term "connected" as used herein may mean either a direct connection between components or an indirect connection between components via other components.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and 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,
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 fr(fr＜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 phi1a(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, phi1a(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.
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