CN111578856B - High-vibration-resistance electronic speckle interference real-time phase measurement system and method - Google Patents

High-vibration-resistance electronic speckle interference real-time phase measurement system and method Download PDF

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CN111578856B
CN111578856B CN202010415402.3A CN202010415402A CN111578856B CN 111578856 B CN111578856 B CN 111578856B CN 202010415402 A CN202010415402 A CN 202010415402A CN 111578856 B CN111578856 B CN 111578856B
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CN111578856A (en
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刘斌
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Shanghai University of Engineering Science
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
    • G01B11/161—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by interferometric means
    • G01B11/162—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by interferometric means by speckle- or shearing interferometry

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Abstract

Provide a high vibration resistance electronA speckle interferometry real-time phase measurement system, comprising: a michelson interferometer comprising a phase-shifting mirror and a high-speed camera; the piezoelectric ceramic is used for moving the phase shift mirror back and forth; a driver for driving the piezoelectric ceramic; the controller is respectively connected with the driver and the high-speed camera, the high-speed camera collects A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of the rising section of the sinusoidal voltage signal by a period t, and corresponding light intensity distribution I is obtainedA、IB、IC、IDThe displacement of the phase shift mirror is 3 lambda/8 in the 4t time, and lambda is the wavelength of interference light; and a processor for converting the IA、IB、IC、IDAnd n equal divisions are carried out, the n equal divisions of the sub-images are subjected to multi-thread parallel calculation to obtain n sub-phase diagrams, and the n sub-phase diagrams are spliced to obtain the real-time phase representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object.

Description

High-vibration-resistance electronic speckle interference real-time phase measurement system and method
Technical Field
The invention relates to a high-vibration-resistance electronic speckle interference real-time phase measurement system and method, belonging to the field of photoelectric detection.
Background
Electronic Speckle interference (ESPI) is a precision optical measurement technology, has the advantages of rapid, full-field, large-area measurement and the like, and is widely applied to precision displacement measurement and nondestructive inspection in the fields of aerospace, national defense and military industry, ship electronics, automobiles and the like. The application of the phase shift technology greatly improves the image quality of speckle interferograms, and the measurement precision of electronic speckle interference is improved from micron level to nanometer level, so that the technology is gradually developed into a reliable high-precision optical measurement means.
When the existing electronic speckle interference system carries out displacement test or nondestructive inspection on an actual engineering field, the phase diagram quality and the phase information accuracy are not ideal, so that the precision measurement of displacement or displacement derivative can not be carried out. The time phase shift method requires that the measurement system and the object to be measured should be kept as still as possible during the process of acquiring a plurality of speckle images with fixed phase difference. The 'static' state can be barely met on an optical laboratory vibration isolation platform, but is extremely difficult to realize on the actual engineering site.
For example, chinese patent 201210086926.8 discloses a real-time phase shifting method for electronic speckle interference with high signal-to-noise ratio, which uses a piezoelectric phase shifter to generate multi-step phase shifts, a camera synchronously acquires a plurality of phase-shifted speckle images, and calculates phase diagrams of speckle interference fringes through special image acquisition sequence design and fast algorithm, wherein the phase-shifted speckle diagrams include phase information representing deformation of an object at the current time, and can be demodulated through phase. The method can complete the calculation and display from the original image acquisition to the phase shift image within 100-.
For example, chinese patent 201510556415.1 discloses a fast processing method for increasing the real-time phase shift frame rate of laser interference fringes. The method utilizes a piezoelectric phase shifter to generate four-step phase shift, a camera synchronously acquires a plurality of speckle interference images, the loaded interference images are subjected to special partition processing, a parallel computing method is used for four-step phase shift and mean value filtering computation, and then a phase-phase diagram of interference fringes is solved. However, this method uses the step control piezoelectric phase shifter interval pi/2, the display frame rate is 10 frames per second, and the measurement needs to be performed in a vibration isolation environment, otherwise it will be interfered by the environmental vibration.
That is, the existing electronic speckle interference systems generally adopt a step-by-step piezoelectric ceramic phase shift calculation method, which greatly limits the dynamic response of piezoelectric ceramic and the image acquisition frame rate of a camera, and requires at least 100ms to complete one phase measurement. During the measurement period, the phase difference deviation of the collected speckle images can be caused by environmental vibration and air disturbance, so that the phase calculation result is inaccurate, the phase image quality is poor, the precise measurement cannot be realized, and the vibration resistance is not required to be improved, and the real-time phase precise measurement and the real-time phase display are not required.
In view of the above, the present invention is directed to a high vibration resistance electronic speckle interferometry real-time phase measurement system and method to solve one or more of the above technical problems.
Disclosure of Invention
In order to solve one or more technical problems in the prior art, according to an aspect of the present invention, a high vibration resistance electronic speckle interference real-time phase measurement system is provided, which can significantly reduce the influence of air disturbance and environmental vibration, and can realize fast calculation and real-time display of a phase image, thereby dynamically measuring a phase in real time on an engineering site, and further realizing high-precision nondestructive inspection and other works. This high anti vibration nature electron speckle interference real-time phase measurement system includes:
a michelson interferometer comprising a phase-shifting mirror and a high-speed camera;
the piezoelectric ceramic is used for moving the phase shift mirror back and forth;
a driver for driving the piezoelectric ceramic;
the controller is respectively connected with the driver and the high-speed camera and used for sending out a first signal and a second signal which are synchronous, the first signal is used for controlling the high-speed camera to adopt pictures, and the second signal is a sinusoidal voltage signal and is used for driving the piezoelectric ceramics; the high-speed camera collects A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of the rising segment of the sinusoidal voltage signal by the period t to obtain corresponding light intensity distribution IA、IB、IC、IDThe displacement of the phase shift mirror is 3 lambda/8 in the 4t time, and lambda is the wavelength of interference light; and
a processor for converting the IA、IB、IC、IDAnd n equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through multi-thread parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object.
According to another aspect of the invention, the high vibration resistance electronic speckle interference real-time phase measurement system further comprises a display unit for displaying the phase value of the measured object in real time, wherein 4T is less than the period T of air disturbance or environmental vibration.
According to yet another aspect of the invention, the 4T is less than T/4, T/8, T/10, T/20 or T/30.
According to yet another aspect of the invention, IA、IB、IC、IDFor phase calculation, the phase difference between two is pi/2, which is expressed as follows:
Figure BDA0002494793390000031
Figure BDA0002494793390000032
Figure BDA0002494793390000033
Figure BDA0002494793390000034
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure BDA0002494793390000035
are random phase values of the speckle pattern.
According to still another aspect of the invention, the four speckle images comprise two or more sets of the four speckle images captured by a high speed camera, the two or more sets of the four speckle images forming a sequence { [ I ]A0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi]I is a natural number;
[ I ] of the first set of four speckle imagesA0，IB0，IC0，ID0]For calculating the initial random phase of the object to be measured
Figure BDA0002494793390000036
Of the ith group of four speckle imagesAi，IBi，ICi，IDi]For calculating phase corresponding to deformation of object to be measured
Figure BDA00024947933900000316
i is a natural number,
Figure BDA0002494793390000037
Figure BDA0002494793390000038
the processor is used for pairing
Figure BDA0002494793390000039
And
Figure BDA00024947933900000310
mean value filtering is carried out to eliminate noise, and the mean value filtering and the noise elimination are respectively obtained
Figure BDA00024947933900000311
And
Figure BDA00024947933900000312
the phase difference of the measured object caused by deformation at each moment can be obtained
Figure BDA00024947933900000313
The display unit is also used for displaying the phase difference in real time.
According to another aspect of the invention, a real-time out-of-plane displacement measurement system is further provided, which comprises the high vibration resistance electronic speckle interferometry real-time phase measurement system, wherein the processor is used for calculating out-of-plane displacement of a measured object
Figure BDA00024947933900000314
According to yet another aspect of the invention, the processor is configured to calculate an out-of-plane displacement derivative
Figure BDA00024947933900000315
Where is the shear number.
According to another aspect of the present invention, there is provided a high vibration resistance electronic speckle interferometry real-time phase measurement method, comprising the following steps:
the controller sends out a first signal and a second signal which are synchronous;
controlling a high-speed camera to pick up images according to the first signal, driving piezoelectric ceramics to move the phase shift mirror back and forth according to the second signal,the second signal is a sinusoidal voltage signal, wherein the high-speed camera collects A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of the rising segment of the sinusoidal voltage signal by the period t, and obtains the corresponding light intensity distribution IA、IB、IC、IDThe displacement of the phase shift mirror is 3 lambda/8 in the 4t time, and lambda is the wavelength of interference light;
subjecting the said IA、IB、IC、IDAnd n equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object.
According to another aspect of the invention, the phase value of the measured object is displayed in real time, wherein 4T is less than the period T of air disturbance or environmental vibration; preferably, the 4T is less than T/4, T/8, T/10, T/20 or T/30.
According to yet another aspect of the invention, IA、IB、IC、IDFor phase calculation, the phase difference between two is pi/2, which is expressed as follows:
Figure BDA0002494793390000041
Figure BDA0002494793390000042
Figure BDA0002494793390000043
Figure BDA0002494793390000044
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure BDA0002494793390000045
are random phase values of the speckle pattern.
According to still another aspect of the invention, the four speckle images comprise two or more sets of the four speckle images captured by a high speed camera, the two or more sets of the four speckle images forming a sequence { [ I ]A0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi]I is a natural number;
[ I ] of the first set of four speckle imagesA0，IB0，IC0，ID0]For calculating the initial random phase of the object to be measured
Figure BDA0002494793390000046
Of the ith group of four speckle imagesAi，IBi，ICi，IDi]For calculating phase corresponding to deformation of object to be measured
Figure BDA0002494793390000047
i is a natural number,
Figure BDA0002494793390000048
Figure BDA0002494793390000051
to pair
Figure BDA0002494793390000052
And
Figure BDA0002494793390000053
mean value filtering is carried out to eliminate noise, and the mean value filtering and the noise elimination are respectively obtained
Figure BDA0002494793390000054
And
Figure BDA0002494793390000055
the deformation of the measured object at each moment can be obtainedIs not equal to
Figure BDA0002494793390000056
And displaying the phase difference in real time.
According to another aspect of the present invention, there is also provided a high vibration resistance electronic speckle interferometry real-time out-of-plane displacement and/or out-of-plane displacement derivative measurement method, which is characterized by comprising the following steps:
the controller sends out a first signal and a second signal which are synchronous;
controlling a high-speed camera to acquire images according to the first signal, driving piezoelectric ceramics to move a phase shift mirror back and forth according to the second signal, wherein the second signal is a sinusoidal voltage signal, the high-speed camera acquires A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of a rising section of the sinusoidal voltage signal by a period t, and obtains corresponding light intensity distribution IA、IB、IC、IDThe displacement of the phase shift mirror is 3 lambda/8 in the 4t time, and lambda is the wavelength of interference light;
subjecting the said IA、IB、IC、IDN equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object;
calculating the phase difference of the measured object caused by deformation at each moment according to the real-time phase
Figure BDA0002494793390000057
And out of plane displacement
Figure BDA0002494793390000058
And/or out-of-plane displacement derivatives
Figure BDA0002494793390000059
Where is the shear number.
Compared with the prior art, the invention has one or more of the following technical effects:
firstly, the system can carry out high vibration resistance electronic speckle interference real-time phase measurement on an engineering site;
secondly, compared with the step control piezoelectric ceramics (phase shifter) in the prior art, the acquisition time of four phase shift graphs can be greatly shortened, for example, the acquisition time can reach 2.5ms and is even faster, which is less than the period (more than 10ms) of general air disturbance and environmental vibration, so that the system can obviously reduce the sensitivity of the air disturbance and the environmental vibration;
thirdly, the frequency of the camera trigger signal is several times or more than ten times of the PZT phase shift driving signal, and the PZT phase shift driving signal is a sinusoidal signal (replacing the stepping control signal in the prior art), so that an ideal piezoelectric performance curve is easy to obtain, and the precise measurement of the real-time phase can be ensured;
fourthly, a fast algorithm of multi-thread parallel computing is adopted to realize fast real-time phase computing and phase image display.
Drawings
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments. The drawings relate to preferred embodiments of the invention and are described below:
FIG. 1 is a schematic diagram of a control signal (second signal) for driving a piezoelectric ceramic and collecting a plurality of sets of four speckle images according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of multi-threaded parallel computation of real-time phase shifts (corresponding to the sets of four speckle images in FIG. 1) in accordance with a preferred embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a high vibration resistance electronic speckle interferometry real-time phase measurement system according to a preferred embodiment of the invention;
FIG. 4 is a schematic diagram of the synchronous control between the high-speed camera pattern and the piezo-ceramic phase shifter according to a preferred embodiment of the present invention;
FIG. 5 is a schematic diagram showing real-time display (10 s time interval, 30s total) of the out-of-plane displacement derivative phase difference caused by thermal deformation in a project site by internal defects of a rubber-metal bonded structure according to a preferred embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. The examples are provided by way of explanation and are not meant as limitations. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. It is intended that the present invention encompass such modifications and variations.
In the following description of the drawings, like reference numerals designate identical or similar structures. Generally, only the differences between the individual embodiments will be described. Descriptions of parts or aspects in one embodiment can also be applied to corresponding parts or aspects in another embodiment, unless explicitly stated otherwise.
Example 1
Referring to fig. 1-3, fig. 1 is a schematic diagram of a control signal (second signal) for driving a piezoelectric ceramic according to a preferred embodiment of the present invention and acquiring a plurality of groups of four speckle images, fig. 2 is a schematic diagram of a multithread parallel computing real-time phase shift (corresponding to the plurality of groups of four speckle images in fig. 1) according to a preferred embodiment of the present invention, and fig. 3 is a schematic structural diagram of a high vibration resistance electronic speckle interferometry real-time phase measurement system according to a preferred embodiment of the present invention. This high anti vibration nature electron speckle interference real-time phase measurement system includes:
a michelson interferometer comprising a phase-shifting mirror and a high-speed camera;
the piezoelectric ceramic is used for moving the phase shift mirror back and forth;
a driver for driving the piezoelectric ceramic;
the controller is respectively connected with the driver and the high-speed camera and used for sending out a first signal and a second signal which are synchronous, the first signal is used for controlling the high-speed camera to adopt pictures, and the second signal is a sinusoidal voltage signal and is used for driving the piezoelectric ceramics; wherein the high speed camera is at the sinusoidal voltage signal with a period tA, B, C and D four speckle interference images are collected at equal time intervals in the middle 4t time of the ascending section to obtain corresponding light intensity distribution IA、IB、IC、IDThe displacement of the phase shift mirror is 3 lambda/8 in the 4t time, and lambda is the wavelength of interference light; and
a processor for converting the IA、IB、IC、IDAnd n equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through multi-thread parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object.
It should be noted that the michelson interferometer is a prior art, and typically includes a laser, a beam splitter and a shearing mirror. Referring to fig. 3, laser emitted by a laser device is incident on the surface of a test piece, reflected to a spectroscope, split by the spectroscope, transmitted to a phase shift mirror, reflected by the phase shift mirror and the spectroscope in sequence, incident to a high-speed camera, reflected by the shearing mirror, transmitted by the spectroscope, and incident to the high-speed camera.
It can be understood that the sinusoidal voltage signal synchronized with the first signal controls the piezoelectric ceramic to drive the phase shift mirror to move, so that high-frequency dynamic response can be realized, an ideal piezoelectric performance curve is easy to obtain, and the problem that high-frequency dynamic response cannot be realized due to stepping control in the prior art is solved.
Preferably, the high-speed camera of the present invention is, for example, a 1.6kHz high-speed camera, but the present invention is not limited thereto as long as the time for acquiring four speckle interference images can be realized to be less than the period of air disturbance or environmental vibration. For example, it may be a high speed camera greater than 1.6kHz, such as a 2kHz high speed camera, and so forth. The processor of the present invention may be various components having a data processing function, such as a CPU, a computer, and the like.
According to still another preferred embodiment of the present invention, referring to fig. 5, as an example, the phase difference of the internal defect of the rubber-metal bonded structure due to thermal deformation in the engineering site is shown in real time (10 s time interval therebetween, 30s in total).
According to another preferred embodiment of the present invention, the system for measuring the phase of the object in real time by using electronic speckle interferometry with high vibration resistance further comprises a display unit for displaying the phase value of the object to be measured in real time, wherein 4T is less than the period T of air disturbance or environmental vibration. It will be appreciated that this may reduce or prevent disturbances of the air or vibrations of the environment from interfering with the measurements.
According to a further preferred embodiment of the present invention said 4T is less than T/4, T/8, T/10, T/20 or T/30. Studies have shown that this can further prevent disturbances of the air and/or vibrations of the environment from disturbing the measurements, while at the same time the cost of the system can be relatively reduced.
According to still another preferred embodiment of the present invention, IA、IB、IC、IDFor phase calculation, the phase difference between two is pi/2, which is expressed as follows:
Figure BDA0002494793390000081
Figure BDA0002494793390000082
Figure BDA0002494793390000083
Figure BDA0002494793390000084
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure BDA0002494793390000085
are random phase values of the speckle pattern.
According to a further preferred embodiment of the invention, the four speckle images comprise images acquired by a high-speed cameraTwo or more groups of the four speckle images, the two or more groups of the four speckle images forming a sequence { [ I ]A0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi]I is a natural number;
[ I ] of the first set of four speckle imagesA0，IB0，IC0，ID0]For calculating the initial random phase of the object to be measured
Figure BDA0002494793390000086
Of the ith group of four speckle imagesAi，IBi，ICi，IDi]For calculating phase corresponding to deformation of object to be measured
Figure BDA0002494793390000087
i is a natural number,
Figure BDA0002494793390000088
Figure BDA0002494793390000089
the processor is used for pairing
Figure BDA0002494793390000091
And
Figure BDA0002494793390000092
mean value filtering is carried out to eliminate noise, and the mean value filtering and the noise elimination are respectively obtained
Figure BDA0002494793390000093
And
Figure BDA0002494793390000094
the phase difference of the measured object caused by deformation at each moment can be obtained
Figure BDA0002494793390000095
The display unit is also used for real-time displayThe phase difference.
According to another preferred embodiment of the present invention, there is further provided a real-time out-of-plane displacement measurement system, including the foregoing high vibration resistance electronic speckle interferometry real-time phase measurement system, wherein the processor is configured to calculate out-of-plane displacement of a measured object
Figure BDA0002494793390000096
In accordance with yet another preferred embodiment of the present invention the processor is operative to calculate an out-of-plane displacement derivative
Figure BDA0002494793390000097
Where is the shear number.
According to another preferred embodiment of the present invention, there is provided a high vibration resistance electronic speckle interferometry real-time phase measurement method, including the steps of:
the controller sends out a first signal and a second signal which are synchronous;
controlling a high-speed camera to acquire images according to the first signal, driving piezoelectric ceramics to move a phase shift mirror back and forth according to the second signal, wherein the second signal is a sinusoidal voltage signal, the high-speed camera acquires A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of a rising section of the sinusoidal voltage signal by a period t, and obtains corresponding light intensity distribution IA、IB、IC、IDThe displacement of the phase shift mirror is 3 lambda/8 in the 4t time, and lambda is the wavelength of interference light;
subjecting the said IA、IB、IC、IDAnd n equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object.
According to another preferred embodiment of the present invention, the phase value of the measured object is displayed in real time, wherein 4T is less than the period T of the air disturbance or the environmental vibration; preferably, the 4T is less than T/4, T/8, T/10, T/20 or T/30.
According to still another preferred embodiment of the present invention, referring to FIG. 1, IA、IB、IC、IDFor phase calculation, the phase difference between two is pi/2, which is expressed as follows:
Figure BDA0002494793390000098
Figure BDA0002494793390000099
Figure BDA00024947933900000910
Figure BDA0002494793390000101
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure BDA0002494793390000102
are random phase values of the speckle pattern.
According to another preferred embodiment of the present invention, the four speckle images include two or more groups of the four speckle images collected by a high-speed camera, and the two or more groups of the four speckle images form a sequence { [ I ]A0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi]I is a natural number;
[ I ] of the first set of four speckle imagesA0，IB0，IC0，ID0]For calculating the initial random phase of the object to be measured
Figure BDA0002494793390000103
Of the ith group of four speckle imagesAi，IBi，ICi，IDi]For calculating phase corresponding to deformation of object to be measured
Figure BDA0002494793390000104
i is a natural number,
Figure BDA0002494793390000105
Figure BDA0002494793390000106
to pair
Figure BDA0002494793390000107
And
Figure BDA0002494793390000108
mean value filtering is carried out to eliminate noise, and the mean value filtering and the noise elimination are respectively obtained
Figure BDA0002494793390000109
And
Figure BDA00024947933900001010
the phase difference of the measured object caused by deformation at each moment can be obtained
Figure BDA00024947933900001011
And displaying the phase difference in real time.
According to another preferred embodiment of the present invention, there is provided a high vibration resistance electronic speckle interferometry real-time out-of-plane displacement and/or out-of-plane displacement derivative measurement method, which is characterized by comprising the following steps:
the controller sends out a first signal and a second signal which are synchronous;
controlling a high-speed camera to acquire images according to the first signal, driving piezoelectric ceramics to move a phase shift mirror back and forth according to the second signal, wherein the second signal is a sinusoidal voltage signal, the high-speed camera acquires A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of a rising section of the sinusoidal voltage signal by a period t, and corresponding light intensity components are obtainedCloth IA、IB、IC、IDThe displacement of the phase shift mirror is 3 lambda/8 in the 4t time, and lambda is the wavelength of interference light;
subjecting the said IA、IB、IC、IDN equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object;
calculating the phase difference of the measured object caused by deformation at each moment according to the real-time phase
Figure BDA00024947933900001012
And out of plane displacement
Figure BDA00024947933900001013
And/or out-of-plane displacement derivatives
Figure BDA00024947933900001014
Where is the shear number.
According to another preferred embodiment of the present invention, there is provided a high vibration resistance electronic speckle interferometry real-time phase measurement method, including the steps of:
1) two groups of continuous voltage signals are synchronously sent out by a controller (the controller can comprise a signal generator) to respectively control the high-speed camera and the piezoelectric ceramics.
2) In the step 1), one path of signal of the signal generator is a square wave voltage signal and is used for triggering the high-speed camera to pick up the picture, the period of the square wave signal is t, namely the period of the sequence picking up the picture of the high-speed camera is t.
3) The other path of signal of the signal generator in step 1) is a sinusoidal voltage signal with a period of, for example, 16t (the present invention is not limited thereto, as long as the mapping requirement of step 4) can be achieved), and the voltage signal is amplified by a piezoelectric ceramic voltage amplifying circuit and then used for driving a piezoelectric ceramic (PZT) phase shift mirror in the michelson interference optical path to move, so that one beam of light in the interference optical path generates a given optical path difference.
4) The invention adopts a four-step time phase shift method for phase processing, referring to fig. 4, in the middle 4t time of the rising section of the sinusoidal voltage signal in the step 3), four speckle images [ I ] used for four-step phase shift calculation are collected at equal intervals tA，IB，IC，ID]。
5) And (3) modulating the peak value of the sinusoidal voltage signal to ensure that the displacement of the piezoelectric ceramic phase shift mirror is 3 lambda/8 in the middle 4t time of the rising section of the sinusoidal voltage signal in the step 4), so that the optical path difference of one beam of light in the Michelson interference optical path is 3 lambda/4. Research shows that the voltage in the middle part of the rising segment of the sine curve is approximately linearly changed along with time, and four speckle images [ I ] collected in the step 4)A，IB，IC，ID]The phase difference between two should be exactly pi/2, expressed as follows;
Figure BDA0002494793390000111
Figure BDA0002494793390000112
Figure BDA0002494793390000113
Figure BDA0002494793390000114
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure BDA00024947933900001210
are random phase values of the speckle pattern.
6) Speckle images [ I ] collected in the step 4)A，IB，IC，ID]Dividing n equally along the width direction (n depends on the number of cores of the selected computer processor), and sequentially dividing into: [ I ] ofA，IB，IC，ID]1、[IA，IB，IC，ID]2……[IA，IB，IC，ID]nThe image to be equally divided needs to keep a part of the overlapped area.
7) Respectively carrying out four-step phase shift calculation on the four sub-images in the n subareas obtained in the step 6) by using a formula (2), wherein the calculation of the n image subareas is completed on n cores of a computer processor in parallel, and the obtained phase is
Figure BDA0002494793390000121
Wherein the content of the first and second substances,
Figure BDA0002494793390000122
8) phase map of n sections calculated in step 7)
Figure BDA0002494793390000123
Splicing and reducing the n subarea phase diagrams into a complete phase diagram according to the reverse process of the step 6)
Figure BDA0002494793390000124
9) Continuously acquiring and storing the speckle images in the deformation process of the measured object in real time according to the step 4) { [ I ]A0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi](i＝0，1，2…)}。
10) According to the processing from step 6) to step 8), the phase corresponding to the deformation of the object can be calculated in each phase shift period (16t)
Figure BDA0002494793390000125
11) According to the initial phase calculated in step 10)
Figure BDA0002494793390000126
The phase change caused by the deformation of the object relative to the initial moment can be calculated
Figure BDA0002494793390000127
Then eliminating noise by mean value filtering, and obtaining the phase difference of the object caused by deformation at any moment (the period is 16t)
Figure BDA0002494793390000128
Figure BDA0002494793390000129
12) Continuously repeating the steps 4) to 11), synchronously performing phase calculation of each partition in the step 7) by adopting computer multithread parallel calculation, so that the fast real-time phase shift calculation and the phase display can be realized, and the period of the phase shift calculation and the display is 16 t.
It can be understood that the method utilizes the signal generator to synchronously control the sequence acquisition of the high-speed camera and the driving voltage of the high-frequency response piezoelectric ceramic phase shift generator, and then carries out phase processing by a four-step phase shift method based on a multithread parallel computing fast algorithm, and can realize electronic speckle interference dynamic phase measurement and real-time nondestructive flaw detection in an engineering field. Taking a high-speed digital camera with an image acquisition frame rate of 1.6kHz as an example, the acquisition time for completing the four phase shift images is only 2.5ms, and air disturbance and environmental vibration in the time interval can be basically ignored. Because the typical air turbulence and ambient vibration frequency is usually within 100Hz, the corresponding period is 10ms, which is much longer than the time required for completing the acquisition of four phase-shift maps by the method of the present invention. The period of phase measurement of the method is approximately the same as that of a PZT driving signal, when a high-speed digital camera with the frame rate of 1.6kHz is selected, the calculation and display time of four-step phase shift in each phase shift period is controlled within 7.5ms by multi-thread parallel calculation, the phase measurement and display period can be 10ms, and the high-vibration resistance electronic speckle interference real-time phase measurement and phase display are completed.
According to another preferred embodiment of the present invention, there is provided a high vibration resistance electronic speckle interference real-time phase measurement method, taking a rubber-metal bonding structure with internal prefabricated defects under thermal radiation loading for engineering field measurement as an example, including the following steps:
1) two groups of continuous voltage signals are synchronously sent out through a signal generator, a sequence chart of a high-speed camera and the driving voltage of a high-frequency response time phase shift system are respectively controlled, a piezoelectric ceramic phase shifter changes the optical path of one beam of light in a Michelson interferometer by driving a phase shift mirror to move back and forth, and a given phase difference is introduced;
2) one path of signal of the signal generator is a square wave voltage signal and is used for triggering the high-speed camera to acquire images, and the rising edge of the square wave signal is used for triggering the camera to acquire images. If a high-speed camera with a frame rate of 1.6kHz is selected, the period t of the square wave signal is 0.625ms, as shown in FIG. 4;
3) the other path of signal of the signal generator is a sinusoidal voltage signal (see fig. 4) with a period of 16t (namely 10ms), and the voltage signal is provided to a piezoelectric ceramic (PZT) in a michelson interference optical path to drive the phase shift mirror to move after being amplified by the PZT driver;
4) performing phase processing by adopting a four-step time phase shift method, and collecting A, B, C and D four speckle interference images [ I ] at equal time intervals in the middle 4t (2.5ms) of the rising section of the sinusoidal voltage signal in the step 3)A，IB，IC，ID]See fig. 4.
5) By modulating the peak value of the sinusoidal voltage, in the middle 4t (2.5ms) of the rising section of the sinusoidal voltage signal in step 4), the piezoelectric ceramic pushes the phase shift mirror to displace 3 λ/8 (a green laser is selected, and is 512nm), that is, the optical path difference of one light in the michelson interference optical path is 3 λ/4, as shown in fig. 4. Research shows that the change of the voltage in the middle of the rising section of the sine curve along with time is approximately linear, the phase difference between every two speckle images collected in the step 4) is exactly pi/2, and the expression is as follows;
Figure BDA0002494793390000141
Figure BDA0002494793390000142
Figure BDA0002494793390000143
Figure BDA0002494793390000144
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure BDA0002494793390000145
are random phase values of the speckle pattern.
6) In order to realize real-time phase processing and real-time phase display and improve the phase calculation speed, the computer with the i7 or 8-core processor is selected for use in the embodiment. Each group of speckle images [ I ] collected in the step 5)A，IB，IC，ID]The width direction is divided into 8 equal parts, which are sequentially divided into: [ I ] ofA，IB，IC，ID]1、[IA，IB，IC，ID]2……[IA，IB，IC，ID]8The halved image should preserve the overlapping area of 10 pixels.
7) Respectively carrying out four-step phase shift calculation on the four sub-graphs in the 8 subareas obtained in the step 6) by using the following formula to obtain respective phases
Figure BDA0002494793390000151
As shown in fig. 2.
Figure BDA0002494793390000159
8) The phase map of 8 subareas calculated in the step 7) is processed
Figure BDA0002494793390000152
Splicing and reducing into a complete phase diagram according to the reverse process of the step 6)
Figure BDA0002494793390000153
9) Continuously acquiring and storing the speckle images in the deformation process of the measured object in real time according to the step 5) { [ I ]A0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi](i＝0，1，2…)}。
10) Calculating the phase corresponding to the deformation of the object according to the processing from the step 6) to the step 8)
Figure BDA0002494793390000154
Figure BDA0002494793390000155
11) According to the initial phase calculated in step 10)
Figure BDA0002494793390000156
The phase change caused by the deformation of the object relative to the initial moment can be calculated
Figure BDA0002494793390000157
Then eliminating noise through mean value filtering, and obtaining the phase difference of the object caused by deformation at any moment
Figure BDA0002494793390000158
12) Continuously repeating the steps 5) to 11), synchronously calculating the phase of each subarea in the step 7) by adopting computer multithread parallel calculation, so that the rapid real-time phase shift calculation and phase display can be realized, wherein the phase shift calculation and display period is 10ms, namely the real-time phase shift calculation and display frame rate can reach 80-100 frames/second, which is far higher than the phase shift frame rate (less than 10 frames/second) of the existing electronic speckle interference system, and therefore, the real-time precision measurement and real-time nondestructive detection of the dynamic phase of the engineering site can be realized. Fig. 5 shows the real-time display of the phase difference of the rubber-metal bonding structure caused by thermal radiation loading, the time interval of two phase diagrams is 10s, it can be seen that the phase diagrams are stable, the image quality is high, and the method can be used for the real-time measurement and the nondestructive detection of the dynamic out-of-plane displacement derivative.
Compared with the prior art, the invention has one or more of the following technical effects:
firstly, the system can carry out high vibration resistance electronic speckle interference real-time phase measurement on an engineering site;
secondly, compared with the step control piezoelectric ceramics (phase shifter) in the prior art, the acquisition time of four phase shift graphs can be greatly shortened, for example, the acquisition time can reach 2.5ms and is even faster, which is less than the period (more than 10ms) of general air disturbance and environmental vibration, so that the system can obviously reduce the sensitivity of the air disturbance and the environmental vibration;
thirdly, the frequency of the camera trigger signal is several times or more than ten times of the PZT phase shift driving signal, and the PZT phase shift driving signal is a sinusoidal signal (replacing the stepping control signal in the prior art), so that an ideal piezoelectric performance curve is easy to obtain, and the precise measurement of the real-time phase can be ensured;
fourthly, a fast algorithm of multi-thread parallel computing is adopted to realize fast real-time phase computing and phase image display.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the present invention, and the features of the embodiments that do not violate each other may be combined with each other. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (13)

1. The utility model provides a real-time phase place measurement system of high anti vibration nature electronic speckle interference which characterized in that includes:
a michelson interferometer comprising a phase-shifting mirror and a high-speed camera;
the piezoelectric ceramic is used for moving the phase shift mirror back and forth;
a driver for driving the piezoelectric ceramic;
the controller is respectively connected with the driver and the high-speed camera and used for sending out a first signal and a second signal which are synchronous, the first signal is used for controlling the high-speed camera to adopt pictures, and the second signal is a sinusoidal voltage signal and is used for driving the piezoelectric ceramics; the high-speed camera collects A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of the rising segment of the sinusoidal voltage signal by the period t to obtain corresponding light intensity distribution IA、IB、IC、IDModulating the peak value of the sinusoidal voltage signal to enable the displacement of the phase shift mirror to be 3 lambda/8 within the 4t time, so that a beam of light in an interference light path generates a given optical path difference, wherein lambda is the wavelength of the interference light; and
a processor for converting the IA、IB、IC、IDAnd n equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through multi-thread parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object.
2. The system of claim 1, further comprising a display unit for displaying the phase value of the object to be measured in real time, wherein the 4T is less than the period T of the air disturbance or the environmental vibration.
3. The high vibration resistance electronic speckle interferometry real-time phase measurement system of claim 2, wherein 4T is less than T/4, T/8, T/10, T/20 or T/30.
4. The high vibration resistance electronic speckle interference chip of any one of claims 1-3A time phase measuring system, characterized in that IA、IB、IC、IDFor phase calculation, the phase difference between two is pi/2, which is expressed as follows:
Figure FDA0002759496290000011
Figure FDA0002759496290000021
Figure FDA0002759496290000022
Figure FDA0002759496290000023
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure FDA0002759496290000024
random phase values of the speckle pattern.
5. The system of claim 4, wherein the four speckle images comprise two or more sets of the four speckle images captured by a high speed camera, the two or more sets forming a sequence { [ I ] of the four speckle imagesA0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi]I is a natural number;
[ I ] of the first set of four speckle imagesA0，IB0，IC0，ID0]For calculating the initial random phase of the object to be measured
Figure FDA0002759496290000025
Of the ith group of four speckle imagesAi，IBi，ICi，IDi]For calculating phase corresponding to deformation of object to be measured
Figure FDA0002759496290000026
i is a natural number,
Figure FDA0002759496290000027
Figure FDA0002759496290000028
the processor is used for pairing
Figure FDA0002759496290000029
And
Figure FDA00027594962900000210
mean value filtering is carried out to eliminate noise, and the mean value filtering and the noise elimination are respectively obtained
Figure FDA00027594962900000211
And
Figure FDA00027594962900000212
the phase difference of the measured object caused by deformation at each moment can be obtained
Figure FDA00027594962900000213
The display unit is also used for displaying the phase difference in real time.
6. A real-time out-of-plane displacement measurement system comprising the high vibration resistance electronic speckle interferometry real-time phase measurement system of claim 5, wherein the processor is configured to calculate the out-of-plane displacement of the measured object
Figure FDA00027594962900000214
7. A real-time off-plane displacement measurement system according to claim 6, wherein the processor is configured to calculate an off-plane displacement derivative
Figure FDA00027594962900000215
Where is the shear number.
8. A high vibration resistance electronic speckle interference real-time phase measurement method is characterized by comprising the following steps:
the controller sends out a first signal and a second signal which are synchronous;
controlling a high-speed camera to acquire images according to the first signal, driving piezoelectric ceramics to move a phase shift mirror back and forth according to the second signal, wherein the second signal is a sinusoidal voltage signal, the high-speed camera acquires A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of a rising section of the sinusoidal voltage signal by a period t, and obtains corresponding light intensity distribution IA、IB、IC、IDModulating the peak value of the sinusoidal voltage signal to enable the displacement of the phase shift mirror to be 3 lambda/8 within the 4t time, so that a beam of light in an interference light path generates a given optical path difference, wherein lambda is the wavelength of the interference light;
subjecting the said IA、IB、IC、IDAnd n equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object.
9. The method according to claim 8, wherein the phase value of the object to be measured is displayed in real time, and the 4T is smaller than the period T of the air disturbance or the environmental vibration.
10. The method of claim 9, wherein the 4T is less than T/4, T/8, T/10, T/20 or T/30.
11. The method for high vibration resistance electronic speckle interferometry real-time phase measurement according to any of claims 8-10, wherein I isA、IB、IC、IDFor phase calculation, the phase difference between two is pi/2, which is expressed as follows:
Figure FDA0002759496290000031
Figure FDA0002759496290000032
Figure FDA0002759496290000033
Figure FDA0002759496290000034
wherein, I0Background light intensity of the speckle pattern, mu is amplitude of the modulated light intensity,
Figure FDA0002759496290000035
are random phase values of the speckle pattern.
12. The method of claim 11, wherein the four speckle images comprise two or more groups of the four speckle images captured by a high speed camera, the two or more groups forming a sequence { [ I ] of the four speckle imagesA0，IB0，IC0，ID0]；[IA1，IB1，IC1，ID1]…[IAi，IBi，ICi，IDi]I is a natural number;
[ I ] of the first set of four speckle imagesA0，IB0，IC0，ID0]For calculating the initial random phase of the object to be measured
Figure FDA0002759496290000041
Of the ith group of four speckle imagesAi，IBi，ICi，IDi]For calculating phase corresponding to deformation of object to be measured
Figure FDA0002759496290000042
i is a natural number,
Figure FDA0002759496290000043
Figure FDA0002759496290000044
to pair
Figure FDA0002759496290000045
And
Figure FDA0002759496290000046
mean value filtering is carried out to eliminate noise, and the mean value filtering and the noise elimination are respectively obtained
Figure FDA0002759496290000047
And
Figure FDA0002759496290000048
the phase difference of the measured object caused by deformation at each moment can be obtained
Figure FDA0002759496290000049
And displaying the phase difference in real time.
13. A high vibration resistance electronic speckle interference real-time out-of-plane displacement and/or out-of-plane displacement derivative measuring method is characterized by comprising the following steps:
the controller sends out a first signal and a second signal which are synchronous;
controlling a high-speed camera to acquire images according to the first signal, driving piezoelectric ceramics to move a phase shift mirror back and forth according to the second signal, wherein the second signal is a sinusoidal voltage signal, the high-speed camera acquires A, B, C four speckle interference images at four moments D at equal time intervals within the middle 4t time of a rising section of the sinusoidal voltage signal by a period t, and obtains corresponding light intensity distribution IA、IB、IC、IDModulating the peak value of the sinusoidal voltage signal to enable the displacement of the phase shift mirror to be 3 lambda/8 within the 4t time, so that a beam of light in an interference light path generates a given optical path difference, wherein lambda is the wavelength of the interference light;
subjecting the said IA、IB、IC、IDN equal divisions are carried out, partial overlapping areas of the equally divided sub-images are reserved, n sub-phase diagrams are obtained through parallel calculation of the n equal divided sub-images, and the n sub-phase diagrams are spliced to obtain real-time phases representing the out-of-plane displacement or the out-of-plane displacement derivative of the measured object;
calculating the phase difference of the measured object caused by deformation at each moment according to the real-time phase
Figure FDA00027594962900000410
And out of plane displacement
Figure FDA00027594962900000411
And/or out-of-plane displacement derivatives
Figure FDA00027594962900000412
Where is the shear number.
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