CN113587806A - High-precision speckle interference phase shift fringe dynamic measurement system and method - Google Patents

High-precision speckle interference phase shift fringe dynamic measurement system and method Download PDF

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CN113587806A
CN113587806A CN202110896224.5A CN202110896224A CN113587806A CN 113587806 A CN113587806 A CN 113587806A CN 202110896224 A CN202110896224 A CN 202110896224A CN 113587806 A CN113587806 A CN 113587806A
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phase
speckle
deformation
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camera
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吴�荣
刘燕德
周建民
蒋小刚
李斌
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East China Jiaotong University
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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
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02094—Speckle interferometers, i.e. for detecting changes in speckle pattern
    • G01B9/02095—Speckle interferometers, i.e. for detecting changes in speckle pattern detecting deformation from original shape
    • 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
    • G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
    • G01B9/0201—Interferometers characterised by controlling or generating intrinsic radiation properties using temporal phase variation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02015—Interferometers characterised by the beam path configuration
    • G01B9/02027—Two or more interferometric channels or interferometers
    • G01B9/02028—Two or more reference or object arms in one interferometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02015—Interferometers characterised by the beam path configuration
    • G01B9/02029—Combination with non-interferometric systems, i.e. for measuring the object
    • G01B9/0203—With imaging systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02083—Interferometers characterised by particular signal processing and presentation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02083—Interferometers characterised by particular signal processing and presentation
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Abstract

The invention relates to a high-precision speckle interference phase shift fringe dynamic measurement system and a method, comprising a laser which is used as a light source and emits laser; the piezoelectric ceramic can move and is provided with a reflector, and the reflector is used for reflecting laser and generating a phase-shift speckle pattern on the surface of an object; a camera for capturing an image; a michelson interferometer for generating interference fringes; the signal synchronization module is used for manufacturing a synchronization signal generation circuit; a computer for displaying the image captured by the camera and calculating an interference fringe pattern; the synchronous signal generating circuit can generate a square wave signal and a step signal, the rising edges of the square wave signal and the step signal are synchronous, the square wave signal is used for controlling image acquisition of a camera, and the step signal is used for controlling movement of the piezoelectric ceramic to generate a phase shift diagram; the step wave generates step voltage, the voltage difference value of each step is equal, and the displacement of the piezoelectric ceramic motion corresponding to the maximum voltage and the minimum voltage difference is equal to one wavelength of the light source of the laser.

Description

High-precision speckle interference phase shift fringe dynamic measurement system and method
Technical Field
The invention relates to the technical field of photoelectric detection, in particular to a high-precision speckle interference phase shift fringe dynamic measurement system and method.
Background
The laser speckle interferometry (ESPI) technology is widely applied to the precise measurement of the surface deformation of an object and the nondestructive detection of materials due to the advantages of high measurement precision, wide measurement area, simple light path, low requirement on environment and the like.
Laser speckle interferometers usually give measurement results in the form of an interference fringe phase pattern, and in order to improve the measurement accuracy of interference fringes, a time phase shift method is most widely used at present. The time phase shift method drives an optical lens by means of precise piezoelectric ceramics (PZT) so as to control the phase precision movement of laser, simultaneously uses a CCD camera to capture a phase shift pattern, and finally uses a computer to calculate and obtain an interference fringe phase diagram. However, in dynamic measurement applications, the obtained fringe pattern has an unstable phenomenon, that is, the fringes appear jitter, which brings errors to measurement and detection. Although the CCD camera can capture PZT phase shift images by software triggering and time delay, the uncontrollable time of software triggering and time delay can cause that the CCD cannot capture the specified phase shift images completely and accurately during the measurement process, which can cause inaccurate calculation of phase shift fringes and instability of the fringes, which greatly limits the application of laser speckle interference.
To solve this problem, the inventors have proposed a technique for fringe interference resistance. For example, chinese patent CN202022357977.2 discloses a high-precision high-stability electronic speckle interference real-time phase measurement system, which uses square waves to drive a camera to capture images, uses triangular waves to drive PZT to move, and uses the interval period of the square waves to synchronously trigger PZT to move, so as to ensure that the camera captures phase shift images generated by PZT to move. However, through further research by the applicant, the method utilizes square wave interval periods to trigger PZT movement, which causes higher requirements on square wave signal generation circuits, the period of the square wave must be strictly kept unchanged in the measurement process, otherwise, triggered PZT signals are inaccurate, so that a camera cannot accurately capture corresponding phase shift images; in addition, the PZT phase shift diagram triggered by the triangular wave is acquired by using the same time interval, so that the requirement on the slope precision of the triangular wave is high, namely the slope of the triangular wave is required to be 1; additionally, camera exposure time inconsistencies will also cause capture errors in the phase shift speckle pattern. These limitations all lead to difficulties in the implementation of this approach.
Disclosure of Invention
The invention provides a high-precision speckle interference phase shift fringe dynamic measurement system and method, which can not only keep the precision of the traditional speckle interference phase shift method, but also stably and dynamically display a speckle interference phase image, thereby improving the measurement precision of speckle interference and solving the above-mentioned technical problems.
The technical purpose of the invention is realized by the following technical scheme:
a high-precision speckle interference phase shift fringe dynamic measurement system comprises:
a laser as a light source for emitting laser light;
the piezoelectric ceramic can move and is provided with a reflector, and the reflector is used for reflecting laser and generating a phase-shift speckle pattern on the surface of an object;
a camera for capturing an image;
a michelson interferometer for generating interference fringes;
the signal synchronization module is used for manufacturing a synchronization signal generation circuit;
a computer for displaying the image captured by the camera and calculating an interference fringe pattern;
the synchronous signal generation circuit can generate a square wave signal and a step signal, the rising edges of the square wave signal and the step signal are synchronous, the square wave signal is used for controlling image acquisition of the camera, and the step signal is used for controlling movement of the piezoelectric ceramic to generate a phase shift diagram;
the step wave can produce step voltage, the voltage difference value of each step is equal, and the displacement of the piezoelectric ceramic motion corresponding to the maximum voltage and the minimum voltage difference is equal to one wavelength of the light source of the laser.
Further, the step wave may generate 3-step voltage, 4-step voltage, 5-step voltage.
Further, when the step wave generates 4 steps of step voltage, the piezoelectric ceramics respectively generate 0, lambda/4, lambda/2 and 3 lambda/4 displacements, the corresponding phases are respectively 0, pi/2, pi and 3 pi/2, and a speckle pattern of the phase shift phase is generated on the surface of the object; the camera starts exposure under the control of the square wave, after exposure time t, the camera can accurately capture a corresponding speckle pattern, and the speckle pattern before deformation is represented as follows:
Figure BDA0003198023930000021
the speckle pattern after deformation is expressed as:
Figure BDA0003198023930000022
wherein R isi(x, y) is the speckle image collected before deformation, Di(x, y) is a speckle image acquired after deformation, and i is 0,1,2, 3; a (x, y) and B (x, y) are background and amplitude, respectively;
Figure BDA0003198023930000023
the speckle phase before deformation.
Further, the computer is provided with an independent calculation thread which is only responsible for calculating the phase difference image, the speckle patterns of the object before and after deformation are accurately captured by the camera, and the phase distribution before deformation can be obtained through calculation:
Figure BDA0003198023930000031
the phase distribution after deformation is:
Figure BDA0003198023930000032
subtracting the phase before deformation from the phase after deformation to obtain the phase difference caused by deformation
Figure BDA0003198023930000033
Namely interference fringes:
Figure BDA0003198023930000034
further, the computer may divide each speckle pattern captured by the camera into n equal parts, n being the core number of the computer CPU or GPU;
the figures before deformation are:
Figure BDA0003198023930000035
the deformed figure is;
Figure BDA0003198023930000036
wherein i is 1,2,3, 4; j is 1,2,3 … n; j represents the processor core number;
parallel computation in each core in the computer processor obtains an interference fringe:
Figure BDA0003198023930000037
and combining the images to obtain a complete interference fringe image:
Figure BDA0003198023930000038
a high-precision speckle interference phase shift fringe dynamic measurement method comprises the following steps:
s1: building a phase shift speckle interference system;
s2: manufacturing a synchronous signal generating circuit;
s3: the laser generates displacement through a piezoelectric ceramic reflector under the control of step waves, and a phase-shift speckle pattern is generated on the surface of an object;
s4: the camera accurately captures a speckle pattern under the control of synchronous square waves and exposure time;
s5: after the speckle patterns before and after deformation are captured, a new thread is opened up for calculating a phase diagram;
wherein, the interference system built in S1 includes:
a laser as a light source for emitting laser light;
the piezoelectric ceramic can move and is provided with a reflector, and the reflector is used for reflecting laser and generating a phase-shift speckle pattern on the surface of an object;
a camera for capturing an image;
a michelson interferometer for generating interference fringes;
the signal synchronization module is used for manufacturing a synchronization signal generation circuit;
a computer for displaying the image captured by the camera and calculating an interference fringe pattern;
the synchronous signal generation circuit can generate a square wave signal and a step signal, the rising edges of the square wave signal and the step signal are synchronous, the square wave signal is used for controlling image acquisition of the camera, and the step signal is used for controlling movement of the piezoelectric ceramic to generate a phase shift diagram;
the step wave can produce step voltage, the voltage difference value of each step is equal, and the displacement of the piezoelectric ceramic motion corresponding to the maximum voltage and the minimum voltage difference is equal to one wavelength of the light source of the laser.
Further, the step wave may generate 3-step voltage, 4-step voltage, 5-step voltage.
Further, in S4, when the step wave generates 4 steps of step voltages, the piezoelectric ceramics generate displacements of 0, λ/4, λ/2, and 3 λ/4, respectively, and the corresponding phases are 0, pi/2, pi, and 3 pi/2, respectively, so as to generate a speckle pattern of the phase shift phase on the surface of the object;
in S5, the camera starts exposure under the control of the square wave, and after an exposure time t elapses, the camera can accurately capture a corresponding speckle pattern, where the speckle pattern before deformation is represented as:
Figure BDA0003198023930000041
the speckle pattern after deformation is expressed as:
Figure BDA0003198023930000042
wherein R isi(x, y) is the speckle image collected before deformation, Di(x, y) is a speckle image acquired after deformation, and i is 0,1,2, 3; a (x, y) and B (x, y) are background and amplitude, respectively;
Figure BDA0003198023930000043
the speckle phase before deformation.
Further, in S5, the computer has an independent calculation thread only responsible for calculating the phase difference image, the speckle patterns before and after the object deformation are accurately captured by the camera, and the phase distribution before the deformation is calculated as:
Figure BDA0003198023930000044
the phase distribution after deformation is:
Figure BDA0003198023930000045
subtracting the phase before deformation from the phase after deformation to obtain the phase difference caused by deformation
Figure BDA0003198023930000051
Namely interference fringes:
Figure BDA0003198023930000052
further, in S5, the computer may divide each speckle pattern captured by the camera into n equal parts, where n is the core number of the computer CPU or GPU;
the figures before deformation are:
Figure BDA0003198023930000053
the deformed figure is;
Figure BDA0003198023930000054
wherein i is 1,2,3, 4; j is 1,2,3 … n; j represents the processor core number;
parallel computation in each core in the computer processor obtains an interference fringe:
Figure BDA0003198023930000055
and combining the images to obtain a complete interference fringe image:
Figure BDA0003198023930000056
the invention has the beneficial effects that:
1. compared with the traditional PZT (piezoelectric ceramic) control mode of triangular wave, sine wave or software time delay, the mode of synchronously controlling the PZT and the camera by the step wave and the square wave can accurately and quickly capture the required speckle phase diagram, thereby completing the accurate calculation of the interference fringe diagram. The method has low requirement on the circuit, does not need to strictly control time synchronization, and can realize the required target only by synchronizing the rising edge of the square wave and the rising edge of the step wave.
2. The independently opened interference fringe pattern calculation thread can effectively avoid the problem that the camera image acquisition cannot be synchronous with PZT due to large fringe pattern calculation amount, and further ensure that an accurate and stable interference fringe pattern is obtained.
3. Compared with the existing fringe pattern single-core calculation mode, the method provided adopts multi-core parallel calculation in the fringe pattern calculation process, can improve the calculation efficiency of the interference fringe pattern by n times (n is the core number of a computer) compared with the single-core calculation method, and further improves the dynamic display speed of the fringe to a greater extent.
4. The invention reduces the requirement of measuring vibration isolation and improves the reliability of detection.
Drawings
FIG. 1 is a schematic diagram of a phase shift speckle pattern accurate control and capture implementation, using a 4-step phase shift method as an example;
FIG. 2 is a schematic diagram of a high-precision speckle interference phase shift fringe dynamic measurement system;
FIG. 3 is a schematic diagram of the respective operations of a computer phase shift image acquisition thread and a phase difference fringe pattern calculation display thread in the present invention;
FIG. 4 is a high precision speckle interference phase shift fringe dynamic timing image in accordance with a preferred embodiment of the present invention;
FIG. 5 is a flow chart of the steps of a high-precision speckle interference phase shift fringe dynamic measurement method.
Detailed Description
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
The invention provides a high-precision speckle interference phase shift fringe dynamic measurement system, which comprises:
a laser as a light source for emitting laser light;
the piezoelectric ceramic can move and is provided with a reflector, and the reflector is used for reflecting laser and generating a phase-shift speckle pattern on the surface of an object;
a camera for capturing an image;
a michelson interferometer for generating interference fringes;
the signal synchronization module is used for manufacturing a synchronization signal generation circuit;
a computer for displaying the image captured by the camera and calculating an interference fringe pattern;
the synchronous signal generating circuit can generate a square wave signal and a step signal, the rising edges of the square wave signal and the step signal are synchronous, the square wave signal is used for controlling image acquisition of a camera, and the step signal is used for controlling movement of the piezoelectric ceramic to generate a phase shift diagram;
the step wave can generate step voltage, the voltage difference value of each step is equal, and the displacement of the piezoelectric ceramic motion corresponding to the maximum voltage and the minimum voltage difference is equal to one wavelength of a light source of the laser.
The method is used for the hardware synchronous driving mode and the exposure time of the camera, so that the speckle pattern shot by the camera each time can be ensured to accurately capture the required phase diagram, and the phase of the current position is accurately calculated through a multi-step phase shift algorithm.
Optionally, the step wave may generate a 3-step voltage, a 4-step voltage, and a 5-step voltage. For the commonly used 3-step, 4-step and 5-step phase shift methods, step waves respectively generate 3-step, 4-step and 5-step voltages, the voltage difference value of each step is equal, and the movement displacement of the piezoelectric ceramics corresponding to the maximum voltage and the minimum voltage difference is required to be equal to one wavelength of the used laser light source. It should be noted that the following description uses a 4-step phase shift method as an example, and the 3-step and 5-step phase shift methods are similar.
Optionally, when the step wave generates 4 steps of step voltages, the piezoelectric ceramics generate displacements of 0, λ/4, λ/2 and 3 λ/4 respectively, the corresponding phases are 0, pi/2, pi and 3 pi/2 respectively, and a speckle pattern of the phase shift phase is generated on the surface of the object; the camera starts exposure under the control of the square wave, after exposure time t, the camera can accurately capture a corresponding speckle pattern, and the speckle pattern before deformation is represented as follows:
Figure BDA0003198023930000071
the speckle pattern after deformation is expressed as:
Figure BDA0003198023930000072
wherein, (x, y) is the spatial pixel coordinates of the image; ri(x, y) is the speckle image collected before deformation, Di(x, y) is a speckle image acquired after deformation, and i is 0,1,2, 3; a (x, y) and B (x, y) are background and amplitude, respectively;
Figure BDA0003198023930000073
the speckle phase before deformation.
The moving step wave for driving the piezoelectric ceramics and the square wave for controlling the camera to collect the images are synchronous signals, so that the required speckle phase image can be accurately and quickly captured, and the accurate calculation of the interference fringe image is further completed. The method has low requirement on the circuit, does not need to strictly control time synchronization, and can realize the required target only by synchronizing the rising edge of the square wave and the rising edge of the step wave.
Optionally, the computer has an independent calculation thread only responsible for calculating the phase difference image, the speckle patterns before and after the object deformation are accurately captured by the camera, and the phase distribution before the deformation is obtained by calculation as follows:
Figure BDA0003198023930000081
the phase distribution after deformation is:
Figure BDA0003198023930000082
subtracting the phase before deformation from the phase after deformation to obtain the phase difference caused by deformation
Figure BDA0003198023930000083
Namely interference fringes:
Figure BDA0003198023930000084
an independent interference fringe pattern calculation thread is opened up, the problem that camera image acquisition cannot be synchronized with PZT due to large fringe pattern calculation amount can be effectively avoided, and accurate and stable interference fringe patterns are further ensured to be obtained.
Optionally, the computer may divide each speckle pattern captured by the camera into n equal parts, where n is the core number of the CPU or GPU of the computer;
the figures before deformation are:
Figure BDA0003198023930000085
the deformed figure is;
Figure BDA0003198023930000086
wherein i is 1,2,3, 4; j is 1,2,3 … n; j represents the processor core number;
parallel computation in each core in the computer processor obtains an interference fringe:
Figure BDA0003198023930000087
and combining the images to obtain a complete interference fringe image:
Figure BDA0003198023930000088
by using multi-core parallel computation in the process of computing the fringe pattern, the computation efficiency of the interference fringe pattern can be improved by nearly n times (n is the core number of a computer) compared with a single-core computation method, and the dynamic display speed of the fringe is further improved to a greater extent.
The invention also provides a high-precision speckle interference phase shift fringe dynamic measurement method, which comprises the following steps:
s1: building a phase shift speckle interference system;
s2: manufacturing a synchronous signal generating circuit;
s3: the laser generates displacement through a piezoelectric ceramic reflector under the control of step waves, and a phase-shift speckle pattern is generated on the surface of an object;
s4: the camera accurately captures a speckle pattern under the control of synchronous square waves and exposure time;
s5: after the speckle patterns before and after deformation are captured, a new thread is opened up for calculating a phase diagram;
wherein, the interference system built in S1 includes:
a laser as a light source for emitting laser light;
the piezoelectric ceramic can move and is provided with a reflector, and the reflector is used for reflecting laser and generating a phase-shift speckle pattern on the surface of an object;
a camera for capturing an image;
a michelson interferometer for generating interference fringes;
the signal synchronization module is used for manufacturing a synchronization signal generation circuit;
a computer for displaying the image captured by the camera and calculating an interference fringe pattern;
the synchronous signal generating circuit can generate a square wave signal and a step signal, the rising edges of the square wave signal and the step signal are synchronous, the square wave signal is used for controlling image acquisition of a camera, and the step signal is used for controlling movement of the piezoelectric ceramic to generate a phase shift diagram;
the step wave can generate step voltage, the voltage difference value of each step is equal, and the displacement of the piezoelectric ceramic motion corresponding to the maximum voltage and the minimum voltage difference is equal to one wavelength of a light source of the laser.
Optionally, the step wave may generate a 3-step voltage, a 4-step voltage, and a 5-step voltage.
Optionally, in S4, when the step wave generates 4 steps of step voltages, the piezoelectric ceramic generates displacements of 0, λ/4, λ/2, and 3 λ/4, respectively, and the corresponding phases are 0, pi/2, pi, and 3 pi/2, respectively, so as to generate a speckle pattern of the phase shift phase on the surface of the object;
in S5, the camera starts exposure under the control of the square wave, and after an exposure time t elapses, the camera can accurately capture a corresponding speckle pattern, where the speckle pattern before deformation is represented as:
Figure BDA0003198023930000091
the speckle pattern after deformation is expressed as:
Figure BDA0003198023930000092
wherein R isi(x, y) is the speckle image collected before deformation, Di(x, y) is a speckle image acquired after deformation, and i is 0,1,2, 3; a (x, y) and B (x, y) are background and amplitude, respectively;
Figure BDA0003198023930000093
to becomeSpeckle phase before formation.
Optionally, in S5, the computer has an independent calculation thread only responsible for calculating the phase difference image, the speckle patterns before and after the object deformation are accurately captured by the camera, and the phase distribution before the deformation is calculated as:
Figure BDA0003198023930000101
the phase distribution after deformation is:
Figure BDA0003198023930000102
subtracting the phase before deformation from the phase after deformation to obtain the phase difference caused by deformation
Figure BDA0003198023930000103
Namely interference fringes:
Figure BDA0003198023930000104
optionally, in S5, the computer may divide each speckle pattern captured by the camera into n equal parts, where n is the core number of the CPU or GPU of the computer;
the figures before deformation are:
Figure BDA0003198023930000105
the deformed figure is;
Figure BDA0003198023930000106
wherein i is 1,2,3, 4; j is 1,2,3 … n; j represents the processor core number;
parallel computation in each core in the computer processor obtains an interference fringe:
Figure BDA0003198023930000107
and combining the images to obtain a complete interference fringe image:
Figure BDA0003198023930000108
in S4, after the speckle patterns before and after deformation are captured, a new thread is created for calculating the phase map, and all the speckle patterns are divided into n blocks, where n is the core number of the computer. The calculation process refers to the above formula, then to improve the dynamic display speed of the phase diagram, phase calculation is performed on each image, each image is allocated to the core of the CPU or GPU for parallel calculation, and then the phase distribution before deformation is:
Figure BDA0003198023930000109
the phase distribution after deformation is:
Figure BDA00031980239300001010
the phase difference map, i.e. the interference fringe map, caused by the distortion can be determined in each processor core
Figure BDA00031980239300001011
Under the condition that the interference fringes do not interfere with each other, calculation is rapidly completed, and finally, the interference fringe images are combined and displayed.
In the second deformation state, the camera only needs to acquire one speckle image D5 in the current state, and obtain the phase difference fringe pattern in the deformation state by the same parallel calculation method instead of the image D1. Similarly, in the next deformation state, only one speckle pattern in the current state needs to be updated, and the three speckle patterns acquired at the latest moment are used as the four-step phase shift pattern of the deformation state to participate in calculation, so that the phase difference fringe pattern of the deformation state is quickly obtained. The step is repeated continuously, the display speed of the interference fringe pattern can be increased, the display speed of the interference fringe pattern is related to the number of cores of a computer, the calculation time of the interference fringe pattern of a complete image needs about 100ms, namely, the phase pattern display can only reach 10fps, for a multi-core parallel calculation algorithm (the number of cores of the computer is 8 in the embodiment), the provided method can improve the calculation speed by 7-8 times, namely, the display frame rate can reach 70-80fps, and the high-precision, quick and stable measurement of the speckle interference fringe pattern is really realized (the actually measured fringe pattern is shown in fig. 4).
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.

Claims (10)

1. A high-precision speckle interference phase shift fringe dynamic measurement system is characterized by comprising:
a laser as a light source for emitting laser light;
the piezoelectric ceramic can move and is provided with a reflector, and the reflector is used for reflecting laser and generating a phase-shift speckle pattern on the surface of an object;
a camera for capturing an image;
a michelson interferometer for generating interference fringes;
the signal synchronization module is used for manufacturing a synchronization signal generation circuit;
a computer for displaying the image captured by the camera and calculating an interference fringe pattern;
the synchronous signal generation circuit can generate a square wave signal and a step signal, the rising edges of the square wave signal and the step signal are synchronous, the square wave signal is used for controlling image acquisition of the camera, and the step signal is used for controlling movement of the piezoelectric ceramic to generate a phase shift diagram;
the step wave can produce step voltage, the voltage difference value of each step is equal, and the displacement of the piezoelectric ceramic motion corresponding to the maximum voltage and the minimum voltage difference is equal to one wavelength of the light source of the laser.
2. The system according to claim 1, wherein the speckle-interference phase-shift fringe dynamic measurement system comprises:
the step wave can generate 3-step voltage, 4-step voltage and 5-step voltage.
3. The system according to claim 2, wherein the speckle-interference phase-shift fringe dynamic measurement system comprises:
when the step wave generates 4 steps of step voltage, the piezoelectric ceramics respectively generate 0, lambda/4, lambda/2 and 3 lambda/4 displacement, the corresponding phases are respectively 0, pi/2, pi and 3 pi/2, and a speckle pattern of the phase shift phase is generated on the surface of an object; the camera starts exposure under the control of the square wave, after exposure time t, the camera can accurately capture a corresponding speckle pattern, and the speckle pattern before deformation is represented as follows:
Figure FDA0003198023920000011
the speckle pattern after deformation is expressed as:
Figure FDA0003198023920000012
wherein R isi(x, y) is the speckle image collected before deformation, Di(x, y) is a speckle image acquired after deformation, and i is 0,1,2, 3; a (x, y) and B (x, y) are background and amplitude, respectively;
Figure FDA0003198023920000021
the speckle phase before deformation.
4. The system according to claim 3, wherein the speckle-interference dynamic phase-shift fringe measurement system comprises:
the computer is provided with an independent calculation thread which is only responsible for calculating the phase difference image, the speckle patterns of the object before and after deformation are accurately captured by the camera, and the phase distribution before deformation can be obtained through calculation:
Figure FDA0003198023920000022
the phase distribution after deformation is:
Figure FDA0003198023920000023
subtracting the phase before deformation from the phase after deformation to obtain the phase difference caused by deformation
Figure FDA0003198023920000024
Namely interference fringes:
Figure FDA0003198023920000025
5. the system according to claim 4, wherein the speckle-interference phase-shift fringe dynamic measurement system comprises:
the computer can divide each speckle pattern captured by the camera into n equal parts, wherein n is the core number of a CPU or a GPU of the computer;
the figures before deformation are:
Figure FDA0003198023920000026
the deformed figure is;
Figure FDA0003198023920000027
wherein i is 1,2,3, 4; j is 1,2,3 … n; j represents the processor core number;
parallel computation in each core in the computer processor obtains an interference fringe:
Figure FDA0003198023920000028
and combining the images to obtain a complete interference fringe image:
Figure FDA0003198023920000029
6. a high-precision speckle interference phase shift fringe dynamic measurement method is characterized by comprising the following steps:
s1: building a phase shift speckle interference system;
s2: manufacturing a synchronous signal generating circuit;
s3: the laser generates displacement through a piezoelectric ceramic reflector under the control of step waves, and a phase-shift speckle pattern is generated on the surface of an object;
s4: the camera accurately captures a speckle pattern under the control of synchronous square waves and exposure time;
s5: after the speckle patterns before and after deformation are captured, a new thread is opened up for calculating a phase diagram;
wherein, the interference system built in S1 includes:
a laser as a light source for emitting laser light;
the piezoelectric ceramic can move and is provided with a reflector, and the reflector is used for reflecting laser and generating a phase-shift speckle pattern on the surface of an object;
a camera for capturing an image;
a michelson interferometer for generating interference fringes;
the signal synchronization module is used for manufacturing a synchronization signal generation circuit;
a computer for displaying the image captured by the camera and calculating an interference fringe pattern;
the synchronous signal generation circuit can generate a square wave signal and a step signal, the rising edges of the square wave signal and the step signal are synchronous, the square wave signal is used for controlling image acquisition of the camera, and the step signal is used for controlling movement of the piezoelectric ceramic to generate a phase shift diagram;
the step wave can produce step voltage, the voltage difference value of each step is equal, and the displacement of the piezoelectric ceramic motion corresponding to the maximum voltage and the minimum voltage difference is equal to one wavelength of the light source of the laser.
7. The method according to claim 6, wherein the speckle-interference phase-shift fringe dynamic measurement method comprises the following steps:
the step wave can generate 3-step voltage, 4-step voltage and 5-step voltage.
8. The method according to claim 7, wherein the speckle-interference phase-shift fringe dynamic measurement method comprises the following steps:
in S4, when the step wave generates 4 steps of step voltage, the piezoelectric ceramics generate displacements of 0, lambda/4, lambda/2 and 3 lambda/4 respectively, the corresponding phases are 0, pi/2, pi and 3 pi/2 respectively, and a speckle pattern of the phase shift phase is generated on the surface of the object;
in S5, the camera starts exposure under the control of the square wave, and after an exposure time t elapses, the camera can accurately capture a corresponding speckle pattern, where the speckle pattern before deformation is represented as:
Figure FDA0003198023920000031
the speckle pattern after deformation is expressed as:
Figure FDA0003198023920000041
wherein R isi(x, y) is the speckle image collected before deformation, Di(x, y) is a speckle image acquired after deformation, and i is 0,1,2, 3; a (x, y) and B (x, y) are background and amplitude, respectively;
Figure FDA0003198023920000042
the speckle phase before deformation.
9. The method according to claim 8, wherein the speckle-interference phase-shift fringe dynamic measurement method comprises the following steps:
in S5, the computer has an independent calculation thread only responsible for calculating the phase difference image, the speckle patterns before and after the object deformation are accurately captured by the camera, and the phase distribution before the deformation is calculated as:
Figure FDA0003198023920000043
the phase distribution after deformation is:
Figure FDA0003198023920000044
subtracting the phase before deformation from the phase after deformation to obtain the phase difference caused by deformation
Figure FDA0003198023920000045
Namely interference fringes:
Figure FDA0003198023920000046
10. the method according to claim 9, wherein the speckle-interference phase-shift fringe dynamic measurement method comprises:
in S5, the computer may divide each speckle pattern captured by the camera into n equal parts, where n is the core number of the computer CPU or GPU;
the figures before deformation are:
Figure FDA0003198023920000047
the deformed figure is;
Figure FDA0003198023920000048
wherein i is 1,2,3, 4; j is 1,2,3 … n; j represents the processor core number;
parallel computation in each core in the computer processor obtains an interference fringe:
Figure FDA0003198023920000049
and combining the images to obtain a complete interference fringe image:
Figure FDA00031980239200000410
CN202110896224.5A 2021-08-05 2021-08-05 High-precision speckle interference phase shift fringe dynamic measurement system and method Pending CN113587806A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114485448A (en) * 2022-01-25 2022-05-13 上海大学 Self-adaptive speckle interferometry method and system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114485448A (en) * 2022-01-25 2022-05-13 上海大学 Self-adaptive speckle interferometry method and system
CN114485448B (en) * 2022-01-25 2022-11-15 上海大学 Self-adaptive speckle interferometry method and system
WO2023142628A1 (en) * 2022-01-25 2023-08-03 上海大学绍兴研究院 Adaptive speckle interferometry method and system

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