CN117147565A - Nondestructive testing device and method based on laser shearing speckle interference - Google Patents
Nondestructive testing device and method based on laser shearing speckle interference Download PDFInfo
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- CN117147565A CN117147565A CN202311174973.2A CN202311174973A CN117147565A CN 117147565 A CN117147565 A CN 117147565A CN 202311174973 A CN202311174973 A CN 202311174973A CN 117147565 A CN117147565 A CN 117147565A
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- 238000010008 shearing Methods 0.000 title claims abstract description 48
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000009659 non-destructive testing Methods 0.000 title claims abstract description 16
- 230000010363 phase shift Effects 0.000 claims abstract description 27
- 239000004973 liquid crystal related substance Substances 0.000 claims abstract description 26
- 238000003384 imaging method Methods 0.000 claims abstract description 21
- 230000010287 polarization Effects 0.000 claims description 7
- 230000005540 biological transmission Effects 0.000 claims description 4
- 230000001427 coherent effect Effects 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 2
- 230000007547 defect Effects 0.000 abstract description 11
- 238000005259 measurement Methods 0.000 abstract description 5
- 238000001514 detection method Methods 0.000 abstract 1
- 238000005516 engineering process Methods 0.000 description 14
- 238000006073 displacement reaction Methods 0.000 description 4
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- 238000003908 quality control method Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
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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
- G01B11/168—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of polarisation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
- G01N2021/8887—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges based on image processing techniques
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Abstract
The invention provides a nondestructive testing device and method based on laser shearing speckle interference. Comprising a shear phase shift module, an interference imaging module, a laser beam expansion module and a housing portion. The shearing phase shift module, the interference imaging module and the laser beam expanding module are fixed on the shell. The shear phase shift module comprises a Wollaston prism, a liquid crystal phase shifter, a polaroid, a circular shell, a rear shell and a sleeve. The interference imaging module comprises an imaging lens, a CCD camera and a computer control system. The laser beam expanding module comprises a 532nm laser and a laser beam expanding device. The detection method is that the measured object is shot before and after physical loading, the obtained picture is analyzed, and the deformation of the measured object is detected. The invention adopts an integrated structure to make the equipment smaller and more portable, and in general, the Wollaston prism structure is more stable. The shearing direction can be adjusted by rotating the prism while ensuring the measurement accuracy so as to more accurately detect defects of various shapes.
Description
Field of the art
The invention belongs to the field of laser nondestructive testing, and provides a nondestructive testing device and method based on laser shearing speckle interference.
(II) background art
With the rapid development of modern technology, high-performance materials are widely used in a plurality of industrial fields. However, these materials often suffer from minor defects. Over time, the external environment will gradually damage these defects, making them unable to continue to function properly, and thus causing irrecoverable losses. The non-destructive testing (NDT) is a multidisciplinary comprehensive testing technology which integrates knowledge in a plurality of fields, and can evaluate the internal and external defects or other relevant parameter characteristics of materials by using an advanced testing technology on the premise of not damaging or damaging an object to be tested, so that the NDT is widely applied to industrial practice.
The nondestructive testing technology is an application technology with low input cost and high return, with the continuous progress of modern technology and the appearance of different new materials and new technologies, most fields and scientific research institutions in industry attach great importance to the technology, and the technology is used on different products as much as possible, so that the nondestructive testing technology plays an indispensable role in product quality control, can also be used for checking running equipment, and can effectively avoid unnecessary losses and accidents.
Laser speckle non-destructive testing techniques originate from the development of optical interferometry. The interference technology utilizes the fluctuation property of light to study the optical phenomenon, and the principle is that two beams of coherent light are mutually overlapped to form interference fringes, and the information of an object to be measured is obtained by observing the change of the fringes. The laser speckle nondestructive testing technology is developed based on laser interference technology, and uses the speckle phenomenon generated by laser irradiation on the surface of an object to measure and analyze. The technology adopts the principle of shearing electronic speckle interference to measure the out-of-plane displacement derivative of an object. When a defect exists in the composite material part and is subjected to external load, the surface where the defect exists can generate partial deformation. The laser speckle technique shows these non-uniform deformations in the form of interference fringes and can accurately measure the size of the defect while precisely locating the position of the defect.
The Chinese patent publication No. CN108426528A of a laser speckle device and a measuring method for measuring the out-of-plane and in-plane displacement of an object can realize the simultaneous measurement of the in-plane displacement and the out-of-plane displacement of the object, but is only applicable to light-transmitting objects and cannot be used for measuring opaque objects. Chinese patent publication No. CN114018827A, which is a laser ultrasonic nondestructive testing device and method based on shearing speckle interference, has considerable effect, but can cause certain limitation on the application due to inconvenient operation and lack of real-time adjustment capability. The present invention employs an integrated structure that allows the device to be smaller and more portable and, in general, uses Wollaston prisms more pronounced fringes than those produced by the use of polarizers. The shearing direction can be adjusted by rotating the prism while ensuring the measurement accuracy so as to more accurately detect the deformation of various shapes.
(III) summary of the invention
The invention aims to provide a laser shearing speckle interference device and a method for measuring deformation of an object, which have simple and compact structure and are easy to operate and adjust. The polarization light shearing device and the polarization phase shift system are combined, and the integrated structure enables the device to be smaller and portable, so that the shearing direction can be adjusted through the rotating prism while the measurement accuracy is ensured, and defects of various shapes can be detected more accurately.
The technical scheme of the invention is as follows:
a nondestructive testing device and method based on laser shearing speckle interference is characterized by comprising the following steps: a shear phase shift module, an interference imaging module, a beam expanding illumination module, and a housing portion.
The beam expanding illumination module comprises a 532nm laser and a beam expanding device positioned at the front end of the laser. Two identical lasers are placed on two sides of the device, laser generated by the lasers is converted into divergent beams by a beam expander, and a large-view-field uniform illumination area is formed on the surface of the measured object.
The shear phase shift module includes a Wollaston prism providing shear, a liquid crystal phase shifter forming a phase retardation, a polarizer adjusting a polarization direction of light and forming interference, a circular housing, a rear housing, and a sleeve. The interference imaging device comprises an imaging lens, a CCD camera and a computer control system. The imaging lens is provided with a focusing ring and an aperture ring, and the aperture and the focal length can be adjusted within a specified range. The laser irradiates the surface of the measured object to reflect to form diffuse reflection light, the diffuse reflection light is divided into two linearly polarized light beams with mutually perpendicular polarization directions after passing through the Wollaston prism, and the voltage of the liquid crystal phase shifter is regulated to enable the light beams to pass through the liquid crystal phase shifter to realize phase delay; in the shearing phase shift module, the shearing direction axis of the Wollaston prism and the fast axis and the slow axis of the liquid crystal phase shifter form 90 degrees respectively, the light after phase delay is synthesized through the polaroid to form interference, the light transmission axis of the polaroid and the fast axis of the liquid crystal phase shifter form an included angle of 45 degrees, the light transmission axis is perpendicular to the slow axis to form an included angle of 90 degrees, and finally the light is collected by the CCD camera through the imaging lens. The computer control system can be used for controlling focusing and aperture on the imaging lens and exposure of the CCD camera, and simultaneously collecting pictures shot by the CCD camera for image processing to obtain the deformation of the measured object.
Further comprises: the CCD camera is fixed on the camera base; the camera base is fixed on the bottom plate; the beam expanding device is connected with a 532nm laser and is fixed on the bottom plate; the Wollaston prism is fixed on a round shell of the shearing phase shift module; the liquid crystal phase shifter is attached to the Wollaston prism; the polaroid is attached to the liquid crystal phase shifter and fixed on the rear shell of the shearing phase shift module; the circular shell and the rear shell of the shear phase shift module are combined and connected with the sleeve of the shear phase shift module to be fixed on the bottom plate; the shell is connected with the bottom plate through screws.
The specific method for measuring the deformation of the measured object by using the device is as follows:
and adjusting the imaging lens and the shearing phase shift device to enable the speckle pattern diffusely reflected by the surface of the measured object to be clearly displayed on the CCD camera.
The computer control system controls the CCD camera to shoot the shot image I of the measured object before loading and the shot image I' after loading, 0 is added through the liquid crystal phase shifter,π,/>phase shift, the light intensity before and after deformation can be expressed as:
to obtain the variation delta, four graphs before and after deformation are processed to obtain the phase quantity before and after deformation of the object to be measured:
wrapping the phase difference by the interference fringe pattern before and after deformationThe method comprises the following steps:
for wrapping phaseUnwrapping to obtain a true phase difference Δφ, the Wollaston edgesThe mirror shear direction is transverse, so only the true phase difference in x direction and the derivative of deformation are calculated>Is a relationship of (3).
Wherein lambda is the laser wavelength; δx is the shearing amount, and the calculating formula of the shearing amount is:
wherein D is the distance from 532nm laser to the measured object; d is the distance from the measured object to the Wollaston prism; alpha is the beam splitting angle of the Wollaston prism.
And integrating the deformation derivative to obtain the deformation:
the invention has the advantages that: the invention adopts an integrated structure, so that the device becomes smaller and more portable. The shearing direction can be adjusted through the rotating prism while the measurement accuracy is ensured, so that defects of various shapes can be detected more accurately, and the practicability of the device is improved.
(IV) description of the drawings
FIG. 1 is a top view of a laser shearing speckle interference device for measuring deformation of an object according to an embodiment of the invention.
Fig. 2 is a schematic diagram of an optical path of a laser shearing speckle interference device for measuring deformation of an object according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of an external structure of a laser shearing speckle interference device for measuring deformation of an object according to an embodiment of the invention.
FIG. 4 is a side view of a laser shearing speckle interference device for measuring deformation of an object without housing, according to an embodiment of the invention.
FIG. 5 is a diagram showing the connection between the modules of a laser shearing speckle interference device for measuring deformation of an object according to an embodiment of the invention.
Fig. 6 is a schematic view of a shear phase shift module according to an embodiment of the invention.
(fifth) detailed description of the invention
The invention is further illustrated in the following with reference to fig. 1-6, but should not be taken to limit the scope of the invention.
As shown in fig. 1-6, the laser shearing speckle interference device for measuring deformation of an object comprises a 532nm laser (1), a beam expanding device (2), an object to be measured (3), a Wollaston prism (4), a liquid crystal phase shifter (5), a polaroid (6), a circular shell (7), a rear shell (8), a sleeve (9), an imaging lens (10), a CCD camera (11), a computer control system (12), a shell (13), a camera base (14) and a bottom plate (15).
Wherein the 532nm laser (1) and the beam expanding device (2) form part of the beam expanding illumination device of the invention. The Wollaston prism (4), the liquid crystal phase shifter (5), the polaroid (6), the round shell (7), the rear shell (8) and the sleeve (9) form a shearing phase shift module part of the invention. The imaging lens (10), the CCD camera (11) and the computer control system (12) connected with the CCD camera (11). Forming part of the interferometric imaging module of the invention.
In the embodiment, a CCD camera (11) is fixed on a camera base (14); the camera base (14) is fixed on the bottom plate (15) through screws; the beam expanding device (2) is connected with the 532nm laser (1) and is fixed on the bottom plate (15); the Wollaston prism (4) is fixed on a round shell (7) of the shearing phase shift module; the liquid crystal phase shifter (5) is attached to the Wollaston prism (4); the polaroid (6) is attached to the liquid crystal phase shifter (5) and is fixed on the rear shell (8) of the shearing phase shift module; the circular shell (7) and the rear shell (8) of the shear phase shift module are combined and connected with the sleeve (9) of the shear phase shift module to be fixed on the bottom plate (15); the shell (13) is connected with the bottom plate (15) through screws.
The working process of the laser shearing speckle interference device for measuring the deformation of an object is as follows:
the method comprises the steps of placing a measured object (3) at a position 500mm away from a device, changing a 532nm laser (1) into a divergent beam through a beam expanding device (2), irradiating the laser after beam expansion to diffuse reflection light formed by surface reflection of the measured object (3), dividing the diffuse reflection light into two linearly polarized light beams with mutually perpendicular polarization directions after passing through a Wollaston prism (4), adjusting the voltage of a liquid crystal phase shifter (5), changing the voltage input once every 100ms to enable the light to pass through the liquid crystal phase shifter (5), realizing phase delay, forming a coherent light field after passing through a polaroid (6), finally acquiring four pictures through an imaging lens (10), suspending 5000ms by the camera (11), loading the measured object (3), adjusting the voltage of the liquid crystal phase shifter (5) once every 100ms, repeatedly acquiring the deformed picture data of the four measured object (3), and processing the acquired data by a computer control system (12) to obtain deformation variables and defects of the measured object (3).
The measured object (3) is used for shooting an image I before loading and an image I' after loading, 0 is added through a liquid crystal phase shifter,π,/>phase shift, the light intensity before and after deformation can be expressed as:
to obtain the variation delta, four images before and after deformation are processed to obtain the phase quantity before and after deformation of the measured object (3):
wrapping the phase difference by the interference fringe pattern before and after deformationThe method comprises the following steps:
for wrapping phaseUnwrapping to obtain a true phase difference delta phi, wherein the shearing direction of the Wollaston prism (4) is transverse, so that only the true phase difference in the x direction and the derivative of the deformation are calculated>Is a relationship of (3).
Wherein lambda is the laser wavelength; δx is the shearing amount, and the calculating formula of the shearing amount is:
wherein D is the distance from the 532nm laser (1) to the measured object (3); d is the distance from the measured object to the Wollaston prism (4); alpha is the beam splitting angle of the Wollaston prism (4).
And integrating the deformation derivative to obtain the deformation:
although the embodiments of the present invention are described above, the embodiments are only used for facilitating understanding of the present invention, and are not intended to limit the present invention. Any person skilled in the art can make any modification and variation in form and detail without departing from the spirit and scope of the present disclosure, but the scope of the present disclosure is still subject to the scope of the appended claims.
Claims (5)
1. A nondestructive testing device and method based on laser shearing speckle interference. The method is characterized in that: a shear phase shift module, an interference imaging module, a laser beam expansion module, and a housing portion. The shearing phase shift module at least comprises a Wollaston prism (4) for providing shearing, a liquid crystal phase shifter (5) for forming phase delay, a polaroid (6) for adjusting the polarization direction of light and forming interference, a circular shell (7), a rear shell (8) and a sleeve (9). The interference imaging module at least comprises an imaging lens (10), a CCD camera (11) and a computer control system (12) connected with the CCD camera (11). The laser beam expanding module at least comprises a 532nm laser (1) and a beam expanding device (2) positioned at the front end of the laser.
2. The laser shearing speckle interference system for measuring deformation of an object under test of claim 1, wherein: the 532nm laser (1) is changed into a divergent beam through a beam expanding device (2), the laser after beam expansion irradiates to the surface of a measured object (3) to be reflected to form diffuse reflection light, the diffuse reflection light is divided into two linearly polarized lights with mutually perpendicular polarization directions after passing through a Wollaston prism (4), the voltage of a liquid crystal phase shifter is regulated to enable the light to realize phase delay after passing through the liquid crystal phase shifter (5), a coherent light field is formed after passing through a polaroid (6), and finally the light is collected by a CCD camera (11) through an imaging lens (10).
3. The laser shearing speckle interference system for measuring deformation of an object of claim 1, wherein: the shearing direction axis of the Wollaston prism (4) forms an angle of 90 degrees with the fast axis and the slow axis of the liquid crystal phase shifter (5) respectively, light after phase delay is synthesized through a polaroid to form interference, the light transmission axis of the polaroid (6) forms an included angle of 45 degrees with the fast axis of the liquid crystal phase shifter (5), the light transmission axis is perpendicular to the slow axis to form an included angle of 90 degrees, the included angle between the shearing direction axis and the fast axis and the slow axis of the liquid crystal phase shifter (5) can be adjusted and switched through rotating the Wollaston prism (4), the imaging lens (10) comprises a focusing ring and a light ring, the aperture size and the focal length can be adjusted, and the beam expanding device (2) is installed on the laser (1) through screws.
4. The laser shearing speckle interference system for measuring deformation of an object of claim 1. The housing portion is characterized by: comprises a bottom plate (15) and a shell (13). The CCD camera (11) is fixed on the camera base (14); the camera base (14) is fixed on the bottom plate (15); the beam expanding device (2) is connected with 532nm lasers (1) respectively placed at two sides of the whole device and is fixed on a bottom plate (15); the Wollaston prism (4) is fixed on a round shell (7) of the shearing phase shift module; the liquid crystal phase shifter (5) is attached to the Wollaston prism (4); the polaroid (6) is attached to the liquid crystal phase shifter (5) and is fixed on the rear shell (8) of the shearing phase shift module; the circular shell (7) and the rear shell (8) of the shear phase shift module are combined and connected with the sleeve (9) of the shear phase shift module to be fixed on the bottom plate (15); the shell (13) is connected with the bottom plate (15) through screws.
5. A nondestructive testing device and method based on laser shearing speckle interference are characterized in that the method comprises the steps of adjusting an imaging lens (10) and a laser (1) to enable speckle patterns after diffuse reflection on the surface of a tested object (3) to be clearly displayed on a CCD camera (11).
The CCD camera (11) is controlled by the computer control system (12) to shoot the shot image I before loading and the shot image I' after loading of the measured object (3), 0 is added through the liquid crystal phase shifter,π,/>phase shift, the light intensity before and after deformation can be expressed as:
to obtain the variation delta, four images before and after deformation are processed to obtain the phase quantity before and after deformation of the measured object (3):
wrapping the phase difference by the interference fringe pattern before and after deformationThe method comprises the following steps:
for wrapping phaseUnwrapping to obtain a true phase difference delta phi, wherein the shearing direction of the Wollaston prism (4) is transverse, so that only the true phase difference in the x direction and the derivative of the deformation are calculated>Is the relation of:
wherein lambda is the laser wavelength; δx is the shearing amount, and the calculating formula of the shearing amount is:
wherein D is the distance from the 532nm laser (1) to the measured object (3); d is the distance from the measured object (3) to the Wollaston prism (4); alpha is the beam splitting angle of the Wollaston prism (4).
And integrating the deformation derivative to obtain the deformation:
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| CN118154597A (en) * | 2024-05-10 | 2024-06-07 | 四川大学 | Defect detection method, device, equipment and medium |
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| CN118154597A (en) * | 2024-05-10 | 2024-06-07 | 四川大学 | Defect detection method, device, equipment and medium |
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