CN210665618U - Laser optoacoustic composite non-contact detection system for elements and defects - Google Patents
Laser optoacoustic composite non-contact detection system for elements and defects Download PDFInfo
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Abstract
The utility model belongs to the field of laser material detection, and discloses a laser optoacoustic composite non-contact detection system for elements and defects, which comprises a pulse laser, a spectrum detection unit, an ultrasonic detection unit, a sample stage unit and an analysis control unit, wherein the spectrum detection unit is used for detecting visible light spectrum emitted by plasma to obtain information about elements in a sample to be analyzed; the ultrasonic detection unit is used for carrying out non-contact detection on ultrasonic waves, and based on the principle of interferometer detection or high-Q-value resonator detection, ultrasonic signals can be obtained on the premise of not contacting a sample, and information about defects in the sample to be analyzed is obtained. The utility model discloses a structure to each subassembly in the device and setting up the mode etc. and improve, adopt known non-contact ultrasonic detection unit to carry out non-contact detection to the ultrasonic wave that produces along with laser excitation, can realize carrying out non-contact detection and analysis simultaneously to the element and the defect of sample.
Description
Technical Field
The utility model belongs to laser material detection area, more specifically relates to a compound non-contact detection system of laser optoacoustic of element and defect, realizes adopting the compound non-contact detection that laser arouses the elemental composition and defect distribution, and this system is specifically mainly surveyed and the analysis through light, the acoustic signal that laser arouses the back production, realizes the element and the defect non-contact detection simultaneously to the target.
Background
In industrial application, the material defects not only bury potential safety hazards for product use, but also greatly reduce the stability and mechanical properties of the material. In the field of nondestructive testing of structural defects, the most mature and widespread testing technique currently used in the industrial field is Ultrasonic Testing (UT). Ultrasonic detection is a technology which utilizes the fact that when ultrasonic waves propagate in a detected material, the acoustic characteristics of the material and the change of internal tissues have certain influence on the propagation of the ultrasonic waves, and the change of the material performance and structure is known through the detection of the influenced degree and the condition of the ultrasonic waves. The laser ultrasonic detection technology is one of ultrasonic detection technologies, and has the advantages of no damage, safety and high precision and good detection performance.
In the laser ultrasonic detection technology, the conventional ultrasonic detection adopts a contact type transduction method, i.e. most of the energy of ultrasonic waves is transmitted into a detected workpiece by using an acoustic coupling medium such as grease or water between an ultrasonic probe and a detected material or member. However, in the industries of chemical industry, medicine, light industry, food and the like, a plurality of pressure containers are provided with heat insulation layers, and the pressure containers all operate for a long time. The pressure vessels are required to be periodically checked, the machine is stopped to remove the heat-insulating layer, the surface of the tested vessel is polished, a large amount of manpower and material resources are wasted in the preparation work, and the removed heat-insulating layer is difficult to recover in many times. In addition, in a high-temperature or high-speed production line, a general ultrasonic probe cannot be stably coupled to a workpiece to be inspected, and thus the non-contact photoacoustic technique is important.
Chinese patent "air coupling ultrasonic non-contact detection system for defects of inner surface layer of gas transmission pipeline" (CN 108896663, published 2018, 11 and 27) introduces an air coupling ultrasonic non-contact detection system for defects of inner surface layer of gas transmission pipeline, which uses non-contact ultrasonic to detect the defects of inner surface layer of pipeline. In the prior art, an air coupling excitation probe excites ultrasonic longitudinal waves, the longitudinal waves are incident on the wall surface of a pipeline to generate surface waves, the propagation range of the surface waves is in the surface layer of the pipeline, and the excitation probe only detects defects on the surface layer of the pipeline. Therefore, the prior art can not detect the internal defects of the structure, and the defect detection precision is not high (the frequency of ultrasonic waves excited by the probe is not high, and is mostly KHz-MHz).
In terms of elemental analysis, conventional detection means include chemical analysis, XRF, ICP-OES, and the like. However, these methods have the disadvantages of sample damage, long time consumption, and the like, and cannot meet the requirements of rapid, in-situ, micro-damage, even no-damage and the like of modern element detection, so that a new spectrum detection technology, namely Laser Induced Breakdown Spectroscopy (LIBS) technology, comes along.
The LIBS technology is a novel atomic spectrum analysis technology, and is characterized in that laser is focused on the surface of a substance to ablate to generate plasma, and the plasma spectrum is collected to analyze elements of the substance so as to obtain the element types and content of the substance. The LIBS technology has the characteristics of multi-element synchronous real-time analysis, simplicity or no need of sample pretreatment, high speed, nondestructive detection and the like, so the LIBS technology has wide application prospects in the fields of metal metallurgy, environmental protection, national defense industry, food safety and the like.
In summary, although the LIBS technology and the laser ultrasonic detection technology have excellent performance, the elements and defects of the material are respectively analyzed by a single technical means at present, the analysis time is long, and the detection cost is high. The existing ultrasonic detection technology is mostly contact detection, a couplant is coated between a probe and a sample to be detected to avoid signal attenuation of ultrasonic waves, but the coupling coating amount cannot be controlled and the ultrasonic detection technology is difficult to operate on irregular samples, so that the detection stability is greatly reduced, and the application range of ultrasonic detection is limited.
The present invention discloses a laser optoacoustic composite detection method and system for elements and defects (see chinese patent document CN107607520A), which also discloses using a pulse laser to emit plasma and ultrasonic waves onto an analysis sample to simultaneously analyze the element components and structural defects of the sample, but the ultrasonic detection module used in the method is a water immersion type ultrasonic probe, and the contact detection is inconvenient in application and limits the application range of ultrasonic detection.
So far, no laser-optoacoustic composite non-contact detection device of elements and defects is available.
SUMMERY OF THE UTILITY MODEL
Aiming at the above defects or improvement requirements of the prior art, the utility model aims to provide a laser optoacoustic composite non-contact detection system of element and defect, through improving the structure of each subassembly in the system device and the setting mode thereof, and the like, the single pulse laser is adopted as the excitation light source to ablate the tested sample, the excitation generates plasma, and on one hand, the spectrometer is adopted to collect the emission spectrum of the plasma; on the other hand, non-contact detection of ultrasonic waves generated along with laser excitation is performed by using a non-contact ultrasonic detection unit component (a commercially available component can also be directly used) based on the interferometer detection or high-Q resonator detection principle, so that elements and defects of a sample can be simultaneously detected and analyzed in a non-contact manner. The utility model discloses utilize pulse laser to incide and produce plasma and ultrasonic wave on the analysis sample, analysis sample element component and structural defect simultaneously to the utilization detects based on the supersound non-contact detection of interferometer detection, high Q value syntonizer detection principle, has avoided the use of acoustic coupling medium, can widen this detecting system's application scope greatly.
To achieve the above object, according to the present invention, there is provided a laser-optoacoustic composite non-contact detection system for elements and defects, comprising a pulse laser (3), a spectrum detection unit, an ultrasonic detection unit, and a sample stage unit, wherein,
the sample stage unit comprises a displacement platform, the displacement platform is used for placing a sample (9) to be analyzed and can drive the sample (9) to be analyzed to move, so that the adjustment of the spatial position of the sample (9) to be analyzed is realized,
a pulsed laser (3) for emitting pulsed laser light for incidence on a sample to be analyzed to simultaneously generate plasma and ultrasonic waves,
the spectrum detection unit is used for detecting the visible light spectrum emitted by the plasma flame, the visible light spectrum carries information about elements in a sample to be analyzed,
the ultrasonic detection unit is used for carrying out non-contact detection on ultrasonic waves and can detect based on an interferometer or the Q value of the ultrasonic detection unit satisfies 105～107The high-Q resonator detection principle obtains ultrasonic signals on the premise of not contacting with a sample, and obtains the ultrasonic signals carrying defect information in the sample to be analyzed.
As a further preferred aspect of the present invention, the ultrasonic detection unit detects ultrasonic waves based on the interferometer detection principle, and includes a beam splitter (14), a helium-neon laser (15), a laser interferometer (16) and a digital oscilloscope (12), wherein the laser interferometer (16) and the digital oscilloscope (12) are electrically connected, and the digital oscilloscope (12) is used for displaying ultrasonic signals;
alternatively, the ultrasonic detection unit satisfies 10 specifically based on the Q value5～107The high Q value resonator detection principle of the ultrasonic wave detection unit comprises an optical fiber laser (17), and the Q value of the ultrasonic wave detection unit satisfies 105～107A high Q value resonator (18), a photoelectric detector (19) and a digital oscilloscope (12), the photoelectric detector (19) and the digital oscilloscope (1)2) And the digital oscilloscope (12) is electrically connected and used for displaying the ultrasonic signals.
As a further optimization of the utility model, the spectrum detection unit comprises a half-transmitting and half-reflecting mirror (8), a total reflecting mirror (4), a focusing objective lens (10), a spectrometer acquisition probe (2), a spectrometer (1) and an enhanced charge coupled device (6), wherein,
the light outlet of the pulse laser (3) and the semi-transparent and semi-reflective mirror (8) are sequentially positioned on the same horizontal light path, the transmission surface of the semi-transparent and semi-reflective mirror (8) forms an angle of 45 degrees with the horizontal light path,
the total reflector (4) is movably arranged, when the total reflector is positioned on the light path, the total reflector (4) is parallel to the semi-transparent and semi-reflective mirror (8), the total reflector (4) and the focusing objective (10) are sequentially positioned on the reflection light path of the semi-transparent and semi-reflective mirror (8), the distances among the semi-transparent and semi-reflective mirror (8), the total reflector (4) and the focusing objective (10) can be adjusted,
the spectrometer acquisition probe (2) is positioned above the semi-transparent semi-reflecting mirror (8) and is connected with the spectrometer (1) through an optical fiber, the enhanced charge-coupled device (6) is arranged on the spectrometer (1), and the spectrometer (1) is used for detecting spectral information.
As a further preferred aspect of the present invention, for the optical splitter (14), the he-ne laser (15) and the laser interferometer (16), the he-ne laser (15) is used for emitting a probe laser, and is divided into two beams of light with the same frequency by the optical splitter (14), one beam of light is used as a reference light, and the other beam of light is used as a probe light and is applied to the sample (9) to be analyzed, and the probe light is influenced by the ultrasonic micro-vibration, and after the phase of the probe light changes, the probe light interferes with the reference light in the laser interferometer (16), and then the optical signal is converted into an electrical signal by the electro-optical modulator, and the ultrasonic signal is displayed on the digital oscilloscope (12);
for the optical fiber laser (17), the high-Q-value resonator (18) and the photoelectric detector (19), when the high-Q-value resonator (18) is subjected to the action of ultrasonic wave stress, the refractive index in the high-Q-value resonator (18) is changed due to the photoelastic effect, so that the spectrum of the resonator is shifted; the fiber laser (17) couples the incident laser into the high Q-value resonator, the wavelength is shifted due to the spectral shift of the resonator, and finally the information of the ultrasonic signal can be obtained by the photodetector (19).
As the utility model discloses a further preferred, displacement platform specifically is 3D displacement platform, can drive and treat that analysis sample (9) can be followed X to, Y to and Z to removing to the realization is treated the position control of analysis sample in three-dimensional direction.
As a further preference of the present invention, the pulse laser (3) is specifically a nanosecond pulse laser or a picosecond pulse laser.
As a further preferred aspect of the present invention, when the ultrasonic detection unit satisfies 10 on the basis of the Q value5～107According to the detection principle of the high-Q resonator, the resonant cavity detection structure is packaged by the heavy water cladding.
Through the utility model discloses above technical scheme who thinks adopts laser to arouse the sample that awaits measuring as the excitation source to produce ultrasonic wave and plasma simultaneously, through adopting the known subassembly among the prior art, and utilize their whole cooperation to gather sound, light signal, thereby obtain the element and the defect information of material simultaneously, construct the compound non-contact detection device of laser optoacoustic of element and defect. Compared with the prior art, the single pulse laser is used as an excitation light source to ablate the sample to be detected and excite the sample to generate plasma, and on one hand, a spectrometer is used for collecting the emission spectrum of the plasma; on the other hand, it is particularly important to perform non-contact detection on ultrasonic waves generated along with laser excitation by synchronously using a non-contact ultrasonic detection unit based on the interferometer detection or high-Q resonator detection principle. The utility model discloses detection device can realize the compound non-contact detection of laser optoacoustic and analysis of element and defect, has avoided the ultrasonic coupling agent to use simultaneously, has improved the range of application that optoacoustic detected greatly.
The utility model discloses well laser excitation goes out the longitudinal wave sound wave, excites on sample surface, receives bottom the sample. The acoustic wave propagates inside the sample, and internal defects of the sample can be detected. The utility model discloses in adopt among the prior art the non-contact ultrasonic wave detection unit subassembly based on the interferometer detection, or the syntonizer detection principle of having (like commercially available non-contact ultrasonic wave detection unit subassembly based on the interferometer detection, or syntonizer detection principle etc.), obtain ultrasonic signal under the prerequisite of contactless sample, operate under normal air circumstance can, the use of couplant has been avoided in this kind of non-contact detection, broken the application limitation that the contact detected. The utility model discloses well utilize the ultrasonic frequency range that laser excitation goes out to be wideer, reach MHz-GHz, when changing laser pulse width, for example when using the picosecond laser instrument, sound wave frequency can reach more than GHz. Because the frequency is higher, the defect precision of detection just is higher, the utility model discloses can realize the detection of high accuracy.
The resonant cavity detects ultrasonic signals in a non-contact mode, broadband ultrasonic signals excited by laser ultrasonic waves vibrate according to a photoelastic effect, and the broadband acoustic signals carry detection information. When the broadband ultrasonic stress influences the refractive index in the resonant cavity, the refractive index can be changed, so that the frequency spectrum in the resonant cavity is shifted. Then, the optical signal can be converted into an electrical signal by using a photoelectric detector, and the electrical signal can be analyzed to detect and analyze. The air coupling probe of single frequency channel detects the acoustic signal and can only receive the acoustic signal information of this single frequency channel, and resonant cavity detection technique can remain all frequency acoustic wave information of wide band ultrasonic signal completely, and the detection information is comprehensive. It is found in the concrete research that the narrow band of laser ultrasonic is vibrate the degree of accuracy that can reduce the resonant cavity and detect, the utility model discloses preferred heavy water (D) of adopting2The O) cladding packaged ring-shaped resonant cavity can achieve the effect of inhibiting oscillation and avoid using common water (H)2O) absorbs light in the 1550nm band during packaging. The utility model discloses, the Q value of the annular resonant cavity of encapsulation with heavy water cladding can reach 3 x 105The laser energy is 2.1mJ, and the detected sound pressure signal is 2 pa. According to empirical formula, the shorter the laser pulse width, the higher the ultrasonic frequency that laser supersound arouses, utilize the utility model provides a system, if change the laser pulse width, for example change the laser from nanosecond laser to picosecond laser and examine time measuring, because the supersound central frequency that nanosecond laser corresponds is MHz, and the supersound central frequency that picosecond laser corresponds is GHz, if adopt traditional ultrasonic probe to examine time measuring, need change the probe for corresponding higher frequency's probe, but the utility model discloses in, owing to adopt the ultrasonic detection unit based on the principle that high Q value syntonizer surveyed, still can adopt this resonant cavity to carry outAnd (3) non-contact detection is carried out, a sound wave signal above GHz is obtained, and a high-frequency ultrasonic signal realizes a detection effect with higher precision.
The interferometer detects ultrasonic signals in a non-contact manner, and utilizes broadband ultrasonic signals excited by laser ultrasonic to generate tiny disturbance on a sample piece, so that the phase of detection light is changed. The affected probe light interferes with the reference light, the interfered light signal carries detection information, and information of all frequency sound waves of the broadband ultrasonic signal is completely reserved. The optical signal can be converted into an electric signal through the photoelectric modulator, and the electric signal can be analyzed to perform detection and analysis. According to empirical formula, the laser pulse width is shorter more, and the ultrasonic frequency that laser supersound arouses is higher, utilizes the utility model provides a system, if change the laser pulsewidth, for example change the laser instrument into picosecond laser detection from nanosecond laser equally, if adopt traditional ultrasonic probe to examine time measuring, need change the probe for corresponding higher frequency probe equally, but the utility model discloses in, owing to adopt the ultrasonic detection unit based on the principle that the interferometer surveyed, still can adopt this interferometer to carry out non-contact detection, obtain the sound wave signal more than GHz, high frequency ultrasonic signal realizes the detection effect of higher accuracy.
Drawings
Fig. 1 is the structure schematic diagram of the laser optoacoustic composite non-contact detection system based on the elements and defects of the interferometer ultrasonic detection system of the present invention.
Fig. 2 is the structural schematic diagram of the laser optoacoustic composite non-contact detection system based on the elements and defects of the resonator ultrasonic detection system.
Fig. 3 is a sound wave curve of the metal Cr detected by the non-contact detection of the resonant cavity of the present invention, and a frequency spectrum diagram obtained further; fig. 3 (a) corresponds to the acoustic wave curve and (b) corresponds to the spectrum curve.
The meanings of the reference symbols in the figures are as follows: 1 is a spectrometer; 2, a spectrometer acquisition probe; 3 is a pulse laser; 4 is a total reflection mirror; 5 is a 3D displacement platform; 6 enhanced charge coupled device (ICCD); 7 is a computer (optional and not necessary); 8 is a semi-transparent semi-reflecting mirror; 9 is a sample to be analyzed; 10 is a focusing objective lens; 11 is a digital delay generator (optional and not necessary); 12 is an oscilloscope; 14 is a light splitter; 15 is helium neon laser; 16 is a laser interferometer; 17 is a fiber laser; 18 is a resonator; and 19 is a photodetector.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features mentioned in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
The utility model provides a compound non-contact detecting system of laser optoacoustic of element and defect to the realization detects when distributing and structural defect to the element.
Fig. 1 is a schematic structural view of a system for detecting material defects and material element information simultaneously by using an interferometer according to the present invention. Fig. 2 is a schematic structural diagram of a system for detecting material element information while detecting a material defect by a resonator according to the present invention. In fig. 1-2, the light exit of the pulse laser 3 and the half mirror 8 are sequentially located on the same horizontal light path, and an included angle between the transmission surface of the half mirror 8 and the substrate is 45 degrees, and also forms an angle of 45 degrees with the horizontal light path. The total reflection mirror 4 is movably installed and is parallel to the half mirror 8 when being positioned on the light path. The total reflection mirror 4 and the focusing objective lens 10 are sequentially positioned on a reflection light path of the half-transmitting mirror 8. The distances among the half-transmitting and half-reflecting mirror 8, the total reflecting mirror 4 and the focusing objective lens 10 can be adjusted horizontally and vertically through connecting a screw rod and a guide rail.
The spectrometer acquisition probe 2 is positioned above the semi-transparent semi-reflecting mirror 8 and is connected with the spectrometer 1 through an optical fiber. The enhanced charge coupled device ICCD6 is mounted on the spectrometer 1 (in another embodiment, the spectrometer 1 may be connected to the computer 7 by an optical cable). The 3D displacement platform 5 can realize the precise movement in the horizontal X, Y direction through the motor drive lead screw in the horizontal direction and the guide rail, can realize the precise movement in the vertical Z direction through the motor drive lead screw in the vertical direction and the guide rail, and the horizontal motor and the vertical motor act simultaneously to form an x-y-Z three-dimensional motion system. The sample 9 to be analyzed is placed on the 3D translation stage 5 (in another embodiment, the 3D translation stage 5 may be connected to the computer 7 through a control cable so that the computer can precisely control the position of the sample 9 to be analyzed).
The laser interferometer 16 is connected to the beam splitter 14, and the beam splitter 14 splits two beams: the probe light and the reference light. The probe light is transmitted to the surface of the sample 9 to be measured by an optical fiber, changes phase under the influence of ultrasonic vibration, interferes with the reference light in the laser interferometer 16, and is measured by the laser interferometer 16 (in a preferred embodiment, the laser interferometer 16 is connected to the digital oscilloscope 12 through a cable).
The resonator 18 may be placed at a distance of about 4mm from the sample 9 to be measured, on both sides of the sample, respectively, with the pulsed laser 3. In a preferred embodiment, the resonator 18 may be connected to the photodetector 19 by a cable, and the photodetector 19 may be further connected to the digital oscilloscope 12 by a cable. In the experiment, the acoustic curve of the metal Cr is detected through non-contact detection of the resonant cavity, and the spectrogram is obtained, wherein the acoustic curve and the spectral curve are shown in FIG. 3.
The pulse laser 3 mainly functions to excite the interaction of high-energy laser and a sample 9 to be detected, and excite plasma and ultrasonic signals which are respectively used for detecting elements and defects.
The main roles of the ICCD6 are: and the spectrometer 1 together form a sample spectroscopic system and a detector, and are used for collecting emission line signals generated by plasma on the surface of a measured object and imaging spectral lines of various elements obtained by decomposing plasma light by the spectrometer 1, so as to perform qualitative and quantitative analysis on the elements of the sample.
In another embodiment, a computer 7 and a digital delay generator 11 may be incorporated to achieve automated detection. The digital delay generator 11 can be used for controlling the delay time among the light emission of the pulse laser 3, the collection of the spectrometer 1, the movement of the 3D displacement platform 5, the detection of the laser interferometer 16, the detection of the photoelectric detector 19 and the computer 7. The digital time delay generator 11 is connected with the pulse laser 3, the spectrometer 1, the 3D displacement platform 5, the oscilloscope 12 and the computer 7 through cables. The digital delay generator is mainly used for time sequence control, so that a pulse laser, a spectrometer, a 3D displacement platform, an ultrasonic probe and a computer which are electrically connected with the digital delay generator and are controlled by the digital delay generator can execute work at set time, the acquisition efficiency is optimized, and the digital delay generator and the computer do not conflict with each other.
At this time, the 3D displacement platform 5 can achieve a more preferable effect, for example, the 3D displacement platform 5 controls the motor in the horizontal X, Y direction to work in cooperation with the motor in the vertical Z direction by receiving the control signal transmitted by the control cable. Specifically, the motor in the horizontal X direction is adjusted to rotate forwards and backwards, and the platform is controlled to move left and right. Adjusting the defocusing amount by matching with the focusing objective lens 10; adjusting the positive rotation and the negative rotation of a motor in the vertical Z direction, and controlling the platform to lift; regulating the positive rotation and the negative rotation of a motor in the horizontal Y direction to control the front and back translation of the platform; the platform moves in the Z direction and the Y direction together to realize the surface scanning collection of the sample 9 to be analyzed.
The laser interferometer 16 is used for detecting the ultrasonic signal of the sample 9 to be measured, converting the phase information of the light beam into intensity information, and then extracting phase encoding information by using a phase demodulation method (such as Fourier transform and wavelet analysis) known in the prior art. In a preferred embodiment, the acoustic signal may be converted to an electrical signal and may be further connected to a digital oscilloscope 12 via probe connections and the acoustic signal waveform displayed on the oscilloscope. In another embodiment, the digital oscilloscope 12 may be further connected to the computer 7 through a cable, and the ultrasonic signal is analyzed on the computer to obtain the defect information of the sample 9 to be measured.
The resonator 18 functions to shift its frequency spectrum under the influence of ultrasonic vibrations, thereby causing a shift in the wavelength of the incident laser light, and the change in the ultrasonic waves is characterized by measuring the change in the intensity of the output laser light. In a preferred embodiment, the photodetector 19 may be used to convert the optical signal to an electrical signal and connected to the digital oscilloscope 12 via a cable and display the acoustic signal waveform on the oscilloscope. In another embodiment, the digital oscilloscope 12 may be connected to the computer 7 through a cable, and the ultrasonic signal is analyzed on the computer to obtain the defect information of the sample 9 to be measured.
In another embodiment, the computer 12 may be a desktop computer or a notebook computer, and is connected to the digital delay generator 11, the spectrometer 1, the 3D displacement platform 5, and the oscilloscope 12 through a USB interface, a cable, or a network cable. Further preferably, functions of automatic scanning, atomic spectrum peak searching, qualitative identification, quantitative conversion calculation, acoustic wave information processing conversion model and the like can be realized by utilizing known software function modules in the prior art.
The following are specific examples of several corresponding detection flow methods:
the method for non-contact detection of defect information and simultaneous detection of material element information using the system shown in fig. 1 may be as follows: laser light is incident on the surface of the sample, and plasma and ultrasonic waves are simultaneously excited. The method comprises the steps that a spectrometer collects spectral signals to obtain element information of a sample, a helium-neon laser in an ultrasonic detection unit emits detection laser, the detection laser is divided into two beams of light with the same frequency through a light splitter, one beam of light serves as reference light, the other beam of light serves as detection light and strikes the sample, the detection light is influenced by ultrasonic micro vibration, the phase of the detection light is changed and then interferes with the reference light in a laser interferometer, optical signals can be converted into electric signals through a photoelectric detector, and the ultrasonic signals are displayed on a digital oscilloscope. In practical application, the laser is used for line and surface scanning analysis of a sample, and element and defect distribution of a measured object can be obtained simultaneously on the premise of micro-damage or even no damage to the sample.
The method for non-contact detection of defect information and simultaneous detection of material element information by using the system shown in fig. 2 can be as follows: laser light is incident on the surface of the sample, and plasma and ultrasonic waves are simultaneously excited. The spectrometer collects the spectrum signals to obtain the element information of the sample, and when a resonator in the ultrasonic detection unit is under the action of ultrasonic stress, the refractive index in the resonator changes due to the photoelastic effect, so that the spectrum of the resonator shifts. The incident laser of the fiber laser is coupled into the resonator, the wavelength is shifted due to the spectrum shift of the resonator, and the information of the ultrasonic signal can be obtained through the photoelectric detector. The optical signal can be converted into an electrical signal by the photodetector, and the ultrasonic signal is displayed on the digital oscilloscope. In practical application, the laser is used for line and surface scanning analysis of a sample, and element and defect distribution of a measured object can be obtained simultaneously on the premise of micro-damage or even no damage to the sample.
In another embodiment, the 3D displacement platform can be used to realize three-dimensional movement of the sample to be analyzed, and the automatic acquisition motion can be completed by a digital delay timer and a computer in the analysis control unit. Of course, other displacement platforms may be used to replace the 3D displacement platform, as long as the displacement platform can drive the sample to realize the adjustment of the spatial position of the sample in the target direction or plane. For example, the sample can be subjected to line and surface scanning analysis by laser by utilizing the matching of the sample table unit, so that the ultrasonic non-contact detection can be performed, and the element and defect distribution of the object to be detected can be obtained simultaneously on the premise of micro-damage or even no damage to the sample.
The utility model discloses in non-contact ultrasonic detection unit who adopts (i.e. survey based on the interferometer, or Q value satisfies 105～107The ultrasonic detection unit of the high-Q resonator detection principle) may directly employ commercially available components. The visible spectrum carrying information about the elements in the sample to be analyzed, and the ultrasound signal carrying information about the defects in the sample to be analyzed, as with prior art CN107607520A, can be directly referred to for further analysis.
It will be understood by those skilled in the art that the foregoing is merely a preferred embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Claims (7)
1. The laser optoacoustic composite non-contact detection system for elements and defects is characterized by comprising a pulse laser (3), a spectrum detection unit, an ultrasonic detection unit and a sample stage unit, wherein,
the sample stage unit comprises a displacement platform, the displacement platform is used for placing a sample (9) to be analyzed and can drive the sample (9) to be analyzed to move, so that the adjustment of the spatial position of the sample (9) to be analyzed is realized,
a pulsed laser (3) for emitting pulsed laser light for incidence on a sample to be analyzed to simultaneously generate plasma and ultrasonic waves,
the spectrum detection unit is used for detecting the visible light spectrum emitted by the plasma flame, the visible light spectrum carries information about elements in a sample to be analyzed,
the ultrasonic detection unit is used for carrying out non-contact detection on ultrasonic waves and can detect based on an interferometer or the Q value of the ultrasonic detection unit satisfies 105～107The high-Q resonator detection principle obtains ultrasonic signals on the premise of not contacting with a sample, and obtains the ultrasonic signals carrying defect information in the sample to be analyzed.
2. The laser photoacoustic composite non-contact detection system for elements and defects according to claim 1, wherein the ultrasonic detection unit is specifically based on the interferometer detection principle to detect ultrasonic waves, and comprises a beam splitter (14), a helium-neon laser (15), a laser interferometer (16) and a digital oscilloscope (12), the laser interferometer (16) and the digital oscilloscope (12) are electrically connected, and the digital oscilloscope (12) is used for displaying ultrasonic signals;
alternatively, the ultrasonic detection unit satisfies 10 specifically based on the Q value5～107The high Q value resonator detection principle of the ultrasonic wave detection unit comprises an optical fiber laser (17), and the Q value of the ultrasonic wave detection unit satisfies 105～107The high-Q-value resonator (18), the photoelectric detector (19) and the digital oscilloscope (12) are electrically connected, and the digital oscilloscope (12) is used for displaying ultrasonic signals.
3. Laser photo-acoustic composite non-contact detection system of elements and defects according to claim 1, characterized in that the spectrum detection unit comprises a half mirror (8), a total reflection mirror (4), a focusing objective (10), a spectrometer collecting probe (2), a spectrometer (1) and an enhanced charge coupled device (6), wherein,
the light outlet of the pulse laser (3) and the semi-transparent and semi-reflective mirror (8) are sequentially positioned on the same horizontal light path, the transmission surface of the semi-transparent and semi-reflective mirror (8) forms an angle of 45 degrees with the horizontal light path,
the total reflector (4) is movably arranged, when the total reflector is positioned on the light path, the total reflector (4) is parallel to the semi-transparent and semi-reflective mirror (8), the total reflector (4) and the focusing objective (10) are sequentially positioned on the reflection light path of the semi-transparent and semi-reflective mirror (8), the distances among the semi-transparent and semi-reflective mirror (8), the total reflector (4) and the focusing objective (10) can be adjusted,
the spectrometer acquisition probe (2) is positioned above the semi-transparent semi-reflecting mirror (8) and is connected with the spectrometer (1) through an optical fiber, the enhanced charge-coupled device (6) is arranged on the spectrometer (1), and the spectrometer (1) is used for detecting spectral information.
4. The laser optoacoustic composite non-contact detection system for elements and defects according to claim 2, wherein, for the beam splitter (14), the he-ne laser (15) and the laser interferometer (16), the he-ne laser (15) is used for emitting detection laser, and is split into two beams of light with the same frequency through the beam splitter (14), one beam of light is used as reference light, and the other beam of light is used as detection light to be applied to the sample (9) to be analyzed, the detection light is affected by the ultrasonic micro-vibration, after the phase change, the detection light interferes with the reference light in the laser interferometer (16), and then the optical signal is converted into an electrical signal through the photoelectric modulator, and the ultrasonic signal is displayed on the digital oscilloscope (12);
for the optical fiber laser (17), the high-Q-value resonator (18) and the photoelectric detector (19), when the high-Q-value resonator (18) is subjected to the action of ultrasonic wave stress, the refractive index in the high-Q-value resonator (18) is changed due to the photoelastic effect, so that the spectrum of the resonator is shifted; the fiber laser (17) couples the incident laser into the high Q-value resonator, the wavelength is shifted due to the spectral shift of the resonator, and finally the information of the ultrasonic signal can be obtained by the photodetector (19).
5. The laser photoacoustic composite non-contact detection system for elements and defects according to claim 1, wherein the displacement platform is a 3D displacement platform, and can drive the sample to be analyzed (9) to move in the X direction, the Y direction, and the Z direction, thereby realizing the position adjustment of the sample to be analyzed in the three-dimensional direction.
6. Laser optoacoustic composite non-contact detection system of elements and defects according to claim 1, characterized in that the pulsed laser (3) is in particular a nanosecond pulsed laser or a picosecond pulsed laser.
7. The laser-optoacoustic composite non-contact element and defect inspection system of claim 1, wherein the ultrasonic detection unit satisfies 10 on the basis of a Q-value5～107According to the detection principle of the high-Q resonator, the resonant cavity detection structure is packaged by the heavy water cladding.
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