A method and apparatus for detecting subsurface damage based on optical phased array

Abstract

This invention belongs to the field of optical precision measurement technology and discloses a method and device for detecting subsurface damage based on an optical phased array. The method includes: emitting a laser beam, polarizing and shaping the laser beam into a flat-top beam, splitting it into multiple parallel beams, and collimating them onto the sample under test via a phased array; generating a specific phase difference between adjacent elements of the phased array, thereby causing interference enhancement of the parallel beams in a specific direction, deflecting the beams at a specific angle and scanning them into the sample under test, and scattering them multiple times at the subsurface damage site to form a scattered beam; collecting the light intensity data of the scattered beam using a silicon photomultiplier tube; repeating the scanning multiple times until the entire surface of the sample under test is scanned, and analyzing and comparing the collected light intensity data with the light intensity data of a normal sample to determine the location and morphology of the subsurface damage in the sample under test. This invention can achieve rapid and high-precision subsurface damage detection and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of optical precision measurement technology, and more specifically, relates to a method and apparatus for detecting subsurface damage based on an optical phased array. Background Technology

[0002] In materials science and engineering, the detection and analysis of surface and subsurface defects are crucial. Surface and subsurface defects can lead to reduced material performance, component failure, and even accidents. Traditional material defect detection methods typically only detect defects on the material surface, while detecting subsurface defects requires more sophisticated techniques.

[0003] A common method for detecting subsurface defects is to use optical techniques. This method uses a laser beam to illuminate the sample surface and then observes the intensity and distribution of the scattered light to infer the location and morphology of the subsurface defect. For example, patent document CN113607750A discloses a device for detecting subsurface defects in optical components. This device uses a dispersive mirror group to simultaneously focus an excitation laser and a detection laser to different depths of the optical component. The excitation laser induces ultrasonic vibrations on the subsurface of the optical component, and the detection laser observes and records these ultrasonic vibrations. Spectral confocal technology is used to obtain the spatial distribution and scattering spectrum information of the scattered light at the location of the subsurface defect. By using the above techniques, multi-dimensional information such as the reflection spectrum, scattering spectrum, three-dimensional shape, and defect depth of the defect is obtained, enabling accurate detection of subsurface defects. However, this optical detection technology suffers from drawbacks when detecting subsurface defects. The detection device has a complex structure and is difficult to operate. Furthermore, due to the limited optical resolution of the detection device, it cannot detect very small defects. Additionally, the control of the incident light angle relies on the mechanical control of the motion platform, resulting in large motion control errors. Therefore, the detection accuracy of this method is also limited.

[0004] To overcome these limitations, there is an urgent need for a detection method and device that can improve the accuracy of subsurface damage detection in materials, obtain more light intensity information about subsurface defects, and achieve rapid and accurate detection of the morphology and location of subsurface damage. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method and apparatus for detecting subsurface damage based on optical phased arrays, thereby solving the problems of existing detection devices having complex structures, corresponding detection methods having complex steps and being difficult to operate, and being unable to perform rapid and accurate detection, resulting in inaccurate detection results.

[0006] To achieve the above objectives, the present invention provides a method for detecting subsurface damage based on an optical phased array, comprising the following steps:

[0007] S1. Emit a laser beam, polarize and shape the laser beam into a flat-top beam, then split it into multiple parallel beams, and collimate the parallel beams onto the sample to be tested via a phased array.

[0008] S2. Adjust the phase of the array elements of the phased array to generate a specific phase difference between adjacent array elements, thereby causing the parallel beam to interfere and enhance in a specific direction in the phased array based on the specific phase difference to form a deflected beam. The deflected beam is deflected at a specific angle and enters the sample to be tested for scanning, and is scattered multiple times at the subsurface damage site to form a scattered beam with a changed polarization state.

[0009] S3. Collect the light intensity data of the scattered beam using multiple silicon photomultiplier tubes;

[0010] S4. Repeat steps S2-S3 multiple times until the entire surface of the sample to be tested is scanned. Analyze and compare the collected light intensity data with the light intensity data of normal samples to determine the location and morphology of subsurface damage in the sample to be tested.

[0011] Furthermore, in step S2, the specific phase difference between adjacent array elements is different from the previous one after each adjustment, thereby making the deflection angle of the deflected beam formed each time different from the previous one.

[0012] Furthermore, the data acquisition end of each silicon photomultiplier tube is oriented towards the test surface of the sample under test.

[0013] Furthermore, the silicon photomultiplier tubes are arranged on a hemispherical contour surface above the sample under test with the sample under test as the center, and the radii of the hemispherical contour surfaces are the same or different.

[0014] Furthermore, the spacing between adjacent silicon photomultiplier tubes may be equal or unequal; preferably, when the spacing between adjacent silicon photomultiplier tubes is unequal, the central angle spacing between adjacent silicon photomultiplier tubes is 5° within a central angle range of ±30°; preferably, the central angle spacing between adjacent silicon photomultiplier tubes is 10° within a central angle range of -80° to -30°; more preferably, the central angle spacing between adjacent silicon photomultiplier tubes is 10° within a central angle range of 30° to 80°.

[0015] Furthermore, the phased array is made of an electro-optic crystal; preferably, by applying different voltages to the phased array in real time, different phase differences are generated between adjacent array elements in real time; more preferably, the relationship between the phase difference and the voltage is expressed by the following mathematical formula:

[0016]

[0017] in, For the phase difference, n o denoted as λ, where λ is the refractive index of the electro-optic crystal for o-light, r is the linear electro-optic coefficient, V is the applied voltage, and λ is the wavelength of the Gaussian beam.

[0018] Furthermore, before acquiring the light intensity data of the scattered beam, interfering scattered beams that do not change the polarization state when irradiating the rough surface of the sample under test are filtered out, thereby retaining the scattered beams whose polarization state has changed.

[0019] Furthermore, the maximum power of the Gaussian beam is 100mW; preferably, the distance between adjacent elements in the phased array is 1µm-3µm; more preferably, the distance between adjacent elements in the phased array is 2µm.

[0020] According to another aspect of the present invention, a subsurface damage detection device based on an optical phased array is also disclosed, comprising a central control processor and a laser source, a source modulation system, a phased array, and a scattering data detection system respectively connected and communicating with the central control processor, wherein:

[0021] The laser source is used to emit a laser beam and collimate the laser beam into the light source modulation system;

[0022] The light source modulation system is used to convert the laser beam into a polarized Gaussian beam, shape the Gaussian beam into a flat-top beam, and split the flat-top beam into multiple parallel beams that enter the phased array.

[0023] The phased array is used to change the phase of the array elements so that the parallel beam will be interfered and enhanced in a specific direction to form a deflected beam. The deflected beam is deflected at a specific angle and enters the sample under test in a specific direction, and is scattered multiple times at the subsurface damage site of the sample under test to form a scattered beam with a changed polarization state.

[0024] The scattering data detection system is used to collect the light intensity signal of the scattered beam and send it to the central control processor;

[0025] The central control processor is used to control the phased array to change the phase of the array elements, and is also used to receive the light intensity data and compare the light intensity data with the light intensity data of the normal sample to determine the location and morphology of the subsurface damage of the sample under test.

[0026] Furthermore, the light source modulation system includes a beam shaping system and a beam splitter coaxially arranged with the laser light source beam emitting end. The beam shaping system is used to convert the laser beam into a polarized Gaussian beam, and then shape the polarized Gaussian beam into a flat-top beam and inject it into the beam splitter. The beam splitter is used to split the flat-top beam into multiple parallel beams and collimate them into the phased array. Preferably, the scattering data detection system includes a hemispherical support shell and multiple silicon photomultiplier tubes arranged on the hemispherical support shell. The hemispherical support shell is positioned above the sample to be tested, and the data acquisition ends of the silicon photomultiplier tubes all face the sample to be tested. More preferably, the surface of the hemispherical support shell is coated with a light-absorbing coating and / or light-absorbing micro / nano structures to prevent the light beam passing through the shell from being scattered. Even more preferably, the data acquisition ends of the silicon photomultiplier tubes are all provided with polarizers, which are used to filter out interfering scattered beams that do not change the polarization state when irradiating the rough surface of the sample to be tested.

[0027] Compared with the prior art, the above-described technical solutions conceived in this invention have the following main advantages:

[0028] 1. This invention can shape a Gaussian beam into a collimated flat-top beam with evenly distributed output energy, and then split it into multiple parallel beams that are injected into a phased array. By adjusting the phase of the array elements, a specific phase difference is generated between adjacent elements. When the parallel beams pass through the phased array, optical path differences are generated based on different phases, which causes the parallel beams of different phases to interfere. That is, interference superimposes in a specific direction and cancels out in other directions, ultimately causing the laser to deflect at a specific angle in a specific direction, thereby achieving fast and accurate adjustment of the incident angle. There is currently no application of using laser phased arrays to detect subsurface damage of workpieces.

[0029] 2. This invention achieves rapid and precise adjustment of the incident angle, thereby causing interference of a parallel light beam in a specific direction. This deflects the beam at a specific angle and directs it into the sample under test along a specific direction, forming a scattered beam at the subsurface damage site. Due to multiple scatterings, the polarization state of the scattered beam changes. The low-noise defect light signal in the scattered beam is then amplified by a silicon photomultiplier tube, and the intensity data of the scattered beam is collected as analytical data to determine the morphology of the subsurface damage. This non-contact detection method avoids damage and contamination to the sample under test. Furthermore, because this detection method utilizes a silicon photomultiplier tube, it can efficiently and rapidly acquire light intensity data, completing multiple tests without relying on complex detection equipment and operating procedures.

[0030] 3. The phased array in this invention is made of electro-optic crystal material. Due to the birefringence of electro-optic crystal material, its phase can be changed at any time by applying different voltages in real time. This causes the light beam to generate an optical path difference when passing through the phased array, resulting in interference. The deflection angle and incident direction of the enhanced beam generated by the interference can also be changed in real time with the change of the phase of adjacent array elements. This allows the phased array to accurately and quickly deflect the incident beam and achieve faster and more accurate scanning of the incident beam, which can greatly improve the detection efficiency and accuracy. In addition, the array element spacing is between 1μm and 3μm, corresponding to different scanning angles. For the same subsurface damage in the sample, laser beams incident from different directions and with different incident angles will result in scattered light with different field strength distributions. Therefore, this invention can obtain more information about subsurface damage through repeated scanning to further increase the accuracy of detection.

[0031] 4. This invention utilizes multiple silicon photomultiplier tubes located above the sample to collect light intensity data. Silicon photomultiplier tubes have advantages such as high sensitivity, large signal amplification ratio, and fast response speed, enabling efficient collection and amplification of low-noise defect signals from the sample during the detection process. Furthermore, the data acquisition ends of the silicon photomultiplier tubes are all oriented towards the sample, and they are evenly arranged above the sample along the hemispherical contour with the sample as the center. Depending on different acquisition requirements, the arrangement and density of the silicon photomultiplier tubes vary, thus enabling accurate collection of scattered light signals at different azimuth and scattering angles, which are then converted into electrical signals for amplification, providing a reliable data foundation for subsequent data processing and visualization of the detection results.

[0032] 5. Before acquiring the light intensity data of the scattered beam, this invention first filters out the scattered light whose deflection state has not changed. This is because the scattered light comes from the rough surface of the sample. The incident light undergoes simple scattering on the rough surface and the polarization state does not change. However, it undergoes multiple scatterings at the subsurface damage site and the polarization state changes. Therefore, filtering out the scattered light whose polarization has not changed can eliminate the influence of the sample surface roughness, thereby expanding the detection application range of this invention.

[0033] 6. The detection device of the present invention has a simple structure, comprising only a laser source, a source modulation system, a phased array, a scattering data detection system, and a central control processor. The central control processor can control the phased array to adjust the phase of the array elements in real time, so as to quickly and accurately adjust the direction of the incident laser. At the same time, it can also receive the scattered light intensity information of different azimuth angles and different scattering angles collected by the scattering data detection system, and can process the collected data in real time, so that the light intensity of different scattering angles corresponding to different incident angles is integrated into a scattering matrix, thereby obtaining more information on the changes in the morphology related to the depth of subsurface damage and outputting visualized light intensity information. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the subsurface damage detection device based on an optical phased array provided by the present invention.

[0035] Figure 2 This is a schematic diagram of the beam shaping principle in the light source modulation system of this invention.

[0036] Figure 3 This is a schematic diagram illustrating the principle of phased array controlling laser beam deflection at a specific angle in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the arrangement of silicon photomultiplier tubes on the hemispherical support shell in an embodiment of the present invention.

[0038] In the diagram: 1-Laser source, 2-Polarizer, 3-Beam shaping system, 301-Gaussian beam, 302-Aspherical shaping lens, 303-Flat-top beam, 4-Beam splitter, 5-Phase array, 6-Sample under test, 7-Hemispherical support shell, 8-Silicon photomultiplier tube, 81-Analyzer, 9-Central control processor, 10-Wave controller. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 and not intended to limit the invention.

[0040] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] This invention provides a method for detecting subsurface damage based on an optical phased array, which can be implemented on a device for detecting subsurface damage based on an optical phased array. The device includes: a laser source, a source modulation system, a phased array, a scattering data detection system, and a central control processor. The method includes the following steps:

[0044] S1. Emit a laser beam, polarize and shape the laser beam into a flat-top beam, then split it into multiple parallel beams, and collimate the parallel beams into the phased array, and after exiting the phased array, collimate them into the sample to be tested.

[0045] S2. Adjust the phase of the array elements of the phased array to generate a specific phase difference between adjacent array elements, thereby causing the parallel beam to interfere and enhance in a specific direction in the phased array based on the specific phase difference to form a deflected beam. The deflected beam is deflected at a specific angle and enters the sample under test in a specific direction for scanning, and is scattered multiple times at the subsurface damage site of the sample under test to form a scattered beam with a changed polarization state.

[0046] S3. Collect light intensity data of the scattered beam using multiple silicon photomultiplier tubes;

[0047] S4. Repeat steps S2-S3 multiple times until the entire surface of the sample to be tested is scanned. Analyze and compare the collected light intensity data with the light intensity data of normal samples to determine the location and morphology of subsurface damage in the sample to be tested.

[0048] In a preferred embodiment, steps S3-S4 are repeated to collect light intensity data of multiple sets of scattered beams, and the phase of each array element is adjusted to be different from the previous one each time, so that the deflection angle of the deflected beam formed each time is different from the previous one.

[0049] In a preferred embodiment, the data acquisition end of each silicon photomultiplier tube is oriented towards the surface of the sample under test, which can more accurately and comprehensively cover the light intensity data of the scattered beam.

[0050] In a more preferred embodiment, the aforementioned plurality of silicon photomultiplier tubes are arranged on the same or different hemispherical contour surfaces above the sample to be tested, with the sample to be tested as the center. That is, the hemisphere on which each silicon photomultiplier tube is located has the sample to be tested as the center, but the radius of the hemisphere can be the same or different. This allows for more precise control of the position of the silicon photomultiplier tubes, thereby enabling more accurate acquisition of the light intensity data of the required scattered beam.

[0051] In a preferred embodiment, in step S5, the spacing between adjacent silicon photomultiplier tubes is equal or unequal; and when the spacing between adjacent silicon photomultiplier tubes is unequal, within a sphere central angle range of ±30°, the sphere central angle spacing between adjacent silicon photomultiplier tubes is 5°, that is, the distribution density is denser, and more light intensity data can be collected.

[0052] In a more preferred embodiment, the distance between the central angles of adjacent silicon photomultiplier tubes is 10° within the range of -80° to -30°.

[0053] In a further preferred embodiment, the central angle of adjacent silicon photomultiplier tubes is 10° in the range of 30° to 80°. Different silicon photomultiplier tube arrangements can enable the silicon photomultiplier tubes to quickly acquire light intensity data of scattered beams at different azimuth angles and different scattering angles when the enhanced polarized beam under a specific phase difference is irradiated onto the sample under test and scatters.

[0054] In a preferred embodiment, the phased array is made of an electro-optic crystal. Since the refractive index of an electro-optic crystal changes under the influence of an electric field, and this change is proportional to the electric field strength, it is called the linear electro-optic effect or Pockels effect, i.e., Δn = rE, where r is the linear electro-optic coefficient. By changing the refractive index, the optical path difference of the light beam passing through the electro-optic crystal material can be altered, thereby changing the phase difference. Therefore, phase adjustment can be easily achieved by applying a linear voltage, where the applied voltage V = E * L, and L is the length of the light beam passing through the electro-optic crystal. The operation is simple.

[0055] In a more preferred embodiment, by applying different voltages to the phased array in real time, different phase differences are generated between adjacent array elements in real time; the relationship between the phase difference and the voltage is expressed by the following mathematical formula:

[0056]

[0057] in, For the phase difference, n o λ is the refractive index of the electro-optic crystal for o-light, r is the linear electro-optic coefficient, V is the applied voltage, λ is the wavelength of the Gaussian beam, and o-light refers to ordinary light.

[0058] In a preferred embodiment, the maximum power of the Gaussian beam emitted by the laser source is 100mW. If this power is exceeded, it will cause damage to the detection device. To avoid device damage, the energy of the laser beam needs to be controlled through a complex adjustment method.

[0059] In a preferred embodiment, in step S3, before acquiring the intensity data of the scattered beam, the interfering scattered beams that do not change polarization when irradiating the rough surface of the sample are filtered out, thereby retaining the scattered beams whose polarization has changed, and avoiding the influence of the intensity data of the interfering scattered beams on the subsequent analysis and comparison results. Specifically, since the polarized beam undergoes one scattering on the rough surface of the sample and its polarization does not change, while at the subsurface damage site, the polarized beam undergoes multiple scatterings and its polarization changes (for details, see Fung AK, Li Z, Chen KS. Backscattering from a randomly rough dielectric surface. IEEE Trans Geosci Rem Sens 1992; 30:356–69), filtering out the interfering scattered beams that do not change polarization when irradiating the rough surface of the sample, and only allowing light with a polarization different from that of the incident beam to enter, can eliminate the influence of the intensity of scattered light from the rough surface, and further improve the detection accuracy.

[0060] In a preferred embodiment, the distance between adjacent array elements in the aforementioned phased array is set to 1µm-3µm, and the optimal distance between adjacent array elements in the phased array is 2µm. The corresponding scanning angle range is better and can meet the scanning angle requirements of the detection method of the present invention.

[0061] The relationship between the aforementioned phase difference and the specific angle of deflection of the deflected beam is expressed by the following formula:

[0062]

[0063] Where λ is the wavelength of the Gaussian beam, θ is a specific angle, d is the distance between adjacent array elements, and Δφ is the phase difference between adjacent array elements;

[0064] Using formula (2) for calculation, since the applied linear voltage can change in real time, it means that the phase difference can also change in real time. The electro-optic crystal can provide a phase change of 0-2π. The optimal spacing between adjacent array elements is 2 micrometers. Therefore, the theoretical scanning range that a single beam can reach is ±30°. The actual scanning range is related to the arrangement of phased array elements, etc., and can be changed accordingly as needed.

[0065] The present invention also provides a subsurface damage detection device based on an optical phased array. The subsurface damage detection method based on an optical phased array in any of the foregoing embodiments can be implemented on this detection device. The device includes a central control processor 9 and a laser source 1, a source modulation system, a phased array 5, and a scattering data detection system, which are respectively connected and communicate with the central control processor 9, wherein:

[0066] Laser source 1 is used to emit a Gaussian beam and collimate the Gaussian beam into the light source modulation system;

[0067] The light source modulation system is used to shape the Gaussian beam into a flat-top beam with uniform energy distribution, and also to split the flat-top beam into at least two parallel beams that enter the phased array 5.

[0068] The phased array 5 is composed of multiple electro-optic crystal phase shifters. The phased array 5 is used to change the phase of the array elements so that the parallel beams interfere to form a deflected beam. The deflected beam is deflected at a specific angle and enters the sample under test along a specific direction. It is scattered multiple times at the subsurface damage site of the sample under test to form a scattered beam with a changed polarization state. Specifically, this detection device also includes a wave controller 10 connected to the phased array 5. The central control processor 9 controls the wave controller 10 to apply different voltages to the phased array 5. The electro-optic effect of the electro-optic crystals is used to generate a phase difference between adjacent array elements (i.e., adjacent electro-optic crystal phase shifters).

[0069] The scattering data detection system is equipped with silicon photomultiplier tubes, which are used to collect the light intensity signal of the scattered beam and send it to the central control processor 9. Specifically, before collecting the light intensity signal of the scattered beam, the analyzer 81 set at the acquisition end of each silicon photomultiplier tube can filter out the interference beams that only undergo single scattering on the rough surface of the sample and whose polarization state does not change. This is because these scattered beams are scattered from the rough surface of the sample. The incident light undergoes simple scattering on the rough surface and the polarization state does not change. However, multiple scattering occurs at the subsurface damage site and the polarization state changes.

[0070] The central control processor 9 is equipped with a corresponding control program, which is used to control the phased array 5 to change the phase of the array elements, and also to receive light intensity data and compare the light intensity data with the light intensity data of normal samples to determine the location and morphology of subsurface damage in the sample under test.

[0071] In a preferred embodiment, the light source modulation system includes a beam shaping system 3 and a beam splitter 4, both coaxially arranged with the beam emitting end of the laser light source 1. The beam shaping system 3 is used to first polarize the laser beam emitted by the laser light source 1 into a polarized Gaussian beam, and then shape the polarized Gaussian beam into a flat-top beam with uniform energy before it is injected into the beam splitter 4. The beam splitter 4 is used to split the flat-top beam into multiple parallel beams and collimate them into the phased array 5.

[0072] In a more preferred embodiment, the scattering data detection system includes a hemispherical support shell 7 and a plurality of silicon photomultiplier tubes 8 arranged on the inner or outer spherical surface of the hemispherical support shell 7. The hemispherical support shell 7 is positioned above the sample to be tested, and the data acquisition ends of the silicon photomultiplier tubes 8 are all facing the sample to be tested. The central control processor 9 can control the silicon photomultiplier tubes 8 to move on the spherical surface of the hemispherical support shell 7 to adjust their pose.

[0073] In a more preferred embodiment, such as Figure 4 As shown, the hemispherical support shell 7 can also be multiple support shells with different radii at the same center. Each support shell is provided with a silicon photomultiplier tube 8, and the silicon photomultiplier tubes 8 on the multi-layer support shells are evenly or unevenly distributed.

[0074] In other preferred embodiments, in addition to the hemispherical support shell, the fixing member for fixing the silicon photomultiplier tube can also be a support rod of different lengths. The silicon photomultiplier tube 8 is fixed to the upper end of each support rod, and the line connecting each silicon photomultiplier tube forms a hemispherical outline with the same center. During testing, the sample to be tested can be placed at the center of the sphere.

[0075] In a more preferred embodiment, the silicon photomultiplier tube 8 can move on the spherical surface of the hemispherical support shell 7 so as to adjust the position of each silicon photomultiplier tube 8 at any time.

[0076] In a further preferred embodiment, the surface of the hemispherical support shell 7 is coated with a light-absorbing coating and / or light-absorbing micro / nano structures to prevent light beams passing through the shell from being scattered.

[0077] To illustrate the implementation details of the present invention, the following embodiments are provided to explain the specific steps of the evaluation method of the present invention. However, the following embodiments do not represent a further limitation on the scope of protection of the present invention.

[0078] Example 1

[0079] like Figure 1 The diagram shown is a schematic of the subsurface damage detection device based on an optical phased array provided in this embodiment. It includes a central control processor 9, and a laser source 1, a source modulation system, a phased array 5, and a scattering data detection system that are respectively capable of data communication with the central control processor 9.

[0080] The laser source 1 emits a Gaussian beam with a wavelength of λ = 1064 nm and a maximum power of 100 mW. The Gaussian beam first enters the light source modulation system, which includes a beam shaping system 3 and a beam splitter 4 coaxially arranged with the beam emitting end of the laser source 1. The beam shaping system 3 includes a polarizer 2 coaxially arranged with an aspherical shaping lens 302. The Gaussian beam is first converted into a polarized Gaussian beam by the polarizer 2, and then the aspherical shaping lens 302 converts the polarized Gaussian beam into a flat-top beam with uniform energy distribution. It is then collimated and split into 5 beams, which are then collimated and incident into the phased array 5. The distance between the elements of the phased array is d = 2 μm.

[0081] The principle of beam shaping is as follows: Figure 2 As shown, polarizer 2 changes the polarization state of the incident Gaussian laser, resulting in a non-uniform energy distribution in the Gaussian beam 301. Figure 2 The density of light at different spatial positions is used to characterize the beam. After passing through two aspherical shaping lenses 302, the light energy is redistributed, resulting in a flat-top beam 303 with the same light density at different spatial positions and an evenly distributed output energy. This completes the beam shaping and collimation. The flat-top beam 303 is then split into n light waves by a beam splitter 4 and enters the phased array 5. The phased array 5 is made of electro-optic crystal material, and the distance between each phased array element is d = 2 μm.

[0082] The scattering data detection system includes a hemispherical support shell 7 and four uniformly arranged silicon photomultiplier tubes 8 on the hemispherical support shell 7. The hemispherical support shell 7 is coated with a light-absorbing coating and light-absorbing micro-nano structures. The six silicon photomultiplier tubes 8 are arranged in an array inside the hemispherical support shell 7 along a hemispherical outline, and the central angles between each pair of silicon photomultiplier tubes 8 are not equal. That is, the silicon photomultiplier tubes 8 are more densely arranged near the top of the hemispherical support shell 7 and more sparsely arranged away from the top of the hemispherical support shell 7. The hemispherical support shell 7 is set above the sample 6 to be tested, and the data acquisition ends of the silicon photomultiplier tubes 8 are all facing the sample 6 to be tested. A polarizer 81 is also set at the data acquisition end of the silicon photomultiplier tubes 8 to filter the light intensity data of the interfering beam.

[0083] The above-mentioned detection device is used to detect subsurface damage in the sample to be tested. The specific detection steps include:

[0084] Step 1: Emit a laser beam. Specifically, emit a Gaussian beam with a wavelength of λ = 1064 nm and a power of 100 mW. The Gaussian beam first passes through the light source modulation system and is then polarized by polarizer 2. The aspherical shaping lens 302 transforms the Gaussian beam into a flat-top beam with uniform energy distribution. The flat-top beam is collimated and emitted into beam splitter 4, thus splitting into 5 beams. The 5 parallel beams are collimated and incident on the phased array 5, and the distance between adjacent array elements of the phased array is d = 2 μm. At this time, no voltage is applied to the phased array, i.e., no phase difference is introduced. The incident angle of the parallel beams is 0°. The laser collimates and scatters on the quartz sample to be tested.

[0085] Step 2: By applying a voltage to the phased array 5, a phase difference is introduced to complete the deflection of the parallel beam, such as... Figure 3 As shown, the control wave controller 10 adjusts the phase of each array element and applies a linear voltage to adjacent array elements of the phased array 5 to generate a corresponding phase difference (i.e., a specific phase difference) between adjacent array elements. This causes the deflection beam emitted from the phased array to be deflected at an angle of θ before entering the sample under test for scanning. The deflection beam illuminates the sample under test and scatters in different states on the sample under test, thus completing one scan. Since the voltage can be adjusted and changed in real time in this embodiment, it means that the specific phase difference can also be changed in real time.

[0086] Step 3: Control the scattering acquisition system to collect the light intensity data of the enhanced deflected beam after scattering on the sample under test; specifically, the analyzer 81 can first filter out the interfering beams so that the silicon photomultiplier tube 8 collects only the light intensity data of the scattered beams whose polarization state has changed.

[0087] Step 4: Repeat steps 2-3, changing the incident angle θ of the enhanced polarized beam on the sample multiple times to ensure the entire surface of the sample is scanned. Then, acquire multiple sets of light intensity signals from scattered beams at different azimuth and scattering angles, convert them into electrical signals, amplify them, and transmit them to the central control processor 9. The central control processor 9 compares and analyzes the received signals with pre-stored theoretical light intensity data for undamaged normal samples. Specifically, it integrates the light intensity data corresponding to different incident angles and scattering angles into a scattering matrix and plots a visualized three-dimensional graph of scattering intensity-incident angle-scattering angle correlation. This three-dimensional graph is then compared with the light intensity data of a sample without subsurface damage to obtain information related to the depth and morphology of subsurface damage.

[0088] The advantages of this invention are that it uses phased array and silicon photomultiplier tube technology to quickly and accurately detect subsurface damage. It can not only detect minute defects and deformations, but also obtain various information related to subsurface damage, such as the location, morphology, size, and depth of the subsurface, by processing the signal output by the detector in real time. This can provide strong support and experimental evidence for research in related fields. In addition, compared with traditional subsurface damage detection methods, this invention uses non-contact detection, avoiding damage and contamination to the sample being tested, while also being highly efficient and fast, which can significantly improve work efficiency and detection accuracy.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting subsurface damage based on an optical phased array, characterized in that, Includes the following steps: S1. Emit a laser beam, polarize and shape the laser beam into a flat-top beam, then split it into multiple parallel beams, and collimate the parallel beams onto the sample to be tested via a phased array. S2. Adjust the phase of the array elements of the phased array to generate a specific phase difference between adjacent array elements, thereby causing the parallel beam to interfere and enhance in a specific direction in the phased array based on the specific phase difference to form a deflected beam. The deflected beam is deflected at a specific angle and enters the sample to be tested for scanning, and is scattered multiple times at the subsurface damage site to form a scattered beam with a changed polarization state. S3. Multiple silicon photomultiplier tubes are used to collect the light intensity data of the scattered beam. The data acquisition end of each silicon photomultiplier tube is facing the test surface of the sample to be tested. The silicon photomultiplier tubes are arranged on a hemispherical contour surface above the sample to be tested with the sample to be tested as the center. The radii of the hemispherical contour surfaces are the same or different. The spacing between adjacent silicon photomultiplier tubes is equal or unequal. S4. Repeat steps S2-S3 multiple times until the entire surface of the sample to be tested is scanned. Analyze and compare the collected light intensity data with the light intensity data of normal samples to determine the location and morphology of subsurface damage in the sample to be tested.

2. The method for detecting subsurface damage based on an optical phased array as described in claim 1, characterized in that, In step S2, the specific phase difference between adjacent array elements is different from the previous one after each adjustment, so that the deflection angle of the deflected beam formed each time is different from the previous one.

3. The method for detecting subsurface damage based on an optical phased array as described in claim 1, characterized in that, When the spacing between adjacent silicon photomultiplier tubes is not equal, the central angle spacing between adjacent silicon photomultiplier tubes is 5° within the range of ±30°; the central angle spacing between adjacent silicon photomultiplier tubes is 10° within the range of -80° to -30°; and the central angle spacing between adjacent silicon photomultiplier tubes is 10° within the range of 30° to 80°.

4. The method for detecting subsurface damage based on an optical phased array as described in claim 1, characterized in that, The phased array is made of electro-optic crystal; by applying different voltages to the phased array in real time, different phase differences are generated between adjacent array elements in real time; the relationship between the phase difference and the voltage is expressed by the following mathematical formula: Δφ = (2πn o 3 r / λ) * V Where Δφ is the phase difference, n o denoted as λ, where λ is the refractive index of the electro-optic crystal for o-light, r is the linear electro-optic coefficient, V is the applied voltage, and λ is the wavelength of the Gaussian beam.

5. The method for detecting subsurface damage based on an optical phased array as described in claim 1, characterized in that, Before acquiring the light intensity data of the scattered beam, interfering scattered beams that do not change polarization state when irradiating the rough surface of the sample under test are filtered out, thereby retaining the scattered beams whose polarization state has changed.

6. The method for detecting subsurface damage based on an optical phased array as described in claim 4, characterized in that, The maximum power of the Gaussian beam is 100mW.

7. The method for detecting subsurface damage based on an optical phased array as described in claim 1, characterized in that, The distance between adjacent elements in the phased array is 1µm-3µm.

8. The method for detecting subsurface damage based on an optical phased array as described in claim 1, characterized in that, The distance between adjacent elements in the phased array is 2 μm.

9. A device for detecting subsurface damage based on an optical phased array, characterized in that, It includes a central control processor (9) and a laser source (1), a source modulation system, a phased array (5), and a scattering data detection system, all connected to the central control processor (9), wherein: The laser source (1) is used to emit a laser beam and collimate the laser beam into the light source modulation system; The light source modulation system is used to convert the laser beam into a polarized Gaussian beam and shape the Gaussian beam into a flat-top beam. It is also used to split the flat-top beam into multiple parallel beams that enter the phased array (5). The phased array (5) is used to change the phase of the array elements so that the parallel beam will be interfered and enhanced in a specific direction to form a deflected beam. The deflected beam is deflected at a specific angle and enters the sample to be tested along a specific direction, and is scattered multiple times at the subsurface damage site to form a scattered beam with a changed polarization state. The scattering data detection system is used to collect the light intensity signal of the scattered beam and send it to the central control processor (9). The central control processor (9) is used to control the phased array (5) to change the phase of the array elements, and is also used to receive the light intensity data and compare the light intensity data with the light intensity data of the normal sample to determine the location and morphology of the subsurface damage of the sample to be tested.

10. The subsurface damage detection device based on an optical phased array as described in claim 9, characterized in that, The light source modulation system includes a beam shaping system (3) and a beam splitter (4) coaxially arranged with the beam emitting end of the laser light source (1). The beam shaping system (3) is used to convert the laser beam into a polarized Gaussian beam, and then shape the polarized Gaussian beam into a flat-top beam and inject it into the beam splitter (4). The beam splitter (4) is used to split the flat-top beam into multiple parallel beams and collimate them into the phased array (5). The scattering data detection system includes a hemispherical support shell (7) and a beam splitter arranged on the hemispherical support shell (7). Multiple silicon photomultiplier tubes (8) are mounted on a hemispherical support shell (7). The hemispherical support shell (7) is positioned above the sample to be tested. The data acquisition ends of the silicon photomultiplier tubes (8) all face the sample to be tested, and the data acquisition ends of each silicon photomultiplier tube face the test surface of the sample to be tested. The silicon photomultiplier tubes are arranged on a hemispherical contour surface above the sample to be tested with the sample to be tested as the center. The radii of the hemispherical contour surfaces are the same or different. The spacing between adjacent silicon photomultiplier tubes is equal or unequal.

11. The subsurface damage detection device based on an optical phased array as described in claim 10, characterized in that, The surface of the hemispherical support shell (7) is coated with a light-absorbing coating and / or a light-absorbing micro / nano structure to prevent light beams passing through the shell from being scattered.

12. The subsurface damage detection device based on an optical phased array as described in claim 10, characterized in that, Each of the silicon photomultiplier tubes (8) is equipped with a polarizer (81) at its data acquisition end. The polarizer (81) is used to filter out interfering scattered beams that do not change the polarization state when they irradiate the rough surface of the sample to be tested.

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