CN117147565A - A nondestructive testing device and method based on laser shearing speckle interference - Google Patents
A nondestructive testing device and method based on laser shearing speckle interference Download PDFInfo
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Abstract
本发明提供的是一种基于激光剪切散斑干涉的无损检测装置及方法。包括剪切相移模块、干涉成像模块、激光扩束模块和外壳部分。剪切相移模块、干涉成像模块和激光扩束模块固定在外壳上。剪切相移模块包括沃拉斯顿棱镜、液晶相移器、偏振片、圆形外壳、后壳和套筒。干涉成像模块包括成像镜头、CCD相机和计算机控制系统。激光扩束模块包括532nm激光器和激光扩束装置。检测方法为通过将被测物进行物理加载前后拍摄，对得到的图片进行分析，对被测物体的变形量进行检测。本发明采用了一体化结构使得设备变得更小巧便携，而且一般情况下，使用沃拉斯顿棱镜结构比较稳定。在保证测量精度的同时，也可以通过旋转棱镜调整剪切方向，以便更准确地检测各种形状的缺陷。
The invention provides a non-destructive testing device and method based on laser shearing speckle interference. Including shear phase shift module, interference imaging module, laser beam expansion module and housing part. The shear phase shift module, interference imaging module and laser beam expansion module are fixed on the casing. The shear phase shift module includes Wollaston prism, liquid crystal phase shifter, polarizer, circular housing, back housing and sleeve. The interference imaging module includes imaging lens, CCD camera and computer control system. The laser beam expansion module includes a 532nm laser and a laser beam expansion device. The detection method is to take pictures before and after physical loading of the object to be measured, analyze the resulting pictures, and detect the deformation of the object to be measured. The present invention adopts an integrated structure to make the device more compact and portable, and in general, the structure using a Wollaston prism is relatively stable. While ensuring measurement accuracy, the shearing direction can also be adjusted by rotating the prism to more accurately detect defects of various shapes.
Description
(一)技术领域(1) Technical field
本发明属于激光无损检测术领域，提供一种基于激光剪切散斑干涉的无损检测装置及方法。The invention belongs to the field of laser non-destructive testing and provides a non-destructive testing device and method based on laser shearing speckle interference.
(二)背景技术(2) Background technology
随着现代科技的飞速发展，高性能材料在众多工业领域得到了广泛应用。然而，这些材料常常会存在微小缺陷。随着时间的推移，外部环境的影响会逐渐损害这些缺陷，使其无法继续正常运作，从而造成无法挽回的损失。无损检测技术(NDT)是一种多学科综合检测技术，它融合了众多领域的知识，我们可以在不损坏或损伤待测物体的前提下，运用先进的检测技术来评估材料的内外部的缺陷或者其他相关参数特性，因而在工业实践中得到了广泛应用。With the rapid development of modern science and technology, high-performance materials have been widely used in many industrial fields. However, these materials often contain tiny imperfections. Over time, the influence of the external environment will gradually damage these defects, making them unable to continue to function normally, causing irreparable losses. Non-destructive testing technology (NDT) is a multi-disciplinary comprehensive testing technology that integrates knowledge from many fields. We can use advanced testing technology to evaluate internal and external defects of materials without damaging or damaging the object to be tested. or other related parameter characteristics, so it has been widely used in industrial practice.
无损检测技术是一种投入成本低、回报高的应用技术，随着现代科技的不断进步和不同新材料和新工艺的出现，工业上大多领域和科研机构都高度重视起了这种技术，并且尽可能的多在不同产品上进行使用，它不仅在产品质量控制中扮演着不可或缺的角色，也可以对正在运行的设备进行检查，可以有效地避免一些不必要的损失和事故发生。Non-destructive testing technology is an application technology with low investment cost and high return. With the continuous advancement of modern science and technology and the emergence of different new materials and new processes, most fields in industry and scientific research institutions have attached great importance to this technology, and Use it on as many different products as possible. It not only plays an indispensable role in product quality control, but can also inspect running equipment, which can effectively avoid unnecessary losses and accidents.
激光散斑无损检测技术起源于光学干涉技术的发展。干涉技术利用光的波动性质研究光学现象，其原理是两束相干光相互叠加形成干涉条纹，通过观察条纹的变化来获取待测物体的信息。激光散斑无损检测技术是在激光干涉技术的基础上发展而来的，它利用激光照射在物体表面产生的散斑现象进行测量和分析。该技术采用了剪切电子散斑干涉的原理，进行测量物体离面位移导数。当复合材料部件内部存在缺陷并受到外部载荷时，缺陷所在位置的表面会产生部分的形变。激光散斑技术以干涉条纹的形式显示了这些非均匀变形，并可以准确测量缺陷的大小，同时精确定位缺陷的位置。Laser speckle non-destructive testing technology originated from the development of optical interference technology. Interference technology uses the wave nature of light to study optical phenomena. The principle is that two beams of coherent light are superimposed on each other to form interference fringes. Information about the object to be measured is obtained by observing changes in the fringes. Laser speckle non-destructive testing technology is developed on the basis of laser interference technology. It uses the speckle phenomenon generated by laser irradiation on the surface of an object for measurement and analysis. This technology uses the principle of sheared electron speckle interference to measure the off-plane displacement derivative of an object. When a composite component has internal defects and is subjected to external loads, partial deformation will occur on the surface where the defect is located. Laser speckle technology displays these non-uniform deformations in the form of interference fringes and can accurately measure the size of the defect while pinpointing its location.
中国专利《一种测量物体离面与面内位移的激光散斑装置及测量方法》公开号为CN108426528A，可以实现同时测量物体面内位移与离面位移，但是只适用于透光物体，不能用于不透光的物体的测量。中国专利《一种基于剪切散斑干涉的激光超声无损检测设备及方法》公开号为CN114018827A，尽管该方法的效果可观，但是由于其不便利的操作和缺乏实时调节的能力，可能会对其应用造成一定的限制。本发明采用了一体化结构使得设备变得更小巧便携，而且一般情况下，使用沃拉斯顿棱镜比使用偏振器所产生的条纹更明显。在保证测量精度的同时，也可以通过旋转棱镜调整剪切方向，以便更准确地检测各种形状的变形。The Chinese patent "A Laser Speckle Device and Measurement Method for Measuring Off-Plane and In-Plane Displacements of Objects" publication number is CN108426528A. It can simultaneously measure the in-plane and out-of-plane displacements of objects, but it is only applicable to light-transmitting objects and cannot be used. For measurements on opaque objects. The Chinese patent "A laser ultrasonic non-destructive testing equipment and method based on sheared speckle interference" publication number is CN114018827A. Although the effect of this method is considerable, it may be criticized due to its inconvenient operation and lack of real-time adjustment capabilities. The application imposes certain limitations. The present invention adopts an integrated structure to make the device smaller and more portable, and generally, the fringes produced by using a Wollaston prism are more obvious than using a polarizer. While ensuring measurement accuracy, the shearing direction can also be adjusted by rotating the prism to more accurately detect deformations of various shapes.
(三)发明内容(3) Contents of the invention
本发明的目的在于提供一种结构简单紧凑、操作调节容易的测量物体形变的激光剪切散斑干涉装置及方法。采用了偏振光剪切器和偏振相移系统结合，一体化的结构使得设备变得更小巧便携，在保证测量精度的同时，也可以通过旋转棱镜调整剪切方向，以便更准确地检测各种形状的缺陷。The object of the present invention is to provide a laser shearing speckle interference device and method for measuring the deformation of an object with a simple and compact structure and easy operation and adjustment. It adopts a combination of polarization shear and polarization phase shift system. The integrated structure makes the device more compact and portable. While ensuring the measurement accuracy, the shearing direction can also be adjusted by rotating the prism to more accurately detect various Shape defects.
本发明的技术解决方案如下：The technical solution of the present invention is as follows:
一种基于激光剪切散斑干涉的无损检测装置及方法，其特征在于，包括：剪切相移模块、干涉成像模块、扩束照明模块和外壳部分。A non-destructive testing device and method based on laser shearing speckle interference, which is characterized by including: a shearing phase shift module, an interference imaging module, a beam expansion illumination module and a housing part.
所述扩束照明模块包括532nm激光器、位于激光器前端的扩束装置。将两个同样的激光器放置在装置两侧，激光器产生的激光由扩束器转换为发散光束，且在被测物体表面形成大视场均匀照明区域。The beam expansion illumination module includes a 532nm laser and a beam expansion device located at the front end of the laser. Two identical lasers are placed on both sides of the device. The laser generated by the laser is converted into a divergent beam by a beam expander, and a large field of view and uniform illumination area is formed on the surface of the object being measured.
所述剪切相移模块包括提供剪切的沃拉斯顿棱镜、形成相位延迟的液晶相移器、调节光的偏振方向和形成干涉的偏振片、圆形外壳、后壳和套筒。所述干涉成像装置包括成像镜头、CCD相机和计算机控制系统。成像镜头带有调焦环和光圈环，可在规定范围内调整光圈和焦距大小。激光照射至被测物体表面反射形成漫反射光，经过沃拉斯顿棱镜后分成两束偏振方向相互垂直的线偏振光，调节液晶相移器的电压使光经过液晶相移器后实现相位延迟；在剪切相移模块中沃拉斯顿棱镜的剪切方向轴与液晶相移器的快轴和慢轴分别成90°角，相位延迟后的光线经过偏振片合成形成干涉，所述的偏振片的透光轴与液晶相移器的快轴成45°夹角，透光轴与慢轴垂直，形成90°的夹角，最后通过成像镜头被CCD相机采集。计算机控制系统可用于控制成像镜头上的对焦和光圈以及CCD相机的曝光，同时采集CCD相机拍摄的图片进行图像处理，获得被测物体的变形量。The shear phase shift module includes a Wollaston prism that provides shear, a liquid crystal phase shifter that forms phase retardation, a polarizer that adjusts the polarization direction of light and forms interference, a circular casing, a back casing, and a sleeve. The interference imaging device includes an imaging lens, a CCD camera and a computer control system. The imaging lens has a focusing ring and an aperture ring, which can adjust the aperture and focal length within a specified range. The laser irradiates the surface of the object to be measured and reflects to form diffusely reflected light. After passing through the Wollaston prism, it is divided into two beams of linearly polarized light with polarization directions perpendicular to each other. The voltage of the liquid crystal phase shifter is adjusted to achieve phase delay after the light passes through the liquid crystal phase shifter. ; In the shear phase shift module, the shear direction axis of the Wollaston prism is at an angle of 90° with the fast axis and slow axis of the liquid crystal phase shifter respectively, and the phase-delayed light is synthesized by the polarizer to form interference, as described The transmission axis of the polarizer forms an angle of 45° with the fast axis of the liquid crystal phase shifter, and the transmission axis is perpendicular to the slow axis, forming an angle of 90°. Finally, it is captured by the CCD camera through the imaging lens. The computer control system can be used to control the focus and aperture on the imaging lens and the exposure of the CCD camera. At the same time, the pictures taken by the CCD camera are collected for image processing to obtain the deformation of the measured object.
进一步包括：所述CCD相机固定在相机底座上；所述相机底座固定在底板上；所述扩束装置与532nm激光器连接并且固定在底板上；所述沃拉斯顿棱镜固定在剪切相移模块的圆形外壳上；所述液晶相移器贴在沃拉斯顿棱镜上；所述偏振片贴在液晶相移器上，且固定在剪切相移模块的后壳上；剪切相移模块的圆形外壳和后壳组合并与剪切相移模块的套筒连接固定在底板上；所述外壳与底板通过螺丝连接。It further includes: the CCD camera is fixed on the camera base; the camera base is fixed on the base plate; the beam expansion device is connected to the 532nm laser and fixed on the base plate; the Wollaston prism is fixed on the shear phase shift on the circular shell of the module; the liquid crystal phase shifter is attached to the Wollaston prism; the polarizing plate is attached to the liquid crystal phase shifter and fixed on the rear shell of the shear phase shift module; the shear phase The circular shell and rear shell of the shift module are combined and connected to the sleeve of the shear phase shift module and fixed on the base plate; the shell and the base plate are connected by screws.
使用该装置测量被测物体形变的具体方法如下：The specific method of using this device to measure the deformation of the measured object is as follows:
调节成像镜头和剪切相移装置使被测物体表面漫反射的散斑图样在CCD相机上清晰显示。Adjust the imaging lens and shear phase shift device so that the speckle pattern of diffuse reflection on the surface of the measured object is clearly displayed on the CCD camera.
由计算机控制系统控制CCD相机拍摄被测物体在加载前拍摄图像I和加载后拍摄图像I′，通过液晶相移器添加0,π,/>相移，则变形前后的光强可以表示为：The CCD camera is controlled by the computer control system to capture the object under test. The image I is captured before loading and the image I′ is captured after loading. The liquid crystal phase shifter is used to add 0, π,/> Phase shift, then the light intensity before and after deformation can be expressed as:
为求变化量Δ，将变形前后的四幅图进行处理，得到待测物变形前后的相位量：In order to find the amount of change Δ, the four images before and after deformation are processed to obtain the phase amount of the object under test before and after deformation:
变形前后干涉条纹图包裹相位差为：Interference fringe pattern wrapping phase difference before and after deformation for:
对包裹相位进行解包裹得到真实相位差Δφ，所述沃拉斯顿棱镜剪切方向为横向，所以只需计算x方向真实相位差与变形量导数/>的关系。Phase to package Unwrapping is performed to obtain the true phase difference Δφ. The shear direction of the Wollaston prism is transverse, so only the true phase difference and deformation derivative in the x direction need to be calculated/> Relationship.
其中λ为激光波长；δx为剪切量，剪切量计算公式为：Where λ is the laser wavelength; δx is the shear amount, and the shear amount calculation formula is:
其中D为532nm激光到被测物体距离；d为被测物体到沃拉斯顿棱镜的距离；α为沃拉斯顿棱镜的分束角。Among them, D is the distance from the 532nm laser to the measured object; d is the distance from the measured object to the Wollaston prism; α is the beam splitting angle of the Wollaston prism.
对变形量导数进行积分，可得变形量：By integrating the deformation derivative, the deformation can be obtained:
本发明具有的优势：本发明采用了一体化结构使得设备变得更小巧便携。在保证测量精度的同时，也可以通过旋转棱镜调整剪切方向，以便更准确地检测各种形状的缺陷，提高了装置实用性。Advantages of the present invention: The present invention adopts an integrated structure to make the device smaller and more portable. While ensuring measurement accuracy, the shearing direction can also be adjusted by rotating the prism to more accurately detect defects of various shapes, improving the practicability of the device.
(四)附图说明(4) Description of drawings
图1为本发明实施例的用于测量物体形变的激光剪切散斑干涉装置俯视图。Figure 1 is a top view of a laser shearing speckle interference device used to measure object deformation according to an embodiment of the present invention.
图2为本发明实施例的用于测量物体形变的激光剪切散斑干涉装置光路示意图。Figure 2 is a schematic diagram of the optical path of a laser shearing speckle interference device used to measure object deformation according to an embodiment of the present invention.
图3为本发明实施例的用于测量物体形变的激光剪切散斑干涉装置外部结构示意图。Figure 3 is a schematic diagram of the external structure of a laser shearing speckle interference device used to measure object deformation according to an embodiment of the present invention.
图4为本发明实施例的用于测量物体形变的激光剪切散斑干涉装置无外壳侧面视图。Figure 4 is a side view of a laser shearing speckle interference device without a housing for measuring object deformation according to an embodiment of the present invention.
图5为本发明实施例的用于测量物体形变的激光剪切散斑干涉装置各个模块之间连接图。Figure 5 is a connection diagram between various modules of the laser shearing speckle interference device used to measure object deformation according to the embodiment of the present invention.
图6为本发明实施例的剪切相移模块结构示意图。Figure 6 is a schematic structural diagram of a shear phase shift module according to an embodiment of the present invention.
(五)具体实施方式(5) Specific implementation methods
下面结合附图1-附图6来进一步阐述本发明，但不应以此限制本发明的保护范围。The present invention will be further described below in conjunction with Figures 1 to 6, but this should not limit the scope of the present invention.
如图1-图6所示，本发明的用于测量物体形变的激光剪切散斑干涉装置，包括，532nm激光器(1)、扩束装置(2)、被测物体(3)、沃拉斯顿棱镜(4)、液晶相移器(5)、偏振片(6)、圆形外壳(7)、后壳(8)、套筒(9)、成像镜头(10)、CCD相机(11)、计算机控制系统(12)、外壳(13)、相机底座(14)、底板(15)组成。As shown in Figures 1 to 6, the laser shearing speckle interference device for measuring object deformation of the present invention includes a 532nm laser (1), a beam expansion device (2), the measured object (3), and a Vola Ston prism (4), liquid crystal phase shifter (5), polarizer (6), circular housing (7), back housing (8), sleeve (9), imaging lens (10), CCD camera (11 ), a computer control system (12), a casing (13), a camera base (14), and a bottom plate (15).
其中532nm激光器(1)、扩束装置(2)构成本发明的扩束照明装置部分。沃拉斯顿棱镜(4)、液晶相移器(5)、偏振片(6)、圆形外壳(7)、后壳(8)和套筒(9)构成本发明的剪切相移模块部分。成像镜头(10)、CCD相机(11)和CCD相机(11)相连的计算机控制系统(12)。构成本发明的干涉成像模块部分。Among them, the 532nm laser (1) and the beam expansion device (2) constitute part of the beam expansion illumination device of the present invention. Wollaston prism (4), liquid crystal phase shifter (5), polarizer (6), circular housing (7), back housing (8) and sleeve (9) constitute the shear phase shift module of the present invention part. The imaging lens (10), the CCD camera (11) and the computer control system (12) connected to the CCD camera (11). It forms part of the interference imaging module of the present invention.
本实施例中CCD相机(11)固定在相机底座(14)上；所述相机底座(14)通过螺丝固定在底板(15)上；所述扩束装置(2)与532nm激光器(1)连接并且固定在底板(15)上；所述沃拉斯顿棱镜(4)固定在剪切相移模块的圆形外壳(7)上；所述液晶相移器(5)贴在沃拉斯顿棱镜(4)上；所述偏振片(6)贴在液晶相移器(5)上，且固定在剪切相移模块的后壳(8)上；剪切相移模块的圆形外壳(7)和后壳(8)组合并与剪切相移模块的套筒(9)连接固定在底板(15)上；所述外壳(13)与底板(15)通过螺丝连接。In this embodiment, the CCD camera (11) is fixed on the camera base (14); the camera base (14) is fixed on the base plate (15) through screws; the beam expansion device (2) is connected to the 532nm laser (1) and is fixed on the base plate (15); the Wollaston prism (4) is fixed on the circular shell (7) of the shear phase shift module; the liquid crystal phase shifter (5) is attached to the Wollaston prism. on the prism (4); the polarizer (6) is attached to the liquid crystal phase shifter (5) and fixed on the rear shell (8) of the shearing phase shift module; the circular shell (8) of the shearing phase shift module 7) Combine with the rear shell (8) and connect with the sleeve (9) of the shear phase shift module and fix it on the base plate (15); the outer shell (13) and the base plate (15) are connected by screws.
用于测量物体形变的激光剪切散斑干涉装置工作过程如下所述：The working process of the laser shearing speckle interference device used to measure object deformation is as follows:
将被测物体(3)放置在距离装置500mm的位置，532nm激光器(1)经扩束装置(2)变为发散光束，扩束后的激光照射至被测物体(3)表面反射形成的漫反射光，经过沃拉斯顿棱镜(4)后分成两束偏振方向相互垂直的线偏振光，调节液晶相移器(5)的电压，每间隔100ms更改一次电压输入，使光经过液晶相移器(5)后实现相位延迟，经过偏振片(6)后形成相干光场，最后通过成像镜头(10)被CCD相机(11)采集，在采集完四张图片之后，相机(11)暂停5000ms，并且对被测物体(3)进行加载，然后再每间隔100ms调节一次液晶相移器(5)的电压，重复采集四张被测物体(3)变形后的图片数据，采集后的数据由计算机控制系统(12)进行图像数据处理，获得被测物体(3)的形变量和缺陷。Place the object to be measured (3) at a distance of 500mm from the device. The 532nm laser (1) is transformed into a divergent beam through the beam expander (2). The expanded laser irradiates the diffuse beam formed by the surface reflection of the object to be measured (3). The reflected light is divided into two beams of linearly polarized light with polarization directions perpendicular to each other after passing through the Wollaston prism (4). Adjust the voltage of the liquid crystal phase shifter (5) and change the voltage input every 100ms, so that the light passes through the liquid crystal phase shifter. The phase delay is achieved after the detector (5), and a coherent light field is formed after passing through the polarizer (6). Finally, it is collected by the CCD camera (11) through the imaging lens (10). After collecting four pictures, the camera (11) pauses for 5000ms. , and load the measured object (3), and then adjust the voltage of the liquid crystal phase shifter (5) every 100ms, and repeatedly collect four deformed picture data of the measured object (3). The collected data is The computer control system (12) performs image data processing to obtain the deformation amount and defects of the measured object (3).
被测物体(3)在加载前拍摄图像I和加载后拍摄图像I′，通过液晶相移器添加0,π,/>相移，则变形前后的光强可以表示为：The measured object (3) takes the image I before loading and the image I′ after loading, and adds 0 through the liquid crystal phase shifter. π,/> Phase shift, then the light intensity before and after deformation can be expressed as:
为求变化量Δ，将变形前后的四幅图进行处理，得到被测物体(3)变形前后的相位量：In order to find the change amount Δ, the four images before and after deformation are processed to obtain the phase amount of the measured object (3) before and after deformation:
变形前后干涉条纹图包裹相位差为：Interference fringe pattern wrapping phase difference before and after deformation for:
对包裹相位进行解包裹得到真实相位差Δφ，所述沃拉斯顿棱镜(4)剪切方向为横向，所以只需计算x方向真实相位差与变形量导数/>的关系。Phase to package Unwrapping is performed to obtain the true phase difference Δφ. The shear direction of the Wollaston prism (4) is transverse, so it is only necessary to calculate the true phase difference and deformation derivative in the x direction/> Relationship.
其中λ为激光波长；δx为剪切量，剪切量计算公式为：Where λ is the laser wavelength; δx is the shear amount, and the shear amount calculation formula is:
其中D为532nm激光器(1)到被测物体(3)距离；d为被测物体到沃拉斯顿棱镜(4)的距离；α为沃拉斯顿棱镜(4)的分束角。Among them, D is the distance from the 532nm laser (1) to the measured object (3); d is the distance from the measured object to the Wollaston prism (4); α is the beam splitting angle of the Wollaston prism (4).
对变形量导数进行积分，可得变形量：By integrating the deformation derivative, the deformation can be obtained:
虽然本发明所揭露的实施方式如上，但所述的内容只是为了便于理解本发明而采用的实施方式，并非用以限定本发明。任何本发明所属技术领域内的技术人员，在不脱离本发明所揭露的精神和范围的前提下，可以在实施的形式上及细节上作任何的修改与变化，但本发明的专利保护范围，仍须以所附的权利要求书所界定的范围为准。Although the embodiments disclosed in the present invention are as above, the described contents are only used to facilitate the understanding of the present invention and are not intended to limit the present invention. Any person skilled in the technical field to which the present invention belongs may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the patent protection scope of the present invention shall not The scope defined by the appended claims shall prevail.
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