CN105371778A

CN105371778A - Real-time measurement method and system for digital cutting speckle interference

Info

Publication number: CN105371778A
Application number: CN201510716373.3A
Authority: CN
Inventors: 高瞻; 张小琼; 秦洁
Original assignee: Beijing Jiaotong University
Current assignee: Beijing Jiaotong University
Priority date: 2015-10-29
Filing date: 2015-10-29
Publication date: 2016-03-02

Abstract

Embodiments of the present invention provide a real-time measurement method and system for digital shear speckle interference, which relate to the field of measurement. The method includes: using a laser as a light source, filtering and expanding the polarized light output by the light source through a spatial filter and a beam expander, and then irradiating the surface of the measurement target; the reflected light on the surface of the measurement target passes through The first polarizer forms linearly polarized light; the linearly polarized light passes through a Wollaston prism shearing device, and the ordinary light o light and the extraordinary light e light pass through the second polarizer; the ordinary light o light Interfering with the extraordinary light e light to form a speckle interferogram, the charge-coupled device CCD collects the imaged speckle interferogram, and obtains at least two captured speckle interferograms in time series; for at least Image subtraction is performed on two acquired speckle interferograms to generate at least one subtracted speckle interferogram; and at least one subtracted speckle interferogram is displayed.

Description

Real-time measurement method and system for digital shearing speckle interferometry

技术领域technical field

本发明涉及激光散斑干涉测量领域，尤其涉及一种数字剪切散斑干涉的实时测量方法和系统。The invention relates to the field of laser speckle interferometry, in particular to a real-time measurement method and system for digital shear speckle interferometry.

背景技术Background technique

当激光照射在具有漫反射性质的物体表面时，从物体表面反射的光在空间相干叠加，就会在整个空间发生干涉，形成随机分布的亮斑和暗斑，称为激光散斑。20世纪70年代初，激光散斑干涉测量方法得到了发展，它除了具有全息干涉测量方法的非接触、可以直观给出全场情况等一系列优点外，还具有光路简单，对试件表面要求不高，对实验条件要求较低，计算方便等特点。When the laser is irradiated on the surface of an object with diffuse reflection properties, the light reflected from the surface of the object will coherently superimpose in space, and interference will occur in the entire space, forming randomly distributed bright and dark spots, which are called laser speckle. In the early 1970s, the laser speckle interferometry method was developed. In addition to a series of advantages such as the non-contact of the holographic interferometry method and the fact that the whole field can be intuitively given, it also has a simple optical path, and the requirements for the surface of the specimen It is not high, has low requirements on experimental conditions, and is easy to calculate.

电子散斑干涉(ESPI)是在本世纪初就已经被广泛应用于漫射体表面位移或变形监测。它具有精度高、全场，非接触等优点。ESPI技术自问世以来就得到广泛的应用.它的应用领域有位移和变形测量，应变分析，动态测试，无损探伤等。可以应用于检测工程机械领域的各种变形、振动、冲击、表面粗糙度、刚度和硬度等特性；检测复合材料、集成电路、压力容器和焊接物体的表面或内部缺陷，并且还可以用于土木结构和水利设施的变形测量。总之，ESPI在机械、土木、水利、电器、航空航天、兵器工业以及生物医学领域具有非常重要的地位和广阔的前景。Electron speckle interferometry (ESPI) has been widely used in the monitoring of surface displacement or deformation of diffusers since the beginning of this century. It has the advantages of high precision, full field, non-contact and so on. ESPI technology has been widely used since its inception. Its application fields include displacement and deformation measurement, strain analysis, dynamic testing, non-destructive flaw detection, etc. It can be applied to detect various deformation, vibration, impact, surface roughness, stiffness and hardness in the field of engineering machinery; detect surface or internal defects of composite materials, integrated circuits, pressure vessels and welding objects, and can also be used in civil engineering Deformation measurement of structures and hydraulic installations. In short, ESPI has a very important position and broad prospects in the fields of machinery, civil engineering, water conservancy, electrical appliances, aerospace, weapon industry and biomedicine.

ESPI的局限性在于：由于参考光的引入，使得物光与参考光的光程差较大，因此对光源的相干长度要求较高；在实际应用中，往往需要得到物体的应变和挠度等物理量，而ESPI只能测量物体位移，需要对实验数据进行进一步处理，这对精度有一定的影响；在若干应用中，对测量系统的抗震性能要求较高，而ESPI对于噪声信号敏感性较高。针对ESPI存在的问题，出现了剪切散斑干涉术。The limitation of ESPI is: due to the introduction of reference light, the optical path difference between the object light and the reference light is relatively large, so the coherence length of the light source is required to be high; in practical applications, it is often necessary to obtain physical quantities such as strain and deflection of the object , while ESPI can only measure the displacement of objects, and further processing of the experimental data is required, which has a certain impact on the accuracy; in some applications, the seismic performance of the measurement system is high, and ESPI is more sensitive to noise signals. In response to the problems of ESPI, shearing speckle interferometry appeared.

剪切散斑干涉术最初由Hung和Leendertz提出，他们分别对基于渥拉斯顿棱镜和迈克尔逊干涉仪的剪切散斑干涉系统进行了研究。研究中，他们得到了剪切散斑干涉图，并阐述了相关原理和关键问题。此后，这一技术被引入工程领域，并被命名为剪切散斑干涉术(Shearography)。Shearing speckle interferometry was first proposed by Hung and Leendertz, who studied the shearing speckle interferometry system based on Wollaston prism and Michelson interferometer respectively. In the research, they obtained the sheared speckle interferogram, and explained the relevant principles and key issues. Since then, this technique has been introduced into the field of engineering and named as shear speckle interferometry (Shearography).

剪切散斑干涉术可以对位移的一阶微分(应变)进行直接测量，省略了测量位移后的微分计算，简化了数据处理过程，对提高测量精度有很大帮助。它的实现形式有很多，基于渥拉斯顿棱镜的测量系统中，视场角相对更大，无需引入参考光，而且抗干扰能力较强，无需特殊隔震，并可在不避光环境下进行测试，有较强的实用价值。Shear speckle interferometry can directly measure the first-order differential (strain) of the displacement, omitting the differential calculation after measuring the displacement, simplifying the data processing process, and greatly helping to improve the measurement accuracy. It can be realized in many forms. In the measurement system based on the Wollaston prism, the field of view is relatively larger, no reference light is required, and the anti-interference ability is strong, no special vibration isolation is required, and it can be used in a light-proof environment. It has strong practical value for testing.

但是，现有技术中，并不能对物体进行实时测量。However, in the prior art, it is not possible to measure objects in real time.

发明内容Contents of the invention

本发明的实施例提供了一种数字剪切散斑干涉的实时测量方法和系统，能够对测量物体进行实时测量。Embodiments of the present invention provide a real-time measurement method and system for digital shear speckle interference, capable of real-time measurement of a measurement object.

为了实现上述目的，本发明采取了如下技术方案。In order to achieve the above object, the present invention adopts the following technical solutions.

一方面，提供一种数字剪切散斑干涉的实时测量方法，包括：On the one hand, a real-time measurement method of digital shear speckle interference is provided, including:

使用激光器作为光源，将所述光源输出的偏振光经过空间滤波器和扩束器进行滤波和扩束后，照射在测量目标的表面；Using a laser as a light source, filtering and expanding the polarized light output by the light source through a spatial filter and a beam expander, and then irradiating the surface of the measurement target;

所述测量目标表面的反射光经过第一偏振片，形成线偏振光；The reflected light from the surface of the measurement target passes through the first polarizer to form linearly polarized light;

所述线偏振光经过沃拉斯顿棱镜剪切装置，所述沃拉斯顿棱镜剪切装置使得每束所述线偏振光被剪切成偏振方向互相垂直的寻常光o光和非常光e光；The linearly polarized light passes through the Wollaston prism shearing device, and the Wollaston prism shearing device makes each beam of the linearly polarized light be sheared into ordinary light o light and extraordinary light e light whose polarization directions are perpendicular to each other Light;

所述寻常光o光和所述非常光e光经过第二偏振片，所述第二偏振片使得所述寻常光o光和所述非常光e光的偏振方向一致；The ordinary light o-light and the extraordinary light e-light pass through a second polarizer, and the second polarizer makes the polarization directions of the ordinary light o-light and the extraordinary e-light consistent;

所述寻常光o光和所述非常光e光经过相互干涉形成散斑干涉图，所述散斑干涉图经过成像镜头成像于电荷耦合元件CCD上；The ordinary light o-light and the extraordinary light e-light interfere with each other to form a speckle interferogram, and the speckle interferogram is imaged on a charge-coupled device CCD through an imaging lens;

所述电荷耦合元件CCD采集成像的所述散斑干涉图，得到时间序列上的至少两幅采集后的散斑干涉图；The charge-coupled device CCD collects and images the speckle interferogram, and obtains at least two speckle interferograms after collection in time series;

对所述至少两幅采集后的散斑干涉图进行图像相减，生成至少一个相减后的散斑干涉图；performing image subtraction on the at least two acquired speckle interferograms to generate at least one subtracted speckle interferogram;

显示所述至少一个相减后的散斑干涉图。Displaying the at least one subtracted speckle interferogram.

所述对所述至少两幅采集后的散斑干涉图进行图像相减，生成至少一个相减后的散斑干涉图的步骤包括：The step of performing image subtraction on the at least two acquired speckle interferograms to generate at least one subtracted speckle interferogram includes:

将第2幅到第N幅采集后的散斑干涉图分别减去第一幅采集后的散斑干涉图，得到至少一个相减后的散斑干涉图，N为采集后的散斑干涉图的总数量，N为大于1的自然数。Subtract the first acquired speckle interferogram from the second to Nth acquired speckle interferograms respectively to obtain at least one subtracted speckle interferogram, where N is the acquired speckle interferogram The total number of , N is a natural number greater than 1.

所述方法还包括：The method also includes:

对所述至少一个相减后的散斑干涉图的每一点的光强进行傅立叶变换，获得频谱图；performing Fourier transform on the light intensity of each point of the at least one subtracted speckle interferogram to obtain a spectrogram;

根据所述频谱图，获得所述测量目标的在平行于所述光源方向上的基于时间的相位变化量；Obtaining a time-based phase change of the measurement target in a direction parallel to the light source according to the spectrogram;

根据所述测量目标的基于时间的相位变化量，计算得到所述测量目标在平行于所述光源方向上的随着时间的位移变化量；calculating, according to the time-based phase change of the measurement target, the displacement change over time of the measurement target in a direction parallel to the light source;

根据所述测量目标在平行于所述光源方向上的随着时间的位移变化量，计算生成所述测量目标在平行于所述光源方向上的应变。Calculate and generate the strain of the measurement target in the direction parallel to the light source according to the time-dependent displacement variation of the measurement target in the direction parallel to the light source.

所述根据所述测量目标在平行于所述光源方向上的随着时间的位移变化量，计算生成所述测量目标在平行于所述光源方向上的应变的步骤根据以下公式计算：The step of calculating and generating the strain of the measurement target in the direction parallel to the light source according to the displacement variation over time of the measurement target in the direction parallel to the light source is calculated according to the following formula:

$\frac{\partial \partial w w}{\partial \partial x x} ((x x,, y the y,, t t)) = = \frac{Δ Δ ((x x,, y the y,, t t))}{44 π π} \cdot \cdot λ λ \cdot \cdot \frac{11}{Δ Δ x x};;$

其中，为测量目标在平行于所述光源方向上的应变，Δx表示x方向的剪切量；λ表示光源的波长；Δ(x，y，t)为测量目标在平行于所述光源方向上的随着时间的位移变化量。in, In order to measure the strain of the target in the direction parallel to the light source, Δx represents the shear amount in the x direction; λ represents the wavelength of the light source; The amount of displacement change with time.

另一方面，提供一种数字剪切散斑干涉的实时测量系统，包括：On the other hand, a real-time measurement system for digital shear speckle interferometry is provided, including:

激光器、空间滤波器和扩束器、第一偏振片、沃拉斯顿棱镜剪切装置、第二偏振片、成像镜头和电荷耦合元件CCD、计算机；Laser, spatial filter and beam expander, first polarizer, Wollaston prism shearing device, second polarizer, imaging lens and charge-coupled device CCD, computer;

所述激光器用于，作为光源，输出线偏振光；The laser is used, as a light source, to output linearly polarized light;

所述空间滤波器和扩束器用于，将所述光源输出的偏振光进行滤波和扩束后，照射在测量目标的表面；The spatial filter and the beam expander are used to filter and expand the polarized light output by the light source, and irradiate the surface of the measurement target;

所述第一偏振片用于，使得所述测量目标表面的反射光经过所述第一偏振片后，形成线偏振光；The first polarizer is used to make the reflected light on the surface of the measurement target pass through the first polarizer to form linearly polarized light;

所述沃拉斯顿棱镜剪切装置用于，对所述线偏振光进行沃拉斯顿棱镜剪切，使得每束所述线偏振光被剪切成偏振方向互相垂直的寻常光o光和非常光e光；The Wollaston prism shearing device is used to perform Wollaston prism shearing on the linearly polarized light, so that each beam of the linearly polarized light is sheared into ordinary light and o light whose polarization directions are perpendicular to each other. very light e light;

所述第二偏振片用于，使所述寻常光o光和所述非常光e光经过所述第二偏振片后，偏振方向一致；The second polarizer is used to make the ordinary ray o and the extraordinary e ray have the same polarization direction after passing through the second polarizer;

所述电荷耦合元件CCD和成像镜头用于，将所述寻常光o光和所述非常光e光经过相互干涉形成的散斑干涉图，由成像镜头成像于电荷耦合器件CCD上；The charge-coupled device CCD and the imaging lens are used to image the speckle interference pattern formed by the mutual interference of the ordinary light o-light and the extraordinary light e-light on the charge-coupled device CCD by the imaging lens;

所述计算机用于，控制所述电荷耦合元件CCD采集成像的所述散斑干涉图，得到时间序列上的至少两幅采集后的散斑干涉图，对所述至少两幅采集后的散斑干涉图进行图像相减，生成至少一个相减后的散斑干涉图；显示所述相减后的至少一个散斑干涉图。The computer is used to control the charge-coupled device CCD to collect and image the speckle interferogram to obtain at least two collected speckle interferograms in a time series, and for the at least two collected speckle interferograms Image subtraction is performed on the interferograms to generate at least one subtracted speckle interferogram; and the at least one subtracted speckle interferogram is displayed.

所述计算机对所述至少两幅采集后的散斑干涉图进行图像相减，生成至少一个相减后的散斑干涉图具体为：The computer performs image subtraction on the at least two acquired speckle interferograms to generate at least one subtracted speckle interferogram specifically as follows:

所述计算机还用于；The computer is also used to;

所述根据所述相位变化量，计算生成所述测量目标在平行于所述光源方向上的应变具体根据以下公式：The calculation and generation of the strain of the measurement target in a direction parallel to the light source according to the phase change amount is specifically according to the following formula:

$\frac{\partial \partial w w}{\partial \partial x x} ((x x,, y the y,, t t)) = = \frac{Δ Δ ((x x,, y the y,, t t))}{44 π π} \cdot \cdot λ λ \cdot &Center Dot; \frac{11}{Δ Δ x x};;$

其中，为测量目标在平行于所述光源方向上的的应变，Δx表示x方向的剪切量；λ表示光源的波长；Δ(x，y，t)为测量目标在平行于所述光源方向上的随着时间的位移变化量。in, In order to measure the strain of the target in the direction parallel to the light source, Δx represents the shear amount in the x direction; λ represents the wavelength of the light source; Δ(x, y, t) is the strain of the measurement target in the direction parallel to the light source The amount of displacement change over time.

由上述本发明的实施例提供的技术方案可以看出，本发明实施例中，能够对测量物体进行实时测量。It can be seen from the technical solutions provided by the above embodiments of the present invention that, in the embodiments of the present invention, real-time measurement can be performed on the measurement object.

本发明附加的方面和优点将在下面的描述中部分给出，这些将从下面的描述中变得明显，或通过本发明的实践了解到。Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description, or may be learned by practice of the invention.

附图说明Description of drawings

为了更清楚地说明本发明实施例的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

图1为本发明所述的数字剪切散斑干涉的实时测量方法的流程图。Fig. 1 is a flow chart of the real-time measurement method of digital shear speckle interference according to the present invention.

图2为本发明所述的数字剪切散斑干涉的实时测量系统的连接图。Fig. 2 is a connection diagram of the real-time measurement system of digital shear speckle interferometry according to the present invention.

图3为本发明应用场景中基于沃拉斯顿棱镜的外差剪切散斑干涉测量系统的光路图。Fig. 3 is an optical path diagram of a heterodyne shearing speckle interferometry system based on a Wollaston prism in an application scenario of the present invention.

图4为本发明应用场景中渥拉斯顿棱镜原理图。Fig. 4 is a schematic diagram of the Wollaston prism in the application scene of the present invention.

具体实施方式detailed description

下面详细描述本发明的实施方式，所述实施方式的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施方式是示例性的，仅用于解释本发明，而不能解释为对本发明的限制。Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

本技术领域技术人员可以理解，除非特意声明，这里使用的单数形式“一”、“一个”、“所述”和“该”也可包括复数形式。应该进一步理解的是，本发明的说明书中使用的措辞“包括”是指存在所述特征、整数、步骤、操作、元件和/或组件，但是并不排除存在或添加一个或多个其他特征、整数、步骤、操作、元件、组件和/或它们的组。应该理解，当我们称元件被“连接”或“耦接”到另一元件时，它可以直接连接或耦接到其他元件，或者也可以存在中间元件。此外，这里使用的“连接”或“耦接”可以包括无线连接或耦接。这里使用的措辞“和/或”包括一个或更多个相关联的列出项的任一单元和全部组合。Those skilled in the art will understand that unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the word "comprising" used in the description of the present invention refers to the presence of said features, integers, steps, operations, elements and/or components, but does not exclude the presence or addition of one or more other features, Integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Additionally, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

本技术领域技术人员可以理解，除非另外定义，这里使用的所有术语(包括技术术语和科学术语)具有与本发明所属领域中的普通技术人员的一般理解相同的意义。还应该理解的是，诸如通用字典中定义的那些术语应该被理解为具有与现有技术的上下文中的意义一致的意义，并且除非像这里一样定义，不会用理想化或过于正式的含义来解释。Those skilled in the art can understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein Explanation.

为便于对本发明实施例的理解，下面将结合附图以几个具体实施例为例做进一步的解释说明，且各个实施例并不构成对本发明实施例的限定。In order to facilitate the understanding of the embodiments of the present invention, several specific embodiments will be taken as examples for further explanation below in conjunction with the accompanying drawings, and each embodiment does not constitute a limitation to the embodiments of the present invention.

如图1所示，为本发明所述的一种数字剪切散斑干涉的实时测量方法，包括：As shown in Figure 1, it is a real-time measurement method of digital shear speckle interference according to the present invention, including:

步骤11，使用激光器作为光源，将所述光源输出的偏振光经过空间滤波器和扩束器进行滤波和扩束后，照射在测量目标的表面；Step 11, using a laser as a light source, filtering and expanding the polarized light output by the light source through a spatial filter and a beam expander, and then irradiating the surface of the measurement target;

步骤121，所述测量目标表面的反射光经过第一偏振片，形成线偏振光；Step 121, the reflected light on the surface of the measurement target passes through the first polarizer to form linearly polarized light;

步骤13，所述线偏振光经过沃拉斯顿棱镜剪切装置，所述沃拉斯顿棱镜剪切装置使得每束所述线偏振光被剪切成偏振方向互相垂直的寻常光o光和非常光e光；寻常o光和非常e光在空间分离，因此目标物上一点的寻常o光和另一点的非常e光在剪切之后会在空间重合。也就是说，目标物上一点经渥拉斯顿棱镜后分成两点；空间的两点经过渥拉斯顿棱镜后变成一点。Step 13, the linearly polarized light passes through the Wollaston prism shearing device, and the Wollaston prism shearing device makes each beam of the linearly polarized light be sheared into ordinary light and o light whose polarization directions are perpendicular to each other. Extraordinary e-ray; ordinary o-ray and extraordinary e-ray are separated in space, so the ordinary o-ray at one point on the object and the extraordinary e-ray at another point will coincide in space after clipping. That is to say, a point on the object is divided into two points after passing through the Wollaston prism; two points in space become one point after passing through the Wollaston prism.

步骤14，所述寻常光o光和所述非常光e光经过第二偏振片，所述第二偏振片使得所述寻常光o光和所述非常光e光的偏振方向一致；Step 14, the ordinary light o-light and the extraordinary light e-light pass through a second polarizer, and the second polarizer makes the polarization directions of the ordinary light o-light and the extraordinary e-light consistent;

步骤15，所述寻常光o光和所述非常光e光经过相互干涉形成散斑干涉图，所述散斑干涉图经过成像镜头成像于电荷耦合元件CCD上；Step 15, the ordinary ray o and the extraordinary e ray interfere with each other to form a speckle interferogram, and the speckle interferogram is imaged on a charge-coupled device CCD through an imaging lens;

步骤16，所述电荷耦合元件CCD采集成像的所述散斑干涉图，得到时间序列上的至少两幅采集后的散斑干涉图；Step 16, the charge-coupled device CCD acquires the imaged speckle interferogram, and obtains at least two acquired speckle interferograms in time series;

步骤17，对所述至少两幅采集后的散斑干涉图进行图像相减，生成至少一个相减后的散斑干涉图；Step 17, performing image subtraction on the at least two acquired speckle interferograms to generate at least one subtracted speckle interferogram;

步骤18，显示所述至少一个相减后的散斑干涉图。Step 18, displaying the at least one subtracted speckle interferogram.

步骤17包括：Step 17 includes:

所述方法还包括：The method also includes:

步骤19，对所述至少一个相减后的散斑干涉图的每一点的光强进行傅立叶变换，获得频谱图；Step 19, performing Fourier transform on the light intensity of each point of the at least one subtracted speckle interferogram to obtain a spectrogram;

步骤110，根据所述频谱图，获得所述测量目标的在平行于所述光源方向上的基于时间的相位变化量；Step 110, according to the spectrogram, obtain the time-based phase change of the measurement target in a direction parallel to the light source;

步骤111，根据所述测量目标的基于时间的相位变化量，计算得到所述测量目标在平行于所述光源方向上的随着时间的位移变化量；Step 111, according to the time-based phase change of the measurement target, calculate the displacement change over time of the measurement target in a direction parallel to the light source;

步骤112，根据所述测量目标在平行于所述光源方向上的随着时间的位移变化量，计算生成所述测量目标在平行于所述光源方向上的应变。Step 112 : Calculate and generate the strain of the measurement target in the direction parallel to the light source according to the displacement change over time of the measurement target in the direction parallel to the light source.

步骤112根据以下公式计算：Step 112 is calculated according to the following formula:

其中，为测量目标在平行于所述光源方向上的应变，Δx表示x方向的剪切量；λ表示光源的波长；Δ(x，y，t)为测量目标在平行于所述光源方向上的随着时间的位移变化量。该步骤中，预先建立坐标系，以平行于光源方向为X轴，在垂直于光源方向的平面设立Y轴和Z轴。in, In order to measure the strain of the target in the direction parallel to the light source, Δx represents the shear amount in the x direction; λ represents the wavelength of the light source; The amount of displacement change with time. In this step, a coordinate system is established in advance, with the X axis parallel to the direction of the light source, and the Y axis and Z axis set up on a plane perpendicular to the direction of the light source.

如图2所示，为本发明所述的一种数字剪切散斑干涉的实时测量系统，包括：As shown in Figure 2, it is a real-time measurement system of digital shear speckle interference according to the present invention, including:

激光器21、空间滤波器和扩束器22、第一偏振片23、沃拉斯顿棱镜剪切装置24、第二偏振片25、成像镜头26和电荷耦合元件CCD27、计算机28；Laser 21, spatial filter and beam expander 22, first polarizer 23, Wollaston prism shearing device 24, second polarizer 25, imaging lens 26 and charge coupled device CCD27, computer 28;

所述激光器21用于，作为光源，输出偏振光；The laser 21 is used as a light source to output polarized light;

所述空间滤波器和扩束器22用于，将所述光源输出的偏振光进行滤波和扩束后，照射在测量目标的表面；The spatial filter and beam expander 22 are used to filter and expand the polarized light output by the light source, and irradiate the surface of the measurement target;

所述第一偏振片23用于，使得所述测量目标表面的反射光经过所述第一偏振片后，形成线偏振光；The first polarizer 23 is used to make the reflected light of the measurement target surface pass through the first polarizer to form linearly polarized light;

所述沃拉斯顿棱镜剪切装置24用于，对所述线偏振光进行沃拉斯顿棱镜剪切，使得每束所述线偏振光被剪切成偏振方向互相垂直的寻常光o光和非常光e光；The Wollaston prism shearing device 24 is used to perform Wollaston prism shearing on the linearly polarized light, so that each beam of the linearly polarized light is sheared into ordinary light o light whose polarization directions are perpendicular to each other and extraordinary light e light;

所述第二偏振片25用于，使所述寻常光o光和所述非常光e光经过所述第二偏振片后，偏振方向一致；The second polarizer 25 is used to make the polarization directions of the ordinary ray and the extraordinary ray pass through the second polarizer in the same direction;

所述电荷耦合元件CCD27和成像镜头26用于，将所述寻常光o光和所述非常光e光经过相互干涉形成的散斑干涉图，由成像镜头成像于电荷耦合器件CCD上；The charge-coupled device CCD27 and the imaging lens 26 are used to image the speckle interference pattern formed by the mutual interference of the ordinary light o-light and the extraordinary light e-light on the charge-coupled device CCD by the imaging lens;

所述计算机28用于，控制所述电荷耦合元件CCD采集成像的所述散斑干涉图，得到时间序列上的至少两幅采集后的散斑干涉图，对所述至少两幅采集后的散斑干涉图进行图像相减，生成至少一个相减后的散斑干涉图；显示所述相减后的至少一个散斑干涉图。The computer 28 is used to control the charge-coupled device CCD to collect and image the speckle interferogram to obtain at least two collected speckle interferograms in time series, and to obtain at least two collected speckle interferograms in time series, and to obtain the at least two collected speckle interferograms. Image subtraction is performed on the speckle interferogram to generate at least one subtracted speckle interferogram; and the at least one subtracted speckle interferogram is displayed.

所述计算机28还用于；The computer 28 is also used for;

$\frac{\partial \partial w w}{\partial \partial x x} ((x x,, y the y,, t t)) = = \frac{Δ Δ ((x x,, y the y,, t t))}{44 π π} \cdot &Center Dot; λ λ \cdot &Center Dot; \frac{11}{Δ Δ x x};;$

本发明不需要具体测量物体的位移，可以得到物体的变形梯度。The invention does not need to specifically measure the displacement of the object, but can obtain the deformation gradient of the object.

以下描述本发明的应用场景。The application scenarios of the present invention are described below.

本发明所述的基于沃拉斯顿棱镜的数字剪切散斑干涉的实时测量方法，包括以下几个步骤：The real-time measurement method of the digital shear speckle interference based on the Wollaston prism of the present invention comprises the following steps:

步骤一：选择输出频率为ω的激光器作为光源；Step 1: Select a laser with an output frequency of ω as the light source;

步骤二：输出的线偏振光经过空间滤波器和扩束器进行滤波和扩束后，照射在测量目标的表面。线偏振光有三个相对独立的测量子系统，分别为面内X、Y方向的测量子系统和离面Z方向测量子系统。本测量系统可以测量离面Z方向。Step 2: After the output linearly polarized light is filtered and expanded by the spatial filter and the beam expander, it is irradiated on the surface of the measurement target. Linearly polarized light has three relatively independent measurement subsystems, which are the measurement subsystems in the in-plane X and Y directions and the out-of-plane Z direction measurement subsystem. The measurement system can measure the Z direction from the plane.

步骤三：光照射在测量目标表面后的反射光携带了测量目标表面变形信息。反射光经过第一偏振片P1，使反射光的偏振方向一致。Step 3: The reflected light after the light is irradiated on the measurement target surface carries the deformation information of the measurement target surface. The reflected light passes through the first polarizer P1, so that the polarization directions of the reflected light are consistent.

步骤四：经偏振片P1后的线偏振光经过剪切装置。本测量系统中所用的剪切装置为沃拉斯顿棱镜，经沃拉斯顿棱镜后，一束光被剪切成两束偏振方向互相垂直的o光和e光。Step 4: The linearly polarized light passing through the polarizer P1 passes through the shearing device. The shearing device used in this measurement system is a Wollaston prism. After passing through the Wollaston prism, a beam of light is sheared into two beams of o-ray and e-ray whose polarization directions are perpendicular to each other.

步骤五：两束偏振方向互相垂直的o光和e光经过第二偏振片P2，偏振方向一致，两束偏振光相互干涉形成散斑干涉图。Step 5: Two beams of o-light and e-light whose polarization directions are perpendicular to each other pass through the second polarizer P2 with the same polarization direction, and the two beams of polarized light interfere with each other to form a speckle interference pattern.

步骤六：将该散斑干涉图成像于CCD上，用计算机进行采集和数据处理。Step 6: Image the speckle interferogram on the CCD, and use a computer to collect and process data.

步骤七：利用图像相减程序，把第二幅开始的每一幅图像都减去第一幅，得到相减后的图形。可以在计算机上实时观察干涉图形，在测量目标有缺陷的区域有蝴蝶斑状条纹，通过观察蝴蝶斑可以实时获得物体的缺陷等信息。Step 7: Use the image subtraction program to subtract the first image from each image starting from the second image to obtain the image after subtraction. The interference pattern can be observed on the computer in real time, and there are butterfly-like stripes in the defective area of the measurement target. By observing the butterfly spots, the defect and other information of the object can be obtained in real time.

步骤八：用计算机对CCD获得的散斑图进行傅立叶变换，获得频谱图，通过频谱图获得物体基于时间的相位变化量，从而算出基于时间的形变的一阶导数即物体的应变。Step 8: Use a computer to perform Fourier transform on the speckle pattern obtained by the CCD to obtain a spectrogram, and obtain the time-based phase change of the object through the spectrogram, so as to calculate the first derivative of the time-based deformation, that is, the strain of the object.

目前的数字剪切散斑测量装置均无法完成对物体的实时测量。本发明通过一套时域剪切散斑测量系统，完成对物体离面位移梯度的直接测量，以及对测量目标缺陷的实时观察，具有实时、精确、抗干扰性的特点，可以实时检测物体的缺陷，直接测量物体的应变。None of the current digital shear speckle measurement devices can complete real-time measurement of objects. The invention uses a set of time-domain shear speckle measurement system to complete the direct measurement of the off-plane displacement gradient of the object and the real-time observation of the measurement target defect, which has the characteristics of real-time, accuracy and anti-interference, and can detect the object defects, directly measure the strain on the object.

也就是说，本发明针对剪切散斑干涉测量中存在的问题，提出了一种物体应变以及缺陷的实时直接测量方法。本发明的一种基于沃拉斯顿棱镜的数字剪切散斑干涉实时测量方法，结合时域散斑的优点，可以完成数字剪切散斑干涉的实时动态测量，不仅具有测量的非接触性、高精度、高灵敏度以及全场测量等优点外，还可对应变直接测量以及结构简单等特点，成为测量物体位移、应变、缺陷、震动和粗糙度等物体信息的有效工具。另外，随着机械工业、航空航天和国防工业等领域的飞速发展，对于散斑干涉测量技术提出了更高的要求，能够实时精确测量被测物体的缺陷位移和应变(位移梯度)很重要，本发明很好地解决了这个问题。That is to say, the present invention proposes a real-time direct measurement method for object strain and defects aiming at the problems existing in shear speckle interferometry. A real-time measurement method of digital shearing speckle interference based on Wollaston prism of the present invention, combined with the advantages of time-domain speckle, can complete real-time dynamic measurement of digital shearing speckle interference, not only has the non-contact nature of measurement In addition to the advantages of high precision, high sensitivity, and full-field measurement, it can also directly measure strain and simple structure, making it an effective tool for measuring object information such as object displacement, strain, defect, vibration, and roughness. In addition, with the rapid development of the machinery industry, aerospace and national defense industries, higher requirements are put forward for speckle interferometry technology. It is very important to be able to accurately measure the defect displacement and strain (displacement gradient) of the measured object in real time. The present invention solves this problem well.

以下对本发明的发明思想和原理进行介绍。The inventive thought and principle of the present invention are introduced below.

1.离面位移梯度测量：1. Out-of-plane displacement gradient measurement:

单光束照明小剪切量条件下，数字剪切散斑干涉系统可以测量离面位移梯度。当光路照明方向与x-z和y-z两个平面均平行时，测量系统对两个面内位移梯度因子和均不敏感，其中，为光线在y-z平面，剪切方向为x方向时的面内位移梯度，为光线在x-z平面，剪切方向为x方向时的面内位移梯度。因此，此情况下可以单独分离出离面位移梯度是光线在x-y平面，剪切方向为x方向时的离面位移梯度。采用相似的光路布置，调整剪切方向后，就可得到等多个方向的离面位移梯度，是光线在x-y平面，剪切方向为y方向时的离面位移梯度。The digital shear speckle interferometry system can measure the out-of-plane displacement gradient under the condition of single beam illumination and small shear amount. When the illumination direction of the optical path is parallel to the two planes xz and yz, the measurement system will measure the displacement gradient factor of the two planes and are not sensitive, among which, is the in-plane displacement gradient when the light is on the yz plane and the shear direction is the x direction, is the in-plane displacement gradient when the ray is on the xz plane and the shear direction is the x direction. Therefore, in this case the out-of-plane displacement gradient can be isolated separately is the out-of-plane displacement gradient of the ray in the xy plane when the shear direction is the x direction. Using a similar optical path arrangement, after adjusting the shearing direction, we can get Out-of-plane displacement gradients in multiple directions, is the out-of-plane displacement gradient of the ray in the xy plane when the shear direction is the y direction.

2.面内应变测量：2. In-plane strain measurement:

面内应变可由式2-1表示：The in-plane strain can be expressed by Equation 2-1:

$\begin{matrix} {ϵ ϵ}_{x x} = = \frac{\partial \partial u u}{\partial \partial x x} \\ {ϵ ϵ}_{y the y} = = \frac{\partial \partial v v}{\partial \partial y the y} \end{matrix} - - - - - - ((22 - - 11))$

${γ γ}_{x x y the y} = = \frac{\partial \partial v v}{\partial \partial x x} + + \frac{\partial \partial u u}{\partial \partial y the y}$

其中，ε_x、ε_y和ε_z分别为正应变，u，v，w分别是x，y，z方向的位移；Among them, ε _x , ε _y and ε _z are positive strains respectively, u, v, w are displacements in x, y, z directions respectively;

是光线在x-z平面，剪切方向为x方向时的面内位移梯度； is the in-plane displacement gradient of the light in the xz plane and the shear direction is the x direction;

是光线在y-z平面，剪切方向为y方向时的面内位移梯度； is the in-plane displacement gradient of the ray in the yz plane and the shear direction is the y direction;

是光线在y-z平面，剪切方向为x方向时的面内位移梯度； is the in-plane displacement gradient of the light in the yz plane and the shear direction is the x direction;

是光线在x-z平面，剪切方向为y方向时的面内位移梯度。 is the in-plane displacement gradient of the ray in the xz plane and the shear direction is the y direction.

单光束照明条件下，离面位移梯度的因子不可能为零，所以不能分离出面内位移梯度。但是，双光束照明条件下，可以将此因子消去。假设照明双光束关于y-z平面对称，则两束光产生的相位变化可分别表示为：Under single-beam illumination, the factor of the out-of-plane displacement gradient cannot be zero, so the in-plane displacement gradient cannot be separated. However, under double-beam lighting conditions, this factor can be eliminated. Assuming that the illumination double beams are symmetrical about the y-z plane, the phase changes produced by the two beams can be expressed as:

${Δ Δ}_{11} = = ((\frac{22 π π}{λ λ})) ((((sin sin α α)) \frac{\partial \partial u u}{\partial \partial x x} + + ((11 + + c c o o s the s α α)) \frac{\partial \partial ω ω}{\partial \partial x x})) Δ Δ x x - - - - - - ((22 - - 22))$

${Δ Δ}_{22} = = ((\frac{22 π π}{λ λ})) ((((- - s the s i i n no α α)) \frac{\partial \partial u u}{\partial \partial x x} + + ((11 + + c c o o s the s α α)) \frac{\partial \partial ω ω}{\partial \partial x x})) Δ Δ x x - - - - - - ((22 - - 33))$

方程(2-2)与(2-3)相减，得到相位变化之差Δ_d：Equation (2-2) is subtracted from (2-3) to obtain the difference Δ _d of phase change:

${Δ Δ}_{d d} = = {Δ Δ}_{11} - - {Δ Δ}_{22} = = ((\frac{44 π π}{λ λ})) ((s the s i i n no α α)) ((\frac{\partial \partial u u}{\partial \partial x x})) Δ Δ x x - - - - - - ((22 - - 44))$

其中，Δ₁为第一束光产生的相位变化；Δ₂为第二束光产生的相位变化；Δ_d为两束光的相位差；Wherein, Δ ₁ is the phase change that the first beam of light produces; Δ ₂ is the phase change that the second beam of light produces; Δ _d is the phase difference of two beams of light;

是光线在x-y平面，剪切方向为x方向时的离面位移梯度； is the out-of-plane displacement gradient of the light in the xy plane and the shear direction is the x direction;

Δx是x方向的剪切量。Δx is the shear amount in the x direction.

相位差Δ_d与方程1-1中的正应变分量ε_x相对应。对照明方向和剪切方向进行调节后，可分离出任意方向的面内正应变，并且可以对剪应变进行计算。The phase difference _Δd corresponds to the positive strain component _εx in Equation 1-1. After adjusting the illumination direction and shear direction, the in-plane normal strain in any direction can be separated, and the shear strain can be calculated.

3.应变与空间位移梯度：3. Strain and spatial displacement gradient:

应变矢量S可以由下式表示：The strain vector S can be expressed by the following formula:

$S S = = [\begin{matrix} {ϵ ϵ}_{x x} & {γ γ}_{x x y the y} & {γ γ}_{x x z z} \\ {γ γ}_{y the y x x} & {ϵ ϵ}_{y the y} & {γ γ}_{y the y z z} \\ {γ γ}_{z z x x} & {γ γ}_{z z y the y} & {ϵ ϵ}_{z z} \end{matrix}]$

$= = [\begin{matrix} \frac{\partial \partial u u}{\partial \partial x x} & \frac{11}{22} ((\frac{\partial \partial u u}{\partial \partial y the y} + + \frac{\partial \partial v v}{\partial \partial x x})) & \frac{11}{22} ((\frac{\partial \partial u u}{\partial \partial z z} + + \frac{\partial \partial w w}{\partial \partial x x})) \\ \frac{11}{22} ((\frac{\partial \partial v v}{\partial \partial x x} + + \frac{\partial \partial u u}{\partial \partial y the y})) & \frac{\partial \partial v v}{\partial \partial y the y} & \frac{11}{22} ((\frac{\partial \partial v v}{\partial \partial z z} + + \frac{\partial \partial w w}{\partial \partial y the y})) \\ \frac{11}{22} ((\frac{\partial \partial w w}{\partial \partial x x} + + \frac{\partial \partial u u}{\partial \partial z z})) & \frac{11}{22} ((\frac{\partial \partial w w}{\partial \partial y the y} + + \frac{\partial \partial v v}{\partial \partial z z})) & \frac{\partial \partial w w}{\partial \partial z z} \end{matrix}] - - - - - - 33 - - 11))$

其中，ε_x、ε_y和ε_z为正应变，γ_xy、γ_xz、γ_yx、γ_yz、γ_zx以及γ_zy为切应变。由于关于z方向的空间位移梯度不能由数字剪切散斑干涉术直接测量，因此，应变矩阵中只有可通过数字剪切散斑干涉术直接测量。本发明对离面位移梯度进行测量，它可以反映在剪切散斑干涉条纹中。Among them, ε _x , ε _y and ε _z are normal strains, and γ _xy , γ _xz , γ _yx , γ _yz , γ _zx and γ _zy are shear strains. Since the spatial displacement gradient with respect to the z direction cannot be directly measured by digital shear speckle interferometry, in the strain matrix only Can be directly measured by digital shearing speckle interferometry. The present invention is to the out-of-plane displacement gradient Measurements are made and it can be reflected in sheared speckle interference fringes.

其中，u，v，w分别是x，y，z方向的位移；Among them, u, v, w are the displacements in the x, y, and z directions respectively;

是光线在x-z平面，剪切方向为y方向时的面内位移梯度； is the in-plane displacement gradient when the light is on the xz plane and the shear direction is the y direction;

是光线在x-y平面，剪切方向为y方向时的离面位移梯度。 is the out-of-plane displacement gradient of the ray in the xy plane when the shear direction is the y direction.

4.条纹形成原理和解释4. Streak formation principle and explanation

剪切散斑图像光强可由下式表示：The light intensity of the sheared speckle image can be expressed by the following formula:

其中，I为CCD像面接收到的被测物体表面散斑图样光强；I₀为背景光强；γ为散斑图样的调制能见度，为随机相位分布。Among them, I is the light intensity of the speckle pattern on the surface of the measured object received by the CCD image plane; I ₀ is the background light intensity; γ is the modulation visibility of the speckle pattern, is a random phase distribution.

物体表面发生微小形变后，I会相应变化为I(t):After a slight deformation occurs on the surface of the object, I will change accordingly to I(t):

其中，Δ(t)表示由于形变产生的随时间变化的相位变化。where Δ(t) represents the time-varying phase change due to deformation.

由于随机相位未知，所以无法从散斑图像中直接看出有用信息。然而，如果将两幅散斑图进行减法运算，随机相位将会被消除，相减后的图样将会呈现为包含形变信息的条纹图：due to random phase Unknown, so useful information cannot be directly seen from the speckle image. However, if the two speckle images are subtracted, the random phase will be eliminated, and the subtracted pattern will appear as a fringe image containing deformation information:

其中，暗条纹对应整数周期Δ＝2nπ(n＝0，1，2……)，亮条纹对应半周期Δ＝(2n+1)π(n＝0，1，2……)。Wherein, the dark stripes correspond to integer periods Δ=2nπ (n=0, 1, 2...), and the bright stripes correspond to half periods Δ=(2n+1)π (n=0, 1, 2...).

公式中的Δ为在t时刻由于形变产生的相位变化。Δ in the formula is the phase change due to deformation at time t.

散斑干涉图的相位由式(4-4)决定:The phase of the speckle interferogram is determined by formula (4-4):

其中，λ为激光波长，n为介质折射率，L为两束光线的光程差，为相位常量。Among them, λ is the laser wavelength, n is the refractive index of the medium, L is the optical path difference of the two beams, is a phase constant.

对(4-4)式求导，可得：Deriving formula (4-4), we can get:

$Δ Δ φ φ = = \frac{\partial \partial φ φ}{\partial \partial λ λ} Δ Δ λ λ + + \frac{\partial \partial φ φ}{\partial \partial n no} Δ Δ n no + + \frac{\partial \partial φ φ}{\partial \partial L L} Δ Δ L L = = - - \frac{22 π π n no L L}{{λ λ}^{22}} Δ Δ λ λ + + \frac{22 π π L L}{λ λ} Δ Δ n no + + \frac{22 π π n no}{λ λ} Δ Δ L L - - - - - - ((44 - - 55))$

其中，Δφ表示相位变化量，Δλ，Δn和ΔL则分别表示激光波长、介质折射率以及两束光线光程差的变化量。Among them, Δφ represents the amount of phase change, and Δλ, Δn, and ΔL represent the changes in laser wavelength, medium refractive index, and optical path difference between two beams of light, respectively.

由于在一般实验条件下，激光波长以及介质折射率(空气中n＝1)的变化可被忽略，所以(4-5)式可被简化为：Since the change of laser wavelength and medium refractive index (n=1 in air) can be ignored under general experimental conditions, formula (4-5) can be simplified as:

$Δ Δ φ φ = = \frac{22 π π}{λ λ} Δ Δ L L = = \frac{22 π π}{λ λ} ((A A Δ Δ u u + + B B Δ Δ v v + + C C Δ Δ w w)) - - - - - - ((44 - - 66))$

其中，Δu，Δv和Δw分别表示位移矢量的三个分量，A，B和C为几何关系影响因子，它们由光源坐标S(x_s，y_s，z_s)和相机坐标O(x_o，y_o，z_o)决定，定义式如下：Among them, Δu, Δv and Δw represent the three components of the displacement vector respectively, and A, B and C are the geometric relationship influencing factors, which are composed of the light source coordinates S(x _s , y _s , z _s ) and the camera coordinates O(x _o , y _o , z _o ), the definition formula is as follows:

$\begin{matrix} A A = = \frac{((x x - - {x x}_{00}))}{\sqrt{{x x}_{00}^{22} + + {y the y}_{00}^{22} + + {z z}_{00}^{22}}} + + \frac{((x x - - {x x}_{s the s}))}{\sqrt{{x x}_{s the s}^{22} + + {y the y}_{s the s}^{22} + + {z z}_{s the s}^{22}}} \\ B B = = \frac{((y the y - - {y the y}_{00}))}{\sqrt{{x x}_{00}^{22} + + {y the y}_{00}^{22} + + {z z}_{00}^{22}}} + + \frac{((y the y - - {y the y}_{s the s}))}{\sqrt{{x x}_{s the s}^{22} + + {y the y}_{s the s}^{22} + + {z z}_{s the s}^{22}}} \\ C C = = \frac{((z z - - {z z}_{00}))}{\sqrt{{x x}_{00}^{22} + + {y the y}_{00}^{22} + + {z z}_{00}^{22}}} + + \frac{((z z - - {z z}_{s the s}))}{\sqrt{{x x}_{s the s}^{22} + + {y the y}_{s the s}^{22} + + {z z}_{s the s}^{22}}};; \end{matrix} - - - - - - ((44 - - 77))$

当剪切发生在x方向时，(4-7)式可改写为：When the shear occurs in the x direction, equation (4-7) can be rewritten as:

$Δ Δ φ φ = = \frac{22 π π}{λ λ} ((A A \frac{Δ Δ u u}{Δ Δ x x} + + B B \frac{Δ Δ v v}{Δ Δ x x} + + C C \frac{Δ Δ w w}{Δ Δ x x})) Δ Δ x x - - - - - - ((44 - - 88))$

其中Δx表示像面上相互干涉的两个点在物面上的距离，即x方向上的剪切量。Among them, Δx represents the distance between two points on the object plane that interfere with each other on the image plane, that is, the shear amount in the x direction.

在小剪切量条件下，可以用微分项表示式(4-8)中的差分项：Under the condition of small shear amount, the differential term in formula (4-8) can be expressed by differential term:

$Δ Δ φ φ = = \frac{22 π π}{λ λ} ((A A \frac{\partial \partial u u}{\partial \partial x x} + + B B \frac{\partial \partial v v}{\partial \partial x x} + + C C \frac{\partial \partial w w}{\partial \partial x x})) Δ Δ x x - - - - - - ((44 - - 99))$

其中和分别表示位移分量u，v和w在x方向上的偏导数，即位移分量在x方向的空间梯度。in and Represent the partial derivatives of the displacement components u, v and w in the x direction, that is, the spatial gradient of the displacement components in the x direction.

如果剪切发生在y方向，则式(2-11)相应变为：If the shear occurs in the y direction, the equation (2-11) correspondingly becomes:

$Δ Δ φ φ = = \frac{22 π π}{λ λ} ((A A \frac{\partial \partial u u}{\partial \partial y the y} + + B B \frac{\partial \partial v v}{\partial \partial y the y} + + C C \frac{\partial \partial w w}{\partial \partial y the y})) Δ Δ y the y - - - - - - ((44 - - 1010))$

其中Δy表示测量系统在y方向的剪切量。where Δy represents the shear amount of the measurement system in the y direction.

如果照明和接收装置均平行于z轴，则敏感因子A和B可被视为0。因此，根据式(4-10)，坐标为(x，y)的点在t时刻的离面位移梯度和相位变化的关系可以表示为：Sensitivity factors A and B can be considered to be zero if both the illuminating and receiving devices are parallel to the z-axis. Therefore, according to formula (4-10), the relationship between the out-of-plane displacement gradient and phase change of a point with coordinates (x, y) at time t can be expressed as:

$\frac{\partial \partial w w}{\partial \partial x x} ((x x,, y the y,, t t)) = = \frac{Δ Δ ((x x,, y the y,, t t))}{44 π π} \cdot \cdot λ λ \cdot \cdot \frac{11}{Δ Δ x x} - - - - - - ((44 - - 1111))$

其中，Δx表示x方向的剪切量，λ表示激光波长。根据式(4-11)，可知离面位移梯度与相位变化量成正比。Among them, Δx represents the shear amount in the x direction, and λ represents the laser wavelength. According to formula (4-11), it can be seen that the out-of-plane displacement gradient is proportional to the phase change.

参考光路图，当对测量物体施加压力的时候，测量物体会发生变形，包括xyz三个方向的。本系统可以测量z方向的变形。施加压力是一个持续的过程，时间越长，施加的力越大，z的变形越大。Δ(x，y，t)是测量物体在z轴方向随着时间的位移变化量。Referring to the optical path diagram, when pressure is applied to the measuring object, the measuring object will be deformed, including the three directions of xyz. The system can measure deformation in the z direction. Applying pressure is a continuous process, the longer the time, the greater the force applied and the greater the deformation of z. Δ(x, y, t) is the amount of displacement of the measured object in the z-axis direction over time.

对一个发生侧向位移的圆盘来说，条纹图样分别表示和可以看作是离面位移梯度的等高线。For a disc displaced laterally, the fringe patterns represent and can be viewed as contour lines of out-of-plane displacement gradients.

5.相位和位移变化的关系，见公式。5. For the relationship between phase and displacement change, see the formula.

$Δ Δ φ φ = = \frac{22 π π}{λ λ} Δ Δ L L - - - - - - ((55 - - 11))$

Δφ为相位，ΔL为统称的位移。Δφ is the phase, and ΔL is the collective displacement.

6.线应变6. Line strain

在直角坐标中所取单元体为正六面体时，三条相互垂直的棱边的长度在变形前后的改变量与原长之比，定义为线应变，用ε表示。一点在x、y、z方向的线应变分别为ε_x、ε_x、ε_y、ε_z。线应变以伸长为正，缩短为负。When the unit body taken in Cartesian coordinates is a regular hexahedron, the ratio of the change in length of three mutually perpendicular edges before and after deformation to the original length is defined as line strain, expressed by ε. The linear strains of a point in the x, y, and z directions are ε _x , ε _x , ε _y , and ε _z , respectively. Linear strain is positive for elongation and negative for shortening.

7.切应变7. Shear strain

单元体的两条相互垂直的棱边，在变形后的直角改变量，定义为角应变或切应变，用γ表示。一点在x-y方向、y-z方向z-x方向的切应变，分加别为γ_xy、γ_yz、γ_zx。切应变以直角减少为正，反之为负。The amount of right angle change after deformation of two mutually perpendicular edges of the unit body is defined as angular strain or shear strain, expressed by γ. The shear strain of a point in xy direction, yz direction and zx direction are respectively γ _xy , γ _yz , γ _zx . When the shear strain decreases at right angles, it is positive, otherwise it is negative.

8.如图4所示，渥拉斯顿棱镜由两块光轴相互垂直的直角棱镜粘合而成。由于棱镜材料为双轴晶体(如石英)，垂直入射的光将会被剪切成沿不同方向传播的两束光线。8. As shown in Figure 4, the Wollaston prism is made of two rectangular prisms whose optical axes are perpendicular to each other. Since the prism material is a biaxial crystal (such as quartz), the vertically incident light will be sheared into two beams of light propagating in different directions.

从左侧进入渥拉斯顿棱镜的光线可以看作是振动方向相互垂直的两束光线(寻常光o光和非寻常光e光)的组合。当它垂直入射到左侧直角棱镜时，由于入射方向与光轴垂直，所以传播方向不发生偏折，但是由于双折射晶体对于两束光的折射率不同，所以o光和e光分别以v_o和v_e传播。当o光和e光传播至粘合界面时，由于右侧棱镜光轴方向相对左侧棱镜旋转了90°，故此时左侧棱镜中的o光和e光分别变为e光和o光，折射率也由n_o和n_e变为n_e和n_o。本文使用渥拉斯顿材料为石英，对于石英，n_o<n_e，根据折射定律，在粘合界面上e光靠近法线方向传播，o光远离法线方向传播，因此，两束光在右侧棱镜中分开一定角度，且振动方向相互垂直。当两束光线从渥拉斯顿棱镜出射到空气中时，将发生二次折射。根据斯奈尔定律，两束光线的夹角表达式为：The light entering the Wollaston prism from the left can be regarded as a combination of two beams of light (ordinary light o-ray and extraordinary light e-ray) whose vibration directions are perpendicular to each other. When it is vertically incident on the right-angle prism on the left, since the incident direction is perpendicular to the optical axis, the propagation direction will not be deflected, but because the birefringent crystals have different refractive indices for the two beams of light, the o-ray and e-ray are respectively represented by v _o and _ve spread. When the o-light and e-light propagate to the bonding interface, since the optical axis direction of the right prism is rotated by 90° relative to the left prism, the o-light and e-light in the left prism at this time become e-light and o-light respectively, The refractive index is also changed from n _o and n _e to n _e and n _o . In this paper, the Wollaston material is used as quartz. For quartz, n _o <ne _e , according to the law of refraction, e light propagates close to the normal direction on the bonding interface, and o light propagates away from the normal direction. Therefore, the two beams of light are in The right prisms are separated by a certain angle, and the vibration directions are perpendicular to each other. When the two beams of light exit the Wollaston prism into the air, double refraction will occur. According to Snell's law, the angle expression between two beams of light is:

θ＝2sin^-1[(n_e-n_o)tanβ](8-1)；θ=2sin ^-1 [(n _e -n _o )tanβ](8-1);

其中，θ为分束角；β为渥拉斯顿棱镜的楔角。Among them, θ is the beam splitting angle; β is the wedge angle of the Wollaston prism.

x方向的剪切量Δx＝2*L*tan(θ)，L为沃拉斯顿棱镜到CCD的距离，通过测量L和获取的θ，可以得到x方向的剪切量。The shear amount in the x direction Δx=2*L*tan(θ), L is the distance from the Wollaston prism to the CCD, and the shear amount in the x direction can be obtained by measuring L and the acquired θ.

由渥拉斯顿棱镜分束原理可知，物面上的一点在像面上将呈现两个错位的像，即产生剪切，剪切方向由渥拉斯顿棱镜的光轴方向决定。由于出射的两束光为振动方向相互垂直的线偏光，因此，要使这两束光产生干涉，必须在棱镜后加一偏振片，使其偏振方向与两束光的偏振方向都成45°。According to the beam splitting principle of the Wollaston prism, a point on the object surface will present two misplaced images on the image plane, that is, shearing occurs, and the shearing direction is determined by the optical axis direction of the Wollaston prism. Since the outgoing two beams of light are linearly polarized light whose vibration directions are perpendicular to each other, to make the two beams of light interfere, a polarizer must be added after the prism so that the polarization direction of the two beams of light is 45° to that of the two beams of light. .

由于被渥拉斯顿棱镜剪切后的两束光线共路，所以该元件具有极强的抗干扰能力。此外，相比其他剪切装置，其光学效率更高，视场范围更大。渥拉斯顿棱镜的缺点在于相移比较困难，不适合利用四步相移法进行计算。本文中使用时间序列散斑干涉技术，无需进行相移操作，避免了使用渥拉斯顿棱镜时相移困难的缺点。因此，本文采用渥拉斯顿棱镜作为剪切装置。Since the two beams of light cut by the Wollaston prism share the same path, the component has a strong anti-interference ability. Additionally, it offers higher optical efficiency and a wider field of view than other shearing devices. The disadvantage of the Wollaston prism is that the phase shift is relatively difficult, and it is not suitable for calculation using the four-step phase shift method. In this paper, the time-series speckle interferometry technique is used without phase shift operation, which avoids the disadvantage of phase shift difficulty when using Wollaston prism. Therefore, the Wollaston prism is used as the shearing device in this paper.

本领域普通技术人员可以理解：附图只是一个实施例的示意图，附图中的模块或流程并不一定是实施本发明所必须的。Those skilled in the art can understand that the accompanying drawing is only a schematic diagram of an embodiment, and the modules or processes in the accompanying drawing are not necessarily necessary for implementing the present invention.

通过以上的实施方式的描述可知，本领域的技术人员可以清楚地了解到本发明可借助软件加必需的通用硬件平台的方式来实现。基于这样的理解，本发明的技术方案本质上或者说对现有技术做出贡献的部分可以以软件产品的形式体现出来，该计算机软件产品可以存储在存储介质中，如ROM/RAM、磁碟、光盘等，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本发明各个实施例或者实施例的某些部分所述的方法。It can be seen from the above description of the implementation manners that those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the essence of the technical solution of the present invention or the part that contributes to the prior art can be embodied in the form of software products, and the computer software products can be stored in storage media, such as ROM/RAM, disk , CD, etc., including several instructions to make a computer device (which may be a personal computer, server, or network device, etc.) execute the methods described in various embodiments or some parts of the embodiments of the present invention.

本说明书中的各个实施例均采用递进的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。尤其，对于装置或系统实施例而言，由于其基本相似于方法实施例，所以描述得比较简单，相关之处参见方法实施例的部分说明即可。以上所描述的装置及系统实施例仅仅是示意性的，其中所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部模块来实现本实施例方案的目的。本领域普通技术人员在不付出创造性劳动的情况下，即可以理解并实施。Each embodiment in this specification is described in a progressive manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and for relevant parts, refer to part of the description of the method embodiments. The device and system embodiments described above are only illustrative, and the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, It can be located in one place, or it can be distributed to multiple network elements. Part or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. It can be understood and implemented by those skilled in the art without creative effort.

以上所述，仅为本发明较佳的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应该以权利要求的保护范围为准。The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims

1. A real-time measurement method for digital shearing speckle interference is characterized by comprising the following steps:

using a laser as a light source, filtering and expanding polarized light output by the light source through a spatial filter and a beam expander, and irradiating the polarized light on the surface of a measurement target;

the reflected light of the surface of the measurement target passes through a first polaroid to form linearly polarized light;

the linearly polarized light passes through a Wollaston prism shearing device, and each linearly polarized light is sheared into ordinary light o light and extraordinary light e light with mutually vertical polarization directions by the Wollaston prism shearing device;

the ordinary ray o light and the extraordinary ray e light pass through a second polarizing plate, and the second polarizing plate enables the polarization directions of the ordinary ray o light and the extraordinary ray e light to be consistent;

the ordinary ray o light and the extraordinary ray e light form a speckle interference pattern through mutual interference, and the speckle interference pattern is imaged on a Charge Coupled Device (CCD) through an imaging lens;

the CCD acquires the imaged speckle interferogram to obtain at least two acquired speckle interferograms on a time sequence;

performing image subtraction on the at least two collected speckle interferograms to generate at least two subtracted speckle interferograms;

displaying the at least one subtracted speckle interferogram.

2. The method of claim 1, wherein the step of performing image subtraction on the at least two collected speckle interferograms to generate at least one subtracted speckle interferogram comprises:

and respectively subtracting the first collected speckle interference image from the 2 nd to the Nth collected speckle interference images to obtain at least one subtracted speckle interference image, wherein N is the total number of the collected speckle interference images, and is a natural number greater than 1.

3. The method of claim 1, further comprising:

carrying out Fourier transform on the light intensity of each point of the speckle interferogram after the subtraction to obtain a spectrogram;

obtaining a time-based phase change amount of the measurement target in a direction parallel to the light source from the spectrogram;

calculating the displacement variation of the measuring target in the direction parallel to the light source along with the time according to the time-based phase variation of the measuring target;

and calculating and generating the strain of the measuring target in the direction parallel to the light source according to the displacement variation of the measuring target in the direction parallel to the light source along with the time.

4. The method according to claim 3, wherein the step of calculating the strain of the measurement target in the direction parallel to the light source according to the amount of change in the displacement of the measurement target in the direction parallel to the light source with time is calculated according to the following formula:

\frac{\partial w}{\partial x} (x, y, t) = \frac{Δ (x, y, t)}{4 π} \cdot λ \cdot \frac{1}{Δ x};

wherein,in order to measure the strain of the target in the direction parallel to the light source, Δ x represents the shearing amount in the x direction; λ represents the wavelength of the light source; Δ (x, y, t) is a displacement variation amount of the measurement target in a direction parallel to the light source with time.

5. A real-time measurement system for digital shearing speckle interferometry, comprising:

the device comprises a laser, a spatial filter, a beam expander, a first polaroid, a Wollaston prism shearing device, a second polaroid, an imaging lens, a Charge Coupled Device (CCD) and a computer;

the laser is used as a light source and outputs polarized light;

the spatial filter and the beam expander are used for filtering and expanding polarized light output by the light source and irradiating the polarized light on the surface of a measurement target;

the first polaroid is used for enabling the reflected light of the surface of the measurement target to form linearly polarized light after passing through the first polaroid;

the Wollaston prism shearing device is used for shearing the linearly polarized light by the Wollaston prism, so that each beam of linearly polarized light is sheared into ordinary light o light and extraordinary light e light with mutually vertical polarization directions;

the second polaroid is used for enabling the polarization directions of the ordinary ray o light and the extraordinary ray e light to be consistent after passing through the second polaroid;

the CCD and the imaging lens are used for imaging the speckle interference pattern formed by the mutual interference of the ordinary ray o light and the extraordinary ray e light on the CCD by the imaging lens;

the computer is used for controlling the CCD to collect the imaged speckle interferogram to obtain at least two collected speckle interferograms on a time sequence, and carrying out image subtraction on the at least two collected speckle interferograms to generate at least one subtracted speckle interferogram; displaying the subtracted at least one speckle interferogram.

6. The system according to claim 5, wherein the computer performs image subtraction on the at least two collected speckle interferograms to generate at least one subtracted speckle interferogram specifically as:

7. The system of claim 5, wherein the computer is further configured to;

8. The system according to claim 7, wherein the calculating the strain of the measurement target in the direction parallel to the light source according to the phase variation is specifically according to the following formula:

\frac{\partial w}{\partial x} (x, y, t) = \frac{Δ (x, y, t)}{4 π} \cdot λ \cdot \frac{1}{Δ x};

wherein,to measure the strain of the target in the direction parallel to the light source, Δ x represents the amount of shear in the x-direction; λ represents the wavelength of the light source; Δ (x, y, t) is a displacement variation amount of the measurement target in a direction parallel to the light source with time.