CN106289089B - Test the optimization preparation method of speckle field - Google Patents
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Abstract
本发明公开了一种实验散斑场的优化制备方法，根据计算机散斑设计程序和散斑质量评估准则选择较优的数字散斑场，并且利用转印(水转印、热转印等)、激光切割、丝网印刷、光敏印章、镂空模板等间接制备方法将数字散斑场的整体信息转移到待测量物体的表面，为数字图像相关测量提供精度高、一致性好的散斑场。本发明通过优化选择和间接转移计算机生成的数字散斑场，解决了由于散斑场的质量不稳定导致数字图像相关方法测量精度不确定，以及由于传统的喷漆制作随机散斑场等方法对技术人员操作熟练程度存在依赖性等问题，从而保证了数字图像相关方法在科研和实际工程测量中的可靠性。
The invention discloses an optimized preparation method of an experimental speckle field, which selects a better digital speckle field according to a computer speckle design program and a speckle quality evaluation criterion, and utilizes transfer printing (water transfer printing, heat transfer printing, etc.) Indirect preparation methods such as laser cutting, screen printing, photosensitive stamps, and hollow templates transfer the overall information of the digital speckle field to the surface of the object to be measured, providing a speckle field with high precision and good consistency for digital image correlation measurement. The invention solves the uncertain measurement accuracy of the digital image correlation method due to the unstable quality of the speckle field by optimizing the selection and indirect transfer of the digital speckle field generated by the computer, as well as the traditional method of making random speckle fields by spraying paint. There are problems such as dependence on the proficiency of personnel, thus ensuring the reliability of the digital image correlation method in scientific research and actual engineering measurement.
Description
技术领域technical field
本发明属于光测力学技术领域，涉及一种适用于数字图像相关方法中的数字化、可控的散斑场生成办法。The invention belongs to the technical field of photometry and relates to a digital and controllable speckle field generation method suitable for digital image correlation methods.
背景技术Background technique
数字图像相关方法是一种新型的非接触式光学测量方法，现被应用于多个学科领域。其以附着在被测物体表面随机分布的散斑作为载体，通过追踪散斑、分析其变形前后的概率相关性，来确定物体的运动和变形特征。因此，制作高质量的散斑是数字图像相关方法精确测量的前提。Digital image correlation method is a new type of non-contact optical measurement method, which is now applied in many disciplines. It uses the randomly distributed speckle attached to the surface of the measured object as a carrier, and determines the motion and deformation characteristics of the object by tracking the speckle and analyzing the probability correlation before and after deformation. Therefore, making high-quality speckle is the premise of accurate measurement by digital image correlation method.
而在实际应用中，由于不同方法或不同人员制作得到的散斑存在较大差异，进而导致实际散斑场的质量不同，使数字图像相关的计算结果出现差异：相同的变形量在随机散斑场下表现出不一致的变形场信息。现有的随机散斑制作方法，如人工喷涂哑光白漆、黑漆，喷枪喷涂碳粉、白粉等涂料，记号笔点等，都会制作的随机散斑无重复性、精度不可以控制以及制作过程繁琐等不同因素，无法得到学术界和工业界的认可。However, in practical applications, due to the large differences in the speckle produced by different methods or different personnel, the quality of the actual speckle field is different, and the calculation results related to digital images are different: the same deformation amount in random speckle The field shows inconsistent deformation field information. The existing random speckle production methods, such as manual spraying of matte white paint and black paint, spray gun spraying of toner, white powder and other paints, marker pen spots, etc., will produce random speckle without repeatability, precision cannot be controlled and production Various factors such as cumbersome process cannot be recognized by academia and industry.
发明内容Contents of the invention
技术问题：本发明提供了一种能够解决散斑精度在实际应用中精度和一致性较差问题，实现可控制的转移高质量实验散斑场，可重复、精度可控、制作简单的实验散斑场的优化制备方法。Technical problem: The present invention provides an experimental speckle field that can solve the problem of poor accuracy and consistency of speckle accuracy in practical applications, realize controllable transfer of high-quality experimental speckle fields, repeatable, controllable precision, and simple production. Optimal preparation method of spot field.
技术方案：本发明的实验散斑场的优化制备方法，包括以下步骤：Technical solution: The optimized preparation method of the experimental speckle field of the present invention comprises the following steps:
(1)按如下方法，对数字散斑场的随机上限rand进行优化：(1) Optimize the random upper limit rand of the digital speckle field as follows:
a)固定散斑直径d值不变，改变随机上限rand，生成不同rand值对应的数字散斑场，且同一rand值重复生成S个数字散斑场，S≥5，并计算每个数字散斑场的平均灰度梯度MIG和自相关系数C，分别得到S组rand-MIG曲线和S组rand-C曲线；a) Fix the speckle diameter d value unchanged, change the random upper limit rand, generate digital speckle fields corresponding to different rand values, and repeatedly generate S digital speckle fields with the same rand value, S≥5, and calculate each digital speckle field The average gray gradient MIG and autocorrelation coefficient C of the patch field are obtained from the rand-MIG curve of the S group and the rand-C curve of the S group;
b)计算S个平均灰度梯度MIG的方差σMIG和S个自相关系数C的方差σc，得到rand-σMIG曲线和rand-σc曲线；b) Calculate the variance σ MIG of the S average gray gradient MIG and the variance σ c of the S autocorrelation coefficients C, and obtain the rand-σ MIG curve and the rand-σ c curve;
c)分别找出S组rand-MIG曲线中平均灰度梯度MIG取最大值时对应的随机上限rand值rand1，S组rand-C曲线中自相关系数C取最大值时对应的随机上限rand值rand2；分别找出rand-σMIG曲线中方差σMIG取最小值时对应的随机上限rand值rand3，rand-σc曲线中方差σc取最小值时对应的随机上限rand值rand4，得到优化的rand值为(rand1+rand2+rand3+rand4)/4；c) Find out the random upper limit rand value rand 1 corresponding to the maximum value of the average gray gradient MIG in the rand-MIG curve of the S group, and the random upper limit rand corresponding to the maximum value of the autocorrelation coefficient C in the rand-C curve of the S group value rand 2 ; respectively find the random upper limit rand value rand 3 corresponding to the variance σ MIG taking the minimum value in the rand-σ MIG curve, and the random upper limit rand value rand 4 corresponding to the variance σ c taking the minimum value in the rand-σ c curve , the optimized rand value is (rand 1 +rand 2 +rand 3 +rand 4 )/4;
(2)按如下方法，对数字散斑场的参数d进行优化：(2) Optimize the parameter d of the digital speckle field as follows:
a)固定随机上限rand为步骤(1)中优化的rand值，改变散斑直径d，生成不同d值对应的数字散斑场，并计算每个数字散斑场平均灰度梯度MIG，得到d-MIG曲线；a) Fix the random upper limit rand to the rand value optimized in step (1), change the speckle diameter d to generate digital speckle fields corresponding to different d values, and calculate the average gray gradient MIG of each digital speckle field to obtain d - MIG curve;
b)找出所述步骤a)的曲线d-MIG中平均灰度梯度MIG取最大值时对应的d，为优化的d值；b) find out the corresponding d when the average gray gradient MIG takes the maximum value in the curve d-MIG of the step a), which is the optimized d value;
(3)由所述步骤(1)中优化的rand值和步骤(2)中优化的d值生成优化的数字散斑场；(3) generate an optimized digital speckle field by the optimized rand value in the step (1) and the optimized d value in the step (2);
(4)将所述步骤(3)中生成的优化的数字散斑场输出为矢量图，输出的散斑物理尺寸为D，其中，D由公式D＝W×d/Rs确定，式中W为待测量区域的长边边长，Rs为相机测量该边长方向的分辨率；(4) Output the optimized digital speckle field generated in step (3) as a vector diagram, and the physical size of the output speckle is D, where D is determined by the formula D=W×d/Rs, where W is the length of the long side of the area to be measured, and Rs is the resolution of the camera in the direction of the side length;
(5)根据实验的测量条件，将所述步骤(4)中输出的矢量图制作到待测量试件表面，作为实验散斑场。(5) According to the measurement conditions of the experiment, make the vector diagram output in the step (4) on the surface of the test piece to be measured as the experimental speckle field.
进一步的，本发明方法中，步骤(1)、(2)和(3)中均按如下步骤生成数字散斑场：Further, in the method of the present invention, in steps (1), (2) and (3), the digital speckle field is generated according to the following steps:
1)根据n＝int(w2/(2π×d2))计算边长为w的数字散斑场的散斑个数n，按照下式计算所有散斑中心点的坐标，生成散斑中心间隔为的规则排列散斑场：1) According to n=int(w 2 /(2π×d 2 )), calculate the speckle number n of the digital speckle field whose side length is w, and calculate the coordinates of all speckle center points according to the following formula to generate the speckle center The interval is Regularly arranged speckle field of :
其中，（x′i，y′i)为第i个散斑中心点的坐标，和分别为的余数和整数，d为散斑直径；Among them, (x′ i , y′ i ) is the coordinate of the i-th speckle center point, and respectively The remainder and integer of , d is the speckle diameter;
2)按照下式计算所有散斑中心点的坐标，生成数字散斑场：2) Calculate the coordinates of all speckle center points according to the following formula to generate a digital speckle field:
其中，(xi，yi)为数字散斑场中第i个散斑中心点的坐标，f(0，rand)表示区间为(0，rand)的伪随机函数，rand为随机上限，rand∈(0，1]，数字散斑场的第i个散斑中心点与规则散斑场的第i个散斑中心点对应。Among them, ( xi , y i ) is the coordinates of the i-th speckle center point in the digital speckle field, f(0, rand) represents a pseudo-random function with an interval of (0, rand), rand is the upper limit of randomness, and rand ∈(0, 1], the i-th speckle center point of the digital speckle field corresponds to the i-th speckle center point of the regular speckle field.
进一步的，本发明方法中，步骤(1)、(2)中，采用sobel算子计算数字散斑场的平均灰度梯度MIG，采用互相关函数计算数字散斑场的自相关系数C。Further, in the method of the present invention, in steps (1) and (2), a sobel operator is used to calculate the average gray gradient MIG of the digital speckle field, and a cross-correlation function is used to calculate the autocorrelation coefficient C of the digital speckle field.
进一步的，本发明方法中，步骤(5)中将矢量图制作到待测量试件表面的方法是指能够将图案间接转移到目标物体上、并且不改变物体原有特征的一切转移方法。Further, in the method of the present invention, the method of making the vector diagram on the surface of the test piece to be measured in step (5) refers to all transfer methods that can indirectly transfer the pattern to the target object without changing the original characteristics of the object.
本发明方法根据待测试件、实验环境等选择合适的制备方法：The inventive method selects suitable preparation method according to test piece, experimental environment etc.:
按照试件大小和相机、镜头的分辨率确定测量视场，从而选择合适的散斑物理尺寸；进一步了解待测试件的形状、加载温度等信息，结合每种转移方法的制作精度和使用环境，选择合适的数字散斑转移方法，为了使转移得到的实验散斑场与数字散斑场具有一致的散斑信息。本发明中提供的能够成功完成散斑转移任务的制备方法包括：转印(水转印、热转印等)、激光切割、丝网印刷、光敏印章、镂空模板等间接散斑制备技术，此处列出的多种技术能够将计算机生成的散斑场图案复制到不同状况下的待测量试件的表面。Determine the measurement field of view according to the size of the test piece and the resolution of the camera and lens, so as to select the appropriate physical size of the speckle; further understand the shape of the test piece, loading temperature and other information, combined with the production accuracy and use environment of each transfer method, To select an appropriate digital speckle transfer method, in order to make the transferred experimental speckle field and digital speckle field have consistent speckle information. The preparation methods provided in the present invention that can successfully complete the task of speckle transfer include: indirect speckle preparation techniques such as transfer printing (water transfer printing, thermal transfer printing, etc.), laser cutting, screen printing, photosensitive stamps, and hollow templates. A variety of techniques, listed here, enable the replication of computer-generated speckle field patterns to the surface of a test piece to be measured under different conditions.
本发明方法实现高质量的数字散斑转移，为数字图像相关方法提供高质量的实验散斑场：The method of the present invention realizes high-quality digital speckle transfer, and provides high-quality experimental speckle fields for digital image correlation methods:
本发明方法将计算机可控的高质量数字散斑直接转移到试件表面，且转移方法不改变散斑场的数字信息，从而预备出高质量的实验散斑场，这种方法无疑是数字图像相关方法中简便制作高精度、一致性散斑最直接可靠的方法。The method of the present invention directly transfers computer-controlled high-quality digital speckle to the surface of the test piece, and the transfer method does not change the digital information of the speckle field, thereby preparing a high-quality experimental speckle field. This method is undoubtedly a digital image Among related methods, it is the most direct and reliable method to easily produce high-precision and consistent speckle.
本发明方法制备的实验散斑场和被转移的数字散斑场信息一致，能够实现此目的散斑制备方法有转印(水转印、热转印等)、激光切割、丝网印刷、光敏印章、镂空模板等，且不限于以上几种制备方法；高质量的数字散斑场通过散斑转移技术，制作形成高质量的实验散斑场，使得数字图像相关方法的精度计算机可控。The information of the experimental speckle field prepared by the method of the present invention is consistent with that of the transferred digital speckle field. Speckle preparation methods that can achieve this purpose include transfer printing (water transfer printing, thermal transfer printing, etc.), laser cutting, screen printing, photosensitive Stamps, hollow templates, etc., and are not limited to the above preparation methods; high-quality digital speckle fields are produced through speckle transfer technology to form high-quality experimental speckle fields, making the accuracy of digital image correlation methods computer controllable.
有益效果：本发明与现有技术相比，具有以下优点：Beneficial effect: compared with the prior art, the present invention has the following advantages:
(1)本发明采用数字散斑场作为制作实验散斑场的基础。数字散斑场由计算机生成，数字散斑的随机性、颗粒大小可以控制。传统的散斑场是实验人员随机制作的，未对散斑随机性、颗粒大小做定量控制，导致每次制作散斑场都不一致。因此相对于实验人员随机喷制的散斑场，由数字散斑场制作出的实验散斑场在随机性和颗粒大小方面可以控制，使得每次实验能够得到精度相同、一致性好的实验散斑场；(1) The present invention uses a digital speckle field as the basis for making an experimental speckle field. The digital speckle field is generated by a computer, and the randomness and particle size of the digital speckle can be controlled. The traditional speckle field is randomly produced by the experimenters, and the randomness and particle size of the speckle are not quantitatively controlled, which leads to the inconsistency of the speckle field every time. Therefore, compared with the speckle field sprayed randomly by the experimenters, the experimental speckle field produced by the digital speckle field can be controlled in terms of randomness and particle size, so that each experiment can obtain experimental speckle fields with the same accuracy and good consistency. spotted field;
(2)本发明采用的制作实验散斑场的数字散斑场是经过优化的。计算机控制生成的数字散斑场的参数随机上限rand和散斑直径d，计算多组散斑场的平均灰度梯度MIG和自相关系数C，优化的rand和d能够使得MIG和C取得稳定的最大值。传统的散斑场由于实验人员制作的随机性导致其不具备定量或定性分析MIG和C的特点。(2) The digital speckle field used in the present invention to make the experimental speckle field is optimized. The random upper limit rand and speckle diameter d of the generated digital speckle field parameters are controlled by the computer, and the average gray gradient MIG and autocorrelation coefficient C of multiple groups of speckle fields are calculated. The optimized rand and d can make MIG and C stable. maximum value. The traditional speckle field does not have the characteristics of quantitative or qualitative analysis of MIG and C due to the randomness made by the experimenter.
(3)本发明采用转移的办法将优化的数字散斑场间接复制到试件表面，作为实验散斑场。转移之前可根据测量区域大小输出对应的数字散斑场矢量图，得到的实验散斑场中的散斑通过相机采集后，得到固定像素尺寸的散斑点。而传统的实验散斑场难以制作出固定大小的散斑点。(3) The present invention adopts the transfer method to indirectly copy the optimized digital speckle field to the surface of the specimen as the experimental speckle field. Before the transfer, the corresponding digital speckle field vector diagram can be output according to the size of the measurement area, and the obtained speckle in the experimental speckle field is collected by the camera to obtain speckle points with a fixed pixel size. However, it is difficult to produce speckle spots with a fixed size in the traditional experimental speckle field.
(4)本发明采用转移的办法将优化的数字散斑场间接复制到试件表面，作为实验散斑场。传统的实验散斑场是直接在试件表面进行操作，难以控制实验散斑场的制作质量，导致浪费试件、重新制作等问题；且每次制作都存在散斑场差异，导致实验散斑场可重复性差。而采用转移的方法将数字散斑场间接复制到待测试件表面，得到的实验散斑场与数字散斑场一致，不仅排除了实验人员操作的随机性使得实验散斑场效果更好，还能够达到多个试件可制作相同实验散斑场的效果，比传统方法的可重复性更强；数字化转移过程使得实验散斑制作简单、紧凑，能够满足学术研究和工业测量测量可靠性需求。(4) The present invention adopts the transfer method to indirectly copy the optimized digital speckle field to the surface of the specimen as the experimental speckle field. The traditional experimental speckle field is directly operated on the surface of the specimen, it is difficult to control the production quality of the experimental speckle field, resulting in waste of specimens, re-production and other problems; and there are speckle field differences in each production, resulting in experimental speckle Field repeatability is poor. However, the transfer method is used to indirectly copy the digital speckle field to the surface of the test piece, and the obtained experimental speckle field is consistent with the digital speckle field, which not only eliminates the randomness of the experimenter's operation, but also makes the experimental speckle field better. It can achieve the effect that multiple specimens can make the same experimental speckle field, which is more repeatable than the traditional method; the digital transfer process makes the experimental speckle production simple and compact, which can meet the reliability requirements of academic research and industrial measurement.
附图说明Description of drawings
图1本发明的具体操作流程图；The specific operation flowchart of Fig. 1 the present invention;
图2本发明的优化散斑场：图2a为规则排列的散斑场，图2b为本发明提供的一类高质量散斑场，该类散斑场的参数为：随机性上限rand等于0.7，散斑颗粒直径d为4个像素Figure 2 The optimized speckle field of the present invention: Figure 2a is a regularly arranged speckle field, and Figure 2b is a type of high-quality speckle field provided by the present invention. The parameters of this type of speckle field are: the upper limit of randomness rand is equal to 0.7 , the speckle particle diameter d is 4 pixels
具体实施方式Detailed ways
下面结合实施例和说明书附图对本发明作进一步的说明。The present invention will be further described below in conjunction with embodiment and accompanying drawing.
图1为本发明的流程图，该流程图主要被分为(1)(2)(3)三个部分，可按照如下操作步骤实现精度可控、操作简单的可重复实验散斑场制备：Fig. 1 is a flow chart of the present invention, which is mainly divided into three parts (1) (2) (3), and the preparation of repeatable experimental speckle field with controllable precision and simple operation can be realized according to the following operation steps:
(1)计算机生成高质量的数字散斑场：(1) Computer generated high-quality digital speckle field:
a.数字散斑场的生成：a. Generation of digital speckle field:
首先，对任意给定的散斑大小d，可按照下式给出富含d、rand等参数信息的规则排列的散斑场(如图2a)：First, for any given speckle size d, a regularly arranged speckle field rich in d, rand and other parameter information can be given according to the following formula (as shown in Figure 2a):
其中，（x′i，y′i)为规则排列散斑场的第i个散斑中心点坐标，和分别为的余数和整数，即n个散斑点依照从左到右、从上到下的顺序排列，n＝int(w2/(2π×d2))，为散斑总个数，w为散斑场的边长。由上述公式生成的规则排列散斑场的散斑中心间隔为 Among them, (x′ i , y′ i ) is the coordinates of the i-th speckle center point of the regularly arranged speckle field, and respectively The remainder and the integer, that is, the n speckle points are arranged in order from left to right and from top to bottom, n=int(w 2 /(2π×d 2 )), is the total number of speckles, w is the speckle The side length of the field. The speckle center interval of the regularly arranged speckle field generated by the above formula is
其次，对任意给定的散斑大小d、随机性上限rand，按照下式计算所有散斑中心点的坐标，生成数字散斑场，如图(如图2b)：Secondly, for any given speckle size d and randomness upper limit rand, the coordinates of all speckle center points are calculated according to the following formula to generate a digital speckle field, as shown in the figure (as shown in Figure 2b):
其中，(xi，yi)为数字散斑场中第i个散斑中心点的坐标，f(0，rand)表示区间为(0，rand)的伪随机函数，rand为随机上限，rand∈(0，1]，数字散斑场的第i个散斑中心点与规则散斑场的第i个散斑中心点对应。Among them, ( xi , y i ) is the coordinates of the i-th speckle center point in the digital speckle field, f(0, rand) represents a pseudo-random function with an interval of (0, rand), rand is the upper limit of randomness, and rand ∈(0, 1], the i-th speckle center point of the digital speckle field corresponds to the i-th speckle center point of the regular speckle field.
b.数字散斑场的优化：b. Optimization of digital speckle field:
根据生成的数字散斑场的平均灰度梯度MIG和自相关系数C，来综合评价散斑场质量。计算中，采用索贝尔(sobel)算子计算数字散斑场的平均灰度梯度MIG，采用互相关函数计算数字散斑场的自相关系数C。优化d和rand，使得平均灰度梯度MIG和自相关系数C取得稳定的最大值。具体方法如下：According to the average gray gradient MIG and autocorrelation coefficient C of the generated digital speckle field, the speckle field quality is comprehensively evaluated. In the calculation, a Sobel (sobel) operator is used to calculate the average gray gradient MIG of the digital speckle field, and a cross-correlation function is used to calculate the autocorrelation coefficient C of the digital speckle field. Optimize d and rand, so that the average gray gradient MIG and autocorrelation coefficient C achieve a stable maximum value. The specific method is as follows:
首先，对数字散斑场的随机上限rand进行优化：First, optimize the random upper bound rand of the digital speckle field:
a)固定散斑直径d值不变，改变随机上限rand，生成不同rand值对应的数字散斑场，且同一rand值重复生成S个数字散斑场，S≥5，并计算每个数字散斑场的平均灰度梯度MIG和自相关系数C，分别得到S组rand-MIG曲线和S组rand-C曲线；a) Fix the speckle diameter d value unchanged, change the random upper limit rand, generate digital speckle fields corresponding to different rand values, and repeatedly generate S digital speckle fields with the same rand value, S≥5, and calculate each digital speckle field The average gray gradient MIG and autocorrelation coefficient C of the patch field are obtained from the rand-MIG curve of the S group and the rand-C curve of the S group;
b)计算S个平均灰度梯度MIG的方差σMIG和S个自相关系数C的方差σc，得到rand-σMIG曲线和rand-σc曲线；b) Calculate the variance σ MIG of the S average gray gradient MIG and the variance σ c of the S autocorrelation coefficients C, and obtain the rand-σ MIG curve and the rand-σ c curve;
c)分别找出S组rand-MIG曲线中平均灰度梯度MIG取最大值时对应的随机上限rand值rand1，S组rand-C曲线中自相关系数C取最大值时对应的随机上限rand值rand2；分别找出rand-σMIG曲线中方差σMIG取最小值时对应的随机上限rand值rand3，rand-σc曲线中方差σc取最小值时对应的随机上限rand值rand4，得到优化的rand值为(rand1+rand2+rand3+rand4)/4；c) Find out the random upper limit rand value rand 1 corresponding to the maximum value of the average gray gradient MIG in the rand-MIG curve of the S group, and the random upper limit rand corresponding to the maximum value of the autocorrelation coefficient C in the rand-C curve of the S group value rand 2 ; respectively find the random upper limit rand value rand 3 corresponding to the variance σ MIG taking the minimum value in the rand-σ MIG curve, and the random upper limit rand value rand 4 corresponding to the variance σ c taking the minimum value in the rand-σ c curve , the optimized rand value is (rand 1 +rand 2 +rand 3 +rand 4 )/4;
其次，对数字散斑场的参数d进行优化：Second, optimize the parameter d of the digital speckle field:
a)固定随机上限rand为步骤(1)中优化的rand值，改变散斑直径d，生成不同d值对应的数字散斑场，并计算每个数字散斑场平均灰度梯度MIG，得到d-MIG曲线；a) Fix the random upper limit rand to the rand value optimized in step (1), change the speckle diameter d to generate digital speckle fields corresponding to different d values, and calculate the average gray gradient MIG of each digital speckle field to obtain d - MIG curve;
b)找出所述步骤a)的曲线d-MIG中平均灰度梯度MIG取最大值时对应的d，为优化的d值；b) find out the corresponding d when the average gray gradient MIG takes the maximum value in the curve d-MIG of the step a), which is the optimized d value;
c.高质量数字散斑场的生成：c. Generation of high-quality digital speckle fields:
将优化的d和rand值，代入下式，生成优化的数字散斑场，即是高质量的数字散斑场：Substitute the optimized d and rand values into the following formula to generate an optimized digital speckle field, which is a high-quality digital speckle field:
本发明提供的高质量散斑场是按照上式，对图2a中给一个随机性上限rand等于0.7后形成的，散斑大小d为4像素，满足此特征的高质量散斑场如图2b所示。此图代表着有相同特征的一类散斑场，不限制散斑场颜色、不限制随机性上限rand值的微小变化、不限制牺牲数字图像计算精度换来的随机性上限rand值的变化等；The high-quality speckle field provided by the present invention is formed by setting a random upper limit rand equal to 0.7 in Fig. 2a according to the above formula, and the speckle size d is 4 pixels. The high-quality speckle field satisfying this characteristic is shown in Fig. 2b shown. This picture represents a type of speckle field with the same characteristics, without restrictions on the color of the speckle field, small changes in the upper limit rand value of randomness, and changes in the upper limit rand value of randomness at the expense of digital image calculation accuracy, etc. ;
(2)根据待测试件、实验环境等选择合适的制备方法：(2) Select the appropriate preparation method according to the test piece, experimental environment, etc.:
按照试件大小和相机、镜头的分辨率确定测量视场，从而选择合适的散斑物理尺寸；进一步了解待测试件的形状、加载温度等信息，结合每种转移方法的制作精度和使用环境，选择合适的数字散斑转移方法，为了使转移得到的实验散斑场与数字散斑场具有一致的散斑信息。本发明中提供的能够成功完成散斑转移任务的制备方法包括：转印(水转印、热转印等)、激光切割、丝网印刷、光敏印章、镂空模板等间接散斑制备技术，此处列出的多种技术能够将计算机生成的散斑场图案复制到不同状况下的待测量试件的表面。Determine the measurement field of view according to the size of the test piece and the resolution of the camera and lens, so as to select the appropriate physical size of the speckle; further understand the shape of the test piece, loading temperature and other information, combined with the production accuracy and use environment of each transfer method, To select an appropriate digital speckle transfer method, in order to make the transferred experimental speckle field and digital speckle field have consistent speckle information. The preparation methods provided in the present invention that can successfully complete the task of speckle transfer include: indirect speckle preparation techniques such as transfer printing (water transfer printing, thermal transfer printing, etc.), laser cutting, screen printing, photosensitive stamps, and hollow templates. A variety of techniques, listed here, enable the replication of computer-generated speckle field patterns to the surface of a test piece to be measured under different conditions.
(3)实现高质量的数字散斑转移，为数字图像相关方法提供高质量的实验散斑场：(3) Realize high-quality digital speckle transfer and provide high-quality experimental speckle fields for digital image correlation methods:
a.将优化的数字散斑场输出为矢量图，输出的散斑物理尺寸为D，其中，D由公式D＝W×d/Rs确定，式中W为待测量区域的长边边长，Rs为相机测量该边长方向的分辨率；a. Output the optimized digital speckle field as a vector diagram, and the physical size of the output speckle is D, where D is determined by the formula D=W×d/Rs, where W is the length of the long side of the area to be measured, Rs is the resolution of the camera measuring the side length direction;
b.采用转移的方法，将上述输出的矢量图制作到待测量试件表面，作为本发明最终的高质量实验散斑场。b. Using a transfer method, the above-mentioned output vector diagram is made onto the surface of the test piece to be measured, as the final high-quality experimental speckle field of the present invention.
本发明提出的一种实验散斑场优化的优化制备方法，可以解决因随机制作的散斑无重复性、精度不可以控制以及制作过程繁琐等因素导致的数字图像相关方法测量精度和一致性较差等问题。与传统散斑制作技术相比，本发明给出的数字散斑场的制作方法具有可重复性、精度可控、过程简单紧凑等特点，能够使数字图像相关更好的获得学术界和工业界认可。An optimized preparation method for experimental speckle field optimization proposed by the present invention can solve the problem of low measurement accuracy and consistency of digital image correlation methods caused by randomly produced speckles without repeatability, uncontrollable precision, and cumbersome production process. Bad question. Compared with the traditional speckle production technology, the digital speckle field production method provided by the present invention has the characteristics of repeatability, controllable precision, simple and compact process, etc., and can make digital image correlation better obtained by academic and industrial circles. recognized.
上述实施例仅是本发明的优选实施方式，应当指出：对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和等同替换，这些对本发明权利要求进行改进和等同替换后的技术方案，均落入本发明的保护范围。The foregoing embodiments are only preferred implementations of the present invention. It should be pointed out that those skilled in the art can make several improvements and equivalent replacements without departing from the principle of the present invention. Technical solutions requiring improvement and equivalent replacement all fall within the protection scope of the present invention.
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