高精度数字图像相关测量系统及其技术研究

Research of High-Accuracy Digital Image Correlation Measurement System

研制双CCD长距显微数字图像相关测量系统,它融合光电子、数字图像相关方法和散斑技术于一体,具有非接触式、高精度、宽量程、准实时、测试方法简便等优点,它可用于材料力学性能(特别是柔性高分子材料力学性能)测量、低膨胀系数新型材料线胀系数等的测量。若将其用于应变测量,灵敏度优于1με,而传统数字图像相关方法测量应变的理论灵敏度为20με。利用列阵光学元件解决了0.05 mm高衬比度微小标记的方便设置;提出消除了数字图像灰度噪声的时间平均法,使相关测量精度稳定地达到0.01 pixel。还给出金属材料拉应变的测量结果,实验结果与经典理论值相当接近。此外,还阐述数字图像相关测量技术是一种超光学系统衍射极限分辨力的测量技术。

A new high-accuracy digital image correlation measurement system based on double long-focus CCD microscope is presented. Combining photoelectric, digital image correlation and speckle technology, it has advantages of non-contact measurement, high accuracy, wide range, quasi real time, convenient operation, and can be used to measure mechanical property of materials （especially flexible high molecular synthetic materials） and linear expansibility of novel low expansibility material. Sensitivity is less than 1 με when the system is used in strain measurement, while the theoretical sensitivity of conventional digital image correlation technology is 20 με. Array optical element is used to set the micro high contrast mark of 0.05 ram. Time-average method is used to eliminate the gray noise of digital image and makes the correlation measureme.nt accuracy achieve 0.01 pixel stably. Experimental result of the tension stress measurement for metal material is listed, and the result shows the accordance with the theoretical value. Moreover, digital image correlation measurement method is described as a measurement technique which has better resolution than Rayleigh criterion.