Research of high-accuracy digital image correlation measurement system

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 mm. Time-average method is used to eliminate the gray noise of digital image and makes the correlation measurement 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.