Optical EngineeringPrinciples and research of a high accuracy digital image correlation measurement system
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We present a new, high-accuracy digital image correlation measurement system based on a double long-focus CCD microscope. This has many advantages, such as noncontact measurement, high accuracy, quasi real time, and convenient operation. It can be used in the measurement of strain (especially in strain measurement of flexible high-molecular synthetic material, where the strain measured is averaged data) and linear expansibility of new material that has low expansibility. It can measure strain that is less than 1 με when it is used in strain measurement. The conventional digital image correlation technology can measure strain that should be more than 20 με. An array optical element is used to set the mark of 0.05 mm. The time-average method is used to eliminate CCD noise and bad effects caused by liberation, so the correlation measurement sensitivity is up to 0.01 pixel. The result of the strain test for metal material is listed. Moreover, we illustrate that the digital image correlation measurement method is the technology of a high-point diffraction resolving ratio in a super optics system.