A flexible and easy-to-implement single-camera microscopic 3D digital image correlation technique

摘要

We propose a novel, flexible and easy-to-implement single-camera microscopic three-dimensional digital image correlation (3D-DIC) technique for accurate full-field shape, motion and deformation measurements at the microscale. The established microscopic 3D-DIC system comprises a single 3CCD color camera, a high-magnification zoom lens, and a specially designed color separation device using a beam splitter, two optical bandpass filters and three plane mirrors. To perform accurate stereo measurement, color images of a test sample surface are recorded by the 3CCD camera, which observes the test sample via the microscopic imaging system from two different optical paths with the aid of the color separation device. The recorded color images can be subsequently separated to red and green channel sub-images which constitute stereo pairs corresponding to different perspectives. The separated stereo pairs can be subsequently analyzed using regular 3D-DIC to extract full-field 3D shape and deformation of the test object surface. The method was first validated by a series of benchmark tests, involving the 3D shape reconstruction of steel balls with different diameters, in-plane and out-of-plane translation tests. Surface 3D deformation measurement of a planar acrylic plate with micro-features was also performed to show the practicality of the proposed method. This method provides new simple and practical avenues for performing shape and deformation measurement at microscale, showing great potential in both material testing and bio-tissue characterization.