Single-camera microscopic stereo digital image correlation using a diffraction grating.

A simple, cost-effective but practical microscopic 3D-DIC method using a single camera and a transmission diffraction grating is proposed for surface profile and deformation measurement of small-scale objects. By illuminating a test sample with quasi-monochromatic source, the transmission diffraction grating placed in front of the camera can produce two laterally spaced first-order diffraction views of the sample surface into the two halves of the camera target. The single image comprising negative and positive first-order diffraction views can be used to reconstruct the profile of the test sample, while the two single images acquired before and after deformation can be employed to determine the 3D displacements and strains of the sample surface. The basic principles and implementation procedures of the proposed technique for microscopic 3D profile and deformation measurement are described in detail. The effectiveness and accuracy of the presented microscopic 3D-DIC method is verified by measuring the profile and 3D displacements of a regular cylinder surface.