One main limitation of conventional digital image correlation (DIC) methods is their incapacity to treat with large, discontinuous displacements. This paper seeks to resolve this issue using a variational method. Specifically, the objective function is written in a form of L1‐norm instead of L2‐norm for discontinuity preservation. This convex, non‐differentiable objective function is resolved by a proximal gradient method. Then, the entire correlation process is embedded into a multi‐level image pyramid, enabling large displacements to be measured accurately. The proposed method is first validated on images with prescribed small displacements; its performance to treat with discontinuous, large displacements is then examined. The results show that the proposed method exhibits an acceptable performance when measuring some extreme displacements up to 16.5 pixels in a 500 × 500 pixels resolution image. Concerning subpixel accuracy, the errors can be lessened to a very low level with optimised parameters even for a dense correlation at each pixel. Good performance is also demonstrated in forms of noise proof and illumination fluctuation tolerance. Finally, an application is conducted on an experiment concerned with cracking in desiccated soils, in which the proposed method succeeds in tracking the nucleation and propagation processes of multiple cracks.

With the development of modern engineering such as micro-electro-mechanical system (MEMS) and new material, the deformation measurement of 3D displacement field is required. Moiré interferometry has become common for measuring the deformations of two-dimension in-plane displacement field. To solve the problem of 3D displacement field, a system for measuring the deformations of 3D displacement field is designed. By using this system, we can measure the out-of-plane displacement by appending a set of electronic speckle interference system based on Moiré interferometry system. Adjusting the incident angle of the incident light, the transmitting direction of the first order diffracted wave in a Moiré interferometry system is assigned to deviate with a small angle from the vertical direction of the specimen surface. Thus the first order diffracted wave is separated from the place of the appended interference field. The striated patterns of the deformations of 3D displacement field can be obtained at the same time. These striated patterns are recorded respectively by three CCD cameras and are stored and processed by a computer. The synchronous measuring method brings certain amount of measuring errors into the measurement of in-plane displacement. This measuring error is analyzed in theory. When real-time measurement is not required, this system can be changed into another system in which the in-plane and the out-of-plane displacement field are measured by time sharing to reduce the measuring errors. The theoretical derivation and a part of experimental results for verification are presented.