Geometric phase analysis method using a subpixel displacement match algorithm.

The geometrical phase analysis (GPA) method, which is an efficient and powerful noncontact method to obtain the strain field, has already been widely applied in deformation measurement in micro- and nano-scale. It is easy to get the strain field accurately; however, the displacement field is unreliable in some cases. Therefore, a subpixel displacement match method hereby is applied in the GPA method for the first time, to the best of our knowledge, to overcome this defect. The presented algorithm's limit error of 0.01 pixel under ideal conditions can match two corresponding local areas in reference and deformation image, and, thus, the displacement with subpixel precision of this point can be established. Owing to the continuity of the displacement field, the displacements of other points can be obtained subsequently. The error that is associated with the existing method will be dealt with in detail and verified by simulation further. Combined with simulation, the performance of the presented method is demonstrated; furthermore, the noise introduced by the imaging system is taken into consideration. Finally, a typical bending test was performed, and the result agrees well with the theoretical analysis. Both the simulation and experiment results prove that the presented method is effective and robust.

Deformation grating fabrication technique based on the solvent-assisted microcontact molding.

A deformation grating fabrication technique based on solvent-assisted microcontact molding (SAMIM) is reported in this paper. The fabrication process can be divided into three steps: imprinting a grating on a medium polymer substrate (MPS) by SAMIM, coating a thin metal film on the MPS, and transferring the film to the measured surface. In order to increase the stiffness of the elastic mold without decreasing its conformal contact formation ability, a re-useable, glass-embedded polydimethylsiloxane (PDMS) mold is used. In addition, a characterization method based on the Fourier transform and phase analysis is proposed to check the quality of the fabricated grating. Verified by experiment, the proposed fabrication technique can fabricate a high-frequency large-area grating on different specimens, which can be a qualified deformation sensor for the moiré method.