Direct determination of strain with diffraction-limit accuracy by moiré deflectometry.
In-plane strain is traditionally mapped by fixing a grating onto a test object and monitoring its displacements under stress by either a moiré method or interferometry. The strain (or displacement derivative) is obtained by an additional mathematical or moiré shearing technique. We suggest an application of moiré deflectometry that will yield the strain directly. The setup is much simpler than existing methods and has the additional advantages of tunable sensitivity and immunity to mechanical shock and vibration.