Single-Shot Time-Averaged Shearography for Vibration Strain Mode Shape Visualization

A single-shot time-averaged shearography system is developed for mechanical vibration sensing. Unlike conventional shearography systems that rely on multiple phase-shifted shearograms to visualize vibration strain mode shapes, our developed shearography system utilizes merely a single frame of shearogram for visualization. The spatial carrier method is employed to convey the information of the vibration strain mode shape within a shearogram, enabling the single-shot visualization in the retrieved binary phase map. To ensure the successful retrieval of the vibration-induced phase, a well-distributed spatial frequency spectrum is established by disentangling the shear operation from the spatial carrier through the creation of two intermediate real images in the system. The physical principle of the single-shot time-averaged shearography, as well as the spatial carrier during the vibration event, is demonstrated, and the generation of the binary phase map induced from the vibration is investigated. A series of preliminary experiments were carried out to verify the feasibility and performance of the developed single-shot time-averaged shearography system.