Design of digital shearography with wide angle of view based on 4f system

Digital shearography has broad application prospects in the field of industrial non-destructive inspection. However, the traditional Michelson-interfero-meter-based digital shearography suffers from the small angle of view due to the structure,which limits its employments in industrial application . We demonstrated a novel digital shearography system with a large angle of view by embedding a 4f optical system between the separate lens and camera, achieving the lens outside of the instrument housing. Theoretical analysis shows that the angle of view has no limit to the setup but it is based on the focus length of the imaging lens and the size of the imaging sensor inside the camera. A novel digital shearography system was built and experimental results prove that the new shearography system is a good tool to conduct the full field inspection of a big size sample at a short working distance. At a working distance of 1m, the measuring area of the novel shearography system is 800 mm 600 mm, compared with only 250 mm200 mm of the traditional one.