Enhancement of surface inspection by Moiré interferometry using flexible reference gratings

We have extended the use of shadow Moiré technique to be implemented in simple curved surfaces by using a flexible grating. Dynamic visual inspection of surface micro-damages is significantly favored by the use of well adapted pliable gratings compared to the use of flat reference gratings. The experimental set-up consists of a plastic foil with a printed Ronchi grating stretched between three points which adapts to any cylindrical or conical convex surface independently of the relative orientation grating/surface. Static quantification of defects profiles is also possible with an attached CCD camera. Visual detection of defects in the range of ~30 microm in depth is obtainable.