GRAZING HOLOGRAPHIC PROJECTION OF OBJECT-ADAPTED FRINGES FOR SHAPE MEASUREMENTS WITH ENHANCED SENSITIVITY

A new method of fringe projection for shape measurement is presented. We use a combination of object-adapted fringes and holographic grazing projection to determine shape deviations of a turbine blade. If the s hape of a test object is correct, a fringe grid with constant period i s detected by the camera. The object-adapted fringes are projected coh erently onto the master object, and a hologram is taken. If the hologr am is reconstructed, grazing incidence of object-adapted fringes can b e realized. Grazing holographic projection allows for higher triangula tion angles and therefore increased sensitivity. Even small shape devi ations can be detected and quantitatively evaluated with fast algorith ms. The method can be extended to multiple exposed holograms to examin e deep objects. (C) 1998 Optical Society of America.