Measurement of Small Angle Using Phase Shifted Lau Interferometry

An incoherent white-light source illuminates a set of two identical gratings placed in tandem, resulting in the generation of the Fresnel image. This image is projected onto a reflecting object and the reflected images from the object are projected onto the third grating. The resulting moire fringes are recorded using CCD camera. Inclination angle of the object is a function of the interferometric phase. Phase shifting interferometry has been used for the determination of interferometric phase. Hence accurate determination of small tilt angle of object surface could be successfully undertaken. Technique is automated and provides high precision in measurement.