PHASE MEASUREMENT BY DIFFERENTIATING INTERFEROMETRIC FRINGES

In this paper we discuss a method of wavefront phase detection by differentiation of the interferometric fringes. We show that only one phase step is required to determine the wavefront phase. In the process of differentiation, Moire fringes are formed. Conditions on the angle of tilt introduced between the interfering beams to overcome the formation of Moire fringes are also presented. The method is shown to be suitable for techniques such as null optical testing or interferometric methods where comparison is made between a master and a test. We present in this paper the theory of the method and experimental results obtained for both specular and speckle interferometric fringes.