Quantitative evaluation of digital shearing interferogram using the spatial carrier method

Abstract

In this paper we describe a digital shearing interferometer system. The set-up is composed of a Mach - Zehnder interferometer which allows us to split the image of one object and to recombine the two images shifted and tilted. The tilt between the two images is chosen in order to produce a carrier frequency. The spatial carrier phase-shifting method is used for the quantitative evaluation. Two separate shearograms of an object under test are recorded using a CCD-sensor and stored in a frame grabber. The phases of the two shearograms are calculated from the complex amplitudes and the gradient is obtained from the phase difference. Experimental results are presented.