Image-shearing speckle pattern interferometer with quadrolens

A new optical element–a quadrolens that is used as part of a shearing speckle interferometer (shearograph) to provide the measurements of stress-strain states of objects simultaneously in two mutually perpendicular directions, has been proposed. The quadrolens consists of four identical sections cut from the original round lens and spaced from each other. It builds four object images that are shifted relative to the optical axis by a distance that depends on the size of the gaps between the sectors. The phase reconstruction using a single speckle interferogram has been performed by the spatial phase-shifting method based on the Fourier transform. An aperture diaphragm with four holes has been placed in front of the quadrolens sectors to increase the contrast of interference fringes and polarization channel isolation can be used to separate the channels and reduce the influence of cross interference. The experimental results of using a speckle interferometer with quadrolens for the study of microdeformation of a round membrane have been presented.