Two-step dc-term-suppressed phase shifting technique in DSPI

Abstract

Digital speckle pattern interferometry (DSPI) is a tool for making qualitative as well as quantitative measurements of deformation of objects. Temporal and spatial phase shifting techniques have been introduced in DSPI for extracting quantitative deformation data from the system. Temporal phase-shifting technique requires at least three phase shifted intensity patterns for phase measurement. On the other hand, spatial phase shifting technique though require single frame before and after the object deformation, gives low spatial resolution result. In this paper we propose a temporal phase shifting technique that uses only two phase shifted speckle patterns before and after the object deformation by suppressing the dc-term from the intensity pattern either by an averaging technique in spatial domain or low-pass filter operation in the frequency domain. Both the simulation and experimental results are presented to validate the effectiveness of the proposed technique.