Digital speckle pattern interferometry (DSPI) using optical polarization phase shift for measurement of temperature field in thermal flow

In this paper a digital speckle pattern interferometry (DSPI) based on an optical polarization phase shift for measurement of temperature fields in thermal flow is presented. First, the principle and physical-mathematical models of the phase shift digital speckle pattern interferometry (PSDSPI) are proposed. Second, the experimental arrangement of PSDSPI is described. Third,the effects of experimental parameters on PSDSPI, e.g. spatial location of speckle source, intensity ratio of objective to reference beam, F-number of image lens and angle between objective and reference beam are analyzed in detail. Finally, some experimental results are presented. The PSDSPI is based on optical polarization phase shift technique, which uses a quarter-wave plate and a plane polarizer. When the relative position between the quarter-wave plate and the polarizer is rotated, a phase shift can be introduced. Comparing to piezoelectric transducer phase shift device, the optical polarization phase shift is more convenient, because no complex calibration is needed. As an application example PSDSPI is used for temperature field measurements in a natural convection flow generated by a heated vertical plate. The investigations show that the PSDSPI is a fast and real-time measurement method for optical diagnostic of thermal flow.