Fringe carrier methods in double-pulsed addition ESPI

We report the introduction of carrier fringes in double-pulsed addition electronic speckle pattern interferometry (ESPI) which has enabled interference phase to be calculated directly from a single fringe pattern. The technique is suitable for transient deformation and harmonic vibration measurements. Experimental results are presented for a test object vibrating harmonically, for which we calculate the vibration amplitude and phase. Interference phase is calculated with the spatial synchronous detection and Fourier transform methods for interferograms with and without carrier. It is shown that applying a band-pass filter with spatial synchronous detection without carrier (rather than a low-pass filter) eliminates a stage in calculating the phase. (C) 1997 Elsevier Science B.V.