Utilization of photorefractive crystals for holographic double-exposure interferometry with nanosecond laser pulses

A holographic double-exposure interferometer for deformation and vibration analysis of diffusely reflecting objects in quasi real-time is presented. Writing of holographic gratings with 3 ns laser pulses in photorefractive sillenite-type crystals enables recording of sequences of double-exposure interferograms. A repetition rate of 12.5 Hz is achieved with the set-up used. Automatic phase evaluation of the interferograms is performed with a spatial-heterodyne technique. Photorefractive recording in a BTO:Cd crystal with pulsed illumination is investigated and discussed in view of the application in double-exposure interferometry. The performance of the interferometer is investigated by observing deformations of a vibrating test object.