Phase control strategies for stabilization of photorefractive holographic interferometer

A current problem encountered in holographic interferometry systems is the phase variations that arise from vibrations, from the use of optical fiber in one arm, by air convection or by unwanted movement between the object and the measurement device. The holographic device developed by CSL based on photorefractive BSO crystals has the advantage of high resolution fringes with the capability of self-processing and indefinite reusability. The weakness of the technique is a response time that is often slow compared to external perturbations. For applications outside the laboratory, we decided to find solutions adapted to the holographic camera and which tend to limit or to eliminate the effect of such phase variations. An error signal is measured from one or another technique which measure the phase variations and which counteracts on an active element in the interferometer to stabilize the phase during recording. Different solutions have been analysed and are presented here. Interferograms were obtained with and without implementation of the phase control system that show the interest of such approach. Some of the system presented are only adapted to photorefractive holographic interferometry, making use of some crystal diffraction properties. Other systems can be used with other kind of interferometers.