REAL-TIME DISPLACEMENT AND TILT ANALYSIS BY A SPECKLE TECHNIQUE USING Bil2SiO20-CRYSTALS
نویسندگان
چکیده
Speckle photography is becoming an important method for deformation, displacement and tilt measurements. The technique will be even more attractive to the engineer when its application is in real time. Therefore, the developing process of speckle photography and the subsequent optical Fourier transformation of the photographs will be replaced. Bismuth silicon oxyde Bil2SiO20. has electrical and electrooptical properties which make it attractive for dynamic holography and speckle applications. The basic principle for application of the crystal to holographic storage, double-exposure and time average interferometry of transparent or mirror like structures was reported [ 1,2]. Upon readout of the hologram at the same wavelength the reconstructing light beam erases the stored information. Therefore, by the double-exposure technique, tile second exposure partially erases the stored information. By the reconstruction, the resulting image with the interference fringes superimposed, can be stored by means of a video storage device or on film. For real time holography and holographic interferometry the BSO crystal is biased with a transverse electric field E 0 in the 1 10 crystallographic direction. When the crystal is illuminated with spatially structured illumination in the /10 direction, a space.charge field is built up. A photoinduced space-charge density due to salurotion
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