Interferometric system for non-destructive testing based on large diameter bacteriorhodopsin films

A system for holographic interferometry using bacteriorhodopsin films as an erasable optical recording medium is presented. Bacteriorhodopsin is a photochromic protein found in archaebacteria. Bacteriorhodopsin films with an aperture of 90×90mm are used for highresolution lensless recording (5000lines/mm). The holograms are recorded in reflection-type geometry in order to achieve a compact design. A frequency-doubled Nd:YVO4 laser, emitting at 532nm, is used for recording and incoherent blue light is employed for photochemical erasure. The system is suitable for a variety of different interferometric techniques like double-exposure, time-averaging and real-time interferometry. As an example for the application of the BR-based non-destructive testing system the inspection of ceramic motor valves, made from silicone nitride (Si3N4), under mechanical load is reported.