Adjacent-Pair Imaging Shearography Using Bacteriorhodopsin

In a developmental technique of real-time adjacent-pair imaging shearography, a thin film of bacteriorhodopsin is used to record shearograms in argon-laser light for immediate readout in helium/neon-laser light. Unlike conventional silver-halide-based photographic film, bacteriorhodopsin can be used as a real-time recording medium because it yields an image immediately upon exposure and is optically erasable. Bacteriorhodopsin also offers the advantage of resolution as high as 5,000 lines/mm — comparable to the resolutions of silver-halide-based films and much greater than the 80 lines/mm typical of the charge-coupled-device video cameras used heretofore in real-time shearography. Issues to be addressed in subsequent development include the difficulty of recording over a previously recorded image at the recording wavelength, the need for Fourier-transform optics for readout, the need to optimize the optics to realize the full potential for high resolution, and the relative insensitivity of bacteriorhodopsin film (about a tenth of that of silver-halide-based film).