Optical aberrations in underwater holography and their compensation
John R. Watson, J. M. Kilpatrick · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1991
Underwater holography is attracting attention in the offshore oil and gas industries as a potential technique for high-resolution inspection and measurement of subsea structures and components. Real image reconstruction in the laboratory is employed to produce a high- fidelity image of the underwater scene upon which direct dimensional measurement may be performed. The refractive index change between recording in water and replaying in air introduces aberrations, like those observed by viewing an object from air at the bottom of a swimming pool, into the replayed image. The authors discuss the influence of such aberrations on the fidelity of underwater holograms and report experimental verification of a simple and effective method of minimizing their effect, by replaying in-air at a wavelength reduced in proportion to the refractive index of water.