Photorefraction filtering

Potential applications of photorefractive materials are manifold. To date, demonstrated effects include real time holography, correlation filtering, and various "novelty filter applications, one of which is the development of a microscope which distinguishes moving objects (such as living cells) from a stationary background.(149) The latter application employed BaTiC>3 as the active material. 

There are other applications of photorefractive materials that have been investigated, including associative optical memories that identify a clear image from a corrupted input [1], novelty filters to detect only changing features in an image [2], and neural networking in analogy with the human brain [3],... 

Other applications that were recently demonstrated with photorefractive polymers include homodyne detection of ultrasonic surface displacements using two-wave mixing [115]. With the development of new photorefractive polymers with response times in the millisecond range, numerous optical processing techniques can be performed at video rates. Image amplification and novelty filtering at video rates were demonstrated recently [116]. All-optical processing techniques compete with computational methods. Therefore, it is important that photorefractive polymers exhibit faster response times in the future. 

Yin, S. Zhu, X. Chung, K. All-fiber all-optic tunable filter based on the combination of long-period grating and photorefractive cladding layer. Proc. SPlE-lnt. Soc. Opt. Eng. 2000, 4110, 190-194. 

J., Tschudi, T., Chamrai, A.V., Bryksin, V.V., and Petrov, M.P. (2003) Optical on-line controllable filters based on photorefractive crystals. J. Opt. A Pure Appl. Opt., 5, S471-S476. 

Optical Correlation, Imaging through Scattering Media, and Novelty Filtering. Using a photorefractive polymer, optical correlation can be made all-optical, eliminating the need for a computer or any other such devices. Such a device was demonstrated in a 100-yum-thick photorefractive polymer using a... 

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