18 August 1995 Shift and rotation invariant photorefractive crystal-based associative memory
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A shift and rotation invariant photorefractive (PR) crystal based associative memory is addressed. The proposed associative memory has three layers: the feature extraction, inner- product, and output mapping layers. The feature extraction is performed by expanding an input object into a set of circular harmonic expansions (CHE) in the Fourier domain to acquire both the shift and rotation invariant properties. The inner product operation is performed by taking the advantage of Bragg diffraction of the bulky PR-crystal. The output mapping is achieved by using the massive storage capacity of the PR-crystal. In the training process, memories are stored in another PR-crystal by using the wavelength multiplexing technique. During the recall process, the output from the winner-take-all processor decides which wavelength should be used to read out the memory from the PR-crystal.
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Chii-Maw Uang, Chii-Maw Uang, Wei-Feng Lin, Wei-Feng Lin, Ming-Huei Lu, Ming-Huei Lu, Guowen Lu, Guowen Lu, Mingzhe Lu, Mingzhe Lu, } "Shift and rotation invariant photorefractive crystal-based associative memory", Proc. SPIE 2529, Photorefractive Fiber and Crystal Devices: Materials, Optical Properties, and Applications, (18 August 1995); doi: 10.1117/12.217001; https://doi.org/10.1117/12.217001

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