The Mellin radial harmonic filter and the logarithmic harmonic filter are useful for performing optical scale- and projection-invariant pattern recognition, respectively. To our knowledge, on the basis of the harmonic-function method, no one has been able to obtain more than one invariant property (in addition to the shift invariance) when using the matched-filter approach. A new method of combining the scale-, the projection-, and the shift-invariance properties is proposed, based on two decomposition stages of the input pattern. Computer simulations are presented as well as preliminary experimental results.
High efficiency optical logic devices and interconnect elements are required for digital optical experiments. Nonlinear interference filters, capable of acting as optical gates, have been demonstrated to switch with -2 mW input power and -50 As recovery time. Switch contrast of 20:1 has been achieved with multicavity designs. Switch energies for micrometre-dimension transversely isolated pixels of <25 pJ are predicted. Holographic input and interconnect components with >90% diffraction efficiencies have been fabricated in dichromated gelatin and assessed.
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