Raymond Chevallier

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We present an optical implementation of an improved version of the Kohonen map neural network applied to the recognition of handwritten digits taken from a postal code database. Improvements result from the introduction of supervision during the learning stage, a technique that also simplifies the map layer labeling. The experimental implementation is based(More)
2014 Consideration of the eigenproblem of the synaptic matrix in Hopfield’s model of neural networks suggests to introduce a matrix built up from an orthogonal set, orthogonal to the original memories. With this new scheme, capacity storage is significantly enhanced and robustness at least conserved. Revue Phys. Appl. 22 (1987) 1321-1325 OCTOBRE 1987, PAGE(More)
Local and nonlocal models for the diffusion of photopolymers are applied to the dynamic formation of transmission gratings recorded in photopolymers and holographic polymer-dispersed liquid crystals (H-PDLCs). We retrieve the main parameters of H-PDLCs (refractive-index modulation and diffusion coefficient) by combining a solution of the one-dimensional(More)
The optimization of the experimental parameters of two multiplexed holographic transmission gratings recorded in holographic polymer-dispersed liquid crystals is investigated. Two methods are used to record the holograms: simultaneous and sequential multiplexing. These two processes are optimized to produce two multiplexed Bragg gratings that have the same(More)
Two methods of reducing the dynamic range of the transmittance of computer-generated interconnection holograms are presented and compared. The holograms are used in an optical implementation of an associative memory to connect the input and the output planes but are representative of more generalN(4) interconnection holograms. Because the holograms play a(More)
We report the design and fabrication of a chirped switchable reflective grating (CSRG) recorded in a holographic polymer-dispersed liquid-crystal material. This CSRG is a spatial wavelength-selective flattener in a free-space dynamic gain equalizer for use in wavelength-division multiplexing (WDM) networks. Prelimenary experimental results show that this(More)
In the first part of this paper we present frequency multiplexed raster (FMR) optical implementation of neural networks. A hidden difficulty for hardware (optical and electronic) implementation is that the dimension of the synaptic matrix is twice that of the input and output matrices or vectors. For 2-D images, which is we believe one of the greatest(More)
The purpose of this paper is to investigate the performance of microoptics for telecommunication systems using free-space interconnects. This concerns mainly distribution or switching and routing tasks. In order to evaluate the interconnection capability of free-space microoptics, we impose severe conditions on the interconnects. These conditions correspond(More)