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Proceedings Paper

Concept of a neural system for real-time evaluation of spectroscopic measurements
Author(s): L. Redei; Miklos Fried; Tivadar Lohner; O. Polgar; Istvan Barsony; Sz. Forizs; Zoltan G. Horvath; Josef Humlicek; H. Wallinga
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Paper Abstract

A hardware implementation of a Backpropagation feedforward neural network has been designed. The tool was proposed for reflectometric measurements integrated together with photosensor arrays. The intelligent reflectometric sensor is being implemented in a multi-chip-module approach. A logarithmic input transformation is applied for easing the misalignment and parameter scatter correction. It also allows for easy ratio calculation by subtraction for normalization with the reference value. The neural network was designed for complexities up to 100 inputs, 30 hidden neurons and 5 outputs. The digital building blocks (neurons) utilize a logic approximation of the sigmoid nonlinearity and the possibility of weight scaling. These hardware solutions result in a simultaneous area reduction and speed gain, at the cost of slightly decreased performance. Simulations of the proposed neural system prove applicability for evaluation of optical measurements were performed for reflectometric and ellipsometric data thin porous layers. Hardware simulations showed good correspondence to the optimum-case neural software simulations.

Paper Details

Date Published: 19 August 1998
PDF: 5 pages
Proc. SPIE 3573, OPTIKA '98: 5th Congress on Modern Optics, (19 August 1998); doi: 10.1117/12.320999
Show Author Affiliations
L. Redei, Research Institute for Technical Physics and Materials Science (Hungary)
Miklos Fried, Research Institute for Technical Physics and Materials Science (Hungary)
Tivadar Lohner, Research Institute for Technical Physics and Materials Science (Hungary)
O. Polgar, Research Institute for Technical Physics and Materials Science (Hungary)
Istvan Barsony, Research Institute for Technical Physics and Materials Science (Hungary)
Sz. Forizs, Research Institute for Solid State Physics (Hungary)
Zoltan G. Horvath, Research Institute for Solid State Physics (Hungary)
Josef Humlicek, Masaryk Univ. (Czech Republic)
H. Wallinga, Univ. of Twente (Netherlands)


Published in SPIE Proceedings Vol. 3573:
OPTIKA '98: 5th Congress on Modern Optics
Gyorgy Akos; Gabor Lupkovics; Andras Podmaniczky, Editor(s)

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