[OPTICAL REVIEW Vol. 4, No. 5 (1997) 572-577]

Optoelectronic Thresholder for Pattern Recognition with Double Feedback Module


1Institute of Physics, Department of Technical Physics and Applied Mathematics, Warsaw University of Technology, ul.Koszykowa 75, 00-662 Warsaw, Poland, 2Group d'Optica, Departmento de Fisica, Universitat Autonoma de Barcelona, Edifici Cc, 08193 Bellaterra, Spain, 3Institute of Geophysics, Department of Physics, Warsaw University, ul.Pasteura 7, 02-093 Warsaw, Poland

(Received November 14, 1996; Accepted May 7, 1997)

The present paper proposes a modification of a simple optoelectronic architecture (A. Bergeron et al.: Appl. Opt. 33 (1994) 1463) for carrying out optical thresholding operations. The threshold operation is achieved by means of a feedback loop. The setup is modified by inserting an attenuator adapted in each iteration to the total incident energy measured by an intensity detector. The proposed architecture does not need an additional light source, assures translation invariance and does not break the beam propagation path. The adaptive attenuator permits working under different lighting conditions (illumination, partially occluded objects, etc.). This kind of architecture is suitable for an optical pattern recognition task, optical neural network or optical associative memory. Application of the modified thresholder to the recognition task based on an optical correlator is reported.

Key words : optoelectronic thresholder, optical neural networks, optical associative memory, optical pattern recognition, winner-take-all