[OPTICAL REVIEW Vol. 1, No. 1 (1994) 44-46]

Optical Learning Neural Network Using a Selfoc Microlens Array for Pattern Recognition

Masahiko MORI,1 Yoshio HAYASAKI,2 Ichiroh TOHYAMA3 and Toyohiko YATAGAI3

1Optical Information Section, Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki, 305 Japan, 2Photodynamics Research Center, The Institute of Physical and Chemical Laboratory, 19-1399 Koeji, Nagamachi, Aoba-ku, Sendai, Miyagi, 980 Japan, 3Institute of Applied Physics, University of Tsukuba, 1-1 Tennodai, Tsukuba, Ibaraki, 305 Japan

(Accepted August 15, 1994)

An optical system for learning neural networks with a 2-D architecture was constructed using a Selfoc microlens array. Using this system, we achieved pattern recognition of typed alphabet characters detected directly with a CCD camera. The system learned 4 characters according to a random search algorithm in order to avoid the difficulties and the costs of calculations of learning signals, optical alignments and addressing to the device which display the weight tensors.

Key words : optical neural network, two-dimensional architecture, Selfoc lens, microlens array, pattern recognition, random search algorithm