Pulse mode light sensing using four-layer semiconductor structures and their application in neural networks

• Main Author: Siganos, Ioannis
• Other Authors: Karunasiri, Gamani
• Published: Monterey, California. Naval Postgraduate School 2012
• Online Access: http://hdl.handle.net/10945/3775

Existing semiconductor photodetectors produce a steady current or voltage output in response to incident light that depends on the intensity of the light beam. In contrast, biological vision systems produce a stream of pulses with pulse rate representing the amount of incident light power. The goal of this thesis is to explore the use of a four-layer PNPN semiconductor structure as an optical detector that produces pulses instead of steady current or voltage output. The first task of this thesis is to show that the pulse interval distribution is dependent on the intensity of the incident light beam, and that the distribution of pulse intervals is described by a renewal process statistical model. The second task of this thesis is to use the unique characteristics of the pulse generating circuit along with a neural network to construct a 2D sensor array capable of recognizing visual patterns, and thus modeling, to some extent, the human visual cortex.