Abstract

A computer-simulated retina called IRIS is described which discriminates small differences in reflected light when these differences occur in a restricted domain of space and time and maintains sensitivity to these differences for a wide range of light environments. As prevailing light levels de crease and photon noise becomes significant, IRIS automatically reduces its spatiotemporal resolution to provide greater redundancy. The temporal resolution depends on light intensity because each receptor’s response is governed by photopigment kinetics whose rate increases with light level. The spatial resolution depends on light intensity because the receptors are individual circuits (with voltage sources and photoconductors) coupled by a passive conducting grid. At high light intensity, the conductances within each receptor circuit are much greater than the lateral conductance, hence the receptor circuits are effectively uncoupled. Decreasing light intensity causes the lateral conductance to become more significant, thereby coupling the receptors and reducing spatial resolution. The simulation (implemented in FORTRAN) is adapted from the dissertation work of one of the authors.¹ Simulation results are presented, and parallels to human vision are noted—including implications for trichromatic vision. The conducting grid might be achieved by tight-junction coupling of receptors and horizontal-cell interconnections that form an effective syncytium.

© 1987 Optical Society of America