The Positive Afterimage and Measurements of Light and Dark Adaptation

摘要

In many practical situations it is desirable to know the extent to which adaptation at the center of the fovea undergoes change and to what extent this affects performance of a given task. This paper describes an attempt to solve this problem by constructing a system with a sensor which will simulate the changes in position and direction of an eye and provide a running record of changes in retinal illuminance at the center of the fovea. The next step is to build an analog computer which will compute changes in mechanisms of adaptation found in the photoreceptors. An analog computer was designed to do this and takes into consideration the primary and secondary responses of the photoreceptors. A study of the positive afterimage was carried out with the aim of making allowance for its effect on the state of adaptation. The problems of chromatic adaptation were considered, but the analog computer described in this report is basically a device for computing changes in bright and dark adaptation. The equations and constants used in designing the computer are based primarily on Rushton's measurements of retinal bleaching and Wright's subjective measurements of bright and dark adaptation. (Author)