Optical stimulation systems for studying human vision

Abstract

This chapter describes the most common setups that scientists use for generating lightstimulation, from lab-made approaches to commercially available technologies. The studiedoptical stimulation systems are divided into nonimage-forming and image-forming arrangements.Two classical systems widely used are among the first: the Maxwellian view systemand the Ganzfeld stimulator. Between the image-forming arrangements, the focus is onapproaches that consider off-the-shelf devices and the recent appearance of multi-primarydisplays, which allow the inclusion of more primaries and the generation of stimulation forindependent and combined photoreceptor and postreceptoral excitations. Some of the severallimitations that can have important implications in research practice are also examined, such asthose related to color gamut, sampling frequency, light range, and spatial resolution.Since experimentation on how optical radiation is processed by the human neural systemrequires the reliability of the parameters and variables under study to be assured, the characterizationand consequent calibration of experimental devices are essential. Therefore the chapterdiscusses a set of characterization and calibration principles that researchers should considerwhen carrying out experiments with the described optical stimulators. Outstanding characteristicsare stimulator response curve, primaries’ spectral power distribution, additivity, modulationtransfer function, and temporal stability. Finally, some possible sources of artifacts that researchersshould consider when these stimulators are used are presented. Throughout this lastsection, data based on different optical stimulator measurements is provided.