Visual Acuity for High-Contrast Tri-bar Targets Illuminated with Spectra Simulating Night Vision Goggle (NVG) Displays and the No-moon Night Sky

Abstract

Abstract : This report presents two studies that measured unaided visual acuity using a 50-in square high-contrast U.S. Air Force (USAF) 1951 Tri-Bar chart viewed from 12 ft at luminance levels ranging from 0.00046 fL (much darker than a night vision goggle [NVG] display of an overcast starlight scene) to 21.5 fL (much brighter than a NVG display of a full-moon scene). To avoid visual noise artifacts, these studies did not use actual NVG displays. The studies were designed to support general modeling efforts at the U.S. Army Research Development and Engineering Command (RDECOM) Communications-Electronics Research Development and Engineering Center (CERDEC), Night Vision and Electronic Sensors Directorate (NVESD). For Study 1, the Tri-Bar chart was back-lit with a spectrum similar to the standard yellowish-green (P43) phosphor NVG display. In Study 2, the chart was back-lit with tungsten illumination, similar to a 2856 K blackbody spectrum. In addition to providing measures of unaided visual acuity, we introduced a new technique-the Green-appearance Scale-to determine the luminance levels at which participants transitioned from scotopic viewing of the Tri-Bar chart to mesopic viewing, and from mesopic viewing to photopic viewing. We describe this technique and present the data as part of the methodology and results of Study 1.