Image Contrast and Visual Acuity Through Night Vision Goggles.

Abstract : Night vision goggles (NVGs) intensify ambient illumination making it possible to see in the dark despite insufficient light for normal vision. NVGs are used for military and civilian operations, and as visual aids for night blindness. The quality and quantity of vision achieved through NVGs depends on several factors including the intensity of ambient radiation, the integrity of NVG electro-optical components, and the luminance, contrast and resolution of the NVG display. The purpose of this study was to investigate effects of display contrast and luminance on visual resolution through NVGs. Computer-generated letter charts were used to measure visual acuity across the range of luminances and contrasts one can encounter when viewing an NVG display. The results indicate that display luminance cannot, in itself, account for the level of acuity achieved through NVGs. An attenuation of contrast through NVGs better explains the level of resolution obtained. Understanding the contrast and luminance transfer of NVGs is important for predicting human visual performance, and for developing improved night vision devices.