No abstract

This study was undertaken to determine the utility of a dynamic visual acuity assessment methodology for examining the effects of looking through a transparent component on visual performance. The different types of transparent components that can be investigated using this methodology include, but are not limited to, night vision goggles, tinted visors, laser eye protection spectacles, and aircraft windscreens. Transparency attributes that can be investigated include transmission coefficient, reflection coefficient, glare, light level, target contrast, target type, resolution, spectral transmission, haze, scratches, and distortion. The visual task may be a target detection or a target recognition type of task, performed with or without search. The methodology used in this study consists of smoothly and continuously decreasing the distance between the observer and a visual test target, until the observer can accurately perform the required visual task. In this study, the observer was required to visually search and detect a circular black dot in a quadrant, while viewing through a tinted visor. The lighting conditions were not at a level for which the tinted visor was intended to be used, so it was expected that the visor would reduce visual acuity instead of aiding visual performance, as it normally would be expected to do. The objective of the study was to determine the 95% reproducibility limit for the methodology. This limit was found to be on the order of 10% to 15%, which is quite good for an assessment of this type that involves human observers performing a visual task over an extended period. The methodology appears to be viable.

In order for night vision goggles (NVGs) to be effective in aircraft operations, it is necessary for the cockpit lighting and displays to be NVG compatible. It has been assumed that the cockpit lighting is compatible with NVGs if the radiance values are compliant with the limits listed in Mil-L-85762A and Mil-Std-3009. However, these documents also describe a NVG-lighting compatibility field test procedure that is based on visual acuity. The objective of the study described in this paper was to determine how reliable and precise the visual acuity-based (VAB) field evaluation method is and compare it to a VAB method that employs less expensive equipment. In addition, an alternative, objective method of evaluating compatibility of the cockpit lighting was investigated. An inexpensive cockpit lighting simulator was devised to investigate two different interference conditions and six different radiance levels per condition. This paper describes the results, which indicate the objective method, based on light output of the NVGs, is more precise and reliable than the visual acuity-based method. Precision and reliability were assessed based on a probability of rejection (of the lighting system) function approach that was developed specifically for this study.

No abstract