Night vision imaging system lighting evaluation methodology

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.