Effect of Incompatible Light on Modified Class B Night Vision Goggle-Aided Visual Acuity and Contrast Sensitivity.

MIL-L-85762A, Lighting, Aircraft, Interior, Night Vision Imaging System NVIS Compatible, defines criteria for assessing night vision goggle NVG compatibility of cockpit lighting. As part of the assessment procedures, NVG aided visual acuity VA is measured using the USAF Tri-Bar Chart. A cockpit light is incompatible if NVG aided VA is degraded. An alternative method of measuring NVG aided VA uses an NVG Chart. This research assessed whether the two NVG aided VA assessment techniques reveal the same levels of degradation in NVG aided VA. NVG aided contrast sensitivity CS also was measured to determine its usefulness in assessing the compatibility of a cockpit light. Three NVG CS charts were developed having spatial frequencies of 3, 6, and 12 cycles per degree cpd. NVG performance was degraded by incompatible light, and the amount of degradation was assessed using the two VA and CS measures. Measurements were made using a modified Class B NVG. Another objective of this research was to assess the compatibility of the modified Class B NVG with compatible cockpit light defined in MIL-L-85762A. The results revealed that NVG aided VA did not differ between the two VA charts. For the green light, NVG aided CS was degraded only for the high spatial frequency 12 cpd. However, for the red light, NVG aided CS was degraded for all three spatial frequencies. NVG aided CS was sensitive to the presence of incompatible light. The modified Class B NVG is compatible with the lighting requirements defined in MIL-L-85762A.