A comparison between phosphors for aviator's night vision imaging system.

BACKGROUND The visual display on night vision goggles (NVG's) is green and isochromatic (P22 phosphor). Future systems are expected to use a P43 phosphor which has a narrower visible spectrum and is yellowish green, while the P22 is deeper green. In transitioning to the P43, some NVG's may have P22 and P43 phosphors paired in the same NVG. The purpose of this study was to evaluate the suitability of the P43 phosphor and the effect of mixing phosphors in the same NVG. METHODS We tested three systems: one with P22 phosphors in both tubes (P22), one with P43 in both tubes (P43), and one with P22 in the right and P43 in the left tube (mixed). Visual acuity (VA), contrast sensitivity (CS), flicker sensitivity, and dynamic CS were measured in six subjects with measures repeated across the three systems (P22, P43 and mixed). RESULTS There was no difference between systems in VA or CS across a range of simulated night sky conditions. There also was no difference between systems in sensitivity to flicker. Performance on dynamic CS was slightly better with the P43 display, which may relate to the faster decay time of this phosphor. CONCLUSIONS These results provide no contraindication for using the P43 phosphor in NVG's (paired or unpaired), but it would be prudent to minimize mixing of phosphors in the same NVG. Additional factors that may affect performance with different color displays are discussed.