Visual acuity through Night Vision Goggles (NVGs): A comparative assessment between Gen 2⁺⁺ and Gen 3 NVGs under different illumination conditions

Abstract

Introduction: During night flying operations, Night Vision Goggles (NVGs) help the aircrew to visualize by intensifying lights reflected from an object. Night sky illumination and image intensification mechanism are the two important factors that affect visual acuity (VA) through NVG. Hence, assessment of visual acuity through Gen 2++ and Gen 3 NVG under different illumination conditions and comparative analysis between the two NVGs was the desired objective of the study. Material and Methods: In a prospective repetitive measure design, a total of 60 volunteered subjects were examined for their VA through Gen 2++ and Gen 3 NVGs using USAF Tri-Bar Chart in the eye lane room of the NVG Lab. The VA was measured under four different illumination conditions; full moon (FM), half moon (HF)quarter moon (QM), and starlight (SL) conditions. The measured VA was converted to logMAR values and analyzed. Results: VA deteriorated significantly with decreasing illuminations through both Gen 2++ (χ2 = 149.9, P < 0.001) and Gen 3 NVGs (χ2 = 156.5, P < 0.001). For Gen 2++ NVG, the difference in VA was statistically significant in all conditions other than between FM and HM. Whereas, it was almost significant for all illumination conditions for Gen 3 NVG. The VA through Gen 2++ was better than Gen 3 in all conditions and the difference in VA widened with decreasing illuminations. Conclusion: VA declined with decreasing illuminations for Gen 2++ as well as Gen 3 NVG, even though, the difference was not significant between FM and HM for Gen 2++ NVG. VA was observed to be consistently better through Gen 2++ NVG compared to Gen 3 across all four illumination conditions. However, keeping in view the dynamic changes in night sky illuminations during flying operations, the findings of the study need to be validated in operational conditions.

Study of performance characteristics of ANVIS MK-III night-vision goggle and comparison with other NVGs for aviation usage

“…VA has been commonly used to compare visual performance of NVG under different conditions of illumination and varying contrast. [3,6] In this study, VA performance for ANVIS Mk-III NVG showed decreasing trend with decreasing illumination [Table 2]. This is expected with any NVG and is due to increase in noise due to decreasing illumination.…”

“…This is expected with any NVG and is due to increase in noise due to decreasing illumination. [1,3] However, when compared to other NVGs [Figure 5], VA was found to be consistently better even in low light illumination like the QM and SL conditions. This is an interesting finding and is definitely advantageous in target resolution under varying illumination conditions.…”

“…Gen III NVGs have been claimed to have superior physical and performance characteristics compared to Gen II, Gen II+, and Gen II++ NVGs. [2,3] The performance characteristics of NVGs are defined by physical features, [4] their resolution limit or visual acuity (VA) performance, [5] contrast sensitivity, [6] and field of vision performance.…”