Discomfort Glare Comparison for Various LED Cap Lamps

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are investigating different lighting technologies with the objective of improving mine safety. This paper presents the results from an ongoing study that compares discomfort glare for different light-emitting diode (LED) cap lamps using the de Boer glare rating scale. The cap lamps tested included two commercially-available LED cap lamps and one NIOSH prototype LED cap lamp tested at three different illumination levels. Prior research indicated that the NIOSH prototype enabled much better visual performance as compared to other LED cap lamps. It uses three LEDs that produce multiple illumination areas in comparison to commercially-available cap lamps that use one LED and projects a narrow spot pattern. Across subjects and cap lamp test conditions, measured illuminances (averaged at both eyes) varied from 0.62 to 3.73 lx, whereas the de Boer glare ratings varied from 4.86 to 7.71. An analysis of variance based on 15 subjects indicated a significant difference in the discomfort glare due to cap lamps (F_{4, 52} = 18.01, p <; 0.001). Post hoc tests indicate that one of the commercially available cap lamps exhibited lower discomfort scores, with no statistically significant differences detected between the others. Thus, the NIOSH prototype cap lamp does not cause excessive discomfort glare yet enables better visual performance.