Mining Publication: Visual Performance for Incandescent and Solid-State Cap Lamps in an Underground Mining Environment

• Cap lamps
• Hazard recognition
• Improving visibility

Miners depend most heavily on visual cues to recognize underground mining hazards; consequently, illumination plays a critical role in miners' safety. Some hazards are located in the miners' peripheral field of view (10 degrees to about 60 degrees off axis) or on axis (0 degrees). The objective of this research was to determine if there were visual performance improvements when using solid-state cap lamps with light-emitting diodes (LEDs) as compared to incandescent light bulbs commonly used in miner cap lamps. Recent research has indicated that an increased short-wavelength content of the spectral power distribution of LEDs relative to incandescent lamps improves peripheral visual performance for low-light (mesopic) conditions. The visual performances of nine subjects were quantified by measuring the subjects' speed and accuracy in detecting floor objects located on axis and at + / - 20 degrees off axis. The objects were located near field (1.83 m) and far field (3.66 m). Upon presentation of the objects, the subjects would count and point to each object using a red-laser pointer. The object detection response time and number of missed objects were recorded. The results of the visual performance comparison for an LED, a prototype LED, and an incandescent cap lamp are presented. There were no missed objects when the subjects used the LED-based cap lamps, but there were three missed-object occurrences when the subjects used the incandescent cap lamp. The mean detection time when using the incandescent cap lamp was 55.3 percent greater than that of the prototype LED cap lamp and 43.5 percent greater than that of the LED cap lamp. It can be inferred from these data that the spectral distribution of LED-based cap lamps could enable significant visual performance improvements as compared to incandescent cap lamps. Keywords Mining-industry; Mining-equipment; Light-source; Lighting-systems; Underground-mining; Miners