Advanced high intensity discharge light sources
Conventional high intensity discharge (HID) lamps are commonly used in outdoor applications such as street lighting. They are also commonly found in indoor high bay applications such as factories and sport counts. HID lamps produce light by mean of an electric arc column across tungsten electrodes. In general, about one-third of the input electric power is utilized to produce visible light, while the rest electric power loss as heat. Advanced HID lamps would shift infrared energy from the arc to near UV or visible emission to improve their efficiencies. This type of lamp would need to operate with electronic ballasts, and would increase average luminous efficacy
(please click for definition) by about 40%.
Conventional lighting technology only focuses on luminous efficacy and light output, colour temperature and spectral balance are always being ignored. Research in the past dacade have put efforts on how eyes respond to different parts of the spectrum. "Scotopic" lighting which stimulates the eyes' photoreceptors called rods, is one of the research focuses. It might have lower measured luminous efficacy than "photopic" illumination (which activates photoreceptors called cones). However, well-chosen scotopic lighting can provide higher efficiency, diminished glare (at computer screens), and greater comfort. Visual acuity is not affected by using this kind of technology when lights are dimmed, thus saves energy.
Luminous efficacy: Luminous efficacy represents the light output (in lumen, lm) that the lamp can produce per unit of power input.