According to the researchers, conventional street lamps - which use high-pressure sodium or mercury vapour - scatter up to 20% of their energy horizontally or vertically because it is difficult to control their beams.
It is easier to direct light from LEDs because it is being emitted from a smaller area.
So, while manufacturers controlled the direction of the light rays from older lamps using a reflector typically made out of polished aluminium, they can now take advantage of lenses to be more precise.
The researchers say the best LED (light-emitting diode) streetlamps on the market direct about 10% of their energy horizontally or vertically.
But they claim their own invention could further reduce the amount to just 2%.Their proposed lamp uses three features to ensure the vast majority of its light is limited to a pre-determined rectangular shape covering the road:
• A special "total internal reflection" lens for each LED designed to focus its light's rays so that they travel parallel to each other in a single direction. This is rather than criss-crossing and diverging from each other causing many to spill beyond the target area.• A reflecting cavity into which the lens-covered LEDs are fitted. This helps "recycle" any light rays which fail to travel the desired path.• A diffuser through which the focused light passes to help tackle unwanted glare.
The researchers suggest that the set-up would also save on electricity costs since it should require between 10 and 50% less power to illuminate a section of road than current LED streetlamps.
Via Dr. Stefan Gruenwald