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Old 09-06-2011, 03:45 PM   #9
HipToBeSquare
Scooby Specialist
 
Member#: 119958
Join Date: Jul 2006
Location: (IA) flyover cornfield country
Vehicle:
2005 Legacy GT Ltd.
Garnet Red Pearl

Default

So much misconception here it is insane.

any light can blind. some do it faster than others, but a laser-based headlight would not necessarily blind, or even be any higher risk than halogen, HIR, HID, or LED.

Lumens are lumens.

A laser of equal electrical input may indeed provide 1000 times the light of an LED or LED array. That is only a flat comparison with no context.

LEDs are not the brightest light source, but for what light they do output, they are electrically efficient by not generating as much heat until they are pushed pretty hard, towards 10 or more watts per emitter. They start to behave more and more like other light sources, that generate significant amounts of heat per watt of electrical input.

Conversely, A Laser that puts out the same light output as an LED, or LED array. may use hundreds of times less wattage.

math works both ways, and making a laser-based headlight that puts out enough lumens to be effective, and not 1000 times more light than what is effective, is conversely more energy efficient, and possibly less heat intensive.

The issue with LEDs is putting out enough lumens, with far enough down-range throw, in an LED array that is small enough to fit in a headlight housing, and not over-heat themselves, and reduce their functional lifespan. high intensity LEDS, especially arrays of dozens of them, are expensive. Far more expensive than a HID ballast and arc bulb, let alone an auto-parts-store halogen bulb. But LEDs last far longer, if they don't thermally degrade by being pushed too hard.

Plus there is the whole issue of optics. LEDs have narrow emitter angles, which can be somewhat widened by optics, but each emitter has to have them, and a single emitter is not the brightest source of light, so there have to be many emitters clustered together. That isn't bad, but it isn't a single light source throwing light further down-range.

A laser has almost inverse issues as a halogen or HID bulb. arcs and filaments radiate photons in a 360 degree spherical pattern. Lasers emit a coherent beam by definition, in one direction.

A bulb has to have reflectors and lenses to corral and direct the light in one general direction with prescribed vertical and horizontal pattern angles.

A Laser would actually need to be spread by a lens, to defray a tight beam into that same pattern, but would be more efficient at it, as almost none of the light would be wasted in directions not directed through the de-focusing lens.

With cutoff shields and lens optics, the pattern would be just as efficient or even more so, than the best HID projector headlights, and waste less light output, and waste less electrical energy as heat output, as well.

And lens adjustment could also provide beam adjustment more precisely, as well, making a laser-source headlight possibly even more versatile than a steerable halogen/hid projector, or an adaptive LED array which would have to house more emitters to be able to differentially select active emitters, and have enough of them active at any given time to have the appropriate amount of lumen output.
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