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Old 09-06-2011, 07:38 PM   #21
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Originally Posted by Len View Post
When working properly, yes. But while it's fundamentally impossible to focus regular light source in a way that it will stay as a narrow beam over a long distance, (Liouville's theorem) high intensity laser is a serious hazard when left undiffused. Granted, it's not easy to imagine a scenario where the laser source would be exposed and still running, but it is at least an added safety concern.
I highly doubt a laser emitter would be so dis-associated with it's diffusion lens, that it would be left as a raw laser emitter without the diffusion lens after some sort of damage condition. A failure like that would probably disable the emitter, as well, or trigger a failure mode that shuts it down.

A HID high/low beam projector with the low-beam cutoff-shield down, and the projector lens absent, would probably blind people as well.

We don't know that a laser emitter would be outputting more lumens than that. But at equal light output, the laser is probably far more efficient, cooler, and with less electrical draw.

We don't know that BMW is trying to make the lights' net output onto the road to be significantly higher, just that they are using a more efficient laser emitter source for it, rather than LEDs.

I love LEDs. I think everything else on the car should be LED lit, except the headlights that seem to push the requirements beyond what LEDs can easily do, in a confined, enclosed headlight unit sort of space with a given net output and pattern focus.

HIDs are great... but they still require high voltage startup, and don't react particularly well to rapid start and stop, like high beam demands often require.

Halogens have been a workhorse, but we are seeing that both HID and solid-state have significant improvements over thermally inefficient halogen bulbs.

We don't know how "high-intensity" these laser emitters would need to be to match the net output of today's better headlight technologies. To match the total output of the light unit, one laser emitter would probably match dozens or hundreds of LED emitters, and exceed a single HID source. Higher efficiency per emitter doesn't necessarily equate to tremendously higher net output.

EDIT: Also, I disagree with the idea that laser is the "logical" next step in automobile lighting technology. An ideal lighting for humans would be diffused white light, with full spectrum of visible light (although really you just need RGB) and little directionality. Laser is the EXACT OPPOSITE of what we would consider a natural light. I get that the auto headlamps cannot be fully natural due to the need to avoid blinding the oncoming traffic, but I fail to see how the least natural light source we have is the LOGICAL next step in this field, apart from the fact that the word laser sounds really cool in your PR material.
The article mentions outputting white light. No artificial light source is natural, it is just a matter of how well they can approximate natural light.

LEDs are not full-spectrum, either, and in order to create white light combine blue-frequency emitters with yellow phosphors to mix the two into varying color temperatures of white. They don't even add red frequency, usually.

I'll repeat what I said earlier. Given that we have this concern about not blinding other cars, having a brighter beam likely requires an even sharper cutoff, a combination that makes it more difficult to see anything outside the zone of illumination. I'm not sure if this is really a good thing, and consequently I'm not convinced that brighter is always better.

If this is just about energy efficiency, then fine. Given the cost of laser, I find it hard to believe that this could be cost effective, but who knows.
Again, output per emitter, and net output of the light fixture are two different things.

Per emitter, one laser emitter is significantly different than one LED emitter.

One laser emitter need not be putting out many times more lumens than an array of hundreds of LEDs to do the same job.

And one laser emitter takes up far less space, and creates less heat than 100+ 10Watt Cree or other high-output LED emitters in close proximity to each other in a housing.
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