
BMW's Laser Headlights - merraksh
http://wot.motortrend.com/bmw-shows-us-how-its-laser-headlights-and-dynamic-lightspot-work-126103.html
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christoph
It might just be me, mainly because I drive an "old" car that doesn't
dim/adjust my rear view mirror based on others drivers lights, but I find the
uber brightness of other drivers lights to be a real pain these days. Often on
the motorway I struggle to see ANYTHING as i'm being constantly blinded by
other drivers high power lights behind me and when oncoming. I get its meant
to be a safety feature, but for a lot of other road users it's a real nuisance
to be blinded on a daily basis.

A good solution would be for modern cars to detect ambient light and adjust
accordingly. On a well lit highway with lots of other road users, there's no
reason to have these things turned up to 11 all the time. They could safely
dial back to 3 or 4.

~~~
rhizome
I have a VW with xenon projectors and the self-leveling feature should ensure
this doesn't happen, but occasionally people do flash me. I assume their eyes
are dilated from the weed.

~~~
blahedo
Xenon lights are obnoxious because they are so much bluer than standard
lights, they are that much more blinding; outdoor lights that are too blue (or
full-spectrum) have the paradoxical effect of making everything _darker_ by
contrast, and much harder to see.

I can't stand cars that have xenon lights, and I was glad to see their numbers
start to decline in the last couple years.

~~~
StavrosK
My car also self-levels its xenon lights, and they are never at the other
drivers' level. I never see anyone being bothered by them at all.

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auctiontheory
_I never see anyone being bothered by them at all._

WTF. How on earth would you know whether drivers going in the opposite
direction were being blinded by your lights?!

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fsckin
You can see _very_ clearly where the higher intensity area of the beam cuts
off, and he probably doesn't get flashed by oncoming cars.

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lutorm
My understanding has always been that lasers have a very low efficiency. I
don't understand how it can possibly be more efficient to use a laser than an
LED. But maybe my thinking dates back to the days of gas discharge lasers and
solid state lasers are just that more efficient?

~~~
dredmorbius
Some solid-state lasers have pretty high efficiencies, as much as 74% in this
case: [http://phys.org/news/2011-05-scientists-high-efficiency-
cera...](http://phys.org/news/2011-05-scientists-high-efficiency-ceramic-
laser.html)

I think I've seen references to 50-60% efficiency for production lasers,
though I could be mistaken on that. Given the very low efficiency of lighting
systems in general (incandescent bulbs waste 95%+ of input energy, even CFLs
and LEDs are in 20-40% range AFAIR), that's very high.

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belluchan
> Like Xenon headlights, power is immediately cut to the laser headlights in
> the event of any damage.

As a software engineer this statement really bugs me. Once something is
damaged in the real world you can't assume control over the system anymore.
The part that cuts or provides the power to the laser might have been the
thing damaged. Maybe if they had added a qualifier like "power should be cut"
instead of such certitude.

~~~
pandler
There is a concept in mechanical engineering where something can have a
"normally closed position." You see this often with valves. The idea is that
the normal resting position of the actuator prevents flow throw the valve. The
effect is that the valve automatically shuts itself in the event of power loss
or system failure. I presume they have implemented something similar. I might
guess that the lasers may not be turned on if the system cannot somehow
validate the integrity of the lens the lasers shine into. Same thing with the
part that cuts or provides power to the laser. It's been a while since I
studied circuits as a mechanical engineering undergrad, but I believe that you
can also design circuits that behave in a similar fashion.

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Cairn
"BMW says its laser system is 1000 times brighter than LED headlights but uses
half the power." Yeah, that's bull, unless they're using some very creative
definition of "brighter". LED headlights put out about as much light as do
standard halogen incandescents, about 1000-1500 lumens per fixture. A million
lumens? You'd be hard pressed to tell that apart from the sun. Also
theoretically impossible, as LEDs are already at 10-25% maximum luminous
efficacy.

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jawns
I googled "yellow phosphorus," and this page, run by an Angelo State
University professor, says that it's the same as white phosphorus, which I
understood to be dangerous.

[http://www.angelo.edu/faculty/kboudrea/demos/burning_phospho...](http://www.angelo.edu/faculty/kboudrea/demos/burning_phosphorus/burning_phosphorus.htm)

The page explains: "White phosphorus is highly reactive, and spontaneously
ignites at about 30°C in moist air. It is usually stored under water, to
prevent exposure to the air. It is also extremely toxic, even in very small
quantities."

Aside from cutting power to the headlights, I wonder how BMW keeps the white
phosphorus from causing trouble during a crash.

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brokentone
Bear with me here-- I understand lasers to be highly specific wavelength diode
light that is bounced around in a combination of prisms and mirrors to create
highly concentrated, highly directional light.

In this case, it's then diffused again through a yellow phosphorus lens.

I'm not doubting the numbers in efficiency gain, but I'm having a hard time
figuring them out. Seems that there can only be loss from converting this
light "back and forth" (but more than likely I don't understand how lasers
work).

~~~
MBCook
Well, let's assume these lasers are 10x as efficient as LEDs used in
headlights. Even if you lost 70% of the light in the process of exciting
phosphorus, you'd still have a net gain.

My question would be: are modern headlights really that much of a drain?

~~~
Cairn
Decent LEDs are, currently, about 6x less efficacious than the theoretical
maximum of any light emitter, as measured by the human eye. Incandescents are
much poorer performers, of course.

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CraigJPerry
Be interesting to see how these compare in the real world to my current
favorite headlights, the Hella brand units fitted to higher end Volkswagens
since 2009.

They're a much better "daylight" approximation than comparable systems, e.g.
the units fitted on the Jaguar XF are pretty jarring in comparison.

The beam shape adjusts based on roadspeed and window wiper activity, the rain
pattern is _excellent_ when snow is falling.

For the manufacturer the part is cheaper than comparable high end units,
partly due to removing the need for external ride height sensors. Most HID
setups have a ride height sensor on the front suspension and one on the rear,
the Hella units have gyroscopes packaged inside the cluster removing the need
for external parts.

The final winning point for me is the freedom left to the manufacturer in
designing the rest of the headlight cluster around the HID unit. Consequently
replacing any other bulbs in one of these units is complete child's play.
Contrast this with 0.5 hours "book time" for the new BMW X5 - the front bumper
has to be removed (involves disconnecting headlight washer pipes and plenty
more besides).

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yread
I don't get all this commotion about laser lights and their 1000x efficiency
when that's just a concept maybe 5 years in the future. The lightspot
technology (looking with IR cameras for people and highlighting them, so that
drivers see them 112 feet sooner) seems much more interesting and should safe
a lot more lives than lights with different technology that scale better.

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spullara
I'm concerned about the responses in this article. I drive on the same roads
every day and have never experienced an issue with other cars having very
bright normal lights to the point of blinding me. Perhaps they should get
their vision checked and see whether it is safe for them to drive at night. It
may be that their eyes are too senstive for it to be safe.

~~~
Cairn
Well, I'm glad that you, specifically, have never had that issue. Might you
have noticed the large number of complaints registered in the years since HID
lights became common?

~~~
spullara
I think it is possible that they are more sensitive to the particular color of
those lights. If the majority of the population doesn't have the problem, it
may never be fixed without identifying what the issue might be. It might be
like a color blind person complaining that red and green lights on the road
look the same when most people don't think they do.

Also, no, until this article & comments, I have never heard this complaint.

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ericcumbee
Audi is putting them on the 2014 LMP car.

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ck2
Wait for the Chinese clones of this that every idiot will retrofit to their
car, thereby endangering everyone on the road like the do now with their
illegal blue headlights.

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agsamek
Can somebody explain the 1000 times efficiency gain? I thought that LED is
over 10% effective on power so I don't get this.

~~~
birschtl
I guess one factor in this "1000 times more efficient" scam is the higher
photon output per surface area. LEDs efficiency drop a lot when maximizing
photon per surface area. Edge emitting blue lasers have a much better power
conversion rate than LEDs when driven at higher input power. The much better
photon/surface area plus higher input power create a much narrower and
brighter beam. Therfore only ~10% loss opposed to ~30% with LEDs...

[http://m.phys.org/news/2013-11-laser-
diodes.html](http://m.phys.org/news/2013-11-laser-diodes.html)

[http://www.winlab.rutgers.edu/~crose/capstone12/entries/Soli...](http://www.winlab.rutgers.edu/~crose/capstone12/entries/SolidStateLightingwBlueLaserDiodes-
Revised.pdf)

