Dark or blackout tail lamps

Is anyone familiar with a tail lamp that creates a "blackout" or high
contrast tail lamp using a polarizer or liquid crystal or some other
approach to create a high contrast of off to on with a brake lamp?

On Tue, 22 Feb 2005 wrote:

> Is anyone familiar with a tail lamp that creates a "blackout" or high
> contrast tail lamp using a polarizer or liquid crystal or some other
> approach to create a high contrast of off to on with a brake lamp?

No such device currently exists, to my knowledge. There are Federal and
international standards for all vehicle signal and lighting functions,
including minimum and maximum allowable intensity, minimum intensity ratio
between dim "tail" mode and bright "brake" mode, specific color, angles of
visibility, etc.

What are you trying to accomplish? Sounds like maybe you are trying to
increase the daytime contrast between the "off" and "on" state of a
vehicle signal (brake lamp, turn signal, etc.) to try and alleviate
sunlight-induced low contrast. If that's a correct guess, and you can
implement it without running afoul of the standards mentioned above, it
would be a good contribution to the performance of vehicle signal lights.
Loss of on/off contrast due to external light (sunlight) is a problem that
has not really been addressed yet.

DS

Daniel J. Stern wrote:

> On Tue, 22 Feb 2005 wrote:
>
>
>>Is anyone familiar with a tail lamp that creates a "blackout" or high
>>contrast tail lamp using a polarizer or liquid crystal or some other
>>approach to create a high contrast of off to on with a brake lamp?
>
>
> No such device currently exists, to my knowledge. There are Federal and
> international standards for all vehicle signal and lighting functions,
> including minimum and maximum allowable intensity, minimum intensity ratio
> between dim "tail" mode and bright "brake" mode, specific color, angles of
> visibility, etc.
>
> What are you trying to accomplish? Sounds like maybe you are trying to
> increase the daytime contrast between the "off" and "on" state of a
> vehicle signal (brake lamp, turn signal, etc.) to try and alleviate
> sunlight-induced low contrast. If that's a correct guess, and you can
> implement it without running afoul of the standards mentioned above, it
> would be a good contribution to the performance of vehicle signal lights.
> Loss of on/off contrast due to external light (sunlight) is a problem that
> has not really been addressed yet.
>
> DS

This is just a guess, but wouldn't a matte finish on the taillamps
accomplish that rather nicely? Along with a nice smoke tint, ASSuming
of course that one could produce same while still maintaining
appropriate light output.

Of course, a matte finish anything is a cast iron biotch to maintain,
'cause you can't polish it when it's scratched...

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

On Tue, 22 Feb 2005, Nate Nagel wrote:

> >>Is anyone familiar with a tail lamp that creates a "blackout" or high
> >>contrast tail lamp using a polarizer or liquid crystal or some other
> >>approach to create a high contrast of off to on with a brake lamp?

> > Maybe you are trying to increase the daytime contrast between the
> > "off" and "on" state of a vehicle signal (brake lamp, turn signal,
> > etc.) to try and alleviate sunlight-induced low contrast. This would
> > be a good contribution to the performance of vehicle signal lights.
> > Loss of on/off contrast due to external light (sunlight) is a problem
> > that has not really been addressed yet.

> This is just a guess, but wouldn't a matte finish on the taillamps
> accomplish that rather nicely? along with a nice smoke tint

Not really. Matte or glossy finish has nothing to do with the question at
hand; we're talking about sunlight making the signals look as though
they're on when they're not -- not about simple specular reflection off
the outermost lens surface. As far as smoke or other tints or matrices:
No, not without exacting a very high toll on efficiency/overall output. If
you've enough extra output that you can afford to throw away a significant
amount of it on transmissivity losses from a smoke tint, jolly good, but
if you have that much extra output, and you're an automaker, you had
better believe that a beancounter is going to take away your extra output
and get himself a promotion with the parts cost savings.

> ASSuming of course that one could produce same while still maintaining
> appropriate light output.

Depends on what you mean by "appropriate". Most of the factory smoke-tint
lights I can think of are at the low end of allowable intensity (Jaguar
sedans and hardtops of the '80s, current Mercedes C-klasse, '90s Saab
9000, assorted VWs, etc.). There have been some brighter-than-bare-minimum
smoked lights (certain GM sedans of the '90s) but these were LARGE lights
with relatively high-intensity light sources.

DS

You are right on the money. The reason for my question is that my
group is doing a project for the FMCSA (Federal Motor Carrier Safety
Administration). Through our research, we have determined that the
large majority of rear end accidents for tractor trailor trucks are
daytime accidents. With that thought in mind, we are looking for
numerous conspicuity improvements. One of them would be high intensity
stop lights during the day and part of that might be contributed by
high contrast stop lights. Thus, my question. I thought that this
newsgroup might have some ideas to contribute.

wrote:

> One of them would be high intensity
> stop lights during the day and part of that might be contributed by
> high contrast stop lights. Thus, my question. I thought that this
> newsgroup might have some ideas to contribute.

LEDs have fairly narrow bandwidth. The narrower the bandwidth, the
darker the color filter can be to sunlight while still transmitting the
same amount of monochromatic light.

Or go the other way around: make the filter a neutral color, and have it
turn red when LEDs come on. As long as there is a transmission window at
the LED color you do not use too much light.



Thomas

Zak wrote:

> wrote:
>
>> One of them would be high intensity
>> stop lights during the day and part of that might be contributed by
>> high contrast stop lights. Thus, my question. I thought that this
>> newsgroup might have some ideas to contribute.
>
>
> LEDs have fairly narrow bandwidth. The narrower the bandwidth, the
> darker the color filter can be to sunlight while still transmitting the
> same amount of monochromatic light.
>
> Or go the other way around: make the filter a neutral color, and have it
> turn red when LEDs come on. As long as there is a transmission window at
> the LED color you do not use too much light.
>

I was thinking that as well, but that leads us to (gasp) clear taillight
lenses

Seriously, I think LEDs might be an interesting idea to try, assuming
you can work around the angle of visibility issues.

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

wrote:
> You are right on the money. The reason for my question is that my
> group is doing a project for the FMCSA (Federal Motor Carrier Safety
> Administration). Through our research, we have determined that the
> large majority of rear end accidents for tractor trailor trucks are
> daytime accidents. With that thought in mind, we are looking for
> numerous conspicuity improvements. One of them would be high
intensity
> stop lights during the day and part of that might be contributed by
> high contrast stop lights. Thus, my question. I thought that this
> newsgroup might have some ideas to contribute.

I'd like to hope that avoidance of being rear-ended doesn't rely on
the illumination of some red lights on the rear of my vehicle.. rather,
the following driver notices the increasing size of my vehicle through
their windshield, and the recognition that this is an important
observation, requiring input on their part.

Talking with someone who mentioned that 'their buddy' ran into the
back of them recently.. 'their buddy' explained that the reason this
happened was because this individual's brake lights weren't working.

Had the situation allowed it, I would have seriously considered taking
a 'clue by four' to 'their buddy'.

Regards,

Jim

LED's are already one of the features we are going to use. They are
used in a fairly high percentage of lighting functions for trucks now.
The reason we are using them is that they are instantaneous turning
on. This has a theoretical advantage in giving extra time for the
following vehicle to stop.

In sci.engr.lighting wrote:
> LED's are already one of the features we are going to use. They are
> used in a fairly high percentage of lighting functions for trucks now.
> The reason we are using them is that they are instantaneous turning
> on. This has a theoretical advantage in giving extra time for the
> following vehicle to stop.

Looking at the brake pedal position and position change, and turning on the
lights if it'll reach full lock in 100ms may knock another bit off.
IIRC, a brighter (150%) 20ms pulse helps a small amount in reaction time
too.

I'd not be surprised if you could get 100ms with this, which is 2.5 meters
on the road.

Me, I'd like to mandate an always-on IR emitter in each light, modulated
with a digital code giving speed, minimum traction (have any wheels broken
free, and if so at what best-guess torque), accelleration in the X-Y axes,
and commanded accelleration in the X-Y axes.
Which could be read by a camera in following vehicles.

X-Y accelleration should be measured at each light independantly, for
fault detection.