LED lights
LED lights
(OP)
I didn't want to change the topic on my first thread.
I'm curious, about some of the LED tail lights used on some vehicles. Are there any that are laser diodes? And how bad are they for our eyes? I know there are some that cause comet trails when moving eyes rapidly side to side. Wouldn't coherent light cause that?
I'm curious, about some of the LED tail lights used on some vehicles. Are there any that are laser diodes? And how bad are they for our eyes? I know there are some that cause comet trails when moving eyes rapidly side to side. Wouldn't coherent light cause that?





RE: LED lights
Do you have a link or reference to "comet trails"? I think I get them from some light source in my flat, but can't work out which or when. Thought I was going mad/blind or drinking the wrong stuff.
- Steve
RE: LED lights
LED read lamps are multiplexed and PWM controlled to differentiate between read- and brake intensity.
Unforunately, the designers (at least in the beginning) opted for a too low pulse frequency (below 100 Hz). This is not a problem with incandescent lamps due to the inherent brightness integration, but with LEDs it is highly disturbing, specially in the periphery of your field of vision.
LED pulsing should be at frequecies above 200...300 Hz for this effect to disappear.
From a car with LED lamps passing across your field of vision, you'll even see a kind og pearl-chain effect.
Benta.
RE: LED lights
Benta.
RE: LED lights
Cheers
Greg Locock
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RE: LED lights
RE: LED lights
- Steve
RE: LED lights
I've had a kind of OCD thing since I was a little kid and saw my first LED display on the move. I had a calculator with such a low strobe rate that if I passed it from right to left in a pretty straight line, I could see each individual segment. It used to fascinate me, and even today I will often test new things by passing them back and forth in front of my eyes. (Yes, I'm weird). A couple hundred Hz seems to do the trick, though.
Good on ya,
Goober Dave
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RE: LED lights
But that is because the after-glow of the phosphor helps.
With LEDs it pure on/off and it is disturbing also above 100 Hz.
Benta.
RE: LED lights
Comet trails are most likely due to saturation/persistence of your retina, since you're probably only seeing them when ambient lighting is low.
Frame rate is highly dependent on intrascene motion; gamers tend to want frame rates in the 100-Hz range, or even higher, because the brain can detect the stop-start motion going from frame to frame. Interesting, intentional blurring of the image tends to quell that phenomenon, and lower frame rates can be used under those circumstances.
TTFN

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RE: LED lights
Steve, I recall reading somewhere that as we age, we tend to become more easily fatigued and lose eye coordination (ability to keep the eye focused in a single spot), which exacerbates the POV problem noted above, especially if you are reading in a flickering light source (fluourescents, especially as they age, can be bad this way). I have started wearing reading glasses, they help quite a bit.
There's also this "syndrome" - try rose colored glasses? :
http://e
RE: LED lights
RE: LED lights
A lot more taillights out there are direct drive rather than PWM'ed... companies like cheap, which means directly driving them from the battery with a resistor or two and parallel blanks of LEDs. On older third brakelights you'd often see a strip or two of dead LEDs.
Now, my animated tailights use a PWM-like method, but that's after-market equipment
Dan - Owner

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RE: LED lights
ht
Someone said they can't use lasers????
RE: LED lights
Dan - Owner

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RE: LED lights
I'm hopeful they'll wise up and increase the multiplex frequency to help these old eyes a bit.
Mike Halloran
Pembroke Pines, FL, USA
RE: LED lights
I think Aus was a colony until well after American independence.
It's almost my lifetime since we got Cadillacs here and I don't see that changing any time soon.
There is a case here for exceptionally bright lights for use in the remote outback where the risk of collision with livestock and large wild animals is very real.
Regards
Pat
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RE: LED lights
Dan - Owner

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RE: LED lights
Regards
Pat
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RE: LED lights
Dan - Owner

http://www.Hi-TecDesigns.com
RE: LED lights
The issue has never been about how bright a tail-light is in clear weather, but how bright they are in heavy rain or fog, particularly the latter, when "driving like a bat out of hell" FORWARD in fog and not seeing brake lights ahead is the problem.
Note that the Google car's usage of a laser radar doesn't necessarily solve that problem, although, the NIR wavelength of the laser radar helps a tiny bit. It's unclear how good that ladar is in poor weather. An RF-based obstacle avoidance system might be needed for freeway driving in poor weather.
TTFN

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RE: LED lights
TTFN

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