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There was an idea posted previously for instant
darkening lenses, wherein I posited (speaking entirely out
of my arse) that transition lenses darken pretty quickly. I
didn't actually own a pair, and was basing my claim solely
on a very misleading television advertisement. I
wholeheartedly apologize
for
that.
I now do own a pair, and now know exactly what
prompted the poster of that idea to get creative about
finding a solution. Even in full, direct sunlight, it can take
up to a full minute for these things to darken sufficiently
to be considered, by any reasonable measure,
sunglasses. Once inside, they take up to 10 minutes to go
clear again. I don't have a solution to the indoor clearing
delay, but I think I have one for the darkening delay issue.
My idea is for a hat with a UV lamp under the bill. It can
be a narrow, low profile pair of bulbs with a simple
switch. When you're about to go outside into the
sunshine, turn on the UV lamps a minute or so before
actually going outside to predarken them. A small solar
cell on the top of the hat can serve as a safety kill switch
to turn them off automatically once exposed to sunlight
to save you forgetting and accidentally giving yourself a
sunburn. A two minute timer switch might work as well.
Turning 3D shutter glasses into automatic sunglasses
http://hackaday.com...tomatic-sunglasses/
This looks like a fun experiment [xaviergisz, Jun 03 2014]
[link]
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Unless you're on the water and racing from the
dark hold to take the wheel before you run into a
sailboat that came at you out of the glare, the
darkening time is rarely critical. The do transition
quickly enough that by the time you actually have
to look at a glare you are fine.
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The reverse can, sometimes, be a problem, and I
have learned to take my glasses off and shield
them for a bit before entering certain locations
(mostly historic ones where they get annoyed if
you hold up the line and the floors tend to be
uneven). |
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MechE, it can be problematic when driving out of a
wooded area with lots of shade that has a curve
just outside the exit. |
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My auto-darkening welding hood activates in 1/100,000 of a
second or so (much faster than it takes the arc flair to go
the distance between the visor and my eye). Since mine is
a really really nice one, it has variable shade settings from
9 to 13 (sunglasses typically run from shades .75 to 1.5, but
I've seen some as dark as 2.5) and it has a sensitivity
adjustment that can be set high for low-light shop
conditions but turned down for outdoor work to prevent it
from being accidentally triggered by the sun.
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I've long wondered why this tech hasn't hit the sunglasses
market yet. I've seen plenty of rich idiots who spent more
on their shades than I did on my welding hood (about
$300). It seems like a no-brainer. |
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This idea came to me today again whilst driving, because
transitions, being UV activated, don't darken in a car because the
windshield has a UV filter. And yes, I do have a very nice (and
expensive) pair of prescription sunglasses. I had left them in my
other car by mistake when I set out for Wallace, ID and had to
make the westward drive home into the setting sun. It sucked. |
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