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From: email@example.com (William J. Beaty)
Subject: Re: Make infrared goggles inexpensively (like $10!!!)
Date: 17 Sep 2002 01:13:55 -0700
References: <firstname.lastname@example.org> <4Aoh9.15391$1C2.email@example.com>
NNTP-Posting-Date: 17 Sep 2002 08:13:55 GMT
"Tom Del Rosso" wrote in message news:<4Aoh9.15391$1C2.firstname.lastname@example.org>...
> "William J. Beaty" wrote in
> message news:email@example.com...
> > New article just added, check it out:
> > Make your own passive IR filter-goggles
> > http://amasci.com/amateur/irgoggl.html
> > Human eyes can see IR light if it's very bright. Sunny days
> > have quite a bit of IR in them.
> Whether or not you are really seeing the IR, it is certainly true that a
> lot of IR is entering your open pupils. I think more consideration for
> safety is needed before I would try it.
I was paranoid about them when I first started messing with
this. But I never experienced any afterimages, nor the famous
burning pain of UV corneal damage (snow blindness.) The goggles
have glass lenses, and the filters are polycarbonate, so they do
take out lots of UV. The only trouble is that the sun looks like
a dim red disk when viewed through the goggles. It might be harmful
to stare fixedly at it and focus the invisible part of the IR
output on my fovea. So I don't. These goggles probably aren't
so great as a mass-produced toy, but smart hobbyists probably
won't hurt themselves.
> If the sky is almost black, then what happens if you gaze around and
> your eyes unexpectedly find the sun?
> What hue is the almost black sky?
Everything viewed through the goggles is a dull red. The sky looks
dark red. If I use Lee #120 "deep blue" instead of "congo blue",
the sky looks totally black.
The lack of color suggests that our red cones have a much greater
response in the IR than the other cones.
> Considering that our brains process
> signals from only a few types of receptors, you should be able to
> determine, from the hue, what combination of receptors is responding to
> whatever you see. That might help to gauge the likelihood that it is
> really IR, or just a low level of visible colors getting through the
That's the first thing I tried. A stack of blue filters gives a
dim blue-greyish-violet world with bright red foliage. Adding
one layer of Lee #106 red filter eliminates most of the blue-purple
part yet doesn't affect the bright foliage. A second layer of
#106 red will remove all leftover traces of purple, but additional
layers of red don't give any visible effects. The red filter
apparently removes all of Congo Blue's "blue peak", while leaving
the lowpass IR part of the curve unaffected.
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William J. Beaty SCIENCE HOBBYIST website
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Seattle, WA 206-789-0775 unusual phenomena, tesla coils, weird sci
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