Re: interesting surplus?

[Joshua_Putnam <josh@xxxxxxxxxxxx>]

Some time ago I posted to the list about a poorly-identified
surplus IR filter available from American Science & Surplus.
Mine arrived today, and while I haven't had time to put it to any
practical use, I figured I'd give what details I have.

The filter is visually black, glass, about 14cm diameter.  It's
domed, about 2cm or so.  The rim has a black rubber gasket around
it.  The filter looks like it's for a light source or sensor, but
not for imaging -- the outside is nice and smooth, but the inside
has visible casting marks.  The only identification on the filter
is ~K4301.

I don't have equipment to test what spectrum it transmits, but I
have done a few simple tests.  It doesn't transmit visible light,
not even a dim glow when I set off a GN104 (feet) flash behind
it.  But it transmits enough of the energy from the flash that I
can feel the warmth of it on my cheek when it fires.  It passes
the light from the IR diodes on my television and stereo remote
controls -- anybody know what wavelength those usually are?  I
know they're short enough to show up on video cameras, so they
must be fairly near IR.  So I'm guessing this is somewhere in the
87-something range.  Anyone have suggestions on more precise
tests?

Anyway, I'll have to try sticking it in front of a flood lamp and
see if I now have a good invisible IR flood.  I may make up a
small box for it that lets me stick various light sources behind
it.  Perhaps just a standard light socket so I can choose
incandescent bulbs, my big studio flash, or those huge old
screw-base flash bulbs if they're still available.  I expect a
heavy glass filter won't start to buckle and fade in front of a
flash like the 87 gel I've used before.


In case anyone is interested:

American Science & Surplus
3605 Howard St.
Skokie, IL  60076

www.sciplus.com

Item no.27816, IR filter, $24.50 ea.


- -- 

 Josh@xxxxxxxxxxxx  is  Joshua Putnam / P.O. Box 13220 / Burton, WA 98013
                       "My other bike is a car."                   
                     http://www.wolfenet.com/~josh/
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End of Infrared-Digest V0 #731
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