Jeff Liebermann wrote in
:

On Fri, 16 Mar 2012 19:26:12 -0700, josephkk
wrote:

Now what do they make lenses out of for that wavelength range?

Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital
cameras do near IR. The ideal material for mid IR is germanium.
However, that's rather expensive.
http://www.edmundoptics.com/products...d=11&subcatid=
314

Much cheaper are various plastic formulations, that pass IR.
http://www.fresneltech.com/materials.html
http://www.fresneltech.com/materials_graph.html
http://www.eplastics.com/Plastic/Ple..._Infrared_Tran
smitting

For tinkering, the IR motion detectors (PIR) lenses are cheap and
easy:
http://www.glolab.com/pirparts/pirparts.html
http://www.futurlec.com/PIR_Sensors.shtml

There are also a tangle of band pass, low pass, and specialty filters.
http://www.edmundoptics.com/products/browse.cfm?categoryid=41

Or, you can just be weird:
http://amasci.com/amateur/irgoggl.html



often,they use curved mirrors instead of lenses,for IR.

and sapphire for a window. ;-)

--
Jim Yanik
jyanik
at
localnet
dot com