On Aug 23, 2008, at 12:48 PM, John Griessen wrote: > Eric Brombaugh wrote: >> Dave McGuire wrote: > >>> I'd be shocked and amazed if they could detect thermal IR. >> >> Agree - there's a big difference between the short-wave IR that's >> used >> by common IR remote controls (which is easily seen on most any >> webcam) >> and the long-wave IR used in thermal imaging. > > Ohh... we can control the situation to get near enough IR. We're > looking for shorts > anyway, not normal operating temps of + 1 degree... Seeing just > the really hot spots > -- meaning 120 deg F is plenty good, and the amount of near IR in > that temperature surface is > enough to see with a CCD I bet.
Nope. Quantum efficiency of silicon detectors drops like a rock just beyond 1 µm wavelength: the radiation just goes right through without interacting. Indeed, Si wafers make excellent entrance windows for for thermal IR detectors. A 350 K blackbody emits ~271 µW/mm^2 of thermal radiation, but only ~4.4 fW/mm^2 of that is short of 1 µm. With very fast optics, cryogenic temperatures, a state of the art scientific CCD, the extremely low noise video chains I design for astronomy, and rigorous exclusion of every optical photon, you might be able to see something. With commercial/industrial technology, not a chance. On the other hand, a 350 K component is pretty easy to find with your finger... John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ [EMAIL PROTECTED] _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
