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July 5, 2011
Research Engineer, U. of Washington Seattle
about 2 years ago
The $1K cameras with 2cm lens can see a 1f-2f deg change. Perhaps experiment by prying off the tiny lens and swapping in a much larger germanium lens found on eBay.
I wonder if these can be used in a “gas fumes” camera, Gas FindIR™ or similar?
I think those devices work at around 7u wavelength, so Lepton might work if the dynamic range is large enough. Or maybe it would need a lens swap.
The quick/dirty version would be to record and store a background image, then subtract it from a live image, crank up the contrast. Tripod mounted of course. Then hold up a gasoline-soaked rag, see if hydrocarbon vapors show up. Or a realtime version: two adjacent Lepton kits 50cm apart, adjusted to aim at the same distant background. Subtract the video streams, adust bright/contr, then present a gasoline rag to just one camera’s view.
I suspect that the professional versions use two imagers behind one lens, one with a narrowband IR filter on the hydrocarbon IR absorption line, so they get a large difference-signal. See youtube examples on my thermal vids page, about nine videos down.
Note: germanium lenses are less absorptive than silicon lenses. Does Lepton use silicon? If so, then one experiment would be to pry off the lens and substitute it for a $100 version (often seen on eBay, I have a couple of those.) I don’t know if this will improve it, since a very small (thin !) lens of Si might have insignificant absorption. Of course sometimes one can find a focus/zoom military germanium lens on eBay, pricey but cheaper than a Fluke or Flir camera. And in the other direction, polyethelene DIY plastic lenses!
News - According to Pete - July …
about 5 years ago
Wow, I never met anyone else who realized this. All diodes are PN diodes, right? :) Shottky NnN catswhisker transistors!
But if the magic isn’t all in the PN junction …we’re lost, forever lost.
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