Re: Any regular FLIR-/thermal-imagers capable of looking through glass?


"Willem-Jan Markerink" <w.j.markerink@xxxxx> wrote in message
news:Xns99F82360E50Awjmarkerinka1nl@xxxxxxxxxxxxxxx
Many years ago, I understood from both theory and reality that thermal-
imagers were not capable of looking through (ordinary) glass windows, with
glass blocking just that (broad?) spectral range in which the imagers had
no
sensitivity at all (hence also all using very expensive types of lenses
(opaque to the human eye).
But I also recall more than one type of imager, with different spectral
ranges, also requiring different lenses (still all in the heat-spectrum,
but
quite far apart).

My question: Any imagers that can look through glass, past/present/future?

(I want to debunk a myth that recently appeared in Dutch media)
('burglars studying people indoors, in remote villa's, with military
thermal-
sensor equipment')
(of course, still possible they also mixed up near-IR & thermcal, but
near-IR
isn't as military-limited as it was 2 decades ago)


Window glass has some transparency from visible wavelengths out to about 3.8
microns or so (there is a very strong absorption band centered at about 2.7
microns, but transmission begins again at longer wavelengths). Thus, if the
thermal imager is sensitive to wavelengths shorter than 3.8 microns, it can
see through window glass. There are thermal imagers for the "3 to 5" micron
band, so these can do it, but I don't know if any of the cheap ones have
sensitivity in this range.


.

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  • Any regular FLIR-/thermal-imagers capable of looking through glass?
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