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

"Dave Schaack" <dschaack@xxxxxxxx> wrote in
news:A8ydnSRL_LuEjc3anZ2dnUVZ_tCrnZ2d@xxxxxxxxxxx:


"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.

Which partly raises another question: do firebrigades typically choose the
more expensive, glass-penetrating version, or would that aspect be of no
use to them, in reality?
(the hap-snap articles I have seen about such purchases, is that they were
never on the lower end of the price-scale (imaginable for real in-building
fire-combat, helm-mounted devices, but not for external/global
assessments))

--
Bye,

Willem-Jan Markerink

The desire to understand
is sometimes far less intelligent than
the inability to understand

<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]
.

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  • Any regular FLIR-/thermal-imagers capable of looking through glass?
    ... glass blocking just that spectral range in which the imagers had no ... sensitivity at all (hence also all using very expensive types of lenses ... (of course, still possible they also mixed up near-IR & thermcal, but near-IR ...
    (sci.optics)