On Mon, 20 Mar 2000, Michael S. Lorrey wrote:
> James Rogers wrote:
> > As I understand it, the fabrics/dyes used in BDUs are non-reflective in the
> > IR spectrum so that you don't stand out when painted with an IR beam
> > (e.g. from near spectrum devices like night vision). You can't effectively
> > shield a person against far infrared e.g. FLIR. For hunters, there is a UV
> > issue with some detergeants and brighteners, since certain animals can see
> > into the UV spectrum.
>
> From my own experience in Panama during the invasion to get Noriega,
> and as SOP for other deployments and exercises, we weren't allowed to
> starch our BDUs or use common consumer detergents. I've seen first hand
> what starch in BDUs does to its 'non-reflective' capabilities when
> viewed through tactical Night Vision Goggles, I would imagine its the
> same effect with FLIR. Makes you light up like a street light.
Most "night vision" equipment operates in the near infrared and operates
on reflected light in the same way visual spectrum equipment does. This
is why they have IR emitters for use with night vision; they act as
flashlights to increase the amount of reflected IR light. The dyes in the
BDU fabric are designed to be non-reflective in the infrared spectrum in
the same way they are designed to be non-reflective in the visible
spectrum.
FLIR is a passive far infrared technology that resolves black body
radiation being emitted by heat sources, something which cannot be easily
shielded and which humans emit in abundance. The FIR and NIR are
fundamentally different in their theory of operation. The difference is
analogous to passive and active sonar technologies. NIR devices like
night vision rely on reflected signals for discrimination, FIR devices
like FLIR rely on finding anomalous patterns in the ambient environment
for discrimination.
-James Rogers
jamesr@best.com
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