IR Blocking.

One idea that I thought about is to simply use frosted glass. The police/
/FBI/CIA/other using the IR cameras don't just want to recieve IR light;
they want it in a coherent pattern. Using frosted glass, the light is 
dispersed in (mostly) all directions. The spooks should then only be able
to percieve some fuzzy shapes. Oh, they'll be able to know if the lights
are on, but for all they know, you are just having a quiet game of bridge.
(I am not absolutely certain about the va .. veracity of this method, but I
gathered that if frosted glass disperses normal light, it should do the
same for IR. The range of refractive indices would be different, and that's
about it.) Any criticisms of this method would be appreciated. Peter Murphy.

Peter Murphy <pkm@maths.uq.oz.au> wrote:

> One idea that I thought about is to simply use frosted glass. The police/
> /FBI/CIA/other using the IR cameras don't just want to recieve IR light;

The FBI and CIA are operating in Australia now?  wow...  :)

> they want it in a coherent pattern. Using frosted glass, the light is
> dispersed in (mostly) all directions. The spooks should then only be able
> to percieve some fuzzy shapes. Oh, they'll be able to know if the lights
> are on, but for all they know, you are just having a quiet game of bridge.
> (I am not absolutely certain about the va .. veracity of this method, but
> I gathered that if frosted glass disperses normal light, it should do the
> same for IR. The range of refractive indices would be different, and that's
> about it.) Any criticisms of this method would be appreciated. Peter Murphy.

Acutally, since longer wavelegnths are scattered at greater angles,
frosted glass will scatter infrared better than visible light.  It
probably doesn't amount to a large difference tho...and if it did, they
might move up to ultraviolet.  But UV is much easier you to detect, so
they probably wouldn't risk it.  :)

Here's an idea to piss them off....  How about pulling down your shades,
and on the inside of the shades, we paste big letter made from aluminum foil
that say "Big Brother Go Home" or some such letting'em know that you know
they're there...

BTW: What's the FBI, Cops, etc. supposed to do when their "suspect" is
aware that they're being watched?  Do they knock down your door and
stop you from attempting to foil their investigation because they have
a warrant??  Or do they just go home with their tails between their legs?

>
   >One idea that I thought about is to simply use frosted glass. The police/
   >/FBI/CIA/other using the IR cameras don't just want to recieve IR light;
   >they want it in a coherent pattern. Using frosted glass, the light is 
   >dispersed in (mostly) all directions. The spooks should then only be able
   >to percieve some fuzzy shapes. Oh, they'll be able to know if the lights
   >are on, but for all they know, you are just having a quiet game of bridge.
   >(I am not absolutely certain about the va .. veracity of this method, but I
   >gathered that if frosted glass disperses normal light, it should do the
   >same for IR. The range of refractive indices would be different, and that's
   >about it.) Any criticisms of this method would be appreciated. Peter Murphy
   > .


*** Hmm
  
    The wavelength of IR is longer than that of visible light, so objects
    that appear diffuse/ matt optically may appear shiny/clear in IR.

    As I understand it, high-power military IR targetting lasers 
    being pre-flight tested at airfields have caused nasty eye-accidents
    because of the unexpectedly high reflectivity of concrete walls etc

    Regards

    Ed