From: Ed Switalski <E.Switalski@bnr.co.uk>
Date: Wed, 16 Mar 94 01:16:34 PST
To: Peter Murphy <pkm@maths.uq.oz.au>
Subject: Re: IR Blocking.
In-Reply-To: <9403160244.AA02855@axiom.maths.uq.oz.au>
Message-ID: <199403160915.26495@bnsgs200.bnr.co.uk>
MIME-Version: 1.0
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   >
   >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