CDR: Re: Re; cover your glass

[jim bell]

There is a easily-available kind of architectural glass  called "Azurelite"
(PPG Industries) (read:  "Cheap") which would transmit less than 2% (single
pass) of 900nm infrared in a 45 degree "brewster window" configuration.  For
two passes, that's 0.03% reflection even if the underlying scope optics
reflected 100%.  In other words, vastly less reflection than even a black
piece of paper.

----- Original Message -----
From: <keyser-soze at hushmail.com>
To: <k92t3rd at hushmail.com>; Cypherpunks <cypherpunks at cyberpass.net>
Sent: Wednesday, September 20, 2000 21:58 PM
Subject: Re: Re; cover your glass


> I'd be willing to be that placing a semi-reflective glass wedge in the
optical
> path ahead of the scope's front lens would defeat such laser detection
systems.
>  Any incoming light not reflected off the wedge's front surface (and
perhaps
> trapped in an adjoining baffle) would almost surely be reflected off the
> wedge's other front surface denying the laser's operator enough of a
return
> signal to work with.
>
> That the lasers are probably working in the IR (so as not to be easily
detectable
> by the snipper) makes the wedge even easier to use as it needn't
appreciably
> reduce the visible component most useful to the sniper.
>
> At 12:30 PM 12/31/99 -0500, you wrote:
> Old news:
> See below
>
> ---------- Reply to ----------
> Date: 31 Dec 1999 04:20:45 -0000
> Subject: cover your glass
> From: lcs Mixmaster Remailer <mix at anon.lcs.mit.edu>
> Reply-to: lcs Mixmaster Remailer <mix at anon.lcs.mit.edu>
> To: cypherpunks at algebra.com
>
> Re: acoustic shooter detection systems in LA
>
> Just FYI: Some time ago I read of the development of
> sniper-detection systems which looked for
> reflections off the 'scope glass.
>
> This probably isn't ready for prime time,
> being in development maybe a year ago,
> and isn't mentioned in the article,
> so you're probably safe taking your time,
> sighting in.
>
> BMGMonger
> -----------------------------------------------------
>
> Here in my stack of oddball periodicals I have a copy
> of the July/August 1998 issue of Revue Aerospatiale
> A french aerospace journal, wherein we have an article
> Lasers:
> Hard-Hitting Watchdogs
>
> The best way to dissuade snipers is to deprive them of their impunity by
> ensureing they know that their exact location has been pinpointed. CILAS
> demonstrated this at Eurosatory with its directed-optics
> laser detector- the first production unit intended ultimately for delivery
> to the French army. This ground-breaking technology can be expected to
bring
> other developments in its wake.
>
> It goes on;
>
> Quietly, free from media hype, things (this is in ref to background on why
> snipers are bad)
> have suddenly changed since a prototype of the SLD400 was received by the
> French armed
> forces. Behind this mundane designation lurks a device capable of
detecting,
>  locating and indentifying the optics with which snipers are equipped.
>
> More;
>
> The scope of application of the SLD400 is much wider and can include the
> protection of VIPs and pinpointing sharpshooters of the binoculars of
terrorists
> preparing criminal acts. (it actually says that)
>
> The article goes on to describe building databases of specific optical
device
> signature and such. So that they not only know that you are there, they
> also know what you have deployed to better asses threat level and so on.
>
> Assume they know, always.
>
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