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From: greg@endor.UUCP
Newsgroups: sci.electronics,sci.physics
Subject: Re: Laser eavesdropping
Message-ID: <1505@husc6.UUCP>
Date: Thu, 26-Mar-87 13:14:59 EST
Article-I.D.: husc6.1505
Posted: Thu Mar 26 13:14:59 1987
Date-Received: Sat, 28-Mar-87 04:27:26 EST
References: <499@sw1e.UUCP>
Sender: news@husc6.UUCP
Reply-To: greg@endor.UUCP (Greg)
Organization: Harvard
Lines: 17
Keywords: modulation
Xref: utgpu sci.electronics:419 sci.physics:967

In article <499@sw1e.UUCP> uusgta@sw1e.UUCP (uusgta) writes:
>I was thinking about the commonly mentioned electronic snooping technique
>of pasting a reflective dot to a window and listening to conversations in the
>room by bouncing a laser off this vibrating mirror.

My understanding is that a window is reflective enough by itself that you don't
need to put anything on it in order for this device to work.  This way you can
bug a room without ever being within 100 feet of it.

>How *could* such a signal
>be encoded?

Probably the reflected laser light is combined with the laser source, and the
interference pattern is measured.  The coherence length of the laser must be
much greater than the distance from the laser to the window.
----
Greg