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From: howard@cpocd2.UUCP
Newsgroups: sci.electronics,sci.physics
Subject: Re: Laser eavesdropping
Message-ID: <550@cpocd2.UUCP>
Date: Wed, 1-Apr-87 20:15:30 EST
Article-I.D.: cpocd2.550
Posted: Wed Apr  1 20:15:30 1987
Date-Received: Sat, 4-Apr-87 12:41:33 EST
References: <499@sw1e.UUCP> <1505@husc6.UUCP> <560@sdiris1.UUCP> <503@sw1e.UUCP>
Reply-To: howard@cpocd2.UUCP (Howard A. Landman)
Organization: Intel Corp. ASIC Services Organization, Chandler AZ
Lines: 24
Xref: utgpu sci.electronics:452 sci.physics:1017

In article <503@sw1e.UUCP> uusgta@sw1e.UUCP (uusgta) writes:
>	1) Can someone think of a method for determining the sign of the
>	velocity of the window at a given time.  It seems that waiting 
>	for acceleration to pass zero is the only indication of the window 
>	passing back through an earlier position.

Quadrature.  You need two (or more) closely-spaced detectors.  One will lead
when the velocity is one way, and the other way the other will be leading.

>	5) Could someone decribe the inerferometer setup.  How would you
>	prevent vibration at the measuring site from ruining the measure?

You just need to make sure it's smaller than the motion of the beam.  If you
use angular effects instead of distance ones, then the farther away you are
the bigger deflection you get!  It was not uncommon in the 60's & 70's for
a "light show" at a rock concert to use a light beam bounced off of a mirror
attached to a speaker or special double (stereo) speaker, giving the effect
of an X-Y oscilloscope projected on the wall.  Similar techniques on a smaller
scale allow piezoelectric control of laser beam scanning.
-- 

Copyright (c) 1987 Howard A. Landman.  Transmission of this material
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