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From: depolo@eniac.seas.upenn.edu (Jeff DePolo)
Newsgroups: rec.autos,sci.electronics,misc.consumers
Subject: Re: Correct Terminology (was Re: Radar Detectors (Ka band) ...)
Keywords: radar, laser, lidar?
Message-ID: <8260@netnews.upenn.edu>
Date: 21 Feb 89 23:35:36 GMT
References: <603@icus.islp.ny.us> <7944@netnews.upenn.edu> <1895@tank.uchicago.edu> <5632@homxc.ATT.COM> <4057@alvin.mcnc.org>
Sender: news@netnews.upenn.edu
Reply-To: depolo@eniac.seas.upenn.edu.UUCP (Jeff DePolo)
Organization: University of Pennsylvania
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In article <4057@alvin.mcnc.org> bishel@mcnc.org.UUCP (Geoffrey R. Bishel) writes:
>In article <5632@homxc.ATT.COM> h16@homxc.ATT.COM (D.JACOBOWITZ) writes:
>>
>>A laser will spread 3.5 feet in 1/5 mile?
>>Are you sure?
>>That doesn't sound like coherent light.
>
>You've got to remember that the beam is passing thru the air, and dust, dirt,
>water molecules, etc. will all diffract the beam to some extent.  Thus you get
>a spreading of the beam.  
>-- 
>Geoff Bishel                    "Parlez en anglais, for Christ's sake," said the
>(bishel@mcnc.org)               Corporal. "Je ne parle pas francais."
>Standard Disclaimers apply      "Neither do I," answered Yossarian...
>(Picture your ad here!)               (Joseph Heller - _Catch 22_)

Another thing to think about - a beam a few feet wide is going to reflect
a beam a bit bigger than that, but not much.  If the copper is on the side
of the road, he's going to have to "wiggle" the laser around until it hits
a perpendicular plane on your car.  If, for example, he hits the hood, most
of the beam is going to be angled upwards into the sky.  His best bet is to
aim somewhat low, since it isn't going to bounce off of the windshield
or any other part of the car.  The grill/radiator/bumber would probably
be the best bet.  As far as the scope - it had better be pretty damn
accurately aligned.  If it's off by only 4 or 5 feet, it would be very easy
to hit a car next to you.  Or what if a semi was coming up from behind you
at a pretty good pace - if he aimed at your windsheid, it would go through
the front windshield, through the passenger's compartment, through the rear
windshield, and bounce off the semi.  Kind of scary.

							--- Jeff



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|  Jeff DePolo  [depolo@eniac.seas.upenn.edu]  | o  The best things in life   |
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