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From: chuck@mitlns.mit.edu
Newsgroups: sci.electronics
Subject: Re: Bad News- Lasers replace Radar guns
Message-ID: <1990Jan18.220833.9502@athena.mit.edu>
Date: 18 Jan 90 22:02:59 GMT
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In article <354@egrunix.UUCP>, besler@egrunix.UUCP (Brent Besler) writes...

>The IM&C device is a Class I laser device, which means its use is basically un
>regulated.  The power output is pretty low.  It uses rapid, very short duration
>pulses.  Similar devices have been used for years to measure distances in the
>military and construction. This device just computes speed from succesive
>distance measurements.  Wether or not halogen bulb output will jam it is 
>anybodies guess.  I am sure it has a filter to admit only the .9 micron 
>wavelength.  The sophistication of the detction electronics would play a part 
>in the effectuveness of jamming.  Good electronics will be able to filter out
>background radiation of the .9 nm frequency.  The advantage of the jamming
>light is that its intensity varies as the square of the distance whereas the
>received intesnity of the meauring laser will vary as the fourth power of 
>the distance.

  Not so! the laser beam is so small that ALL of it hits your car and is
reflected back. Thus unless the air is dirty (absorptive) it will fall
off as 1/r**2.
					Chuck Parsons
					CHUCK@MITLNS.MIT.EDU