[ST] Re: Radar detectors...question

["Eric Gustafson" <ericsg@xxxxxxxxx>]

Here's how LIDAR (there's technically no such thing as laser radar) works:
    A semiconductor laser is used and when the trigger is pulled, hundreds
of light pulses per second are transmitted.  When a pulse is transmitted, a
timer is also started, then when the reflected pulse from the target is
received, the timer is stopped.  The unit then compares the elapsed time
between the transmission and reception of the pulse with the speed of light
(~186,262 miles per second) and the unit can then calculate the range to the
target.  After making many successive range measurements, the data is
analyzed in a processing alogorithm.  So, the vehicle speed is then
determined by way of a series of time and range measurements.  Not only do
you get a reading of speed on the target, you also get the precise range at
which the value was obtained.
    As for the beam itself, LIDAR wavelength is 904 to 905 nanometers with a
frequency of 330 terahertz.  One of the biggest reasons it's so effective is
its tight beam providing target accuracy and little reflection.  A lidar
beam is only two feet wide at 500 feet and four feet wide at 1,000 feet.
Unlike doppler radar, the size, shape, and composition of the target isn't a
factor for LIDAR, it only has to reflect light.
    By the way, as for LIDAR scramblers and such, frankly they don't work.
Here's why.  The laser diode switches the laser energy on and off in less
than one billionth of a second, so the lidar unit only transmits on a narrow
band of frequencies.  The LIDAR's receiver is 'tuned' to the exact
wavelength of the laser diode so it only sees the reflected laser signal and
filters out all others.
    One of the most (if not the most) popular models of LIDARs used by law
enforcement is the ProLaserIII made by LaserCraft in Georgia.

Good luck!
Eric
Portland, OR
'01 BRG ST

==ORIGINAL MESSAGE==
>Date: Tue, 19 Feb 2002 20:54:32 +0100
> From: "Enrico" <enrico@xxxxxx>
> Subject: Re: [ST] Radar detectors...question
>
> - -----Ursprüngliche Nachricht-----
> Von: "Kevin Liske" <thxnc@xxxxxxxx>
> An: <ST@xxxxxxxxxxxxxx>
> Gesendet: Dienstag, 19. Februar 2002 19:44
> Betreff: [ST] Radar detectors...question
>
>
> >
> >
> > Maybe I haven't done enough homework and research to
> > answer this question myself.  I understand that for
> > radar, our bags and bodies are transparent.  But for
> > the laser detection, I'm a little confused.  Are the
> > lasers microwave (masers actually)?  Coherent light is
> > still light and keeping a detector in a light opaque tankbag
> > is not going to let it "see" the light.  So how does
> > laser detection work?
>
> A laser beam is directed to your bike. The laser is on for instance for 1
> µsec pulstime. A sensor sees the reflected light pulse. Then another light
> pulse is sent and the reflection will go back to the receiver. The time
> difference between pulse #1 and #2 is measured and will give the speed of
> the object.
>
> It is in principle the same system for measuring a fault in a cable - but
> there you will know the distance of the fault and for motorbikes they want
> to know the speed...
>
> BTW: most of this laser speed measuring systems are coming from a small
> company in Austria which has patented the principle...
>
> BTW2: if you will send laser pulses with undefined repeating frequency in
> the same wavelength as the sender the measuring system will go crazy and
> shows .... nothing!
> So it is (in Austria) not allowed to send laserpulses.... *g*
>
> Enrico
> 00 Sprint ST 'BlueBelle'
> Vienna, Austria
>
> >
> > Kevin Liske
> > '99 Sprint in Black
> >
> > Be careful with that, honey....we're using Technology!



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