>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 21 January 2005 17:19
>To: piclist@mit.edu
>Subject: [OT] Police "LADAR"?
>
>
>Does anyone know the details on police "LADAR" (laser based 
>speed detection). I'm wondering about optical wavelength, 
>pulse width, and pulse repetition rate.
>
>Thanks!
>
>Harold

This was posted some time ago on http://www.pistonsheads.co.uk, a UK car
forum.  The device in question is a Marksman LTI 2020, one of the most
common speed guns in the UK.

"There is a 905nm Infra red solid state laser module with deam
divergence of approx 3mrad. It flashes 44 pulses of IR over a period of
0.3 seconds. This light is aimed at something very reflective, ideally
the numberplate of a car which who's backing material has the same
reflective properties of a 'corner cube' mirror, known as a reflex
reflector (it reflects light in the direction in which it came to a
tolerence of +/- 3 degrees) The reflected light pulses are picked up by
an IR dependent resistor network behind refracting optics in the LTI
2020 and the time intervals are recorded into memory. The time intervals
plotted against time create a gradient which directly correlates to the
distance travelled by the point of reflection, and therefore the
velocity. The LTI must recieve at least 30 similar reflected pulses to
achieve a legitimate reading. It does this by applying the mathematical
'least squares' algorithm."

One of the members owns one of these guns, and it seems that it is not
very diffcult at all to confuse it or vastly reduce it's range.  Metalic
silver cars have the greatest detection range apparently.

Regards

Mike

=======================================================================
This e-mail is intended for the person it is addressed to only. The
information contained in it may be confidential and/or protected by
law. If you are not the intended recipient of this message, you must
not make any use of this information, or copy or show it to any
person. Please contact us immediately to tell us that you have
received this e-mail, and return the original to us. Any use,
forwarding, printing or copying of this message is strictly prohibited.
No part of this message can be considered a request for goods or
services.
=======================================================================

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist