At 11:45 PM -0500 1/15/00, Francesco Fontanot G. wrote:
the other day i was told that the best laser gun jammer and inexpensive
trick is to put a CD facing outside of the car between the mirror and the
windshield. The guy told me that the CD absorbs the laser rays from the guy
and don´t reflect thems back to the gun so it would read something wierd.
Any ideas?
Excuse my French, but it's a total load of crap. If CDs
absorbed infrared laser radiation then CD players wouldn't work, as
they all use an infrared diode laser to read the tracks of pits on
the CD! The only arguement that could possibly be made is that since
the CD has a periodic structure, it acts as a diffraction grating and
would disperse the laser light. This is why you see the spectral
pattern in a CD. Since the laser gun relies on the Doppler shift of
the reflected light to calculate speed differential, it could
potentially 'confuse' the gun. However, the laser is highly
monochromatic, and any diffraction simply diverts the light into
higher order which then propagates off to the side, and since the
vast majory of light incident on a CD is specularly reflected anyway,
this could just make your car _more_ visible to a laser gun! Laser
guns have a relatively small angular divergence, and the beam width
100 yards is still quite narrow, on the order of a foot, I believe;
wider than a laser pointer, but much narrower than radar. Therefore,
the gun must be aimed accurately, but the benefits are better target
discrimination and less stray radiation (tougher to detect), as
compared to radar. Cops usually aim at the front liscense plate,
which is retro-reflecting (at least in CA) and therefore returns the
most energy. Removing the front plate, having pop-up (or covered)
headlights and a dark color car are the best ways to make your car
'stealthy' to laser guns. It doesn't mean that you car is
'invisible', just that the detection range is reduced.
Lee
P.S. Sorry for the long-winded and somewhat technical explanation,
but I felt obliged to respond because of my eduational background:
B.S. Optics
M.S. Electrical Engineering
coming soon: Ph.D. Electrical Engineering - Applied Optics and Photonics
W. Lee Hendrick
[email protected]
http://soliton.ucsd.edu/~hendrick/
_____________
List Sponsor: http://www.netsville.com
To remove yourself from this list, send mail to [email protected] with
'unsubscribe a2_16v' in the body of your message
See us on the web at http://www.a2-16v.com
Visit the 16V Homepage at http://www.gti16v.org
