Photo Radar

[Chris Conlon]

At 11:56 AM 1/8/99 -0700, David Sagers wrote:

> The secretary here has a louver screen on the front of her monitor
> so that people can't read sensitive information over her shoulder.
> The screen looks black if you are more than 30 degrees off center
> on the horizontal plane, but it does not block the view if you are
> above or below center.

Has everyone seen those billboards that show different images as
you move from dead-on to viewing from a shallow angle? *That's* what
we need alright! ;)  One with the State Governor's plate # would
be pretty popular...

Another issue with louver film is that the camera may be taking a
picture when you're well down the road, and thus it'd be seeing the
plate pretty much straight on. My car (thank you Toyota!) has the
plate in a recessed area compares to the taillights, which already
obscures a letter or 2 at extreme viewing angles.

> The problem with louver film is that it would be very visible to the
> eye and you would be a target for police.  A better alternative
> would be a sheet of polarizing film.  Polarizing film would appear 

Agree with the comments on polarizing. Perhaps this is part of a
solution to LIDAR as well? Actually while thinking about LIDAR
countermeasures I stumbled across "circular polarizing" filters,
used for laptop screens. Incoming light was polarized in such a
way that the reflected light didn't make it back through the filter
again. (Sorry, the details elude me.) Light coming *out* from the
laptop display got polarized once, but made it through ok. Maybe
you could mount such a filter 1" or so off the place, so that the
license plate lights would still illuminate it ok, but outside light
(LIDAR, photo radar flash) would not make it through as easily?

Does the plate itself (and/or the corner reflector material) also
have a polarizing effect too?


As for it being illegal to obstruct the plate, I'm sure it
technically is here (MD/DC/VA area in the USA), but lots of people
do it and seem to get by ok. Also at least in some places it would
be a cheap, no-points fix-it ticket, and if it saves you from an
expensive, points-carrying speeding ticket... well, might be worth
it.

   Chris