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Loooong distance IR detection, and IR collimation

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Rich Grise

Jan 1, 1970
0
Is an interesting topic I've never heard of or thought of before.

First, what is an Opticon?

Then, how does a (self-actuated) traffic-light work?

It contains a *camera* of some kind?

(I had imagined that it used some kind of sonar to tell when
a car appeared.)

It "photographs" in red? Or infra-red (heat)? Or what?

Interesting stuff -- please do elaborate a bit.

Well, an "Opticon", in this context, to the best of my knowledge, is a
photocell (electric eye) mounted up on the stoplight bracket, and
ambulances and fire trucks (and, presumably, the cops) have some secret
code that they flash through their windshield with a strobe - the Opticon
picks up that signal, and changes the cross-lights to red, and changes
the light for the emergency vehicle green. Some guy had decoded that code,
and was breezing through town, but presumably got caught because the
red-light cameras were timed to the moment when the light was
_supposed_ to have turned red - there was this car in the intersection,
and the "switch to red" signal had been overridden!

They caught the guy. :)

Cheers!
Rich
 
David said:
Then, how does a (self-actuated) traffic-light work?

It contains a *camera* of some kind?

The answer to this is "it depends". Some use coils embedded under the
road (often used at highway on-ramps in Long Island, for instance).

The more modern scheme is a camera in the traffic light that exploits
the highly reflective license plate on a car to detect if the
intersection is occupied.

I read something - here maybe - about a motorcyclist who was tired of
not triggering this type of detector. He put a strip of orange
reflector tape on his helmet and all was well.
 
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