Subject:
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Re: Autonomous Robot
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 9 Aug 2000 06:23:36 GMT
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Viewed:
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782 times
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"Ian Warfield" <ipw47@hotmail.com> wrote:
> How exactly do the retroreflectors work? I was under the impression that • you
> couldn't selectively reflect light unless you had a parabolic dish - and • then
> it would all focus on one point. Do your reflectors have a convex mirror, • or
> some other arrangement?
No, there are no convex mirror, just triangular prisms, like small pyramids.
Their angles are designed to reflect the light back to the direction it came
from (thru' two reflections). I can provide an example in two dimensions:
draw an isosceles right-angle triangle and a ray that crosses the base,
enters the triangle and reflects against one cathetus. Following the
reflection laws draw the reflected ray, that goes against the other cathetus
and reflects again out of the triangle. You'll see that the outgoing ray is
parallel to the incoming one!
I deliberately ignored the rifraction effect the ray is subjected to when it
enter a different material (the prism), but as it exits the base of the
triangle with the same angle of incidence it entered the two refractions
effects compensate each other.
My example also explains why these retroreflectors don't work if the ray
enters with an angle of incidence lower than 45°.
Ciao
Mario
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Message is in Reply To:
 | | Re: Autonomous Robot
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| How exactly do the retroreflectors work? I was under the impression that you couldn't selectively reflect light unless you had a parabolic dish - and then it would all focus on one point. Do your reflectors have a convex mirror, or some other (...) (24 years ago, 9-Aug-00, to lugnet.robotics)
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