Subject:
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RE: !!! Laser attachments for Mindstorms !!!
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 9 Oct 1999 05:35:34 GMT
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Viewed:
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523 times
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> Of Chris Phillips wrote:
SNIP
> 2. Low power lasers are not great when it comes to fast scanning. If you
> sweep the pointer quickly across a screen you don't really get much of a
> residual trace. High-power lasers that will leave a trace are
> large and bulky
> and can burn holes in metal (and plastic!) and vaporize small rocks.
SNIP
Big rocks, too. :>)
The problem is not so much the laser, as it is your scanning. Unless you
are projecting against a phorescent screen, there is no "residual" trace,
regardless of power. It is the speed at which the eye can't tell the
difference between a point of light, or a continuous line. The analogy is
the motion picture, 32 frames a second, and you can't tell the difference.
Most laser scanners use a multi-faceted mirror. Think of a circular disk,
with concave scallops on the outside edge. The laser is pointed at the edge
of the spinning disk. As the disk rotates, the laser sweeps, and sweeps
again, etc. Most planetarium type "spirograph" shows oscillate a mirror
back and forth, in two primary axii. The mirrors vibrate back and forth,
and don't spin at all.
Speed is the issue here. I don't know how fast these thing oscillate, but
my guess would be at least a few hundred hertz. Anything slower, and you're
likely to see "spots".
Jeff
jeffrey.hazen@northmill.net
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Message is in Reply To:
 | | Re: !!! Laser attachments for Mindstorms !!!
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| (...) I was actually working on something like this using one of those cheap little $8 laser pointers. The idea is to use a pair of mirrors that can be rotated to specific angular locations to build an X-Y Laser Plotter. One mirror rotates (...) (25 years ago, 9-Oct-99, to lugnet.robotics)
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