Mechanical scanning has been around since the very beginning of
television.

However your horizontal scan mirror would not work with 525 faces
since you'd only be in the beam for 360degrees/525 =0.68 degressx2,
which is a pretty darned narrow image.

Such a system would typically have a polygon mirror with 16 sides,
giving a 45D scan angle, and use a galvanometer for the vertical
scan (since 120Hz is relatively easy to achieve). Since rotating
at 60,000RPM is a bit of a challenge (15734Hz/16), the beam is
split into several, which are independently modulated such that
you get several lines scanned at once. Essentially the picture
gets show 4 or 8 lines at once.

Today they would use AOM/AOD (acustoptical modulators/deflector) so
there are no moving parts, but the efficiencies of lasers are sooooo
poor that AFAIK there is no commercial system using them now.

Everyone has moved to DLP (Digital Light Processor, Texas Instuments
memory device which uses tiny mirrors deflected by the charge
stored in a RAM cell [grossly simplified explanation]) when
high brightness is required or LCD's when you're not trying
to fill a stadium.


Harold M Hallikainen wrote:
>
>         Not quite 3D, but I've always wondered about using a cylinder with
> mirror facets on it to do the horizontal and vertical scanning of a laser
> video projection system. For the US, there'd be 525 mirror faces around
> the cylinder, and it would rotate 30 revolutions per second. As the
> cylinder rotates, the reflected beam would get a horizontal scan. At the
> end of the horizontal scan, another mirror face would rotate into
> position dropping the reflected beam down a little and throwing it back
> to the left side of the image. Some fancy machining, but seems like it'd
> be possible.
>
> Harold
>
> FCC Rules Online at http://hallikainen.com/FccRules
> Lighting control for theatre and television at http://www.dovesystems.com
>
> ________________________________________________________________
> GET INTERNET ACCESS FROM JUNO!
> Juno offers FREE or PREMIUM Internet access for less!
> Join Juno today!  For your FREE software, visit:
> http://dl.www.juno.com/get/tagj.
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.