--- In Homebrew_PCBs@y..., Alexandre Guimarães <alexg@i...> wrote:
> Hi,
>
> > speed (> 10 rev/sec) and the light source (red LED laser diode and
>
>
> Usually cheap laser diodes are very bad source for points. The
light
> spreads unevenly and in a weird pattern. The optics to make it a
point
> source would probably end up being more expensive than using another
laser
> source.
Actually, this is not a big deal. A sphere lens collects the
light well, a piece of aluminum foil with a small hole masks
off the stray beams. A microfiche lens focuses a .001" spot
quite easily. The software is the killer! Also, the phase locked
loop to multiply a standard shaft encoder to a reasonable number
of pulses. I have made it work, though. See
http://pico-systems.com/photoplot.html for more details.