--- In
Homebrew_PCBs@yahoogroups.com, Robert LaBudde <ral@p...> wrote:
>
> At 02:19 AM 10/17/2005, Leon wrote:
> > >>Why do you need a laser? A UV LED with a collimating lens should be
> > >>sufficient. You don't need coherent light, and the only
advantage then to
> > >>a
> > >>laser is the smaller beam divergence initially.
> >
> >UV LEDs don't have anything like enough power.
>
> What's the power requirement to expose a photosensitive board?
>
> Remember a 5000 millicandela LED will focused down to a 0.0254 mm point.
>
It becomes a problem of parallax error.
http://www.polyphoto.com/tutorials/LaserTag/ParallaxError01.pdfYou can reduce the apparent size of the source by either cutting off
the end of the LED flat, moving it further from the lense, or choking
it off with a pinhole.
It seems to me someone calculated all this in the past and it came out
to taking a ridiculously long time to expose a board this way.
Steve Greenfield