"Peter L. Peres" wrote:
>
> On Sun, 10 Nov 2002, Robert Rolf wrote:
>
> *>It is oval shaped and requires special optics to
> *>get a fine gaussian beam. On the other hand you could just blast
> *>it through a pin hole to get something appropriate to the scale
> *>a DIY board would handle.
>
> Pinholes do not sharply image laser beams. You would get a first class
> diffraction pattern from it. You would need to pass it through a pinhole

Yes, you do, but it's a much better shape than what you get with a
straight beam. And two stacked pinholes gets a near perfect beam
when the 2nd PH is a touch bigger than the first and removes the 1st
order diffraction ring.

> and image the pinhole with an additional lens.

That works too.

>This will lose a lot of power.

Yes, it does. Tradeoffs as always.

> Fiber that passes UV is expensive.

Who said anything about UV? The guy was talking about using a pen
laser. That's red and is incapable of exposing most UV resist. Plastic
fiber would suffice for photosensitive resist with any kind of red
sensitivity. Of course he could use a blue LED to get closer to the
exposure band level.


> CD laser heads include all the parts required to make a secondary-scanned
> imaging device, if the laser and mirror are replaced with a UV one. This

Great idea but the focus detectors probably wouldn't work at UV wavelengths.

> could be mounted on a plotter and do the job. Probably with fixed focus.
> The tracking coild could be driven with ac to make a wider path.

Except that it only tracks in one axis, so you'd have a hard time
drawing wide lines in the other axis.

So what's wrong with printing to film and just exposing the board
through it? This makes the replication process much faster, and
makes two sides boards easier too.

Robert

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