Homebrew PCBs

Note, my example had nothing to do with obtaining a small spot for
developing artwork or PCBs.  It is a common method for obtaining a "clean"
laser beam focused on infinity.  It was used for optical experiments.  A
beam expander will not remove any secondary laser beams, they too will be
expanded.

 

A beam expander plus an aperture presumably will be the same as just an
aperture of a smaller size directly in the beam.  For example, if the laser
beam is 1 x 3mm, a 1mm aperture would give a 1mm beam.  Would that not be
identical to a 10X beam expander with a 10mm aperture?

Bertho

From: Cristian   Sent: Tuesday, November 19, 2013 02:42



>To get a as clean beam as possible I have done the opposite to the 
>beam expander:
>
>Using microscope objectives, the beam is focused on a very small pin 
>hole. Any secondary beams or distortions does not get through the 
>pin hole. The beam is collimated afterwards with a matching second
objective.

Your solution is the same as with an expander: the pin hole has to be 
of 0.06mm diameter (the smallest beam dimension) and you will loose 
the same amount from the perpendicular dimension
as in the expander variant.
Try the led version, it is near square, and the laser's coherency is of no
use.
Cristian

Note, my example had nothing to do with obtaining a small spot for developing artwork or PCBs. It is a common method for obtaining a \u201cclean\u201d laser beam focused on infinity. It was used for optical experiments. A beam expander will not remove any secondary laser beams, they too will be expanded.

A beam expander plus an aperture presumably will be the same as just an aperture of a smaller size directly in the beam. For example, if the laser beam is 1 x 3mm, a 1mm aperture would give a 1mm beam. Would that not be identical to a 10X beam expander with a 10mm aperture?

Bertho

I understand about lost power.   In my example the beam was round to start
with but I had to filter out secondary beams to provide an as clean beam as
possible and I was not looking for max power.

 

My point was exactly that:  The beam expander + big aperture would be
similar to a small aperture and no beam expander: both would lose
significant power.

 

To preserve power as discussed, use either a curved mirror in one dimension
or a cylindrical lens.

Bertho

From: Slavko Kocjancic   Sent: Tuesday, November 19, 2013 03:59



On 11/19/2013 09:39 AM, Boman33 wrote:

Note, my example had nothing to do with obtaining a small spot for
developing artwork or PCBs.  It is a common method for obtaining a "clean"
laser beam focused on infinity.  It was used for optical experiments.  A
beam expander will not remove any secondary laser beams, they too will be
expanded.

A beam expander plus an aperture presumably will be the same as just an
aperture of a smaller size directly in the beam.  For example, if the laser
beam is 1 x 3mm, a 1mm aperture would give a 1mm beam.  Would that not be
identical to a 10X beam expander with a 10mm aperture?

Bertho

Doesn't matter. 
If beam is 1x3mm and I need 1x1mm with this method I lost 2/3 of power. It's
only masking unwanted portition. And expanding and companding losse some
power too. I just wonder if I can remove that with lens (colimator) tilted.
Or some additional lens tilted...  ...need to try, but for now I'm focused
ti try the LED aproach