On 2009-05-06, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:

[ ... ]

And the degree of final expansion a function of the focal
lengths and the spacing of the lenses.

Yep.


The metal post and parallel fin look like they are designed to allow
vertical adjustment while preventing rotation. This is convenient on an
optical bench.

Yes -- but the polished surfaces are uncommon in an optical
table which has lasers involved, as the potential danger from specular
reflection is significant, depending on the type of laser.

It may be intended for use in teaching, and/or assume a HeNe laser.

Not all lasers are weapons-grade.

Yes -- but even HeNe lasers with less than 1mW output power
(such as the Spectra Physics one which I have) still bear warnings to
not let the beam hit someone's eye -- and specular reflections *can*
cause that to happen.

Granted -- I was a *lot* more worried about it with the Nd-Yag
ones I used at work. :-)

Enjoy,
DoN.

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