[Laser] laser stuff

[Andrew T. Flowers, K0SM]

That's what I'm doing--first lens is the usual single collimating lens 
that I've screwed "too close" to the diode and thus diverges the beam. 
 The second lens recollimates it.  The point of this is *not* to get a 
beam that diverges less, but rather to decrease the power density to 
saf(er) levels in the near field.  I doubt I have the capability of 
decreasing the divergence too much with my apartment/lab equipment. 
Bascially I adjusted the beam to be the same size just in front of the 
lens as it was on the wall 20 ft away.  Then I pointed it at the 
concrete building 100yds away and it wasn't much bigger.  That seemed to 
be about right.  I'll add some stuff to the page tonight--part #'s, etc.

The lenses I'm using are 100mm diameter with a 200mm focal length 
uncoated DCV glass.  Any idea how much different the focal length is 
between 660 and 780nm on such a thing?

Andy
K0SM


TWOSIG@aol.com wrote:

>Andy
>
>I looked at your expander and was expecting a small lens near the laserdiode. 
> Are you adjusting the collimating lens to expand the beam and then using the 
>4" lens to collimate it again?
>
>James
>
>
>
>
>Hi folks,
>
>I put some new stuff on my website.  I put up a drawing of the beam 
>expander I've been working on and the modulator design that goes with 
>it.  It seems to work pretty well on the tropo-backscatter tests I've 
>been running from my apartment window.
>
>http://mail.rochester.edu/~af006m/radio.html
>
>Andy
>K0SM/2
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