[Laser] Newbie

[Tim Toast]

Hi Keith and Clint
I just wanted to jump in here and point out that you don't have to use expensive optics to use a laser. You can collimate a laser at least as well or better than the LED with a cheap fresnel lens. The type of laser coherence Clint is talking about is lost shortly after it leaves the transmitter. Another aspect of coherence is the bandwidth of the light source. Both the laser and the LED have a certain bandwidth. The bandwidth stays the same regardless of the type of optics used.

-toast

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   - Coherent light.  The use of "coherent" light from a laser can 
dramatically increase the degree of scintillation on the transmitted 
beam.  The use of coherent light also limits the sorts of optics one can 
use to collimate the beam:  The use of "diffraction-limited" optics 
(e.g. extremely accurate and precise lenses) is required to avoid 
disrupting the beam from a laser.  If one wishes to obtain a large beam 
diameter, you'll need a piece of glass that large, along with the 
weight, expense, fragility and awkwardness that goes along with it.  
After traveling some distance through the atmosphere (a couple of km - 
at most - will do it!) the beam loses its coherent properties, anyway.
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