Am 09.09.2011 21:17, schrieb Cousin Ricky:
> "roll"<nomail@nomail>  wrote:
>> i have started creating a animation where a laserbeam should go through a solid,
>> rounded glass box. So i created a hollow cone with gaussian distributed red
>> glowing media in it.
>> [snip]
>
> This is a nit pick, but if the beam is conical, then technically, it's not a
> laser.

That - to do some nitpicking of my own - is untrue.

LASER is Light Amplification by Stimulated Emission of Radiation, and is 
a way of producing coherent light - that is, a stream of photons all 
having the same wavelength and phase. Those photons do not need to 
propagate in the same direction though, as long as they create a common 
wavefront.

As a matter of fact, solid-state lasers (i.e. laser diodes) typically 
produce light that spreads out quite significantly in one plane, and 
require additional optics to focus the beam to a point at infinite distance.

Which brings us to the fact that even the classic lasers that /do/ emit 
a unidirectional stream of photos can be combined with optics to produce 
a cone-shaped stream of photos.

As for the practical side, CD and DVD players even /need/ a strongly 
cone-shaped beam, focused on the data-carrying layer, to read out 
individual bits without getting distracted by impurities in the 
transparent carrier material, dirt on the surface, minor scratches, or 
dust in the air gap.

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