On Tue, Dec 20, 2005 at 08:54:08AM -0800, Bob Blick wrote:
> There seem to be a lot of replies, I hope this message doesn't get lost in
> all the noise.
> 
> I have lots of experience with lasers. The output from a laser diode is an
> oval. It is usually about 4:1 although some newer and more expensive
> diodes are 2:1. The usual way to make it round is to clip the beam. There
> is a company that makes laser diodes with circular correcting optics
> inside although you pay dearly for it:
> http://www.blueskyresearch.com/index.htm
> The diodes are called CircuLaser. If you want the best beam quality, start
> with one of these. They also sell laser modules but I have no experience
> with those.

Ahh, that explains a lot! The nice circular point laser pointers I have
are probably the "clipping" type, I've noticed they always place a round
hole some distance away from the diode assembly...

CircuLaser looks nice, though it's probably overkill. I'll suggest that
if the client isn't happy!

> Any red laser module decently constructed should have a very long lifetime
> - green is where the reliability would be more of an issue.

Well, very long yes, but most of the ones I see list a MTTF of 10,000
hours. Running constantly that's really only a little over a year. 10
years guaranteed running time would be much perferable.

Superpermarket checkout scanners (bottom scan) use lasers if I'm not
mistaken. I'd assume they have fairly long lifetimes, so what sort of
laser do they use now?

-- 
pete@petertodd.ca http://www.petertodd.ca
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