Beam Collimators - One thing I don't understand

[White-Light]

Ok, one thing I don't understand about beam collimators - when this was raised in another thread, a link to the vendors web site was put up and this showed pictures of collimators - they were small round tubes.

Being small round tubes, they're obviously meant to be fitted internally in something like a dichro holder.

However, won't making the laser beam a fat beam internally make it miss the mirrors?

I would have thought that to collimate a beam you'd have had to do it externally by fitting the collimator over the glass on the beam aperture.

Anyone answer this?

[Zoof]

to collimate literally means to make parallel. If you have a tight beam I don't see why collimators cannot be small tubes with small lenses.

[steve-o]

It depends on whether you're talking about a gas laser or diode laser w/ elliptical beam profile. Sometimes a beam expander (reverse telescope type; fatter beam at the scanners) is used to make a smaller beam at a distance. It's the laws of optics - y'can fight 'em but ya just cant win- believe me, I've tried

[White-Light]

to collimate literally means to make parallel. If you have a tight beam I don't see why collimators cannot be small tubes with small lenses.

Yeah but the principle of collimating is to expand the beam to make the laser fat beam and thus safer. We already know from the Red beam modules we all buy as standard that you can have problems with beam width causing the beam to miss the mirror straight out of the box. Surely collimating a beam to 10-14mm (a common fat beam size) is going to make most of it miss the mirrors entirely as most mirrors are less than that across.