improving collimation (need optics experts :-))

[Showlaser.dk]

Hello Guys !

I have 2 dpss lasers, that i would like to improve the collimation on, but i am seeking some suggestions to the best way to do it..

They are multimode lasers and the collimation is quite poor.. much like the melles griot 2w lasers.. i dont have any specs on them, but at 200 feet i have a spot around 5" in diameter, so surely not optimal..

I dont know much about how collimators work, but what i would like to do is move the focal point of the laser to infinity (or at least very far away) so i have a thinner beam a long way..

I have an assortment of lenses here that might be usefull, or otherwise i will have to buy whatever is needed..
25mm (1") diameter biconvex lenses in 20, 30 and 40 mm and possibly also some bi/cx and pl/cx 10mm lenses.

So if anyone could help me with suggestions to the best way to setup some lenses to improve the collimation of these lasers, it would be greatly appreciated.

Thanks a lot !

Regards, Simon

[steve-o]

A "reverse telescope" is one way of making a smaller beam profile at a distance, however the beam is larger coming out of the optics. It may not fit scanner mirrors etc.

[LesioQ]

Take measurement what diameter is the beam at the laser exit. Then make up Your mind how big beam can You accept at the galvos. This will give You the magnification factor. Then You take a pair of lenses both positive or one long focus positive and one short f.l. negative. The magnification factor says how many times the shorter f.l. one should be shorter than long focus f.l. Then You assemble a telescope from them by mounting them at a distance of sum of focal lengths of both (for 2 positive setup), or at a distance of long focal length minus short (negative) focal length. Proper lenses spacing will allow You to see through this simple telescope with good focus at an object at the distance of c.a. 1m. The assembly will require slight focusing action of one of the lenses (varying lenses spacing).

Practise says: usually 2-8x factor is good. Input - short focal length. ca 10mm dia, -10mm f.l. Output lens 30mm dia, +30mm f.l. This gives spacing of c.a. 20mm, so telescope is short - easy to fit anywhere.
This one would increase initial beam diameter 3 times and will allow You to tune where the waist will be, usually at distance >50m.

...or simply buy one For low power laser this can be a Meade finderscope for $5, but might require slightly longer lenses spacing (testing req-d).

Piotr.K