What lens to get the smallest dot size possible with 405nm @ ~250mm?

[Meduza]

Hello

What lens should i use for 405nm laser if i am after the smallest dot size possible at 200-300mm focal length?

I am not concerned about power losses (50% would propably be OK), but i want a round small spot from a standard 405nm laser module (this is for building a galvo based SLA 3D printer)

 

[Blaster]

A glass 3 element coated lens for 405 nm should give the smallest dot size ...why at 250mm most times i focus its about 10 ...12 cm.

 

[NKO29]

Actually i think if you get a LFL G2 lens, it will give the best dot. LFL= long focal length.

 

[steve001]

Hello

What lens should i use for 405nm laser if i am after the smallest dot size possible at 200-300mm focal length?

I am not concerned about power losses (50% would propably be OK), but i want a round small spot from a standard 405nm laser module (this is for building a galvo based SLA 3D printer)

I believe all that you need acquire is a lens with a focal length of 200-300mm. there are some lenses here you could experiment with.
http://www.anchoroptics.com/catalog/product.cfm?id=253

 

[cev1]

At that focal length, the lens quality is virtually irrelevant to spot size assuming:
1. Your beam size at the lens is much smaller than your focal length (less than a factor of 10, say).
2. you aren't using a drinking glass.