correcting a NDG7475 - How to do it?

[DrEvil]

I'm wanting a NDG7475 but don't want to deal with a rectangular beam. What's the best way to make it square is a fairly small space?

[catalanjo]

I'm wanting a NDG7475 but don't want to deal with a rectangular beam. What's the best way to make it square is a fairly small space?

How big is the small space?

What EXACTLY do you mean by "best" (price, size,shape, elegance, ease of construction, robustness, flexibilty, temperature control, cleanliness, adjustability, stability) etc ?
Roughly ... the cheapest shortest-FL collimator lens followed by two cyl lenses mounted on an enclosed rigid surface at room temp.!

Cheers
PS. Nice cat!

[DrEvil]

By best, I mean the "dot" is as close to being round or square as possible without one side growing longer than the other over an indefinite distance.

[catalanjo]

That's just a question of adjusting the Cyl lens positions accurately, and adding a Planter's style razor blade spatial filter if you don't like the muck round the edges.
(Although this requires extra space.)

One simple axiom ....the bigger the initial beam size the smaller the final long distance spot.

Cheers