Collimating a Monochromatic Beam of Light

[dartz003]

I am trying to collimate a monochromatic diverging beam of light. Since the size of the beam is quite large, and I want to capture as much of that light as possible, I'd like to place a convex lens as close to the Monochromator as possible to focus or collimate it.

say with an beam with divergence angle ø, and I use a convex lens with focal length f, what would be resulting focal length and diverging/converging angle of the resulting beam going through said lens. I wasn't sure if the thin lens equation is what I should be using

 

[Andy Resnick]

Put the lens a distance 'f' from the output face, and make sure the diameter of the lens is larger than the beam diameter (at the lens). The finite area of the output face places a limit on the minimum possible divergence angle.

Orient the convex side of the lens facing away from the laser to minimize aberrations.