Hi everyone,

I have an optics question that I hope someone could help a poor chemist out with. I have a Xenon lamp that directs most of the white light in a liquid light guide that then comes out and is collimated at 1" with a lens of the same size. If I wanted to collimate the beam at say 1/4", what is the best way of selecting the appropriate lens to use? There seem to be a bunch of lens equations and I'm not sure which to use for a collimating application. For what its worth my point source is like 0.125" and I think my beam divergence is something like 25.5 degrees. (0.125" goes to 4" beam when viewed 4" away.)

Thanks so much for your help!

The xenon lamp is not a point source, it will never be perfectly collimated.

 

I can give you a good method for creating a more collimated beam than you would otherwise have if you require better collimation than you have.

 

As for reducing your beam width, you have two options, first using a shorter focal length lens closer to the source. Or using a telescope, that is two lenses with different focal lengths (f1 and f2), you place the long focal length lens first and the second ~f1+f2 away, the exact distance will depend on your source. This will reduce your beam width by f1/f2, so if 2f2 = f1. you will have a beam that is half as wide. (you'll want to check that I've not used that method in well over 2 years).