DIY Laser levelling using webcam and laser level

[AndyUK]

I don't think they are round, rather half round, I maybe wrong. The better ones are made out of something called K9 glass, again I don't know what this is. Maybe Andy can jump in here?

Watching the thread with interest, but unfortunately its been many years since I studied optics, and I'm not massively useful at this point! But I whole-heartedly agree that you want to keep the guassian characteristic where possible, as its a nice structure to fit to. You could use the FWHM from a flat-top profile, but I'd trust the guassian fit better as the regression uses the entire curve, rather than just the penumbras.

Re. lenses; It all depends on the incoming beam width, the radius of the rod/lens, and the refractive index of the material being used; in general I'd guesstimate that given a beam focused to infinity, you're likely to get a wider output spread by using a full rod, but there are so many variables here to play with, i'd be tempted to just go with an off the shelf lens designed for the job which will also guarantee clarity of the beam to a certain extent.