DIY Laser levelling using webcam and laser level

[devmonkey]

Don't get me wrong I understand how refraction works, what we need to understand is given the light source is not perfect nor perfectly collimated and cylinder is not perfect can these imperfections add up to a line that is bent, or just a line that is noisy (which is fine for our purposes). Presuming that the ideal model of refraction we get taught is not what actually occurs in the real world.

[Michael Gilligan]

... can these imperfections add up to a line that is bent, or just a line that is noisy

Hopefully this was evident from my last response, but:
For clarity, the short answer to that question would be Yes, all results are possible.
... You will see that the quoted specification addresses that ‘uncertainty’ by stating tolerance bands.

MichaelG.