Collimating light beams

Auto collimation is much discussed in texts on precision measument. It is the means by which surface plates are judged flat, and
measurements of extreme precision are made. I just read the paragraph on the subject on the subject in "Fundimentals of
Dimensional Metrology" by Ted Busch, and am still unenlightened. Any takers?

David M. Munro

Ian Wright wrote:

> Hi,
>
> I was pulling an old laser printer to pieces the other day when an old
> engineer friend turned up. I had just dismantled the laser assembly and in
> it is an accurate hexagonal mirror. Seeing this his eyes lit up and he
> started muttering about this being absolutely essential in a good workshop.
> Since he tends to go a bit incomprehensible when he gets excited, I didn't
> quite grasp the details of how you use such a thing, but he referred to it
> as 'a polygon' and was muttering about 'collimating light beams' and such
> like. Perhaps this could be a source of an accurate set-up tool - maybe used
> with one of the 'pocket laser pointers'? Or is this all just rubbish??? ;o)
>
> Ian