On Dec 21, 4:21*pm, Richard J Kinch wrote:
...
All of the follow-ups to date of my critique ignore the optical
principles that prevent this entire scheme from working. *Specifically,
Gaussian beam optics, beam waisting, and beam divergence. *Laser beams
are narrow but they still start at millimeters wide and spread out to
inches as they project. Have a friend stand 50 feet away and see what
kind of spot you get on a target from a good-quality laser pointer.

The one I tried was about 0.2" wide at 10 feet. The spot wasn't too
far from circular and its intensity fell off sharply at the edges, so
I was able to align both edges with marks on the scale the same
distance from the 1" line, in this case the lines at 0.920" and
1.080". The alignment only has to be repeatable, not absolutely
accurate.

jsw