Laser Linear Scales

This may have been covered before but ...

With the availability of good quality laser diodes these days wouldn't it be
possible to build a low cost/high precision linear position sensor based on
Laser Interferometry?

... I assume not, or I'd see them everywhere. What's the sticking point?

I suspect that one of the problems might be the ability to track fringes caused
by normal machine vibration.

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck