I built an interpolating interferometer at work that can see 10 nanometer steps.
With the case off and the vertical baseplate exposed, body heat causes a measurable bias from 6 meters away.
We can detect footsteps 20 meters away.
The laser system in use, a heterodye interferometer by HP, has a baseline cost of about 20,000$ for the stabilized laser and another 15,000$ for the motion controller, and is the same model of interferometer used controlling diamond turning machines for custom lenses.
Given the cost of just the measuring laser, are you really sure you want your own machine for this?
Contract out the work to a professional.
Steve
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...