Hope you are sitting down when you see the price. Wouldn't want you to fall down and hurt yourself.
Laser interferometers are used as feedback devices in ultra-precision machine tools (like diamond turning lathes for making optics), high end CMMs, and semiconductor processing.
Commonly used to calibrate machine tools but there is no way you are going to map out a 3 axis machine in 30 minutes. More like 6-10 hours.
You can get glass scales with resolutions down to 1/10 of a micron and they are much more forgiving. Accuracy without external calibration can approach 1 micron.
Are you trying to build something like a video CMM.
http://www.acu-gage.com/
When building this type of equipment pitch, yaw, roll, straightness, and squareness errors from your slides will be your biggest design challenges.
Maintaining less than .0003 abbe error over a 2 meter assembly will demand very high end bearings and a very rigid base.
Bob