How do Laser Range Finders/Meters measure distance?

I am trying to find the most effective/accurate method for measuring distance using laser technology.

I am aware of a few methods that are available:

1. Time of flight
2. Multiple frequency phase-shift
3. Interferometry
4. Using triangulation / trigonometry

Which method are current range finders, ie. the PD30 Range Meter (created by HILTI), and other similar range finders, using to measure distance with such accuracy (+ - 1/16")?

Any insight is much appreciated.