I'd recommend an alteration that that would serve a few benefits. You should have the person getting the haircut sit on something like a massage chair where they can put their face into that circular hole.
This would (a) keep their face in a designated predefined place and position and serve as a reference point for the haircut, (b) allow you to embed a sensor into the face rest so you know when they pick their face up and can pause the robot, and (c) you can provide a monitor to display shows they can watch during the haircut, or ads (not that I necessarily approve of this).
hanniabu, this is an excellent suggestion. We were thinking about a chin rest (like what you see at an optometrist) but we didn't like how constricting it would be. I do like the idea of a headrest embedded with some sensors, though.
This would (a) keep their face in a designated predefined place and position and serve as a reference point for the haircut, (b) allow you to embed a sensor into the face rest so you know when they pick their face up and can pause the robot, and (c) you can provide a monitor to display shows they can watch during the haircut, or ads (not that I necessarily approve of this).