Had this wild idea after reading about the touch probe. How about using a distance measuring laser mounted by the router. There is an AR200 that looks interesting but isn’t cheap. Its output is analog though. There is also an adafruit but the resolution is 1mm.
I can’t find any specs on the spot size that they are measuring.
Investigated some more. Doesn’t seem feasible considering the devices I saw. There is too big of a target to get a good 3D redering. Oh well, it was an idea!