Patent ID: 8028343

Claim:
An apparatus comprising: a rod characterized by a rod axis, said rod comprising a tip on a first end thereof and a cavity extending from said first end of said rod to a second end of said rod, said rod comprising a moveable reflector mounted within said cavity at a location proximate to said tip, said tip being disposed such that said tip is forced against a sample when a force is applied to said rod; an interferometer that generates a light beam within said cavity that is reflected from said moveable reflector, said interferometer determining a distance between a reference location and said moveable reflector; a force actuator that applies a force to said rod in a direction parallel to said rod axis in response to a force control signal coupled to said actuator; a controller that receives said determined distance from said interferometer and generates said force control signal; and a stage actuator that moves a sample in a plane perpendicular to said rod axis such that portions of said sample are contacted by said tip.