Patent ID: 7219538

Claim:
Apparatus for characterizing a surface of a sample with a probe, the apparatus comprising: an actuator; a first member carried by the actuator and having a distal end which is extensible and retractable relative to the surface; a second member carried by the actuator and having a distal end which is extensible and retractable relative to the surface; a detector that produces a signal corresponding to the location of the probe relative to the surface; a first control device operatively connected to the detector and the first and second members which causes the distal ends of the first and second members to extend or retract substantially synchronously and in response to the signal of the detector, and that controls movement of the probe at a first rate relative to the surface in response to a first feedback signal; and a second control device operatively connected to the first control device and the actuator that causes the actuator to move the probe at a second rate relative to the surface in response to a second feedback signal.