Atomic force microscope system with multi-directional voice coil actuator for controlling the stylus

摘要

An atomic force microscope (AFM) system has a bidirectional actuator to move the AFM tip or stylus in a plane parallel to the surface of the sample to be scanned as well as perpendicularly to the surface of the sample. The actuator is a modified voice coil motor actuator of the type used in compact disc (CD) drives. The stylus is mounted at the end of a support arm that is held in the actuator by a flexure, the flexure permitting movement in the two directions. A set of permanent magnets and two sets of independently controllable electric coils allow the support arm to be moved in the two directions. In a data storage application, a data disk has a series of surface features that represent machine-readable data and the bidirectional actuator is supported by a secondary actuator that moves the primary actuator along a radius of the disk. This allows the bidirectional actuator with the attached stylus to be located to a coarse position within a desired band of data tracks. Tracking control circuitry connected to one set of coils allows the stylus to be maintained on a specific data track within a band and moved to other tracks Within the band. Load control circuitry connected to the other set of coils allows the perpendicular load on the stylus to be maintained generally constant so that deflections of the cantilever due to the disk surface features can be decoded as data.