Abstract: A digital system for controlling the quality factor in a resonant device. The resonant device can be any mechanically driven resonant device, but more particularly can be a device that includes a cantilever within its system, such as an atomic force microscope. The quality factor can be digitally controlled to avoid noise effect in the analog components. One of the controls can use a direct digital synthesizer implemented in a way that provides access to the output of the phase accumulator. That output is a number which usually drives eight lookup table to produce a cosine or sign output wave. The output wave is created, but the number is also adjusted to form a second number of the drives a second lookup table to create an adjustment factor. The adjustment factor is used to adjusts the output from the cosine table, to create an adjusted digital signal. The adjusted digital signal than drives a DA converter which produces an output drive for the cantilever.

Abstract: An apparatus and method for measuring optically the position or angle of a variety of objects or arrays of objects, including cantilevers in scanning probe microscopy, micromechanical biological and chemical sensors and the sample or a probe in surface profilometry. The invention involves the use of one or more diffractive optical elements, including diffraction gratings and holograms, combined with conventional optical elements, to form a plurality of light beams, each with a selectable shape and intensity, from a single light source, reflect the beams off mechanical objects and process the reflected beams, all to the end of measuring the position of such objects with a high degree of precision. The invention may also be used to effect mechanical changes in such objects.

Abstract: A method for determining physical properties of micromachined cantilevers used in cantilever-based instruments, including atomic force microscopes, molecular force probe instruments and chemical or biological sensing probes. The properties that may be so determined include optical lever sensitivity, cantilever spring constant and cantilever-sample separation. Cantilevers characterized with the method may be used to determine fluid flow rates. The method is based on measurements of cantilever deflection resulting from drag force as the cantilever is moved through fluid. Unlike other methods for determining such physical properties of cantilevers, the method described does not depend on cantilever contact with a well-defined rigid surface. Consequently, the method may be employed in situations where such contact is undesirable or inconvenient.

Abstract: A linear variable transformer (LVDT) for use in a transducer. The LVDT has a non-ferromagnetic core which may eliminate Barkhausen noise and thereby improve the sensitivity of the resulting measurements. In one aspect, this system may be used in an atomic force microscope.

Abstract: A transducer that reduces noise, increases sensitivity, and improves the time response of a linear variable differential transformer (LVDT). The device replaces the primary coil and the high permeability ferromagnetic core of conventional LVDTs with a primary wound around a moving non-ferromagnetic core. In addition to reducing or eliminating Barkhausen noise, this approach reduced or eliminated a number of other undesirable effects in conventional LVDTs including excessive eddy current heating in the core, non-linearities associated with high permeability materials and the length scale of the flux circuit. These improvements are coupled with improved LVDT signal conditioning circuitry. The device is also an actuator and may be used to convert differential voltages into force.