Abstract: A variable-capacitance transducer detects the angular position of a rotatable member. The transducer includes a first capacitance plate having a plurality of electrically conductive capacitance electrodes, a second capacitance plate spaced therefrom, and a dielectric element located between the plates. At least two of the electrodes are interconnected by a conductive trace. The dielectric element or one of the plates is fixedly mounted on the rotatable member. The electrodes on the first capacitance plate, in conjunction with the second capacitance plate, form a plurality of capacitances that vary as the angular position of the rotatable member changes. A conductive guard partially envelopes the conductive trace and a conductive guard partially envelopes the electrodes on the first capacitive plate.

Abstract: An optical scanner has a visco-elastic material within a flexible coupling in its shaft assembly. The flexible coupling serves to permit bending of the assembly in response to lateral vibration. However, in response to the bending, the visco-elastic material disposed therein undergoes viscous deformation, thereby acting upon the shaft to rapidly damp the vibration.

Abstract: A two-dimensional scanner employs first and second pivotable mirrors (36 and 40) to control the position of the target point that a light spot assumes in a target phase (44). The second mirror (40) is driven in a resonant mode. An f.multidot..theta. lens (42) converts the pincushion error that would otherwise result into a barreling error, which can be compensated for by controlling the amplitude of the second-mirror oscillations.

Abstract: A resonant rotationally oscillating mechanical system has masses supported by a resilient structure held at both ends on a stationary base to define a natural resonance frequency of intended rotational motion about an axis relative to the base. The resilient structure is asymmetrical along the axis. The masses are subject to additional motion relative to the base in directions different from the direction of intended motion. For a selected mode of motion, the masses and the asymmetrical resilient structure are mutually configured, in accordance with equations of motion, to substantially preclude angular motion of one of the masses relative to the base about an axis other than the axis of the intended rotational motion. In another aspect, the resilient structure has one end attached to the base by a coupler that permits that end to move relative to the base, but only at frequencies different from the natural resonance frequency of motion.

Abstract: An element that moves resonantly has its resonant frequency dynamically tuned to a desired frequency by two components that cooperate via magnetic fields, one component being mounted for motion with the moving element.

Abstract: A resonant scanner has at least one torsionally rigid damper located at at least one torsional node point of a torsion bar. At least one node of an unwanted vibrational mode is determined to be at a distinct node point, whereby the damper damps the unwanted vibrations while passing desired torsional oscillations. The damper serves as the only physical coupling of the torsion bar to the housing and damps transmission of vibrations into and out of the scanner. One or both ends of the torsion bar may be configured as the rotor of a motor. The rotor fits within but is not physically coupled to a bobbin coupled to the frame. Two coils are wound on the bobbin at approximate right angles to each other to minimize a cross-coupling between the coils.

Abstract: A resonant rotationally oscillating mechanical system has a plurality of masses supported by a resilient structure held at both ends on a stationary base to define a natural resonance frequency of intended rotational motion about an axis relative to the base. The resilient structure is asymmetrical along the axis. The masses are subject to additional motion relative to the base in directions different from the direction of intended motion. For a selected mode of motion, the masses and the asymmetrical resilient structure are mutually configured, in accordance with equations of motion, to substantially preclude angular motion of one of the masses relative to the base about an axis other than the axis of the intended rotational motion. In another aspect, the resilient structure has one end attached to the base by a coupler that permits that end to move relative to the base but only at frequencies different from the natural resonance frequency of motion.

Abstract: The natural resonant frequency (and phase) of a resonant mechanical system (having an spring structure that includes a material whose elastic properties change with temperature, e.g., by at least 0.05% per .degree.C.) is tuned to a desired value by changing the temperature of at least part of the spring structure. A two-dimensional image is generated on a surface by tunign a resonant driver (having such a temperature sensitive element) to a natural resonant frequency in coordination with modulation of a beam that is raster scanned on the surface by the resonant driver.

Abstract: A reference mirror (50) in an interferometer is fixed in position with respect to a laser (34). A refractive block (40) having parallel upper and lower surfaces is mounted for pivoting about a pivot axis (60) parallel to the reference mirror (40). The refractive block (40) is disposed in the path of the light beam (36) produced by the laser (34), and it includes a partially reflective surface (42) on its lower face that divides the incident beam (36) into two components (44 and 46), which travel along different paths, in which they are reflected from different portions (48 and 54) of the surface of the reference mirror (50) and from different portions (52 and 56) of a reflective surface on the upper face of the refractive block (40). A second partially reflective coating (58) rejoins portions of the two components to form an exit beam (32) in which the radiation from the two beams interferes in accordance with the angle of the refractive block (40).

Abstract: A surface scanning system defining an optical path for scanning a planar surface, in which an angularly moving scanner deflects a portion of the path, an optical element aligned with stationary portions of the optical path is driven in rectilinear sinusoidal motion for providing focus correction as the surface is scanned, and in which the sinusoidal motion of the optical element and the motion of the scanner are caused to be interdependent in frequency and phase. The sinusoidal motion of the optical element maintains accurate focus on the planar surface. In another aspect a device for moving an optical element in linear resonant motion includes a cantilevered resilient support structure arranged to permit only linear motion of the element, and means for driving the element resonantly.

Abstract: A surface-scanning system of the kind that defines an optical path and has a scanning assembly comprised of X and Y angularly oscillating scanners for deflecting a portion of the path, and first and second optical elements aligned with stationary portions of the optical path and driven in rectilinear oscillating motion along the path to provide focus correction respectively for the X and Y scanners. The X direction scanner is of the resonant type and has a mechanism for dynamically tuning its resonant frequency, the first optical element is mounted to oscillate in rectilinear resonant motion, and the tuning mechanism of the X direction scanner is arranged to receive a signal representing the oscillations of the first optical element and to tune the resonant frequency of the X direction scanner to synchronize its resonant motion with that of the first optical element.

Abstract: A recorder or printer device including apparatus for threading a continuous web of printable material from a supply through a main drive nip, including a main drive nip formed by a drive surface of a rotatable roll and a main presser which urges the web against the roll, a loop-introducing guide surface arranged relative to the drive surface of the roll, to form a convergent channel leading to the drive nip, and an initial presser for urging the web against the roll at an initial drive nip spaced from the main drive nip. The initial presser has a second position separate from the drive roll for enabling placement of a leader portion of the web between the initial presser and the roll with the leader extending past the initial nip.

Abstract: A dynamically resonant system including a linearly movable element having a neutral position and a range of excursion centered on the neutral position, a spring-like element for urging the movable element toward the neutral position, the resonant system having a natural resonant frequency dependent on the spring characteristics of the spring-like element, the spring-like element having a temperature sensitive member that causes the spring characteristics to vary with temperature of the member.

Abstract: Radial free play is reduced in rotor bearings of a limited rotation electromechanical actuator of the kind having a stator assembly with a plurality of stator pole faces, a rotor with a plurality of rotor pole faces, two bearings supporting opposite ends of the rotor and means for establishing magnetic flux across the gaps. In various aspects, the stator and rotor pole faces are cylindrical and the central axis of the rotor pole faces is tilted relative to the central axis of the stator pole faces; a region of a gap between the stator and rotor pole faces produces both the radial free-play-reducing forces and at least part of the driving torque; the gap rotor varies in size along its length but nowhere is so great as to have an effectively infinite reluctance; the gap varies continuously along its length; and each bearing has radial free play equal to at least 10% of twice the difference in the diameters of the stator and rotor pole faces.

Abstract: A capacitive position sensor for sensing changes in the position of a rotating element, in which there are two sets of stationary capacitive surfaces, one set forming a first integral unit, the other set forming a second integral unit; the two units are held together with the surfaces of each set resting in corresponding spaces in the other unit such that all surfaces of both sets intersect a common radial plane and the surfaces of one set are electrically isolated from the surfaces of the other set.

Abstract: An angular position sensor for determining the angular position of a shaft relative to a fixed support to which the shaft is rotatably connected, including a pair of interactive sensor elements respectively on the shaft and on the support, the elements being arranged for cooperation so that an electrical characteristic of at least one of the elements varies in accordance with the relative rotational positions of the elements, the cooperation being between two corresponding axially directed surfaces, one on each of the elements, a rigid spacer between and engaged upon the surfaces, and another member for permitting motion of one element along the axis of the shaft, for preventing motion of that one element in other directions than along the axis, and for applying a biasing force tending to press the elements toward each other against the corresponding surfaces of the spacer, for contact, whereby the spacing between the surfaces is kept constant by the spacer.

Abstract: A mount for attaching an optical element to a rotating shaft combines a first portion which bears the optical element and is sufficiently rigid to limit dynamic distortion of the optical element, a clamp portion spaced axially from the first portion for clamping the mount to the shaft using a force which causes mechanical distortion in the clamp portion, and a strain decoupling means connecting the first portion to the clamp portion and configured to transmit rotation of the shaft faithfully to the element, while isolating the mechanical distortion in the clamp portion from being transmitted axially to the first portion.

Abstract: A resonant electromechanical oscillator which includes a base portion, a driven portion, a cantilevered sheet-form flexural suspension which spaces the driven portion from the base portion for oscillation about an axis in the plane of the sheet-form suspension, and an electromagnetic drive which includes cooperating portions on the base and driven portions for oscillating the driven portion at a resonant frequency. The ends of the sheet-form suspension are coupled to the base and driven portions with at least one end coupling being adjustable to select the resonant frequency of the oscillator by changing the effective length of the sheet suspension. Fixed surfaces on the base portion limit angular excursion of the driven portion and limit buckling distortion of the sheet-form suspension. Preferred embodiments of the oscillator have a driven portion with a mass in the range of two to ten grams, and withstand impact loads of at least five hundred g's.

Abstract: In an actuator having a stator assembly which defines a pair of stator pole faces, a permeable rotor assembly which is positioned to rotate relative to the stator assembly, and which defines a driving pole face separated from each of the stator pole faces by a flux permeable driving gap, the rotor assembly having an operational range of rotor angular positions over which drive flux passing across the driving gap drives the rotor assembly, the extent of the driving gap at one of the stator pole faces being reduced as the rotor assembly rotates toward the limit of the operational range, the improvement including a flux-permeable compensating gap between the driving pole face and each stator pole face which provides a secondary path for drive flux as the rotor assembly rotates toward the limit of the operational range, the compensating gap being less permeable than the driving gap.

Abstract: An optical element positioner in which a carriage holding the optical element is driven in response to electrical control signals to selected locations along an optical path by a moving-iron, limited-rotation actuator, with the reflected load inertia substantially matched to the actuator rotor and crank arm inertia.