Control system for oscillating optical element in scanners
AssigneeSymbol Technologies, Inc.
InventorsJames Giebel, Thomas Mazz, Constanzo DiFazio, Mik Stern, David Goren
Life of this patent
Estimating the term…
Abstract
A miniature light beam scanner includes a moving optical element formed on a substrate with electrodes for driving the optical element and sensing its motion as indicated by a varying capacitance between the optical element and the substrate. Control and driver circuitry responsive to the variation in capacitance drives the optical element to move at a resonant frequency and predetermined amplitude.
Claims30
A light beam scanner for directing a light beam used to traverse a symbol to be read comprising:
- a light source;
- a mirror for reflecting light from the light source,
- a drive electrode for applying electrostatic force to the mirror to vary its position so that the direction of reflected light is varied;
- a pick-up electrode for sensing the position of the mirror;
- and
- feedback circuitry for modifying the applied electrostatic force in response to the sensed mirror position,
- wherein the electrostatic force is periodically applied to the mirror by imposing a periodic voltage on the drive electrode and wherein the position of the mirror is sensed by detecting variations in the capacitance between the mirror and the pick-up electrode, and
- wherein a carrier signal is applied to the mirror and a voltage is induced on the pick-up electrode, which induced voltage corresponds to the carrier signal, amplitude modulated in response to changes in distance between the mirror and the pick-up electrode.
A miniature light beam scanner formed on a semiconductor substrate for detecting optical properties of a scanned target comprising:
- means for directing a light beam in a direction dictated by the position of said means;
- means for applying a driving force to vary the position of said directing means and for electrically sensing the position of said directing means;
- and
- means for modifying the driving force in response to the sensed position of said directing means to cause the light beam directing means to oscillate at a resonance frequency and predetermined amplitude,
- wherein the means for sensing the position of the directing means comprises one or more electrodes on the semiconductor substrate coupled by an electric field to the means for directing the light beam.
A method for controlling a moving mirror which reflects a light beam in a light beam scanner comprising the steps of
- applying a periodically varying electrostatic force to the mirror to vary its position;
- sensing the position of the mirror;
- and
- modifying the applied electrostatic force in response to the sensed mirror position,
- wherein the position of the mirror is sensed by detecting variation in the capacitance between the mirror and a conductive pick-up pad located in proximity to the mirror.
Electromechanical oscillator and control system for light scanning, comprising:
- an optical element at least a portion of which is moveable in relation to a supporting substrate;
- an electrically activated driver for applying a driving force to the optical element;
- a sensor for sensing movement of the optical element;
- feedback circuitry for varying the applied driving force, wherein at least a portion of the optical element is driven to oscillate near a resonance frequency at a predetermined amplitude;
- and
- electronic circuitry for imposing a carrier signal on the optical element, wherein the sensor includes at least one electrode in proximity of the optical element in which a voltage is induced corresponding to the carrier signal whose amplitude has been modulated by movement of the optical element.
A control system for an oscillating optical element in light beam scanner, comprising:
- an electrostatic driver for inducing oscillating motion of the optical element relative to a substrate on which the optical element is mounted;
- a sensor on the substrate in which a varying voltage signal is induced containing information concerning the amplitude and phase of the movement of the optical element relative to the sensor;
- and
- feedback circuitry for controlling the electrostatic driver responsive to said signal, to drive the optical element at a resonant frequency and predetermined amplitude.
Dependencies are inferred from the claim text.