Patent ID: 6824060
Filing Date: 2004-11-30
Classification: G06K

Abstract:
A bi-directional motor drive arrangement for scanning a light beam at a scan angle over indicia to be electro-optically read, comprising:a) a resonant motor having a rotor oscillatable about an axis; b) a permanent magnet jointly oscillatable with the rotor; c) a scanning element jointly oscillatable with the rotor, and operative for directing the light beam at the indicia; d) a drive coil in operational proximity with the magnet, and operative for generating a drive signal having an amplitude sufficient to drive the rotor, the magnet and the scanning element in opposite directions about the axis to sweep the light beam at the scan angle over the indicia at a resonant frequency; e) a feedback winding in operational proximity with the magnet, and operative for generating a feedback signal having a feedback frequency corresponding to the resonant frequency during oscillation of the magnet, and a magnitude proportional to a velocity of the rotor; and f) a feedback circuit for feeding the feedback signal to opposite ends of the drive coil, the circuit including a field effect transistor (FET) biased to operate in a linear current/voltage characteristic to function as a variable resistor to adjustably attenuate the magnitude of the feedback signal fed to the opposite ends of the drive coil, and to adjustably control the amplitude of the drive signal to maintain the scan angle at a substantially constant value during scanning.