Electromagnetic optical beam controller having an eddy current damper for arresting mechanical resonance

Claim 1

In an optical image-reproducing system in which program information stored in a generally spiral track is retrieved by scanning the track with a beam of optical energy and in which is derived a pair of correction signals related to the radial tracking and to the timing of said beam relative to said track, an improved beam control apparatus comprising: a first ring-shaped, axially poled magnet; a second axially-poled magnet having a pivot bearing associated therewith and poled in the same direction as said first magnet; support means comprising a pin cooperating with said bearing for pivotally positioning said second magnet coaxially with and in such proximity to said first magnet that said second magnet is magnetically captivated upon said pin but free for tilting displacement with respect to a pair of orthogonally related axes; an optical element positioned so that said beam is incident thereon and mechanically coupled to said second magnet for concurrent displacement therewith to redirect the path of said beam; electromagnetic means positioned along an assigned one of said axes in close proximity to said second magnet and responsive to one of said correction signals to develop a magnetic field, having a magnitude and direction determined by the amplitude and polarity of said applied correction signal, for reacting with the field of said second magnet to effect a desired displacement of said optical element about the other one of said axes; and damping means comprising a conductive member disposed adjacent to and completely surrounding said second magnet and responsive to the magnetic flux of the field of said second magnet for developing a counter electromagnetic force for reacting with said field of said second magnet to arrest random or uncontrolled movement of said second magnet about said support pin without inhibiting said desired displacement of said optical element.