Magnetically Actuated System

Abstract

A magnetically actuated system includes a conductor and a magnetic field apparatus to generate a magnetic field. The magnetic field apparatus includes magnets and magnetically permeable materials to focus the magnetic field in areas of the conductor that produce a drive torque when the conductor carries a current.

1 - 12 . (canceled) 
     
     
         13 . An apparatus comprising:
 a first magnet oriented with a south pole facing down and a north pole facing up;   a second magnet oriented parallel to the first magnet, the second magnet having a north pole facing down and a south pole facing up;   a movable platform having a conductive coil nominally oriented in a platform plane above the first and second magnets;   a third magnet above the first magnet and the platform plane, the third magnet having a south pole facing up and a north pole facing down;   a fourth magnet above the second magnet and the platform plane, the fourth magnet having a south pole facing down and a north pole facing up; and   at least one focusing plate of magnetically permeable material positioned between the platform plane and the third and fourth magnets to focus a resulting magnetic field in the platform plane.   
     
     
         14 . The apparatus of  claim 13  wherein the movable platform includes a reflective surface facing up, and the third and fourth magnets are shaped to allow light to impinge on the reflective surface. 
     
     
         15 . The apparatus of  claim 13  wherein the conductive coil has an outer outline and the focusing plates are shaped to be outside the outer outline of the conductive coil. 
     
     
         16 . The apparatus of  claim 15  further comprising a magnetically permeable core positioned between the first and second magnets and beneath the movable platform. 
     
     
         17 . A projection apparatus comprising:
 a light source to produce light;   a mirror to reflect the light, the mirror mounted on a movable platform, the movable platform including a conductive coil;   at least one magnet to produce a magnetic field; and   at least one piece of magnetically permeable material positioned to modify the magnetic field in the conductive coil.   
     
     
         18 . The projection apparatus of  claim 17  wherein the at least one piece of magnetically permeable material includes two focusing plates in a plane parallel to a plane of the conductive coil when the movable platform is at rest. 
     
     
         19 . The projection apparatus of  claim 18  wherein the two focusing plates are positioned on a first side of the movable platform in common with the mirror, and wherein the at least one magnet includes two magnets on an opposite side of the movable platform. 
     
     
         20 . The projection apparatus of  claim 19  wherein the at least one piece of magnetically permeable material further comprises a core of material positioned between the two magnets on the opposite side of the movable platform.