Patent ID: 8466762

Claim:
A projection apparatus comprising: a base plate comprising magnetically permeable material; a first magnet coupled to the baseplate, wherein the first magnet has a first magnetic orientation; a second magnet coupled to the baseplate, wherein the second magnet has a second magnetic orientation opposite and parallel the first magnetic orientation; a movable platform having a conductive coil nominally oriented in a platform plane above the first and second magnets, wherein the movable platform is not connected to any magnets; a magnetically permeable core beneath the movable platform and between the first and second magnets; a third magnet above the first magnet and the platform plane, wherein the third magnet has the second orientation; and a fourth magnet above the second magnet and the platform plane, wherein the fourth magnet has the first magnetic orientation; 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; and a top plate comprising magnetically permeable material above the third and fourth magnets, wherein the base plate and the top plate contribute to closing a magnetic circuit in the projection apparatus.