Switchable Permanent Magnet Bias Coil
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-30
Magnetooptic recording requires a switchable magnetic field for write/erase operations. This function is typically performed by a fast switching electromagnet with soft iron center cores or by a permanent magnet that can be rotated by a slowly responding stepping motor or a solenoid. The disadvantage of the electromagnet is its high power dissipation and inductive losses of the assembly that will slow down the switching time as well as heating up the media and machine. Power needs to be on all the time during write/erase operation. The disadvantage of using the permanent magnet to be rotated mechanically is its slow response, thereby reducing its accessibility.