Patent ID: 8373528

Claim:
A magnetic field control method of controlling a magnetic field generated by a pair of magnetic field generation units provided axially of a predetermined axis to face each other with a gap in between, each of the units having a gap-side main surface formed with a magnetic pole of an opposite polarity for each other, each magnetic pole being so disposed as to cause a magnetic flux density near the gap-side main surface to attain a local maximum off the predetermined axis, the magnetic field being controlled on a predetermined plane perpendicular to the predetermined axis and between the pair of magnetic field generation units, where the control method comprises a step of moving a local maximum point of magnetic field intensity n a predetermined plane by performing at least a first operation of revolving one of the magnetic field generation units about the predetermined axis in a direction opposite to the other of the magnetic field generation units, in the first operation and a second operation of revolving the pair of magnetic field generation units about the predetermined axis in a same direction by a same angle.