Patent ID: 9462733
Filing Date: 2016-10-04
CPC Classification: G01R,H05K

Claim Text:
1. A magnetic shielding apparatus comprising: a passive shield housing extending in a first direction; a correction target space that is defined in an inner space of the passive shield housing, the correction target space including a center of the passive shield housing; a first coil that corrects a magnetic field in the inner space in the passive shield housing, the first coil being provided at a first edge of the passive shield housing in the first direction; a first magnetic sensor that is provided at the first edge of the passive shield housing in the first direction and that measures a first magnetic field so as to output a first value corresponding to the first magnetic field; a second magnetic sensor that is arranged in the inner space of the passive shield housing so that the second magnetic sensor is closer to the center of the passive shield housing than the first magnetic sensor, the second magnetic sensor measuring a second magnetic field so as to output a second value corresponding to the second magnetic field; a driving circuit that applies a first current to the first coil; and a controller that is configured to calculate a magnetic field gradient between the first and second magnetic sensors based on the first and second values and a distance between the first and second magnetic sensors in the first direction, wherein the controller controls the first current based on the magnetic field gradient.