PROBLEM TO BE SOLVED: To provide a method and a system for active magnetic shield capable of cancelling such a disturbed and fluctuated magnetic field that a magnetic flux density distribution varies with the elapse of time.SOLUTION: A coil 1 for generating a compensation magnetic field to cancel the disturbed and fluctuated magnetic field is installed at an objective position P to be shielded, the position Q1 of a magnetic field generating source 20a moving within a range T affecting the objective position P is detected while detecting a disturbed magnetic field at a prescribed sensor position Sa around the objective position P, the magnetic moment of the generating source 20a is computed from the detected magnetic field at the sensor position Sa and the detected position Q1 of the generating source 20a, the compensation magnetic field to be generated at the objective position P is computed from the detected position Q1 of the generating source 20a and the magnetic moment to drive the coil 1, and a cycle from the detection of the disturbed magnetic field till drive of the coil 1 is repeated. Preferably, the distance attenuation formula of the disturbed magnetic field in the range T affecting the objective position P is obtained in advance, and the magnetic moment of the generating source 20a and the compensation magnetic field at the objective position Sa are computed based on the distance attenuation formula.COPYRIGHT: (C)2012,JPO&INPIT【課題】磁束密度分布が時間と共に変化するような外乱変動磁場を打ち消すことができるアクティブ磁気シールド方法及びシステムを提供する。【解決手段】シールド対象位置Pに外乱変動磁場を打ち消す補償磁場の発生用コイル1を設置し、対象位置P周辺の所定センサ位置Saで外乱磁場を検知しながら対象位置Pに影響が及ぶ範囲T内を移動する磁場発生源20aの位置Q1を検出し、センサ位置Saの検知磁場と発生源20aの検出位置Q1とから発生源20aの磁気モーメントを算出し、発生源20aの検出位置Q1と前記磁気モーメントとから対象位置Pに発生すべき補償磁場を算出してコイル1を駆動し、前記外乱磁場の検知からコイル1の駆動までのサイクルを繰り返す。好ましくは、対象位置Pに影響が及ぶ範囲Tの外乱磁場の距離減衰式を予め求め、その距離減衰式に基づき発生源20aの磁気モーメント及び対象位置Saの補償磁場を算出する。【選択図】図1
