| 摘要 |
PURPOSE:To simultaneously suppress the effect of a disturbance magnetic field to each device by providing a detection coil to each device together with a compact coil for generating a cancellation magnetic field that forms a pair with this detection coil and generating a magnetic field for local cancellation. CONSTITUTION:A compact output coil 11 for cancelling a disturbance magnetic field is provided in the vicinity of a lens-barrel and the output of a detection coil 3 is supplied to an addition circuit 12 through an amplifier 4 and an integration circuit 5. The output signal of this addition circuit 12 is supplied to an amplifier 14. The output signal of the amplifier 14 is supplied to the output coil 11 and is also supplied to the addition circuit 12 through an attenuator 13. In the same way, a detection coil is also provided in the vicinity of another analyzer unit 8 and a compact coil 16 for cancelling a disturbance magnetic field is provided and then the output signal of the x detection coil 15 is supplied to a similar feedback control system 17. As a result, the disturbance magnetic field and the magnetic field for cancellation are just offset at each position and the magnetic field can be set to 0. |
