| 摘要 |
PURPOSE:To prevent expansion of magnetic distribution on the axis up to the lower side of lens even when magnetization energy is intensified by providing a compensating lens which formes the compensating magnetic field in the reverse porality to that formed by the upper and lower magnetic pole pieces in the area near the lower magnetic pole piece. CONSTITUTION:A compensating lens 11 is removably provided at the lower surface of a lower magnetic pole piece 2 and a magnetization coil 11a of this lens 11 is connected to a magnetization current controller 12. Accordingly, a compensating magnetic field a having the polarity opposing to the magnetic field d formed by the upper and lower magnetic pole pieces 1, 2 can be formed by controlling a magnetization current. Thereby, a conbined magnetic field f can be obtained by cancelling a part of magnetic field. As a result, an intensive magnetic field does not expand up to the lower side of lens, the spherical aberration can be reduced to a small value and a high performance objective having high resolution can be obtained. |
