Patent ID: 8957389
Filing Date: 2015-02-17
Classification: H01J

Abstract:
1. An electromagnetic lens comprising: an electromagnetic coil wound to be rotationally symmetrical about an optical axis of an electron beam; and a pole piece including an inner wall covering an inner circumference side of the electromagnetic coil, an upper end wall covering the electromagnetic coil at an entering side of the electron beam, a lower end wall covering the electromagnetic coil at an emitting side of the electron beam, an outer wall covering an outer circumference side of the electromagnetic coil, and a gap formed by cutting out at least a part of the inner wall, the lower end wall, and the upper end wall to be rotationally symmetrical about the optical axis, wherein a thickness of the inner wall is thinnest at a portion close to the gap, and gradually becomes thicker as a distance from the gap increases, and a width of the electromagnetic coil in a radial direction is more increased as being closer to the gap.