| 主权项 |
1. A desktop electron microscope, comprising:
an electron gun, for providing an electron beam; and at least a wide range tunable magnetic lens, comprising: a coil support, for winding a coil according to a central axis, the center of the coil support having a central opening for the electron beam passing through the central opening, and the coil is around the central axis, and when the coil is fed with current, a magnetic field which has a direction along the central axis is generated; an inner pole piece, covering the coil support, having an inner top pole shoe and an inner down pole shoe, the inner top pole shoe and the inner down pole shoe located at the central opening of the coil support for forming a first magnetic-circuit gap, wherein the inner pole piece surrounds the coil; a permanent magnet, forming an annular structure according to the central axis, the permanent magnet disposed at the outer side of the inner pole piece away from the central axis; a first outer pole piece, adjacently disposed at an upper-side of the permanent-magnet, and extending to the central hole of the coil support for forming a first outer pole shoe; and a second outer pole piece, adjacently disposed at the under-side of the permanent-magnet, and extending to the central hole of the coil support for forming a second outer pole shoe, wherein the first outer pole shoe and the second outer pole shoe form a second magnetic-circuit gap, wherein first outer pole piece and the second outer pole piece are spaced apart from the coil, wherein the first outer pole piece and the second outer pole piece are formed of iron or ferromagnetic metals; wherein the inner pole piece is spaced apart from the first outer pole piece. |
