Patent ID: 8901511

Claim:
An electrostatic charged particle beam lens comprising: an electrode including a flat plate having a first surface having a normal line extending in a direction of an optical axis and a second surface opposite to the first surface, the electrode having a through-hole extending from the first surface to the second surface, wherein, when an opening cross section is defined as a cross section of the through-hole taken along a plane perpendicular to the normal line and a representative diameter is defined as a diameter of a circle obtained by performing regression analysis of the opening cross section, a representative diameter D 1 of the opening cross section in a first region that is on the first surface side and a representative diameter of the opening cross section in a second region that is on the second surface side are each smaller than a representative diameter D 2 of the opening cross section in a third region that is a region in the electrode disposed between the first surface and the second surface, and wherein 0.4<D 1 /D 2 <1.0.