Patent ID: 8624478

Claim:
A projection lens ( 5 ) for use in a charged particle system, said projection lens comprising: a first metal part ( 36 ) in the form of a projection lens housing of said projection lens, having an outer wall to be set at an electrical potential; a lens stack ( 35 ); a substantially thin second metal part ( 39 ) in electrical contact with said lens stack ( 35 ); said second metal part ( 39 ) included in said projection lens ( 5 ) and to be set at an electrical potential that is lower than the electric potential of the first metal part ( 36 ); said second metal part ( 39 ) positioned at a distance to said first metal part ( 36 ) and comprising one or more edge parts; said distance between said first and second metal parts defining a discharge region in which an electric field is present; said projection lens further comprising an insulator ( 40 ); said discharge region being arranged in the plane of the second metal part ( 39 ), wherein said one or more edge parts facing the discharge region are encapsulated by the insulator ( 40 ), and the second metal part ( 39 ) being included as a conductive coating.