公开(公告)号：US12164093B2

公开(公告)日：2024-12-10

申请号：US17505591

申请日：2021-10-19

Applicant: KLA CORPORATION

Inventor： Alex Zheng ,  Jun Wang ,  David Y. Wang ,  Chunxia Li ,  Changfei Yan ,  Rui Ni ,  Lansheng Dong ,  Yang Zhou ,  Hai-Yang You ,  Haijing Peng ,  Walter H. Johnson ,  Shankar Krishnan ,  Jianou Shi

IPC: G02B17/06 ,  G02B5/10

Abstract: A Cassegrain or quasi-Cassegrain structure objective lens is used in a polar MOKE metrology system. The quasi-Cassegrain reflective objective lens includes a primary concave mirror and a secondary mirror. The primary concave mirror has a wider diameter than the secondary mirror and defines an aperture through which the laser beam is configured to be transmitted toward the secondary mirror. The secondary mirror can be convex, concave, or have a flat surface.