| 摘要 |
PROBLEM TO BE SOLVED: To enable an irradiation system to be partially improved in flexibility by a method wherein the irradiation system is made to contain a control element which generates a multi-polar irradiation mode and is capable of continuously changing, at least, a spatial parameter of a multi-polar irradiation mode. SOLUTION: A multi-polar mode generating element provided in an irradiation system is equipped with four triangular blades 41, 42, 43 and 44 that are called malta aperture blades, inserted in a beam trajectory on a pupil plane, each having an apex angle ofβ, and capable of providing a continuously variable four-pole irradiation mode. Electrodes can be changed in radial position by adjusting an axicon optical device, radial width by adjusting a zoom lens, and tangential width by inserting another set of blades such as a malta cross having a different apex angle ofβ.
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