Optical: systems and elements – Compound lens system – With curved reflective imaging element
Reexamination Certificate
2007-04-03
2007-04-03
Nguyen, Thong Q (Department: 2872)
Optical: systems and elements
Compound lens system
With curved reflective imaging element
C359S365000, C359S857000, C378S034000
Reexamination Certificate
active
11183877
ABSTRACT:
A projection lens for imaging a pattern arranged in an object plane onto an image plane using electromagnetic radiation from the extreme-ultraviolet (EUV) spectral region has several imaging mirrors between its object plane and image plane that define an optical axis of the projection lens and have reflective coatings. At least one of those mirrors has a graded reflective coating that has a film-thickness gradient that is rotationally symmetric with respect to a coating axis, where that coating axis is acentrically arranged with respect to the optical axis of the projection lens. Providing at least one acentric, graded, reflective coating allows designing projection lenses that allow highly uniform field illumination, combined with high total transmittance.
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Hudyma Russell M.
Mann Hans-Juergen
Ulrich Wilhelm
Carl Zeiss SMT AG
Nguyen Thong Q
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