Optical: systems and elements – Lens – With reflecting element
Patent
1995-12-12
1997-09-16
Epps, Georgia Y.
Optical: systems and elements
Lens
With reflecting element
359732, 359736, G02B 1700
Patent
active
056686722
ABSTRACT:
This invention relates to a catadioptric optical system in which, a large numerical aperture is attained on the image side and, while securing a sufficient working distance, the size of the beam splitter is reduced, thereby attaining a resolution of a quarter micron unit, and an exposure apparatus using the same. In order to form a reduced image of a pattern of a first surface on a second surface, this catadioptric optical system comprises, at least, a first lens group, a beam splitter, a concave mirror having an enlarging magnification, and a second lens group. These constitutional elements of the catadioptric optical system are disposed such that light from the first surface passes through the first lens group, the beam splitter, the concave mirror, the beam splitter, and the second lens group in this order. In particular, the rear-side principal plane of the second lens group is on the second surface side with respect to a light-entering surface of the second lens group on which the light having passed through the beam splitter is incident. In addition, the concave mirror functions to collimate the light having passed through the beam splitter and then make thus collimated light re-enter the beam splitter.
REFERENCES:
patent: 5089913 (1992-02-01), Singh et al.
patent: 5220454 (1993-06-01), Ishihara
patent: 5241423 (1993-08-01), Chiu et al.
patent: 5289312 (1994-02-01), Hashimoto
patent: 5402267 (1995-03-01), Furter
patent: 5530586 (1996-06-01), Yasugaki
Cornely John P.
Epps Georgia Y.
Nikon Corporation
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