| 摘要 |
PROBLEM TO BE SOLVED: To exhibit high optical performance over the entire exposure region, easily achieve a higher NA and give a wide exposure region by providing a projection optical system having at least one aspherical lens which is aspherical at both surfaces thereof so that distortions, curvature of field, astigmatism, coma, spherical aberrations, and the like can be corrected satisfactorily. SOLUTION: A whole optical system is formed of a plurality of lens groups which include a group of lenses of positive refracting power and a group of lenses of negative refracting power, and its power (refracting power) distribution is set properly. A projection optical system 909 includes at least a single lens which is aspherical at both surfaces thereof. Even if one or more aspherical lenses are used, one of such aspherical lenses must be aspherical at both surfaces thereof, or each of all such aspherical lenses must be aspherical at both surfaces thereof. Differences in aberration correcting performance between a both-sided aspherical lens and a single-sided aspherical lens become noticeable, when the lens is applied to a projection optical system up to higher-degree aberration corrections is required.
|
