| 摘要 |
PROBLEM TO BE SOLVED: To obtain high resolving power and a wide exposure range by arranging a lens having positive refractive power between two sets of lens groups constituted of facing concave surfaces. SOLUTION: A projection lens system includes 13 positive lenses and seven negative lenses and its numerical aperture(NA) is set to >=0.40. For example, a 7th surface R7 and a 8th surface R8, and a 13th surface R13 and a 14th surface R14 constitute the concave surfaces facing to each other. Then, one lens having the positive refractive power is arranged between two sets of lens groups constituted of the facing concave surfaces. In order to set the numerical aperture to >=0.40, the main positive lens group is constituted of four or more lenses having the positive refractive power. By providing the lens having the positive refractive power, the respective concave surfaces of two sets of lens groups arranged before and behind the lens surface and having the facing concave surfaces have the appropriate refractive power to Petzval's sum and coma aberration. Thus, the high resolving power with severalμm order accuracy is made compatible with the wide exposure range.
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