| 摘要 |
PROBLEM TO BE SOLVED: To provide the near ultraviolet objective lens which has the chromatic aberration compensated form the near ultraviolet to the visible region, has its curvature of field compensated without adopting a Gaussian type, and also has a long operation distance and relatively high NA. SOLUTION: This objective lens consists of a 1st lens group G1 which has at least one meniscus lens having a concave surface on the side of an object S and at least one cemented lens and also has positive refracting power on the whole, a 2nd lens group G2 which has at least three cemented lenses and has positive refracting power on the whole, and a 3rd lens group G3 which has at least three single lens or cemented lenses and has negative refracting power on the whole; and at least two of at least the three cemented lenses in the 2nd lens group G2 composed of three-element cemented lenses and conditions of 1<f1 /f<4, f2 >|f4|, and 1<|f3|/f<4 are met, where f1 , f2 and f3 are the focal lengths of the 1st lens group G1 , 2nd lens group G2 , and 3rd lens group G3 , respectively and (f) is the focal length of the whole system.
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