| 摘要 |
An objective of some 10 magnifications usable with microscopes, etc. which has an increased numerical aperture and working distance, including a first lens component that is a cemented lens consisting of negative and positive lens elements, a second lens component a third lens component, a fourth lens component consisting of a cemented lens and a fifth lens component having a positive refractive power, characterized by satisfying the following conditions: nu I2- nu I1>20 (1) nI1-nI2>0.2 (2) wherein: nI1 is the refractive index of d-line of the negative lens element of the first component, nu I1 is the Abbe's number of said negative lens element of the first lens component, nI2 is the refractive index for d-line of the positive lens element of the first lens component, and nu I2 is the Abbe's number of said positive lens element of the first lens component.
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