| 摘要 |
PURPOSE: To provide an objective lens for an achromat-class microscope of low magnification compensating various aberrations, correcting off-axial chromatic aberration solely by the objective lens and having an extremly flat image plane over a wide visual field in spite of a comparatively short focal distance and the simple lens constitution. CONSTITUTION: This lens is composed of a first lens group G1 having a positive lens, a second lens group G2 composed of a single negative lens and a third lens group G3 having a joined lens of a positive refractive power and, by representing the focal distance of a whole system by (f), the focal distance of the first lens group by f1 , the focal distance of the second lens group by f2 , the Abbe number of the positive lens of the first lens group byν1 and the Abbe number of the negative lens of the second lens group byν2 , the respective conditions: (ν2 -ν1 )>10, 0.05<=|f2 /f|<=0.12, 0.28<=|f2 /f1|<=0.40 are satisfied.
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