| 摘要 |
<p>A variable magnification optical system suppresses a deterioration in performance caused by a fluctuation of temperature, while maintaining a small size, a wide angle, a large relative aperture, and excellent performance. Further, cost is reducible. The variable magnification optical system includes a negative first lens group, a stop and a positive second lens group, arranged from the object side of the variable magnification optical system in the order mentioned above. The magnification of the variable magnification optical system is changed by changing a distance between the first lens group and the second lens group in the direction of an optical axis. The first lens group includes a negative plastic lens, and the second lens group includes a positive plastic lens. Further, the following formulas (1) and (2) are satisfied: 5.0 < fpp / fw < 7.5 and - 7.0 < fpn / fw < - 6.0 where
fpn is the focal length of the plastic lens having negative refractive power,
fpp is the focal length of the plastic lens having positive refractive power, and
fw is the focal length of the entire system of the variable magnification optical system at a wide angle end.</p> |
