| 摘要 |
A zoom lens includes, in the order from the object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power. The first and third lens units are stationary. The second lens unit is moved in one direction to vary the magnification. The fourth lens unit is moved so as to compensate for the shift of an image plane resulting from the variation of the magnification, and focusing is performed by moving the fourth lens unit. The third lens unit has a bi-convex lens and a negative meniscus lens having a strong concave surface facing the object side, and the fourth lens unit has a negative meniscus lens having a strong concave surface facing the image side, a bi-convex lens and a positive lens having a strong convex surface facing the object side.
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