| 摘要 |
A zoom lens optical system is provided to make the structure compact, to correct chromatic aberration, and to cut down the manufacturing cost with keeping a high image magnification ratio. A zoom lens optical system has a first lens group(I) having positive refractive force, a second lens group(II) having negative refractive force, a third lens group(III) having positive refractive force, and a fourth lens group(IV) having positive refractive force, which are arranged from an object(OBJ) in order. In changing a wide angle range into a telescopic range, the first, second, and third lens groups are magnified to increase the gap between the first and second lens groups, reduce the gap between the second and third lens groups, and widen the gap between the third and fourth lens groups. The magnification of the lens groups satisfies the following formula, 6<=LW/FW+Lt/Ft<=8, where LW is the distance from the first surface of a lens of the first lens group facing the object to an upside(IMG) in the wide angle range, Lt is the distance from the first surface of the lens of the first lens group facing the object to the upside in the telescopic range, FW is the total focal distance in the wide angle range, and Ft is the total focal distance in the telescopic range.
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