| 摘要 |
A variable power optical system for a copying machine includes a first lens group having a negative power, a second lens group having a positive power, and a third lens group having a negative power. All three lens groups are moved to vary distances D1 and D2 between the first and second lens groups and between the second and third lens groups, to thereby vary the magnification in a range from an actual size to an enlargement range, while maintaining a constant distance between an object and an object image. In the range from the actual size to the enlargement range, the optical system satisfies the relationship defined by 0.60<|(Dm1-De1)/(Dm2-De2)|<0.85, wherein "Dmi" designates a value of Di (i=1,2) at a maximum magnification, and "Dei" designates a value of Di (i=1,2) at an actual size, respectively.
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