| 摘要 |
PROBLEM TO BE SOLVED: To make the entire system of a zoom lens used as a projection lens in an image projecting device such as a liquid crystal projector smaller in size than hitherto while completely compensating an aberration such as chromatic aberration. SOLUTION: This zoom lens used as a projection lens is provided with a 1st group having negative refractive power, a 2nd group having negative refractive power, a 3rd group having positive refractive power, a 4th group having negative refractive power and a 5th group including at least one diffraction optical device and having positive refractive power in order from an enlargement conjugate side. The 2nd group, the 3rd group and the 4th group are moved in the case of varying power from a wide-angle end to a telephoto end.
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