| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable focal finite zoom lens constituted, so that a large screen is obtained by a projecting lens for enlarging/projecting a DMD, a very bright projection screen is obtained with less distortions, and a high definition image may be obtained, even though the zoom lens is provided with power-varying function. SOLUTION: The zoom lens is constituted by arranging a 1st group, a 2nd group, a 3rd group and a 4th group, in this order from a screen side. In the case of varying the power between a wide-angle side and a telephoto side, the 2nd group, the 3rd group and the 4th group are moved in non-linear fashion. Each focal distance F1 to F4 up to the 1st to 4th groups and the total focal distance Fw at the wide-angle side satisfy prescribed conditions, and abnormal dispersion lenses are used for two or more lenses in the 2nd group and the rear group lens in the 4th group, and a low dispersion lens is used for the final lens of the front group in the 4th group.
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