| 摘要 |
PURPOSE:To reduce aberrational variation during power variation and to realize compact constitution by providing at least one distributed index lens in the 2nd lens group. CONSTITUTION:The lens system consists of the 1st positive lens group I and the 2nd negative lens group II successively from an object side and the object- side lens of the 2nd lens group II consisting of two lens elements is the radial type distributed index lens having positive transfer power, thus forming a two- group type compact zoom lens wherein the 1st lens group I and the 2nd lens group II move during power variation. Thus, the distributed index lens is applied so as to suppress an increase in astigmatism on a high field angle at a wide-angle end normally to the contrary, thereby reducing the astigmatism at the wide angle end. Further, the spherical aberration at the final end R6 of the 1st lens group I which tends to become under at a telephoto end is compensated to an over side by the transfer power in the distributed index lens to compensate the spherical aberration.
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