| 摘要 |
PROBLEM TO BE SOLVED: To obtain a projection lens for a projector where peripheral extinction is reduced, which can be made nearly telecentric on a reducing side, and whose the aperture ratio can be made large and the various kinds of aberration can be made excellent by making an angle formed by a main light beam from a lens and an optical axis to be <=2.5 deg. and satisfying a specified expression. SOLUTION: A first lens L1 consisting of a biconvex lens, a second lens L2 consisting of a positive meniscus lens, a third lens L3 consisting of a biconcave lens, a joint lens of a fourth lens L4 consisting of a biconcave lens and a fifth lens L5 consisting of a biconvex lens, an eighth lens L8 consisting of a joint lens biconvex lens of a sixth lens L6 consisting of a biconcave lens and a seventh lens L7 consisting of a biconvex lens and a ninth lens L9 consisting of a positive meniscus lens are arrayed in this order and also satisfy expressions [I]-[IV]. The expression [I] is 0.40<F/F56<1.4, the expression [II] is 1.75<nAVE, the expression [III] is 35<υAVE<55, the expression [IV] is -2.5<F/F2<-0.5 and provided that, F means the focal distance of all systems and F56 means the synthetic focal distance of the fifth lens group and the sixth lens group.
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