| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection lens which has excellent performance and is suitable as the projection lens for a single-plate type rear liquid crystal projec tor. SOLUTION: This lens has a negative and positive refracting power distribution from its enlargement side to its reduction side and an aperture stop S in the lens system and includes a meniscus negative lens which is convex to the enlargement side as a 2nd lens 12 counted from the enlargement side, a negative lens as a 3rd lens 13, and positive lenses as 1st and 2nd lenses 19 and 18 counted from the reduction side; and those 1st and 2nd lenses counted from the reduction side have their convex surfaces opposite each other and one is a biconvex lens and other one is a meniscus positive lens or vice versa and has telecentric even on the reduction side, and they meet a condition of (1)νd P-νd M>25, where yap is the mean number of the Abbe number of the material used for the positive lens positioned more on the reduction side than the aperture stop andνd M is the mean value of the Abbe number of the material used for a negative lens.
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