| 摘要 |
A projection lens which is, despite the use of plastic lenses, capable of performing appropriate temperature correction, compact and of low cost, and capable of attaining excellent image forming performance. The projection lens has a first lens group having negative refracting power and a second lens group having positive refracting power, in that order from the screen side. The first lens group includes a negative meniscus lens (1b), a plastic lens, having a nonspherical surface whose convex surface is directed toward the screen side. The second lens group includes a negative lens (2b), a plastic lens, having a nonspherical surface and includes two or more positive lenses exhibiting anomalous dispersion and a negative refractive index temperature coefficient. Image surface variation in temperature variation caused by the negative refractive index temperature coefficient of the plastic lenses (1b, 2b) in the first and second lens groups is corrected by a specified negative refractive index temperature coefficient of these positive lenses. ® KIPO & WIPO 2007
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