| 摘要 |
A projection zoom lens includes a first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, and a fourth lens group having a positive refracting power, which are arranged in that order from a screen side toward an image plane side along an optical axis. The first and the fourth lens group are kept stationary, and the second and the third lens group are moved along the optical axis to vary power from a limit wide angle power toward a limit telephoto power. The second lens group includes a 2nd-group 1st positive lens, a 2nd-group 1st compound lens formed by joining a 2nd-group 2nd positive lens having a convex surface on the image plane side and a 2nd-group 1st negative lens having a concave surface on the screen side, and a 2nd-group 3rd positive lens arranged in that order from the screen side toward the image plane side. The third lens group includes a 3rd-group 1st meniscus lens having a concave surface on the image plane, a 3rd-group 1st compound lens formed by joining a 3rd-group 1st negative lens having opposite concave surfaces and a 3rd-group 1st positive lens having opposite convex surfaces, and a 3rd-group 2nd meniscus lens having a convex surface on the image plane side arranged in that order from the screen side toward the image plane side. The first lens group has a focal length f1, the 2nd-group 1st positive lens and the 2nd-group 1st compound lens have a composite focal length f2AB of a sign opposite to that of the focal length f1, and the focal length f1 and the composite focal length f2AB meet an inequality: 0.5<|f1/f2AB|<2.0.
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