| 摘要 |
The present invention is directed to provide a compact and light-weighted projection lens system that is capable of projecting an image at an angle as wide as 75 degrees with sufficient field angle and brightness as represented by F number of approximately 2.4, that is capable of effectively correcting chroic aberration of magnification and aberration of distortion and exhibiting optical stability against environmental variations, and that is suitable to obtaining an extraordinarily fine image by the magnification and projection. In the projection lens system that comprises first to third groups of lenses in the order from the closest a magnified image where the first lens group of negative refractive power includes one or more aspherical lenses each having an aspherical plane on one or both of the surfaces, the second lens group of positive refractive power includes one or more positive lenses, and the third lens group of positive refractive power includes one or more cemented triplet lenses comprised of three lenses of positive, negative, and positive attributes joined in this order, a projection lens system is characterized by terms and conditions defined as in the following formulae: 0.9<=|f1|/|<=1.4 (1) 2.1<=f2/f<=3.4 (2) 1.9<=f3/f<=2.8 (3)
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