| 摘要 |
PROBLEM TO BE SOLVED: To obtain a projection lens whose entire length is short, which secures long back focus though it is compact, by which even the periphery of an image plane is made bright and whose distortion aberration and transverse chromatic aberration are completely compensated by providing four lens groups, constituting the 2nd to 4th lens groups of two lenses, respectively, and making the lens satisfy a specified expression. SOLUTION: This projection lens is provided with the 1st lens group 1 having negative power, the 2nd lens group 2 having positive power, a 3rd lens group 3 having negative power and the 4th lens group 4 having positive power in order from a screen side. The 2nd to the 4th lens groups 2 to 4 are constituted at least two lenses, respectively. When it is assumed that the focal distance of the entire system of the projection lens is f0, the focal distances of the 1st to the 4th lens groups 1 to 4 are f1g to f4g, respectively, and a distance at the time of setting space from the rear end of the final lens to an image surface to all air is (bf), the projection lens satisfies relation expressed by expressions (1) -0.8<f1g/f0<-0.6, (2) 0.5<f2g/f0<0.7, (3) -0.7<f3g/f0<-0.4, (4) 0.7<f4g/bf<0.9.
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