| 摘要 |
PROBLEM TO BE SOLVED: To improve the image quality of the periphery part of an image plane, to make performable high-quality video projection all over the area of the image plane and to improve the illuminance of the periphery part of the image plane. SOLUTION: This projection lens is equipped with a 1st lens group G1 having negative refractive power, a 2nd lens group G2 having positive refractive power and a 3rd lens group G3 having positive refractive power in order from an image surface side. A 1st lens component L1 turning its convex surface to an image side and turning its concave surface to an object side adjacently to an aperture diaphragm St is arranged on the side of the 2nd lens group G2 nearest to the object side. A 2nd lens component L2 turning its concave surface to the object side and having negative refractive power is arranged on the side of the 3rd lens group G3 nearest to the image surface side, and a 3rd lens component L3 having negative refractive power is arranged on the side of the 3rd lens group G3 nearest to the object side. By such basic constitution, aberration is excellently compensated to the periphery of image height while keeping back focus equal to or above a specified value.
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