| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection lens designed so as to ensure satisfactory performance while having a brightness of about FNo1.8 to FNo1.9, a wide angle and a large aperture with a half field angle of about a little less than 60 degrees during projection. SOLUTION: The projection lens magnifies a plane image and projects and images it. The projection lens includes a first lens group G1 having positive refractive power, and a second lens group G2 having positive refractive power in that order from the magnifying side with the largest air interval between them. In the projection lens, the focal distance f of the entire system and the back focus Bf on the reducing side in the air of the entire system satisfies the following conditions: (1) 3≤Bf/f. COPYRIGHT: (C)2007,JPO&INPIT
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