| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve a projection lens which is inexpensive because the number of lenses is small, has a wide angle of view, a long back focus, and a telecentric performance on a reduction side, is reduced in various aberrations, and can obtain a bright image having an F number of about 1.8. <P>SOLUTION: The projection lens is configured in such a manner that a first lens group I having negative refractive power and a second lens group II having positive refractive power are arranged in order from an enlargement side to the reduction side, and an aperture diaphragm S is arranged in the vicinity of a lens arranged on the most enlargement side of the second lens group, and the projection lens is telecentric on the reduction side. The first lens group I comprises a 1A group, a 1B group, and a 1C group in order from the enlargement side to the reduction side. The second lens group II is configured in such a manner that a positive lens having a large curvature on the enlargement side, a lens having an aspherical surface, a cemented lens CB obtained by sticking three lenses, and a positive lens having a large curvature on the reduction side are arranged in order from the enlargement side to the reduction side. A back focus Bf, the focal distance f of the entire system, the focal distance f1 of the first lens group, the focal distance f2 of the second lens group and a half angle of view (degree) ω satisfy conditions (1) to (4). <P>COPYRIGHT: (C)2011,JPO&INPIT |
