| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection lens which offers a long back focus, a wide view angle, and good performance and can be manufactured at low cost with a small number of lenses.SOLUTION: A projection lens comprises a first lens group I having negative refractive power and a second lens group II having positive refractive power, arranged in order from the expansion side with a largest air gap in the lens system therebetween, and is substantially telecentric on the reduction side. The first lens group I comprises a 1A group, a 1B group, and a 1C group, where the 1A group includes a lens having an aspherical surface on each side, and the 1B group comprises a negative meniscus lens having convex surface on the expansion side, a negative lens having a larger curvature on the reduction side, and a biconcave lens, while the 1C group includes at least one positive lens. The second lens group II includes one lens having an aspherical surface, two sets of three lenses, and an aperture stop located near a lens on the most expansion side, where each set of three lenses comprises either three lenses arranged close to each other, or three lenses of which two or more lenses are cemented together. |
