| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection lens having a wide field angle, a long back focus and telecentricity, and having a short projection distance and a short entire lens length.SOLUTION: The projection lens include, in the order to a minification side, a negative first lens group I and a positive second lens group II, and is telecentric to the minification side. The first lens group is disposed with a 1A group, a 1B group, and a 1C group. The 1A group is disposed with a double-sided aspherical lens and two negative lenses that are concave in the minification side. The 1B group is disposed with a negative lens that is concave in the minification side, a biconcave lens, and a biconvex lens. The 1C group comprises a positive lens that is concave in the minification side. The second lens group is disposed with a positive lens that is concave in the minification side, an aperture stop, a double-sided aspherical lens, two triplets, a positive lens that is concave in a magnification side, and a double-sided lens. The projection les satisfies the following expressions: 3.0<fb/f<5.0, 6.<|f1/f|<12.0, and 4.2<f2/f<5.4. The fb represents the back focus, and the f, f1, and f2 represent the focal lengths of the entire system, the first lens group and the second lens group respectively. |
