| 摘要 |
A projection lens for projecting image information displayed on a reduction side conjugate position to a magnification side conjugate position, including a negative first lens group, a positive second lens group, a positive third lens group, and a positive fourth lens group arranged in this order from the magnification side, which satisfies predetermined conditional expressions. |
| 主权项 |
1. A projection lens for projecting image information displayed on a reduction side conjugate position to a magnification side conjugate position, the projection lens comprising:
a first lens group having a negative power, a second lens group having a positive power, a third lens group having a positive power, and a fourth lens group having a positive power arranged in this order from the magnification side, wherein the projection lens satisfies conditional expressions (1), (2-1), (3), and (5) given below:
Bf/f≦1.0 (1);0.7≦d34/f≦2.0 (2-1);0.5≦YI/f (3); andf×YP/(YI×YA)≦3.0 (5),where:
Bf is a back focus on the reduction side (air equivalent length); f is a focal length of the entire projection lens, including said first, second, third, and fourth lens groups; d34 is an air equivalent distance on the optical axis between the third lens group and fourth lens group; YI is a maximum height of effective luminous flux at the reduction side conjugate position; YP is a maximum height of an off-axis principal ray in the projection lens; and YA is a maximum height of axial luminous flux in the projection lens; wherein said projection lens comprises a total of six or fewer lenses. |
