| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact and inexpensive projector lens which corrects well for aberrations, offers a high magnification ratio, and is compatible with various types of light valves.SOLUTION: A projection lens comprises a negative first lens group G1 and a positive second lens group G2 arranged in order from the expansion side, where the first lens group comprises a negative first front group G11 and a positive first rear group G12 and the second lens group comprises a positive second front group G21 and a negative second rear group G22. The first rear group comprises a single positive meniscus lens having a convex surface on the expansion side. The second front group comprises two positive lenses arranged in contact with each other and the second rear group comprises a biconcave lens and a biconvex lens. The two positive lenses of the second front group are made of a same glass material and have a same lens surface shape. The entire system comprises no more than eight lenses and a diameter of each lens becomes gradually smaller from a lens L11 on the most expansion side toward a lens L24 on the most reduction side. When zooming from the wide angle end to the telephoto end, the first lens group moves toward the reduction side and the second lens group moves toward the expansion side. |
