| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-performance, small and lightweight zoom lens for projection which is suitable for enlarging and projecting an image from the light valve of a DMD (Digital Micro-mirror Device) or the like. SOLUTION: The zoom lens for projection has a 1st lens group G1 having negative refractive power, a 2nd lens group G2 having positive refractive power, and a 3rd lens group G3 having positive refractive power in order from an enlargement side. In the case of varying power from a wide angle end to a telephoto end, the 1st lens group G1 and the 2nd lens group G2 are moved and the 3rd lens group G3 is fixed. The 3rd lens group G3 is arranged in front of the light valve I, and transmits an incident light beam from an illumination optical system and a reflected light beam from the light valve. In the case of focusing, only the 1st lens group G1 is moved to perform focusing. The zoom lens for projection satisfies a conditional expression (1) concerning the movement of the 1st lens group. COPYRIGHT: (C)2006,JPO&NCIPI
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