| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact zoom lens having high performance for enlarging and projecting an image from a light bulb for forming the image by changing the direction of reflection of light such as DMD or the like and having small lens aperture. SOLUTION: The zoom lens having variable power is composed of a group of first lenses having negative refractive power on the whole, a group of second lenses having positive refractive power on the whole, and a group of third lenses having positive refractive power on the whole, arranged in this order from an enlargement side. The group of first lenses includes five lenses, namely, the negative lens, the negative lens, the positive lens, the negative lens, and the positive lens arranged in this order from the enlargement side. The group of second lenses includes five lenses, namely, the positive lens, the negative lens having a meniscus shape being recessed on the enlargement side, the positive lens, the negative lens, and the positive lens, arranged in this order from the enlargement side. The group of third lenses is constituted by arranging one positive lens. COPYRIGHT: (C)2011,JPO&INPIT
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