| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact high-performance zoom lens with a small lens aperture which projects an image from a light valve such as a DMD that forms an image by changing reflecting directions of light onto a screen or the like in an enlarged fashion. SOLUTION: The zoom lens is constituted of a first lens group having a positive or negative refractive power as a whole, a second lens group having a negative refractive power as a whole, a third lens group having a positive refractive power as a whole, and a fourth lens group having a positive refractive power as a whole in order from an enlargement side, wherein a variable power as a whole lens system is established by configuring such that the first lens group and the fourth lens group are left fixed while a variable power is effected, the second lens group is made to move on an optical axis in a direction from the enlargement side to a reduction side over a range from a wide angle end to an intermediate area, and in a direction from the reduction side to the enlargement side over a range from the intermediate area to a telephoto end, and the third lens group is made to move on the optical axis in a direction from the reduction side to the enlargement side over a range from the wide angle end to the telephoto end. COPYRIGHT: (C)2008,JPO&INPIT
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