| 摘要 |
There is provided a compact zoom lens with a small lens aperture which projects an image from a light bulb such as mainly a DMD (Digital Micromirror Device) which forms an image by changing reflecting directions of light on to a screen or the like in an enlarged fashion. To attain the object, there is provided a zoom lens including 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, wherein a variable power as a whole lens system of the zoom lens 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 in a direction from a magnifying side to a contracting side over a range from a wide angle end to an intermediate area and is made to move on an optical axis in such a manner as to move in a direction from the contracting side to the magnifying 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 such a manner as to move in a direction from the contracting side to the magnifying side over a range from the wide angle end to the telephoto end.
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