| 摘要 |
PROBLEM TO BE SOLVED: To provide compact, low-cost and satisfactory optical performance with which the angle of view at a wide angle end is wide, the angle of view at a telescopic end is narrow and a standard focal distance is provided by satisfying a specified conditional expression with the focal distance or the like of a lens group. SOLUTION: A first lens group I has a negative lens and a positive lens from the side of an object, has at least one non-spherical surface formed so as to weaken negative refraction power gradually from the center of an optical axis to the outer peripheral part of the lens, and satisfies the following conditions of 0. 7<|f1|/SKw<0.9, 0.6<|M2|/SKw<0.9 and -0.1<M1 /M2 <0.2. In this case, f1 expresses the focal distance of the first lens group I, SKw expresses a distance from the surface of the final lens at the wide angle end to an image surface, M1 and M2 respectively express the moving amounts of first and second lens groups I and II in the case of magnification from wide angle end to telescopic end and concerning a code, the advancing direction of light is positive. In the case of zooming from the wide angle end to the telescopic end, the first lens group I is moved to the side of the image surface first and moved to the side of the object from the middle, the second lens group II is moved to the side of the object, and a third lens group III is fixed.
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