| 摘要 |
PURPOSE:To facilitate aberration corrections, by providing the 1st- the 3rd lens groups having a positive, a negative, and a positive refracting power and making the paraxial lateral magnification of the 2nd negative lens group positive at both a telephoto and a wide-angle position. CONSTITUTION:This lens system consists of the 1st movable lens group I having the positive refracting power, the 2nd lens movable lens group II having the negative refracting power, and the 3rd fixed lens group III having the positive refracting power. When the whole system has the longest total focal length, the 1st and the 2nd lens groups I and II are close to each other and when it has the shortest focal length, on the other hand, the 2nd and 3rd lens groups II and IIIare close to each other. This is a variable power lens system which holds the paraxial lateral magnification of the 2nd lens group II positive by changing the focal length; the 1st lens group I includes at least two lenses and one negative lens and the 2nd lens group II includes at least one positive lens and one negative lens. |
