| 摘要 |
PURPOSE:To obtain a compact lens system while correcting spherical aberration, etc., by moving the 1st - the 3rd lens groups to an object side for focusing so that the air gap between the 1st and the 2nd lens groups and the air gap between the 2nd and the 3rd lens groups both increase. CONSTITUTION:The lens system consists of three groups, i.e. the 1st lens group I having positive refracting power, the 2nd group II having positive refracting power, and the 3rd lens group III having negative refracting power successively from the object side. When focusing from an infinite-distance object to a short-distance object is performed, the lens groups are all moved so that the air gap between the 1st lens group I and the 2nd lens group II and the air gap between the 2nd lens group II and the 3rd lens group III both increase. Further, the lens system is composed so that inequalities I and II may hold. |
