| 摘要 |
PURPOSE:To provide easily a variable power optical system having good optical performance by having at least two lens groups, and changing the refracting power of at least one lens group thereof thereby changing the focal length of the entire system. CONSTITUTION:A variable power optical system is constituted of two lens groups, wherein the fracting power of the 1st lens, successively from an object side, is designated as psi1, the refracting power of the 2nd lens group as psi2, and the space between the principal points of these lens groups as E. The variable power optical system maintaining the constant focal plane from focal length 35mm. to 70.417mm. is realized by disposing, for example, the refracting powers in the reference state of the variable power optical system at psi1=-1/50, psi2=1/35, E=35, moving the 2nd lens group by 25mm. on the optical axis, and at the same time by changing continuously the refracting power of the 2nd lens group to 0.02857 0.02771 0.02850. The variable power optical system which is compact and is simple in lens barrel is thus obtd. |
