| 摘要 |
A zoom lens unit, including in order from an object side to an image side: a first lens group (I) having a positive refracting power; a second lens group (II) having a negative refracting power; a third lens group (III) having a positive refracting power; and a fourth lens group (IV) having a positive refracting power, an aperture stop (S) being disposed between the second and the third lens groups, and the third lens group having a positive lens made of an optical glass material which satisfies the following formulae: (1) 1.52 < n d < 1.62; (2) 65.0 < vd < 75.0; (3) 0.015 < Pg,F - (-0.001802×½ d + 0.6483) < 0.050, where, nd represents a refractive index, ½ d represents an Abbe number, and Pg,F represents a partial dispersion ratio being defined as follows: Pg,F=(ng-nF)/(nF-nC), where, ng, nF and nC represent refractive indexes for g line, F line and C line, respectively. |
