| 摘要 |
PROBLEM TO BE SOLVED: To obtain a zoom lens which easily obtains a high zoom ratio, also, properly corrects axial chromatic aberration at a telephoto side, and which can be easily reduced in size and weight. SOLUTION: The zoom lens includes, in order from an object side to an image side: a first lens group which is stationary in zooming and has positive refractive power; a second lens group which moves for changing magnification and has negative refractive power; a third lens group which moves to correct image plane variation caused by the variable power, and has negative refractive power; and a fourth lens group which is stationary in zooming and has positive refractive power. The first lens group comprises, in order from the object side to the image side: a negative lens; a positive lens; a positive lens; and a positive lens. An Abbe's numberνof a material of the negative lens of the first lens group and a partial dispersion ratioθof the material are denoted asνn andθn, respectively, an average value of Abbe's numberνof materials of the positive lenses of the first lens group and an average value of partial dispersion ratioθof the materials are denoted asνpa andθpa, and the refractive power of the negative lens of the first lens group is denoted asΦn, each of which is properly set. COPYRIGHT: (C)2011,JPO&INPIT |
