Patent ID: 7522348
Filing Date: 2009-04-21
Classification: G02B

Abstract:
1. A zoom lens comprising in order from a magnification side: a first lens group having a negative refractive power, the first lens group which is fixed during varying of a power of the zoom lens and which executes focusing; a second lens group having a positive refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power, wherein the second, third and fourth lens groups move interrelatedly so as to continuously vary the power of the zoom lens and to correct movement of an image plane caused by the continuous varying of the power of the zoom lens; and a fifth lens group having a positive refractive power, the fifth lens group which is fixed during the varying of the power of the zoom lens, wherein: the first lens group consists of two single lenses including: where Nd denotes refractive index with respect to d-line, and