Patent ID: 7599124

Claim:
In a large-aperture-ratio inner-focusing telephoto zoom lens that has four groups of lens pieces, namely, the 1st lens group of positive refractive power, the 2nd lens group of negative refractive power, the 3rd lens group of positive refractive power, and, the 4th lens group of positive refractive power arranged in series on the basis of “closer to a subject first,” and that has the 2nd and 3rd lens groups moved along the optical axis to vary a magnification power, the 1st lens group includes the leading subgroup of lens pieces or foremost lens subgroup G 1 F and the trailing subgroup of lens pieces or rear lens subgroup G 1 R where the G 1 F has two of a negative lens and a positive lens cemented into a single piece of composite lens while the G 1 R has a composite lens of one negative lens and two positive lenses in series, and the rear lens subgroup G 1 R is moved along the optical axis for the focusing, and the telephoto zoom lens has an optical property that satisfies requirements as follows: 1.3 <f 1 /fw< 1.9 (1) where f 1 is a focal length of the 1st lens group, and fw is a focal length of the telephoto zoom lens in the wide-angle view mode.