Patent ID: 7450315

Claim:
A zoom lens comprising, in order from an object side: a first group having a positive refractive power; a second group having a negative refractive power; a diaphragm; a third group having a positive refractive; and a fourth group following the third group, wherein: when a power of the zoom lens varies from a wide-angle end to a telephoto end, the second group is moved along an optical axis toward an image side with the first and third groups fixed to the optical axis so as to vary the power and the fourth group is moved along the optical axis to perform correction of a position of the image plane, which is associated with the variation of the power, and focusing, and the first group comprises, in order from the object side, a first lens of the first group having a positive refractive power, a second lens of the first group having a positive refractive power and a third lens of the first group having a negative refractive power.