Patent ID: 9557538
Date: 2017-01-31
CPC Classifications: G02B

Claim:
1. A projection zoom lens, consisting of: a first lens group, which is provided most toward the magnification side, has a negative refractive power, and is fixed while changing magnification; a final lens group, which is provided most toward the reduction side, has a positive refractive power, and is fixed while changing magnification; and an intermediate group provided between the first lens group and the final lens group, constituted by a plurality of moving lens groups that move independently of each other along the optical axis while changing magnification; the moving lens group provided most toward the reduction side within the intermediate group comprising a lens having a negative refractive power, a lens having a positive refractive power, a lens having a negative refractive power, and a lens having a positive refractive power, provided in this order from the magnification side; and the projection zoom lens satisfying Conditional Formulae (1), (2), and (9) below: wherein Rf2 is the radius of curvature of the front surface of the second lens from the magnification side within the lens group most toward the reduction side from among the lens groups that move while changing magnification, Rr2 is the radius of curvature of the rear surface of the second lens from the magnification side within the lens group most toward the reduction side from among the lens groups that move while changing magnification, Rf3 is the radius of curvature of the front surface of the third lens from the magnification side within the lens group most toward the reduction side from among the lens groups that move while changing magnification, Bf is the back focus of the entire system at the reduction side at the wide angle end as an air converted length, and Imφ is the maximum effective image circle diameter at the reduction side.