Patent ID: 9638902
Date: 2017-05-02
CPC Classifications: G02B

Claim:
1. A projection zoom lens consisting of: a first lens group having a positive refractive power fixed while changing magnification, a second lens group having a negative refractive power that moves while changing magnifications, a third lens group having a negative refractive power that moves while changing magnification, a fourth lens group having a positive refractive power that moves while changing magnification, and a fifth lens group having a positive refractive power that is fixed while changing magnification in this order from the magnification side; and an aperture stop positioned between adjacent moving lens groups or within one moving lens group, wherein the numerical number of the zoom lens is set to be constant over the entire zoom range, the reduction side is configured to be telecentric, and the projection zoom lens satisfies conditional formulas (4) and (5): where, Bf: the back focus, which is an air converted length, at the reduction side of the entire system at the wide angle end, Imφ: the maximum effective image circle diameter, and L: the distance between the most-magnification-side lens surface and the most-reduction-side lens surface along the optical axis when the projection distance is infinite.