Patent ID: 9739989
Date: 2017-08-22
CPC Classifications: G02B,H04N

Claim:
1. A projection zoom lens consisting of, in order from the magnification side to the reduction side: a first lens group having a negative refractive power, which is fixed when changing magnification; a second lens group having a positive refractive power, which moves when changing magnification; three third lens groups, which move when changing magnification; and a final lens group, which is fixed when changing magnification, wherein the distances among all adjacent lens groups change when changing magnification, the first lens group has a sub lens group consisting of a first lens, a second lens, and a third lens from the magnification side, the sub lens group having a negative refractive power, the first lens is a single lens having an aspherical surface with a concave surface toward the magnification side in the paraxial region and a negative refractive power in the paraxial region, the second lens is a single lens having an aspherical surface, the intersection between the surface of the first lens toward the magnification side and a principal light ray at a maximum angle of view is positioned more toward the reduction side than the intersection between the surface of the first lens toward the magnification side and the optical axis, the intersection between the surface of the first lens toward the reduction side and the principal light ray at the maximum angle of view is positioned more toward the reduction side than the intersection between the surface of the first lens toward the reduction side and the optical axis, the intersection between the surface of the second lens toward the magnification side and the principal light ray at the maximum angle of view is positioned more toward the reduction side than the intersection between the surface of the second lens toward the magnification side and the optical axis, the intersection between the surface of the second lens toward the reduction side and the principal light ray at the maximum angle of view is positioned more toward the reduction side than the intersection between the surface of the second lens toward the reduction side and the optical axis, and all of conditional formulae (1) through (3) below are satisfied: and wherein dn