Patent ID: 9715125
Date: 2017-07-25
CPC Classifications: G02B

Claim:
1. A zoom lens including a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power and a fifth lens group having negative refractive power in order from an object side, wherein a surface of the fifth lens group disposed closest to the object side is concave; wherein the lens groups move in magnification change from a wide angle end to a telephoto end such that a gap between the first lens group and the second lens group increases and a gap between the second lens group and the third lens group decreases; a negative lens group disposed closer to an image plane side than a diaphragm among all lens groups is set as a focusing lens group, and the focusing lens group moves toward the image plane side in focusing from infinity to a close object; the zoom lens satisfies conditional expression (1) and conditional expression (3); and the focus lens group is composed of a single lens block of a meniscus shape provided with a concave surface at an image plane side; and satisfies conditional expression (2) below: [Expression 1] where β5T: Lateral magnification in telephoto end of fifth lens group [Expression 2] where ra4: Curvature radius of object side surface of focus lens group rb4: Curvature radius of image plane side surface of focus lens group [Expression 3] where f1: Focal length of first lens group fw: Focal length of the zoom lens at the wide angle end ft: Focal length of the zoom lens at the telephoto end.