Patent ID: 9075224
Filing Date: 2015-07-07
Classification: G02B

Abstract:
1. A zoom lens substantially consisting of, in order from an object side: a first lens group that has a positive refractive power and is fixed during magnification change, wherein the first lens group substantially consists of, in order from the object side, a first-group first lens sub-group and a first-group second lens sub-group; a second lens group that has a negative refractive power and is moved along an optical axis during magnification change; a third lens group that has a negative refractive power and corrects for fluctuation of an image plane along with magnification change; and a fourth lens group that has a positive refractive power and is fixed during magnification change, wherein focusing of an object at a distance between infinity and a predetermined distance is achieved by moving the first-group second lens sub-group along the optical axis, focusing of an object at a closer distance than the predetermined distance is achieved by moving the third lens group along the optical axis, and the conditional expressions below are satisfied: where f3 is a focal length of the third lens group, ft is a focal length of the entire system at a telephoto end, and k3 is an amount of movement of the third lens group to achieve focusing in the range between the predetermined distance and a minimum object distance at the telephoto end.