Zoom lens and video camera using the same

摘要

A zoom lens is described that includes: a first lens group having positive refracting power and fixed with respect to an image plane; a second lens group having negative refracting power and varying power, wherein the power is varied by moving along an optical axis; a third lens group having positive refracting power and fixed with respect to the image plane; and a fourth lens group having: positive refracting power and moving along an optical axis so as to keep the image plane varied by movement of the second lens group and an object at a predetermined position from a reference surface. The first, second, third, and fourth lens groups are disposed from the object side to the image plane side in this order. The second lens group is composed of two negative lenses and one positive lens. The third lens group is composed of two positive lenses and one negative lens. The fourth lens group is composed of a positive lens. The second to fourth lens groups include at least one aspherical surface, respectively.