Patent ID: 7855842

Claim:
A zoom lens unit comprising, in order from an object side to an image surface side: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; and a fourth lens group having a positive refracting power, wherein when changing magnification from a wide-angle end to a telephoto end, an interval between the first lens group and the second lens group increases, an interval between the second lens group and the third lens group decreases, and an interval between the third lens group and the fourth lens group increases, wherein when performing focusing on a close range object at least at the telephoto end, with reference to a focused state on an infinite object, the first lens group and the second lens group are fixed, generally only the fourth lens group is moved to the object side, and when the focusing becomes impossible to be accomplished by only moving the fourth lens group, the third lens group is moved to the image surface side to perform the focusing.