Zoom lens unit, imaging apparatus and portable information terminal device

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, the third lens group is capable of being moved to the image surface side, and the fourth lens group is capable of being moved to the object side, and
• wherein a focusing range of the zoom lens unit at least at the telephoto end includes a first range in which focusing on a subject located in a region from infinity to a specific range is possible, and a second range in which focusing on a subject located in a closer range including the specific range is possible, wherein when the subject is in the first range, only the fourth lens group is moved to the object side to perform the focusing, when the subject is in the second range, after the third lens group is moved to a position which is different from that when the focusing is performed on a subject located in the first range and is fixed, the fourth lens group is moved to the object side, to perform the focusing.

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, the third lens group is capable of being moved to the image surface side, and the fourth lens group is capable of being moved to the object side, and
• wherein the following formula is satisfied;
• −0.5<βTmax<−0.1 (1) in which βTmax represents a maximum image magnification at the telephoto end.