Patent ID: 8817384

Claim:
A zoom lens device comprising a focusing lens group on an object side and a variator lens group next thereto, and a temperature sensor, wherein the focusing lens group includes a focusing lens and a temperature-based correction lens as part of the focusing lens group, the temperature-based correction lens being located closest to an object in the focusing lens group for correcting a change in focal point caused by a temperature change around the focusing lens group, wherein the zoom lens device further comprises a temperature-based correction lens driving mechanism for moving the temperature-based correction lens independently of the positions of the focusing lens and the variator lens group, and a temperature-based correction controller, wherein the temperature-based correction lens is moved separately from the focusing lens of the focusing lens group by the temperature-based correction lens driving mechanism along an optical axis to a position corresponding to a temperature detected by the temperature sensor without any correction based on temperature of positions of the focusing lens and the variator lens group, based on a corresponding relationship between a position of the temperature-based correction lens for correcting a change in focal point caused by an ambient temperature change around the focusing lens group and an ambient temperature detected by the temperature sensor, the corresponding relationship being stored in the temperature-based correction controller as an initial setting, and wherein the focusing lens group, the variator lens group, a compensator lens group, and a master lens group are arranged in this order from the object side, and wherein part of the master lens group is moved by a temperature-based correction lens driving mechanism for the master lens group along the optical axis to a position corresponding to a temperature detected by the temperature sensor.