| 摘要 |
PROBLEM TO BE SOLVED: To maintain magnification and focus, even if temperature change occurs in an optical apparatus. SOLUTION: The optical instrument includes: an optical system having a plurality of lens groups, including a focus lens group and a variator lens group; a lens drive means driving the focus lens group and the variator lens group; a temperature detection means for detecting the temperature of the construction member of the optical system; and a control means moving the focus lens group, so as to correct the change of an image forming surface due to the movement of the variator lens group. When the temperature detected by the temperature detection means is higher than a predetermined value, the control means drives the focus lens group and the variator lens group, so as to maintain a predetermined positional relation, thereby correcting the fluctuation of an image forming surface position. COPYRIGHT: (C)2010,JPO&INPIT
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