| US 7,526,190 B2 | ||
| Automatic focusing apparatus and optical instrument including automatic focusing apparatus | ||
| Takashi Kato, Utsunomiya (Japan) | ||
| Assigned to Canon Kabushiki Kaisha, Tokyo (Japan) | ||
| Filed on Sep. 11, 2006, as Appl. No. 11/530,545. | ||
| Claims priority of application No. 2005-266059 (JP), filed on Sep. 13, 2005. | ||
| Prior Publication US 2007/0058960 A1, Mar. 15, 2007 | ||
| Int. Cl. G03B 17/00 (2006.01); G03B 13/34 (2006.01) | ||
| U.S. Cl. 396—73 [396/71; 396/80; 396/123; 359/672] | 7 Claims |
| 1. An optical instrument including an automatic focus adjustment device, comprising:
an image taking optical system, including a focus lens unit and a magnification unit, configured to form a subject image;
a focal length switching unit for changing a focal length of the image taking optical system in accordance with a magnification
level established by said magnification unit;
a position detecting unit for detecting a position of the focal length switching unit;
a focus detecting unit for detecting a focusing position of the subject image;
a focus detection area setting unit for setting a focus detection area in response to detection of said focusing position
by the focus detecting unit; and
a control unit for controlling a position of the focus lens unit based on a detection result of the focus detecting unit,
wherein:
the control unit prevents movement of the focus lens unit when the position detecting unit detects that the focal length switching
unit is being changed from a predetermined magnification level to another magnification level, and
when the focus detection area gets out of a predetermined imaging range, the focus detection area is adjusted in accordance
with the position of the focal length switching unit such that the subject image constantly maintains the focusing position.
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