Patent ID: 7526190
Filing Date: 2009-04-28
Classification: G02B,H04N

Abstract:
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.