Patent ID: 8824063

Claim:
An optical device comprising: at least first and second lens groups which move in a direction of an optical axis to perform an optical zoom operation; an operation member which instructs the optical zoom operation; a first lens group position detection unit which detects a position of the first lens group that moves in accordance with an operation of the operation member; a second lens group position detection unit which outputs a signal corresponding to a position of the second lens group; a storage unit which stores positional relationship information indicating a positional relationship between the first lens group and the second lens group associated with a focal length at the zoom operation; and a control unit which controls the movement of the second lens group based on positional information of the first lens group detected by the first lens group position detection unit and the positional relationship information stored in the storage unit; wherein the second lens group position detection unit includes: a detection element which moves in the direction of the optical axis integrally with the second lens group and includes a light-emitting portion and a light-receiving portion; and a comb tooth member which includes light-shielding regions where a light-shielding state is brought between the light-emitting portion and the light-receiving portion and transmitting regions where a transmitting state is brought between the light-emitting portion and the light-receiving portion, and which is formed by alternately aligning the light-shielding regions and the transmitting regions in the direction of the optical axis; wherein in the light-shielding regions are formed with a first width, the transmitting regions are formed with a second width, and the light-shielding region or the transmitting region corresponding to the initializing position of the second lens group is formed with a third width which is different from the first and second widths; while light is emitted from the light-emitting portion, the control unit determines whether the control state of the second lens group is abnormal based on a signal corresponding to the position o the second lens group which is output from the light-receiving portion of the second lens group position detection unit when the second lens group moves, and the control positional information during the control of the movement of the second lens group, when the control unit determines that the control state of the second lens group is abnormal, the control unit moves the second lens group to the initializing position to perform an initializing operation.