Lens controller

1. A lens controller which electrically controls a focus and a zoom of a taking lens, the lens controller comprising:

an AF control device which automatically controls the focus of the taking lens so that a given subject imaged by the taking lens is in focus; and

a view angle correction device which keeps an angle of view of the taking lens constant by moving the zoom of the taking lens to prevent a variation of the angle of view associated with a movement of the focus moved by the AF control device, wherein

when the focus is moved by the AF control device, the view angle correction device detects a current absolute position of the focus by a position detecting device, obtains a position of the zoom for preventing the variation of the angle of view associated with the movement of the focus moved by the AF control device based on the detected current absolute position of the focus and according to previously stored view angle correction data, and moves the zoom to the obtained position, and

the view angle correction device obtains the position of the zoom for preventing the variation of the angle of view by interpolating a relationship between focus positions and corresponding zoom positions for which the variation of the angle of view is prevented, based on the view angle correction data.

2. The lens controller according to claim 1 , further comprising

an MF control device which controls the focus of the taking lens to be in a target focus position specified based on a manual operation, wherein

the view angle correction device obtains the position of the zoom for preventing the variation of the angle of view based on the target focus position and moves the zoom to the obtained position when the focus is moved by the MF control device.

3. The lens controller according to claim 1 , wherein the view angle correction data comprises mathematic expression data, and the relationship between focus positions and zoom positions for preventing the variation of the angle of view comprises a constant view angle curve calculated by interpolation based on the mathematical expression data.

4. A method for controlling a focus and a zoom of a taking lens to prevent a variation of the angle of view associated with a movement of the focus, comprising:

when the focus is moved by an AF control device which automatically controls the focus of the taking lens so that a given subject imaged by the taking lens is in focus,

detecting a current absolute position of the focus;

obtaining a position of the zoom for preventing the variation of the angle of view associated with the movement of the focus moved by the AF control device based on the current absolute position of the focus, according to previously stored view angle correction data; and

moving the zoom to the obtained position, wherein

obtaining the position of the zoom for preventing the variation of the angle of view comprises interpolating a relationship between focus positions and corresponding zoom positions for which the variation of the angle of view is prevented, based on the view angle correction data.

5. The method according to claim 4 , further comprising:

when the focus is moved by an MF control device which controls the focus of the taking lens to be in a target focus position specified based on a manual operation,

obtaining the position of the zoom for preventing the variation of the angle of view based on the target focus position, and

moving the zoom to the obtained position.