DE3443558

The disclosed automatic focus adjusting device is of the active type whose focusing apparatus becomes operative either when an image of an object goes out of focus, or when the object image has started to move. In one embodiment, a first detecting circuit receptive of index signals reflected from the object detects when the object becomes out of focus based on the high frequency component of the index signal. A second detecting circuit also receptive of index signals reflected from the object detects when the object has moved. An automatic focus control circuit reinstitutes the focusing operation in response to either or both of the detecting circuits. Accordingly, an in-focus object is kept in-focus despite changes in object brightness or movement.