Abstract: A camera system includes a zoom driving mechanism driven by a motor for varying the focal length of a lens, a detecting device for detecting the focal length of the lens, and a controller for automatically stopping the motor after a predetermined time period from the time when the detecting means detects the fact that the focal length of the taking lens reaches a telephoto end or a wide-angle end.

Abstract: This invention concerns with a drive circuit for a vibratory-wave motor and, in particular, is to provide a motor drive circuit in which there is provided a voltage variable circuit for automatically varying the voltage applied to the motor to follow up the variation of the frequency of a driving high-frequency signal to the motor, whereby the voltage that affords an optimum drive efficiency in response to the frequency variation is applied to the motor.

Abstract: The present invention provides a camera system comprising: a zoom driving means driven by a battery as a power source, for varying a focal length of a taking lens; other driving means driven from the battery as a power source; a detecting means for detecting whether the other driving means are being executed or the other driving means are to be executed; and a control means for prohibiting the execution of the zoom driving means when the detecting means detects the fact that the other driving means are being executed or that the other driving means are to be executed.

Abstract: In a drive circuit for a vibratory-wave motor, there is provided a changeover circuit for alternately changing over a direction in which a current is supplied to a primary coil of a transformer in response to a frequency signal, a low-voltage power source is used as a power source of the changeover circuit, and a low voltage is boosted by the switching operation of the changeover circuit to obtain a frequency high voltage for driving the vibratory-wave motor.