Method of driving vibration actuator, drive device, and image pickup apparatus

An image pickup apparatus comprising:

• a lens;
• a vibration actuator that moves said lens in an optical axis direction;
• an image pickup element that picks up an optical image formed by said lens;
• and
• a drive device that drives said vibration actuator,
• said vibration actuator including:
• a vibrating body formed by attaching an electromechanical energy conversion element to an elastic body, and
• a driven body in pressure contact with the vibrating body,
• wherein relative movement between the vibrating body and the driven body is caused by vibration excited in the vibrating body,
• said drive device including:
• a drive unit configured to apply a first drive signal and a second drive signal for exciting vibration, to the electromechanical energy conversion element of the vibrating body,
• an acquisition unit configured to acquire information on a relative position between the driven body and the vibrating body, and
• a control unit configured to switch the first drive signal and the second drive signal applied from said drive unit to the electromechanical energy conversion element, to a third drive signal and a fourth drive signal, respectively, based on the information acquired by said acquisition unit, to thereby change a position at which a largest one of peaks of amplitude of vibration excited in the vibrating body is formed.

A method of controlling a drive device for driving a vibration actuator that includes a vibrating body and a driven body in pressure contact with each other, and causes relative movement between the vibrating body and the driven body by vibration excited in the vibrating body, the method comprising:

• applying a first drive signal and a second drive signal for exciting vibration, to an electromechanical energy conversion element of the vibrating body;
• acquiring information on a relative position between the vibrating body and the driven body;
• and
• switching the first drive signal and the second drive signal applied to the electromechanical energy conversion element, to a third drive signal and a fourth drive signal, respectively, based on the information acquired by said acquiring, to thereby change a position at which a largest one of peaks of amplitude of vibration excited in the vibrating body is formed.

A method of driving a vibration actuator including a vibrating body formed by attaching an electromechanical energy conversion element to an elastic body, and a driven body in pressure contact with the vibrating body, relative movement between the vibrating body and the driven body being caused by vibration excited in the vibrating body, the method comprising:

• applying a first drive signal and a second drive signal having a predetermined frequency to the electromechanical energy conversion element with a fixed phase difference, thereby exciting progressive vibration in the vibrating body;
• acquiring a speed profile indicative of a relationship between a position and a speed of the driven body with respect to the vibrating body in a case where the relative movement between the driven body and the vibrating body is caused by the vibration excited in the vibrating body;
• detecting a lowest-speed position at which the speed of the driven body with respect to the vibrating body becomes lowest, from the speed profile acquired by said acquiring;
• and
• acquiring information on a relative position between the driven body and the vibrating body, and switching the first drive signal and the second drive signal applied to the electromechanical energy conversion element to a third drive signal and a fourth drive signal, respectively, based on the information on the relative position and the lowest-speed position, thereby changing a position at which a largest one of peaks of amplitude of the progressive vibration excited in the vibrating body is formed.

A method of driving a vibration actuator including a vibrating body formed by attaching an electromechanical energy conversion element to an elastic body, and a driven body in pressure contact with the vibrating body, relative movement between the vibrating body and the driven body being caused by vibration excited in the vibrating body, the method comprising:

• applying a first drive signal and a second drive signal having a predetermined frequency to the electromechanical energy conversion element with a fixed phase difference, thereby exciting progressive vibration in the vibrating body;
• detecting vibration generated in the vibrating body;
• acquiring a phase difference profile indicative of a relationship between a position of the driven body with respect to the vibrating body in a case where relative movement between the driven body and the vibrating body is caused by the vibration excited in the vibrating body, and a phase difference between a signal produced by detecting the vibration and the first drive signal or the second drive signal;
• detecting a lowest-phase difference position at which the phase difference becomes lowest, from the phase difference profile acquired by said acquiring;
• and
• acquiring information on a relative position between the driven body and the vibrating body, and switching the first drive signal and the second drive signal applied to the electromechanical energy conversion element to a third drive signal and a fourth drive signal, respectively, based on the information on the relative position and the lowest-phase difference position, thereby changing a position at which a largest one of peaks of amplitude of the progressive vibration excited in the vibrating body is formed.