In recent years, imaging devices such as a digital camera, which can perform not only static image capturing but also moving image capturing and sound recording at the same time, are in practical use. Regarding the moving image capturing, there is a device in which the maximum frame rate is 60 fps in accordance with reproduction of moving image in a High-Vision TV device. When capturing an image of a moving object, it is possible to suppress unnatural change of a captured moving image and capture a high quality image by increasing the frame rate of the moving image, for example, increasing the frame rate to 120 fps.
An interchangeable lens device including an auto-focus (hereinafter referred to as “AF”) mechanism performs wobbling (hereinafter referred to as “Wob”) driving of an AF operation in which a focus lens in the AF mechanism is reciprocated along the optical axis within the depth of focus in synchronization with the frame rate of the moving image and the focal position of the object is searched for and the focus lens is moved to a focus position on the basis of contrast evaluation value (hereinafter referred to as “AF evaluation value”) obtained from spatial brightness variation of images acquired at each frame rate. Therefore, in the AF mechanism, when the focus lens is Wob-driven in accordance with the high frame rate of the moving image, inertial force during lens driving increases due to a shortened cycle of Wob driving, and vibration during driving and reaction vibration of a support member that supports the focus lens increase, so that driving sound generated during lens driving increases. As a result, there is a problem that the driving sound is collected by a sound-collecting microphone as noise when a moving image is captured.
Therefore, an AF mechanism is known in which a motor such as a voice coil motor (hereinafter referred to as “VCM”) is employed as a drive unit that drives the focus lens in order to realize high-speed Wob driving and reduce vibration and noise during Wob driving (for example, see Patent Literature 1). According to this technique, in the Wob driving while a moving image is captured, a rapid acceleration change of the focus lens drive unit is suppressed by suppressing the maximum speed while the moving of the focus lens is controlled, so that the vibration and noise are suppressed.
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