[Problem] To realize a large aperture ratio optical system that uses an inner focus method while reducing the weight of a focus lens.
[Background Art] [0002] In recent years, with the spread of imaging devices such as digital still cameras and video cameras, the number of pixels in imaging devices has rapidly increased, and an imaging optical system with higher image quality is required. There is.
[0003] Also, high-speed and accurate focus driving is required. If the weight of the focus lens group increases, it is not preferable because the speed of focus drive decreases or the noise during focus drive increases. Further, there is a problem in that the actuator for moving the lens becomes large and the lens barrel becomes large.
[0007] The present invention has been made in view of the above situation, and an object of the present invention is to provide a large aperture ratio optical system that employs an inner focus method while reducing the weight of a focus lens.
