An optical system and an imaging apparatus are provided that are bright and large-aperture lenses with a small F-number and that suppress image plane fluctuations and chromatic aberrations when the focus fluctuates.
2. Description of the Related Art
In recent years, as the demand for full-size mirrorless cameras has increased, there has been a demand for lenses capable of handling high resolutions as the number of pixels in sensors increases and the resolution of monitors increases.
[0006]
However, in the optical system described in Patent Document 1, the power distribution of the first lens group and the second lens group is not appropriate, so the diameter of the lenses constituting the first lens group is relatively large. As a result, the entire product becomes large. In addition, correction of image plane fluctuation and chromatic aberration during focusing is insufficient, and an improvement in optical performance is required.
[0007] In
the optical system described in Patent Document 2, since the single lens group is used for focusing, the image plane fluctuates greatly when focusing from infinity to the closest object. Therefore, it is required to suppress the fluctuation of the image plane over the entire focusing range.
[0008]
The optical system described in Patent Document 3 performs focusing by a floating focus method. Glass with low anomalous dispersion is used for the lens used in the lens group that moves during focusing. As a result, axial chromatic aberration and chromatic aberration of magnification are insufficiently corrected over the entire focusing range, and color fringing on the imaging plane becomes conspicuous.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical system and an image pickup apparatus in which fluctuations in the image plane and chromatic aberration are suppressed in the entire in-focus range while using a bright, large-aperture lens with a small F-number.