PROBLEM TO BE SOLVED: To provide a single focus lens in which various aberrations capable of quick autofocus with a large aperture ratio of about F1.4 are satisfactorily corrected.
BACKGROUND
ART [0002] In
a single-focus photography optical system used in an optical device such as a digital camera, a large-diameter ratio is required to support high-speed photography and expression that makes use of blur. .. Further, as the pixel density of the image pickup device is increased, it is required to further correct various aberrations and achieve high performance. Conventionally, in the imaging optical system for a single-lens reflex camera, the retrofocus type is often adopted because it is necessary to secure the back focus as the movable range of the mirror. A photographic lens that uses a retrofocus type to achieve long back focus, a large aperture ratio, and high performance is known.
[0004]
Patent Document 1 discloses an example having a lens configuration having a role of a wide converter composed of a concave lens and a convex lens component on the object side of a double Gauss type lens configuration that has been widely used for a lens having a standard angle of view. There is. This optical system has a large aperture with an FNO of about 1.4. However, mainly the aberration correction in the sagittal direction is insufficient, and the image spreads widely in the high part of the peripheral image. Patent Document 2 discloses an optical system having a lens configuration having a role of a wide converter on the object side of a double Gauss type as in Patent Document 1. Although this optical system has a large number of lenses constituting a lens group having a role of a wide converter and enables close-up photography as compared with Patent Document 1, aberration correction in the sagittal direction is insufficient and an image in a high peripheral image is obtained. The spread of is large.
[0005]
The present invention has been made in view of such a situation, and an object of the present invention is to provide a single focus lens in which various aberrations capable of quick autofocus with a large aperture ratio of about F1.4 are satisfactorily corrected. And.