Imaging optical system, and imaging apparatus incorporating the same

An imaging optical system, comprising, in order from an object side to an image side thereof,

• a front lens group comprising a plurality of lenses including a first negative lens concave on the image side,
• an aperture stop, and
• a rear lens group having positive refracting power, wherein:
• said rear lens group comprises, in order from the object side, a lens subgroup having positive refracting power and a focus lens group that has positive refracting power and moves upon focusing;
• a lens group that moves in an optical axis direction is only said focus lens group;
• and
• said first negative lens is a lens of negative lenses in said front lens group, which lens is located on the closest to object side, with satisfaction of the following conditions (4) and (7):
• 1.5≦Σd/IHω≦6.0 (4)
• −25%<DT<−7% (7)
• where Σd is a length on an optical axis of the imaging optical system from an entrance surface to an exit surface thereof,
• IHω is a distance from an optical axis of a position where a chief ray from a maximum incident half angle of view (ω) upon focusing on an object point at infinity is imaged at the imaging plane, and
• DT is a quantity of distortion:
• DT=[(IHω−f·tan ω)/(f·tan ω)]×100(%)
• where ω is a maximum incident half angle of view upon focusing on an object point at infinity.

An imaging optical system, comprising, in order from an object side to an image side thereof,

• a front lens group comprising a plurality of lenses including a first negative lens concave on the image side,
• an aperture stop, and
• a rear lens group having positive refracting power, wherein:
• said rear lens group comprises, in order from the object side, a lens subgroup having positive refracting power and a focus lens group that has positive refracting power and moves upon focusing;
• a lens group that moves in an optical axis direction is only said focus lens group (LRF);
• and
• said first negative lens is a lens of negative lenses in said front lens group, which lens is located on the closest to object side, with satisfaction of the following conditions (3) and (6):
• −3.5≦fn/flr≦−0.8 (3)
• −2≦f11/flr≦−0.3 (6)
• where fn is a focal length of a negative lens of negative lenses in said front lens group, which negative lens is located on the closest to object side,
• flr is a focal length of said rear lens group of positive refractive power, and
• f11 is a combined focal length of two lenses:
• one located on the closest to object side in the imaging optical system and one located just after the image side therein.