Imaging optical system and imaging device

An imaging optical system 10 includes, in order from an object side, a front group LF, an aperture stop S, and a rear group LB. The front group LF includes a first lens L1 having a negative refractive power. The rear group LB includes: a fourth lens L4 disposed closest to the object side and having a positive refractive power; and a seventh lens (L7) disposed closest to the image side and having a negative refractive power, the surface of the image side having an extreme value at a position other than the point of intersection with the optical axis. The imaging optical system 10 satisfies the following conditional expressions. 0.6 lt; (R1-R2)/(R1 + R2) lt; 1.0... (1) where R1 is the radius of curvature of the object-side surface of the first lens, and R2 is the radius of curvature of the image-side surface of the first lens. 摄像光学系统10从物体侧起依次具备前组LF、孔径光阑S、以及后组LB。前组LF包括具有负的光焦度的第1透镜L1。后组LB包括：最靠物体侧地配置且具有正的光焦度的第4透镜L4；以及最靠像侧地配置且具有负的光焦度，像侧的面在与光轴的交点以外的位置处具有极值的第7透镜L7。摄像光学系统10满足以下的条件式。0.6