An imaging optical system includes, sequentially from an object side toward an image side, a first lens group; an aperture stop; and a second lens group. The first lens group includes a negative lens; and a positive lens formed of a plastic lens. The second lens group includes a plastic lens and satisfies Conditional Expressions (1) and (2) as follows:
c31a>c32a, and  (1)
c31b<c32b,  (2)
where c31a is an on-axis curvature of an object-side surface of the plastic lens of the second lens group, c32a is an on-axis curvature of an image-side surface of the plastic lens of the second lens group, c31b is an off-axis curvature of the object-side surface of the plastic lens of the second lens group, and c32b is an off-axis curvature of the image-side surface of the plastic lens of the second lens group.

The imaging lens consists of, in order from the object side, a front group that includes a stop and has a positive refractive power, and a rear group. During focusing, the entire front group integrally moves, and the rear group remains stationary with respect to an image plane. The rear group includes one or more air lenses formed by two concave lens surfaces facing toward each other. The imaging lens satisfies Conditional Expressions: 0.1<Bf/f<0.9 and −0.7<(Rrf+Rrr)/(Rrf-Rrr)<-0.025, where a back focal length of a whole system is Bf, a focal length of the whole system is f, and a curvature radius of an object side surface of the air lens in the rear group is Rrf and a curvature radius of an image side surface of the air lens in the rear group is Rrr.

The imaging lens consists of, in order from the object side, a front group that includes a stop and has a positive refractive power, and a rear group. During focusing, the entire front group integrally moves, and the rear group remains stationary with respect to an image plane. The rear group includes one or more air lenses formed by two concave lens surfaces facing toward each other. The imaging lens satisfies Conditional Expressions: 0.1<Bf/f<0.9 and −0.7<(Rrf+Rrr)/(Rrf-Rrr)<-0.025, where a back focal length of a whole system is Bf, a focal length of the whole system is f, and a curvature radius of an object side surface of the air lens in the rear group is Rrf and a curvature radius of an image side surface of the air lens in the rear group is Rrr.

An optical system includes, in order from an object side to an image side, a front unit of a positive refractive power, a diaphragm, and a rear unit of a positive refractive power. The front unit includes, in order from the object side to the image side, a positive lens L11, a positive lens L12, and a negative lens L13. The rear unit includes, in order from the object side to the image side, a negative lens L21, a positive lens L22, and a positive lens L23. A predetermined condition is satisfied.

An optical system includes, in order from an object side to an image side, a front unit of a positive refractive power, a diaphragm, and a rear unit of a positive refractive power. The front unit includes, in order from the object side to the image side, a positive lens L11, a positive lens L12, and a negative lens L13. The rear unit includes, in order from the object side to the image side, a negative lens L21, a positive lens L22, and a positive lens L23. A predetermined condition is satisfied.

An imaging lens is configured by, in order from an object side, an object side group including at least one lens group and having positive refractive power as a whole and an image side group configured by one lens group and having negative refractive power. Focusing is performed by moving the object side group in an optical axis direction, and a predetermined conditional expression is satisfied. The image side group includes a subgroup satisfying a predetermined conditional expression. Further, an imaging device includes the optical system and an image sensor.

An imaging lens is configured by, in order from an object side, an object side group including at least one lens group and having positive refractive power as a whole and an image side group configured by one lens group and having negative refractive power. Focusing is performed by moving the object side group in an optical axis direction, and a predetermined conditional expression is satisfied. The image side group includes a subgroup satisfying a predetermined conditional expression. Further, an imaging device includes the optical system and an image sensor.

A solid-state imaging apparatus and an electronic device that are capable of improving a use efficiency of incident light while avoiding overlap of incident light among adjacent solid-state imaging devices are provided. A solid-state imaging apparatus that includes plural pixels arranged in a matrix shape on an imaging device surface, and each of the pixels includes at least one solid-state imaging device; and at least one light guiding unit that is arranged on a subject side of the solid-state imaging device, and the light guiding unit includes a first transparent body; a first lens group having a positive optical power; a light shielding unit having an opening portion; and a second lens group having a positive optical power, sequentially toward a solid-state imaging device side from the subject side along a light guiding direction of the light guiding unit is provided.

A solid-state imaging apparatus and an electronic device that are capable of improving a use efficiency of incident light while avoiding overlap of incident light among adjacent solid-state imaging devices are provided. A solid-state imaging apparatus that includes plural pixels arranged in a matrix shape on an imaging device surface, and each of the pixels includes at least one solid-state imaging device; and at least one light guiding unit that is arranged on a subject side of the solid-state imaging device, and the light guiding unit includes a first transparent body; a first lens group having a positive optical power; a light shielding unit having an opening portion; and a second lens group having a positive optical power, sequentially toward a solid-state imaging device side from the subject side along a light guiding direction of the light guiding unit is provided.

An imaging lens includes a positive first lens group and a second lens group, which are continuous in order from the position closest to the object side, as lens groups. During focusing, the distance between the first lens group and the second lens group changes. A stop is disposed closer to the image side than a lens which is second from the object side. A combined refractive power of all lenses closer to the object side than the stop is positive. The imaging lens includes an LA positive lens and an LB positive lens that satisfy a predetermined conditional expression at a position closer to the object side than the stop. An Abbe number of the LB positive lens is the maximum among Abbe numbers of all positive lenses closer to the object side than the stop.