Abstract: Each lens of a multi-segment lens is a Fresnel lens in which a second surface, being the reverse side surface of a first surface, has a plurality of lens surfaces. At least one of the plurality of lens surfaces is configured from a part of a side surface of an elliptical cone having a central axis oblique to a normal line of the first surface. Any normal line intersecting with the lens surface configured from the part of the side surface of the elliptical cone among normal lines of respective points on the first surface is non-parallel to a central axis of the elliptical cone corresponding to the lens surface with which the any normal line intersects.

Abstract: A Fresnel lens comprises a first surface, and a second surface being the reverse side surface of the first surface and having a plurality of lens surfaces. Each lens surface is configured from a part of a side surface of an elliptical cone, which has an apex located on the second surface side and a bottom surface located on the first surface side. Here, in the Fresnel lens, any normal line intersecting with the lens surface configured from the part of the side surface of the elliptical cone among normal lines of respective points on the first surface is non-parallel to a central axis of the elliptical cone corresponding to the lens surface with which the any normal line intersects.

Abstract: A collecting lens comprises a first surface and a second surface. Said first surface lens is defined as an opposite surface of said collecting lens from said second surface. Said second surface has a lens surface. Said lens surface includes a plurality of lens function surfaces. Each of said lens function surfaces is defined as part of a side surface of corresponding one of elliptical cones. A particular normal line which is arbitrarily selected from normal lines at respective points on said first surface and crosses one of said lens function surface is not parallel to a central axis of the elliptical cone corresponding to said lens function surface crossed by said particular normal line. Said central axes of the elliptical cones are not parallel to each other.

Abstract: A collecting lens comprises a first surface and a second surface. Said first surface lens is defined as an opposite surface of said collecting lens from said second surface. Said second surface has a lens surface. Said lens surface includes a plurality of lens function surfaces. Each of said lens function surfaces is defined as part of a side surface of corresponding one of elliptical cones. A particular normal line which is arbitrarily selected from normal lines at respective points on said first surface and crosses one of said lens function surface is not parallel to a central axis of the elliptical cone corresponding to said lens function surface crossed by said particular normal line. Said central axes of the elliptical cones are not parallel to each other.

Abstract: Each lens of a multi-segment lens is a Fresnel lens in which a second surface, being the reverse side surface of a first surface, has a plurality of lens surfaces. At least one of the plurality of lens surfaces is configured from a part of a side surface of an elliptical cone having a central axis oblique to a normal line of the first surface. Any normal line intersecting with the lens surface configured from the part of the side surface of the elliptical cone among normal lines of respective points on the first surface is non-parallel to a central axis of the elliptical cone corresponding to the lens surface with which the any normal line intersects.