Abstract: An optical unit of plastic provided with a surface for incident light and a surface for outgoing light, wherein the surface for incident light is designed to face a light source and the surface for outgoing light is designed to face an element for receiving light so as to optically connect the light source and the element for receiving light and wherein the optical unit is so shaped that light that comes from the light source and is incident on the surface for incident light forms a first image of the light source within the optical unit and a second image of the light source after having gone through the surface for outgoing light and the optical unit is provided with an attenuating portion for attenuating the quantity of light passing therethrough in the vicinity of the position where the first image is formed.

Abstract: An optical element to be interposed between an optical transmission line and a light-emitting element or a light-receiving element such that an optical path from one side to the other passes through the optical element is provided. At least one surface of the optical element is provided with a first light-collecting area and a second light-collecting area. A surface of the first light-collecting area is configured such that light from the one side is received by the other side. A surface of the second light-collecting area is an annular surface or a part of the annular surface and is configured such that light that has passed through the second light-collecting area forms an image in the shape of a ring or a part of the ring at a position between the optical element and the other side.

Abstract: An optical element to be interposed between an optical transmission line and a light-emitting element or a light-receiving element such that an optical path from one side to the other passes through the optical element is provided. At least one surface of the optical element is provided with a first light-collecting area and a second light-collecting area. A surface of the first light-collecting area is configured such that light from the one side is received by the other side. A surface of the second light-collecting area is an annular surface or a part of the annular surface and is configured such that light that has passed through the second light-collecting area forms an image in the shape of a ring or a part of the ring at a position between the optical element and the other side.