| 摘要 |
PURPOSE:To use even an optical fiber having the small number of apertures as an optical transmission line having the large number of apertures by connecting one end of a lens, which has one end formed into a flat surface and has the other end formed into a convex three-dimensional curved surface and has the refractive index reduced gradually toward the other end from one end in the lengthwise direction, to the end face of an optical fiber. CONSTITUTION:The refractive index of a numerical aperture converting convex lens 2 in a plane vertical to an optical axis 4 is equal in the center part and the peripheral edge part, and the refractive index in the axial direction is raised gradully toward the exit end face, which is connected to an optical fiber 3 for communication, from an incidence end face 1. A light 5 made incident on the convex of the lens 2 at an incident angle theta is so bent that the angle of the light to the optical axis 4 is reduced, and this light is made incident on a core part 6 of the optical fiber 3 for comminication at an exit angle considerably smaller than the incidence angle theta. Consequently, the light having a maximum incidence angle, which is prescribed by the number of apertures of the optical of the optical fiber 3, or large can be led to the core part though the number of apertures of the optical fiber is smaller than that of the incidence end face 1 of the convex lens 2. |
