| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the ununiformity of a light quantity and the insufficiency of the light quantity and to reduce the size and weight over the entire part of a light guide by using multiple optical fibers lowered in light loss by bending. SOLUTION: The multiple optical fibers 2 have a sea-and-island structure in which fiber materials are formed as islands and a sheath material having the refractive index lower than the fefractive index of the fiber material is formed as a sea in its section. In such a case, the diameter at the section of the multiple optical fibers 2 to be used is about 0.2 to 2mm. The diameter of the fibers is 1 to 500μm. The loss of the light quantity is larger as the diameter of the fibers is larger and, therefore, the fibers are preferably formed to the smallest possible diameter. The lower limit at which the stable production is possible is 1μm. The upper limit at which the light loss is permissible is 500μm. Further, the number of the fibers within one piece of the optical fiber is >=7 pieces. The reason thereof lies in that the larger number of the fibers is more preferable in order to make the section uniform. The multiple optical fibers 2 are bundled by bending the fibers to a bending radius of >=20nm and are housed in a small-sized housing 5.
|
