Optical waveguides – Optical fiber waveguide with cladding
Utility Patent
1999-05-19
2001-01-02
Lee, John D. (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
C385S901000, C362S552000, C362S560000
Utility Patent
active
06169836
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an optical transmission tube including an optically transparent tubular clad, and an optically transparent core having a reflective index higher than the clad, and a method for making the same. More particularly, the invention relates to an optical transmission tube wherein light emission from outer surfaces of the clad is enhanced, and a method for making such a tube.
As is known in the art, with an optical transmission tube, which is constituted of a tubular clad and a core having a refractive index higher than the core, luminance at side faces is not generally high. This is because such an optical transmission tube sends light to the tip thereof in a quantity as much as possible. In order to increase luminance, there is used a method wherein a clad is made irregular at inner surfaces thereof so that the luminance at the side faces of an optical transmission tube is raised. However, where an optical transmission tube is made by filling a polymerizable liquid monomer used to form a core in a tubular clad and polymerizing the monomer under pressure, such an irregular clad is liable to break, thus making it difficult to carry out the above method.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an optical transmission tube which ensures emission of light at high luminance from the outer surfaces of the transmission tube.
It is another object of the invention to provide an optical transmission tube wherein light can be emitted from the entire outer surfaces of the tube.
It is a further object of the invention to provide a method for making an optical transmission tube of the type mentioned above in a simple way.
It is a still further object of the invention to provide a method for easily making an optical transmission tube with its length being from as short as 1 to 2 m to as 10 long as 5 to 10 m.
The above objects can be achieved, according to one embodiment of the invention, by an optical transmission tube which comprises a tubular clad and a core covered with the tubular clad and having a refractive index higher than the tubular clad, wherein the core contains light-scattering particles uniformly dispersed throughout the core whereby light passing through the core is reflected and scattered at individual light-scattering particles and is allowed to be emitted from outer surfaces of the clad.
In the practice of the invention, it is preferred that the particles have an average size of 0.1 to 30 &mgr;m. It is also preferred that the tube further comprises a reflective protection layer formed at part a of the outer surfaces of the clad. Moreover, the tubular clad is preferably made of a fluoropolymer, and the core is made of an acrylic polymer.
According to another embodiment of the invention, there is also provided a method for making an optical transmission tube of the type which comprises a tubular clad and a core covered with the tubular clad and having a refractive index higher than the tubular clad, the method comprising dispersing light-scattering particles in a solution containing a monomer capable of forming a core through its polymerization, charging the solution into a tubular clad, polymerizing the monomer in the solution while vibrating and/or rotating the tubular clad to permit the light-scattering particles to be uniformly dispersed throughout the solution whereby the resultant solid polymer core has the light-scattering particles uniformly dispersed in or throughout the core.
The optical transmission tube of the invention is formed by uniformly dispersing light-scattering particles throughout the core, so that intense light passing through the inside of the core in the greatest quantity thereof is scattered by means of the particles, and thus, intense light is released or emitted from all azimuthal directions of the outer surfaces of the clad. Thus, very high luminance is obtained and very high brightness results. When the light-scattering particles are formed, for example, of silicone resins, polystyrene resin, metal oxides or the like, very high light emission is attained. Moreover, when a metallic sheet or a reflective coating wherein light-scattering particles are dispersed is formed, as a reflective protection film, in a pattern on the outer surfaces of the clad, the tube can be imparted with directivity in light emission according to the pattern.
When using a method for making such an optical transmission tube as mentioned above according to the invention, there can be very simply and accurately formed a core wherein light-scattering particles are uniformly dispersed. Thus, an optical transmission tube, which is very high in luminance, can be readily fabricated in long size. It may occur to one that when a core is formed, scattering particles are dispersed in an organic solvent of a polymer used to form a core, and the resultant dispersion is charged, for example, into an FEP (tetrafluoroethylene-hexafluoropropylene copolymer) tube, followed by removing the organic solvent under reduced pressure to form a core. However, this procedure is disadvantageous in that a limitation is placed on the length of the core along which the solvent is efficiently evaporated. It is difficult to make a long-size tube because of the poor manufacturing efficiency.
REFERENCES:
patent: 5542017 (1996-07-01), Koike
patent: 5982969 (1999-11-01), Sugiyama et al.
Ishiharada Minoru
Morimura Yasuhiro
Sugiyama Hideo
Tanuma Itsuo
Terahama Tatsuo
Bridgestone Corporation
Connelly-Cushwa Michelle R.
Lee John D.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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