Optical waveguide with diffuse light extraction

Details Optical waveguide with diffuse light extraction Optical waveguide with diffuse light extraction

1997-10-24

2001-10-09

Lee, John D. (Department: 2874)

Optical waveguides

Optical fiber waveguide with cladding

C362S558000, C362S559000, C385S031000, C385S901000

Reexamination Certificate

active

06301418

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed generally to an optical waveguide and, more particularly, a fiber-type optical waveguide which is structurally adapted for extraction of diffuse light.
BACKGROUND OF THE INVENTION
Although optical waveguides, such as optical fibers, have been designed for delivering light over long distances with little attenuation in the intensity of the light, there are many applications in which it is desirable that light also be extracted from the waveguide at various points along its length. There are two types of extraction: directed and diffuse.
Directed extraction methods provide extracted light in a particular desired direction. A variety of structures for directed light extraction, many of which use prisms, have been developed. These extractors are particularly useful for applications requiring, for example, light to be directed toward a particular point or object.
Diffuse light extraction methods provide light that is directed over a range of directions. There are a variety of applications that require diffuse rather than directed light. Such applications range from lighted display signs to lamps for offices or other workplaces. Neon lighting has been used for these applications. However, optical waveguides with diffuse light extractors have several advantages over neon lighting. For example, the optical waveguide typically uses a low voltage light source as opposed to the neon light which requires high voltage for operation. Importantly, optical waveguides can use a variety of light sources including incandescent and electrical arc sources, that may be more energy efficient than neon. Furthermore, the optical waveguide can provide light of any desired color by using an appropriately colored light source or light filter. The color can be easily changed by changing the light source or filter. Neon lighting, on the other hand, requires either a particular choice of gas or phosphor coatings in the tubing of the neon lighting or, alternatively, the use of colored translucent glass tubing. Finally, neon lighting is made of glass which is rigid and cannot be subsequently adapted to alterations in the desired lighting design. Optical waveguides, on the other hand, can be made from flexible and durable materials which can be altered to form a variety of different configurations depending on the need.
While there are many advantages to using optical waveguides and diffusional light extractors, progress in this field has been slow. Existing products show that the industry has long struggled, with little success, to provide a practical design that is also efficient.
SUMMARY OF THE INVENTION
The instant invention is directed to optical waveguides, and methods for their manufacture, which are structurally adapted to provide efficient extraction of diffuse light. One embodiment is an optical waveguide which has a core and a cladding. The core is made from a light transmitting material and has an axis in the general direction of light flow through the optical waveguide. The cladding surrounds the core and has an index of refraction that is less than the index of refraction of the core. The cladding has an inner surface which is roughened along a length of the cladding with indentations to extract light from the core. The inner surface is roughened in a non-uniform manner to produce a predetermined light extraction pattern from the waveguide. In addition, the indentations on the inner surface of the cladding are substantially non-parallel with respect to the axis of the core.
Another embodiment of the invention includes a method of making an optical waveguide with diffuse light extraction. A cladding is formed as a hollow tube along an axis and provided with a first end and an inner surface. At least a portion of the inner surface of the cladding is roughened by forming indentations on the inner surface. The indentations are substantially non-parallel with respect to the axis of the cladding and the inner surface is roughened in a non-uniform manner to produce a predetermined light extraction pattern. A core material is disposed within the cladding to form the optical waveguide.
The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.


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