Optical waveguides – With optical coupler – Input/output coupler
Patent
1998-05-21
1999-11-16
Ullah, Akm E.
Optical waveguides
With optical coupler
Input/output coupler
362559, G02B 626
Patent
active
059871997
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates broadly to optical fibers for guiding light and more specifically to an improved optical fiber for linearly guiding light from a light source and emitting the light out of the sides of the optical fiber along its length.
BACKGROUND ART
Fiber optic light conduits have been used for many years to transport light from one point to another through many different light transmitting media such as glass, plastic, and liquid using the principle of Total Internal Reflection (TIR). In each of these cases, some light is lost while traveling along the length of the light conduit for various reasons such as, but not limited to, absorption, light rays that exceed the critical angle of the optic, and diffusion due to optical imperfections such as bubbles, voids and debris.
It has been the goal of fiber optic manufacturers to minimize the amount of light loss along the optical conduit to maximize the light coming out of the output end thereby creating a more efficient optical fiber for end lighting purposes.
In recent years, there has been an interest in having a fiber optic that is efficient in maximizing the light output along the longitudinal axis to create a "glowing rod" effect that emulates a cathode tube, such as a fluorescent light. One problem has been that fiber optic conduits have not been able to create the intensity needed to be used in functional lighting applications as opposed to decorative type lighting.
Standard cathode lighting used for functional purposes generally requires some type of holder and/or reflector or lens to achieve the desired effect. One such example is in illuminating refrigerator interiors where the primary light target is at the front of the shelves. The cathode lamp output is very diffused and the refrigerator manufacturers presently use higher wattage lamps and special holder and/or reflectors to direct the amount of light required on the desired target area. However, higher wattage lamps result in higher heat output which is undesirable, because the refrigerator cooling elements may expend additional energy in order to compensate for the added heat.
Edge lighting with etched glass is another type of lighting which can be achieved with cathode tubes. However, one problem with this type related to efficiently directing the light into the edge of the glass, where the surface is typically 1/4 inch to 1/2 inch wide. This small area limits the ability of the cathode tube, even aided by a holder and/or reflector, to direct the light into the glass because the cathode tube is often the same width of the glass or larger, hence preventing a holder and/or reflector from focusing the light from the back side of the tube into the glass. Higher wattage lamps are required to achieve the desired illumination of the glass wasting even more light which is directed off away from the glass edge.
Many other problems exist with conventional linear functional and decorative lighting systems. Lamps are typically easily broken and eventually need to be replaced, thus the lamps must be installed in a protected chamber that must also provide access for lamp changing thereby creating construction and maintenance problems. Lamps typically cannot be bent or shaped easily and contain electrical components that can produce problems such as electrical shock or fire hazards, hence more complicated system designs are required to accommodate conventional lighting systems.
Many attempts have been made over the last several years to create a directional fiber optic light conduit that would provide a commercially acceptable side lighting as a light source to replace conventional linear lighting, such as cathode lighting. In U.S. Pat. No. 5,432,876, Appledorn discloses the creation of various cuts and notches that can be used to achieve back lighting as an alternative to conventional fluorescent light fixtures, but not as an alternative for direct lighting. One problem has been obtaining adequate brightness and directionality to achieve useful end product for direct light
REFERENCES:
patent: 4969703 (1990-11-01), Fyfe et al.
patent: 5067831 (1991-11-01), Robbins et al.
patent: 5221387 (1993-06-01), Robbins et al.
Holme James A.
Robbins John A.
Sitar Dennis
Zarian James R.
Lumenyte International Corporation
Ullah Akm E.
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