EP1317683A1

EP1317683A1 - Optical conduit

Info

Publication number: EP1317683A1
Application number: EP01970717A
Authority: EP
Inventors: William J. Grothe; Sandford R. Willford; Alfred Goldsmith; Paul E. Robbins
Original assignee: Lumenyte International Corp
Current assignee: Lumenyte International Corp
Priority date: 2000-09-08
Filing date: 2001-09-07
Publication date: 2003-06-11
Also published as: AU2001290695A1; WO2002021177A1

Abstract

An optically interrupted linear fiber optic light strip (30) that includes a core (32), a clad (34), a first jacket material (36) that is made of substantially a translucent, white or other light color material, a second jacket (40), made of a black or dark opaque material, and a plurality of cuts, notches or other indented optical interruptions (38) in the form of 'Vs', squares or rectangles or other configurations extending through the two jackets, the cladding and into the fiber optic core, together with, optionally, a third or outermost jacket, made of a clear, protective material, which fiber optic strip may, optionally be illuminated with relatively high power LED source(s), or conventional incandescent light source(s) by placing the light sources at either end or both ends of the light guides.

Description

OPTICAL CONDUIT

Technical Field

The present invention relates to improvements to the appearance, and to the efficiency of light emission from optically interrupted linear fiber optic strip lighting in particular, the appearance and amount of light emitted along a length of linear fiber optical lighting having optical interruptions along its length for either or both functional and decorative purposes, especially in conjunction with use of light emitting with (LED's) as the light source.

Background Art

Functional and decorative lighting have had a long history of use. The primary purpose of functional lighting is to provide illumination into an otherwise dark or insufficiently lit area. Street overhead lighting is a good example of functional lighting. The primary purpose of decorative lighting is to provide emphasis or distinction to an area. Christmas tree lighting is a good example of decorative lighting. It is not unusual to provide lighting that is both functional and decorative, as, for example, aisle lighting in a movie theater. The most prevalent theater aisle lighting include strips of individual incandescent light bulbs that are spaced apart from each other and provide a low level of functional lighting for spatial orientation, as well as provide a decorative, star-like look along the aisle.

In this field, usually referred to as large core fiber optic technology, light in the visible spectrum is transmitted along a light transmitting form that includes at least a light transmitting core and a cladding. This form is also typically referred to as a fiber optic, conduit, light guide, light form, or simply as an "optic". The transmitted light may, in some applications, be emitted out one end of the optic (end lit applications), or in other applications, be emitted radially outward, (side lit applications) or both. The core is typically made of a polymeric material, and the cladding typically is made of a fluoropolymer material, for example that sold under the Teflon brand. In some applications the clad core is surrounded with a finish jacket, also typically made of a polymeric material. These types of fiber optics are described in U.S. Patent Nos. 5,298,327; 5,221,381; and RE 36,157, all of which are incorporated by reference herein. In addition to large core fiber optic technology, cladded plastic rods and other linear light forms or conduit that use a light source external to the light form (conduit) are well known and are used to provide functional and decorative lighting.

Fiber optic technology has developed to the extent that optical interruptions, such as those created by making cuts or indentations along the length of the fiber optic, provide an appearance similar to that of individual light strips, which typically include individual light bulbs spaced apart from each other. Until the advent of linear fiber optic light strips, strip lighting included primarily a series of individual incandescent lights spaced apart at various distances from one another along the length of the strip, or panel, and each light was powered through an electrical connection to a power source. The power source could be low voltage (12 volts for example) or high voltage (110 volts or high, for example). Individual strip lighting is used for many functional applications, including aisle lighting for theaters, step lighting for stairways or steps leading into motor vehicles. Individual strip lighting is used for decorative purposes such as outlining edges of buildings, parapets and the like. Individual strip lighting also uses individual LEDs, spaced apart along the length of the strip, to provide a star-like appearance.

One of the major differences between individual light bulb strips and fiber optic light strips is that the individual light strips have numerous individual lights (usually incandescent, or LED lights) positioned along the linear product, but fiber optic light strips have a single light source positioned only at one end, or two light sources, one at each end of the fiber optic, with cuts or indentations placed in a side of the fiber optic and that function to provide an appearance of individual lights along the light strip.

One of the problems associated with conventional, individual light source strip lighting is that whenever an individual light, whether incandescent or LED, reaches the end of its operating life, the light goes out. A non-lighted space appears then appears and creates a void in an otherwise even appearing linear light form. In some instances the entire lighting strip must be replaced. In other types of individual strip lighting, each burned out bulb must be individually replaced.

Conventional, large core optical fiber applications have also been adapted for use as strip lighting. In these applications, light is transmitted continuously along the length of the fiber optic, and the fiber optic further includes optical interruptions along its length, in the form of cuts, indentations, notches and the like in the fiber optic. Such interruptions cause some of the light being transmitted along the length of the conduit to be emitted at the points of the optical interruptions, which creates the appearance of having a string of individual lights spaced apart from each other. This optically interrupted fiber optic strip lighting overcomes the problem associated with individual light source failure. In one fiber optic strip lighting application, a light source placed at each end of the fiber optic light guide ensures that if one light terminates, the light at the other end continues to provide illumination to the strip.

Conventional linear fiber optic strip light guides utilize optical interruptions that include a rigid, semi-rigid, or flexible light transmitting core surrounded by a substantially clear, or translucent clad of internal reflecting material, such as a fluoropolymer, to form a clad core. The clad core is encased in a jacket material that may be clear, translucent or opaque. In these fiber optic strip applications the optical interruptions are cut or formed through the outer jacket, the inner clad and into the core material. This type of configuration causes some of the light flux from the interior of the core to exit at each optical interruption. A relatively higher contrast between the points of interruption and the surrounding material results when the outer jacket is made of a black or dark opaque material, compared to that of a fiber optic strip that is identical except that it is jacketed with a clear or relatively light colored translucent material.

Disclosure of Invention

In its many embodiments the present invention improves the appearance of, and increases the efficiency of light emission from optically interrupted linear light guides by increasing the area of light transmission, and/or by creating a greater contrast between the clad and the outer layer of the fiber optic, by placing a white, preferably translucent material between the clad and an outer black or opaque jacket. The present invention also includes use of LED' s, together with the use of a light, preferably white translucent inner jacket and a dark, preferably black outer jacket in a linear, fiber optic strip light that has a plurality of cuts or notches placed along its length.

In a first preferred embodiment, a light colored, preferably white translucent polymer inner jacket is placed outside of the clad core, and inside of an outer dark colored, preferably black jacket, with a plurality of notches cut through the jackets, clad and into the core along the length of the strip. When illuminated, this strip emits bright light at the notches, and provides the appearance similar to that of a light strip that has a plurality of individual lights placed along its length.

In a second preferred embodiment, an additional relatively transparent, preferably clear jacket is placed around the outer dark jacket. This clear jacket functions to provide protection to the inner fiber optic strip. The clear outermost jacket may be impregnated with UV inhibitors, fungicides, and/or other materials that provide a protective function.

In all preferred embodiments of the present invention, an LED light source may be used, at either end, or both ends of the light source for a linear, fiber optic strip light having optical interruptions. Recently, relatively powerful LED light sources have been developed, such as those manufactured by Hewlett Packard, Everlight or Nichia. The Nichia High Power NSPW 500 BS is a preferred LED for use in any present invention. These LED light sources normally emit less light flux than conventional incandescent light sources currently used in the field, even though they emit more light flux than prior LEDs and are especially preferred for use in, and as part of the present invention. In order to obtain the benefits of the relatively high powered LEDs, and an improvement in the emission of light along linear light forms, such as fiber optics as well as from rigid rods of acrylic, polycarbonate materials, it is advantageous to use these relatively high power LED light sources rather than conventional light sources with the relatively light, translucent inner jacket and relatively dark, opaque out jacket of the present invention..

Various cross-sectional shapes for the fiber optic strip lights may be used, and various shapes for the cuts or notches may be used.

Brief Description Of The Drawings

Figure I is a cross-sectional view of a prior art fiber optic linear light strip having optical interruptions.

Figure 2 is a side, perspective view of the Figure 1 linear light strip.

Figure 3 is a cross-sectional view of a first preferred embodiment of the present invention fiber optic light strip having optical interruptions.

Figure 4 is a side, perspective view of the Figure 3 fiber optic strip. Figure 5 is a cross-sectional view of a second preferred embodiment of the present invention.

Figure 6 is a side, perspective view of a conventional fiber optic strip-light using a white, translucent jacket.

Figure 7 is a side, perspective view of a linear fiber optic having rectangular optical interruptions.

Best Mode for Carrying Out the Invention

To illustrate and further describe various applications and embodiments of the present invention, reference will be made to Figures 1-7, and several examples.

Figure 1 is a cross-sectional view of a conventional fiber optic strip light 20 that shows the core 22, clad 24, jacket 26 and, in dashed lines, a cut 28. Figure 2 is a side, perspective view of the Figure 1 prior art linear light guide.

With reference to Figures 3 and 4, the present invention is a fiber optic strip-light 30 that includes adding to the exterior of a clad inner core 32, a jacket material 36 that , preferably, of substantially a translucent, white or other light color and which functions to enhance the apparent brightness of the color of the light being transmitted through and out of the core material 32, and then covering the core 32, clad 34, and white or other light colored translucent j acket 36, with another j acket 40 made of a black or dark opaque material. After j acketing of the linear light guide with the black or opaque j acket 40, cuts or indented optical interruptions 38, in the form of "Vs", squares, rectangles or other configurations are cut through the two jackets 36, 40, the cladding 34 and into the fiber optic core 32. The thickness of the black or dark opaque second, or outer jacket 40 need be only thick enough to ensure that no light emits through this j acket 40 except at the points of optical interruptions 38. The cuts, indentations or notches 38 may be of different configurations, and each different configuration will produce a unique emitted light pattern. All of the alternate notch shapes are preferred, depending upon the end result or effect desired.

Shown in Figure 5 is an alternative embodiment to the foregoing illustrated in Figures 3 and 4. The Figure 5 embodiment fiber optic strip 42 includes a core 44, with a clear clad 46, a substantially white, translucent jacket 48, a black or dark opaque outer jacket 50, the disruptive indentations or cuts 52, and the final clear jacket 54. After completing the cutting or indenting of the notches, the entire j acketed fiber optic is covered with another, third, outer jacket made of a substantially transparent material 54. This third jacket 54 functions to provide protection of the linear light form from external causes. The third jacket, as well as the first, and second jackets are placed around the clad core through use of conventional extrusion techniques. In additional, preferred alternate embodiments, known protective ingredients may be added to the last outer jacket to provide protection against ultra violet, infrared and other sources of damage to the fiber optic.

The present invention may use any size of linear light form within the range of those currently in use in the field. Currently in use in the industry are nominal core diameters of 1/8", 3/16", 3/8", W, and 3/4" (3mm, 4.5mm, 6mm, 9mm, 12mm and 18mm, respectively). The depth of the notches formed in each of the various sized optics may be adjusted to be related to the diameter of the fiber optic or linear light guide clad core, and the thickness of the surrounding white and black jackets.

The light source for the optically interrupted linear light guide of the present invention may be any source of light. As stated above, a preferred light source is a relatively high power, LED light source, such as a Nichia High Power NS PW 500 BS. The light source is placed either at one end of the light guide, or at both ends.

As a result of the contrast between the light, first, inner j acket material, as well as the ability of light to emit through the edges of the translucent material at the optical interruptions and the surrounding dark, second, jacket material, the star-like appearance of the fiber optic linear strip light is greatly enhanced.

The optical core (inner core material) can be any light transmitting material with a refractive index greater than its cladding, such as that used in Lumenyte International Corporation' s ("Lumenyte") fiber linear lighting light guides, and as described in U.S . Patent No. 5,298,327 or RE 36,157, both of which are incorporated by reference. The cladding material should have a refractive index less than that of the core, but grater than or equal to that of air, and should be substantially clear, such as Teflon® brand fluoropolymer manufacture by E.I. DuPont. The inner translucent jacket material is preferably white PVC, such as the 346/XF-95 polyvinylchloride ("PVC") manufactured by Alphagary of Leominster, Maine. This jacket is formed, preferably by conventional extrusion over the fluoropolymer clad core. The preferable interspace jacket is white, but other colors that are relatively light in color, and that contrast well with black or other dark, opaque materials, may be used in the present invention.

The black, or dark opaque covering jacket can be of any number of materials. The preferred material is black PVC, manufactured by Alphagary of Leominster, Maine, under the part number GWX-95-755D BLK LA 95. This jacket is preferably extruded over the white jacket using conventional extrusion techniques. The dark opaque covering jacket is preferably black, but other colors that are relatively dark in color, and that contrast well with the interspace, relatively light jacket material may be used.

It has been determined that the most preferable angle for the cut of the "V" shaped notches s is 42.5 degrees from vertical (total angle of 84 degrees). However, it has also been discovered that the angle of the cut of the notches, may be varied any number of degrees including use of a rectangular cut, as described in Example 3, Figure 7, without losing the usefulness of the visual effect.

The final or outermost protective clear material jacket preferably is a clear PVC jacket, available from Alphagary, for example, under its part number 346/XF-95 Clear. It also is formed by conventional extrusion techniques, i.e., by extruding it over the optically interrupted linear light guide.

Light sources for the light guide can be any of numerous conventional LEDs, quartz- halogen illuminators, metal halide illuminators, lasers, sunlight or other illuminators. Color wheels, known in the art, can be used as an alternative to a fixed light. Fixed lights may be of any color within the range of light sources available.

The emission light at the optical interruptions of the light guide of the present invention are remarkably more visible to the naked eye, than are the emissions of light emitted from conventional, optically interrupted linear light guides. Visible light attenuation along the lengths of the light guide is greatly reduced with the present invention light guides.

As used in the present invention, "contrast" is defined as the difference in light intensity between the emitting, or reflecting, area and the adj acent background. The emitting or reflecting area is the area of light emission at the optical interruptions, including the area of the exposed light colored, translucent interspace jacket. The adjacent background is defined as the adjacent dark opaque jacket. The contrast ratio is defined as ((l(e)-l(b)) divided by 1(b), where 1(b) is the intensity of the background and 1(e) is the intensity of the emitting source. The optical interruptions, or notches provide, and define the emitting source. The adjacent dark, opaque jacket provides, and defines the non-emitting, but reflecting background. If the background color is black, a minimum amount of visible light will be reflected back into the viewer' s eye(s), with a corresponding increase in contrast. On the other hand, if the background color was white (or another highly reflective color in the wavelength(s) of interest), the ambient light (background) would reflect into the viewer's eye(s), and the emitting area would have less contract with respect to the background. Any positive value resulting from data taken using the above formula is considered adequate, and therefore, a useful contrast for purposes of this invention.

Example 1 In a first example, a 3-foot long fiber optic strip 56, illustrated in Figure 6, a linear fiber optic manufactured by Lumenyte was used, namely an SWN200, 3/16 inch (4 to 5mm) nominal core diameter linear light form. The SWN200 is a standard Lumenyte International flexible fiber optic including a light-transmitting core 58, tightly clad with Teflon brand polymer clad 60. At 3-inch intervals, "V" shaped notches, one of which is shown at 62, were cut into the core at an angle of 42-degrees from vertical (84-degree total arc), through the clad, perpendicular to the length axis of the fiber optic. Alphagary 346/XF-95 clear PVC jacketing material was then extruded over the notched SWN200 optic. The jacketing material was extruded in a conventional form used in the limousine market that provides a flat base 66 and rounded enclosure or jacket 64. The flat side of the jacket 70 was coated with white labeling ink in order to provide the optic with a reflective background. The labeling ink is manufactured by GEM, and sold as its Model 6500 white ink. When illuminated by Nichia High Power NSPW500BS white LEDs from each end (not shown), light was visible through the entire length of the fiber optic and also, but much more brightly visible at each of the optical interruptions 62.

Example 2 In a second example, a sixteen foot length of Lumenyte PLS-301W (stock polymeric core, tightly Teflon® polymer cladded, translucent Alphagary 346/XF-95 PVC white jacketed 1/4" (6mm) side light optic was used as well as a fifteen foot length of Lumenyte SEL300 (stock black jacketed end light optic) to compare the effect of notches cut into two differently colored jacket materials to the effect of the notches cut into clear jacket material. Each of the notches were cut into the optic, at three-inch spacing therebetween, through the jacket material and into the core, again using a 42-degree cut from vertical. The cuts were again made in a "V" shape and the cut material was removed. A Nichia High Power NSPW500BS white LED was used to illuminate each of the optics. To the naked eye, the light emitted at the optical interruptions of the black-jacket sample was less visible than that emitted from the translucent white-jacketed sample. The cut portions of both the white and black jacketed samples had been cut through the clad and part of the fiber optic core.

Example 3

In a third example, illustrated in Figure 7, a test was conducted using a two-foot long, black-jacketed fiber optic 72 similar to the one used in Example 2, but the cuts, or notches 74, 76 were made in a rectangular pattern rather than in a "V" pattern, with the cuts at each end of the rectangle 78, 80, 82, 84 cut perpendicular to the length axis of the fiber optic 72. The alternate cuts 74, 72 were intended to provide a larger visible surface for the emission of the light. The fiber optic 72 includes core 86, clad 88, and black jacket 90. A Nichia High Power NSPW500BS white LED was used. The light emitted from the notched areas 74, 76 appeared to be wider than the light emitted from the Example 2 samples.

Example 4

Example 4 combines the reflective properties of a white background and enhanced light emission from a cut or notched area through use of a white translucent jacketed fiber optic, that is otherwise contained within, or surrounded by a black jacketed material. Two three-foot long lengths of conventional 1/4" (6mm) Teflon® brand polymer clad fiber optic were jacketed with a translucent white jacket, Alphagary 346/XF-95 PVC, which measured 0.040 inches in thickness for each sample, and then jacketed, by conventional extrusion techniques, with a thinner substantially black Alphagary 346/XF-95 PVC jacket material, have a thickness of 0.020 inches for each sample. One optic was notched with 84-degree total angle notches, cut to a depth of approximately .112 inches, measured vertically through the jackets, clad and into the core, and the other optic was notched with 84-degree angle notches cut to a depth of .122 inches. The notches in both samples were spaced three inches apart. The notch depth was based upon the thickness of the black and white jackets and the distance into the core that previous experimentation had shown to provide for acceptable light emissions as well as acceptable light retention, i.e., for light to remain in the interior of the core to provide for an acceptable amount of light transmission along the length. The second optic was identical to the first, except that its notches were cut to a depth of approximately .122 inches. Each optic had 3 inches of spacing between the notches.

A single white end seal (white opaque covering at one end of a linear light guide) was placed at one end of each sample. A Nichia High Power NSPW500BS white LED was used to illuminate each sample. The lighting was considered to be exceptional, on the basis that, to the naked eye, it showed a beautiful bright, white color. No yellow was visible and no attenuation was visible, and the emitted light appeared to be completely even. The light emission at the interruptions appeared to be brighter than any prior fiber optic or light guide tested with LEDs used as the light source. The inner white jacket with the surrounding black jacket covering provided superior results in comparison to the other samples.

Example 5

Example 5 used a twelve-foot 1/4" (6mm) optical fiber with the 84-degree total angle "V" cut, to the depth of approximately 0.112 inches. Spacing of the notches was set at four inches. The twelve-foot optic was lit from both ends using a Nichia High Power NSPW500BS white LED. Even with the relatively low-level light from a LED light source, the notches emitted bright, white and even light. The Example 5 fiber optic is suitable for use as aisle lighting in a theater.

Example 6

Example 6 included extruding over the core, clad, white Alphagary PVC jacket and the opaque black Alphagary PVC jacket, which had been notched, a jacket of the clear flexible Alphagary PVC. The final, clear over-jacket can also contain fungicides, UV blockers and absorbers, and other protecting materials to allow the final product to be used in exterior, as well as interior environments. The light being emitted from the Example 6 linear optic continued to be bright, distinct and preferred for applications requiring star-like linear light forms.

It has been determined that LED light sources, as described above, provide a uniform light throughout the length of fiber optic linear forms up to fifty feet in length, with eight inch spacing between the notches. Quartz halogen and metal halide light sources, such as Lumenyte PH 1000 and PH 3000 illuminators, commonly used in the industry, provided even brighter results and over longer distances, such as one hundred feet. It has also been determined that various spacing distances between the notches can be used to yield different desired end results, without loss of utility in the final product.

While the present invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but to the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit of the invention, which are set forth in the appended claims, and which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures.

Claims

What is claimed is:

1. A linear light form comprising: an inner light transmitting core; a clad surrounding said core, said clad made of a material having a lower index of refraction than the core; a first jacket made of a translucent material that has a first color, said first jacket surrounding said clad; a second jacket made of an opaque material that is relatively dark in comparison to the color of said first jacket, said second jacket surrounding said first jacket; and a plurality of optical interruptions positioned along the length of the linear light form, each of said interruptions extending through the second jacket, the first jacket and the clad, and extending into the core to thereby form a plurality of emitting light sources.

2. The light form of claim 1 wherein the first j acket material color is substantially white.

3. The linear light form of claim 1 wherein: each emitting light source is defined as having a positive value contrast ratio, with the contrast ratio defined as l(e)-l(b)/l(b), where

1(e) is intensity of light of the emitting source, and 1(b) is intensity of light reflected from the opaque material.

4. The linear light form of claim 1 further including a third jacket that is made of a substantially transparent material and that surrounds the second jacket, the first jacket, the clad and the core.