WO2010090992A1

WO2010090992A1 - Light guide with irregularities on the outer- or side-surface to improve light emission

Info

Publication number: WO2010090992A1
Application number: PCT/US2010/022831
Authority: WO
Inventors: Rodney J. Tindall
Original assignee: Johnson Controls Technology Company
Priority date: 2009-02-09
Filing date: 2010-02-02
Publication date: 2010-08-12

Abstract

This invention relates to a light guide (100) and methods of manufacturing a light guide (100). The surface is covered with numerous ideally randomly distributed nicks (102). The nicks (102) act as points at which light will be directed out of the light guide (100). The distribution of nicks (102) across the surface of the light guide (100) results in approximately omni-directional emission of light from the light guide (100) (i.e., light is emitted from the light guide (100), ideally, in generally equal amounts, in all directions along all treated surfaces. In various exemplary embodiments, the outer or side surface is treated with, for example, rollers, dies, lasers, chemical etching, sandpaper or abrasive material, sandblasting, bead blasting or abrasive blasting, to create an irregular surface with numerous nicks and/or facets.

Description

LIGHT GUIDE WITH IRREGULARITIES ON THE OUTER- OR SIDE-SURFACE TO IMPROVE LIGHT EMISSION

Claim of Priority

[0001] The present application claims the benefit of the filing date of

U.S. Provisional Application Serial No. 61/150,964 (filed February 9, 2009), and the entirety of the contents of this application being hereby expressly incorporated by reference.

Field of the Invention

[0002] This invention relates to a light guide and methods of manufacturing a light guide.

Related Art

[0003] It is known to provide a variety of lights in a vehicle interior for a number of practical and aesthetic purposes. Examples include lights for various indicators and controls on the dashboard, lights to illuminate all or part of the passenger compartment or trunk, and/or ambient or decorative lights. Light may be directed to a point or across an area. For example, light may be emitted across an area of an instrument panel or into a control knob.

[0004] Light guides function in a way that is analogous to a pipe. A light guide is typically a solid strand of material. Light guides are typically made of transparent polymers, such as acrylic and polyurethane. Light guides are commonly made using a variety of processes, including casting, molding, and extrusion. Light that enters one end surface of a light guide is transmitted down the light guide by repeatedly striking the outer or side surface of the light guide and reflecting back into the light guide until it reaches the end surface. If the outer or side surface of a cylindrical light guide were perfectly smooth, at least nearly all light would pass down the light guide to the end surface without any side surface emissions. However, in many applications, emission of light out the outer or side surface of a light guide is desirable or necessary along all or a part of its length. SUMMARY

[0005] This invention relates to a light guide comprising a light conductor with an outer or side surface having multiple facets, depressions, indentations, notches, disruptions, irregularities, surface irregularities, textures and/or nicks, whereas, in the subsequent document, "facets" and/or "nicks" are used as a synonym for one or all of them. In various exemplary embodiments, the facets and/or nicks are randomly distributed across at least a portion of the outer or side light guide surface.

[0006] This invention also relates to a method of producing a light guide comprising treating the outer or side surface of a light guide to create an irregular outer or side surface. In various exemplary embodiments, the outer or side surface is treated with, for example, rollers, dies, lasers, chemical etching, sandpaper or abrasive material, sandblasting, bead blasting, or abrasive blasting, to create an irregular surface with numerous nicks and/or facets.

[0007] This invention also relates to a method of producing a light guide comprising forming a light guide in a mold wherein at least a portion of the inner surface of the mold includes multiple facets.

[0008] These and other features and advantages of various embodiments of systems and methods according to this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of various devices, structures, and/or methods according to this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various exemplary embodiments of the systems and methods according to the present disclosure will be described in detail, with reference to the following figures, wherein:

[0010] Fig. 1 is a partial perspective view of an exemplary embodiment of a light guide according to this invention; and

[0011] Fig. 2 is a graphical representation of the typical performance of a conventional light guide and an exemplary embodiment of a light guide according to this invention. DETAILED DESCRIPTION

[0012] Light guides are commonly used to transport light from a source to another location. A light guide refers is typically a single, thin fiber or to a bundle of fibers. Light guides used for automotive applications are typically larger in diameter and are typically of a single, solid nominal cross section. They could be round or of a different cross section. For example, one might be a flat, thin strip that is much wider in cross section than it is thick. They may also be used to distribute light from a point source across a larger area such as, for example, along an elongated strip. In general, light guides transport most light to their end surface rather than emitting light along their outer or side surface(s). Thus, in applications where emission of light along the outer or side surface rather than at the end surface is desired or required, a significant portion of the light may be "lost" in that the "lost" light is not emitted where it is needed. The emission of light out of the light guide's outer or side surface may be increased by introducing surface irregularities along those outer or side surfaces. Light striking a non-smooth surface is more likely to exit the light guide than light striking a relatively smooth side-surface. However, conventional light guide manufacturing methods produce light guides with generally smooth outer or side surfaces. This invention addresses methods for producing light guides with at least some non-smooth outer or side surfaces.

[0013] In various exemplary embodiments, the light guide may be manufactured by conventional methods with generally smooth outer or side surfaces and further processed to change the characteristics of its outer or side surfaces. In various other exemplary embodiments, the light guide may be manufactured with a non-smooth outer or side surface that may or may not be further processed.

[0014] Fig. 1 shows a section of an exemplary light guide 100. The surface is covered with numerous ideally randomly distributed nicks 102. The nicks 102 act as points at which light will be directed out of the light guide 100. The distribution of nicks 102 across the surface of the light guide 100 results in approximately omni-directional emission of light from the light guide 100 (i.e., light is emitted from the light guide 100, ideally, in generally equal amounts, in all directions along all treated surfaces). In general, creating more facets and/or nicks in a given portion of the outer or side surface of the light guide 100 increases its light emission or illuminance in that portion. In various exemplary embodiments, the distal end 104 of the light guide 100 furthest from the light source may be smooth or treated. Treating the distal end 104 of the light guide 100 will not appreciably affect the illuminance produced at the distal end 104 as virtually all light that reaches the distal end 104 will be emitted, but the distal end 104 may be treated to diffuse and/or scatter the light that is emitted at the distal end 104.

[0015] Fig. 2 compares the illuminance from a light guide that is smooth to the illuminance of a light guide according to this invention. In this test, a light source was placed at both ends of the light guides. Table 1 shows the data upon which Fig. 2 is based. The y-axis is illuminance and the x-axis is distance along the light guide from the light source. The outer or side surface of the light guide was treated by rolling the light guide over coarse (60 grit) sandpaper. Line 112 represents the smooth or untreated light guide's performance. Line 114 represents the treated light guide's performance, a light guide according to this invention will emit more light than a similarly illuminated and dimensioned conventional smooth and/or untreated light guide. It follows that a light guide 100 according to this invention can emit the same amount of light as a conventional light guide using a dimmer light source, reducing power demands for lighting. Table 1

Illuminance

Distance (in) Distance (mm) Untreated Treated

0 0 0.08 0.31

2 50.8 0.10 0.37

4 101.6 0.13 0.46

6 152.4 0.16 0.53

8 203.2 0.18 0.55

10 254.0 0.18 0.55

12 304.8 0.17 0.52

14 355.6 0.15 0.46

16 406.4 0.12 0.39

18 457.2 0.09 0.31 average 0.136 0.445

[0016] In various exemplary embodiments, the light guide 100 is treated by rolling or compressing the light guide 100 over or through one or more dies or rollers. The surface of the dies or rollers contain multiple, tiny projections and/or facets. After treatment, the surface of the light guide 100 will contain numerous nicks 102 and/or facets, creating numerous small facets in and/or on the outer or side surface of the light guide 100. In various exemplary embodiments, the rollers or dies may be configured such that all of the light guide's outer or side surface is treated or such that only select portions of the outer or side surface are treated. In various exemplary embodiments, the light guide 100 may be passed through one or more sets of dies or rollers.

[0017] In various exemplary embodiments, a light guide 100 is treated with an abrasive surface such as, for example, sandpaper. The treated outer or side surface of the light guide 100 will contain numerous randomly-located nicks that act as small, facets. In various exemplary embodiments, the light guide 100 may be treated on all, or only on a portion, of its outer or side surface, as desired for a particular application.

[0018] In various other exemplary embodiments, the light guide 100 is treated by sandblasting the light guide 100. The treated surfaces will contain numerous randomly-located nicks that act as small facets. In various exemplary embodiments, the light guide 100 may be treated on all, or only on a portion, of its outer or side surface, as desired for a particular application. In various exemplary embodiments, the light guide 100 may be treated using bead or abrasive blasting with the same effect as sandblasting.

[0019] In still other exemplary embodiments, the light guide 100 is treated with a laser to create small nicks and/or facets across at least a portion of the surface of the light guide 100. In various exemplary embodiments, different portions of the outer or side surface may receive more or less treatment to create more or fewer nicks and/or facets than other portions of the outer or side surface of the light guide 100. In various exemplary embodiments, the light guide 100 may be treated on all, or only on a portion, of its outer or side surface, as desired for a particular application.

[0020] In various other exemplary embodiments, the light guide 100 is treated by laser etching the light guide 100. The treated surfaces will contain numerous randomly-located nicks that act as small facets. In various exemplary embodiments, the light guide 100 may be treated on all, or only on a portion, of its outer or side surface, as desired for a particular application.

[0021] In yet other exemplary embodiments, the light guide 100 is molded in a mold, where the mold has an inner surface provided or formed with numerous small projections and/or facets. The surface of the light guide 100 will mirror the surface of the mold and have numerous facets.

[0022] In various exemplary embodiments, the treatment may be varied at different points of the light guide 100. This may be done to alter the light guide's light emission profile. For example, light guides tend to become dimmer at distances further from the light source, because there is less light (fewer photons) available to be emitted the farther a particular portion of the light guide 100 is from the illuminated end of that light guide 100. Accordingly, the light guide 100 may be treated to create more nicks and/or facets in portions farther from the illuminated end, relative to portions nearer to the illuminated end. This tends to increase the amount of the available light emitted from such more distant portions. The light guide 100 may also be treated to create areas of greater or lesser illuminance independent of distance from the illuminated end of the light guide 100.

[0023] In various exemplary embodiments, the light guide 100 is treated on all surfaces. Such a light guide 100 may be installed without regard for how it is oriented (i.e., there is no designated show surface, as all surfaces may function as the show surface).

[0024] It should be understood that the drawings are not necessarily to scale. In certain instances, details that are not necessary to the understanding of the invention or render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein.

[0025] It is also important to note that the construction and arrangement of the light guide, as shown in the various exemplary embodiments, is illustrative only. While the light guide, according to this invention, has been described in conjunction with the exemplary embodiments outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that are or may be presently unforeseen, may become apparent. Accordingly, the exemplary embodiments of the light guide, according to this invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention. Therefore, the description provided above is intended to embrace all known or later- developed alternatives, modifications variations, improvements, and/or substantial equivalents.

Claims

Claims:

1. Light guide to transport light from a source to another location, with an outer- or side-surface, characterized in, that it comprises, at least locally, surface irregularities on the outer- or side-surface to improve light emission along the outer- or side-surface.

2. Light guide according to claim 1 , whereas the outer- or side-surface is at least locally irregular with numerous nicks and/or facets.

3. Light guide according to claim 1 , whereas only a preselected area of the outer- or side-surface comprises irregularities.

4. Light guide according to claim 1 , whereas the outer- or side-surface is roughened.

5. Method for producing a light guide, comprising at least partially treating the outer- or side-surface of a light guide to create an irregular outer or side surface.

6. Method according to claim 5, whereas the irregularities are inserted into originally smooth outer- or side-surface

7. Method according to claim 5, whereas the outer- or side-surface is treated with a roller, a die, sandpaper or abrasive material, a laser, by chemical etching, sandblasting, bead-blasting and/or abrasive blasting.

8. Method according to claim 5, whereas the light guide is molded and the mould has an inner surface provided with numerous small projections and/or facets.

9. Method according to claim 5, whereas certain portions of the outer- or side- surface are treated with two or more processes.