DE102013223969B4 - Flat light guide with spatially varying thickness - Google Patents

Flat light guide with spatially varying thickness

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Publication number
DE102013223969B4
DE102013223969B4 DE102013223969.6A DE102013223969A DE102013223969B4 DE 102013223969 B4 DE102013223969 B4 DE 102013223969B4 DE 102013223969 A DE102013223969 A DE 102013223969A DE 102013223969 B4 DE102013223969 B4 DE 102013223969B4
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Germany
Prior art keywords
light guide
light
broadside
curvature
center
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DE102013223969.6A
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German (de)
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DE102013223969A1 (en
Inventor
Hubert Zwick
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Automotive Lighting Reutlingen GmbH
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Automotive Lighting Reutlingen GmbH
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Priority to DE102012221338 priority Critical
Priority to DE102012221338.4 priority
Application filed by Automotive Lighting Reutlingen GmbH filed Critical Automotive Lighting Reutlingen GmbH
Priority to DE102013223969.6A priority patent/DE102013223969B4/en
Publication of DE102013223969A1 publication Critical patent/DE102013223969A1/en
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B6/00Light guides
    • G02B6/0001Light guides specially adapted for lighting devices or systems
    • G02B6/0011Light guides specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033Means for improving the coupling-out of light from the light guide
    • G02B6/0035Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/0045Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide
    • G02B6/0046Tapered light guide, e.g. wedge-shaped light guide
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21SNON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S43/00Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights
    • F21S43/20Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights characterised by refractors, transparent cover plates, light guides or filters
    • F21S43/235Light guides
    • F21S43/236Light guides characterised by the shape of the light guide
    • F21S43/239Light guides characterised by the shape of the light guide plate-shaped
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21SNON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S43/00Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights
    • F21S43/20Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights characterised by refractors, transparent cover plates, light guides or filters
    • F21S43/235Light guides
    • F21S43/242Light guides characterised by the emission area
    • F21S43/245Light guides characterised by the emission area emitting light from one or more of its major surfaces
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21SNON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S43/00Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights
    • F21S43/10Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights characterised by the light source
    • F21S43/13Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights characterised by the light source characterised by the type of light source
    • F21S43/14Light emitting diodes [LED]

Abstract

Flat optical waveguide (10), which is adapted to guide light through total internal reflections occurring at interfaces of the optical waveguide along a beam path curved or bent in space, which curves or kinks around a center of curvature (M) and which optical waveguide is on its Side facing away from the center of curvature has an outer edge (18), wherein the light guide has a respective lying between the outer edge and the center of curvature first broad side (12) and second broad side (14), and wherein a thickness of the lying between the two broad sides of the material material Light guide along a line extending between the two broad sides and ends in the center of curvature line (15) increases when approaching the center of curvature, each pointing into the interior of the light guide and the line intersecting normal vector (17, 19) of the first broadside and the second broadside e has a directional component, which points in the direction of increase of the thickness of the light guide, so that perpendicular to the said straight line in the light guide propagating light when hitting one of the broad sides undergoes a direction of curvature centering direction change.

Description

  • The present invention relates to a planar light guide.
  • From the US 2004/0136203 A1 For example, an optical waveguide is known which has a first side serving as a transport surface and a second side opposite the first side and serving as a transport surface, the optical waveguide material lying between the first side and the second side having a thickness which differs at different points of the planar optical waveguide is large and constantly changing between two points of different thickness.
  • The known light guide is used in a motor vehicle light and extends there within the lamp in front of the transparent cover of the lamp. It has an average thickness which corresponds approximately to the thickness of the cover. In directions transverse to the thickness it has approximately the dimensions of the light exit opening of the lamp. The luminaire has a multiplicity of light-emitting diodes which are arranged on narrow sides of the light guide in such a way that they introduce light into the light guide. The incoming light undergoes internal total reflections on the first side and the second side and thereby propagates in the planar light guide. The first page and the second page act insofar as transport surfaces for the light. Over the surface of the first side and / or the second side decoupling elements are arranged distributed, at which light is coupled out of the light guide in the direction of the cover. The thickness of the planar light guide is substantially constant. There is a thickening in the area of the coupling. Furthermore, the decoupling elements are associated with local thickness variations.
  • The decoupling elements are, in particular, local tilts of the surface which delimit elevations and / or depressions in the first side and / or the second side. It is accompanied by the tilting that the optical waveguide has locally thicknesses which are different within a decoupling element than on a surface element serving as a transport surface and which change continuously between two points of different thickness.
  • The tiltings are designed in the prior art so that they provide for a decoupling of light. This is done so that either the conditions for total internal internal reflections are not met or that there incident light is deflected so that it exits the next time it encounters an interface of the light guide by refraction from the light guide. Examples of such decoupling elements have a prismatic shape which protrude as positive locally from the first side and / or second side or which are realized as negatives in the form of local depressions in the first side and / or the second side. Such planar light guides are used, inter alia, to produce luminous surfaces, which are also referred to as light curtains. Each decoupling element acts as a separate light source when viewed and is therefore referred to as a virtual light source. The light curtain effect results from the multiplicity and the areal distribution of the virtual light sources.
  • From the US Pat. No. 7,147,356 B2 For example, an annular light guide is known, which is delimited by a cylindrical inner edge surface and a cylindrical outer edge surface as well as by two base or cover surfaces. The center of the cylindrical inner edge surface is offset from the center of the cylindrical outer edge surface. The light is coupled in via a tangentially formed on the annular light guide light path, which has a suitable for the light coupling face, which is arranged perpendicular to the base or top surfaces. The light extraction takes place via one of the two base or top surfaces.
  • From the DE 10 2009 053 581 B3 a light module is known which has semiconductor light sources arranged in the manner of a matrix, that is to say in particular LEDs. By switching on and off certain LEDs of the matrix, the resulting light distribution, which generates the light module on the road, can be changed. Each LED generates a kind of pixel of the light distribution. The light distribution results as the sum of all pixels. In order for each pixel to be uniformly illuminated in itself, each LED feeds a more rod-shaped light guide, which has an outer contour that transforms the light beam of the LED in a suitable manner. The transverse to the propagation of light in the optical fiber cross section of the light guide varies between a square and a rectangular shape. The light is coupled in at one end of the rod-shaped light guide and coupled out at the other end. The light exit surface of the rod-shaped light guide is projected by a projection optics on the street.
  • The DE 10 2011 077 636 A1 used instead of the above-described matrix-like arranged rod-shaped light guide, differently shaped light guide whose light exit surfaces are formed as vertical stripes, said light guides can be considered at least in sections as a planar light guide.
  • Each strip effectively replaces a column of the matrix from the DE 10 2011 077 636 A1 , This will be opposite to the DE 10 2009 053 581 B3 significantly reduces the number of light sources used. It will be in The document made various proposals for adjusting the brightness distribution, which, however, open only limited possibilities.
  • From the DE 10 2006 037 797 A1 a motor vehicle lamp is known in which a Lichtauskoppelbereich in cross-section of a bent light guide has a semi-elliptical base and the Lichtumlenkbereich has a trapezoidal or rectangular base and the two areas adjacent to each other along a transverse center plane of the light guide. The trapezoidal light deflection region is intended to reflect light back into the light guide, so that it is again available for controlled decoupling via the semi-elliptical base surface. However, this document does not show a planar light guide.
  • The DE 10 2006 053 537 A1 shows a light distribution of transparent material consisting of radially arranged wedge sections with a light source arranged in the center.
  • The JP 2003 241003 A shows a signal transmission device with annular and tangentially wedge-shaped light guides, which are separated by a gap and are rotated against each other. In one of the light guide end-coupled light passes through the gap to the other light guide. The US 2003/0235046 A1 shows a substantially wedge-shaped light guide with stepwise decreasing thickness from outside to inside. Radially coupled-in light from the outside is deflected axially at inclined steps and decoupled via a broadside. The US 6,874,924 B1 shows a substantially tubular waveguide with arranged in its interior parallel to its longitudinal axis LEDs for simulating a neon tube. The DE 20 2012 101 129 U1 shows a lighting device with a wedge-shaped light guide and on the blunt end face of the wedge, which is opposite to the wedge tip, arranged light source. Their light enters the wedge and experiences total internal reflection, which makes it steeper and steeper on the broad side of the wedge, so that the light finally escapes there. The US 2012/0014127 A1 shows a linear light source, consisting of a linear light guide with reflective surfaces, which favor a decoupling of light.
  • The present invention is based on the aforementioned prior art, as it is known from US 2004/0136203 A1 is known.
  • A disadvantage of the known optical waveguide is that the coupled-in light propagates in the surface and is thereby preferably reflected on the first side and the second side. It is not reflected or at least only to a lesser extent on other narrow sides of the light guide. This is due to the planar geometry, in which parallel to the surface between two reflections extending light paths can be relatively long. This has the disadvantage that the light propagates as a result of the lack or only a small number of deflecting reflections on the side walls comparatively uncontrolled in the planar light guide, which contributes to an inhomogeneous light distribution in the light guide. This can lead to undesirably low light in some places and unnecessarily much light for decoupling at other locations.
  • Against this background, the object of the invention in the specification of a planar light guide, which allows an efficient influence on the propagation direction of the light within the planar light guide.
  • This object is achieved with the features of claim 1. The flat optical waveguide according to the invention is adapted to guide light through internal total reflections at interfaces of the optical waveguide along a curved or bent beam path that curves or kinks around a center of curvature and which optical waveguide has an outer edge on its side remote from the center of curvature wherein the optical waveguide has a first broad side and a second broad side lying respectively between the outer edge and the center of curvature, and wherein a thickness of the material lying between the two broad sides of the planar waveguide along a running between the two broad sides and ends in the center of curvature at a straight line Approaching the center of curvature increases, each pointing into the interior of the light guide and the line intersecting normal vector of the first broadside and the second broadside a Richtungskompo NEN, which points in the direction of increase in the thickness of the light guide, so that perpendicular to the said line in the optical fiber propagating light when hitting one of the broad sides undergoes a direction of curvature centering direction change.
  • In this application, a flat optical waveguide is to be understood as meaning an optical waveguide which is distinguished by the fact that the optical waveguide material lying between a first broad side and the second broad side has a thickness and wherein the first broad side and the second broad side have dimensions lying transversely to the thickness, which are at least five times as large as the thickness and wherein the dimensions lying transversely to the thickness differ by a maximum of a factor of 5.
  • By these features arise on the broad sides of the planar light guide as Transport surface serving surface elements, so that the light guide is adapted to guide light along a running between the first side and the second side path which is transverse to the radial center of curvature leading straight line, along which the thickness preferably changes continuously. As a result, the light is not coupled out of the optical waveguide there, as is the case with local tilting elements of the aforementioned known optical waveguide serving as decoupling elements. Instead, the light is deflected at the area serving as transport surfaces surface elements within the light guide so that it undergoes an internal total reflection there at the next impact on an interface of the light guide there.
  • The planar light guide according to the invention allows a very efficient influencing of the light propagation direction in the light guide. In contrast to the above-mentioned prior art, in which the propagation directions of most light rays are completely uncontrollable due to the planar geometry, the invention allows a targeted deflection of the light rays in a sense within the area, without requiring reflections on narrow edge sides of the sheet-like light guide. The direction of the light in such a reflection point thus always has a component which is parallel to a tangential plane of the reflection surface at this point. As a result, even such light can be redirected specifically in the light guide, which would not penetrate to the edge due to the flat geometry.
  • The invention enables a realization of extremely strong curvatures of the light path, which are not possible even in curved elongated light guides. It is possible to keep certain areas of the light guide free of light by targeted reflections on the transport surfaces, which are determined by specifically generated local inclinations of the transport surfaces. These areas of the light guide can be printed, painted or molded using a multi-color spray technique of opaque plastics, for example, to realize fasteners such as domes, eyelets, clips or the like.
  • The deflection is preferably such that the light receives a change in direction towards the direction of increasing thickness. As a result, the angular distribution of the propagating in the surface of the planar light guide light can be changed by reflections on the wide transport surfaces.
  • Further advantages will be apparent from the dependent claims, the description and the attached figure.
  • It is understood that the features mentioned above and those yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.
  • drawings
  • An embodiment of the invention is illustrated in the drawing and will be explained together with further embodiments in the following description. Show it:
  • 1 An embodiment of a light guide according to the invention in a schematic form.
  • 2 a side view of a section through a motor vehicle lamp having an embodiment of a light guide according to the invention;
  • 3 a decoupling element, which in one side of the light guide of the 1 is arranged;
  • 4 an embodiment of a light guide having a partially trapezoidal cross-section;
  • 5 a plan view of the subject of 4 ; and
  • 6 a plan view of a similar in plan view light guide, but has a constant cross-section.
  • The same reference numerals in different figures are intended to denote the same elements.
  • The 1 shows a planar light guide 10 , The planar light guide 10 is essentially a circular first broadside 12 and a circular second broadside 14 limited. The center M of the first broadside 12 and the midpoint M 'of the second broadside 14 are at a distance A on a common axis 16 arranged. The two broadsides 12 . 14 are inclined against each other, giving them a common edge 18 have and a discus-like body 20 form.
  • In the illustrated embodiment, both the first broadside 12 as well as the second broadside 14 the shape of a cone coat.
  • The illustrated body 20 has a cylindrical recess 22 on, concentric to the axis 16 is arranged. This shows the light guide 10 a central edge surface 24 on. There is also a sector 26 out of the body 20 except. The recess is along radial extending cross sections of the discus-shaped body 20 , One through the recess 26 exposed first cut surface 28 is in the illustrated embodiment relative to the rest of the body 20 arranged so that their surface normal transverse to the axis 16 lies. The first cut surface 28 forms a light entrance surface.
  • One through the recess 26 exposed second cut surface 30 is in the illustrated embodiment relative to the rest of the body 20 also arranged so that their surface normal transverse to the axis 16 lies. The second cut surface 30 forms in the illustrated embodiment, a light exit surface.
  • In a preferred embodiment, the first broad side or the second broad side has outcoupling elements in the form of local elevations and / or depressions. In the illustrated embodiment, the light exit surface is opposite the light entry surface. This has the advantage that light exiting via the light exit surface falls onto the light entry surface and is coupled back into the light guide. This will make this light back into the body 20 coupled and is available for a desired, taking place via said decoupling elements decoupling in further rounds available.
  • The light of a light source 32 that in the exempted sector 26 is placed above the light entry surface 28 in the body 20 coupled there and propagated there as light 31 , The light source 32 is preferably a semiconductor light source. It preferably has one or more LEDs. For automotive applications, it is common and also preferred to use LEDs with a nearly flat light exit surface, wherein the light exit surface of an LED is square or rectangular and the edge length is between 0.3 and 2 mm. The plane light exit surface of the LED is preferably very close, preferably at a distance of the order of a tenth of a millimeter in front of the light entry surface 28 without touching them. As a result, an efficient light coupling is achieved.
  • In the subject of 1 are the broadside 12 and the second broadside 14 so inclined or curved against each other that they have a common edge 18 exhibit. The thickness of the body 20 increases inward from the outer, common edge, ie toward the central axis. As a result, each points into the interior of the optical fiber material of the body 20 pointing normal vector of the first broadside 12 and the second broadside 14 a directional component, which in the direction of the growing cross section of the optical waveguide material of the body 20 So, to the axis 16 has.
  • This ensures that every ray of light, at any angle on the first broadside 14 or the second broadside 16 meets and meets the conditions for a total reflection, there repeatedly experiences deflections, the light in the sum of the reflections around the axis 16 to propagate around.
  • Preferably, all normals of the first broad side and the second broad side have an intersection with the axis 16 on, with the intersection then each closer to the other broadside. The normals thus cut an imaginary median plane of the body 20 that from the common edge 18 is limited.
  • Because the two broadsides 12 . 14 have a common edge where they are connected to each other, the light guide has no outer edge surface over which light is reflected or decoupled. The deflecting reflections are found only on the transport surfaces 12 and 14 instead of.
  • In the illustrated embodiment, the approximately the center of the body results 20 circumferential movement of the light through the disc-like shape of the light guide. Such a body can be easily manufactured by manufacturing processes such as casting, in particular injection molding of transparent plastics such as polycarbonate (PC) or polymethyl methacrylate (PMMA).
  • Due to the disc-shaped shape of the double cone, the two broad sides 12 . 14 form in this embodiment, an angle of inclination of the base or top surfaces to each other is spatially varied. As a result, a predetermined influence on the light propagation in the light guide, which can be calculated thereby, can be used for directing the light.
  • The 1 thus shows in particular a planar light guide 10 with a first broadside serving as a transport surface 12 and one of the first broadside 12 opposite and serving as a transport surface second broadside 14 , being between the first broadside 12 and the second broadside 14 lying optical fiber material has a thickness which is different at different points of the planar light guide and which varies continuously between two points with different thickness. The planar light guide 10 is characterized in that the thickness changes so that at the two points of the planar light guide differently inclined and serving as transport surfaces surface elements in the transport surfaces and that the light guide is adapted to light along one between the first broadside and the second Broadside running path that runs transversely to a plane in which the thickness changes continuously, these two points in one Cut curve of the first broadside or the second broadside lie with said plane. This results in the illustrated embodiment in that already the light entry surface 28 a level is between the first broadside 12 and the second broadside 14 lies and forms a cross section of the optical fiber material that meets the conditions mentioned. The optical waveguide material thus has a thickness in the cross-sectional plane which varies in size at different points and which changes continuously between two points of different thickness.
  • In the example shown, the thickness increases starting from the center in the radial direction to the edge 18 down continuously. The invention is not limited to such a special embodiment.
  • That from the light source 32 outgoing and in the body 20 coupled light there initially spreads within a cone whose measured to the Lot of the light entrance surface opening angle because of the refraction of light when entering the optically denser light guide material of the body 20 is less than 90 °.
  • When hitting the first broadside 12 or the second broadside 14 the light experiences internal total reflections. In each case, they lie at one point of the surface of the respective broadside 12 . 14 incident beam, the reflected beam emanating from there and the surface normal at that point in a plane, and the angle of incidence is equal to the angle of reflection.
  • Consequently, every ray of light, at any angle, that satisfies the conditions for total internal reflection, and that on one of the two broadsides 12 or 14 meets, from this, to the other opposite broadside 14 or 12 diverted. Thus, each light beam receives at the latest at the second reflection on one of the broadsides 12 . 14 , an impulse in the direction of the axis 16 ,
  • Light rays, which meets the conditions for a total reflection at any angle of the central edge surface 24 meet at this point in the direction of the broadsides 12 or 14 reflected, so that from the central edge surface 24 reflected light rays also at the latest at the second reflection on one of the broadsides 12 or 14 a pulse in the direction of the axis 16 receive.
  • As a result of the reflections, the processes described above lead to an axis 16 along a path 21 circulating movement of light in the light guide 10 , the way 21 runs transverse to a plane in which the thickness changes steadily. The circulating movement is reflected by reflections on the extended broad sides serving as transport surfaces 12 and 14 of the light guide 10 achieved.
  • It is possible to realize extremely strong curvatures of the light path, which would not even be possible in curved elongated light guides. Basically, the light spreads after its coupling into the light guide initially within an opening cone. It is essential, in particular, that the degree of parallelism, or the divergence of the light propagation determines the strongest curvature of the light guide, in which just no light exits at the transport surfaces, and that the degree of parallelism defines the opening of the bundle, after exit the light from the light guide is present. The divergence of the beam thus restricts the possible curvatures of an elongated light guide in which no light is yet to emerge.
  • When flat waveguides are used, the width of the waveguide cross-section alone results in a reduction in the effects of parallelizing reflections on the conveyor walls. This is due to the planar geometry, in which parallel to the surface between two reflections extending light paths can be relatively long. The propagation directions of individual light beams in the known planar light guide are therefore largely uncontrollable and therefore random and very limited use. It is a particular advantage of the invention that it additionally makes parallelizing effects possible by allowing a targeted deflection at the extended transport surfaces in planes lying parallel to the respective transport surface.
  • Certain areas of the light guide are free of light in the illustrated embodiment. In them, no or only a comparatively negligible transport of light energy takes place. In the illustrated embodiment, these are light-free areas 36 inside and outside the ring 21 in which the light moves. These areas are not needed in the illustrated embodiment for the light deflection and direction of the light. In particular, an outer edge surface is not needed. Such an outer edge surface is also absent due to the outwardly tapered discus cross section in the illustrated embodiment.
  • These areas 36 For example, in preferred embodiments, they are printed or painted or otherwise coated to produce a desired appearance of the light pipe. In an alternative or additional embodiment, opaque plastic parts are molded by means of the so-called multi-color injection technique, which are also used as design Elements and / or serve as fastening and / or support elements such as hooks, eyes, screw domes or the like.
  • In the light-guiding areas 21 are preferably Auskoppelelemente on the first broadside 12 or the second 14 Broadside arranged distributed, with which light is coupled out of the light guide. For example, the light becomes parallel to the axis 16 decoupled. The decoupling direction can be determined by the design of the decoupling elements. It can therefore be determined by the designer depending on the installation position of the light guide in a motor vehicle light and in dependence on the light distribution to be generated. With the coupled-out light, a specific light distribution is preferably generated, and / or a specific luminous appearance of the light-fed light guide is generated. Such a particular appearance is also referred to as a signature because it is deliberately used by vehicle manufacturers as a distinguishing feature.
  • As a preferred embodiment of the light guide is designed as a light guide for generating a light curtain and / or as a light guide for the realization of individual light functions of bow or tail lights of motor vehicles. Examples of such light functions are position light, parking light, side marker light, daytime running light, flashing light, without this being intended to represent a concluding enumeration.
  • 2 shows in detail a side view of a motor vehicle light 1 on average. The lamp 1 has a housing 2 on, the light exit opening through a transparent cover 3 is covered. Inside the housing, an inventive optical fiber is arranged. In the illustrated embodiment, the light guide 10 the light guide 10 from the 1 , At different points 4 . 5 of the planar light guide 10 this has different thicknesses d4, d5. The arrows 11 represent light coming out of the light guide 10 disconnected and from the light 1 is emitted.
  • 1 and 2 show together a flat light guide 10 which is set to light through at interfaces 12 . 14 of the light guide 10 internal total reflections take place along a curved or bent beam path in space 21 to guide, which is curved or bent around a center of curvature M around and which optical fiber on its side facing away from the center of curvature M an outer edge 18 wherein the optical fiber has a respective first broad side lying between the outer edge and the center of curvature 12 and second broadside 14 and wherein a thickness d of the material lying between the two broad sides of the planar light guide along a running between the two broad sides and ending in the center of curvature straight line 15 increases with an approach to the center of curvature, each pointing into the interior of the light guide and the line intersecting normal vector 17 the first broadside 12 and normal vector 19 the second broadside 14 a direction component which points in the direction of the increase in the thickness of the light guide, so that perpendicular to the said straight line propagating in the light guide light when hitting one of the broad sides undergoes a direction of curvature centering direction change. This applies analogously to light, which is only one perpendicular to the line 15 has lying direction component. This is partly true for example in the beam path 21 propagating light too.
  • The 3 shows an example of a single decoupling element 6 as a local depression in the first broadside 12 is realized. The decoupling element 6 has a decoupling surface 7 , which are opposite to the remaining first broadside serving as a transport surface 12 is tilted. As a result of tilting is on the decoupling surface 7 from the light guide inside forth incident light 31 out there from the light guide 10 decoupled and as a decoupled light 11 radiated.
  • The discus form shown represents merely a simple exemplary embodiment of the invention. In principle, the light guide according to the invention has its advantages, in particular in the case of three-dimensionally curved planar light guides. As an example of a three-dimensionally curved optical waveguide, one may think of a curved, strip or band-shaped plane in space, which, like a toy race track, has right and left curved and / or upwardly or downwardly curved roadway sections.
  • A particular advantage results from the fact that the light-directing properties of optical fibers according to the invention can be used there, ie in the case of three-dimensionally curved optical waveguides, in particular to compensate for the influence of the three-dimensional curvature of the optical waveguide on the directions of the light propagating in it. For example, it may be that the three-dimensional curvature of a light guide of constant thickness causes certain locations of the light guide no light or little light, since the light is preferably reflected due to the geometry of the light guide in other areas in the interior of the light guide.
  • In the in 1 illustrated embodiment, these are, for example, the light-free areas 36 and in particular the subareas of these light-free areas 36 that are near knots 37 located in the interior of the light guide 10 adjusting light distribution lie. At such, little or no light-conducting areas 36 is then only correspondingly little light for decoupling available, which leads to undesirable dark spots (black holes), when there are decoupling elements are arranged. In such cases, the invention makes it possible to specifically reflect light in such areas, these reflections taking place on the reflecting surfaces designed according to the invention.
  • A further preferred use of an embodiment of a light guide according to the invention results in front headlamps with sub-beam light functions, as already mentioned above DE 10 2009 053 581 B3 and DE 10 2011 077 636 A1 are known. In the DE 10 2009 053 581 B3 each pixel of the light distribution should be evenly illuminated in itself. The rather rod-shaped optical fiber used for this purpose, which converts the light bundle of the LED in a suitable manner, has, transversely to the propagation of light in the light guide, a cross section which varies between a square and a rectangular shape.
  • The DE 10 2011 077 636 A1 uses differently shaped light guide whose light exit surfaces are formed as vertical stripes, said light guide can be considered at least in sections as a planar light guide. The individual strips should not be illuminated homogeneously. The strips are aligned transversely to the horizon at a light module used as intended in the motor vehicle.
  • In the area of the horizontal, a strong maximum is desired, and starting from this maximum, the brightness should decrease continuously towards the top. In the DE 10 2011 077 636 A1 Various proposals for the realization of such a light distribution are already disclosed, which, however, open only limited possibilities.
  • In a further exemplary embodiment, it is provided for such a light guide that it has a trapezoidal or wedge-shaped cross-section at least in sections. 4 shows an embodiment of such a light guide 40 which partially has a trapezoidal cross-section. The light guide 40 has a coupling-in section 42 , a first section 44 with trapezoidal cross-section and a second section 46 with trapezoidal cross-section on. The sections 42 . 44 . 46 are preferably sections of a cohesively coherent and thus one-piece light guide 40 , The coupling section 42 is preferably plate-shaped, wherein the light via a light entrance surface 28 serving narrow side of the section 42 is coupled. The light coupling is preferably carried out as described above in connection with the subject of 1 has been described.
  • The first paragraph 44 with trapezoidal cross section has a trapezoidal light entrance surface 44.1 , a trapezoidal light exit surface 44.2 , serving as a transport surface first broadside 44.3 , serving as a transport surface second broadside 44.4 , a broad base area 44.5 and a narrow base area 44.6 on.
  • The second section with a trapezoidal cross-section likewise has a trapezoidal light entry surface, a trapezoidal light exit surface, a first broad side serving as a transport surface, a second broad side serving as a transport surface, a broad base surface and a narrow base surface.
  • The light exit surface 44.2 of the first section forms the light entry surface of the second section. If the first section 44 and the second section 46 are not integral, are the light entrance surface of the second section 46 and the light exit surface of the first section 44 arranged so that from the light exit surface from the first section 44 exiting light over the light entry surface in the second section 46 entry. The first paragraph 44 and the second section 46 are designed such that their broad base sides enclose an angle α.
  • Due to the trapezoidal shape of the optical fiber cross-section, the coupled-in light follows, of which, by way of example, three beams 48.1 . 48.2 . 48.3 are shown a way 34 inside the light guide 40 , which way 34 the direction change of the light guide 40 by the angle α in the middle of the light rays follows. The way 34 can therefore also be used as a beam path 34 be designated. If one considers the legs which form the angle α as the tangents of a circle, then the center of this circle represents a center of curvature M coinciding with the center of curvature M of the object 1 and 2 is comparable.
  • The change in direction takes place in each case by internal total reflections on serving as transport surfaces first broadsides and serving as transport surfaces second broadsides, wherein the light guide the light along a running between the first broad side and the second broadside path 34 leads, which runs transversely to a plane, in which the thickness of the light guide 40 changes constantly, ie transversely to the trapezoidal surfaces.
  • 5 shows a plan view of the subject of 4 , 5 shows in particular how the light path 34 inside the light guide 40 the direction change of the light guide 40 follows without any reflections on base surfaces 44.6 . 46.6 the sections 44 . 46 occur. In the illustrated embodiment, the light passes over a trapezoidal light exit surface of the second section 46 out.
  • 6 on the other hand shows a plan view of a similar in plan view light guide 50 which has the same directional change by the angle α. The light guide of the 6 but should be in the range of sections 44 and 46 of the light guide 40 from the 4 and 5 have a constant cross section, ie in particular a rectangular shape instead of the trapezoidal shape. As 6 for some exemplarily selected rays 52 In this case, the light path does not follow the direction change by the angle α. At the outer surface, light strikes at an angle at which total reflection no longer takes place, so that undesired decoupling takes place.
  • 4 and 5 show together a flat light guide 40 which is set to light through at interfaces 44.3 . 44.4 of the light guide 40 internal total reflections take place along a curved or bent beam path in space 34 to guide, which is around a center of curvature (center M of the circle, the tangents of which form the angle α) curved or kinked and which light guide on its side facing away from the center of curvature an outer edge 44.6 , 46.6 wherein the optical fiber has a respective first broad side lying between the outer edge and the center of curvature M 44.1 and second broadside 44.3 and wherein a thickness d of the material lying between the two broad sides of the planar light guide along a running between the two broad sides and ending in the center of curvature straight line 15 increases when approaching the center of curvature M, wherein each pointing into the interior of the light guide and the line intersecting normal vector 17 the first broadside 44.1 and normal vector 19 the second broadside 44.3 a direction component which points in the direction of the increase in the thickness of the light guide, so that perpendicular to the said straight line propagating in the light guide light when hitting one of the broad sides undergoes a direction of curvature centering direction change. This applies analogously to light, which is only one perpendicular to the line 15 has lying direction component. This is partly true for example in the beam path 34 propagating light too.

Claims (10)

  1. Flat light guide ( 10 ), which is adapted to guide light through internal total reflections taking place at interfaces of the optical waveguide along a beam path curved or bent in space, which curves or kinks around a center of curvature (M) and which optical waveguide is on its side averted from the center of curvature outer edge ( 18 ), wherein the optical waveguide each lying between the outer edge and the center of curvature first broad side ( 12 ) and second broadside ( 14 ), and wherein a thickness of the material lying between the two broad sides of the planar light guide along a running between the two broad sides and in the center of curvature ending straight line ( 15 ) increases when approaching the center of curvature, each normal vector pointing into the interior of the light guide and intersecting the straight line ( 17 . 19 ) of the first broad side and the second broad side has a directional component which points in the direction of increasing the thickness of the light guide, so that perpendicular to said straight line in the light guide propagating light when hitting one of the broad sides undergoes a direction of curvature centering direction change.
  2. A planar light guide according to claim 1, characterized in that the first broad side and the second broad side have transversely to the thickness lying dimensions which are at least five times as large as the thickness and wherein the transverse thickness to the dimensions differ by a maximum of a factor of 5.
  3. Flat light guide ( 10 ) according to claim 1 or 2, characterized in that it passes through a light entry surface ( 28 ), through a light exit surface ( 30 ), the first broadside ( 12 ), the second broadside ( 14 ) and an edge surface ( 24 ), the first broadside ( 12 ) and the second broadside ( 14 ) are opposite one another and are inclined or curved in such a way that they extend over a common edge line ( 18 ) feature.
  4. Flat light guide ( 10 ) according to one of the preceding claims, characterized in that the first broadside ( 12 ) and the second broadside ( 14 ) have the shape of a cone sheath.
  5. Flat light guide ( 10 ) according to one of the preceding claims, characterized in that it is arranged by arrangement and inclination of surface elements of the first broadside and the second broad side to certain areas of the light guide by targeted reflections on the two broadsides, which determined by specifically generated local inclinations of broadsides be free from light.
  6. Flat light guide ( 10 ) according to claim 5, characterized in that these areas of the light guide are coated.
  7. Flat light guide ( 10 ) according to claim 6, characterized in that these areas of the light guide are printed or painted.
  8. Flat light guide ( 10 ) according to claim 6 or 7, characterized in that these areas of the light guide are molded onto opaque plastics to realize, for example, fasteners such as domes, eyelets or clips.
  9. Flat light guide ( 10 ) according to one of the preceding claims, characterized in that the first broadside ( 12 ) and the second broadside ( 14 ) are inclined or curved against each other so that they have a common edge ( 18 ) exhibit.
  10. Use of a planar light guide ( 10 ) according to one of the preceding claims, characterized in that the use takes place in a motor vehicle lamp.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003241003A (en) * 2002-02-19 2003-08-27 Yazaki Corp Signal transmission device
US6874924B1 (en) * 2002-03-14 2005-04-05 Ilight Technologies, Inc. Illumination device for simulation of neon lighting
US20030235046A1 (en) * 2002-06-25 2003-12-25 Visteon Global Technologies, Inc. Optical element and lamp assembly utilizing the same
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