Optical waveguide structures for vehicle lighting

[0002] This application claims priority from Provisional Application Ser. No. 60/069,118, “HID DRIVEN FOCUS-LESS OPTICS SYSTEM,” filed Dec. 9, 1997 and application Ser. No. 09/009,836, “DISTRIBUTED LIGHTING SYSTEM,” filed Jan. 20, 1998, both of which are incorporated by reference.

[0003] The invention relates to distributed lighting systems.

[0004] Distributed lighting systems distribute light from one or more light sources in central locations to one or more remote locations. A distributed lighting system promises several advantages over conventional lighting techniques, including low power consumption, extended life, heat reduction where the light is emitted, and increased design flexibility.

[0005] The invention provides a distributed lighting system (DLS) for use, for example, in an automobile. Issues associated with incorporating a distributed lighting system into an automobile are discussed by Hulse, Lane, and Woodward in “Three Specific Design Issues Associated with Automotive Distributed Lighting Systems: Size, Efficiency and Reliability,” SAE Technical Paper Series, Paper No. 960492, which was presented at the SAE International Congress and Exposition, Detroit, Mich., Feb. 26-29, 1996 and Hulse and Mullican in “Analysis of Waveguide Geometries at Bends and Branches for the Directing of Light,” SAE Technical Paper Series, Paper No. 981189, which are incorporated herein by reference.

[0006] A practical distributed lighting system for an automobile must address size, efficiency, and reliability issues. To this end, an implementation of the invention employs focus-less optics components, such as collector elements and waveguides. These components are inexpensive to manufacture, since they can be formed from plastic (acrylic, for example) in an injection molding process. In addition, they have high collecting efficiency and are very compact. For example, a collector element may be smaller than one cubic inch (16.4 cubic centimeters). Components that must handle high heat levels (e.g., components are placed in proximity to the light source) may require a ventilation system or may include portions formed from heat resistant materials, such as glass or Pyrex™.

[0007] The DLS may incorporate different types of optical waveguide structures to distribute light throughout the vehicle, including joints, elements with epoxy coatings, pinched end collector portions, integrated installation snaps, integrated input optics and integrated output lenses. The DLS may also include waveguide structures to provide illumination to portions of the vehicle interior, including cup holders, assist grips, and storage pockets.

[0008] In one aspect, generally, an optical waveguide for illuminating the interior of a cup holder in a vehicle is formed from a piece of solid material. The solid material has a ring portion that is sized and shaped to be received within a cup holder and that releases light into the cup holder. An input face receives light from a light source. An input portion extends between the input face and the ring portion, confines light through internal reflection, and directs light from the input face to the ring portion.

[0009] Embodiments may include one or more of the following features. The ring portion may define an inner circumference and may release light around the inner circumference. The ring portion may have a protruding angled portion around the inner circumference that directs light down toward a bottom portion of the cup holder. The upper surface of the angled portion may be stippled. An upper surface of the angled portion may be covered with an opaque material. The ratio of an inner radius of the ring portion to the width of the ring portion may be greater than or equal to 3:1.

[0010] The ring portion may include a first arm and a second arm that define a gap in the inner circumference. The second arm may have a smaller cross-section and a smaller length than the first arm. The ring portion may have a web portion that extends between the first and second arms. The web portion may release light along its edge. The ring portion may include a tab that extends from the inner circumference between the first and second arms. The tab may have a rectangular cross-section and may curve toward the bottom of the cup holder. The tab may have a chamfered leading edge.

[0011] The optical waveguide described above may be included in an illuminated cup holder having a bottom surface. A side wall may extend from the bottom surface and define a volume shaped and sized to receive a cup. A rim may be positioned around the upper edge of the side wall.

[0012] In another aspect, an optical waveguide illuminates the inside of an assist grip in a vehicle. The waveguide is a piece of solid material having an illumination portion with an inner surface and an outer surface. The illumination portion is sized and shaped to be received within a channel along the length of the assist grip and releases light from the inner surface. An input face at one end of the illumination portion receives light from a light source.

[0013] Embodiments may include one or more of the following features. The inner surface may be stippled. The ratio of the inner radius of a bend to the width of the waveguide may be greater than or equal to 3:1. The waveguide may have snaps extending from the outer surface that hold the illumination portion in place within the channel. A lens positioned adjacent to the light source may focus light from the light source to form a courtesy light. An illuminated assist grip for a vehicle including the waveguide described above also may have a handle portion formed of solid material, a channel formed along the length of the handle and a light source receptacle configured to receive a light source.

[0014] In another aspect, an optical waveguide for a vehicle door illuminates an area beneath the vehicle. The door has a bottom surface that meets a floor surface of the vehicle when the door is closed. The waveguide includes a door portion positioned inside the door and extending to the bottom surface of the door. A floor portion extends from the floor surface to the underside surface of the vehicle. The door portion and the floor portion meet when the door is closed so that light may pass through the door portion and the floor portion to illuminate the area beneath the vehicle. Embodiments may include a branch that extends from the door portion to an interior surface of the door to illuminate the interior of the vehicle.

[0015] In another aspect, an illuminated storage pocket for a vehicle has a surface that defines a storage volume and a rim around an edge of the surface. A waveguide formed from a piece of solid material has an illumination portion that has an inner surface and an outer surface. The illumination portion is received within a channel along the rim of the storage pocket and releases light from the inner surface. An input face at one end of the illumination portion receives light from a light source.

[0016] Embodiments may include one or more of the following features. The inner surface of the waveguide may be stippled. The waveguide may include snaps that extend from the outer surface and hold the illumination portion in place within the channel.

[0017] In another aspect, an optical waveguide includes a first and a second piece of solid material. The first piece has a transmission portion with a rectangular cross-section. The end of the transmission portion is convex in one dimension. The second piece has a transmission portion with a rectangular cross-section. The end of the transmission portion is concave in one dimension. The end of the first piece and the end of the second piece form an interface between the first and second pieces.

[0018] Embodiments may include one or more of the following features. The waveguide may include a third piece of solid material having a transmission portion with a rectangular cross-section. The end of the transmission portion may be concave in one dimension. The end of the third piece and the end of the first piece may form an interface between the first and third pieces. A band may hold the first, second and third pieces together.

[0019] The waveguide may include a third piece of solid material having a transmission portion with a rectangular cross-section. The end of the transmission portion may be convex in one dimension. The end of the third piece and the end of the second piece form an interface between the second and third pieces. A band may hold the first, second and third pieces together.

[0020] In another aspect, an optical waveguide accepts light from a light source and transmits the light. The waveguide is formed from a piece of solid material having an input face, a transmission portion and an end portion between the input face and the transmission portion. A cross-sectional area of the end portion gradually decreases from the transmission portion to the input portion.

[0021] Embodiments may include one or more of the following features. The end portion may have planar sides angled from a longitudinal axis of the transmission portion. The angle formed between the sides and the longitudinal axis may be about 5°. The end portion may increase the acceptance angle of the waveguide. A lens portion may be formed on the input face.

[0022] In another aspect, an optical waveguide has integrated installation elements. The waveguide includes first and second sections. The first section has an input face, an output end and a transmission portion extending from the input face to the output end. A key is positioned on the output end and mates with a socket of the second section. The second section has an input face, an output end and a transmission portion extending from the input face to the output end. A socket is positioned on the output end and mates with the key of the first section.

[0023] Embodiments may include one or more of the following features. The waveguide may include a snap positioned on the transmission portion of the first or second section. The snap may mate with an installation fitting of a vehicle. The outer surface of the waveguide may be covered with epoxy.

[0024] In another aspect, an optical waveguide has integrated installation elements. The waveguide includes first and second sections. The first section has an input face, an output end and a transmission portion extending from the input face to the output end. A claw is positioned on the output end and mates with a detent of the second section. The second section has an input face, an output end and a transmission portion extending from the input face to the output end. A detent is positioned near the output end and mates with the claw of the first section.

[0025] Embodiments may include one or more of the following features. A snap may be positioned on the transmission portion and may mate with an installation fitting of a vehicle. An outer surface of the waveguide may be covered with epoxy.

[0026] In another aspect, an optical waveguide has an output element for providing illumination in a vehicle. The waveguide includes an input face and a transmission portion extending from the input face. The transmission portion widens at an end to form an output element having a convex lens at the end of the output element. The output element may be formed to leave an air gap between the lens and the end of the transmission portion.

[0027] Other features and advantages will be apparent from the following detailed description, including the drawings, and from the claims.

[0028] FIG. 1 is a block diagram of a vehicle distributed lighting system with hybrid lighting subsystems.

[0029] FIG. 2 shows a hybrid headlamp subsystem.

[0030] FIG. 3 shows a hybrid headlamp subsystem with a movable lens.

[0031] FIGS. 4A-4D show headlamp beam forming structures.

[0032] FIG. 5 shows a light source with a diffusion grating.

[0033] FIGS. 6A-6F show waveguide outputs modulated with electromechanical or liquid crystal light valves.

[0034] FIG. 7 shows a hybrid tail light subsystem.

[0035] FIG. 8 shows a compact incandescent cartridge.

[0036] FIGS. 9A and 9B show a waveguide output bend for a tail light.

[0037] FIGS. 10A and 10B show a combination security/puddle light.

[0038] FIGS. 11A-11F show various embodiments of a cup holder illumination component.

[0039] FIG. 12A is a rear view of a waveguide installed in a handgrip.

[0040] FIG. 12B is a cross-section view of a waveguide and light source installed in a handgrip.

[0041] FIG. 12C shows a waveguide with integrated snaps for installation into a handgrip.

[0042] FIG. 13 is a cross-section view of an optical waveguide.

[0043] FIGS. 14A and 14B are side and bottom views of a waveguide joint.

[0044] FIG. 15 is a cross-section view of an epoxy-coated optical waveguide.

[0045] FIGS. 16A-16C are cross-section views of non-tapered and tapered waveguide inputs.

[0046] FIGS. 17A and 17B are cross-section views of waveguide sections having integrated installation components and an integrated output structure.

[0047] FIG. 18 shows a leaky waveguide bend and focusing lens.

[0048] FIGS. 19A and 19B show cross-section views of optical manifolds.

[0049] Referring to FIG. 1, a vehicle distributed lighting system (DLS) 100 includes hybrid headlamp subsystems 105, turn signal subsystems 110 and 140, and hybrid tail light subsystems 130. The hybrid headlamp subsystems 105 provide primary forward illumination for the vehicle. The headlamp subsystems 105 are also light sources for other exterior lights, such as front turn signals of the subsystems 110 and side markers 115, as well as interior lights, such as dashboard lights 120 and dome lights 125. These other lights are connected to the headlamp subsystems by optical waveguides 135. Similarly, the tail light subsystems 130 provide light for rear turn signals 140 and a center high mounted stop light (CHMSL) 145. The subsystems of the DLS are interconnected so that the light source of one subsystem serves as a redundant light source for another subsystem.

[0050] The DLS incorporates different types of optical waveguide structures to distribute light throughout the vehicle. These include joints, elements with epoxy coatings, pinched end collector portions, integrated installation snaps, integrated input optics and integrated output lenses. The DLS also includes waveguide structures to provide illumination to portions of the vehicle interior, including cup holders, assist grips, and storage pockets.

[0051] FIG. 2 illustrates a hybrid headlamp subsystem 105. The subsystem includes a light source 205 that may be implemented using, for example, a high-intensity discharge (HID) lamp. Light produced by the light source 205 is collected by a reflector 210 and directed through a lens 215 to provide the primary forward illumination for the vehicle. The reflector may be implemented as a parabolic or complex reflector.

[0052] The hybrid headlamp subsystem 105 provides both high beam and low beam illumination. To this end, the subsystem may employ a number of different beam forming techniques, as shown in FIGS. 3-5. For example, FIG. 3 shows a simple Fresnel lens 305 that is moved by an actuator 310 between a high beam position and a low beam position. The movement of the lens 305 shifts the position of the “hot spot” (i.e., the area of most concentrated light) of the headlamp beam in the far field between the appropriate positions for the high and low beams. Other portions of the beam also will shift as the lens moves. In addition to lens, other optical elements, such as wedges, may be used to control the beam pattern.

[0053] FIGS. 4A-4D show the use of a solid molded plastic form 405 (FIGS. 4A-4C) or a bundle of plastic or glass fibers 410 (FIG. 4D) to generate a desired headlamp beam pattern. Light from light source 205 passes through the form 405 or bundles 410 and then passes through a focusing lens 415. The shape of the output end 420 of the solid form or bundles, in conjunction with the properties of the focusing lens, determines the beam pattern in the far field. To increase light collection efficiency, the shape of the input end 425 of the solid form may be configured to act as a collector element to receive light from a light source. A reflector 215 may also be used to control the beam pattern, as in FIGS. 2 and 3. FIGS. 4A-4C show dimensions in mm [inches] of a thickness profile that might be used to achieve a desired beam pattern. Similarly, the bundle of fibers can be formed into a desired profile. As with the implementation shown in FIG. 3, the lens 305 may be moved to shift the hot spot of the beam between high beam and low beam positions.

[0054] FIG. 5 shows the use of a diffraction grating 500 to control the headlamp beam pattern (the diffraction grating may also be used for other lighting functions, such as stop lights and turn signals). The diffraction grating 500 includes essentially transparent material that has a series of ridges 505 on its surface. The width 510 of the ridges is approximately equal to the wavelength of the light produced by the light source 205. A portion 515 of the light passing through the diffraction grating 500 is reflected back into the light source, with the size of the portion depending upon the exit angle (θ) of the light ray. Most of the light 520 travelling in a direction close to perpendicular (θ=0°) passes through the grating undisturbed. By limiting the exit angle (θ) of the headlamp illumination, the grating 500 may provide, for example, a more focused headlamp beam in the far field. The grating 500 may be used alone or in conjunction with lenses 305, solid forms 405 or fiber bundles 410 described above to provide a desired headlamp beam pattern.

[0055] In addition to providing the primary forward illumination, the light source 205 acts as a light source for other parts of the system. As shown in FIG. 2, waveguides 135 having collector elements 220 at their ends are positioned close to the light source 205 to receive light and transmit the light to other locations in the vehicle, such as to provide turn signals, interior lighting, fog lights, and side markers. The waveguides 135 may also carry light to other lighting subsystems to provide redundancy, such as the opposite side headlamp or the tail lights. The number of collector elements 220 may be increased as necessary to supply light for other lighting functions. The collector elements 220 may be glass rods (such as Pyrex) with ends that are polished so as to be faceted or pinched. The pinched ends increase the acceptance angle of the collector element.

[0056] FIG. 2. shows a waveguide 225 that carries light from the source to a side marker light 115. The waveguide 225 may include colored plastic filters 230 to provide a desired output color (e.g., amber) for the side marker 115. This configuration eliminates the need for an electrical connection and light bulb in the side marker 115.

[0057] Another waveguide provides light to the turn signal subsystem 110. Alternatively, the turn signal subsystem 110 may include an independent light source and may use the input from the headlamp subsystem 105 for redundancy.

[0058] As shown in FIGS. 6A-6D, some implementations of the turn signal subsystem use an electromechanical shutter 605 (FIGS. 6A and 6B) while others use a liquid crystal light valve (LCLV) 610 (FIGS. 6C and 6D) to modulate the light produced by the turn signal. A plastic colored filter provides amber color for the turn signal. The use of a colored filter eliminates the need for light bulbs enclosed in cadmium-doped glass.

[0059] The electromechanical modulator 605, as shown in FIGS. 6A and 6B, includes an opaque shutter 615 that is moved between an ON (FIG. 6A) and OFF (FIG. 6B) position by a solenoid 620. In the ON position, the shutter 615 is moved away from the illumination path, so that essentially all of the light is transmitted. In the OFF position, the shutter 615 blocks the illumination path so that no light is transmitted. The use of an electromechanical modulator 605 with an amber-colored plastic filter provides a desirable aesthetic effect (i.e., the turn signal appears amber when ON but has no color when OFF).

[0060] The LCLV illustrated in FIGS. 6C and 6D has no mechanical components. This increases the reliability of the LCLV relating to systems that include mechanical components. The LCLV 610 has two states. In the OFF state (FIG. 6D) the LCLV 610 reflects or scatters most of incident light. In the ON state (FIG. 6C) the LCLV 610 becomes largely transparent (i.e., greater than 80% of incident light passes through the LCLV). The ratio of the light transmitted in the ON state relative to the light transmitted in the OFF state (i.e., the contrast ratio) is approximately 5:1, which meets SAE requirements for a turn signal. A contrast ratio of 5:1 also meets the SAE requirements for stop lights used as turn signals. An infrared reflecting mirror (not shown) may be used to shield the LCLV from infrared energy from the source, thereby increasing the expected life of the LCLV.

[0061] As shown in FIGS. 6E and 6F, LCLV modulators 610 may be combined with diffraction gratings 500 to improve the contrast ratio and achieve a desired beam pattern. As discussed above, light from the light source (waveguide 135) is scattered when the LCLV is OFF (FIG. 6F). The diffraction grating 500 lessens the amount of forward scattered light that is emitted. Focusing optics, such as lenses 630, may also be used to provide further beam pattern control.

[0062] Referring again to FIG. 1, waveguides also may carry light from the headlamp subsystem to other subsystems that have their own light sources, such as the opposite headlamp subsystem (waveguide 137) or the corresponding tail light subsystem (waveguide 138), to provide light source redundancy. When redundancy is employed and, for example, one of the headlamps fails, light from the operational headlamp will dimly illuminate the failed headlamp. This is safer for the operator of the vehicle than having only one operational headlamp. Redundancy also may be used to reduce the effects of failure of other lighting components. For example, an incandescent PC bulb may be used as a source for trunk lighting and may be connected to provide redundancy to interior reading lights.

[0063] The tail light subsystems 130 of FIG. 1 operate similarly to the headlamp subsystems. As shown in FIG. 7, a tail light subsystem 130 has a light source 705 that provides primary rear illumination through a lens 710. The light source 705 may be a HID lamp or another type of lighting source, such as an incandescent lamp, since the lighting requirement (in lumens) generally is less than the requirement for a headlamp. In general, an incandescent source is significantly less expensive than an HID source.

[0064] A compact incandescent cartridge 800, such as shown in FIG. 8, may be employed as the light source 705. The cartridge 800 includes a housing 805 having reflective, heat-dissipating interior surfaces 810. An incandescent bulb 815 is positioned in the center of the housing 805. Waveguide collector elements 220 are positioned around the light source. The incandescent cartridge 800 has a compact size, stays cool, and reduces lamp placement error, which increases efficiency. In addition, construction of the waveguide collector elements 220 from injection molding is easy and inexpensive. The cartridge 800 or similar incandescent sources may also be used as light sources elsewhere in the DLS, depending on lighting requirements. In addition, networks of cartridges 800 or incandescent sources may be interconnected to provide redundant light sources for interior or exterior lighting functions in the DLS.

[0065] Referring again to FIG. 7, waveguide collector elements 220 in the tail light subsystem are positioned close to the source 705 to receive light and transmit the light to other lighting elements, such as the rear turn signals 140, backup lights 150, and center high-mounted stop light (CHMSL) 145. A combination stop/rear turn signal light may be modulated with a LCLV 610, as discussed above with respect to the forward turn signals. The backup lights 150 and CHMSL 145, however, are modulated with electromechanical shutters 615, since they must be completely dark in the OFF mode.

[0066] The rear turn signals subsystems 140 also may be implemented in the manner shown in FIGS. 9A and 9B. In particular, a waveguide section 900 may be used to provide a desired beam pattern for the rear turn signal. Light from a collector element 220 or an independent light source is received at the input 910 of the waveguide section 900 and is internally reflected by the surfaces of the waveguide as it propagates. The waveguide 900 includes a bend 920 immediately prior to the output 930. The outer surface of the bend 920 is s-shaped, which changes the distribution of light across the output surface 930 and hence the far field beam pattern of the turn signal. As an example, FIG. 9B shows dimensions in mm [inches] of a waveguide 900 that might be used to provide a desired beam pattern.

[0067] The DLS also may be used to provide other lighting functions. For example, a waveguide 1000 may be installed in the door 1005, as shown in FIGS. 10A and 10B, to provide a security/puddle light. The waveguide 1000 runs from a light source, such as the hybrid headlamp subsystem 105 (FIG. 1), to the bottom edge 1010 of the door 1005. A waveguide branch 1012 may be used to implement a interior door light. When the door 1005 is closed, as in FIG. 10A, a door waveguide section 1015 connects to a waveguide 1020 that passes through the floor 1025. The floor waveguide section 1020 provides a security light that illuminates the area 1030 underneath the vehicle. When the door 1005 is open, as in FIG. 10B, the door waveguide 1015 provides a puddle light that illuminates the ground 1035 between the open door and the vehicle. The bend 1040 in the door waveguide section 1015 may have a bend angle (θ_B) of, for example, 20°. The bend 1040 helps to direct the output of the waveguide 1000 to the desired area. Alternatively, the security/puddle light may be implemented as a hybrid subsystem that has an independent light source. The independent light source may directly provide interior lighting for the vehicle in addition to being connected to the waveguide 1000 as a light source for the security/puddle light.

[0068] Another waveguide carries light from hybrid headlamp subsystem to the interior of the vehicle to provide, for example, dashboard lighting, dome lights, and reading lights. Waveguides also provide unique, aesthetically pleasing lighting effects for certain interior structures, such as cup holders, map pockets, and assist grips.

[0069] For example, as shown in FIGS. 11A and 11B, a ring-shaped waveguide element 1100 may be installed under the lip 1105 of a cup holder 1110. Although the shape of the waveguide 1100 in FIGS. 11A and 11B is circular, any shape may be used depending upon the shape and size of the cup holder 1110. The efficiency of the waveguide may be improved by selecting a ratio of the inner radius (r) of the waveguide relative to the width (w) of the waveguide. For example, a waveguide with an inner radius to waveguide width ratio (r/w) of 3:1 will lose less light than a ratio of 1:1 or 0.1:1.

[0070] The waveguide 1100 may have a protruding, angled upper region 1115 to reflect and/or transmit light downward toward the bottom 1120 of the cup holder 1110. The upper surface 1125 of the angled portion 1115 may be stippled and may be covered with a layer of opaque material to prevent leakage of light in the upward direction. A small incandescent bulb 1130 at the input 1135 of the waveguide is used as a source. Light entering the input 1135 is transmitted to the ring-shaped portion 1136 of the waveguide 1100 via an input portion 1137 that is tangentially connected to the ring-shaped portion 1136. A colored filter 1145 may be placed between the source 1130 and the input 1135 to achieve a desired illumination color. When illuminated, the interior 1140 of the cup holder 1110 glows faintly so as not to interfere with the driver's vision. The glowing illumination allows the occupants of the vehicle to discern the location of the cup holder 1110. Light for the waveguide 1100 also may be provided by a waveguide 135 connected to one of the lighting subassemblies.

[0071] Another embodiment of the cup holder illumination waveguide 1100 is shown in FIGS. 11C-11D. These “wishbone” shaped waveguides 1100 are configured for cup holders having a gap 1150 to accommodate a mug handle. Light for the waveguide 1100 enters the input 1135 and is split essentially equally to the two arms 1155 of the wishbone. The split in the waveguide 1100 may lead to a dark area in the illumination of the cup holder. Therefore, as shown in FIG. 11C, a web portion 1160 is included between the two arms 1155. The web portion is thinner than the rest of the waveguide 1100 and provides additional illumination to the portion of the interior 1140 of the cup holder directly beneath the split in the wishbone.

[0072] Alternatively, as shown in FIG. 11D, a tab 1165 that is thinner than the rest of the waveguide 1100 may extend downward from the split to reflect and/or transmit light toward the bottom of the cup holder. The tab 1165 has a generally rectangular cross-section and curves downward toward the bottom 1120 of the cup holder. As shown in FIG. 11E, the tab 1165 may have a chamfered leading edge 1170.

[0073] Yet another embodiment of the cup holder illumination waveguide 1100 is shown in FIG. 11F. As in the previous embodiment, the waveguide 1100 is configured for cup holders having a gap 1150 to accommodate a mug handle. Light enters the input 1135 and is split unequally between a primary arm 1175 and a secondary arm 1180. The secondary arm has a smaller cross-section, (i.e., is thinner and narrower than the primary arm 1175. Since the secondary arm 1180 is shorter than the primary arm 1175, there is less loss along its length. The smaller cross-section of the secondary arm 1180 allows less light to enter the secondary arm, which balances the light in the two arms 1175 and 1180 provides uniform illumination around the circumference of the cup holder.

[0074] Similar structures may be used in the interior of a map pocket or, as shown in FIGS. 12A-12C, along the interior surface 1205 of a assist grip 1200. A length of waveguide 1210 is installed along the inner surface 1205. The waveguide includes bends 1212 at the ends to conform to the shape of the assist grip. A small incandescent bulb 1215 provides a light source. The bulb may be used in conjunction with a lens (not shown) to provide a courtesy light. Alternatively, the assist grip 1200 may be connected by a waveguide to another light source in the DLS. As shown in FIG. 12C, the waveguide 1210 may be formed with snaps 1220 and 1225 to make installation into the assist grip 1200 easier.

[0075] Different types of waveguide structures may be used in the DLS to transmit light from the sources to the lighting outputs. A basic waveguide, as shown in FIG. 13, may be formed from optically transparent material such as acrylic or glass. If the waveguide is formed from acrylic or a similar material, it can be manufactured using an injection molding process. The manufacture of waveguide elements using injection molding results in very low manufacturing costs compared to fiber optics. In addition, molded acrylic waveguide elements are more rigid than fiber optics, can be installed by robots, and generally do not require maintenance, waveguide elements can also achieve much smaller bend radii than fiber.

[0076] As shown in FIG. 13, a light ray 1305 entering the input face 1310 proceeds through the waveguide 1300 until the light ray 1305 reaches an outer surface 1315 of the waveguide 1300, i.e. an interface between the material of the waveguide 1300 and air. At the outer surface 1315, light is reflected in accordance with Snell's law. If the angle of incidence (θ_i) of the light ray 1305 at the outer surface 1315 is less than a threshold referred to as the critical angle (θ_c), then the light ray 1305 is reflected internally, with no light escaping. This phenomenon is known as total internal reflection. The critical angle depends on the index of refraction of the material of which the waveguide is composed relative to that of the material surrounding the waveguide, (e.g., air). For example, if the waveguide were made from acrylic, which has an index of refraction of approximately 1.5, and surrounded by air, the critical angle, θ_c, would be:

[0077] θ_c=arcsin(n_a/n_b)=arcsin(1/1.5)=41.8

[0078] where n_ais the index of refraction of air (1.0) and n_bis the index of refraction of acrylic (1.5).

[0079] Referring to FIGS. 14A and 14B, a waveguide joint 1400 may be used to distribute light in the DLS. For example, the joint may be used to provide light to a door of the vehicle. The waveguide joint 1400 has a trunk section 1405 with a convex curved end 1410. Branch sections 1415 having convex curved ends 1420 adjoin the trunk section 1405. The branch sections may be held in place by a plastic band 1425 surrounding the joint region or by epoxy or snaps. Light input to the trunk section 1405 is essentially split among the branches 1415. The branches 1415 may be positioned to carry light to different sections of the vehicle. It is also possible to reconfigure the branches 1415 in the event of design changes. Epoxy that has an index of refraction approximately equal to that of the waveguide, i.e., that is index-matched, may be used to hold the branches 1415 in place. The joint 1400 may have only a single branch 1415 that is used to change the direction of the trunk 1405 or to provide a hinged connection. A hinged connection using the joint 1400 may be installed, for example, in a car door. Index-matched fluid may be used to lubricate and reduce discontinuity at the interface between the trunk 1405 and the branch 1415, which will reduce the loss through the joint 1400.

[0080] FIG. 15 shows a waveguide core 1500 encased in a layer of epoxy 1505. The epoxy coating 1505 may be applied by dipping the waveguide core 1500 (which may be formed, for example, from acrylic) in a reservoir of epoxy and allowing the coating to dry. The epoxy 1505 has a lower index of refraction than the waveguide 1500, so that most of the light rays 1510 passing through the waveguide core 1500 are internally reflected at the acrylic/epoxy interface 1515. A portion of the light rays are reflected at the outer epoxy/air interface 1520. The distribution of light in the waveguide peaks at the center of the waveguide and diminishes toward the edges of the waveguide. Overall, a significant portion of the light is confined within the waveguide core 1500 and only a small portion of the light reaches the outer epoxy/air boundary 1520.

[0081] The epoxy coating 1505 offers several advantages compared to an uncoated waveguide. For example, contaminants on the surface of an uncoated waveguide can cause light at the waveguide/air interface to be scattered and transmitted outside of the waveguide instead of being internally reflected, which increases loss in the uncoated waveguide. The epoxy layer 1505 increases the distance between the contaminants and the waveguide core 1500, which reduces the amount of light that reaches the waveguide/air interface. In addition, plastic coatings can be applied to the outside surfaces 1520 of the epoxy layer, and clamps and other fixtures can be attached to the outside surfaces 1520 with minimal effect on light transmission through the waveguide 1500. One also could use a waveguide formed from polycarbonate (which has an index of refraction of 1.58) with an outer coating of epoxy (which has an index of refraction of 1.4). Alternatively, one could use a waveguide having a glass core and an outer coating having a lower index of refraction.

[0082] As shown in FIGS. 16A-C, a waveguide 1600 may have a pinched end that acts as a collector element 1605. The collector element 1605 increases the acceptance angle (α) of the waveguide 1600 and thereby increases light collection efficiency. The end of the waveguide 1600 may be pinched in two dimensions to form an essentially trapezoidally shaped collector element 1605. The collector element 1605 may be formed on the end of a waveguide 1600 having a rectangular or round cross-section.

[0083] For example, FIG. 16A shows a waveguide 1610 without a pinched end. If the critical angle (θ_c) of the waveguide is 45°, the acceptance angle (α) will also be 45°. Light 1615 from a light source 1620 entering the waveguide 1610 at an angle greater than 45° will exit the waveguide 1610 rather than being reflected at the outer surface 1625. A waveguide 1600 having a pinched end, as shown in FIG. 16B, may have an acceptance angle (α) greater than the critical angle (θ_c). Assuming θ_c=45° and the inclined walls 1630 of the waveguide are inclined at an angle of 5° on each side, then the acceptance angle (α) will be 50°. As shown in FIG. 16C, the pinched end of the waveguide 1600 may be formed so that an excess of material at the tip of the waveguide 1600 bulges outward to form a lens 1635 with a desired focal length. The lens 1635 focuses received light, further increasing the acceptance angle of the waveguide 1600.

[0084] The waveguides may be formed as a set of standard components that may be easily interconnected and used as building blocks for different applications. For example, FIG. 17A shows waveguides 1700 and 1705 having integrated installation elements, such as snaps 1710 and detents 1715. Snaps 1710 can be formed during the injection molding of the waveguide 1700 and provide a convenient means for securing the waveguide 1700 within the vehicle. The snaps are sized and angled to minimize light loss through the snap. For example, the snap may form a 60° angle with the waveguide (toward the direction that light is travelling through the waveguide). The vehicle may have brackets to receive the snaps 1710 or a screw may be inserted into a snap 1710 to secure the waveguide to a mounting surface. The detents 1715 enable the waveguide 1700 to be securely connected to another waveguide 1705 having an integrated claw structure 1720. Each waveguide may be formed with a detent 1715 at one end and a claw structure 1720 at the other.

[0085] FIG. 17B shows waveguides with integrated connection elements. A waveguide 1740 may have a key 1745 formed at one end. The key 1745 is configured to mate with a socket 1750 of another waveguide 1755. These connection elements may cause a loss of approximately 4% at the interface, however, the connection elements increase the ease with which waveguide components can be installed. Index-matched epoxy or fluid may be used at the interface to secure the connection and reduce losses.

[0086] In addition to the installation and connection elements, the waveguide 1700 widens at one end into an output element 1725 having a convex curved surface 1730. The curved surface 1730 of the output element 1725 essentially acts as a lens to provide a desired light output characteristic. The output element 1725 may form an illumination element for the vehicle, e.g., a courtesy light in the door of a vehicle. A portion of the widened waveguide end may be eliminated, leaving an air gap 1735, while maintaining desired output characteristics. The air gap 1735 decreases the weight and cost of the waveguide 1700.

[0087] Another configuration for an output element is shown in FIG. 18. A waveguide 1800 has a bend 1805 that is configured to allow a portion of the light travelling in the waveguide to escape at the bend 1805. A lens 1810 may be used to focus the light to form a desired beam pattern. The amount of light released at the bend 1805 can be controlled by determining the inner radius (r) of curvature of the bend 1805 relative to the width (w) of the waveguide 1800. For example, a bend with a inner bend radius to waveguide width ratio (r/w) of 3:1 will lose less than 5% of the light in the bend. A bend ratio of 1:1 will result in a loss of approximately 30-35%, and a bend ratio of 0.1:1 will result in a loss of approximately 65-70%. Not all of the light released at the bend enters the lens, however the amount of light entering the lens will be proportional to the amount of light released at the bend.

[0088] An optical manifold 1900, as shown in FIGS. 19A and 19B, is another useful building block for a DLS. Light enters the optical manifold 1900 through one or more inputs 1905 and is split to one or more of the output arms 1910. Alternatively, light may enter through one or more output arms 1910 and exit through the inputs 1905. The output arms 1910 may branch off at multiple points from the optical manifold in multiple directions to direct light to other subsystems of the DLS in various locations within the vehicle. The size of the output arms 1910 and their locations determines the proportion of the light input to the manifold that is split to each arm.

[0089] As shown in FIG. 19B, the optical manifold 1900 may include integrated output elements 1915. The output element 1915 may be lens-like structures that provide lighting functions within the vehicle, such as a reading lights or dashboard lights. The manifold 1900 may have multiple input 1905 and output arms 1910 and a portion 1920 where light from the various inputs is combined. Each input and output may use colored filters to achieve desired lighting effects.

[0090] Other embodiments are within the scope of the following claims.