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Title:
SEMICONDUCTOR-BASED LIGHTING SYSTEMS AND LIGHTING SYSTEM COMPONENTS FOR AUTOMOTIVE USE
Document Type and Number:
WIPO Patent Application WO/2007/062275
Kind Code:
A2
Abstract:
A modulator semiconductor light source assembly includes a semiconductor light source (24), such as a light emitting diode, which is mounted on a substrate ((28) which supplies electricity to the light source (24) and which assists in removing waste heat therefrom. Substantially all of the light emitted by the LED (24) is transferred to a lens (40) by a light pipe (36), the cross section of the light pipe (36) increasing from the light source (24) to the lens (40) and the lens (40) having a general D-shape such that the light pattern formed by the lens (40) is constrained in a first direction orthogonal to a second direction. The assembly can be combined with other similar assemblies or other light sources in a light fixture to produce a desired overall beam pattern such as a automobile headlamp or high beam pattern.

Inventors:
WILSON CHRISTOPHER HENRY (CA)
LAMBERT CHAD DALTON (CA)
WOODWARD RONALD OWEN (US)
Application Number:
PCT/US2006/045737
Publication Date:
May 31, 2007
Filing Date:
November 28, 2006
Export Citation:
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Assignee:
MAGNA INT INC (CA)
WILSON CHRISTOPHER HENRY (CA)
LAMBERT CHAD DALTON (CA)
WOODWARD RONALD OWEN (US)
International Classes:
H01L33/00
Foreign References:
US20050018446A1
US20040027834A1
Attorney, Agent or Firm:
PARANJPE, Jay, S. et al. (500 Woodward AvenueSuite 350, Detroit MI, US)
Download PDF:
Claims:

What is claimed:

1. A modular semiconductor light source assembly comprising: a substrate; a semiconductor light source mounted to the substrate, the substrate providing electrical power to the semiconductor light source and removing waste heat generated by the semiconductor light source; a heat sink in thermal communication with the substrate to remove waste heat therefrom; a light pipe having a first end adjacent the semiconductor light source, to capture substantially all of the light emitted from the semiconductor light source, and a second end; and a lens having a general D-shape, the second end of the light pipe engaging the lens such that the light from the emitted by the semiconductor light source is emitted from the lens in a pattern wherein the emitted light is spread in a first direction and is constrained in a second direction, the second direction being orthogonal to the first.

2. The modular semiconductor light source assembly of claim 1 wherein the semiconductor light source is a light emitting diode.

3. The modular semiconductor light source assembly of claim 1 wherein the cross- sectional area of the light pipe increases from the first end to the second end.

4. The modular semiconductor light source assembly of claim 1 wherein the centerline of the light pipe is offset from the centerline of the lens to further constrain the pattern of the light emitted from the lens.

5. The modular semiconductor light source assembly of claim 1 further comprising a second semiconductor light source mounted to the substrate and a second light pipe to transfer light emitted from the second semiconductor light source to the lens.

6. The modular semiconductor light source assembly of claim 1 wherein the lens is cruciform in shape with each arm of the cruciform being generally D-shaped such that the light from the emitted by the semiconductor light source is emitted from the lens in

a pattern wherein the emitted light is constrained in both first and second orthogonal directions.

Description:

Semiconductor-Based Lighting Systems And Lighting System Components For

Automotive Use

FIELD OF THE INVENTION

[0001] The invention relates to lighting sources for automotive lighting. More specifically, the invention relates to semiconductor-based lighting systems and lighting system components for use in automotive lighting systems.

BACKGROUND OF THE INVENTION

[0002] With recent advances in semiconductor light sources, such as high output white light emitting diodes, interest has developed in employing light elements with semiconductor light sources in automotive lighting systems such as headlamps and signaling lamps. Such semiconductor light elements can offer a variety of advantages over conventional incandescent and gas discharge lighting elements, including much smaller required volumes for the light elements, resulting in a wider range of possible designs and styling, as well as increased longevity and reliability.

[0003] However, such semiconductor light elements also suffer from disadvantages, including lower light output levels than comparable incandescent and/or gas discharge light elements and a sensitivity to over-heating of the semiconductor light source which can result in failure of the semiconductor light sources.

SUMMARY OF THE INVENTION

[0004] According to a first aspect of the present invention, there is provided modular semiconductor light source assembly comprising: a substrate; a semiconductor light source mounted to the substrate, the substrate providing electrical power to the semiconductor light source and removing waste heat generated by the semiconductor light source; a heat sink in thermal communication with the substrate to remove waste heat therefrom; a light pipe having a first end adjacent the semiconductor light source, to capture substantially all of the light emitted from the semiconductor light source, and a second end; and a lens having a general D-shape, the second end of the light pipe engaging the lens such that the light from the emitted by the semiconductor light source is emitted from the lens in a pattern wherein the emitted light is spread in a first direction and is constrained in a second direction, the second direction being orthogonal to the first.

[0005] Preferably, the semiconductor light source is a light emitting diode.

[0006] The invention provides a modular semiconductor light source assembly which includes a semiconductor light source, such as a light emitting diode, which is mounted on a substrate which supplies electricity to the light source and which assists in removing waste heat therefrom. Substantially all of the light emitted by the LED is transferred to a lens by a light pipe, the cross section of the light pipe increasing from the light source to the lens and the lens having a general D-shape such that the light pattern formed by the lens is constrained in a first direction orthogonal to a second direction. The assembly can be combined with other similar assemblies or other light sources in a light fixture to produce a desired overall beam pattern such as a automobile headlamp low beam or high beam pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

Figure 1 shows a side view of a modular semiconductor light source assembly in accordance with the present invention;

Figure 2 shows a ray diagram illustrating the refraction of light through a light pipe and lens of the assembly of Figure 1 ;

Figure 3 shows a resulting beam pattern produced by light emitted from the lens of the assembly of Figure 1 ;

Figure 4 shows a side view of another embodiment of a modular semiconductor light source assembly in accordance with the present invention;

Figure 5 shows a ray diagram illustrating the refraction of light through a light pipe and lens of the assembly of Figure 4;

Figure 6 shows a resulting beam pattern produced by light emitted from the lens of the assembly of Figure 4;

Figure 7 shows a side view of yet another embodiment of a modular semiconductor light source assembly in accordance with the present invention;

Figure 8 shows another embodiment of a lens and light pipe for use with a modular semiconductor light source assembly in accordance with the present invention; and

Figure 9 shows an automotive headlamp fixture constructed with modular semiconductor light source assemblies in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0008] As described above, light elements constructed with semiconductor light sources suffer from disadvantages in that the amount of light emitted by semiconductor light sources, such as light emitting diodes (LEDs) is generally less than the light emitted by incandescent or gas discharge light sources. Further, semiconductor light sources are sensitive to overheating conditions and operation of the semiconductor light source with excessive semiconductor junction temperatures will decrease the expected operating lifetime of the semiconductor light source.

[00091 Accordingly, the present inventors have determined that semiconductor lighting systems must include optics which are carefully designed to efficiently form desired beam patterns with the light emitted by the semiconductor light source. Further, the semiconductor lighting systems must allow for sufficient cooling of the semiconductor light source therein to prevent the semiconductor junction temperature from exceeding the acceptable operating temperature range during normal operating conditions.

[0010] At the same time, the present inventors have also determined that automotive lighting systems employing semiconductor light sources are particularly suited to construction from modular light source components.

[0011] In Figure 1 a modular semiconductor light source assembly in accordance with the present invention is indicated generally at 20. Light source assembly 20 includes a semiconductor light source, such as light emitting diode (LED) 24, which is mounted to a substrate 28. Substrate 28 can be any suitable substrate on which LED 24 can be mounted, but preferably substrate 28 is a printed circuit board which provides electrical connections to LED 24 and which assists in transferring waste heat from LED 24. For example, substrate 28 can be an epoxy or phenolic-based member which include electrically conductive traces on its surface and which includes a layer of heat transfer material, such as aluminum or copper. A heat sink 32 is attached to substrate 28 to accept heat waste heat from LED 24 via substrate 28. Heat sink 32 can be formed from aluminum or any other suitable heat transfer material as will occur to those of skill in the art. It is contemplated that, if it is desired to employ two or more of assemblies 20 in a light fixture, as described below, then heat sink 32 and/or substrate 28 can be common to each assembly 20.

[0012] The light which is emitted by LED 24 at its surface opposite substrate 28 is captured by a light pipe 36 which abuts the emitting surface of LED 24 to capture substantially all of the light emitted by LED 24. Light pipe 36 can be a fiber optic cable, a light

guide manufactured from polycarbonate or transparent silicone rubber or moldable acrylic resins, such as Acrymid™ 815, sold by CYRO Industries of Rockaway, NJ, or any other suitable method of transferring light from a light source to a desired location [0013] To ensure the capture of substantially all of the light emitted by LED 24, the diameter of light pipe 36 preferably tapers from its smallest cross section, adjacent LED 24 where it is preferably at least as large as the light emitting surface of LED 24, to a larger cross section where light pipe 36 contacts a lens 40. Lens 40 can be fabricated of any suitable material, such as polycarbonate, silicone rubber or moldable acrylic resins, such as Acrymid™ 815, provided only that the selected material preferably has an index of refraction which is less than or equal to the index of refraction of light pipe 36. [0014] Light pipe 36 is optically connected to lens 40 such that substantially all of the light emitted by LED 24 is transferred to lens 40. If light pipe 36 is fabricated from the same material as lens 40, such as if both are acrylic, then light pipe 40 can be optically connected to the lens by fusing light pipe 36 to lens 40. If light pipe 36 and lens 40 are dissimilar materials, such as transparent silicone rubber and acrylic respectively, then light pipe 36 can be optically connected to lens 40 by abutting it against lens 40 and applying a suitable adhesive or by any other manner as would occur to those of skill in the art. [0015] In the present invention, it is presently preferred that light pipe 36 and lens 40 be manufactured as a single component, for example by molding them from acrylic, to avoid tolerancing difficulties which may otherwise in aligning the optical interfaces/connections between light pipe 36 and lens 40.

[0016] The present inventors have determined that many automotive lighting systems require the production of light patterns, such as headlamp beam patterns, with specific shapes and characteristics. In particular, many automotive lighting needs require beam patterns wherein the emitted light is spread horizontally but constrained vertically. Accordingly, in the embodiment of Figure 1 , lens 40 is preferably D-shaped in cross section such that light entering lens 40 from light pipe 36 is constrained vertically and spread horizontally, relative to the orientation of lens 40 in Figure 1 , as best seen in Figures 2 and 3. [0017] Figure 4 shows another embodiment of a modular semiconductor light source assembly 100 in accordance with the present invention wherein components which are similar to those of the embodiment of Figure 1 are indicated with like reference numerals. As shown, in this embodiment LED 24 is located on substrate 28 offset from the vertical centerline 44 of lens 40. While light pipe 36 still transfers substantially all of the light emitted by LED 24 to

lens 40, the offset (or tilt) of the centerline of light pipe 36 with respect to the centerline of lens 40 results in the modified beam pattern illustrated in Figures 5 and 6. As can be seen, by offsetting LED 24 below the centerline of lens 40, the resulting beam pattern of light emitted from lens 40 is further constrained vertically.

[0018] As will now be apparent to those of skill in the art, LED 24 and light pipe 36 can be positioned in a variety of locations with respect to vertical centerline 44 to alter the vertical constraint of the beam pattern produced by modular semiconductor light source assembly 100.

[0019] Figure 7 shows yet another embodiment of a modular semiconductor light source assembly 200 in accordance with the present invention wherein components which are similar to those of the embodiments of Figure 1 and 4 are indicated with like reference numerals. As shown in this embodiment, substrate 28 includes two LEDs 24a, 24b mounted on it, each with a respective light pipe 36a, 36b to transfer the light produced by the respective LED 24a, 24b to lens 40. By positioning LEDs 24a and 24b appropriately on substrate 28, one or both of light pipes 36a and 36b can be offset with respect to vertical centerline 44. Thus assembly 200 can produce beam patterns from the combined outputs of LEDs 24a and 24b and larger patterns can be formed or patterns can be formed with relative "hotspots" wherein the light from LEDs 24a and 24b overlap in the pattern.

[0020] Figure 8 shows another embodiment of a lens 220 for use with assemblies 20, 100 and/or 200. As illustrated, lens 220 is generally cruciform in cross section, comprising a pair of orthogonally oriented D-shaped members, each similar to lens 40. Lens 220 thus can create a beam pattern which is constrained both horizontally and vertically. If the centerline of light pipe 224, which transfers light emitted by LED 24 is located at the centerline of each of the D-shaped members, then the resulting beam pattern is generally square. However, other shaped beam patterns can easily be obtained by moving the centerline position of light pipe 224 with respect to the centerline of each of the D-shaped members forming lens 220. [0021] As should now be apparent, desired beam patterns can advantageously be formed with combinations of the above-described modular light source assemblies and/or other light sources.

[0022] Figure 9 shows a headlamp fixture 300 which has been constructed from a combination of assemblies 20, 100 and/or 200 and a projector device 304, such as that described in pending U.S. application 11/290,853 filed on Nov. 30, 2005 and assigned to the assignee of the present invention. As mentioned above, when multiple assemblies 20, 100

and/or 200 are employed in a fixture, such as headlamp fixture 300, two or more assemblies 20, 100 and/or 200 can share a common heat sink. In the illustrated fixture 300, two of assemblies 20, 100 and/or 200 of the bottom tier and four of the assemblies 20, 100 and/or 200 of the top tier share heat sink 32a, while the remaining three of assemblies 20, 100 and/or 200 of the bottom tier and three of the assemblies 20, 100 and/or 200 of the top tier share heat sink 32b.

[0023] Some of assemblies 20, 100 or 200 can be employed to provide fill light for desired beam patterns while projector device 304 can provide any necessary hotspots for those beam patterns. For example, the bottom five assemblies 20, 100 or 200 can be used for producing fill light for a low beam headlamp pattern while the top seven assemblies 20, 100 or 200 can be used for producing fill light for a high beam headlamp pattern. Alternatively, or in addition, one or more of assemblies 20, 100 Or 200 can be illuminated when the steering wheels of the vehicle are turned to provide steering light to illuminate the road in the direction the vehicle will travel.

[0024] As will be apparent from Figure 9, the thickness of lens 40 in assemblies 20, 100 and/or 200 can be varied to alter the horizontal spread of the beam pattern produced by assemblies 20, 100 and/or 200. In fixture 300, some of assemblies 20, 100 and/or 200 have relatively thick lenses 40, while others have relatively thin lenses 40 to obtain the desired beam pattern.

[0025] In addition to headlamp fixtures, it is contemplated that a variety of other automotive lighting systems can be constructed with modular semiconductor light source assemblies in accordance with the present invention, including taillight fixtures and/or daytime running light fixtures.

[0026] The present invention provide a modular semiconductor light source assembly which includes a semiconductor light source, such as a light emitting diode, which is mounted on a substrate which supplies electricity to the light source and which assists in removing waste heat therefrom. Substantially all of the light emitted by the LED is transferred to a lens by a light pipe, the cross section of the light pipe increasing from the light source to the lens and the lens having a general D-shape such that the light pattern formed by the lens is constrained in a first direction orthogonal to a second direction. The assembly can be combined with other similar assemblies or other light sources in a light fixture to produce a desired overall beam pattern such as an automobile headlamp low beam or high beam pattern.

[0027] The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.