Patent Application
20140268848
N/A
The present disclosure relates to lighting systems, and, more particularly, to an automotive headlamp having a light guide assembly.
Lighting systems are well-known and are used in a wide variety of applications, including automotive applications. Generally, an automotive headlamp, for example, includes a light source and optical components, such as lenses and reflectors to collect and shape light emitted by the light source and to project the resulting beam pattern forward of the vehicle in a light distinct pattern.
The incorporation of solid-state light sources, such as light emitting diodes (LEDs) into headlamps has been a goal from some manufacturers in the lighting industry due to the many benefits provided by LEDs. Some current LED headlamp systems are either multiple source per beam (i.e. multiple LED sources) or single source per beam (i.e. single LED source) design. The multiple source design is generally expensive to manufacture and requires exact alignment between the multiple sources, thus making a multiple source design difficult to construct. The single source design is generally easier to build, but has some styling limitations similar to halogen or HID-based headlamps.
Generally, a single LED source headlamp will have either a reflector optic or a projector lens, or a combination of both. As generally understood, direct projector lenses (without a reflector) are thick, complex lenses. Projector lenses may be interesting for styling purposes, but may be difficult and expensive to manufacture. Headlamps incorporating reflector optics are generally inexpensive and relatively easy to manufacture, but resemble conventional halogen headlamps.
Although LEDs provide numerous benefits, direct viewing of an LED can be uncomfortable for a viewer. As such, manufacturers recognized that the light emitted from the LED needs to be needs to redirected to create a well spread, yet sufficiently directed or focused at the intended subject area (e.g. area in front of the vehicle in a low or high-beam pattern) and not directed into the eyes of oncoming traffic. Some current LED-based headlamps include a fixed glare baffle to block stray light emitted from the LED to avoid glare caused by the headlamp that may distract and blinding oncoming traffic. Some current headlamp systems further include specific components (other than typical reflector optics and project lenses) integrated into the headlamp for directing portions of light emitted by the light source in a desired pattern. For example, some headlamp systems include distributed lighting systems having optical waveguides, or light guides. Examples of such headlamp systems are found, for example, in U.S. Pat. No. 6,186,650 (Hulse); U.S. Pat. No. 6,637,921 (Coushaine); and U.S. Pat. No. 6,652,129 (Aoki).
Reference should be made to the following detailed description which should be read in conjunction with the following figures, wherein like numerals represent like parts:
For a thorough understanding of the present disclosure, reference should be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present disclosure is described in connection with exemplary embodiments, the disclosure is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient. Also, it should be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
By way of an overview, one aspect consistent with the present disclosure may feature an automotive headlamp. The headlamp includes a solid-state light source (i.e. a single string of one or more LEDs) and a reflector having a light collecting region adapted to receive a first portion of light emitted by the solid-state light source and reflect the first portion of light in a first illumination pattern. Generally, the first portion of light is emitted by the solid-state light source in a direction towards the light collecting region of the reflector.
The headlamp further includes a light guide assembly adapted to receive a second portion of light emitted by the solid-state light source and redirect the second portion of light in a second illumination pattern. Generally, the second portion of light is emitted by the solid-state light source in a direction towards the first end of the light guide element. As generally understood, the second portion of light may include stray light, wherein, if allowed to emit from the headlamp, the stray light may result in glare that can distract and temporality affect the vision of oncoming drivers. The light guide assembly includes at least one light guide element including a body having a first end and a second end. The first end of the light guide element is positioned adjacent to the solid-state light source and adapted to collect the second portion of light and the body is adapted to transmit the collected second portion of light from the first end to the second end. The second end of the light guide element is adapted to redirect the collected second portion of light in the second illumination pattern to decrease the potential for glare.
In one embodiment, the first illumination pattern is a low-beam illumination pattern, in which visible light is generally reflected from the reflector and emitted from the headlamp below or at and below a horizontal plane and the second illumination pattern includes visible light redirected by the light guide assembly and emitted from the headlamp generally below the horizontal plane, thereby reducing the potential for glare. When light is directed below or at and below the horizontal plane, it is generally emitted in a direction directed below or at and below the horizon, which is a virtual plane located far ahead of the vehicle.
A light guide assembly consistent with the present disclosure is configured to improve the overall performance of a headlamp having a solid-state light source (e.g. LED). In particular, the light guide assembly replaces the conventional fixed glare baffle found in some current LED-based headlamps and, rather than completely blocking stray light (the general function of a fixed glare baffle), the light guide assembly is configured to collect stray light, including stray light emitted from the solid-state light source and/or stray light reflected by a reflector of the headlamp, and further redirect the stray light in a specific illumination pattern to reduce the potential for glare for oncoming drivers. The collection and redirection of stray light, that would otherwise be blocked by a fixed glare baffle, increases the overall collection efficiency of the headlamp and thereby improves overall performance and quality of light output of the headlamp. Additionally, the inclusion of the light guide assembly further allows a wider range of headlamp designs and styling that may distinguish such a headlamp from current headlamp designs.
Turning now to
The headlamp 10 further includes a reflector 16 having a light collecting region 18 having a reflective surface 20. As described in greater detail herein, the light collecting region 18 is adapted to receive a first portion of light emitted by the solid-state light source 14 and reflect the first portion of light in a first illumination pattern. As shown, the light collecting region 18 has a generally parabolic shape. It should be noted that the light collecting region 18 (and/or the reflector 16 in general) may include a variety of shapes and/or dimensions depending on desired light distribution.
As shown, the light engine 12 is positioned adjacent to the reflector 16. As generally understood by one skilled in the art, the light engine 12 may be side-mounted, or side-loaded, with respect to the reflector 16. The solid-state light source 14 is adapted to emit a first portion of light in a direction towards the reflective surface 20 of the light collecting region 18 of the reflector 16. In turn, the reflective surface 20 is configured to receive and reflect the first portion of light emitted by the solid-state light source 14 such that the headlamp 10 projects a first illumination pattern based on light reflected from the reflective surface 20 of the light collecting region 18.
The headlamp 10 further includes a light guide assembly 22 positioned adjacent to the light engine 12. The light guide assembly 22 includes at least one light guide element 24. The light guide element 24 includes a body 26 having a first end 28 and a second end 30 and is defined by two spaced surfaces 32, 34 extending from the first end 28 to the second end 30. In the illustrated embodiment, the first end 28 of the light guide element 24 is positioned adjacent to the solid-state light source 14. The solid-state light source 14 is adapted to emit a second portion of light in a direction towards the first end 28. In turn, the first end 28 of the light guide element 24 is adapted collect the second portion of light and the body 26 is further adapted to transmit the collected second portion of light from the first end 28 to the second end 30. The second end 30 of the light guide element 24 is adapted to redirect the collected second portion of light such that the headlamp 10 projects a second illumination pattern based on light redirected by the second end 30 of the light guide element.
As described in greater detail herein, the automotive headlamp 10 may further include a housing 56 and outer lens 58. However, the housing 56 and outer lens 58 are not shown in
The following description is directed to one embodiment of the headlamp 10 in which the first illumination pattern is a low-beam illumination pattern. More specifically, the reflective surface 20 of the light collecting region 18 of the reflector 16 is configured to receive and reflect the first portion of light emitted by the solid-state light source 14 in a low-beam illumination pattern, such that visible light is emitted from headlamp 10 generally below or at and below a horizontal plane PH. The second illumination pattern generally includes visible light redirected by the light guide assembly 22 and emitted from the headlamp 10 generally below the horizontal plane PH.
In other embodiments, the first illumination pattern may be a high-beam illumination pattern, such that light reflected by the reflective surface 20 of the light collecting region 18 of the reflector 16 is emitted from the headlamp 10 generally above and below the horizontal plane PH. In other embodiments, particularly in embodiments in which the reflector 16 is configured to reflect light in a high-beam illumination pattern, the second illumination pattern may continue to include visible light redirected by the light guide assembly 22 generally below the horizontal plane PH or the second illumination pattern may include visible light redirected by the light guide assembly 22 and emitted from the headlamp 10 generally above the horizontal PH.
Local laws and regulations governing vehicle standards, such as Federal Motor Vehicle Safety Standards (FMVSS) and Regulations, may include specific regulations regarding the placement of low-beam and or high-beam projecting portions of the headlamp. As such, depending on the region-specific laws and regulations, the mounting orientation of the headlamp 10 may vary in order to comply with such laws and regulations. For example, the headlamp 10 may be mounted in the chassis of a vehicle such that a horizontal plane PH, extending through the reflector 16 and the body 26 of the light guide element 24, is substantially parallel to a horizontal plane (not shown) along a length of the vehicle. As generally understood, the headlamp 10 may be mounted in different orientations.
As previously described, the first end 28 of the body 26 is adapted collect the second portion of light emitted by the solid-state light source 14. It should be noted that the first end 28 of the body 26 may also be adapted to collect light reflected by the reflector 16 in addition to collecting the second portion of light emitted by the solid-state light source 14. In the illustrated embodiment, the first end 28 has an input surface 36 defining a generally concave shape adapted to improve light collection efficiency. For example, the concave shape of the input surface 36 increases the overall area of the first end 28 exposed to the second portion of light emitted by the solid-state light source 14, thereby increasing the collection efficiency of the first end 28 and input surface 36.
As shown, the second end 30 of the body 26 has an output surface 38 defining a plurality of discrete optic elements 40. As described in greater detail herein, each optic element 40 is configured to redirect light collected by the first end 28 in a particular direction. In most instances, in an effort to reduce the potential for glare, each optic element 40 configured to redirect light generally below the horizontal plane PH extending through the body 26 of the light guide element 24 (shown in
As previously described, upon collecting the second portion of light emitted by the solid-state light source 14, the body 26 of the light guide element is adapted to transmit the collected second portion of light 46 from the first end 28 to the second end 30. As shown, upon entering the input surface 36 of the first end 28 of the body 26, the collected second portion of light 46 proceeds through the body 26 until the light 46 reaches the output surface 38 of the second end 30 of the body 26. As generally understood, the body 26 may include any known or later discovered material adapted to provide optical transmission of light. In one embodiment, the body 26 may include a thermoplastic polymer, such as, for example, a polycarbonate resin. At the output surface 38, each optic element 40 defined thereon is adapted to redirect the collected second portion of light 46 generally in a direction to prevent glare, such as, for example, in a downward direction toward a foreground in front of the headlamp 10 and vehicle.
Referring to
In some embodiments, the body 26 of the light guide element 24 may shaped, sized and/or be composed of a material allowing internal reflection of light. For example, as shown in
As generally understood, the angle at which the light 50, 54 of
As shown in
The solid-state light source 14 is further adapted to emit a second portion of light (e.g., illustrated schematically as light beams B2, B3, Bn) in a direction towards the light guide assembly 22, specifically towards the first end 28 of the light guide body 26. As previously described, the second portion of light may generally include stray light, wherein, if allowed to emit from the headlamp 10, the stray light may result in glare that can distract and temporality affect the vision of oncoming drivers. In turn, the input surface 36 surface of the first end 28 is adapted to collect, as indicated by arrow 64, the second portion of visible light from the solid-state light source 14. It should be noted that the input surface 36 may also be adapted to collected light reflected from the reflector 16 that would otherwise be stray light. The collected second portion of light is then transmitted from the first end 28 to the second end 30 of the body 26. As shown, the collected second portion of light may propagate, as indicated by arrow 66, through the body 26. In some instances, the material of which the light guide body 26 is composed may allow internal reflection, as indicated by arrow 68, of the collected second portion of light. Upon reaching the second end 30, the collected second portion of light is redirected, as indicated by arrow 70, by the one or more optic elements 40 defined on the output surface 38 of the second end 30.
As shown, the optical elements 40 are adapted to redirect the collected second portion of visible light toward the open end 62 of the reflector 16, such that the visible light B2, B3, Bn is projected from the headlamp 10 in the second illumination pattern, generally below the horizontal plane PH. In the illustrated embodiment, each optical element 40 is shown to be redirecting the collected second portion of light with a similar angle as other optical elements 40. It should be noted that the output surface 38 may include a combination of optical elements 40, wherein some of the optical elements 40 may have different associated refractive indexes, such that some of the optical elements 40 are adapted to redirect the collected second portion of light in different angles with respect to the horizontal plane PH.
As used herein, the phrase “below the horizontal plane PH” means the visible light emitted from the headlamp 10 is emitted generally downwardly from the headlamp 10 and towards the ground and the phrase “at and below the horizontal plane PH” means the visible light emitted from the headlamp 10 is emitted generally parallel to ground and/or downwardly from the headlamp 10 and towards the ground, referenced to a condition where the headlamp 10 is mounted in the vehicle.
A headlamp including a light guide assembly consistent with the present disclosure was simulated for output performance (luminous flux). Simulations were performed using ASAP® (Advanced System Analysis Program) optical engineering and design software offered by Breault Research Organization (Tucson, Ariz.). The headlamp included a light engine sold under the trade designation JOULE JFL2, including a 5 chip LED array having a total flux of 1000 lm. The headlamp further included a reflector having the following dimensions: 93 mm height; 100 mm width; and approximately 70 mm depth. The distance from the center of the LED array of the light engine was approximately 28 mm. The light guide assembly included at least one light guide element having a width of 5 mm, and the first end having a height of approximately 7 mm and the second end having a height of approximately 60 mm. Simulations were performed on a headlamp without a light guide assembly and including a conventional fixed glare baffle and a headlamp having a light guide assembly having a single light guide element having a substantially planar shape (i.e., the two spaced surfaces 32, 34 of the body were substantially planar).
Upon simulation, it was found that the headlamp without the light guide assembly produces a luminous flux of approximately 541 lm in the beam, produced by the reflector. It was found that the headlamp with the light guide assembly produces a luminous flux of approximately 625 lm, wherein the light guide assembly was found to collect approximately 150 lm, of which, approximately 80 lm were redirected and combined with the output of the reflector. Accordingly, a light guides consistent with the present disclosure increases the overall performance of the headlamp.
As shown, in
It should be noted that the low and high-beam patterns projected from the headlamp 10 conform to current U.S. Department of Transportation (DOT) Federal Motor Vehicle Safety Standards (FMVSS) 108 specifications for the low and high-beam output of a vehicle headlamp. It should be noted that the low and high-beam patterns projected from the headlamp 10 may also conform to current international ECE Regulations specifications for the low and high-beam output of a vehicle headlamp.
In the illustrated embodiments described herein, reflective surface 20 of the reflector 16 is shaped and/or sized to reflect visible light from the solid-state light source 14 out of the reflector 16 in a low-beam illumination pattern, generally below or at and below the horizontal plane PH and not above the horizontal plane PH. In other embodiments, the reflective surface 20 of the reflector 16 may be shaped and/or sized to reflect visible light from the solid-state light source 14 out of the reflector 16 in a high-beam illumination pattern, generally above and below the horizontal plane PH and the second solid-state light source 46 is configured to emit visible light out of the reflector 26 below or at and below the horizontal plane PH and not above the horizontal plane PH. The light guide assembly 22 is generally adapted to redirect stray light emitted by the solid-state light source 14 and/or reflected by the reflector 16 generally below the horizontal plane and not above the horizontal plane PH so as to reduce the potential for glare caused by the stray light.
As such, a headlamp consistent with the present disclosure does not require fixed glare baffle to aid in the blocking of stray light. Accordingly, a headlamp consistent with the present disclosure requires less components, which may reduce manufacturing costs. A light guide assembly consistent with the present disclosure is adapted to collect stray light that would otherwise be blocked by a fixed glare baffle, and further redirect the collected stray light in a desired illumination pattern, thereby utilizing the stray light in the output of the headlamp. Accordingly, a headlamp consistent with the present disclosure increases the overall collection efficiency of the headlamp and thereby improves overall performance and quality of light output of the headlamp.
The shape of the reflector 16 may include, but is not limited to, known parabolic, elliptical and sphero-elliptical configurations including those with faceted interior surfaces as well as truncated reflector cups. The phrase “truncated reflector cup” means a portion of a reflector cup, as may be realized, for example, by dividing a reflector cup along a plane intersecting the longitudinal axis (e.g., intersecting a first end and a second end). A truncated reflector may thus be configured as one-half of a reflector cup, but may be more or less than half of a reflector cup. For example, a truncated reflector cup may have a semi-parabaloid or semi-ellipsoid shape.
As generally understood by one of ordinary skill in the art, the reflective surface 20 of the reflector 26 may include parametric and/or non-parametric surface definition types including, but not limited to, non-uniform rational basis spline (NURBS) curves and/or surfaces configured to reflect the light received from the solid-state light source 14 in the desired pattern (i.e. low-beam and high-beam patterns). Commercially available software including, but not limited to, computer-aided design (CAD), computer-aided manufacturing (CAM), and computer-aided engineering (CAE) software, may be used for the design of NURBS curves and/or surfaces of the reflector 16. For example, a reflector consistent with the present disclosure may be designed using LucidShape computer-aided lighting software offered by Brandenburg GmbH (Paderborn, Germany).
The reflector 16 may be selected to have a high reflectivity. For example, the reflector 16 may have a reflectivity equal to or greater than 85%. According to one embodiment, the reflector 16 may include a metal (such as, but not limited to, aluminum, copper, silver, gold, or the like), metal alloys, plastics (e.g., but not limited to, doped plastics), as well as composites. It should be appreciated that the arrangement, shape and/or contour of the light engine 12, the reflector 16 and light guide assembly 22 will depend on the specific application of the headlamp 10 and may include (but is not limited to) such factors as the overall size constraints on the headlamp 10, desired aesthetic appearance of the headlamp 10, as well as the desired luminosity of the headlamp 10.
Accordingly, consistent with one embodiment of the present disclosure, an automotive headlamp 10 is provided. The automotive headlamp 10 includes a solid-state light source 14 and a reflector 16 having a light collecting region 18 adapted to receive a first portion of light emitted by the solid-state light source 14 and reflect the first portion of light in a first illumination pattern. The automotive headlamp 10 further includes a light guide assembly 22 adapted to receive a second portion of light emitted by the solid-state light source 14 and redirect the second portion of light in a second illumination pattern. The light guide assembly 22 includes at least one light guide element 24 includes a body 26 having a first end 28 and a second end 30 and being defined by two spaced surfaces 32, 34 extending from the first end 28 to the second end 30. The first end 28 is positioned adjacent to the solid-state light source 14 and adapted to collect the second portion of light. The body 26 is adapted to transmit the collected second portion of light from the first end 28 to the second end 30 and the second end 30 is adapted to redirect the collected second portion of light in the second illumination pattern.
The term “coupled” as used herein refers to any connection, coupling, link or the like by which signals carried by one system element are imparted to the “coupled” element. Such “coupled” devices, or signals and devices, are not necessarily directly connected to one another and may be separated by intermediate components or devices that may manipulate or modify such signals.
While the principles of the present disclosure have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the disclosure. The features and aspects described with reference to particular embodiments disclosed herein are susceptible to combination and/or application with various other embodiments described herein. Such combinations and/or applications of such described features and aspects to such other embodiments are contemplated herein. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.
The following is a non-limiting list of reference numerals used in the specification:
