Patent Application
20170343172
The invention describes an integral lighting assembly and an automotive headlamp arrangement.
In lighting assemblies used in automotive applications, for example, a particular requirement is that the bright/dark “cut-off” line of the light output by the lighting assembly satisfies certain regulations. Furthermore, this bright/dark cut-off line should be adaptable. The overall beam of light output by the lighting assembly should be adjustable, for example, to produce a low beam for illuminating the region directly in front of the vehicle and a high beam for extending the illuminated area. Adaptability of the light output is also desirable in certain situations, such as when driving into a bend, so that the area in the bend can be better illuminated with a resulting increase in safety. Furthermore, it may be advantageous to influence the amount of light in the foreground of the beam pattern, i.e. in a region of the beam closest to the vehicle, depending on traffic conditions and/or terrain, weather conditions, etc.
The high beam and low beam have conventionally been generated using separate light sources in two separate lighting arrangements. Using conventional filament lamps or gas-discharge lamps, generally two lighting units are mounted in close proximity in a headlamp arrangement and configured so that the high beam and low beam are projected correctly into the relevant regions in front of the vehicle. Although headlamp optical systems do not use true “imaging” optics, usually one edge of the source or an edge of a shield element is “imaged” in order to obtain the required cut-off for the beam distribution. The quality of the light beams must satisfy certain requirements. For example, the shapes or contours of the light beams that would be projected onto a vertical transverse plane located at a standard distance from the headlamp, e.g. 25 meters, are covered by national and international specifications such as ECE (Economic Commission for Europe) R112.
Lighting units or lighting assemblies using semiconductor light sources such as light-emitting diode (LED) chips are becoming more popular as advances in technology have led to economic and yet very bright semiconductor light sources. Since semiconductor light sources are compact, it would be convenient to combine two such light sources for two different beam functions into a single arrangement. However, known solutions have not shown satisfactory results. Because the light from each light source is directed at the single optical element, the physical separation between the two sources is also imaged and appears as a ‘gap’ between the projected beams, for example as a dark area between a low beam and a high beam. Even a minimal gap between the light source images results in a visual gap in the beam distribution. This can be a safety hazard when driving, since anything in this region is effectively invisible to the driver. In particular the verge or curb region to the side of the vehicle is critical, since pedestrians, animals or hazards in this region are then effectively invisible to the driver. Furthermore, because the secondary optic is ‘shared’, it must of necessity be larger, and the overall arrangement is about as large as an arrangement having separate optical systems for each function, so that the advantage of a compact light source is lost. The optical element could be designed to distort the beams in order to close this gap, but such a distortion unavoidably has a detrimental effect on the bright/dark cut-off line, which may then no longer satisfy the requirements. Furthermore, any corrective measures of the optical element affect both beams, so that a controlled correction of separate beams is not feasible.
Therefore, it is an object of the invention to provide an improved lighting arrangement that avoids the problems mentioned above.
The object of the invention is achieved by the integral lighting assembly of claim 1, and by the automotive headlamp arrangement of claim 14.
According to the invention, an integral lighting assembly comprises an optical arrangement, a first light source for generating a first beam of light and a first collimator for directing the first beam at the optical arrangement, and a second light source for generating a second beam of light and a second collimator for directing the second beam at the optical arrangement, whereby the first and second beams are directed at essentially separate regions of the optical arrangement. Thereby, the optical arrangement is realized to manipulate the first and second light beams to give a first exit beam and a second exit beam such that the first exit beam and the second exit beam at least partially overlap in an overlap region on a projection plane located at a predefined distance from the integral lighting assembly. The ‘projection plane’ is to be understood as a virtual plane or screen at a standard distance from the integral lighting arrangement, whereby the distance depends on the application for which the integral lighting arrangement is used. For example, for an automotive headlamp application, the standard ECE R112 mentioned in the introduction requires that such a virtual projection plane be located vertically in front of the vehicle, transverse to the direction of travel, and at a norm distance of 25 m from the headlamp arrangement.
An obvious advantage of the integral lighting assembly according to the invention is that a region in front of the vehicle is always optimally illuminated, without any dark or non-illuminated ‘gap’ between the two exit beams. Furthermore, this can be achieved without having separate units, for example for ‘low-beam’ and ‘high-beam’ arrangements. This does away with the need for careful alignment of separate lighting units that is required for prior art solutions. The separation of the first and second beams upon arrival at the optical arrangement allows the optical arrangement to separately manipulate the exit beams to give the desired overlap region on the projection plane. Furthermore, since the first exit beam and second exit beam are realized using a single optical arrangement, the overall integral lighting arrangement can be realized in a cost-effective manner.
According to the invention, an automotive headlamp arrangement comprises such an integral lighting assembly. With the integral lighting arrangement according to the invention, it is possible to structure the beam for each beam function and still obtain a compact optical system, which is attractive for cost-effective LED headlamp solutions.
The dependent claims and the following description disclose particularly advantageous embodiments and features of the invention. Features of the embodiments may be combined as appropriate to arrive at further embodiments.
In the following, without restricting the invention in any way, it may be assumed for some realizations that the first and second collimators are arranged one above the other, so that the first and second beams are projected one above the other. In this case, one collimator may be referred to as the ‘upper’ collimator and the other may be referred to as the ‘lower’ collimator. Also, for the sake of simplicity, the first exit beam may be referred to in the following as a ‘low’ beam, and the second exit beam may be referred to as a ‘high’ beam. In some realizations which will be described below, the collimators may be arranged essentially symmetrically about an optical axis of the optical arrangement.
The integral lighting arrangement according to the invention can be used to simply refract or deflect the light from the first light source in the optical arrangement (also referred to in the following as the ‘secondary optic’) to give a first exit beam, and similarly to refract or deflect the light from the second light source to give a second exit beam. However, it can be advantageous to manipulate the first and second beams so that the first and second exit beams satisfy certain functional requirements. Therefore, in a preferred embodiment of the invention, the optical arrangement of the integral lighting assembly comprises a spreading element for horizontally spreading any light incident at the spreader element and/or a shifting element for vertically shifting any light incident at the shifting element. The secondary optic can be only partially covered by these additional functional elements, or they can essentially completely cover the secondary optic.
In automotive applications, a low beam or fog beam is used to illuminate a lower region in front of the vehicle. It is desirable to illuminate as wide an area as possible, in particular to illuminate the side of the road closer to the verge. Therefore, in a particularly preferred embodiment of the invention, the spreading element is realized to spread at least part of the first beam prior to manipulation by the optical arrangement such that the first exit beam is projected to give two overlapping first beam regions in the projection plane. These first beam regions comprise essentially a wider, more ‘stretched’ low beam as well as a non-manipulated low beam.
In automotive applications, a high beam is preferably not only directed upwards, but also partly downwards so that the road is well illuminated. Therefore, in a particularly preferred embodiment of the invention, the shifting element is realized to shift at least part of the second beam prior to manipulation by the optical arrangement such that the second exit beam is projected to give two overlapping second beam regions in the projection plane. In this way, the manipulated part of the high beam can be ‘pushed down’ to overlap the low beam region, while the non-manipulated part of the high beam remains dedicated to the illumination of a higher region in front of the vehicle.
In one embodiment of the invention, the optical arrangement preferably comprises a projection lens. A shifting element and/or a spreading element can be realized by mounting or attaching suitably shaped micro-structures on the back of the lens (i.e. the side of the lens facing towards the light sources). These micro-structures act to generate the optimal beam shape for each function. For example, in a preferred embodiment of the invention, the shifting element comprises a plurality of prism elements mounted on the projection lens and arranged to vertically shift the light incident at the shifting element prior to refraction by the projection lens. A series of such thin prism elements can be attached to a region of the lens and be arranged for example to shift the light away from the optical axis, prior to refraction by the projection lens. These prism elements can be used to shift part of the high beam, for example in a downward direction, so that the high beam illuminated area comprises two high beam regions, giving a more optimal beam performance.
In another preferred embodiment of the invention, the spreading element comprises a plurality of cylindrical lens elements mounted on the projection lens and arranged to refract and horizontally spread the light incident at the spreader element prior to refraction by the projection lens. For example, a series of half-cylinder lenses can be attached to one region of the lens in order to refract and horizontally spread the incoming beam of light prior to refraction by the projection lens, for example to at least partially spread the low beam, so that the low beam illuminated area comprises two low beam regions, giving a more optimal low-beam performance.
Alternatively, the optical arrangement can comprise a reflector enclosing the collimators and open at one end to allow the light beams to be directed outwards. In an integral lighting arrangement using a reflector, a shifting element and/or spreading element can be formed by manipulating the surface of the reflector, for example by creating suitably shaped facets in certain regions of the reflector. In an integral lighting arrangement realized using a reflector instead of a lens, the collimators are not necessarily arranged symmetrically about an optical axis of the reflector, and the reflector itself may be realized in an asymmetric manner.
A separation of the beams upon arrival at the secondary optic is desirable for the purpose of an optimal beam shaping. Therefore, in one preferred embodiment of the invention, the integral lighting assembly comprises a collimator arrangement in which each collimator is arranged to direct its beam of light essentially at a region of the optical arrangement on the same side of an optical axis of the integral lighting assembly such that the first beam and the second beam overlap by at most 20°, more preferably at most 15°, most preferably at most 10° in a first/second beam overlap before arriving at the optical arrangement and wherein the projection plane overlap region corresponds to the first/second beam overlap. By appropriately shaping the collimators, it can be achieved that little or no light from a collimator crosses the optical axis. This optimal partial beam separation on the secondary optic can be achieved by using a “bi-cavity” collimator having only a thin dividing wall between the two neighboring cavities, i.e. the two collimators may be essentially realized as a single entity. Preferably, therefore, the first and second collimators are realized as a bi-cavity structure with a shared dividing wall, whereby each collimator comprises an essentially parabolic outer wall, which parabolic outer wall comprises a focal point close to the shared dividing wall. The advantage of such realizations over known prior art solutions is that the special near-die collimators allow a favorable directional partial separation of the beams originating from the two light sources. This leads to a corresponding partial separation on the secondary optic. In these areas, the beams for the two separate light functions (e.g. high beam; low beam) can be shaped individually, whereas the overlap area allows for a more compact headlamp system.
A beam separation can be obtained in an alternative manner. In another preferred embodiment of the invention, therefore, the integral lighting assembly comprises a collimator arrangement in which the collimators are arranged such that a collimator on one side of an optical axis of the lighting assembly directs its beam of light essentially at a region of the optical arrangement on the other side of the optical axis so that the first beam crosses the second beam before arriving at the optical arrangement. In other words, an ‘upper’ collimator is arranged to direct its beam of light at a ‘lower’ region of the secondary optic, and a ‘lower’ collimator directs its beam of light at an ‘upper’ secondary optic region. Light beams passing through the focal point of a secondary optic will leave the secondary optic in an essentially parallel manner. In other words, for this ‘crossing beams’ realization, the light ‘on’ the focal plane that originates from the light exit opening of a collimator will effectively be projected by the optical arrangement to create the ‘image’ of that light exit opening. Therefore, in a high beam/low beam application, the ‘upper’ light source can be used to generate the low beam, while the ‘lower’ light source is used to generate the high beam. This realization is quite advantageous, since the collimator design can be favorably simple. The light sources, or more precisely the light exit openings of the collimators, are imaged on the virtual screen or projection plane. To obtain the desired overlap in the projection plane, the secondary optic can be modified by adding an additional functional element, for example a prism element, to shift part of the low beam upward, or part of the high beam downward, to obtain the desired overlap region.
In a preferred embodiment of the invention, however, the projection plane overlap region is obtained by manipulating the first and second beam appropriately before they arrive at the secondary optic. Therefore, in a particularly preferred embodiment of the invention, the integral lighting unit comprises a collimator arrangement in which the collimators are arranged so that the first and second beams intersect at least partially in a focal plane overlap region on a focal plane of the optical arrangement so that the projection plane overlap region corresponds to the focal plane overlap region.
A larger beam overlap on the focal plane will be associated with a larger overlap region on the projection plane or screen. However, it is generally desirable to have distinct exit beams with distinct illuminated areas, and a narrow overlap region on the projection plane. The light beams exiting the collimators should preferably only overlap very slightly on the focal plane. Also, since the light on the focal plane originating from a collimator will effectively be used to create the ‘image’ for the light source, as mentioned above, in a further preferred embodiment of the invention, the integral lighting assembly comprises a collimator arrangement in which light exit openings of the first collimator and the second collimator are located in close proximity to the focal plane of the optical arrangement. Here, the term ‘close proximity’ is to be understood to mean that the beams overlap only slightly on the focal plane. The actual distance between light exit openings and focal plane will depend on the dimensions of the integral lighting arrangement and the application for which it is intended. For example, using LED light sources in collimators of about 10 mm in length for a high beam/low beam automotive headlamp arrangement, this distance preferably comprises 2 mm, more preferably 1 mm, most preferably 0.5 mm.
To allow the beams to cross, the collimators may be arranged at an angle to each other. However, from a manufacturing point of view, it may be preferable and more economical to mount both light sources on a common, essentially flat carrier instead of having two carriers arranged at an angle. Therefore, in a preferred embodiment of the invention, the integral lighting arrangement preferably comprises a collimator arrangement in which a prism element is mounted onto the light exit opening of one or both collimators. Such a prism element is preferably realized to refract the light beam towards the optical axis, allowing the first and second beams to overlap while at the same time allowing the light sources to be mounted onto a common flat carrier.
Any suitable light source can be used that is sufficiently small and bright and which can be partially enclosed in a collimator. However, in a particularly preferred embodiment of the integral lighting assembly according to invention, the light source comprises an LED source. Very bright thin-film ‘white’ LEDs are available, for example, the Luxeon® Altilon LED. Without restricting the invention in any way, the first and/or second beams can be generated using one or more such light sources arranged in functional groups. For example, an array of LEDs in a corresponding collimator arrangement can be driven to generate a collective beam of light.
A collimator enclosing a light source for a realization in which the light beams cross before arriving at the secondary optic or optical arrangement can be shaped in any suitable way. For example, the walls of the collimator can be arranged to give a rectangular cross-section (so that the corresponding beam is also essentially rectangular in cross-section) and can have a tapered form, a parallel form, etc. Preferably, the walls are shaped to give a beam of light that essentially retains its cross-section before arriving at the secondary optic. The walls of the collimators are preferably thin enough, so that when collimators are arranged at an angle to touch or almost touch (to allow a crossing of the beams), the light exit openings are as close together as possible. Therefore, a collimator wall thickness of about 0.1 mm to 1 mm is preferable. A collimator for directing its light beam at a region of the secondary optic on the same side of the optical axis is preferably shaped to result in a first/second beam overlap area of at most 20°, as described above. The length of the collimator can be chosen according to the system in which it is to be incorporated. For example, a short collimator with a length of about 6 mm could be used, or a long collimator with a length of about 18 mm. Preferably, for an automotive application such as an integral lighting arrangement for a headlamp, a collimator preferably comprises a near-die collimator with a length in the region of 12 mm, for instance 10-14 mm.
In the drawings, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale; in particular, the elements and relative positions of an optical arrangement such as a lens and a collimator are only indicated in a very simplified manner.
Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. The integral lighting arrangement described herein can be used for any combination of two different types of light, for example high-beam/DRL (daytime running lights), fog/DRL, high-beam/fog, etc.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10157348.3 | Mar 2010 | EP | regional |
This application is a continuation of U.S. patent application Ser. No. 13/635,798, filed Sep. 18, 2012, and titled “Integral Lighting Assembly”, issuing Aug. 15, 2017 as U.S. Pat. No. 9,732,923, which is a 371 National Stage Application of PCT/IB2011/051158, filed Mar. 21, 2011, which claims priority to European Patent Application No. 10157348.3, filed on Mar. 23, 2010. U.S. patent application Ser. No. 13/635,798, International Application No. PCT/IB2011/051158, and European Patent Application No. 10157348.3 are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13635798 | Sep 2012 | US |
| Child | 15676712 | US |
