Patent Application
20140056018
This application is based upon and claims priority to German Patent Application 10 2012 202 290,2 filed on Feb. 15,2012.
1. Field of Invention
The invention relates to a lamp module for a motor-vehicle headlamp having a light source exhibiting at least two light-emitting surfaces each of which emits a luminous flux that can be controlled individually.
2. Description of Related Art
A lamp module of this type is known from, for example, EP 2 306 074, and suitable for generating a glare-fee high beam for motor vehicles. A glare-free high beam is understood to be high-beam light distribution in which partial regions can be dimmed if there is someone located in these partial regions who could be blinded therefrom. This could be, for example, the driver of a preceding or oncoming vehicle. A lighting function of this type is referred to a “partial high beam.”
The invention serves to, in particular, provide a high beam of this type without the need for mechanically complex and expensive adjustment systems.
Projection systems axe known in this context, the light sources of which include a configuration of individually controllable light-emitting diodes. A configuration of this type shall be referred to in the following as a “matrix.” A headlamp that exhibits a configuration of this type is also referred to as a “matrix headlamp.”
With the known systems, an intermediate image lying within the headlamp is generated from the light-emitting surfaces of the light-emitting diodes using a primary lens, which is subsequently projected onto the street in front of the lamp by a secondary lens system exhibiting a projection lens, as the light distribution of the headlamp in its forward region. By switching light-emitting diodes “off,” partial, regions of the light distribution can be dimmed in a controlled manner. A system of this type is known from, for example, DE 2008 013 603.
With DE 10 2010 023 360, a glare-free high beam has been realized using an LED matrix (LED=light-emitting diode), in which the individual LEDs are separately disposed as “surface-mounted devices” (SMD-LEDS) (components separately disposed at a spacing from one another). The resulting separation of the light-emitting surfaces of the LEDs is rectified by a matrix of primary lenses, which generates an intermediate image from the separated light-emitting surfaces in the form of a coherently bright area. Due to the imprecisions in the positioning of the SMD-LEDs, unfavorable conditions for the generation of a good intermediate image exist, which primarily is to be distinguished by its homogeneity and sharply focused edges of its partial regions formed by individual LEDs.
Other problems arise with systems of this type in that the light-retracting secondary lenses inevitably generate undesired color fringes at “light/dark” borders. This, then, becomes critical when, in particular, it has not been determined on which side of the “light/dark” border the bright region is located because this can vary depending on the traffic situation. To prevent such color fringes with a matrix headlamp having a light-refracting projection lens, it is known from the aforementioned EP 2 306 074 A that achromatic lenses made of two lenses can be used, increasing the weight and costs for a headlamp.
With this background, an objective of the invention includes providing a lamp module for a motor-vehicle headlamp with which a glare-free high beam can be generated and that does not exhibit the aforementioned disadvantages (or exhibits any of them to only a slight degree). Reflectors are also a fundamental possibility, but they are accompanied by other problems.
The invention overcomes disadvantages in the related art in a lamp module for a motor-vehicle headlamp. The lamp module comprises a light source defining at least one light-emitting surface that emits a luminous flux and defines a horizontally oriented longitudinal edge and at least one other edge running at a right angle thereto. A reflector maps the light-emitting surface without generating an actual intermediate image in front of the lamp module and defines at least two reflecting and strip-shaped facets longitudinal axes of which are more parallel rather than transversal to the longitudinal edge of the light-emitting surface and disposed at a spacing to the light source where the light-emitting surface is mapped with the same mapping scale in front of the lamp module such that the light-emitting surface is mapped with a longitudinal edge running horizontally and another edge running vertically.
The lamp module according to the invention is distinguished, in particular, in that the light-emitting surfaces border one another directly disposed in a row that is oriented horizontally with the intended application of the lamp module in the motor vehicle and it exhibits a reflector that is equipped and disposed to map the light-emitting surfaces of the light source without generating an actual intermediate image in front of the lamp module, which exhibits at least two reflecting and strip-shaped meets. The longitudinal axes of the facets are oriented more parallel rather than transversal to the row of light-emitting surfaces and, in each case, are disposed at a distance from the light source, where they map the light-emitting surfaces with the same mapping scale in font of the lamp module. A single light-emitting surface, in each case, is mapped as a vertically oriented and coherent strip in the light distribution formed as an image of the light-emitting surface.
In that the light-emitting surfaces directly bordering one another are disposed in a row, a coherent light-emitting surface of the light source is already obtained within the headlamp without the need for a primary lens that, with one or the other headlamps of the prior art, first generates a coherent intermediate image including individual light-emitting surfaces of light-emitting diodes.
The horizontal configuration of the light-emitting surfaces is transferred, with the invention, to the configuration of its images in the light distribution in front of the lamp module on the street. By tire horizontal configuration of the light-emitting surfaces, it is possible (in conjunction with the individual controllability of the luminous flux via the respective light-emitting surfaces) to dim partial regions of the high-beam-light distribution in the horizontal plane (with a width depending on one of the numerous light-emitting surfaces) in a controlled manner to reduce the danger of blinding or brighten in a targeted manner to generate a “spotlight” type narrow strip of light. The partial regions vary in terms of their horizontal positions in the light distribution. In this respect, it is possible to distinguish partial regions that are more to the right, more to the left, or substantially in the center.
Because the mapping takes place by a reflector without generating an actual intermediate image, installation times are eliminated, which are necessary with systems functioning with an intermediate image for generating the intermediate image between a primary lens and a projection lens. The use of a reflector in place of a lens has the advantage that chromatic aberrations occurring with refracting lenses are eliminated. Furthermore, reflectors can be more easily and cost-effectively produced than lenses and do not cause any undesired diffusion as a result of “Fresnel effects.” On the other hand, reflectors have the disadvantage that with larger numbers of apertures, aperture failures occur. This also applies to refractive lenses, but, in this case, can be corrected with more lenses.
In addition, different reflector zones have different enlarging effects such that the images generated by them exhibit different mapping scales. Moreover, with abaxial beams, offsetting occurs, thus resulting in coma. A quadratic light source or light-emitting surface is then not mapped as a square, but, rather, as a trapezoid or distorted to a mushroom shape, wherein the size, position, and orientation of the light-source images in the image space are strongly dependent on the position of the light source in the object space.
A system that is to generate numerous light distributions from numerous light-emitting surfaces (composed of lineal and sharply bordered images from individual light-emitting surfaces in the form of a mosaic having a defined position for “light/dark” borders) must primarily have characteristics that map in a manner that is true to shape and position. A light distribution of this type, therefore, should, in particular, be constructed from images of the individual light-emitting surfaces having the same size and same orientation.
This is achieved with the invention in that the reflector exhibits at least two reflecting and strip-shaped facets the longitudinal axes of which are oriented to be more parallel rather than transversal to the row of light-emitting surfaces and, in each case, disposed at a spacing from the light source, where they map the light-emitting surfaces with the same mapping scale in front of the lamp module. A single light-emitting surface, in each case, is mapped as a vertically oriented and coherent strip in the light distribution adjusted as an image of the light-emitting surface.
With the invention, the light-emitting surfaces are mapped without front lenses and shutters by using a specialized reflector, which ensures that the images generated from different regions of the reflector are at least nearly identical in size.
This is not necessarily the case. With a simple parabolic shape, the problem arises that images originating from close to the vertex are larger than images generated from regions lying further away from the vertex of the reflector. As a result, it is not possible to generate a sufficiently sharp vertical “light/dark” border.
A partial high beam (composed of individual strips each of which is generated by a direct mapping, without generating an intermediate image, of a light source exhibiting different light-emitting surfaces) requires a constant width of the strip over the course of the length of the strip. The invention enables the generation of a partial high beam of this type having a significantly lower number of components in comparison with the prior art, which represents an advantage with respect to the cost expenditures, assembly and adjustment expenditures, and weight. Through the combining of numerous light-emitting surfaces in a reflector or a reflector chamber the coherent reflector surfaces of which are illuminated by luminous fluxes from numerous light-emitting surfaces, an extensive adjustment of the individual strips in relation to one another during the assembly is also eliminated. Numerous lamp modules can be combined with one another. In this case, an adjustment of the lamp module is provided.
Other objects, features, and advantages of the invention are readily appreciated as it becomes more understood while the subsequent detailed description of at least one embodiment of the invention is read taken in conjunction with the accompanying drawing thereof.
Identical reference symbols in different figures indicate the same components or at least components having the same functions.
In an embodiment, each light-emitting surface belongs to one LED chip (LED=light-emitting diode). The LED chips are installed on a common interconnect device 14. The supply of electric energy and the control are obtained via the interconnect device.
The LEDs can be individually controlled as single units and/or in groups such that the luminous flux emitted from each light-emitting surface can be controlled individually. The controllability includes, thereby, in an embodiment, not only a switching between permanently “on” and permanently “off,” but also a control of the brightness, which, for example, can take place by an activation with a duty cycle having a signal frequency that is high enough that the human sense of vision perceives an average brightness. The main beam direction of the light is oriented perpendicular to the depicted plane and to the observer in the subject matter of
Each individual light-emitting surface is rectangular in an embodiment (specifically, square). The lengths of the edges are between 0.3 and 2 mm. In an embodiment, the light-emitting surface is flat. LEDs emitting white light having these characteristics are used serially in motor-vehicle headlamps (or at least as an option) and are, thereby, available.
The LED chips lie directly adjacent to one another such that their light-emitting surfaces abut to the greatest degree possible. For this, they are disposed such that edges of neighboring light-emitting surfaces opposite one another are parallel. They are, in particular, disposed horizontally in a plane along a horizontal line, wherein the reference to the horizon is obtained here in a pre-defined intended use of the lamp module in a motor vehicle.
“Disposed directly adjacent to one another” is understood here to mean, in particular, that the light-emitting surfaces are directly neighboring, and activated LEDs are not perceived as separate light-emitting surfaces by observers.
The interconnect device is attached to a cooling element such that the cooling element can accommodate hear discharged in the chips when the LEDs are in operation. The cooling element is configured in terms of its heat capacity and shape to accommodate this heat and discharge the heat into the environment, wherein the discharge occurs, in particular, via structures having a large surface area (i.e., via cooling fins, as is depicted in
The light-emitting surfaces can be “exit” ends of fiber optics, which are individually supplied with light via light-entry surfaces lying spatially separated from, the light-emitting surfaces.
A light distribution of this type is obtained on a flat measurement screen 20 (disposed in front of a motor vehicle oriented such that its surface norm lies in a hypothetical extension of a parallel to the longitudinal axis of the vehicle) in front of the vehicle. A horizontal line “H” marks the position of the horizon. A vertical line “V” divides the field in front of the lamp module into a right half and a left half. The units on both axes are angular.
The light distribution depicted in
Each light-emitting surface 12.1-12.5 generates a light distribution (with an activated LED, in the embodiment, in the form of a partial-high-beam strip 18.1-18.5) having a greater expansion in the vertical axis than in the horizontal axis. For this, the width measured parallel to the horizontal “H” of each of the strips is nearly constant. With the light distribution depicted in
Furthermore,
The facets are configured, in particular, and (with respect to the shape of their reflector surfaces) shaped such that a single light-emitting surface of the light source in each case is mapped as a vertically oriented and coherent strip in the light distribution forming an image of the light-emitting surfaces. In doing so, the mapping of the light-emitting surfaces of the light source in front of the lamp module is obtained, in particular, without generating au actual intermediate image, as is the case with normal projection systems having a primary lens and a secondary lens.
Each facet, in an embodiment, exhibits a focal point and is configured to reflect light diverging from the focal point as a light bundle exhibiting substantially parallel light. With substantially parallel, it is to be understood here that the light with angles of beam spread is converted to a light distribution that is normal for light distributions conforming to the standard for motor vehicles for a non-pivotal high beam.
The reflector surfaces are, for the most part, parabolic and orient the light arriving from the focal point such that it is parallel. Because the light source is not punctiform, a diverging light bundle is obtained (
From
The characteristic exhibited by the reflector facets, which are oriented horizontally and disposed vertically above one another in their intended use, is fundamental. By this distribution of the reflectors to numerous facets (which, in an embodiment, exhibit “paraboloid” forms having different focal lengths from one facet to another with a common focal point and a common central axis as well as basically uniform spacing to the local point), only limited “aperture” errors occur for beams close to the axes (i.e., for beams that arrive from the focal point and from close to the focal point). The common focal point of the facets, in an embodiment, lies in the center of the light-emitting surfaces of the light source.
The individual facets 30, 32, in an embodiment, have the shape of a section of a paraboloid of revolution in the shape of a strip. The edges bordering the respective strip in the vertical plane and In the horizontal plane correspond, in an embodiment (as is also depicted in
With respect to the relative configuration of the reflector 24 and the light source 10, in an embodiment, the light-emitting surfaces are disposed such that they are adjacent to one another and directly border one another in a row, which is oriented at a right angle to the central axis 28 and parallel to a longitudinal axis of the strip-shaped facets of the reflector. The longitudinal axis of the facets is parallel to line 26 in
The line 26, aligned along the light-emitting surfaces 12.1-12.5, is parallel to the horizon in an intended use of the lamp module in a motor vehicle in which, for example, the light distribution depicted in
With respect to the configuration of the facets in relation to one another, in an embodiment, they are disposed adjacently to one another such that they are directly neighboring one another in a plane perpendicular to the longitudinal axis of the facets and to the central axis.
That the individual facets, in an embodiment, have the shape of a section from a paraboloid of revolution in the form of a strip applies here as well. When the number of facets lying on top of one another is increased, the vertical angle width, which is filled by the light bundle of a facet, can be reduced accordingly. The horizontal width can accordingly also be better maintained at a constant value as well. The broken lines, which are each continuations of the shape of the facets in the vertical plane, are parabolas in an embodiment.
The facets are, in an embodiment, disposed such that the optical axis of each facet coincides with the optical axis of each of the other facets. The optical axis, in an embodiment, corresponds to the axis of rotation of the paraboloid, which determines the shape of the facets. This axis of rotation, in an embodiment, is aligned to the central axis 29 and, thereby, to the main axis of light emission of the lamp module or at least lies parallel to the central axis 28.
In an embodiment, the facets of a reflector are disposed such that the focal point of each arbitrary facet of the reflector coincides with the focal point of each arbitrary other facet of the reflector in a common focal point 36.
It is necessarily the case that the focal length of the facets decreases from one facet to the next as the spacing from the central axis 28 increases. The vertical planes are, in an embodiment, substantially parabolas with different focal lengths and a common focal point. Of course, small deviations from the shape of a parabola are allowed as long as the optical effect, as expressed in the light distribution in front of the vehicle, is not impaired such that, in particular, the standard conformity is no longer obtained. Small deviations could even serve to improve the conformity to the standard. As a rule, however, in an embodiment, the “paraboloid” shape has the required mapping characteristics. In an embodiment, the “paraboloid” shape constitutes at least fifty percent of the surface of the facets.
That the focal length of the paraboloid strips lying farther out then automatically becomes shorter can be derived from the following: With an increasing spacing from the vertex, a parabola increasingly distances itself from an arc that abuts the parabola at its apex and has there the same tangents and norms. To compensate for the increasing distance (which would distort the mapping), a narrower parabola may be used (i.e., a parabola having art increased “expansion” factor “a” with a parabola of “y=ax2”). Because the focal length “f=(¼)a” is inversely proportional to the expansion factor “a,” an enlargement of the expansion factor is accompanied by a shortening of the focal length.
The common focal length 36 in the design, depicted in
In an embodiment, the light source is disposed in relation to the reflector such that the main beam directions of its at least two light-emitting surfaces (each emitting one luminous flux) are directed onto the facets of the reflector and form an acute angle with the central axis of the reflector (in particular, an angle “φ” of less than 45°). This applies to an angle that lies in the drawing, plane of
The convergent lens 56 bundles the light arriving Torn the light source 10. The bundle then falls on the reflector 24 at an acute angle to the central axis of the reflector. If one observes the beam path in the reverse direction, then the reflector 24 focuses on a point 54 lying behind the light source 10 in this configuration and generates an enlarged virtual image of the light source behind the light source. The light source in this design is disposed between the focal point of the reflector 54 and the reflector surface of the reflector 24.
The convergent lens 56 is, in an embodiment disposed such that it reinforces the bundling effect of the reflector 24. This configuration is depicted in
By the supplementary lens in the form of a convergent lens 58, the object plane of the lens system can be leveled such that the light-emitting surfaces having a greater spacing to the parabolic focal, point can be mapped with a sharp focus. The light-emitting surfaces (in particular, the light-emitting surfaces of LED chips), in an embodiment, lie in a single plane because this is advantageous from the perspective of production expenditures than a configuration on a curved surface in space (in which, for example, a flat circuit board for the electrical connection of all of the LED chips could not be used). A convex mirror (i.e., a parabolic mirror) functions in this sense in the same manner as that of a convergent lens.
To level the object field, the curvatures of the “Petzval” surfaces of the individual lens elements must decrease to the greatest extent possible (i.e., the “Petzval” sum as a sum of the reciprocal “Petzval” radii of the individual elements should be as small as possible or equal to zero):
1/RP=1/RP1+1/1RP2+. . . +RPH.
For this, “RP1 with i=1 . . . n” indicates the “Petzval” radii of the individual lens elements with an index of “i.” According to the sign convention, the signs for the “Petzval” radii of convergent lenses and divergent reflectors are positive while the “Petzval” radii of divergent lenses and convergent reflectors (concave mirrors) are negative. If a concave mirror is combined with a convergent lens or a divergent mirror (convex mirror), the “Petzval” surface of the overall system can be leveled.
In detail, the “Petzval” radii are calculated as follows:
R
Plens
=n
lens
×f
lens (applies only to thin lenses),
wherein “nlens” is the refractive index of the lens, “flens” is its focal length, RPreflector=(−1)×freflector, and “freflector” is the focal length of the reflector.
In contrast to the convergent supplementary lens (M5 ff.) described above, the refractive power of the main reflector must be increased for the diffracting (hyperbolic) reflector (i.e., its local length must be decreased). The diffractive supplementary reflector generates, specifically, reduced chip images. This redaction of the reflector focal length is first disadvantageous, but is more than compensated for by the object-field leveling. It is advantageous that the supplementary reflector is entirely free of chromatic aberrations. By this measure, the entire length of the lens system is also reduced accordingly.
The supplementary lenses represent designs with which all of the changes caused by the lenses to the orientation and the shape of the light bundle emitted by the light source are distributed over numerous lens elements. This distribution of the changes to the orientation and/or the shape of the light bundle enables the reduction of the aberrations in the overall lens system and, thereby, causes the quality of the mapping to be improved.
In an embodiment, the supplementary lens is astigmatic. With this, the refractive power (i.e., the extent of the intended change in orientation) is greater in the vertical plane than in the horizontal plane. In this manner, light-source images can be generated having a greater vertical expansion than the horizontal expansion. As a result, the high-beam strips depicted in
In an embodiment, the convergent supplementary lens is an astigmatic convergent lens having different diffractive powers in the vertical and horizontal planes. In an embodiment, the convergent lens is designed as a convex/concave meniscus lens, wherein the concave surface faces the light source. In an embodiment, an additional divergent lens is disposed in the beam path.
The divergent lens, in an embodiment, includes organic or inorganic glasses having a high degree of color dispersion (i.e., having a lower “Abbe” number). The convergent lens includes, in this case, an organic or inorganic glass having a limited color dispersion (i.e., with a greater “Abbe” number). In an embodiment, the convergent lens and the divergent lens are connected to one another by an optical putty. The optical putty is a transparent organic thermoset material or elastomer the retractive index of which is as close as possible to the refractive indices of the lenses that are to be connected. Moreover, in an embodiment, the convergent lens is designed as a combined refractive/diffractive lens, and the diffractive structures are applied to the back surface of the lens facing the light source.
In an embodiment, the convergent lens is created as a plano-convex lens having a diffractive structure on the planar surface.
In an embodiment, the convergent supplementary lens is a half-shell/concave mirror (in particular, a hyperboloid). The half-shell reflector is disposed in the beam path such that the supplementary reflector reflects at an acute angle (i.e., substantially counter to the direction of the light beam of the main reflector). Because the supplementary reflector deflects the beam path, the light source radiates into the supplementary reflector and not into the main reflector. In an embodiment, the supplementary reflector is an astigmatic concave mirror having different diffractive powers in the vertical and horizontal planes.
In an embodiment, the lamp module—including the reflector, the light source with a cooling element, and (optionally) a convergent supplementary lens—is implemented such that it can be pivoted about a vertical axis by a motor. Pivotal lamp modules are known such that the details for implementing the drive and the bearing are not necessary here. With a lamp module that is pivotally implemented and otherwise in accordance with the invention, lighting function—such as dynamic curve lights, partial high beams (e.g. only dimmed in a strip), or marker lights (e.g., only bright in a strip)—can be realized. The pivotal property can selectively also be used tor the adjustment of a vertical “light/dark” border. The pivotal axis is, in m embodiment, located in the vicinity of the common reflector focal point.
In an embodiment, the lamp module is equipped with a mechanical adjustment device for the horizontal setting of the “light/dark” border with which the light source and, if applicable; the supplementary lens can be displaced horizontally with respect to the reflector.
To now, the emphasis has been on a design in which the light source exhibits numerous light-emitting surfaces. The invention can also be used, however, in conjunction with light sources exhibiting only one light-emitting surface, insofar as the light-emitting surface has a longitudinal edge and an edge running at a right angle thereto (as is the case, in particular, with rectangular and quadratic light-emitting surfaces). To illustrate this, one can imagine (for example, in a purely qualitative manner) a single, coherent light-emitting surface (such as that in
With this background, an embodiment of the invention is a lamp module 22 for a motor-vehicle headlamp including a light source 10 that defines at least one luminous-flax- and light-emitting surface, an edge (in an intended use of the lamp module in a motor vehicle) oriented to the horizontal plane, and at least one other edge running at a right angle thereto. A reflector 24 is oriented and configured to map the light-emitting surface without generating an actual intermediate image in front of the lamp module. The reflector has at least two reflecting and strip-shaped facets 3:0, 32, 34 the longitudinal axes of which are oriented such that they are more parallel rather than transversal to the longitudinal edge of the light-emitting surface and, in each case, disposed at a spacing “R” from the light source where the light-emitting surface is mapped with the same mapping scale such that the light-emitting surface is mapped (in the intended use) with a horizontally running longitudinal edge and another edge that runs vertically.
In an embodiment, the common focal point lies in the center of an area of the light-emitting surfaces of the light source.
In an embodiment, the common focal point lies exactly between two adjacent light-emitting surfaces of the light source.
Furthermore, in an embodiment, the lamp module 22 exhibits a convergent lens for each of the light-emitting surfaces, which are disposed with spacing to one another. The convergent lenses are disposed such that a virtual image (generated by a convergent lens) of the light-emitting surface allocated to this convergent lens (lying behind the allocated light-emitting surface when seen from the location of the convergent lens) abuts, accordingly, the virtual Image of a light-emitting surface adjacent to the light-emitting surface (generated by a convergent lens directly adjacent to the convergent lens).
The invention has been described above in an illustrative manner. It is to be understood that the terminology that has been used above is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 202 290.2 | Feb 2012 | DE | national |
