OPTICAL SYSTEM FOR AN AUTOMOTIVE HEADLAMP

Abstract

An optical system for use in a headlamp of a motor vehicle includes condenser optics formed by a condenser lens matrix and being provided to focus incoming light beams. It further includes at least one reflective shield being provided to reflect at least a subset of the focused light beams and to create a cut-off line of outgoing light beams. It further includes imaging optics formed by an imaging lens matrix, which is provided to project the focused light beams and the reflected light beams in front of the headlamp, such that the reflected light beams contribute to an intensity hotspot on one side of the cut-off line.

Claims

1. An optical system for use in a headlamp of a motor vehicle, comprising: condenser optics formed by a condenser lens matrix and being provided to focus incoming light beams, a plurality of reflective shields being provided to reflect at least a subset of the focused light beams and to create a cut-off line of outgoing light beams, and imaging optics formed by an imaging lens matrix and being provided to project the focused light beams and the reflected light beams in front of the headlamp such that the reflected light beams contribute to an intensity hotspot on one side of the cut-off line, wherein at least one of the plurality of reflective shields comprises a kink at an edge facing the imaging optics.

2. The optical system according to claim 1, wherein the at least one reflective shield is arranged between the condenser optics and the imaging optics, such that a main plane of extension of the condenser optics is generally parallel to a main plane of extension of the imaging optics, and a main plane of extension of the reflective shield is generally perpendicular or traverse with respect to the main plane of extension of the imaging optics.

3. The optical system according to claim 1, wherein the condenser lens matrix comprises a plurality of condenser lenses, and wherein the imaging lens matrix comprises a plurality of imaging lenses, each of the imaging lenses being assigned to one of the condenser lenses, forming respective channels of light beams within the optical system.

4. The optical system according to claim 3, wherein in a vertical direction there is an offset between the imaging lens and a respective condenser lens to which the imaging lens is assigned, where the vertical direction runs perpendicular to the main plane of extension of the at least one reflective shield.

5. The optical system according to 3, further comprising at least one absorbing shield arranged between the condenser optics and the imaging optics, the at least one absorbing shield being provided to prevent crosstalk between the channels of light beams.

6. The optical system according to claim 1, wherein a focal plane of the condenser optics at least approximately matches a focal plane of the imaging optics such that the condenser optics focusses the incoming light beams onto the focal plane of the imaging optics.

7. The optical system according to claim 1, wherein the condenser lens matrix comprises a plurality of condenser lenses, and wherein at least one condenser lens of the condenser lens matrix is formed as an axially symmetrical lens, such that a main surface of the respective condenser lens approximates a spherical, elliptical or parabolic surface.

8. The optical system according to claim 1, wherein the condenser lens matrix comprises a plurality of condenser lenses, and wherein at least one condenser lens of the condenser lens matrix is formed as a segment of an axially symmetrical lens such that the main surface of the respective condenser lens approximates a slice from a spherical, elliptical or parabolic surface.

9. The optical system according to claim 1, wherein the condenser lens matrix comprises a plurality of condenser lenses, and wherein at least one condenser lens of the condenser lens matrix is formed as an astigmatic lens, in particular a cylinder lens, or such that the main surface of the respective condenser lens is formed as a free-form surface.

10. The optical system according to claim 1, wherein the condenser optics is configured such that its focal plane is between the imaging optics and an edge of the at least one reflective shield facing the imaging optics, but closer to said edge.

11. The optical system according to claim 1, further comprising collimating optics for providing collimated incoming light beams, the collimating optics comprising a light source and a collimator lens, wherein the collimator lens is arranged between the light source and the condenser lens matrix, and the condenser lens matrix is arranged between the collimator lens and the imaging lens matrix.

12. The optical system according to claim 11, wherein the collimator lens is integrated in the condenser optics, such that the collimator lens is arranged on a rear side of the condenser optics facing the light source and the condenser lens matrix is arranged on a main surface of the condenser optics facing the imaging optics.

13. The optical system according to claim 1, wherein the imaging lenses of the imaging lens matrix are separated by a mesh of additional absorbing shields, the mesh being provided to prevent crosstalk between the outgoing light beams.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The following description of Figures may further illustrate and explain aspects of the optical system. Components and parts of the optical system that are functionally identical or have an identical effect are denoted by identical reference symbols. Identical or effectively identical components and parts might be described only with respect to the Figures where they occur first. Their description is not necessarily repeated in successive Figures.

[0047] FIG. 1 shows an example of an optical system.

[0048] FIG. 2 shows another example of an optical system.

[0049] FIG. 3 shows another example of an optical system.

[0050] FIGS. 4a-c show examples of a condenser lens matrix of an optical system.

[0051] FIG. 4d shows another example of a condenser lens matrix in an optical system.

[0052] FIGS. 5a-b show examples of an imaging lens matrix of an optical system.

[0053] FIGS. 6a-b show examples of an optical system comprising collimating optics.

[0054] FIGS. 7a-c show examples of light distributions of an optical system.

DETAILED DESCRIPTION

[0055] FIG. 1 shows an example of an optical system 1 in a cross-section. The optical system 1 can be used in a headlamp of a motor vehicle. The optical system 1 according to FIG. 1 comprises condenser optics 2 being formed by a condenser lens matrix 3. In this case, the condenser lens matrix 3 comprises one condenser lens 4. The condenser optics is provided to focus incoming light beams 5. The condenser optics 2 is provided to focus the incoming light beams 5 in a focal point 6 of the condenser optics 2. The incoming light beams are collimated, i.e. parallel to each other. The condenser optics 2 comprises a rear side 7 facing the incoming light beams 5. The condenser optics further comprises a main surface 8, which faces the focal point 6 and where the incoming light beams 5 are refracted. In the example of FIG. 1 the condenser lens 4 is formed as a segment of an axially symmetrical lens such that the main surface of the condenser lens approximates a slice from a spherical, elliptical or parabolic surface.

[0056] The optical system 1 according to FIG. 1 further comprises a reflective shield 9. A main plane of extension of the reflective shield 9 is generally perpendicular to a main plane of extension of the condenser lens matrix 2. In a vertical direction z, the reflective shield is arranged under the condenser lens 4. The vertical direction z refers to a direction which is perpendicular to the main plane of extension of the reflective shield 9.

[0057] The reflective shield 9 is provided to reflect at least a subset of focused light beams 10. The focused light beams 10 which are reflected at the reflective shield 9 are called reflected light beams 18. The reflective shield 9 is further provided to create a cut-off line 33 (not shown) of outgoing light beams 11. The cut-off line 33 refers to a line above which in the vertical direction z no or relatively few outgoing light beams 11 are projected for illuminating the road. The subset of focused light beams 10, that is reflected, comprises in particular focused light beams 10 which are near the optical axis of the condenser lens 4.

[0058] The reflective shield 9 is attached to the condenser optics 2 at a first side 12 below the condenser lens 4. At a second side 13 opposite to the first side 12 the reflective shield 9 comprises an edge 14, which faces the focal point 6 of the condenser lens 4. The edge 14 may be close to the focal point 6.

[0059] The optical system 1 further comprises imaging optics 15 being formed by an imaging lens matrix 16. In this case, the imaging lens matrix 16 comprises one imaging lens 17. A main plane of extension of the imaging optics 15 is generally parallel to the main plane of extension of the condenser optics 2. In the direction x of light propagation, the reflective shield 9 is arranged between the condenser optics 2 and the imaging optics 15. In the vertical direction z, there is an offset between the imaging lens 17 and the condenser lens 4. This means that a mass center of the imaging lens 17 is arranged below a mass center of the condenser lens 4.

[0060] The imaging lens 17 has a focal point 6 which at least approximately matches the focal point 6 of the condenser lens 4. Therefore, the condenser optics 2 focusses the incoming light beams 5 onto a focal plane of the imaging optics 15. The focal point 6 is located between the imaging optics 15 and the edge 14 of the reflective shield 9 facing the imaging optics 15. In FIG. 1, the imaging lens 17 is assigned to the condenser lens 4, forming a respective channel of light beams 19 within the optical system 1.

[0061] The imaging optics 15 is provided to project the focused light beams 10 and the reflected light beams 18 in front of the headlamp such that the reflected light beams 18 contribute to an intensity hotspot 34 (not shown) on one side of the cut-off line 33. The side of the cut-off line 33, where the intensity hotspot 34 is created, faces the road. In other words, in the vertical direction z the intensity hotspot 34 is below the cut-off line 33. The outgoing light beams 11 may mainly be parallel.

[0062] The optical system 1 according to FIG. 1 may be understood as one channel of a module 20 of an optical system 1, as shown in the following Figures. This means that further channels can be combined. The channels can be arranged next to each other in a lateral direction y or the vertical direction z. Moreover, several modules 20 can be combined such that an overall optical system 1 is formed. Correspondingly, the features described in context of FIG. 1 showing an optical system 1 comprising only one channel may also apply to the embodiments according to the following Figures comprising several channels.

[0063] In FIG. 2 another example of an optical system 1 is shown in a perspective view. The embodiment of FIG. 2 can be seen as combination of several channels according to FIG. 1, such that a module 20 of an optical system 1 is formed.

[0064] In this case the condenser lens matrix 2 comprises a plurality of condenser lenses 4, namely fifteen condenser lenses 4, which are arranged in three rows and five columns, respectively. The condenser optics 2 including the condenser lenses 4 may be formed by one single substrate comprising a transparent material. For example, glass or plastic can be used. The condenser optics 2 is fabricated by injection molding, for example. The number of rows and/or columns shown in FIG. 2 is merely arbitrary. As such, the condenser lens matrix 3 can comprises a different number of rows and/or columns. The condenser lenses 4 within the condenser lens matrix 3 may focus incoming light beams 5 in different focal points 6 (not shown). However, the focal points may be located on a common plane, also called focal plane.

[0065] In the vertical direction z a respective reflective shield 9 is arranged under each row of the condenser lens matrix 3. Thus, the embodiment of FIG. 2 comprises three reflective shields. The reflective shields 9 are arranged parallel to each other.

[0066] The imaging optics 15 is formed by the imaging lens matrix 16, which in this case comprises fifteen imaging lenses 17 arranged in three rows a five columns. Thus, in this example, each of the imaging lenses 17 is assigned to one of the condenser lenses 4. The module 20 of FIG. 2 therefore forms fifteen channels of light beams 19. In particular, each of the imaging lenses 17 of a particular row of the imaging lens matrix 16 is assigned to a respective condenser lens 4 of a corresponding row of the condenser lens matrix 3. In other words, the module 20 of FIG. 2 comprises three rows of light beam channels 19.

[0067] Each of the imaging lenses 17 projects the focused and reflected light beams 10, 18 in front of the headlamp, forming outgoing light beams 11, as shown in FIG. 1. This means that each imaging lens 17 contributes to the road illumination by projecting an image. Said images are superimposed at least partially. A sharp cut-off line 33 (not shown) is generated as a superimposed image of the reflective shields 9. Moreover, as the reflective light beams 18 are also projected by the imaging optics 15, they are not lost, but are used for road illumination, too. In particular, they contribute to the intensity hotspot 34 (not shown) directly below the cut-off line 33, i.e. on the side of the cut-off line 33 which faces the road.

[0068] The embodiment of FIG. 2 further comprises three absorbing shields 21. Each of the absorbing shields 21 is arranged between the condenser optics 2 and the imaging optics 15 in the direction x of light propagation. The absorbing shields 21 are provided to prevent crosstalk between the channels of light beams 19. In particular, they are provided to prevent crosstalk between light beams channels 19 of different rows of the module 20.

[0069] The absorbing shields 21 may comprise an opaque material. As shown in FIG. 2, each absorbing shield 21 is mounted on a respective reflective shield 9 at a first side 22, and on the imaging optics 15 at a second side 23. The first side 22 of the absorbing shield 21 is mounted on a rear side 24 of the reflective shield 9. The rear side 24 of the reflective shield 9 is opposite to a main surface of the reflective shield, where the light beams are reflected. The second side 23 of the absorbing shield 21 is mounted on the imaging optics 15 between two corresponding rows of the imaging lens matrix 16. The absorbing shields 21 are generally parallel to each other. A main plane of extension of each of the absorbing shields 21 is inclined with respect to the main plane of extension of the reflective shields 9.

[0070] In FIG. 3 another example of an optical system 1 is shown in a perspective view. The embodiment according to FIG. 3 is different from the embodiment of FIG. 2 in that it shows several kinks 25 in the topmost reflective shield 9. The kinks are formed by recesses/cutouts at the edge 14 facing the imaging optics 15. Each kink 25 is assigned to one of the light beam channels 19. The exact number, position and shape of the kinks 25 shown in FIG. 3 is merely exemplary and depends on the desired light distribution of outgoing light beams 11. In the example of FIG. 3 the cutouts have a triangular shape, but different shapes are likewise possible. Rays crossing the cutout in the reflective shield are not reflected. Instead, these rays are projected by the imaging optics above the cut-off line 33 (not shown). This makes it possible to adjust the light distribution in individual regions. For example, the right-hand side of the road can be illuminated in such a way that road signs are easier to see.

[0071] It should be mentioned, that the modules 20 shown in FIG. 2 and FIG. 3 can be combined. For example, the modules 20 can be arranged next to each other in the lateral direction y or on top of each other in the vertical direction z.

[0072] Additionally, the optical system 1 can comprises further modules 20, wherein the distance of the reflective shield's edge 14 to the focal plane can vary from one module 20 to another. Moreover, each module 20 can comprise its own light source (not shown) or the modules can comprise a common light source. By turning on or off the light source of the respective module 20, the light distribution of outgoing light beams 11 can be adjusted according to the requirements of the road illumination. For example, an optical system 1 comprising such modules 20 can enable both low and high beam functionality.

[0073] FIGS. 4a to 4c show examples of condenser lenses 4 within the condenser lens matrix 3 in a cross-section. In FIG. 4a three rows of condenser lenses 4 are shown, wherein each condenser lens 4 is formed as an axially symmetrical lens, such that the main surface 8 of the respective condenser lens 4 approximates a spherical, elliptical or parabolic surface.

[0074] In FIG. 4b three rows of condenser lenses 4 are shown, wherein each condenser lens 4 is formed as a segment of an axially symmetrical lens such that the main surface 8 of the respective condenser lens 4 approximates a slice from a spherical, elliptical or parabolic surface. In particular, the condenser lenses 4 are formed by half of an axially symmetrical lens. Such condenser lenses 4 have been shown also in FIGS. 1 to 3.

[0075] In FIG. 4c three rows of condenser lenses 4 are shown, wherein the main surface 8 of the respective condenser lens 4 is formed as a free-form surface.

[0076] FIG. 4d shows an optical system with another example of a condenser lens matrix. In that example, the condenser lenses 4 of the condenser lens matrix 3 are formed as astigmatic lenses, in particular as segments of a cylinder lens. This means that the condenser lens matrix 3 is formed by rows of condenser lenses 4, wherein at least one row forms a segment of a cylinder lens. In that case, imaging lenses 17 of a respective row of the imaging lens matrix 16 are assigned to the same condenser lens 4.

[0077] It should be mentioned that the condenser optics 2 can comprise different kinds of condenser lenses 4 (as shown in FIGS. 4a-d) in the same condenser lens matrix 3. It is also possible, that the optical system 1 comprises several modules wherein the condenser lenses 4 of different modules are differently shaped. For example, a module 20 comprising condenser lenses 4 formed as cylinder lenses as shown in FIG. 4d is suitable to provide a wide field of illumination.

[0078] FIG. 5a shows an example of the imaging optics 15 formed by the imaging lens matrix 16 in a perspective view. As the condenser lens matrix 3, the imaging lens matrix 16 may be formed by one single substrate comprising a transparent material. For example, glass or plastic can be used. The imaging optics 15 is fabricated by injection molding, for example. The number of rows and/or columns shown in FIG. 5a is merely arbitrary. As such, the imaging lens matrix 16 can comprise a different number of rows and/or columns, i.e. the number of imaging lenses 17 is arbitrary.

[0079] FIG. 5b shows another example of the imaging optics 15 in a perspective view. In this example, the imaging lenses 17 of the imaging lens matrix 16 are separated by a mesh 26 of additional absorbing shields 17. The mesh 26 of additional absorbing shields 27 is provided to prevent crosstalk between the outgoing light beams 11 (not shown). This means that between two neighboring imaging lenses 17 within the imaging lens matrix 16 there is an additional absorbing shield 27. The absorbing shield comprises an opaque material, e.g. a plastic material.

[0080] For example, the mesh 26 of additional absorbing shields 27 is fabricated by injection molding to form a holder. Then, individual imaging lenses 16 are inserted into the mesh 26 in order to form the imaging lens matrix 16. In this case, the imaging lenses 17 and the mesh 26 of additional absorbing shields 27 are separated pieces, which are assembled.

[0081] Alternatively, the imaging lens matrix 16 is formed by a single transparent substrate, which is molded into the desired shape, such that the plurality of imaging lenses 17 is formed. Then, the mesh 26 is generated by over-molding the substrate with an opaque material. In that case, the imaging lens matrix 16 and the mesh 26 are forming one piece of the optical system 1.

[0082] In FIG. 6a an optical system 1 that comprises collimating optics 28 is shown in a cross-section. The collimating optics 28 provides collimated incoming light beams 5. The collimating optics 28 comprises the light source 29 and a collimator lens 30. The collimator lens 30 is arranged between the light source 29 and the condenser optics 2 comprising the condenser lens matrix 3. The condenser lens matrix 3 is arranged between the collimator lens 30 and the imaging optics 15.

[0083] As shown in FIG. 6a, the light source can emit light in a wide range of directions. In other words, emitted light beams 31 are highly divergent. The collimator lens 30 redirects the emitted light beams 31, such that approximately parallel incoming light beams 5 are created. The collimator lens 30 may comprise a plastic material. The collimator lens 30 can be formed by injection molding, for example. In the example of FIG. 6a the collimator lens 30 forms a separate piece of the optical system 1.

[0084] However, the collimator lens 30 can also be integrated in the condenser optics 2, as shown in FIG. 6b. The collimator lens is arranged on the rear side 7 of the condenser optics 2 facing the light source 29. The condenser lens matrix 3 is arranged on the main surface 8 of the condenser optics 2 facing the imaging optics 15. This means that the collimator lens 30 and the condenser lens matrix 3 are formed by one piece of the optical system 1. In particular, the collimator lens 30 and condenser lens matrix 3 comprise the same material, e.g. a plastic material. Both the collimator lens 30 and the condenser lens matrix 3 can be formed in the same step of the fabrication process.

[0085] The collimator lens 30 may redirect the emitted light beams 31 by means of refraction and/or by means of total internal reflection (TIR). TIR occurs when light in one medium reaches the boundary with another medium at a sufficiently slanting angle, provided that the second (external) medium is transparent to the waves and allows them to travel faster than in the first (internal) medium. The angle of incidence at said boundary must exceed a certain value, called critical angle of total reflection. Light then no longer enters the second medium (in this case the ambient air) but is almost completely reflected in the first medium (the collimator lens). Therefore, in order for TIR to occur, the refractive index of the collimator lens may be larger than the refractive index of surrounding air. The inclination of at least some surfaces of the collimator lens with respect the light propagation may be such that the angle of incidence exceeds the critical angle. In the example of FIG. 6b, the center part of the collimator lens 30 redirects the emitted light beams 31 by means of light beam refraction, while the outer parts of the collimator lens 30 redirect the emitted light beams 31 by means of TIR.

[0086] FIG. 7a shows a mapping of the light intensity 32 of outgoing light beams 11 of an optical system 1 according to FIG. 2 or FIG. 4. The light intensity 32 is determined by simulation results and is shown on a rectangular detector screen at a distance from the optical system 1. The light intensity 32 is shown as a function of the position on the screen in the lateral direction y and the vertical direction z. However, the scaling of the y-axis and the z-axis is rather arbitrary.

[0087] The light distribution is symmetrical in relation to the lateral position at y=0. Moreover, it can be seen that there is a sharp light/dark boundary, also called cut-off line 33, at the vertical position at z=0, which is marked by a dashed line. The light intensity has a maximum below the cut-off line 33, i.e. for values z<0. The light intensity 32 rapidly decreases for values z>0. The maximum of the light intensity 32 is also called hotspot 34.

[0088] In FIG. 7b a graph is shown representing the light intensity 32 at the lateral position y=0 as a function of the vertical position z according to FIG. 7a. The linear scaling of the z-axis is rather arbitrary, as is the linear scaling of the intensity axis (I-axis). It can be seen the intensity raises up to the maximum, i.e. the hotspot 34, below the vertical position at z=0. The light intensity 32 rapidly decreases for values z>0, thus creating the cut-off line. The distribution of the light intensity 32 can be designed according to the requested illumination of the road.

[0089] FIG. 7c shows another mapping of the light intensity 32 of outgoing light beams 11 of the optical system 1 according to FIG. 3. As in FIG. 7a, the light intensity 32 is determined by simulation results and is shown on a rectangular detector screen at a distance from the optical system 1. In the example of FIG. 7c the light distribution is not axially symmetrical. Instead, on the right-hand side light beams 11 are projected above the cut-off line 33. There is therefore a region 35 above the cut-off line 33 in which the intensity value is not vanishing. As described above, this light distribution can be caused by one or more kinks in at least one reflective shield 9 of the optical system 1 (see FIG. 3). This light distribution makes it easier to see road signs on the right-hand side of the road, for example.

[0090] The embodiments of the optical system disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the idea. Although preferred embodiments have been shown and described, many changes, modifications, equivalents and substitutions of the disclosed concepts may be made by one having skill in the art without unnecessarily departing from the scope of the claims.

[0091] It will be appreciated that the disclosure is not limited to the disclosed embodiments and to what has been particularly shown and described hereinabove. Rather, features recited in separate dependent claims or in the description may advantageously be combined. Furthermore, the scope of the disclosure includes those variations and modifications, which will be apparent to those skilled in the art and fall within the scope of the appended claims.

[0092] The term comprising, insofar it was used in the claims or in the description, does not exclude other elements or steps of a corresponding feature or procedure. In case that the terms a or an were used in conjunction with features, they do not exclude a plurality of such features. Moreover, any reference signs in the claims should not be construed as limiting the scope.