Lighting system for a vehicle lamp

Abstract

The invention relates to a lighting system (20) for a vehicle lamp, comprising at least one light source (22, 24, 26) and a first micro lens array (10, 34) with a plurality of optical channels (14). Each optical channel (14) comprises at least one incident lens (16) through which light from the at least one light source (22, 24, 26) can enter the first micro lens array (10, 34), and at least one exit lens (18) through which the light can exit the first micro lens array (10, 34). The at least one light source (22, 24, 26) and the first micro lens array (10, 34) are positioned relative to each other such that the at least one light source (22, 24, 26) irradiates light on the first micro lens array (10, 34) at different angles such that the majority of the light flux of the at least one light source (22, 24, 26) irradiated at at least one of the different angles changes between optical channels (14) when passing through the first micro lens array (10, 34), resulting in a first predetermined beam pattern (42).

Description

[0001] The invention relates to a lighting system for a vehicle lamp, in particular a vehicle headlamp.

[0002] Several solutions are known to create vehicle headlamps with adaptive driving beam function (ADB) that allows to selectively decrease the light intensity in the direction of upcoming traffic and / or cars driving in front of the own vehicle in order to avoid dazzling other drivers.

[0003] Most of these solutions use a multitude of individual light emitting diodes (LEDs), which are also referred to as pixels, and a macroscopic projection optic. The number of pixels can range from 5 to several 10000 and is currently limited by the commercially available LEDs (micro-LEDs). Another optical solution is to apply digital micromirror devices (DMDs).

[0004] However, all of these solutions require large lenses with an at least horizontal extension in the range of at least 30 mm to 50 mm. Therefore, a certain installation space is required, which interferes with car styling criteria, both inside building space requirements and outside appearance.

[0005] Micro lens arrays (MLA), on the other hand, are known for their compact size and flexibility of arrangement. They fit well within today's preferred slim headlamp architectures and are therefore an interesting alternative to the bulky projection systems based on macroscopic lenses.

[0006] Conventional micro lens arrays consist of a plurality of optical channels, each comprising at least one incident lens for light to enter the micro lens array and one exit lens for the light to exit the micro lens array. The optical channels of a micro lens array are commonly regarded as the projections of the incident lenses on the exit lenses along the main optical axis of the whole system.

[0007] Since these lenses are arranged closely spaced to each other, crosstalk into adjacent channels cannot be avoided.

[0008] Crosstalk is the phenomenon of light entering into an optical channel of a micro lens array, but exiting the micro lens array through a neighboring channel.

[0009] In general, crosstalk is not welcome. It contradicts the idea of many parallel projectors being formed by the lens pairs of the respective channels, each of them contributing to the projected pattern via collimated light traveling along the optical axis of each projector.

[0010] Most literature and micro lens array designs focus on avoiding crosstalk, because it does not directly contribute to the projected image and typically results in distorted and de-focused projected patterns.

[0011] Furthermore, known micro lens array solutions for vehicle lights offer only limited dynamics in terms of light output variability and do not meet the expectations of original equipment manufacturers (OEMs) and their customers.

[0012] The object of the invention is therefore to provide a compact lighting system for vehicle lamps capable of performing improved ADB functions.

[0013] The object of the invention is solved by a lighting system for a vehicle lamp, comprising at least one light source and a first micro lens array with a plurality of optical channels. Each of the channels comprises at least one incident lens through which light from the at least one light source can enter the first micro lens array, and at least one exit lens through which the light can exit the first micro lens array. The at least one light source and the first micro lens array are positioned relative to each other such that the at least one light source irradiates light on the first micro lens array at different angles. Furthermore, the arrangement is such that the majority of the light flux of the at least one light source irradiated at at least one of the different angles changes between optical channels when passing through the first micro lens array, resulting in a first predetermined beam pattern.

[0014] The effect of irradiating light on the first micro lens array at different angles with one light source can be achieved for example by splitting a light beam from the light source into two partial beams that are guided onto the micro lens array at different angles.

[0015] Alternatively or additionally, two or more light sources can be located relative to the first micro lens array such that they illuminate the first micro lens array at different angles.

[0016] The invention is based on the observation that crosstalk can be used in a beneficial way to achieve an improved light output in directions deviating from the main optical axis of the first micro lens array (perpendicular to the micro lens array surface).

[0017] The lighting system according to the invention exploits the crosstalk phenomenon by positioning the first micro lens array and the at least one light source relative to each other such that light from the at least one light source entering an incident lens is output through several output lenses of different channels simultaneously. This allows to output light from the first micro lens array at several different angles (with respect to the main optical axis of the micro lens array) and thus to create a desired light distribution.

[0018] Furthermore, ADB functions can be introduced by individually addressing the at least one light source or different light sources, in particular by selectively illuminating the micro lens array at certain incident angles.

[0019] In a preferred embodiment, the lighting system further comprises a second micro lens array with a plurality of optical channels, each optical channel comprising at least one incident lens through which light from the at least one light source can enter the second micro lens array, and at least one exit lens through which the light can exit the second micro lens array.

[0020] The at least one light source and the second micro lens array are positioned relative to each other such that the at least one light source irradiates light on the second micro lens array at different angles. Furthermore, the arrangement is such that most of the light flux of the at least one light source irradiated at at least one of the different angles changes between optical channels when passing through the second micro lens array, resulting in a second predetermined beam pattern.

[0021] The first beam pattern created by the first micro lens array and the second beam pattern created by the second micro lens array superimpose to a desired beam pattern.

[0022] Applying two micro lens arrays increases the variability of the final (superimposed) beam pattern even further. In particular, areas within the projection of the first beam pattern created by the first micro lens array with insufficient intensity can be selectively illuminated with light exiting from the second micro lens array.

[0023] In simplified terms, the first and second beam pattern can be created such that they fit together to form a desired headlight beam pattern.

[0024] To create matching predetermined first and second beam patterns, the incident lenses and the exit lenses of at least one of the micro lens arrays are positioned offset to each other.

[0025] It is conceivable that the incident and exit lenses of at least one of the micro lens arrays are located in two parallel planes on different sides of a substrate. Regular arrays of lenses are formed in both parallel planes. In this context, the term "offset" means that these lens arrays are shifted relative to each other within their respective planes.

[0026] To achieve an uninterrupted final beam pattern, all projection angles within a certain range (e.g. horizontally + / - 20° with respect to the main optical axis of the micro lens arrays) have to be illuminated. This is achieved by applying differently shaped multi lens arrays (in particular with different horizontal offsets) and by placing the light source(s) at the appropriate positions towards them.

[0027] When the lighting system according to the invention is installed in a vehicle, the offset is in particular a horizontal offset. In other words, the incident lenses and the exit lenses of at least one of the micro lens arrays are shifted in a horizontal direction relative to each other (When looking at the front of the vehicle, the incident and exit lenses are shifted relative to each other to the left or to the right).

[0028] The offset distance is a fraction of the lens lateral dimension. As an example without limiting the scope of the invention: If the lenses of a micro lens array have a lateral dimension of 1 mm, a typical offset would be between 0 mm and 0.5 mm, for example 0.3 mm. It has been found out, that such small offset is sufficient to effectively influence the resulting beam pattern.

[0029] In one variant of the invention, the first micro lens array and the second micro lens array are oriented parallel to each other. In particular, the micro lens arrays can be stacked on top of each other in a space saving arrangement.

[0030] To further improve the variability of the created beam patterns, the at least one light source can comprise a pixelated LED package. Single or multiple LEDs can be individually (de)activated, resulting in an ADB functionality of the lighting system.

[0031] In a further variant of the invention, the at least one light source comprises an elongated luminous surface. The elongated luminous surface is for example formed by a row of LEDs.

[0032] Regarding the intended use of the lighting system inside a vehicle headlamp, the elongated luminous surface is in particular oriented vertically. With such a setup, it is possible to simultaneously illuminate two or even more micro lens arrays stacked on top of each other, and thus to create multiple predetermined beam patterns, superimposing to a desired headlight beam pattern.

[0033] In a simple and space saving variant of the lighting system comprising at least a second light source, the light sources are located in a common plane. In particular, they can be located in a plane parallel to the micro lens arrays.

[0034] Alternatively, the individual light sources can be located in different planes.

[0035] In another embodiment of the invention, at least one of the micro lens arrays comprises a mask layer located substantially at a focal plane of the respective exit lenses. Additionally or alternatively, the lighting system comprises one or more masks in front of or behind the micro lens array(s). The mask layers or masks selectively block light. They are useful to influence the beam shape and / or to remove unwanted optical features from the resulting beam patterns.

[0036] Of course, the invention is not limited to lighting systems with only two micro lens arrays. In particular, setups with a third and / or fourth micro lens array and / or a third light source are possible. With a higher number of micro lens arrays (preferably with different offsets), a finer subdivision of the resulting beam pattern and thus individually addressable ADB channels is achieved.

[0037] Further advantages and features will become apparent from the following description of the invention and from the appended figures, which show a nonlimiting exemplary embodiment of the invention and in which: Figure 1 schematically shows a top view on a micro lens array illuminated at a first angle; Figure 2 schematically shows a top view on the micro lens array of figure 1 illuminated at a second angle; Figure 3 schematically shows a top view of an embodiment of a lighting system for a vehicle lamp according to the invention; Figure 4 schematically shows a side view of the embodiment of figure 3; Figure 5 schematically shows the light path through a first micro lens array of the lighting system of figure 3 (top view); and Figure 6 schematically shows the light path through a second micro lens array of the lighting system of figure 3 (top view).

[0038] Figure 1 schematically shows a top view on a micro lens array 10, which can be applied in a vehicle headlamp.

[0039] The micro lens array 10 comprises a substrate 12 and has a plurality of optical channels 14. Each optical channel 14 comprises at least one incident lens 16 through which light can enter the micro lens array 10, and at least one exit lens 18 through which the light can exit the micro lens array 10.

[0040] In figure 1, the micro lens array 10 is illuminated in the direction of its main optical axis (substantially perpendicular to the surface of the micro lens array 10). Most of the light illuminated on the incident lenses 16 passes the micro lens array 10 without changing between optical channels 14.

[0041] When the same micro lens array 10 is illuminated at a different angle, crosstalk occurs.

[0042] Figure 2 shows this effect. The majority of the light flux illuminated on the incident lenses 16 changes into neighboring optical channels 14 when passing through the micro lens array 10.

[0043] The invention makes use of this crosstalk effect to achieve an improved light output in directions deviating from the main optical axis of the micro lens array 10.

[0044] Figure 3 schematically shows a top view of an embodiment of a lighting system 20 for a vehicle lamp according to the invention.

[0045] Figure 4 shows a side view of the embodiment of figure 3.

[0046] The lighting system 20 comprises a first light source 22, a second light source 24, and a third light source 26.

[0047] In the embodiment, all light sources 22, 24, 26 are located in a common plane.

[0048] Each of the light sources 22, 24, 26 comprises a pixelated LED package 28 with a plurality of individually addressable LEDs 30.

[0049] In the embodiment, the LEDs 30 are arranged in rows and form an elongated luminous surface 32.

[0050] In a typical installation situation within a vehicle headlamp, the elongated luminous surfaces 32 of the light sources 22, 24, 26 are oriented in a vertical direction. This is of course not limiting the invention. Other orientations are possible.

[0051] The lighting system 20 further comprises a first micro lens array 34 and a second micro lens array 36.

[0052] For example, the micro lens array 10 shown in figures 1 and 2 can be applied as first micro lens array 34 or second micro lens array 36 within the lighting system 20.

[0053] In the embodiment, the first micro lens array 34 and the second micro lens array 36 are stacked on top of each other and oriented in parallel, as shown in figure 4. This is of course not limiting the invention. Other arrangements are possible.

[0054] The first as well as second micro lens array 34, 36 each comprise a plurality of optical channels 14. Each of the optical channels 14 is defined by at least one incident lens 16 through which light from the first, second and third light source 22, 24, 26 can enter the respective micro lens array 34, 36, and at least one exit lens 18 through which the light can exit the respective micro lens array 34, 36.

[0055] In the embodiment, the first micro lens array 34 and second micro lens array 36 each comprise an optional mask layer 38 buried in the substrate 12 and located at a focal plane of the respective exit lenses 18. The purpose of the mask layers 38 is to selectively obstruct part of the light from passing through the respective micro lens array 34, 36, thus influencing the beam shape.

[0056] Furthermore, the lighting system 20 can comprise additional optical elements 40, for example collimators and / or lenses, to influence the light path through the lighting system 20.

[0057] As shown in figure 3, the first, second and third light source 22, 24, 26 are spaced apart from each other. They are positioned relative to the first and second micro lens array 34, 36 such that that they each irradiate light on the micro lens arrays 34, 36 at different angles.

[0058] Figure 5 schematically shows the light path through the first micro lens array 34 of the lighting system 20.

[0059] In the embodiment, the second light source 24 is positioned such that it illuminates the first micro lens array 34 in a substantially perpendicular direction. Hence, no or very little crosstalk occurs. The illumination situation is similar to the one depicted in figure 1.

[0060] The first and third light source 22, 26 on the other hand are positioned such that they illuminate the first micro lens array 34 at an angle substantially different from 90°. As a result, crosstalk occurs and the majority of the light flux of the first and third light source 22, 26 changes between optical channels 14 when passing through the first micro lens array 34. The illumination situation is similar to the one of figure 2.

[0061] By simultaneously illuminating the first micro lens array 34 with the first, second and / or third light source 22, 24, 26, a first predetermined beam pattern 42 is created.

[0062] In the embodiment the first predetermined beam pattern 42 exhibits several intensity maxima 44 at distinct projection angles and intensity minima 46 in between them.

[0063] To improve this situation, a second predetermined beam pattern 48 is created with the second micro lens array 36 and superimposed with the first predetermined beam pattern 42 to form a desired beam pattern.

[0064] Figure 6 schematically shows the light path through the second micro lens array 36 of the lighting system 20 and resulting second predetermined beam pattern 48. The illumination situation is similar to the one of figure 5.

[0065] However, in the second micro lens array 36, the incident lenses 16 and the exit lenses 18 are slightly offset to each other.

[0066] In the embodiment, the offset 50 is between 0.1 mm and 1 mm, preferably less than 0.5 mm, for example 0.3 mm. The offset 50 can also be regarded as a split of the optical channels 14 into two partial channels.

[0067] Due to the offset 50, the second predetermined beam pattern 48 differs from the first predetermined beam pattern 42.

[0068] In the embodiment, the second predetermined beam pattern 48 exhibits several intensity maxima 44, at distinct projection angles at which the first predetermined beam pattern 42 exhibits intensity minima 46.

[0069] The superposition of both predetermined beam patterns 42, 48 thus results in a desired homogeneous beam pattern.

[0070] In other words, the intensity maxima 44 of the second predetermined beam pattern 48 fill the gaps between the intensity maxima 44 of the first predetermined beam pattern 42, as schematically shown in figure 5.

[0071] In figures 5 and 6, the projection angle range is divided into distinct regions, which are in the following referred to as ADB channels 52. For example, each ADB channel has a width of 2°.

[0072] The intensity minima 46 as well as the intensity maxima 44 are located within the different ADB channels 52. By selectively switching the different light sources 22, 24, 26 or individual LEDs 30 on or off, the light intensity within the ADB channels 52 can be adjusted. In this way, an ADB functionality is introduced to the lighting system 20.

[0073] Of course, it is also possible to apply more than two micro lens arrays 10, in particular with different offsets 50, to achieve even better homogeneity of the superimposed beam pattern.

[0074] With each micro lens array 10, up to four different ADB channels 52 can be addressed. This means that for a headlamp comprising a lighting system 20 according to the invention with four micro lens arrays 10 with different offsets 50, a maximum of twelve to sixteen ADB channels would be possible. With two headlamps and partially overlapping beams, twenty individually addressable ADB channels 52 are conceivable. If pixelated light sources 22, 24, 26 are used, this number can be increased substantially.

Claims

1. A lighting system for a vehicle lamp, comprising at least one light source (22, 24, 26); and a first micro lens array (10, 34) with a plurality of optical channels (14), each optical channel (14) comprising at least one incident lens (16) through which light from the at least one light source (22, 24, 26) can enter the first micro lens array (10, 34), and at least one exit lens (18) through which the light can exit the first micro lens array (10, 34), wherein the at least one light source (22, 24, 26) and the first micro lens array (10, 34) are positioned relative to each other such that the at least one light source (22, 24, 26) irradiates light on the first micro lens array (10, 34) at different angles such that the majority of the light flux of the at least one light source (22, 24, 26) irradiated at at least one of the different angles changes between optical channels (14) when passing through the first micro lens array (10, 34), resulting in a first predetermined beam pattern (42).

2. The lighting system according to claim 1, further comprising a second micro lens array (10, 36) with a plurality of optical channels (14), each optical channel (14) comprising at least one incident lens (16) through which light from the at least one light source (22, 24, 26) can enter the second micro lens array (10, 36), and at least one exit lens (18) through which the light can exit the second micro lens array (10, 36), wherein the at least one light source (22, 24, 26) and the second micro lens array (10, 36) are positioned relative to each other such that the at least one light source (22, 24, 26) irradiates light on the second micro lens array (10 36) at different angles such that most of the light flux of the at least one light source (22, 24, 26) irradiated at at least one of the different angles changes between optical channels when passing through the second micro lens array (10, 36), resulting in a second predetermined beam pattern (48), wherein the first and second predetermined beam pattern (42, 48) superimpose to a desired beam pattern.

3. The lighting system according to claim 2, wherein in the first and / or second micro lens array (10, 34, 36), the incident lenses (16) and the exit lenses (18) are offset to each other.

4. The lighting system according to claim 3, wherein the offset (50) is less than 0.5 mm.

5. The lighting system according to any of the claims 2 to 4, wherein the first micro lens array (10, 34) and the second micro lens array (10, 36) are oriented parallel to each other.

6. The lighting system according to any of the previous claims, wherein the at least one light source (22, 24, 26) comprises a pixelated LED package (28).

7. The lighting system according to any of the previous claims, wherein the at least one light source (22, 24, 26) comprises an elongated luminous surface (32).

8. The lighting system according to any of the previous claims, comprising at least a second light source, wherein the light sources (22, 24, 26) are located in a common plane.

9. The lighting system according to any of the previous claims, wherein at least one of the micro lens arrays (10, 34, 36) comprises a mask layer (38) located at a focal plane of the respective exit lenses (18).

10. The lighting system according to any of the previous claims, comprising a third and / or fourth micro lens array (10) and / or a third light source (26).

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