ILLUMINATION DEVICE FOR A MOTOR VEHICLE HEADLIGHT

Description

[0001] The invention relates to a lighting device for a motor vehicle headlight, according to the preamble of claim 1.

[0002] In the development of current headlight systems, the desire is increasingly to be able to project a light image onto the road with the highest possible resolution, which can be quickly changed and adapted to the respective traffic, road and lighting conditions, whereby the most compact design and size possible is also desired.

[0003] The term "roadway" is used here for the sake of simplicity, because it naturally depends on the local conditions whether a photograph is actually on the roadway or extends beyond it, for example to the edge of the road.

[0004] In principle, the light image is described by means of a projection onto a vertical surface in accordance with the relevant standards relating to automotive lighting technology, whereby a variably controllable reflector surface is formed from a plurality of micromirrors and reflects light rays emitted by a first illuminant in a radiation direction of the headlight.

[0005] Any lighting function with different light distributions can be implemented, such as low beam, cornering light, city light, highway light, curve light, high beam, or glare-free high beam. Symbol projections, such as hazard symbols, navigation arrows, manufacturer logos, or similar, are also possible.

[0006] For the micromirror array, the so-called "Digital Light Processing" projection technology (DLP for short) is preferably used. This technology generates images by modulating a digital image onto a light beam. A rectangular array of movable micromirrors, also known as pixels, splits the light beam into sub-areas and then reflects or redirects them pixel by pixel, either into or out of the projection path.

[0007] The basis for this technology is preferably an optoelectronic component that contains the rectangular arrangement in the form of a matrix of micromirrors and their control technology, for example a "Digital Micromirror Device" - DMD for short.

[0008] A DMD microsystem is a spatial light modulator (SLM) consisting of a matrix of micromirror actuators, i.e., tiltable or pivotable reflective surfaces, for example, with an edge length of approximately 7 µm. The mirror surfaces are designed to be movable by the action of electrostatic fields.

[0009] Each micromirror can be individually adjusted in angle and usually has two stable final states, between which it can switch up to 5000 times within one second, for example.

[0010] The number of micromirrors corresponds to the resolution of the projected image, with each micromirror representing one or more pixels. DMD chips with high resolutions in the megapixel range are now available.

[0011] In currently used motor vehicle headlights, the generated light distribution, for example for a glare-free high beam, can be dynamically controlled in such a way that oncoming vehicles are detected and the light distribution generated, for example, by a matrix of LED light sources is darkened in the direction of the oncoming vehicle.

[0012] DMD lighting always requires the illumination of flat surfaces. Unlike cinema or business meeting projectors, which strive for uniform or homogeneous illumination of the entire DMD surface, automotive applications attempt to adapt the illumination to typical light distributions, such as high beams. This typically means maximum brightness in the center of the DMD or the illuminated DMD surface, with a decrease in illuminance toward the edges.

[0013] In general, the field of high-resolution lighting systems, especially in the field of DMD technology, is that fully functional lighting cannot be expected due to limitations imposed by the light source that can be used to illuminate the DMD. In particular, a fully functional high beam with a high maximum (greater than 100 lx) and a width of + / - 20° (measured using an ECE measuring screen) cannot be achieved. The high beam distribution generated by a DMD or DLP module is relatively narrow, with maximum expected widths of + / - 10°. Lighting devices are known from DE 10 2015 221049 A1, US 2018 / 031202 A1, DE 10 2018 204282 A1, or DE 10 2014 013202 B3.

[0014] For this reason, additional modules must be added to create the full width of the high beam or high beam distribution. These additional modules typically have to be placed somewhere in the headlight and are undesirable in terms of design and the space taken up in the vehicle headlight.

[0015] It is an object of the invention to provide an improved lighting device.

[0016] This object is achieved in that the illumination device comprises at least two expansion optics with a focal point, preferably exactly two expansion optics, wherein each light source is assigned exactly one expansion optic, which is configured to expand the light beam emitted by the light source in the direction of the first emission direction, wherein the expanded light beams partially overlap, and wherein the at least two light sources are arranged in the direction of the first emission direction between the at least one expansion optic and the focal point of the expansion optic.

[0017] The term "expansion" or "expanding" refers to the enlargement of an optical beam diameter to a specific size. Expansion can be achieved using various optical lens systems. However, this is well known to those skilled in the art and is only mentioned here for the sake of completeness.

[0018] Because the at least one light source is arranged between the expansion optics and the focal point of the expansion optics, the light source or the luminous surface of the light source is virtually imaged behind the light source, opposite to the first emission direction or the main emission direction of the light source. The virtual imaging of the light source magnifies the emitted light beam at the first deflection device. This has the effect that a larger area of ​​the first deflection device can be irradiated while simultaneously minimizing the optical path between the light source and the first deflection device, i.e., the overall installation space of the lighting device can be reduced.

[0019] The term "main radiation direction" is understood to mean the direction in which at least one light source emits the strongest or most light due to its directivity.

[0020] It can be provided that the second deflection device is designed as a digital micromirror array with a plurality of micromirrors arranged next to one another in an array-like manner and controllable individually or in groups.

[0021] Advantageously, the second deflection device can be designed as a DMD.

[0022] When using a DMD, care should be taken to work with very small light entry angle ranges, i.e. if light rays hit the micromirrors of the DMD too steeply or too flatly, this can lead to backlighting of the micromirrors, which in turn leads to scattered light in the projected light image and thus to poor light-dark contrast, which is extremely important when used for a motor vehicle headlight.

[0023] Each micromirror can be individually adjusted in its angle and usually has two stable final states between which it can be tilted.

[0024] By specifically moving individual or a group of selected deflection elements, the shape of the light beam distribution of the lighting device as well as the luminous intensity distribution within the light beam distribution can be varied. The light beam distribution can thus be dynamically changed both in terms of its shape (extension and / or extent) and in terms of its brightness distribution. The control of the deflection elements, and thus the variation of the light beam distribution, can be dependent on the operating parameters of the motor vehicle (e.g., vehicle speed, load, steering angle, lateral acceleration, etc.). Environmental parameters of the vehicle (e.g., outside temperature, precipitation, other road users detected in the vicinity of the vehicle, etc.) can also be taken into account when controlling the deflection elements.

[0025] It is provided that the at least two light sources are each designed as at least one light-emitting diode.

[0026] The lighting device comprises at least two light sources, preferably exactly two light sources.

[0027] When using two light sources, each with an expansion optic, according to the invention, the respectively expanded light beams are arranged partially overlapped.

[0028] By enlarging the light beams, the desired overlap can be adjusted and thus the center of the second deflection device can be illuminated with greater brightness.

[0029] It is provided that the illumination device comprises at least two expansion optics, preferably exactly two expansion optics, wherein each light source is assigned exactly one expansion optic.

[0030] It can be provided that the first radiation direction is parallel to the third radiation direction.

[0031] It is intended that the deflection surface of the first deflection device is designed as a hyperbolic, parabolic or ellipsoidal reflector.

[0032] It can be provided that the first deflection device focuses the light beam of the at least one light source onto a point which is located behind the second deflection device in the direction of the second radiation direction.

[0033] The object is also achieved by a motor vehicle headlight with at least one lighting device according to the invention.

[0034] The invention is explained in more detail below with reference to exemplary drawings. Here,

[0035] Fig. 1 a schematic representation of an exemplary lighting device.

[0036] Fig. 1 shows an exemplary lighting device 10 for a motor vehicle headlight, which lighting device10 a light source 50 for emitting a light beam in a first radiation direction X1 , where the light source 50 is designed as a light-emitting diode or LED, and a first deflection device 100 with a deflection surface 110 , which is designed to reflect at least part of the light beam from the light source 50 in a second radiation direction X2 to redirect.

[0037] Furthermore, the lighting device 10 comprises a second deflection device 200 with a plurality of independently controllable and movable deflection elements for deflecting at least part of the light beam of the first deflection device 100 deflected light beam into a third radiation direction X3 and to generate a light distribution in front of the lighting device 10 .

[0038] The second deflection device 200In the example shown, it is designed as a digital micromirror array (also called DMD) with a large number of micromirrors arranged next to one another in an array and controllable individually or in groups.

[0039] Furthermore, the lighting device 10 an expansion optic 300 with a focal point F1 on which expansion optics 300 the light source 50 assigned and is set up to be emitted by the light source 50 emitted light beams in the direction of the first emission direction X1 to expand, whereby the light source 50 in the direction of the first radiation direction X1 between the expansion optics 300 and the focal point F1 the expansion optics 300 is arranged.

[0040] The term "expansion" or "expanding" refers to the enlargement of an optical beam diameter to a specific size. Expansion can be achieved, for example, using various optical lens systems. However, the example shown uses a single expansion lens. 300 or lens and not an optical system consisting of several lenses.

[0041] This means that the light emitted by the light source 50 emitted beam of rays, which is directed to the expansion optics 300 hits, on the light entry side of the expansion optics 300 has a certain beam diameter, whereby the beam diameter of the light beam is determined by the expansion optics 300 after leaving the light exit side of the expansion optics 300 has a larger beam diameter.

[0042] Because the light source 50 between the expansion optics300 and the focal point F1 the expansion optics 300 is arranged, the light source 50 or the luminous surface of the light source 50 opposite to the first radiation direction X1 or the main radiation direction of the light source 50 behind the light source 50 By virtually mapping the light source 50 the emitted light beam is deflected at the first deflection device 100 This has the effect that a larger area of ​​the first deflection device 100 can be irradiated, while minimizing the optical path between the light source 50 and first deflection device 100 , ie the overall installation space of the lighting device 100 be reduced.

[0043] The term "main radiation direction" is understood to mean the direction in which a light source 50emits the strongest or most light due to its directivity.

[0044] It is intended that the deflection surface 110 the first deflection device 100 as a hyperbolic, parabolic or ellipsoidal reflector. Furthermore, the first deflection device 100 the light beam of the light source 50 to a point, which point is in the direction of the second radiation direction X2 behind the second deflection device 200 is located.

[0045] As a further development of the exemplary lighting device in Fig. 1 Exactly two light sources can also be provided, with each light source being assigned exactly one expansion optic. LIST OF REFERENCE SYMBOLS

[0046] Lighting device 10 light source 50 First deflection device 100 Deflection surface 110 Second deflection device 200 Expansion optics 300 Focus F1 First radiation direction X1 Second radiation direction X2 Third radiation direction X3

Claims

1. Lighting device (10) for a motor vehicle headlamp, which lighting device comprises the following: - at least two light sources (50) for emitting at least two light beams in a first emission direction (X1), preferably exactly two light sources (50), the at least two light sources (50) each being designed as at least one light-emitting diode, - a first deflection device (100) with a deflection surface (110) which is set up to deflect at least part of the respective light beam of each of the at least two light sources (50) in a second emission direction (X2), the deflection surface (110) of the first deflection device (100) being designed as a hyperbolic, parabolic or ellipsoidal reflector, and - a second deflecting device (200) with a plurality of independently controllable and movable deflecting elements for deflecting at least a part of the light beam of the light beam deflected by the first deflecting device (100) into a third radiation direction (X3) and for generating a light distribution in front of the lighting device (10), characterized in that the illumination device comprises at least two expansion optics (300) with a focal point (F1), preferably precisely two expansion optics (300), each light source (50) being assigned precisely one expansion optic (300) which is set up to expand the light beam emitted by the light source (50) in the direction of the first emission direction (X1), wherein the expanded light beams partially overlap, and wherein the at least two light sources (50) are arranged in the direction of the first radiation direction (X1) between the at least one expansion optics (300) and the focal point (F1) of the expansion optics (300).

2. Lighting device according to claim 1, characterized in that the second deflection device (200) is designed as a digital micromirror array with a plurality of micromirrors which are arranged next to one another in an array-like manner and can be controlled individually or in groups.

3. Lighting device according to one of claims 1 or 2, characterized in that the first direction of radiation (X1) is parallel to the third direction of radiation (X3).

4. Lighting device according to one of claims 1 to 3, characterized in that the first deflecting device (100) focuses the light beam of the at least one light source (50) onto a point which is located behind the second deflecting device (200) in the direction of the second direction of radiation (X2).

5. Motor vehicle headlamp with at least one lighting device according to one of claims 1 to 4.