EP2846077B1 - Projection lens for use in an LED module of a motor vehicle headlight, and LED module and motor vehicle headlamp with such a projection lens - Google Patents

Description

The present invention relates to an LED module of a motor vehicle headlight. The LED module has a light source in the form of an LED matrix, which comprises a plurality of LED chips arranged side by side and / or one above the other, a primary optic which comprises a plurality of primary optical elements arranged side by side and / or one above the other, for bundling the one of the Light source emitted light and the projection optics. The projection optics project an exit surface of the primary optics to generate a predetermined light distribution onto a roadway in front of a vehicle.

The present invention also relates to a motor vehicle headlight having such a headlight
LED module.

Motor vehicle headlights with a light source in the form of an LED matrix, which comprises a plurality of LED chips arranged side by side and / or one above the other, are also referred to as matrix headlights. The LED matrix can consist of a single row or column with several LED chips or of several rows or columns arranged one above the other or next to one another, each with several LED chips. Matrix headlights generate a light distribution on the road in front of the motor vehicle, which has a plurality of partial light distributions arranged next to or above one another in the form of pixels or strips. As a rule, each LED chip generates its own partial light distribution. By targeted control, in particular switching on / off or dimming, of the individual LED chips of the matrix light source, it is possible to influence the shape and intensity of the light distribution. In this way, a matrix headlamp without movable parts can be used to generate an adaptive light distribution. In particular, a low-beam headlight distribution with a horizontal light-dark boundary, a conventional low-beam light distribution with an asymmetrical light-dark boundary, a high beam distribution, a partial high beam distribution in which areas are specifically excluded from the light distribution where other road users have been detected, or a marker light distribution in which the objects detected on the road ahead of the vehicle are generated. Matrix headlights are known in different embodiments from the prior art, cf. e.g. EP 2 306 073 A2 , EP 2 306 074 A2 , EP 2 306 075 A2 or DE 10 2008 013 603 A1 .

Furthermore, for example DE 10 2011 077 132 A1 and the DE 10 2011 077 636 A1 Approaches specifically known for so-called strip headlights, in which the generated Light distribution comprises a plurality of strip-shaped partial light distributions arranged next to one another.

From the DE 10 2010 046 626 B4 approaches for designing a color-correcting projection optics for matrix headlights are known.

Finally, in the EP 2 280 215 A2 proposed to improve the homogeneity and the resolution of the image in the resulting light distribution by using several LED modules in one headlight. Each primary optic is assigned an individual projection optic (or secondary optic). For the known headlight, two light source modules, at least two primary optics modules and at least two secondary optics modules are therefore always combined. At least two light exit surfaces per matrix headlight are therefore visible from the outside. A so-called facet-eye headlight module is created. The strip-shaped partial light distributions projected onto the roadway have a relatively large angular width of at least 2 ° horizontally or even significantly more. The superimposition of such wide stripes improves the homogeneity of the light distribution, but reduces the achievable resolution. The known headlamp requires at least two complete, mutually independent light modules per headlamp, each light module having an LED matrix, a primary optic and a secondary optic. Such a headlamp thus consists of at least two light sources, two primary optics and two secondary optics.

With all matrix headlights known from the prior art, however, there is the problem that the resulting light distribution leads to color and Fluctuations in intensity come. These are mainly caused by the dispersion (change in the refractive index of optical materials depending on the light wavelength) and aberrations of the projection optics. The color fluctuations occur particularly at the edge of the individual partial light distributions.

Based on the described prior art, the present invention is based on the object
To design and develop an LED module of the type mentioned at the outset such that the headlight with a single primary optic and a single projection optic has improved homogeneity of the resulting light distribution, the light distribution being visible from the outside from a single light exit opening or from a single projection optic should emerge from the headlight.

To solve this problem, starting from
In the LED module of the type mentioned at the outset, it is proposed that the projection optics be designed in such a way that on its image side it generates at least two separate images of the exit surface of the primary optics which are offset from one another in the horizontal direction, so that superimposition of the images produced improves homogeneity of the light distribution .

With the LED module according to the invention, it is possible to generate the desired improved and more homogeneous matrix light distribution from a single visible and tangible outlet opening (so-called one-eye matrix headlights). The proposed projection optics compensate for color effects and homogeneity or intensity fluctuations up to half a pixel width without the use of Special glasses or plastics are required and without reducing the image sharpness, in particular the pixel edge sharpness. Thanks to the proposed projection optics, color compensation and homogeneity improvement can thus be achieved in a matrix headlamp without additional loss of sharpness, in particular in relation to the periodically appearing color, homogeneity and imaging errors.

An important aspect of the present invention can be seen in the fact that a single matrix-like light source, which is preceded by a single integral primary optics, whose exit light distribution on the light exit surface is imaged on the roadway via a single integral projection optics such that at least two separate primary optics images are created , so that pixel edges and steepness of boundaries are retained in their interaction and the remaining periodically occurring color and homogeneity or intensity fluctuations compensate each other. There are various ways of designing the projection lens in the sense of the invention that it produces the effect described above.

To implement the LED module according to the invention, it is conceivable to vary one or more active optically active surfaces of the projection optics. In particular, this can be a light entry surface, a light exit surface and / or any other surface in between (for example in the case of an achromatic lens). The active optically active surface of the projection optics is preferably divided and / or shifted in such a way that the at least two separate images of the light exit surface of the primary optics which are shifted in the horizontal direction are produced. Each of the images generated contributes part of the common luminous flux or part of the intensity and illuminance. The proportion that each image contributes depends on the number of separate images generated. The proportion is preferably 50% for two images and accordingly 33% for three images of the common value of the resulting light distribution.

The projection optics are advantageously designed such that the separate images of the exit surface of the primary optics are each offset by a value b / n, where b is a width, in particular an angular width, of a pixel formed by the imaging of an individual light exit surface of an individual primary optic element and n is a number of separate images of the exit surface of the primary optics generated by the projection optics. If the projection optics are designed, for example, to generate two separate images of the light exit surface of the primary optics, these two images are preferably offset from one another by half a pixel width.
Accordingly, the images of the light exit surface of the primary optics are preferably offset from one another by a third of the pixel width if the projection optics are designed to produce three separate images. In this way, a particularly homogeneous light distribution can be generated.

An important aspect of the present invention can be seen in the fact that a single matrix-like light source, which is preceded by a single integral primary optics, whose exit light distribution on the light exit surface is imaged on the roadway via a single integral projection optics such that at least two separate ones Primary optics images are created so that pixel edges and steepness of boundaries are retained in their interaction and the other periodically occurring fluctuations in color and homogeneity or intensity compensate each other. There are various ways of designing the projection lens in the sense of the invention that it produces the effect described above.

According to a first advantageous development of the present invention, it is proposed that the projection optics have at least two separate optical axes. The separate optical axes of the projection optics preferably run in the same horizontal plane. The horizontal plane preferably comprises a module axis of an LED module which is provided with the projection lens. The module axis preferably runs from the center of the light exit surface of the primary optics in the direction of travel. The distance between the optical axes is relatively small. It is chosen so that separate images of the light exit surface of the primary optics are generated, which are offset from one another in the horizontal direction by a fraction of a pixel. The different optical axes of the projection optics mean that different images of the light exit surface of the primary optics are generated. The number of separate images generated by the projection lens corresponds to the number of separate optical axes. The images of the light exit surface of the primary optics are offset from one another in accordance with the course of the optical axes. The fact that the optical axes run in the same horizontal plane means that the separate images are only offset from one another in the horizontal direction. If the optical axes were arranged in different horizontal planes, this would result there is also a vertical offset of the images to each other.

According to a preferred embodiment of the invention, it is proposed that the separate optical axes of the projection optics run parallel and at a distance from one another. Alternatively, it is proposed that the separate optical axes of the projection optics run at an angle to one another. In this case, the optical axes of the projection optics preferably intersect in a plane of the light exit surface of the primary optics. The plane of the light exit surface is preferably perpendicular to the horizontal plane in which the optical axes are arranged. It is particularly preferred if the oblique optical intersect at an intersection of the module axis with the light exit surface of the primary optics.

According to another preferred embodiment of the present invention, it is proposed that at least one active optical surface of the projection optics be provided with alternating optical regions arranged next to and / or one above the other for generating essentially identical images of the exit surface of the primary optics, a first group of the optical ones Areas produces a first image of the exit surface of the primary optics and at least one further group of the optical regions generates an at least one further image of the exit surface of the primary optics, the generated images being arranged offset from one another in the horizontal direction in the resulting light distribution. In this sense, at least one active optical surface of the projection optics can be provided with the alternating regions in the manner of a strip or checkerboard. Each group of areas is assigned its own optical axis, which is separate from the optical axes of the other groups of areas.

The alternating optical regions are preferably formed on a light exit surface of the projection optics. It is further preferred that the alternating optical regions are designed in the form of strips, the strips extending in the vertical direction. If the projection optics produce two separate images of the light exit surface of the primary optics, the strip-shaped areas are preferably assigned alternately to one of two groups. Accordingly, every third strip-shaped area is preferably assigned to one of three groups if the projection optics generate three separate images of the light exit surface of the primary optics.

According to a further preferred embodiment of the invention, it is proposed that the active optical surface of the projection optics be provided with a plurality of prisms arranged alongside one another, which extend over the entire surface and whose longitudinal axes run parallel to one another, with a prism surface of the prisms being the first image of the exit surface of the Primary optics and the other prism surface of the prisms creates the second image of the exit surface of the primary optics. The prism surfaces can be flat or curved.

According to yet another preferred embodiment of the present invention, it is proposed that a tip of the prisms be flattened over their entire longitudinal extent, so that there is a roof surface of the prisms, which produces a further image of the light exit surface of the primary optics, which corresponds to the other two images in FIG is offset in the horizontal direction. In this way, the projection optics can be three separate ones in horizontal Create images of the light exit surface of the primary optics that are offset in relation to one another. The images are preferably offset from one another by b / 3, where b is the width, in particular an angular width, of a pixel of the resulting light distribution, that is to say a partial image of a partial light exit surface of a primary optic element.

According to yet another preferred embodiment of the invention, it is proposed that the prism surfaces of the prisms are each divided into two partial surfaces over their entire longitudinal extent, a line of contact of the partial surfaces of a prism surface of a prism running parallel to the longitudinal axis of the prism, the partial surfaces each being a separate one and generate a staggered image of the light exit surface of the primary optics to the other images. In this way, the projection optics in a prism with a tip can produce four separate images of the light exit surface of the primary optics which are offset from one another in the horizontal direction. In the case of a prism with a flattened tip and roof surface, the projection lens can even produce five separate images of the light exit surface of the primary optics which are offset from one another in the horizontal direction. The images are preferably offset from one another by w '/ 4 or w' / 5, where w 'is the width, in particular an angular width, of a pixel of the resulting light distribution, that is to say a partial image of a partial light exit surface of a primary optic element.

Of course, other suitable structures can also be provided for generating the separate images of the light exit surface of the primary optics. Furthermore, it is conceivable to add the structures for generating the separate images using any scattering structure overlay.

Finally, it is proposed that the alternating optical regions formed on the at least one active optical surface of the projection optics have an amplitude of less than 0.1 mm, preferably less than a few tens of micrometers, very particularly preferably of a few micrometers.

By using an LED module according to the invention, a
headlights according to the invention can be realized.

Fig. 1

einen erfindungsgemäßen Kraftfahrzeugscheinwerfer gemäß einer bevorzugten Ausführungsform;

Fig. 2

ein erfindungsgemäßes LED-Modul eines Kraftfahrzeugscheinwerfers gemäß einer bevorzugten Ausführungsform;

Fig. 3

eine Lichtverteilung eines aus dem Stand der Technik bekannten Matrix-Scheinwerfers;

Fig. 4

eine erste Abbildung einer Lichtaustrittsfläche einer Primäroptik eines erfindungsgemäßen LED-Moduls;

Fig. 5

eine zweite Abbildung einer Lichtaustrittsfläche einer Primäroptik des erfindungsgemäßen LED-Moduls;

Fig. 6

eine aus einer Überlagerung der Abbildungen aus den Fig. 4 und 5 resultierende Lichtverteilung des erfindungsgemäßen LED-Moduls;

Fig. 7

eine beispielhafte Lichtverteilung mit ISO-Linien auf einem Messschirm eines aus dem Stand der Technik bekannten LED-Moduls;

Fig. 8

eine der Lichtverteilung aus Fig. 7 entsprechende beispielhafte Lichtverteilung eines erfindungsgemäßen LED-Moduls;

Fig. 9

eine erfindungsgemäße Projektionsoptik mit parallelen optischen Achsen;

Fig. 10

eine erfindungsgemäße Projektionsoptik mit schräg stehenden optischen Achsen;

Fig. 11

eine erfindungsgemäße Projektionsoptik mit alternierenden optisch wirksamen Bereichen auf der Lichtaustrittsfläche;

Fig. 12

eine erfindungsgemäße Projektionsoptik mit einer Prisma-Struktur auf der Lichtaustrittsfläche;

Fig. 13

verschiedene Beispiele für Strukturen auf einer optisch aktiven Fläche einer erfindungsgemäßen Projektionsoptik;

Fig. 14

weitere Beispiele für Strukturen auf einer optisch aktiven Fläche einer erfindungsgemäßen Projektionsoptik;

Fig. 15

ein Ausschnitt einer Prisma-Struktur auf einer optisch aktiven Fläche einer erfindungsgemäßen Projektionsoptik; und

Fig. 16

weitere Beispiele für Strukturen auf einer optisch aktiven Fläche einer erfindungsgemäßen Projektionsoptik.

Further features and advantages of the invention are explained in more detail below with reference to the figures. Show it:

Fig. 1

a motor vehicle headlight according to the invention according to a preferred embodiment;

Fig. 2

an inventive LED module of a motor vehicle headlight according to a preferred embodiment;

Fig. 3

a light distribution of a matrix headlight known from the prior art;

Fig. 4

a first image of a light exit surface of a primary optics of an LED module according to the invention;

Fig. 5

a second image of a light exit surface primary optics of the LED module according to the invention;

Fig. 6

one from an overlay of the images from the Fig. 4 and 5 resulting light distribution of the LED module according to the invention;

Fig. 7

an exemplary light distribution with ISO lines on a measuring screen of an LED module known from the prior art;

Fig. 8

one of the light distribution Fig. 7 corresponding exemplary light distribution of an LED module according to the invention;

Fig. 9

projection optics according to the invention with parallel optical axes;

Fig. 10

projection optics according to the invention with inclined optical axes;

Fig. 11

projection optics according to the invention with alternating optically effective areas on the light exit surface;

Fig. 12

projection optics according to the invention with a prism structure on the light exit surface;

Fig. 13

various examples of structures on an optically active surface of a projection optics according to the invention;

Fig. 14

further examples of structures on an optically active surface of a projection optics according to the invention;

Fig. 15

a section of a prism structure on an optically active surface of a projection optics according to the invention; and

Fig. 16

further examples of structures on an optically active surface of a projection optics according to the invention.

In Figure 1 A motor vehicle headlight according to the invention is designated in its entirety with reference number 1. The headlight 1 has a housing 2, which is preferably made of plastic. In a light exit direction 3, the headlight housing 2 has a light exit opening 4, which is closed by means of a transparent cover plate 5. The cover plate 5 is made of glass or plastic. At least in some areas, optically effective profiles (for example prisms or cylindrical lenses) can be arranged on the cover plate 5 in order to scatter the light passing through (so-called diffuser plate). However, it is also conceivable that the cover plate 5 is designed without such optically active elements (so-called clear plate).

A light module 6 is arranged in the interior of the headlight housing 2. The light module 6 can be used to generate any headlight function or a part thereof. In particular, the light module 6 can be used to generate a low beam distribution, a high beam distribution, a fog light distribution or any adaptive light distribution. Furthermore, a further light module 7 can be arranged in the housing 2. This is used, for example, to generate a further headlight function. But it would also be conceivable that the light modules 6, 7 together form one generate certain headlight function. For example, the light module 7 could generate a low-beam basic light distribution with a relatively wide scatter and a horizontal cut-off line. The light module 6 could then produce a low beam spot light distribution which is relatively strongly concentrated in comparison with the low beam basic light distribution of the light module 7 and has an asymmetrical light-dark boundary on the upper side. A superimposition of the basic light distribution and the spot light distribution results in a conventional low beam distribution. Of course, it is conceivable that in addition to the light modules 6, 7, further light modules are arranged in the headlight housing 2. In addition, only one light module, for example the light module 6 without the light module 7, can be arranged in the headlight housing 2. Finally, it is possible that one or more light modules, such as the light module 8 shown by way of example, are also arranged in the housing 2. The lamp module 8 is used to generate any lamp function, for example a flashing light, a position light, a daytime running light, etc.

The light module 6 is preferably designed as an LED module according to the invention. The LED module 6 is in detail in Figure 2 shown. The LED module 6 has a light source in the form of an LED matrix, which is designated in its entirety by the reference number 10. The LED matrix 10 has a plurality of LED chips 11 arranged side by side and one above the other in a matrix. Furthermore, the LED module 6 comprises a primary optic, which is designated in its entirety by the reference number 12. The primary optics 12 have a plurality of primary optics elements 13 arranged side by side and one above the other in a matrix. In the illustrated In the exemplary embodiment, each LED chip 11 is assigned its own primary optical element 13. As shown in section I, which shows such a primary optic element 13 together with an LED chip 11 assigned to it, the LED chip 11 emits light in a main emission direction 14, which largely couples into the primary optic element 13 via a light entry surface 15. The primary optics element 13 itself can be designed as a conventional reflector for specular reflection or as a so-called attachment optics element made of a transparent material (for example glass or plastic) for total reflection. In the example shown, the primary optics element 13 is designed as a totally reflective front lens made of a transparent plastic material. The primary optics 12 can bundle the light emitted by the LED matrix 10. Finally, the LED module 6 comprises projection optics 16 which are designed as an optical lens. The projection optics 16 is also referred to as secondary optics. It projects an exit surface 17 of the primary optics 12 for generating a predetermined light distribution onto a roadway in front of a vehicle equipped with the headlamp 1 and the LED module 6. The projection optics 16 can be designed as a conventional optical lens or as an achromatic lens.

The headlamp 1 with the LED module 6 is also referred to as a matrix headlamp, since it generates a light distribution with a plurality of pixel or strip-shaped partial light distributions arranged next to and / or one above the other. The individual partial light distributions that are generated by the light of an LED 11 and the associated primary optical element 13 are also referred to as pixels. Each of the partial light distributions is shown by imaging a partial light exit surface of an individual primary optical element 13 the primary optics 12 are generated by means of the projection optics 16. In Figure 3 a light distribution of a matrix headlight 1 known from the prior art is shown by way of example. The light distribution 20 is shown on a measuring screen 21, which is arranged at a defined distance from the headlight 1 or the LED module 6 in front of the motor vehicle. A horizontal HH and a vertical VV running perpendicular to it are also drawn on the measuring screen. It can be clearly seen that the light distribution 20 shown here by way of example has a large number of pixels 22, 23, 24 arranged next to and above one another. In particular, the pixels 22, 23, 24 in the exemplary embodiment shown are arranged in three rows and in thirty columns. The pixels of the upper row are designated by the reference symbol 22, the pixels of the middle row by the reference symbol 23 and the pixels of the lower row by the reference symbol 24. Each pixel 22, 23, 24 of the light distribution 20 shown is generated by an LED chip 11 in cooperation with the associated primary optics element 13 after projection by the secondary optics 16.

By specifically controlling the individual LED chips 11 of the LED matrix 12, it is possible to vary the resulting light distribution 20 almost as desired. For example, it is conceivable to temporarily switch off those LED chips 11 in whose pixel area of the light distribution 20 other road users have been detected. In this way, driving can be carried out continuously with high beam, whereby glare to other road users is prevented by the pixels 22, 23, 24 which are locally removed from the light distribution 20 (so-called partial high beam). It would also be conceivable that the LED module 6 generates a low beam distribution with an asymmetrical upper cut-off line, the LED chips 11 for generating the upper row of pixels 22 are switched off except for a few LED chips 11 for generating pixels 22 on the own traffic side. In addition, it would be conceivable to switch on objects detected on a roadway in front of the motor vehicle by deliberately switching on individual LED chips 11 to generate one or more pixels 22, 23 above the cut-off line of the low beam so that the objects detected in front of the roadway are illuminated in a targeted manner can be (so-called marker light or marker light). Any other adaptive light distributions 20 can also be achieved by specifically switching the LEDs 11 on / off and / or dimming them.

In particular, along the edge of the individual pixels 22, 23, 24, the resulting light distribution 20 can have an undesirable color fringe. In addition, there can be clearly visible intensity fluctuations in the light distribution 20. The aim of the present invention is to improve the homogeneity of the light distribution 20 with regard to disturbing color effects and intensity fluctuations.

In particular, the present invention proposes a special homogenizing projection optics (or secondary optics) 16 as a component of a matrix headlight 1 for motor vehicles, in which a light exit surface 17 of the primary optics 12 consists of a plurality of periodic structures that are lined up in a pixel or stripe fashion by the special projection optics 16 is projected onto the road to implement a dynamic low beam, partial high beam, matrix light or high beam function. The projection optics 16 generate at least two separate ones on the image side, ie on the roadway or on a measuring screen 21 Figures 25, 26 (cf. Figures 4 and 5 ) of the light exit surface 17 of the primary optics 12 on the object side. A superimposition of the at least two separate images 25, 26 results in a resulting light distribution 27 (cf. Figure 6 ), the at least two images 25, 26 being offset from one another in the horizontal direction in such a way that there is a clear improvement in the homogeneity of the light distribution 27. In particular, undesired color effects or intensity fluctuations in the light distribution 27 are selectively reduced or even completely eliminated. The separate images 25, 26 of the light exit surface 17 of the primary optics 12 are generated by a common projection optics 16.

A first image 25 of the light exit surface 17 of the primary optics 12, which can be generated by the projection optics 16 according to the invention, is exemplified in FIG Figure 4 shown. Figure 25 from Figure 4 is offset by about 1/4 pixel to the left with respect to the vertical VV in the example shown. In Figure 5 A second image 26 of the light exit surface 17 of the primary optics 12 is shown. The second separate figure 26 is shifted by about ¼ pixel to the right with respect to the vertical VV in the exemplary embodiment shown. The first and second images 25, 26 are thus offset relative to one another by approximately 1/2 pixel. Each figure 25, 26 contributes half the common luminous flux to the resulting total light distribution 27, or half the intensity and half the illuminance to the total value of the light distribution 27. Since the edges of the pixels 22, 23, 24 and the pixel centers of figures 25, 26 do not lying on top of one another, color and intensity inhomogeneities compensate for one another by superimposing the figures 25, 26. So that's it with the The present invention makes it possible to generate a significantly more homogeneous light distribution 27 from only one LED module 6 with a primary optic 12 and a projection optic 16 than is possible in the prior art under comparable conditions or conditions.

The intensity of the individual images 25, 26 depends on the length of the prism surfaces or on the proportion of the prism base surface which is assigned to the corresponding prism surface. A preferred embodiment comprises prisms with the same prism base area proportions.

To illustrate the invention, reference is made to the in the Figures 7 and 8 shown light distributions 20, 27 with drawn ISO lines (Isolux lines to denote areas of the same illuminance). In Figure 7 Shown is the light distribution 20 that was generated using a conventional LED module. The light distribution 20 shown is a low beam or partial high beam, the entire area of the oncoming lane having been removed from the light distribution 20 in order to prevent oncoming road users from being dazzled. The light distribution 20 is shown on a measuring screen 21. It can be clearly seen that the lines 30 of the same intensity or illuminance have inhomogeneities which are recognizable by the restless line course. In contrast to this, the lines 31 of the same intensity or illuminance have significantly fewer inhomogeneities in the light distribution 27 generated with the matrix headlamp 1 according to the invention or the LED module 6 according to the invention, which is recognizable by the much quieter line profile.

The Figures 7 and 8 show by way of example the same low beam pattern 20, 27 of a matrix headlight 1 with an LED matrix light source 10 with three lines. All LED chips 11 of the LED matrix 10 which generate pixels of the upper and lower lines on the left side of the light distribution 20, 27, plus one pixel on the right side of the light distribution 20, 27 next to the HV point, are switched off, so as not to dazzle oncoming traffic. The ISO lines 30 in Figure 7 are much more restless. The ISO lines 31 from the light distribution 27 Figure 8 on the other hand are smoother and have fewer deviations

In Figure 9 An LED module 6 according to the invention with a projection optics 16 according to the invention is shown in detail. The embodiment of the projection optics 16 shown is used to generate two separate images 25, 26 of the light exit surface 17 of the primary optics 12. Of course, the projection optics 16 can also be designed such that they produce more than two separate images that are shifted in the horizontal direction. The projection optics 16 has two parallel optical axes, which are designated by the reference numerals 40 and 41. The reference numeral 42 denotes a module axis of the LED module 6, which runs from the center of the primary optics 12 in the direction of travel 3. The distance between the optical axes 40, 41 is small and only so large that the projection optics 16 can project two separate images 25, 26 with 1/2 pixel spacing onto the road in front of the motor vehicle. The optical axes 40, 41 are preferably arranged on a common horizontal plane, which preferably also includes the module axis 42. In the exemplary embodiment shown, the projection optics 16 are in two halves 16a, 16b along a vertical central plane, which includes the module axis 42 divided. The one half 16a is preferably assigned the optical axis 41 and the other half 16b is preferably the optical axis 40.

It is not necessary that all active optical surfaces of the projection optics 16 have to experience a division and / or displacement of the generating surfaces. It is entirely sufficient if only one of these surfaces is shaped in a corresponding manner. This can be, for example, a light entry surface, a light exit surface or an intermediate surface of the primary optics 16. At least one of the active optical surfaces of the projection optics 16 must, however, be modified such that the at least two images 25, 26 of the light exit surface 17 of the primary optics 12 can be generated, which are offset from one another in the horizontal direction.

In Figure 10 Another embodiment of an LED module 6 according to the invention is shown with two optical axes 43, 44 which run obliquely to one another. The optical axes 43, 44 preferably intersect in a plane of the light exit surface 17 of the primary optics 12. Also the optical axes 43, 44 are preferably arranged on a common horizontal plane, which preferably also includes the module axis 42. In the embodiment shown, a first half 16a is assigned to the projection optics 16 of the optical axis 44 and a second half 16b is assigned to the projection optics 16 of the optical axis 43.

Another preferred embodiment of the projection optics 16 according to the invention is based on a special structure on one of the active optical surfaces of the projection optics 16. In Figure 11 is a corresponding one Embodiment shown, wherein alternating optical regions 16c, 16d arranged side by side are formed on the light exit surface of the projection optics 16. In the exemplary embodiment shown, the regions 16c, 16d are arranged in strips on the light exit surface of the projection optics 16. Of course, the areas can also be designed like a checkerboard or in any other way. Furthermore, it is conceivable that the optical areas 16c, 16d are not formed on the light exit surface, but on the light entry surface or any other surface between the light entry surface and the light exit surface of the projection optics 16. The optical regions 16c, 16d are designed to generate essentially identical images 25, 26 of the exit surface 17 of the primary optics 12. All areas 16c together produce a first image of the light exit surface 17 and all areas 16d together produce a second image 26 of the exit surface 17. The first optical areas 16c are preferably the first optical axis 40 and the second optical areas 16d are preferably the second optical axis 41 assigned. In this way too, projection optics 16 can be implemented, which can produce several separate images 25, 26 of the light exit surface 17 of the primary optics 12, which are offset relative to one another in the horizontal direction. In the embodiment Figure 11 Thus, the first optical regions 16c form a first group, which produce the first image 25 of the exit surface 17, and the second regions 16d form a second group, which generate the second image 26 of the exit surface 17 of the primary optics 12.

In Figure 11 the first areas 16c are marked with hatching. However, this serves first Line for identification and for better differentiation of the two areas 16c, 16d from each other. This does not necessarily mean that an optically effective structure, for example a scattering structure, is formed in the areas 16c on the light exit surface of the projection optics 16, whereas such a structure is not formed in the areas 16d. However, this would be entirely possible. It would also be conceivable to provide a scattering structure on the entire light exit surface of the projection optics 16.

In Figure 12 A further exemplary embodiment of an LED module 6 according to the invention or a projection optics 16 according to the invention is shown. In this case, an active optical surface of the projection optics 16, in the exemplary embodiment shown the light exit surface, is provided with a plurality of prisms which are arranged next to one another and which extend over the entire surface and whose longitudinal axes run parallel to one another and in the vertical direction. A first prism surface 16e of the prisms produces a first image 25 of the exit surface 17 of the primary optics 12. Another prism surface 16f of the prisms produces a second image 26 of the exit surface 17 of the primary optics 12. Thus, a first prism surface 16e with a second prism surface 16f forms one of the Prisms on the light exit surface of the projection optics 16. The first prism surfaces 16e are preferably assigned the first optical axis 41 and the other prism surfaces 16f the second optical axis 42. In this way too, separate images 25, 26 of the exit surface 17 of the primary optics 12 can be generated, which are offset from one another in the horizontal direction.

The amplitudes of the prism structure on the light exit surface of the projection optics 16 Figure 12 are relatively small, making them difficult to see with the naked eye. In particular, the magnitude of the amplitudes is thought to be from a few micrometers to a few tens of micrometers. The structures are perceived by an observer from outside the headlight 1 through the cover plate 5 at best as slightly indicated strips or alternatively as a relatively unobtrusive checkerboard pattern on the projection optics 16.

In Figure 13 Various design options for the prism structure are proposed on the optically active surface of the projection optics 16. In each of the partial figures 13a), 13b), 13c), a cross section through one of the prisms is shown above, and below that are the images of the light exit surface 17 of the primary optics 12 that can be achieved by the prism structure shown.

The prism structure Figure 13a ) corresponds to the prism structure, which in the embodiment of the projection optics 16 Figure 12 was applied. The images 25 and 26 that can be achieved in this way are offset from one another by 1/2 pixel width w '. In the embodiment Figure 13b ), a tip of the prisms 16e, 16f is flattened over their entire longitudinal extent, so that there is a roof surface 16g of the prisms, which generates a further image 28 of the light exit surface 17 of the primary optics 12, which leads to the other two images 25, 26 which are formed by the prism surfaces 16e, 16f are generated, is offset in the horizontal direction. The three images 25, 26, 28 are preferably offset from one another in the horizontal direction by 1/3 pixel width w '. In order to achieve the desired division to 1/3 of the pixel or stripe width w ', the prism angle α must be adapted in a suitable form. The Surface 16g creates an image 28 in the center of the light distribution. In the embodiment Figure 13c ) are the prism surfaces 16e, 16f of the prisms over their entire longitudinal extent in each case in two partial surfaces 16e1, 16e2; 16f1, 16f2 divided. Here, a line of contact of the partial areas 16e1, 16e2; 16f1, 16f2 of a prism surface 16e; 16f of a prism parallel to a longitudinal axis of the prism. The partial areas 16e1, 16e2; 16f1, 16f2 of a prism surface 16e; 16f produce two separate and offset images 25, 28; 26, 29, which also go with the other figures 26, 29; 25, 28 are offset. In particular, it is proposed that the four images 25, 26, 28, 29 of the light exit surface 17 of the primary optics 12 are each offset by 1/4 pixel width w 'from one another.

Of course, it would also be conceivable to generate more than four images of the light exit surface 17 of the primary optics 12 by means of other configurations of the prism structure. So it would be conceivable, for example, that the prism structure Figure 13c ) the tip of the prisms is flattened over their entire longitudinal extent, so that a roof surface similar to the roof surface 16c of the prism structure Figure 13b ), which produces a further image of the light exit surface 17 of the primary optics 12.

In Figure 14 Further possible configurations of the prism structure are shown on the optically active surface of the projection optics 16. The real prisms of Figure 14a ), 14b), 14c) essentially correspond to the prisms from the Figures 13a ), 13b), 13c). In the embodiment Figure 14 however, straight sections 16h are provided between the individual prisms 16e, 16f. This makes it possible to use the prism structure out Figure 14a ) to generate a total of two plus one three separate images of the light exit surface 17 of the primary optics 12. It is the same with the prism structure Figure 14b ) possible to create a total of two plus two four separate images. The strips 16g and 16h can produce identical images, because the optical axes are not tilted towards one another, and the images therefore lie one above the other. In a corresponding manner, the prism structure can be used Figure 14c ) four plus one five images of the light exit surface 17 of the primary optics 12 are generated.

h =

Prismenhöhe in Millimeter,

w =

Wellenlänge (eine Periode) der Prismenstruktur (oder Basisbreite eines Prismas) in Millimeter,

ε =

Lichteinfallswinkel bezüglich einer Flächennormalen der Prismenfläche 16f,

ω =

Lichtauskoppelwinkel bezüglich der Flächennormalen der Prismenfläche 16f,

δ =

ω - ε = Winkeldifferenz zwischen einfallendem Lichtstrahl und ausgekoppeltem Lichtstrahl,

α =

Prismenwinkel bezüglich eines Lots bzw. Winkel einer Prismenfläche 16e, 16f bezüglich einer Lotfläche, und

ϕ =

Pixelbreite in Winkelgrad.

Based on Figures 15 and 16 It is explained below how the height of the prism structure of a projection lens 16 according to the invention can be calculated. Thereby in Figure 15 exemplary of the prism structure according to Figure 12 and Figure 13a ) went out. In Figure 15 mean:

h =

Prism height in millimeters,

w =

Wavelength (one period) of the prism structure (or base width of a prism) in millimeters,

ε =

Light incidence angle with respect to a surface normal of the prism surface 16f,

ω =

Light decoupling angle with respect to the surface normal of the prism surface 16f,

δ =

ω - ε = angle difference between incident light beam and outcoupled light beam,

α =

Prism angle with respect to a plumb or angle of a prism surface 16e, 16f with respect to a plumb surface, and

ϕ =

Pixel width in degrees.

In the prism structure Figure 15 the following relationship applies: $$\tan \propto =\frac{H}{\frac{w}{\mathrm{2nd}}}=\frac{\mathrm{2nd}H}{w}$$

The Snell equation also applies: $$\frac{\sin \epsilon }{\sin \omega }=\frac{n_L}{n_{\mathit{PMMA}}}$$

This results after the forming and with n _L = 1 for air: $$\sin \omega =n_{\mathit{PMMA}}\cdot \sin \epsilon$$

For ω we get: $$\omega =\arcsin \left(n_{\mathit{PMMA}}\cdot \sin \epsilon \right)$$

The following also applies: $$\delta =\omega -\epsilon =\arcsin \left(n_{\mathit{PMMA}}\cdot \sin \epsilon \right)-\epsilon \stackrel{!}{=}\frac{1}{\mathrm{4th}}\stackrel{\phi }{\overbrace{\mathit{Pixel\; width}\left[°\right]}}$$

und nach einer Umformung $$n_{\mathit{PMMA}}\cdot \sin \epsilon =\sin \left(\frac{\phi }{4}+\epsilon \right)$$

bzw. $$n_{\mathit{PMMA}}\cdot \sin \epsilon =\sin \frac{\phi }{4}\cdot \cos \epsilon +\mathit{cos}\frac{\phi }{4}\cdot \sin \epsilon$$

und $$\left(n_{\mathit{PMMA}}-\mathit{cos}\frac{\phi }{4}\right)\cdot \sin \epsilon =\sin \frac{\phi }{4}\cdot \cos \epsilon$$

The angle difference must therefore be +/- 1/4 pixel width for two separate images 25, 26 of the light exit surface 17 of the primary optics 12, so that the two images 25, 26 are offset from one another by 1/2 pixel width. This results from equation (4): $$\arcsin \left(n_{\mathit{PMMA}}\cdot \sin \epsilon \right)=\frac{\phi }{\mathrm{4th}}+\epsilon$$

and after reshaping $$n_{\mathit{PMMA}}\cdot \sin \epsilon =\sin \left(\frac{\phi }{\mathrm{4th}}+\epsilon \right)$$

respectively. $$n_{\mathit{PMMA}}\cdot \sin \epsilon =\sin \frac{\phi }{\mathrm{4th}}\cdot \cos \epsilon +\mathit{cos}\frac{\phi }{\mathrm{4th}}\cdot \sin \epsilon$$

and $$\left(n_{\mathit{PMMA}}-\mathit{cos}\frac{\phi }{\mathrm{4th}}\right)\cdot \sin \epsilon =\sin \frac{\phi }{\mathrm{4th}}\cdot \cos \epsilon$$

bzw. $$\epsilon =\arctan \left(\frac{\sin \frac{\phi }{4}}{n_{\mathit{PMMA}}-\cos \frac{\phi }{4}}\right)$$

This results in $$\tan \epsilon =\frac{\sin \frac{\phi }{\mathrm{4th}}}{n_{\mathit{PMMA}}-\cos \frac{\phi }{\mathrm{4th}}}$$

respectively. $$\epsilon =\arctan \left(\frac{\sin \frac{\phi }{\mathrm{4th}}}{n_{\mathit{PMMA}}-\cos \frac{\phi }{\mathrm{4th}}}\right)$$

For α = ε we get: $$\epsilon =\arctan \left(\frac{H}{\frac{w}{\mathrm{2nd}}}\right)=\arctan \left(\frac{\mathrm{2nd}H}{w}\right)$$

From equations (10) and (11) it follows: $$\frac{\mathrm{2nd}H}{w}=\frac{\sin \frac{\phi }{\mathrm{4th}}}{n_{\mathit{PMMA}}-\cos \frac{\phi }{\mathrm{4th}}}$$

So for a 1/2 pixel offset for the required prism height h: $${\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{2nd}}\mathit{Pixel\; offset}}=\frac{w}{\mathrm{2nd}}\cdot \frac{\sin \frac{\phi }{\mathrm{4th}}}{n_{\mathit{PMMA}}-\cos \frac{\phi }{\mathrm{4th}}}$$

With a 1/2 pixel offset, the images 25, 26 um ϕ / 2 shifted to each other (+/- ϕ / 4). This is a so-called first-order compensation. For a 2nd order compensation, two groups of two must be shifted towards each other. The following explains how the prism height h can be determined for a 2nd order compensation: $${\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{2nd}}\mathit{Pixel\; offset}}=\mathit{Pixel\; offset}\mathit{of}\frac{\phi }{\mathrm{4th}}=+/-\frac{\phi }{\mathrm{8th}}$$

This results in the prism height h: $${\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{2nd}}\mathit{Pixel\; offset}}=\frac{\mathrm{2nd}w}{\mathrm{2nd}}\frac{\sin \frac{\phi }{\mathrm{8th}}}{n_{\mathit{PMMA}}-\cos \frac{\phi }{\mathrm{8th}}}$$

For very small angles: $$\begin{array}{l}\sin \vartheta =\vartheta \mathit{and}\sin \frac{\vartheta }{\mathrm{2nd}}=\frac{\vartheta }{\mathrm{2nd}}\mathit{and}\sin \frac{\vartheta }{\mathrm{8th}}=\frac{1}{\mathrm{2nd}}\sin \frac{\phi }{\mathrm{4th}}\\ \cos \frac{\phi }{\mathrm{4th}}\approx \cos \frac{\phi }{\mathrm{<figure-callout\; id="1"\; label="8th\; \approx "\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">8th\; </figure-callout>}}\approx 1\end{array}$$

The prism height h for 2nd order compensation is: $${\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{4th}}\mathit{Pixel\; offset}}=\frac{\mathrm{2nd}w}{\mathrm{2nd}}\cdot \frac{1}{\mathrm{2nd}}\frac{\sin \frac{\phi }{\mathrm{4th}}}{n_{\mathit{PMMA}}-\cos \frac{\phi }{\mathrm{4th}}}={\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{2nd}}\mathit{Pixel\; offset}}$$

In summary, it can thus be said that for small angles, the 1st order, 2nd order etc. compensation takes place with triangular structures which overlap and which have a 2-fold, 4-fold etc. wavelength and the same amplitude. In Figure 16 is an example of a section of a surface structure for an optically active surface of a projection optics 16 according to the invention shown. The structure of the 1st order is shown with a solid line 50, a structure of the 2nd order with a dashed line 51 and a sum of the two structures 50, 51 with the reference symbol 52.

The first-order structure 50 generates two separate images 25, 26 of the light exit surface 17 of the primary optics 12, which are shifted from one another by 1/2 pixel width. The second-order prism structure 51 has half the frequency (double period) and, with one of its flanks (prism surfaces), always tilts two adjacent flanks (an entire period) of the first-order structure 50 and thus leads to a shift of the images from each other by 1 / 4 pixel width.

The prism structure 52 is the sum (resulting) of the 1st order prism structure 50 and the 2nd order prism structure 51.

The amplitude h of the 1st order structure 50 is related to the required deflection angle of +/- 0.3 °. With a period (wavelength w) of 2 mm and a refractive index n _PMMA = 1.49 and n _air = 1.0, the following results for the prism height h: $${\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{2nd}}\mathit{Pixel\; offset}}=\frac{w}{\mathrm{2nd}}\cdot \frac{\sin 0.3°H}{n_{\mathit{PMMA}}-\cos 0.3°H}=10.7\mathit{\mu m}$$

The calculated prism height h = 10.7 µm is relatively large. Therefore, the wavelength w is halved from the original 2 mm to 1 mm. This then results in the amplitude h of the prism structure: $${\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{2nd}}\mathit{Pixel\; offset}}=\frac{w=1\mathit{mm}}{\mathrm{2nd}}\cdot \frac{\sin 0.3°H}{1.49-\cos 0.3°H}=5.3\mathit{\mu m}$$

The prism structure 51 is placed over the 1st order prism structure 50, but should only reach half the deflection (1/2 × 1/2 pixel → +/- 0.15 ° H). From equation (14) we get: $${\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\frac{1}{\mathrm{4th}}\mathit{Pixel\; offset}}=\frac{\mathrm{2nd}w}{\mathrm{2nd}}\frac{\sin 0.15°H}{1.49-\cos 0.15°H}=5.3\mathit{\mu m}$$

Thus, the result from equation (15) is confirmed. The second-order prism structure 51 has the same amplitude h as the first-order prism structure 50. In principle, higher-order adaptations can also be generated in the manner described.

Claims (16)

1. LED module (6) of a motor vehicle headlamp (1), the LED module (6) having a light source (10) in the form of an LED matrix which comprises a plurality of LED chips (11) arranged next to and/or above one another in a matrix-like manner, a primary optic (12) which comprises a plurality of primary optic elements (13) arranged next to and/or above one another in a matrix-like manner, for focusing the light emitted by the light source (10), and a projection optic (16), which projects an exit surface (17) of the primary optic (12) onto a roadway in front of a vehicle in order to produce a predetermined light distribution (27), characterized in that the projection optic (16) is designed in such a way that it produces on its image side at least two separate images (25, 26) of the exit surface (17) of the primary optic (12), which images are offset relative to one another in the horizontal direction, so that a superposition of the images (25, 26) produced improves homogeneity of the light distribution (27).
2. LED module (6) according to claim 1, characterized in that the separate images (25, 26, 28, 29) of the light exit surface (17) of the primary optic (12) are each offset relative to one another by a value w'/n, where w' is a width, in particular an angular width, of a pixel formed by imaging a single light-emitting surface of a single primary optical element (13) in the resulting light distribution (27), and n is a number of separate images (25, 26, 28, 29) of the light-emitting surface (17) of the primary optical element (12) produced by the projection optic (16).
3. LED module (6) according to claim 1 or 2, characterized in that the projection optic (16) improves the homogeneity of the light distribution (27) with respect to a compensation of intensity fluctuations and undesired colour effects in the light distribution.
4. LED module (6) according to any of claims 1 to 3, characterized in that the projection optic (16) has at least two separate optical axes (40, 41; 43, 44).
5. LED module (6) according to claim 4, characterized in that the separate optical axes (40, 41; 43, 44) of the projection optic (16) run in the same horizontal plane.
6. LED module (6) according to claim 4 or 5, characterized in that the separate optical axes (40, 41) of the projection optic (16) run parallel to and spaced apart from one another.
7. LED module (6) according to claim 4 or 5, characterized in that the separate optical axes (43, 44) of the projection optic (16) run at an angle to one another.
8. LED module (6) according to claim 7, characterized in that the optical axes (43, 44) of the projection optic (16) intersect in a plane of the light-emitting surface (17) of the primary optic (12).
9. LED module (6) according to any one of claims 1 to 3, characterized in that at least one active optical surface of the projection optic (16) is provided with alternating optical regions (16c, 16d) arranged next to and/or above one another for generating substantially identical images (25, 26) of the exit surface (17) of the primary optic (12), wherein a first group (16c) of the optical regions generates a first image (25) of the light exit surface (17) of the primary optic (12) and at least one further group (16d) of the optical regions generates at least one further image (26) of the exit surface (17) of the primary optic (12), wherein the generated images (25, 26) are arranged offset to each other in the resulting light distribution (27) in horizontal direction.
10. LED module (6) according to claim 9, characterized in that the alternating optical regions (16c, 16d) are formed on a light exit surface of the projection optic (16).
11. LED module (6) according to claim 9 or 10, characterized in that the alternating optical regions (16c, 16d) are formed into stripes, the stripes extending in a vertical direction.
12. LED module (6) according to any one of claims 9 to 11, characterized in that the active optical surface of the projection optic (16) is provided with a plurality of prisms (16e, 16f) which extend over the entire surface, are arranged next to one another and whose longitudinal axes run parallel to one another, one prism surface (16e) of the prisms, which forms a first optical region, produces the first image (25) of the light exit surface (17) of the primary optic (12) and the other prism surface (16f) of the prisms, which forms a further optical region, produces the second image (26) of the exit surface (17) of the primary optic (12).
13. LED module (6) according to claim 12, characterized in that a tip of the prisms (16e, 16f) is flattened over their entire longitudinal extension, so that a roof surface (16g) of the prisms is obtained, which produces a further image (28) of the light exit surface (17) of the primary optic (12), which is offset in the horizontal direction relative to the other two images (25, 26).
14. LED module (6) according to claim 12 or 13, characterized in that the prism faces (16e, 16f) of the prisms are each divided over their entire longitudinal extent into two partial faces (16e1, 16e2; 16f1, 16f2), a line of contact of the partial faces (16e1, 16e2; 16f1, 16f2) of a prism face (16e; 16f) of a prism runs parallel to the longitudinal axis of the prism, wherein the partial faces (16e1, 16e2; 16f1, 16f2) each produce a separate image (25, 26, 28, 29) of the light exit surface (17) of the primary optic (12), which image is offset relative to the other images (25, 26).
15. LED module (6) according to one of claims 9 to 14, characterized in that the alternating optical regions (16c, 16d; 16e, 16f) formed on the at least one active optical surface of the projection optic (16) have an amplitude of less than 0.1 mm, preferably of less than a few tens of micrometers, very particularly preferably of a few micrometers.
16. Motor vehicle headlamp (1) having an LED module (6) which has a light source (10) in the form of an LED matrix which comprises a plurality of LED chips (11) arranged next to and/or above one another in a matrix-like manner, a primary optic (12) which comprises a plurality of primary optic elements (13) arranged next to and/or above one another in a matrix-like manner, for focusing the light emitted by the light source (10), and a projection optic (16), which projects an exit surface of the primary optic (16) onto a roadway in front of a vehicle in order to produce a predetermined light distribution (27), characterized in that the projection optic (16) is designed in such a way that, on its image side, it produces at least two separate images (25, 26) of the exit surface (17) of the primary optic (12), which images are offset with respect to one another in the horizontal direction, so that a superposition of the images (25, 26) produced improves homogeneity of the light distribution (27).

Images