DE102008027320B4 - Headlights for vehicles - Google Patents

Abstract

Headlights for vehicles with a plurality of LED light sources which are arranged in a group in an LED field on a substrate and which each emit a partial light beam of a light beam which is imaged by means of an upstream optical unit to produce a predetermined light distribution, wherein the optical unit (3) has a first optical element (5) with a light coupling surface (7) facing the LED field (2) and a light coupling surface (9) facing away from the LED field (2), on the one hand, and a second optical element (6) with a light coupling surface (8) facing the first optical element (5) and a light coupling surface (10) facing away from the first optical element (5), characterized in that the light coupling surfaces (7, 8) and the light coupling surfaces (9, 10) of the two optical elements (5, 6) are designed in such a way that the LED light sources (1) are imaged to form light spots (17) towards infinity, so that when the light distribution (L) is projected onto a measuring screen, a vertical and horizontal edge region of adjacent light spots (17) lie directly next to one another, and that the light coupling surface (7) and the light coupling surface (9) of the first optical element (5) and the light coupling surface (8) and the light coupling surface (10) of the second optical element (6) are coordinated with one another in such a way that the light spots (17) of the LED light sources (1) shown have the same dimension.

Description

The invention relates to a headlight for vehicles according to the preamble of patent claim 1.
From the EN 10 2005 041 234 A1 A headlight for vehicles is known which, to form an LED field, has a plurality of LED light sources arranged on a common substrate on the one hand and an optical unit arranged in front of the LED field in the direction of light emission on the other. The LED light sources each emit a partial light beam which is imaged into a light spot by means of the optical unit. Because the known headlight has at least two optical units, each with a different imaging characteristic, light spots of different sizes can be superimposed to form the specified light distribution. For example, the small light spots can be used to image a 15° rise in a light-dark boundary of the low beam distribution. When only a single optical unit is used, however, it has been shown that vertical light gaps arise between the light spots imaged on a measuring screen, which are perceived as disturbing. Depending on the optical unit used, an undesirable color fringe can also arise in the area of the light-dark boundary of the light distribution. If an attempt is made to avoid vertical light gaps by roughening one or more surfaces of the optical unit, the light-dark boundary of the light distribution will be softened and relatively high absorption losses will occur due to the stochastic scattering effect. A targeted cutout of the light distribution to reduce glare for oncoming traffic, for example, is therefore not possible with the known headlight. To do this, the individual light spots would have to be addressable, and they would have to be clearly separated from one another to form the cutout area or glare-free area. This is because the cutout area of the light distribution would change in size and location depending on time.

From the DE 101 29 743 C2 A headlight for vehicles with a plurality of LED light sources is known, which has a first optical element and a second optical element arranged in front of the first optical element in the main radiation direction. The first optical element collimates the light emitted by the LED light sources, whereby a divergence occurs due to the size of the LED light sources. The second optical element is designed as a diffuser element, which further increases the divergence in the horizontal direction and vertical direction.

The object of the present invention is therefore to further develop a headlight for vehicles in such a way that a predetermined light distribution is created with sharply demarcated LED light sources, so that by switching off one or more LED light sources, a defined recess area or glare-free area of the light distribution is made possible to glare another road user.

To solve this problem, the invention has the features of patent claim 1.

The invention provides an optical unit with two lens-shaped optical elements that are arranged one behind the other in the light emission direction. A first optical element and a second optical element each have a light coupling surface and a light coupling surface that are shaped in such a way that the LED light sources are each imaged into light spots that have a relatively high optical correction state. In order to achieve a high optical quality or a low dispersion effect, the aberration effect is distributed over the four refractive surfaces (light coupling surface, light coupling surfaces) of the two optical elements. Sharply delimited light distributions of the LED light sources in the angular space can advantageously be realized, with LED light sources located further away from the optical axis producing only a slight blurring or distortion. Thus, according to the invention, the first optical element has no primary optical function and the second optical element has no secondary optical function. Instead, the light coupling surfaces or light coupling surfaces of the first optical element and the second optical element are coordinated with one another in such a way that a light distribution consisting of preferably equally sized light spots can be formed, with vertical and horizontal edges of adjacent light spots lying directly next to one another. This advantageously allows defined recess areas to be created in the light distribution. According to the invention, the optically effective surfaces of the first optical element and the second optical element are coordinated with one another in such a way that light spots of the same dimension are created, which are arranged essentially directly next to one another to form the high beam distribution. Because the imaging errors of the lenses are distributed or "balanced" across the four refractive surfaces, even LED light sources arranged relatively far from an optical axis of the headlight can be imaged relatively correctly.

According to a preferred embodiment of the invention, the LED light sources are combined as LED chips in a horizontally extending, elongated LED field, so that a high beam distribution can be generated when all LED chips are switched on. This generates an addressable high beam, in which a portion of the high beam distribution can be excluded to reduce glare for other road users.

According to a development of the invention, the LED light sources of the LED field can be controlled by a control unit, so that in a high beam position all LED light sources are switched on to generate a high beam distribution and so that in a glare-free position only some of the LED light sources are switched on, namely the part that is not responsible for glaring other road users. In the glare-free position, the high beam distribution changes dynamically, whereby, depending on the detection means detecting other road users, those LED light sources that would contribute to illuminating the road user are switched off or dimmed down. The fact that neighboring light spots are clearly next to or on one another in the vertical and horizontal directions ensures optimal addressability of the light spots, so that a transition between the glare-free area and the illuminated area of the light distribution is realized with a relatively high luminous intensity gradient.

According to a development of the invention, the first optical element and the second optical element are each arranged rotationally symmetrically and at a distance from one another.

At least three of these optical surfaces have aspherizations, so that correct imaging across the horizontal width of the LED field is guaranteed.

Further advantages of the invention emerge from the further subclaims.

An embodiment of the invention is explained in more detail below with reference to the drawings.

• 1 eine schematische Seitendarstellung eines Scheinwerfers,
• 2 eine perspektivische Rückansicht des Scheinwerfers,
• 3 eine Vorderansicht eines LED-Feldes des Scheinwerfers,
• 4 eine exemplarische Darstellung von auf einem Messschirm projizierten Lichtflecken (Lichtbildern) von vier in horizontaler Richtung benachbarten LED-Lichtquellen und
• 5 eine schematische Darstellung einer Fernlichtverteilung, wobei alle in einer 4x20-Matrix angeordneten LED-Lichtquellen eingeschaltet sind.

Show it:

• 1 a schematic side view of a headlight,
• 2 a perspective rear view of the headlight,
• 3 a front view of an LED field of the headlight,
• 4 an exemplary representation of light spots (light images) projected on a measuring screen from four horizontally adjacent LED light sources and
• 5 a schematic representation of a high beam distribution with all LED light sources arranged in a 4x20 matrix switched on.

A headlight for vehicles according to the invention essentially consists of a plurality of LED light sources 1, which are arranged in a group in an LED field 2 on a common carrier (substrate), and of an optical unit 3, which is arranged in front of the LED field 2 in the light emission direction 4.

The optical unit 3 consists of a first optical element 5 arranged at a distance from the LED field 2 and a second optical element 6 arranged at a distance from the first optical element 5. The first optical element 5 and the second optical element 6 are each approximately plano-convex in shape, with a quasi-planar light coupling surface 7 of the first optical element 5 facing the LED field 2 being curved inwards and a quasi-planar light coupling surface 8 of the second optical element 6 facing the LED field 2 being curved outwards. The first optical element 5, which is arranged between the LED field 2 and the second optical element 6 at a distance from the latter, has a convex-shaped light output surface 9, the curvature or degree of curvature of which is less than a light output surface 10 of the second optical element 6 facing away from the LED field 2. The light input surfaces 7, 8 and the light output surfaces 9, 10 form optically effective surfaces of the optical elements 5, 6.

As from 1 As can be seen, the first optical element 5 has a smaller transverse extension or a smaller diameter than the second optical element 6. The transverse extension of the second optical element 6 is measured in such a way that a main beam H and an edge beam R, which is refracted by the first optical element 5, are still captured. The first optical element 5 and the second optical element 6 are each rotationally symmetrical.

As from 3 As can be seen, the LED field 2 is elongated and extends in a horizontal direction. The LED light sources 1 are each designed as LED chips that have at least one LED module. The LED chips 1 are arranged in a matrix-like manner in a field with twenty vertical columns S ₁ , ... S ₂₀ and four horizontal rows Z ₁ , Z ₂ , Z ₃ Z ₄ . In total, the LED field 2 consists of eighty LED chips 1, which are controlled in a high beam position of the headlight by means of a control unit 14 such that all eighty LED chips 1 are switched on. In the high beam position of the headlight, a high beam distribution L is thus created according to 5 generated, whereby the high beam division L is formed by arranging the example formed by means of the optical unit 3, in 4 illustrated light spots (light images) 17 of the LED chips 1.

Due to the design of the light coupling surfaces 7, 8 and light coupling surfaces 9, 10 described below, the LED chips 1 imaged to infinity lie directly next to one another, with vertical edges 15 and horizontal edges 16 of adjacent light spots 17 lying directly next to one another. The light images 17 are created by imaging the partial light beams emitted by the LED chips 1, which form a light beam by superimposing them, by means of which the high beam distribution L is generated.

The high beam distribution L according to 5 is relatively long in the horizontal direction and relatively short in the vertical direction. The high beam distribution L is made up of preferably equally sized light images (light spots 17) of the matrix-like arranged LED chips 1 according to 3 which can preferably be displayed in rectangular or square contours on a measuring screen, see 4 . Preferably, the LED chips 1 have a square or rectangular contour. For the sake of simplicity, 3 circular LED chips 1 are shown.

If the LED chips 1 are circular or oval-shaped, the light spots can also be circular or oval-shaped according to an alternative embodiment not shown.

It is essential that the light spots 17 have a high optical quality, i.e. preferably have a low aberration effect. This makes it possible for selected and well-defined areas of the light distribution L to be left out in a glare-reduction position of the headlight, preferably depending on the change in the traffic situation detected by the detection means 18, by switching off the corresponding LED chips 1, so that unwanted glare of other road users is prevented. A camera can serve as the detection means 18, for example, which detects an oncoming road user, so that depending on the sensor data determined by the detection means, the control unit 14 adaptively switches a number of LED chips 1 off or on again, so that the other road user is prevented from being glared by the headlight. The light distribution L is thus made up of an illumination area 19 and an anti-glare area 20, with the LED chips 1 assigned to the anti-glare area 20 being switched off, so that the oncoming road object located in this area is not blinded. The illumination area 19 and the anti-glare area 20 change dynamically depending on the relative position of the oncoming traffic object to the headlight. As the relative distance between the oncoming traffic object and the headlight decreases, the anti-glare area 20 gradually becomes larger until the oncoming traffic object has passed the vehicle equipped with the headlight, so that the illumination area 19 now corresponds to the long-distance light distribution L when no more oncoming traffic objects are approaching.

The first optical element 5 has a thickness d1 of approximately 20 mm and the second optical element 6 has a thickness d2 of approximately 34 mm. The clear distance between the first optical element 5 and the second optical element 6 is approximately 24 mm.

wobei
z = z-Koordinate auf der entsprechenden Fläche,
r = Lateralabstand eines Punktes auf der optischen Fläche von der z-Achse,
c = Scheitelkrümmung der optisch wirksamen Fläche,
k = konische Konstante (hier zu 0 gewählt),
α = Asphärenkoeffizient.In the present exemplary embodiment, the light coupling surface 7 of the first optical element 5 has a vertex curvature radius of -100.0 mm, the light coupling surface 9 of the first optical element 5 has a vertex curvature radius of -49.99876 mm, the light coupling surface 8 of the second optical element 6 has a vertex curvature radius of 7,179.91267 mm, the light coupling surface 10 of the second optical element 6 has a vertex curvature radius of -76.374567 mm. The light coupling surface 7, the light coupling surface 9 of the first optical element 5 and the light coupling surface 10 of the second optical element 6 are designed as aspherical surfaces and the light coupling surface 8 of the second optical element 6 is designed as a spherical surface. The light coupling surface 7 and the light output surface 9 of the first optical element 5 as well as the light output surface 10 of the second optical element 6 are determined according to the following lens surface equation: $$z=\frac{c{r}^2}{1+\sqrt{1-\left(1+k\right)c^2{r}^2}}+{\displaystyle \sum _{k=1}^5{\alpha }_{2k}{r}^{2k}},$$

where
z = z-coordinate on the corresponding surface,
r = lateral distance of a point on the optical surface from the z-axis,
c = vertex curvature of the optically effective surface,
k = conical constant (here chosen to be 0),
α = aspheric coefficient.

$$\mathrm{\alpha }4=-\mathrm{3,529144}*{10}^{-6}$$

$$\mathrm{\alpha }6=\mathrm{1,239178}*{10}^{-9}$$

$$\mathrm{\alpha }8=\mathrm{6,718262}*{10}^{-13}$$

$$\mathrm{\alpha }10=-\mathrm{5,51439}*{10}^{-16}.$$

The light coupling surface 7 of the first optical element 5 has the following asphere coefficients: $$\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}\text{2}=\mathrm{5,13198}*{10}^{-3}$$

$$\mathrm{<figure-callout\; id="4"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}4=-\mathrm{3,529144}*{10}^{-6}$$

$$\mathrm{<figure-callout\; id="6"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}6=\mathrm{1,239178}*{10}^{-9}$$

$$\mathrm{\alpha }\mathrm{8th}=\mathrm{6,718262}*{10}^{-13}$$

$$\mathrm{<figure-callout\; id="10"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png,DE102008027320B4\_0015.png"\; state="\{\{state\}\}">\alpha </figure-callout>}10=-\mathrm{5,51439}*{10}^{-16}.$$

$$\mathrm{\alpha }4=-\mathrm{1,33673}*{10}^{-7}$$

$$\mathrm{\alpha }6=\mathrm{3,341364}*{10}^{-10}.$$

The light output surface 9 of the first optical element 5 has the following asphere coefficients: $$\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}2=\mathrm{4,1585506}*{10}^{-3}$$

$$\mathrm{<figure-callout\; id="4"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}4=-1.33673*{10}^{-7}$$

$$\mathrm{<figure-callout\; id="6"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}6=3.341364*{10}^{-10}.$$

$$\mathrm{\alpha }4=-\mathrm{2,391277}*{10}^{-7}$$

$$\mathrm{\alpha }6=\mathrm{2,207928}*{10}^{-11}.$$

The light output surface 10 of the second optical element 6 has the following asphere coefficients: $$\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}2=-4.57459*{10}^{-3}$$

$$\mathrm{<figure-callout\; id="4"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}4=-2.391277*{10}^{-7}$$

$$\mathrm{<figure-callout\; id="6"\; label="\alpha "\; filenames="DE102008027320B4\_0014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}6=\mathrm{2,207928}*{10}^{-11}.$$

By designing the optically effective surfaces 7, 8, 9, 10 of the first optical element 5 or the second optical element 6, light images or light spots 17 are generated with a relatively precise and defined area, so that the LED chips 1 are imaged precisely to infinity. If gaps in the light distribution L are perceptible between the light spots 17, these can be closed by isotropic expansion of the light distribution L. For isotropic expansion, the parameters of the corresponding optically effective surfaces described above are modified accordingly.

List of reference symbols

1

LED light sources

2

LED field

3

Optical unit

4

Light emission direction

5

first optical element

6

second optical element

7

Light coupling surface

8th

Light coupling surface

9

Light output surface

10

Light output surface

11

Circular cutout segments / circular ring cutout segments

12

Circular cutout segments / circular ring cutout segments

13

optical axis

14

Control unit

15

vertical margins

16

horizontal margins

17

Light spots

18

Detection agents

19

Lighting area

20

Glare control range

H

Main beam

R

Edge beam bundle

S

Split

Z

Line

L

High beam distribution

d1

Thickness of the first optical element

d2

Thickness of the second optical element

Claims (8)

Headlights for vehicles with a plurality of LED light sources which are arranged in a group in an LED field on a substrate and which each emit a partial light beam of a light beam which is imaged by means of an upstream optical unit to produce a predetermined light distribution, wherein the optical unit (3) has a first optical element (5) with a light coupling surface (7) facing the LED field (2) and a light coupling surface (9) facing away from the LED field (2), on the one hand, and a second optical element (6) with a light coupling surface (8) facing the first optical element (5) and a light coupling surface (10) facing away from the first optical element (5), characterized in that the light coupling surfaces (7, 8) and the light coupling surfaces (9, 10) of the two optical elements (5, 6) are designed in such a way that the LED light sources (1) are imaged to form light spots (17) towards infinity, so that when the light distribution (L) is projected onto a measuring screen, a vertical and horizontal edge region of adjacent light spots (17) lie directly next to one another, and that the light coupling surface (7) and the light coupling surface (9) of the first optical element (5) and the light coupling surface (8) and the light coupling surface (10) of the second optical element (6) are coordinated with one another in such a way that the light spots (17) of the imaged LED light sources (1) have the same dimension. Headlights after Claim 1 , characterized in that the LED light sources (1) are each designed as LED chips which contain at least one LED component, that the LED chips (1) are arranged in the LED field (2) in a matrix-like manner with vertical columns (S) and horizontal rows (Z), and that the LED field (2) is designed to be elongated in the horizontal direction, the number of vertical columns (S) being at least three times as large as the number of horizontal rows (Z). Headlights after Claim 1 or 2 , characterized in that a control unit (14) is provided for controlling the LED light sources (1) in such a way that in a high beam position all LED light sources (1) are switched on to generate a high beam distribution (L) and that in a glare-free position some of the LED light sources (1) are switched off or dimmed down depending on the change in the traffic situation detected by detection means (18) to generate a clearly delimited glare-free area (20) in the light distribution (L) in which another traffic object is located. Headlights after one of the Claims 1 until 3 , characterized in that the first optical element (5) and the second optical element (6) are each approximately plano-convex in shape, wherein the convex-shaped light output surfaces (9, 10) of the first optical element (5) and of the second optical element (6) are arranged facing away from the LED field (2), and that the first optical element (5), which is preferably arranged in a central region between the LED field (2) and the second optical element (6), has a smaller transverse extension than the second optical element (6). Headlights after one of the Claims 1 until 4 , characterized in that the first optical element (5) and the second optical element (6) are each rotationally symmetrical. Headlights after one of the Claims 1 until 4 , characterized in that the light coupling surface (7) of the first optical element (5) is curved inwards and the light coupling surface (8) of the second optical element (6) is curved outwards. Headlights after one of the Claims 1 until 6 , characterized in that at least three of the light coupling surfaces (7, 8) and the light coupling surfaces (9, 10) of the first optical element (5) and the second optical element (6) have aspherizations. Headlights after one of the Claims 1 until 7 , characterized in that the light coupling surface (7) and the light coupling surface (9) of the first optical element (5) and the light coupling surface (10) of the second optical element (6) are determined by means of the lens surface equation $$z=\frac{c{r}^2}{1+\sqrt{1-\left(1+k\right)c^2{r}^2}}+{\displaystyle \sum _{k=1}^5{\alpha }_{2k}{r}^{2k}}$$

where z = z-coordinate on the corresponding surface, r = lateral distance of a point on the optical surface from the z-axis, c = vertex curvature of the optically effective surface, k = conical constant (here chosen to be 0), α = aspheric coefficient.

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