DE102013113807A1 - Lighting device for a motor vehicle - Google Patents

Abstract

The invention relates to a lighting device for a motor vehicle, comprising at least one light source (100), a means for polarization rotation (103; 200; 300) and a polarizing filter means (104; 105; 400), wherein the light source (100) is adapted to light (109) and wherein the illumination device is configured such that the light (109) emitted by the light source (100) reaches the means for polarization rotation (103; 200; 300) and the polarization filter element (104; 105; 400), wherein the illumination device comprises a polarizing beam splitter (101) and a mirror means (102), wherein the illumination device is designed so that the light (109) reaches the polarizing beam splitter (101) and the mirror means (102).

Description

The invention relates to a lighting device for a motor vehicle according to the preamble of claim 1 and a motor vehicle with such a lighting device.

Such lighting devices are known from the prior art. They are used to achieve different lighting types of the roadway in motor vehicles (eg high beam, city lights, cornering lights, etc.). The US 4,985,816 shows a lighting device with a light source and a liquid crystal panel. The liquid crystal panel operates on a principle known from liquid crystal displays (LCDs). In front of and behind a liquid crystal element, polarization filters rotated by 90 ° with respect to each other are arranged. The polarizing filters have the property that they transmit light with a certain linear polarization direction. The rest of the light is absorbed by them.

An electrical voltage can be applied to the liquid crystal element. When the voltage is not applied, the liquid crystal element rotates the polarization of incident light by 90 ° or 270 °. When the voltage is applied, the liquid crystal element does not rotate the polarization of the light. In the arrangement of the liquid crystal element between two polarizers, a liquid crystal panel is created in this way. The light of the light source can thus shine through the liquid crystal panel when no voltage is applied to the liquid crystal element. When voltage is applied, no light passes through the aperture. By a parallel orientation of the polarizing filter, a reverse operation can be achieved, so that the light radiates through the diaphragm when applied to the liquid crystal element voltage.

In the liquid crystal panel, only about half of the light emitted from the light source is usable. The rest is absorbed by one of the polarizing filters.

In contrast, the present invention has the object, a lighting device in which a greater proportion of the light is available, and to provide a motor vehicle with such a lighting device.

This object is achieved by the lighting device according to claim 1 and by the motor vehicle according to claim 10. Embodiments of the invention are indicated in the dependent claims.

The illumination device comprises at least one light source, a means for polarization rotation and a polarization filter means. The light source can emit light in an on state. This light reaches the means for polarization rotation and the polarizing filter means. In this case, the light can also be reflected once or several times by other components and / or transmitted.

The illumination device also comprises a polarizing beam splitter and a mirror means. The light of the light source reaches the polarizing beam splitter and the mirror means. The polarizing beam splitter is designed so that it divides the incident light into two beam paths, each of these two beam paths consisting of linearly polarized light. The polarization directions of the two beam paths can preferably be perpendicular to one another. The mirror means is adapted to reflect light and to maintain the polarization direction. Preferably, the mirror means comprises a mirror surface which reflects more than 50%, for example more than 90%, of the incident light. The polarizing beam splitter may, for example, be a wire-grid polarizer which slopes relative to the optical path of the light, e.g. at an angle of about 45 °.

The light source may be for example an LED or a laser diode. It is also possible that the illumination device comprises a plurality of light sources and that for each or all light sources there is in each case a means for polarization rotation, a polarization filter means, a beam splitter and a mirror means. The polarizing filter means may be a polarizer. For example, a polarizer can transmit linearly polarized light. The remaining portions of the light are reflected or absorbed. The transmitted linearly polarized light may have a parallel or a perpendicular polarization. This may depend on the orientation of the polarizer. The vertical polarization is rotated by 90 ° to the parallel polarization. A polarizer may in particular be a polarization filter.

The means for polarization rotation is adapted to rotate the polarization of incident light. This can be achieved for example by a liquid crystal element. Preferably, the means for polarization rotation is adapted to rotate the polarization of incident light by 90 °.

By the targeted control of the polarization direction can be controlled whether light from the lighting device, for example, on a roadway, should emerge.

According to one embodiment of the invention, the polarizing beam splitter can be arranged between the light source and the means for polarization rotation be arranged. Thus, two mutually perpendicularly linearly polarized beams can be directed to the means for polarization rotation. Depending on the operating mode of the means for polarization rotation, the polarization of both beams, no beam or only one of the beams can be rotated.

According to one embodiment of the invention, the means for polarization rotation between the polarizing beam splitter and the polarizing filter means may be arranged. Thereby, the polarization of one of the two linearly polarized beams or the two linearly polarized beams can be rotated before they reach the polarizing filter means. In this way, the polarization of the two linearly polarized beams can be chosen so that both beams are transmitted or absorbed by the polarizing filter means. It is also possible that one of the beams is absorbed while the other is being transmitted.

According to one embodiment of the invention, the means for polarization rotation, at least in some areas in an active and in an inactive state be switched. In this case, light which strikes an active subarea is transmitted while rotating its polarization. Light that strikes an inactive subarea is transmitted without rotation of its polarization. The means for polarization rotation may comprise, for example, at least one liquid crystal element. It is to be expressly understood that there are embodiments of the invention in which portions of the polarization rotation means may be individually switched to the active and inactive states, as well as embodiments of the invention in which the polarization rotation means is only over its entire range can be switched to the active and inactive state.

Firstly, for differently linearly polarized light beams, the means for polarization rotation can be adjusted so that all or only some of the light beams radiate through the polarization filter means. For example, if there are two optical paths having different linear polarizations, the polarization of one of the optical paths can be rotated so that both optical paths have the same linear polarization and both are absorbed or transmitted by the corresponding polarization filter means.

The means for polarization rotation may also have more than two subregions. Then, the polarization rotation means may be used to give linear linear polarization to certain light beams so as to be absorbed by the polarizing filter means. Accordingly, other light beams can be given a linear polarization so that they are transmitted through the polarizing filter means. In this case, the later transmitted or absorbed light beams may have the same linear polarization before the means for polarization rotation. This is particularly advantageous in order to achieve a desired illumination with the illumination device. Certain unwanted light rays may be filtered out while other desired light rays are transmitted. Thus, a desired light image of the illumination device can be achieved with the illumination device by means of an individually adapted circuit of the partial regions of the means for polarization rotation.

According to one embodiment of the invention, the polarizing beam splitter can transmit a first light part with a first linear polarization and reflect a second light part with a second linear polarization. The second linear polarization is different from the first linear polarization. Preferably, the first linear polarization is rotated by 90 ° to the second linear polarization. The polarizing beam splitter, the mirror means and the polarization rotation means may be arranged such that the first light part from the polarizing beam splitter reaches the polarization rotation means and the second light part reaches the polarization rotation means via the mirror means. In this way it can be achieved that the two light parts are parallel to each other. This is advantageous so that the radiation direction of the illumination device is determined.

According to one embodiment of the invention, the means for polarization rotation may have at least two regions which are independently switchable into the active and the inactive state. This can be achieved, for example, by using two separate liquid crystal elements. Another possibility is the use of a single liquid crystal element having electrical connections at least in three places. By means of a suitable circuit, the areas between each of the two electrical connections can then be individually switched to the active and the inactive state.

According to one embodiment of the invention, the polarization filter means may comprise a first and a second polarization filter element. The first polarizing filter element can transmit light having a first linear polarization while the second polarizing element transmits light having a second linear polarization. This is particularly advantageous so that the light emerging from the illumination device does not have only a single linear polarization. This could be for a motor vehicle driver who wears sunglasses with a polarizing filter, not be visible.

It is also possible that the first polarizing filter element transmits light with the second linear polarization, while the second polarizing element transmits light with the first linear polarization.

Another possibility is that both the first polarizing filter element and the second polarizing filter element transmit light having the same linear polarization. This may be particularly advantageous when the means for rotating the polarization direction comprises two subregions which are separately switchable into the active and the inactive state. In this case, the polarization of one of the beams can be rotated so that both beams have the same linear polarization.

It is also possible that the polarization filter means comprise only a single polarization filter element. Such a construction simplifies the construction of the lighting device.

According to one embodiment of the invention, the polarization rotation means may comprise at least one liquid crystal element. The liquid crystal element is particularly easy to switch by applying a voltage from the active to the inactive state. It should be noted that the liquid crystal element is in an inactive state when applied voltage, so the polarization direction of light does not change, while it is in the active state when the voltage is not applied and the polarization direction of light, preferably by 90 ° or 270 °, rotates.

According to one embodiment of the invention, the light can reach the polarizing beam splitter at an angle of approximately 45 °. With such a geometry, it is particularly easy to obtain two light beams whose linear polarization is rotated by 90 ° to each other.

In a further aspect, the invention relates to a motor vehicle with a lighting device according to an embodiment of the invention.

Reference to the accompanying drawings, the invention is explained in more detail by way of example only. In this case, the same reference numerals are used for the same or similar component and components with the same or similar functions. Showing:

1 a schematic view of an embodiment of the invention with a liquid crystal element with two areas;

2 a schematic view of an embodiment of the invention with a liquid crystal element which can be activated only over its entire range;

3 a schematic view of an embodiment of the invention with two liquid crystal elements; and

4 a schematic view of an embodiment of the invention with only a single polarizing filter in the beam path behind the liquid crystal element.

In 1 a lighting device is shown, which is a light source 100 , a polarizing beam splitter 101 , a mirror 102 , a liquid crystal element 103 , two polarizing filters 104 and 105 and lenses 106 includes. The liquid crystal element 103 has two areas 107 and 108 on. The areas 107 and 108 can be electrically switched to an active state and to an inactive state. When activated, the areas rotate 107 and 108 the polarization direction of incident light by 90 °. In the inactive state, no rotation of the polarization direction takes place. The two areas 107 and 108 can be switched separately. It should be noted that the active state means that no electrical voltage is applied to the respective area, while in the inactive state, an electrical voltage is applied to the respective area.

The light source 100 emits unpolarized light 109 , The light 109 meets the polarizing beam splitter 101 , The polarizing beam splitter 101 share the light 109 in a first beam path 110 and a second beam path 111 on. Both beam paths 110 and 111 have a linear polarization. The polarization of the first beam path 110 is at 90 ° to the polarization of the second beam path 111 turned. The second beam path 111 is from the mirror 102 in the direction of the liquid crystal element 103 reflected. The first beam path 110 is directly from the polarizing beam splitter 101 in the direction of the liquid crystal element 103 transmitted.

The two mutually perpendicular linearly polarized beam paths 110 and 111 hit the liquid crystal element 103 , The beam path 110 meets the first area 107 and the beam path 111 meets the area 108 , Now, through a targeted circuit of the two areas 107 and 108 be selected, whether the two beam paths 110 and 111 after passing through the liquid crystal element to have the same linear polarization or by 90 ° to each other rotated linear polarizations. In the present example they should have the same linear polarization. Therefore, only becomes one of the two areas 107 and 108 switched to the active state. After passing through the liquid crystal element 103 So have the two beam paths 110 and 111 the same linear polarization.

Due to the separately switchable areas 107 and 108 can the linear polarization of the two beam paths 110 and 111 be chosen freely. If it is desired that light be emitted by the illumination device to the outside, the linear polarization is chosen so that the light through the polarization filter 104 and 105 which are aligned parallel to each other, passes through. If no light is to exit the illumination device, the linear polarization is chosen so that the light from the polarizing filters 104 and 105 is absorbed.

The lenses 106 serve to give the light emerging from the lighting device a desired direction.

In the 2 The illumination device shown differs from the illumination device 1 in that the liquid crystal element 200 has no distinct areas. The liquid crystal element 200 thus has the same state (active or inactive) over its entire range. This arrangement is cheaper to implement.

Characterized in that the liquid crystal element always only either in any of the beam paths 110 and 111 or both beam paths 110 and 111 the linear polarization direction can rotate, the polarizing filters must 104 and 105 be arranged rotated by 90 ° to each other. Depending on the arrangement of the polarizing filters 104 and 105 can be achieved, whether with active or inactive liquid crystal element 200 Light leaks out or not.

In 3 a lighting device is shown, the two liquid crystal elements 200 and 300 includes. The operation is similar as regards 1 described. The two liquid crystal elements 200 and 300 can be similar to the two areas 107 and 108 switch separately from one another to the active and the inactive state.

The use of two liquid crystal elements has the particular advantage that a limited functionality is provided in the event of failure of a liquid crystal element.

In 4 a lighting device is shown which only has a single polarizing filter 400 in the beam path behind the liquid crystal element 103 includes. This means that only linearly in the same direction polarized light from the illumination device can escape to the outside. Therefore, the liquid crystal element has 103 similar to in 1 two separately switchable into the active and the inactive state areas 107 and 108 on. Similar to in 1 can by choosing which of the areas 107 and 108 is in the active state, decide whether the two beam paths 110 and 111 from the polarizing filter 400 be transmitted or absorbed.

LIST OF REFERENCE NUMBERS

100

light source

101

Polarizing beam splitter

102

mirror means

103

liquid crystal element

104

polarizing filter

105

polarizing filter

106

lens

107

First region of the liquid crystal element

108

Second region of the liquid crystal element

109

Emitted light

110

First ray path

111

Second ray path

200

liquid crystal element

300

liquid crystal element

400

polarizing filter

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4985816 [0002]

Claims (10)

Lighting device for a motor vehicle, comprising at least one light source ( 100 ), a means for polarization rotation ( 103 ; 200 ; 300 ) and a polarizing filter means ( 104 ; 105 ; 400 ), the light source ( 100 ) is adapted to light ( 109 ), and wherein the illumination device is designed such that the light emitted by the light source ( 100 ) emitted light ( 109 ) the means for polarization rotation ( 103 ; 200 ; 300 ) and the polarizing filter element ( 104 ; 105 ; 400 ), characterized in that the illumination device comprises a polarizing beam splitter ( 101 ) and a mirror agent ( 102 ), wherein the illumination device is designed such that the light ( 109 ) the polarizing beam splitter ( 101 ) and the mirror agent ( 102 ) reached. Lighting device according to claim 1, characterized in that the polarizing beam splitter ( 101 ) between the light source ( 100 ) and the means for polarization rotation ( 103 ; 200 ; 300 ) is arranged. Lighting device according to one of the preceding claims, characterized in that the means for polarization rotation ( 103 ; 200 ; 300 ) between the polarizing beam splitter ( 101 ) and the polarizing filter means ( 104 ; 105 ; 400 ) is arranged. Lighting device according to at least one of the preceding claims, characterized in that the means for polarization rotation ( 103 ; 200 ; 300 ) is switchable at least in some areas in an active and in an inactive state, wherein in the active state, the polarization direction of the light is rotated, and wherein in the inactive state, the polarization direction of the light is not rotated. Lighting device according to at least one of the preceding claims, characterized in that the polarizing beam splitter ( 101 ) a first part of the light ( 110 ) is transmitted with a first linear polarization and a second part of the light ( 111 ) with a second linear polarization that is different from the first, and that the polarizing beam splitter ( 101 ), the mirror agent ( 102 ) and the means for polarization rotation ( 103 ; 200 ; 300 ) are arranged such that the first light part ( 110 ) from the polarizing beam splitter ( 101 ) the means for polarization rotation ( 103 ; 200 ; 300 ) and that the second light part ( 111 ) via the mirror agent ( 102 ) the means for polarization rotation ( 103 ; 200 ; 300 ) reached. Lighting device according to one of claims 4 or 5, characterized in that the means for polarization rotation ( 103 ; 200 ; 300 ) at least two areas ( 107 ; 108 ) independently switchable to the active and inactive states. Lighting device according to at least one of the preceding claims, characterized in that the polarization filter means a first and a second polarization filter element ( 104 ; 105 ), wherein the first polarizing filter element ( 104 ) Transmits light having a first linear polarization, and wherein the second polarization element ( 105 ) Transmits light with a second linear polarization. Lighting device according to at least one of the preceding claims, characterized in that the means for polarization rotation at least one liquid crystal element ( 103 ; 200 ; 300 ). Lighting device according to at least one of the preceding claims, characterized in that the illumination device is designed so that the light is the polarizing beam splitter ( 101 ) is reached at an angle of about 45 °.  Motor vehicle, comprising at least one illumination device according to at least one of the preceding claims.

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