Description

The present invention relates to a lighting device according to the preamble of claim 1.

A lighting device of the aforementioned type is known from DE 10 2007 053 399 A1. This lighting device is a headlamp for vehicles. The lighting device comprises a light source, a reflector, a lens and a linear drive, which can move the lens. The movement of the lens changes the direction of the light emitted by the headlamp. For instance, changing the direction of the emitted light can adapt the output of a headlamp for ve hicles in the case of a curve in front of the vehicle.

The movement of the lens is considerably slow due to the mass of the lens and the linear drive. Furthermore, the lens can be moved by the linear drive in only one direc tion.

The problem to be solved by the present invention is thus to provide a lighting device of the aforementioned kind, which can adapt the direction of the light emitted by the lighting device more effectively.

This is attained with the invention by a lighting device of the aforementioned kind with the characterizing features of claim 1. The dependent claims relate to preferred em bodiments of the invention.

According to claim 1 , the means for influencing the direction of the light comprise an array of phase modifiers, through which the light generated by the at least one light source can pass. Due to the phase modifiers the lighting device does not need mova ble parts like lenses to adapt the direction of the emitted light. Therefore, the lighting device can be thinner than devices with movable lenses. This can result in an attrac tive design of the lighting device. Additionally, the lighting device can be produced more cost-efficiently. Furthermore, the lighting device can adapt the direction of the emitted light very flexible and effective as the array of phase modifiers can be config ured and controlled electronically.

The lighting device could be a lighting device for vehicles, especially a headlamp for vehicles. In a preferred embodiment of the invention the lighting device is an automo tive headlamp. Another exemplary embodiment of the invention is a motorcycle head lamp. Another exemplary embodiment of the invention is a stage lighting device as on stages there is also a need for adaptive lighting.

It may be provided that the phase modifiers are constructed as liquid crystal-based modifiers, electro-optical modifiers or acousto-optical modifiers. An example of liquid crystal-based modifiers can be found in W. Vogel, M. Berroth,“Liquid Crystal Phase Shifter for Optically Generated RF-Signals”, 30 ^th European Microwave Conference, EuMC conference proceedings, Vol. 2, 2000, pp. 45 - 48.

The potential exists that the array of phase modifiers is a one-dimensional or a two- dimensional array. A one-dimensional array could be used for adapting the direction of the emitted light in for example the horizontal direction of a headlamp, which is able to adapt the lighting of the headlamp in the case of a curve. Furthermore, a two- dimensional array could be used for adapting the direction of the emitted light in for example the horizontal and the vertical direction of a headlamp, wherein the headlamp could also adapt the direction of the emitted light vertically on slopes of a road or an uneven road surface. Furthermore, a two-dimensional array could be used for adapt ing the direction of the emitted light in two perpendicular directions of a stage lighting device. This is a useful feature for stage light as persons move to the left and right and to the front and rear on the stage while the emitted light has to follow those persons.

It may be provided that the at least one light source is a coherent light source, wherein in particular the at least one light source is a laser light source, especially a laser di ode. The potential exists that the at least one light source is an RGB laser light source, wherein in particular the RGB laser light source comprises three single lasers, which emit a red, a green and a blue laser light, respectively. It is furthermore possible that the lighting device comprises three arrays of phase modifiers, wherein in particular each of the three lasers is assigned to one of the arrays of phase modifiers. The laser light of the three lasers can be overlapped after passing through the three arrays of phase modifiers so that white light is emitted by the lighting device. This is an appro priate measure for a headlamp of a vehicle or other lighting devices which need an output of white light.

In an alternative embodiment the lighting device could comprise conversion means for converting the light into white light after passing through the array of phase modifiers.

It may be provided that the lighting device comprises a plurality of optical fibers ar ranged between the at least one light source and the array of phase modifiers for di recting the light to the array of phase modifiers, wherein in particular each of the opti cal fibers is assigned to one of the phase modifiers. This configuration may facilitate the arrangement of the components in the lighting device.

The potential exists that the lighting device comprises an array of lenses arranged be tween the at least one light source and the array of phase modifiers for directing the light to the array of phase modifiers, wherein in particular each of the lenses is as signed to one of the phase modifiers. Each lens could focus a part of the light of the at least one light source onto an entrance face of one of the phase modifiers.

Preferred exemplary embodiments of the invention are described below in detail by means of the enclosed drawing. The drawing shows: figure 1 a schematic diagram of a lighting device according to the invention.

In the figure, identical or functionally identical parts or light beams are designated with identical reference numerals. The lighting device illustrated in figure 1 can be a headlamp for a vehicle. Alternative ly, the lighting device could be a stage lighting device or a lighting device for other ar eas of applications with a need for adaptive lighting.

The lighting device comprises at least one laser light source (not shown), which emits coherent light 1. The light can be separated into a plurality of light beams. The separa tion into a plurality of light beams could be achieved by a plurality of optical fibers (not shown). In another embodiment the separation into a plurality of light beams 1 could be achieved by an array of lenses (not shown).

Furthermore, the lighting device illustrated in figure 1 comprises an array 2 of phase modifiers 3, especially phase shifters. The phase modifiers 3 may, for example, be constructed as liquid crystal-based modifiers, electro-optical modifiers or acousto- optical modifiers. Furthermore, the array 2 of phase modifiers 3 could be a one dimensional or a two-dimensional array.

Each of the light beams impinges on an entrance face of one of the phase modifiers 3. If the phase modifiers 3 are not activated, the light 1 is not deviated and continues to propagate in a direction that corresponds to the input direction of the light 1. If the phase modifiers are activated, they modify the phases of adjacent light beams relative to each other. Due to interference effects, the modifications applied to the individual beams cause the light to emerge from the array 2 at an angle to the input direction.

Accordingly, mutually neighboring parts of the wavefront of the emerging light 4 have a phase difference d (see figure 1 ). The effect of this phase difference d is that the light 4 can emerge from the array 2 of phase modifiers 3 only in particular directions, for which there is constructive interference between the individual parts of the light 4. This situation is approximately similar to that at the output of a grating.

If the lighting device is for example a headlamp of a vehicle, the light emitted by the lighting device should be white light. This can be achieved by providing conversion means (not shown) for converting the light 4 emerging from the array 2 of phase modi fiers 3 into white light.

In an alternative embodiment the headlamp could comprise an RGB laser light source having three single lasers (not shown), which emit a red, a green and a blue laser light, respectively. Furthermore, this embodiment of the lighting device comprises three separate arrays 2 of phase modifiers 3, wherein each of the three lasers is as signed to one of the arrays of phase modifiers. The red, the green and the blue light 4 is being overlapped after passing through the three arrays 2 of phase modifiers 3 so that white light is emitted by the lighting device.

List of reference symbols

1 light emitted by the at least one light source

2 array of phase modifiers

3 phase modifier

4 light emerging from the array of phase modifiers d phase difference