DE102016208146A1 - Move a converter device - Google Patents

Abstract

The color distribution in a laser converter system should be made more homogeneous. Therefore, a lighting apparatus having a laser device (2) for generating laser light and a converter device (3) for converting a part of the laser light incident on the converter device in a main irradiation direction into converted light is proposed. The lighting device also has a movement device for moving the converter device (3) with at least one direction component perpendicular to the main direction of irradiation. Thus, a homogeneous temperature distribution and thus a more homogeneous conversion can be achieved.

Description

The present invention relates to a lighting device having a laser device for generating laser light and a converter device for converting a portion of the laser light, which meets the converter device in a main direction of irradiation, into converted light. Moreover, the present invention relates to a method of operating a lighting device comprising a laser device and a converter device by converting laser light to the laser device and converting part of the laser light incident on the converter device in a main irradiation direction into a converted one Light.

Lighting devices of the above type are used in particular for headlights of motor vehicles. However, such lighting devices are also suitable for other vehicles or for lighting systems and buildings. In addition, such lighting devices can also be used for special effects.

With laser light, a high light intensity can usually be achieved. However, laser light is usually monochrome, so that so-called converters are usually used to generate white light. For example, blue laser light of a Ce: YAG laser is directed to a converter with phosphor which at least partially converts the blue light into yellow light. Together with the blue light results in a suitable mixing ratio in about white light.

So far, a blue central area has always been observed in very small focused blue excitation spots in the central area of the converted spot, and a yellow / green corona in the outer areas. These relationships are evident in transmissive conversion as well as in reflective systems. Especially for dynamically scanning systems (e.g., LARP systems: Laser Activated Remote Phosphor), this inhomogeneity presents a problem, as here e.g. several lines (e.g., six lines) are superimposed to illuminate the converter and achieve the desired light distribution on the road. Gradients or inhomogeneities are undesirable.

The object of the present invention is thus to provide a lighting device with a laser device and a converter device, which makes it possible to generate white light over a larger area from the laser light of the laser device. In addition, a corresponding method for operating a lighting device, which has a laser device and a converter device, be provided, wherein also large-area white light is generated.

The above object is achieved by a lighting device according to claim 1. In addition, the invention provides a method according to claim 10. Advantageous developments of the invention will become apparent from the dependent claims.

According to the present invention, therefore, there is provided a lighting apparatus having a laser device for generating laser light. The laser device provides a high light intensity. In addition, the lighting device has a converter device for converting a part of the laser light into converted light. It is not the entire laser light converted into converted light, but only a part of it. The reason for this is that the converted light together with the unconverted part of the laser light preferably generates a predefinable light distribution over the frequency. In particular, this spectral light distribution may be the distribution of white light.

The lighting device has, in addition to the laser device and the converter device, a movement device for moving the converter device. By thus moving the converter device, the conversion efficiency of the laser light into converted light can be influenced. Of particular importance in moving is that at least one directional component is perpendicular to the main direction of radiation. This means that the laser beam constantly strikes another section of the converter device. As a result, the same section of the converter device is not permanently illuminated and heated by the laser beam. As a result, the converter device is heated more uniformly over the surface, so that the conversion efficiency over the surface of the converter device is also uniform. Finally, this leads to the fact that the colored light distribution of the light generated by the lighting device is more homogeneous than without this movement of the converter device.

In a special embodiment, the laser device is designed to continuously change the direction of the laser light. The laser device may therefore be a so-called scanning laser, which scans a surface, for example line by line, meander-shaped or the like. In this embodiment, therefore, both the laser beam and the converter device moves relative to an external fixed point. As a result, under certain circumstances, the range of motion of the movement or converter device relative be reduced to the fixed point, since the relative movement of the laser beam relative to the fixed point contributes to the total relative movement of the laser beam relative to the converter device with. It is advantageous if the two movements are coordinated.

Only such a synchronous guidance of laser device and movement device makes it possible to achieve a high homogeneity of the light conversion over the entire converter surface of the converter device even in scanning systems.

The laser device can be designed, for example, to generate blue laser light, and the converter device can have a phosphor for converting the laser light. The phosphor converts the blue light into yellow light and, given a suitable conversion rate, the sum of blue laser light and yellow, converted light gives correspondingly white light. A similar phenomenon can be achieved, for example, with gadolinium (Gd) as converter. With it green laser light can be converted into red conversion light. In total, the green, unconverted laser light together with the red, converted light again results in white light, provided that a correspondingly suitable ratio is given.

In a preferred embodiment, the movement device is designed to carry out the movement of the converter device continuously or at least for a major part of a time duration of the conversion. The impact area of the laser beam on the converter device is thus changed continuously by the movement device. Thus, a high homogeneity of the desired radiation distribution over the surface (in particular white distribution) can be achieved, since the location of the largest heat input into the converter device changes continuously.

According to another embodiment, the converter device is periodically reciprocable by the moving means. For such a periodic motion, a simple sinusoidal drive can be used. As an electromechanical transducer can be used in this case, for example, a piezoelectric actuator.

According to a further embodiment, the converter device is movable by the movement device in a direction with at least one direction component perpendicular to the movement of the laser light or laser beam. This means that converter device and laser beam move in any case relative to each other, since both movements can not complement each other to zero (no relative movement to each other). Under certain circumstances, the degree of freedom of motion of the laser beam and the converter device can thus be limited without the goal of achieving as much converter surface as possible to be irradiated in succession. For example, the laser beam can only be moved in the Y direction and the converter device only in the X direction, that is, only orthogonal to one another.

In another embodiment, the converter device is two-dimensionally movable by the movement device. This would have the advantage that the laser beam does not move or the main irradiation direction of the laser device does not have to be changed. As a result, the laser device can be made mechanically simpler.

According to a further embodiment, the lighting device is equipped with a control device and at least one color sensor, wherein the movement device is regulated in dependence on a signal of the color sensor by the control device. Such a control has the advantage that automatically the range of motion of the moving means and / or the laser beam, i. the main irradiation direction of the laser light can be tuned to a (possibly location-based) conversion efficiency. Thus, e.g. At different laser powers (for example for low beam and high beam) a high homogeneity of the color distribution can be achieved automatically.

Further, the direction of the laser light may be changeable according to a first frequency, and the moving means may be configured to move the converter means at a frequency of change of the direction of the laser light having a second frequency different from the first one. By such different frequencies in the movements of the laser light or laser beam and the converter device can be ensured that both do not move uniformly over long periods of time. In fact, with uniform movement, there would be no relative movement of laser beam and converter device.

In a preferred embodiment, a motor vehicle is equipped with an above-mentioned lighting device. In particular, the lighting device can be realized as a headlight. It can thus achieve a very homogeneous light distribution in the illumination of the road.

The above object is also achieved by a method of operating a lighting device having a laser device and a converter device by generating laser light with the laser device and converting a laser device Part of the laser light, which meets the converter device in a main direction of irradiation, in converted light. There is a movement of the converter device with at least one direction component perpendicular to the main radiation direction. As a result, there is no overheating of a single area, the conversion efficiency would be reduced. Rather, a high conversion efficiency is maintained even in a central Einstrahlbereich. Thus, a desired spectral distribution and in particular a homogeneous white light distribution can be realized.

The developments and advantages described above in connection with the lighting device can also be transferred to the method according to the invention.

The present invention will now be explained in more detail with reference to the accompanying drawings, in which:

1 a lighting device according to an example of the present invention in a 3D view; and

2 a plan view of a converter device with converter holder.

The embodiments described in more detail below represent preferred embodiments of the present invention. It should be noted that the individual features can be realized not only in the described feature combination, but also in isolation or in other technically meaningful combinations of features.

As mentioned in the beginning, the phenomenon of light conversion, for example from blue to yellow, is highly sensitive to temperature. From a typical temperature range converters break the converter mechanisms and show the so-called roll-over effect. This means that the efficiency of the light conversion breaks down. This results in the color inhomogeneity described at the outset, for example, in the case of a blue excitation spot, with a blue central area and a yellow-green corona in the outer areas.

To counteract this color inhomogeneity possibly even with local peaks in the excitation spot, you can move the converter device mechanically. Appropriate movement of this converter means (e.g., converter holders including converter dies) may be accomplished via a separate, small drive. This movement device can, for example, periodically move the holding device back and forth in one direction. For example, a one-dimensional right-left movement or a one-dimensional up-down movement would be conceivable. In addition, a two-dimensional movement, such as along a Lissajous figure in question. In such a movement of the converter device, there is a distribution of the local Leistungsmaxima over a larger area of the converter or converter plate and avoiding the local roll-over, resulting in a homogeneous white mixed color.

1 shows a three-dimensional view of a lighting device, with a more homogeneous color distribution can be realized. Such a lighting device can be used to illuminate rooms, buildings, grounds and facilities. However, an application is preferably carried out in a motor vehicle and in particular in a motor vehicle headlight. There, for example, a dimming function, a high beam function and / or all additional lighting functions of modern AFS systems (curve, city, bad weather, etc.) and signal light functions can be implemented with such a lighting device.

In the example of 1 the lighting device has a housing 1 in which a laser device 2 is arranged. For example, blue light can be generated with the laser device.

For example, on one side of the housing 1 there is a converter device 3 , It represents a kind of window from which the laser light and any converted parts from the housing 1 penetrate to the outside.

2 shows the converter device 3 alone on a larger scale and in front view. This exemplary converter has a frame-shaped converter holder 4 which in turn has an eg rectangular opening 5 features. The edge 6 this opening 5 may be beveled like this 1 and 2 clarify. In the middle of this opening 5 holds the converter holder 4 a converter plate 7 ,

The converter plate 7 is with the in the housing 1 generated laser light irradiated. As a result of this irradiation, a high temperature is produced in the center of the laser spot, and correspondingly temperature-reduced areas result at the edge of the laser spot. Such a conditional inhomogeneous temperature distribution would result in a corresponding temperature-dependent color distribution due to the temperature dependence of the conversion, in particular if, for example, blue laser light passes through the converter plate 7 (eg based on phosphorus) in yellow / green light is converted.

Now to a homogeneous conversion due to a homogeneous temperature distribution on the converter plate 7 to reach the converter tile 7 moved relative to the optical path of the laser beam or the laser beams. The optical path of the laser beams or the main direction of irradiation in the lighting device, which can form a module, can be fixed, for example. Alternatively, the laser beam in the module or the illumination device can also be movable transversely to the beam direction. This is the case, for example, when the laser beam is scanning and moving in the scanning direction.

Regardless of the movement (scanning) or non-movement of the laser beam, according to the present invention, the converter device is movable relative to the laser beam or to the housing of the illumination device with at least one directional component perpendicular to the main direction of irradiation. For this movement, for example, on the housing 1 a movement device (in 1 not shown) arranged to the converter device 3 to move transversely to the laser beam direction (main radiation direction).

In the concrete embodiment of 1 is the converter frame 4 constructed in several parts and has a front part and a rear part. Both are plate-shaped and have a corresponding opening 5 , Between both parts is the converter plate 7 clamped. So if the converter frame 4 is moved, so is also the converter plate 7 emotional. The different degrees of freedom of movement of the converter device 3 perpendicular to the laser beam are with the arrow formation 8th in 2 indicated. The converter device can therefore be moved in one plane, for example from right to left and vice versa and / or from top to bottom and vice versa. As mechanical drives for such movements piezo actuators are conceivable. In addition, other electromechanical transducers could be used. Such actuators preferably operate with response times of a few microseconds.

The displacement of the converter device relative to the housing or the laser beam may be dependent on the spot size of the laser beam. If the size of the blue spot is e.g. 500μm, so the displacement should be at least half the spot diameter of about 250μm. As a result, "yellow / green" areas of the emerging light are superimposed by rays from the "blue" center of the spot. Depending on the proportion / size of the yellow or blue areas and depending on the spot size, you can specifically adjust the displacement. Of course, this technology is also available for other colors, i. can be used for other lasers and converters. By spectral measurements or size measurements, one parameter or several parameters of the displacement can be regulated. If, for example, the blue component of the total light, including the laser light and the converted light, is too high, the displacement and / or the displacement frequency can be increased in order to reduce the temperature of the converter or of the converter chip in the spot area and thus increase the conversion rate. The higher proportion of yellow or green reduces the proportion of blue, which leads to a more homogeneous color composition of the resulting light.

In addition, the shift frequency may also vary depending on the power of the excitation spot. For dynamic 1-dimensional scanners, the shift frequency of the converter, i. the converter device or the converter plate, not be identical to the scanning frequency. Both the direction and the magnitude of the two movements should be different. With 1-dimensional, non-linear movement of the scanning beam, the mechanical movement of the converter can also perform a non-linear movement. In any case, the movement of the converter device should be different than that of the laser beam or the laser beams.

For example, the generation of the blue light will be by a Ce: YAG laser. The converter may comprise a single crystal of phosphor. Alternatively, other lasers, e.g. Cerium-based and corresponding other converter types conceivable.

In a specific embodiment, the output light of the lighting device can be measured with two color sensors that are sensitive to different wavelengths. The two signals of the color sensors are set in relation. Depending on this relation, the movement of the movement device or the movement of the converter device can then be regulated.

By (fast) movement of the converter device as described above in or perpendicular to the laser beam direction or scanning direction in a dynamic system, local power peaks can be avoided, and a more homogeneous (white) color distribution occurs e.g. a spot to be imaged in the far field. Another advantage of this design and the avoidance of local overheating is the reduced risk of so-called "dark spots". For very focused, blue laser spots, oxidation of organic material in the converter device may occur. By a permanent relative movement of the excitation radiation (laser beams) in relation to the converter device can greatly reduce the risk of oxidation. The benefits of a more homogeneous color and lower oxidation risk are important, for example, for static and dynamic Automotive Laser Activated Remote Phosph (AM LARP) systems.

LIST OF REFERENCE NUMBERS

1

 casing

2

 laser device

3

 Converter device

4

 Converter Holder

5

 opening

6

 edge

7

 Converter platelets

8th

 arrow formations

Claims (12)

Lighting device with - a laser device ( 2 ) for generating laser light and - a converter device ( 3 ) for converting a part of the laser light, which in a main direction of irradiation on the converter device ( 3 ), in converted light, characterized by - a movement device for moving the converter device ( 3 ) with at least one directional component perpendicular to the main direction of irradiation. Lighting device according to claim 1, wherein the laser device ( 2 ) is adapted to continuously change the direction of the laser light. Lighting device according to claim 1 or 2, wherein the laser device ( 2 ) is designed to generate blue laser light, and the converter device ( 3 ) Has phosphorus for converting the laser light. Lighting device according to one of the preceding claims, wherein the movement device is designed to prevent the movement of the converter device ( 3 ) continuously or at least for a major part of a period of the conversion. Lighting device according to one of the preceding claims, wherein the converter device ( 3 ) is periodically reciprocable by the moving means. Lighting device according to one of claims 2 to 5, wherein the converter device ( 3 ) is movable by the moving means in a direction having at least one directional component perpendicular to the movement of the laser light. Lighting device according to claim 5 or 6, wherein the converter device ( 3 ) is two-dimensionally movable by the moving means.  Lighting device according to one of the preceding claims, comprising a control device and at least one color sensor, wherein the movement device is regulated in response to a signal of the color sensor by the control device. A lighting device according to claim 2, wherein the direction of the laser light is changeable according to a first frequency, and the moving means is arranged at such a change frequency of the direction of the laser light, the converter means ( 3 ) with one of the first different second frequency. Lighting device according to one of the preceding claims, wherein a speed of moving the converter device ( 3 ) by the moving means of a power of the laser device ( 2 ) is dependent.  Motor vehicle with a lighting device according to one of the preceding claims. Method for operating a lighting device comprising a laser device ( 2 ) and a converter device ( 3 ) by - generating laser light with the laser device ( 2 ) and - converting a portion of the laser light, which in a main direction of irradiation on the converter device ( 3 ), in converted light, characterized by - moving the converter device ( 3 ) with at least one directional component perpendicular to the main direction of irradiation.

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