Generating a light emission pattern in a far field

Abstract

Various embodiments may relate to a lighting apparatus for a headlight for generating a light emission pattern in a far field, including at least one light source for emitting primary light onto an illumination surface, at least two different phosphor surfaces which are introducible into the illumination surface, at least partly alternately by at least one translational movement, and a control device for positioning the phosphor surfaces in relation to the illumination surface. A respectively associated light emission pattern is generatable in a predetermined position of the phosphor surfaces. The control device is configured, for the purpose of setting a specific light emission pattern, to move at least one phosphor surface provided for this purpose into the illumination surface by at least one translational movement.

Claims

1. A lighting apparatus for a headlight for generating a light emission pattern in a far field, comprising: at least one light source for emitting primary light onto an illumination surface; the illumination surface further comprising at least two different phosphor surfaces; wherein the at least two different phosphor surfaces are at least partly alternated by at least one translational movement; and a control device for positioning the phosphor surfaces in relation to the illumination surface; wherein respectively associated light emission pattern is configured to be generated in a predetermined position of the phosphor surfaces; and the control device is configured, for the purpose of setting a specific light emission pattern, to move at least one phosphor surface provided for this purpose into the illumination surface by at least one translational movement.

2. The lighting apparatus as claimed in claim 1, wherein the phosphor surface is movable into the illumination surface by a pure translational movement.

3. The lighting apparatus as claimed in claim 1, wherein the phosphor surface is movable into the illumination surface by a translational movement and additionally a rotational movement.

4. The lighting apparatus as claimed in claim 1, wherein the light emission patterns have a different shape, a different light color or a different color distribution.

5. The lighting apparatus as claimed in claim 3, wherein at least two light emission patterns have a differently white light color.

6. The lighting apparatus as claimed in claim 1, wherein a light emission pattern is generatable by at least one primary light beam aligned in a stationary fashion.

7. The lighting apparatus as claimed in claim 1, wherein a light emission pattern is generatable by a movement of at least one primary light beam.

8. The lighting apparatus as claimed in claim 1, wherein a plurality of phosphor surfaces are arranged fixedly on a common, at least translationally movable carrier.

9. The lighting apparatus as claimed in claim 1, further comprising a plurality of carriers which are at least translationally displaceable independently of one another and each have a plurality of phosphor surfaces, wherein a phosphor surface of a respective carrier is in each case introducible simultaneously into the illumination surface.

10. The lighting apparatus as claimed in claim 1, wherein at least one phosphor surface has a uniform distribution of phosphor.

11. The lighting apparatus as claimed in claim 1, wherein at least one phosphor surface has a nonuniform distribution of at least one phosphor.

12. The lighting apparatus as claimed in claim 11, wherein at least one phosphor surface comprises a plurality of phosphors which are distributed over the phosphor surface nonuniformly with respect to one another.

13. The lighting apparatus as claimed in claim 1, wherein the headlight is an Adaptive Frontlighting System or Adaptive Driving Beam headlight.

14. The lighting apparatus as claimed in claim 1, wherein the light emission patterns have a different shape, a different light color and a different color distribution.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the disclosed embodiments. In the following description, various embodiments described with reference to the following drawings, in which:

(2) FIG. 1 shows as a sectional illustration in side view a lighting apparatus in accordance with a first embodiment with a linearly displaceable carrier;

(3) FIG. 2 shows in plan view a linearly displaceable carrier with a plurality of phosphor surfaces;

(4) FIG. 3 shows as a sectional illustration in side view a lighting apparatus in accordance with a second embodiment; and

(5) FIG. 4 shows as a sectional illustration in side view a lighting apparatus in accordance with a third embodiment.

(6) FIG. 1 shows a lighting apparatus 1, e.g. for a vehicle headlight E. The vehicle headlight E may be installed e.g. in a motor vehicle, e.g. in an automobile, a truck or a motorcycle. The vehicle headlight E generates a light emission pattern L in a far field F around the vehicle, in particular in front of the vehicle.

DETAILED DESCRIPTION

(7) The lighting apparatus 1 includes a plate- or sheet-like carrier 2 for three surface-like phosphor volumes, which are designated hereinafter as phosphor surfaces 3a to 3c. The phosphor surfaces 3a, 3b and 3c bear alongside one another in a series on a planar surface of the carrier 2. The phosphor surfaces 3a to 3c may have been sprayed or printed onto the carrier 2, for example. Alternatively, the phosphor surfaces 3a to 3c may have been applied, e.g. adhesively bonded, onto the carrier 2 as respectively prefabricated laminae (e.g. ceramic laminae).

(8) The lighting apparatus 1 furthermore includes a light source in the form of a laser 4, which emits e.g. blue primary light P. The blue primary light P has preferably, but not necessarily, a peak wavelength in the wavelength range of 360 nm to 480 nm, in particular of 400 nm to 460 nm. The laser 4 may include e.g. one or a plurality of laser diodes. The primary light P is radiated through a small window 5 in a shell-shaped reflector 6 obliquely onto the carrier 2, where it can generate an illumination surface 7 corresponding to the luminous spot. Light losses as a result of reflection into the laser 4 are low on account of the window 5 being only small and on account of the oblique incidence.

(9) The beam path of the primary light P remains unchanged over time, that is to say stationary. A temporally unchanging (static) areal provision of the illumination surface 7 is achieved as a result.

(10) An optical unit 8, indicated here by a lens, is interposed between the laser 4 and the illumination surface 7, e.g. for the purpose of beam collimation. Moreover, the primary light P impinging on the illumination surface 7 may be approximately parallelized, instead of being focused as indicated. If a focusing beam path is used, it is also possible, for example, for the phosphor surfaces 3a to 3c not to be placed at the focus of the beam of the primary light beam P (i.e. in particular also to be positioned downstream of the focus or in the beam that diverges again), in order to be able to set the size of the illumination surface 7 more simply.

(11) In one development, the laser 4 and the optical unit 8 possibly present are situated in a common housing and together form one unit. It is alternatively possible to guide the primary light P via an optical fiber to the carrier 2 or to the phosphor surfaces 3a, 3b or 3c thereof.

(12) The carrier 2 can be displaced along its extended plane by a translational linear movement, here along a displacement direction V. The carrier 2 here assumes different positions in which in each case one of the phosphor surfaces 3a, 3b or 3c lies in the illumination surface 7 or the phosphor surfaces 3a to 3c are introducible alternately into the illumination surface 7. To put it in yet another way, the carrier 2 can be linearly displaced such that one of the phosphor surfaces 3a, 3b or 3c in each case is illuminatable by the primary light beam P. The phosphor surfaces 3a to 3c here are each shown as larger than the illumination surface 7. However, this need not necessarily be the case, but affords the advantage that free regions of the carrier 2 are not concomitantly illuminated. The illumination surface 7 can be delimited by a mechanical diaphragm. The latter can be connected to the carrier 2.

(13) The illumination surface 7 preferably has an extent (e.g. of a diameter or an edge length) of at least 20 micrometers. An extent of the illumination surface 7 of 50 m to 500 m is particularly preferred. If achieving a high luminance is not of primary importance as the goal, a maximum extent of up to 1000 m is preferred. These values apply in particular to illumination or irradiation using a laser 4 in the form of a laser diode and an impinging radiation power of 0.25 W to 60 W. For higher laser powers, it is possible to use these extent values with correspondingly higher achievable luminances. With higher laser powers, however, it is also possible to use larger extents, e.g. a doubling of the area defined by the maximum extent in the case of doubling of the laser power, etc.

(14) At the illuminated phosphor surface (shown here as 3b) the blue primary light P is converted at least partly into yellow secondary light S. In this case, overall blue-yellow or white mixed light is emitted as useful light P, S by the phosphor surface 3b. Depending on the concentration and/or layer thickness of the blue-yellow converting phosphor, the useful light P, S may have a neutral white, a bluish white or a yellowish white color. Preferably, the useful light P, S of each of the phosphor surfaces 3a to 3c is at least regionally within an ECE color space (that is to say not necessarily white, but for example also yellow, red, etc.).

(15) The phosphor surfaces 3a to 3c are formed differently, for example with regard to their shape and/or phosphor composition. A phosphor composition may be understood to mean for example presence of one or more specific phosphors, the concentration thereof, the layer thickness thereof and/or the areal distribution thereof or variation of this/these. The phosphor surfaces 3a to 3c may have in particular a phosphor composition that is uniform over their area.

(16) In the case of the reflective arrangement shown, the useful light P, S is emitted from the same side on which the primary light P is also incident. For this purpose, the carrier 2 is formed in a reflective fashion at its side facing the phosphor surfaces 3a to 3c. The carrier 2 is preferably embodied in a specularly reflective or mirroring fashion, in particular for all wavelengths present, in order that the primary radiation P passing through the phosphor surfaces 3a, 3b or 3c and impinging on the carrier 2 and also the secondary radiation S emitted in the direction of the carrier 2 can be effectively reflected back into the phosphor surfaces 3a, 3b or 3c and thus used further. This increases a conversion efficiency.

(17) For effective dissipation of heat from the phosphor surfaces 3a, 3b and 3c, the carrier 2 preferably consists of metal or a sapphire-on-metal layer stack. It is also possible to arrange a dichroic layer between a nonreflective carrier 2 and the phosphor surfaces 3a, 3b and 3c, which dichroic layer transmits the primary light P, but reflects converted secondary light S. In this regard, a primary light proportion of the useful light P, S can be reduced. Such an arrangement is advantageous in particular for the transmissive case (here primary light must pass, whereas secondary light should be reflected for achieving a higher efficiency).

(18) The useful light P, S emitted by the phosphor surface 3a, 3b or 3c impinges on a downstream secondary optical unit, which is shown here on the basis of the shell-like reflector 6. The reflector 6 may have for example a spherical, paraboloidal or freeform-shaped reflection surface, which if appropriate may be multiply faceted. The position of the illumination surface 7 and thus also the position of the respectively illuminatable phosphor surface 3a, 3b or 3c correspond here to a focal spot of the reflector 6. The useful light P, S is coupled out as light emission pattern L into the far field F by the secondary optical unit.

(19) The secondary optical unit may include even further elements (not illustrated) for beam shaping of the useful light P, S, e.g. at least one lens, at least one reflector, a diaphragm or shutter, etc. This may be effected, for example, such that the reflector 6 directs the useful light P, S into a near-field intermediate plane, which can possibly also contain a shutter (not illustrated). The intermediate plane can then be imaged into the far field F (e.g. by a refractive optical unit).

(20) By alternately introducing the differently configured phosphor surfaces 3a to 3c into the illumination surface 7, respectively associated, different light emission patterns L are generatable. The light emission patterns L may differ with regard to their shape, color and/or color distribution.

(21) In this case, a specific light emission pattern L is generated non-sequentially. This means that a light emission pattern L is generatable completely with the carrier 2 and thus also the phosphor surfaces 3a to 3c in exactly one position (corresponding to a specific position) of the carrier 2. In order to generate a light emission pattern, therefore, the carrier 2 does not need to move two or more of the phosphor surfaces 3a, 3b or 3c one after another through the primary light P, rather a desired light emission pattern L is generated by illuminating exactly one of the phosphor surfaces 3a to 3c.

(22) It is also possible to change a brightness or laser power of the primary light P by changing the position of the carrier 2. As a result, the light emission pattern L can be dimmed, e.g. in order to generate a daytime running light or a position light.

(23) By way of example, in a first (linear) position of the carrier 2, only the phosphor surface 3a may be irradiated by the primary light P. As a result, e.g. a light emission pattern L may be generated which has a bluish white color and has a shape and intensity suitable for use as a daytime running light.

(24) By a linear displacement of the carrier 2 by one position such that now only the phosphor surface 3b is irradiated by the primary light P, a second light emission pattern L is generated. The second light emission pattern L differs from the first light emission pattern L at least with regard to its shape and/or color, if appropriate also with regard to its brightness. In order to differentiate the color of their light emission patterns L, the phosphor surfaces 3a and 3b may have a different concentration or layer thickness of the phosphor contained therein. The second light emission pattern L may emit yellow useful light for example for use with a flashing indicator function. For this purpose, a higher proportion of blue-yellow converting phosphor may be present for example in the phosphor surface 3a (e.g. on account of a higher concentration and/or layer thickness).

(25) If the carrier 2 is linearly displaced further by another position, such that now only the phosphor surface 3c is irradiated by the primary light P (that is to say only the phosphor surface 3c is situated in the illumination surface 7), a third light emission pattern L is generated, e.g. for use as a fog light or the like.

(26) Additionally or alternatively, at least one phosphor surface can be present which generates yet another light emission pattern L, e.g. for use as a low beam, as a high beam, etc. At least two light emission patterns L may also be present for the same purpose, e.g. as daytime running light, which differ only in a light color, e.g. in a different whitish hue, for example in order to be able to react to parameters of the surroundings of the vehicle, such as rain, and/or a state of the driver, such as fatigue of the latter, e.g. in the context of an AFS or ADB.

(27) The number of phosphor surfaces is unrestricted and may be e.g. two, three or else more than three.

(28) The linear movement of the carrier 2 for positioning the phosphor surfaces 3a to 3c in relation to the illumination surface 7 is effected by a motor, in particular a linear motor 10. The linear motor 10 may include for example at least one electric motor (in particular stepper motor) or at least one actuator (e.g. at least one piezo-actuator with or without stroke amplification).

(29) The linear motor 10 is coupled to a control device 11, which drives the linear motor 10. The linear motor 10 and the control device 11 may also be integrated in a single component. The control device 11 is configured to drive the linear motor 10 such that a phosphor surface 3a, 3b or 3c provided for a specific light emission pattern L is thereby moved linearly into the illumination surface 7. For driving the linear motor 10, the control device 11 can receive control commands ST which predefine the light emission pattern L to be generated. Said control commands ST are converted into driving signals for the linear motor 10 by the control device 11, and the driving signals are then made available to the linear motor 10 in order to predefine the linear movement thereof. The control commands ST may originate for example from a vehicle electronic unit (not illustrated). The control commands ST may be based on operating processes by a driver of the vehicle, e.g. on switching-on of a specific light function such as a high beam, and/or on an automatic selection by the vehicle. The automatic selection may be based e.g. on measurement values of at least one sensor of the vehicle. In this regard, the light emission pattern L may be changed depending on brightness, weather conditions (e.g. rain or fog), recognition of an object in front of the vehicle, the driver's attention, etc.

(30) In principle, it is also possible to displace the carrier 2 linearly in two planar directions. In this case, in particular, the phosphor surfaces can be distributed on the carrier 2 two-dimensionally, e.g. in a matrix-shaped fashion, in a cruciform fashion, etc. By a movement of the carrier 2 in both planar directions (in the direction V and in a direction perpendicular thereto in the image plane), it is possible to move to all the different phosphor surfaces. By a two-dimensional arrangement, more phosphor surfaces can be accommodated compactly, in comparison with an only one-dimensional (e.g. strip-shaped) arrangement.

(31) It is also possible to excite the phosphor surfaces 3a, 3b or 3c by a plurality of lasers 4, in particular laser diodes, or to generate the illumination surface 7 by primary light P of a plurality of lasers 4. The light thereof can pass through the same window 5 in the reflector 6, but can alternatively also pass through different windows to the phosphor surface 3a, 3b or 3c.

(32) Scanning illumination may also be used instead of the stationary illumination.

(33) FIG. 2 shows a frontal view of a further possible carrier 12, which can be used e.g. instead of the carrier 2 in the lighting apparatus 1. The carrier 12 includes four phosphor surfaces 13a, 13b, 13c and 13d arranged alongside one another in a 22 matrix pattern. Only one phosphor surface 13a, 13b, 13c or 13d in each case is illuminated. Each individual phosphor surface 13a, 13b, 13c or 13d can thus generate a complete light emission pattern L. By a linear movement of the carrier 12 in its plane (e.g. generated by the linear motor 10), said carrier can be moved such that each of the phosphor surfaces 13a, 13b, 13c or 13d is in each case introducible into the illumination surface 7. The linear movement is indicated by the double-headed arrows.

(34) The individual phosphor surfaces 13a, 13b, 13c or 13d contain different distributions of phosphors.

(35) By way of example, the phosphor surface 13a may be covered homogeneously with a blue-yellow converting phosphor having a first layer thickness, in order to generate and emit a cold white light. The phosphor surface 13b may be covered homogeneously with a blue-yellow converting phosphor having a second layer thickness, which is thicker than the first layer thickness. As a result, a yellowish white light can be generated and emitted. A warmer hue can also be achieved by adding a blue-red converting phosphor. The phosphor surface 13c may be covered homogeneously with a blue-yellow converting phosphor having a third layer thickness, which is smaller than the first layer thickness. As a result, a bluish white light can be generated and emitted. The phosphor surface 13d may include a plurality of partial regions each covered differently homogeneously with a blue-yellow converting phosphor. In this regard, two outer regions may be covered similarly to the phosphor surface 13c and a central region may be covered similarly to the phosphor surface 13a.

(36) However, a (22) pattern of the individual phosphor surfaces need not necessarily be used. Any other arbitrary division into an (nm) pattern is thus possible, wherein n and m are integers, at least one of which is greater than one. Additionally, a length-to-width ratio or aspect ratio of the individual phosphor surfaces is freely selectable. The individual phosphor surfaces need not be rectangular, but rather can also assume other shapes. Regions that are free of phosphor can also be present between the phosphor surfaces. Moreover, an irregular arrangement of the phosphor surfaces is possible. Likewise, the arrangement of the phosphors within a phosphor surface is not limited. Any desired division can be used. Realizations are possible both in a transmissive use (transmitted-light arrangement, as shown) and in a reflective use of the phosphor.

(37) The downstream secondary optical unit may be a reflector shell, as described, but can e.g. also be a refractive optical unit which images into the far field. Said refractive optical unit may be advantageous in particular for the transmitted-light arrangement.

(38) The carrier 12 may be e.g. a metallic carrier for a reflective construction and e.g. a glass or sapphire carrier for a transmissive construction.

(39) FIG. 3 shows a lighting apparatus 21, e.g. for a vehicle headlight E, which is constructed similarly to the lighting apparatus 1. However, two reflectors 6a and 6b or corresponding reflection regions of a reflector 6a, 6b are now present. Moreover, phosphor surfaces 3a and 3d, 3b and 3e, and 3f and 3c arranged on opposite surfaces or flat sides of the carrier 2 can now be irradiated simultaneously, specifically by different lasers 4a and 4b, respectively. In other words, a first illumination surface 7a can be provided at a first flat side of the carrier 2 and a second illumination surface 7b can be provided at a second flat side of the carrier 2.

(40) The reflectors 6a and 6b in turn are illuminated by the phosphor surfaces 3a, 3b or 3c and, respectively, 3d, 3e or 3f. A light emission pattern L in the far field F (not illustrated) can then be established by a superimposition of the useful light (not illustrated) emitted by both reflectors 6a and 6b. This corresponds to an addition of the useful light generated by opposite phosphor surfaces 3a and 3d, 3b and 3e, and 3f and 3c.

(41) In this case, for a specific light emission pattern both lasers 6a, 6b do not need to be in operation. By way of example, a high beam may be generated by operation of both lasers 6a, 6b, whereas a low beam may be generated e.g. by operation of only one of the lasers 6a or 6b. Consequently, different light emission patterns can be made available by optionally activating the lasers 6a or 6b in an identical position of the carrier 2. Further light emission patterns can be generated by linear displacement of the carrier 2 into a different position, specifically by joint and/or respective activation of the lasers 4a and 4b.

(42) A light color and/or shape of the light emission patterns emitted by the two reflectors 6a and 6b may be identical or different. Moreover, a light color of the primary light P emitted by the two lasers 6a, 6b may be identical or different.

(43) FIG. 4 shows a lighting apparatus 31, e.g. for a vehicle headlight E, in the case of which a plurality of (here for example four perpendicularly aligned) strip-like carriers 2a, 2b, 2c and 2d each having phosphor surfaces A1 to A3, B1 to B3, C1 to C3 and D1 to D3, respectively, arranged alongside one another in a series are now present. The carriers 2a, 2b, 2c and 2d are displaceable parallel to one another along their longitudinal axes, as indicated by the double-headed arrows. The carriers 2a to 2d are arranged directly adjacently to one another (i.e. here: separated only by a practically negligibly narrow gap).

(44) Instead ofas in the case of the lighting apparatus 1, the phosphor surfaces A2 to D2 situated in an illumination surface 32 being irradiated with the primary light P over a large area at one point in time (in a stationary fashion) and said phosphor surfaces A1 to D3 being used as quasi-light source for a downstream optical unit, the phosphor surfaces A2 to D2 situated in the illumination surface 32 are now swept over or scanned in a time-dependent manner (dynamically) by a concentrated primary light beam P. For the scanning, in particular line-like, illumination of the illumination surface 32, the primary light P may be deflectable onto the illumination surface 32 in particular via at least one movable, in particular pivotable, mirror 33, e.g. in a manner similar to that in the case of a flying spot method. The pivotable mirror 33 may be e.g. an MEMS component. The laser 4 may be able to be switched on and off (or dimmable) in a targeted manner. The light emission pattern thus generated may be varied by changing the illumination pattern given a fixed position or rotational position of the carriers 2a, 2b, 2c and 2d.

(45) The illumination surface 32, which is now illuminatable by the laser 4 in a scanning manner line by line, includes a line of phosphor surfaces A1 to A3, B1 to B3, C1 to C3, and D1 to D3, arranged alongside one another transversely with respect to the displacement direction thereof, e.g. a line including the phosphor surfaces A2, B2, C2 and D2. Therefore, a phosphor surface of a strip-shaped carrier 2a to 2d is in each case illuminatable simultaneously. Since the carriers 2a to 2d are linearly displaceable independently of one another, all possible adjacent phosphor surfaces A1 to A3, B1 to B3, C1 to C3, and D1 to D3 can be combined.

(46) The phosphor surfaces A1 to A3, B1 to B3, C1 to C3, and D1 to D3 of a respective strip-shaped carrier 2a to 2d can have in particular a different phosphor composition (e.g. with regard to a type, quantity and/or areal distribution of phosphor) and thereby generate a differently shaped and/or differently colored part of the entire light emission pattern.

(47) A specific light emission beam pattern can be set for example by an arbitrary, but then fixedly chosen combination of the phosphor surfaces A1 to A3, B1 to B3, C1 to C3, and D1 to D3. The light generated in this case can again be projected into the far field F by an optical unit (not illustrated), in particular an imaging optical unit.

(48) Respective linear motors 10a to 10d may be used for the linear movement of the carriers 2a, 2b, 2c and 2d, said linear motors being jointly controllable by the control device 11. Here, too, the control device 11 can receive control commands ST for driving the linear motors 10a to 10d, said control commands predefining the light emission pattern L to be generated. Said control commands ST are converted into driving signals for the linear motors 10a to 10d by the control device 11, in order to bring the combination of the phosphor surfaces A1 to D3 that is appropriate for the desired light emission pattern into the illumination surface 32.

(49) Alternatively, instead of the scanning illumination, a stationary illumination of the phosphor surfaces A2 to D2 situated in the illumination surface 32 may be carried out, e.g. by a stationary beam of the primary light P that is of appropriate width.

(50) In principle, the number of independently movable carriers is unrestricted and may also encompass hundreds or even thousands of independently movable carriers.

(51) Moreover, the illuminatable region 32 can include a plurality of lines.

(52) The lighting apparatus 31 may be implemented in a reflective arrangement or in a transmissive arrangement.

(53) Although the invention has been more specifically illustrated and described in detail by the embodiments shown, nevertheless the invention is not restricted thereto and other variations can be derived therefrom by the person skilled in the art, without departing from the scope of protection of the invention.

(54) In this regard, a choice may be made, in principle, between a stationary and a scanning irradiation of a phosphor surface.

(55) Moreover, an at least one phosphor surface displaced on a curved trajectory or movement path may be used instead of or in addition to a linear translational movement.

(56) Moreover, a rotational movement of the at least one phosphor surface may be superimposed on the translational movement, in particular in order to achieve a pivoting of the phosphor surface.

(57) Generally, a(n), one, etc. can be understood to mean a singular or a plural, in particular in the sense of at least one or one or a plurality, etc., as long as this is not explicitly excluded, e.g. by the expression exactly one, etc.

(58) Moreover, a numerical indication can encompass exactly the indicated number and also a customary tolerance range, as long as this is not explicitly excluded.