Lighting apparatus with conversion device

Abstract

Various embodiments may relate to a lighting apparatus, including at least one primary light source for generating primary light, a reflector having two spaced-apart focal spots, a guiding optical unit disposed downstream of the at least one primary light source and serving for guiding the primary light to a first focal spot of the reflector, and a conversion device for at least partly converting the primary light into secondary light having a different wavelength which is situated at the second focal spot. The reflector has a first reflective partial region, to which the two focal spots are assigned, and a second reflective partial region, which is a partial region retroreflective for the second focal spot. The primary light emitted by the at least one primary light source is incident on the first partial region.

Claims

1. A lighting apparatus comprising: at least one primary light source for generating primary light, a reflector having two spaced-apart focal spots, a guiding optical unit disposed downstream of the at least one primary light source and serving for guiding the primary light to the first focal spot of the reflector, and a conversion device for at least partly converting the primary light into secondary light having a different wavelength which is situated at the second focal spot, wherein the reflector has a first reflective partial region, to which the two focal spots are assigned, and a second reflective partial region, which is a partial region retroreflective for the second focal spot, and wherein the primary light emitted by the at least one primary light source is incident on the first partial region.

2. The lighting apparatus as claimed in claim 1, wherein the first partial region has an elliptical basic shape and the second partial region has a spherical basic shape.

3. The lighting apparatus as claimed in claim 2, wherein the first partial region corresponds to an illumination region of the primary light emitted by the guiding optical unit on the reflector.

4. The lighting apparatus as claimed in claim 1, wherein the guiding optical unit has at least one light guide whose light exit surface is arranged at the first focal spot.

5. The lighting apparatus as claimed in claim 4, wherein an optical wave guide is embodied as a light mixing guide.

6. The lighting apparatus as claimed in claim 5, wherein the light guide has an angular cross-sectional shape.

7. The lighting apparatus as claimed in claim 1, wherein the conversion device has a converting phosphor layer applied on a light-transmissive carrier.

8. The lighting apparatus as claimed in claim 7, wherein the carrier is arranged in a light path of the primary light upstream of the phosphor layer, and the carrier is provided with a dichroic coating which is transmissive to the primary light and reflects the secondary light.

9. The lighting apparatus as claimed in claim 1, wherein the conversion device has a converting phosphor layer applied on a reflective carrier.

10. The lighting apparatus as claimed in claim 1, wherein the at least one light source comprises at least one semiconductor light source.

11. The lighting apparatus as claimed in claim 1, wherein the lighting apparatus constitutes a part of a vehicle lighting system.

12. The lighting apparatus as claimed in claim 1, wherein the first reflective partial region and the second reflective partial region adjoin one another.

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) FIGS. 1 to 3 show lighting apparatus in accordance with a first, second and third embodiment, respectively, as a sectional illustration in side view.

DETAILED DESCRIPTION

(3) FIG. 1 shows a lighting apparatus 1 in accordance with a first embodiment as a sectional illustration in side view. The lighting apparatus 1 includes a primary light source in the form of a laser 2, which radiates blue primary light P into a guiding optical unit. The guiding optical unit is embodied here as a light mixing guide in the form of a light mixing rod 3 composed of light-transmissive glass or plastic. A first end face 4 of the light mixing rod 3 serves as a light entrance surface for the primary light P. The primary light P passes through the light mixing rod 3 in its longitudinal direction and is mixed in the process. A light spot made more uniform in respect of its intensity arises at the second end face 5 of the light mixing rod 3, said second end face serving as a light exit surface. Said light spot is largely independent of an exact position of the primary light beam P at the first end face 3. In order to support a homogenous light spot at the second end face 5, a cross-sectional shape of the light mixing rod 3 is shaped in an angular fashion, e.g. in a rectangular or hexagonal fashion.

(4) The second end face 5 is situated at a first focal spot BF1 (e.g. a region having a diameter of approximately 1 mm with the first focal point as midpoint) of an elliptical first partial region 8 of a reflector 7. The reflector 7 is embodied such that it is in particular specularly reflective or reflective in a mirroring fashion and thus constitutes a deflection mirror. A second focal spot BF2 of the first partial region 8 is spaced apart from the first focal spot BF1.

(5) A second partial region 9 having a spherical basic shape is adjacent to the first partial region 8. The sole focal spot of the second partial region 9 corresponds to the second focal spot BF2 of the first partial region 8. A phosphor layer 11 of a conversion device 10 is situated at the second focal spot BF2. Primary light P emitted from the second end face 5 of the light mixing rod 3 impinges only on the first partial region 8 and not on the second partial region 9. The first partial region 8 thus corresponds to at least one illumination region of the primary light P emitted by the light mixing rod 3 on the reflector 7.

(6) The primary light P is deflected by the first partial region 8 onto the second focal spot BF2 and in this case impinges on the conversion device 10. The conversion device 10 has a laminar, transparent carrier 12 composed of sapphire, for example, in addition to the phosphor layer 11. A front side 13 of the carrier 12 faces the reflector 7 and is covered with an antireflection layer 14. A rear side 15 of the carrier 12 is covered with a dichroic coating 16 which transmits the primary light P practically completely (i.e. completely apart from practically negligible losses).

(7) The phosphor layer 11 is applied on the dichroic coating 16 and converts the primary light P transmitted through the dichroic coating 16 at least partly into secondary light S having a longer wavelength, e.g. into yellow secondary light. This construction corresponds to a transmissive construction. The dichroic coating 16 is configured such that it is reflective for the secondary light S, such that the latter incurs no light losses as a result of backscattering.

(8) In particular, a phosphor may generate yellow secondary light S which, together with non-converted blue primary light P produces a yellow-blue or white mixed light P, S. The mixed light P, S can be coupled out further as useful light, e.g. by a reflector R disposed optically downstream.

(9) The phosphor layer 11 may include as necessary two or even more phosphors which further convert the primary light P or previously converted secondary light S.

(10) Primary light P backscattered from the phosphor layer 11 through the dichroic coating 16 onto the second partial region 9 of the reflector 7 is reflected back onto the second focal spot BF2 and can enter the phosphor layer 11 again there. In this regard, light losses are reduced further and a luminance and system efficiency are increased.

(11) The lighting apparatus 1 may constitute e.g. a part of a vehicle headlight, e.g. for generating an additional light, a fog light, a high beam, a low beam, a cornering light, etc.

(12) FIG. 2 shows a lighting apparatus 21 in accordance with a second embodiment as a sectional illustration in side view. The lighting apparatus 21 has a reflective construction in which primary light P reflected by a first reflective partial region 22 having an elliptical basic shape is incident directly on a phosphor layer 11, namely here on a front side 11a. The phosphor layer 11 is applied by its rear side on a reflective carrier 23 and forms with the latter a conversion device 11, 23. The carrier 23 may consist of metal, for example, in order to be able to act as an effective and inexpensive heat sink. Light (e.g. both primary light P and secondary light S) emitted by the phosphor layer 11 and impinging on the carrier 23 is reflected back into the phosphor layer 11, such that light losses are avoided at the carrier 23.

(13) In order to avoid light losses even further, the front side 11a of the phosphor layer 11 may also be coated with an antireflection layer (not illustrated).

(14) The mixed light P, S emitted by the phosphor layer 11 within a predetermined solid angle region W from the front side 11a can be used further as useful light. A second reflective partial region 24 having e.g. a spherical basic shape can be arranged at a solid angle region lying alongside the first reflective partial region 22 and the solid angle region W. The second partial region 24 may reflect in particular light (e.g. both primary light P and secondary light S) emitted outside the solid angle region W back onto the phosphor layer 11, from where it can be emitted again at least partly into the solid angle region W. In this regard, light losses can be reduced further in the case of a reflective construction as well.

(15) FIG. 3 shows a lighting apparatus 31 in accordance with a third embodiment as a sectional illustration in side view. The lighting apparatus 31 has a transmissive construction in a manner similar to the lighting apparatus 1. In contrast to the lighting apparatus 1, the guiding optical unit here is embodied as a light mixing guide in the form of a readily flexible optical hollow guide 32 composed of light-transmissive glass or plastic. The optical hollow guide 32 includes one or more light guiding fibers. The optical hollow guide 32 can be made particularly diversely and thereby reduces a dependence of a position of the at least one light source on a position and attainability of the first focal spot BF1.

(16) In addition, the optical unit used for coupling out the mixed light P, S emitted as useful light by the conversion device 10 now exhibits a lens L.

(17) The illustration furthermore shows, as a dashed line, a sectional contour of an ellipse associated with the first partial region 8 of the reflector 7 with its major semi-axis, on which lie the focal points BF1 and BF2. A sectional contour of a circle associated with the second partial region 9 of the reflector 7 is also depicted as a dashed line.

(18) While the disclosed embodiments have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosed embodiments as defined by the appended claims. The scope of the disclosed embodiments is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

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