LIGHTING APPARATUS

Abstract

A lighting apparatus is disclosed with a light generating device, at least one collimator lens, first and second parabolic mirrors, an optical diaphragm embodied in a light reflecting fashion, and a spherical mirror. The diaphragm is arranged between the parabolic mirrors, extending as far as a common focus of them. The parabolic mirror, the device and the lens are arranged so that light emitted by the device and collimated by the lens is directed onto the first parabolic mirror reflection surface and light reflected by the first parabolic mirror reflection surface impinges on the second parabolic mirror reflection surface or on the diaphragm. The spherical mirror is arranged so that its focus is arranged at the common focus of the parabolic mirrors and light reflected at the diaphragm impinges on the spherical mirror reflection surface and is directed from the reflection surface onto the second parabolic mirror reflection surface.

Claims

1. A lighting apparatus comprising a light generating device and at least one collimator lens which serves for collimating the light emitted by the light generating device, further comprising, a first parabolic mirror, an optical diaphragm embodied in a light reflecting fashion, a second parabolic mirror, wherein the diaphragm is arranged between the two parabolic mirrors and extends as far as a common focus of the two parabolic mirrors, and wherein the parabolic mirror and the light generating device and the at least one collimator lens are arranged in such a way that light which is emitted by the light generating device and collimated by the at least one collimator lens is directed onto the reflection surface of the first parabolic mirror and light reflected by the reflection surface of the first parabolic mirror impinges on the reflection surface of the second parabolic mirror or on the diaphragm, and a spherical mirror, which is arranged in such a way that its focus is arranged at the common focus of the parabolic mirrors and light reflected at the diaphragm impinges on the reflection surface of the spherical mirror and is directed from the reflection surface onto the reflection surface of the second parabolic mirror.

2. The lighting apparatus as claimed in claim 1, wherein the spherical mirror is arranged and embodied in such a way that it generates an image of a light distribution with a magnification factor having the absolute value 1 at the common focus.

3. The lighting apparatus as claimed in claim 1, wherein the spherical mirror is embodied integrally with the first parabolic mirror.

4. The lighting apparatus as claimed in claim 1, wherein the spherical mirror is movable.

5. The lighting apparatus as claimed in claim 1, wherein the optical diaphragm is movable.

6. The lighting apparatus as claimed in claim 1, wherein the light generating device comprises at least one semiconductor light source and a light wavelength conversion element.

7. The lighting apparatus as claimed in claim 6, wherein the at least one semiconductor light source is embodied as a laser diode.

8. The lighting apparatus as claimed in claim 1, wherein the lighting apparatus is embodied as a vehicle headlight or as part of a vehicle headlight.

9. The lighting apparatus as claimed in claim 1, wherein the at least one collimator lens is embodied in an aspherical fashion.

Description

BRIEF DESCRIPTION OF THE DRAWING(S)

[0018] 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:

[0019] FIG. 1 shows a plan view of the lighting apparatus in accordance with one preferred embodiment of the present disclosure in a schematic illustration.

DETAILED DESCRIPTION

[0020] The lighting apparatus in accordance with the preferred embodiment of the present disclosure is part of a motor vehicle headlight and has a light generating device 1, an aspherical collimator lens 2, a first parabolic mirror 3 having a concave reflection surface 30 shaped as a paraboloid of revolution, and an optical diaphragm 5 embodied in a light reflecting fashion, and also a second parabolic mirror 4 having a concave reflection surface 40 shaped as a paraboloid of revolution, and a spherical mirror 6 having a concave, spherical reflection surface 60.

[0021] The light generating device 1 consists of a plurality of laser diodes which emit blue light during operation, and a light wavelength conversion element, onto which the light emitted by the laser diodes is directed. The light wavelength conversion element includes a yellow phosphor (YAG:Ce) that converts the blue light (also called primary light) emitted by the laser diodes proportionally into yellow light (also called secondary light), such that white light that is a mixture of blue primary light and yellow secondary light is emitted from the surface of the light wavelength conversion element. The light emitting surface of the light wavelength conversion element is advantageously embodied in a circular-disk-shaped fashion. In FIG. 1, the reference sign 1 denotes the light generating device or the light emitting surface of the light wavelength conversion element of the light generating device.

[0022] The collimator lens 2 is arranged at a distance of 1 to 5 mm, for example, from the light emitting surface of the light wavelength conversion element of the light generating device 1. The collimator lens 2 reduces the divergence of the white light emitted by the light emitting surface of the light wavelength conversion element of the light generating device 1 and directs it onto the concave reflection surface 30 of the first parabolic mirror 3.

[0023] At the concave reflection surface 40 of the second parabolic mirror 4, the light is directed back in its original direction. The distance between the parabolic mirrors 3, 4 corresponds to the sum of the focal lengths of both parabolic mirrors 3, 4. The optical diaphragm 5 embodied in a light reflecting fashion is arranged between the two parabolic mirrors 3, 4 and extends as far as the common focus of the parabolic mirrors 3, 4.

[0024] The spherical mirror 6 is arranged directly alongside the first parabolic mirror 3 in such a way that its focus coincides with the common focus of the two parabolic mirrors 3, 4 and light which is reflected at the optical diaphragm 5 is directed onto the concave, spherical reflection surface 60 of the spherical mirror 6 and is directed from said reflection surface to the concave reflection surface 40 of the second parabolic mirror 4.

[0025] The aspherical collimator lens 2 and the first parabolic mirror 3 generate an image of the circular-disk-shaped light emitting surface of the light generating device 1 in the region of the common focus of the two parabolic mirrors 3, 4. Said image is likewise circular-disk-shaped. The diameter D2 of said image is calculated from the diameter D1 of the circular-disk-shaped light emitting surface of the light generating device 1, the focal length F1 of the collimator lens 2 and the focal length F2 of the first parabolic mirror 3 as D2=D1×F2/F1.

[0026] By means of the optical diaphragm 5 extending right into the common focus, part of the light emitted by the circular-disk-shaped light emitting surface of the light generating device 1 is masked out and directed onto the reflection surface 60 of the spherical mirror 6. By way of example, the diaphragm 5 is arranged in such a way that half of the light emitted by the circular-disk-shaped light emitting surface of the light generating device 1 and thus half of the abovementioned circular-disk-shaped image is masked out. This image therefore assumes the shape of half a circular disk and is referred to hereinafter as first image. That part of the light emitted by the circular-disk-shaped light emitting surface of the light generating device 1 which is not reflected by the diaphragm 5 is directed from the reflection surface 30 of the first parabolic mirror 3 directly to the reflection surface 40 of the second parabolic mirror 4.

[0027] The light which is directed from the diaphragm 5 onto the spherical mirror 6 and is reflected at the reflection surface 60 of the spherical mirror 6 generates at the common focus of the parabolic mirrors 3, 4 and of the spherical mirror 6 a second image of the circular-disk-shaped light emitting surface of the light generating device 1, which image likewise has the shape of half a circular disk and has the same size and alignment as the first image. The first image is superimposed with the second image at the common focus of the parabolic mirrors 3, 4 and projected by means of the second parabolic mirror 4 into the far field of the lighting apparatus or into the area in front of a motor vehicle headlight. In this case, the light intensities of both images are added together, thereby virtually doubling the light intensity of the light distribution in the abovementioned far field or area in front.

[0028] FIG. 1 illustrates schematically by way of example by means of solid lines the light beam path for a light beam which passes through the optical arrangement of the two parabolic mirrors 3, 4 without reflection at the diaphragm 5 and at the spherical mirror 6 and serves for generating the first image at the common focus. Moreover, FIG. 1 illustrates schematically by way of example by means of dashed lines the light beam path for a light beam which passes through the optical arrangement of the two parabolic mirrors 3, 4 after reflection at the diaphragm 5 and at the spherical mirror 6 and serves for generating the second image at the common focus.

[0029] The lighting apparatus is configured, as a light module of a motor vehicle headlight by itself or in interaction with other light modules of said headlight or of a different headlight, to generate a standard-conforming light distribution in the area in front of the motor vehicle, in particular a bright-dark boundary, for example the bright-dark boundary of a low-beam light.

[0030] To that end, the light which is emitted by the light wavelength conversion element of the light generating device 1 and which consists proportionally of non-converted blue primary light emitted by the laser diodes and directed onto the light wavelength conversion element, and of secondary light generated by the yellow phosphor of the light wavelength conversion element, is collimated by a, advantageously aspherical, converging lens or collimator lens disposed downstream of the light wavelength conversion element, in the case of which lens both the entrance side and the exit side are embodied in an aspherical fashion.

[0031] In this case, the collimator lens 2, which is embodied as an asphere or as an achromat, collimates the light from the light generating device 1 and directs it onto the concave reflection surface 30 of the first parabolic mirror 3, which then generates an image of the light emitting surface of the light generating device 1 or of the light wavelength conversion element of the light generating device 1 in an intermediate image plane. The intermediate image plane is situated at the common focus of the two parabolic mirrors 3, 4. The concave reflection surface 40 of the second parabolic mirror 4 then sharply images the intermediate image thus generated into the far field or into infinity. The cross section of the intermediate image or of the image of the light wavelength conversion element is embodied in a circular fashion in the case of a circular-disk-shaped light wavelength conversion element.

[0032] The light from the light wavelength conversion element of the light generating device 1 is thus light composed of portions of non-converted primary light of the blue-emitting laser diodes and the secondary light of the yellow phosphor, that is to say produces white, or multichromatic, light.

[0033] The light wavelength conversion element advantageously has a circular-disk-shaped emission surface or is itself embodied as a circular-disk-shaped light wavelength conversion element. Alternatively, the light wavelength conversion element can also have a polygonal contour, in particular a rectangular or square contour. The light emitting surface of the light wavelength conversion element facing the collimator lens 2 can also be provided with a cover, such that only a desired surface region, for example a circular-disk-shaped segment, contributes to the emission of light.

[0034] The surface of the light wavelength conversion element is advantageously configured in a planar fashion.

[0035] The diaphragm 5 is fitted in the abovementioned intermediate image plane, said diaphragm reflecting part of the beam path. In this case, the diaphragm 5 is positioned such that a region of the light beam path is covered in such a way that a correctly positioned bright-dark boundary forms in the far field. In this case, the edge of the diaphragm 5 is advantageously shaped rectilinearly. Alternatively, insofar as a non-straight bright-dark boundary is desired, a freeform edge shape of the diaphragm can be chosen.

[0036] In this case, the thickness of the diaphragm is chosen such that no disturbing cast shadows are formed. In this regard, the diaphragm thickness at the shading region can be from a few tenths of a millimeter to a few millimeters; alternatively, the diaphragm edge of the shading region can also taper in the shape of a knife edge and form a pointed edge. The diaphragm 5 can be embodied in a solid fashion, for example made from a metal having good thermal conductivity.

[0037] By means of the spherical mirror 6, that part of the light emitted by the light generating device 1 which is masked out by the diaphragm 5 is recycled and likewise used for generating the desired light distribution in the far field of the lighting apparatus or in the area in front of a motor vehicle headlight.

[0038] 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.