Headlights with optical arrangement

Description

[0001] Headlight with an optical arrangement The invention relates to a headlight with an optical arrangement.

[0002] This patent application claims priority from German patent application 10 2016 107 011. 4.

[0003] US 2008 / 0198372 A1 discloses a motor vehicle headlight in which the light emitted by a light source is modified by a spatial light modulator (SLM) to achieve a desired light distribution in front of the vehicle. The SLM has a two-dimensional array of pixels that generates a light distribution in the image plane corresponding to the pixel array.

[0004] This type of spatial modulation of the light distribution takes advantage of the fact that individual pixels of the SLM can be electronically controlled to become transparent, while the remaining pixels are reflective or absorbent. In this way, a desired light distribution can be created. However, it is accepted that the light from the light source that strikes the non-transparent pixels is lost from the total emitted light output.

[0005] Another known method for generating spatial light distribution uses an electronically controlled oscillating mirror to deflect a laser beam. However, this method requires high-frequency and usually complex control of the oscillating mirror. Furthermore, this method is relatively susceptible to vibrations, which can be particularly problematic when used in automotive headlights.

[0006] The invention is based on the object of providing an optical arrangement for a headlight with which a desired spatial radiation characteristic of the headlight can be specifically adjusted without significant portions of the light output emitted by the light source being lost due to reflection or absorption. Furthermore, the optical arrangement should be relatively insensitive to vibrations.

[0007] This object is achieved by the headlight according to independent claim 1. Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0008] The headlight comprises an optical arrangement and further comprises at least one aperture for absorbing light deflected by the diffractive optical element into diffraction orders outside the first diffraction order. The at least one aperture is arranged such that light emitted into the 0th diffraction order, the 2nd diffraction order, higher diffraction orders, or negative diffraction orders (-1st diffraction order, -2nd diffraction order, etc.) is absorbed by the aperture.

[0009] In the case of a headlight with an optical arrangement, a desired spatial radiation characteristic of the headlight is generated by achieving a desired intensity distribution in the first order of diffraction using the diffractive optical element. This makes it possible to deflect the majority of the emitted optical power into the first order of diffraction and simultaneously set a desired spatial radiation characteristic. The modification of the light distribution takes place in the case of a headlight with an optical arrangement.

[0010] Arrangement not by adjustable absorption or reflection, which would result in losses, but by a targeted distribution of the light output in diffraction orders.

[0011] By calculating the phase function of the diffractive optical element using an iterative Fourier transform algorithm (IFTA), the intensity in the first diffraction order can be controlled with high spatial resolution. This allows the headlight to generate virtually any intensity distribution, allowing almost all of the light energy to be utilized. The production of a diffractive optical element using an iterative Fourier transform algorithm is known per se from the publication DE 102013003441 A1 and will therefore not be explained in detail here.

[0012] Compared to generating a spatial intensity distribution using an oscillating mirror, the advantages of the spotlights with an optical arrangement described here lie in their lower vibration sensitivity and a higher light conductance (etendue) of the optical arrangement. High-frequency modulation of the laser light source and complex synchronous data processing are advantageously not required.

[0013] In the invention, at least 80% of the light power emitted by the at least one laser light source is diffracted into the first diffraction order. Particularly preferably, at least 85% of the emitted light power is diffracted into the first diffraction order. Thus, a very high proportion of the emitted light power can be emitted by the headlight.

[0014] If the diffractive optical element fails, the optical arrangement advantageously produces only the 0th order of diffraction, which is absorbed at the aperture. This is particularly advantageous for safety reasons due to the use of a laser light source. In contrast, if, for example, an oscillating mirror is not used for beam deflection in accordance with the invention, there could be a risk that a high light output concentrated at one point would be emitted from the headlight if the electronic control system failed. In the optical arrangement described here, a measurement of the intensity in the aperture plane can also be used for a safety shutdown. For this purpose, the optical arrangement can, for example, have a detector in the area of ​​the aperture for such a safety shutdown.

[0015] According to at least one embodiment, the diffractive optical element has a temporally variable diffraction structure. In this case, the diffraction structure is temporally variable, in particular by electronic control.

[0016] In this embodiment, the diffractive optical element is preferably a phase-shifting LCoS display (liquid crystal on silicon) or a phase-shifting micromirror array (piston micromirror array). The electronic control of a phase-shifting LCoS display or a phase-shifting micromirror array is advantageously comparatively simple; in particular, no high-frequency modulation of the laser light source and no complex synchronous data processing are necessary.

[0017] In an alternative embodiment, the diffractive optical element has a static diffraction structure. In this case, the diffraction structure cannot be changed over time. In this embodiment, the diffractive optical element is, for example, a surface grating or a computer-generated hologram (CGH). The diffractive optical element can be designed, for example, as a transmission diffraction grating or as a reflection diffraction grating. The diffractive optical element is manufactured, for example, lithographically by producing a surface structure in a carrier. The carrier can in particular be a transparent carrier. The surface structure can be calculated, as described above, for example using an iterative Fourier transform algorithm to achieve a desired phase function.

[0018] In one embodiment of the optical arrangement, the diffractive optical element is configured to perform a rotational movement about at least one axis and / or a translational movement in at least one direction. In particular, the diffractive optical element can have an electronically controllable drive for performing the rotational movement or translational movement. In this embodiment, the movement of the diffractive optical element can bring about a change in the light distribution, for example to adapt the emitted light distribution to various functions of the headlight. In this way, the emitted light distribution can be varied even when using a diffractive optical element with a static diffraction structure.

[0019] According to an advantageous embodiment, a lens follows the diffractive optical element in the beam path, which lens is particularly suitable for generating an intermediate image of the light diffracted by the diffractive optical element. The lens functions in particular as a Fourier lens. The lens is arranged in the beam path of the optical arrangement, in particular between the diffractive optical element and the aperture.

[0020] In one embodiment, the lens following the diffractive optical element is movable. In this case, the lens is advantageously configured to perform a rotational movement about at least one axis and / or a translational movement in at least one direction. In particular, the lens can have an electronically controllable drive for performing the rotational movement or translational movement. In the case of a translational movement, the lens is displaced, for example, perpendicular to the optical axis. A rotational movement of the lens can influence the beam deflection, in particular if the lens is not rotationally symmetrical or the pivot point is not on the optical axis. The movement of the lens can bring about a change in the light distribution, for example to adapt the emitted light distribution to various functions of the headlight.In this way, the emitted light distribution can be varied even when using a diffractive optical element with a static diffraction structure. When using a movable lens, the diffractive optical element itself does not need to be movable to vary the light distribution over time. The movable diffractive optical element and the movable lens thus represent alternative options for enabling a variable light distribution with a static diffraction structure, thus adapting the headlight's beam characteristics to different lighting situations.

[0021] According to at least one embodiment, the at least one laser light source is a semiconductor laser. This allows for a particularly compact design and high efficiency.

[0022] The headlight with optical arrangement can advantageously have a plurality of laser light sources, in particular a plurality of semiconductor lasers. For example, a plurality of laser light sources can be provided, the beams of which impinge on the diffractive optical element next to one another. In this case, the radiation from the plurality of laser light sources can be combined into an intermediate image by a lens acting as a Fourier lens downstream of the diffractive optical element. In a further embodiment, the beams from a plurality of laser light sources can impinge on the diffractive optical element at different angles. In this embodiment, the radiation from the plurality of laser light sources can also be combined into an intermediate image by a lens acting as a Fourier lens downstream of the diffractive optical element.The multiple laser light sources can be used for targeted three-dimensional adjustment of a light distribution, for example to focus the emitted light at different distances.

[0023] It is also possible for the radiation from multiple laser light sources to be combined before it strikes the diffractive optical element, for example by a beam splitter cube. In this way, in particular, the radiation from multiple laser light sources with different polarization directions can be combined, for example by a polarization beam splitter cube. In one embodiment, the multiple laser light sources can be provided for emitting light of different colors. In particular, it is possible for the optical arrangement to have multiple laser light sources of different colors in order to generate mixed light, in particular white light, through additive color mixing. For this purpose, semiconductor lasers of the colors red, green, and blue can be provided, for example.In this case, it is also possible that the optical arrangement has several semiconductor lasers for one or more of the colors, whereby the number of semiconductor lasers per color can be different (for example 2x green, 1x blue, 3x red).

[0024] In a further advantageous embodiment, the at least one laser light source emits light in the blue or ultraviolet spectral range, wherein a conversion element is arranged in the beam path for generating white light, which converts a portion of the emitted blue or ultraviolet light into light of a longer wavelength. The conversion element can have at least one conversion substance that absorbs a portion of the emitted blue or ultraviolet light and emits light of a longer wavelength, for example, yellow light, so that white mixed light is generated by mixing the blue or ultraviolet light with, for example, the yellow light of the conversion substance.

[0025] The headlight can in particular be a motor vehicle headlight.

[0026] The headlight can have at least one projection lens in the beam path behind the aperture of the optical arrangement, which is intended, for example, to expand the light distribution generated by the optical arrangement. The projection lens can be formed by an arrangement of several lenses. In the case of a motor vehicle headlight, for example, the light distribution generated by the optical arrangement is projected onto the road by the projection lens. Any imaging errors in the projection optics or laser collimation, such as defocus, spherical aberration, or longitudinal chromatic aberration, can be advantageously compensated by adapting the phase function generated in the diffractive optical element.

[0027] With the optical arrangement described herein, various light distributions, such as low beam, high beam, highway light, or cornering light, can be efficiently generated in a motor vehicle headlight. As described above, the light distribution can be specifically modified by an electronically controllable, time-variable diffractive optical element, by an electronically controllable, movable diffractive optical element, and / or by a movable lens following the diffractive optical element in the beam path. In this way, the light distribution can be adapted to the various lighting functions.

[0028] When using a temporally variable diffractive optical element, the beam angle of the headlight can advantageously be varied horizontally or vertically without mechanical adjustment elements. For example, it is possible to implement height correction in a vehicle headlight by adjusting the vertical linear phase of the diffractive optical element. Furthermore, cornering lights, for example, can be implemented by adjusting the horizontal linear phase of the diffractive optical element.

[0029] Additional functions can also be implemented with the optical arrangement in the headlight. For example, it is possible to highlight hazards, obstacles, or other areas through stronger illumination or a changed color temperature or color. It is also conceivable to project information onto the road or display a graphic sequence when the vehicle headlight is switched on.

[0030] Further advantageous embodiments of the headlight will become apparent from the following description of embodiments in connection with the Figures 1 to 6 .

[0031] They show: Figures 1 to 4 each a schematic representation of a cross section through an optical arrangement according to various embodiments, and Figures 5 and 6 a schematic representation of a cross-section through a region of the headlamp which includes the aperture of the optical assembly and a projection lens.

[0032] Identical or functionally identical elements are provided with the same reference numerals in the figures. The components depicted in the figures, as well as their relative sizes, are not to scale.

[0033] The Figure 1 The first embodiment of the optical arrangement shown has a laser light source 1, which is preferably a semiconductor laser. Following the semiconductor laser in the beam path is a collimating lens 2 to collimate the emitted light. The collimated light impinges on a diffractive optical element 3 in the optical arrangement, which in the embodiment of the Figure 1 is designed as a reflective diffractive optical element. The diffractive optical element 3 diffracts the light into several diffraction orders, Figure 1Light rays of the 1st diffraction order 6b, the 0th diffraction order 6c and the -1st diffraction order 6d are shown as examples.

[0034] The diffracted light rays are imaged into an intermediate image 6 by a lens 4 following the diffractive optical element 3 in the beam path. Further, following the diffractive optical element 3 and the lens 4 in the beam path is an aperture 7 arranged to transmit light of the first diffraction order 6b but absorb light of other diffraction orders. In particular, the 0th diffraction order 6c and the -1st diffraction order 6d, for example, are absorbed at the aperture 7.

[0035] The diffractive optical element 3 has a diffraction structure suitable for diffracting the majority of the emitted light into the first diffraction order 6b. At least 80% or even at least 85% of the light output emitted by the laser light source 1 is diffracted into the first diffraction order 6b. The losses occurring at the aperture 7 due to the absorption of the remaining diffraction orders are therefore minimal. The diffractive optical element 3 has a phase function that is preferably calculated using an iterative Fourier transform algorithm.

[0036] The diffractive optical element 3 can, in particular, be a time-variable diffractive optical element, such as a phase-shifting LCoS display or a phase-shifting micromirror array (piston micromirror array). In this way, the light distribution in the first diffraction order 6b, which is emitted through the aperture 7, can be specifically changed in order to adapt the radiation characteristics of the headlight to different lighting situations. For example, the radiation characteristics in the vertical direction can be changed by changing the phase in the vertical direction. In the case of a motor vehicle headlight, height adjustment can be achieved in this way, for example. Analogously, the radiation characteristics in the horizontal direction can be changed by changing the phase in the horizontal direction, for example to implement cornering lights.

[0037] Alternatively, it is also possible for the diffractive optical element 3 to have a static diffraction structure that does not change over time. In this case, a temporally variable radiation characteristic can be generated by moving the diffractive optical element 3 and / or the lens 4 via an electronic control. Both a translational movement and a rotational movement of the diffractive optical element 3 and / or the lens 4 are possible.

[0038] The Figure 2The second exemplary embodiment of an optical arrangement shown differs from the first exemplary embodiment in that the light source is formed by two laser light sources 1, which are preferably two semiconductor lasers 1. In this case, laser light of two different polarization directions is generated by the use of a polarization beam splitter cube 9, which is directed onto the diffractive optical element 3. Since the diffractive optical element 3 can have different diffraction properties for the light of the different polarization directions, the possibilities for targeted adjustment of the three-dimensional light distribution are expanded by the use of several laser light sources with different polarization directions. With regard to further advantageous configurations, the second exemplary embodiment otherwise corresponds to the first exemplary embodiment.

[0039] In a third embodiment of the optical arrangement, which is shown in Figure 3As shown, two laser light sources 1 are used, as in the second exemplary embodiment. In this exemplary embodiment, the emission directions of the laser light sources 1 run obliquely to one another, so that the emitted light strikes the diffractive optical element 3 at two different angles of incidence. The diffractive optical element 3 is in this case a transmissive diffractive optical element. In the beam path, behind the transmissive diffractive optical element 3, there are two Fourier lenses 4, each of which generates an intermediate image 6. In the beam path behind the diaphragms 7 of the optical arrangement, one or more projection lenses (not shown here) can be arranged in the headlight, which combine the light distributions generated in the two intermediate images 6, so that the emission characteristic of the headlight is formed by the combination of both light distributions.

[0040] In the Figure 4In the further exemplary embodiment shown, the optical arrangement contains a plurality of laser light sources 1a, 1b, 1c, which are semiconductor lasers of different colors. In particular, a first semiconductor laser 1a can emit blue light with a wavelength of, for example, approximately 450 nm, a second semiconductor laser 1b can emit green light with a wavelength of, for example, approximately 520 nm, and a third semiconductor laser 1c can emit red light with a wavelength of, for example, approximately 635 nm. Alternatively, it is also possible to use a plurality of semiconductor lasers of one color in order to increase the proportion of this color when mixing the color to form white light and thus specifically set a certain color temperature. For example, it would be possible to use one blue semiconductor laser, two green semiconductor lasers, and three red semiconductor lasers. In this way, for example, the red and green color components in the emitted light spectrum are increased.

[0041] In the illustrated embodiment, the light beams from the plurality of semiconductor lasers 1a, 1b, 1c impinge essentially parallel to one another on the diffractive optical element 3, which, as in the previous embodiment, is designed as a transmissive diffractive optical element. The diffraction orders of the individual laser beams generated by the diffractive optical element 3 are imaged into a common intermediate image by a lens 4 arranged downstream of the diffractive optical element 3 in the beam path. An aperture 7 is arranged in the plane of the intermediate image and absorbs light in diffraction orders 6c, 6d outside the first diffraction order 6b. Since the light from the differently colored semiconductor lasers 1a, 1b, 1c is superimposed in the optical arrangement, white light can advantageously be generated by additive color mixing of the colors red, green, and blue.

[0042] In Figure 51 shows a section of a region of the headlight according to a further exemplary embodiment, which comprises the aperture 7 and a subsequent projection lens 8. The optical arrangement up to the aperture 7 can, for example, be designed as in one of the previous exemplary embodiments and is not shown here for the sake of simplicity. The diffraction orders 6a, 6b, 6c, 6d generated by the diffractive optical element 3 impinge on the aperture 7 of the optical arrangement. The aperture 7 is arranged such that the light of the first diffraction order 6b can pass through the aperture 7, while the light of other diffraction orders 6a, 6c, 6d is absorbed at the aperture 7. The first diffraction order 6b transmitted by the aperture 7 has a light distribution generated by the diffractive element 3. A projection lens 8 is arranged behind the aperture 7 and, in the exemplary embodiment shown here, is formed from a two-part lens system.The projection lens 8 can, for example, increase the beam angle of the headlight.

[0043] In Figure 6 a further embodiment of a region of the headlight according to a further embodiment is shown, which essentially corresponds to the embodiment of the Figure 5 In contrast to the embodiment of the Figure 5 A conversion element 10 is arranged in the plane of the aperture 7, in particular in the passage opening of the aperture 7. By means of the conversion element 10, white light can advantageously be generated from the laser light in the first diffraction order 6b.

[0044] For this purpose, for example, the laser light source of the optical arrangement contains at least one semiconductor laser emitting in the blue or ultraviolet spectral range, and the conversion element 10 has at least one conversion substance suitable for converting a portion of the blue or ultraviolet light into a complementary color, for example, yellow light. By color mixing the blue or ultraviolet light and the complementary light emitted by the conversion substance, a white mixed layer is advantageously created, which is emitted by the headlight.

Claims

1. A headlight having an optical arrangement, the optical arrangement comprising - at least one laser light source (1), - a diffractive optical element (3) configured to diffract light emitted from the laser light source (1) into a plurality of diffraction orders, wherein a predominant part of the light is diffracted into the first diffraction order (6b), and - at least one diaphragm (7) which transmits the light of the first diffraction order and absorbs light in diffraction orders (6a, 6c, 6d) outside the first diffraction order (6b), wherein a phase function of the diffractive optical element (3) is calculated such that at least 80% of the light power emitted by the at least one laser light source (1) is diffracted into the first diffraction order.

2. The headlight according to claim 1, wherein the diffractive optical element (3) comprises a time-variable diffraction structure.

3. The headlight according to claim 2, wherein the diffractive optical element (3) is a phase-shifting LCoS display or a phase-shifting micromirror array.

4. The headlight according to claim 1, wherein the diffractive optical element (3) comprises a static diffraction structure.

5. The headlight according to claim 4, wherein the diffractive optical element (3) is a surface grating or a computer-generated hologram.

6. The headlight according to any one of the preceding claims, wherein the diffractive optical element (3) is configured to perform a rotational movement about at least one axis and / or a translational movement in at least one direction.

7. The headlight according to any one of the preceding claims, wherein a lens (4) for generating an intermediate image (6) of the light diffracted at the diffractive optical element (3) is arranged in the beam path downstream of the diffractive optical element (3), and wherein the lens (4) is configured to perform a rotational movement about at least one axis and / or a translational movement in at least one direction.

8. The headlight according to any one of the preceding claims, wherein the at least one laser light source (1) is a semiconductor laser.

9. The headlight according to any one of the preceding claims, comprising a plurality of laser light sources (1a, 1b, 1c).

10. The headlight according to claim 9, wherein the plurality of laser light sources (1a, 1b, 1c) comprise different colors for generating white light by additive color mixing.

11. The headlight according to any one of claims 1 to 9, wherein the at least one laser light source (1) emits blue light or ultraviolet light, and wherein a conversion element (10) is arranged in the beam path for generating white light, which converts a part of the emitted blue or ultraviolet light into radiation of a longer wavelength.

12. The headlight according to any one of the preceding claims, wherein the headlight is a motor vehicle headlight.