Laser light module for a vehicle headlight

Abstract

Laser light module (31) for a motor vehicle headlight (10) comprising a laser (18), a converter (22) arranged in the beam path of a laser radiation (30) emanating from the laser, which converter scatters part of the incident laser radiation from the laser and converts part of it into secondary radiation with a wavelength longer than that of the laser radiation, a detector (40) arranged in a beam path of radiation emanating from the converter and which generates a measured value as an actual value dependent on the amount of radiation emanating from the converter and incident on the detector, and a control unit (26) which compares the actual value with a target value and controls the laser depending on the comparison of the actual value with the target value, characterized in that the laser light module has a light deflection unit (20) with which different sub-areas (22.a, 22.1, 22.b) of the converter can be illuminated with laser radiation separately from each other in time and wherein the detector records sub-area-specific actual values ​​for different sub-areas and wherein the control unit is set up, in particular programmed, to determine the target value for a first sub-area as a function of an actual value that has been determined for a different sub-area.

Description

[0001] The present invention relates to a laser light module according to the preamble of claim 1 and a method according to the preamble of the independent method claim.

[0002] Such a laser light module is known from DE 10 2012 220 481 A1 and comprises a laser, a converter, a detector, and a control unit. The converter is arranged in the beam path of the laser radiation emanating from the laser and scatters a portion of the incident laser radiation and converts a portion of the incident laser radiation into secondary radiation with a longer wavelength than the laser radiation. The detector is arranged in the beam path of radiation emanating from the converter and generates a measured value, the actual value of which depends on the intensity of the radiation emanating from the converter and incident on the detector. The control unit compares the actual value with a setpoint and controls the laser accordingly.A ray path is understood to be a spatial region in which radiation propagates from a first location to a second location.

[0003] A generic method for controlling a laser light module of a motor vehicle headlight, comprising a laser, a converter arranged in the beam path of a laser radiation emanating from the laser, a detector which generates a measured value as an actual value dependent on an intensity of radiation emanating from the converter and incident on the detector, and a control unit which compares the actual value with a setpoint and controls the laser depending on the comparison of the actual value with the measured value, is also known from DE 10 2012 220 481 A1.

[0004] Laser-activated light generation using fluorescent lamps enables the creation of compact, high-luminance white light sources. This technique is known as LARP (Laser Activated Remote Phosphor). The incident laser radiation excites the lamp to fluoresce. The fluorescent light generated in the lamp has longer wavelengths and a wider spectral range than the incident laser light. By mixing light and, if applicable, radiation components with different wavelengths, the lamp emits mixed white light. Here, the term "radiation" also refers to components with wavelengths shorter than those of visible light. Ultraviolet radiation is an example of such radiation.

[0005] This technology enables the construction of headlights with extremely high illuminance, which are finding initial applications in the automotive sector. Further advantages of the technology include the fact that the high luminance allows for a reduction in geometric dimensions.

[0006] Generating luminous flux with lasers is still very expensive compared to generating comparable luminous flux with LEDs. Therefore, it is important to achieve the highest possible conversion efficiency for converting the laser radiation into white light, so that as few expensive lasers as possible are needed to produce a compliant headlight beam pattern.

[0007] Furthermore, the color tone of the white light should be as constant as possible within the light distribution.

[0008] One disadvantage of laser headlights is that if a headlight is damaged, laser radiation can escape from it undiminished. This risk is particularly high if the fluorescent lamp is damaged. Such damage can be caused by cracks resulting from aging, vibrations, or temperature fluctuations. While switching off the laser in case of a defect prevents an undesirable increase in the laser radiation intensity emitted from the light module, it also severely impairs the headlight's ability to produce light.

[0009] AT 514 438 A4 discloses a vehicle headlight with a laser light source, the laser beam of which is deflected via a micromirror which can be pivoted about an axis to a luminous surface with a light conversion phosphor in order to scan this surface to create a luminous image which can be projected onto a roadway via optics.

[0010] In this headlight, a photosensor is positioned relative to the illuminating surface with the light conversion phosphor in such a way that it detects a secondary laser beam emanating from the illuminating surface in predetermined deflection positions of the micromirror and is set up to emit a signal.

[0011] US 8,400,011 B2 discloses a lighting device with a semiconductor laser element that serves as an excitation light source and emits laser light. A phosphor plate contains a phosphor to emit light of a desired color. A light-receiving element detects the light reflected from the phosphor plate. A light source control element controls the laser light emitted by the semiconductor laser element based on a detection signal from the light-receiving element.

[0012] Against this background, the object of the invention is to provide a laser light module of the type mentioned above, which has high efficiency and color stability, and in which the risk of laser light leakage through a defect is very low, and in which, in the event of a defect, an increase in the emitted laser radiation intensity can be avoided without impairing the light-generating function of the laser light module more than absolutely necessary. The most important advantage is the possibility of reliable and simple defect detection.

[0013] This problem is solved with regard to the apparatus aspects of the invention by the features of claim 1 and differs from the prior art mentioned at the outset by the characterizing features of claim 1.

[0014] The headlight according to the invention is therefore characterized in that the laser light module has a light deflection unit with which different sub-areas of the converter can be illuminated with laser radiation separately from one another in time, and wherein the detector records sub-area-specific actual values ​​for different sub-areas, and wherein the control unit is set up, in particular programmed, to determine the target value for a first sub-area as a function of an actual value that has been determined for another sub-area.

[0015] With regard to its process aspects, the present invention is characterized in that different sub-areas of the converter are illuminated with laser radiation at different times, sub-area-specific actual values ​​are recorded for different sub-areas, a target value for a first sub-area is determined as a function of an actual value that has been determined for another sub-area, the target value formed for the first sub-area is compared with the actual value recorded for this first sub-area, and that if the deviation of the actual value from the target value exceeds a predetermined threshold, the radiation directed on the corresponding sub-area of ​​the converter is reduced.

[0016] By reducing the radiation directed at the area where a deviation exceeding the threshold has been detected, an undesirable increase in the emitted laser radiation intensity can be avoided. Because this reduction is performed individually for each area, the intensity of the laser radiation directed at the remaining areas can be maintained, thus preserving the light-generating function of these areas or allowing the headlight to operate at least until the next repair opportunity.

[0017] A preferred embodiment is characterized in that the laser is a laser diode whose radiant power is controlled by the control unit and which laser diode emits the laser radiation with wavelengths from the ultraviolet or blue part of the electromagnetic wave spectrum.

[0018] It is also preferred that the laser light module has a first beam shaping optic, which has a converging lens and / or a focusing concave mirror reflector and / or a focusing catadioptric optic and is arranged in the beam path between the laser and the light deflection unit.

[0019] Furthermore, it is preferred that the converter consists of a material that is excited to fluorescence by the incident laser radiation.

[0020] Another preferred embodiment is characterized by the fact that the light deflection unit has a micromirror coupled to an actuator and moving quickly.

[0021] It is also preferred that the actuator is an electrostatically operating MEMS actuator (MEMS = micro electromechanical system) and forms the light deflection unit together with the micromirror.

[0022] Furthermore, it is preferred that the converter is arranged in a converter-side focal area of ​​a projection optic.

[0023] Another preferred embodiment is characterized by a beam splitter which is arranged in the beam path of the laser radiation emanating from the laser between the laser and the light deflection unit.

[0024] It is also preferred that the beam splitter consists of a dichroic mirror which has a high reflectance for fluorescence light generated by the converter from the laser radiation and which is arranged in such a way that it directs incident fluorescence light onto the detector.

[0025] Furthermore, it is preferred that the beam splitter is a metallically coated glass plate in which the thickness of the layer is so small that a high transmission is achieved for a beam path serving as a transmission channel, which leads from the laser via the beam splitter and the light deflection unit to the converter, and a much smaller reflection is achieved for another beam path serving as a detection channel, which leads from the converter via the light deflection unit and the beam splitter to the detector.

[0026] Another preferred embodiment is characterized by the fact that the transmission is greater than 95%, in particular equal to 98%, while the reflection is preferably less than 5%, in particular equal to 2%.

[0027] It is also preferred that the beam splitter is a polarizing beam splitter and that the laser emits light that is polarized in a direction that matches the polarization direction of the polarizing beam splitter.

[0028] Furthermore, it is preferred that the beam splitter is a glass plate arranged in the beam path at the known Brewster angle.

[0029] From a procedural perspective, one design is characterized by the fact that the radiation is reduced whenever the laser beam is directed at the relevant sub-area. It may also be possible to stop the laser beam entirely, particularly if the damage affects multiple sub-areas.

[0030] Further advantages will become apparent from the following description, the drawings, and the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the present invention.

[0031] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description.

[0032] These show, each in schematic form: Fig. 1 a motor vehicle headlight with a known laser light module; Fig. 2 the laser light module from the Fig. 1 with a damaged converter; Fig. 3 an embodiment of a laser light module according to the invention; Fig. 4 the laser light module from the Fig. 3 with a damaged converter; Fig. 5 a further embodiment of a laser light module according to the invention; and Fig. 6 A flowchart as an example of process aspects of the invention.

[0033] In this context, identical reference symbols in different figures denote identical elements or at least elements comparable in function.

[0034] In detail, the Fig. 1. A motor vehicle headlight 10 with a housing 12, the light output aperture of which is covered by a transparent cover plate 14. A laser light module 16 is arranged inside the housing 12. The laser light module 16 comprises a laser 18, a light deflection unit 20, a converter 22, a projection optic 24, and a control unit 26. Optionally, the laser light module 16 also comprises a first beam shaping optic 28.

[0035] The laser 18, for example, is a laser diode whose radiation power is controlled by the control unit 26 and which laser diode emits laser radiation 30 with wavelengths from the ultraviolet (370 to 420 nm wavelength) or blue part (440 to 460 nm wavelength) of the electromagnetic wave spectrum.

[0036] The laser radiation 30 is directed towards a micromirror 32 of the deflection unit 20. The beam shaping optics 28 have a converging lens and / or a focusing concave mirror reflector and / or a focusing catadioptric optics and are arranged in the beam path between the laser 18 and the light deflection unit 20 and focus the laser radiation 30 onto the converter 22.

[0037] The light deflection unit 20 directs the laser radiation 30 successively onto different sub-areas 22a, 22b of the converter 22. Beams 30a and 30b represent beams emanating from the light deflection unit 20 at different times, illuminating different sub-areas 22a, 22b of the converter 22. Beam 30a results from a first mirror position, and beam 30b corresponds to a second mirror position of the micromirror 32, with the laser beam scanning a total area of ​​approximately 2 to 3 cm horizontally and approximately 1 cm vertically. These figures are to be understood as rough guidelines only. The size of the sub-areas is determined by the spot size of the laser on the converter and is typically 0.1 to 1 mm.

[0038] Converter 22 consists of a material that is excited to fluorescence by the incident laser radiation 30, 30a, 30b. Such converters, for example, consist of cerium-doped YAG phosphorus and are known from the prior art. A portion of the primary laser radiation incident on converter 22, whether ultraviolet or blue light, is converted into secondary radiation in the form of fluorescent light from the yellow / red part of the electromagnetic spectrum. Another portion of the focused incident primary laser radiation is scattered in converter 22 without wavelength conversion.

[0039] With a suitable intensity ratio of scattered primary radiation and wavelength-converted secondary radiation, additive mixing produces white mixed light 34, which is also usable as headlight light in terms of its color tone. The white mixed light 34 emanating from the converter 22 is directed by the projection optics 24, which may include a lens and / or a reflector and / or a catadioptric optic, through the transparent cover plate 14 into the area in front of the headlight, where, in normal use, the road is located.

[0040] The mirror or micromirror 32 of the light deflection unit 20 is coupled to an actuator 36, for example, an electrostatically operating MEMS actuator, and is rapidly movable. The actuator 36, together with the micromirror 32, forms a preferred example of a light deflection unit 20. Such an actuator-mirror combination is known, for example, from the publication "Micro Machines 2012, 3(2), 509-528: http: / / www.mdpi.com / 2072-666x / 3 / 2 / 509)." According to this publication, the micromirror can be adjusted at a frequency in the kHz range, where adjustment here refers to a change in the angle between the mirror surface and the direction of the incident beam. The actuator 36, and thus the angular position of the micromirror 32 in the laser beam path, is preferably controlled by the control unit 26.By controlled movement of the micromirror 32, the laser beam 30a, 30b can be directed in rapid succession onto different sub-areas of the converter 22, so that different sub-areas of the converter 22 are excited to emit white mixed light 34. Examples of such sub-areas are sub-areas 22a, 22b. The converter 22 is preferably arranged in the converter-side focal area of ​​the projection optics 24 and is therefore imaged by the projection optics 24 into the foreground of the spotlight 10.

[0041] Depending on the position of the micromirror 32, a different point or small area in the headlight field is illuminated. A specific light distribution is generated by moving the micromirror 32 across the converter 22 in a sequence, whereby the shape of the desired light distribution results from the sum of all sequentially illuminated small areas. The sequence is continuously repeated at such a high frequency (> 100 Hz) that the human eye perceives only a moderate brightness in the repeatedly illuminated small areas. Virtually any desired light distribution can be generated by the controlled scanning movement of the laser beam 30 across the converter surface. This is particularly true when the control unit 26 modulates the laser radiation power synchronously with the scanning.

[0042] Fig. Figure 2 shows elements of the laser light module 16 from the Fig. 1, where converter 22 here, in contrast to the Fig. 1. shows damage. This damage is located in the Fig. 2 in a central sub-area 22.1 of the converter 22. As a result of the damage, which may be, for example, a crack or the detachment of part of the converter 22's material from a transparent support, a locally increased transmission of the converter 22 occurs. Consequently, whenever the light deflection unit 20 directs the laser beam 30 onto the damaged area 22.1 of the converter 22, high-energy laser radiation 30 passes through the converter 22 and is directed by the projection optics 24 into the headlight field, which is undesirable.

[0043] The damage can be detected with the laser spotlight according to the invention. If such damage is detected, the invention enables a reduction or even a prevention of the unwanted emission of laser radiation by intervening in the control of the laser power.

[0044] Fig. Figure 3 shows an embodiment of a laser light module 31 according to the invention. The laser light module 31 according to the invention is based on the known laser light module 16 of the Fig. 1. In that respect, the description of the Fig. 1 and the features shown therein also as a description of the Fig. 3 and the features shown therein are to be understood, unless expressly described otherwise.

[0045] The one in Fig. The embodiment 3 shown of a laser light module 31 according to the invention has, in addition to the features already described in the Fig. The features shown in Figure 1 include a beam splitter 38 and a detector 40. Furthermore, the control unit 26 is configured to evaluate signals received from the detector 40.

[0046] In this context, the term "control unit" refers to all electronic assemblies that output and process signals, are not part of the detector or the actuator, and are involved in controlling the beam direction and evaluating the detector signals, regardless of whether these assemblies are combined into a single structural unit and / or in a common housing, or whether they are distributed throughout the headlight. In the illustrated embodiment, the control unit 26 is configured to evaluate signals from the detector 40 and to control the light deflection unit 20 and the laser 18.

[0047] In a first preferred embodiment, the beam splitter 38 consists of a dichroic mirror that transmits the blue or ultraviolet laser radiation and reflects the fluorescence light generated in the converter 26. The fluorescence light generated in the converter does not have a pronounced preferred direction and is therefore partially emitted in the direction of the micromirror 32. The micromirror 32 reflects incident fluorescence light onto the beam splitter 38, which has a high reflectivity for fluorescence light and is arranged such that it directs incident fluorescence light onto the detector 40.

[0048] A beam path leading from the laser 18 via the beam splitter 38 and the light deflection unit 20 to the converter 22 is hereinafter also referred to as the transmission channel. Another beam path leading from the converter 22 via the light deflection unit 20 and the beam splitter 38 to the detector 40 is hereinafter also referred to as the detection channel.

[0049] In a second preferred alternative, the beam splitter is coated such that a large amount of light (preferably more than 98%) is directed into the transmission channel and only a small amount of light, preferably less than 2%, is directed into the detection channel. The transmission is preferably greater than 95%, and particularly equal to 98%, while the reflection is then necessarily less than 5%.

[0050] In a third preferred alternative, the beam splitter is a so-called polarizing beam splitter, and the laser emits radiation that is preferably polarized in a direction that coincides with the polarization direction of the polarizing beam splitter. This light is then transmitted by the beam splitter in the transmission channel with only small losses. The light scattered from the converter into the reflection channel is partially depolarized, and thus a portion of this light is directed from the beam splitter to the detector. With total depolarization, this portion is 50% of the total light scattered from the converter into the reflection channel.

[0051] A fourth preferred alternative beam splitter is a glass plate arranged in the beam path at the known Brewster angle. At the Brewster angle, polarized laser light, whether fully polarized or only partially polarized, is transmitted in the transmission channel with high transmission (more than 80%), and the laser light scattered by the converter into the detection channel, and thus depolarized, is reflected by more than 10% and therefore partially directed towards the detector. Optionally, the laser light module also includes the first beam shaping optics and a wavelength-selective filter 42.

[0052] The wavelength-selective color filter is preferably arranged in the beam path between the beam splitter 38 and the detector 40 and serves to improve the detection sensitivity. The wavelength-selective color filter 42 is configured to transmit either preferably the laser light, in particular only the laser light, or preferably the fluorescence light, in particular only the fluorescence light.

[0053] The following describes the function of the light module 31 according to the invention with regard to the detection of damage to the converter 22. For this purpose, an undamaged converter 22 is initially assumed.

[0054] The laser beam generated by the laser passes through the beam splitter 38 and is shaped by the first beam shaping optics 28 and guided via the light deflection unit 20 to the converter 22. The laser beam is moved across the converter by means of the scanner / light deflection unit 20, whereby, for example, the beam between beams 30a and 30b in the Fig. One horizontal angle is swept over.

[0055] A small portion of the laser radiation incident on the converter (primary radiation) is reflected by the converter material or scattered back towards the micromirror 32. Similarly, a certain portion of the secondary radiation, which is emitted in principle in all directions, is also emitted towards the micromirror. At the micromirror 32, the radiation incident there from the currently illuminated section of the converter 22 is reflected via the first beam-shaping optic 28 onto the beam splitter 38. The beam splitter divides a portion of this radiation from the beam path directed from the first beam-shaping optic 28 to the laser 18 and directs it onto the detector 40, which is sensitive to at least one component of the radiation, be it the primary radiation (laser radiation) or the secondary radiation (fluorescence light).

[0056] The power of the radiation incident on the detector 40 from the beam splitter 38 is reflected in the detector signal. The detector signal is evaluated in the control unit 26.

[0057] During the scanning process, the laser beam emanating from the light deflection unit 20 (scanner) moves across the surface of the converter 22. For an undamaged, homogeneous converter 22, the proportion of light (fluorescent light or scattered laser light) entering the detection channel from the converter 22 should be nearly constant relative to the laser intensity. A homogeneous converter 22 is defined as one that reflects uniformly across its surface. This requires, in particular, a constant thickness and material composition across the scanned area. The portion of the radiation reflected back from the converter 22 to the scanner should be approximately proportional to the instantaneous radiant power of the laser.

[0058] This condition is detected by directing the light (fluorescent light or scattered laser light) backscattered by the converter 22 onto the detector 40 via the beam splitter 38. With an undamaged converter 22, the output signal of the detector 40 then only reflects the modulation of the laser radiation power specified by the control unit 26. With an undamaged, homogeneous converter 22 and a constant radiation power independent of location (i.e., irradiation independent of the currently irradiated section of the converter 22), the backward-scattered light component (fluorescent light or scattered laser light) should then be nearly constant. However, there can also be special converter designs that, for example, exhibit a targeted variation, such as becoming increasingly efficient near the area that is represented as the light-dark boundary.

[0059] Fig. 4 shows the subject of the Fig. 3 with a locally damaged converter. The damage is located, as with the object of the Fig. 2, in the middle area 22.1 of converter 22.

[0060] Such localized damage is associated, for example, with a crack or chipping of material. As a result, the transmission of the laser radiation converter increases in that area, so that more unconverted, high-energy laser radiation exits the headlight at precisely that damaged section than would be the case without the damage.

[0061] As a result of the locally increased transmission of the converter 22 for the laser radiation incident there, the reflected light component decreases at exactly this point.

[0062] The control unit 26 detects this drop by evaluating the detector signal. Simultaneously, the control unit 26 can assign the drop to a location / sub-area on the converter because the control unit 26 also controls the light deflection unit 20 and thus determines which sub-area of ​​the converter the laser beam 30 is currently directed at.

[0063] In this way, the invention allows spatially resolved detection of defects in the converter layer for sub-areas of the converter layer by means of spatially resolved analysis of the changes in the radiation components led from the converter 22 to the detector 40.

[0064] The signal strength of the back-reflected light is preferably normalized to the current light power of the laser. This is preferably done by dividing the detector signal by the laser's radiant power. Changes in the back-reflected light component can be detected very sensitively, as they are insensitive to temperature fluctuations and aging processes of the converter and laser. This design is particularly advantageous when the laser's light power is modulated depending on the desired light distribution.

[0065] In a preferred embodiment, the control unit is configured to reduce the laser power to a safe level when a fault is detected.

[0066] It is particularly preferred that the control unit is configured to reduce the radiant power only at the critical, damaged section of the converter. This ensures that the headlight can continue to be used, at least partially, until the next service appointment, even if the converter is damaged, and does not fail completely. This reduced operating state is only possible with spatially resolved fault correction, as enabled by the invention.

[0067] Fig. Figure 5 shows a further embodiment of device aspects of the invention. In this embodiment, the converter 22 is provided with a reflective coating 23. The reflective coating 23 is arranged on a side of the converter 22 that faces away from both the laser radiation incident from the laser 18 and the projection optics. In contrast to the embodiments of the Fig. 3 and Fig. 4, in which the operation of the converter 22 can be described as transmission operation due to its arrangement in the beam path and its design without a reflective layer, the converter 22 is in the Fig. 5 is arranged in the beam path and designed with its reflective layer 23 in such a way that its operation can be described as reflective operation. From a purely functional point of view, the transmission channel of the objects is defined according to the Fig. 3 and Fig. 4 regarding the subject of the Fig. 5 replaced by a reflection channel. The embodiment according to the Fig. 5 is characterized by a difference compared to the embodiments of the Fig. 3 and Fig. 4 increased conversion efficiency, i.e. a higher fraction of the primary radiation that is converted into secondary radiation of longer wavelength.

[0068] In the event of damage to a section of converter 22, less primary radiation is converted into secondary radiation in the damaged section than would be the case without the damage, even in this embodiment. Consequently, in this embodiment as well, more primary radiation is emitted from the damaged section than from the undamaged section, which is undesirable.

[0069] Another difference in the subject matter of the Fig. 5 to the items of the Fig. 3 and Fig. 4 consists in the arrangement of the detector 40. Regarding the subject of the Fig. 3 and Fig. 4. It was possible to distinguish a detection channel from a transmission channel. Regarding the subject of the Fig. 5. Does the reflection channel fulfill the function that the transmission channel performs in the object of the Fig. 3 and Fig. 4 is fulfilled. Due to their function of transporting light, both the reflection channel and the transmission channel each represent a transport channel.

[0070] Regarding the subject of Fig. 3 and Fig. 4 The light deflection unit 20 is located in the transport channel and in the detection channel. The detection channel leads there ( Fig. 3, Fig. 4) from the converter via the light deflection unit and the beam shaping optics 28 and the optionally available filter 42 to the detector 40. Regarding the object of the Fig. The deflection unit is located in the transport channel (position 5), but not in the detection channel. The detection channel extends along the Fig. 5 from converter 22 to detector 40, without passing through the light deflection unit 20. The detection channel thus runs separately from the light deflection unit 20. In a preferred embodiment, a further beam-shaping optic 44, preferably implemented as a lens, collects light emanating from the converter surface and directs the collected light onto the detector 40. Imaging of the converter surface is not necessary, so a simple optic, such as a single plastic lens, is sufficient. Spatially resolved detection is achieved, as in the embodiment of Fig. 3, achieved via the light deflection unit 20.

[0071] In one embodiment, the detector arrangement is arranged according to the Fig. 3 and Fig. 4 in conjunction with the remaining item, i.e., the item not relating to the detector arrangement, of the Fig. 5 is used. Conversely, in a further embodiment, the detector arrangement is arranged according to the Fig. 5 in conjunction with the remaining item, i.e., the item not relating to the detector arrangement, of the Fig. 3 and Fig. 4 used.

[0072] Just as in the embodiment according to the Fig. 3 and Fig. 4. The intensity of the radiation propagating in the detection channel also changes at the object of the Fig. 5. This occurs when the laser beam scanning the converter sub-areas hits a damaged sub-area. In the reflected arrangement, the reflected laser light and / or the fluorescence light can again be used for detection.

[0073] The Fig. Figure 6 shows an embodiment of a method according to the invention. The control unit 26 is configured, and in particular programmed, to execute the method by processing the program. In step 100, the light deflection unit 20 and the laser radiation power are controlled as described above with the aim of generating a desired light distribution.

[0074] In step 102, the signals from detector 40 are read in with spatial resolution relative to the surface of the converter. Spatial resolution in this context means that signals from the detector are read in individually for different sub-areas of the converter.

[0075] In step 104, the spatially resolved signals are evaluated to detect damage to the converter. In one embodiment of step 104, a setpoint for the radiation incident on the detector in the detection channel is established for a first sub-section of the converter. This setpoint is preferably determined as a function of the radiation propagated to the detector in the detection channel from at least one other sub-section of the converter. Most preferably, the setpoint is calculated as the average of the radiation incident on the detector in the detection channel from sub-sections of the converter adjacent to the first sub-section. Modulation to generate the desired light distribution is preferably taken into account.

[0076] In step 106, the target value calculated for the first sub-area is compared with the actual value of the radiation incident on the detector in the detection channel. If the deviation of the actual value from the target value does not exceed a predetermined threshold, which is, for example, a specified fraction of the target value, the first sub-area is considered undamaged. In this case, the procedure branches back to step 100 and checks the next sub-area. If the converter is undamaged, the loop formed by steps 100 to 106 is repeated while simultaneously scanning the converter's surface, traversing each sub-area from the first to the last (and then back to the first). Fig. 5 not shown). A modulation of the laser radiation power carried out in step 100 with the aim of generating a specific light distribution is not changed.

[0077] If, however, the deviation of the actual value from the target value exceeds the predetermined threshold, the program branches to step 108. In step 108, which is reached when a section of the converter is damaged, the value applied to the damaged section in the transmission channel of the Fig. 3, Fig. 4 or reflection channel of the Fig.5. Directed radiation is reduced. This is preferably achieved by reducing the laser radiation power whenever the laser beam is directed at the damaged area. In the undamaged areas, the laser radiation power is preferably not reduced. As an alternative or supplement to reducing the laser radiation power, one embodiment modifies the control of the light deflection unit so that the laser beam is no longer directed at the damaged area. Optionally, an error message is stored and / or displayed to the driver so that the fault can be easily noticed during maintenance and / or the driver is alerted to the limitation. From step 108, the program returns to step 100.In the subsequent control process in step 100, the sub-area-specific restrictions implemented in step 108 are maintained and / or taken into account. In case of an error, the loop from steps 100 to 108 is therefore executed repeatedly.

[0078] As a result, the laser radiation source is controlled spatially (i.e., section-specifically) depending on the results of the evaluations of the spatially resolved signals from detector 40. In a preferred embodiment, the spatially resolved control is achieved such that the laser's radiation power is reduced precisely when the deflection unit directs the laser beam onto a damaged section of the converter. It can also be provided that the laser power is reduced overall for all positions. In a further embodiment, the setpoint for comparison is determined by storing identical setpoint values ​​for all positions of the light deflection unit in a memory.Each position of the light deflection unit determines the position of the laser beam on the converter, i.e., the respective illuminated area, and thus indirectly also angular positions within the light distribution, as they are displayed as horizontal and vertical angles on a screen in front of the vehicle during normal use. In a further embodiment, local upper and lower setpoint values ​​of the detector signal are stored in a memory of the control unit for specific positions of the light deflection unit, in particular for all positions. If the measured actual value of the detector signal lies outside a permissible deviation from these setpoint values, this is interpreted as damage to the converter specific to that area, and the laser beam is switched off or at least attenuated for the damaged area. In a preferred embodiment, the setpoint values ​​are automatically adjusted after a learning cycle.It is also preferred to use individual target values ​​with regard to the color of the detected light.

[0079] To determine or better define the target values / thresholds of the arrangement / sub-areas, a learning cycle can be implemented before the headlight's initial operation. During this cycle, the laser beam scans the area, and the target values ​​are determined based on the actual values ​​of the undamaged headlight. This determination of the target values ​​can also be repeated each time the headlight is used, assuming it is undamaged. The laser energy can also be gradually increased to full operating level.

Claims

[1] Laser light module (31) for a motor vehicle headlight (10) comprising a laser (18), a converter (22) arranged in the beam path of a laser radiation (30) emanating from the laser, which converter scatters part of the incident laser radiation from the laser and converts part of it into secondary radiation with a wavelength longer than that of the laser radiation, a detector (40) arranged in a beam path of radiation emanating from the converter and which generates a measured value as an actual value which depends on the amount of radiation emanating from the converter and incident on the detector, and a control unit (26) which compares the actual value with a setpoint and controls the laser depending on the comparison of the actual value with the setpoint, characterized by, that the laser light module has a light deflection unit (20) with which different sub-areas (22.a, 22.1, 22.b) of the converter can be illuminated with laser radiation separately from one another in time and wherein the detector records sub-area-specific actual values ​​for different sub-areas and wherein the control unit is set up, in particular programmed, to determine the setpoint for a first sub-area as a function of an actual value that has been determined for a different sub-area. [2] Laser light module (31) according to claim 1, characterized by , that the laser (18) is a laser diode whose radiant power is controlled by the control unit (26) and emits the laser radiation (30) with wavelengths from the ultraviolet or blue part of the electromagnetic wave spectrum. [3] Laser light module (31) according to any one of the preceding claims, characterized by, that the laser light module has a first beam shaping optic (28) which has a converging lens and / or a focusing concave mirror reflector and / or a focusing catadioptric optic and is arranged in the beam path between the laser (18) and the light deflection unit (20). [4] Laser light module (31) according to any one of the preceding claims, characterized by , that the converter (22) consists of a material which is excited to fluorescence by the incident laser radiation (30, 30a, 30b). [5] Laser light module (31) according to any one of the preceding claims, characterized by , that the light deflection unit (20) has a rapidly moving micromirror (32) coupled to an actuator (36). [6] Laser light module (31) according to claim 5, characterized by that the actuator is an electrostatically operating MEMS actuator and together with the micromirror (32) forms the light deflection unit (20). [7] Laser light module (31) according to any one of the preceding claims, characterized by , that the converter (22) is arranged in a converter-side focal area of ​​a projection optic (24). [8] Laser light module (31) according to any one of the preceding claims, characterized by a beam splitter (38) which is arranged in the beam path of the laser radiation emanating from the laser between the laser and the light deflection unit. [9] Laser light module (31) according to claim 4, characterized by , that the beam splitter (38) consists of a dichroic mirror which has a high reflectance for fluorescence light generated by the converter from the laser radiation and which is arranged in such a way that it directs incident fluorescence light onto the detector (40). [10] Laser light module (31) according to claim 8, characterized by, that the beam splitter (38) is a metallically coated glass plate, in which the thickness of the layer is so small that a high transmission is achieved for a beam path serving as a transmission channel, which leads from the laser (18) via the beam splitter (38) and the light deflection unit (20) to the converter (22), and a smaller reflection is achieved for another beam path serving as a detection channel, which leads from the converter (22) via the light deflection unit (20) and the beam splitter (38) to the detector (40). [11] Laser light module (31) according to claim 10, characterized by that the transmission is greater than 95%, in particular equal to 98%, while the reflection is preferably less than 5%, in particular equal to 2%. [12] Laser light module (31) according to claim 8, characterized by, that the beam splitter (38) is a polarizing beam splitter and that the laser emits light that is polarized in a direction that matches the polarization direction of the polarizing beam splitter. [13] Laser light module (31) according to claim 8, characterized by , that the beam splitter (38) is a glass plate arranged in the beam path at the known Brewster angle. [14] Method for controlling a laser light module (31) of a motor vehicle headlight (10) comprising a laser (18), a converter (22) arranged in the beam path of a laser radiation (30) emanating from the laser, a detector (40) which generates a measured value as an actual value dependent on an amount of radiation emanating from the converter and incident on the detector, and a control unit (26) which compares the actual value with a setpoint and controls the laser depending on the comparison of the actual value with the setpoint, characterized by, that different sub-areas (22.a, 22.1, 22.b) of the converter are illuminated with laser radiation at different times, sub-area-specific actual values ​​are recorded for different sub-areas, a target value for a first sub-area is determined as a function of an actual value that has been determined for another sub-area, the target value formed for the first sub-area is compared with the actual value recorded for this first sub-area, and then, if the deviation of the actual value from the target value exceeds a predetermined threshold, the radiation directed on the corresponding sub-area of ​​the converter is reduced. [15] Method according to claim 14, characterized by , that the radiation is always reduced when the laser beam is directed at the corresponding sub-area.

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