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DE-102015202253-B4 - Laser light module for a vehicle headlight

DE102015202253B4DE 102015202253 B4DE102015202253 B4DE 102015202253B4DE-102015202253-B4

Abstract

Laser light module (31) for a motor vehicle headlight (10) comprising a laser (18), a converter (22) arranged in the beam path of 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 setpoint and controls the laser depending on the comparison of the actual value with the setpoint, 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 one another in time, and wherein the detector is capable of sub-area-specific control for different sub-areas. Actual values recorded and wherein the control unit is set up, in particular programmed, to determine the target value for a first sub-area depending on an actual value that has been determined for a different sub-area.

Inventors

  • Joachim Knittel

Assignees

  • MARELLI GERMANY GMBH

Dates

Publication Date
20260513
Application Date
20150209

Claims (15)

  1. Laser light module (31) for a motor vehicle headlight (10) comprising a laser (18), a converter (22) arranged in the beam path of 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 setpoint and controls the laser depending on the comparison of the actual value with the setpoint, 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 one another in time, and wherein the detector is capable of providing sub-area-specific information for different sub-areas. Actual values are recorded and the control unit is configured, in particular programmed, to determine the target value for each initial sub-area depending on an actual value. determine which has been designated for a different sub-area.
  2. Laser light module (31) according to Claim 1 , characterized in 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 one of the preceding claims, characterized in 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 one of the preceding claims, characterized in 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 one of the preceding claims, characterized in that the light deflection unit (20) has a micromirror (32) coupled to an actuator (36) and moving quickly.
  6. Laser light module (31) according to Claim 5 , characterized in 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 one of the preceding claims, characterized in that the converter (22) is arranged in a converter-side focal area of a projection optic (24).
  8. Laser light module (31) according to 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 in 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 such that it directs incident fluorescence light onto the detector (40).
  10. Laser light module (31) according to Claim 8 , characterized in 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 in 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 in that the beam splitter (38) is a polarizing beam splitter and that the laser emits light that is polarized in a direction that corresponds to the polarization direction of the polarizing beam splitter.
  13. Laser light module (31) according to Claim 8 , characterized in that the beam splitter (38) is a glass plate arranged in the beam path at the known Brewster angle.
  14. A 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 in that different sub-areas (22.a, 22.1, 22.b) of the converter are illuminated with laser radiation separately from one another in time, sub-area-specific actual values are recorded for different sub-areas, a setpoint for each first sub-area is determined depending on an actual value that has been determined for a different sub-area, the setpoint 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 setpoint exceeds a If the predetermined threshold is exceeded, the radiation directed at the corresponding sub-area of the converter is reduced.
  15. Procedure according to Claim 14 characterized in that the radiation is always reduced when the laser beam is directed onto the corresponding sub-area.

Description

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. Such a laser light module is made from the DE 10 2012 220 481 A1 The system is known and comprises a laser, a converter, a detector, and a control unit. The converter is positioned in the beam path of the laser radiation emitted by the laser and scatters the incident laser radiation into a (first) portion and converts the incident laser radiation into secondary radiation with a longer wavelength compared to the laser radiation. The detector is positioned in the beam path of radiation emitted by the converter and generates a measured value, the actual value of which depends on the intensity of the radiation emitted by the converter and incident on the detector. The control unit compares the actual value with a setpoint and controls the laser accordingly. A beam path is understood to be a spatial region in which radiation propagates from a first location to a second location. 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 that generates a measured value as an actual value dependent on the intensity of radiation emanating from the converter and incident on the detector, and a control unit that 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 derived from the DE 10 2012 220 481 A1 known. 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. 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. 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. Furthermore, the color tone of the white light should be as constant as possible within the light distribution. 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. AT 514 438 A4 reveals a vehicle headlight with a laser light source, the laser beam of which is deflected via a micromirror that can be pivoted around an axis to a luminous surface with a light conversion phosphor in order to scan and generate a luminous image which can be projected onto a roadway via optics. 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. US 8 400 011 B2 Disclosure reveals 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 fluorescent plate. A light source control unit controls the laser light emitted by the semiconductor laser element based on a detection signal from the light-receiving element. 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