Monitoring apparatus for monitoring the operating state of a laser vehicle headlamp

Abstract

The invention relates to a monitoring apparatus for monitoring the operating state of a laser vehicle headlamp (4), wherein the laser vehicle headlamp (4) comprises at least one laser light source (5) and a light conversion element (6) that can be illuminated by the laser light source (5) and therefore can be excited to emit visible light, wherein the monitoring apparatus has at least one photosensitive device (3) and one comparison device (1), wherein the photosensitive device (3) comprises at least one LED (D1) that is set up to convert light received from the laser light source (5) into an electrical signal (U.sub.D) that is supplied to the comparison device (1), wherein the comparison device (1) is set up to compare the electrical signal (U.sub.D) with a preselectable value and to output a fault signal (U.sub.0) on the basis of the result of the comparison.

Claims

1. A monitoring apparatus for monitoring an operating state of an automotive laser headlight (4), wherein the automotive laser headlight (4) comprises at least one laser light source (5) and a light conversion element (6) that is configured to be illuminated by the at least one laser light source (5) and excited to emit visible light, the monitoring apparatus comprising: at least one photosensitive device (3); and one comparison device (1), wherein the at least one photosensitive device (3) comprises at least one LED (D1), which is configured to convert light received by the at least one laser light source (5) into an electric signal (U.sub.D), which is sent to the comparison device (1), wherein the comparison device (1) is configured to compare the electric signal (U.sub.D) with a preselectable value and to output a fault signal (U.sub.0) as a function of a result of the comparison, wherein the at least one photosensitive device (3) has at least two LEDs, one of the at least two LEDs being equipped to measure laser light and another one of the at least two LEDs being equipped to measure a remaining light converted by the light conversion element (6), and wherein the at least two LEDs are connected antiparallel to one another.

2. The monitoring apparatus according to claim 1, wherein the comparison device (1) comprises a comparator (10), which is configured to compare the electric signal (U.sub.D) with a threshold value (U.sub.ref) and to output the fault signal (U.sub.0) on exceeding the threshold value (U.sub.ref).

3. The monitoring apparatus according to claim 1, wherein the fault signal (U.sub.0) is a electric signal having a voltage level not equal to 0 V against ground.

4. The monitoring apparatus according to claim 1, wherein the fault signal (U.sub.0) is an electric direct electric signal having a voltage level equal to 0 V against ground.

5. The monitoring apparatus according to claim 1, wherein the at least one photosensitive device (3) has at least one blue LED.

6. The monitoring apparatus according to claim 1, wherein a spectral sensitivity of the at least two LEDs is at a peak for measuring the laser light in a wavelength range of the laser light, and the LED of the at least two LEDs for measuring the remaining light converted by the light conversion element (6) has a spectral sensitivity with a maximum in a wavelength range of the visible light minus the wavelength range of the laser light.

7. The monitoring apparatus according to claim 6, wherein the LED of the at least two LEDs for measuring the laser light is a blue LED, and the LED of the at least two LEDs for measuring the remaining light converted by the light conversion element (6) is a red LED.

8. The monitoring apparatus according to claim 1, wherein output signals of the at least two LEDs, which are output as a result of the measurements, are sent to the comparison device (1) and compared with one another by the comparison device, and the fault signal (U.sub.0) is determined by taking into account the output signals.

9. An automotive laser headlight comprising at least one monitoring apparatus according to claim 1.

10. The automotive laser headlight (4) according to claim 9, wherein the at least one LED of the at least one photosensitive device (3) is an LED adapted to a spectrum of the at least one laser light source (5).

11. A motor vehicle comprising at least one automotive laser headlight (4) according to claim 10.

12. The vehicle according to claim 11, wherein the vehicle has a control unit connected to the comparison device (1) for controlling the at least one laser light source (5), wherein the control unit is configured to deactivate the at least one laser light source (5) when the fault signal (U.sub.0) occurs.

13. The automotive laser headlight (4) according to claim 9, wherein the automotive laser headlight (4) has a control unit connected to the comparison device (1) for controlling the at least one laser light source (5), wherein the control unit is configured to deactivate the at least one laser light source (5) when the fault signal (U.sub.0) occurs.

Description

(1) The invention is explained in greater detail below on the basis of an exemplary embodiment, which is illustrated in the figures and is not restrictive. In the drawings:

(2) FIG. 1 shows a schematic diagram of a detail of an automotive laser headlight according to the invention,

(3) FIG. 2 shows a schematic diagram of a photosensitive device,

(4) FIG. 3 shows an example of an electric circuit of a monitoring apparatus according to the invention, and

(5) FIG. 4 shows a plot of electric signals of the monitoring device as a function of time.

(6) Unless otherwise indicated, the same reference numerals in the following figures denote the same features.

(7) FIG. 1 shows a schematic diagram of a detail of an automotive laser headlight 4 according to the invention. The automotive laser headlight 4 in the present exemplary embodiment comprises a laser light source 5, a light conversion element 6, which can be illuminated by the laser light source 5 and can thus be excited to emit visible light, wherein a lens 7 is arranged between the light conversion element 6 and the laser light source 5, a light-sensitive device 3, a reflector 8 and a comparison device 1, which is equipped to compare the electric signal with a predefinable value and to output a fault signal as a function of the result of the comparison.

(8) The laser light source 5, the lens 7 and the light conversion element 6 are combined to form a lighting fixture 2 in the present case which may be embodied as a component installed into a separate housing, for example.

(9) The automotive laser headlight 4 comprises a monitoring apparatus according to the invention, which in turn has the aforementioned photosensitive device 3 and the comparison device 1. The photosensitive device 3 is permanently connected to the reflector 8 and/or accommodated in an opening in the reflector 8, which is preferably arranged in a position in which the laser light source 5 would be illuminated primarily in the absence of the conversion element 6. It is possible in particular to provide that the side of the photosensitive device 3 facing the lighting fixture 2 has a light-absorbent surface to prevent unwanted reflection of laser light in the event of a fault and thus prevent light from escaping from the automotive headlight.

(10) FIG. 2 shows a schematic diagram of the photosensitive device 3. The device 3 has two LEDs, namely one blue LED D1 and one red LED D2, which are arranged in a shared housing 3a in the present exemplary embodiment, but as an alternative, may also be arranged in separate housings. The housing 3a and/or the LEDs D1 and D2 are electrically connected to a printed circuit board 3b, which in the present embodiment has a plug connection 3c for electrical connection to the comparison device 1 and has boreholes 3d for mechanical connection to the reflector 8. The comparison device 1 and/or its electrical implementation may also be arranged directly on the printed circuit board 3b, so that external connecting components such as connecting cables from the photosensitive device 3 to the comparison device 1 may be omitted. The plug connection 3c could then be equipped for direct connection to a control unit in the motor vehicle.

(11) FIG. 3 shows an example of an electric circuit of a monitoring apparatus according to the invention, in which the comparison device 1 comprises a comparator 10, which is equipped to compare the electric signal U.sub.D emitted by the antiparallel circuit of the diodes D1 and D2 with a threshold valued U.sub.ref and to deliver a fault signal in the event the threshold value U.sub.ref is exceeded, said fault signal being equated with the voltage level U.sub.0 in the high state in the present example (see FIG. 4). As an alternative to that, the fault signal could also correspond to the low state with respect to ground, for example 0 V.

(12) FIG. 4 shows a plot of electric signals of the monitoring device, more specifically the signals I.sub.D, U.sub.D, U.sub.ref and U.sub.0 plotted as a function of time. A signal plot of the aforementioned signals in the fault-free state is shown for an initial duration N. In the following period F, a malfunction of the automotive laser headlight was detected by the monitoring apparatus on the basis of the threshold value U.sub.ref being exceeded, for example, so that the diode current I.sub.D and the output voltage U.sub.D rise and the output signal U.sub.0 is switched to the logic state high (e.g., 5 V). There is therefore robust and inexpensive detection of fault states.

(13) In view of this teaching, those skilled in the art are able to arrive at other embodiments of the invention, which are not shown here, without making any inventive contribution. Therefore, the invention is not limited to the embodiment shown here. Individual aspects of the invention and/or the embodiment may also be taken up and combined with one another. What is important is the ideas on which the invention is based, which can be implemented by those skilled in the art with knowledge of this description in a variety of ways and nevertheless be upheld as such are essential.