FR3059760B1 - LIGHTING SYSTEM FOR A MOTOR VEHICLE WITH PASSIVE SAFETY - Google Patents

Abstract

The invention relates to a lighting system (SE) for a motor vehicle comprising: at least one light source (11) configured to emit light radiation (L, L1); means for detecting (24) the operation of said system for direct or indirect reception of a fraction of the light radiation (L) and capable of converting it into an electrical signal; - means for interrupting (M2) the normal power supply of the light source (11); ) which are controlled according to the signal transmitted by the detection means (24); characterized in that, in steady state, the interrupting means (M2) is kept in a closed state directly by the signal from said detecting means (24).

Description

Lighting system for a motor vehicle with passive safety

The present invention relates to the technical field of lighting systems for a motor vehicle. More specifically, the invention relates to a security device of a lighting system, in particular a lighting system provided with a laser source.

Some vehicle lighting devices are very powerful and / or produce a highly concentrated beam of light and it is necessary to prevent the radiation emitted from the optical device of the vehicle, for example as a result of an impact, and hit the eyes or skin of people near the vehicle.

From EP 2 767 751 there is known a lighting system for a motor vehicle comprising a primary light source emitting light radiation, a scanning system which receives the light radiation from the primary light source and scans it on a conversion device of length of light. wave having a mirror. The wavelength conversion device re-emits the light radiation in the form of white light radiation. The lighting system further comprises means for reflecting the light radiation to means for detecting a scanning defect. In the event of a failure of the scanning system, the detection means transmit to conventional means for checking the correct operation of the scanning system, such as a control electronics, information characterizing the fact that the mirror is no longer scanned in such a way that normal. As a result, the control means automatically sends an instruction to stop the power supply of the laser source. It is therefore an active system.

Such a lighting system makes it possible to use very powerful light sources by minimizing the dispersions of the laser radiation. However the security of such a lighting system is dependent on the proper functioning of control organs, their good power, which is a drawback. The invention aims to provide a lighting system for the use of very powerful light sources with improved security. For this purpose the invention relates to a lighting system for a motor vehicle comprising: - at least one light source configured to emit light radiation, - means for detecting the operation of said lighting system, arranged to receive directly or indirectly a fraction of the light radiation and able to convert it into an electrical signal,

means for interrupting the normal power supply of the light source which are controlled as a function of the signal emitted by the detection means, in which, in the steady state, the interruption means are kept in a closed state directly by the signal from said detection means. RI

Such a system has good security because the operation of the lighting depends on the reception of a fraction of the light radiation emitted by the light source by detection means. These detection means, in normal operation, convert this fraction of light radiation into an electrical signal (voltage and / or intensity), and the existence of this signal itself is necessary for the operation of the light source. It is therefore a looped system and fully passive safety because it is no longer dependent on the proper functioning of a control body - the light source receives a power supply only if the detection means receive a luminous radiation.

Advantageously, the detection means may comprise at least one photodetector. R2

By photodetector is meant any component capable of reacting and providing a signal of electrical nature under the effect of illumination; it can be a generation of voltage and / or current, as for example in the case of a CCD sensor ("Charge Coupled Device"), or the variation of a voltage and / or a current, for example from a zero voltage to a voltage V, an ohmic resistance variation ...

In the case of a voltage and / or current generator, the at least one photodetector converts the light it receives into a voltage. This signal is not necessarily continuous.

Advantageously, the lighting system may comprise a passive electronic circuit which comprises the interruption means (M2) and which is designed to receive the signal coming from the detection means and to control the light source. R3

The signal, for example a current signal, from the detection means is used by the passive electronic circuit to allow the supply of the light source voltage from the vehicle battery.

By passive electronic circuit is meant that it is fed directly by the detection means. The open or closed state of the interruption means is thus directly controlled by the signal emitted by the detection means.

Advantageously, the passive electronic circuit may be configured to cut off the power supply of the light source when it does not receive the signal from the detection means. R4

In the absence of the signal coming from the detection means, the electronic circuit blocks the supply of the light source. It behaves like a switch.

Alternatively, the passive electronic circuit may be configured to reduce power to the light source when it does not receive the signal from the detection means. R5

Sufficient security can be achieved simply by reducing the supply voltage of the light source and thus the emitted light power.

Advantageously, the interruption means may comprise at least one field effect transistor or an insulated gate transistor. R6

A field effect transistor or insulated gate bipolar transistor can be used as an electronic switch, these components are highly reliable. Their resistance in conduction position can be very low, thus avoiding their heating.

The control circuit of the light source being looped, it is advantageous to have an initialization circuit to provide at least one pulse at startup of the lighting system. This pulse replaces the radiation emitted by the light source when it is in operation. The initialization circuit plays no role in safety: if it fails, the lighting system does not work at startup; it can therefore be a circuit comprising active components. The invention proposes three embodiments of such an initialization circuit:

It can be configured to provide an electrical pulse to the passive electronic circuit at the start of said lighting system, R7

It can be configured to provide a light pulse to the detection means at the start of said lighting system, R8

It can be configured to provide an electrical pulse to the light source at the start of said lighting system. R9

Advantageously, the light source may comprise a laser source, such as a laser diode. RIO

Laser sources such as laser diodes have many advantages as a light source, but may pose a danger to people in the event that the laser beam "leaks" from the housing or component containing this type of source. A passive safety device is therefore particularly advantageous in the case of a lighting system whose light source is a laser source.

In particular embodiments: the lighting system may further comprise, in the path of a primary light radiation emitted by the light source, a scanning device adapted to receive the primary light radiation and to reemit it in a radiation primary swept and in that the detection means are arranged to receive, directly or indirectly, a fraction of the scanned radiation. R11 the scanned primary radiation may be transmitted to a wavelength-changing device adapted to receive the swept primary radiation and to re-emit it to a secondary light radiation of different wavelength, R12 the primary light radiation is not of white color and in that the wavelength-changing device comprises a scanning surface coated with a substrate capable of modifying the color of the light radiation, so that the secondary light radiation re-emitted is of a white color R13

A lighting system having a laser source is frequently used with a scanner for the primary radiation emitted by the laser source. This is particularly the case when it is necessary to modify the wavelength of the primary radiation. The scanner receives the primary radiation and retransmits it to a wavelength-changing device having a reflective surface coated with a substrate called phosphor effecting this wavelength change. The scanned radiation is the radiation re-emitted by the scanning device and the secondary radiation the radiation reflected by the reflecting surface. In this configuration, the detection means are advantageously arranged to receive either the scanned radiation or the secondary radiation according to the embodiments, so, in normal operation, to periodically intercept a radiation fraction. Periodically, it is meant that they are in the beam path only a fraction of the scanning time, for example at one end of the scanning cycle. In a normal operating mode, the electrical signal generated by the detection means allows the laser source to provide radiation.

The scanning device can cause a malfunction of the lighting system and therefore a risk for people in two situations: - The scanned radiation comes out of the limits of the reflecting surface, - The scanning is stopped and the radiation swept is fixed.

If the scanned beam out of the predicted limits, it no longer illuminates the detection means and they stop generating an electrical signal, which causes the stop of the laser source.

If the scanning is stopped, the scanned beam becomes fixed and two cases can occur: - the detection means are no longer lit: then, as in the previous case, the detection means no longer generate a signal and the source laser stops, and / or the scanned beam continuously illuminates the detection means: in this case, advantageously the detection means are configured to be destroyed by prolonged continuous exposure to primary or scanned light radiation R15; the destruction of the detection means causes the laser source to stop because they no longer emit the signal necessary for closing the interrupting means.

In another embodiment, the lighting system may comprise a component comprising: a laser source capable of emitting radiation at a first wavelength; a light converter; detection means arranged in such a way as to: receiving a fraction of the radiation re-transmitted by said light converter. R14

In this embodiment, the laser source is incorporated into a component that includes the substrate for changing the color of the beam, so that such a component can emit a white primary beam. A malfunction situation is then that the substrate disengages from the laser source. In this case, the detection means cease to receive the light re-emitted by the substrate, which causes the laser source to stop. As before, the detection means are configured to be destroyed by prolonged continuous exposure to the light radiation. The invention also relates to: - a lighting system comprising an imaging optical system receiving primary light radiation or secondary light radiation and configured to project this light in front of the vehicle to form a lighting beam, R16 - a lighting system comprising an imaging optical system receiving the primary light radiation or the secondary light radiation and configured to project that light behind the vehicle. R17 The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings in which:

FIG. 1 represents a block diagram of a first embodiment of the lighting system according to the invention,

FIG. 2 represents a block diagram of a second embodiment of the lighting system according to the invention,

FIG. 3 represents a detailed diagram of a lighting system according to the invention, comprising a first embodiment of a passive electronic circuit,

FIG. 3 represents a diagram of another embodiment of a passive electronic circuit.

The lighting system SE1 illustrated in FIG. 1 is a loop circuit comprising: a light source 11, for example a laser diode, emitting a primary light radiation L; this primary light radiation can be very powerful and / or highly concentrated and the lighting system includes means to prevent it from injuring a person, - a photodetector 24 placed to receive a portion of the light radiation L, - and a circuit passive electronics 200 which will be described in detail later.

When it receives the radiation L, the photodetector emits an electrical signal in the form of a voltage V; the voltage V is transmitted to the passive electronic circuit 200 which will be described in more detail below. The passive electronic circuit 200 is placed in an electrical circuit comprising a voltage source 12, for example the battery of the vehicle in which the lighting system, the light source 11 and the mass are implanted. The passive electronic circuit 200 includes interrupting means M2 of the normal power supply of the light source 11 which are arranged in series between the voltage source 12 and the light source 11.

The interruption means M2 are supplied directly by the photodetector 24. The normal power supply interrupt means M2 default to an open state. The normal power supply interruption means M2 are maintained in their closed state directly by the energy of the electrical signal emitted by the photodetector 24.

As long as the passive electronic circuit 200 receives the voltage V of the signal emitted by the photodetector 24, the normal power supply interruption means M2 close the electric circuit under the effect of the electrical power of the signal and the light source is supplied with power normally. . Conversely, if the light radiation L no longer hits the photodetector 24, the latter stops transmitting the voltage V and the interrupting means M2 of the normal supply of the passive circuit 200 open, causing the extinction of the IL light source This stopping of the illumination of the photodetector 24 by the light source 11 may be the sign of an offset of the light source relative to its case, consequence of an impact. The luminous radiation L is likely to escape from the box and stopping its emission is a safety measure.

An activation and shutdown command of the lighting system, for example a switch, may be located on the branch between the battery 12 and the light source 11, between the light source 11 and the passive circuit 200, or even between the passive circuit 200 and the photodetector 24.

In steady state, the interrupting means M2 of the normal power supply of the light source 11 are kept in the closed position directly by the signal coming from the photodetector 24. However, it is conceivable that such a system can not pass from the stop to a start without "assistance". Thus, in transient initialization mode, closing the switch will not be sufficient to generate the voltage V which closes the interrupting means M2 of the passive circuit 200. An initialization device is useful for this purpose. The invention proposes three different means: the lighting system may comprise an electronic initialization circuit 300 connected to the passive electronic circuit 200 and provided to provide an electrical pulse to said passive electronic circuit at the start of the system, this pulse electrical being sufficient to close the means of interruption M2; alternatively, the electronic initialization circuit could be connected to the photodetector 24; this initialization circuit will be described in detail later; the lighting system may comprise an initialization electronic circuit 320 connected to the light source 11 and designed to provide an electrical pulse to said light source at the start of the system; the lighting system may comprise an initialisation light source 310 designed to illuminate the photodetector 24 by means of radiation L 'at the start of the system.

These three embodiments of electronic initialization circuit are illustrated in Figure 1, but heard only one is sufficient.

Alternatively, as will be described in more detail in connection with FIG. 4, the passive electronic circuit 210 may be provided to maintain the supply of the light source 11 but at a reduced level, lower than that of the normal power supply. when it does not receive the signal from the detection means 24 so as to make the primary light radiation L less dangerous.

Figure 2 illustrates a second embodiment of a lighting system SE2. In certain circumstances, particularly when the light source is a laser diode whose wavelength must be changed, a scanning device 14 is provided which receives the primary radiation L1 of the light source 11, of a certain length of time. wave, and sweeps on a scanning surface 19 having a mirror, adapted to receive the scanned light radiation L2 and reemit in the form of secondary light radiation B whose wavelength is different.

The light source 11 is a laser source comprising for example a laser diode, emitting for example a primary radiation Ll whose wavelength is between 400 nanometers and 500 nanometers, and preferably around 450 to 460 nanometers. These wavelengths correspond to colors ranging from blue to near ultraviolet.

The light source 11 may alternatively comprise an optical device combining in a single beam several laser rays, for example using optical fibers or devices taking advantage of the different polarizations of different laser sources.

The scanning system 14, of conventional type, comprises in the example described a single micro-mirror, mobile about two orthogonal axes and controlled by a control unit, such as those used in optical scanning systems called " scanners ".

The scanning system re-transmits the primary light radiation L1 into a scanned radiation L2 to a wavelength conversion device 15 which transmits the radiation to a conventional imaging optical system 17.

The wavelength conversion device 15 comprises a scanning surface 19 comprising a mirror coated with a continuous and homogeneous layer of a phosphorescent material. The scanning system 14 and the imaging optical system 17 are arranged on the same reflecting side of the mirror.

The source 11 generates a primary laser beam L1 which is deflected in two directions by the scanning system 14, and emanates a scanned radiation L2 included in a solid angle intercepting the scanning surface 19.

In a known manner, each point of the layer 20 of the wavelength-converting scanning surface 19 receiving the scanned L2 radiation, essentially monochromatic and coherent, re-transmits, to the imaging system 17, a beam B of length different wave, and in particular a light that can be considered "white", that is to say that has a plurality of wavelengths between about 400 nanometers and 800 nanometers, that is to say included in the spectrum of visible light. This emission of light occurs, according to a lambertian emission diagram, that is to say with a uniform luminance in all directions.

Since the layer 20 of phosphorescent material is deposited on the reflecting mirror for the scanned radiation L2, it is ensured that the radiation L2 which would not have encountered a grain of phosphorescent material 20 before having completely passed through the layer 20 of phosphorescent material, may meet a grain of phosphorescent material after being reflected by the mirror.

The scanning surface 19 is formed at least in part by the surface of the layer 20 of phosphorescent material covering the mirror. This layer 20 is continuous and homogeneous so that the partition of the layer 20 of phosphorescent material into distinct elements makes it possible to obtain the desired precision in the retransmission of white light, particularly at the points situated at the boundary between two of these distinct elements. .

The layer 20 of phosphorescent material is located in the immediate vicinity of the focal plane of the imaging optical system 17, which then forms at infinity an image of the layer 20 of phosphorescent material, or more exactly points of this layer that emit light. white light in response to the laser excitation they receive. In other words, the imaging optical system 17 forms a light beam with the light B emitted by the different points of the layer 20 of phosphorescent material illuminated by the scanned radiation L2.

It is thus possible to illuminate the layer 20 of phosphorescent material with the scanned radiation L2 so as to form an image on this layer 20, this image being formed of a succession of lines each formed of a succession of points more or less bright, in the same way as an image on a CRT television screen.

With reference to FIG. 2, it can be seen that the wavelength converting device 15 has a substantially rectangular shape and comprises reflection means 22, arranged at the locations of the angles of the contour of the scanning surface 19 and designed to reflect in a radiation B 'the scanned radiation L2 they receive to detection means 24. In other embodiments not shown, the reflection means 22 may be positioned only on two adjacent sides of the contour or evenly distributed on the sides. The reflection means 22 may be formed by mirrors attached to the edges of the scanning surface 19 or may be integral with the mirror. Of course, the contour of the scanning surface 19 could have a different shape, for example a substantially polygonal shape other than rectangular.

The optical system SE2 further comprises: a passive circuit 200 connected to the detection means 24 and to the light source 11; as has been seen previously, the light source can only work if the means of interruption of the passive circuit 200 are closed, that is to say if it receives a signal from the detection means 24; an initialization circuit 300 connected to the passive circuit 200, but as has been seen previously, other initialization devices 310, 320 are within the scope of the invention.

The detection means 24 receive the radiation B 'which is derived from the scanned radiation L2, so it is not itself permanent. Consequently, the passive circuit 200 must comprise delay means to remain closed despite the intermittency of the radiation B 'received by the detection means 24.

In another embodiment not shown, the detection means 24 could be placed around the perimeter of the scanning surface 19 in place of the reflection means 22.

We will now describe a passive circuit 200 provided for the lighting system SE1, SE2 of the invention. Such a circuit and an initialization circuit 300 are represented in FIG.

In this figure, the light source 11 is schematized by a resistor RI and the detection means 24 by a photodetector II connected in series with a diode D6, designed to generate a voltage V2 when it is illuminated by the radiation L of the source light. The voltage source 12 delivers a voltage V1.

The interruption means of the passive circuit are formed by a MOS transistor M2 comprising a gate G2, a drain D2 and a source S2. Between the gate G2 and the source S2 are connected in parallel a resistor R2 and a capacitor C1. The drain D2 is connected to the light source 11.

In operation, the voltage V2 delivered by the photodetector 24 is sufficient to maintain the charge of the capacitor C1; the voltage between the source S2 and the gate G2 is thus maintained higher than the saturation threshold of the transistor M2. In this condition, the transistor M2 allows the passage of a current between the source S2 and the drain D2 and the light source 11 is powered.

If the photodetector 24 sends only brief pulses, the circuit R2 - C1 between the gate and the source acts as a retarder and the transistor M2 remains conductive until the arrival of the next pulse. The transistor only cuts if the voltage between the gate and the source becomes lower than the saturation voltage due to the discharge of the capacitor C1. In another embodiment, the capacitor C1 is absent, the circuit uses the parasitic capacitance which exists in the transistor between the gate G2 and the source S2.

The initialization circuit 300 comprises a pulse generator 12 delivering a voltage V3, connected in series with a resistor R3 and a diode D5. A pulse generated by this circuit is sufficient to charge the capacitor C1, thus to make the transistor M2 conductive, and thus to supply the light source 11, the charge of the capacitor C1 being then maintained by the detection means 24.

In this example, typical values are: VI = 5 V RI = 2.2 Ω R2 = 47 ΙΟ6 Ω Cl = 1 nF R3 = 10 k Ω

All things being equal, FIG. 4 shows the diagram of a passive circuit 210 by which, if the photodetector 24 no longer delivers voltage, the light source 11 continues to be powered but with a lower voltage. In the circuit 210, the mounting of the MOSFET transistor M2 is recognized. It associates a second MOSFET transistor M1, connected in parallel with the MOSFET transistor M2, and whose drain D1 is connected to the light source 11. This second transistor M1 is still in operation but it only intervenes if the transistor M2 opens . In this case, the light source is powered by the MOSFET transistor M1 but at a level depending on the resistor R5 between the gate G1 and the ground and a supply voltage Vref which may be different from VI.

Of course, the passive security system that has just been described could be completed by an active security system mounted in series.

Claims (14)

claims 1. Lighting system (SE) for a motor vehicle comprising: at least one light source (11) configured to emit light radiation (L, Ll); means for detecting (24) the operation of said lighting system. , arranged to directly or indirectly receive a fraction of the light radiation (L) and able to convert it into an electrical signal, - interrupting means (M2) of the normal power supply of the light source (11) which are controlled according to the signal transmitted by the detection means (24); characterized in that, in steady state, the interrupting means (M2) is held in a closed state directly by the signal from said detecting means (24); and in that the system further comprises, in the path of a primary light radiation (L1), a scanning device (14) adapted to receive the primary light radiation and to retransmit it into a scanned primary radiation (L2) and in that the detection means (24) are arranged to receive, directly or indirectly, a fraction of the scanned radiation. 2. Lighting system according to claim 1, wherein the detection means (24) comprise at least one photodetector. 3. Lighting system according to one of claims 1 or 2, comprising a passive electronic circuit (200) which comprises the interruption means (M2) and which is adapted to receive the signal from the detection means (24). and to control the light source (11). The lighting system according to claim 3, wherein the passive electronic circuit (200) is configured to cut off power to the light source (11) when it does not receive the signal from the detection means (24). . An illumination system according to claim 3, wherein the passive electronic circuit (200) is configured to reduce power to the light source (11) when it does not receive the signal from the detection means (24) . 6. Lighting system according to one of claims 3 to 5, wherein the interruption means comprise at least one field effect transistor (M2) or an insulated gate transistor. The lighting system according to one of claims 3 to 6, further comprising an initialization device (300) configured to provide an electrical pulse to the passive electronic circuit (200) at the start of said lighting system. . 8. Lighting system according to one of claims 3 to 6, further comprising an initialization device (310) configured to provide a light pulse (L ') to the detection means (24) at the start of said lighting system. 9. Lighting system according to one of claims 3 to 6, further comprising an initialization device (320) configured to provide an electrical pulse to the light source (11) at the start of said lighting system. . 10. Lighting system according to one of the preceding claims, wherein the light source (11) comprises a laser source, such as a laser diode. Illumination system according to one of the preceding claims, characterized in that the scanned primary radiation (L2) is emitted to a wavelength-changing device (15) adapted to receive the scanned primary radiation and to the retransmitting to a secondary light radiation (B) of different wavelength. Lighting system according to one of claims 1 to 10, characterized in that the primary light radiation (L1) is not white and that the wavelength-changing device (15) comprises a scanning surface (19) coated with a substrate (20) adapted to change the color of the light radiation, so that the secondary light radiation (B) reemitted is white. 13. Lighting system according to one of claims 1 to 9, comprising a component, said component comprising: - a laser source capable of emitting radiation at a first wavelength, - a light converter, - means detecting means arranged to receive a fraction of the radiation re-emitted by said light converter. 14. Lighting system according to one of the preceding claims, wherein the detection means (24) are configured to be destroyed by prolonged continuous exposure to the primary light radiation (L, L1) or scanned (L2).