FR3007820A1 - SECURE OPTICAL MODULE FOR MOTOR VEHICLE COMPRISING A LASER SOURCE - Google Patents

Abstract

The invention relates to an optical module for a motor vehicle comprising a light source (18) capable of emitting laser radiation (L) and a shaping system (20) capable of receiving the laser radiation (L) and to the direct to at least one conversion device (22) of the white light radiation (B). The optical module also comprises a detector (34) adapted to receive a residual light (R) emanating from the source (18) and coming from the conversion device (22). The invention also relates to a projector and a motor vehicle comprising such a module and a control method of this module.

Description

The present invention relates to projectors for a motor vehicle, more particularly to secure projectors comprising a laser source. Motor vehicles having lighting projectors comprising an optical module comprising a laser source, a scanning system and a device for converting the laser radiation into white light are known. When the laser source emits radiation, this radiation is received by the scanning system which directs it to the conversion device. The conversion device receives monochromatic and coherent laser radiation and re-emits white light radiation used to form the illumination beam at the front of the vehicle. However, when the vehicle is struck, the scanning system and / or the conversion device may be damaged, or the laser source may be misaligned. These failures can also occur without the vehicle being shocked. It must then be avoided that the module can emit out of the module a potentially dangerous laser radiation if it touches a person. The object of the invention is to remedy these drawbacks by providing a secure optical module. For this purpose, the subject of the invention is an optical module for a motor vehicle comprising: at least one light source able to emit laser radiation; at least one shaping system capable of receiving the laser radiation and directing it towards at least one device for converting the radiation into white light, the conversion device being able to re-emit the white light towards at least one optical system, and a detector capable of receiving a residual light emanating from the source and coming of the conversion device. With this module, it is thus possible to measure a parameter or a series of parameters of the light reflected or transmitted by the conversion device 30 and coming from the light source. This light being reflected or transmitted by the shaping system before reaching the conversion device, any malfunction of the source, the shaping system and / or the conversion device modifies the residual light received by the converter. -2- detector. Thus, the anomaly can come from a failure of the detector, a misalignment of the laser source, a malfunction of the shaping system and / or degradation of the conversion device. This module, in cooperation with a control unit, thus makes it possible to detect a large number of different anomalies. Thus, if the residual radiation received by the detector is not in accordance with the expected radiation, a malfunction of one of the elements of the optical module is detected very quickly. The module may further comprise one or more of the following features, taken alone or in combination.

It can be provided that the module comprises a control unit able to compare at least one parameter of the laser radiation emitted by the source with at least one parameter of the residual light received by the detector. Thus, the control unit is included in the module. Advantageously, the module comprises a receiving box of the conversion device, the detector being positioned facing an opening of the housing. The arrangement of the different elements of an existing optical module must not be modified. An opening is made in the module housing and the detector is located therein. Advantageously, the detector is positioned facing the shaping system. Even more advantageously, the detector comprises a photodiode. Indeed, this type of detector is simple and can reliably detect the residual light reflected by the conversion device and turn it into an electrical signal that can be easily processed by the control unit. Preferably, the module comprises a filter disposed between the conversion device and the detector. With this filter, it is possible to reduce the stray light that can enter the module from an oncoming vehicle and / or ambient light, for example. We can also consider using a cheaper detector. It can also be provided that the module comprises a sensor for measuring the temperature. Thanks to this sensor, it is possible to take into account the temperature of the -3- module and to compare more precisely the residual light with that expected during normal operation of the module. It can be envisaged that the residual light does not pass through the optical system.

It is therefore understood that the residual light comes from the conversion device, without passing through the optical system before reaching the detector. It can also be envisaged that the residual light passes through the optical system. Thus, the residual light is reflected by the optical system, for example by glassy reflection, before reaching the detector. The shaping system and the optical system may be located on the same side of the conversion device. The conversion device is therefore used in reflection. According to another variant, the shaping system and the optical system are located on either side of the conversion device. The conversion device is then used in transmission. The invention also relates to a headlamp for a motor vehicle comprising at least one module as defined above. Another object according to the invention is a motor vehicle comprising at least one module according to the present invention. The invention also relates to a method for controlling an optical module for a motor vehicle comprising the following steps: a light source emits laser radiation to a shaping system, the shaping system directs the radiation laser to a white light radiation converting device; the converting device re-emits white light to at least one optical system; and a detector detects residual light reflected from the source and from the conversion device. Advantageously, the method further comprises the following steps: a control unit calculates at least one parameter of the light to be received by the detector from the laser radiation emitted by the source, and the control unit compares the calculated parameter with at least one parameter of the residual light detected by the detector. For example, the control unit calculates the intensity of the light that the detector should receive and compares it with the actual intensity measured by the detector.

When the detector is a photodiode, it is also possible to compare the intensity of electric current supplying the light source and the intensity of electric current leaving the photodiode. The control unit may also control that the ratio of the intensity of the light emitted by the light source and the intensity of the residual light actually measured by the detector is between two predefined threshold values over time. It can also be envisaged that the control unit calculates the intensity of the light that the detector should receive as a function of the position of the laser radiation on the conversion system. Two series of parameters that can be presented graphically in the form of two curves are thus compared, the series calculated from the emission data of the source and that obtained from the residual radiation received by the detector. Preferably, in the presence of an anomaly of a predetermined type, the control unit controls at least one of the following actions: the emission of an audible and / or visual signal for the attention of a driver of the vehicle; stopping the emission of the laser radiation; and decreasing the power of the laser radiation emitted so that the radiation that can exit the optical module is radiation of class 2 or lower. Thus, as soon as an anomaly is detected, it is possible to warn the driver by emitting an audible signal and / or a visual signal to his attention. It is also possible, depending on the type of anomaly, either to stop the emission of the laser radiation or to reduce its power so that the laser radiation coming out of the optical module is laser radiation of class 2 or lower. In the latter case, there is a degraded operation of the module but it still emits a beam allowing the driver to have a minimum of light on the road. The invention will be better understood on reading the description which follows, given solely by way of non-limiting example of the scope of the invention and with reference to the figures, in which: FIG. 1 FIGS. 2 to 4 are schematic views of a module according to a first, a second and a third embodiment of the invention, 6 are views of a fourth embodiment of the invention, respectively in perspective and in section, - FIG. 7 a graphical representation as a function of time of the intensity of the electric current supplying the laser source and of the intensity. the electrical current that should come from the detector, and - Figure 8 is a graphical representation as a function of time of the ratio between the intensity of the electric current supplying the laser source and the intensity of the measured electric current from the die detector. There is shown in Figure 1 a projector 10 for a motor vehicle. This projector comprises three modules 12, 14, 16. In this example shown in FIG. 2, the first module 12 comprises a laser light source 18, a laser radiation shaping system 20, a radiation conversion device 22 in white light and an optical system 24. In this embodiment, the shaping system 20 comprises a scanning system 26 comprising a micro-mirror mounted to move about two orthogonal axes. The module 12 may also comprise conventional means 19 for focusing the source 18, these means 19 being interposed between the source 18 and the scanning system 26. The laser light source 18, the focusing means 19 of the source and the The microoptoelectromechanical system, called MOEMS according to the acronym for "Micro-Opto-Electro-Mechanical Systems", is an optical system comprising, in the present case, at least one laser light source and a scanning system. MOEMS are compact, reliable, easy-to-use devices that provide high accuracy and flexibility in redirecting radiation to the conversion device. The laser light source 18 is in this case a laser diode capable of emitting laser radiation L whose wavelength is between 400 and 500 nanometers (nm), preferably between 450 and 460 nm. The conversion device 22 comprises a support 28 reflecting the laser radiation on which is deposited a continuous layer 30 of phosphorescent material. Note that the scanning system 26 and the optical system 24 are located on the same side of the conversion device 22, i.e. the conversion device 22 is used in reflection. Advantageously, the support 28 is chosen from materials that are thermally good conductors. It is therefore possible to limit the degradation of the layer 30 of phosphorescent material by limiting the temperature rise of the conversion device 22 and the layer 30. When the laser light source 18 emits radiation L, this radiation is received by the scanning system 26 which directs it to the conversion device 22. The conversion device 22 receives monochromatic and coherent L laser radiation and re-emits white light B radiation, i.e. comprising a plurality of wavelengths between about 400 and 800 nm. This emission of light occurs according to a lambertian emission diagram, that is to say with a uniform luminance in all directions of emission. Since the conversion device 22 is situated in the vicinity of the focal plane of the optical system 24, such as a lens, the white light B thus obtained is emitted in particular towards the optical system 24 and forms, on the opposite side of the lens, to the lens. infinite, an image of the points of the layer 30 of phosphorescent material that emit white light B in response to laser radiation L received. Since the scanning of the points of the layer 30 is carried out at a high speed, the white light B emitted by the conversion device 22 makes it possible to form a light beam F, in this case a portion of the light beam produced by the projector 10 which The portion of the laser radiation L received by the conversion device 22, i.e. the layer 30 of phosphorescent material, is reflected without being converted and forms a residual laser light R which does not is not directed towards the optical system 24. This residual laser light R is in particular received by a detector 34 comprising a photodiode. This residual light R is therefore of the same wavelength as the light source 18. Thus, if the laser light source 18 is a blue light source, the residual light will also be blue. The detector 34 may therefore be chosen with a low amplitude range of detected wavelengths, for example the laser radiation may typically be 445 nm and the photodiode has a detection range of between 435 and 455 nm. The module 12 further comprises a control unit 32 which makes it possible in particular to control the power of the laser light source 18, the movements of the scanning system 26 and to compare a parameter of the laser radiation L emitted by the source 18 with a parameter residual laser light R received by the detector 34. The module 12 also comprises a sensor 42 for measuring the temperature. It makes it possible to measure the temperature in the module 12 and to supply this information to the control unit 32. In the embodiments of FIGS. 2 to 4, the detector 34 is situated opposite the scanning system 26, that is to say that the detector 34 and the scanning system 26 are arranged on either side of a line orthogonal to the plane of the conversion device 22. The shape and the intensity of the part of the beam formed by the Module 12 depends in particular on the intensity of the laser light source 18 and the displacements of the scanning system 26. In FIG. 2, there is shown a module 12 which comprises a single laser light source 18, a single laser light source 18. 26, a single device 22 for converting the radiation into white light and a single optical system 24. However, it will be understood that the module 12 may comprise, for example, two laser light sources 18 each emitting radiation towards the same system. 26. Alternatively, the two sources 18 may emit radiation to separate respective scanning systems 26. The scanning systems 26 may emit the laser radiation L to the same conversion device 22 or different devices 22. The optical device 24 can receive the white light B from one or more conversion devices 22. The module 12 can also comprise more than two sources 18. In the following, the elements common to the various embodiments are identified by the same numerical references. FIG. 3 shows a second embodiment of the module 12. The module 12 further comprises a housing 36 receiving the light source 18, the scanning system 26 in the form of a MOEMS 21 and the conversion device 28. The detector 34 is positioned outside the housing 36 facing an opening 38 of the housing 36. The opening 38 is itself positioned opposite the MOEMS 21, that is, that is, the detector 34 and the scanning system 26 are arranged on either side of a line orthogonal to the plane of the conversion device 22. The module 12 of FIG. 4 is similar to that of FIG. has interposed a filter 40 between the scanning system 26 and the detector 34.

In FIGS. 5 and 6, the module 12 comprises a static shaping system 20. It will be noted that the shaping system 20 and the optical system 24 are not situated on the same side of the conversion device 22, i.e., the conversion device 22 is used in transmission. In contrast to the previous embodiments, the residual laser light R coming from the conversion device 22 is directed towards the optical system 24 and at least part of this residual light R is then reflected, for example by vitreous reflection, towards the detector 34 provided with of a filter 40. The control method of the module 12 comprises the following steps: the light source 18 emits laser radiation L towards the shaping system 20, the shaping system directs the laser radiation L to the conversion device 22 of the radiation L in white light B, the conversion device 22 re-emits the white light B in particular to the optical system 24, the detector 34 detects residual light R emanating from the source and coming from the conversion device 22. In the first, second and third embodiments, the residual light R does not pass through the optical system 24 whereas in In the fourth embodiment, the residual light R is reflected by the optical system 24. The method may also comprise the following steps: the control unit 32 calculates at least one parameter of the light to be received by the detector 34 from the laser radiation L emitted by the source 18, and the control unit 32 compares the calculated parameter with at least one parameter of the residual light R detected by the detector 34. It is therefore clear that the unit of control 32 compares at least one parameter of the laser radiation L emitted by the source 18 to at least one parameter of the residual light R received by the detector 34. The parameters of the laser radiation L may for example be a series of parameters calculated from the emission data of the source 18, this series of parameters being able to be represented in the form of a curve. Advantageously, this curve is corrected by the control unit 32 taking into account the temperature measured by the sensor 42. In FIG. 7, a curve 44 is shown representing the evolution of the intensity of the electric current in amps supplying power. the laser source as a function of time in milliseconds as well as a curve 46 representing the evolution of the intensity of the calculated electric current which should come from the detector 34, in this case a photodiode. The intensity of the electric current supplied to the laser source is proportional to the light intensity of the laser radiation emitted and the photodiode reliably detects the residual light reflected by the conversion device and transforms it into an electrical signal which can be easily processed by the control unit 32. The control unit 32 therefore compares the intensities of the electric current respectively calculated and measured by the detector 34 as a function of time. When the difference between these two values exceeds a predetermined threshold, an anomaly is noted.

FIG. 8 illustrates a curve 48 representing the ratio between the intensity of the electric current supplying the laser source and the intensity of the measured electric current coming from the detector 34 over time. This curve 48 can change over time between a low limit 50 and a high limit 52. When the curve 48 is not between the low and high limits, an anomaly is found. The values illustrated in Figures 7 and 8 are given for information only and not limiting. Then, when the parameter of the residual light R received by the detector 34 is not in accordance with what has been calculated from the emission data of the source 18, an anomaly is noted. The control unit 32 then controls the emission of an audible and / or visual signal to the attention of the driver of the motor vehicle and / or performs one of the following actions: - stopping the emission of the laser radiation L or - the decrease of the power of the laser radiation L emitted so that the laser radiation coming out of the optical module is laser radiation of class 2 or lower. It will be understood that this control method is similar for the different embodiments of the module 12. The optical module 12 can be used in the projector 10 to notably form a passing beam, a driving beam, a fog light, a anti-glare or bad weather beam, called AWL according to the English acronym for "Adverse Weather 15 Light". The invention is not limited to the embodiments presented and other embodiments will become apparent to those skilled in the art. Thus, the projector 10 may comprise a first module according to the invention and second and third modules not comprising a laser light source. The projector 10 may also comprise two modules each comprising at least one laser light source 18, at least one scanning system 20 and at least one device for converting the radiation into white light 22 and a third module that does not include one. The projector 10 may also comprise two modules. If desired, the non-laser source module (s) may have a conventional light source, such as an LED. In addition, it will be understood that the modules of the first and second embodiments may comprise a filter 40, that the modules of the third and fourth embodiments may not comprise a filter 40, that the modules of the second, third and fourth modes of embodiment may comprise a sensor 42 and that the module of the first embodiment may not include a sensor 42. It will also be understood that the control unit 32 may not be integral and that, within the meaning of FIG. invention, this element comprises different parts making it possible in particular to carry out the functions of control of the light source 18, of calculation of the parameter of the light to be received by the detector 34, of comparison of this parameter with the parameter of the residual light R received by the detector 34 and control actions to perform when detecting an anomaly. These different parts can however be located at different locations in the vehicle.

Claims (14)

REVENDICATIONS1. Optical module (12, 14, 16) for a motor vehicle, characterized in that it comprises: - at least one light source (18) capable of emitting laser radiation (L), - at least one shaping system (20) adapted to receive the laser radiation (L) and direct it towards at least one conversion device (22) of the white light radiation (B), the conversion device (22) being able to re-emit the white light ( B) to at least one optical system (24), and - a detector (34) adapted to receive a residual light (R) emanating from the source (18) and coming from the conversion device (22). 2. Module (12, 14, 16) according to the preceding claim, comprising a control unit (32) capable of comparing at least one parameter of the laser radiation (L) emitted by the source (18) to at least one parameter of the residual light (R) received by the detector (34). Module (12, 14, 16) according to at least one of the preceding claims, comprising a housing (36) for receiving the conversion device (22), the detector (34) being positioned facing an opening (38) of the housing (36). 4. Module (12, 14, 16) according to at least one of the preceding claims, wherein the detector (34) is positioned opposite the forming system (20). 5. Module (12, 14, 16) according to at least one of the preceding claims, wherein the detector (34) comprises a photodiode. The module (12, 14, 16) according to at least one of the preceding claims, comprising a filter (40) disposed between the conversion device (22) and the detector (34). 7. Module (12, 14, 16) according to at least one of the preceding claims, comprising a sensor (42) for measuring the temperature. The module (12, 14, 16) according to at least one of the preceding claims, wherein the residual light (R) does not pass through the optical system (24). The module (12, 14, 16) according to at least one of claims 1 to 7, wherein the residual light (R) passes through the optical system (24). 10. Projector (10) for a motor vehicle, characterized in that it comprises at least one optical module (12, 14, 16) according to at least one of the preceding claims. 11. Motor vehicle, characterized in that it comprises at least one optical module (12, 14, 16) according to at least one of claims 1 to 6. 12. A method for controlling an optical module (12, 14, 16) for a motor vehicle, characterized in that it comprises the following steps: a light source (18) emits laser radiation (L) to a system shaping device (20), - shaping system (20) directing laser radiation (L) to white light radiation converting device (22) (B), - converting device (22) re-emits white light (B) to at least one optical system (24), and - a detector (34) detects residual light (R) emanating from the source (18) and from the conversion device (22). The method according to claim 10, further comprising the following steps: a control unit calculates at least one parameter of the light to be received by the detector (34) from the laser radiation (L) emitted by the source (18), and the control unit (32) compares the calculated parameter with at least one parameter of the residual light (R) detected by the detector (34). 14. Method according to the preceding claim, wherein, in the presence of an anomaly of a predetermined type, the control unit (32) controls at least one of the following actions: - the emission of an audible signal and / or visual to the attention of a driver of the vehicle, - stopping the emission of laser radiation (L), and -14- - decreasing the power of the laser radiation (L) emitted so that the radiation that can emerge from the optical module is radiation of class 2 or lower.