DEVICE AND METHOD FOR CONTROLLING MATRIX LIGHT SOURCES

Description

[0001] The invention relates to lighting modules for motor vehicles. In particular, the invention relates to such modules involving matrix light sources.

[0002] A light-emitting diode, LED, is a semiconductor electronic component capable of emitting light when passed through it by an electric current having at least a threshold intensity. In the automotive field, LED technology is increasingly used for various light signaling solutions. LED matrices are particularly interesting in the field of automotive lighting. Matrix light sources can be used for "leveling" type functions, i.e., adjustment of the height of the emitted light beam, depending on the vehicle's attitude and the road profile.Other applications include DBL ("Digital Bending Light"), which corresponds to the adjustment of the direction of the emitted light beam, to follow the road in the horizontal plane, ADB ("Adaptive Driving Beam"), which corresponds to an anti-glare function that generates shadow zones in the light beam emitted by a main beam so as not to disturb other road users, but also functions for projecting patterns on the ground using the pixelated light beam.

[0003] It is known to use light sources of different types of technologies for the lighting applications mentioned. This is for example the monolithic technology, according to which a large plurality of elementary sources of the LED type, equivalent to pixels, are etched in a common semiconductor substrate. Integrated electrical connections make it possible to activate the pixels independently of each other. Another known technology is that of microLEDs, which generates a matrix of LEDs of small dimensions, typically less than 150µm. There are also micro-mirror type modules, DMD (Digital Micro-Mirror Device), which involve a projection technology using an intensity modulator on a uniform beam.Micro-mirrors, whose position is controlled by means of piezoelectric elements, are oriented so as to selectively reflect an incident light beam, so that each micro-mirror corresponds to an elementary source of the pixel matrix thus generated. The light from a source is directed onto the micro-mirror matrix by an optic. This light therefore has a variable distribution from one module to another, due to the positioning and manufacturing tolerances of the optics and the light source. This results in a variable maximum intensity from one module to another, for a given pixel. In this case, each pixel will have a different maximum intensity depending on the command transmitted to it. Such lighting devices are designed by mass production methods.There must be clearance between the constituent elements of the lighting and / or signaling device, on the one hand to allow easy assembly, and on the other hand because the parts are generally not machined but rather molded in plastic, which reduces the production cost.

[0004] It is particularly important to emphasize the difficulty of perfectly aligning a micro-mirror matrix with the optical projection part, which generally comprises at least one lens. Due to the large numerical aperture of the objective used for the projection function, the projection quality of the image deteriorates significantly as soon as the lateral offset of the optical axis reaches a few micrometers. In practice, distortions of the projected image are therefore inevitable when using solutions known in the art. Each projection module of this type has its own set of optical characteristics, in particular geometric aberration characteristics, including optical distortion and spherical aberration properties. When producing micro-mirrors, geometric aberrations can be introduced. All of these elements result in non-homogeneous behavior of the matrix light source.

[0005] All of these aforementioned modules have their own characteristics related to the combination of manufacturing tolerances of the components. During the production of semiconductor components such as LEDs or LED matrices, variations in direct current are currently unavoidable. It follows that in a given LED matrix, at equal load current, the LEDs emit light beams of variable, non-homogeneous intensities.

[0006] Documents FR3072531 A1 and FR3055980 A1 show that it is known to store calibration data in a lighting module.

[0007] The invention aims to overcome at least one of the problems posed by the prior art. More specifically, the invention aims to propose a lighting module and a control method that make it possible to calibrate the luminous and / or geometric behavior of the elementary light sources grouped in a matrix light source of a motor vehicle. The aim is to provide the means to produce a homogeneous light beam that conforms to a predetermined setpoint, independently of the instance of the matrix light source installed in the lighting module.

[0008] According to a first aspect of the invention as defined in claim 1, a lighting module for a motor vehicle is provided. The lighting module comprises a matrix light source grouping a plurality of elementary light sources, a data receiving unit for receiving a lighting setpoint, and a control unit intended to control said matrix light source as a function of said lighting setpoint. The lighting module comprises a memory element to which the control unit has read access, and in which calibration data specific to each of the elementary light sources are recorded.

[0009] The receiving unit may preferably include a network interface capable of receiving data on a data bus internal to the motor vehicle. For example, the bus may be an Ethernet bus, a Gigabit Multimedia Serial Link, GMSL, bus, or a Low Voltage Differential Signaling, LVDS, technology bus, such as an FPD-Link III bus.

[0010] The control unit may preferably comprise a microcontroller element. The control unit may preferably comprise a chip of the “Field Programmable Gate Array”, FPGA, “Application Specific Integrated Circuit”, ASIC, or “Complex Programmable Logic Device”, CPLD type. These elements are configured by means of an appropriate computer program to implement the described functionalities.

[0011] The matrix light source may preferably comprise a monolithic source, comprising elementary electroluminescent light sources with semiconductor elements etched in a common substrate and activatable independently of each other.

[0012] The matrix light source may preferably comprise a micro LED type matrix, comprising a matrix of elementary sources produced by light-emitting diodes, LEDs, of small dimensions, typically less than 150 µm.

[0013] The matrix light source may preferably comprise a micro-mirror device, DMD, (“Digital micromirror device”), in which an elementary source comprises a micro-mirror of a matrix, which selectively reflects an incident light beam depending on its position.

[0014] Preferably, said lighting instruction may comprise an elementary instruction per elementary light source.

[0015] Said lighting instruction may preferably comprise an image. Preferably, at least one pixel of the image may correspond to an elementary light source. The resolution of the image may preferably be greater than the projection resolution of the matrix light source. Preferably, one pixel of the image may correspond to an elementary light source.

[0016] Preferably, the calibration data may include for each elementary source an indication of the light intensity emitted as a function of an electric charging current.

[0017] Preferably, the calibration data may include an indication of a geometric aberration of a light beam that the module is capable of emitting.

[0018] According to the invention, the control unit can be configured to transmit at least part of said calibration data to a control module of the motor vehicle.

[0019] The lighting module may preferably comprise a second memory element in which data for authenticating the module is stored. Preferably, the lighting module may comprise a processor programmed to encrypt and / or sign data using a cryptographic key stored in said memory element.

[0020] A lighting device for a motor vehicle is provided which comprises at least one lighting module according to the preceding aspect of the invention.

[0021] According to another aspect of the invention, as defined in claim 6, a method of controlling a matrix light source of a lighting module for a motor vehicle is provided. The lighting module is in accordance with one aspect of the invention.

[0022] Preferably, the at least part of the calibration data transmitted to the control module of the motor vehicle may comprise data indicating a geometric aberration.

[0023] The control method may preferably comprise a step of generating a default lighting setpoint, determined using said calibration data as well as data relating to the motor vehicle, and a step of recording the default lighting setpoint in a memory element of the lighting module.

[0024] Preferably, the generation of said default lighting setpoint can be carried out by the control module of the motor vehicle following the reception of said calibration data from the control unit of the lighting module. The setpoint can then preferably be transmitted to said control unit which records it in a memory element.

[0025] The default setpoint may preferably replace the lighting setpoint received in step a) if a fault in the lighting module and / or the control module of the motor vehicle is detected.

[0026] Preferably, at least part of the data exchanged between the control module of the motor vehicle and the control unit of the lighting module can be encrypted and / or signed using at least one cryptographic key.

[0027] Preferably, a failure at the lighting module and / or the control module of the motor vehicle can be detected when the decryption of the data is not successful or when said signature cannot be validated.

[0028] In one embodiment, a method for pairing between a lighting module for a motor vehicle, according to one aspect of the invention, and a control module of a motor vehicle is provided. The method is remarkable in that it comprises the following steps: at the lighting module control unit, transmitting the calibration data stored in the memory element to the control module of the motor vehicle; at the control module, using data relating to the motor vehicle, such as for example the attitude, the position of the lighting module, the position of other lighting modules, generating a default lighting setpoint and transmitting it to the lighting module control unit; at the lighting module control unit, storing the default setpoint in a memory element.

[0029] Preferably, the default instruction may include an image corresponding to a low beam illumination. Preferably, the default instruction may include a low beam cutoff.

[0030] According to another aspect of the invention, a computer program comprising a sequence of instructions is provided. When the instructions are executed by a processor, they cause the processor to implement the method according to one aspect of the invention.

[0031] According to a final aspect of the invention, a non-transitory computer-readable storage medium is provided. The medium stores a computer program according to one aspect of the invention.

[0032] By using the measurements proposed by the present invention, it becomes possible to propose a lighting module as well as a control method which make it possible to calibrate the luminous and / or geometric behavior of the elementary light sources grouped in a matrix light source of a lighting module of a motor vehicle. Aspects of the invention make it possible to produce a homogeneous light beam conforming to a predetermined setpoint, independently of the instance of the matrix light source installed in the lighting module. To achieve this, in accordance with aspects of the invention it is proposed that the calibration parameters are stored in a memory fixed to the lighting module, said parameters comprising for example brightness or electric current correction values ​​for each pixel of a matrix source, or geometry corrections of the beam produced by the light module.In this way, it is ensured that the data associated with the module are physically attached to it, in particular when pairing the lighting module with the motor vehicle. This makes it possible to avoid an additional parameterization step which could cause errors when assembling a vehicle headlight using the lighting module. By using the measures of the invention, an assembly or a change of module can be carried out without software manipulation: for example, there is no need to transfer or update data relating to the module in a memory of the motor vehicle controller.

[0033] Other features and advantages of the present invention will be better understood with the aid of the description of the examples and the drawings among which: there Fig. 1 is an illustration of a light module according to an exemplary embodiment which is not according to the invention, the Fig. 2 is an illustration of a light module in accordance with a preferred embodiment of the invention; the Fig. 3 shows the sequence of the main steps of a method according to an exemplary embodiment which is not according to the invention; Fig. 4 shows the sequence of the main steps of a method in accordance with a preferred embodiment of the invention.

[0034] The description focuses on the elements of a lighting module for a motor vehicle that are necessary for understanding the invention. Other elements, which are known to be part of such modules, will not be mentioned or described in detail. For example, the presence and operation of a converter circuit involved in the power supply of a matrix light source, known per se, will not be described in detail. The same applies to optical elements such as lenses, for example.

[0035] The illustration of the figure 1 shows a lighting module 100 for a motor vehicle according to an exemplary embodiment. The module comprises a matrix light source 110 grouping together a plurality of elementary light sources 112. In the example illustrated, it is a matrix of LEDs without the invention being limited to this example. The matrix light source can also be produced by a micro-mirror device, for which each mirror is adapted to generate an elementary light beam of a matrix. The module comprises a data reception unit 120, this is for example an interface capable of receiving and decoding messages on a data bus internal to the motor vehicle, such as a CAN (Controller Area Network) type bus. The data reception unit 120 is capable of receiving a lighting instruction 10, typically determined by a control module (not illustrated) of the motor vehicle.The ignition instruction may for example comprise a brightness value, such as a gray level, encoded on a predetermined number of bits and to be produced by each of the elementary light sources 112. The ignition instruction may therefore be a digital image, and it may in particular be a frame of a stream of such images, constituting a video signal. A control unit 130 is intended to control said matrix light source as a function of said lighting instruction. The control unit may be connected to, or comprise, a circuit for controlling the electrical power supply of the elementary light sources 112, which is controlled to supply the elementary light sources so as to produce the instruction 10.The module 100 further comprises a memory element 140, such as a flash-type memory, to which the control unit 130 is operatively connected and has read access, and in which calibration data 150 specific to each of the elementary light sources 112 are recorded. For example, the data may comprise for each elementary light source 112 a value indicating the difference in brightness relative to the average brightness of the matrix source 110, possibly over a range of charging current intensities. In order to guarantee a homogeneous light intensity, the control unit 130 adjusts the received setpoint values ​​10 by adding or subtracting the respective differences therefrom, before controlling the elementary light sources in accordance with the result.The data 150 may nevertheless comprise more complex optical or geometric calibration parameters, without departing from the scope of the present invention. In such a case, instead of acting solely at the level of each light source or each pixel individually, the correction of the setpoint 10 may advantageously generate a correction at the level of the entire setpoint, i.e. of the entire image to be projected, or at the level of at least one part or zone of this image. For example, the projected image without the setpoint correction could have a concave curved appearance due to the projection optics at the edges of the projection zone. The realization of the pre-corrected setpoint, which takes into account the calibration data including the geometric deformation inflicted by the projection optics, results in a projected image having a geometry closer to the desired non-curved geometry.To apply a correction of geometric aberrations, it is useful to apply a deformation to the entire setpoint image 10. Since it is discretized, this deformation causes a degradation of the information contained in the initial image. It is therefore advantageous for the setpoint image transmitted from the vehicle control unit to the control unit to have a resolution higher than the projection resolution of the light module. The control unit 130 comprises a microcontroller element having sufficient computing power to correct the setpoint 10, or a stream of setspoints, in real time, by applying the calibration data 150 thereto.

[0036] The illustration of the figure 2 shows a lighting module 200 for a motor vehicle according to one embodiment of the invention. The module comprises a matrix light source 210 grouping together a plurality of elementary light sources 212. The module comprises a data reception / transmission unit 220, 222. The data reception unit 220 is capable of receiving a lighting instruction 10, typically determined by a control module 20 of the motor vehicle. The lighting instruction may for example comprise a brightness value, such as a gray level, encoded on a predetermined number of bits and to be produced by each of the elementary light sources 212. A control unit 230 is intended to control said matrix light source as a function of said lighting instruction.The module 200 further comprises a memory element 240, such as a flash-type memory, to which the control unit 230 is functionally connected and has read access, and in which calibration data 250 described in the context of the preceding embodiment, and specific to each of the elementary light sources 212 are recorded. For example, the data may comprise for each elementary light source 212 a value indicating the difference in brightness compared to the average brightness of the matrix source 210, possibly over a range of charging current intensities. The illustrated lighting module is arranged to transmit at least part of the calibration data 250, and preferably all of this data, to the control module 20. This is for example carried out during an initialization phase of the lighting module.In order to guarantee a homogeneous light intensity, the control module 20 takes into account the calibration values ​​250 thus received to determine the setpoint image 10. For example, the control module 20 adjusts the setpoint values ​​10 by adding or subtracting the respective differences, before transmitting the result to the lighting module 200. The data 250 may nevertheless comprise more complex optical or geometric calibration parameters, without departing from the scope of the present invention. In this embodiment, the control unit 230 is freed from the task of correcting the setpoint, and it can be carried out by a less expensive microcontroller element with less computing power.

[0037] There figure 3 shows schematically the control process implemented using the example embodiment which has just been described in relation to the figure 1 . In step a), the lighting setpoint 10 is determined by the control module of the motor vehicle and transmitted to the lighting module, which corresponds to step a1). Upon receipt of the setpoint 10, the control unit 130 controls the matrix light source 110 by correcting the setpoint 10 using the calibration data 150 stored in the memory element 140, which corresponds to step b).

[0038] There figure 4 shows schematically the control method carried out using the embodiment of the invention which has just been described in relation to the figure 2 . In the preliminary step i), at least a part of the calibration data 250 stored in the memory element 240 is transmitted from the lighting module 200 to the control module 20 of the motor vehicle. In step a), the lighting setpoint 10 is determined by the control module of the motor vehicle and corrected according to the received calibration data 250, and transmitted to the lighting module, which corresponds to step a2). In step b), the control unit 230 of the lighting module 200 controls the matrix light source 210 of the lighting module according to said lighting setpoint, which now already depends on the calibration data 250 stored in the memory element 240.

[0039] The exchange of data between the light module 200 and the control module 20 of the motor vehicle when the two modules are paired allows other interesting applications. In particular, it is proposed to combine data relating to the vehicle, such as for example parameters of orientation, position, or attitude of the vehicle, or even information relating to light fluxes emitted by other headlights of the vehicle, which are a priori only available at the level of the control module 20, with the calibration data 250, available at the level of the lighting module 200 and specific to the matrix source 210 embedded in it. This information is used, typically but in a non-limiting manner by the control module 20 of the motor vehicle to generate a default instruction or image.Indeed, the control module of the motor vehicle generally has an increased computing capacity compared to the control unit 230 of the lighting module. Alternatively, this calculation can be carried out by the control unit 230 of the lighting module after a corresponding exchange of the data required for this calculation between the control unit of the motor vehicle on the one hand, and the control unit of the lighting module on the other hand. A default image is an image which is projected by the module when a fault or a breakdown is detected. Thus, the module may preferably comprise an electronic error detection circuit, or a microprocessor programmed for this purpose by an appropriate computer program.The error detection circuit is configured to detect, for example, that the data received by the control module of the motor vehicle are inconsistent, or that the connection between the control module of the motor vehicle and the lighting module 200 is no longer reliable. Following this error detection, the default image is projected instead of the target image, in order to avoid potential dazzling of other road users. The default image is generated to take into account the specificities of the matrix light source 210 on the one hand, and of the vehicle with which it is equipped on the other hand. Thus, the default image can, for example, be generated accurately and automatically for each motor vehicle and each lighting module with which it is equipped. Preferably, the default image resulting from this method is transmitted to the lighting module, which stores it permanently in a dedicated memory element.In the event of a communication failure between the control module 20 of the motor vehicle and the lighting module 200, the default setpoint then serves as a control for the matrix light source. The default image or setpoint may, for example, correspond to dipped beam lighting. In particular, this image may correspond to a dipped beam cut-off. Indeed, the cut-off must be well defined to comply with the regulations in force.

[0040] The data exchange between the control module 20 of the motor vehicle and the lighting module 200 previously defined and as illustrated by the figure 4 also allows to add an authentication function between the two modules 20 and 200 respectively.

[0041] It should be noted that this authentication function can also be implemented independently of the calibration function and / or the exchange of calibration / attitude data and without the presence of the memory element 240 at the level of the lighting module 200.

[0042] The authentication function may for example comprise the exchange of public cryptographic keys between the two modules in question, thus allowing verification by each of the authenticity of signed data using the corresponding private cryptographic keys. Alternatively or cumulatively, the control unit 230 of the lighting module 200 sends an acknowledgment of receipt to the control module 20 for a received data packet, the acknowledgment of receipt comprising a part making it possible to authenticate the microcontroller. The data packet may for example contain calibration data, and / or default image data and / or data for generating a default image and / or all or part of an image and / or a group of images, and / or a packet of a compressed video stream. In a preferred embodiment, this authentication is not performed on all the packets.In this way, the corresponding computational load is reduced and smoothed over time. Alternatively, the authentication function may comprise sending, from the control module 20 of the motor vehicle to the control unit 230 of the lighting module, a header for a sent data packet, the header comprising a part making it possible to authenticate the control module 20, the data packet being of the same type as previously defined. Advantageously, this authentication is not carried out on all the packets. In this way, the corresponding computational load is reduced and smoothed over time.

[0043] In order to carry out the authentication function, the lighting module 200 as well as the control module 20 of the motor vehicle comprise calculation means for generating the header respectively the acknowledgment of receipt used for authentication. Preferably, the generation is done according to of a time or date, which can be expressed in any unit of time, for example in milliseconds, or of a counter counting exchanges or calculation cycles, or of another element which evolves with the number of exchanges, which can be reset when it exceeds a predefined size.

[0044] In the event that authentication between the controller and the microcontroller fails, the lighting function can be put into a communication failure mode. Advantageously, the failure mode is only activated when authentication failures are repeated, which makes it possible to avoid activating the failure mode if the link has been disturbed, for example by transient electromagnetic disturbances, which is particularly advantageous in the case of an authentication function using headers or acknowledgments.

[0045] In the case where the control unit 230 comprises a computer, it can implement a data exchange encryption function, in which data encrypted by the control module 20 of the motor vehicle are decrypted by the computer. Advantageously, the computer has a method for determining whether the stream is not decoded correctly. If the stream is not decoded correctly, the computer can enter a communication failure mode. The communication failure mode can involve the following procedures, taken alone or in combination: stopping the lighting function or the projection by the lighting module of a default image, the generation by the control module 20 of a failure signal transmitted to a central management system of the automobile, the passage of the calculator into an authentication mode where the calculator continues to launch an authentication procedure with the calculator of the control module 20 (or vice versa). In the authentication mode, the sending of data packets can be interrupted.

[0046] It goes without saying that the embodiment described does not limit the scope of protection of the invention. By using the description just given, other embodiments are conceivable without departing from the scope of the present invention.

[0047] The scope of protection is determined by the claims.

Claims

1. A lighting module (200) for a motor vehicle comprising a matrix light source (210) grouping together a plurality of elementary light sources (212), a data reception unit (220) for receiving a lighting setpoint (10), and a control unit (230) intended to control said matrix light source according to said lighting setpoint, the module comprising a memory element (240) to which the control unit (230) has read access, and in which calibration data (250) specific to each of the elementary light sources (212) are stored, characterized in that the control unit is configured to transmit at least some of said calibration data (250) to a control module (20) of the motor vehicle.

2. The lighting module as claimed in the preceding claim, characterized in that said lighting setpoint (10) comprises an elementary setpoint per elementary light source (212).

3. The lighting module as claimed in the preceding claim, characterized in that said lighting setpoint (10) comprises an image, of which at least one pixel corresponds to an elementary light source (212).

4. The lighting module as claimed in one of the preceding claims, characterized in that the calibration data (250) comprise, for each elementary source (212), an indication of the light intensity emitted as a function of an electric load current and / or an indication of a geometric aberration of a light beam that it is capable of emitting.

5. The lighting module (200) as claimed in one of the preceding claims, characterized in that the module comprises a second memory element in which data allowing the module to be authenticated are stored.

6. A method for controlling a matrix light source of a lighting module (100, 200) for a motor vehicle as claimed in one of claims 1 to 7, characterized in that the method comprises a preliminary transmission step, at the control unit (230) for the lighting module, at least some of the calibration data (250) stored in the memory element (240) to a control module (20) of the motor vehicle connected to the control module by a communication channel, and in that the method further comprise the following steps: a) at a control module (20) of the motor vehicle, determining a lighting setpoint (10), correcting the setpoint by using the calibration data received, and transmit said corrected lighting setpoint (10) to the control unit (230) of the light module; b) at the control unit (230) for the lighting module, controlling the matrix light source (210) of the lighting module according to said corrected lighting setpoint.

7. The control method as claimed in claim 6, characterized in that it comprises a step of generating a default lighting setpoint, determined by using said calibration data (250) as well as data relating to the motor vehicle, and a step of storing the default lighting setpoint in a memory element of the lighting module.

8. The control method as claimed in claim 7, characterized in that said default lighting setpoint is generated by the control module (20) of the motor vehicle following the reception of said calibration data (250) from the control unit (230) for the lighting module, and in that the setpoint is then transmitted to said control unit (230) which stores it in a memory element.

9. The control method as claimed in either of claims 7 and 8, characterized in that the default setpoint replaces the lighting setpoint (10) received in step a) if a failure at the lighting module (200) and / or at the control module (20) of the motor vehicle is detected.

10. The control method as claimed in one of claims 6 to 9, characterized in that at least some of the data exchanged between the control module (20) of the motor vehicle and the control unit (230) for the lighting module (200) are encrypted and / or signed by means of at least one cryptographic key.

11. The control method as claimed in claim 10, characterized in that a failure at the lighting module (200) and / or at the control module (20) of the motor vehicle is detected when the decryption of the data is unsuccessful or when said signature cannot be validated.