Patent Publication Number: US-2023141722-A1

Title: Method for managing image data, and vehicle lighting system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is filed under 35 U.S.C. § 371 U.S. National Phase of International Application No. PCT/EP2021/060608 filed Apr. 22, 2021 (published as WO2021214262), which claims priority benefit to French Application No. 2004089 filed on Apr. 23, 2020, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to the field of vehicle lighting systems, and more particularly to managing image data for controlling a vehicle&#39;s light sources. 
     BACKGROUND OF THE INVENTION 
     Current lighting systems comprise, in particular, light sources that now make it possible to project a high-definition light beam. The desired projection of high-definition light can be obtained via the light sources and from images, or image patterns, that the sources receive in order to display them and thus project a given light beam. These images or image patterns can achieve very high resolutions now, in particular depending on the resolution of the light source used. By way of example, the light source can have at least 4 000 to 30 000 pixels, thus making it possible to generate a light beam from an image with this level of resolution. 
     BRIEF SUMMARY OF THE INVENTION 
     To succeed in generating such high-definition light beams, multiple light sources can be used, or combined, which requires controlling them and finely synchronizing these sources in order to provide well-controlled, varied and adaptive lighting functionalities. 
     Vehicles therefore bear increasingly greater numbers of light sources, which use increasingly heavy high-definition image data, involving a large amount of data that must be managed by a vehicle control unit and communicated via a transmission means between the control unit and the one or more light sources. To do this, for example, a CAN protocol data bus is often used to transfer such data between the control unit and the light source. However, these data transmission means have the drawback of having a limited bandwidth, not allowing, for example, a bit rate of 2 to 5 Mbps to be exceeded in general. As a result, difficulties arise in transmitting the large amount of data required for said high-definition images over these limited networks. In addition, these networks are also used for the communication of other vehicle data, which means that the bandwidth available for high-definition image data can be even lower, for example limited to a range of 70 to 90% of the maximum bit rate possible over the data transmission network. 
     By way of example, to communicate high-definition image data for the projection of a lighting function with a resolution of 20 000 pixels, the bit rate required over a CAN-FD transmission network would generally be 10 to 12 Mbps. However, such a CAN-FD network is currently actually limited to 5 Mbps (or even 2 Mbps in most cases). There is therefore a need to optimize the data transmitted over these networks, and in particular to compress the data that are communicated in order to transmit a stream of high-definition image data that is sufficient to ensure the one or more associated lighting functions, while observing the bit rate and bandwidth constraints of this same network. 
     Known compression methods have been considered to overcome this problem. However, they have all proven to be inadequate with respect to high-beam specificity, thereby hindering a sufficient reduction in the bandwidth as required by vehicle manufacturers. 
     To achieve this, provision could be made for multiple levels or iterations of data compression to be carried out, until succeeding in meeting a desired bandwidth. Still, such an approach has a very significant impact on the display quality of the projected lighting functions, since with each compression performed, display quality is affected; it is reduced. 
     However, for certain lighting functions, for example adaptive driving beams (ADBs) and road writing (RW), display quality cannot be overly degraded, as otherwise the user experience will be significantly lessened, with the light information projected by the light beam being made unclear, inadequate or even illegible. 
     A solution to these problems is therefore sought in order to overcome the drawbacks mentioned above. 
     According to a first aspect of the invention, the invention provides a solution to the stated problems by means of a method for managing image data in a vehicle lighting system, the lighting system comprising:
         at least one lighting module capable of projecting lighting functions on the basis of compressed image data, and   a multiplexed bus for transmitting compressed image data to said at least one lighting module,       

     the method comprising the following steps:
         receiving an instruction to trigger at least one lighting function, said at least one lighting function being configured to be generated by the at least one lighting module from compressed image data corresponding to lighting patterns displayed in a given frequency range,   determining, for the generation of at least one lighting function at a first frequency chosen in said frequency range, a bit rate level required to transmit the compressed image data over said multiplexed bus,   comparing the determined bit rate level with a bit rate threshold value of the multiplexed bus,   compressing the image data of the at least one lighting function at:   said first frequency when the determined bit rate level is lower than or equal to said bit rate threshold value, and at   a second frequency chosen in said frequency range such that the second frequency is lower than the first frequency, when the determined bit rate level is greater than said bit rate threshold value,   transmitting the image data compressed at one of the first and second frequencies to said at least one lighting module via said multiplexed bus in order for the at least one lighting function to be generated.       

     This method thus aims to use a display frequency for the compressed image data which is dynamic, and in particular lower when the bit rate required to transmit these data is greater than the capabilities of the data transmission bus. By limiting the display frequency, at least temporarily, it is then possible to:
         reduce the amount of data to be communicated via the multiplexed bus (decrease the number of images),   maintain a high level of image data compression while observing the maximum allowed bandwidth,   maintain good image quality without having, for example, to degrade it by further compressing the already compressed image data in order to succeed in observing the maximum bit rate of the multiplexed bus,   provide for the transmission of high-definition image data over the multiplexed bus while only temporarily negatively affecting the display fluidity of the lighting function.       

     In this case, the temporary limitation on the display speed will have a small impact on the display fluidity of the lighting functions. This will not be, or be only very slightly, noticeable on lighting functions such as low beam and high beam, and will have a limited impact on the user&#39;s experience when using functions such as adaptive driving beam ADB and road writing RW. 
     According to one advantageous embodiment, the given frequency range is between 10 Hz and 120 Hz. 
     This frequency range makes it possible to address the display constraints of various lighting functions, such as, for example:
         Low beam (LB),   High beam (HB),   adaptive driving beam (ADB) or road writing (RW).       

     According to one advantageous embodiment, said first frequency is chosen between 50 Hz and 60 Hz and the second frequency is chosen between 30 Hz and 40 Hz. 
     By way of example, for a lighting function such as adaptive driving beam ADB or road writing RW, the first frequency from 50 Hz to 60 Hz may be used for good display fluidity and the second frequency from 30 Hz to 40 Hz may be used for lower fluidity in order to provide for the transmission of high-definition image data over the multiplexed bus in the event of limited bandwidth. 
     According to one advantageous embodiment, the compression of the image data of the at least one lighting function is performed with a compression rate greater than or equal to 75%. 
     A compression of at least 75% is a compression rate that allows image data for a high-definition lighting feature, or a combination of high-definition lighting features, to go over bandwidth-limited vehicle-to-vehicle transmission buses. Further preferably, the compression rate is greater than or equal to 85%. 
     According to one advantageous embodiment, the at least one lighting function is at least one light function chosen from high beam, adaptive driving beam and road writing. 
     According to one advantageous embodiment, multiple lighting functions may be generated simultaneously by the lighting system. 
     According to one advantageous embodiment, following the step of compressing the image data, when the image data are compressed at the second frequency, the method further comprises steps of:
         determining, for the generation of the at least one lighting function at the second frequency, a bit rate level required to transmit the compressed image data over said multiplexed bus,   comparing the determined bit rate level with the bit rate threshold value of the multiplexed bus,   transmitting, to said at least one lighting module via the multiplexed bus:   image data compressed at the second frequency when the determined bit rate level is lower than or equal to said bit rate threshold value, and   image data of the last image transmitted via the multiplexed bus when the determined bit rate level is greater than the bit rate threshold value.       

     According to this embodiment, in the event that the bit rate over the multiplexed bus is insufficient to allow the image data compressed at the second frequency through, provision is made to continue broadcasting the image data for the last displayed image in order to ensure that the light source will maintain a lighting function, for the safety of the driver and of other road users. 
     According to a second aspect of the invention, the invention also relates to a lighting system comprising:
         at least one lighting module capable of projecting lighting functions on the basis of compressed image data,   a multiplexed bus for transmitting compressed image data to said at least one lighting module, and   a control system configured to implement the method for managing image data as described above.       

     According to another advantageous embodiment, the control system comprises:
         a first control unit, provided with a processor unit, configured to:   compress image data according to one of the first and second frequencies for generating the at least one lighting function,   transmit, to said at least one lighting module via said multiplexed bus, the compressed image data,   a second control unit, provided with a processor unit, configured to:   receive compressed image data that are transmitted via said multiplexed bus,   decompress the received image data,   generate the at least one lighting function according to one of the first and second frequencies from the received and decompressed image data.       

     According to another advantageous embodiment, the at least one lighting module comprises at least one semiconductor light source, such as LEDs, and in particular a pixelated LED source. 
     In comparison with incandescent lighting, semiconductor lighting generates visible light with lower heat production and less energy dissipation. The generally low weight of a semiconductor electronic lighting device affords greater resistance to impacts and vibrations than brittle glass tubes/bulbs and long, thin filament wires. They are also not subject to filament evaporation, which may increase the service life of the lighting device. Some examples of these types of lighting comprise solid-state light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), or polymer light-emitting diodes ( 60   s ) as light sources instead of electrical filaments, plasma or gas. The high-definition lighting functions may be provided by projecting one or more light beams projected by an LED source or a set of LEDs, or by a pixelated LED source. 
     Unless otherwise defined, all terms (including technical and scientific terms) used in this document should be interpreted in accordance with the standard practices of the profession. It is also understood that terms in common use are to be interpreted as customary in the relevant art and not in an idealized or overly formal sense, unless expressly defined as such herein. 
     In this text, the term “comprises” and derivatives thereof (such as “comprising”, etc.) should not be understood in an exclusive sense, i.e. these terms should not be interpreted as excluding the possibility that what is described and defined may include other elements, steps, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To supplement the description and to allow better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate one embodiment of the invention, which should not be interpreted as limiting the scope of the invention, but merely as an example of how the invention may be carried out. The drawings comprise the following figures: 
         FIG.  1    shows a first embodiment of the lighting system according to the invention. 
         FIG.  2    shows a second embodiment of this lighting system. 
         FIG.  3    shows a third embodiment of this lighting system. 
         FIG.  4    shows a first representation of steps of the method for managing image data according to the invention. 
         FIGS.  5 A and  5 B  show the result on the compression rate obtained by virtue of the frequency change when the method according to the invention is used. 
         FIG.  6    shows a vehicle lighting device comprising at least a portion of the lighting system according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In these figures, the following references have been used:
           2  Low-beam lighting function     4  High-beam lighting function     6  Adaptive driving beam lighting function     8  Road writing lighting function     10  Lighting system     20  Control system     30  Lighting function driver module     40  Multiplexed data transmission bus     50  Lighting module     60 ,  62 ,  64 ,  66 ,  68  Semiconductor light source     70  First control unit     72  Second control unit     80  First processor unit     82  Second processor unit     52  First lighting module     54  Second lighting module     100  Instruction-receiving step     110  Determining step     120  Comparing step     130  Compressing image data step     140  Transmitting compressed image data step     200  First compression frequency     205  Second compression frequency     210  First compression rate     215  Second compression rate     90  vehicle lighting device     95  lighting optic       

     The exemplary embodiments are described in sufficient detail to allow those of ordinary skill in this art to carry out and implement the systems and methods described herein. It is important to understand that these embodiments may be provided in a number of alternative forms and should not be construed as being limited to the examples presented here. 
     Consequently, although the embodiments may be modified in various ways and take various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below by way of example. No limitation to the particular examples disclosed is intended. Rather, all modifications, equivalents and alternatives falling within the scope of the appended claims are to be included. 
     Reference is first made to  FIG.  1    which shows a first embodiment of the lighting system  10  according to the invention. The lighting system  10  comprises in particular: 
     at least one lighting module  50  capable of projecting lighting functions on the basis of compressed image data, 
     a multiplexed bus  40  for transmitting compressed image data to the lighting module  50 , and 
     a control system  20  configured to implement the method for managing image data as proposed, with a view to generating given lighting functions. 
     To this end, the control system  20  may receive instructions from a vehicle control unit (not shown in the figures) to generate each of the lighting functions independently of each other or, conversely, in combination. For example, the lighting functions may be combined with each other in pairs. According to another example, three or four lighting functions, or even all of the possible lighting functions, may be combined with each other. 
     The vehicle control unit may generate the instructions for generating lighting functions from a lighting command given by the driver, or from a lighting command determined by a detection unit, such as a camera or a light detector. 
     The instructions received by the control system  20  may, in particular, be instructions for generating a light beam corresponding to the following lighting functions:
         Low beam  2 ,   High beam  4 ,   Adaptive driving beam  6 , or   Road writing  8 .       

     What is meant by adaptive driving beam  6  is any lighting function that allows the lighting beam to be varied dynamically in order to adapt it to vehicle traffic situations. For example, this may relate to a function in which the lighting is projected with high-beam type photometry while avoiding dazzling other road users. As a variant or in addition, the function may relate to: 
     a photometry that allows dynamic directional lighting, in other words a horizontal displacement of the maximum intensity of an LB  2  or HB  4  photometry depending on the rotational angle of the steering wheel of a motor vehicle (also known as DBL for dynamic bending light); 
     lighting that makes it possible to avoid glare from road signs as a result of the projection of light beams from the motor vehicle (also known as TSAG for traffic sign anti-glare); 
     lighting that allows the projection of line-type patterns on the road, in particular to delimit a portion of road to be taken by the motor vehicle or to present an obstacle avoidance strategy (also known as LA for line assist). 
     What is meant by road writing  8  is any lighting function that allows the projection on the road of patterns visible to the driver and/or road users, in particular driving aids, signaling symbols or other indicators for navigation, for example. 
     The control system  20  may further comprise a driver module  30  for driving the vehicle&#39;s light sources, which is able to receive the instructions for generating lighting functions and to control the vehicle&#39;s light sources so as to generate the desired light beam for the requested lighting function. To do this, the control module  30  may, in particular, interface with the multiplexed bus  40  to transmit the required image data to the lighting module  50  in order to project the desired lighting functions. 
     The multiplexed bus may be chosen from any data transmission bus known in the vehicle field, and in particular a CAN or CAN-FD protocol data bus. 
     To generate light beams associated with lighting functions to be triggered, the lighting module  50  comprises at least one light source, and in particular a semiconductor light source  60 , such as LEDs, and in particular a pixelated LED source. 
     In this way, the lighting system  10  is able to cause light beams to be projected by the light source  60  based on compressed image data received via the multiplexed bus  40 . In addition, the lighting system  10  aims to compress the image data via the control system  20 , for example at the level of the driver module  30 , according to the desired lighting functions and the implementation of the proposed method for managing image data. 
     Reference is now made to  FIG.  2    which shows a second embodiment of the lighting system  10 , in which the control system  20  further comprises:
         a first control unit  70  (for example integrated into the driver module  30 ) equipped with a processor unit  80  configured to:   compress image data for lighting functions HB  4 , ADB  6 , RW  8 ,   transmit the compressed image data to the lighting module  50  via the multiplexed bus  40 ,   a second control unit  72  (for example integrated into the lighting module  50 ) equipped with a processor unit  82  configured to:   receive compressed image data that are transmitted via said multiplexed bus  40 ,   decompress the received image data,   generate the at least one lighting function HB  4 , ADB  6 , RW  8  based on the received and decompressed image data.       

     Reference is now made to  FIG.  3    which shows a third embodiment of the lighting system  10  in which the control system  20  comprises a first lighting module  52  and a second lighting module  54 , which may be configured to be:
         each integrated into a different headlamp of the vehicle, for example the first module  52  into the right headlamp of the vehicle and the second module  54  into the left headlamp of the vehicle;   integrated into one and the same headlamp of the vehicle.       

     In addition, each module  52  and  54  may comprise a plurality of light sources  62 ,  64 ,  66 ,  68  to allow the light beams of the desired lighting functions LB  2 , HB  4 , ADB  6 , RW  8  to be generated. The light sources  62 ,  64 ,  66 ,  68  may, in particular, be semiconductor light sources  60 , such as LEDs, and in particular pixelated LED sources, for example having a resolution of 2 500, 4 000 or 20 000 pixels. 
     To compress the image data, the desired compression rate is preferably higher than or equal to 75%, or even more preferably higher than or equal to 85%. This is because a compression of at least 75% is a compression rate that allows image data for a high-definition lighting feature, or a combination of high-definition lighting features, to go over bandwidth-limited vehicle-to-vehicle transmission buses, such as the multiplexed bus  40 . 
     Reference is now made to  FIG.  4    which shows a representation of the steps of the method for managing image data according to the invention. The method comprises, in particular, the following steps:
         receiving  100  an instruction to trigger at least one lighting function HB  4 , ADB  6 , RW  8 , the at least one lighting function HB  4 , ADB  6 , RW  8  being configured to be generated by the at least one lighting module  50  from compressed image data corresponding to lighting patterns displayed in a given frequency range (FPSRg),   determining  110 , for the generation of at least one lighting function HB  4 , ADB  6 , RW  8  at a first frequency  200  (FPS50) chosen in the frequency range (FPSRg), a bit rate level (NvDbReq) required to transmit the compressed image data over the multiplexed bus  40 ,   comparing  120  the determined bit rate level (NvDbReq) with a bit rate threshold value (NvDb0) of the multiplexed bus  40 , compressing  130  the image data of the at least one lighting function HB  4 , ADB  6 , RW  8  at:   the first frequency  200  (FPS50) when the determined bit rate level (NvDbReq) is lower than or equal to (output N of  120 ) the bit rate threshold value (NvDb0), and at   a second frequency  205  (FPS40) chosen in the frequency range (FPSRg) such that the second frequency  205  (FPS40) is lower than the first frequency  200  (FPS50), when the determined bit rate level (NvDbReq) is greater than (output Y of  120 ) the bit rate threshold value (NvDb0),   transmitting  140  the image data (COMPR_DATA) compressed at one of the first  200  (FPS50) and second  205  (FPS40) frequencies to said at least one lighting module  50  via said multiplexed bus  40  in order for the at least one lighting function HB  4 , ADB  6 , RW  8  to be generated.       

     The display frequency for the compressed image data is thus driven dynamically. This dynamic management of the display frequency makes it possible, in particular, to adapt the compression rate for the image data so that they may be transmitted adequately via the multiplexed bus  40 . 
     The given frequency range (FPSRg) may, in particular, be between 10 Hz and 120 Hz. This frequency range (FPSRg) may also be expressed as a number of images per second, also called FPS for frames per second, which means that the given frequency range (FPSRg) may be between 10 FPS and 120 FPS. 
     This frequency range (FPSRg) makes it possible to address the display constraints of various lighting functions, such as, for example:
         Low beam  2 ,   High beam  4 ,   Adaptive driving beam  6 , or   Road writing  8 .       

     In particular, the first frequency may be chosen between 50 Hz and 60 Hz (which is equivalent to 50 to 60 FPS) and the second frequency may be chosen between 30 Hz and 40 Hz (which is equivalent to 30 to 40 FPS). 
     By way of example, for a lighting function such as adaptive driving beam  6  or road writing  8 , the first frequency from 50 Hz to 60 Hz (50 to 60 FPS) may be used for good display fluidity and the second frequency from 30 Hz to 40 Hz (30 to 40 FPS) may be used for lower fluidity in order to provide for the transmission of high-definition image data over the multiplexed bus  40 . 
     For the compression of the image data as performed in step  130 , whether at the first frequency  200  (FPS50) or the second frequency  205  (FPS40), the desired compression rate is preferably greater than or equal to 75%. This is because a compression of at least 75% is a compression rate that allows image data for a high-definition lighting function, or a combination of high-definition lighting functions, to go over bandwidth-limited vehicle transmission buses, such as the multiplexed bus  40 . 
     In the compressing step  130 , depending on the instruction to trigger a lighting function that is received, the compressed image data may be:
         those for one and the same lighting function, in particular chosen from high beam  4 , adaptive driving beam  6  and road writing  8 ,   those resulting from the combination of multiple lighting functions such as, for example, the combination of adaptive driving beam  6  and road writing  8 .       

     Furthermore, in the step of compressing  130  the image data, when the image data are compressed at the second frequency  205  (FPS40), 
     the method may further comprise additional steps (not illustrated in the figures) of:
         determining, for the generation of the at least one lighting function HB  4 , ADB  6 , RW  8  at the second frequency  205  (FPS40), a bit rate level (NvDbReq) required to transmit the compressed image data over the multiplexed bus  40 ,   comparing the determined bit rate level (NvDbReq) with the bit rate threshold value (NvDb0) of the multiplexed bus  40 ,   transmitting, to the lighting module  50  via the multiplexed bus  40 :   image data compressed at the second frequency  205  (FPS40) when the determined bit rate level (NvDbReq) is lower than or equal to the bit rate threshold value (NvDb0), and   image data of the last image transmitted via the multiplexed bus  40  when the determined bit rate level (NvDbReq) is greater than the bit rate threshold value (NvDb0).       

     Thus, in the event that the bit rate over the multiplexed bus  40  is insufficient to allow the image data compressed at the second frequency  205  (FPS40) through, provision is made to continue broadcasting the image data for the last displayed image in order to ensure that the light source will keep at least one lighting function in operation, for the safety of the driver and of other road users. 
     Reference is now made to  FIG.  5 A  and  FIG.  5 B  which show the result on the compression rate that is obtained by virtue of the frequency change when the method according to the invention is used. By limiting the display frequency, that is to say by changing the display frequency for the function to be displayed from a first frequency  200  (FPS50) to a second frequency  205  (FPS40), which is lower, the amount of image data to be compressed is reduced. As a result, the total required compression rate  210  (over the set of images per second) for the first display frequency  200  (FPS50) may be improved, and change to a compression rate value  215  that is higher than  210 . 
     By virtue of the method, it is then possible to:
         reduce the amount of image data to be communicated via the multiplexed bus,   maintain a high level of image data compression while observing the maximum allowed bandwidth,   maintain good image quality without having, for example, to degrade it by further compressing the already compressed image data in order to succeed in observing the maximum bit rate of the multiplexed bus,   provide for the transmission of high-definition image data over the multiplexed bus while only temporarily negatively affecting the display fluidity of the lighting function.       

     Reference is now made to  FIG.  6    which shows a vehicle front-headlamp lighting device  90 , this lighting device  90  comprising:
         the lighting module  50  comprising at least one light source  60 ;   an optic  95  associated with the light source  60  to generate light beams for desired lighting functions;   the control unit  72  to perform the steps of receiving and decompressing the compressed image data.       

     The invention has been described with reference to particular embodiments, which are not limiting. Of course, the present invention is not limited to the embodiment described by way of an example and it extends to other alternative embodiments. 
     For example, the invention could also apply to a lighting system comprising at least one vehicle taillight and/or one vehicle signaling light and/or one vehicle interior lighting module with a view to generating the lighting functions associated therewith while benefiting from the advantages proposed by and obtained using the invention by means of the technique of compressing image data according to a dynamic display frequency.