Automotive vehicle lighting system equipped with a light module capable of emitting a pixelated light beam
The vehicle lighting system uses high-frequency alternating control signals to achieve precise luminous intensity control at gantry and glare points, ensuring regulatory compliance and user comfort without additional bit resolution, addressing the limitations of conventional PWM methods.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-11-10
- Publication Date
- 2026-03-13
AI Technical Summary
Existing vehicle lighting systems struggle to precisely control luminous intensity at gantry points and glare points, as the regulatory thresholds are close and conventional PWM control methods with limited bit resolution fail to achieve seamless compliance without increasing cost or perceptibility.
A vehicle lighting system with a controller that alternates control signals for critical light sources at high frequency, allowing intermediate luminous intensities between regulatory thresholds, using a single duty cycle value to ensure compliance without additional bits.
The system achieves regulatory compliance by reducing the step size of luminous intensity changes, ensuring gantry points meet minimum intensity while avoiding glare, without increasing bit resolution, thus maintaining road user comfort and safety.
Abstract
Description
Title of the invention: Automotive vehicle lighting system equipped with a light module capable of emitting a pixelated light beam
[0001] The invention relates to the field of automotive lighting. More specifically, the invention relates to a motor vehicle lighting system equipped with a light module capable of emitting a pixelated light beam.
[0002] Most states, countries, or regions define regulations with which a motor vehicle must comply in order to be driven. For example, some regulations require that the lighting emitted by a motor vehicle's headlight meet certain requirements under specific conditions. This is particularly true for low-beam headlights, which, according to most regulations, must be produced by a beam of light with a high cutoff, delineating an illuminated area from an unlit area, and exhibiting, at certain points, a luminous intensity greater than a given value and at other points, a luminous intensity less than a given value.
[0003] In order to assess the compliance of a projector with regulations, the light beam emitted by this projector is projected onto a screen equipped with an orthonormal coordinate system and a photometric grid consisting of points placed on this screen and defining maximum or minimum thresholds of luminous intensity. The luminous intensity value of the beam at the points with respect to the maximum and minimum thresholds of these points makes it possible to verify whether the light beam complies with the regulations.
[0004] Some of these points are positioned above the horizontal axis of the reference frame to correspond to the unilluminated area above the cutoff of the light beam, in order to assess whether the light beam is dazzling or not. In particular, it is important to prevent the luminous intensity of the beam at points of glare, located above the cutoff, from exceeding the maximum thresholds imposed by regulations.
[0005] These regulations may also define minimum light intensity values for other points located above the cutoff. This is particularly the case for points called gantry points, which correspond to locations of traffic signs that must be illuminated by a dipped beam. However, these gantry points pose several problems. Indeed, their locations are close to the glare points located above the cutoff. It is therefore necessary to be able to delimit, within the light beam, areas associated with gantry points, whose light intensities are greater than those of the minimum thresholds of these gantry points, and areas associated with glare points, whose light intensities are less than those of the maximum thresholds of these gantry points.
[0006] To address these problems, it is known to use light modules comprising a sufficient number of selectively activatable light sources, called elementary light sources, combined with an optical device, to enable the creation of pixelated light beams, for example, containing at least 500 pixels, each pixel being formed by an elementary light beam emitted by one of the elementary light sources. Beyond the fact that this type of module allows for advanced lighting functions, such as anti-glare road markings, road writing, floor markings, or reception lighting, it also allows for the definition and control of light intensity in precisely delimited areas.It is therefore possible to juxtapose an area of light intensity below a maximum threshold and an area of light intensity above a minimum threshold, and thus to meet the regulatory requirements relating to both glare points and gantry points, even when these points are close together.
[0007] While this type of module partially addresses the problem of gantry points, some issues remain unresolved. Specifically, the minimum thresholds associated with gantry points are close to the maximum thresholds associated with these glare points. Furthermore, the areas corresponding to the gantry points must be broadly defined to accommodate the projector's adjustment tolerances. Consequently, an area with a luminous intensity exceeding the minimum threshold of a gantry point may overlap with an area where the luminous intensity must be below a maximum threshold. To prevent this situation from causing regulatory compliance problems, it is therefore necessary to precisely control the luminous intensity of each pixel in the light beam.
[0008] In this context, the light sources of light modules capable of generating a pixelated beam are generally controlled, via a controller, by pulse-width modulation, also known as PWM (Pulse Width Modulation). The luminous intensity of the pixel formed by a light source is thus defined by the duty cycle of the signal with which it is controlled. However, the value of this duty cycle is defined numerically by the controller, using a given number of bits. It is therefore impossible to define a duty cycle whose value is below the first non-zero value that can be encoded using this number of bits. Since the minimum threshold values of the gantry points and the maximum values of the glare points are small, and since the difference The value between these two points can be less than this first non-zero value. Therefore, with known solutions, it is difficult to ensure that a group of pixels forming an area associated with a gantry point does not violate the regulatory requirements for a glare point. One solution would be to increase the number of bits available to set the duty cycle value, but this solution is unsatisfactory because it introduces an additional cost and does not allow the reuse of controllers already designed to adapt to a change in regulations. The invention aims to address this problem.
[0009] It should also be noted that a similar problem, related to this first non-zero value of a duty cycle, can arise for dynamic lighting functions involving changes in pixel brightness. Indeed, in known solutions, changing the brightness of a pixel results in a stepwise increase in the duty cycle of the signal controlling the light source that produces that pixel. The pixel's brightness therefore increases or decreases gradually, in steps corresponding to this first non-zero value that the duty cycle can take. Depending on the number of bits available to encode the duty cycle, the stepwise change in a pixel's brightness can therefore become perceptible to road users and disrupt their comfort or safety.
[0010] In this context, there is therefore a need to be able to decrease the value of the step of modification of the light intensity of a pixel without increasing the number of bits available to encode the value of the duty cycle of the signal controlling the light source realizing this pixel.
[0011] The present invention falls within this context and aims to meet these needs.
[0012] To this end, the invention relates to a lighting system for a motor vehicle, including: a. a first light module comprising a plurality of selectively controllable elementary light sources, the light module being capable of emitting a first pixelated light beam, b. a controller capable of receiving an instruction to emit a given lighting function, the controller being arranged to selectively control each of the elementary light sources of the first light module according to said instruction so that this elementary light source emits an elementary light beam forming one of the pixels of the first pixelated light beam, the controller being capable of generating, for each of the elementary light sources and according to said instruction, a control signal for said light source determining the light intensity intended to be emitted by said elementary light source, the controller periodically controlling said elementary light source using said control signal.
[0013] The system according to the invention is characterized in that the controller is arranged to generate, for at least one given elementary light source of the first light module, called critical source, and according to said instruction, a first control signal determining a first light intensity intended to be emitted by said critical source and a second control signal determining a second light intensity intended to be emitted by said critical source, the second light intensity being distinct from the first light intensity, the controller periodically controlling said critical source alternately with said first control signal and said second control signal.
[0014] In the invention, all the elementary light sources are controlled by a controller conforming to known solutions. For example, each elementary light source can be driven by a PWM-type signal generated by the controller, the duty cycle of this signal being defined according to the instruction received by the controller. The set of elementary light beams thus forms a pixelated light beam exhibiting predetermined photometric characteristics according to said instruction, each pixel thus exhibiting a luminous intensity above and / or below a threshold value defined by the regulations governing the lighting function indicated by the instruction received by the controller.
[0015] Since the lighting module must be able to respond dynamically to a new instruction, such as a change or modification of function, the control signal for each elementary light source is refreshed periodically, at a frequency high enough that this refresh is imperceptible to the eyes of the vehicle driver or a road user. In other words, the control signal for each elementary light source is generated periodically by the controller.
[0016] The invention thus proposes to take advantage of this periodic generation of the control signal at a high frequency to alternately vary the parameters of this control signal defining the luminous intensity of the elementary light beam emitted by a so-called critical light source, intended, for example, to create a pixel at a point on a gantry or participating in a transition of a lighting function. For this critical light source, the same instruction received by the controller thus leads to the control of this critical light source according to two control signals encoding distinct luminous intensities. Given the refresh rate, these two control signals alternate very rapidly, so that the average luminous intensity of the elementary light beam can then reach intermediate values, situated between consecutive values. luminous intensity can be defined by the control signal. In other words, it is possible with the invention to decrease the value of the step size for modifying the luminous intensity of a pixel without increasing the number of bits available to encode the value of the duty cycle of the signal controlling the light source that creates that pixel.
[0017] In the particular case of gantry points and control by a PWM signal, if the first light intensity corresponds to the first non-zero value of the duty cycle that can be coded on a given number of bits and if the second light intensity corresponds to a zero value, it is in particular possible to obtain a pixel whose average light intensity is less than that corresponding to this first non-zero value, and therefore to ensure that this pixel can achieve a gantry point, without being dazzling.
[0018] In the invention, a pixelated light beam is defined as a beam composed of a plurality of pixels arranged in a plurality of rows and / or columns. This beam has a resolution defined in particular as a function of the dimensions of each pixel and the size of the emission area associated with this beam.
[0019] According to the invention, the lighting system may include a computer capable of issuing instructions to emit a given lighting function, for example, based on vehicle traffic parameters, and in particular its speed and / or the presence of road users who must not be dazzled, notably detected by a sensor system on the vehicle. The central computer may, for example, receive information from various sensors such as a camera filming the road, a steering angle sensor, or a navigation system, in order to then determine which type of pixelated lighting function should be emitted by the first light module, and thus periodically send an instruction to emit this desired function to the controller of the first light module.The instructions sent by the computer generally contain the type of function and associated parameters, such as the position of a vehicle not to be dazzled, the position of a display area for a pictogram or road marking, and / or the position of a dark anti-glare zone. Upon receiving a transmission instruction, the controller of the first lighting module defines, for each elementary light source, the light intensity that source must emit so that the elementary light beam it is capable of emitting creates the pixel necessary to perform the desired pixelated lighting function.
[0020] Advantageously, upon receiving the creation instruction for a given lighting function, an intermediate control unit can be arranged to generate a digital image realizing a portion of said given lighting function within a frame whose dimensions and resolution correspond to those of the first pixelated light beam. If necessary, the controller is arranged to determine, for each elementary light source, a control signal from that elementary light source to the second light module so that the elementary light beam that this source emits reproduces the associated pixel on the road.
[0021] In one embodiment of the invention, the controller is, for example, capable of selectively receiving at least one instruction to transmit a high-beam lighting function, a non-glaring high-beam lighting function, an instruction to transmit a low-beam lighting function, and an instruction to transmit an urban lighting function. These examples are given by way of illustration; other functions could be considered without departing from the scope of the present invention, and in particular, functions for motorway lighting or lighting for adverse weather conditions.
[0022] According to one embodiment of the invention, the first light module is arranged so that the first pixelated light beam is a light beam comprising a plurality of pixels, for example, 500 pixels with dimensions between 0.05° and 0.3°, distributed in a plurality of rows and columns, for example, 20 rows and 25 columns. For example, the first light module may comprise a plurality of elementary light sources and an optical device arranged to emit said first pixelated light beam together. A light source is understood to be any light source, possibly associated with an electrooptical element, capable of being selectively activated and controlled to emit an elementary light beam whose luminous intensity is controllable.This could include, in particular, a light-emitting semiconductor chip, a light-emitting element of a monolithic pixelated light-emitting diode, a portion of a light-converting element excitable by a light source, or a light source associated with a liquid crystal or a micromirror.
[0023] In one embodiment of the invention, the lighting system comprises a second light module capable of emitting a second light beam having an upper cutoff, the first and second light modules being arranged such that at least a portion of the first pixelated light beam extends above the upper cutoff of the second light beam, in particular such that the first pixelated light beam extends both below and above the upper cutoff of the first light beam. Where applicable, said critical source may be capable of emitting an elementary light beam extending above the upper cutoff of the second light beam. For example, the upper cutoff of the second light beam is a substantially flat cutoff.In this embodiment, the overall beam, formed by the union of the first and second light beams, can satisfy the regulatory requirements governing the realization of . said given lighting function.
[0024] The overall beam can thus perform different functions, and in particular, alternatively or cumulatively: a. A crossing-type lighting function for which the pixels of the first light beam are controlled to form part of an upper cut of the overall beam formed by the union of the first and second light beams, a portion of this upper cut being aligned or not with the upper cut of the second light beam, the upper cut of the first light beam thus forming, alone or in combination with the upper cut of the second light beam, a regulatory crossing-type cut; b. A non-glaring road lighting function in which pixels of the first light beam, located above the upper cutoff of the second light beam, are controlled to form a dark area in the overall beam formed by the union of the first and second light beams, the rest of the pixels remaining illuminated, c. A ground writing function in which pixels of the first light beam, located below the upper cutoff of the second light beam and situated in a display area, are controlled to materialize a pictogram or ground marking, for example by negative or positive contrast, in the overall beam formed by the union of the first and second light beams.
[0025] Advantageously, the second light beam may be a second pixelated or non-pixelated light beam. If so, the resolution of the first pixelated light beam, in particular its vertical and / or horizontal resolution, may be greater than that of the second light beam.
[0026] According to one embodiment of the invention, the second light module comprises at least one light source, a collector with a reflective surface configured to collect and reflect the light rays emitted by the light source into a light beam along an optical axis of the module, an optical device, in particular a lens, configured to project the light beam, the optical device being configured to form an image of the reflective surface of the collector and having a focus, in particular a focus line, located at the rear of the collector, so as to essentially image the rear edge of its reflective surface, the upper cutoff of the second light beam being made by this rear edge.
[0027] In another embodiment of the invention, the second light module comprises at least one light source, a collector configured to collect and reflect the light rays emitted by the light source into a light beam along an optical axis of the module, an optical device, in particular a lens, configured to project the light beam and a shield arranged between the collector and the optical device and having a cut-off edge, the optical device having a focus, in particular a focus line, located at the cut-off edge, so as to essentially image the cut-off edge, the upper cut-off of the second light beam being made by this cut-off edge.
[0028] Advantageously, the first pixelated light beam extends horizontally over a range from approximately -20° to +20° and vertically over a range from approximately -4° to +4°, preferably from +2° to +4°. In this example, the coordinates of the range are understood in particular when the first light beam is projected onto a vertical screen equipped with an orthonormal coordinate system and positioned at a sufficiently distant distance from the first light module with regard to its dimensions, for example, 25 meters. In this coordinate system, the coordinates correspond to horizontal and vertical angles measured from the origin of the system.Positive abscissas correspond to the half-plane located to the right of the vertical axis, negative abscissas correspond to the half-plane located to the left of the vertical axis, positive ordinates correspond to the half-plane located above the horizontal axis, and negative ordinates correspond to the half-plane located below the horizontal axis.
[0029] Advantageously, the elementary light beam emitted by the critical source, when projected onto a screen, forms a pixel extending at least horizontally around a point located horizontally at -4° and vertically at +2°. In this example, the pixel constitutes a gantry point defined in the American regulation FMVSS 108, from the English "Federal Motor Vehicle Safety Standard," and commonly referred to as 2U-4L. The luminous intensity of this pixel must therefore be greater than 135 cd to constitute this 2U-4L gantry point, but less than 380 cd to avoid exceeding the maximum threshold of neighboring glare points.Alternatively or cumulatively, other gantry points may be made by the pixel formed by the critical source, or by another critical source, such as point 4U-8L, located horizontally at -8° and vertically at +4° or point S100LL defined by European regulation ECE -R12 and R149, from the English "Economy Commission for Europe".
[0030] According to one embodiment of the invention, upon receiving said instruction, the controller is arranged to selectively control each of the elementary light sources, other than the critical source, of the first light module so that the pixels of the first pixelated light beam form part of an upper cut of the overall beam formed by the union of the first and second light beams.
[0031] In another embodiment of the invention, the controller may be arranged to control, according to said instruction, the first light module so as to implement one or more of the following operations, sequentially or simultaneously: a. Modify the vertical and / or horizontal dimensions of the first pixelated light beam, b. Add, delete, move and / or modify the shape, dimensions and / or position of an upper cutoff of the first pixelated light beam, c. Add, delete, move and / or modify the shape, dimensions and / or position of a dark area in the first pixelated light beam, d. Add, delete, move and / or modify the shape, dimensions and / or position of a pictogram and / or ground marking in the first pixelated light beam, e. Increase or decrease the local or global light intensity of the first pixelated light beam.
[0032] Where appropriate, the critical source may be an elementary light source intended to form a pixel whose light intensity must vary to perform one or more of the operations mentioned above.
[0033] Advantageously, the controller is arranged to generate, for each of the elementary light sources of a plurality of sources other than the critical source, and according to said instruction, a unique control signal for said light source determining the luminous intensity intended to be emitted by said elementary light source, the controller periodically controlling said elementary light source using this unique control signal. In particular, it may be provided that the refresh rate of the luminous intensity of the elementary light sources, and therefore the control frequency, is greater than 60 Hz.
[0034] In one embodiment of the invention, the controller is arranged to generate, for the critical source, and according to said instruction, a first control signal determining a first light intensity intended to be emitted by said critical source and a second control signal determining a second light intensity intended to be emitted by said critical source, the second light intensity being lower than the first light intensity, the controller periodically controlling said critical source alternately with said first control signal and said second control signal.
[0035] In one embodiment of the invention, the controller is capable of generating, for each of the elementary light sources and according to said instruction, a value of a duty cycle coded on a predetermined number of bits and of periodically generating a pulse forming said control signal of said source luminous, the pulse width being determined from said determined value of the duty cycle. If necessary, the controller can be arranged to determine, for said critical source, and according to said instruction, a first value of a duty cycle and a second value of a duty cycle lower than the first value, the controller generating control signals periodically and alternately using the first and second values of the duty cycle. The predetermined number of bits may be set to 8.
[0036] In this context, the control signal generated periodically by the controller consists of a single pulse followed by silence. The duration, or width, of the pulse is determined from the period and the duty cycle value set by the controller. The repetition of this control signal thus forms a pulse train that modulates the electrical power intended to be supplied to the elementary light source. The average luminous intensity of the elementary light beam emitted by this elementary light source is therefore a function of the electrical power, which is regulated to remain constant, and of the duty cycle value set by the controller. The power supply to the elementary light source is thus controlled by the control signal, or pulse-width modulated.
[0037] Advantageously, the controller is arranged to fix, for said critical source, and according to said instruction, the first value of the duty cycle to the smallest possible non-zero value of a duty cycle encoded on a given number of bits, and the second value of the duty cycle to a value of zero. The second control signal thus corresponds to total silence for a complete period. This operation is therefore equivalent to extending the duration of the silence following a pulse, and thus to dividing the value of the duty cycle. It is thus understood that the average luminous intensity of the elementary light beam emitted by the critical source can thus be reduced by at least half, without increasing the number of bits used to encode the value of the duty cycle.
[0038] Advantageously, upon receiving said instruction, the controller is configured to periodically monitor said critical source alternately using said first control signal and a repetition of the second control signal. The second control signal may, for example, be repeated two or more times after each first control signal, so as to further increase the resolution of the average luminous intensity value of the elementary light beam emitted by the critical source. In particular, in the case where the second control signal is silence, it is thus possible to divide the duty cycle value by an integer greater than or equal to 3.
[0039] The invention also relates to a method for controlling a lighting system according to the invention, the method comprising the following steps: a. Receipt by the controller of an instruction to transmit a given lighting function; b. Generation by the controller, for each of the elementary light sources of a plurality of elementary light sources of the first light module, and according to said instruction, of a unique control signal of said light source determining the light intensity intended to be emitted by said elementary light source; c. Generation by the controller, for at least one given elementary light source of the first light module, called the critical source, distinct from the elementary light sources of said plurality, and according to said instruction, of a first control signal determining a first light intensity intended to be emitted by said critical source and of a second control signal determining a second light intensity intended to be emitted by said critical source, the second light intensity being distinct from the first light intensity; d. Simultaneous control by the controller of the elementary light sources of said plurality of elementary light sources of the first light module and of at least one critical source of the first light module, the controller periodically controlling each elementary light source of said plurality using the single control signal of that source and the controller periodically controlling said critical source alternately using said first control signal and said second control signal.
[0040] The present invention is now described by means of purely illustrative and in no way limiting examples of the scope of the invention, and from the accompanying drawings, in which the various figures represent:
[0041] [Fig-1] represents, schematically and partially, a lighting system according to an embodiment of the invention;
[0042] [Fig.2] represents, schematically and partially, a lighting function achieved by the lighting system of [Fig. 1]; and
[0043] [Fig.3] represents, schematically and partially, control signals of the light sources of the lighting system of [Fig.1] to perform the function of [Fig.2],
[0044] In the following description, identical elements, by structure or by function, appearing on different figures retain, unless otherwise specified, the same references.
[0045] A partial view of a lighting system 1 of a motor vehicle according to an embodiment of the invention is shown in [Fig.1].
[0046] The lighting system 1 comprises a projector 11 in which is arranged a first light module 2 capable of forming a pixelated HD light beam.
[0047] The light module 2 includes, in particular, a pixelated light source 21 associated with a lens 22. In the example described, the pixelated light source 21 is a monolithic pixelated light-emitting diode, each of whose light-emitting elements forms an elementary light source 21^ that can be selectively activated and controlled by an integrated controller 23 to emit light towards the lens 22, which thus projects an elementary light beam HD;j onto the road, the luminous intensity of which is controllable. Each elementary light beam HDij is projected by the lens into a given emission cone, defined by a given emission direction and a given angular aperture.Thus, in the example described, the set of elementary light beams HD^ forms a second pixelated lighting beam HD with 500 pixels distributed over 25 columns and 20 rows, extending into an emission zone defined horizontally by an angular range of 24°, from -15° to +9°, and vertically by a vertical angular range of 6.5°, from -3.5° to +3°, and of which each pixel is formed by one of these elementary light beams HD^. Each elementary light beam HD^ emitted by one of the elementary light sources 21ij of the source 21 has a horizontal and vertical aperture of less than 1°, for example 0.3°.
[0048] The lighting system includes a second light module 3, comprising a light source 31 and an optical unit 32, arranged to form a second light beam F. In the example described, the second light beam F is a non-pixelated beam having a substantially flat upper cutoff CF. The first and second light modules 2 and 3 are arranged such that the emission area of the first light beam HD extends below and above the flat cutoff of the second light beam F.
[0049] The global beam G, formed by the union of the first pixelated light beam HD and the second light beam F when they are emitted simultaneously, is thus capable of performing several advanced lighting functions, such as different crossing type lighting functions, non-glaring road type lighting, a ground writing function, the pixels formed by the elementary light beams HDi j being selectively controlled according to the function that this global beam G must perform.
[0050] For these purposes, the lighting system 1 includes a control unit 12 from the motor vehicle, which receives various data, notably from different sensor systems of the motor vehicle, such as the speed of the motor vehicle or the presence of road users downstream of the motor vehicle. The control unit 12 is configured to issue, based on this received data, instructions for the headlight 11 to emit a given lighting function.
[0051] The projector 11 includes a calculation unit 5, receiving instructions issued by the computer 12. This calculation unit 5 is arranged to determine, from an instruction to issue a given lighting function received from the computer 12, a control command for the second light beam F and to control the emission by the second light module 3 of the second light beam F according to the determined light intensity command.
[0052] The processing unit 5 is also arranged to generate, according to this received instruction, a digital image realizing a portion of said given light function within a frame whose dimensions and resolution correspond to those of the emission zone ZE of the second pixelated lighting beam HD. The processing unit 5 is also arranged to send the generated digital image to the integrated controller 23 of the pixelated light source 21.
[0053] Upon receiving this digital image, the integrated controller 23 determines, for each of the elementary light sources 21ij, a light intensity setpoint that this light source must emit so that the elementary light beam HDij that it is capable of emitting reproduces the pixel of the digital image associated with this source on the road. The integrated controller 23 then selectively controls each of the elementary light sources 21ij with a control signal PWMLJ corresponding to the determined setpoint, for switching on, switching off, and / or modifying the light intensity of the elementary light beam HDij. The second pixelated lighting beam HD thus reproduces the digital image generated in the emission zone necessary to perform the desired pixelated lighting function.
[0054] More specifically, for each of the elementary light sources 21^ and as a function of the grey level of the pixel of the digital image associated with this source 21^, the controller 23 determines the value of a duty cycle Tjj allowing this source 21jj to emit an elementary light beam HDLJ whose intensity corresponds to this grey level.
[0055] The controller 23 thus generates a pulse Pjj forming a control signal for said light source, the width of the pulse Pjj being determined from said determined value of the duty cycle Tjj. This pulse Pjj is repeated periodically, for example 60 times per second, so as to form a pulse-width modulated signal PWMy. This PWMy signal thus comprises, for each period T, a pulse Pjj whose width Ljj is determined by the duty cycle Tij, the latter corresponding to the ratio between the width Ljj and the period T, and a silence completing the period T. This PWMy signal can thus modulate a constant electrical power, so that the average electrical power supplied to the elementary light source 21ij, which therefore depends on the duty cycle, allows for obtaining a luminous intensity of the elementary light beam HD;j corresponding to the level of grey.
[0056] A new image is regularly provided by the computing unit 5 to the controller 23, so that the latter can periodically refresh the duty cycle Tjj.
[0057] In the invention, the controller 23 has an architecture enabling it to manipulate words of a predetermined number of bits, for example, 8 bits. In other words, the duty cycle Tjj, when calculated by the controller 23, is encoded using this predetermined number of bits. It thus expresses, in numerical form, the ratio between the width Uj of the pulse P^j and the period T, and is therefore between 0 and 1. In an 8-bit architecture, the sequence 00000000 encodes a duty cycle value of 0 and the sequence 11111111 encodes a duty cycle value of 1.
[0058] It should therefore be noted that the smallest non-zero value rmin that the controller 23 can encode on a number N of bits corresponds to a succession of Nl "0"s followed by a single "1", and is therefore:
[0059] r . =-l- 1 mm
[0060] In other words, the controller 23 is unable to control an elementary light source 21^ to emit an elementary light beam HDij whose light intensity is less than that corresponding to this smallest non-zero value of the duty cycle rmin, or whose light intensity is strictly between two light intensities corresponding to consecutive multiples of this value rmin.
[0061] However, this limit of the controller 23 poses a problem in various cases, and in particular in the case of so-called gantry points.
[0062] Figure 2 shows a projection of the first and second light beams F and HD onto a screen equipped with an orthonormal coordinate system and positioned 25 meters from the projector. In this coordinate system, the coordinates correspond to horizontal and vertical angles measured from the origin of the system. Positive abscissas correspond to the half-plane located to the right of the vertical axis VV, negative abscissas correspond to the half-plane located to the left of the vertical axis VV, positive ordinates correspond to the half-plane located above the horizontal axis HH, and negative ordinates correspond to the half-plane located below the horizontal axis HH.
[0063] As shown in [Fig. 2], some of the elementary light sources 21ij are activated while others are deactivated, so that the first light beam HD, formed by the elementary light beams HD^ emitted by the activated sources, has an upper cutoff. Part of this upper cutoff is aligned with the flat cutoff FC of the second light beam F, the light beam global resulting from the superposition of these two beams F and HD thus presenting an upper cut of the "crossing" type.
[0064] A 2U-4L zone has been reported on this screen, this zone being located around a point positioned horizontally at -4° and vertically at +2°. US regulation FMVSS 108 stipulates that the luminous intensity of the overall G beam measured in this 2U-4L zone must be greater than 135 cd. This point is designated as the "gantry point" and is intended, in particular, to illuminate traffic signs positioned at a height.
[0065] This zone 2U-4L is close to another zone ZI, located at points of glare where the overall beam intensity G must be less than 380 cd to avoid dazzling opposing vehicles. However, zone 2U-4L must be large enough to meet the adjustment tolerances of the first light module 2, and it is therefore possible that it may overlap with zone ZI.
[0066] It is therefore necessary that the luminous intensity of the light beam(s) HDij forming the pixel(s) positioned at the level of this 2U-4L zone be greater than 135 Cd and less than 380 Cd.
[0067] In order to make this constraint compatible with the limitation of controller 23, controller 23 then adopts a control of the light sources 2 hforming the pixels at the level of this zone 2U-4L different from that of the other light sources 2^-
[0068] For each of these sources 21^^-, called critical sources, i.e., those whose intensity setpoint cannot be reached with the controller architecture 23, the controller 23 sets a first value of the duty cycle rC j- to the smallest possible non-zero value rmin and a second value of the duty cycle r2; j to a value of zero. The controller then alternately generates, throughout the refresh period, pulses according to these first and second values rlret T2rj'.
[0069] Figure 3 shows a PWMLJ signal generated for elementary light sources 21^ forming pixels outside the 2U-4L zone and a PWMi j- signal generated for critical sources 21r
[0070] With regard to the PWMf signal r, this signal is composed of first control signals SI, each formed by a pulse Pmin, the width of which is defined by the small possible non-zero value of the duty cycle Tmin taking into account the first value of the duty cycle rh j- and completed by a silence during the period T. Second control signals S2, forming a complete silence during the period T taking into account the second zero value of the duty cycle r2; j- are interspersed between the first control signals SI.
[0071] It is thus understood that the duration of the silence following a Pmin impulse is extended by a period T, and therefore the duty cycle value of the signal is divided by 2 compared to a PWM signal which would classically be composed of Pmin pulses, as shown in [Fig. 3]. Consequently, the average luminous intensity of the elementary light beam HD; j emitted by the critical source 21^- can thus be reduced and meet the constraint of the gantry points, without increasing the number of bits used to encode the duty cycle value.
[0072] The controller 23 could also repeat the second control signal S2 several times between the control signals SI, so as to divide the value of the duty cycle of the PWMf signal r and therefore of the average luminous intensity of the elementary light beam HD; j emitted by the critical source 21r>r.
[0073] It should be noted that the functions mentioned above are listed by way of example, and that the computer 12 may generate instructions for the emission of other types of light functions by the projector 11, the controller 23 then being able to control the elementary light sources 21ij for: a. Modify the vertical and / or horizontal dimensions of the first HD pixelated light beam, b. Add, delete, move and / or modify the shape, dimensions and / or position of an upper cut of the first HD pixelated light beam, c. Add, delete, move and / or modify the shape, dimensions and / or position of a dark area in the first HD pixelated light beam, d. Add, delete, move and / or modify the shape, dimensions and / or position of a pictogram and / or ground marking in the first HD pixelated light beam; e. Increase or decrease the local or global light intensity of the first HD pixelated light beam.
[0074] In this context, the controller 23 may vary the luminous intensity of an elementary light beam HDij from a first setpoint to a second setpoint. The elementary light source 21^ responsible for this beam HDij may then become a critical source.
[0075] In this case, the controller 23 will be able to increment or decrement the value of the duty cycle Ti >r by an increment equal to the value rmin, while interspersing control signals generated from another value of this duty cycle, which may or may not be zero, in order to be able to vary the value of the duty cycle outside the values allowed by the number of bits of the controller 23.
[0076] The preceding description clearly explains how the invention achieves its objectives, in particular by providing a vehicle lighting system capable of emitting a pixelated light beam and reducing the value of the step size for modifying the light intensity of a pixel without The goal is to increase the number of bits available to encode the duty cycle value of the signal controlling the light source that produces this pixel. This is achieved, in particular, by alternately varying the parameters of this control signal, which defines the light intensity of the elementary light beam, in order to control the light source using two control signals that encode distinct light intensities.
[0077] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically feasible combination of these means. In particular, other types of light module than the one described may be considered, and in particular a light module comprising an association of a light source and an array of micromirrors or selectively activatable liquid crystals.
[0078] It may also be possible to consider controlling the lighting system for the emission of other light functions than those described, and in particular motorway-type lighting functions or functions for adverse weather conditions, or even light functions in which other types of pictograms or ground markings are provided.
Claims
Demands
1. Lighting system (1) of a motor vehicle, comprising: a. a first light module (2) comprising a plurality of selectively controllable elementary light sources (21^), the light module being capable of emitting a first pixelated light beam (HD), b. a controller (23) capable of receiving an instruction to emit a given lighting function, the controller being arranged to selectively control each of the elementary light sources (21ij) of the first light module (2) according to said instruction so that this elementary light source emits an elementary light beam (HD;j) forming one of the pixels of the first pixelated light beam (HD), the controller (23) being capable of generating, for each of the elementary light sources and according to said instruction, a control signal (PWMjj) of said light source determining the light intensity intended to be emitted by said elementary light source, the controller periodically controlling said elementary light source using said control signal; characterized in that the controller (23) is arranged to generate, for at least one given elementary light source (21^^-) of the first light module, called critical source, and according to said instruction, a first control signal (SI) determining a first light intensity intended to be emitted by said critical source and a second control signal (S2) determining a second light intensity intended to be emitted by said critical source, the second light intensity being distinct from the first light intensity, the controller (23) periodically controlling said critical source (21^-) alternately using said first control signal (SI) and said second control signal (S2).
2. Lighting system (1) according to the preceding claim, characterized in that it comprises a second light module (3) capable of emitting a second light beam (F) having a higher cutoff (CF), the first and second light modules (2, 3) being arranged in such that at least part of the first pixelated light beam (HD) extends above the upper cutoff of the second light beam, and in that said critical source (21^^-) is capable of emitting an elementary light beam (HD,,) extending above the upper cutoff of the second light beam.
3. Lighting system (1) according to the preceding claim, characterized in that the first pixelated light beam (HD) extends horizontally, in a range from substantially -20° to +20° and, vertically, in a range from substantially -4° to +4°.
4. Lighting system (1) according to the preceding claim, characterized in that the elementary light beam (HD,,) emitted by the critical source (21^-) forms, when projected onto a screen, a pixel extending at least horizontally around a point located horizontally at -4° and vertically at +2°.
5. Lighting system (1) according to the preceding claim, characterized in that, upon receipt of said instruction, the controller (23) is arranged to selectively control each of the elementary light sources (21ij), other than the critical source (21^-), of the first light module (2) so that the pixels of the first pixelated light beam (HD) form part of an upper cut (CF) of the overall beam (G) formed by the union of the first and second light beams (HD, F).
6. Lighting system (1) according to any one of the preceding claims, characterized in that the controller (23) is arranged to generate, for each of the elementary light sources (21^) of a plurality of sources other than the critical source (21^), and according to said instruction, a unique control signal (PWMjj) of said light source determining the luminous intensity intended to be emitted by said elementary light source, the controller periodically controlling said elementary light source using this unique control signal.
7. Lighting system (1) according to any one of the preceding claims, characterized in that the controller (23) is arranged to generate, for the critical source (21), and according to said instruction, a first control signal (S1) determining a first luminous intensity intended to be emitted by said critical source and a second control signal (S2) determining a second luminous intensity intended to be emitted by said critical source, the second luminous intensity being lower than the first light intensity, the controller periodically controlling said critical source alternately using said first control signal and said second control signal.
8. Lighting system (1) according to any one of the preceding claims, wherein the controller (23) is capable of generating, for each of the elementary light sources (21^) and according to said instruction, a value of a duty cycle coded (Tjj) on a predetermined number of bits and of periodically generating a pulse (Pîj) forming said control signal of said light source, the width of the pulse (Ljj) being determined from said determined value of the duty cycle, characterized in that the controller is arranged to determine, for said critical source (21^), and according to said instruction, a first value (xl; j) of a duty cycle and a second value (12^-) of a duty cycle lower than the first value, the controller generating control signals (SI, S2) periodically and alternately using the first and second values of the duty cycle.
9. Lighting system (1) according to the preceding claim, wherein the controller (23) is arranged to fix, for said critical source (21^-), and according to said instruction, the first value (tL j ) of the duty cycle to the smallest possible non-zero value (rmin) of a duty cycle coded on a given number of bits and the second value (12^-) of the duty cycle to a zero value.
10. Lighting system (1) according to any one of the preceding claims, characterized in that, upon receiving said instruction, the controller is arranged to periodically control said critical source (21^) alternately using said first control signal (S1) and a repetition of the second control signal (S2).
11. A method for controlling a lighting system (1) according to any one of the preceding claims, the method comprising the following steps: a. Reception by the controller (23) of an instruction to issue a given lighting function; b. Generation by the controller, for each of the elementary light sources (21) of a plurality of elementary light sources of the first light module (2), and according to said instruction, of a single control signal (PWMij) of said light source determining the intensity luminous intended to be emitted by said elementary light source; c. Generation by the controller, for at least one given elementary light source of the first light module, called critical source (21^-), distinct from the elementary light sources of said plurality, and according to said instruction, of a first control signal (SI) determining a first light intensity intended to be emitted by said critical source and of a second control signal (S2) determining a second light intensity intended to be emitted by said critical source, the second light intensity being distinct from the first light intensity; d. Simultaneous control by the controller of the elementary light sources of said plurality of elementary light sources of the first light module and of at least one critical source of the first light module, the controller periodically controlling each elementary light source of said plurality using the single control signal of that source and the controller periodically controlling said critical source alternately using said first control signal and said second control signal.