Automotive vehicle lighting system equipped with a light module capable of emitting a pixelated light beam

Abstract

The invention relates to a lighting system (1) for a motor vehicle, comprising a light module (2) having selectively controllable light sources (21i,j) to emit a pixelated light beam (HD); a controller (23) arranged to periodically and selectively control each of the light sources according to an instruction to emit a given lighting function by means of a control signal (PWMi,j) determining the light intensity to be emitted by said light source; characterized in that the controller is arranged to periodically control a critical source (21i',j') alternately by means of a first control signal (S1) determining a first light intensity and a second control signal (S2) determining a second light intensity distinct from the first light intensity. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Motor 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 provided 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 able to circulate. There are thus regulations requiring that the lighting emitted by a front headlight of a motor vehicle meets certain constraints under certain conditions. This is particularly the case for dipped-beam lighting which, in most regulations, must be achieved by a light beam having a higher cut-off, delimiting an illuminated area from an area not illuminated by this lighting, and having, at certain points, a luminous intensity greater than a given value and at other points, a luminous intensity lower than a given value.

[0003] In order to assess the compliance of a projector with a regulation, the light beam emitted by this projector is projected onto a screen provided with an orthonormal reference mark and a photometric grid consisting of points placed on this screen and defining maximum or minimum thresholds of luminous intensity. The value of the luminous intensity 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 regulation.

[0004] Some of these points are positioned above the horizontal axis of the marker to correspond to the unlit area, above the cut-off of the light beam, in order to assess whether the light beam is dazzling or not. In particular, it is appropriate to prevent the light intensity of the beam at the level of dazzling points, located above the cut-off, from exceeding the maximum thresholds imposed by the regulations.

[0005] These regulations may also define, for other points located above the cut-off, minimum values ​​of luminous intensity. This is particularly the case for points called gantry points, which correspond to locations of traffic signs which 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 cut-off. It is therefore necessary to be able to delimit, in the light beam, zones associated with the portico points, whose light intensities are higher than those of the minimum thresholds of these portico points, and areas associated with glare points, whose light intensities are lower than those of the maximum thresholds of these portico points.

[0006] In order to address these problems, it is known to use light modules comprising a sufficient number of selectively activatable light sources, called elementary light sources, associated with an optical device, to enable the production 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 makes it possible to carry out advanced lighting functions, for example of the anti-glare road type, ground writing, ground marking or reception scenario, it also makes it possible to define and control the light intensity in precisely delimited areas.It is therefore possible to juxtapose a zone of light intensity lower than a maximum threshold and a zone of light intensity higher than a minimum threshold and therefore to meet the regulatory requirements relating to both glare points and gantry points, even when these points are close.

[0007] While this type of module partially addresses the problem of gantry points, there are still unresolved problems. Indeed, the minimum thresholds associated with the gantry points are close to the maximum thresholds associated with these glare points. Furthermore, the zones corresponding to the gantry points must also be broadly delimited, in order to be able to adapt to the adjustment tolerances of the projector. It may thus happen that a zone, the luminous intensity of which is higher than a minimum threshold of a gantry point, overlaps a zone in which the luminous intensity must be lower than a maximum threshold. In order to avoid this situation leading to a problem of compliance with the regulations, it is therefore necessary that the luminous intensity of each pixel of the light beam can be precisely controlled.

[0008] In this context, the light sources of the light modules capable of generating a pixelated beam are generally controlled, via a controller, by a pulse width modulation, also called PWM (from the English Pulse Width Modulation). The light 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 digitally by the controller, on 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 coded on this number of bits. To the extent that the minimum threshold values ​​of the gantry points and the maximum values ​​of the glare points are low and to the extent that the difference between these values ​​may be lower than this first non-zero value, it is therefore complicated, with the known solutions, to ensure that a group of pixels forming an area associated with a gantry point does not violate the regulatory requirements of a glare point. One solution would thus be to increase the number of bits available to set the value of the duty cycle, but this solution is not satisfactory 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 thus aims to address this problem.

[0009] It should also be noted that a similar problem, linked to this first non-zero value of a duty cycle, can arise for dynamic lighting functions involving modifications to the light intensities of the pixels. Indeed, the modification of the light intensity of a pixel results, in known solutions, in a step-by-step increase in the value of the duty cycle of the signal controlling the light source producing this pixel. The light intensity of the pixel therefore increases or decreases gradually, according to a step corresponding to this first non-zero value that the duty cycle can take. Depending on the number of bits available to code the value of the duty cycle, the modification of the light intensity of a pixel by step can therefore become perceptible to road users, and disrupt their comfort or safety.

[0010] In this context, there is thus a need to be able to reduce the value of the step of modification of the luminous intensity of a pixel without increasing the number of bits available to code the value of the duty cycle of the signal controlling the light source producing this pixel.

[0011] The present invention is placed in this context and aims to meet these needs.

[0012] For these purposes, the invention relates to a lighting system for a motor vehicle, including: a. a first light module comprising a plurality of elementary light sources that can be selectively controlled, 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 as a function of 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 as a function of 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 as a function of 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 using said first control signal and said second control signal.

[0014] In the invention, all of the elementary light sources are controlled by a controller conforming to known solutions. For example, each elementary light source can be controlled 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. All of the elementary light beams thus form a pixelated light beam having predetermined photometric characteristics according to said instruction, each pixel thus having a light intensity greater than and / or less than a threshold value defined by the regulations governing the lighting function indicated by the instruction received by the controller.

[0015] Since the light module must be able to respond dynamically to a new instruction, such as a change or modification of function, the control of each elementary light source is refreshed periodically, at a frequency high enough for this refresh to be imperceptible to the eyes of the driver of the vehicle or a road user. In other words, the control signal of 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 vary, alternately, the parameters of this control signal defining the light intensity of the elementary light beam emitted by a so-called critical light source, intended for example to produce a pixel at a gantry point or participating in a transition of a lighting function. For this critical light source, the same instruction received by the controller thus causes the control of this critical light source according to two control signals encoding distinct light intensities. Taking into account the refresh frequency, these two control signals alternate very quickly, so that the average light intensity of the elementary light beam can then reach intermediate values, located between consecutive values of light intensity that can be defined by the control signal. In other words, it is possible with the invention to reduce the value of the step of modification of the light intensity of a pixel without increasing the number of bits available to code the value of the duty cycle of the signal controlling the light source producing this 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 lower than that corresponding to this first non-zero value, and therefore to ensure that this pixel can produce a gantry point, without being dazzling.

[0018] In the invention, the term “pixelated light beam” means 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 dimension of the emission zone associated with this beam.

[0019] According to the invention, the lighting system may comprise a computer capable of issuing instructions for issuing a given lighting function, for example as a function of traffic parameters of the motor vehicle, and in particular its speed and / or the presence of road users not to be dazzled, in particular detected by a sensor system of the motor vehicle. The central computer may, for example, receive information from different sensors such as a camera filming the road, a steering wheel angle sensor, or a navigation system, to then determine what type of pixelated lighting function must be issued by the first light module, and thus periodically send an instruction for issuing this desired function to the controller of the first light module.The instructions sent by the computer generally contain the type of function and the associated parameters, such as for example the position of a vehicle not to be dazzled, a position of a display zone of a pictogram or a marking on the road and / or a position of a dark anti-glare zone. The controller of the first light module, each time it receives an emission instruction, defines, for each elementary light source, what intensity of light this light source must emit so that the elementary light beam that it is capable of emitting produces the pixel necessary to produce the desired pixelated lighting function.

[0020] Advantageously, upon receipt of creation of said instruction to transmit a given lighting function, an intermediate control unit can be arranged to generate a digital image realizing a portion of said given lighting function in a frame whose dimensions and resolution correspond to those of the first pixelated light beam. Where appropriate, the controller is arranged to determine, for each elementary light source, a control signal for this elementary light source of 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 road type lighting function, a non-glare road type lighting function, an instruction to transmit a dipped beam type lighting function and an instruction to transmit an urban type lighting function. These examples have been listed for information purposes, other functions being able to be envisaged without departing from the scope of the present invention and in particular lighting functions for motorways or lighting for adverse weather conditions.

[0022] According to an exemplary 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 together said first pixelated light beam. The term "light source" means any light source possibly associated with an electro-optical element, capable of being activated and selectively controlled to emit an elementary light beam whose light intensity is controllable.This could include 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 micro-mirror.

[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 so that at least a portion of the first pixelated light beam extends above the upper cutoff of the second light beam, in particular so that the first pixelated light beam extends below and above the upper cutoff of the first light beam. Where appropriate, 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 production of. said given lighting function.

[0024] The overall beam can thus perform different functions, and in particular, alternatively or cumulatively: a. A dipped-beam lighting function for which the pixels of the first light beam are controlled to form a portion of an upper cutoff of the overall beam formed by the union of the first and second light beams, a portion of this upper cutoff being aligned or not with the upper cutoff of the second light beam, the upper cutoff of the first light beam thus forming, alone or in combination with the upper cutoff of the second light beam, a regulatory dipped-beam cutoff; b. A non-glare road lighting function for which pixels of the first light beam, located above the upper cut-off 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 lit, c. A ground writing function for which pixels of the first light beam, located below the upper cut-off of the second light beam and located in a display area, are controlled to materialize a pictogram or a 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 light beam or not. Where appropriate, the resolution of the first pixelated light beam, in particular its vertical resolution and / or its horizontal resolution, may be greater than that of the second light beam.

[0026] According to an exemplary 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 produced by this rear edge.

[0027] In another exemplary embodiment of the invention, the second light module comprises at least one light source, a collector configured to collect and reflecting 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 cover 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 level of the cut-off edge, so as to essentially image the cut-off edge, the upper cut-off of the second light beam being produced by this cut-off edge.

[0028] Advantageously, the first pixelated light beam extends horizontally, in a range going substantially from -20° to +20° and, vertically, in a range going substantially from -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 provided with an orthonormal reference frame and positioned at a distance sufficiently far from the first light module with regard to these dimensions, for example 25 meters. In this reference frame, the coordinates correspond to horizontal and vertical angles, measured from the origin of the reference frame.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 still, the elementary light beam emitted by the critical source forms, when it is projected onto a screen, a pixel extending at least horizontally around a point located horizontally at -4° and vertically at +2°. In this example, the pixel forms a gantry point defined in the American regulation FMVSS 108, from the English “Federal Motor Vehicle Safety Standard”, and usually referenced under the name 2U-4L. The luminous intensity of this pixel must thus be greater than 135 Cd to be able to form this 2U-4L gantry point, but be less than 380 Cd so as not to risk being above the maximum threshold of the neighboring glare points.Alternatively or cumulatively, other portal 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 an exemplary embodiment of the invention, upon receipt of 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 a part of an upper cutoff of the overall beam formed by the union of the first and second light beams.

[0031] In another exemplary embodiment of the invention, the controller may be arranged to control, as a function of 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 cut-off 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 road marking in the first pixelated light beam, e. Increase or decrease a light intensity, local or global, 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 carry out 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 as a function of said instruction, a single 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 this single control signal. In particular, it may be provided that the refresh frequency of the light 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 as a function of 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 using 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 as a function of said instruction, a value of a duty cycle coded on a predetermined number of bits and for periodically generating a pulse forming said control signal of said source. light, the width of the pulse being determined from said determined value of the duty cycle. Where appropriate, the controller may be arranged to determine, for said critical source, and as a function of 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 comprises a single pulse followed by silence, the duration, or width, of the pulse being determined from the period and the value of the duty cycle set by the controller. The repetition of this control signal thus forms a pulse train modulating an electrical power intended to be supplied to the elementary light source. The average light intensity of the elementary light beam emitted by this elementary light source is thus a function of the electrical power, which is regulated to be constant, and of the value of the duty cycle, set by the controller. The electrical power supply of the elementary light source is thus controlled by the control signal, or is modulated in pulse width.

[0037] Advantageously, the controller is arranged to set, for said critical source, and as a function of said instruction, the first value of the duty cycle to the smallest possible non-zero value of a duty cycle coded on a given number of bits and the second value of the duty cycle to a zero value. The second control signal thus corresponds to total silence for a complete period. This operation thus amounts to extending the duration of the silence following a pulse, and therefore to dividing the value of the duty cycle. It is thus understood that the average light 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 making it possible to code the value of the duty cycle.

[0038] Advantageously, upon receipt of said instruction, the controller is arranged to periodically control 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 value of the average light intensity of the elementary light beam emitted by the critical source. In particular, in the case where the second control signal is a silence, it is thus possible to divide the value of the duty cycle 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 as a function of said instruction, of a single 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 critical source, distinct from the elementary light sources of said plurality, and as a function of 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 the 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 this 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 with the aid of examples which are purely illustrative and in no way limitative of the scope of the invention, and from the appended drawings, 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.l]; and

[0043] [Fig.3] represents, schematically and partially, control signals of the light sources of the lighting system of [Fig.l] to achieve the function of [Fig.2],

[0044] In the following description, elements that are identical, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

[0045] [Fig.l] shows a partial view of a lighting system 1 of a motor vehicle according to one embodiment of the invention.

[0046] The lighting system 1 comprises a projector 11 in which is arranged a first light module 2 capable of forming an HD pixelated light beam.

[0047] The light module 2 comprises 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 activated and selectively controlled by an integrated controller 23 to emit light towards the lens 22, which thus projects onto the road an elementary light beam HD;j whose light intensity is controllable. Each elementary light beam HDij is projected by the lens in a given emission cone, defined by a given emission direction and a given angular aperture.Thus, in the example described, all of the elementary light beams HD^ thus form a second pixelated lighting beam HD having 500 pixels distributed over 25 columns and 20 lines, extending in an emission zone defined horizontally by an angular range of 24°, from -15° to +9°, and vertically by an angular vertical range of 6.5°, from -3.5° to +3°, and each pixel of which 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 opening of less than 1°, for example 0.3°.

[0048] The lighting system comprises 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 cut-off CF. The first and second light modules 2 and 3 are arranged so that the emission zone of the first light beam HD extends below and above the flat cut-off of the second light beam F.

[0049] The overall 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 dipped beam 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 overall beam G must perform.

[0050] For these purposes, the lighting system 1 comprises a computer 12 of the motor vehicle, receiving different data, in particular from different sensor systems of the motor vehicle, such as in particular the speed of the motor vehicle or the presence of road users downstream of the motor vehicle. The computer 12 is arranged to transmit, as a function of these received data, instructions for transmitting a given lighting function, by the headlight 11.

[0051] The projector 11 comprises a calculation unit 5, receiving the instructions emitted by the computer 12. This calculation unit 5 is arranged to determine, from an instruction to emit a given lighting function received from the computer 12, a control instruction 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 instruction.

[0052] The calculation unit 5 is also arranged to generate, as a function of this received instruction, a digital image realizing a portion of said given light function in a frame whose dimensions and resolution correspond to those of the emission zone ZE of the second pixelated lighting beam HD. The calculation 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 HD ij 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 achieve the desired pixelated lighting function.

[0054] More precisely, for each of the elementary light sources 21^ and as a function of the gray 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 gray 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 P^j is repeated periodically, for example 60 times per second, so as to form a pulse width modulated signal PWMy. This signal PWM;j thus comprises, for each period T, a pulse P^ whose width L;,j is determined by the duty cycle Tij, the latter corresponding to the ratio between the width L;,j and the period T, and a silence completing the period T. This signal PWMLJ 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 -¾, makes it possible to obtain a luminous intensity of the elementary light beam HD;j corresponding to the gray level.

[0056] A new image is regularly provided by the calculation 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 coded on this predetermined number of bits. It thus expresses, in digital form, the ratio between the width Uj of the pulse P^j and the period T, and it is therefore between 0 and 1. In an 8-bit architecture, the sequence 00000000 thus codes a duty cycle value of 0 and the sequence 11111111 codes a duty cycle value of 1.

[0058] It should thus be noted that the smallest non-zero value rmin that the controller 23 can code on a number N of bits corresponds to a succession of N1 “0” followed by a single “1”, and is therefore:

[0059] r . =-l- 1 mm

[0060] In other words, the controller 23 is incapable of controlling an elementary light source 21^ so that it emits an elementary light beam HDij whose light intensity is lower than that corresponding to this smallest non-zero value of the duty cycle rmin, or even 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 different cases, and in particular in the case of so-called gantry points.

[0062] [Fig. 2] shows a projection of the first and second light beams F and HD onto a screen equipped with an orthonormal reference frame and positioned 25 meters from the projector. In this reference frame, the coordinates correspond to horizontal and vertical angles measured from the origin of the reference frame. The positive abscissas correspond to the half-plane located to the right of the vertical axis VV, the negative abscissas correspond to the half-plane located to the left of the vertical axis VV, the positive ordinates correspond to the half-plane located above the horizontal axis HH and the 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. A 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 F and HD beams thus presenting a higher cutoff 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°. The American regulation FMVSS 108 stipulates that the luminous intensity of the overall beam G measured in this 2U-4L zone must be greater than 135 Cd. This point is called a “gantry point” and is intended in particular to illuminate traffic signs positioned at height.

[0065] This zone 2U-4L is close to another zone ZI, located at the level of glare points at which the light intensity of the overall beam G must be less than 380 Cd, in order to avoid situations of dazzling opposing vehicles. However, the zone 2U-4L must be sufficiently wide to be able to meet the adjustment tolerances of the first light module 2, and it is therefore possible that it encroaches on the zone ZI.

[0066] It is therefore necessary that the light intensity of the light beam(s) HDij forming the pixel(s) positioned at the level of this zone 2U-4L be greater than 135 Cd and less than 380 Cd.

[0067] In order to be able to make this constraint and the limitation of the controller 23 compatible, the controller 23 then adopts a control of the light sources 2 h forming 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, that is to say whose intensity setpoint cannot be reached with the architecture of the controller 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 zero value. The controller then alternately generates, throughout the refresh period, pulses according to these first and second values ​​rlret T2rj'.

[0069] [Fig.3] shows a PWMLJ signal as generated for the elementary light sources 21^ forming pixels outside the 2U-4L zone and a PWMi j- signal as generated for the critical sources 21r

[0070] As regards the signal PWMf r, this signal is composed of first control signals SI, each formed by a pulse Pmin, the width of which is defined by the smallest 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 interposed between the first control signals SI.

[0071] It is thus understood that the duration of the silence following a Pmin pulse is extended by a period T, and therefore that the value of the duty cycle of the signal is divided by 2 with respect to a PWMÿ signal which would classically be composed of Pmin pulses, as shown in [Fig.3]. Therefore, the average light 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 allowing the value of the duty cycle to be coded.

[0072] The controller 23 could also repeat the second control signal S2 several times between the control signals SI, so as to divide by the same amount the value of the duty cycle of the signal PWMf r and therefore the average light intensity of the elementary light beam HD; j emitted by the critical source 21r>r.

[0073] It should be noted that the functions cited above are listed for information purposes, and that the computer 12 will be able to generate instructions for emitting 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. Adding, deleting, moving and / or modifying the shape, dimensions and / or position of an upper cut-off of the first HD pixelated light beam, c. Adding, deleting, moving and / or modifying the shape, dimensions and / or position of a dark area in the first HD pixelated light beam, d. Adding, deleting, moving and / or modifying the shape, dimensions and / or position of a pictogram and / or a road marking in the first HD pixelated light beam; e. Increase or decrease a light intensity, local or global, of the first HD pixelated light beam.

[0074] In this context, the controller 23 may be required to vary the light intensity of an elementary light beam HDij from a first setpoint to a second setpoint. The elementary light source 21^ responsible for this beam HD;j may then become a critical source.

[0075] In this case, the controller 23 will be able to progressively increment or decrement the value of the duty cycle Ti >r by an increment equal to the value rmin, while interposing 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 ​​authorized by the number of bits of the controller 23.

[0076] The preceding description clearly explains how the invention makes it possible to achieve the objectives it has set itself, and in particular by proposing a lighting system for a vehicle capable of emitting a pixelated light beam and of reducing the value of the step of modification of the light intensity of a pixel without increase the number of bits available to code the value of the duty cycle of the signal controlling the light source producing this pixel. These objectives are achieved in particular by varying, alternately, the parameters of this control signal defining the light intensity of the elementary light beam in order to obtain control of the light source according to two control signals coding distinct light intensities.

[0077] In any event, the invention cannot be limited to the embodiments specifically described in this document, and extends in particular to any equivalent means and to any technically effective combination of these means. In particular, other types of light module than that described may be envisaged, and in particular a light module comprising a combination of a light source and a matrix of micro-mirrors or liquid crystals that can be selectively activated.

[0078] It will also be possible to envisage controlling the lighting system for the emission of other light functions than those which have been described, and in particular motorway type lighting functions or for unfavourable weather conditions, or even light functions in which other types of pictogram or ground marking are provided.

Claims

Claims

1. Lighting system (1) of a motor vehicle, comprising: a. a first light module (2) comprising a plurality of elementary light sources (21^) which can be selectively controlled, 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) as a function of 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 as a function of 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 as a function of 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 an upper cut-off (CF), the first and second light modules (2, 3) being arranged in such that at least a portion of the first pixelated light beam (HD) extends above the upper cut-off 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 cut-off 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 going substantially from -20° to +20° and, vertically, in a range going substantially from -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 it is 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-off (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 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 as a function of said instruction, a single 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 this single control signal.

7. Lighting system (1) according to one of the preceding claims, characterized in that the controller (23) is arranged to generate, for the critical source (21^-), and as a function of 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 less 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 one of the preceding claims, in which the controller (23) is capable of generating, for each of the elementary light sources (21^) and as a function of said instruction, a value of a coded duty cycle (Tjj) on a predetermined number of bits and for 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 as a function of 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, in which the controller (23) is arranged to set, for said critical source (21^-), and as a function of 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 one of the preceding claims, characterized in that, upon receipt of said instruction, the controller is arranged to periodically control said critical source (21^) alternately using said first control signal (SI) and a repetition of the second control signal (S2).

11. Method for controlling a lighting system (1) according to one of the preceding claims, the method comprising the following steps: a. Reception by the controller (23) of an instruction to emit 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 as a function of said instruction, of a single control signal (PWMij) of said light source determining the intensity light 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 as a function of 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 the 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 this source and the controller periodically controlling said critical source alternately using said first control signal and said second control signal.

Images