LIGHTING SYSTEM FOR MOTOR VEHICLES

Description

[0001] The invention relates to the field of lighting and / or signaling, in particular for motor vehicles. More particularly, the invention relates to a lighting system for a motor vehicle and a method for controlling the lighting system.

[0002] A motor vehicle is generally equipped with headlights intended to illuminate the road in front of the vehicle, at night or when the light is reduced, that is to say when the ambient light is low or even insufficient, such as for example in a tunnel, in an underground car park, at dawn, at dusk, when the sky is overcast, etc. Motor vehicles are increasingly often equipped with driving assistance devices, which make it possible to adapt the shape of the light beams emitted by the headlights according to the traffic conditions.

[0003] These driver assistance functions may be used in combination with an acquisition device, such as a camera, for acquiring images of the scene located in front of the vehicle. Such a device may in particular be used to detect the marking strips of the edges of the traffic lane on which the vehicle is located, in front of the vehicle, in order to allow a system in the vehicle to issue an alert to warn the driver in the event of deviation from the vehicle's trajectory or in the event of crossing a marking strip. The acquisition device may also make it possible to measure the distance between the vehicle and the vehicle being followed in order to ensure that a sufficient safety distance is maintained. It may also make it possible to detect the presence of other vehicles on the road and to adapt the projected beam so as not to dazzle the drivers of other vehicles.

[0004] However, at night or when the light is reduced and in rainy weather or when the road is wet, the visibility of the road marking strips, and in particular the marking strips at the edges of the traffic lane in which the vehicle is located, is greatly reduced. In fact, a layer of water covers the marking strips and reduces the visibility of the marking strips for the driver and for the acquisition device, in particular due to Fresnel losses.

[0005] One solution to improve visibility of the marking strips is to increase the lighting of the scene in front of the vehicle. However, this solution is not satisfactory since this increase in lighting must be significant for the camera to have better visibility of the scene, which causes discomfort for the driver of the vehicle and dazzles the drivers of passing or following vehicles due to the reflection of light on the layer of water. Drivers are then disturbed in their driving, which poses a risk to their safety.

[0006] An aim of the invention is therefore to provide a lighting system making it possible to increase the visibility of the scene located in front of the vehicle, for an acquisition device, at night or when the brightness is reduced and in rainy weather or on a wet road, and which does not have the drawbacks of the previous solutions.

[0007] It is also known: EP 1 978 295 A1 which describes a light signaling system for vehicles. A first light source is used for signaling. A camera captures the exterior of the vehicle and measures the contrast of the images. If the contrast falls below a certain threshold, a second, more powerful light source is used. US 2012 / 116632 A1 which describes a system that automatically activates fog lights based on the contrast detected in images of the exterior of the vehicle. JP 2005 085621 A which describes a night vision system for vehicles. An infrared light is activated intermittently and an infrared sensor captures images synchronously with the emission frequency of the infrared light. EP 2 026 097 A1 which describes a lighting system for vehicles for illuminating the surroundings of the vehicle and which can simultaneously be used to detect the distance of objects in the direction of said light.A light source is modulated in such a way that the modulation is not perceptible to outsiders.

[0008] For this purpose, the invention provides a motor vehicle lighting system comprising: a device for acquiring the scene located at the front of the vehicle comprising an image sensor, a first lighting device comprising at least one light source capable of emitting a first light beam of a first intensity illuminating said scene so as to increase the contrast of the images captured by the image sensor, a second lighting device comprising a light source emitting a second light beam of a second intensity performing a lighting and / or regulatory signaling function at the front of the vehicle, a control unit which actuates the first lighting device when a first contrast value called raw contrast of the images captured by the image sensor is less than a predefined threshold contrast, said raw contrast of the images captured by the image sensor corresponding to the contrast of the images captured when the lighting device is not actuated, characterized in that the light source of the first lighting device is configured to generate modulated lighting at a frequency greater than 50 Hz, and in that the acquisition device is capable of acquiring an image at the moment of modulation when the intensity of the source is highest, the modulation thus being imperceptible to the driver of said vehicle or an external observer.

[0009] Thus, thanks to the present invention, the scene located in front of the vehicle can be made visible to the acquisition device without causing discomfort to the driver and without dazzling the drivers of the vehicles passing or being followed. Indeed, the drivers do not perceive the modulation of the lighting generated by the light source of the first lighting device. The average intensity that they perceive is much lower than the maximum intensity emitted by the first lighting device during the modulation which allows the image sensor to capture images with better contrast.

[0010] In the present invention, external observer means the drivers of vehicles passed or followed, the passengers of these vehicles and pedestrians on the verge or on the road.

[0011] Lighting modulation consists of varying the intensity emitted by the light source of the first lighting device over time.

[0012] The modulation of the lighting generated by the light source of the first lighting device is imperceptible to the driver either because of the wavelengths emitted by the source or because of the variation in the intensity of the source for a duration less than the time of perception of the flickering of the eye so that the variation in intensity of the source is imperceptible to the driver.

[0013] Indeed, the human eye no longer detects variations in intensity when the variation occurs at a frequency higher than a frequency called the cut-off frequency equal to 50Hz, or even higher than 75Hz. The eye therefore does not perceive a variation in intensity when the variations occur over a time less than a time, called the eye's flicker perception time, which is equal to 1 / 50s, preferably 1 / 75s.

[0014] The modulation of the illumination generated by the light source of the first illumination device is perceptible by the acquisition device which is either sensitive to the wavelengths emitted by the light source, and / or is capable of performing an image acquisition at the moment of modulation when the intensity of the source is the highest.

[0015] To the applicant's knowledge, there is currently no system for improving the visibility of the marking strips at night and in the rain for an acquisition device without hindering the perception of the scene lighting by the driver of the vehicle or the drivers of the vehicles being crossed or followed.

[0016] The regulatory lighting and / or signaling function at the front of the vehicle may be a high beam, low beam or position light function. As in the context of the invention, the focus is on wet road conditions and when the light is reduced or at night, the second lighting device is therefore activated even before the first lighting device is activated.

[0017] Advantageously, the lighting system according to the invention comprises a unit for processing the images captured by the image sensor to determine the contrast of these images, preferably this processing unit is integrated into the acquisition device.

[0018] In a first example, not covered by the invention, the first lighting device comprises an infrared light source and an image sensor sensitive to infrared light.

[0019] In the present application, a light source may comprise one or more light emitters.

[0020] This infrared light source emits a light beam making the scene located in front of the vehicle visible to the acquisition device, and in particular to the image sensor, while not disturbing the drivers. Indeed, the infrared light emitted by the light source of the first device is not perceptible to the human eye. Thus, the driver does not perceive the modulation of the lighting generated by the light source of the first lighting device. He is therefore not hindered in his driving. And the drivers of the vehicles passing or being followed are also not dazzled.

[0021] However, the image sensor is sensitive to infrared light. This addition of infrared light therefore increases the contrast of the images captured by the image sensor.

[0022] The infrared light source can generate modulated lighting by emitting a light beam intermittently so as to illuminate said scene discontinuously. The infrared light source is successively switched on and off. The scene located in front of the vehicle becomes visible to the acquisition device when the infrared light source is switched on and emits the light beam. The acquisition of at least one image by the image sensor is then synchronized with the emission of the first light beam.

[0023] Preferably, the infrared light source can generate modulated illumination by emitting a light beam continuously. The infrared light source is permanently switched on so as to illuminate said scene permanently. Where appropriate, the infrared light source can emit a light beam with a periodic light intensity profile having: a first part consisting of one or more segments where the light intensity is constant and equal to a positive nominal intensity, and a second part where the light intensity is greater than the nominal intensity for a duration greater than the duration of acquisition of an image by the image sensor, the sum of the duration of two parts being equal to the duration of a period.

[0024] The acquisition time of an image by the image sensor can for example be less than 33 ms, preferably less than 16 ms.

[0025] The scene located in front of the vehicle is permanently illuminated, and is particularly visible to the image sensor during the second part of the intensity profile of the periodic light beam. It is then particularly advantageous for the acquisition device to acquire an image of the scene located in front of the vehicle, during this second part. During the first part, the light beam emitted by the infrared light source may not be sufficiently intense to significantly increase the contrast of the images that would be captured by the image sensor, but it can be used for other purposes, such as for example to detect the presence of living beings on the road or in its vicinity such as animals or people.

[0026] In a second example, the first lighting device comprises a visible light source. The lighting system also comprises a compensation device for compensating the first and second intensities of the light beams of the first and second lighting devices so that the modulation of the lighting generated by the visible light source of the first lighting device is imperceptible to the driver.

[0027] In this second example, the image sensor is sensitive to visible light emitted by the visible light source.

[0028] To compensate for the first and second intensities, the compensation device controls the first and / or second light intensity.

[0029] According to a first variant, the first lighting device and the second lighting device are distinct.

[0030] When the first lighting device is actuated, the visible light source emits a first periodic light beam with a periodic light intensity profile having a first part consisting of one or more segments where the light intensity is constant and equal to a positive or zero nominal intensity and a second part where the light intensity is greater than the nominal intensity, the sum of the duration of two parts being equal to the duration of a period, the duration of the period being less than the flicker perception time of the human eye, and the compensation device decreasing the second intensity so as to compensate the first and second intensities.

[0031] As a reminder, within the framework of the invention, the second lighting device is activated even before the first lighting device is activated.

[0032] The compensation device reduces the second intensity so that the average intensity of the beam projected onto the road, resulting from the superposition of the light beams from the first and second lighting devices, is identical throughout the time the first lighting device is activated. Thus, the modulation of the lighting generated by the light source of the first lighting device is imperceptible to the driver or an external observer.

[0033] According to a second variant, the first lighting device and the second lighting device are combined.

[0034] Where appropriate, the light source of the first lighting device may be identical to the light source of the second device. Le The lighting system then has a smaller footprint.

[0035] In this variant, when the first lighting device is not actuated, this means that the light beam emitted by the device corresponds to the second light beam. The device therefore makes it possible to illuminate the road. When the first lighting device is actuated, the first light beam overlaps with the second light beam. Activation of the first lighting device corresponds to a modification of the control of the second lighting device in order to be able to carry out the function of the first lighting device.

[0036] Advantageously, the compensation device controls the visible light source so that it emits a light beam with a periodic light intensity profile having: a first part consisting of one or more segments where the light intensity is constant and equal to a positive nominal intensity, a second part where the light intensity is greater than the nominal intensity, and a third part consisting of one or more segments where the light intensity is less than the nominal intensity for a duration such that the average intensity of the light beam is constant and equal to the nominal intensity over a period, the sum of the duration of each of the three parts being equal to the duration of a period, and the sum of the duration of the second and third parts, called the compensation time, being less than the flicker perception time of the human eye.

[0037] The compensation time must be short compared to the flicker perception time so that the modulation is not perceptible to the human eye. Thus, it must be less than 1 / 50s, preferably less than 1 / 75s.

[0038] In particular, the nominal intensity is equal to the second intensity.

[0039] Advantageously, when the light source of the first device emits a light beam with a periodic light intensity profile, the acquisition of at least one image by the image sensor is synchronized with the second part of the light intensity profile.

[0040] "Synchronized with the second part of the light intensity profile" means that the image acquisition by the image sensor is triggered substantially at the same time as the second part of the light intensity profile. The acquisition of an image by the image sensor is carried out during a determined duration which depends on the acquisition device. At least a part of this determined duration must occur at the time when the second part of the intensity profile is transmitted, and preferably, the entirety of this determined duration occurs at the time when the second part of the intensity profile is transmitted.

[0041] The second part of the light intensity profile has a higher light intensity than the light intensity of all other parts of the light intensity profile. The road in front of the vehicle is therefore better lit, which allows the acquisition device, and in particular the image sensor, to have better visibility of the scene in front of the vehicle. Since the scene is better lit, the captured image is less affected by sensor noise. There is therefore a better signal-to-noise ratio on the image captured during the second part of the intensity profile, which allows an image with better contrast to be obtained.

[0042] Advantageously, the light source of the first lighting device emits P-type polarized light. P-type polarized light is less reflected than unpolarized light at the interface between the air and the layer of water formed on the road. It therefore passes through the layer of water better and a greater portion of the emitted light is then reflected onto the road, for a given intensity, which allows the driver to see the road better.

[0043] Where appropriate, the first lighting device may comprise a laser diode type light source emitting polarized light, which avoids having to introduce a polarizer which would reduce the intensity of the beam emitted by the source.

[0044] Thus, whatever the embodiment, thanks to the first lighting device, better visibility of the marking strips and / or ground markings is obtained for the acquisition device. The expression "better visibility" means that the acquisition device detects more distinctly the marking strips and / or ground markings located close to the vehicle and that it also detects marking strips and / or ground markings that it did not detect before the increase in the lighting of the scene.

[0045] Advantageously, the motor vehicle lighting system comprises a restitution device making it possible to restore to the driver the scene located in front of the vehicle and captured by the acquisition device with a higher contrast than that of the same scene perceived by the driver without the restitution device.

[0046] The restitution device can be activated by the control unit.

[0047] The restitution device can be taken indifferently from: a head-up display, an electronic video display screen, a liquid crystal screen integrated into the vehicle or a portable electronic device.

[0048] Preferably, the restitution device is a complementary lighting device for illuminating towards the front of the vehicle. Advantageously, the complementary lighting device is arranged to illuminate the marking strips of the edges of the traffic lane on which the vehicle is located, at the front of the vehicle.

[0049] According to a first variant, the complementary lighting device is distinct from the first lighting device and the second lighting device.

[0050] According to a second variant, the complementary lighting device is merged with the second lighting device.

[0051] According to a third variant, the complementary lighting device is merged with the first lighting device.

[0052] In the case where the complementary lighting device and the first lighting device are combined, a distinction is made between the first light beam and the light beam emitted for restitution. The modulation of the lighting generated by the light source of the first lighting device is not perceived by the driver, due to the compensation carried out with the second light beam. On the other hand, the driver perceives the light beam emitted for restitution.

[0053] The complementary lighting device comprises a matrix of micro-mirrors, in particular a DMD type component (for the English acronym Digital Micro-mirror Device).

[0054] Alternatively, the complementary lighting device comprises a matrix of light sources. Preferably, the matrix comprises 20 rows and 10 columns. Advantageously, the matrix comprises 40 rows and 20 columns.

[0055] Alternatively, the complementary lighting device comprises a scanning system combining a laser beam and a MEMS pivoting on two orthogonal axes or two MEMS each pivoting on one axis, the axes of said two MEMS being orthogonal to each other.

[0056] Advantageously, the additional lighting device is capable of emitting P-type polarized light. The lighting provided by the additional lighting device is then better perceived by the driver.

[0057] The invention also relates to a control method implementing such a lighting system.

[0058] The ordering process may include the following sequence of steps. Step 1: Acquisition of the scene located in front of the vehicle by the acquisition device, and in particular by the image sensor Step 2: Calculation of the raw contrast of the images captured by the image sensor The calculation of the contrast can in particular be carried out by the processing unit. The term "raw contrast" refers to the contrast of the images captured by the image sensor without taking into account the lighting of the first lighting device. When the first lighting device is not activated, it corresponds to the contrast of the images captured by the image sensor, and when the first lighting device is activated, it corresponds to the contrast that the images captured by the image sensor would have if the first lighting device were not activated.Step 3: Comparison of the raw contrast calculated in step 2 with the predefined threshold contrast If the raw contrast is higher than the threshold contrast, go back to step 1. In fact, the first device does not need to be activated. The scene is sufficiently visible for the acquisition device. If the raw contrast is lower than the threshold contrast, go to step 4. In fact, the scene is not sufficiently visible for the acquisition device. The first lighting device must therefore be activated. Step 4: Activation of the first lighting device Step 5: Acquisition of the scene located in front of the vehicle by the acquisition device Step 6: Calculation of the corrected contrast of the images captured by the image sensor The "corrected contrast" is the contrast of the images taking into account the contribution of the lighting from the first lighting device. It corresponds to the contrast of the images captured by the image sensor when the first lighting device is activated.Step 7: Calculation of the raw contrast of the images captured by the image sensor, taking into account the lighting input of the first lighting device in the corrected contrast. Knowing the lighting input of the first lighting device and the corrected contrast calculated in step 6, it is possible to deduce the raw contrast by calculation. Step 8: Comparison of the raw contrast calculated in step 7 to the predefined threshold contrast. Only the raw contrast can be compared to the predefined threshold contrast. Indeed, the raw contrast corresponds to the contrast of the scene without the lighting input of the first lighting device. The corrected contrast is necessarily higher than the threshold contrast. If the raw contrast is higher than the threshold contrast, go to step 9. If the raw contrast is lower than the threshold contrast, go back to step 5.Optionally, the activation of the scene rendering device located at the front of the vehicle can be activated, during a step 10, before resuming at step 5. Step 9: Switching off the first lighting device and resuming at step 1.

[0059] The invention also relates to a motor vehicle comprising such a lighting system or means making it possible to implement such a method.

[0060] Other characteristics and advantages of the present invention will appear more clearly with the aid of the description and the drawings among which: there figure 1 schematically represents in partial section a vehicle equipped with a lighting system according to the present invention; the figure 2a represents the light intensity profiles of the light beams emitted by the first and second lighting devices over time in the case where the two lighting devices are distinct and the acquisition of the images by the image sensor; figure 2b represents the light intensity profile of the beam emitted by the first lighting device over time when it is merged with the second lighting device and the acquisition of images by the image sensor; figure 3a schematically represents the scene located in front of the vehicle in the absence of an active additional lighting device; the figure 3b schematically represents the scene located in front of the vehicle when the additional lighting device is activated; the figure 4 represents the different stages of the method implementing a lighting system according to the present invention.

[0061] In reference to the figure 1 , a partial section of a vehicle 10 is shown schematically, equipped with headlights 9 and driven by a driver symbolized by his eye 11. The driver 11 observes the scene located at the front of the vehicle SA through the windshield 12.

[0062] The headlight 9 is equipped with several lighting devices: a first lighting device 1, a second lighting device 2 and a complementary lighting device 7. The second lighting device 2 is equipped with a light source capable of generating a dipped beam type light beam, complying with the requirements of ECE regulation No. R112, it being understood that those skilled in the art will be able to adapt the invention so that the second lighting device 2 meets the requirements of any other national or regional regulation. On the figure 1 , the first lighting device 1 and the second lighting device 2 are distinct.

[0063] According to the present invention, the vehicle is equipped with an acquisition device 3 capable of acquiring images of the scene located in front of the vehicle SA. The acquisition device 3 comprises an image sensor making it possible to capture images of the scene located in front of the vehicle SA. The acquisition device may in particular take the form of a camera comprising a CMOS sensor for example, or a CCD sensor.

[0064] The acquisition device 3 is connected to a processing unit 5 for the images captured by the image sensor. The processing unit 5 makes it possible to determine the raw contrast of the images captured by the image sensor. In order for the processing unit 5 to calculate the raw contrast of the images captured by the image sensor, it is connected to the activation control of the first lighting device in order to know at all times whether the first lighting device is activated.

[0065] When the first lighting device is actuated, the processing unit 5 can in particular calculate the raw contrast value from the corrected contrast value. By taking into account the lighting contribution of the first lighting device in the contrast of an image captured by the image sensor, the processing unit 5 can calculate the raw contrast.

[0066] The raw contrast value is then transmitted to a control unit 4 which actuates the first lighting device 1 when the raw contrast is below a predefined threshold contrast or which leaves the first lighting device 1 actuated when it is already actuated.

[0067] This predefined threshold contrast corresponds to the contrast from which we can consider that the brightness is too low for the driver and the acquisition device to be able to correctly see the scene located in front of the SA vehicle and in particular the marking strips.

[0068] When the first lighting device 1 is actuated, the modulation of the lighting generated by the light source of the first lighting device 1 is not perceptible by the driver 11 or an external observer whereas it is perceptible by the acquisition device 3. Le acquisition device 3 perceives the effect of the light emitted by the first lighting device 1 on the lighting of the scene SA.

[0069] The light source of the first lighting device 1, not covered by the invention, may be an infrared light source. The radiation from the source is then invisible to the human eye. Only the image sensor must then be sensitive to infrared light. Illuminating the scene using the infrared light source thus allows the image sensor to capture images of the scene located in front of the vehicle SA with better contrast than if there were no lighting.

[0070] The light source of the first device may alternatively be a visible light source. The image sensor is then sensitive to the visible light emitted by the visible light source. In order for the modulation of the lighting generated by the light source of the first lighting device 1 to be imperceptible to the driver 11 or to an external observer, the first lighting device 1 and the second lighting device 2 are connected to a compensation device 8 making it possible to compensate for the first and second intensities of the light beams emitted by the first 1 and second 2 lighting devices. The compensation carried out by the compensation device 8 is detailed in figures 2a And 2b .

[0071] The activation of the first lighting device 1 does not disturb the driver or an external observer since, once activated, the modulation of the lighting generated by the light source of the first lighting device 1 is imperceptible to the driver or an external observer. Thus, once activated and for the entire time that the first lighting device 1 is activated, the lighting of the scene located in front of the vehicle SA is perceived as not being modified by the driver 11 or an external observer. However, the contrast of the images captured by the image sensor is indeed modified. Indeed, the acquisition of images by the image sensor is synchronized with the emission of light from the first lighting device 1 so that the scene located in front of the vehicle SA is visible on at least some of the images captured by the image sensor.The processing unit 5 can in particular detect on these images the position of the marking strips which are not visible to the driver.

[0072] To enable the driver to know the position of these marking strips, the vehicle is equipped with a restitution device. This restitution device may, for example, consist of a head-up display 6 or an electronic video display screen, a liquid crystal screen integrated into the vehicle or a portable electronic device.

[0073] According to a variant also represented on the figure 1 , the restitution device may be a complementary lighting device 7, making it possible to illuminate towards the front of the vehicle. In particular, it makes it possible to illuminate the marking strips of the edges of the traffic lane on which the vehicle is located, at the front of the vehicle.

[0074] There figure 2a represents the light intensity profiles of the beams emitted by the first and second lighting devices, in the case where the light source of the first lighting device 1 is a visible light source and when the first lighting device 1 and the second lighting device 2 are distinct.

[0075] In the context of the invention, the vehicle 10 is traveling at night, or when the light is reduced. The second lighting device 2 is therefore activated.

[0076] When the raw contrast of the scene located in front of the vehicle SA becomes lower than the threshold contrast value, the first lighting device 1 is actuated by the control unit 4.

[0077] When the first lighting device 1 is actuated, the visible light source emits a first light beam periodic in time with a periodic light intensity profile.

[0078] The periodic light intensity profile presents: a first part 21 consisting of two segments 21a and 21b where the light intensity is constant and equal to a positive or zero nominal intensity and, a second part 22 where the light intensity is greater than the nominal intensity.

[0079] The sum of the duration of the first 21 and the second 21 parts is equal to the duration of a period T. The duration of the period is less than the flicker perception time of the human eye.

[0080] Simultaneously, the compensation device 8 decreases the second intensity. The second intensity changes from a maximum value 13 to a value 14 lower than the maximum value 13. The decrease in the second intensity is calculated by the compensation device so that the driver or an external observer does not perceive a change in the lighting of the scene located in front of the vehicle SA during the modulation of the lighting generated by the light source of the first lighting device 1. Depending on the light intensity of the first part 21 of the light intensity profile of the first light beam of the light source of the first lighting device 1, it is possible to play on the visual signature of the vehicle. Indeed, the higher the light intensity of the first part 21, the lower the value 14 of the second intensity.Thus, an observer outside the vehicle 10 will distinguish the first lighting device 1 even more and will see that the second intensity is attenuated.

[0081] The image sensor is synchronized with the second part 22 of the light intensity profile. The acquisition of an image 25 is triggered at the time of transition to the second part 22 of the intensity profile. In addition, the image sensor has a sufficiently high acquisition frequency so as to be able to acquire at least one image 25 during the second part 22 of the light intensity profile of the first light beam of the light source of the first lighting device 1.

[0082] During the acquisition of this image 25, the scene located in front of the vehicle SA is illuminated by the first device 1 with maximum intensity. It is therefore particularly visible on this image 25. The processing unit 5 can in particular detect the position of the marking strips on this image 25 which are not visible to the driver.

[0083] There figure 2b represents the light intensity profiles of the beams emitted by the first and second lighting devices, in the case where the light source of the first lighting device 1 is a visible light source and when the first lighting device 1 is the same as the second lighting device 2.

[0084] In this example, the visible light source producing the first light beam is identical to the light source producing the second light beam.

[0085] In the context of the invention, the vehicle 10 is traveling at night, or when the light is reduced. The second lighting device 2 is therefore activated. The visible light source operates and emits, for example, a dipped beam or high beam type beam.

[0086] When the raw contrast of the scene located in front of the vehicle SA becomes lower than the threshold contrast value, the first lighting device 1 is actuated by the control unit 4.

[0087] When the first lighting device 1 is actuated, the visible light source then emits a periodic light beam combining the first light beam and the second light beam. The compensation device 8 controls the visible light source so that it emits a light beam with a periodic light intensity profile having: a first part 31 where the luminous intensity is constant and equal to a positive nominal intensity. This nominal intensity corresponds to the intensity of the dipped beam type beam. a second part 32 where the luminous intensity is greater than the nominal intensity. a third part 33 where the luminous intensity is less than the nominal intensity for a duration such that the average intensity of the light beam is constant and equal to the nominal intensity over a period.

[0088] The sum of the duration of each of the three parts being equal to the duration of a period. The sum of the duration of the second part 32 and the third part 33 is less than the flicker perception time of the human eye.

[0089] It is notably less than 1 / 50 s, preferably less than 1 / 75 s.

[0090] Since the flicker perception time of the human eye is greater than the duration of the period of the light intensity profile, the intensity perceived by the human eye over a period is equal to the average intensity of the light beam, i.e. the intensity of the dipped beam light beam. Thus, the modulation of the lighting generated by the light source of the first device is imperceptible to the driver or an external observer.

[0091] As in the case where the first lighting device 1 and the second lighting device 2 are distinct, the image sensor is synchronized with the second part 32 of the light intensity profile. The acquisition of an image 35 is triggered at the time of transition to the second part 32 of the light intensity profile.

[0092] During the acquisition of this image 35, the scene located in front of the vehicle SA is illuminated by the first device 1 with maximum intensity. It is therefore particularly visible on this image 35. The processing unit 5 can in particular detect the position of the marking strips on this image 35 which are not visible to the driver.

[0093] Once the marking strips have been identified by the processing unit 5, their position is returned to the driver using the restitution device. This restitution device may be a complementary lighting device 7 making it possible to illuminate towards the front of the vehicle. figures 3a et 3b schematically and respectively represent the scene located in front of the vehicle SA when the additional lighting device 7 is not activated, or when the vehicle does not include an additional lighting device 7, and the scene located in front of the vehicle when the additional lighting device is activated.

[0094] When the additional lighting device 7 is not activated, only the first marking strips 40 close to the vehicle are visible to the driver 11.

[0095] When the additional lighting device 7 is activated, the driver 11 can also see second marking strips 41 located at a greater distance from the vehicle than the first marking strips 40 close to the vehicle and which were not visible when the additional lighting device 7 was not activated. On the figure 3b , only a second marking strip 41 is shown. It is understood that several second marking strips 41 can be made visible thanks to the additional lighting device 7.

[0096] The additional lighting device 7 makes it possible to make the scene located in front of the vehicle SA more visible, and in particular the first marking strips 40 and the second marking strips 41, which increases the safety of the driver.

[0097] The method implemented to implement the lighting system according to the invention and to increase the visibility of the scene located in front of the vehicle SA comprises a large number of steps which are presented in the figure 4 .

[0098] Step 1, E1, consists of the acquisition of the scene located in front of the vehicle SA by the acquisition device 3, and in particular by the image sensor. During step 2, E2, the raw contrast C 0 of the images captured by the image sensor is calculated. The raw contrast C 0 is then compared to the threshold contrast C s predefined during step 3, E3. If the raw contrast C 0 is greater than the threshold contrast C s , the method resumes at step E1. If the raw contrast C 0 is less than the threshold contrast C s , the method proceeds to step 4, E4. Step E4 consists of the activation of the first lighting device 1. In step 5, E5, the acquisition device 3 acquires the scene located in front of the vehicle SA. The corrected contrast C c of the images captured by the image sensor is then calculated at step 6, E6.Then, during step 7, E7 the raw contrast C 0 of the images captured by the image sensor is calculated taking into account the lighting contribution of the first lighting device 1 in the corrected contrast C c . In step 8, E8, the raw contrast C 0 calculated in step E7 is compared to the predefined threshold contrast C s . If the raw contrast C 0 is greater than the threshold contrast C s , the method proceeds to step 9, E9. If the raw contrast C 0 is less than the threshold contrast C s , the method proceeds to step 10, E10. In step E9 the first lighting device is switched off, then the method resumes at step E1. In step E10 the device for rendering the scene located in front of the vehicle SA is activated. Following this step E10, the method resumes at step E5.

Claims

1. A vehicle lighting system comprising: ∘ an acquisition device (3) for the scene located in front of the vehicle SA comprising an image sensor, ∘ a first lighting device (1) comprising at least one light source capable of emitting a first light beam of a first intensity illuminating said scene so as to increase the contrast of the images captured by the image sensor, ∘ a second lighting device (2) comprising a light source emitting a second light beam of a second intensity performing a lighting function and / or regulatory signaling at the front of the vehicle, ∘ a control unit (4) which activates the first lighting device (1) when a first contrast value, called raw contrast Co, of the images captured by the image sensor is lower than a predefined threshold contrast Cs, said raw contrast of the images captured by the image sensor corresponding to the contrast of the images captured when the lighting device is not activated, ∘ the first lighting device (1) and the second lighting device (2) being connected to a compensation device (8) allowing to compensate the first and second intensities of the light beams emitted by the first (1) and second (2) lighting devices, characterized in that the light source of the first lighting device (1) is a visible source configured to generate modulated illumination at a frequency higher than 50Hz, and in that the acquisition device is capable of acquiring an image at the moment of modulation where the intensity of the source is highest.

2. A vehicle lighting system according to claim 1, characterized in that the first lighting device (1) and the second lighting device (2) are distinct.

3. A vehicle lighting system according to claim 1, characterized in that the first lighting device (1) and the second lighting device (2) are combined.

4. A vehicle lighting system according to any of the preceding claims, characterized in that the light source of the first lighting device (1) emits P-type polarized light.

5. A vehicle lighting system according to any of the preceding claims, characterized in that it comprises a restitution device allowing to restore to the driver the scene located in front of the vehicle SA and captured by the acquisition device (3) with a higher contrast than that of the same scene SA perceived by the driver without the restitution device.

6. A vehicle lighting system according to claim 5, characterized in that the restitution device is a complementary lighting device (7) allowing to illuminate towards the front of the vehicle and arranged to illuminate the marking strips (40, 41) of the edges of the road on which the vehicle is located, at the front of the vehicle.

7. A method for controlling a vehicle lighting system according to any of claims 1 to 6, characterized in that it comprises at least the following sequence of steps: Step 1 (E1): Acquisition of the scene located in front of the vehicle SA by the acquisition device (3) Step 2 (E2): Calculation of the raw contrast Co of the images captured by the image sensor Step 3 (E3): Comparison of the raw contrast Co calculated in step 2 (E2) with the predefined threshold contrast Cs If the raw contrast Co is greater than the threshold contrast Cs, resume at step 1 (E1) If the raw contrast Co is less than the threshold contrast Cs, proceed to step 4 (E4) Step 4 (E4): Activation of the first lighting device (1) Step 5 (E5): Acquisition of the scene located in front of the vehicle SA by the acquisition device (3) Step 6 (E6): Calculation of the corrected contrast Co of the images captured by the image sensor Step 7 (E7): Calculation of the raw contrast Co of the images captured by the image sensor taking into account the contribution of the first lighting device (1) to the corrected contrast Co Step 8 (E8): Comparison of the raw contrast Co calculated in step 8 with the predefined threshold contrast Cs If the raw contrast Co is greater than the threshold contrast Cs, proceed to step 9 (Eg) If the raw contrast Co is less than the threshold contrast Cs, resume at step 5 (E5) Step 9 (E9): Extinction of the first lighting device (1) and resume at step 1 (E1)8. A method according to the preceding claim, characterized in that it further comprises, successively at step 8 (E8), when the raw contrast Co is less than the threshold contrast Cs, a step 10 (E10) consisting in activating the restitution device for the scene located in front of the vehicle SA according to one of claims 5 to 6, before resuming at step 5 (E5).