Light system for a motor vehicle

Abstract

Motor vehicle light system including an acquisition device for acquiring the scene in front of the vehicle, including an image sensor, a first lighting device including a light source suitable for emitting a first light beam lighting up the scene so as to increase the contrast of the images captured by the image sensor, a second lighting device including a light source emitting a second light beam performing a regulatory signalling and/or lighting function in front of the vehicle, a control unit which switches on the first lighting device when a first contrast value referred to as raw contrast C.sub.0 of the images captured by the image sensor is lower than a predefined threshold contrast C.sub.s, the light source of the first lighting device being configured to generate modulated lighting, the modulation of which is imperceptible to the driver of the vehicle or an external observer.

Claims

1. Motor vehicle light system including: an acquisition device for acquiring the scene SA located in front of the vehicle, including an image sensor, a first lighting device including at least one light source suitable for emitting a first light beam of a first intensity lighting up said scene so as to increase the contrast of the images captured by the image sensor, a second lighting device including a light source emitting a second light beam of a second intensity performing a regulatory signalling and/or lighting function in front of the vehicle, a control unit which switches on the first lighting device when a first contrast value referred to as raw contrast C.sub.0 of the images captured by the image sensor is lower than a predefined threshold contrast C.sub.s, wherein the light source of the first lighting device is configured to generate modulated lighting, the modulation of which is imperceptible to the driver of said vehicle or an external observer.

2. Motor vehicle light system according to claim 1, wherein the first lighting device includes a source of infrared light and the image sensor is sensitive to infrared light.

3. Motor vehicle light system according to claim 2, wherein the light source of the first lighting device emits P-polarized light.

4. Motor vehicle light system according to claim 2, wherein the source of infrared light emits a first light beam intermittently so as to light up said scene in a discontinuous manner when the first lighting device is switched on, and the acquisition of at least one image by the image sensor is synchronized with the emission of the first light beam.

5. Motor vehicle light system according to claim 2, wherein the source of infrared light emits a first light beam continuously so as to light up said scene SA permanently when the first lighting device is switched on.

6. Motor vehicle light system according to claim 5, wherein, when the first lighting device is switched on, the source of infrared light emits a first light beam with a periodic luminous intensity profile exhibiting: a first part made up of one or more segments in which the luminous intensity is constant and equal to a positive or nil nominal intensity, a second part in which the luminous intensity is higher than the nominal intensity, and has a duration that is longer than the duration of acquisition of an image by the image sensor, the sum of the duration of the two parts being equal to the duration of a period, the acquisition of at least one image by the image sensor being synchronized with the second part of the luminous intensity profile.

7. Motor vehicle light system according to claim 1, wherein the first lighting device includes a source of visible light, and the light system comprises a compensation device for compensating for the first and second intensities of the light beams of the first and second lighting devices such that the modulation generated by the light source of the first lighting device is imperceptible to the driver or an external observer.

8. Motor vehicle light system according to claim 7, wherein the first lighting device and the second lighting device are separate.

9. Motor vehicle light system according to claim 8, wherein, when the first lighting device is switched on, the source of visible light emits a first periodic light beam with a periodic luminous intensity profile exhibiting: a first part made up of one or more segments wherein the luminous intensity is constant and equal to a positive or nil nominal intensity, a second part in which the luminous intensity is higher than the nominal intensity, the sum of the duration of the first part and of the second part being equal to the duration of a period, the duration of a period being less than the flicker perception time of the human eye, and the compensation device reduces the second intensity so as to compensate for the first and second intensities, the acquisition of at least one image by the image sensor being synchronized with the second part of the luminous intensity profile.

10. Motor vehicle light system according to claim 7, wherein the first lighting device and the second lighting device are merged.

11. Motor vehicle light system according to claim 10, wherein the compensation device drives the source of visible light in such a way that it emits a light beam with a periodic luminous intensity profile exhibiting: a first part made up of one or more segments wherein the luminous intensity is constant and equal to a positive nominal intensity, a second part in which the luminous intensity is higher than the nominal intensity, a third part made up of one or more segments wherein the luminous intensity is lower than the nominal intensity over 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 part and the third part being less than the flicker perception time of the human eye, the acquisition of at least one image by the image sensor being synchronized with the second part of the luminous intensity profile.

12. Motor vehicle light system according to claim 1, wherein the light source of the first lighting device emits P-polarized light.

13. Motor vehicle light system according to claim 1, wherein the motor vehicle light system includes a reproduction device for reproducing for the driver the scene SA located in front of the vehicle and captured by the acquisition device with a higher contrast than that of the same scene SA perceived by the driver without the reproduction device.

14. Motor vehicle light system according to claim 13, wherein the reproduction device is assumed to be among a head-up display, an electronic video display screen, a liquid-crystal display integrated in the vehicle or a portable electronic device.

15. Motor vehicle light system according to claim 13, wherein the reproduction device is an additional lighting device for lighting up frontwards of the vehicle and arranged to light up the strips marking the edges of the traffic lane in which the vehicle is located, in front of the vehicle.

16. Motor vehicle light system according to claim 15, wherein the additional lighting device is merged with the second lighting device.

17. Motor vehicle light system according to claim 15, wherein the additional lighting device is merged with the first lighting device.

18. Motor vehicle light system according to claim 15, wherein the additional lighting device is suitable for emitting P-polarized light.

19. Method for controlling a motor vehicle light system according to claim 1, wherein the method comprises at least the following steps in succession: Step 1: Acquisition of the scene SA located in front of the vehicle by the acquisition device Step 2: Calculation of the raw contrast C.sub.0 of the images captured by the image sensor Step 3: Comparison of the raw contrast C.sub.0 calculated at step 2 with the predefined threshold contrast C.sub.s If the raw contrast C.sub.0 is higher than the threshold contrast C.sub.s, go back to step 1 If the raw contrast C.sub.0 is lower than the threshold contrast C.sub.s, proceed to step 4 Step 4: Activation of the first lighting device Step 5: Acquisition of the scene SA in front of the vehicle by the acquisition device Step 6: Calculation of the correct contrast C.sub.c of the images captured by the image sensor Step 7: Calculation of the raw contrast C.sub.0 of the images captured by the image sensor taking into account the contribution of the first lighting device in the correct contrast C.sub.c Step 8: Comparison of the raw contrast C.sub.0 calculated at step 7 with the predefined threshold contrast C.sub.s If the raw contrast C.sub.0 is higher than the threshold contrast C.sub.s, proceed to step 9 If the raw contrast C.sub.0 is lower than the threshold contrast C.sub.s, go back to step 5 Step 9: Switch-off of the first lighting device (1) and return to step 1.

20. Method according to claim 19, wherein the method comprises additionally and successively to step 8, when the raw contrast C.sub.0 is lower than the threshold contrast C.sub.s, a step 10 consisting of the activation of the device for reproducing the scene SA located in front of the vehicle according to one of claims 12 to 17 before going back to step 5.

Description

(1) Other features and advantages of the present invention will become clearer with the aid of the description and the drawings in which:

(2) FIG. 1 schematically represents in partial cross-section a vehicle equipped with a light system according to the present invention;

(3) FIG. 2a represents the luminous intensity profiles of the light beams emitted by the first and second lighting devices over time for the case in which the two lighting devices are separate, and the acquisition of images by the image sensor;

(4) FIG. 2b represents the luminous intensity profile of the light 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;

(5) FIG. 3a schematically represents the scene located in front of the vehicle in the absence of an active additional lighting device;

(6) FIG. 3b schematically represents the scene located in front of the vehicle when the additional lighting device is activated;

(7) FIG. 4 represents the various steps of the method implementing a light system according to the present invention.

(8) With reference to FIG. 1, there is schematically represented a partial cross-section of a vehicle 10 equipped with light units 9 and driven by a driver represented by his/her eye 11. The driver 11 observes the scene SA located in front of the vehicle through the windscreen 12.

(9) The light unit 9 is equipped with several lighting devices: a first lighting device 1, a second lighting device 2 and an additional lighting device 7. The second lighting device 2 is equipped with a light source suitable for generating a low beam type light beam, meeting the requirements of regulation ECE R112, it being understood that a person skilled in the art will know how to adapt the invention in order that this second lighting device 2 satisfies the requirements of any other national or regional regulation. In FIG. 1, the first lighting device 1 and the second lighting device 2 are separate.

(10) In accordance with the present invention, the vehicle is equipped with an acquisition device 3 suitable for acquiring images of the scene SA located in front of the vehicle. The acquisition device 3 includes an image sensor for capturing images of the scene SA located in front of the vehicle. The acquisition device can notably take the form of a camera comprising a CMOS sensor for example, or a CCD sensor.

(11) The acquisition device 3 is connected to a processing unit 5 for processing images captured by the image sensor. The processing unit 5 provides for determining the raw contrast of the images captured by the image sensor. 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 be continuously aware of whether the first lighting device is switched on.

(12) When the first lighting device is switched on, the processing unit 5 can notably calculate the raw contrast value from the correct 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.

(13) The raw contrast value is then transmitted to a control unit 4 which switches on the first lighting device 1 when the raw contrast is lower than a predefined threshold contrast, or which leaves the first lighting device 1 switched on when it is already switched on.

(14) This predefined threshold contrast corresponds to the contrast from which it can be considered that the luminosity is too low for the driver and the acquisition device to be able to correctly see the scene SA located in front of the vehicle and notably the marking strips.

(15) When the first lighting device 1 is switched on, the lighting modulation generated by the light source of the first lighting device 1 is not perceptible to the driver 11 or an external observer while it is perceptible to the acquisition device 3. The acquisition device 3 perceives the effect of the light emitted by the first lighting device 1 on the lighting of the scene SA.

(16) The light source of the first lighting device 1 can be a source of infrared light. The radiation from the source is then invisible to the human eye. Only the image sensor must then be sensitive to infrared light. The lighting-up of the scene with the aid of the source of infrared light thus enables the image sensor to capture the images of the scene SA located in front of the vehicle with better contrast than if there were no lighting.

(17) The light source of the first device can alternatively be a source of visible light. The image sensor is then sensitive to the visible light emitted by the source of visible light. For the lighting modulation 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 for compensating for the first and second intensities of the light beams emitted by the first 1 and second 2 lighting devices. The compensation performed by the compensation device 8 is detailed in FIGS. 2a and 2b.

(18) The activation of the first lighting device 1 does not disturb the driver or an external observer since, once activated, the lighting modulation generated by the light source of the first lighting device 1 is imperceptible to the driver or an external observer. Thus, once activated and throughout the time over which the first lighting device 1 is activated, the lighting of the scene SA located in front of the vehicle is perceived by the driver 11 or an external observer as not being modified. However, the contrast of the images captured by the image sensor is definitely modified. Image acquisition by the image sensor is synchronized with the emission of light from the first lighting device 1 such that the scene SA located in front of the vehicle is visible on at least some of the images captured by the image sensor. The processing unit 5 can notably detect on these images the positions of the marking strips which are not visible to the driver.

(19) To enable the driver to know the positions of these marking strips, the vehicle is equipped with a reproduction device. This reproduction device can for example be formed by a head-up display 6 or even an electronic video display screen, a liquid-crystal screen integrated in the vehicle or a portable electronic device.

(20) According to one variant also represented in FIG. 1, the reproduction device can be an additional lighting device 7, for lighting up frontwards of the vehicle. It notably provides for lighting up the strips marking the edges of the traffic lane in which the vehicle is located, in front of the vehicle.

(21) FIG. 2a represents the luminous intensity profiles of the beams emitted by the first and second lighting devices, for the case in which the light source of the first lighting device 1 is a source of visible light and when the first lighting device 1 and the second lighting device 2 are separate.

(22) In the context of the invention, the vehicle 10 is in nighttime traffic, or when luminosity is reduced. The second lighting device 2 is therefore switched on.

(23) When the raw contrast of the scene SA located in front of the vehicle becomes lower than the threshold contrast value, the first lighting device 1 is switched on by the control unit 4.

(24) When the first lighting device 1 is switched on, the source of visible light emits a first light beam, periodic in time, with a periodic luminous intensity profile.

(25) The periodic luminous intensity profile exhibits: a first part 21 made up of two segments 21a and 21b in which the luminous intensity is constant and equal to a positive or nil nominal intensity, and a second part 22 in which the luminous intensity is higher than the nominal intensity;
The sum of the duration of the first 21 and second 22 parts is equal to the duration of a period T. The duration of a period is less than the flicker perception time of the human eye.

(26) Simultaneously, the compensation device 8 reduces the second intensity. The second intensity changes from a maximum value 13 to a value 14 that is less than the maximum value 13. The reduction in the second intensity is calculated by the compensation device such that the driver or an external observer does not perceive a change in the lighting of the scene SA located in front of the vehicle during the lighting modulation generated by the light source of the first lighting device 1. As a function of the luminous intensity of the first part 21 of the luminous 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. This is because the higher the luminous intensity of the first part 21, the lower the value 14 of the second intensity. Thus, an observer external to the vehicle 10 will distinguish even more the first lighting device 1 and will see that the second intensity is attenuated.

(27) The image sensor is synchronized with the second part 22 of the luminous intensity profile. The acquisition of an image 25 is triggered at the moment of the transition to the second part 22 of the intensity profile. Furthermore, the image sensor exhibits a sufficiently high acquisition frequency so as to be able to acquire at least one image 25 during the second part 22 of the luminous intensity profile of the first light beam of the light source of the first lighting device 1.

(28) During acquisition of this image 25, the scene SA located in front of the vehicle is lit up by the first device 1 with maximum intensity. It is therefore particularly visible on this image 25. The processing unit 5 can notably detect the positions of the marking strips on this image 25 which are not visible to the driver.

(29) FIG. 2b represents the luminous intensity profiles of the beams emitted by the first and second lighting devices, for the case in which the light source of the first lighting device 1 is a source of visible light and when the first lighting device 1 is merged with the second lighting device 2.

(30) In this example, the source of visible light producing the first light beam is identical to the light source producing the second light beam.

(31) In the context of the invention, the vehicle 10 is in nighttime traffic, or when luminosity is reduced. The second lighting device 2 is therefore switched on. The source of visible light operates and emits for example a low beam or high beam type beam.

(32) When the raw contrast of the scene SA located in front of the vehicle becomes lower than the threshold contrast value, the first lighting device 1 is switched on by the control unit 4.

(33) When the first lighting device 1 is switched on, the source of visible light then emits a periodic light beam combining the first light beam and the second light beam. The compensation device 8 drives the source of visible light in such a way that it emits a light beam with a periodic luminous intensity profile exhibiting:

(34) a first part 31 in which the luminous intensity is constant and equal to a positive nominal intensity. This nominal intensity corresponds to the intensity of the low beam type beam;

(35) a second part 32 in which the luminous intensity is higher than the nominal intensity;

(36) a third part 33 in which the luminous intensity is lower than the nominal intensity over a duration such that the average intensity of the light beam is constant and equal to the nominal intensity over a period.

(37) The sum of the duration of each of the three parts is equal to the duration of a period. The sum of the duration of the second part 32 and of the third part 33 is less than the flicker perception time of the human eye.

(38) It is notably less than 1/50 s, preferably less than 1/75 s.

(39) Since the flicker perception time of the human eye is longer than the duration of a period of the luminous 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 low beam light beam. Thus, the lighting modulation generated by the light source of the first lighting device is imperceptible to the driver or an external observer.

(40) As in the case in which the first lighting device 1 and the second lighting device 2 are separate, the image sensor is synchronized with the second part 32 of the luminous intensity profile. The acquisition of an image 35 is triggered at the moment of the transition to the second part 32 of the intensity profile.

(41) During acquisition of this image 35, the scene SA located in front of the vehicle is lit up by the first device 1 with maximum intensity. It is therefore particularly visible on this image 35. The processing unit 5 can notably detect the positions of the marking strips on this image 35 which are not visible to the driver.

(42) Once the marking strips are identified by the processing unit, their positions are reproduced for the driver with the aid of the reproduction device. This reproduction device can be an additional lighting device 7, for lighting up frontwards of the vehicle. FIGS. 3a and 3b schematically and respectively represent the scene SA located in front of the vehicle when the additional lighting device 7 is not activated, or when the vehicle does not comprise an additional lighting device 7, and the scene located in front of the vehicle when the additional lighting device is activated.

(43) 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.

(44) When the additional lighting device 7 is activated, the driver 11 can also see second marking strips 41 located at a more significant 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. In FIG. 3b, only one second marking strip 41 is represented. It is understood that several second marking strips 41 can be made visible by virtue of the additional lighting device 7.

(45) The additional lighting device 7 provides for making the scene SA located in front of the vehicle more visible, and notably the first marking strips 40 and the second marking strips 41, thereby increasing driver safety.

(46) The method set up to implement the light system according to the invention and to arrive at increasing the visibility of the scene SA located in front of the vehicle includes a large number of steps which are presented in FIG. 4.

(47) Step 1, E1, consists of the acquisition of the scene SA located in front of the vehicle by the acquisition device 3, and notably by the image sensor. During step 2, E2, the raw contrast C.sub.0 of the images captured by the image sensor is calculated. The raw contrast C.sub.0 is then compared with the predefined threshold contrast C.sub.s during step 3, E3. If the raw contrast C.sub.0 is higher than the threshold contrast C.sub.s, the method resumes from step E1. If the raw contrast C.sub.0 is lower than the threshold contrast C.sub.s, the method proceeds to step 4, E4. Step E4 consists in activating the first lighting device 1. At step 5, E5, the acquisition device 3 acquires the scene SA located in front of the vehicle. The correct contrast C.sub.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.sub.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 correct contrast C.sub.c. At step 8, E8, the raw contrast C.sub.0 calculated at step E7 is compared with the predefined threshold contrast C.sub.s. If the raw contrast C.sub.0 is higher than the threshold contrast C.sub.s, the method proceeds to step 9, E9. If the raw contrast C.sub.0 is lower than the threshold contrast C.sub.s, the method proceeds to step 10, E10. At step E9, the first lighting device is switched off, and then the method resumes from step E1. At step E10, the device for reproducing the scene SA located in front of the vehicle is activated. Following this step E10, the method resumes from step E5.