METHOD FOR CONTROLLING A LIGHTING DEVICE FOR EMITTING A PIXELATED LIGHT BEAM

Abstract

A method for controlling a lighting device of a motor vehicle including at least one lighting module having a plurality of light sources, each of the light sources being designed to emit a luminous pixel, and a controller able to selectively control each of the light sources by applying thereto an electrical signal having a parameter of a value determined for the emission of a luminous pixel of given brightness.

Claims

1. A method for controlling a lighting device of a motor vehicle comprising at least one lighting module comprising a plurality of light sources, each of the light sources being designed to emit a light pixel, and a controller able to selectively control each of the light sources by applying to it an electrical signal having a parameter of a determined value so as to emit a light pixel with a given light intensity, the method comprising the following steps: defining, in advance, a conversion function of the lighting module for converting the value of said parameter into a light intensity emitted by the light sources by way of at least one measurement of the light intensity emitted by the light sources when the controller applies to them an electrical signal having a predetermined value of said parameter; receiving a plurality of setpoint values for the emission of a desired pixelated light beam, each setpoint value being a light intensity of a light pixel of the desired pixelated light beam to be emitted by one of the light sources of said lighting module; determining, from each setpoint value, a value of said parameter using said conversion function defined in advance; controlling each of the light sources by applying to it said electrical signal having said determined value of said parameter so as to emit the pixelated light beam.

2. The control method as claimed in claim 1, wherein said electrical signal is a pulse width-modulated electrical signal, said parameter being the duty cycle of this electrical signal.

3. The control method as claimed in claim 1, wherein the step of defining the conversion function in advance comprises a single sub-step of measuring the light intensity of the light beam emitted by the lighting module when the controller applies one and the same electrical signal having one and the same predetermined value of said parameter to all of the light sources.

4. The control method as claimed in claim 3, wherein the conversion function defined in advance is a linear function whose coefficient is equal to the ratio between the measured light intensity and the predetermined value of said parameter.

5. The control method as claimed in claim 1, wherein the step of defining the conversion function in advance comprises multiple sub-steps of measuring the light intensity of the light beam emitted by the lighting module when the controller applies one and the same electrical signal having multiple predetermined values of said parameter to all of the light sources.

6. The control method as claimed in claim 5, wherein the conversion function defined in advance is a non-linear function extrapolated from the measured light intensity values.

7. The control method as claimed in claim 1, wherein the step of defining the conversion function in advance comprises storing said function in a memory of the controller.

8. The control method as claimed in claim 1, wherein the step of receiving a plurality of setpoint values for the emission of a desired pixelated light beam comprises a sub-step of receiving a digital image of the desired pixelated light beam, a sub-step of splitting said digital image into a plurality of regions, each region being associated with one of the light sources of the lighting module and a sub-step of computing a setpoint value for each of the light sources of the lighting module from the region associated with this light source.

9. The control method as claimed in claim 1, wherein the step of determining the values of said parameter comprises computing the image from each setpoint value using the reciprocal function of the conversion function defined in advance.

10. A computer program comprising a program code that is designed to implement the method as claimed in claim 1.

11. A data medium on which the computer program as claimed in claim 10 is recorded.

12. The control method as claimed in claim 2, wherein the step of defining the conversion function in advance comprises a single sub-step of measuring the light intensity of the light beam emitted by the lighting module when the controller applies one and the same electrical signal having one and the same predetermined value of said parameter to all of the light sources.

13. The control method as claimed in claim 2, wherein the step of defining the conversion function in advance comprises multiple sub-steps of measuring the light intensity of the light beam emitted by the lighting module when the controller applies one and the same electrical signal having multiple predetermined values of said parameter to all of the light sources.

14. The control method as claimed in claim 2, wherein the step of defining the conversion function in advance comprises storing said function in a memory of the controller.

15. The control method as claimed in claim 2, wherein the step of receiving a plurality of setpoint values for the emission of a desired pixelated light beam comprises a sub-step of receiving a digital image of the desired pixelated light beam, a sub-step of splitting said digital image into a plurality of regions, each region being associated with one of the light sources of the lighting module and a sub-step of computing a setpoint value for each of the light sources of the lighting module from the region associated with this light source.

16. The control method as claimed in claim 2, wherein the step of determining the values of said parameter comprises computing the image from each setpoint value using the reciprocal function of the conversion function defined in advance.

17. A computer program comprising a program code that is designed to implement the method as claimed in claim 2.

18. The control method as claimed in claim 3, wherein the step of defining the conversion function in advance comprises storing said function in a memory of the controller.

19. The control method as claimed in claim 3, wherein the step of receiving a plurality of setpoint values for the emission of a desired pixelated light beam comprises a sub-step of receiving a digital image of the desired pixelated light beam, a sub-step of splitting said digital image into a plurality of regions, each region being associated with one of the light sources of the lighting module and a sub-step of computing a setpoint value for each of the light sources of the lighting module from the region associated with this light source.

20. The control method as claimed in claim 3, wherein the step of determining the values of said parameter comprises computing the image from each setpoint value using the reciprocal function of the conversion function defined in advance.

Description

[0030] In the following description, elements that are identical in terms of structure or in terms of function and that appear in various figures have been designated with the same reference, unless otherwise indicated.

[0031] FIG. 1 shows a right-hand lighting device 1 of a motor vehicle, comprising two lighting modules 2 and 3. The lighting module 2 comprises a light source 21 associated with a lens 22 for emitting a low-beam light beam. The lighting module 3 comprises a pixelated light source 31 associated with a lens 32 for emitting a high-resolution pixelated light beam HD. In the example described, the pixelated light source 31 is a monolithic pixelated light-emitting diode, each of the light-emitting elements of which forms a light source 31.sub.i,j that is able to be selectively activated and controlled by an integrated controller so as to emit an elementary light beam, the light intensity of which is able to be controlled, and thus forming one of the pixels of the pixelated light beam. In the example described, the pixelated light beam HD comprises around 5000 pixels with dimensions of 0.2°, distributed over 135 columns and 37 rows.

[0032] The lighting device 1 comprises a controller 5 designed to control the light source 21 and the integrated controller of the pixelated light source 31 so as to selectively control the turning on, the turning off and the modification of the light intensity of each of the pixels of the pixelated light beam, along with the turning on or the turning off of the beam, based on information received from a computer 6 of the host vehicle.

[0033] More specifically, the controller 5 receives, from the computer 6, a digital image of a pixelated light beam to be emitted defining, in grayscale, the light intensities of this beam. As will be described below, the controller 5 defines a duty cycle value based on this digital image and for each of the light sources 31.sub.i,j, and transmits these values to the integrated controller of the pixelated light source 31, which generates and applies, to each of the light sources 31.sub.i,j, an electrical signal that is pulse width-modulated in accordance with the associated duty cycle value so as to emit a light pixel, the set of pixels thus forming the pixelated light beam to be emitted.

[0034] FIG. 2 shows a method for controlling the lighting device 1, in particular implemented by the controller 5 and the integrated controller of the pixelated light source 31.

[0035] In a first step E1, for example performed at the end of the production of the lighting device 1 or before the first drive of the motor vehicle equipped with the lighting device 1, a conversion function of the lighting module 3 will be defined for converting between the duty cycle values defined by the controller 5 and the light intensity of the elementary light beams emitted by the light sources 31.sub.i,j of the pixelated light source 31.

[0036] To this end, the controller 5 will sequentially transmit a plurality of predetermined duty cycle values to the integrated controller of the pixelated light source 31 in such a way that the pixelated light source 31 emits multiple complete pixelated light beams having various intensities. The predetermined values are duty cycle values increasing at regular intervals, from 0 to 100%. All of the light sources 31.sub.i,j are thus controlled in the same way, all of the pixels thus being turned on for each duty cycle occurrence, each light beam thus forming a “blank page” of increasing intensity. FIG. 3 shows one example of a “blank page” formed by the pixelated light beam HD emitted by the lighting module 3 for a duty cycle of 20%.

[0037] For each duty cycle occurrence, the maximum intensity Imax of the pixelated light beam emitted by the lighting module 3 is measured. Lastly, the various measured light intensity values are extrapolated in order to define a conversion function for converting between duty cycle and light intensity actually emitted. In the example described, the extrapolated conversion function is a second-degree polynomial function defined by the following equation:

I.sub.m=0.76∝+0.24∝.sup.2,   [Math. 1]

where I.sub.m is the light intensity actually emitted and α is the duty cycle of the electrical signal applied to the pixelated light source 31.

[0038] At the end of step E1, the conversion function is stored in a memory of the controller 5.

[0039] In a step E2, the controller 5 receives, from the computer 6, a digital image Im of a pixelated light beam to be emitted by the lighting module 3. One example of a digital image Im has been shown in FIG. 4. Each of the points of the digital image Im represents a light intensity of the desired pixelated light beam in a point in space.

[0040] In a step E3, the controller 5 splits the digital image Im into as many regions R.sub.i,j as the pixelated light source 31 comprises light sources each region R.sub.i,j thus being associated with one of these light sources 31.sub.i,j and corresponding, in terms of size and shape, to the pixel able to be emitted by this light source 31.sub.i,j. One example of a split image Im has been shown in FIG. 5.

[0041] In a step E4, the controller 5 computes, for each of the light sources 31.sub.i,j, a setpoint value I.sub.i,j corresponding to the average light intensity of the region R.sub.i,j associated with this light source 31.sub.i,j. This setpoint value thus corresponds to the light intensity of the pixel to be emitted by this light source 31.sub.i,j, such that the set of pixels forms the desired pixelated light beam.

[0042] In a step E5, the controller 5 determines a duty cycle value α.sub.i,j from each of the setpoint values I.sub.i,j and from the conversion function defined in advance. For example, the duty cycle value may be determined by way of the reciprocal function of the conversion function, defined by the following equation:

α.sub.i,j=1.24I.sub.i,j−0.24I.sub.i,j.sup.2   [Math. 2]

[0043] Finally, in a step E6, all of the duty cycle values α.sub.i,j are transmitted, by the controller 5, to the integrated controller of the pixelated light source 31. This integrated controller 31.sub.i,j generates and applies, to each of the light sources 31.sub.i,j, an electrical signal that is pulse width-modulated in accordance with the associated duty cycle value α.sub.i,j so as to emit a light pixel whose light intensity corresponds substantially to the setpoint value I.sub.i,j.

[0044] The above description clearly explains how the invention makes it possible to achieve the objectives that it has set itself, in particular by proposing a method for controlling a lighting device that, through advance empirical definition of a conversion function for converting between duty cycle and light intensity actually emitted, makes it possible to take into account and compensate for the mutual interference of the light sources of a lighting module, such that the pixelated light beam actually emitted by the lighting module complies with the light intensity instructions given to the lighting module.

[0045] In any event, the invention should not be regarded as being limited to the embodiments specifically described in this document, and extends, in particular, to any equivalent means and to any technically operative combination of these means. In particular, it is possible to contemplate types of conversion function other than the one described, and in particular linear conversion functions determined from a single measurement of the light intensity or even composite conversion functions defined for each light source or else for groups of light sources.