Method of operating an automotive lighting device and automotive lighting device

Abstract

The invention provides a method for operating an automotive lighting device (1) comprising at least two semiconductor lighting modules (2). This method comprises the steps of defining a homogeneity criterion for each color pair, supplying the first lighting module with a first current value which produces a first output color in the first lighting module and supplying the second lighting module with a second current value which produces a second output color in the second lighting module, wherein the first output color - second output color pair fulfills the homogeneity criterion. The invention also provides an automotive lighting device (1) comprising a control unit (3) for carrying out the method steps.Figure for abstract: Figure 3

Description

Title of the invention: Method of operating an automobile lighting device and automobile lighting device

[0001] This invention relates to the field of automotive lighting devices, and more particularly to the management of the colors of these light sources included in these devices.

[0002] Car manufacturers are increasingly adopting digital lighting devices for mid- and high-end products.

[0003] These digital lighting devices generally comprise semiconductor light sources, the operation of which is highly temperature dependent.

[0004] Temperature control in these elements is a very sensitive aspect, and is generally carried out by derating, which means that the value of the current which powers the light source is reduced so that the output flux and the operating temperature decrease accordingly. The performance of the light sources must therefore be greatly oversized to cope with these overheating problems, so that the operating values ​​can be reduced while maintaining acceptable values.

[0005] In addition, these techniques also affect the color of the output pattern. In some cases, when a beam pattern is provided by more than one light module, the color may not be consistent throughout the pattern.

[0006] This issue has been addressed so far, but a solution is being sought.

[0007] The invention provides an alternative solution for managing the output color of the light source patterns by a method of operating an automotive lighting device and an automotive lighting device.

[0008] Unless otherwise defined, all terms (including technical and scientific terms) used herein shall be interpreted in accordance with the usages of the profession. It is also understood that terms in common usage shall be interpreted as being customary in the relevant art and not in an idealized or overly formal sense, unless expressly defined as such herein.

[0009] In this text, the term "includes" and its derivatives (such as "comprising", etc.) should not be understood in an exclusive sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include other elements, steps, etc.

[0010] In a first inventive aspect, the invention provides a method for operating an automotive lighting device comprising at least two semiconductor lighting modules, the method comprising the following steps • Define a homogeneity criterion, where for each pair of colors, the pair is defined as acceptable or unacceptable; • supplying the first lighting module with a first current value that produces a first output color in the first lighting module • supply the second light module with a second current value which produces a second output color in the second light module, in which the first output color - second output color pair meets the homogeneity criterion.

[0011] The term "solid state" refers to light emitted by solid-state electroluminescence, which uses semiconductors to convert electricity into light. Compared to incandescent lighting, solid-state lighting creates visible light with reduced heat output and less power dissipation. The generally low mass of a solid-state electronic lighting device provides greater resistance to shock and vibration than brittle glass tubes / bulbs and long wires with thin filaments. They also eliminate filament evaporation, which can increase the lifespan of the lighting device. Some examples of these types of lighting include solid-state light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), or polymer light-emitting diodes (PLEDs) as lighting sources rather than electric filaments, plasma, or gas.

[0012] The homogeneity criterion is defined as the similarity between a pair of output colors. It may be defined, for example, in terms of RGB gamuts or in terms of distance in a color chart, but any definition by a skilled technician will be within the scope of this invention.

[0013] By means of this method, the lighting device is able to calculate whether the output color is sufficiently homogeneous and can react to an inadmissibility situation by modifying the supply current of at least one of the two modules, so that the color always remains within the limits of the homogeneity criterion.

[0014] In some types of applications, the second current value is calculated from a data sheet and / or experimental data using color and temperature as input values.

[0015] There are many other ways to obtain the output color of the light source. Sometimes manufacturers' data sheets provide reliable and useful information on these parameters, but experimental data can also be used to obtain this tolerance condition.

[0016] In this case, the second current is calculated from the data obtained from the first light module, so that the first light module is at the head of the process and the second light module has a slave configuration in terms of color homogeneity.

[0017] In some particular models, the first current value is calculated from theoretical or experimental data using color and temperature as input values.

[0018] In this case, the first current value can also be calculated, so that a previous decision has been made regarding the color to be projected, and the first and second light modules are adapted to this decision.

[0019] In some particular embodiments, the method further comprises the steps of selecting a first output color and measuring the temperature in the first light module, using the selected color and the measured temperature as input values ​​to calculate the first current value.

[0020] In this particular case, this decision is related to the color, and the first current value is decided based on this preliminary arrangement.

[0021] In some particular embodiments, the temperature in the light module is obtained by a thermistor, such as a negative temperature coefficient thermistor.

[0022] A thermistor is a common element that can be used to measure temperature, thus providing a reliable starting point for this method.

[0023] In certain particular embodiments, the method further comprises the step of increasing or decreasing the first and / or the second current value if the homogeneity criterion is not met.

[0024] The output color of the first and second lighting modules may vary depending on the temperature of the lighting module. For a given value of electrical current, the color may vary depending on the temperature of the module. A correction may therefore be necessary.

[0025] In certain particular cases, the method further comprises the following steps: • define a color tolerance condition, in which, for each temperature-electric current pair, a color is defined as acceptable or unacceptable; • establish a minimum threshold value for luminous flux and a maximum threshold value for luminous flux; • check whether the first and second output colors meet the authorization condition; • increase or decrease the first and / or second current value, in always maintaining the current such that it produces a luminous flux value between the minimum luminous flux threshold value and the maximum luminous flux threshold value and producing a color that satisfies the tolerance condition.

[0026] The homogeneity criterion can be combined, as in this case, with other eligibility criteria. The variation in the current value must be integrated into each requirement, in order to provide a unified and appropriate value of the electric current for each lighting module.

[0027] In some particular embodiments, the step of increasing or decreasing the current value consists of increasing or decreasing the current value from a first value to a second value, where the greater is less than 1.1 times the smaller of them, particularly less than 1.05 times the smaller of them and particularly less than 1.03 times the smaller of them.

[0028] In these examples, the intensity can be increased in small ranges, so that the current value (and temperature) is kept as low as possible within a range that provides acceptable performance. In addition, color deviations can be corrected with the minimum possible impact on performance.

[0029] In certain particular cases, the method further comprises the step of recording a sequence of current value increments for predetermined conditions.

[0030] This sequence can be useful if using a time-based scheme, to avoid continuous temperature measurement.

[0031] In some particular embodiments, at least some of the steps of the method are performed by a control unit that is configured to estimate a time pattern of the electrical current supplied to the first and second lighting modules by • Training the control unit to estimate an electric current for the first and / or second lighting module with a training data set • verification of the control unit with real electric current data.

[0032] The control unit may be subjected to an artificial intelligence strategy to predict the most appropriate evolution of the first and second currents. To do this, the control unit is trained with a set of training data that may include different inputs: current of other modules, external conditions, vehicle speed, driver decisions, etc. With these values, the control unit is trained to predict the best evolution of the first and second current values.

[0033] In another inventive aspect, the invention provides a data processing element comprising means for carrying out the steps of the method according to the first inventive aspect and a computer program comprising instructions which, when the program is executed by a control unit, cause the control unit to carry out the steps of a method according to the first inventive aspect.

[0034] In a second inventive aspect, the invention provides an automotive lighting device comprising: • at least two solid-state light modules, each comprising a matrix arrangement of solid-state light sources; • a control unit for carrying out the steps of the method according to the first inventive aspect;

[0035] This lighting device offers the advantageous functionality of efficiently managing the homogeneity of the colors of the light sources.

[0036] In certain particular cases, the matrix comprises at least 2000 solid-state light sources.

[0037] A matrix arrangement is a typical example of this method. The lines can be grouped into projected distance intervals and each column in each group represents an angle interval. This angle value depends on the resolution of the matrix, which is typically between 0.01° per column and 0.5° per column. Therefore, multiple light sources can be managed at the same time.

[0038] In certain particular cases, the lighting device further comprises a thermistor intended to measure the temperature of the solid-state light sources.

[0039] [Fig.l] shows a general perspective view of an automotive lighting device according to the invention;

[0040] [Fig.2] shows a first diagram in which a light pattern is described as being composed of the projection of two different light modules.

[0041] [Fig.3] shows a graphic diagram which represents the values ​​of the luminous flux produced by the LED when it is powered by a particular electric current and is under a given temperature.

[0042] [Fig.3] shows an example of the evolution of the electric current in the LED according to a method in accordance with the invention.

[0043] In these figures, the following reference numbers have been used:

[0044] 1 Lighting device

[0045] 2 Lighting module

[0046] 3 Control unit

[0047] 4 Minimum threshold value of luminous flux

[0048] 5 Thermistor

[0049] 6 points of inadmissibility

[0050] 7 Maximum luminous flux threshold value

[0051] 11 Total light

[0052] 12 Apartment

[0053] 13 Can

[0054] 14 Homogeneity criterion

[0055] 100 Motor vehicle

[0056] The exemplary embodiments are described in sufficient detail to enable those of ordinary skill in the art to realize and implement the systems and processes described herein. It is important to understand that these examples may be provided in many different forms and should not be construed as limited to the examples presented herein.

[0057] Accordingly, although the embodiment may be modified in various ways and take various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below by way of example. There is no intention to be limited to the particular forms disclosed. Rather, all modifications, equivalents, and alternatives falling within the scope of the appended claims are to be included.

[0058] [Fig.l] shows an overall view of an automotive lighting device according to the invention.

[0059] This lighting device 1 is installed in a motor vehicle 100 and comprises • a matrix arrangement of two light modules 2, intended to provide a light pattern; • a control unit 3 for carrying out a check of the operation of the lighting modules 2; and • a thermistor 5 intended to measure the temperature in the lighting modules 2.

[0060] This matrix configuration is a high-resolution module, having a resolution greater than 2000 pixels. However, no restrictions are attached to the technology used for the production of the projection modules.

[0061] A first example of this matrix configuration comprises a monolithic source. This monolithic source comprises an array of monolithic light-emitting elements arranged in several columns by several rows. In a monolithic array, the light-emitting elements may be grown from a common substrate and are electrically connected to be selectively activated either individually or by a subset of the light-emitting elements. The substrate may consist primarily of a semiconductor material. The substrate may comprise one or more other materials, for example, non-semiconductor materials (metals and insulators). Thus, each element or group of elements electroluminescent elements can form a luminous pixel and can therefore emit light when its material is supplied with electricity. The configuration of such a monolithic matrix allows the arrangement of selectively activatable pixels very close to each other, compared to conventional light-emitting diodes intended to be soldered on printed circuits. The monolithic matrix can comprise electroluminescent elements whose main height dimension, measured perpendicular to the common substrate, is substantially equal to one micrometer.

[0062] The monolithic matrix is ​​coupled to the control center in order to control the generation and / or projection of a pixelated light beam by the arrangement of the matrix. The control center is thus capable of individually controlling the light emission of each pixel of the matrix.

[0063] Alternatively to what has been presented above, the matrix arrangement may comprise a main light source coupled to a matrix of mirrors. Thus, the pixelated light source is formed by the assembly of at least one main light source formed of at least one light-emitting diode emitting light and a set of optoelectronic elements, for example a matrix of micro-mirrors, also known by the acronym DMD, for "Digital Micro-mirror Device", which directs the light rays from the main light source by reflection towards a projection optical element. If necessary, an auxiliary optical element may collect the rays from at least one light source to focus them and direct them towards the surface of the matrix of micro-mirrors.

[0064] Each micro-mirror can pivot between two fixed positions, a first position in which the light rays are reflected towards the optical projection element, and a second position in which the light rays are reflected in a different direction from the optical projection element. The two fixed positions are oriented in the same way for all the micro-mirrors and form, with respect to a reference plane supporting the micro-mirror matrix, a characteristic angle of the micro-mirror matrix defined in its specifications. Such an angle is generally less than 20° and may generally be approximately 12°. Thus, each micro-mirror reflecting a portion of the light beams which are incident on the micro-mirror matrix forms an elementary emitter of the pixelated light source.The actuation and control of the change of position of the mirrors to selectively activate this elementary transmitter in order to emit or not an elementary light beam are controlled by the control center.

[0065] In various embodiments, the array may comprise a laser scanning system in which a laser light source emits a laser beam towards a scanning element which is configured to scan the surface of a wavelength converter with the laser beam. An image of this surface is captured by the element projection optics.

[0066] The scanning of the scanning element can be carried out at a speed high enough that the human eye does not perceive any movement in the projected image.

[0067] The synchronized control of the ignition of the laser source and the scanning movement of the beam makes it possible to generate a matrix of elementary emitters which can be selectively activated on the surface of the wavelength converter element. The scanning means may be a movable micro-mirror making it possible to scan the surface of the wavelength converter element by reflection of the laser beam. The micromirrors mentioned as scanning means are for example of the MEMS type, for "Micro-Electro-Mechanical Systems". However, the invention is not limited to this type of scanning means and may use other types of scanning means, such as a series of mirrors arranged on a rotating element, the rotation of the element causing scanning of the transmission surface by the laser beam.

[0068] In another variant, the light source may be complex and comprise both at least one segment of light elements, such as light-emitting diodes, and a surface portion of a monolithic light source.

[0069] [Fig.2] shows a diagram in which a light pattern is described as being composed of the projection of two different light modules.

[0070] In this example, which corresponds to a dipped beam, the complete projection of the beam 11 can be divided into a first part 12 and a second part 13. In this particular case, the first part 12 is generally called "flat" and the second part 13 is generally called "elbow". A first light module is responsible for projecting the "flat" 12 and a second light module is responsible for projecting the "elbow" 13.

[0071] Since the two parts 12, 13 are intended to form a single pattern 11, it is important that the output colors of these light modules are as similar as possible.

[0072] A homogeneity criterion is defined by the manufacturer, in terms of, for example, a range within the RB G pattern or the distance in a color graphical representation, such as that of [Fig.3].

[0073] [Fig. 3] shows a color graphical representation, where the homogeneity criterion is that the output color pair be contained within the "white area" 14. This is an example criterion, although the skilled technician can establish any similar criterion.

[0074] [Fig.4] shows a graphical diagram that represents the values ​​of the luminous flux produced by the LED when it is powered by a particular electric current and is under a given temperature. In addition, some non-admissibility points 6 have been added to this graph. The points 6 represent combinations of current and temperature which give a color which is outside the homogeneity zone 14 of [Fig.3].

[0075] In this graph, a minimum luminous flux threshold value 4 and a maximum flux threshold value 7 are also represented.

[0076] In this particular embodiment of the method according to the invention, the operation of the light source is controlled under certain conditions.

[0077] The first is that the luminous flux must be maintained between the minimum threshold value of luminous flux 4 and the maximum threshold value of luminous flux 7.

[0078] The second is that the output color must meet the homogeneity criterion, i.e. it must not be found in the non-admissibility points 6 represented in the graph.

[0079] This performance is controlled by the amount of electrical current that is supplied to the LED. Varying the electrical current results in a variation in the luminous flux and a variation in the output color.

[0080] Small variations must therefore be used, in order to provide an accepted performance in terms of color and luminous flux.

[0081] Several options can be used to achieve this goal.

[0082] In a first option, the first module is powered by an electric current between thresholds 4, 7 of [Fig.4]. Then, the first output color is measured and, using theoretical and experimental data, a second current value is chosen to power the second module in order to obtain the same color as the first output color.

[0083] In a second option, a color is chosen from the graph of [Fig.3]. Using the theoretical and experimental data of each module, a first current value and a second current value are obtained to provide first and second output colors that are similar to the one chosen.

[0084] In a third option, the first and second modules are powered with the first and second current values ​​respectively. Then, the output colors are measured and one of the current values ​​is modified if necessary to bring one of the output colors closer to the other.

[0085] [Fig.5] shows an example of the temporal evolution of the electric current in one of the lighting modules of the lighting device according to the invention.

[0086] A first current value 41 is chosen between the threshold values ​​4, 7. Then, when the control unit decides that there is a reason to increase the electric current (to avoid the non-admissibility points 6 or for any other reason), the current value is increased. However, the current value can also be decreased from two values ​​42, 43 if the luminous flux is too high or if, for reasons of homogeneity, it is advisable to do so.

[0087] The control unit can be designed to decide which is the best option (unless one of the options is taken as intended by the car manufacturer) and how these current values ​​should be managed.

[0088] To do this, the control unit can be trained with artificial intelligence algorithms, using data provided by external sensors.

[0089] First, the control unit is trained. To do this, a map like the one in [Fig.4] is provided for each lighting module, so that the boundary conditions are clearly established.

[0090] Then, data is provided by external sensors, with module temperatures, module current values, external temperature, vehicle speed, driver settings, etc. The control unit uses this data to obtain the optimal first and second current values ​​at each time, and these results are tested with the values ​​provided by the manufacturer. When this training test process is completed, the control unit is ready to be installed in the automotive lighting device and to control the current values ​​of the two lighting modules.

Claims

Claims

1. A method of operating an automotive lighting device (1) comprising at least two semiconductor lighting modules (2), the method comprising the following steps: • defining a homogeneity criterion (14), wherein for each pair of colors, the pair is defined as acceptable or unacceptable; • supplying the first lighting module with a first current value which produces a first output color in the first lighting module;• supplying the second light module with a second current value which produces a second output color in the second light module, wherein the pair formed by the first output color and the second output color fulfills the homogeneity criterion characterized in that at least some of the method steps are performed by a control unit which is configured to estimate a temporal model for the electric current supplied to the first and second light modules by: - ​​training the control unit (3) to estimate an electric current for the first and / or the second light module with a training data set - verifying the control unit (3) with real electric current data.;

2. The method of claim 1, wherein the second current value is calculated from a data sheet and / or experimental data using color and temperature as input values.

3. A method according to any preceding claim, wherein the first current value is calculated from theoretical or experimental data using color and temperature as input values.

4. A method according to claim 3, comprising the steps of choosing a first output color and measuring the temperature in the first light module, using the chosen color and the measured temperature as input values ​​to calculate the first current value.

5. A method according to one of the preceding claims, wherein the temperature in the light module is obtained by a thermistor (5), such as a negative temperature coefficient thermistor.

6. A method according to one of the preceding claims, further comprising the step of increasing or decreasing the first and / or second current value if the homogeneity criterion is not met.

7. Method according to one of the preceding claims, further comprising the following steps: • defining a color tolerance condition (6), in which, for each temperature-electric current pair, a color is defined as acceptable or unacceptable; • establishing a minimum luminous flux threshold value (4) and a maximum luminous flux threshold value (7); • checking whether the first and second output colors meet the tolerance condition (6): • increasing or decreasing the first and / or the second current value, always maintaining the current such that it produces a luminous flux value between the minimum luminous flux threshold value (4) and the maximum flux threshold value (7) and producing a color that meets the tolerance condition (6).

8. A method according to one of claims 6 or 7, wherein the step of increasing or decreasing the current value involves increasing or decreasing the current value from a first value to a second value, wherein the larger is less than 1.1 times the smaller, particularly less than 1.05 times the smaller, and particularly less than 1.03 times the smaller.

9. A method according to one of the preceding claims, further comprising the step of recording a sequence of current value increments for predetermined conditions.

10. Data processing element comprising means for executing the steps of a method according to one of the preceding claims. previous.

11. A computer program comprising instructions which, when the program is executed by a control unit, cause the control unit to execute the steps of the method according to one of claims 1 to Q

12. y. Automotive lighting device (1) comprising: • at least two solid-state light modules (2), each comprising a matrix arrangement of solid-state light sources; • a control unit (3) for carrying out the steps of the method according to one of claims 1 to 9.

13. An automotive lighting device according to the preceding claim, further comprising a thermistor (5) for measuring the temperature of the semiconductor light sources.

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