Method for operating a lighting device of a motor vehicle and lighting device of a motor vehicle

Abstract

The present invention provides a method for operating a vehicle lighting device (1) having at least two solid-state light modules (2), comprising the steps of: determining a uniformity criterion for each color pair; powering a first light module with a first current value that produces a first output color in the first light module; and powering a second light module with a second current value that produces a second output color in the second light module, wherein the first and second output colors of the pair meet the uniformity criterion. The present invention also provides a vehicle lighting device (1) having a control element (3) for performing the steps of the method.

Description

Technical Field

[0001] The present invention relates to the field of lighting devices for motor vehicles, and more particularly to the management of the color of these light sources included in these devices.

Background Art

[0002] Digital lighting devices are increasingly being adopted by automobile manufacturers for mid- to high-end market products.

[0003] These digital lighting devices usually include solid-state light sources, but the operation of these light sources is greatly affected by temperature.

[0004] Temperature control in these elements is a very sensitive aspect and is usually accomplished by reducing the output. This means reducing the value of the current supplied to the light source so that the output light flux and the operating temperature decrease accordingly. This gives rise to the fact that the performance of the light source has to be higher than necessary so that the operating value can be reduced while still maintaining an acceptable value to address this overheating problem.

[0005] Furthermore, these technologies also affect the color of the output pattern. Sometimes, when the beam pattern is provided by two or more light modules, the color may not be uniform across the entire pattern.

[0006] This problem has been assumed so far, but a solution for it is being sought.

Summary of the Invention

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

[0008] Unless otherwise defined, all terms (including technical and scientific terms) used herein shall be construed as is customary in the art. Further, common grammatical terms shall also be construed as is customary in the relevant art and shall not be construed in an idealized or overly formal sense unless expressly so defined herein.

[0009] In this specification, the terms "comprises", "comprising", and the like shall not be construed in an exclusive sense. That is, these terms should not be construed so as to exclude the possibility that the things described or defined may include further elements, steps, etc.

[0010] In a first aspect of the invention, the invention is a method for operating an illumination device of a motor vehicle comprising at least two solid-state light modules, - a step of determining a uniformity criterion, in which for each pair of colors consisting of the color emitted by the first light module and the color emitted by the second light module, it is determined whether the pair is acceptable or unacceptable; - a step of supplying power to the first light module with a first current value that generates a first output color in the first light module; - a step of supplying power to the second light module with a second current value that generates a second output color in the second light module; and providing a method, wherein the pair of the first output color and the second output color satisfies the uniformity criterion.

[0011] The term "solid state" refers to light emitted by solid state electroluminescence using semiconductors to convert electrical power into light. Compared to incandescent lighting, solid state lighting reduces heat generation and creates visible light with less energy dissipation. The generally small profile of solid state electronic lighting devices provides greater resistance to shock and vibration compared to fragile glass tubes / spheres and long, thin filament wires. They also have the potential to extend the life of the lighting device by eliminating filament evaporation. Some examples of these types of lighting include semiconductor light emitting diodes (LEDs), organic light emitting diodes (OLEDs), or polymer light emitting diodes (PLEDs) as the light source, rather than an electric filament, plasma, or gas.

[0012] The uniformity criterion is defined as the similarity between a pair of output colors, i.e., the color emitted by the first light module and the color emitted by the second light module. It can be defined, for example, by an RGB range or by a chromaticity diagram, and any definition by those skilled in the art will be part of the scope of this invention.

[0013] As an example, each of the pairs of output colors is determined at a specific measurement time.

[0014] By this method, the lighting device can determine whether the output color is acceptably uniform and can respond to unacceptable situations by changing the supply current of at least one of the two modules. As a result, the color is always maintained within the range of the uniformity criterion.

[0015] In some specific embodiments, the method described above further comprises measuring the temperature within the second light module and using the first output color and the measured temperature within the second light module as input values to calculate a second current value from a data sheet and / or experimental data.

[0016] There are numerous alternative ways to obtain the output color of a light source. Sometimes, reliable and useful information about these parameters is provided by the manufacturer's data sheet, but experimental data may also be used to obtain this tolerance condition.

[0017] In this case, since the second current is calculated based on the data obtained from the first optical module, the first optical module dominates the method, and the second optical module has a subordinate configuration in terms of color uniformity.

[0018] In another example, a selected color and the measured temperature within the second optical module are used as input values, and a second value is calculated from the data sheet and / or experimental data.

[0019] In some specific embodiments, a selected color and the measured temperature within the first optical module are used as input values, and a first current value is calculated from theoretical data and / or experimental data.

[0020] In this case, the method comprises - selecting the color to be emitted by the first optical module, also known as the selected color, - measuring the temperature within the first optical module, and the selected color and the measured temperature within the first optical module are used as input values for calculating the first current value such that when the first optical module is powered with the first current value, the first output color is substantially the same as the selected color.

[0021] In this particular case, this decision is related to color, and the first current value is determined according to this preparation.

[0022] When both the first current value and the second value are calculated based on the selected color, a prior decision regarding the color projected by the lighting device is adopted, and both the first and second optical modules are adapted to this decision.

[0023] In this document, "selected color" means a reference color that conforms to colorimetric (color measurement) regulations and ultimately to the requirements of the lighting device manufacturer.

[0024] In some specific embodiments, the temperature in the first light module and / or the temperature in the second light module is obtained by a thermistor, for example, a negative characteristic (negative temperature coefficient) thermistor.

[0025] Since a thermistor is a common element that can be employed to measure temperature, this method provides a reliable starting point.

[0026] In some specific embodiments, the method further comprises the step of increasing or decreasing the first and / or second current values when the uniformity criterion is not met.

[0027] The output color in either the first or the second light module can also vary depending on the temperature of the light module. For a given current value, the color can change for different module temperatures. Therefore, correction may be required.

[0028] In some specific embodiments, the method - determining the color acceptance conditions for each of the first and second light modules, determining whether the color is acceptable or unacceptable for each pair of temperature and current; - setting the minimum light beam threshold value and the maximum light beam threshold value for each of the first and second light modules; - checking whether the first and second output colors meet their respective acceptance conditions in the first and second light modules; - increasing or decreasing the first and / or second current value to produce a color that meets the acceptance conditions while maintaining the current to produce a light beam value always included between the minimum light beam threshold value and the maximum light beam threshold value; further comprises.

[0029] The uniformity criterion may be combined with another tolerance criterion (as in this case). The change in the current value should be associated with every requirement so as to result in an appropriate current value unified for each optical module.

[0030] It should be noted that the color tolerance conditions for the first optical module and the second optical module may be the same. Furthermore, not only the maximum light beam threshold value but also the minimum threshold value for the first optical module and the second optical module may be the same.

[0031] Furthermore, the method may further comprise the step of determining a first output color and a second output color.

[0032] As an example, the first output color (i.e., the color emitted by the first optical module) and the second output color (i.e., the color emitted by the second optical module) are the same as the selected colors based on prior determination.

[0033] In another example, the selected color is assigned only to the first output color. In this case, the second output color is determined based on theoretical and / or experimental methods by using the first output color as an input value. Alternatively, both the first output color and the measured temperature within the second optical module can be used to determine the second output color.

[0034] In another embodiment, the first optical module and the second optical module are respectively powered by a first current value and a second current value. In this case, the first output color and the second output color are measured by appropriate means (e.g., a color sensor). Alternatively, the first output color is calculated from the first current value and the measured temperature within the first optical module. The second output color is calculated from the second current value and the measured temperature within the second optical module.

[0035] In some specific embodiments, the step of increasing or decreasing the first and / or second current values includes increasing or decreasing the first and / or second current values from a first value to a second value, and the largest of those values is less than 1.1 times the smallest, particularly less than 1.05 times the smallest of those values, and particularly less than 1.03 times the smallest of those values.

[0036] In these examples, the intensity can be increased within a narrow range. As a result, the current value (and temperature) is kept as low as possible within a range that provides acceptable performance. Further, color deviation can be corrected with the least possible impact on performance.

[0037] In some specific embodiments, the method further comprises the step of recording a series of current value increments for a predetermined condition.

[0038] This series can be useful for avoiding continuous temperature measurements when using a time series pattern.

[0039] In some specific embodiments, at least some steps of the method are performed by a control device, which is configured to - train the control device to estimate the current for the first and / or second optical module in a training data set, and - test the control device with real current data, so as to estimate the pattern over time of the current applied to the first and second optical modules.

[0040] The control device may be made to go through an artificial intelligence strategy in order to anticipate the optimal evolution of the first and second currents. To do so, the control device is trained with a training data set that may include various inputs: the currents of other modules, external conditions, vehicle speed, driver decisions... With these values, the control device is trained to anticipate the best evolution at the first and second current values.

[0041] In a further aspect of the invention, the invention provides a data processing element comprising means for performing each step of the method according to the first aspect of the invention, and a computer program comprising instructions which, when executed by a control device, cause the control device to perform each step of the method according to the first aspect of the invention.

[0042] In a second aspect of the invention, the invention provides - at least two solid-state light modules, each comprising a matrix arrangement of solid-state light sources; - a control element for performing each step of the method according to the first aspect of the invention; and provides a lighting device for a motor vehicle. This lighting device provides advantageous functionality for efficiently maintaining the color performance of the light sources.

[0043] In some specific embodiments, the matrix arrangement comprises at least 2000 solid-state light sources.

[0044] The matrix (array) arrangement is a typical example for this method. Each row may be grouped for each range of projection distances, and each column of each group may represent an angular interval. The value of this angle depends on the resolution of the matrix arrangement and is typically included between 0.01° per column and 0.5° per column. Thus, many light sources can be managed simultaneously.

[0045] In some specific embodiments, the lighting device further comprises a thermistor intended to measure the temperature of the solid-state light sources.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0047] In these figures, the following reference numerals are used.

Explanation of Reference Numerals

[0048] 1 Lighting device 2 Light module 3 Control element 4 Minimum luminous flux threshold 5 Thermistor 6 Non - allowable dot 7 Maximum luminous flux threshold 11 Overall light pattern 12 Flat 13 Kink 14 Uniformity criteria 100 Motor vehicle

Modes for Carrying Out the Invention

[0049] Exemplary embodiments are described in sufficient detail to enable those skilled in the art to embody and implement the systems and processes described herein. It is important to understand that each embodiment can be provided in many alternative forms and should not be construed as limited to the examples described herein.

[0050] Accordingly, the embodiments can be modified in various ways and can take various alternative forms, but specific embodiments among them are shown in the drawings by way of example and described in detail below. There is no intention to limit to the specific forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included.

[0051] FIG. 1 shows a schematic perspective view of a lighting device for a motor vehicle according to the present invention.

[0052] This lighting device 1 is installed in the motor vehicle 100 and - a matrix arrangement of two light modules 2 intended to provide a light pattern, and - a control element 3 for controlling the operation of the light module 2, and - a thermistor 5 intended to measure the temperature of the light module 2, are provided.

[0053] This matrix configuration is a high-resolution module having a resolution exceeding 2000 pixels. However, it is not considered that there are limitations in the technology used to manufacture the projection module.

[0054] The first example of this matrix configuration includes a monolithic light source. This monolithic light source includes a matrix of monolithic electroluminescent (field emission) elements arranged in a number of columns by a number of rows. In the monolithic matrix, each electroluminescent element can be grown from a common substrate and is electrically connected so as to be selectively operable either individually or in subsets (groups) of electroluminescent elements. The substrate may be made mainly of a semiconductor material. The substrate may also comprise one or more other materials, such as non-semiconductor materials (metals or insulators). Thus, each electroluminescent element or each group of electroluminescent elements can form a light pixel and can therefore emit light when power is supplied to the material of the element(s). Such a monolithic matrix configuration enables selectively lightable pixels to be arranged much closer to each other compared to a conventional group of light emitting diodes intended to be soldered onto a printed circuit board. The monolithic matrix may include electroluminescent elements having a main dimension of height measured perpendicular to the common substrate of approximately 1 micrometer.

[0055] The monolithic matrix is coupled to a control center so as to control the generation and / or projection of pixelated light beams in a matrix arrangement. Thus, the control center can individually control the light emission of each pixel in the matrix arrangement.

[0056] Instead of what was presented above, the matrix arrangement may comprise a main light source coupled to a matrix of mirrors. Thus, a pixelated light source is formed by an assembly of at least one main light source formed by at least one solid state light source that emits light, and an array of optoelectronic elements that direct the light rays from the main light source towards the projection optical element by reflection. The array of optoelectronic elements is a matrix of micromirrors also known by the acronym DMD of "Digital Micro-mirror Device", for example. Where appropriate, auxiliary optical elements can collect the light rays so as to concentrate the light rays of at least one light source and direct them towards the surface of the micromirror array.

[0057] Each micromirror can pivot between two defined positions, a first position where each light ray is reflected towards the projection optical element and a second position where each light ray is reflected in a direction different from the projection optical element. The two defined positions are oriented in the same way for all the micromirrors and form a specific angle defined by the specifications of the matrix of micromirrors with respect to a reference plane supporting the matrix of micromirrors. Such an angle is generally less than 20° and may typically be about 12°. Thus, each micromirror that reflects a part of the light beam incident on the matrix of micromirrors forms a basic emitter of the pixelated light source. The actuation and control of the position change of each mirror to selectively operate the basic emitter to emit or not emit the basic light beam is controlled by a control center.

[0058] In different embodiments, the matrix arrangement may comprise a scanning laser system in which a laser source (specifically, a laser diode) emits a laser beam towards a scanning element as follows. That is, a scanning element configured to scan the surface of a wavelength converter with the laser beam. An image of this surface is captured by the projection optical element.

[0059] The exploration of the scanning element can be achieved at a speed high enough that the human eye cannot perceive any displacement of the projected image.

[0060] By synchronously controlling the lighting of the laser light source and the scanning movement of the beam, it becomes possible to generate a matrix of basic light emitters that can be selectively lit on the surface of the wavelength conversion element. The scanning means may be a movable micromirror for scanning the surface of the wavelength conversion element by reflection of the laser beam. The micromirror cited as the scanning means is, for example, of the MEMS type representing "Micro-Electro-Mechanical Systems (microelectromechanical system)". However, the present invention is not limited to such scanning means, and other types of scanning means (for example, a series of mirrors arranged on a rotating element, where the rotation of the element causes scanning of the transmission surface by the laser beam, etc.) can be used.

[0061] In another modification, the light source may be complex and include both at least one segment of an optical element (such as a light-emitting diode) and a surface portion of the monolithic light source.

[0062] FIG. 2 is a schematic diagram depicted such that an optical pattern is formed by the projection between two different optical modules.

[0063] In this example (corresponding to the low-beam pattern), the complete pattern projection 11 can be divided into a first portion 12 and a second portion 13. In this particular pattern, the first portion 12 is usually called "flat", and the second portion 13 is usually called "kink". The first optical module is responsible for the projection of "flat" 12, and the second optical module is responsible for the projection of "kink" 13.

[0064] Since both portions 12, 13 are intended to form a certain specific pattern 11, it is important that the output colors of these optical modules are as similar as possible.

[0065] The uniformity criteria are determined by the manufacturer, for example, from the perspective of regions within the RBG pattern or the spread in a color graph representation (such as that in Figure 3).

[0066] Figure 3 shows one color graph representation, where the pairs of output colors being within the "white zone" 14 is the uniformity criterion. This is one example of a criterion, but those skilled in the art could establish any similar one.

[0067] Figure 4 is an illustration by a graph showing the flux values created by an LED when powered by a specific current and at a specific temperature. Further, several non - acceptable dots 6 are added to this graph. Each dot 6 indicates a combination of current and temperature that results in a color outside the uniformity zone 14 of Figure 3.

[0068] This graph also shows the minimum flux threshold 4 and the maximum flux threshold 7.

[0069] In this particular embodiment of the method according to the present invention, the operation of the light source is controlled under several premises.

[0070] The first premise is that the flux should be maintained between the minimum flux threshold 4 and the maximum flux threshold 7.

[0071] The second premise is that the output color should meet the acceptance conditions, that is, it should be kept outside each non - acceptable dot 6 shown in the graph.

[0072] This behavior is controlled by the amount of current applied to the LED. Changes in the current cause changes in the flux and changes in the output color.

[0073] Therefore, small changes should be used to bring about acceptable performance in terms of color and flux.

[0074] Several options can be used to achieve this goal.

[0075] In the first option, the first module is powered with a current included between the thresholds 4 and 7 in FIG. 4. Then, the first output color is measured, and a second current value is selected to power the second module so as to obtain a color similar to the first output color using theoretical or experimental data. In other words, the second current value is selected so that the first output color and the second output color satisfy the uniformity criterion.

[0076] In the second option, one color is selected from the graph in FIG. 3. Using the theoretical or experimental data of each module, a first current value and a second current value are obtained to provide first and second selected colors similar to the selected one and satisfy the uniformity criterion.

[0077] In the third option, the first and second modules are powered with the first and second current values respectively. Then, each output color is measured, and if necessary, one current value is changed so that one output color approaches the other output color to satisfy the uniformity criterion.

[0078] FIG. 5 shows an example of the temporal evolution of the current in one optical module of the lighting device according to the present invention.

[0079] The first current value 41 is selected between the thresholds 4 and 7. And when the control device determines that there is a reason to increase the current (to avoid the non - admissible dot 6 or for any other reason), the current value is increased. However, in the case where the flux is too high in terms of it being advisable to do so (for reasons of uniformity), the current value may be decreased from the two values 42, 43.

[0080] The control device may be designed to determine which is the best option (unless one of the options is accepted as defined by the vehicle manufacturer) and how these current values should be managed.

[0081] To do so, the control device may be trained in an artificial intelligence algorithm using data provided by external sensors.

[0082] In a first process, the control device is trained. To do so, a map such as that of FIG. 4 is provided to each optical module. As a result, the boundary conditions are clearly defined.

[0083] Then, data including module temperature, module current value, external temperature, vehicle speed, driver settings, etc. is provided from external sensors. The control device uses this data to obtain the optimal first and second current values at each instant. And these results are tested with the values given by the manufacturer. When this training - test process is completed, the control device is installed in the lighting device of the motor vehicle and is ready to control the current values of the two optical modules.

Claims

1. A method for operating a lighting device (1) of a motor vehicle, comprising at least two solid-state light modules (2), the method comprising: defining an allowable condition (6) for each output color of a first light module and a second light module, wherein the allowable condition (6) for the output color of the first light module and the second light module is the same, and the allowable condition (6) for the output color is defined such that the output colors emitted by the first light module and the second light module are the same as a selected color determined in advance; setting a minimum luminous flux threshold (4) and a maximum luminous flux threshold (7) for each of the first light module and the second light module; preparing a previously determined relationship shown for each combination of the temperature of the first and second light modules and the value of the current flowing through the first and second light modules, regarding whether the luminous flux values of the light emitted from the first and second light modules and the output colors of the first and second light modules satisfy the respective allowable conditions (6) of the first and second light modules; measuring the temperatures of the first and second light modules; selecting, based on the previously determined relationship, a value of the current flowing through the first and second light modules such that, at the measured temperatures of the first and second light modules, the output colors of the first and second light modules satisfy the allowable condition (6), and the luminous flux values of the light emitted from the first and second light modules are included between the minimum luminous flux threshold (4) and the maximum luminous flux threshold (7); passing the selected current value through the first and second light modules; A method comprising the above steps.

2. The method according to claim 1, wherein the temperature inside the first light module and / or the temperature inside the second light module is measured by a negative temperature coefficient thermistor.

3. The method according to claim 1 or 2, further comprising the step of increasing or decreasing the first and / or second current value when the measured temperatures of the first and second optical modules change, wherein the step of increasing or decreasing the first and / or second current value includes increasing or decreasing the first and / or second current value from a first value to a second value, and the maximum value is less than 1.1 times the minimum value, particularly less than 1.05 times the minimum value, and particularly less than 1.03 times the minimum value.

4. The method according to any one of claims 1 to 3, further comprising the step of recording a series of current value increments for a predetermined condition.

5. At least some steps of the method are performed by a control device, which is configured to - train the control device (3) to estimate the current for the first and / or second optical module in a training data set, and - test the control device (3) with real current data, so as to estimate the temporal pattern of the current applied to the first and second optical modules. The method according to any one of claims 1 to 4.

6. A data processing element comprising means for performing each step of the method according to any one of claims 1 to 5.

7. A computer program comprising instructions for causing the control device to perform each step of the method according to any one of claims 1 to 5 when executed by the control device.

8. - at least two solid-state light modules (2), each having a matrix arrangement of solid-state light sources; and - a control element (3) for performing each step of the method according to any one of claims 1 to 5, A lighting device (1) for a motor vehicle.

9. The lighting device for a motor vehicle according to claim 8, further comprising a thermistor (5) intended to measure the temperature of the solid-state light source.

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