METHOD FOR CORRECTING A LIGHT PATTERN, AUTOMOTIVE LIGHTING DEVICE AND AUTOMOTIVE LIGHTING ASSEMBLY

Abstract

The invention provides a method for correcting a first light pattern provided by a lighting device (1) with a matrix of light sources (2). This method comprising the steps of obtaining a map of the light pattern divided in pixels (4), associating a calibration power value to each pixel (4), depending on the light intensity of each pixel and assigning a new power value to each pixel. Finally, a corrected light pattern is projected with the new power values. The invention also provides an automotive lighting device with a calibrator to perform the steps of this method and an automotive lighting assembly with an external calibrator to perform the steps of this method.

Claims

1. Method for correcting a light pattern provided by a lighting device with a matrix of light sources, the method comprising the steps of a) obtaining a map of the light pattern divided in pixels; b) associating a calibration power value to each pixel, depending on the light intensity of each pixel; c) assigning a new power value to each pixel; d) projecting a corrected light pattern with the new power values.

2. Method according to claim 1, wherein the step a) comprises the sub-steps of projecting all the light sources at the same time, thus generating the first light pattern; capturing and dividing the first light pattern in pixels.

3. Method according to claim 1, wherein the step a) comprises the sub-steps of projecting one light source at a time, generating individual projections; generating a first light pattern gathering all the individual projections, wherein each pixel corresponds to an individual projection.

4. Method according to claim 1, wherein, in the step c), each new power value is inversely proportional to each calibration power value with respect to a reference power value.

5. Method according to claim 1, wherein the step c) comprises the sub-steps of assigning a new power value to each pixel; project a test light pattern and check the uniformity of the test light pattern; and correct the power values assigned to each pixel.

6. Method according to claim 1, wherein the power values are pulse width modulation values.

7. Method according to claim 1, further comprising the step of e) recording a calibration map with the new power values.

8. Automotive lighting device comprising a matrix arrangement of solid-state light sources, intended to provide a light pattern; a calibrator for performing the steps of the method according to claim 1.

9. Automotive lighting device according to claim 1, wherein the matrix arrangement comprises at least 2000 solid-state light sources.

10. Automotive lighting assembly comprising an automotive lighting device; an external calibrator for performing the steps of the method according to claim 1.

11. Method according to claim 2, wherein the step c) comprises the sub-steps of assigning a new power value to each pixel; project a test light pattern and check the uniformity of the test light pattern; and correct the power values assigned to each pixel.

12. Method according to claim 2, wherein the power values are pulse width modulation values.

13. Method according to claim 2, further comprising the step of e) recording a calibration map with the new power values.

14. Automotive lighting device comprising a matrix arrangement of solid-state light sources, intended to provide a light pattern; a calibrator for performing the steps of the method according to claim 2.

15. Automotive lighting assembly comprising an automotive lighting device; an external calibrator for performing the steps of the method according to claim 2.

16. Method according to claim 3, wherein the step c) comprises the sub-steps of assigning a new power value to each pixel; project a test light pattern and check the uniformity of the test light pattern; and correct the power values assigned to each pixel.

17. Method according to claim 3, wherein the power values are pulse width modulation values.

18. Method according to claim 3, further comprising the step of e) recording a calibration map with the new power values.

19. Automotive lighting device comprising a matrix arrangement of solid-state light sources, intended to provide a light pattern; a calibrator for performing the steps of the method according to claim 3.

20. Automotive lighting assembly comprising an automotive lighting device; an external calibrator for performing the steps of the method according to claim 3.

Description

BRIEF LIST OF DRAWINGS AND REFERENCE NUMBERS

[0044] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

[0045] FIG. 1 shows a general perspective view of an automotive lighting device according to the invention.

[0046] FIGS. 2a to 2d represent steps of a method according to the invention.

[0047] FIG. 3 shows an automotive lighting assembly according to the invention. In these figures, the following reference numbers have been used: [0048] 1 Lighting device [0049] 2 LED [0050] 3 Calibrator [0051] 4 Pixel [0052] 5 Reference value (intensity) [0053] 7 Original light pattern [0054] 8 Corrected light pattern [0055] 30 External calibrator [0056] 50 Reference value (PWM) [0057] 100 Automotive vehicle

DETAILED DESCRIPTION OF THE INVENTION

[0058] The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

[0059] Accordingly, while embodiment can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included.

[0060] FIG. 1 shows a general perspective view of an automotive lighting device according to the invention.

[0061] This lighting device 1 is installed in an automotive vehicle 100 and comprises [0062] a matrix arrangement of LEDs 2, intended to provide a light pattern; [0063] a calibrator 3 to carry out an in-situ calibration of the uniformity of the light pattern provided by the matrix arrangement of LEDs 2.

[0064] This matrix configuration is a high-resolution module, having a resolution greater than 2000 pixels. However, no restriction is attached to the technology used for producing the projection modules.

[0065] A first example of this matrix configuration comprises a monolithic source. This monolithic source comprises a matrix of monolithic electroluminescent elements arranged in several columns by several rows. In a monolithic matrix, the electroluminescent elements can be grown from a common substrate and are electrically connected to be selectively activatable either individually or by a subset of electroluminescent elements. The substrate may be predominantly made of a semiconductor material. The substrate may comprise one or more other materials, for example non-semiconductors (metals and insulators). Thus, each electroluminescent element/group can form a light pixel and can therefore emit light when its/their 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 to printed circuit boards. The monolithic matrix may comprise electroluminescent elements whose main dimension of height, measured perpendicularly to the common substrate, is substantially equal to one micrometre.

[0066] The monolithic matrix is coupled to the control centre so as to control the generation and/or the projection of a pixilated light beam by the matrix arrangement. The control centre is thus able to individually control the light emission of each pixel of the matrix arrangement.

[0067] 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 an array 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 to a projection optical element. Where appropriate, an auxiliary optical element can collect the rays of at least one light source to focus and direct them to the surface of the micro-mirror array.

[0068] Each micro-mirror can pivot between two fixed positions, a first position in which the light rays are reflected towards the projection optical element, and a second position in which the light rays are reflected in a different direction from the projection optical element. The two fixed positions are oriented in the same manner for all the micro-mirrors and form, with respect to a reference plane supporting the matrix of micro-mirrors, a characteristic angle of the matrix of micro-mirrors defined in its specifications. Such an angle is generally less than 20° and may be usually about 12°. Thus, each micro-mirror reflecting a part of the light beams which are incident on the matrix of micro-mirrors forms an elementary emitter of the pixelated light source. The actuation and control of the change of position of the mirrors for selectively activating this elementary emitter to emit or not an elementary light beam is controlled by the control centre.

[0069] In different embodiments, the matrix arrangement may comprise a scanning laser system wherein a laser light source emits a laser beam towards a scanning element which is configured to explore the surface of a wavelength converter with the laser beam. An image of this surface is captured by the projection optical element.

[0070] The exploration of the scanning element may be performed at a speed sufficiently high so that the human eye does not perceive any displacement in the projected image.

[0071] 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 that can be activated selectively at the surface of the wavelength converter element. The scanning means may be a mobile micro-mirror for scanning the surface of the wavelength converter element by reflection of the laser beam. The micro-mirrors mentioned as scanning means are for example MEMS type, for “Micro-Electro-Mechanical Systems”. However, the invention is not limited to such a scanning means and can use other kinds of scanning means, such as a series of mirrors arranged on a rotating element, the rotation of the element causing a scanning of the transmission surface by the laser beam.

[0072] In another variant, the light source may be complex and include both at least one segment of light elements, such as light emitting diodes, and a surface portion of a monolithic light source.

[0073] FIGS. 2a to 2d represent steps of a method according to the invention.

[0074] FIG. 2a shows a first step. In this step, all the light sources are projected at the same time, thus generating the first light pattern. This first light pattern is captured and divided into pixels 4. This first light pattern is the light pattern before calibration, so it may contain some non-uniformities which may provide visual discomfort or even errors in the perception of objects which are lighted.

[0075] In some alternatives of the method, this first light pattern may be calculated by the juxtaposition of the individual projections of each light source. Each pixel would correspond to the light projected by a single light source. This is a different way of obtaining this first map, and the convenience of one way or the other will depend on the car manufacturer.

[0076] FIG. 2b shows some example of this non-unformity. In this graphic, the light intensity of a row of pixels is analysed as a function of the pixel's position, represented by the angle associated to each pixel. In this figure, it is shown that not all the pixels have the same light intensity. A reference value 5 is also shown in this figure. This reference value 5 will be used in further steps to correct this non-uniform light pattern.

[0077] Depending on the light intensity which has been captured in each pixel a calibration power value is associated to each pixel. This calibration power value will be directly proportional to the light intensity which has been sensed in the previous step. As a consequence, each pixel will have a calibration power value.

[0078] FIG. 2c shows a graphic which shows the new power values which are assigned to each pixel. These new power values, which are expressed as % PWM, try to compensate the non-uniformities, and are compared with a reference value 50, which represents the % PWM necessary to obtain the reference value of the light intensity (FIG. 2b). If one pixel had a calibration power value which is lower than the reference value, the new power value will be higher than the reference power value to compensate for other phenomena, which are causing a poorer light intensity.

[0079] FIG. 2d shows a similar graphic as the one of FIG. 2b, but in this case, the light intensity of a row of pixels with the corrected light pattern is additionally shown, once that each pixel has been projected with the new power value. As may be seen, the corrected light pattern 8 is far more uniform than the original light pattern 7. If this light pattern is uniform enough, the calibration map with the new power values is recorded and the corrected light pattern is used to be projected.

[0080] In the event the corrected light pattern is not uniform enough, the step of assigning a new power value to each pixel may be iterated with the checking of a test light pattern using these new power values. This iteration would contain the following sub-steps: [0081] assigning a new power value to each pixel; [0082] project a test light pattern and check the uniformity of the test light pattern; and [0083] correct the power values assigned to each pixel.

[0084] In these particular examples, the power values are pulse width modulation values. The light driver in charge of controlling each light source will vary the pulse width modulation value so that each pixel is fed with the suitable value defined by the aforementioned calibration method.

[0085] FIG. 3 shows an automotive lighting assembly according to the invention. In this case, the automotive lighting device is a standard automotive lighting device and there is an external calibrator 30 which is suitable for performing the steps of the method described above. This makes it possible to use this invention also in standard lighting devices which does not comprise an embedded calibrator.