The present invention relates to a device for projecting a light beam and having a mechanical actuator, notably for a motor vehicle, an optical module and a light beam projector of the low beam headlamp or high beam headlamp type, provided with such a projection device.
Motor vehicle headlamps are provided with one or more optical modules arranged in a housing closed by an outer lens in such a way as to obtain one or more light beams at the output of the headlamp. In a simplified way, an optical module of the housing notably comprises a light source, for example one or more light emitting diodes, which emit light rays, and an optical system comprising one or more lenses and, if necessary, an optical element, for example a reflector, for orientating the light beams coming from the light sources in order to form the output light beam of the optical module.
Arrays of light emitting diodes are often used, such a matrices for example, in order to obtain such a beam. Each light emitting diode provides a component of the light beam which emerges from the optical module. Thus, a large number of diodes makes it possible not only to increase the brightness but also to improve the resolution of the lighting obtained. In fact, the beam then comprises more components for a same light beam.
The matrices also make it possible to activate each light emitting diode individually. The individual activation of certain diodes gives the possibility of modulating the shape of the beam, or even to modify its lateral extent when there is potentially a wider beam than the one in use and for which it is only necessary to select a portion of the diodes.
For example, certain technologies make it possible to detect upcoming or followed vehicles upstream of the direction of displacement and to project a light beam with a shadow zone. In other words, the projected beam has light gaps in the direction of the detected vehicle in order to avoid dazzling the driver of the oncoming or followed vehicle, whilst retaining wide illumination on either side of that vehicle. During the use of this function, the light gap or gaps follow the displacement of the detected vehicle; they therefore move within the projected beam. This function requires a high resolution of the beam, notably in order to define the mobile shadow zone with great precision.
Moreover, it is desired to avoid the use of too great a number of light sources simultaneously because this gives rise to high energy consumption and a risk of overheating the optical module.
The purpose of the invention is therefore to obtain a projection device configured for projecting a light beam, which is capable of carrying out functions such as the abovementioned function with high resolution and retaining a small number of diodes.
For this purpose, the invention relates to a device for projecting a light beam and having a mechanical actuator, notably for a motor vehicle, comprising an array of light sources able to emit light rays in order to form the light beam along an optical axis, each light source defining a component of the light beam which has an initial of resolution in a plane.
The device is noteworthy in that it furthermore comprises a mechanical actuator configured for displacing at least one element of the device in such a way that the optical axis of the light beam is moved between at least two projection directions according to a displacement oscillating periodically at a specified frequency of displacement, the projection directions forming between them an angle of displacement substantially coplanar with the angle of resolution, the angle of displacement being equal to a fraction of the initial angle of resolution of the beam.
Thus, by imparting a periodic oscillating displacement of the optical axis of the beam between at least two directions defining an angle of displacement which is a fraction of the initial angle of resolution of the beam, a better final resolution of the light beam is obtained. From then on, for an observer of the light beam, whilst the cut-off edges of the beam are clear, each component will appear as being fractionated.
Consequently, the device makes it possible to increase the resolution of the beam without having to add additional light sources. In particular, the energy consumption and the risks of overheating due to a large concentration of sources are minimized. Moreover, it makes it possible to make use of standard electronic components rather than components that are more complex to produce.
According to different embodiments of the invention, which can be taken together or separately:
The invention also relates to an optical module comprising such a device for projecting a light beam and having a mechanical actuator.
The invention also relates to a motor vehicle headlamp provided with such an optical module.
The invention will be better understood in the light of the following description which is given only by way of indication, which is not intended to limit it and is given with reference to the appended drawings:
In
The light beam emitted by the device emerges through the projection lens 3 along an optical axis 4. The light beam 13, shown diagrammatically in the
In order to increase the optical resolution of the beam 13, and therefore to reduce the angle of resolution, the device 1 is configured for periodically shifting the optical axis of the light beam 13 between two directions of projection.
For this purpose, in the first embodiment shown in
The source assembly 2 is driven with a displacement in a plane substantially parallel with the projection lens 3. The source assembly 2 moves between two extreme positions, the first position corresponding to a first direction of projection of the optical axis of the beam and the second position corresponding to a second direction of projection of the optical axis.
For a beam provided with vertical components 10, such as the one shown in
The two extreme positions are chosen such that the angle of displacement of the optical axis of the beam 13 is equal to a fraction of the angle of resolution of the beam 13. In order to reduce the angle of resolution, for example by half, the angle of displacement between the two positions is preferably substantially equal to half of the angle of resolution, that is to say 0.5° in this case. In
The source assembly 2, and therefore the axis of the beam 13, is moreover moved between the two positions by the actuator 5, at a specified displacement frequency which is not perceptible by the human eye. Such a frequency must be higher than 40 Hz, and is preferably between 100 Hz and 200 Hz.
Thus, an observer looking at the projected beam 13 is not able to discern the two directions of the beam 13. In other words, the observer sees a superimposition of the two directions of the same beam 13, that is to say of the beam 13 shown in
The mechanical actuator 5 is moreover configured for displacing the source assembly 2, and therefore the optical axis of the light beam 13, in a discontinuous manner, such that the optical axis of the light beam 13 is held in each of the two directions for a holding time which is longer than the transition time between the two directions of projection. In other words, the displacement does not follow a movement at constant speed.
In fact, a superimposition of the two orientations of the beam is desired whilst minimizing the superimposition of other directions of the beam which correspond to intermediate positions. As shown in
In a variant embodiment,
As shown in
When the same light source is left inactive whilst the beam changes direction periodically according to the invention, the angle of resolution of the shadow zone is reduced to 0.5°. However, in this case, the shadow zones 21 can only appear on certain components with an angle of resolution of 0.5°, an additional component always being switched on. More precisely, only one out of two components of the beam with an angle of resolution of 0.5° can appear switched off.
According to a first variant embodiment, in order to make shadow zones appear on the other components with an angle of resolution of 0.5°, the light sources are activated at an activation frequency which is synchronized with the frequency of displacement of the mechanical actuator 5. This synchronization is shown in
According to another variant embodiment, which is not shown in the figures, the mechanical actuator 5 is configured for periodically displacing the source assembly 2 between an intermediate position and another position to be chosen from two opposite extreme positions with respect to the intermediate position. The periodic displacement between the intermediate position and the first extreme position makes it possible to cause the appearance of a shadow zone having an angle of resolution of 0.5° on the beam with one inactive light source. The periodic displacement between the intermediate position and the second extreme position makes it possible to cause the appearance of an additional shadow zone having an angle of resolution of 0.5° on the beam with the same inactive light source. Consequently, the axis of the beam is periodically oriented between an intermediate direction and a second direction chosen from two extreme directions corresponding to the displacement of the source element 2.
Thus, depending on the component to be switched off, the mechanical actuator moves the source assembly either between the intermediate position and the first extreme position or between the intermediate position and the second extreme position. Each displacement produces an effect similar to the one shown in
The following embodiments have the same effects and advantages on the light beam as the first embodiment.
In a third embodiment, shown in
According to a fourth embodiment, shown in
In a fifth embodiment, shown in
The description describes examples of the invention having an angle of resolution divided by two. However, the device could be adapted in such a way as to further divide the angle of resolution of the beam. Thus, by choosing to periodically orient the beam in three directions instead of two, it is possible to divide the angle of resolution by three and achieve an angle substantially equal to 0.33° for the abovementioned examples. For this purpose, the actuator 5 is configured for periodically displacing at least one of the elements of the device 1 over three positions. The frequency of the displacement of the beam is therefore chosen such that the displacement is not perceptible by an observer. In the example having three directions, the frequency is at least 60 Hz.
Number | Date | Country | Kind |
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17 52808 | Mar 2017 | FR | national |
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Number | Date | Country |
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2 666 671 | Nov 2013 | EP |
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Entry |
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French Preliminary Search Report dated Nov. 24, 2017 in French Application 17 52808, filed on Mar. 31, 2017 (with English Translation of Categories of cited documents). |
Number | Date | Country | |
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20180283641 A1 | Oct 2018 | US |