Motor vehicle projecting lighting device

Abstract

The invention relates to a lighting device (1) comprising: • three light-emitting means (2, 3, 4), each emitting a collimated light beam of various colours, among which a red light-emitting means (4) emits the red colour, • a beam-mixing means (5) combining the three collimated light beams into a combined light beam directed towards a pivoting mirror device (6), • the pivoting mirror device (6) forming, by reflecting said combined light beam, a beam projected onto a projection area (7), • each light-emitting means (2, 3, 4) comprising at least one laser-emitting source (21, 31, 41). The red light-emitting means (4) comprises a blue or green laser-emitting source (41) and a wavelength conversion material (42) capable of converting the blue or green colour into a red colour.

Description

Automotive Projection Light Device

[0001] The present invention relates to the field of optics and finds particular application in the automotive industry. More specifically, it relates to lighting devices integrated into vehicles for the performance of signaling and / or decorative lighting functions.

[0002] These lighting devices, used both inside and outside vehicles, project light onto various surfaces to form patterns, warnings, or logos. On the exterior, they can serve as safety signals, for example, by projecting open door warnings or parking guidelines onto the ground. Inside, these lighting devices can be implemented to enhance the vehicle's aesthetics and generate purely decorative patterns, but they can also contribute to safety by projecting pictograms representing a risky driving situation into the driver's field of vision, for example.

[0003] Lighting devices for projecting pictograms, signage patterns, or decorative motifs onto a given projection surface can, for example, be based on the use of an RGB (Red, Green, Blue) light emission system composed of three laser light sources. A light beam corresponding to one of these colors can then be combined with the other light beams to create a wide range of colors. These devices also include one or more mirrors onto which the beam corresponding to the combination of laser beams is directed. These mirrors are configured to direct the light beam toward the targeted projection surface and are driven to allow scanning of the targeted projection surface at a sufficiently high scanning speed to give the user the impression that the projected image is stationary.

[0004] Three distinct laser light sources are used: a blue laser, a green laser, and a red laser. Each laser is typically a native laser, meaning it emits light directly from the source in its associated color, without color conversion.

[0005] The use of native red lasers, however, raises several technical issues. These lasers exhibit significant variability in their peak wavelength depending on the temperature, and their efficiency is drastically reduced at high temperatures. The temperature of these native red lasers must therefore not exceed 50°C. These problems are particularly critical in automotive applications, where temperature conditions can vary considerably, especially for lighting devices located behind glass exposed to sunlight. To overcome this limitation, red lasers in vehicles require either a large heat sink or an active cooling system, such as a heat pipe or a Peltier module, to maintain an optimal operating temperature and ensure consistent performance.

[0006] The objective of the invention described in this document is therefore to overcome the disadvantages of the prior art by providing a high-performance lighting device that operates even at high temperatures, thanks to a red light emission method that does not require a large cooling device. According to the invention, the red light emission method uses a laser emission source (blue or green) coupled to a material capable of converting the wavelength, thus making it possible to efficiently generate red light even under high temperatures.

[0007] The present invention thus has as its main object a lighting device comprising: three light emission means respectively configured to emit three different colors and respectively configured to form a collimated light beam of the corresponding color, in which among the three light emission means, a red light emission means is configured to emit the color red, a beam mixing means configured to combine the three collimated light beams into an overall light beam and direct this overall light beam towards a pivoting mirror device, the pivoting mirror device being driven to form, by reflection of said overall light beam, a beam projected onto a predetermined projection area, each light emission means comprising at least one laser emission source.

[0008] According to the invention, the means for emitting red light comprises a blue or green colored laser emission source and a wavelength conversion material capable of converting said blue or green color into a red color.

[0009] According to one embodiment of the invention, the three light-emitting means are configured to emit blue, red, and green light, respectively. Specifically, the blue light-emitting means comprises a blue laser emission source, while the green light-emitting means comprises a green laser emission source. These laser emission sources may, in particular, be native blue and green lasers; that is, as mentioned previously, sources that emit lasers directly in the color associated with that source, without subsequent color conversion. It should be noted that all types of lasers capable of generating a blue or green laser can be used for these laser emission sources, including laser diodes, crystal lasers, fiber lasers, dye lasers, gas lasers, and free-electron lasers.

[0010] Blue laser diodes typically operate using a semiconductor material, such as gallium nitride (GaN), which produces light with a wavelength of approximately 450 nanometers, thus creating blue light. This light is then amplified by resonance in an optical cavity, forming a blue laser.

[0011] Regarding the source of green laser emission, the most commonly used green laser is the Nd:YAG laser (neodymium aluminum garnet-doped). This laser initially emits infrared light at a wavelength of 1064 nanometers. Subsequently, this infrared light is converted into green light at 532 nanometers through a frequency-doubling process. As with other types of lasers, the light produced is then amplified by resonance within an optical cavity. This amplification results in the formation of a green laser.

[0012] The red light emission method uses a blue or green laser emission source, which may be similar to the laser emission sources used for blue and green light emission methods. This laser emission source is a native blue or green laser and is directed at a wavelength conversion material designed to transform the blue or green light into red light.

[0013] By using a blue or green laser emission source, combined with a wavelength conversion method, a red light emission method can be developed, overcoming the problems associated with native red lasers, such as performance variability with temperature. Indeed, native blue or green lasers do not exhibit the temperature sensitivity of native red lasers. This characteristic allows the use of red light emission in vehicles in any geographical area, under any weather conditions, and particularly in applications where the location of the emission source makes it highly sensitive to climatic conditions, for example, behind the windshield when the light source is used for interior lighting.

[0014] The conversion material, typically a phosphorescent material, is chosen for its efficiency in converting shorter wavelengths (blue or green light) into red light. When this conversion material is exposed to blue or green light, it absorbs the light energy, increasing its energy level relative to its ground state. Upon returning to its ground state, the material emits light with a wavelength between 620 and 700 nm, that is, red light.

[0015] Other examples of colors can be implemented without departing from the scope of the invention, provided that one of the light-emitting means is a red light-emitting means conforming to some aspect of the invention. For example, the lighting device may include light-emitting means configured to emit a cyan or turquoise color.

[0016] The light beams emitted respectively by each of the three means of light emission are collimated beams and directed towards the mixing means.

[0017] In the example embodiment using blue, red, and green light emission means respectively, the beam-mixing means functions to merge the collimated blue, red, and green light beams into a single overall light beam. This mixing means then directs this overall light beam toward a pivoting mirror device. It is understood that, depending on whether each of the light emission means is switched on or off at a given moment, the overall light beam arriving at the pivoting mirror device has a specific color at that moment. This overall light beam is then precisely directed onto the area to be illuminated by controlling the orientation of the pivoting mirror device.

[0018] The pivoting mirror device is equipped with one or more pivoting mirrors, generally controlled by an electronic or mechanical system. The pivoting mirror device can operate in different ways depending on the number of pivoting mirrors it contains.

[0019] In cases where multiple pivoting mirrors are present, each mirror can be activated or deactivated by an on / off switching mechanism. In "on" mode, they reflect the overall light beam towards the projection area, while in "off" mode, they reflect the light in a specific direction, absorbing it. This method allows for the creation of a pixelated image by adjusting the configuration of the mirrors in "on" and "off" modes.

[0020] If the pivoting mirror device uses a single pivoting mirror, it can be designed to pivot rapidly around two perpendicular axes. This rapid pivoting allows the entire projection area to be scanned with the overall light beam, thus creating an image that appears stationary to the observer due to the effect of retinal persistence.

[0021] The projection area is usually a flat surface, such as a floor or ceiling, where the overall light beam can be projected accurately.

[0022] According to an optional feature, the pivoting mirror device is driven to form, by reflection of said global light beam, a beam projected by scanning onto a predetermined projection area.

[0023] According to an optional feature, the wavelength conversion material of the red light-emitting means is disposed at the focus of a collimating means, so that the light beam is collimated at the output of the collimating means, the collimated beam then being directed to the beam-mixing means

[0024] It is important to understand that, since the wavelength conversion material is located at the focus of the collimating means, the rays encountering the collimating means after passing through the focus of this collimating means emerge parallel to each other and to an optical axis of the collimating means.

[0025] The focus of the collimation method can just as easily be a focal point, a focal line, or a focal plane.

[0026] According to an optional feature, the collimation means is a parabolic reflector.

[0027] According to an optional feature, the collimation means includes a positioning means configured to maintain the wavelength conversion material at a predetermined distance from the collimation means corresponding to the focal length of said collimation means. In other words, thanks to the positioning means, the wavelength conversion material is precisely positioned at the focus of the collimation means, thereby optimizing the convergence of the converted beam to the mixing means and then to the pivoting mirror device. This configuration allows for higher light output by maximizing the capture of the diffuse red radiation emitted by the conversion material.Indeed, precise positioning at the focus ensures that almost all of the emitted radiation is collected and collimated efficiently, resulting in increased light intensity of the collimated red beam and better chromatic uniformity of the projected image.

[0028] A key advantage is that the positioning means is formed as a single unit with the collimation means. In other words, the positioning means is an integral part of the collimation means. This monolithic structure offers several technical advantages. First, it ensures superior mechanical stability against the vibrations and shocks typical of the automotive environment, thus preventing any optical misalignment that could degrade the device's performance. Second, it guarantees optimal thermal stability by eliminating the problems of differential expansion between separate components, thereby maintaining consistent performance across the vehicle's entire operating temperature range.Finally, this structural integration allows for a significant reduction in the overall size of the red light emission device, facilitating its integration into the limited spaces of modern vehicles, while simplifying the assembly process and reducing manufacturing costs.

[0029] According to an optional feature, the wavelength conversion material of the red light emitting means is a layer of wavelength conversion material disposed on the reflective face of a mirror disposed between the laser emission source and the collimation means, the laser output from the laser emission source being directed towards the wavelength conversion material.

[0030] The laser beam from the laser source first passes through a wavelength-converting material layer applied to the reflective surface of the mirror. This interaction results in the formation of diffuse red radiation that disperses in all directions and has a modified wavelength. Following this interaction, some of the diffuse red radiation is directed towards the collimating device, while another portion reaches the reflective surface of the mirror. This remaining portion is then reflected back towards the collimating device. The presence of the mirror thus increases the efficiency of the red light emission device by maximizing the amount of diffuse red radiation directed towards the collimating device.

[0031] When the wavelength conversion material is placed on the mirror, it is the face of the wave conversion material in contact with the reflective face of the mirror that can be placed at the focus of the collimation means.

[0032] According to an optional feature, the mirror of the red light-emitting means is configured to direct a portion of diffuse red radiation generated by the conversion material towards the collimating means, said collimating means being capable of collimating the portion of diffuse red radiation into a collimated beam directed towards the mixing means.

[0033] This portion of the diffuse red radiation is reflected by the mirror of the red light-emitting device and then collimated by the collimation device. The role of the collimation device is therefore to collimate and direct the portion of the diffuse red radiation reflected by the mirror towards the beam-mixing device. It also ensures that the portion of the diffuse red radiation arriving directly at it is collimated and redirected towards this same mixing device.

[0034] Depending on an optional feature, the thickness of the wavelength conversion material layer is between 0.1 mm and 3 mm.

[0035] The thickness values ​​chosen for the conversion material optimize the conversion of the blue laser to diffuse red radiation. A layer of this material that is too thin would not allow for complete conversion of the blue laser, resulting in an imperfect collimated red beam contaminated by residual blue light. This undesirable mixture of blue light would then compromise the purity of the red color in the collimated beam. Conversely, a wavelength conversion material layer that is too thick would lead to unnecessary waste of this material. Furthermore, an excessive layer could absorb some of the converted diffuse red radiation, thus reducing the efficiency of the red light emission method.

[0036] To measure the thickness of the wavelength conversion material layer, a cross-section must be made through it. A "cross-section" is defined as a cut made perpendicular to the plane formed by the reflective surface of the mirror on which the wavelength conversion material layer is deposited. The layer thickness is then measured in this perpendicular direction, using the reflective surface of the mirror as the zero reference point. The measured thickness should be between 0.1 mm and 3 mm.

[0037] According to an optional feature, the laser emission source of the red light emission means emits a blue colored laser and the wavelength conversion material is a red phosphor.

[0038] It is important to understand that a blue laser refers to a laser with a wavelength between 400 nm and 500 nm, corresponding to the range of blue visible light.

[0039] The term red phosphor refers to materials possessing phosphorescent properties, capable of emitting radiation in the 620 nm to 700 nm range, which corresponds to red light. Various types of red phosphors can be used for this application, for example: quantum dots (QDs), perovskites (OIPs), oxynitrides, nitrides, and activated manganeses (PFS / KFS).

[0040] According to an optional feature, a filter cutting off residual blue light is associated with the wavelength conversion material.

[0041] The filter's function is to eliminate any residual, unconverted blue light before it reaches the collimation device, thus preventing its inclusion in the collimated red beam. This feature helps maintain the color purity of the collimated red beam.

[0042] When the red light emitting means includes a mirror, the filter is positioned between the wavelength conversion material layer and the reflective face of the mirror of the red light emitting means.

[0043] The filter eliminates any residual blue light not converted by the conversion material before it reaches the mirror, thus preventing the mirror from reflecting residual blue light and avoiding its presence in the collimated red beam. Without this filtering, residual blue light could be reflected by the mirror, and some of this light could escape the conversion material unconverted. This residual blue light could then be mixed with the diffuse red radiation resulting from the conversion, altering the color of the collimated red beam.

[0044] According to an optional feature, at least the red light emitting means includes a collimating lens disposed between the laser emitting source of the red light emitting means and the wavelength conversion material.

[0045] The collimating lens makes the laser beams emitted by the laser source parallel to the red light-emitting medium before they reach the wavelength-conversion material layer. The laser is thus precisely directed onto the wavelength-conversion material.

[0046] According to an optional characteristic, the mixing medium is an array of mirrors among which some mirrors are dichroic.

[0047] It is therefore important to understand that collimated beams of light of different colors—for example, blue, green, and red—can be combined into a single overall beam of light using dichroic mirrors. These mirrors have the ability to merge collimated beams of light of different colors into one by selectively reflecting certain wavelengths while allowing others to pass through. They reflect the desired wavelengths for combination, while letting through those that are not needed. This property makes it possible to create an overall beam of light of a precise color, resulting from the combination of different wavelengths.

[0048] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the attached drawings on the other hand, in which:

[0049] is a schematic diagram of a lighting device as defined in the invention.

[0050] is a schematic diagram of a means of emitting red light from the lighting device according to a first embodiment.

[0051] is a schematic diagram of the means of red light emission of the lighting device according to a second embodiment.

[0052] is a schematic diagram of the means of red light emission of the lighting device according to a third embodiment.

[0053] The features and variants of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of the features described below, isolated from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0054] This is a schematic diagram of a lighting device within the meaning of the invention.

[0055] The lighting device 1 comprises three means of light emission, including a means of blue light emission 2, a means of green light emission 3 and a means of red light emission 4. Each of these means of light emission 2,3,4 includes at least one laser emission source.

[0056] The blue light emission means 2 comprises a blue laser emission source 21. This blue laser emission source 21 is a native blue laser and can use various technologies capable of generating a native blue laser, such as laser diodes, crystal lasers, fiber lasers, dye lasers, gas lasers, or free-electron lasers.

[0057] The green light emission means 3 comprises a green laser emission source 31. This green laser emission source is a native green laser and can also utilize any type of technology capable of generating a native green laser.

[0058] Unlike prior art devices that use native red lasers, which directly emit red light without requiring color conversion, the red light emission means 4 comprises a blue laser emission source 41 and a wavelength conversion means 42. The operation of the red light emission means 4 is thus based on the emission of a native blue laser by the blue laser emission source 41 towards the wavelength conversion means 42, which then converts the wavelength of the blue laser to produce red light.

[0059] In addition to the previously mentioned features, further details on the red light emission medium 4 will be provided in the description of the.

[0060] The red light-emitting means 4 produces a collimated red beam which is then directed to a mixing means 5. Similarly, the blue light-emitting means 2 and the green light-emitting means 3 produce respectively a collimated blue beam and a collimated green beam, which are also directed to the mixing means 5.

[0061] Mixing method 5 here consists of a plurality of dichroic mirrors. It should be noted that other mixing technologies, different from dichroic mirrors, can also be used. The key requirement is that these technologies be capable of efficiently combining the three light beams into a single overall light beam, while directing them in a specific direction.

[0062] In this embodiment, the mixing means 5 comprises a blue dichroic mirror 51, a green dichroic mirror 52, and a red mirror 53. The blue dichroic mirror 51, the green dichroic mirror 52, and the red mirror 53 are positioned to intercept the collimated light beams emitted respectively by the blue light-emitting means 2, 3, and 4. Dichroic mirrors have the characteristic of selectively reflecting certain wavelengths while allowing others to pass through. Thus, they make it possible to select and combine the desired wavelengths, creating an overall light beam resulting from the assembly of the three collimated light beams emitted by the light-emitting means 2, 3, and 4.In the arrangement shown in Figure 1, the blue dichroic mirror 51 and the green dichroic mirror 52 are necessarily dichroic because they must reflect blue and green light respectively, while allowing other wavelengths to pass through. The red mirror 53 does not need this dichroic property, as it only needs to reflect red light and is not traversed by any other collimated light beam. In contrast, the blue dichroic mirror is traversed by a beam resulting from the mixing of the collimated green and red beams, and the green dichroic mirror is traversed by the collimated red beam.

[0063] The overall light beam, after being combined by the mixing means 5, is directed to a pivoting mirror device 6. This pivoting mirror device 6 is controlled by an electronic or mechanical control device 61 and in this embodiment comprises a single pivoting mirror.

[0064] This unique pivoting mirror can rotate around two perpendicular axes thanks to the control device 61. The pivoting mirror thus reflects the overall light beam while pivoting rapidly in order to scan the projection area and form an image on that projection area.

[0065] Figure 1 is a schematic diagram of the red light emission means 4 of the lighting device 1 according to a first embodiment. This figure allows for a more detailed observation of the characteristics of this red light emission means 4.

[0066] The red light emission means 4 thus comprises a blue laser emission source 41 and a wavelength conversion material 42. This red light emission means 4 also comprises a mirror 43, as well as a collimation means 44.

[0067] Similar to the blue laser emission source 21 present in the blue light emission means 2, the blue laser emission source 41 of the red light emission means 4 can be based on various technologies capable of generating a native blue laser. These include, in particular, laser diodes, crystal lasers, fiber lasers, dye lasers, gas lasers, and free-electron lasers.

[0068] Wavelength conversion material 42 is designed to convert the light emitted by a blue laser into light with a wavelength between 620 nm and 700 nm, thus producing red radiation.

[0069] This wavelength conversion material, 42 nm, is a phosphorescent material, specifically a red phosphor. The term "red phosphor" refers to a variety of phosphorescent materials capable of emitting red light, that is, radiation with a wavelength between 620 and 700 nm. The red phosphor in this embodiment is capable of converting blue light into red light; therefore, materials such as quantum dots (QDs), perovskites (OIPs), oxynitrides, nitrides, and activated manganeses (PFS / KFS) can be used.

[0070] It should be noted that green laser emission sources could also be used. The red light emission method 4 would then function similarly by converting a wavelength to obtain red light, but the red phosphor used would then be capable of converting green light. Materials such as quantum dots (QDs), perovskites (OIPs), oxynitrides, and nitrides are common examples.

[0071] The native blue laser, produced by the blue laser emission source 41, is directed towards the wavelength conversion material 42. The red light emission means 4 also includes a collimating lens 45, positioned at the output of the blue laser emission source 41. This collimating lens 45 collimates the blue laser towards the wavelength conversion material 42.

[0072] The wavelength conversion material 42 is arranged as a layer on the mirror 43 of the red light emission medium 4.

[0073] When this wavelength-42 conversion material layer is exposed to the native blue laser, it absorbs the laser's energy, causing its energy level to rise above its ground state. When it returns to its initial energy state, the wavelength-42 conversion material layer emits diffuse red radiation that propagates in all directions.

[0074] The wavelength conversion material layer 42 is more particularly positioned on a reflective face of the mirror 43 of the red light emission means 4. When the diffuse red radiation is emitted by the wavelength conversion material 42, part of the diffuse red radiation is directly emitted towards the collimation means 44, while another part of the diffuse red radiation is reflected and directed by the reflective face of the mirror 43 towards the collimation means 44.

[0075] The wavelength conversion material layer 42 must have a thickness between 0.1 mm and 3 mm. A minimum thickness of 0.1 mm ensures that almost all of the blue laser radiation is converted into diffuse red radiation by the wavelength conversion material 42. The maximum thickness, set at 3 mm, is chosen to limit the use of the wavelength conversion material 42 and thus avoid waste. The thickness of this layer, represented by the letter E on the diagram, is measured perpendicular to a plane formed by the reflective face of the mirror 43.

[0076] The collimation device 44 collimates the diffuse red radiation emitted by the wavelength conversion device 42. It thus makes the red rays of the diffuse red radiation parallel and forms a collimated red beam. It directs this collimated red beam towards the mixing device 5 so that this collimated red beam can be mixed with the collimated beams from the blue light emission device 2 and the green light emission device 3.

[0077] In this embodiment, the collimation device 44 is a parabolic reflector. As a parabolic reflector, the collimation device 44 has a curved reflective surface, allowing the light from a focal point to be collimated into a parallel beam. It should be understood that the focal point of the parabolic reflector can be a focal point, a focal line, or a focal plane.

[0078] In this red light emission means 4, the wavelength conversion material layer 42 is positioned at the focal point of the parabolic reflector. More precisely, the face of the wavelength conversion material 42 in contact with the reflective face of the mirror 43 is located at the focal point of the collimation means 44. This feature has the advantage of allowing the capture and efficient collimation of the majority of the diffuse red radiation emanating directly from the wavelength conversion material and / or reflected by the mirror 43.

[0079] Made from materials such as polished metal or aluminum, this parabolic reflector may include a coating to improve its reflectivity. Furthermore, the dimensions and depth of the parabolic reflector, which serves as a collimation aid, are designed to maximize the capture and collimation of diffuse red radiation emanating from the focal point.

[0080] It should be noted that the use of a parabolic reflector as a collimation means 44 is not limiting and any type of technology may be used, provided that it is capable of collimating the diffuse red radiation into a collimated red beam and directing it towards the mixing means 5. Technologies such as diaphragms, collimating lenses, prisms or collimating tubes may be used in particular.

[0081] This is a schematic diagram of the means of emitting red light 4 of the lighting device 1 according to a second embodiment.

[0082] Similar to the first embodiment, the red light emission means 4 includes a blue laser emission source 41 and a collimation lens 45. In addition, the red light emission means 4 includes a wavelength conversion material layer 42 disposed on a mirror 43, and a collimation means 44, which is also in this embodiment, a parabolic reflector.

[0083] In addition, the wavelength conversion material layer 42 is also positioned at the focus of the collimation means 44, i.e. at the focal point of the parabolic reflector.

[0084] The main difference between the second and first embodiments lies in the addition, in the second embodiment, of a filter 46 that blocks residual blue light within the red light-emitting means 4. Various filtration technologies can be used for this filter, provided they are capable of blocking blue light while allowing the passage of red light. Therefore, filters such as dichroic, long-pass, narrow-band, or interference filters are suitable for this application.

[0085] Regarding its positioning, the filter 46 is associated with the mirror 43 of the red light emission means 4. More precisely, the filter 46 is arranged between the wavelength conversion material layer 42 and the reflective face of the mirror 43.

[0086] Filter 46 is particularly useful for preventing residual blue light from entering the collimated red beam. Specifically, filter 46 prevents the reflection by the mirror 43 of the red light-emitting device 4 of any blue light not converted by the wavelength-converting material layer 42. Filter 46 thus prevents the integration of blue light into the collimated red beam by the collimation device 44, thereby avoiding any alteration of its color. Consequently, filter 46 ensures that the final color of the overall light beam from the mixing device 5 is not contaminated by a collimated red beam of the wrong color.

[0087] This is a schematic diagram of the means of emitting red light 4 of the lighting device 1 according to a third embodiment.

[0088] In this third embodiment, the red light emission means 4 comprises a blue laser emission source 41 emitting a native blue laser collimated by a collimating lens 45 towards a wavelength conversion material 42. Similar to the first and second embodiments, the conversion material 42 emits diffuse red radiation which is then collimated by a collimating means 44. The distinctive feature of this embodiment lies particularly in the absence of a mirror 43, unlike the previous embodiments.

[0089] The wavelength conversion material 42 is positioned here at the focal point of the collimation means 44 by a positioning means 47 connected to the collimation means 44. This configuration ensures that the conversion material is not only at the focal point but also close to the collimation means 44.

[0090] The positioning means 47 can be made in the form of a rigid support structure, for example in metal or thermostable polymer, configured to hold the conversion material 42 precisely at the focal distance of the collimation means 44, with a positioning tolerance of less than ±0.1 mm to ensure optimal optical efficiency.

[0091] Positioning the conversion material 42 near the collimation means 44 using the positioning means 47 compensates for the absence of the mirror 43 reflecting part of the diffuse red radiation towards the collimation means 44. This feature thus optimizes the capture and collimation of the diffuse red radiation.

[0092] The specific configuration of the third embodiment, characterized by the absence of a reflecting mirror and the use of a positioning means 47 directly connected to the collimation means 44, offers several technical advantages. First, this configuration significantly reduces optical losses inherent in multiple reflections, resulting in a measurable improvement in the overall luminous efficacy of the device compared to configurations with a mirror. Furthermore, the absence of a mirror eliminates the problems of precise alignment between the mirror and the conversion material, thus reducing manufacturing complexity and improving the reliability of the device under demanding operating conditions, particularly during significant temperature variations.

[0093] Direct positioning of the conversion material 42 by the positioning means 47 at the exact focal point of the collimating means 44 ensures improved thermal stability of the system. This configuration maintains optimal positioning accuracy even during significant temperature variations typical of the automotive environment. Unlike configurations using mirrors, which can experience positioning deviations due to differential material expansion, the direct link between the positioning means and the collimating means minimizes these effects. This superior thermal stability results in remarkably consistent chromatic characteristics of the emitted red light beam across the entire automotive operating temperature range.

[0094] Finally, the elimination of the reflecting mirror and the integration of the positioning means 47 directly into the collimation means 44 not only allow for a substantial reduction in the device's size but also provide improved resistance to vibration and shock. This increased robustness, combined with miniaturization, represents a considerable advantage for integration into the confined spaces of modern vehicles, particularly for interior lighting or projection applications behind the windshield where space is limited and vibration conditions are demanding.

[0095] The examples presented above therefore relate to a lighting device comprising three means of emitting blue, green, and red light, each producing a collimated light beam that is then mixed and projected onto a projection area to display patterns, warnings, or logos. Furthermore, the red light-emitting means includes a wavelength conversion material and a blue or green laser emission source, thus eliminating the need to use a native red laser.

[0096] The invention, illustrated by the examples presented, thus offers a means of emitting red light, and consequently a lighting device, that exhibits less sensitivity to temperature variations. This ensures faithful projection of patterns, warnings, or logos under various temperature conditions, which proves particularly advantageous in several fields of application, notably in the automotive industry.

[0097] The present invention is not limited to the means and configurations described and illustrated herein, and also extends to any equivalent means and configuration as well as any technically operative combination of such means.

Claims

A lighting device (1) comprising: three light-emitting means (2, 3, 4) respectively configured to emit three different colors and respectively configured to form a collimated light beam of the corresponding color, in which among the three light-emitting means, a red light-emitting means (4) is configured to emit the color red, a beam-mixing means (5) configured to combine the three collimated light beams into an overall light beam and direct this overall light beam towards a pivoting mirror device (6), the pivoting mirror device (6) being driven to form, by reflection of said overall light beam, a beam projected onto a predetermined projection area (7), each light-emitting means (2, 3, 4) comprising at least one laser emission source (21, 31, 41),characterized in that the red light emission means (4) comprises a blue or green laser emission source (41) and a wavelength conversion material (42) capable of converting said blue or green color into a red color. Light device (1) according to claim 1, wherein the wavelength conversion material (42) of the red light emission means (4) is disposed at the focus of a collimation means (44), so that the light beam is collimated at the output of the collimation means (44). Light device (1) according to claim 2, wherein the collimation means (44) is a parabolic reflector. Light device (1) according to claim 2 or claim 3, wherein the collimation means (44) includes a positioning means (47) configured to maintain the wavelength conversion material (42) at a predetermined distance from the collimation means (44) corresponding to the focal length of said collimation means (44). Light device (1) according to claim 4, wherein the positioning means (47) is formed in one piece with the collimation means (44). A light device (1) according to any one of claims 2 or 3, wherein the wavelength conversion material (42) of the red light emission means (4) is a layer of wavelength conversion material (42) disposed on the reflective face of a mirror (43) disposed between the laser emission source (41) and the collimation means (44), the laser output of the laser emission source (41) being directed towards the wavelength conversion material (42). Light device (1) according to the preceding claim, wherein the mirror (43) of the red light emission means (4) is configured to direct a portion of a diffuse red radiation generated by the conversion material towards the collimation means (44), said collimation means (44) being capable of collimating the portion of diffuse red radiation into a collimated beam directed towards the mixing means (5). Light device (1) according to any one of claims 6 or 7, wherein the thickness of the wavelength conversion material layer (42) is between 0.1 mm and 3 mm. Light device (1) according to any one of claims 6 to 8, wherein a filter (46) cutting off residual blue light is associated with the wavelength conversion material (42). Light device (1) according to any one of claims 1 to 8, wherein the laser emission source (41) of the red light emission means (4) emits a blue colored laser and the wavelength conversion material (42) is a red phosphor. Light device (1) according to any one of claims 1 to 10, wherein at least the red light emitting means (4) comprises a collimating lens (45) disposed between the laser emitting source (41) of the red light emitting means (4) and the wavelength conversion material (42). Light device (1) according to any one of claims 1 to 11, wherein the mixing means (5) is an array of mirrors among which some mirrors are dichroic.

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