Optical system comprising a laser emitter and a reflective scattering screen

Abstract

The invention relates to an optical projection system (1) comprising a laser emitter (3) configured to emit at least one light beam (Fx), an oscillating mirror device (4), a first optical assembly (6), a second optical assembly (7) and a reflective scattering screen (8), interposed between the first optical assembly (6) and the second optical assembly (7).

Description

Optical system comprising a laser emitter and a reflector diffuser screen

[0001] The invention relates to an optical system comprising a laser emitter and a reflector diffuser screen. The invention also relates to a method of using such an optical system. Finally, it relates to a motor vehicle equipped with an optical system according to the invention.

[0002] Laser light sources typically emit a directional beam of light, offering greater efficiency than LED light sources. However, the high brightness of laser light sources makes them susceptible to eye damage if viewed directly, thus rendering them dangerous if used improperly or unsafely.

[0003] This drawback results in the integration of laser light sources, particularly in the automotive sector, being regulated and limited. For example, the power of laser light sources integrated into vehicle headlights, used for vehicle illumination and / or visibility, or in interior or exterior vehicle information display systems, is significantly limited. Consequently, the level of contrast and detail achievable with such laser light sources is limited, making them poorly suited for projecting information onto projection surfaces, especially in bright daylight.

[0004] Traditionally, it is known to integrate an oscillating mirror device into such optical systems. The angular size of the image projected onto this device is then, for example, on the order of the size of the oscillating mirror device itself, as long as it is functioning and oscillating. The observer's eye then focuses at the level of the oscillating mirror device, and the permissible luminous power of the laser beam is directly related to the size of this device. Thus, the larger the oscillating mirror device, the larger the luminous spot projected onto it, and the higher the brightness of the laser beam can be while remaining safe for an observer.However, at present, existing oscillating mirror devices are unsuitable due to their insufficient resonant frequency and / or their large size which would make their use complex in automotive applications.

[0005] The invention falls within this context and aims to offer an alternative to known optical systems enabling the secure integration of laser light sources, particularly for integration into a motor vehicle.

[0006] The invention relates to an optical projection system, particularly for motor vehicles, comprising a laser emitter configured to emit at least one light beam, an oscillating mirror device configured to reflect at least one light beam, said beam forming a light spot on the oscillating mirror device, and an optical projection device disposed downstream of the oscillating mirror device in a direction of propagation of at least one light beam and configured to project at least one light beam towards a projection surface so as to form a final image.In particular, the optical device comprises a first optical assembly, a second optical assembly and a diffuser reflector screen interposed between said optical assemblies according to the direction of propagation of at least one light beam and comprising a reflective portion, in particular a reflective face and / or a reflective layer, capable of reflecting the light beam towards the projection surface and a diffusing portion, configured to diffuse and / or split the at least light beam.

[0007] In particular, the optical projection system further includes a housing in which the laser emitter is disposed, the reflective portion being capable of directing at least one light beam through an outlet of the housing so that the optical projection device is configured to project at least one light beam through said outlet of the housing to the projection surface.

[0008] In other words, the invention can be extended to an optical projection system, in particular for motor vehicles, comprising a housing in which are disposed a laser emitter configured to emit at least one light beam, an oscillating mirror device configured to reflect the at least one light beam, said beam forming a light spot on the oscillating mirror device, and an optical projection device disposed downstream of the oscillating mirror device in a direction of propagation of the at least one light beam and configured to project the at least one light beam through an exit of the housing towards a projection surface so as to form a final image.In particular, the optical device comprises a first optical assembly, a second optical assembly and a diffuser reflector screen interposed between said optical assemblies according to the direction of propagation of at least one light beam and comprising a reflective portion, in particular a reflective face and / or a reflective layer, capable of reflecting the light beam through the outlet to the projection surface and a diffusing portion, configured to diffuse and / or split the at least light beam.

[0009] Optionally: - the optical device is arranged in the housing so that in the event of failure of the reflector diffuser screen, at least one unreflected light beam does not pass through the output; and / or - the optical system further includes a safety device configured to detect a failure of the reflector diffuser screen in which at least one light beam is not reflected by the reflector diffuser screen.

[0010] According to embodiment examples, an image focus of the first optical assembly is disposed at the diffusing portion of the reflector diffuser screen, so as to form an intermediate image of the luminous spot at the level of said diffusing portion.

[0011] According to exemplary embodiments, the second optical assembly is configured to project an image of the intermediate image onto the projection surface, with an object focal point of the second optical assembly being located: - at the diffusing portion of the reflector-diffuser screen, specifically so as to coincide with the image focal point of the first optical assembly; or - between the reflector-diffuser screen and the second optical assembly, depending on the direction of propagation of at least one light beam.

[0012] According to embodiment examples, an object focus of the second optical assembly is disposed beyond the reflector diffuser screen as seen from the second optical assembly, so that the reflector diffuser screen is arranged between the second optical assembly and the object focus of the second optical assembly.

[0013] Optionally, the reflector diffuser screen is defined by an optical blur greater than or equal to 15%.

[0014] According to embodiment examples, the reflective portion includes a metallic coating, in particular aluminum, or at least a layer made of a metallic material.

[0015] Optionally, the reflector diffuser screen includes a non-uniform heterogeneous structure.

[0016] For example, the heterogeneous structure includes microstructures comprising at least one of: - graining; and / or - an irregular heterogeneous holographic pattern; and / or - a plurality of microscopic prisms.

[0017] According to a particular embodiment, the reflecting diffuser screen is configured so as to comprise a plurality of zones, each having its own diffusion angle, with at least two zones having a distinct diffusion angle, inversely proportional to a distance separating the zone considered from the reflecting diffuser screen from the projection surface.

[0018] Optionally, the optical system includes a correction device configured to modify at least one emitted light beam so as to correct noise generated by the reflector diffuser screen, for example so as to reduce the visibility, or even eliminate the visibility, of said noise in the final image.

[0019] The invention also extends to a method of projecting a light beam onto a projection surface in an optical system according to the invention comprising a correction device, the method comprising: - the determination, by the correction device, of a correction to be applied to at least one light beam so as to reduce, or even eliminate, noise generated by the reflector diffuser screen; and - the projection of at least one light beam, via the laser emitter, to which said determined correction is applied.

[0020] The invention can be further extended to a motor vehicle comprising an optical projection system according to the invention.

[0021] Further details, features and advantages will become clearer upon reading the detailed description given below, which is indicative and not exhaustive, in relation to the various implementation examples illustrated in the following figures:

[0022] This is a general schematic representation of an optical system according to the invention.

[0023] This is a general schematic representation of an alternative optical system according to the invention.

[0024] This is a general schematic representation of an example of an implementation of the optical system including a safety device.

[0025] This is a general schematic representation of an alternative implementation of the optical system including a safety device.

[0026] This is a general schematic representation of an example of the implementation of the reflector diffuser screen of the optical system.

[0027] This is a general schematic representation of an alternative implementation of the reflector diffuser screen of the optical system.

[0028] This is a general schematic representation of an alternative implementation of the reflector diffuser screen of the optical system.

[0029] This is a general schematic representation of an alternative implementation of the reflector diffuser screen of the optical system.

[0030] This is a schematic representation of a first embodiment illustrating the variation in the size of a retinal image as a function of the illumination surface of a second optical assembly.

[0031] This is a schematic representation of the first embodiment illustrating the variation in the size of a retinal image as a function of the illumination surface of a second optical assembly.

[0032] This is a schematic representation of a second embodiment applied to a part of the optical system.

[0033] This is a schematic representation of a third embodiment applied to a part of the optical system.

[0034] Figures 1a to 1b schematically illustrate examples of embodiments of an optical system 1 according to the invention. In particular, the optical system 1 may be integrated into a motor vehicle. According to one non-limiting embodiment, the optical system 1 is integrated into a headlight, in particular a front headlight, of the vehicle so as to provide lighting and / or project specific information onto a projection surface 2 defined on the road surface. According to an alternative embodiment, the optical system 1 is integrated into an information display system located in the vehicle's passenger compartment, such as a head-up display system or a display system projecting information onto a projection surface 2 contained within a bracket framing the vehicle's windshield, a projection screen, the windshield itself, or the passenger compartment's dashboard.

[0035] By convention in the description below, the terms "first" and "second" or "primary" and "secondary" are intended to distinguish similar elements and not to define a hierarchy among said elements. Similarly, the terms "upstream" and "downstream" refer to the direction of propagation of a given light beam.

[0036] In general, the optical system 1 according to the invention comprises a laser emitter 3, an oscillating mirror device 4 and an optical device 5. Optionally, the optical system comprises a housing 11 including an outlet 12 and in which the laser emitter 3, the oscillating mirror device 4 and the optical device 5 are arranged. It is understood that such a housing 11 can be included in the various examples of optical systems 1 described below.

[0037] The laser emitter 3 is configured to emit at least one light beam Fx towards the oscillating mirror device 4 and through the optical device 5. Optionally, but preferably, the laser emitter 3 includes a plurality of laser light sources. For example, these sources include red, green, and / or blue laser light sources. If the laser emitter 3 includes at least one red laser light source, one green laser light source, and one blue laser light source, then the laser emitter 3 is an "RGB laser emitter," capable of emitting a light beam Fx of the desired color. Each laser light source in the laser emitter 3 emits a primary light beam, and these primary light beams are combined to form the light beam Fx. The at least one light beam Fx is then directed towards a reflective surface of the oscillating mirror device 4.In particular, the different laser light sources are controlled independently of each other.

[0038] The oscillating mirror device 4 is configured to reflect at least one light beam Fx emitted by the laser emitter 3 towards the optical device 5. This at least one light beam Fx forms a light spot Tx on the oscillating mirror device 4. The oscillating mirror device 4 includes, in a conventional manner, a movable scanning mirror that reflects the at least one light beam Fx according to the angle of rotation at which it is positioned. The scanning mirror can be of any known type and driven using conventional drive methods.

[0039] For example, the oscillating mirror device 4 is of the MEMS type, from the English "Micro Electro Mechanical Systems," meaning "micro-electromechanical system," allowing the orientation of at least one light beam Fx according to a plurality of angular orientations over time. According to a classic, non-limiting, and undetailed embodiment, the oscillating mirror device 4 is configured to implement a sequential two-dimensional scan along lines to form an image on the projection surface 2, also known as "raster scan" or "raster scanning." Alternatively, the oscillating mirror device 4 is configured to implement a so-called "vector" scan or a "Lissajous" scan, known from the prior art.

[0040] The optical projection device 5 is arranged downstream of the oscillating mirror device 4 in a direction of propagation of at least one light beam Fx and is configured to project the at least one light beam Fx towards a projection surface 2. In particular, the optical projection device 5 is configured to project the at least one light beam Fx through the outlet 12 of the housing 11 and towards the projection surface 2. Optionally, the optical system 1 is configured so that the light beam Fx, when it arrives at the level of the optical projection device 5, is collimated.

[0041] In general, the optical device 5 comprises a first optical assembly 6, a second optical assembly 7 and a reflector diffuser screen 8 capable of reflecting at least one beam of light.

[0042] The reflecting diffuser screen 8 is arranged so as to be interposed between the first optical assembly 6 and the second optical assembly 7, depending on the direction of propagation of at least one light beam Fx. Specifically, the reflecting diffuser screen 8 comprises a first face 81 and a second face 82, facing opposite each other. In this case, the first face 81 is oriented towards the first optical assembly 6. The reflecting diffuser screen 8 also comprises a reflective portion 84. As is known, such a reflective portion 84 comprises a metallic coating, as shown in Figures 2b, 3a, or 3d, or at least one layer made of a metallic material, in particular aluminum, as illustrated in Figures 3b and 3c. According to alternative embodiments, further described below, the reflective portion 84 comprises the first face 81 or the second face 82, or is incorporated into one of these faces.

[0043] The reflecting diffuser screen 8 also includes a diffusing portion 85, that is, a portion configured to at least partially diffuse and / or scatter the at least one light beam Fx. As further detailed below, the diffusing portion 85 extends over all or part of a thickness of the reflecting diffuser screen 8, corresponding to the dimension between the first face 81 and the second face 82 of the reflecting diffuser screen 8, and / or is contained within at least one of the first face 81 or the second face 82. The diffusing portion 85 also extends over all or part of a dimension of the reflecting diffuser screen 8 orthogonal to the thickness, that is, over all or part of a height and / or a width of said screen.

[0044] The reflecting diffuser screen 8 can thus comprise a plurality of distinct layers connected together, one of said layers comprising the diffusing portion 85 and a distinct layer comprising the reflective portion 84 as illustrated in Figures 3b and 3. Alternatively, the diffusing portion 85 and the reflective portion 84 are at least partly coincident, for example within the same layer, a portion of the same layer or within one of the faces of the reflecting diffuser screen 8, as illustrated in Figures 2b or 3a for example when a reflective coating is directly applied to the diffusing portion 85.

[0045] It should also be noted that, optionally, the reflector diffuser screen 8 includes a support portion 86, as shown in the figure, for example made of a plastic material, configured to carry the reflective portion 84 and the diffusing portion 85. It is understood that such a support portion 86 can be integrated into the various embodiments of the reflector diffuser screen 8 described above.

[0046] Preferably, the first optical assembly 6 comprises a primary projection lens or a plurality of primary projection lenses. The first optical assembly 6 is interposed between the oscillating mirror device 4 and the reflecting diffuser screen 8 so that it is configured to form an intermediate image Ix of the light spot Tx, projected onto the oscillating mirror device 4, at the level of the reflecting diffuser screen 8, in particular at the level of the diffusing portion 85 and / or the reflecting portion 84 of the reflecting diffuser screen 8. It should be noted that, due to the scanning performed by the oscillating mirror device 4, it reflects at least one light beam Fx onto at least one portion of the first optical assembly 6, for example, the primary projection lens, for each position of said device, i.e., at a given instant.

[0047] The second optical assembly 7 is configured to project, or image, the intermediate image Ix onto the projection surface 2 so as to form a final image Ifx. In particular, the reflector diffuser screen 8 is configured and arranged so that the reflective portion 84 of said screen is capable of reflecting at least one light beam Fx towards the outlet 12 of the housing 11 in order to allow the projection of information onto the projection surface 2. Thus, the term "reflector" means that the reflector diffuser screen deflects the trajectory of the at least one light beam Fx arriving at said screen, i.e., incident, by reflection, so that the at least one light beam exits the reflector diffuser screen 8 on the same side of said screen as the at least one incident light beam. In particular, such reflection is performed across the entire visible light spectrum.Alternatively, such reflection is implemented for specific wavelengths, particularly those specific to a color emitted by the laser emitter 3.

[0048] As described above, and using non-limiting examples, the projection surface 2 is a portion of the roadway, for example extending in front of a vehicle, a glazed surface, such as a windshield or a screen, or a portion of the passenger compartment, such as a pillar supporting the windshield or the dashboard. As further explained below, the projection surface 2 is a flat and / or inclined surface relative to the second optical assembly 7 and / or relative to the reflector diffuser screen 8.

[0049] In one embodiment, the second optical assembly 7 comprises at least one secondary projection lens. Alternatively, the second optical assembly 7 comprises at least one secondary mirror. For example, the second optical assembly 7 comprises a plurality of secondary mirrors, at least one of which is a reflecting mirror. In an optional example, the second optical assembly 7 comprises a freeform lens or a freeform mirror.

[0050] The reflecting diffuser screen 8 is thus optionally arranged particularly within the optical device 5, and by extension of the optical system 1, in order to direct at least one reflected light beam Fx towards the outlet 12 of the housing 11. Optionally, in order to optimize the eye safety of a user observing the optical system 1 according to the invention, the optical device 5 is arranged so that in the event of failure of the reflecting diffuser screen 8 the light beam, then not reflected due to the failure of said screen, does not pass through the outlet 12, that is to say it remains enclosed within the housing 11 and is not projected, or redirected, towards the projection surface 2 via the reflecting diffuser screen 8.The term "failure" of the reflector diffuser screen 8 refers to the fact that at least one light beam Fx continues to propagate along the same direction, or substantially along the same direction, due to a lack of reflection. This can occur if the reflector diffuser screen 8 is dropped or if it is damaged by breakage, melting, or burning resulting from at least one oscillating mirror device 4 becoming stuck in the same position for an extended period. In particular, the oscillating mirror device 4 is arranged so that it is not visible to a user outside the optical system 1 through the output 12 of the housing 11.

[0051] As illustrated in Figures 2a and 2b, the optionally optical projection system 1 also includes a safety device 9 configured to detect a failure of the reflector diffuser screen 8 in which at least one light beam Fx, or a portion thereof, is not reflected and, consequently, deflected. To this end, the safety device 9 is positioned along the path of at least one light ray of the incident light beam Fx as it reaches the reflector diffuser screen 8. It should be noted that, in the examples shown, the path of at least one light beam Fx is illustrated schematically and in a simplified manner. The potential deflection of the rays of at least one light beam Fx passing through the reflector diffuser screen 8, resulting from the refraction of said rays by the reflector diffuser screen 8, is therefore not shown.

[0052] According to a first, non-limiting alternative embodiment, the safety device 9 comprises a beam trap, also referred to as a light trap. For example, the trap is configured to absorb at least one undeflected light beam Fx or to disperse the beam in the event of a failure of the reflector diffuser screen 8 so as to render it harmless to a potential observer. Alternatively, such a trap is formed by the housing 11.

[0053] Optionally, the safety device 9 further includes at least one sensor configured to detect that at least one light beam Fx reaches the beam trap, i.e., that said beam is not deflected. In particular, by way of non-limiting example, said sensor is a light sensor, a photodiode, or a thermistor. Optionally, in combination with at least one sensor, the safety device 9 includes a control means 91 for the laser emitter 3 capable of interrupting the operation of the laser emitter 3 and the emission of at least one light beam Fx when it is detected that at least one light beam Fx reaches the safety device 9. Thus, when said sensor detects a failure of the reflector diffuser screen 8, it transmits the information to the control means 91, which interrupts the operation of the laser emitter 3.

[0054] According to a second alternative embodiment, the security device 9 includes at least one sensor or the sensor and control means 91 described previously but is devoid of a beam trap and at least one light beam Fx is simply blocked in the housing 11.

[0055] Specifically, the reflector diffuser screen 8 is arranged so that an image focus F1i of the first optical assembly 6 is located at the diffusing portion 85 and / or the reflective portion 84 of the reflector diffuser screen 8, or substantially at the diffusing portion 85 and / or the reflective portion 84, depending on the type of reflector diffuser screen 8 used. "Substantially" here means that the position of the image focus F1i of the first optical assembly 6 is located at a distance less than or equal to 1.00 mm, or even 500 µm or 300 µm from the relevant portion of the reflector diffuser screen 8.

[0056] Optionally, as illustrated in Figure 2a or 2b, the reflecting diffuser screen 8 is arranged so that an object focus F2o of the second optical assembly 7 is located at, or substantially at, the level of the diffusing portion 85 and / or the reflecting portion 84 of the reflecting diffuser screen 8, in particular so as to coincide with the image focus F1i of the first optical assembly 6. This principle can be implemented, in particular, when at least one light beam Fx is collimated. Rays forming the at least one light beam exiting the second optical assembly 7 then extend parallel or substantially parallel to each other, as illustrated in Figure 1. In particular, the optical device 5 is afocal.

[0057] Alternatively, as shown in the figure, the reflector diffuser screen 8 is arranged so that the object focus F2o of the second optical assembly 7 extends between the reflector diffuser screen 8 and the second optical assembly 7 in the direction of propagation of at least one light beam Fx, in particular between the diffusing portion 85 of the reflector diffuser screen 8 and the second optical assembly 7.

[0058] Such a principle can be implemented, in particular, in the case of a non-collimated light beam Fx, notably converging downstream of the reflective portion 84 of the reflecting diffuser screen 8, according to the direction of propagation of at least one light beam Fx. This principle is also implemented when projecting information onto a projection surface 2 located at a given, predefined distance. Rays of the at least one light beam Fx exiting the second optical assembly 7 then converge towards each other. This principle minimizes the size of the intermediate image Ix projected onto the reflecting diffuser screen 8 in order to optimize its resolution and sharpness, while ensuring the eye's safety due to the presence of the reflecting diffuser screen 8 by preventing the eye from accommodating to the oscillating mirror device 4.This also allows the light beam Fx exiting the second optical assembly 7 to be homogenized by avoiding, in particular in certain configurations, the distinct projection of the diffusing structure of the diffusing portion 85. It is understood that such a principle can be applied mutatis mutandis to the different examples of the realization of the reflector diffuser screen 8 illustrated in figures 3a to 3d.

[0059] Thus, for example, the object focus F2o of the second optical assembly 7 is separated from the image focus F1i of the first optical assembly 6 by a distance less than or equal to 1.00mm, or even 500µm, or even 300µm, such a distance being zero when said foci are coincident, as indicated above, and not zero when said foci are distinct.

[0060] For example, a distance separating the reflector diffuser screen 8 from the second optical assembly 7, in particular the distance measured along the optical axis of the second optical assembly 7, is defined by the following relationship:

[0061] Or :

[0062] De_opt2 is the distance separating the reflector diffuser screen 8 from the second optical assembly 7;

[0063] df2 is the focal length of the second optical assembly 7, in particular the secondary projection lens;

[0064] dpj is the distance between the second optical assembly 7, for example at the surface of the secondary lens or the reflective surface of the secondary mirror, and the projection surface 2.

[0065] Alternatively, according to an embodiment not shown in the figures, the reflector diffuser screen 8 is arranged so that the object focus F2o of the second optical assembly 7 extends beyond the reflector diffuser screen 8 seen from the second optical assembly 7, in particular beyond the diffusing portion 85 of the reflector diffuser screen. In other words, the reflector diffuser screen 8, in particular the diffusing portion 85 of the reflector diffuser screen, is arranged between the second optical assembly 7 and the object focus F2o of the second optical assembly 7. Thus, for example, the object focus F2o of the second optical assembly 7 is separated from the image focus F1i of the first optical assembly 6 by a distance less than or equal to 1.00mm, or even 500µm, or even 300µm, such a distance being zero when said foci are coincident, as indicated above, and not zero when said foci are distinct.This allows the light beam Fx exiting the second optical assembly 7 to be homogenized, avoiding, particularly in certain configurations, the distinct projection of the diffusing structure of the diffusing portion 85.

[0066] As indicated above, the reflector diffuser screen 8 has a diffuser function, that is to say it allows in part to diffuse or break up the at least light beam Fx, in particular so as to modify, particularly increase, the angular size and size of the retinal image of the final image Ifx compared to the size of the light spot Tx projected onto the oscillating mirror device 4.For an outside observer, the intermediate image Ix projected onto the reflecting diffuser screen 8 is then the image of the projected source and, due to the positioning of the oscillating mirror device 4 relative to the output 12 of the housing 11 of the optical system, an intermediate image Ix projected onto the reflecting diffuser screen 8 thus becomes the point of accommodation of the observer's eye, for accommodation at infinity of the eye or for the eye at rest, instead of the luminous spot Tx projected onto the oscillating mirror device 4, and this even in the event of failure or blockage of the oscillating mirror device 4.

[0067] Thus, the first optical assembly 6 creates, on the reflecting diffuser screen 8, the intermediate image Ix of the light spot Tx projected onto the oscillating mirror device 4, while the second optical assembly 7 reproduces the intermediate image Ix onto the projection surface 2. Indeed, in the absence of the reflecting diffuser screen 8, as is the case in prior art optical systems, the observer's eye directly perceives the light spot Tx projected onto the oscillating mirror device 4, and the apparent angle of the projected image, and consequently the retinal image, is smaller. It is therefore necessary to limit the brightness, in other words, the illuminance, of the laser emitter 3 in order to ensure the eye safety of any observer present.The integration of the reflecting diffuser screen 8 makes it possible to overcome such a limitation since the observer can no longer directly perceive the luminous spot Tx formed by the laser emitter 3 on the oscillating mirror device 4. The observer's eye accommodates itself on the reflecting diffuser screen 8 without the possibility of focusing on the oscillating mirror device 4, thus focusing on the intermediate image Ix which is itself projected by the second optical assembly 7.

[0068] Advantageously, the second optical assembly 7 allows the size of the final image Ifx, projected onto the target projection surface 2, to be increased relative to a dimension of the intermediate image Ix. The size of at least one light beam Fx is thus greater at the output of the optical system 1, i.e. downstream of the second optical assembly 7, than at its input, i.e. upstream of the oscillating mirror device 4.

[0069] Additionally, optionally, due to the positioning of the oscillating mirror device 4 relative to the output 12 of the housing 11 of the optical system 1, in the event of failure of the reflector diffuser screen 8, at least one light beam Fx is not projected into the external environment towards the projection surface 2 and no accommodation of the eye of a user is possible at the level of the light spot Tx projected onto the oscillating mirror device 4 through the output 12 of the housing 11.

[0070] The optical system 1 according to the invention thus makes it possible to overcome the constraints traditionally applied to ensure eye safety. The oscillation, or scan, frequency of the oscillating mirror device 4 is therefore not defined as a function of the brightness of the laser emitter 3. For example, such an oscillation frequency can be on the order of 25 kHz. In a specific, non-limiting example, the oscillation frequency is on the order of 30 kHz to 40 kHz for creating a line along the slow axis and on the order of 60 kHz along the fast axis.

[0071] Figures 3a to 3d illustrate alternative embodiments of the reflector diffuser screen 8. For example, the diffusing portion 85 is made of a material selected from glass, plastic such as polycarbonate, or ceramic. For example, the diffusing portion 85 of the reflector diffuser screen 8 is produced by injection molding, overmolding, and / or photolithography.

[0072] The reflector diffuser screen 8 is, for example, dimensioned so as to have a surface area greater than or equal to a surface area of ​​the first optical assembly 6, for example of the primary projection lens, and / or greater than or equal to a reflective surface area of ​​the oscillating mirror device 4.

[0073] In particular, and optionally but preferably, the reflector diffuser screen 8, especially the diffusing portion 85, is defined by an optical blur level greater than or equal to 15%. "Optical blur" refers to a haze, also known as reflection mist or "haze." The "optical blur level" is defined as the percentage of light scattered outside a 2.5° cone centered on an axis of specular reflection of at least one light beam Fx.

[0074] According to embodiment examples, the diffusing portion 85 of the reflector diffuser screen 8 includes an optical blur of surface, volumetric or holographic type.

[0075] A surface-type reflector diffuser 8 has a mist at least arranged on one of its faces, particularly on the diffusing portion 85, i.e., for example, the first face 81 or the second face 82, as illustrated in Figures 2a, 2b, 3a, or 3c. Preferably, such a reflector diffuser 8 has an optical blur level greater than or equal to 15%. Also, in the case of a surface diffuser, according to an embodiment illustrated in Figure 1, the same face of the reflector diffuser 8 optionally combines the functions of diffuser and reflector; i.e., the face of the reflector diffuser 8 containing the mist also includes the reflective portion 84, the diffusing portion 85 thus including or bearing the reflective portion 85.For example, the first face 81 is a surface diffuser and includes the reflective portion 84, as illustrated in the figure, the diffusing portion 85 and the reflective portion 84 can then be at least partly confused and include said first face 81.

[0076] According to an alternative embodiment, illustrated at 1a or 1a, the reflective portion 84 and the diffusing portion 85 comprise opposite faces of the reflecting diffuser screen 8, the reflective portion 84 comprising the second face 82 while the diffusing portion 85 comprises at least a part of the first face 81. For example, a part of the reflecting diffuser screen 8, particularly of the first face 81, at the level of which the at least one light beam Fx enters the reflecting diffuser screen 8, is devoid of a diffusing portion 85 while a part of the reflecting diffuser screen 8 and of the first face 81 disposed on the path of the at least one light beam Fx reflected by the reflective portion 84 comprises the diffusing portion 85.In the example illustrated in the figure, the diffusing portion 85 is thus represented, in a non-limiting way, by a dotted line arranged on a lower portion of part of the reflector diffuser screen 8, particularly of the first face 81.

[0077] A volumetric reflector diffuser screen 8 exhibits haze over all or part of its thickness, corresponding to the dimension between the first face 81 and the second face 82, particularly over all or part of the diffusing portion 85, as illustrated in the 3D model. Similar to what was described above with reference to a surface diffuser, the diffusing portion 85 also extends over all or part of a dimension of the reflector diffuser screen 8 orthogonal to its thickness, that is, over all or part of a height and / or width of said screen. The preceding description then applies mutatis mutandis. Preferably, the reflector diffuser screen 8 then exhibits a level of optical blur greater than or equal to 20%, or even 22%.Also, in such a reflecting diffuser screen 8, as illustrated in Figure 1, the reflective portion 84 includes, for example, the second face 82, so that at least one light beam Fx penetrates the thickness of the reflecting diffuser screen 8 before being reflected. Alternatively, when the reflecting diffuser screen 8 includes the support portion 86, as illustrated in Figure 1, the reflective portion 84 can be interposed between the diffusing portion 85 and the support portion 86, the latter possibly including the second face 82.

[0078] A holographic reflecting diffuser screen 8 comprises specific patterns or microstructures, optionally combined with a mist, particularly within all or part of the thickness of said screen and / or on all or part of at least one of the faces of the reflecting diffuser screen 8. In particular, said patterns or microstructures have a regular periodicity. Said patterns are on the order of a micrometer and are arranged so as to diffuse at least one light beam into a preferred field of view, as described below. Preferably, the reflecting diffuser screen 8 then exhibits a level of optical blur greater than or equal to 25%, or even 27%. In such a reflecting diffuser screen 8, the reflective portion 84 comprises, for example, the second face 82, so that at least one light beam Fx penetrates the thickness of the reflecting diffuser screen 8 before being reflected.

[0079] Figures 4a to 6 illustrate various specific embodiments of the optical system 1 according to the invention that may optionally be implemented. It is understood that these embodiments apply mutatis mutandis to the different types of diffusing reflector screens 8 described above, that is, whether they are of the surface, volumetric, or holographic type. Also, the reflective portion 84 may comprise the first face 81 or the second face 82.

[0080] Figures 4a and 4b illustrate a first embodiment, in which the reflecting diffuser screen 8, in particular the diffusing portion 85, comprises a heterogeneous, i.e., non-uniform structure. In other words, at least two distinct areas of the reflecting diffuser screen 8, in particular the diffusing portion 85, exhibit different structures.

[0081] Such heterogeneity aims to optimize the eye safety of an observer by increasing the angular size and apparent size of the image that can be perceived by the observer at the level of the second optical assembly 7, independently of the position of the intermediate image Ix on the reflecting diffuser screen 8 and independently of the proximity of the observer to the second optical assembly 7. In other words, the integration of such a reflecting diffuser screen 8 makes it possible to increase the illuminated area of ​​the component of the second optical assembly 7 under consideration, for example the surface of the secondary projection lens or the secondary mirror, by dispersing, or diffusing, at least one light beam Fx.

[0082] For example, optionally but preferably, the reflecting diffuser screen 8, comprising a heterogeneous structure, is configured so that at least one light beam Fx is projected onto most of the surface of the second optical assembly 7, i.e., onto the surface of at least one secondary mirror or the secondary projection lens, at a given time t. "Most of" here means that at least 50% of a surface of the second optical assembly 7 is illuminated, i.e., 50% of the surface of the secondary projection lens or the reflective surface of the secondary mirror of the second optical assembly 7, for example. Figures 4a and 4b illustrate various examples of projection onto at least 50% of the surface of the second optical assembly 7. Optionally, the structure of the reflecting diffuser screen 8 is configured so that the entire surface of the component of the second optical assembly 7 under consideration is illuminated at a given time t.

[0083] In particular, at least part of the diffusing portion 85 of the reflector diffuser screen 8 has a heterogeneous structure. Specifically, all or part of the thickness of the reflector diffuser screen 8, between the first face 81 and the second face 82, has a heterogeneous structure. Alternatively, the heterogeneous structure may be arranged over all or part of a dimension of the reflector diffuser screen 8 orthogonal to the thickness, that is, over all or part of a height and / or a width of said screen.

[0084] In particular, the heterogeneous structure of the reflector diffuser screen 8 comprises a plurality of microstructures 83 selected from:

[0085] - heterogeneous graining at least arranged at the level of all or part of the diffusing portion 85, for example of the thickness or one of the faces of the diffusing reflector screen 8; and / or- an irregular heterogeneous holographic pattern included in the diffusing portion 85; and / or- a plurality of microscopic prisms included in the diffusing portion 85.

[0086] The heterogeneous structure of the reflector diffuser screen 8 thus depends on its texturing.

[0087] The term "graining" refers to the fact that the reflecting diffuser screen 8, particularly the diffusing portion 85, comprises a plurality of grains. The heterogeneity of the structure is then obtained through heterogeneity of shape, size, and refractive index of said grains and / or heterogeneity of distribution or density of said grains within the reflecting diffuser screen 8. For example, the grains have dimensions on the order of 1 to 10 µm.

[0088] The term "microscopic prisms" refers to the reflecting diffuser screen 8, particularly the diffusing portion 85, comprising a plurality of polyhedra whose dimensions can be on the order of 1 to 10 µm. The heterogeneity of the structure is then obtained by heterogeneity of shapes, dimensions, refractive index, and / or distribution, or density, of said prisms within the reflecting diffuser screen 8.

[0089] The term "holographic pattern" refers to the fact that the reflecting diffuser screen 8, particularly the diffusing portion 85, comprises a plurality of holograms corresponding to microstructures with a regular period. The heterogeneity of the structure is then obtained through heterogeneity of shape, size, inclination, refractive index, and / or distribution, or density, of said holograms within the reflecting diffuser screen 8.

[0090] It is understood that heterogeneity can also be achieved by combining different types of microstructures 83.

[0091] Optionally, but preferably, the heterogeneity, or non-uniformity, of the structure of the reflecting diffuser screen 8 is defined by a transmission function that depends on the position and distance of a given point on the reflecting diffuser screen 8, particularly its diffusing portion 85, relative to the center of said screen. For example, a central area of ​​the reflecting diffuser screen 8 comprises microstructures 83 that diffuse the light beam Fx, while areas distant from this central point also deflect the light beam Fx towards a predefined portion of the second optical assembly 7. The microstructures 83 are then configured such that the further the area is from the central area of ​​the reflecting diffuser screen 8, the greater the deflection of at least one light beam. This deflection can thus be radial with respect to the center of the reflecting diffuser screen 8.The heterogeneous structure of the reflector diffuser screen 8 can thus be at least partly symmetrical, in particular according to a radial symmetry centered on the center of the reflector diffuser screen 8 and / or according to a planar symmetry in which a plane of symmetry passes through the center of said screen and / or includes the optical axis of the optical system 1 which corresponds to the optical axis of the second optical assembly 7.

[0092] Figure 1 illustrates an example of a second embodiment, in which the reflector diffuser screen 8 presents another example of a heterogeneous, i.e., non-uniform, structure. It should be noted that the second embodiment can be combined with the first embodiment without constraint.

[0093] In this embodiment, the projection surface 2 is particularly inclined relative to at least a portion of the reflecting diffuser screen 8 and relative to an image focal plane Pf2i of the second optical assembly 7. As a result, different portions of the reflective portion 84 of the reflecting diffuser screen 8 are positioned at different distances from the projection surface 2, these distances being evaluated along the same direction, here a first direction 100, transverse or even orthogonal to the image focal plane Pf2i. The same applies to the distances separating the projection surface 2 from the second optical assembly 7.Without specific adjustments, projecting information onto an inclined surface results in variations in the sharpness and size of the final image Ifx, depending on the area of ​​the reflector screen 8 illuminated by at least one light beam Fx. This is because the sharpness of the final image Ifx is directly related to the depth of field of the at least one light beam Fx and, consequently, to the diffusion angle β of the reflector screen 8, particularly the area of ​​the reflector screen 8 under consideration. Therefore, the smaller the diffusion angle β, the greater the depth of field, and vice versa.

[0094] In this embodiment, the reflector diffuser screen 8, in particular the diffusing portion 85, is configured to comprise a plurality of zones with distinct diffusion angles β. This heterogeneity of diffusion angles makes it possible to obtain depths of field, schematically illustrated by a rectangle, that vary according to the illuminated area of ​​the reflector diffuser screen 8. Specifically, the reflector diffuser screen 8 is configured such that each zone is defined by its own diffusion angle β, which is inversely proportional to the distance separating the zone of the reflector diffuser screen 8 from the projection surface 2, said distance being defined along the first direction 100.In other words, the further the considered area of ​​the reflecting diffuser screen 8 is from the projection surface 2, the smaller the latter's diffusion angle β and, consequently, the greater its depth of field. Specifically, the diffusion angles β of the different areas of the reflecting diffuser screen 8 are adjusted so that the size of the final image Ifx is equal, or nearly equal, regardless of the illuminated area of ​​the reflecting diffuser screen 8, in order to obtain a uniform, homogeneous, and therefore undistorted projection of the information.

[0095] In particular, the reflector diffuser screen 8 illustrated in Figure 1 comprises at least a first zone Z1 and a second zone Z2, distinct from the first zone Z1. It is understood that such a configuration is in no way limiting and that the reflector diffuser screen 8 may comprise more distinct zones. The first zone Z1 is defined by a first diffusion angle β1 and configured to be positioned at a first distance from the projection surface 2 along the first direction 100. The second zone Z2 is defined by a second diffusion angle β2 and configured to be positioned at a second distance from the projection surface 2, strictly greater than the first distance along the first direction 100, the first diffusion angle β1 being strictly greater than the second diffusion angle β2 of the second zone Z2.

[0096] This principle allows for a variable depth of field, particularly greater for areas of the reflector diffuser screen 8 furthest from the projection surface 2, depending on the illuminated area of ​​the reflector diffuser screen 8, specifically the diffusing portion 85. In this way, the final image Ifx is sharp regardless of the illuminated area of ​​the screen. The variation in size of the final image Ifx, and in particular the distortion of the final image Ifx observed when areas of the reflector diffuser screen 8 furthest from the projection surface 2 are illuminated, is thus reduced or even eliminated.

[0097] Preferably, the variation in the diffusion angle β from one considered area to another of the reflecting diffuser screen 8 is obtained through a plurality of microstructures 83 as described previously with reference to the first embodiment, selected from:

[0098] - heterogeneous graining at least arranged at the level of all or part of the diffusing portion 85, for example of the thickness or one of the faces of the diffusing reflector screen 8; and / or- an irregular heterogeneous holographic pattern included at least in the diffusing portion 85; and / or- a plurality of microscopic prisms included at least in the diffusing portion 85.

[0099] Therefore, the previous description relating to such microstructures 83 applies mutatis mutandis.

[0100] Optionally but preferably, in such an embodiment, the intermediate image Ix, and therefore the surface of the reflecting diffuser screen 8, illuminated by at least one light beam Fx at a given time t, is projected onto a surface less than or equal to 50% of a face of the second optical assembly 7, for example a face of the secondary lens or of the secondary mirror.

[0101] Laillustrates an example of an embodiment of a third embodiment in which the optical projection system 1 further includes a correction device 10 configured to modify at least one light beam Fx emitted so as to correct noise generated by the reflector diffuser screen 8, in particular by the diffusing portion 85 of the reflector diffuser screen 8. This embodiment can be combined with the various embodiments described above.

[0102] Here, "noise" means a parasitic fluctuation or degradation that the final projected image Ifx undergoes due to the reflector diffuser screen 8, in particular due to defects, irregularities, microstructures 83 described previously or a structural granularity of the reflector diffuser screen 8, in particular of the diffusing portion 85.

[0103] The correction device 10 is thus capable of controlling and driving the laser emitter 3 in order to compensate, at least partially, for the noise induced by the reflector diffuser screen 8 so that it is not visible in the final image Ifx. This principle allows for processing the projected image as soon as at least one light beam Fx is emitted, thus ensuring smoothing of the final image Ifx projected onto the projection surface 2 in order to optimize its quality and detail. For example, the processing of the projected image includes: - smoothing a reference image, also called a "white page," pre-recorded or recorded and used for each image projected in real time; - calculating a background image using a "rolling ball" type processing; - removing said background image from each image projected in real time and removing the reference image.

[0104] For example, the correction device 10 includes a memory element on which is pre-recorded or recorded at least one reference image representative of the noise generated by the reflecting diffuser screen 8, for example an image of the irregularities of the diffusing portion 85. Additionally or alternatively, the correction device 10 includes a camera capable of capturing an image representative of the noise generated by the reflecting diffuser screen 8, for example an image of the irregularities of the diffusing portion 85. Additionally, the correction device 10 includes a processing unit, capable of defining a correction to be applied, and a control means 91 for the laser emitter 3.

[0105] The invention also extends to a method of using an optical projection system 1 as defined in the third embodiment. It is understood that the above description, relating to the third embodiment, applies here mutatis mutandis. The method comprises, initially, the determination, by the correction device 10, of a correction to be applied to at least one light beam Fx so as to reduce, or even eliminate, noise generated by the reflector diffuser screen 8, in particular by the diffusing portion 85 of the reflector diffuser screen 8. Such a determination can be made from at least one pre-recorded image representative of the noise generated by the reflector diffuser screen 8 or from an image captured, in real time or at regular time intervals, by the correction device 10 as described above.

[0106] Next, the process includes the projection of at least one light beam Fx, via the laser emitter 3, to which the determined correction is applied so as to obtain a final image Ifx, projected onto the projection surface 2, optimized in which the noise generated by the reflector diffuser screen 8 is attenuated, or even eliminated.

[0107] Thus, the present invention proposes an optical system comprising a laser emitter that ensures the eye safety of potential observers. The reflector-diffusing screen also increases the apparent angle of the projected image, thereby reducing the risk to the eyes. The optical system thus allows for the projection of an image with higher light intensity while remaining compliant with eye safety standards, resulting in improved illumination and optimized image contrast, even during the day.

[0108] The invention is advantageously suited to a cluttered environment, particularly for integration into a vehicle. The invention is also capable of optimizing the quality of the final image projected onto various projection surfaces.

[0109] The present invention is not limited to the means and configurations described and illustrated herein, and also extends to any equivalent means or configuration and to any technically operative combination of such means insofar as they ultimately fulfill the functionalities described and illustrated in this document.

Claims

Optical projection system (1), particularly for motor vehicles, comprising a laser emitter (3) configured to emit at least one light beam (Fx), an oscillating mirror device (4) configured to reflect the at least one light beam (Fx), said beam forming a light spot (Tx) on the oscillating mirror device (4), and an optical projection device (5) disposed downstream of the oscillating mirror device (4) in a direction of propagation of the at least one light beam (Fx) and configured to project the at least one light beam (Fx) onto a projection surface (2) so as to form a final image (Ifx), characterized in that the optical device (5) comprises a first optical assembly (6), a second optical assembly (7) and a reflecting diffuser screen (8) interposed between said optical assemblies in the direction of propagation of the at least one light beam (Fx) and comprising a reflective portion (84),including a reflective face and / or a reflective layer, capable of directing the light beam towards the projection surface (2) and a diffusing portion (85), configured to reflect and / or split the at least light beam (Fx). Optical projection system (1) according to the preceding claim, further comprising a housing (11) in which the laser emitter (3) is disposed, the reflective portion (84) being able to direct at least one light beam (Fx) through an outlet (12) of the housing (11) so that the optical projection device (5) is configured to project at least one light beam (Fx) through said outlet (12) of the housing (11) towards the projection surface (2). Optical projection system (1) according to the preceding claim, wherein: - the optical device (5) is arranged in the housing (11) so that in the event of failure of the reflecting diffuser screen (8), at least one unreflected light beam (Fx) does not pass through the output (12); and / or - the optical system further comprises a safety device (9) configured to detect a failure of the reflecting diffuser screen (8) in which at least one light beam (Fx) is not reflected by the reflecting diffuser screen (8). Optical projection system (1) according to any one of the preceding claims, wherein an image focus (F1i) of the first optical assembly (6) is disposed at the level of the diffusing portion (85) of the reflecting diffuser screen (8), so as to form an intermediate image (Ix) of the luminous spot (Tx) at the level of said diffusing portion (85) Optical projection system (1) according to the preceding claim, wherein the second optical assembly (7) is configured to project an image of the intermediate image (Ix) onto the projection surface (2), an object focus (F2o) of the second optical assembly (7) being disposed: - at the level of the diffusing portion (85) of the reflecting diffuser screen (8), in particular so as to coincide with the image focus (F1i) of the first optical assembly (6); or - between the reflecting diffuser screen (8) and the second optical assembly (7) according to the direction of propagation of at least one light beam (Fx). Optical projection system (1) according to claim 4, wherein an object focus (F2o) of the second optical assembly (7) is disposed beyond the reflector diffuser screen (8) seen from the second optical assembly (7), so that the reflector diffuser screen (8) is arranged between the second optical assembly (7) and the object focus (F2o) of the second optical assembly (7). Optical projection system (1) according to any one of the preceding claims, wherein the reflecting diffuser screen (8) is defined by an optical blur greater than or equal to 15%. Optical projection system (1) according to any one of the preceding claims, wherein the reflecting diffuser screen (8) comprises a non-uniform heterogeneous structure. Optical projection system (1) according to the preceding claim in which the heterogeneous structure comprises microstructures (83) including at least one of: - a graining; and / or - an irregular heterogeneous holographic pattern; and / or - a plurality of microscopic prisms. Optical projection system (1) according to one of claims 8 or 9, wherein the reflector diffuser screen (8) is configured so as to comprise a plurality of zones each having a diffusion angle (β) of its own, at least two zones (Z1, Z2) having a distinct diffusion angle (β, β1, β2), inversely proportional to a distance separating the zone considered from the reflector diffuser screen (8) from the projection surface (2). Optical projection system (1) according to any one of the preceding claims, comprising a correction device configured to modify at least one light beam (Fx) emitted so as to correct noise generated by the reflector diffuser screen (8). Method of projecting a light beam (Fx) in an optical system (1) according to the preceding claim onto a projection surface (2) comprising: - the determination, by the correction device, of a correction to be applied to at least one light beam (Fx) so as to reduce, or even eliminate, noise generated by the reflector diffuser screen (8); and - the projection of at least one light beam (Fx), via the laser emitter (3), to which said determined correction is applied.

Images