FR3044743A1 - OPTICAL PROJECTION SYSTEM, LUMINOUS MODULE AND LIGHTING DEVICE FOR A MOTOR VEHICLE HAVING SUCH A SYSTEM - Google Patents

Abstract

An optical projection system (2) comprising a plurality of lenses, receiving incident light radiation and collimating said radiation. The plurality of lenses comprises: - a first group (21) of optical diopters, receiving the incident radiation, comprising at least one convex surface (221) carried by at least one lens (L1), providing at least a part of said focusing; a second group (22) of optical diopters, receiving the radiation coming from the first group, comprising at least one concave surface (222) carried by at least one lens (L3), ensuring the correction of chromatic aberrations; a third group (23) of optical diopters, receiving the radiation coming from the second group, comprising at least two convex surfaces 231, 232) and forming at least one lens (L4), ensuring at least a part of said focusing to form a picture.

Description

Projection optical system, light module and lighting device for a motor vehicle comprising such a system

TECHNICAL FIELD OF THE INVENTION The invention relates to an optical projection system, as well as a light module incorporating such a system and a lighting device such as a headlamp or a signaling light for a motor vehicle, comprising such a module.

BACKGROUND ART OF THE INVENTION

In the automotive field, it is known to produce lighting devices comprising one or more modules, each module comprising one or more light sources, different optical processing elements, and an optical system or projection lens.

Different constraints are exerted on the projection objective, especially when the light source (s) are laser sources, namely the need for a large print value to allow the passage of the laser beam, as well as optical constraints. photometric and aperture efficiency, and mechanical bulk, weight and cost.

BRIEF SUMMARY OF THE INVENTION The object of the invention is an optical projection system intended to fulfill the above conditions, both optical and mechanical. For this purpose, the subject of the invention is an optical projection system comprising a plurality of lenses, receiving an incident light radiation and ensuring the collimation of said radiation, the plurality of lenses comprising: a first group of optical diopters, receiving the radiation incident, comprising at least one convex surface carried by at least one lens, providing at least a portion of said focusing; a second group of optical diopters, receiving the radiation coming from the first group, comprising at least one concave surface carried by at least one lens, ensuring the correction of chromatic aberrations; a third group of optical diopters, receiving the radiation from the second group, comprising at least two convex surfaces and forming at least one lens, providing at least a portion of said focusing to form an image.

Thus, the configuration of optical dioptres according to the invention makes it possible to achieve a projection objective whose optical efficiency is optimized and the number and the size of the lenses are minimized, while allowing to obtain a print of sufficient value for an application laser.

According to different embodiments of the invention, which can be taken together or separately: the optical system comprises a focal surface, which can in particular be a plane, the system being intended to cooperate with a light source when this source is arranged at the of this focal surface. the number of lenses of the said plurality of lenses is less than or equal to 5. Collimation is a focusing of the said radiation, for example at infinity. one of said diopters of the first group forms an input diopter of said incident light radiation in the projection optical system. the first group of diopters comprises two convex surfaces. - Both convex surfaces are carried by a biconvex lens. Said biconvex lens is preferably made in a crown glass of refractive index, for example greater than 1.7. one of said diopters of the second group forms an output dioptre of said light radiation out of the projection optical system. the second group of diopters comprises two concave surfaces. the two concave surfaces are borne by the same biconcave lens. Said biconcave lens is preferably made in a refractive index flint glass for example greater than 1.75 and constringence for example less than 30. - the second group of diopters further comprises a biconvex lens. - The exit face of the biconvex lens and the entrance face of the biconcave lens are complementary. The optical power of the assembly is preferably close to zero. the exit face of the biconvex lens and the entrance face of the biconcave lens are contiguous, that is to say that these faces are contiguous. the third group of diopters comprises two convex surfaces. the two convex surfaces are carried by the same biconvex lens. Said biconvex lens is preferably made in a crown glass, for example having a refractive index greater than 1.6 and a constringence of greater than 65. The system further comprises a pupil disposed between the second and third groups of diopters. . the pupil is disposed in the vicinity of the third group of diopters. the second group of diopters comprises a concave surface carried by a concave lens and a convex surface carried by a convex lens. the concave surface of the second group forms the exit surface of the concave lens, the entry face of which is flat. the convex surface of the second group forms the entrance surface of the convex lens, the exit face of which is plane. the entry face of the concave lens and the exit surface of the convex lens of the second group are contiguous. the third group of diopters further comprises a concave surface. the concave surface of the third group is carried by a lens whose second face is convex. the concave surface of the third group forms the entrance surface of the lens, the second face of which is convex. The lenses may alternatively be made of plastic material, for example polymethyl methacrylate, polycarbonate, or silicone. at least one diopter of the first, second and third groups of diopters is a surface capable of correcting field aberrations and / or spherical aberrations. the one or more dioptres capable of correcting the field aberrations each have an aspheric form. At least one exit face of the first, second and third groups of diopters, or even each, has an aspherical shape. The invention also relates to a light module comprising a projection optical system, as specified above, further comprising a light emitting means capable of supplying incident light radiation to the projection optical system, the optical system of projection ensuring the collimation of said light radiation.

The light emitting means is preferably a wavelength conversion device, the light module further comprising a light source providing a monochromatic light beam, in particular a laser source. Where appropriate, the monochromatic light beam is preferably collimated.

The module comprises, for example, means for scanning the light beam, the wavelength conversion device receiving the beam coming from the scanning means and supplying the incident light radiation to the projection system.

Preferably, the draw is determined to allow an incident laser beam to scan the surface of the converter, the beam arriving at an incidence of about 60 ° in the center of the converter and scanning a predefined surface, for example plus or minus 10 ° vertical and plus or minus 20 ° horizontally.

In one embodiment of the invention, the scanning means comprise at least one oscillating mirror. The invention finally relates to a lighting and / or signaling device, in particular for a motor vehicle, comprising such a module.

BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will emerge from the detailed description which follows, given for information only and illustrated by the appended drawings, in which: FIG. 1 is a partial schematic view of a embodiment of a light module using an optical projection system according to the invention; FIG. 2 is a schematic view of a first embodiment of the projection optical system according to the invention; FIG. 3 is a schematic view of a second embodiment of the projection optical system according to the invention.

In these different figures, the same references refer to the same elements.

DETAILED DESCRIPTION OF THE FIGURES

In Figure 1, there is shown a partial schematic view of an embodiment of a light module using a projection optical system according to the invention.

In this figure, there is shown a monochromatic incident light beam 10, preferably collimated, for example produced by one or more laser sources (not shown), for example laser diodes, and is then typically blue.

A substantially white light beam, usable for lighting applications for a motor vehicle, is obtained from the laser beam 10 by means of a wavelength-converting optical element 13, often called phosphor.

The beam 10 may have undergone various optical treatments before its arrival on the converter 13, such as for example be passed by means printing a scanning one or two dimensions and / or diffusion means to expand the laser spot.

Of these different treatments, operated in a conventional manner, only illustrated in the figure an oscillating mirror device 11, for example of the MEMS type (initials of Micro Electro-Mechanical System in English for micro electromechanical system), printing beam 10 a one or two dimensional scanning.

FIG. 1 illustrates three possible positions of the beam after passing through the scanning means 11, globally marked 12.

The wavelength converter 13 comprises for example an optical material ensuring the wavelength conversion and a reflective material.

The converter material is formed in any known manner, for example grains, ensuring the conversion of wavelength, embedded in a binder. The grains may be formed of Yttrium-Aluminum garnets (known as YAG for Yttrium Aluminum Garnet in English) and Europium. The binder is for example a silicone-based material.

The converter material and the reflector are for example each in the general form of a wafer, the wafers being advantageously contiguous to each other by any known means.

The light rays emitted by the converter 13, illustrated by globally marked arrows 14, are optically treated by an optical system or projection lens according to the invention, globally marked 2, intended to form a projected light beam on the road and illustrated by globally marked arrows 20.

FIG. 2 represents the diagram of a first embodiment of the projection optical system 2 of FIG. 1.

In this figure, there is shown a plane on which is positioned the output surface of the wavelength converter 13 of Figure 1, this plane is also marked 13 for convenience. The light rays 14 coming from the converter 13 pass through a plurality of lenses forming the optical projection system 2, which system focuses the incident rays 14 to constitute the output beam 20. The plane 13 is located at the focal plane of the objective 2.

According to the invention, the objective 2 comprises three groups of optical dioptres, respectively 21, 22 and 23, arranged in this order on the path of the light rays.

The first group of diopters, 21, has two convex surfaces 211 and 212, preferably forming the input and output faces, respectively, of a single convergent biconvex lens L1.

This first group 21 has the function of focusing the light rays, preferably only in part, the third group 23 also having the function of ensuring the convergence of the beam, as detailed below.

The second group of diopters, 22, comprises at least two concave surfaces 221 and 222. These two concave surfaces can form the input and output faces, respectively, of a single biconcave divergent lens L3.

This second group receives the light rays from the first group 21 and has the function of correcting the chromatic aberrations of light rays.

In an alternative embodiment which is that shown in FIG. 2, two concave surfaces 221 and 222 are added two convex surfaces 223 and 224, forming the input and output faces, respectively, of a second lens L2, arranged on the path of the light rays upstream of the concave surfaces 221 and 222. In this variant, the lenses L2 and L3 are advantageously contiguous, their surfaces 224 and 221 facing each other being complementary. The optical power of the assembly is in this variant close to zero, in order to maintain sufficient optical power to form the desired beam.

The third group of diopters, 23, comprises two convex surfaces 231 and 232. These two convex surfaces 231 and 232 can form the input and output faces, respectively, of a single convergent biconvex lens L4.

This third group 23 receives the light rays from the second group 22 and has the function of focusing the light rays to form a projected image on the road. Advantageously, the complementary convergence of the group 21 makes it possible to finely adjust the draw and the focal length of the objective to the desired values.

FIG. 2 illustrates the radii 14 coming from the converter 13, representing the rays coming from various points of the converter: a central point 130, a point 131 on the periphery of the converter and any three points 132, 133 and 134 disposed between the two.

The central radius 130a from the central point 130 coincides with the optical axis of the objective 2, marked 26; the extremal rays 130b and 130c coming from this same central point 130 illustrate the opening of the system at this point 130, that is to say the limit of the light rays likely to leave the objective 2.

The rays from each of the points 130-134 are deflected conventionally by each of the L1-L4 lenses as a function of their refractive index and their thickness at the point of incidence. The parameters of the lenses, namely in particular the geometry of the input and output dioptres of the lens, the focal length, the refractive index and the relative arrangement of the lenses, are conventionally chosen to obtain the desired beam at the output of the last lens L4. , for example using software for calculating optical systems. By way of example, the output beam 20 extends below the horizontal (assumed in FIG. 2 represented by the optical axis 26), as illustrated on a virtual plane arbitrarily disposed at the output of the lens 24, at close to the latter and perpendicular to the optical axis 26.

The rays coming from the various points 130-134 of the converter 13 intersect in a plane 24, which is the plane where advantageously a physical element, lens or dedicated element, called aperture diaphragm or pupil, which limits the passage of the radii bright and defines the opening of the system.

In the embodiment of Figure 2, it is a dedicated element whose opening is shown in dashed lines, also referenced 24. The opening of the pupil 24 is determined so that the rays from the central point 130 illuminate a maximum surface of the lens L4, maximizing the photometric efficiency and thus limiting the size of the lens L4 and the light power necessary for the same intensity of illumination.

In addition and advantageously, the lens parameters are defined so that this plane 24 is located as close as possible to the output lens L4, to limit the vignetting phenomena.

Various special provisions can be applied to minimize / correct the chromaticism and optical aberrations of the lens.

First, aspherical surfaces can be used for some diopters, to correct field aberrations (ie those that vary depending on the field, such as field curvature) or aperture aberrations (such as spherical aberrations for example). These surfaces are calculated conventionally using, for example, calculation software. For example, the aspherical surfaces may be two in number and carried by the exit faces of the lenses L1 and L4. In an alternative embodiment, the two aspherical surfaces can be carried by the input surfaces of these same lenses.

Also, so-called "special" glasses can be used to make the lenses for the purposes mentioned above and as illustrated in the embodiment given below. By way of example, a projection lens has been produced in accordance with FIG. 2, with the following parameters: focal length of the objective: 25 mm; draw (between converter 13 and lens L1): 10.6 mm - length of the objective: 41.5 mm; - diameter of the lens: 39 mm; - openness of the lens: F / 0.8; L1 lens: crown glass with a high index (greater than 1.7); focal length: 34 mm; thickness on the optical axis: 8 mm; L2 lens: crown glass of high index (greater than 1.7) which may be the same as that of the lens L1; focal length: 39 mm thickness on the optical axis: 13 mm; - L3 lens: flint glass of high index (greater than 1.75) with low constringence (Abbe number less than 30); focal length: - 36 mm; thickness on the optical axis: 3 mm; - L4 crown glass lens with high constringence (Abbe number> = 65) and a fairly high index (about 1.6); focal length: 38 mm; thickness on the optical axis: 10 mm; distances, taken on the optical axis, of the pupil 24 at L4: 0.7 mm, and at L3: 6 mm.

It should be noted that, preferably, the print is determined to allow an incident laser beam 12 to scan the surface of the converter 13, the beam arriving at an incidence of about 60 ° in the center of the converter and scanning a predefined surface, for example, plus or minus 10 ° vertically and plus or minus 20 ° horizontally.

FIG. 3 represents the diagram of a second embodiment of the projection optical system 2 of FIG. 1.

In this figure, there is the wavelength converter 13 from which are emitted the light rays 14, the three groups of optical dioptres 21, 22 and 23 always arranged in this order on the path of the light rays, and a pupil 240 having the same functions as the pupil 24 of Figure 2 and arranged as it between the groups of dioptres 22 and 23, as close as possible to the output group 23.

The first group of diopters, 21, comprises at least one convex surface 112, preferably carried by a convergent lens L11; the surface 112 forms the exit surface of this lens L11, its entry surface 111 being flat in this embodiment.

The second group of diopters, 22, has a concave surface 132 forming for example the exit surface of a diverging lens L13, whose input surface 131 is for example flat. In this embodiment, the diopter group 22 further comprises a convex surface 121 forming the input face of a convergent lens L12, whose output face 122 is for example flat. The faces 122 and 132 are advantageously contiguous.

The third group of diopters, 23, has three convex surfaces, 142, 151 and 152. The first of these surfaces in the path of the light rays, 142, forms the exit surface of a lens L14 whose input surface 141 is concave. The other two convex surfaces, 151 and 152, advantageously form the entry and exit surfaces of the same biconvex lens L15.

FIG. 3 illustrates, as previously, the path of the light rays coming from the central point 130 of the converter 13, the peripheral point 131 and the various intermediate points 132, 133 and 134. It is observed as previously in the plane 25 that the beam output 20 extends below the horizontal.

In this embodiment, aspherical surfaces are for example made on the exit faces of the lenses L11 and L13.

In an exemplary embodiment, an objective according to Figure 3 has a pull of 11 mm, a focal length of 25 mm, an opening of F / 0.8, a length of 44 mm and a diameter of 38 mm. The focal lengths of the lenses L15, L14, L13, L12 and L11 are 101 mm, 76 mm, 20 mm, 29 mm and 26 mm, respectively.

In any of its embodiments, the objective according to the invention is perfectly suited to automobile lighting or signaling, and in particular to the production of projectors with complex functions of the adaptive lighting type, for example for turns or to avoid dazzling other vehicles.

It thus appears that the projection optical system according to the invention constitutes an imaging system which achieves a compromise between the photometric efficiency and an imaging quality which is compatible with the applications envisaged, such as those listed above, and which allows to use a limited number of lenses in a lens whose dimensions are not too large, while allowing a large value of the print to let through the incident laser beam, a large field (greater than 40 °), and a large opening that promotes good photometric efficiency.

Claims (15)

An optical projection system, comprising a plurality of lenses, receiving an incident light radiation (14) and providing collimation of said radiation, the device being characterized in that the plurality of lenses comprises: a first group (21) of optical diopters receiving incident radiation (14), having at least one convex surface (221, 112) carried by at least one lens (L1, L11), providing at least a portion of said focusing; - a second group (22) of optical dioptres, receiving the radiation from the first group, comprising at least one concave surface (222, 132) carried by at least one lens (L3, L13), ensuring the correction of chromatic aberrations; a third group (23) of optical diopters, receiving the radiation coming from the second group, comprising at least two convex surfaces (231, 232; 151, 152) and forming at least one lens (L4, L15), ensuring at least one part of said focusing to form an image. 2. System according to claim 1, characterized in that the first group (21) of diopters comprises two convex surfaces (211,212) carried by a biconvex lens (L1). 3. System according to one of the preceding claims, characterized in that the second group (22) of the dioptres comprises two concave surfaces (221,222). 4. System according to claim 3, characterized in that the second group (22) of diopters further comprises a biconvex lens (L2). 5. System according to claim 4, characterized in that the exit face (224) of the biconvex lens (L2) and the entry face (221) of the biconcave lens (L3) are complementary and contiguous. 6. System according to one of the preceding claims, characterized in that the third group (23) of diopters comprises two convex surfaces (231,232). 7. System according to one of the preceding claims, characterized in that it further comprises a pupil (24, 240), disposed between the second (22) and third (23) groups of diopters. 8. System according to claim 7, characterized in that the pupil (24, 240) is disposed adjacent the third group (23) of diopters. 9. System according to claim 1, characterized in that the second group (22) of diopters comprises a concave surface (132) carried by a concave lens (L13) and a convex surface (121) carried by a convex lens (L12 ). 10. System according to claim 9, characterized in that the concave surface (132) forms the exit surface of the concave lens (L13), whose input face (131) is flat, and that the convex surface ( 121) forms the entrance surface of the convex lens (L12), whose exit face (122) is flat, the entrance face of the concave lens and the exit surface of the convex lens being contiguous. 11. System according to claim 1, characterized in that the third group (23) of diopters further comprises a concave surface (141) carried by a lens (L14) whose second face (142) is convex. 12. System according to one of the preceding claims, characterized in that at least one diopter of the first, second and third groups of diopters is a surface capable of correcting field aberrations and / or spherical aberrations. 13. A light module comprising an optical projection system (2) according to one of the preceding claims, characterized in that it comprises a light emitting means capable of supplying light radiation incident to the projection optical system (14). ), the projection optical system ensuring the collimation of said light radiation. 14. Light module according to the preceding claim, characterized in that the light emitting means is a wavelength conversion device, the light module further comprising a light source providing a monochromatic light beam (10), scanning means (11) of the light beam and a wavelength converting device (13) receiving the beam (12) from the scanning means and supplying the incident light radiation (14) to the projection system. 15. Lighting device and / or signaling including a motor vehicle, characterized in that it comprises a module according to one of claims 13 or 14.