Microlens array for an optical system

Abstract

The present invention relates to a microlens array (1) for an optical system of a vehicle, the array (1) comprising a plurality of microlenses (3) configured to generate an illumination and / or signaling light beam (5, 5a, 5b, 5c, 5d), each microlens (3) comprising at least one diopter (7) configured to be traversed by light rays (4, 4a, 4b, 4c, 4d), each diopter (7) comprising a plurality of straight striations (6) resulting from the manufacture of the microlens array (1), characterized in that the striations (6) of at least one first set of microlenses (2, 2a) extend according to an orientation different from the orientation of the striations (6) of at least one second set of microlenses (2, 2b). The invention also relates to a method for manufacturing such a microlens array (1).

Description

Microlens array for optical system

[0001] The present invention relates to the field of optical lighting and / or signaling systems of a vehicle, and more particularly to a microlens matrix integrated within such optical systems.

[0002] Vehicles, and in particular motor vehicles, are commonly equipped with headlights to generate various lighting functions such as road lighting or vehicle signaling to other road users.

[0003] It is now known, for at least some of these lighting and / or signaling functions, to implement an optical system within the vehicle's headlights, comprising a light source and a microlens array, also known by the acronym MLA for "microlens array". The array includes a plurality of input microlenses and a plurality of output microlenses.

[0004] The microlens array is configured to form light circulation channels extending respectively between at least one of the input microlenses and at least one of the output microlenses, and each microlens is configured so that within a given light circulation channel, focusing that input microlens illuminates an output microlens to achieve the desired lighting function.

[0005] Microlenses can have a diopter, forming an entry or exit face for the rays, measuring 1 mm². The fabrication of an array of such microlenses in this context is achieved either through direct precision machining of the microlenses from a block of suitable transparent material, or via an injection molding operation of this material. In the latter case, precision machining is also necessary to create precise counterforms on the mold corresponding to each of the microlenses to be formed by injection; this can then be referred to as indirect precision machining of the microlenses.

[0006] At this scale, polishing the machined surface after direct or indirect machining of the microlenses is not possible, and the machining operation thus generates striations at the diopters. These striations are fine and faint, but are nevertheless sufficient to generate parasitic diffraction of light rays passing through the microlens array, perpendicular to the orientation of the striations that these light rays encounter.

[0007] The present invention falls within this context and proposes a microlens matrix for a vehicle optical system, comprising a plurality of microlenses configured to generate a light beam for lighting and / or signaling, each microlens comprising at least one diopter configured to be traversed by light rays, each diopter comprising a plurality of straight striations resulting from a fabrication of said microlens matrix, characterized in that the striations formed on the microlenses of at least a first set of microlenses extend in a different orientation from the orientation of the striations formed on the microlenses of at least a second set of microlenses.

[0008] The microlens array according to the invention is configured such that the striations formed on the surface of the microlenses, resulting from the manufacturing of the microlens array, are oriented in different directions. This allows for the generation of multiple diffraction orientations of light rays exiting the optical system equipped with such a microlens array, the orientation of the rays diffracted by the diopter of a microlens being dependent on the orientation of the striations formed on its surface. Such a configuration ensures the attenuation of potential overall diffraction extending in a single direction by reducing the number of rays likely to be diffracted in that direction, and by forcing these rays to diffract in another direction.

[0009] A microlens array comprises a plurality of input microlenses and a plurality of output microlenses, corresponding respectively to the input of light rays emitted by a light source and the output of these rays as a light beam capable of generating illumination. The diopters of the microlenses correspond to one of the input or output faces of the microlens array. In other words, the diopter of a microlens constitutes the face that separates the external environment from the microlens material. It is at this diopter, on a surface facing outwards from the microlens array, that striations are formed. These striations are formed unintentionally as a result of a machining operation used to manufacture the microlens array, either by direct machining or injection molding.Each microlens exhibits a series of parallel striations on its diopter, defining a direction of striation elongation. Thus, within the scope of the invention, the striations are solely a direct consequence of the manufacturing process used for the microlens array. The striations are inherent to said manufacturing process. Therefore, the striations do not correspond to patterns whose detailed shape results from a specific optical design intended to generate a predetermined shape of the light beam. They correspond to the surface roughness of the microlens, that is, of a diopter of the microlens. The roughness measured on a diopter of a microlens corresponds to the arithmetic mean roughness, abbreviated as Ra, which is an absolute average with respect to a fundamental dimension of said diopter of said microlens.

[0010] From a perspective parallel to the optical axis of the microlenses, the striations appear straight; in other words, when the surface of a microlens is viewed head-on, the striations formed on that surface appear straight. It should be noted that in practice, the striations follow the shape of the lens surface and are therefore mostly curved.

[0011] The input and output microlenses are grouped into microlens arrays. Each microlens array comprises a plurality of microlenses that can be grouped together based on their positioning relative to the array or their proximity to each other, and / or the positioning of the light rays that the microlenses transmit within the overall light beam generated by the optical system comprising the microlens array. For example, the microlenses through which the rays that contribute to forming the upper part of the projected light beam pass can be grouped into a first microlens array, and the microlenses through which the rays that contribute to forming the lower part of this projected light beam pass can be grouped into a second microlens array.According to this latter configuration, the microlenses of the same set of microlenses are therefore not necessarily positioned adjacently to each other within the microlens matrix.

[0012] All microlenses in the same microlens set have striations oriented in the same direction. In other words, all the striations formed on the surface of a microlens associated with a microlens set extend parallel to the striations formed on the surface of the microlenses in the same set.

[0013] To achieve the goal of the invention of controlling the refraction phenomenon in the overall projected beam, the striations formed on the microlenses of two distinct sets of microlenses are configured such that the striations associated with one set of microlenses extend in a different orientation than the striations associated with a second set of microlenses. Thus, the light beam generated by the first set of microlenses and the light beam generated by the second set of microlenses each exhibit a diffraction phenomenon extending in a different principal direction relative to the other, which limits the maximum intensity of an overall parasitic diffraction phenomenon by generating several diffraction phenomena in different directions that compensate for each other.

[0014] According to a non-limiting feature of the invention, the striations of the microlenses of two adjacent sets of microlenses extend in a different orientation from one set to the other. In this context, by increasing the number of sets of microlenses, it is possible to maximize the number of different orientations of diffraction phenomena generated and thus limit the magnitude of the overall diffraction phenomenon.

[0015] According to a non-limiting feature of the invention, the microlens array is configured to generate a cutoff beam. Such a cutoff beam can, for example, be used for dipped headlights, the projected shape of which must conform to regulations, with the upper portion of the beam truncated by the cutoff. Since the purpose of this cutoff is, in particular, to prevent dazzling other road users, it is essential to ensure that the cutoff is clean and that the diffraction of the light rays forming the portion of the beam closest to the cutoff is controlled, resulting in little or no stray light beyond the cutoff.

[0016] According to a non-limiting feature of the invention, the microlens array comprises at least one peripheral microlens assembly configured to project a portion of the light beam having a cutoff edge. The striations formed on the surface of the microlenses associated with this peripheral microlens assembly extend in an orientation determined by the orientation of the cutoff edge. In other words, the direct or indirect machining that generates the striations on the microlenses is performed such that these striations associated with a peripheral assembly are oriented according to the direction of the cutoff edge of the light beam generated by an optical system comprising the microlens array, according to this non-limiting aspect of the invention. This configuration makes it possible to enhance the sharpness of the cutoff by preventing the propagation of diffraction phenomena beyond the cutoff edge.

[0017] The term "peripheral," referring to the peripheral microlens array, means that this array projects a peripheral portion of the light beam. It should be noted that this peripheral microlens array is not necessarily arranged at the periphery of the microlens matrix.

[0018] According to a non-limiting feature of the invention, when a light beam is projected onto a screen perpendicular to a principal propagation direction of said light beam, the orthogonal projections onto this screen of the striations formed on a large majority of the microlenses of the peripheral microlens array form segments oriented in a direction perpendicular or substantially perpendicular to a direction of the cutoff edge of the light beam generated by light emanating from these microlenses. As previously stated, the orientation of the rays diffracted by the diopter of a microlens depends on the orientation of the striations formed on the surface of that microlens, and more particularly, the light rays are diffracted perpendicular to the direction of elongation of the striations. Thus, striations perpendicular to the cutoff edge result in a diffraction phenomenon parallel to said cutoff edge.This ensures that the diffraction pattern propagates along the cutoff edge but does not extend beyond it. The projected cutoff beam thus exhibits a clean break, free from stray light rays extending beyond the cutoff.

[0019] According to a non-limiting feature of the invention, the microlens array is configured to project a cutoff light beam comprising a step connecting two parallel edges offset from each other, the peripheral microlens assembly comprising at least a first subset of microlenses configured to generate a portion of the light beam disposed along a parallel edge and a second subset of microlenses configured to generate a portion of the light beam disposed along a slope of the step, the striations of the microlenses associated with the first subset of microlenses being oriented in a direction perpendicular to the direction of one of the two parallel edges, the striations of the microlenses associated with the second subset of microlenses being oriented in a direction perpendicular to the direction of the slope of the step.In the case of a cut-off light beam with a step, the principle is the same as described previously, that is to say that the striations are oriented perpendicular to the edges.

[0020] The first subset of microlenses consists of microlenses positioned to project the portion of the light beam near the parallel edges. When the microlens array is positioned within the optical system, the projected parallel edges form the upper part of the light beam. The striations of the first subset of microlenses are perpendicular to the parallel edges, thus generating a diffraction pattern parallel to the parallel edges, preventing the projection of stray light rays beyond the cutoff of the light beam.

[0021] The principle is identical for the second subset of microlenses that project the portion of the light beam near the step. The striations of the second subset of microlenses are perpendicular to the slope of the step. The orientation of the striations is therefore dependent on the orientation of the step's slope. This generates a diffraction phenomenon that extends parallel to and along the slope of the step.

[0022] Thus, thanks to the configuration of the peripheral microlens assembly, the cutoff beam is perfectly delimited in order to avoid any stray light rays extending beyond the cutoff and originating from a diffraction phenomenon due to the striations of the microlenses.

[0023] According to a non-limiting feature of the invention, the peripheral microlens array represents a portion of the microlenses such that the part of the light beam generated by the microlenses of this peripheral microlens array extends to a height of approximately 20% of the total height of the overall light beam generated by the microlens array. The height of the portion of the light beam generated by the microlenses of this peripheral microlens array represents, in particular, between 15% and 25% of the total height of the overall light beam generated by the microlens array.

[0024] According to a non-limiting feature of the invention, each microlens is offset in a direction perpendicular to the diopter with respect to at least one adjacent microlens. The microlenses can be arranged in a stepped pattern such that the microlens array forms a curvature designed to conform to the shape of a projector within which the optical system comprising said microlens array is arranged.

[0025] It is primarily because of this curved shape of the microlens matrix that it is not possible to polish the microlenses to eliminate striations without compromising the optical quality of the microlens matrix.

[0026] According to a non-limiting feature of the invention, the microlenses of the first set of microlenses are mixed with the microlenses of the second set of microlenses. In other words, for example, a microlens of the second set of microlenses can be completely surrounded by microlenses of the first set of microlenses. Thus, each set of microlenses is distributed across the entire microlens array. This distribution improves the aesthetics of the lighting device as perceived by a third-party observer. Indeed, it allows for the observation of homogeneous illumination across the entire lighting device, and it also ensures that this homogeneous illumination remains consistent regardless of the viewing angle from which the lighting device is observed.

[0027] According to this particular configuration, and as previously mentioned, the microlenses within the same microlens array are not necessarily adjacent to each other. Similarly, the microlenses in the peripheral microlens array are also not necessarily adjacent to each other.

[0028] The invention also covers a method for manufacturing a microlens array as described above, comprising a machining step via a microlens array machining tool or a mold for manufacturing the microlens array, said machining step directly or indirectly generating a plurality of straight striations on a diopter of each microlens, characterized in that the machining step is implemented so as to generate striations of at least a first set of microlenses extending in a different orientation from the direction of the striations of at least a second set of microlenses.

[0029] Whether the microlens matrix is ​​manufactured by direct machining or by molding, striations are necessarily formed on an entry and / or exit face of the microlenses that make up said microlens matrix. In the case of direct machining, the machining tool directly forms the striations on the diopters.

[0030] If the microlens array is formed by molding, the striations are created by the machining tool on the mold, and the subsequent molding operation results in the formation of striations on the microlens diopters. This configuration corresponds to an indirect generation of striations during the machining of the microlens array.

[0031] To manufacture the microlens array according to the invention, the machining tool must therefore machine the microlens array or the mold in such a way as to form striations in different directions for at least two sets of microlenses. The striations thus formed prevent the generation of a diffraction phenomenon extending in a single direction.

[0032] According to a non-limiting feature of the process, the orientation of the striations in the microlens arrays depends on the direction of movement of the machining tool during the machining step. It is the movement of the machining tool in a given direction that generates the striations extending in the same direction. In order to produce microlens arrays with striations in different directions, the machining tool, during the fabrication of the microlens matrix or mold, must change its machining direction to generate these microlens arrays with striations in different directions. Therefore, it is the direction of movement that determines the orientation of the striations.

[0033] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:

[0034] is a schematic representation of an optical system comprising a microlens array according to one aspect of the invention;

[0035] is a perspective view of a microlens array according to the invention, particularly illustrating an array of microlenses,

[0036] is a view of the microlens array illustrating a plurality of microlens sets,

[0037] is a schematic representation of a portion of the microlens array according to the invention, applied to a cutoff light beam.

[0038] In the following description, we will refer to an orientation based on the longitudinal, vertical, and transverse axes as arbitrarily defined by the L, V, T trihedron shown in Figures 1 to 4. The vertical and transverse axes V and T contribute to defining a principal elongation plane of the microlens array, which is part of the optical system. This elongation plane is perpendicular to the longitudinal axis L, which represents the principal direction of propagation of light rays from the emission source and out of the microlens array. The vertical direction V is perpendicular to both the longitudinal and transverse axes L and T. For example, the vertical direction V is perpendicular to the ground on which the vehicle equipped with such an optical system rests. The direction V then represents the vertical direction of the optical system when it is in its normal operating position and orientation.

[0039] The diagram schematically illustrates an optical system 100 comprising a microlens array 1, a collimator 101 and light emission means 102. The optical system is particularly suitable for equipping a motor vehicle, said optical system operating at least one function of lighting and / or signaling the vehicle.

[0040] The light source(s) of the light emission means 102 are arranged in the vicinity of a focal plane comprising a principal optical axis 104 of the optical system, this optical axis being longitudinal here.

[0041] The collimator and the light source(s) are positioned relative to each other so that the light rays emitted by the light-emitting means 102 pass through the collimator 101. This collimator 101 is configured to orient all the light rays emitted by the light-emitting means parallel to each other and to direct them towards the microlens array 1, and more specifically towards an input microlens array.

[0042] The microlens array 1, or matrix device, comprises said input microlens array, an output microlens array and, where applicable, a mask interposed between the input microlens array and the output microlens array, each microlens array and the mask where applicable extend mainly along a vertical and transverse plane, perpendicular to a longitudinal direction L along which extends the principal optical axis 104 previously mentioned.

[0043] The output microlens array forms an illumination surface for the optical system, that is, a surface through which light rays exit to generate a beam of light outside the vehicle. It should be noted that the lighting device may include a transparent or translucent screen downstream of the output microlens array without departing from the scope of the invention.

[0044] The input microlens matrix, respectively output microlens, is formed of a plurality of input microlenses, respectively output microlenses, juxtaposed next to each other, both in the vertical direction, as seen on the, and in the transverse direction.

[0045] Each input microlens is configured within the matrix arrangement so that it presents an image focus on the mask when the mask is interposed between the input and output microlenses, or in the vicinity of the corresponding output microlens. Light rays from collimator 104 and passing through an input microlens converge either directly onto the corresponding output microlens or onto a focal point on the mask, onto which the corresponding output microlens is also focused.

[0046] In the illustrated example, the input microlenses and output microlenses, respectively, are identical except for the orientation of striations formed on their surface, according to the invention and as described below. Without departing from the scope of the invention, the input and output microlenses, respectively, could exhibit other points of difference from one microlens to another, in addition to the orientation of the striations.

[0047] The microlens array 1 comprises a plurality of microlens sets 2, themselves composed of a plurality of microlenses 3. It should be noted that in the illustrated example, the microlens array comprises two microlens sets with a first set comprising three rows of microlenses and a second set comprising eight rows of microlenses, but that this example is given only as information without limitation of the invention.

[0048] Laest is a partial schematic representation of a microlens array 1 according to the invention.

[0049] Such a microlens array 1 is manufactured by machining using a machining tool. Machining can be performed directly on the material of the microlens array 1, or it can enable the fabrication of a mold subsequently used to manufacture the microlens array 1 by molding. In both cases, and as illustrated in Figure 1, which shows a partial representation of a microlens 3 of the microlens array, the machining generates a plurality of striations 6 on a diopter 7 of each microlens 3. These striations 6 are due to the passage of the machining tool over the microlens 3 or over the mold, which subsequently transfers the striations 6 onto the molded microlens array 1.

[0050] Each microlens measures approximately one millimeter, with a diopter, forming an entry or exit face for the rays, measuring 1 mm². Polishing to eliminate these striations 6 is therefore a delicate operation due to the small size of the microlenses 3 and the fact that they can be arranged in a specific configuration, as illustrated. The microlenses 3, or microlens arrays 2, can be arranged with an offset in a direction perpendicular to the diopter 7, forming a stepped pattern. This configuration allows, for example, adaptation to the shape of a projector within which the previously mentioned optical system includes the microlens array 1.

[0051] On the image, the striations 6 are vertical. Such vertical striations 6 generate a horizontal diffraction phenomenon 8 of the light beam FL exiting the microlens array 1, in the transverse direction because the principal propagation of the rays is longitudinal here. This diffraction phenomenon 8 is a parasitic phenomenon resulting from the unwanted presence of the striations 6 on the interface 7 of the microlenses 3. In general, the diffraction phenomenon 8 extends in a direction perpendicular to the principal propagation direction of the light rays and perpendicular to an orientation of the striations 6 causing said diffraction phenomenon 8.

[0052] On the, the striations 6 are present on an input microlens 3 of the light rays 4 but the striations can also be present at the level of a diopter of an output microlens.

[0053] In order to mitigate the impact of the diffraction phenomenon 8, the microlens array 1 according to the invention is configured so that at least a first set of microlenses 2a is formed by microlenses on which it has been ensured that the striations 6 are oriented in a different direction from that of the striations 6 formed on microlenses of at least a second set of microlenses 2b, as illustrated in.

[0054] In this diagram, a portion of the microlens matrix 1 is represented, with four sets of microlenses 2a, 2b, 2c, 2d, each of these microlens sets 2 comprising a plurality of microlenses. The schematic representation and the size of the microlenses do not allow each microlens within one of the sets to be visible, but it is noteworthy that the number of microlenses within a given set can differ from one set to another, and that for a given set, all the microlenses forming part of that set exhibit a common striation orientation, which is schematically illustrated in the diagram.Each set of microlenses 2a, 2b, 2c, 2d is respectively traversed by light rays 4a, 4b, 4c, 4d and generates respectively a light beam 5a, 5b, 5c, 5d, the addition of these light beams 5a, 5b, 5c, 5d allowing at the output of the optical system to generate a global light beam which can be in particular a lighting beam.

[0055] According to the configuration illustrated, the microlenses in each microlens set 2 are grouped so as to be adjacent to one another. However, alternatively, microlenses can be grouped into a single microlens set 2 without being adjacent to each other. A microlens set can then be defined by the direction of its striations 6 and / or by the portion of the light beam 5 that it projects.

[0056] According to the invention, the precision machining carried out to form the microlenses directly or indirectly is carried out in such a way that the diopters of the microlenses of one of the microlens sets 2, 2a, 2b, 2c, 2d comprise striations 6 which are oriented along a common elongation direction which is different from the common elongation direction of the striations 6 formed on the microlenses of another microlens set 2, 2a, 2b, 2c, 2d, and in particular of an adjacent microlens set.

[0057] Since each microlens array 2 comprises striations 6 oriented in a different direction from one microlens array to another, the diffraction phenomenon 8 associated with each light beam 5a, 5b, 5c, 5d, oriented perpendicularly to the orientation of the striations 6, also extends in a different direction from one diffraction phenomenon to another. This configuration according to the invention avoids generating a diffraction phenomenon in a single direction for the entire microlens array 1, which is much more pronounced and disruptive. By generating diffraction phenomena 8 in different directions, the overall diffraction is thus homogenized, and this limits the intensity of stray rays due to unidirectional diffraction.

[0058] In order for the microlens array 1 to be configured to generate diffraction phenomena 8 in different directions, the striations 6 of the microlens arrays 2 must therefore be formed in different directions relative to each other. Advantageously, as illustrated in Figure 1, each striation 6 of a microlens array 2 extends parallel to, in a different orientation from, the striations 6 of the adjacent microlens arrays 2, the striations 6 of said adjacent microlens arrays 2 also extending in a different orientation relative to each other.

[0059] In order to form striations 6 in different directions relative to each other, such a microlens array 1 is obtained via a manufacturing process comprising a machining step using a machining tool as previously mentioned. The machining step is implemented so that at least two sets of microlenses 2 comprise striations 6 oriented specifically from one set to the other, with the striations formed on the microlenses of a first set of microlenses being oriented differently from the striations formed on the microlenses of a second set of microlenses.

[0060] The implementation of such a manufacturing process can be done directly, i.e. by directly machining the material composing the microlens matrix, or indirectly, i.e. by machining the mold subsequently used to perform the molding of the microlens matrix 1.

[0061] To achieve this, the machining tool performs its machining operation in multiple directions to generate grooves in different directions. More specifically, the machining tool is driven to make several passes along a parallel movement direction along the surface of a microlens, or of a mold counterform intended for the injection molding of a microlens surface. This direction of movement of the machining tool can, for example, be maintained until all the microlenses in the microlens set, or all the corresponding mold counterforms, are machined, and this direction is then changed to make passes in a different orientation to machine all the microlenses in another microlens set, or all the corresponding mold counterforms.This can be done, for example, by regularly changing the direction of movement of the machining tool, by programming the latter to change direction with each machining of a new set of microlenses 2.

[0062] This is a view of a microlens array 1 configured to project a cutoff light beam FL. In this particular configuration, the grooves 6 of some of the microlens arrays 2 are oriented to optimize the projection of the cutoff light beam and, in particular, to control the diffraction of the rays within this FL light beam.

[0063] It should be noted that in the schematic representation of the beam, lines representing the orientation of the striations on the microlenses are embedded within the beam to facilitate understanding that the orientation of the striations formed on the microlenses is a function of the orientation of a cutoff edge of the beam. The schematic representation of the light beam FL is that of its projection onto a screen perpendicular to a principal propagation direction of said light beam. The screen is advantageously placed at a large distance relative to the dimensions of the optical system, for example, 25 m. The lines are the segments resulting from an orthogonal projection of the striations onto the screen and are thus representative of the striation orientation.Of course, in the projected FL light beam, the 6 striations are not visible and on the contrary induce a diffraction phenomenon 8 perpendicular to the orientation of the striations and also illustrated schematically on the.

[0064] The cutoff beam is characterized by the presence of a raised section 9 which helps to form two parallel edges 10, 11 offset from each other, the offset being considered along a direction perpendicular to each of the planes in which these parallel edges 10, 11 respectively extend. The shape and size of the raised section 9 are defined in particular by the inclination of a slope 12 connecting the parallel edges 10, 11. This configuration of the FL beam allows for a limited-range lighting function on one side of the road to avoid dazzling oncoming vehicles.

[0065] The parallel edges 10, 11 and the slope 12 of the step 9 form a cut edge 13 delimiting the upper part, or cut part FL2, of the light beam FL generated by the processing of the light rays through the microlenses.

[0066] As mentioned previously, the overall light beam, schematically illustrated in Figure 3, is obtained by adding all the light rays exiting the microlens array. More specifically, a set of microlenses can be identified as associated with a portion of the light beam, insofar as the light rays exiting the microlens array through one of the microlenses in this set are directed onto the road scene to form that portion of the light beam. In the illustrated example, the microlens array 3 is divided into several sets of microlenses 2, with a base set of microlenses 20, which contributes to forming a base portion FL1 of the projected light beam FL, and a peripheral set of microlenses 14, which contributes to forming the cutoff portion FL2 of the projected light beam FL.As previously discussed, it is desirable that the microlenses in the basic microlens set be grouped into subsets within which the microlenses have striations oriented such that the orientation of the striations in one subset of this basic microlens set differs from the orientation of the striations in another subset of this basic microlens set. This ensures that the diffraction of rays projected by these microlenses is not concentrated in a single direction and therefore not potentially perceptible to a vehicle occupant.

[0067] However, in the specific case of the invention described below, where particular attention is paid to the striations formed on the microlenses that define the cutoff point of the light beam, it could be envisaged that no particular attention is paid to the orientation of the striations formed on the microlenses of the basic microlens assembly. This may be the case, in particular, when it is certain that the diffraction of the rays exiting a microlens of the basic microlens assembly does not propagate beyond the cutoff point in the projected light beam.Thus, preferably, in the following example where particular attention is paid to the orientation of the striations of the peripheral microlens assembly 14, it is advantageous for this peripheral microlens assembly 14 to cover an area at least equal to 25% of the total area of ​​the microlens array, in particular at least equal to 50% of said area, and at most equal to 70% of said area, and / or for the height H2 of the cutoff portion FL2 of the beam projected FL by this peripheral microlens assembly 14 to be on the order of 20%, in particular between 15% and 25% of a height H of the entire cutoff light beam FL. This height is, for example, measured on the screen onto which the light beam FL is projected. A large area of ​​the peripheral microlens assembly 14 ensures a high flux level near the beam cutoff.The upper limit of the proportion occupied by this surface allows enough microlenses to be left to generate the other portions of the FL light beam.

[0068] In the illustrated example, the peripheral microlens assembly 14 is composed of microlens subsets, here three in number, with a first subset 141, a second subset 142 and a third subset 143 participating in projecting respectively a first lateral portion 21 of the cut part FL2 of the light beam, delimited by a first parallel edge 10, a central portion 22 of the cut part FL2 of the light beam, delimited by the step 9, and a second lateral portion 23 of the cut part FL2 of the light beam, delimited by a second parallel edge 11.

[0069] The 6 striations formed on the diopters of the microlenses of each of these microlens subsets are oriented so as to avoid as much as possible in the projected light beam a parasitic diffraction phenomenon beyond the cutoff edge 13.

[0070] To achieve this, the striations 6 formed on the diopters of the microlenses associated with the peripheral microlens assembly 14 are advantageously oriented perpendicular to the orientation of the cut edge 13 which these microlenses help to generate in the beam.More specifically, these striations 6 are made with an orientation such that, when the optical system and the microlens array are mounted on the vehicle to project a light beam with a cutoff greater than at least in the horizontal part onto a screen placed in front of the vehicle, the striations are vertical, i.e. perpendicular to the road on which the vehicle rests, when they are formed on microlens diopters intended to project a first or second lateral portion 21, 23 of the cutoff part FL2 of the beam, and they are inclined along an elongation direction perpendicular to the elongation direction of the jump in the cutoff beam when they are formed on microlens diopters intended to project the central portion 22 of the cutoff part FL2 of the beam.In other words, the striations are configured such that, when the vehicle is assembled and a lighting function is activated, the first subset of microlenses 141 and the third subset of microlenses 143 comprise striations 6 that extend perpendicularly along the parallel edges 10, 11 of the cutoff edge 13, i.e., vertically, as in the example above. Thus, the diffraction phenomenon resulting from the projection of a light beam by these subsets of microlenses 141, 143 extends horizontally along the parallel edges 10, 11 and therefore without extending vertically beyond the cutoff edge 13.

[0071] The second subset of microlenses 142 comprises striations 6 oriented perpendicularly to a direction of inclination of the slope 12 of the step 9. The orientation of the striations 6 of the second subset of microlenses 142 is therefore dependent on the orientation of the slope 12 of the step 9. The diffraction phenomenon resulting from the projection of the second subset of microlenses 142 extends along the slope 12 of the step 9 without extending beyond the cut edge 13. The cut edge 13 is thus well delimited without any diffraction phenomenon extending perceptibly beyond it.

[0072] The invention, as described above, achieves its intended purpose and provides a microlens array that optimizes a projected light beam despite parasitic diffraction phenomena caused by striations on the surface of said microlenses. Variations not described here could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they comprise a microlens array conforming to the invention, in which specific attention is paid to the orientation of the striations on the microlens surfaces so that the application of a light beam projected through these microlenses does not generate excessively noticeable diffraction.

Claims

Microlens array (1) for optical system of a vehicle, comprising a plurality of microlenses (3) configured to generate a light beam (FL, 5a, 5b, 5c, 5d) for lighting and / or signaling, each microlens (3) comprising at least one diopter (7) configured to be traversed by light rays (4, 4a, 4b, 4c, 4d), each diopter (7) comprising a plurality of straight striations (6) resulting from a fabrication of said microlens array (1), characterized in that the striations (6) formed on the microlenses of at least a first set of microlenses (2, 2a) extend in a different orientation from the orientation of the striations (6) formed on the microlenses of at least a second set of microlenses (2, 2b). Microlens array (1) according to claim 1, wherein the striations (6) of the microlenses of two adjacent microlens arrays (2, 2a, 2b, 2c, 2d) extend in a different orientation from one array to the other. Microlens array (1) according to claim 1 or 2 and configured to generate a cutoff light beam (FL, 5a, 5b, 5c, 5d). Microlens array (1) according to the preceding claim and comprising at least one peripheral microlens array (14) configured to project a portion of the light beam (FL, 5a, 5b, 5c, 5d) having a cut edge (13), the striations (6) formed on the surface of the microlenses associated with this peripheral microlens array (14) of microlens arrays (2, 2a, 2b, 2c, 2d) extending in an orientation determined according to the orientation of the cut edge (13). Microlens array (1) according to the preceding claim, wherein, when the light beam (FL, 5a, 5b, 5c, 5d) is projected onto a screen perpendicular to a principal propagation direction of said light beam (FL, 5a, 5b, 5c, 5d), the orthogonal projections onto this vertical screen of the striations formed on a large majority of the microlenses of the peripheral microlens array (14) form segments oriented along a direction perpendicular or substantially perpendicular to a direction of the cut edge (13) of the light beam generated by light radiation from these microlenses. Microlens array (1) according to the preceding claim, configured to project a cutoff light beam (5, 5a, 5b, 5c, 5d) comprising a step (9) connecting two parallel edges (10, 11) offset from each other, the peripheral microlens array (14) comprising a first subset of microlenses (141) configured to generate a portion of the light beam disposed along a parallel edge (10, 11) and a second subset of microlenses (142) configured to generate a portion of the light beam disposed along a slope (12) of the step (9), the striations (6) of the microlenses associated with the first subset of microlenses (141) being oriented in a direction perpendicular to the direction of one of the two parallel edges (10, 11),the striations (6) of the microlenses associated with the second subset of microlenses (142) being oriented in a direction perpendicular to the direction of the slope of the step (9). Microlens array (1) according to any one of claims 4 to 6, wherein the peripheral microlens array (14) represents a portion of the microlenses such that the part of the light beam generated by the microlenses of this peripheral microlens array extends over a height of approximately 20% of the height of the entire global light beam (FL, 5a, 5b, 5c, 5d) generated by the microlens array (1). Microlens array (1) according to any one of the preceding claims, wherein each microlens (3) is offset in a direction perpendicular to the diopter (7) with respect to at least one adjacent microlens (3). Microlens array (1) according to any one of the preceding claims, wherein the microlenses (3) of the first set of microlenses (2, 2a) are mixed with the microlenses (3) of the second set of microlenses (2, 2b). A method for manufacturing a microlens array (1) according to any one of the preceding claims, comprising a machining step via a machining tool for the microlens array (1) or a mold for manufacturing the microlens array (1), said machining step directly or indirectly generating a plurality of straight striations (6) on a diopter (7) of each microlens (3), characterized in that the machining step is implemented so as to generate striations (6) of at least a first set of microlenses (2, 2a) extending in a different orientation from the direction of the striations (6) of at least a second set of microlenses (2, 2b). Manufacturing method according to the preceding claim, in which the orientation of the striations (6) of the microlens assemblies (2, 2a, 2b, 2c, 2d) is dependent on a direction of movement of the machining tool during the machining step.

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