Array of microlenses for a lighting device

Abstract

The present invention relates to an array (1) of microlenses for a lighting device (100) of a vehicle, the array comprising a plurality of microlenses (3) configured to generate an illumination and / or signaling light beam, characterized in that, on one and the same face of the array (1) of microlenses, the microlenses (3) of the array (1) of microlenses are divided into at least one first set of microlenses (2, 2a), the diopters (7) of which, participating in defining the face of the array (1) of microlenses, have a surface roughness of between 0.05 µm and 0.1 µm, and into at least one second set of microlenses (2, 2b), the diopters of which, participating in defining the face of the array (1) of microlenses, have a surface roughness that is lower than the surface roughness of the diopters (7) of the first set of microlenses (2, 2a).

Description

Microlens array for lighting device

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

[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 a lighting device 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, which measures 1 mm². The fabrication of an array of such microlenses in this context is achieved through direct precision machining of the microlenses from a block of suitable transparent material.

[0006] At this scale, polishing the machined surface after microlens machining is not possible, and the machining operation thus generates striations at the diopters. These striations are fine and subtle, but are nevertheless sufficient to potentially generate unwanted diffraction of light rays passing through the microlens array, perpendicular to the orientation of the striations encountered by these light rays.

[0007] Furthermore, such manufacturing should ideally be as fast and inexpensive as possible. However, precision machining of the entire microlens array can prove tedious and costly.

[0008] The present invention falls within this context and proposes a microlens array for a vehicle lighting device, comprising a plurality of microlenses configured to generate a light beam for lighting and / or signaling, characterized in that, on the same face of the microlens array, the microlenses of the microlens array are divided into at least a first set of microlenses whose diopters, participating in delimiting said face of the microlens array, have a surface roughness between 0.03 µm and 0.1 µm and into at least a second set of microlenses whose diopters, participating in delimiting said face of the microlens array, have a surface roughness lower than the surface roughness of the diopters of the first set of microlenses.

[0009] By "inferior", we understand in particular that the surface roughness of the diopters of the second set of microlenses is strictly inferior to the surface roughness of the diopters of the first set of microlenses.

[0010] The difference in surface roughness between the microlenses in each microlens array is due to different machining processes. The first microlens array, which has a higher average surface roughness than the second array, is machined to a lower level of finish. However, this lower level of finish does not affect the efficiency of the portion of the light beam projected by the first microlens array. On the contrary, this improved quality is achieved with fewer machining passes, resulting in faster and less expensive production, thus simplifying the manufacturing of the microlens array in several respects.The microlenses in the second set of microlenses are machined with greater precision because they project a portion of the light beam that must be particularly sharp and of high quality. This allows us to limit the number of microlenses that undergo multiple machining passes and to perform these multiple passes only on the microlenses that require them. The roughness measured on the diopters of the microlenses in each set of microlenses corresponds to the arithmetic mean roughness, abbreviated as Ra, which is an absolute average relative to a basic dimension of the diopters of the microlenses in the set under consideration.

[0011] The microlens array is integrated into the lighting device and 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, included within this same lighting device, and to the output of light rays in a light beam intended to ensure the aforementioned lighting and / or signaling function.

[0012] The face of the microlens array corresponds to one of the entrance or exit faces of the microlens array. The diopter of each microlens therefore contributes to forming a separation between the external environment and the material of the microlens array.

[0013] As mentioned, the surface of the diopter of the microlenses of the first set of microlenses is rougher than that of the microlenses of the second set of microlenses due to the more basic machining of the microlenses of the first set of microlenses.

[0014] The microlenses of the first set of microlenses are, for example, configured to ensure the projection of a lower part of a light beam for lighting and / or signaling, while the microlenses of the second set of microlenses are configured to ensure the projection of an upper part of this light beam for lighting and / or signaling.

[0015] According to a non-limiting feature of the invention, the diopter of each microlens comprises a plurality of striations resulting from the fabrication of said microlens matrix. The striations of the microlenses in the first set of microlenses are separated from one another by a first pitch, this first pitch being greater than a second pitch separating the striations of the microlenses in the second set of microlenses. The difference in pitch between the striations of the microlenses in the first set of microlenses and the striations of the microlenses in the second set of microlenses is explained by the different machining of the diopters of the aforementioned microlenses.

[0016] 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.

[0017] Because of the coarser machining of the microlenses in the first set of microlenses, the first pitch is higher than the second pitch, i.e. the striations of the microlenses in the first set of microlenses are further apart from each other than the striations of the microlenses in the second set of microlenses.

[0018] According to a non-limiting feature of the invention, the first step is between 30 µm and 100 µm and the second step is between 1 µm and 30 µm.

[0019] 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.

[0020] Despite this distribution, each microlens is configured, notably by the shape of its diopters, to participate in the part of the light beam allocated to it, regardless of its initial position within the microlens matrix.

[0021] 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.

[0022] According to a non-limiting feature of the invention, the second set of microlenses is configured to project a portion of the cutoff light beam, said portion having a cutoff edge. Since a cutoff light beam must, to be compliant with regulations, meet precise standards regarding the sharpness of the beam projected at the cutoff edge, these standards being more lenient with respect to the sharpness of the rest of the beam, it is therefore the most precisely machined set of microlenses that must project the portion of the light beam delimiting said cutoff edge. This makes it possible, as previously mentioned, to guarantee the sharpest possible cutoff while preventing stray light rays from being projected beyond said cutoff edge.

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

[0024] According to a non-limiting feature of the invention, the striations on the microlenses of the second set of microlenses extend in a specific orientation based on the orientation of the cutoff edge. In other words, the machining that generates the striations on the microlenses, particularly the striations on the microlenses of the second set of microlenses, is performed such that the striations are oriented according to the direction of the cutoff edge of the light beam generated by a lighting device comprising the microlens array, according to this non-limiting aspect of the invention. This configuration enhances the sharpness of the cutoff by preventing diffraction phenomena from propagating beyond the cutoff edge.

[0025] The invention also covers a lighting device comprising a light source and a microlens array as described above. The light source can be powered by an electronic board and generates a plurality of light beams when the light source is active.

[0026] The microlens array is positioned on a path of light rays in order to project the light rays into a light beam as described previously.

[0027] Optionally, the lighting device may include a collimator positioned along the path of the light rays between the light source and the microlens array, in order to deflect the light rays so that each of them is parallel to the others. This configuration allows for better control of the light rays entering the microlens array.

[0028] The invention also covers a method for manufacturing a microlens array as described above, comprising a first machining step in which at least the microlenses of the first set of microlenses are machined, directly or indirectly, according to a first machining configuration, so as to generate the first surface roughness on the diopters of at least the microlenses of the first set of microlenses, and a second machining step in which the microlenses of the second set of microlenses are machined, directly or indirectly, according to a second machining configuration, so as to generate the second surface roughness on the diopters of the microlenses of the second set of microlenses.

[0029] This process results in a different machining quality for each set of microlenses. The machining differs at each stage; at least the first stage ensures rapid machining but without high precision, while the second stage is a slower, more precise machining than the first. The two machining stages can be performed using two different tools or the same tool with adjusted machine tool operating parameters.

[0030] The manufacturing of the microlens matrix can be done directly, i.e. by directly machining the material to form the microlens matrix, or indirectly, i.e. by machining a mold to generate counterforms and subsequently manufacturing the microlens matrix by molding using the previously machined mold.

[0031] According to a non-limiting feature of the process, the second machining step is subsequent to the first machining step. The first machining step comprises machining the microlenses of the first set of microlenses and machining the microlenses of the second set of microlenses, so as to generate the initial surface roughness on the edges of all the microlenses in the microlens array. The second machining step is a finishing step on the microlenses of the second set of microlenses. Thus, it is the machining configurations that generate the surface roughness, as well as the striations mentioned previously, on the edges of the microlenses. Machining the microlenses should be understood to include either machining directly into the material to form the microlenses, or machining the mold counterforms to allow for the subsequent fabrication of the microlens array by molding.

[0032] The first machining step is advantageously performed on all microlenses to facilitate the manufacturing process. The microlenses in the first set are fully machined according to the first machining configuration, while the microlenses in the second set are initially machined using the first configuration. This configuration allows for the creation of a rough shape for the microlenses in the second set during the first machining step, thus accelerating the manufacturing of the microlenses in the second set, rather than machining them entirely with the second machining configuration.Thus, even though the diopters of the microlenses of the second set of microlenses exhibit the first surface roughness at the diopter, this diopter is subsequently machined according to the second machining configuration to generate the second surface roughness.

[0033] Such a process combining roughing and finishing is valid for direct or indirect machining of the microlens matrix.

[0034] According to a non-limiting feature of the process, the first machining step is performed on the microlenses of the second set of microlenses in such a way as to retain excess material. The second machining step is then performed to finish the microlenses of the second set of microlenses by machining away this excess material. This excess material allows the second machining step to be carried out without damaging the structure of the microlenses of the second set of microlenses by machining them too deeply during the second machining step. The second machining step is therefore performed by machining away the excess material to achieve the second surface roughness.

[0035] 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:

[0036] is a schematic representation of a lighting device comprising a microlens array according to one aspect of the invention,

[0037] is a perspective view of a portion of a microlens array according to the invention, particularly illustrating a microlens from a first set of microlenses and a microlens from a second set of microlenses,

[0038] is a view of the microlens array from outside the vehicle, making visible a configuration of two sets of microlenses,

[0039] is a schematic representation of a cutoff beam of light projected by the microlens array,

[0040] is a schematic representation of a manufacturing process for the microlens matrix.

[0041] 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 lighting system. This elongation plane is perpendicular to the longitudinal axis L, which represents the principal direction of propagation of the 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 a lighting system is resting.The direction V is then representative of the vertical direction of the optical system when it is in its normal operating position and orientation.

[0042] The diagram schematically illustrates a lighting device 100 comprising a microlens array 1, a collimator 101 and one or more light sources 102. The lighting device 100 is particularly suitable for equipping a motor vehicle, said lighting device 100 operating at least one function of lighting and / or signaling the vehicle.

[0043] The light source(s) 102 are arranged in the vicinity of a focal plane comprising a principal optical axis 104 of the light device 100, this optical axis 104 being longitudinal here.

[0044] The collimator 101 and the light source(s) 102 are positioned relative to each other so that the light rays emitted by the light source(s) 102 pass through the collimator 101. This collimator 101 is configured to orient all the light rays emitted by the light source(s) 102 parallel to each other and to direct them towards the microlens array 1, and more specifically towards an input microlens array.

[0045] 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.

[0046] The output microlens array forms an illumination surface for the light device 100, that is, a surface through which the light rays exit to generate a beam of light outside the vehicle. It should be noted that the light device 100 may include a transparent or translucent screen downstream of the output microlens array without departing from the scope of the invention.

[0047] 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.

[0048] Each input microlens is configured within the microlens array 1 such 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 the collimator 101 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.

[0049] 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.

[0050] The microlens array 1 comprises a plurality of microlens arrays 2, including a first microlens array 2a and a second microlens array 2b, themselves composed of a plurality of microlens arrays 3. The microlens arrays 3 of the first microlens array 2a and the microlens arrays 3 of the second microlens array 2b are structurally distinct from each other as will be detailed later.

[0051] It should be noted that in the illustrated example, the first set of microlenses 2a comprises eight rows of microlenses and the second set of microlenses 2b comprises three rows of microlenses, but that this example is given only as information without limitation of the invention.

[0052] Figure 1 is a partial schematic representation of a microlens array 1 according to the invention. In Figure 1, light rays 4 emanating from the light source described above are shown propagating through the microlenses 3 of the microlens array 1. Subsequently, the microlenses 3 project the light rays 4 into a light beam 5.

[0053] Such a microlens array 1 is manufactured by machining using a machining tool. Machining can be done directly on the material of the microlens array 1. In both cases, and as illustrated in Figure 1, on which a microlens 3 of the microlens array is partially shown, machining generates a plurality of striations 6 on a diopter 7 of each microlens 3.

[0054] The diopter 7 can, for example, be an entrance or exit face depending on the position of the microlens 3 in the microlens array 1. The size of each microlens 3 is on the order of a millimeter, with, for example, a diopter 7, forming an entrance or exit face for light rays, measuring 1 mm². It is therefore difficult to polish these striations 6 due to the small size of the microlenses 3 and the fact that they can be arranged in a particular configuration, as illustrated. The configuration of these striations 6 has an impact on the surface roughness of the diopter 7 of each microlens 3.

[0055] The microlenses 3 or microlens arrays 2 can be arranged in a staggered pattern in a direction perpendicular to the diopters 7, forming a staircase. This configuration allows, for example, adaptation to the shape of a projector in which the previously mentioned lighting device includes the microlens array 1.

[0056] Figure 1 shows a microlens 3 from the first set of microlenses 2a and a microlens 3 from the second set of microlenses 2b. The microlens array 1 is characterized in that the microlenses 3 from the first set of microlenses 2a and the microlenses 3 from the second set of microlenses 2b are machined differently from each other and thus exhibit different surface roughness depending on whether they belong to the first or second set of microlenses.Of course, within one of the microlens sets, the surface roughness of the microlens diopters can vary from one microlens to another, due to manufacturing tolerances, but it should be understood here that the difference between the surface roughness of the microlenses from one set to another goes beyond the simple manufacturing tolerance, and can for example be on the order of at least 10% of the surface roughness of the least smooth face.

[0057] The microlenses 3 of the first set of microlenses 2a are machined more quickly, with a high tooling speed, than the microlenses 3 of the second set of microlenses 2b. Alternatively, the microlenses 3 of the first set of microlenses 2a can be machined less precisely, i.e., with fewer machining passes, than the microlenses 3 of the second set of microlenses 2b. In both cases, the objective is to combine manufacturing speed and cost reduction for the production of the microlenses 3 of the first set of microlenses 2a. This results in the projection of a lower-quality light beam 5, but one that contributes to a portion of an overall light beam that does not require high precision to be effective and compliant with regulations.This allows high-precision machining implemented only on a part of the microlenses 3, here the microlenses 3 of the second set of microlenses 2b, which ensures a significant time saving during the manufacture of the microlens matrix 1 according to the invention.

[0058] As a result, the light beam 5 projected by the microlenses 3 of the second set of microlenses 2b, which also participates in making a portion of an overall light beam but a portion at the edge of the beam which must be delimited very precisely, is a clear light beam, made possible by precision machining.

[0059] As mentioned, the surface roughness differs depending on whether we consider the microlenses 3 of the first set of microlenses 2a or the microlenses 3 of the second set of microlenses 2b. For example, the microlenses 3 of the first set of microlenses 2a have a surface roughness between 0.05 µm and 0.1 µm while the microlenses 3 of the second set of microlenses 2b have a surface roughness lower than the surface roughness of the microlenses 3 of the first set of microlenses 2a.

[0060] This difference in surface roughness can also be achieved by a difference in pitch between the 6 grooves formed by the tooling during the machining of the microlens diopters. In other words, the 6 grooves of the microlenses 3 in the first set of microlenses 2a are separated from each other by a first pitch P1, while the 6 grooves of the microlenses 3 in the second set of microlenses 2b are separated by a second pitch P2. As illustrated in Figure 1, the first pitch P1 is larger than the second pitch P2. For example, the first pitch P1 is between 30 µm and 100 µm and the second pitch P2 is between 1 µm and 30 µm.

[0061] In the diagram, the striations 6 of the microlenses 3 of the two sets of microlenses 2 are vertical. Such vertical striations 6 generate a horizontal diffraction phenomenon 8 of the light beam 5 exiting the microlens array 1, in the transverse direction, since the principal propagation of the light beams 5 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. Generally, 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.

[0062] Due to the less precise machining of the microlenses 3 of the first set of microlenses 2a, the resulting diffraction phenomenon 8 is more intense than the diffraction phenomenon 8 resulting from the projection of the light beam 5 by the microlenses of the second set of microlenses 2b.

[0063] Figure 1 is a partial schematic representation of the microlens array 1 according to the invention, where a plurality of microlenses 3 distributed in two sets of microlenses 2 are illustrated. Figure 2 represents more particularly a detailed view from outside the vehicle.

[0064] The number of microlenses can vary from one microlens array to another. In the example shown, the microlenses 3 of the second microlens array 2b are represented with a pattern to distinguish them from the microlenses 3 of the first microlens array 2a, which are represented without a pattern. This allows us to see that the microlenses 3 of the second microlens array are in the minority, and this is explained in particular by the fact that the light beams they project contribute to forming only a small portion of the overall light beam resulting from the projection of all the light beams exiting the microlenses 3 of the microlens array 1.

[0065] It follows from the above that the microlenses which have the highest surface roughness form a smaller set of microlenses because they are reserved for the task of forming a targeted part of the overall light beam for which high sharpness is required.

[0066] Furthermore, as can be seen in Figure 1, the microlenses 3 of the second set of microlenses 2b are mixed with the microlenses 3 of the first set of microlenses 2a. A microlens 3 of the second set of microlenses 2b can, for example, be entirely and exclusively surrounded by microlenses of the first set of microlenses 2a, as is the case in Figure 1 for some of the microlenses 3 of the second set of microlenses 2b.

[0067] In this way, the microlenses 3 of the microlens sets 2 are distributed homogeneously or substantially homogeneously over the whole of the microlens matrix 1. This helps to enhance the aesthetics of the lighting device equipped with the microlens matrix 1. Indeed, viewed from outside the vehicle, the light emitted by the overall light beam remains homogeneous, regardless of the distance or angle of view through which the lighting device is observed.

[0068] The diopters of the microlenses are configured to direct the corresponding light beam into the appropriate area of ​​the overall light beam, so that despite a mixed configuration as mentioned, the portions of the overall light beam provided by each set of microlenses 2 are coherent with respect to each other to form a regulatory beam.

[0069] This is a view of a global light beam as mentioned previously, here a cutoff beam, resulting from the activation of the light device described previously.

[0070] The cutoff beam is characterized by the presence of a raised edge 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 edge 9 are defined in particular by the inclination of a slope 12 connecting the parallel edges 10, 11. The parallel edges 10, 11 and the slope 12 of the raised edge 9 form a cutoff edge 13 delimiting the upper part 51 of the cutoff beam 50, and this configuration of the cutoff beam 50 allows for a limited-range lighting function on one side of the road to avoid dazzling oncoming vehicles.

[0071] The cutoff beam 50 can be divided into two parts: an upper part 51, which runs along the cutoff edge 13 and extends to a height of approximately 20%, specifically between 15% and 25%, of the total height of the cutoff beam 50 from the microlens array, and a lower part 52, which forms the remainder of the beam. The heights can be measured, for example, by projecting the cutoff beam 50 onto a screen perpendicular to a principal propagation direction of said cutoff beam. The screen is advantageously placed at a considerable distance relative to the dimensions of the lighting device, for example, 25 m.Because of the presence of the cut edge 13 in the upper part, it is understood that the light beams projected by the microlenses which participate in forming this upper part 51 must be sharp, with a minimum of dispersion so as not to exceed the cut edge, while the sharpness of the light beams participating in forming the lower part 52 is less critical.

[0072] It follows that the upper part 51 of the cutoff light beam 50 is obtained by the superposition of the light beams projected by the microlenses of the second set of microlenses, whose diopters have a lower roughness than that of the diopters of the microlenses of the first set of microlenses, the latter being associated with the realization of the lower part 52 of the cutoff light beam 50.

[0073] Since the upper part 51 in which the sharpness must be beyond a certain threshold is less extensive than the lower part, the number of microlenses in the second set of microlenses is smaller than the number of microlenses in the first set of microlenses, which is advantageous in terms of the cost of obtaining the microlens matrix, since there are more microlenses for which only a moderate number of machining passes are needed.

[0074] The upper part 51 is therefore associated with the projection of light beams by the microlenses of the second set of microlenses. As mentioned in reference to the previous section, these microlenses are scattered throughout the microlens matrix, forming a plurality of subsets. The configuration of the diopters formed by the diopters of the microlenses allows the light beams projected by these microlenses to be grouped together in the upper part 52 of the cutoff light beam 50.

[0075] In the illustrated example, the second set of microlenses is composed of subsets of microlenses, here three in number, with a first subset, a second subset and a third subset participating in projecting respectively a first lateral portion of the upper part 51 of the cutoff light beam 50, delimited by the first parallel edge 10, a central portion of the upper part 51 of the cutoff light beam 50, delimited by the step 9, and a second lateral portion of the upper part 51 of the cutoff light beam 50, delimited by the second parallel edge 11.

[0076] Depending on the portion they contribute to forming within the overall light beam, the microlenses of the second set can be specifically machined so that the resulting striations are oriented in a way that controls the diffraction pattern of the light rays. To illustrate this characteristic schematically, striations have been shown in the various previously mentioned sub-sections of the upper part of the beam, illustrating the orientation of the striations formed on the microlenses' interface to project a light beam corresponding to these different sub-sections.It should be noted that this schematic representation is intended to make clear a characteristic of the orientation of the striations on the microlenses and the impact this has on the diffraction phenomenon 8 which results from the projection of the light beam through a striated microlens diopter, but that the said striations 6 are not visible in the projected cutoff light beam 50.

[0077] In this particular configuration, 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 cutoff light beam 50 a parasitic diffraction phenomenon beyond the cutoff edge 13.

[0078] To achieve this, the striations 6 formed on the diopters of the microlenses associated with the second set of microlenses are advantageously oriented perpendicular to the orientation of the cut edge 13 which these microlenses help to generate in the cutoff light beam 50.More specifically, these striations 6 are made with an orientation such that, when the light device and the microlens array are mounted on the vehicle to project a light beam with a cutoff at least in the horizontal part onto a screen arranged 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 of the upper part 51 of the cutoff light beam 50, and they are inclined along an elongation direction perpendicular to the elongation direction of the bump 9 in the cutoff light beam 50 when they are formed on microlens diopters intended to project the central portion of the upper part 51 of the cutoff light beam 50.In other words, the striations are configured such that, when the vehicle is assembled and a lighting function is activated, the first and third microlens subsets 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 microlens subsets extends horizontally along the parallel edges 10, 11 and therefore without extending vertically beyond the cutoff edge 13.

[0079] The second subset of microlenses 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 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 extends along the slope 12 of the step 9 without extending beyond the cutoff edge 13. The cutoff edge 13 is thus well delimited without any diffraction phenomenon extending perceptibly beyond it.

[0080] Figure 1 is a schematic representation of a manufacturing process 200 for the microlens matrix 1 according to the invention. In Figure 1, a block of transparent plastic material comprising microlenses 3 is shown with the microlenses aligned horizontally. The block of material has an excess of material 30 covering the diopters of the microlenses, this excess material being intended to be machined to give the diopters of the microlenses 1 the desired shape. Schematically, the microlenses 3 of the first set of microlenses 2a are represented by empty squares, while the microlenses 3 of the second set of microlenses 2b are represented by hatched squares.

[0081] In a manner not illustrated, manufacturing process 200 can be implemented on a mold in order to generate counterforms enabling the manufacture of the microlens matrix 1 by molding.

[0082] During the manufacturing process 200, at least two machining steps are carried out to form the microlens matrix 1 according to the invention. Initially, a first machining step 201 is carried out in which at least the microlenses 3 of the first set of microlenses 2a are machined using a first machining configuration 203. This first machining configuration 203 allows for rapid machining but with limited precision, and generates the first surface roughness at least on the diopter 7 of the microlenses 3 of the first set of microlenses 2a.

[0083] Once this first machining step 201 is completed, a second machining step 202, which here corresponds to a finishing step, is implemented during which the microlenses 3 of the second set of microlenses 2b are machined using a second machining setup 204. This second machining setup 204 corresponds to the precision machining described previously in order to generate the second surface roughness on the diopter 7 of the microlenses 3 of the second set of microlenses 2b. Once this second machining step 202 is completed, the manufacturing process 200 is finished.

[0084] The first machining configuration 203 and the second machining configuration 204 can be two different machining tools or two different machining heads of the same machining tool.

[0085] Advantageously, in order to further accelerate the manufacturing process 200, the first machining step 201 includes the machining of the microlenses 3 of the first set of microlenses 2a and the microlenses 3 of the second set of microlenses 2b, making it possible to machine the material 30 at the level of the microlenses 3 of the second set of microlenses 2b faster than when this material 30 is fully machined during the slower second machining step 202.

[0086] In this configuration, concerning the microlenses 3 of the second set of microlenses 2b, the first machining step 201 constitutes a rough machining of the microlenses 3 of the second set of microlenses 2b, while the second machining step 202 constitutes a finishing of the microlenses 3 of the second set of microlenses 2b. Advantageously, the first machining step 201 is carried out on the microlenses 3 of the second set of microlenses 2b in such a way as to retain a surplus 31 of material 30. The second machining step 202 can thus be carried out in such a way as to perform the finishing of the microlenses 3 of the second set of microlenses 2b by machining said surplus 31 of material 30.

[0087] According to another configuration not shown, if the first set of microlenses 2a is exclusively machined via the first machining configuration 203, while the second set of microlenses 2b is exclusively machined via the second machining configuration 204, then, contrary to what is shown in, the two machining steps 201, 202 can also be implemented simultaneously or in a different order.

[0088] The invention, as described above, achieves its intended purpose and provides a microlens array that can be manufactured quickly and affordably without compromising the precision and efficiency of the light beam projected by said microlens array. Variations not described herein 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.

Claims

Microlens array (1) for a vehicle lighting device (100), comprising a plurality of microlenses (3) configured to generate a light beam (5) for lighting and / or signaling, characterized in that, on the same face of the microlens array (1), the microlenses (3) of the microlens array (1) are divided into at least a first set of microlenses (2, 2a) whose diopters (7), participating in delimiting said face of the microlens array (1), have a surface roughness between 0.03 µm and 0.1 µm and into at least a second set of microlenses (2, 2b) whose diopters, participating in delimiting said face of the microlens array (1), have a surface roughness less than the surface roughness of the diopters (7) of the first set of microlenses (2, 2a). Microlens array (1) according to claim 1, wherein the diopter (7) of each microlens (3) comprises a plurality of striations (6) resulting from a fabrication of said microlens array (1), the striations (6) of the microlenses (3) of the first set of microlenses (2, 2a) being separated from each other according to a first step (P1), the first step (P1) being greater than a second step (P2) separating the striations (6) of the microlenses (3) of the second set of microlenses (2, 2b). Microlens array (1) according to claim 2, wherein the first pitch (P1) is between 30 µm and 100 µm and the second pitch (P2) is between 1 µm and 30 µm. 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). Microlens array (1) according to any one of the preceding claims, configured to generate a cutoff light beam (50). Microlens array (1) according to the preceding claim, wherein the second set of microlenses (2, 2b) is configured to project a portion of the cutoff light beam (50), said portion having a cutoff edge (13). Microlens array (1) according to the preceding claim, wherein the second set of microlenses (2, 2b) represents a portion of the microlenses (3) such that the portion of the cutoff light beam (50) generated by the microlenses (3) of the second set of microlenses (2, 2b) extends over a height of approximately 20% of the height of the entire cutoff light beam (50) generated by the microlens array (1). Microlens array (1) according to claim 6 or 7, in combination with claim 2 or 3, wherein the striations (6) of the microlenses (3) of the second set of microlenses (2, 2b) extend in a determined orientation as a function of an orientation of the cut edge (13). Light device (100) comprising at least one light source (102) and a microlens array (1) according to any one of the preceding claims. A method for manufacturing a microlens array (1) according to any one of claims 1 to 8, comprising a first machining step (201) in which at least the microlenses (3) of the first set of microlenses (2, 2a) are machined directly or indirectly according to a first machining configuration (203), so as to generate the first surface roughness on the diopters (7) of at least the microlenses (3) of the first set of microlenses (2, 2a), and a second machining step (202), in which the microlenses (3) of the second set of microlenses (2, 2b) are machined directly or indirectly according to a second machining configuration (204), so as to generate the second surface roughness on the diopters (7) of the microlenses (3) of the second set of microlenses (2, 2b). Manufacturing method (200) according to the preceding claim, wherein the second machining step (202) is subsequent to the first machining step (201), the first machining step (201) comprising the machining of the microlenses (3) of the first set of microlenses (2, 2a) and the machining of the microlenses (3) of the second set of microlenses (2, 2b), so as to generate the first surface roughness on the diopters (7) of all the microlenses (3) of the microlens matrix (1), the second machining step (202) being a finishing of the microlenses (3) of the second set of microlenses (2, 2b). Manufacturing method (200) according to the preceding claim, during which the first machining step (201) is carried out on the microlenses (3) of the second set of microlenses (2, 2b) so as to retain a surplus (31) of material (30), the second machining step (202) being carried out so as to operate the finishing of the microlenses (3) of the second set of microlenses (2, 2b) by machining said surplus (31) of material (30).

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