Microlens Projection Module

Abstract

The invention relates to a microlens projection module (10) comprising a light source (12) and regularly arranged optical channels (K1, K2, ... K i Each of the optical channels (K1, K2, ... K i) contains at least one entrance lens (18), to which an object structure (22) to be imaged and at least one projection lens (20) are assigned. The projection lenses (20) form a projection lens array (16). The distance of the projection lenses (20) to the assigned object structures (22) to be imaged corresponds to a focal length (FA) of the projection lenses (20). The distance of the object structures (22) to be imaged to the assigned entrance lenses (18) is very small compared to the distance of the projection lenses (20) to the assigned object structures (22). The individual projections of the projection lenses (20), each representing a single image, create a superposition of all individual images to form a real composite image on a screen (26) or a virtual composite image. It is proposed that a focal point (F) 18 ) the entrance lens (18) of at least one of the optical channels (K1, K2, ... K i) in the direction of a beam path through the microlens projection module (10) viewed behind the projection lens (20).

Description

[0001] The present invention relates to a microlens projection module comprising a light source and regularly arranged optical channels, each containing at least one entrance lens, to which an object structure to be imaged and a projection lens are assigned, wherein the projection lenses of the optical channels form a projection lens array and a distance of the projection lenses to the assigned object structures to be imaged corresponds to a focal length of the projection lenses, wherein a distance of the object structures to be imaged to the assigned entrance lenses is very small compared to the distance of the projection lenses to the assigned object structures to be imaged, and wherein the individual projections of the projection lenses, each representing a single image, create a superposition of all individual images to form a real overall image on a screen or a virtual overall image.

[0002] From EP 2 443 506 B1, a microlens projection module is known that comprises a light source and regularly arranged optical channels. Each optical channel contains at least one entrance lens, to which an object structure to be imaged and a projection lens are assigned. The projection lenses of the optical channels form a projection lens array or microlens array (MLA). The object structures to be imaged are identical. The distance between the projection lenses and the assigned object structures to be imaged corresponds to the focal length of the projection lenses. The distance between the object structures to be imaged and the assigned entrance lenses is very small. The projection lenses are designed to superimpose the individual projections, each representing a single image of an optical channel, into a real composite image on a screen or a virtual composite image.

[0003] The well-known microlens projection module can be used to project symbols onto the road surface. The object structures to be projected are located near the entrance lenses. The focal lengths of the entrance and projection lenses of the MLA can be the same, since, firstly, Köhler illumination of the projection lenses is to be ensured, and secondly, the object structure located near the entrance lens is to be projected onto the road by the projection lens.

[0004] However, with this optical arrangement, if the exit lenses are uncoated and the object structures have a reflective substrate, reflections at the exit lens can cause disturbing directional scattered light to appear on the road.

[0005] A microlens projection module for projecting symbols onto a roadway is also known from DE 10 2020 126 592 A1. This known module also comprises a light source and a microlens array (MLA). Metallic apertures, representing symbols, for example, are applied to the entrance lenses. These aperture patterns are projected onto the roadway by the projection lenses of each optical channel of the MLA. The apertures are arranged such that the projected individual images on the roadway superimpose to form the overall image. The focal lengths of the entrance and projection lenses of the MLA are the same.

[0006] Since the MLA is usually made of plastic, its surfaces are not coated with an anti-reflective (AR) coating for cost reasons. This results in directional scattered light, which is reflected at the entrance lenses and projected onto the road surface by the projection lenses.

[0007] Based on the described prior art, the present invention aims to provide a microlens projection module in which the disturbing influence of directed scattered light is reduced.

[0008] To solve this problem, a microlens projection module with the features of claim 1 is proposed. In particular, starting from the microlens projection module of the type mentioned above, it is proposed that an entrance lens of at least one of the optical channels is configured such that, viewed in the direction of a beam path through the microlens projection module, a focal point of the entrance lens lies behind the projection lens of the corresponding optical channel. This can be achieved by increasing the focal length of the entrance lens of the corresponding optical channel compared to the prior art. For this purpose, the curvature of the entrance lens can be reduced. This particular configuration widens the angular range of the scattered light on the road surface, at least for the corresponding optical channel.This leads to the maximum illuminance being blurred across this angular range.

[0009] It has been shown that by slightly altering the optical properties, particularly the focal length, of the entrance lenses of an MLA, the imaging properties are only minimally changed, while stray light can be significantly blurred. This is achieved by increasing the focal length of the MLA's entrance lenses, which act as field lenses. This causes more stray light to enter neighboring lenses of the MLA. This blurring reduces stray light peaks.

[0010] Preferably, a predominant number of entrance lenses are used; most preferably, all entrance lenses of the microlens projection module are configured such that the focal points of these entrance lenses lie behind the projection lenses of the corresponding optical channels. In particular, the focal length of the entrance lens of an optical channel is greater than the focal length of the projection lens of the corresponding optical channel.

[0011] A very small distance between the object structures to be imaged and the associated entrance lenses can mean that this distance is very close to the distance between the projection lenses and the associated object structures to be imaged, in order to ensure Köhler illumination of the associated projection lenses. Likewise, a very small distance can also include the case where the object structures to be imaged are arranged, preferably applied, to the entrance lenses themselves. The object structures to be imaged in the different optical channels are preferably identical.

[0012] Additionally, it is conceivable that an entrance lens of at least one of the optical channels is anamorphic. This means that the entrance lens has a different focal point or focal length in an xz-plane (or in the y-direction) than in a yz-plane perpendicular to the xz-plane (or in the x-direction). Preferably, the entrance lenses of a predominant number of optical channels, and particularly preferably of all optical channels of the microlens projection module, are anamorphic.

[0013] Further features and advantages of the present invention are explained in more detail below with reference to the figures. Individual features shown in the figures and described below may also be essential to the invention on their own, even if this is not explicitly stated. Likewise, the features shown and described below can be combined with one another in any way, even if such a combination is not explicitly mentioned. The figures show: Fig. 1 a microlens projection module known from the prior art; Fig. 2 a microlens projection module according to the invention in a preferred embodiment; Fig. 3 Influence of the curvature of an entrance lens of a microlens array on the scattered light in the prior art; Fig. 4. Reduced influence of the curvature of the entrance lens of a microlens array on the scattered light in the present invention; Fig. 5 an example of an anamorphic entrance lens of a microlens projection module according to the invention in a preferred embodiment; Fig. 6 an example of an anamorphic entrance lens of a microlens projection module according to the invention in another preferred embodiment; Fig. 7 a simplified representation of an object structure to be imaged on an entrance lens of a microlens projection module according to the invention in a preferred embodiment; and Fig. 8 a lighting device of a motor vehicle according to the invention with a microlens projection module according to the invention.

[0014] Fig. Figure 1 shows a microlens projection module 100 known from the prior art, such as that described in DE 10 2020 126 592 A1. A light source 102 with collimation optics 104 illuminates a projection lens array or microlens array (MLA) 106 with collimated, approximately parallel light rays 112. The MLA comprises an array of entrance lenses 108 and projection or exit lenses 110. The focal length of the entrance lenses 108 of an optical channel K1; K2; ... K i is chosen such that a focal point or focus F 108 or a focal point cloud of the collimated light rays 112 on an exit lens 110 of the corresponding optical channel K1; K2; ... K iEach of the entrance lenses 108 has at least one object structure 114 applied to it, which is imaged by the associated exit lens 110 onto a roadway 116 or a screen 120. The focal length of the exit lens 110 is in this case equal to the focal length of the entrance lens 108.

[0015] Fig. Figure 2 shows a microlens projection module 10 according to the invention, comprising a light source 12, collimation optics (e.g., collimation lens) 14, and an MLA 16 with regularly arranged optical channels K1, K2, ... Ki, each containing at least one entrance lens 18 and one exit or projection lens 20. At least one object structure 22 is applied to each of the entrance lenses 18, which is imaged by the associated exit lens 20 onto a roadway 24 or a screen 26. The distance between the projection lenses 20 and the associated object structures 22 to be imaged preferably corresponds to a focal length FA of the projection lenses 20. The distance between the object structures 22 to be imaged and the associated entrance lenses 18 is very small compared to the distance between the projection lenses 20 and the associated object structures 22 to be imaged.The individual projections of the projection lenses 20, each representing a single image, superimpose all individual images to form a real overall image on the screen 26 or the roadway 24, or to a virtual overall image. The object structures 22 are, for example, applied directly to the entrance lens 18 as a metallic coating. Of course, the object structures 22 can also be arranged on the entrance lens 18 in other ways, or they can be positioned at a (small) distance from the entrance lens 18. Finally, it would also be conceivable to embed the object structures 22 beneath the entrance lenses 18 in the form of a lithographically structured object mask.

[0016] The light source 12 can be configured as a (nearly) point-like light source, the light of which is directed and distributed onto the entrance lenses 18 of the MLA 16 by the collimation optics 14. The light source preferably comprises one or more semiconductor light sources, e.g., LEDs. However, it would also be conceivable that, instead of a point-like light source, a light source array with a multitude of matrix-like arranged individual light sources is used as the light source 12. In this case as well, the use of collimation optics 14 is advantageous to enable illumination of the MLA 16 with light with the lowest possible divergence. The individual light sources can be configured as LEDs distributed over an area. It is also conceivable that each optical channel K1, K2, ... K i The MLA 16 has its own dedicated light source.

[0017] In this example, the MLA 16 is formed by a single, transparent body, with the entrance lenses 18 being formed by entrance surfaces into the MLA 16 and the projection lenses 20 by exit surfaces from the MLA 16. Of course, it would also be conceivable for the entrance lenses 18 and the projection lenses 20 to be formed separately. In this case, an air gap could then be formed between the entrance lenses 18 and the projection lenses 20.

[0018] In contrast to the state of the art from Fig. 1. A focal point F is located at module 10. 18of an incident light beam 28 collimated (or parallelized) at the entrance lens 18 behind the exit lens 20. This is achieved by increasing the focal lengths FE of the entrance lenses 18, for which purpose the curvature of the entrance lens 18 is reduced. Typical values ​​that achieve the desired result particularly well are FE = C * FA, where FA is the focal length of the exit lens 20 and C is a constant between approximately 1.2 and 2.0. Of course, other values ​​for the constant C of the entrance lens 18 are also conceivable. By the design of the focal lengths FE of the entrance lenses 18 according to the invention, the formation and / or influence of scattered light can be reduced. dw denotes a divergence angle of the light 28 incident on the entrance lenses 18 of the MLA 16.

[0019] Based on the Fig. 3 and Fig. Section 4 will explain in more detail the influence of the curvature of the entrance lens 18 on the scattered light. For entrance lenses 108 with a strong curvature ( Fig. 3) or with a short focal length FE, as is the case in the prior art, a significant proportion of the light 118 reflected at the exit lens 110 and the light 120 reflected at the entrance lens 108 is directed into the exit lens 110, generating a sharp, directional scattered light peak on the road surface 116. The reflection of the scattered light at the entrance lens 108 is particularly strong in a metallically coated area of ​​the object structure 114. Since the MLA 106 is generally made of translucent, preferably transparent, plastic, which is difficult to provide with an antireflection (AR) coating, the proportion of scattered light is high in the prior art.

[0020] If the curvature of the entry lens 18 is less pronounced ( Fig. 4), as is the case with the present invention, a portion of the reflected or mirrored scattered light 29 is directed into the adjacent optical channels K1, K2, ... K i , or the neighboring lenses 18, 20 of the MLA 16 are directed (cf. Fig. 2) This leads to a homogenization of the scattered light on the road surface 24 and reduces disruptive peaks. The invention enables a reduction of scattered light even without applying an AR coating to the MLA 16.

[0021] To further improve the homogenization of the scattered light, the entrance lens 18 can be designed as an anamorphic entrance lens. This is shown by the Fig. 5 and Fig. 6, where the focal lengths FE_X, FE_Y of the entrance lens 18 have different values ​​in the x and y directions (or in the xz plane and in the yz plane). This can also contribute to the compensation of astigmatism in the lens array 16.

[0022] A maximum possible value of the focal length FE_X in the x-direction or FE_Y in the y-direction depends, for example, on the divergence of the illumination beam exiting the light source 12 or the collimation optics 14 and striking the entrance lenses 18 of the MLA 16, and on the maximum extent of the object or object structure 22 bx in the x-direction or ly in the y-direction (see Fig. 7) Accordingly, it is advantageous to choose different focal lengths FE_X and FE_Y for the entrance lenses 18 in the x and y directions. In this case, the lens array 16 is anamorphic. Typical values ​​for the focal lengths of the entrance lenses 18 in the x and y directions are—as mentioned—FE_X = CX * FA and FE_Y = CY * FA, where FA is the focal length of the corresponding exit lens 20 of the optical channel K1; K2; ... K i is and CX and CY are constants that can range between 1.2 and 2.0.

[0023] The exact values ​​for the focal lengths of the entrance lenses 18 depend on the maximum size of the object structure 22 to be imaged or of the object on the entrance lens 18. Fig. Figure 7 shows the maximum dimensions ly and bx for a rectangular object structure 22. If, for example, bx > ly, then FE_X should be < FE_Y. This can be applied analogously to object structures 22 that do not have a rectangular shape, but, for example, an oval or elliptical shape.

[0024] The following approximation formulas provide indicative values ​​for the focal length FE_X of the entrance lens 18 in the x-direction (or in the xz-plane), where Lz corresponds to the length of the lens array 16 and Lax to the distance of the entrance lenses 18 in the array 16 in the x-direction (see Fig. 5 and Fig. 6) The same applies to the focal length FE_Y in the y-direction (or in the yz-plane), where Lay corresponds to the distance of the entrance lenses 18 in the array 16 in the y-direction. FEX=Lax⋅n2⋅Tan(w2−ATan(Lax−bx2⋅Lz)) or FEY=Lay⋅n2⋅Tan(w2−ATan(Lay−by2⋅Lz))

[0025] In the extreme case: w2 <ATan(Lax−bx2⋅Lz) or w2 <ATan(Lay−ly2⋅Lz) The focal length FE_X, FE_Y can be set to infinity along one axis, for example, if thin and long symbols are to be projected onto lane 24. In this case, the 18 entrance lenses can become cylindrical lenses. The MLA 16 then consists of a series of cylindrical lenses 18 on the entrance side and no longer of a matrix of individual lenses as on the output side.

[0026] If equations (3) and (4) are valid for both directions, it would even be possible to design the entrance surface of the MLA 16 to be planar and to completely eliminate curvature. This could offer advantages in positioning tolerances, for example, between the light source 12, the collimation optics 14, and / or the MLA 16.

[0027] A further improvement can be achieved, for example, by varying the focal lengths FE_X, FE_Y of the entrance lenses 18 via the MLA 16. For instance, it would be conceivable that the entrance lenses 18 located further away from an axis (e.g., the optical axis) of the microlens projection module 10 could have a different focal length FE_X and / or FE_Y than the entrance lenses 18 located closer to the axis (e.g., the optical axis) of the microlens projection module 10. A random or irregular variation of the focal lengths FE_X, FE_Y of the entrance lenses 18 via the MLA 16 would also be conceivable.

[0028] In summary, the invention relates to a microlens projection module 10 with an MLA 16, wherein a focal point F 18 the entrance lens 18 of at least one of the optical channels K1; K2; ... K i The image is located behind the projection lens 20 when viewed in the direction of a beam path through the microlens projection module 10. Additionally, the entrance lenses 18 can be configured as anamorphic lenses. The microlens projection module 10 can be used to project images onto a roadway 24. The core of the microlens projection module 10 is a microlens array 16 with multiple optical channels K1; K2; ... K i, in which lenses 18 on the input side and lenses 20 on the output side are each assigned to each other in a channel-wise and pairwise manner. The lenses 18 on the input side preferably contain the same object structure to be imaged, e.g., in the form of a mask, with a symbol, letter, logo, or the like, which is projected onto the roadway 24 by means of the lens 20 on the output side.

[0029] The special design of the entrance lenses 18, in particular their anamorphic lens surfaces, represents an alternative to the Köhler arrangement known from the prior art. Furthermore, this allows the proportion of scattered light in the useful light to be reduced.

[0030] Fig. Figure 8 shows a lighting device 50 for a motor vehicle according to the invention. This device comprises a housing 52 with a light emission opening 56, which is closed by a cover plate 54. The housing 52 preferably consists of an opaque plastic material. It is designed for installation in a designated mounting opening of a motor vehicle. The lighting device 50 can be configured as a headlight or as any type of motor vehicle light for the exterior and interior of a motor vehicle. Furthermore, the lighting device 50 comprises a microlens projection module 10 arranged in the housing 52, which projects light onto the road surface 24, in particular in front of the motor vehicle, through the cover plate to generate a light distribution. The microlens projection module 10 is a microlens projection module 10 according to the invention of the type described above and in the Fig. 1-7 types shown. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 2 443 506 B1

[0002] DE 10 2020 126 592 A1 [0005, 0014]

Claims

[1] Microlens projection module (10) comprising a light source (12) and regularly arranged optical channels (K1, K2, ... K i ), each comprising at least one entrance lens (18), to which each is assigned an object structure (22) to be imaged and at least one projection lens (20), wherein the projection lenses (20) of the optical channels (K1, K2, ... K i) form a projection lens array (16) and a distance of the projection lenses (20) to the associated object structures (22) to be imaged corresponds to a focal length (FA) of the projection lenses (20), wherein a distance of the object structures (22) to be imaged to the associated entrance lenses (18) is very small compared to the distance of the projection lenses (20) to the associated object structures (22) to be imaged, and wherein the individual projections of the projection lenses (20), each representing a single image, create a superposition of all the single images to form a real overall image on a screen (26) or a virtual overall image, characterized by , that a focal point (F 18 ) the entrance lens (18) of at least one of the optical channels (K1, K2, ... K i ) in the direction of a beam path through the microlens projection module (10) viewed behind the projection lens (20). [2] Microlens projection module (10) according to claim 1, wherein the focal points (F 18 ) the entrance lenses (18) of a predominant number of optical channels (K1, K2, ... K i ) of the microlens projection module (10) behind the projection lenses (20) of the corresponding optical channel (K1; K2; ... K i ) lay. [3] Microlens projection module (10) according to claim 1, wherein the focal points (F 18 ) of the entrance lenses (18) of all optical channels (K1, K2, ... K i ) of the microlens projection module (10) behind the projection lenses (20) of the corresponding optical channel (K1; K2; ... K i ) lay. [4] Microlens projection module (10) according to one of the preceding claims, wherein the focal lengths (FE_X; FE_Y) of the entrance lenses (18) in a yz-plane or an xz-plane are selected depending on the maximum size (bx; ly) of the object structures (22) to be imaged in the yz-plane or the xz-plane. [5] Microlens projection module (10) according to claim 4, wherein the focal lengths (FE_X, FE_Y) of the entrance lenses in the yz-plane and the xz-plane, respectively, are selected according to the following equations (1) and / or (2) for the case of rectangular object structures to be imaged: FEX=Lax⋅n2⋅Tan(w2−ATan(Lax−bx2⋅Lz)) FEY=Lay⋅n2⋅Tan(w2−ATan(Lay−ly2⋅Lz)) where Lz corresponds to a length of the projection lens array (16) from the entrance lens (18) to the projection lens (20) and Lax or Lay correspond to a distance between adjacent entrance lenses (18) in the projection lens array (16) in the yz-plane and the xz-plane, respectively. [6] Microlens projection module (10) according to claim 5, wherein for an extreme case of equations (3) and / or (4) w2 <ATan(Lax−bx2⋅Lz) w2 <ATan(Lay−ly2⋅Lz) the focal length (FE_X; FE_Y) of the entrance lenses (18) in a plane is chosen to be infinity. [7] Microlens projection module (10) according to claim 6, wherein for the extreme case of equations (3) or (4) the entrance lenses (18) are designed as cylindrical lenses, preferably several adjacent entrance lenses (18) of different optical channels (K1, K2, ... K i ) of the projection lens array (16) are combined into a common cylindrical lens. [8] Microlens projection module (10) according to claim 6, wherein for the extreme case of equations (3) and (4) the entrance lenses (18) are designed planar. [9] Microlens projection module (10) according to one of the preceding claims, wherein the projection lens array (16) is formed by a one-piece translucent, preferably transparent, body, wherein the entrance lenses (18) are formed by entrance surfaces into the projection lens array (16) and the projection lens (20) as exit surfaces from the projection lens array (16). [10] Microlens projection module (10) according to one of the preceding claims, wherein an entrance lens (18) of at least one of the optical channels (K1, K2, ... K i ), preferably from a predominant number of optical channels (K1, K2, ... K i ), especially preferred by all optical channels (K1, K2, ... K i ) of the microlens projection module (10) is anamorphically designed. [11] Microlens projection module (10) according to one of the preceding claims, wherein the object structures (22) to be imaged are provided by several optical channels (K1, K2, ... K i ), preferably from a predominant number of optical channels (K1, K2, ... K i ), especially preferred by all optical channels (K1, K2, ... K i ) of the microlens projection module (10) are identical. [12] Microlens projection module (10) according to one of the preceding claims, wherein the distance of the object structures (22) to be imaged to the associated entrance lenses (18) is close to the distance of the projection lenses (20) to the associated object structures (22) to be imaged in order to ensure Köhler illumination of the associated projection lenses (20). [13] Microlens projection module (10) according to any one of the preceding claims 1 to 11, wherein the object structures (22) to be imaged are arranged or applied to the associated entry lenses (18). [14] Lighting device (50) of a motor vehicle, comprising a housing (52) with a light outlet opening (56) closed by a cover plate (54) and a microlens projection module (10) arranged in the housing (52), which projects light onto a roadway (24) through the cover plate to produce a light distribution, characterized by, that the microlens projection module (10) is designed according to one of the preceding claims.

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