Indication device

Abstract

The invention relates to a display device having a display panel (11) for linearly polarized light, a light source (12) for unpolarized light, and a polarized light recycler (4). The polarized light recycler (4) comprises the following elements, arranged in succession in the path of the beam coming from the light source (12): a microlens array (41), a shadow mask (43) designed to be reflective at the shadow mask surface facing away from the microlens array (41), a retarder (46), and a reflective polarizer (47). The microlenses (42) of the microlens array (43) are arranged without gaps.

Description

[Technical Field]

[0001] The present invention relates to a display device including a display panel for linearly polarized light as illumination, a light source for unpolarized light, and a polarization recycler. [Background technology]

[0002] Polarization recycling is a widespread method used in display devices to maximize the use of unpolarized light from illumination. In polarization recycling, unpolarized light is converted to polarized light with the desired polarization with as little loss as possible. Light with the desired polarization passes through the polarization recycler, while light with an orthogonal polarization is converted by the polarization recycler primarily into light with the desired polarization. Thus, substantially all of the incident light exits the polarization recycler as light with the desired polarization. This avoids the losses incurred by conventional polarizers, which do not allow light with undesired polarization to pass but instead absorb or reflect it. Because display devices generally include display panels for linearly polarized light and therefore require polarized incident light, illumination light with an unused polarization direction is often filtered by a reflective polarizer and converted to the correct polarization via scattering, thereby making it usable by the display panel. This variant works both in edge-lit systems, where a light source emits light from the side into a light guide, which then outcouples the light toward the display panel, i.e., indirectly illuminating the display panel, and in direct-illumination systems. As an alternative to scattering in the latter case, a method can also be used in which polarization recycling is achieved using polarizing beam splitters and retarder foils.

[0003] US 2005 / 0270439 A1 and WO 2006 / 038417 A1 are examples of indirect illumination and polarization recycling with reflective polarizers and scattering. US 2004 / 0263789 A1 and US 2013 / 0286479 A1 are examples of direct illumination and polarization recycling with polarizing beam splitters and retarders.

[0004] The fact that scattering-based solutions in many applications result in a very wide angular distribution of light that is inefficient, for example in the case of head-up displays (often abbreviated as HUD), should be considered as a drawback of known solutions. Solutions based on polarizing beam splitters are very complex to implement from a technical point of view and require a large amount of space.

[0005] US Patent Application Publication No. 2018 / 0299730A1 discloses a display device including a display panel for linearly polarized light, a light source for unpolarized light, and a polarization recycler, which includes, in succession in the path of the beam coming from the light source, a microlens arrangement, a perforated mask having a reflective embodiment on its side facing away from the microlens arrangement, a retarder, and a reflective polarizer. Summary of the Invention [Problem to be solved by the invention]

[0006] There is a need for related improved displays with polarization recycling. [Means for solving the problem]

[0007] The display device according to the present invention includes a microlens configuration in which the microlenses are arranged without gaps. These microlenses are arranged side by side so that the transition area between two microlenses occupies as little space as possible, and ideally does not exist. The gap-free microlens configuration ensures that all of the light coming from the light source is used directly. This avoids the potential multiple reflection losses of light that would occur in the case of spaced microlenses, which would occur in the case of light entering and being reflected from the intermediate spaces between the microlenses. The microlenses focus the incident light so that it can pass through the holes in the perforated mask. The component of the light reflected by the reflective polarizer is reflected by the reflective region of the perforated mask and, after passing through the retarder multiple times, preferably twice, has the appropriate polarization for the display panel. This enables efficient polarization recycling without significant expense, in which substantially all of the unpolarized light generated by the light source is supplied to the display panel as linearly polarized light. A birefringent / retardant element is provided as the retarder. For example, this could be a quarter-wave plate that converts linearly polarized light to circularly polarized light if the axes of the quarter-wave plate are properly aligned. In this case, two passes are sufficient to obtain a 90° rotation of the polarization direction. The reflective polarizer is aligned so that the light passing through it has the same polarization direction as required by the display panel at its input side.

[0008] According to the present invention, the microlenses of the microlens arrangement are configured so that they convert a parallel incident light beam into an exiting light beam having a conical distribution with a defined aperture angle. This is advantageous in that the desired aperture angle characteristics are already provided by the polarization recycler in the display device. The focal length of the microlenses and their configuration relative to the perforated mask are appropriately selected depending on the desired aperture angle characteristics. The aperture angle characteristics are maintained during polarization recycling. Therefore, the arrangement according to the present invention can be used in display units already designed for parallel incident beams, for example, replacing complex or inefficient polarization recyclers therein. In practical implementations, the incident beam is not ideally parallel, and the exiting beam does not form an ideal cone. Depending on the main surfaces of the microlenses, which can be circular, rectangular, hexagonal, etc., the conical distribution also has an approximately corresponding cross section. In the case of a round cross section, intermediate regions where light is blocked or passing light is not refracted according to the microlenses remain between the microlenses on the microlens arrangement. Such a microlens configuration may be cost-effective to manufacture and produces a light cone with a round cross-section, but leaves light incident on the intermediate region unused. In contrast, microlenses with different cross-sections may be arranged to cover the area, which increases the proportion of usable light, but also entails a light cone with a corresponding cross-section.

[0009] Advantageously, the microlens arrangement comprises a body having two substantially parallel main surfaces arranged at a distance from each other, the microlenses being arranged on one of its main surfaces and the perforation mask being arranged on the other main surface. This has the advantage that the distance of the microlens arrangement from the perforation mask and the relative alignment of these two with respect to each other are guaranteed by the manufacture of the microlens arrangement. Therefore, there is no need to subsequently align these two with respect to each other, thereby reducing sources of error. The perforation mask is located at a defined distance from the microlenses, making it possible to dispense with the complex adjustments that would occur in the case of separately manufactured and subsequently assembled elements.

[0010] According to an advantageous configuration of the present invention, the perforated mask is arranged in the focal plane of the microlens arrangement. This allows the perforated mask to have very small holes, because in the ideal case, the light cone is point-like in the focal plane, and in reality, the light cone generated by the microlens has its area with the smallest diameter there. The smallest possible holes mean the largest possible reflection area and therefore the smallest possible light loss. Only light reflected by the reflective polarizer and incident on the holes in the perforated mask cannot be used for polarization recycling. The position of the perforated mask, i.e., the open locations of its holes, corresponds in this case to the focal point of the microlens arrangement.

[0011] According to an advantageous configuration of the invention, the perforation mask is a reflective coating arranged on the side facing away from the microlens arrangement, such a coating being capable of being produced cost-effectively, for example, by a printing method.

[0012] According to a development of the invention, the body comprises: Ho The microlens is realized as a lens. Ho The perforated mask as a reflective coating is located on one side of the film, and the perforated mask is located on the other side. Ho Advantageously, the film can be produced cost-effectively, yet have precisely predefinable properties.

[0013] According to one development, the display device comprises a transparent support having two substantially parallel main faces arranged at a distance from each other, the perforated mask being arranged on one of the main faces and the retarder being arranged on the other main face, this being in case the retarder is too thin to support itself. HoThe latter is then placed on a thicker support, for example by lamination, so that the support serves as a propagation path. According to an advantageous variant of this development, both the retarder and the reflective polarizer are arranged on this main surface of the support. This development is advantageous in that the retarder and / or the reflective polarizer, as the case may be, are arranged at a defined distance from and in a defined alignment with respect to the perforated mask. They therefore do not need to be aligned and adjusted relative to one another during installation in the display device and are not subject to any undesirable displacement from their adjusted positions during operation. Advantageously, the entire polarization recycler, from the microlens arrangement to the reflective polarizer, is prefabricated as a sandwich. The combination of the microlens arrangement with the support increases stability and allows the microlens arrangement to be designed particularly thin, which would then lack the necessary stability by itself when not connected to the support.

[0014] The stable configuration of the retarder is particularly Ho When embodied as a film or coating system, it can also be advantageously obtained by placing the retarder on the reflective polarizer, e.g., laminating or coating it thereon, without the two being connected by supports to the perforated mask and microlens arrangement. This still allows the distance between the perforated mask and the reflective polarizer to be set at a later manufacturing stage, which may be desirable under certain boundary conditions.

[0015] According to a further development, the microlenses of the microlens arrangement have rectangular apertures, which result in a conical distribution of the emitted light beam with an approximately rectangular cross section. Such a cross section is often desirable, for example, when illuminating the eyebox in a head-up display. In this case, the conical distribution is expressed, for example, by the opening angle of its shortest and longest semi-axes.

[0016] According to a further development, the microlenses of the microlens arrangement are arranged offset. This has the following advantage: the offset results in an overall deflection of the light beam. The polarization recycler can therefore also be used to further deflect incident light. If the offset of the microlenses is not constant but varies over the component, it is also possible to obtain an overall lens effect, e.g. a diverging lens, which does not deflect light in the center of the polarization recycler but allows an even stronger deflection at the sides.

[0017] According to an alternative variant, the perforated mask comprises holes arranged in an irregular structure. In this case, each of these holes is assigned a microlens with the same lens shape. However, the microlens apertures have unequal areas. This is advantageous in that the irregular distribution of the aperture portions results in a variable angular distribution for each microlens, thus resulting in a diffuser effect. A diffuser with polarization recycling is realized according to this development.

[0018] According to an arrangement of the present invention, the reflective polarizer is aligned parallel to the perforated mask so that the reflected light component is rotated in terms of its polarization by passing twice through the retarder and, as a result of reflection at the perforated mask, is superimposed on the directly transmitted component at the reflective polarizer, thus advantageously providing polarization recycling which increases efficiency.

[0019] Further advantageous configurations of the invention are also shown in the following description of exemplary embodiments. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows a schematic diagram of a prior art head-up display for a motor vehicle; [Figure 2] 1 shows a schematic representation of a display device of a head-up display. [Figure 3] 1 shows a schematic representation of a display device according to the invention for a head-up display; [Figure 4]1 shows a schematic representation of a further display device according to the invention for a head-up display; [Figure 5] 1 shows a polarization recycler. [Figure 6] 1 illustrates a microlens configuration with centered microlenses. [Figure 7] 1 shows a microlens configuration with offset microlenses. [Figure 8] 1 shows a polarization recycler with offset microlenses. [Figure 9] 1 shows a plan view of a microlens configuration. DETAILED DESCRIPTION OF THE INVENTION

[0021] In the following, for a better understanding of the principles of the present invention, embodiments of the present invention will be described in more detail with reference to the figures. The same reference numerals are used for the same or functionally identical elements in the figures and are not necessarily described again in each figure. It should be understood that the present invention is not limited to the represented embodiments, and the described features can also be combined or modified without departing from the scope of protection of the present invention as defined in the appended claims.

[0022] 1 shows a schematic diagram of a head-up display for a motor vehicle according to the prior art. The head-up display includes a display device 1, an optical unit 2, and a mirror unit 3. A beam of light rays SB1 is emitted from a display panel 11 and is reflected by a first mirror 21 onto a curved mirror 22, which reflects it towards the mirror unit 3. The mirror unit 3 is represented here as the windshield 31 of the motor vehicle. From there, a beam of light rays SB2 travels in the direction of the observer's eye 61.

[0023] The observer views a virtual image VB located outside the vehicle, above the engine hood, or even in front of the vehicle. Due to the interaction between the optical unit 2 and the mirror unit 3, the virtual image VB is an enlarged representation of the image displayed by the display panel 11. Here, the speed limit, the current vehicle speed, and navigation instructions are represented by symbols. As long as the eye 61 is within an eye box 62, represented by a rectangle, all elements of the virtual image are visible to the eye 61. If the eye 61 is outside the eye box 62, the virtual image VB is only partially observable to the observer or is not observable at all. The larger the eye box 62, the less restrictions the observer has when selecting his or her seating position.

[0024] The curvature of the curved mirror 22 is adapted to the curvature of the windshield 31, ensuring that image distortion is stable across the entire eyebox 62. The curved mirror 22 is rotatably mounted by a mounting 221. This allows rotation of the curved mirror 22 to displace the eyebox 62, thus adapting its position to the position of the eye 61. The first mirror 21 ensures that the path traveled by the light beam SB1 between the display panel 11 and the curved mirror 22 is long, while at the same time ensuring that the optical unit 2 remains compact. The optical unit 2 is separated from the environment by a transparent cover 23. Thus, the optical elements of the optical unit 2 are protected from, for example, dust present inside the vehicle. The anti-reflection protection 24 ensures that light reflected through the interface of the cover 23 is absorbed to prevent the observer from being dazzled. In addition to sunlight SL, light from other stray light sources 64 may also reach the display panel 11.

[0025] FIG. 2 shows a schematic diagram of a display device 1 of a head-up display. It shows a light source 12 whose light is collimated by a collimator 13. A collimated beam of light KLB has a height h in the image plane, perpendicular to its propagation direction ABR1. The beam of light is reflected in the propagation direction ABR1 by a mirror 14 arranged at an angle of α=45°, radiates through the display panel 11 in its propagation direction ABR2 aligned at an angle of 90° to the propagation direction ABR1, and enters the optical unit 2 (not shown here) in the form of a beam of light SB1. The display panel 11 is not arranged perpendicular to the propagation direction ABR2, but at an angle deviating from 90°, which is shown here as a very significant deviation from 90°. The use of the mirror 14 reduces the installation height in the propagation direction ABR2. Other embodiments dispense with such a mirror, so that the two propagation directions ABR1 and ABR2 coincide.

[0026] 3 shows a schematic representation of a display device 1 according to the invention for a head-up display. On the left side, it is possible to distinguish a light source 12 followed by a collimator 13 which generates a collimated light beam KLB having a parallel light beam. Here, the component beams KLB1, KLB2, ... of the collimated light beam KLB are shown. The collimated light beam KLB enters a polarization recycler 4 and emerges from the latter as linearly polarized light which enters the display panel 11, is provided by the latter with image information, and leaves said display panel as a beam of light SB1.

[0027] The polarization recycler 4 includes a microlens arrangement 41 consisting of many microlenses 42. The microlenses are embodied as converging lenses. A perforated mask 43 is located downstream of the microlens arrangement 41 in the beam direction. The perforated mask has a reflective surface on its side 45 facing away from the microlens arrangement 41. A retarder 46 is located downstream of the perforated mask 43 in the beam direction. The retarder is embodied, for example, as a quarter-wave plate. Other retardation elements that retard or change the polarization and phase of light can also be provided as the retarder 46. A reflective polarizer 47 is located downstream of the retarder 46 in the beam direction. The polarization recycler 4 thus includes the elements of the microlens arrangement 41, the perforated mask 43, the retarder 46, and the reflective polarizer 47. The microlens arrangement 41 is located on a first major surface 481 of a body 48, and the perforated mask 43 is arranged on a second major surface 482 of the body. The body 48 is transparent and preferably made of the same material as the microlenses 42. In an advantageous configuration, the microlenses 42 are embodied integrally with the body 48. According to another variant, the body 48 is a glass substrate and the microlenses 42 are applied to the glass substrate using a nanoimprinting method. The main faces 481, 482 are located at a distance A1 from each other, which corresponds to the focal length of the microlenses 42. In an advantageous configuration, the body 48 is Ho The microlens is Ho A reflective coating is applied to the first major surface 481 of the filter and provided with holes 44, to its second major surface 482.

[0028] It can be seen that the microlenses 42 of the microlens arrangement 41 are arranged without gaps. Each microlens 42 converts a parallel incident light beam of a collimated light beam KLBx (x=1, 2, ...) incident on its top into an outgoing light beam with a conical distribution KV1. The conical distribution KV1 has an aperture angle β1. The incident light beam is focused, with the focal plane of the outgoing light beam being located in the plane of the perforated mask 43. The outgoing light beam passes through the retarder 46. Since the outgoing light beam, like the incident light beam, does not have any preferred polarization, it does not have any preferred deflection after passing through the retarder 46. Upon incidence on the reflective polarizer 47, only the components aligned with the reflective polarizer 47 are transmitted, while the components polarized perpendicular to it are reflected. The reflected component passes through the retarder 46, is reflected by the reflective side 45 of the perforated mask 43, and passes through the retarder 46 again. After passing through the retarder 46 twice, the polarization direction is rotated by 90° and the light now passes through the reflective polarizer 47. Therefore, in addition to the component incident on the holes 44 in the perforated mask 43, the light originally reflected by the reflective polarizer 47 is also rotated with respect to its polarization and is supplied with the correct polarization to the display panel 11. The latter is, for example, a display panel 11 provided for linearly polarized light, such as a liquid crystal display (LCD). The distance between the perforated mask 43 and the reflective polarizer 47 is selected so that the back-reflected portion of the light beam KV1 has a diameter at incidence on the reflective side 45 of the perforated mask 43 similar to that of the microlens 42, so that the ratio between the illuminated coating area and the diameter of the holes in the perforated mask 43 is as large as possible. A beam of light SB1 exiting display panel 11 to the right in the image has a conical distribution KV1 defined by microlens 42. In this case, the transmission axis of the reflective polarizer is aligned so that the polarization of the transmitted light is aligned with the polarization axis of display panel 11. Light of the corresponding vertical polarization is reflected.

[0029] FIG. 4 shows a schematic diagram of a further embodiment of a display device according to the invention, for a head-up display. This substantially corresponds to the one depicted in FIG. 3, except that in this case the microlenses 42 have a different focal length. Therefore, the distance A2 between the first main surface 481 and the second main surface 482 is greater than that shown in the previous figures. Therefore, there is also a different aperture angle β2 for the conical distribution KV2. Therefore, by changing the focal length of the microlenses 42 and the distance A2, a conical distribution with a desired aperture angle β can be set.

[0030] In this embodiment, the display panel 11 is drawn at an angle to the light propagation direction ABR2 that deviates from 90°, such a configuration being particularly preferred for certain applications, such as for example head-up displays.

[0031] FIG. 5 shows a polarization recycler 4 corresponding to that shown in FIG. 4, albeit embodied integrally. As described above, the microlens arrangement 41 is disposed on a first major surface 481 of the body 48. The perforated mask 43 is located on the other major surface 482 of the body 48. The perforated mask 43 is connected to a support 49 on the side of the perforated mask facing away from the body 48. The reflective polarizer 47 and the adjacent retarder 46 are disposed on the other major surface of the support 49. The support 49 has a thickness B2. In the exemplary embodiment shown here, all elements of the polarization recycler 4 are connected to form a sandwich-like component. Other embodiment variations not shown here do not provide for all of these elements to be connected to each other. For example, in a variation, the retarder 46 and the reflective polarizer 47 are connected to each other, and the microlens arrangement 41 is connected to the body 48 and the perforated mask 43. These two assemblies are positioned at a distance from each other but are not surface-connected to each other. In this variant, the support 49 is omitted. Another variant provides the support 49 to be areally connected to the retarder 46 or the perforated mask 43, but to be spaced apart from the respective other component. In this case, the support 49 contributes to increased stability of the component that is areally connected to it in each case.

[0032] According to a variant not shown here, the retarder 46 is preferably arranged directly on the perforated mask 43 via lamination. The reflective polarizer 47 is then arranged at a distance from the retarder 46. According to one variant, the support 49 is again arranged between the retarder 46 and the reflective polarizer 47. According to another variant, there is only an air layer between them. In this case, elements that are not surface-connected to each other are fixed and aligned by externally arranged elements (not shown here), for example housing elements. The support 49 can also be designed as a transparent optical foil, the thickness B2 of which, compared to the distance A2 between the main faces 481, 482, is substantially smaller than that depicted here.

[0033] 6 shows a microlens arrangement 41 in which the microlenses 42 have rectangular main surfaces and are arranged in a centered manner. In this case, the microlens arrangement 41 is embodied integrally with a body 48. The microlenses 42 abut against each other at a contact line 421 in each case. The contact line 421 surrounding each microlens 42 forms a rectangle in plan view. The microlenses 42 therefore have rectangular apertures. The perforated mask 43 located below the body 48 is not depicted here. In plan view, its holes 44 are located in the center of each microlens 42, which is therefore centered.

[0034] 7 shows a microlens arrangement 41 in which the microlenses 42 have rectangular main surfaces and are arranged offset. Here, the microlens arrangement 41 is shown without the body 48. The microlenses 42 abut against each other at a contact line 421 in each case. The contact line 421 surrounding each microlens 42 forms a rectangle in plan view. The microlenses 42 therefore have rectangular apertures. The perforated mask 43 located below the body 48 is not shown here. In plan view, its holes 44 are not centered in the rectangular aperture of each microlens 42. The microlenses 42 shown here are therefore offset.

[0035] FIG. 8 shows a polarization recycler 4 with offset microlenses 42. The polarization recycler 4 includes a microlens arrangement 41 consisting of many microlenses 42. The microlenses 42 are embodied as converging lenses and have an offset arrangement similar to that shown in FIG. 7. A perforated mask 43 is located downstream of the microlens arrangement 41 in the beam direction. The perforated mask has a reflective surface on its side 45 facing away from the microlens arrangement 41. A retarder 46 is located downstream of the perforated mask 43 in the beam direction. A reflective polarizer 47 is located downstream of the retarder 46 in the beam direction. The polarization recycler 4 thus includes the elements of the microlens arrangement 41, the perforated mask 43, the retarder 46, and the reflective polarizer 47. The microlens arrangement 41 is located on a first major surface 481 of a body 48, and the perforated mask 43 is arranged on a second major surface 482 of the body. The body 48 is transparent and preferably made of the same material as the microlenses 42. In an advantageous configuration, the microlenses 42 are embodied integrally with the body 48.

[0036] It can be seen that the microlenses 42 of the microlens arrangement 41 are arranged without gaps. Each microlens 42 converts the parallel incident light beam of the collimated light beam KLB incident on its top into an outgoing light beam with a conical distribution KV3. The conical distribution KV3 has an aperture angle β3 and a deflection / tilt of the propagation axis by an angle depending on the degree of deflection of the microlens 42. The incident light beam is focused; in this case, the focal plane of the outgoing light beam is located in the plane of the perforated mask 43. The outgoing light beam passes through the retarder 46. Since the outgoing light beam, like the incident light beam, does not have any preferred polarization, it does not have any preferred polarization after passing through the retarder 46. Upon incidence on the reflective polarizer 47, only the components aligned with the reflective polarizer 47 are transmitted, while the components polarized perpendicular to it are reflected. The reflected component passes through the retarder 46, is reflected by the reflective side 45 of the perforated mask 43, and passes through the retarder 46 again. After passing through the retarder 46 twice, its polarization direction is rotated by 90° and it now passes through the reflective polarizer 47. Therefore, in addition to the component incident on the holes 44 in the perforated mask 43, the light originally reflected by the reflective polarizer 47 is also rotated with respect to its polarization and is supplied to the display panel 11 with the correct polarization. The latter is, for example, a display panel 11 provided for linearly polarized light, such as a liquid crystal display (LCD). The beam of light exiting the display panel 11 to the right within the image has a conical distribution KV3 defined by the microlens 42. In this case, the transmission axis of the reflective polarizer is aligned so that the polarization of the transmitted light is aligned with the polarization axis of the display panel 11. The corresponding vertically polarized light is reflected.

[0037] FIG. 9 shows a plan view of a microlens arrangement 41 with an irregular structure. Each microlens 42 has a triangular main surface and is surrounded by contact lines 421 arranged in a triangular manner. Here, by way of example, a circle is plotted at the center of a selected microlens 42, indicating where the focal point of the microlens is located and where the holes 44 of a perforated mask arranged according to the present invention are located—in this case, below the plane of the drawing. In the microlens arrangement 41 shown here, many such microlenses 42 are arranged in an irregularly distributed manner with irregular triangular aperture areas and the same optical properties. This arrangement corresponds to the irregular structure in which the holes 44 of the perforated mask 43 are arranged. For clarity, only one of the holes 44 is shown. Each hole 44 is assigned a microlens 42. In an ideal case, the arrangement of the holes 44 represents a random distribution.

[0038] The figure shows a microlens arrangement 41 with randomly distributed microlenses 42 with triangular apertures. Advantageously, other apertures allowing full coverage may also be used here, such as square, hexagonal or generally n-gonal apertures or combinations thereof, where n=3, 4, 5...

[0039] In cross section, the beam paths look similar to those shown in Figure 8, albeit with random dimensions. Each triangle formed by the three contact lines 421 still has a curved lens surface, so all parallel light beams incident on its top will converge at a focal point. Now, only the location of the focal point, and therefore the location of the holes 44, follows the distribution of these triangles.

[0040] Since all focal points are located within the plane of the perforated mask 43, there are jumps between the individual triangles at the contact line 421 between two microlenses 42 because the lens surface is, of course, randomly cut and not adapted to adjacent elements. However, since each element is built on the same lens surface, the vertices of the lenses should always be at the same level when placed within their respective triangles. In this case, the apertures are triangular, but in other cases they are "random" in terms of size and orientation. Here, N-gons, where N=3, 4, 5, etc., are also possible. Mixing N-gons with different values ​​of N is also possible. Similarly, curved boundaries, i.e., curved contact lines 421, are not excluded here, but they may be difficult to manufacture.

[0041] The core of the present invention is a microlens array, a microlens arrangement 41 made from converging lenses, and a microlens 42. The microlens arrangement 41 generates a desired angular distribution with an aperture angle β from parallel illumination light. In addition to the aperture angle, many further characteristics of the light distribution, such as the intensity distribution in different angular ranges, can be defined via the shape of the lens surface and the aperture. The converging lens focuses the light so that an array of focal points occurs at a short distance A from the microlens 42. The microlens 42 Ho When applied to the back surface of the lens, in this case the body 48, the lens parameters are selected accordingly, and then the focus of each microlens is set to Ho The second main surface 482, i.e., the surface of the coil, can be disposed in the vicinity of the second main surface 482. HoThe upper side of the mask 43 has a highly reflective coating in all areas not including the focal point. This therefore forms a kind of perforated mask 43, through which the light passes using the microlenses 42. After passing through the components, the light first passes through a quarter-wave plate, or retarder 46. The polarization not used by the display panel 11 is then reflected back by a reflective polarizer 47, and this polarization re-enters the reflective side 45 of the perforated mask 43. However, because the light now propagates divergently due to its pre-focusing, the diameter of each component beam KV significantly widens when it re-enters the perforated mask 43, and most of the component beams are incident on the coated portion of the perforated mask 43 and are reflected back toward the display panel 11. The distance between the perforated mask 43 and the reflective polarizer 47 is selected to be large in dependence on the aperture angle β, at which the reflected light will illuminate the entire perforated mask 43. As a result of two passes through the quarter-wave plate (or multiple passes in the case of a retarder with a retardation different from a quarter wave), the polarization is now rotated so that the light can pass through the reflective polarizer 47 and thus contribute to the overall brightness. This results in a very compact structure and preservation of the angular distribution of the microlens arrangement 42, without the need for complex beam splitter components. Display devices according to the invention may similarly achieve increased efficiency in display systems similar to those in head-up displays, which require very precise control of the angular distribution of the output light.

[0042] In contrast to known solutions in which incoming light beams from multiple light sources are not guided through the length and diameter of the perforated holes through which they pass, but are instead converted into an outgoing light beam with a conical distribution, the present invention provides for the conversion of a collimated or parallel incoming light beam into an outgoing light beam with a conical distribution. Therefore, the solution according to the present invention is particularly suitable for closed, parallel light beams and works without directly increasing the cross-sectional area of ​​the light. Naturally, the etendue increases in the process. Although there is an increase in the cross-sectional area during further propagation, this increase is negligible because, in the preferred exemplary embodiment, the display panel 11 follows directly after the polarization recycler 4. In other words, the polarization recycling in this case occurs within the available area of ​​the light beam. If the operation were instead performed by a beam splitter, the area would be doubled because the incoming beam would be split into two component beams that could not be recombined. Etendue, in simple terms, is a physical quantity resulting from the angular distribution at each point of the light beam and its cross-sectional area. Conservation laws dictate that etendue can always remain the same or can increase during passage through an optical system. In this case, there is an incident beam of parallel light KLB (angular distribution approximately 0°) with a particular cross-sectional area and associated etendue. The divergence angle is increased by the microlens arrangement 41, which increases the etendue.

[0043] For known systems to be efficient, the reflection from the light source below, i.e. below the plate, needs to be a reflection with very little loss, since most of the light needs to undergo so many reflections before passing through the drilled holes. The present invention is particularly suitable for integration into existing polarization recycling of light beams.

[0044] According to the invention, the perforated mask 43 is formed by a reflective coating having holes present therein. In contrast to the elongated perforated holes in known solutions, the plate is present in a thick plate having a reflective coating that is not continuously embodied at the locations of the perforated holes but leaves the perforated holes open.

[0045] One advantage of the solution according to the invention is, in particular, that the microlens arrangement 41 allows the creation of almost any desired light distribution in angular space, and this can be efficiently combined with polarization recycling.

Claims

1. A display device comprising a display panel (11) for linearly polarized light, a light source (12) for unpolarized light, and a polarization recycler (4), which in the path of the beam coming from the light source (12) successively: a microlens arrangement (41), a perforated mask (43) having a reflective embodiment on its side facing away from said microlens arrangement (41); - a retarder (46), - a reflective polarizer (47) and In a display device comprising: The microlenses (42) of the microlens arrangement (41) are arranged without any gaps; The light source (12) is a collimated light source, and the microlens (42) focuses the incident light so that it can pass through the holes in the perforation mask (43). A display device characterized by:

2. 2. The display device of claim 1, wherein the microlenses (42) of the microlens arrangement (41) convert a parallel incident light beam into an outgoing light beam having a conical distribution (KV, KV1, KV2) with defined aperture angles (β, β1, β2).

3. 3. The display device of claim 1 or 2, wherein the microlens arrangement (41) comprises a body (48) having two substantially parallel main surfaces (481, 482) arranged at a distance (A) from each other, the microlens (42) being arranged on one of the main surfaces (481) and the perforated mask (43) being arranged on the other main surface (482).

4. 3. The display device according to claim 1 or 2, wherein the perforated mask (43) is arranged in the focal plane of the microlens arrangement (41).

5. 3. Display device according to claim 1 or 2, wherein the perforated mask (43) is embodied as a reflective coating.

6. 4. The display device according to claim 3, wherein said body (48) is embodied as a foil.

7. 3. A display device as claimed in claim 1 or 2, comprising a transparent support (49) having two substantially parallel main surfaces arranged at a distance (B2) from each other, the perforated mask (43) being arranged on one of the main surfaces and either the retarder (46) or both the retarder (46) and the reflective polarizer (47) being arranged on the other main surface.

8. 3. The display device according to claim 1, wherein the microlenses (42) of the microlens arrangement (41) have rectangular apertures.

9. 3. The display device according to claim 1 or 2, wherein the microlenses (42) of the microlens arrangement (41) are arranged offset.

10. 3. A display device according to claim 1 or 2, wherein the perforated mask (43) comprises holes (44) arranged in an irregular structure, and each of the holes (44) is assigned a microlens (42).

11. 3. The display device of claim 1, wherein the reflective polarizer (47) is aligned parallel to the perforated mask (43) so that the reflected light component is rotated in terms of its polarization by passing twice through the retarder (46) and, as a result of reflection at the perforated mask (43), is superimposed on the directly transmitted component at the reflective polarizer (47).

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