Display 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 linear polarization as illumination, a light source for non-polarization, and a polarization recycler.

Background Art

[0002] Polarization recycling is a widely used method employed in display devices to maximize the utilization efficiency of non-polarized light from illumination. In polarization recycling, non-polarized light is converted into 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 the polarization orthogonal to it is converted by the polarization recycler mainly into light with the desired polarization. Thus, substantially all of the incident light exits the polarization recycler as light with the desired polarization. As a result, losses caused by conventional polarizers that do not allow light to pass through with unwanted polarization but absorb or reflect it are avoided. Display devices generally include a display panel for linear polarization and thus require polarized incident light. Therefore, illumination light with an unused polarization direction is often filtered by a reflective polarizer and converted into the correct polarization through scattering, thereby making it available for use in the display panel. This variant functions in both the case of an edge lighting system where the light source emits light into the light guide from the side and then the latter outputs and couples the light in the direction of the display panel, i.e., indirectly illuminates the display panel, and in the case of direct illumination. As an alternative to scattering in the latter case, a method in which polarization recycling is realized using a polarization beam splitter and a retarder foil can also be used.

[0003] U.S. Patent Application Publication No. 2005 / 0270439A1 and International Publication No. 2006 / 038417A1 pamphlet are examples of indirect illumination and polarization recycling by a reflective polarizer and scattering. U.S. Patent Application Publication No. 2004 / 0263789A1 and U.S. Patent Application Publication No. 2013 / 0286479A1 are examples of direct illumination and polarization recycling by a polarization beam splitter and a retarder.

[0004] The fact that scattering-based schemes in many applications result in a very wide light angular distribution that is inefficient, for example, in the case of a head-up display (often abbreviated as HUD), should be regarded as a drawback of known solutions. The scheme using a polarizing beam splitter is very complex to implement from a technical perspective and requires a large space.

[0005] U.S. Patent Application Publication No. 2018 / 0299730A1 discloses a display device including a display panel for linearly polarized light, a light source for non-polarized light, and a polarization recycler. In this case, the polarization recycler includes, in the beam path coming from the light source, successively, a microlens configuration, a perforated mask having a reflective embodiment on its side facing away from the microlens configuration, a retarder, and a reflective polarizer. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0006] There is a need for an improved display device related thereto and having polarization recycling. MEANS FOR SOLVING THE PROBLEM

[0007] The display device according to the present invention includes a microlens configuration in which microlenses are arranged without gaps. These microlenses are arranged side by side such that the transition region between two microlenses occupies as small a space as possible and ideally does not exist. The gapless configuration of the microlenses ensures that all of the light arriving from the light source is directly utilized. This avoids losses that can occur in the case of potential multiple reflections of light that enters and is reflected in the intermediate space of the microlenses in the case of spaced-apart microlenses. The microlenses focus the incident light so that the incident light 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 has the appropriate polarization for the display panel after passing through the retarder a plurality of times, preferably twice. This enables efficient polarization recycling without significant cost, in which case substantially all of the unpolarized light generated by the light source is supplied to the display panel as linearly polarized light. The birefringent / delay element is provided as a retarder. For example, this is a quarter-wave plate that converts linearly polarized light to circularly polarized light when the axis of the quarter-wave plate is properly aligned. In this case, two passes are sufficient to obtain a 90° rotation of the polarization direction. The reflective polarizer is aligned such 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 configuration are configured such that they convert a parallel incident light beam into an outgoing 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 case of a display device. The focal length of the microlenses and their configuration with respect to the perforated mask are appropriately selected according to the desired aperture angle characteristics. The aperture angle characteristics are maintained also during polarization recycling. Thus, the configuration according to the present invention can be used in a display unit already designed for a parallel incident beam and can, for example, replace a complex or inefficient polarization recycler inside it. In a practical implementation, the incident beam is not ideally parallel and the outgoing beam does not form an ideal cone. Depending on the main surface of the microlenses, which can be circular, rectangular, hexagonal, etc., the conical distribution also has a corresponding cross-section. The intermediate region where light is blocked according to the microlenses or the transmitted light is not refracted remains between the microlenses in the microlens configuration in the case of a round cross-section. Such a microlens configuration can be manufactured cost-effectively and generates a light cone with a round cross-section, but leaves the light incident on the intermediate region unused. In contrast, microlenses with different cross-sections can be arranged to cover their area, which increases the proportion of usable light but also involves a light cone with a corresponding cross-section.

[0009] Advantageously, the microlens configuration includes a body having two substantially parallel main surfaces arranged at a distance from each other, the microlenses are arranged on one of the main surfaces, and the perforated mask is arranged on the other main surface. This has the advantage that the distance of the microlens configuration from the perforated mask and the relative alignment of these two with respect to each other are ensured by the manufacture of the microlens configuration. Thus, there is no need to align these two with respect to each other later, and as a result, the cause of errors is reduced. The perforated mask is located at a defined distance from the microlenses and can be dispensed with without the complex adjustments that would occur in the case of elements manufactured separately and assembled later.

[0010] According to an advantageous configuration of the invention, the perforated mask is arranged in the focal plane of the microlens configuration. This enables the perforated mask to have very small holes because, ideally, the light cone is punctiform in the focal plane and, realistically too, the light cone generated by the microlens has its region of minimum diameter there. As small as possible holes mean the largest possible reflection area and thus the smallest possible light losses. Only the light reflected by the reflective polarizer and incident on the holes of the perforated mask can be used for polarization recycling. The perforated mask, i.e., the position of the locations where its holes are located, corresponds to the focus of the microlens configuration in this case.

[0011] According to an advantageous configuration of the invention, the perforated mask is a reflective coating arranged on the side facing away from the microlens configuration. Such a coating can be produced cost - effectively, for example, by a printing method.

[0012] According to a development of the invention, the body is embodied as a foil. The microlens is located on one side of the foil and the perforated mask as a reflective coating is arranged on the other side. This development is advantageous in that such a foil can be produced cost - effectively and yet has precisely pre - definable properties.

[0013] According to one development form, the display device includes a transparent support portion having two substantially parallel main surfaces arranged at a distance from each other, the perforated mask is arranged on one of the main surfaces, and the retarder is arranged on the other main surface. This enables the retarder to be embodied as a foil that is too thin to support itself. The latter is then arranged on a thicker support portion, for example, by lamination. As a result, the support portion serves as a propagation path. According to an advantageous variant of this development form, both the retarder and the reflective polarizer are arranged on this main surface of the support portion. This development form is advantageous in that, optionally, the retarder and / or the reflective polarizer are arranged at a defined distance from and in a defined alignment with the perforated mask. Thus, during installation into the display device, they do not need to be aligned and adjusted relative to each other and are not exposed to any undesirable displacement from the adjusted position during operation. Advantageously, the entire polarization recycler from the microlens configuration to the reflective polarizer is pre-manufactured as a sandwich. The combination of the microlens configuration and the support portion increases stability and enables the microlens configuration to be designed particularly thin, but in that case, it would lack the necessary stability by itself when not connected to the support portion.

[0014] A stable configuration of the retarder, particularly when the latter is embodied as a foil or coating system, can advantageously also be obtained by arranging the retarder on the reflective polarizer, for example, by laminating or coating it thereon, without these two being connected to the support portion by the perforated mask and the microlens configuration. This still enables 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 development form, the microlens of the microlens configuration has a rectangular aperture. This results in a conical distribution of the outgoing light beam having a substantially rectangular cross-section. Such a cross-section is often desirable, for example, when illuminating an eyebox in a head-up display. In this case, the conical distribution is represented, for example, by the opening angles of its shortest and its longest semi-axes.

[0016] According to a development form, the microlenses of the microlens configuration are arranged offset. This has the following advantages. The offset results in an overall deflection of the light beam. The polarization recycler can thus also be used to further deflect the incident light. If the offset of the microlenses is not constant and varies over the component, it is also possible to obtain an overall lens effect, for example, a diverging lens that does not deflect the light at the center of the polarization recycler but allows for a more powerful deflection at the side.

[0017] According to an alternative variant, the perforated mask includes holes arranged in an irregular structure. In this case, each of these holes is assigned a microlens having 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 and thus involves a diffuser effect. A diffuser with polarization recycling is realized according to this development form.

[0018] According to the configuration of the present invention, the reflective polarizer is aligned parallel to the perforated mask such that the reflected light component is rotated with respect to its polarization by passing through the retarder twice and, as a result of reflection at the hole mask, is superimposed on the directly transmitted component in the reflective polarizer. This is advantageous in that polarization recycling that increases efficiency is thus obtained.

[0019] A further advantageous configuration of the present invention is also shown in the following description of the exemplary embodiments.

Brief Description of the Drawings

[0020]

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DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, 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 drawings. The same or functionally identical elements in the figures are denoted by the same reference numerals and are not necessarily described again for each figure. It should be understood that the present invention is not limited to the embodiments shown and that the features described may also be combined or modified without departing from the scope of protection of the present invention as defined in the appended claims.

[0022] Figure 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 light beam SB1 is emitted from the display panel 11 and reflected onto the curved mirror 22 by the first mirror 21, and the curved mirror 22 reflects it in the direction of the mirror unit 3. The mirror unit 3 is represented here as the windshield 31 of the motor vehicle. From there, the light beam SB2 travels in the direction of the observer's eye 61.

[0023] The observer observes a virtual image VB located outside the motor vehicle, above the engine hood, or further in front of the motor 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 speed of the motor vehicle, and the navigation instructions are represented by symbols. As long as the eye 61 is inside the eye box 62 shown as 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 or not observable at all by the observer. The larger the eye box 62, the smaller the restrictions when the observer selects their seating position.

[0024] The curvature of the curved mirror 22 is adapted to the curvature of the windshield 31, ensuring that the distortion of the image is stable across the entire instrument cluster 62. The curved mirror 22 is rotatably mounted by a mounting 221. The rotation of the curved mirror 22 enabled thereby displaces the instrument cluster 62 and thus enables the position of the instrument cluster 62 to be adapted to the position of the eye 61. The first mirror 21 serves to lengthen the path along which the light beam SB1 travels between the display panel 11 and the curved mirror 22, while at the same time ensuring that the optical unit 2 remains compact despite this. The optical unit 2 is delimited from the environment by a transparent cover 23. Thus, the optical elements of the optical unit 2 are protected, for example, from dust located inside the vehicle. The anti-reflection protection 24 serves to reliably absorb the light reflected through the interface of the cover 23 so that the observer is not misled. In addition to sunlight SL, light from another disturbing light source 64 can also reach the display panel 11.

[0025] Figure 2 schematically shows the display device 1 of the head-up display. This shows a light source 12 whose light is collimated by a collimator 13. The beam KLB of collimated light has a height h in a direction perpendicular to its propagation direction ABR1 within the image plane. The light beam is reflected by a mirror 14 arranged at an angle of α = 45° in the propagation direction ABR1 and radiates through the display panel 11 in its propagation direction ABR2, which is aligned at an angle of 90° with respect to the propagation direction ABR1, and from there enters the optical unit 2 in the form of a light beam SB1 (not shown here). The display panel 11 is arranged at a predetermined angle deviating from 90° and not perpendicular to the propagation direction ABR2, which is shown here as deviating very significantly from 90°. The use of the mirror 14 reduces the installation height in the propagation direction ABR2. Other embodiments manage without such a mirror, with the result that the two propagation directions ABR1 and ABR2 coincide.

[0026] Figure 3 schematically shows the display device 1 according to the present invention of the head-up display. On the left side, it is possible to identify the light source 12 followed by a collimator 13 that generates a collimated light beam KLB having a parallel light beam. Here, a plurality of ray component beams KLB1, KLB2,... of the collimated light beam KLB are shown. The collimated light beam KLB is incident on the polarization recycler 4, exits from the latter as linearly polarized light incident on the display panel 11, is provided with image information by the latter, and exits from the display panel as a light beam SB1 of the ray.

[0027] The polarization recycler 4 includes a microlens configuration 41 composed of many microlenses 42. The microlens is embodied as a converging lens. The perforated mask 43 is located downstream of the microlens configuration 41 in the beam direction. The perforated mask has a reflective embodiment on its side surface 45 facing away from the microlens configuration 41. The 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. It is also possible to provide another retardation element as the retarder 46 that delays or changes the polarization and phase of light. The reflective polarizer 47 is located downstream of the retarder 46 in the beam direction. Therefore, the polarization recycler 4 includes elements of the microlens configuration 41, the perforated mask 43, the retarder 46, and the reflective polarizer 47. The microlens configuration 41 is located on the first main surface 481 of the main body 48, and the perforated mask 43 is disposed on the second main surface 482 of the main body. The main body 48 is transparent and preferably made of the same material as the microlens 42. In an advantageous configuration, the microlens 42 is embodied integrally with the main body 48. According to another variant, the main body 48 is a glass substrate, and the microlens 42 is applied to the glass substrate using a nanoimprint method. The main surfaces 481, 482 are located at a distance A1 corresponding to the focal length of the microlens 42 from each other. In an advantageous configuration, the main body 48 is a foil, the microlens is imprinted on the first main surface 481 of the foil, and a reflective coating provided with holes 44 is applied to its second main surface 482.

[0028] It is possible to identify that the microlenses 42 of the microlens configuration 41 are arranged without gaps. Each of the microlenses 42 converts a parallel incident light beam of the collimated light beam KLBx (x = 1, 2,...) incident on its upper part into an outgoing light beam having a conical distribution KV1. The conical distribution KV1 has an opening angle β1. The incident light beam is focused, and in this case, the focal plane of the outgoing light beam is arranged within the plane of the perforated mask 43. The outgoing light beam passes through the retarder 46. Since the outgoing light beam has no particular polarization, just like the incident light beam, they have no particular deflection after passing through the retarder 46. When incident on the reflective polarizer 47, the latter is passed only by the components aligned according to the reflective polarizer 47, while the components polarized perpendicular to it are reflected. The reflected components pass through the retarder 46, are reflected by the reflective side surface 45 of the perforated mask 43, and pass through the retarder 46 again. After passing through the retarder 46 twice, the polarization direction is rotated by 90°, and thus passes through the reflective polarizer 47 here. Therefore, in addition to the components 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 supplied to the display panel 11 with the correct polarization. The latter is 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 such that the retroreflected part of the beam KV1 of the light rays has a diameter at the time of incidence on the reflective side surface 45 of the perforated mask 43 equivalent to that of the microlenses 42, and as a result, the ratio of the illuminated coating area to the diameter of the holes in the perforated mask 43 is selected to be as large as possible. The beam SB1 of the light rays exiting to the right from the display panel 11 within the image has a conical distribution KV1 defined by the microlenses 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.

[0029] Figure 4 schematically shows a further embodiment of the display device according to the present invention for a head-up display. This substantially corresponds to what is depicted in FIG. 3, where in this case the microlenses 42 have different focal lengths. Accordingly, the distance A2 between the first main surface 481 and the second main surface 482 is larger than that shown in the previous figures. Accordingly, there are also different opening angles β2 for the conical distribution KV2. Accordingly, by changing the focal length of the microlenses 42 and the distance A2, a conical distribution with a desired opening angle β can be set.

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

[0031] Figure 5 shows a polarization recycler 4 corresponding to that shown in FIG. 4, although it is integrally embodied. As described above, the microlens configuration 41 is disposed on the first main surface 481 of the body 48. The perforated mask 43 is located on the other main surface 482 of the body 48. The perforated mask 43 is connected to the support portion 49 at the side surface of the perforated mask facing away from the body 48. The retarder 46 adjacent to the reflective polarizer 47 is disposed on the other main surface of the support portion 49. The support portion 49 has a thickness B2. In the exemplary embodiment shown here, all the elements of the polarization recycler 4 are connected so as to form a sandwich-like component. Variations of other embodiments 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 configuration 41 is connected to the body 48 and the perforated mask 43. These two assemblies are disposed at a distance from each other but are not connected face-to-face. The support portion 49 is omitted in this variation. Another variation provides the support portion 49 so that it is connected face-to-face to the retarder 46 or the perforated mask 43 but is disposed at a distance from each of the other components. In this case, the support portion 49 contributes to the increased stability of the component to which it is connected face-to-face in each case.

[0032] According to a modification not shown here, the retarder 46 is preferably placed directly on the perforated mask 43 via lamination. Then, the reflective polarizer 47 is placed at a distance from the retarder 46. According to one modification, the support 49 is also placed between the retarder 46 and the reflective polarizer 47 in this case. According to another modification, only an air layer exists therebetween. In this case, elements that are not connected planar to each other are fixed and aligned by an element arranged outside (not depicted here), for example a housing element. The support 49 can also be designed as a transparent optical foil, and this thickness B2 is substantially smaller than that depicted here compared to the distance A2 between the main surfaces 481, 482.

[0033] FIG. 6 shows the microlens configuration 41, in which case the microlenses 42 have rectangular main surfaces and are arranged in a centered manner. In this case, the microlens configuration 41 is embodied integrally with the body 48. The microlenses 42 abut against each other with contact lines 421 in each case. The contact lines 421 surrounding each microlens 42 form a rectangle in a plan view. Accordingly, the microlenses 42 have a rectangular aperture. The perforated mask 43 located below the body 48 is not depicted here. In the plan view, the holes 44 are located at the centers of the respective microlenses 42, and thus this is centered.

[0034] FIG. 7 shows a microlens configuration 41, in which case the microlenses 42 have rectangular main surfaces and are arranged offset. Here, the microlens configuration 41 is shown without the body 48. The microlenses 42 abut against each other by contact lines 421 in each case. The contact lines 421 surrounding each microlens 42 form a rectangle in a plan view. Accordingly, the microlenses 42 have a rectangular aperture. The perforated mask 43 located below the body 48 is not depicted here. In the plan view, the holes 44 are not located at the centers of the rectangular apertures of the respective microlenses 42. Accordingly, the microlenses 42 shown here are offset.

[0035] FIG. 8 shows a polarization recycler 4 having offset microlenses 42. The polarization recycler 4 includes a microlens configuration 41 consisting of a plurality of microlenses 42. The microlenses 42 are embodied as converging lenses and have an offset configuration similar to that shown with respect to FIG. 7. The perforated mask 43 is located downstream of the microlens configuration 41 in the beam direction. The perforated mask has a reflective embodiment on its side surface 45 facing away from the microlens configuration 41. The retarder 46 is located downstream of the perforated mask 43 in the beam direction. The reflective polarizer 47 is located downstream of the retarder 46 in the beam direction. Accordingly, the polarization recycler 4 includes the elements of the microlens configuration 41, the perforated mask 43, the retarder 46, and the reflective polarizer 47. The microlens configuration 41 is located on the first main surface 481 of the body 48, and the perforated mask 43 is arranged on the second main 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 is possible to identify that the microlenses 42 of the microlens configuration 41 are arranged without a gap. Each of the microlenses 42 converts a parallel incident light beam of the collimated light beam KLB incident on its upper part into an outgoing light beam having a conical distribution KV3. The conical distribution KV3 has an opening angle β3 and a deflection / tilt of the propagation axis by an angle corresponding to the degree of displacement of the microlens 42. The incident light beam is focused, and in this case, the focal plane of the outgoing light beam is arranged within 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, after passing through the retarder 46, they do not have any preferred polarization. When incident on the reflective polarizer 47, the latter is passed only by the components aligned according to the reflective polarizer 47, while the components polarized perpendicular to it are reflected. The reflected components pass through the retarder 46, are reflected by the reflective side surface 45 of the perforated mask 43, and pass through the retarder 46 again. After passing through the retarder 46 twice, the polarization direction is rotated by 90°, so it passes through the reflective polarizer 47 here. Therefore, in addition to the components 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 supplied to the display panel 11 with the correct polarization. The latter is a display panel 11 provided for linear polarization, such as a liquid crystal display (LCD), for example. The beam of light rays emerging from the display panel 11 to the right in the image has a conical distribution KV3 defined by the microlenses 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 configuration 41 having an irregular structure. The microlenses 42 each have a triangular main surface and are surrounded by contact lines 421 arranged in a triangular pattern. Here, as an example, a circle is plotted at the center of a selected microlens 42, which indicates the location of the focus of the microlens and the location of the holes 44 of the perforated mask arranged according to the present invention - in this case, below the plane of the drawing. In the microlens configuration 41 shown here, many such microlenses 42 are arranged in an irregularly dispersed manner with irregular triangular aperture regions and the same optical properties. Its configuration 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 of the holes 44 is assigned to a microlens 42. Ideally, the configuration of the holes 44 represents a random distribution.

[0038] The drawing shows a microlens configuration 41 having randomly dispersed microlenses 42 with triangular apertures. Advantageously, here, for example, other apertures enabling full coverage such as quadrilateral, hexagonal or generally n-sided apertures or combinations thereof can also be used, where n = 3, 4, 5...

[0039] In the cross-sectional view, the beam path appears similar to that shown in FIG. 8, although having random dimensions. Each triangle formed by the three contact lines 421 still has a curved lens surface, and thus all parallel light beams incident on its upper part converge at the focus. Here, only the location of the focus and thus the location of the holes 44 follow the distribution of these triangles.

[0040] Since all foci are located within the plane of the perforated mask 43, there are jumps between the individual triangles at the contact line 421 between the two microlenses 42 because, of course, the lens surfaces are randomly cut here and do not fit adjacent elements. However, since each element is constructed on the same lens surface, if they are placed within their respective triangles, the vertices of the lenses should always be at the same level. In this case, the aperture is triangular, but in other cases it is "random" with respect to size and orientation. Here, N-gons where N = 3, 4, 5... are equally possible. A mixture of N-gons with different values of N is also the same. Similarly, curved boundaries, i.e., curved contact lines 421, are not excluded here, but they can be difficult to manufacture.

[0041] The core of the present invention lies in the microlens array, the microlens configuration 41 manufactured from a converging lens, and the microlens 42. The microlens configuration 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 such that an array of foci occurs at a short distance A from the microlens 42. When the microlens 42 is applied to the back surface of the foil, in this case the body 48 and the lens parameters are correspondingly selected, and then the foci of the respective microlenses can be arranged in the vicinity of the second main surface 482, which is the surface of the foil. The second main surface 482, i.e., the upper side of the foil, has a highly reflective coating in all regions that do not contain foci. Thus, this forms a kind of perforated mask 43 through which the light passes using the microlens 42. After passing through the component, the light first passes through a quarter-wave plate, i.e., a retarder 46. Then, the polarization not used by the display panel 11 is reflected back by the reflective polarizer 47 and this polarization is incident again on the reflective side surface 45 of the perforated mask 43. However, since the light diverges and propagates here because it was pre-focused, the diameter of each component beam KV significantly expands when it is incident again on 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 in the direction of the display panel 11. The distance between the perforated mask 43 and the reflective polarizer 47 is selected to increase according to the dependence on the aperture angle β such that the reflected light illuminates 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 having a different retardation from a quarter-wave), the polarization is rotated here such that the light can pass through the reflective polarizer 47 and thus contributes to the overall luminance. As a result, a very compact structure and the retention of the angular distribution of the microlens configuration 42 are obtained, and a complex beam splitter component is not required.The display device according to the present invention can similarly achieve an increase in efficiency in a display system similar to that of a head-up display that requires very precise control of the angular distribution of the emitted light.

[0042] Contrary to known solutions where incident light beams coming from multiple light sources are not guided through the length and diameter of the perforated holes they pass through and are converted into an emitted light beam having a conical distribution, the present invention provides for the conversion of a collimated or parallel incident light beam into an emitted light beam having a conical distribution. Thus, the solution according to the present invention is particularly suitable for the case of a closed parallel beam of light and functions without directly increasing the cross-sectional area of the light. Naturally, the étendue increases during the process. There is an increase in cross-sectional area during further propagation, but this increase can be ignored because, in a preferred exemplary embodiment, the display panel 11 directly follows behind the polarization recycler 4. In other words, it is as follows. Polarization recycling occurs within the available area of the beam of light rays in this case. If the operation were instead performed with a beam splitter, the area would double because the incident beam is split into two component beams that cannot be recombined again. Étendue is, simply put, a physical quantity resulting from the angular distribution at each point of a beam of light and its cross-sectional area. The conservation law states that the étendue can either remain the same or increase during passage through an optical system. In this case, there is an incident beam of a parallel beam of light KLB (angular distribution approximately 0°) having a specific cross-sectional area and associated étendue. The divergence angle is increased by the microlens configuration 41, which increases the étendue.

[0043] In order for a known system to be efficient, the reflection by the lower part, i.e., below the plate, by the light source needs to be a reflection with very small losses because most of the light requires a very large number of reflections until it passes through the perforated holes. The present invention is particularly suitable for integration into the polarization recycling of existing light beams.

[0044] According to the present invention, the perforated mask 43 is formed by a reflective coating having holes present therein. In contrast, the elongated perforated holes are present in a thick plate in known solutions. This plate does not have a continuous embodiment at the location of the perforated holes, but has a reflective coating that leaves the perforated holes open.

[0045] One advantage of the solution according to the present invention is that, in particular, the microlens configuration 41 enables the generation of almost any desired light distribution within the angular space, which can be efficiently combined with polarization recycling.

Claims

Claim 1 A display device including a display panel (11) for linearly polarized light, a light source (12) for non-polarized light, and a polarization recycler (4), wherein the polarization recycler (4) is successively arranged in a beam path coming from the light source (12), - a microlens configuration (41), - a perforated mask (43) having a reflective embodiment on its side facing away from the microlens configuration (41), - a retarder (46), - a reflective polarizer (47) In the display device, the microlenses (42) of the microlens configuration (43) are arranged without gaps. The display device is characterized thereby. Claim 2 The microlenses (42) of the microlens configuration (41) convert a parallel incident light beam into an outgoing light beam having a conical distribution (KV, KV1, KV2) with a defined opening angle (β, β1, β2). The display device according to claim 1. Claim 3 The microlens configuration (41) includes a body (48) having two substantially parallel main surfaces (481, 482) arranged at a distance (A) from each other. The microlenses (42) are arranged on one of the main surfaces (481), and the perforated mask (43) is arranged on the other main surface (482). The display device according to claim 1 or 2. Claim 4 The perforated mask (43) is arranged in the focal plane of the microlens configuration (41). The display device according to any one of claims 1 to 3. Claim 5 The perforated mask (43) is embodied as a reflective coating. The display device according to any one of claims 1 to 4. Claim 6 The body (48) is embodied as a foil. The display device according to any one of claims 3 to 5. Claim 7 Including a transparent support (49) having two substantially parallel main surfaces arranged at a distance (B2) from each other. The perforated mask (43) is arranged on one of the main surfaces, and either the retarder (47) or both the retarder (47) and the reflective polarizer (48) are arranged on the other main surface. The display device according to any one of claims 1 to 6. Claim 8 The microlenses (42) of the microlens configuration (41) have a rectangular aperture. The display device according to any one of claims 1 to 7. Claim 9 The microlenses (42) of the microlens configuration (41) are arranged offset, the display device according to any one of claims 1 to 8.

10. The perforated mask (43) includes holes (44) arranged in an irregular structure, and each of the holes (44) is assigned a microlens (42), the display device according to any one of claims 1 to 9.

11. The reflective polarizer (47) is aligned parallel to the perforated mask (43) such that the reflected light component is rotated with respect to its polarization by passing through the retarder (46) twice and, as a result of reflection at the perforated mask (43), is superimposed on the directly transmitted component in the reflective polarizer (47), the display device according to any one of claims 1 to 10.

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