Optical element and method for manufacturing the same

Abstract

The present invention relates to a planarly extended optical element (1) having a light entrance side and a light exit side. The optical element comprises first and second transparent regions (B1, B2) made of materials having first and second different refractive indices (N1, N2), alternating with each other, wherein the first refractive index (N1) is greater than the second refractive index (N2). First and second layers (OB, AB) that are opaque or can be switched to opaque are arranged on the light entrance surface and the light exit surface of the second region (B2). In the case of the opaque layers (OB, AB), light passing through the optical element (1) is restricted in its propagation direction compared to the case of the layers (OB, AB) that are switched to transparent.

Description

Technical Field

[0001] In recent years, great progress has been made in widening the viewing angle of LCDs. However, in many cases, this very large viewing area of ​​the screen can be a disadvantage. Mobile devices such as laptops and tablets are also increasingly storing information, such as bank details or other personal and sensitive data. Therefore, people need to control who sees this sensitive data; they must be able to choose between wide viewing angles to share information on the display with others, such as when viewing holiday photos or for advertising purposes. On the other hand, if they want to keep the image information confidential, a narrower viewing angle is desirable.

[0002] A similar problem exists in vehicle manufacturing: while the engine is running, the driver cannot be distracted by visual content such as digital entertainment programs, while passengers want to enjoy this content while driving. Therefore, a screen that can switch between corresponding display modes is required. Background Art

[0003] Micro-sheet-based additional films have been used on mobile displays for visual data protection. However, these films are not switchable and must always be applied and removed manually. They also have to be transported separately to the display when not needed. A significant disadvantage of using such thin sheet films is the associated light loss.

[0004] US 6,765,550 B2 describes this type of vision protection using micro-lamellae. The biggest disadvantage here is the mechanical removal or mechanical connection of the filter and the light loss in the protection mode.

[0005] US Pat. No. 5,993,940 A describes a method for realizing a viewing protection mode using a film having small prism strips evenly arranged on the surface. The development and production of the film are quite complex.

[0006] In WO 2012 / 033583 A1, switching between free viewing and restricted viewing is achieved by driving liquid crystals between so-called “dye” layers. This results in light losses and is quite costly.

[0007] US2012 / 0235891A1 introduces a very complex screen backlight. According to Figure 1 and Figure 15 , where not only multiple light guides are used, but also other complex optical elements such as micro lens elements 40 and prism structures 50 are used, which convert the light from the rear illumination to the front illumination on the optical path. This is expensive and complex to implement and also causes light loss. Figure 17In a variant of the invention, both light sources 4R and 18 generate light with a narrow radiation angle, and the light from the rear light source 18 is first converted in a complex manner into light with a large radiation angle. This complex conversion strongly reduces the brightness as described above.

[0008] JP2007-155783A uses complex, computationally complex special optical surfaces19 to deflect light into narrow or wide areas depending on the angle of incidence. These structures resemble Fresnel lenses. Interference edges also exist, deflecting light in undesirable directions. Therefore, it remains unclear whether a reasonable light distribution can actually be achieved.

[0009] US2013 / 0308185A1 describes a special light guide with a stepped design that emits light over a large surface in different directions, depending on the direction of light from its narrow edge. Combined with a transmissive image reproduction device, such as an LC display, this creates a screen that can be switched between a free-viewing mode and a restricted-viewing mode. The main disadvantage is that this design can only produce limited visual effects for left / right or up / down, but not for all three simultaneously, as required for a specific payment process. Furthermore, even in restricted-viewing mode, residual light can still be seen from obstructed viewing angles.

[0010] The applicant's WO 2015 / 121398 A1 describes a screen with two operating modes, in which scattering particles are present in the volume of the respective light guide, which are essential for switching between operating modes. However, scattering particles made of polymers generally have the disadvantage of light separation from the two large surfaces. As a result, approximately half of the useful light is misdirected, toward the background lighting, and due to their structure, it cannot be fully recovered there. Furthermore, the scattering particles made of polymers distributed in the volume of the light guide can, in certain cases, especially at high concentrations, lead to scattering effects that reduce the visual protection effect in the protected operating mode.

[0011] The above methods and arrangements generally have the common disadvantage that they significantly reduce the brightness of the basic screen and / or require complex and expensive optical elements to switch modes and / or provide only limited viewing protection and / or reduce the resolution in free viewing mode and / or allow only a narrow viewing area, with the brightness across the entire angular range falling so rapidly that the image seen by the viewer is very uneven in brightness. Summary of the Invention

[0012] The object of the present invention is therefore to develop a planar optical element that can influence the propagation direction of incident light in a defined manner and that can be selectively switched between at least two operating states: a free-viewing mode and a protected-viewing mode. In the protected-viewing mode, light is emitted from the optical element only within a restricted angular range compared to the free-viewing mode, i.e., in fewer propagation directions. The optical element should be inexpensive to implement and universally usable, in particular, with various screen types, so that switching between protected-viewing and free-viewing modes is possible without significantly or only negligibly reducing the resolution of such screens. Furthermore, the optical element should, in principle, make it possible to achieve a top-hat light distribution. This means that the brightness does not decrease by more than 15% within an angular range of at least 7 degrees around the average emission angle.

[0013] This object is achieved by a planarly extended optical element having a light entrance side and a light exit side, the optical element comprising at least first regions made of a transparent first material having a first refractive index and second regions made of a transparent second material having a second refractive index, the first regions and the second regions alternating in a one-dimensional or two-dimensional periodic sequence on the surface of the first optical element, the first refractive index being greater than the second refractive index over the entire wavelength range visible to the human eye. The optical element further comprises a first layer, permanently opaque or switchable between a transparent state and an opaque state, on the light entrance side of each second region, and a second layer, permanently opaque or switchable between a transparent state and an opaque state, on the light exit side of each second region.

[0014] Light incident on the optical element on the light entrance side, due to the first layer being in an opaque state, enters the optical element only through the light entrance surface of the first region. There, depending on the angle of incidence, polarization, and the ratio of the first refractive index to the second refractive index, the light either a) propagates unimpeded within the first region or is totally reflected and then coupled out again at the light exit surface of the corresponding first region; or b) penetrates from the first region into the adjacent second region, propagates therein, and is ultimately absorbed at its light exit surface when the second layer is in an opaque state, or is coupled out when the second layer is in a transparent state; or c) if the light has already penetrated from the first region into the adjacent region, the light penetrates into another adjacent first region and, depending on the propagation direction and subsequently given polarization, is coupled out at the light exit surface or continues to propagate within the optical element until it is coupled out or absorbed. Unimpeded propagation in case a) means that the light does not strike the region boundary but instead passes directly through the first region without being totally reflected.

[0015] Therefore, the light emitted from the optical element on the light exit side is limited in its propagation direction compared to the light incident on the optical element on the light entrance side, as long as at least one of the two layers, the first layer and / or the second layer, preferably the second layer, is opaque.

[0016] The incident angle of light entering the first region specifically refers to its direction vector, which describes the horizontal and vertical incident angles of the first region toward the light incident surface (also called the "lower surface") and is very important for the continued propagation of light in the first region B1 or at the interface with the second region, in addition to the polarization state.

[0017] In principle, case c) should include all rays that do not fall into cases a) or b).

[0018] The "periodic sequence" of the first and second regions does not mean that the first and second regions must always have the same width and / or height, but rather that the first and second regions simply always alternate. However, the sizes of the first and second regions may vary.

[0019] The third case, c), only occurs when light penetrates from a first region into an adjacent second region and from there into another adjacent first region. This corresponds to a light ray that, after crossing a refractive index boundary, passes from the first region into the second region and then from the second region to the adjacent first region on the other side to cross the next refractive index boundary. Depending on the propagation direction and polarization, the light is either coupled out at the light exit surface or continues to propagate in the optical element until it is coupled out or absorbed. This case is particularly useful for special applications, for example, when the light propagation direction should be absorbed within a moderate angle of approximately 30° to 50°, but should be loaded with light in larger and smaller angles. The case mentioned under c) can be included or excluded based on optical simulations of the optical element by appropriately dimensioning the first and second refractive indices and selecting the widths of the first and second regions and their heights. Further details are provided below.

[0020] To achieve the preferred and inventive limitation of the propagation direction of the incident light (i.e., condition a) where only light rays are present), it is essential that the first and second layers are substantially opaque. As long as one of the layers is not opaque, oblique light rays above the actual critical angle for total internal reflection at the interface between the first and second regions can exit at the upper edge of the second region, or, if necessary, can enter the second region below, for example, via the upper edge, i.e., the light exit surface of the first region B1.

[0021] Advantageously, each first layer on the light exit surface of the second region is formed by a permanently absorbing layer and / or by at least one layer that reflects away from the optical element. If only one reflective layer is present, which is possible within the scope of the present invention, then this reflective layer naturally also has opaque properties. This reflective property contributes to increased efficiency, for example, when the optical element according to the present invention is incorporated into a lighting device, such as an LCD panel.

[0022] It is also possible that every other layer on the light exit surface of the second region is formed by a permanently absorbing layer. If, in a certain static configuration, the first and second layers have permanently opaque properties and if the first and second refractive indices do not change, the optical element has a permanent limiting effect on the propagation direction of light incident thereon.

[0023] In a specific configuration of the optical element according to the present invention, the first refractive index (N1) of the material in the first region (B1) and / or the second refractive index (N2) of the material in the second region (B2) can be switched between at least two states, so that: the ratio of the two refractive indices (N1, N2) at the boundary between the first region (B1) and the second region (B2) can be modulated respectively, so that the above-mentioned propagation direction limitation can be changed.

[0024] To this end, at least one of the materials of the first and / or second regions can consist of a liquid crystal in contact with an electrode, so that a change in the refractive index of linearly polarized light in the liquid crystal is induced by changing the voltage across the electrode. The electrodes can be transparent, for example in the form of an indium tin oxide layer (ITO layer), in which case the electrodes are arranged, for example, on the light exit and light entrance surfaces, the top and bottom sides of the first region. However, if electrodes are required to change the second refractive index of the second region, it is also possible, in particular when the first and second layers are configured as permanent absorption layers, to use opaque, possibly even light-proof, electrodes.

[0025] For this configuration with liquid crystals, the first and second layers are preferably permanently opaque, so that generally only the light rays of case a) can exit the optical element upward. However, these light rays of case a) have a narrower or wider angular range of propagation directions, depending on the refractive index difference at the boundary surface between the first and second regions. The greater the refractive index difference, the wider this angular range, while the smaller the refractive index difference, the narrower this angular range.

[0026] On the other hand, if, in other switchable configurations of the present invention, the first layer and / or the second layer can be switched between an opaque and a transparent state, the property of restricting the propagation direction of light incident on the optical element can be turned on and off: the direction of light propagation is restricted only when both layers are opaque (case a). As long as one of the two layers is transparent, the direction of light propagation is no longer restricted (cases a), b), and possibly c). Thus, the optical element can be switched. Even if both layers are switched to transparent, the optical element will only cause light deflection and total internal reflection, depending on the incident direction of the light, but will not block light overall.

[0027] In a preferred switchable configuration, only the upper, second layer is designed to be switchable from opaque to transparent, while the lower, first layer is designed to be permanently opaque (and possibly also reflective). This is sufficient to achieve the desired effect.

[0028] The switchability of the two layers may preferably be based on one or more of the following principles: electrowetting, electrophoresis, electrochromism and / or liquid crystal cells.Other configurations are of course also possible.

[0029] In the case of electrowetting, at least two states of the liquid or liquid mixture subject to electrowetting are defined for at least one of the two layers. In a first operating state, the layer in question covers the corresponding surface of the second region as completely as possible, i.e., is opaque (the propagation direction is then restricted, case a)), and in a second operating state, the layer in question covers the corresponding surface of the second region only to the smallest possible extent, i.e., is as transparent as possible (the propagation direction is then restricted to no or only to a negligible extent, cases a), b), and optionally c).

[0030] In the case of electrophoresis, for at least one of the two layers, electrophoretically mobile, opaque particles are provided in a liquid or gel matrix. Due to the action of an electric field that can be applied via transparent electrodes, these particles then, in a first operating state, cover the corresponding surface of the second region as a corresponding layer as completely as possible, rendering the relevant layer opaque (the propagation direction is then restricted). In a second operating state with a different electric field distribution, the particles, as a corresponding layer, cover the corresponding surface of the second region with the smallest possible area, or are transferred to a reservoir or distributed in a volume, so that the layer becomes transparent (the propagation direction is then not restricted).

[0031] In principle, this embodiment can also be designed using electrophoresis in such a way that for at least one of the two layers, in particular for the second layer, the total internal reflection structure on the surface of the second region is either disrupted (the light is accordingly absorbed by the particles) or not disrupted (the particles are spaced a corresponding distance apart) depending on whether the particles are positioned directly on the second region or remote from the second region (up to a maximum of 100 μm), so that total internal reflection occurs and the corresponding light is at least partially coupled out of the light exit surface of the first region after further propagation in the optical element. In general, all optical switching technologies based on this or similar so-called "frustrated total internal reflection" variants can be used in this context.

[0032] Janus particles can also be considered as particles that can be rotated to a standstill due to an electric field effect, with approximately half of their surface being opaque and the other half being scattering, white, and / or reflective. These Janus particles can also be formed in each of two layers so as to switch between an opaque state and a reflective state. In the latter state, the corresponding light, after further propagation in the optical element, is at least partially coupled out of the light exit surface of the first region due to reflection.

[0033] In the case of electrochromism, the two layers are covered with an electrochromic material, such as some metal oxide (TiO2, NiO, Nb2O, MoO3, Ta2O5, WO3, IrO2, Zr2O5) and a corresponding transparent electrode, such as ITO (IndiumTinOxide, indium-doped tin oxide), FTO (FluorineTinOxide, fluorine-doped tin oxide) or AZO (aluminum-doped zinc oxide), embedded in the electrochromic material. Depending on the voltage applied to the electrodes, at least two states are defined for the two layers. In the first operating state, the relevant layer is opaque (the propagation direction is then restricted), and in the second operating state, the relevant layer is transparent (the propagation direction is then unrestricted).

[0034] The two layers can also be designed as a liquid crystal cell, for example a TN cell with an appropriate pair of polarizers. The layers can then be switched to opaque (then the propagation direction is restricted) or transparent (then the propagation direction is unrestricted) by applying a corresponding electric field or voltage to the electrodes. If the optical element according to the invention is used in conjunction with such an LCD panel, one of the polarizers in the pair can also physically correspond to a polarizer of the LCD panel.

[0035] In general, the smaller the refractive index difference between the first and second refractive indices, the narrower the light distribution of the light leaving the optical element. For a clear physical understanding, it should be noted again that "refractive index" refers to the first or second refractive index at a selected wavelength (e.g., 580 nm), or the corresponding dispersion curve over the entire wavelength range visible to the human eye. In the case of a dispersion curve, the refractive index difference refers to the corresponding value corresponding to the difference between the two refractive indices at the selected visible wavelength λ.

[0036] In this context, it should be noted that optical elements can be designed as very precise wavelength-selective filters in special configurations: If the dispersion curves of the two refractive indices intersect wavelength-dependently, then in the opaque layer, at wavelengths where the second refractive index is greater than the first, the corresponding wavelength range is effectively eliminated—that is, not coupled out of the optical element—while the wavelength range where the first refractive index is greater than the second is coupled out of the optical element. Depending on the configuration of the dispersion curve, such wavelength-selective optical elements must then be operated with obliquely directed light, as the critical angle for total internal reflection at the interface between the first and second regions must be used to separate the spectra. In an exemplary refinement, such wavelength-selective filters are used to separate two spectra, for example, one in a narrow ultraviolet range and one in a broad white light spectrum. If the separation effect is eliminated by reducing the opacity of at least one of the two layers, both spectra can be transmitted through the filter. The ultraviolet light can then be converted into visible white light, thus making it possible to switch between different angular spectra for white light.

[0037] In an advantageous embodiment of the optical element, the first and second regions are arranged alternately in stripes across the surface of the optical element when viewed in a parallel projection perpendicular to the optical element. Thus, the light propagation direction is restricted perpendicular to the stripe-shaped regions, while there is no restriction parallel to the stripe-shaped regions.

[0038] In contrast, another configuration provides that, when viewed in a parallel projection perpendicular to the optical element, the first regions are distributed over the surface of the optical element in the form of dots, circles, ellipses, rectangles, hexagons, or other two-dimensional shapes, and the second regions are each shaped complementary thereto. This effectively restricts the light propagation direction in at least two planes perpendicular to the surface of the optical element. In practice, the effect of such an optical element is typically such that the light propagation direction of the transmitted light is focused at any angle close to or parallel to the perpendicular bisector of the optical element. In this context, "close" means that the deviation from the perpendicular bisector or a line parallel thereto is less than 25° or 30°, depending on the configuration.

[0039] Other shapes of the first and second regions are also possible. It is always important for the functioning of the invention that the first and second regions directly adjoin each other optically, so that an optical step in the refractive index is present without any air gaps.

[0040] Another configuration provides that, when viewed in a section perpendicular to the upper surface of the optical element, the first and second regions are designed as a trapezoid. This configuration of the first and second regions results in a targeted influence on the propagation direction of light leaving the optical element: depending on the configuration, the light is more or less focused on the surface. Furthermore, a peak shift can be achieved by a corresponding inclination of the boundary surface between the first and second regions, for example by a parallelogram-shaped cross-section of the first and second regions. The advantage of the trapezoidal shape is that the angular distribution is better focused, further improving the eye protection pattern.

[0041] Furthermore, it can be advantageous if the at least temporarily opaque first and / or second layer is embedded in the material forming the first region, wherein the material portion of the first region of the optical element preferably transitions seamlessly into the portion embedded in the respective layer.

[0042] It is also possible to apply a lens structure, preferably a convex lens structure, to at least a portion of the first region, preferably to all of the first region, on its light exit side, i.e., the upper side as viewed by the observer. This helps to influence the defined propagation direction of the light emitted from the optical element. Alternatively or additionally, the light entry side of the first region, i.e., the lower side as viewed by the observer, can have a concave or convex lens structure to influence the direction of light entering the first region and, therefore, whether the light ultimately falls into the aforementioned situations a), b), or c).

[0043] Basically, within the scope of the invention, the upper second layer and the lower first layer can be interchanged, ie the first optical element functions, especially if both layers are permanently opaque, and it does not matter which large-area optical element is upper or lower.

[0044] Furthermore, it can be helpful to arrange polarizers, optionally reflective polarizers, below and / or above the optical element to optimize the effect. Using polarizers to control polarization increases the efficiency of using refractive index transitions. Furthermore, p-polarization of the incoming or outgoing light can be used to minimize Fresnel reflections, i.e., to optimize the confinement of the light propagation direction.

[0045] For special applications, at least one first region can be formed on the optical element, where, when viewed in a parallel projection perpendicular to the optical element, its shortest extent is at least twenty times larger than the shortest extent of the optical element. All second regions, viewed in a parallel projection perpendicular to the optical element, ensure that within the at least one first region, except at its edges and ignoring parallel offsets, the propagation direction of light exiting the optical element is unrestricted relative to the light incident on the optical element. This means that the restriction of the propagation direction does not affect the entire surface of the optical element. Such unrestricted first regions can also be repeated multiple times on the optical element without touching each other.

[0046] Furthermore, it may be useful to form, in addition to the first and second regions, further regions having different parameters in shape and / or refractive index from those of the first and second regions, so that light penetrating these further regions and exiting the exit optical element experiences additional confinement in the propagation direction that is different from that in the first regions. Thus, regions distributed across the optical element can be confined in different light propagation directions and can be implemented with different focuses.

[0047] Furthermore, it is conceivable to apply additional reflective and / or absorbing layers to the optical element to further enhance or modulate the effect of limiting the light propagation direction. Furthermore, protective coatings or substrates can be applied to the light entrance and / or exit sides, i.e., above and / or below the optical element. However, the optical dimensioning should take into account the light deflection and the effect on the light direction when coupling out, particularly when coupling out from the first region.

[0048] The present invention is of particular interest in the use of the above-described optical element for an image reproduction unit (e.g. an LCD panel, an OLED or micro LED or any other display technology) or for a transmissive image reproduction unit (e.g. an LCD panel). In the latter case, the optical element will be directly integrated into the lighting device for the transmissive image reproduction unit (e.g. an LCD panel), in particular into a switchable configuration. The lighting device can then be used permanently as a directional backlight (when the first and second layers are permanently opaque) and can be used, for example, in a configuration according to WO 2015 / 121398 or WO 2019 / 002496 of the applicant. Alternatively, such a lighting device comprising at least one surface emitter and an optical element according to the invention can also be used directly as a switchable lighting device for an LCD panel, in which case at least one of the two layers can be switched between a transparent mode and an opaque mode.

[0049] In the above-mentioned application method, a switchable view protection for the image reproduction unit is realized: in a first operating state, in which only the situation a) remains for the light emerging from the optical element, the view protection effect is realized according to the design with a flat-top light distribution (Top-Hat-Lichtverteilung); in a second operating state, in which usually situations a) and b) and only in exceptional cases situation c) also apply to the light emerging from the optical element, a free viewing mode is realized, in which the image reproduction unit can be freely viewed from all directions.

[0050] If the optical element according to the invention is arranged in front of the image reproduction unit in the viewing direction in order to selectively or permanently restrict the direction of its light propagation, an optical device can optionally be present on the image display unit to focus the light emitted by the individual pixels of the image reproduction device into a beam substantially on the surface facing the first area. This is possible, for example, with a microlens grid or lenticular lens having a period approximately equal to the pixel width (or, if necessary, the pixel height). In the best case, the period of the first area should match the period of the pixel width or height.

[0051] Such a screen comprising at least one optical element as described above, also referred to as a first optical element, and an image reproduction unit can be used, for example, in a vehicle or a mobile device. Furthermore, the image reproduction unit can be retrofitted with a first optical element, regardless of whether the first optical element is switchable, by arranging the first optical element in front of the image reproduction unit.

[0052] The present invention also includes a method for producing such a first optical element, comprising the following steps. First, a mold is produced, which has the positive structure of the desired first region and the negative structure of the carrier substrate (i.e., the second region is filled with mold material, while the first region is not filled with mold material; in this case, a cavity for the carrier substrate can be present in the mold, and the carrier substrate is filled with a polymer for the first region in a subsequent step). The mold is then filled with a first polymer, which is initially liquid and has a first refractive index after hardening. The first polymer is then hardened by ultraviolet light or cooling, and the workpiece is subsequently removed from the mold. Subsequently, the structure of the second region in the workpiece is filled with a second polymer, which has a second refractive index after hardening. The second polymer is also hardened by ultraviolet light or cooling.

[0053] Optionally, after the first polymer or the second polymer is hardened, the second area on the surface, i.e., the upper and lower surfaces of the workpiece as viewed from the observer, is evaporated or sputtered with an opaque or transparent-opaque switchable material through a mask protecting the first area to obtain the first layer or the second layer, or is printed with an opaque material.

[0054] Furthermore, the present invention also comprises another method for producing a (first) optical element, which comprises the following steps. First, a plurality of base blocks are produced, which in sequence comprise the following interconnected layers: a second layer serving as an absorption layer, a transparent second layer made of a material having a second refractive index, an opaque first layer and a transparent first layer made of a material having a first refractive index. Subsequently, a plurality of base blocks are stacked together and connected to form a first stacked block. Slices having the thickness of the second layer are cut from the stacked block. These slices are stacked and glued together, with a transparent first layer having the first refractive index and the first layer thickness between each slice, to obtain a second stacked block. Optical elements are then cut from the second stacked block. In this case, the first layer can preferably be made reflective. For example, the base blocks can be connected to each other and / or the slices can be connected to the transparent first layer by vulcanization. The process of cutting slices from the first stacked block and / or cutting optical elements from the second stacked block is preferably carried out perpendicular to the plane of the surface extension of the individual layers.

[0055] In a special configuration of the optical element, the transparent second layer having the second refractive index can also be selected to be absorbing. The second layer serving as an absorbing layer can then be omitted.

[0056] Other alternative production methods include, for example, using two polymers to design the first region B1 and the second region B2 with different refractive indices during 3D printing; etching glass, where the etched region (either the first or second region) is preferably subsequently filled with polymer; crosslinking the polymers differently; and using photo-aligned molecules. In each case, the first and second layers are then applied, for example, as described above. Of course, other methods for manufacturing optical components are also possible.

[0057] The objectives of the present invention are also achieved by a method for limiting the propagation direction of light propagating through a surface region within the wavelength range visible to the human eye, the method comprising the following steps. In a first step, light is surface-modulated through a surface aperture, the surface aperture comprising at least a transparent first region and an opaque second region, the first and second regions alternating in a one-dimensional or two-dimensional periodic sequence across the surface of the aperture. Over the entire wavelength range, the light propagating through the transparent first region is split into the following light rays based on the angular dependence of the refractive index: one light ray is coupled out at an angle less than the critical angle for total internal reflection, at an angle at a refractive index boundary, and ultimately after one or more total internal reflections or unimpeded propagation; and another light ray continues to propagate beyond the critical angle for total internal reflection, i.e., at an angle greater than the critical angle for total internal reflection for the material combination, through the refractive index boundary, and is then absorbed by an absorber. Consequently, the coupled-out light has a restricted light propagation direction compared to the originally planar propagating light.

[0058] The above explanations of the (first) optical element according to the invention in various configurations can be applied here as appropriate, wherein the first and second regions or here can correspond to each other in a transferable manner. For redundancy reasons, no detailed explanation is given here.

[0059] The present invention also includes an optical element comprising a one- or two-dimensional periodic sequence of two transparent complementary shapes, each with a different refractive index, optionally formed on a planar substrate, thereby forming a plane in each of two directions. Advantageously, one refractive index can be equal to one, i.e., the material in one of the molds is, for example, air. Consequently, light incident on the optical element from a preferred direction is transmitted unimpeded, while light incident at an angle greater than 15° from the preferred direction is deflected by the optical element due to total internal reflection and / or Fresnel reflection. The propagation direction of the emitted light is also affected. The above configuration is analogous and will not be elaborated upon here.

[0060] Finally, the present invention also encompasses another planarly extended optical element having a light entrance side and a light exit side. This element comprises at least a first region made of a transparent material with a first refractive index and a second region made of an opaque material with a second refractive index. The first and second regions alternate in a one- or two-dimensional periodic sequence across the surface of the optical element. The first refractive index is greater than the second refractive index across the entire wavelength range visible to the human eye. Due to the opaque material of the second region, light incident on the first large surface of the optical element enters the optical element only through the light entrance surface of the first region. Depending on the geometric direction of incidence, polarization, and the ratio of the first to second refractive indices, the light either a) propagates unimpeded within the first region or is totally reflected and then coupled out again at the light exit surface of the corresponding first region, or b) penetrates from the first region into the adjacent second region and, due to the opaque material of the second region, is absorbed there. Due to the different first and second refractive indices, light penetrating the second region is refracted more strongly away from the vertical. This improves absorption of the light compared to materials with the same refractive index. Therefore, such light rays are extinguished better or more strongly than in the case without the refractive index difference.In general, the propagation direction of light leaving the optical element at its second large face is restricted compared to light incident on the optical element at its first large face.

[0061] This configuration improves upon the prior art in the following ways: firstly, a flat-top light distribution can also be achieved with an optical element similar to a thin-film filter, because, due to total internal reflection, more useful light is transmitted into the desired restricted angular range than would normally be the case in the prior art without total internal reflection. Secondly, the angular range of light penetrating the third optical element is significantly more restricted, because the opaque thin film not only ensures the direction of the light but also ensures a difference in refractive index between the two regions. This means that light penetrating the second region is refracted more strongly away from the vertical and must therefore travel a longer distance through the absorptive material, and is therefore extinguished more strongly than would be the case without this refractive index difference.

[0062] Opaque materials with a second refractive index are so named because of their opaque appearance. Specifically, this material is actually a transparent material with a second refractive index, but with an absorptive material, in particular absorptive particles, mixed in to create an overall opaque effect; in other words, an opaque material is a material with transparent and opaque parts. The opaque material can, for example, consist of a paint or polymer as the transparent part, and for the opaque part, for example, graphite particles with a size of less than 500 nm in the direction of its maximum extension, or carbon black nanoparticles with a size of less than 200 nm, such as soot particles. Alternatively or in combination, the opaque part of the opaque material can also contain a dye or a mixture of dyes. A suitable dye is, for example, Sudan Black, which absorbs all light in the visible range. The mass fraction of absorptive particles in the opaque material should generally not be greater than 50%. However, exceptions are possible.

[0063] In a preferred design, between each of the two second regions, a third region is formed from another opaque material having a third refractive index, which is greater than both the first and second refractive indices. In this particular case, the refractive index difference between the first and second refractive indices should preferably be no greater than 0.1, but a larger difference between the first and third refractive indices is desirable for effectiveness. Furthermore, the second region can be formed between the light incident side of the optical element and the third region, on the one hand, and between the light exit side of the optical element and the light exit surface of the first region, on the other hand. This further enhances the focusing of the light exit angle range, thereby improving the vision protection mode.

[0064] Here, the structure of the further opaque material having a third refractive index is similar to that of the opaque material having a second refractive index, i.e., it includes a transparent portion and an opaque portion, and the mass fraction of the absorbing particles is a maximum of 50%. In this configuration with three different materials, the mass fraction of the absorbing particles in the opaque material having a second refractive index can also be significantly less than 50%, as long as it is sufficiently high in the further opaque material having a third refractive index.

[0065] The optical element just described can advantageously include a reflective portion on one of the large surfaces, preferably the lower large surface, which can be an angle-dependent reflective portion of the entire large surface or a fully reflective portion on the surface of the second region. The explanations given above regarding the specially configured optical element also apply to this optical element and therefore need not be repeated.

[0066] In this regard, the present invention also includes a method for producing the aforementioned optical element, comprising the following steps: First layers composed of a transparent material having a first refractive index and second layers composed of an opaque material having a second refractive index are alternately stacked, wherein the first refractive index is greater than the second refractive index. These first and second layers are then joined together, for example, by vulcanization or gluing. Finally, the optical element is cut from the layer composite.

[0067] In general, for all optical elements, the roughness R at the interface between regions of different refractive index is a It should preferably be less than or equal to 20 nm.

[0068] The various configurations of the present invention described above can also be implemented directly on a self-luminous image reproduction unit. OLED panels, which will be described in more detail below, are particularly suitable here. However, other self-luminous display types are also conceivable.

[0069] For example, this can be achieved as follows: a first region made of a material having a first refractive index is applied directly to the light-emitting area of ​​the OLED pixel. A second region having a structure complementary to the first region is applied to the non-light-emitting area of ​​the OLED panel, the second region being covered with a first layer and / or a second layer that is at least temporarily opaque, i.e., permanently opaque or switchably opaque. The first region is not covered with a scattering structure to increase the light output from the OLED pixel, but is preferably located on the upper side of the at least temporarily opaque first and second layers.

[0070] In principle, if the above parameters are varied within certain limits, the performance of the present invention remains unchanged.

[0071] It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The present invention is explained in more detail below using embodiments with reference to the accompanying drawings, which also disclose features important to the present invention. These embodiments are for illustrative purposes only and should not be construed as restrictive. For example, the introduction of an embodiment with multiple elements or components should not be interpreted as implying that all of these elements or components are necessary for implementation. On the contrary, other embodiments may include alternative elements and components, fewer elements or components, or additional elements or components. Unless otherwise stated, the elements or components of different embodiments may be combined with each other. The modifications and variations described for one of the embodiments may also apply to the other embodiments. To avoid repetition, the same or mutually corresponding elements are marked with the same reference numerals in different figures and are not explained multiple times. Among them:

[0073] Figure 1a A schematic diagram (sectional view) shows a first optical element according to a first configuration in a first state, wherein only the light of case a) is coupled out of the optical element;

[0074] Figure 1b a schematic diagram (sectional view) showing a first optical element according to a first configuration in a second state, wherein only the light from cases a) and b) is coupled out of the optical element,

[0075] Figure 1c a schematic diagram (cross-sectional view) showing the first optical element according to the first configuration in a third state, in which no light is absorbed but only deflected and / or totally reflected;

[0076] Figure 1d A schematic diagram (sectional view) shows a first optical element according to a second configuration in a first state, wherein only light from cases a) and c) is coupled out of the optical element;

[0077] Figure 2 A schematic diagram showing a first region and a second region of an optical element when viewed in a parallel projection perpendicular to the optical element, wherein the first region and the second region are arranged alternately in a strip-like manner on a surface of the optical element;

[0078] Figure 3a A schematic diagram showing a first region and a second region of an optical element when viewed in a parallel projection perpendicular to the optical element, the first region being distributed in a rectangular shape on a surface of the optical element and being completely surrounded by the second region;

[0079] Figure 3b A schematic diagram showing first to fourth regions of the optical element when viewed in a parallel projection perpendicular to the optical element, wherein the first, third, and fourth regions are distributed in a rectangular shape on a surface of the optical element and are completely surrounded by the second region;

[0080] Figure 4a schematic diagram (cross-sectional view) showing a first optical element according to a third configuration;

[0081] Figure 5 a schematic diagram (cross-sectional view) showing a first optical element according to a fourth configuration;

[0082] Figure 6a a schematic diagram (cross-sectional view) showing a first optical element according to a fifth configuration;

[0083] Figure 6b a schematic diagram (cross-sectional view) showing a first optical element according to a sixth configuration;

[0084] Figure 6c a schematic diagram (cross-sectional view) showing a first optical element according to a seventh configuration;

[0085] Figure 7 a schematic diagram (cross-sectional view) showing a first optical element according to an eighth configuration;

[0086] Figure 8 shows a simulation of normalized brightness for three sets of parameters of light emitted from a first optical element in a first configuration plotted against emission angle;

[0087] Figure 9 shows simulations of normalized brightness for three additional sets of parameters of light emitted by the first optical element according to the first configuration, plotted over emission angle, in comparison with a thin layer filter;

[0088] Figure 10 shows a simulation of normalized brightness for three sets of parameters of light emitted by the first optical element according to the second configuration, plotted against emission angle;

[0089] Figure 11 a simulated portion showing the brightness of light emitted from the first optical element according to the first configuration outside the range of 25° to +25°;

[0090] Figure 12 A schematic diagram (sectional view) shows a first optical element according to a ninth configuration in a first state, wherein only the light of case a) is coupled out of the optical element within a narrow angular range;

[0091] Figure 13 A schematic diagram (sectional view) of the first optical element according to the ninth configuration in the second state is shown, wherein only the light of case a) is present, but the light of case b) is present. Figure 12 Compared with the conditions of , the output from the optical element can be coupled out in a wider angle range;

[0092] Figure 14 A schematic diagram showing regions C1 and C2 of a method, wherein these regions are arranged alternately in strips;

[0093] Figure 15 a schematic diagram (cross-sectional view) showing a second optical element according to a first configuration;

[0094] Figure 16 a schematic diagram (cross-sectional view) showing a second optical element according to a first configuration, with exemplary light rays plotted;

[0095] Figure 17 a schematic diagram showing a first optical element according to a tenth configuration;

[0096] Figure 18 shows a comparison of simulations of normalized brightness of light emitted from a first optical element according to first and eighth configurations, plotted with respect to emission angle;

[0097] Figure 19 shows a comparison of simulations of normalized brightness of light emitted from a first optical element according to a ninth configuration in two states, plotted versus emission angle;

[0098] Figure 20 a schematic diagram (cross-sectional view) showing a first optical element in a first configuration in a first state, when used together with a transmissive image reproduction unit and a backlight;

[0099] Figure 21 A schematic diagram (cross-sectional view) shows a first optical element in a first configuration in a first state, when used together with a self-luminous image reproduction unit;

[0100] Figure 22 1. A diagram showing a scheme in which the first optical element according to the first configuration is modified to form a switchable eleventh configuration (cross-sectional view);

[0101] Figure 23 1. A diagram showing a modification of the first optical element according to the first configuration to form a switchable twelfth configuration (cross-sectional view), here the first state;

[0102] Figure 24 1. shows a modification of the first optical element according to the first configuration to form a switchable twelfth configuration (cross-sectional view), here the second state;

[0103] Figures 25a to 25f A schematic diagram for explaining a method for producing a first optical element is shown;

[0104] Figure 26 A schematic diagram showing a third optical element;

[0105] Figures 27a to 27c Different configurations of the third optical element are shown in improved versions;

[0106] Figure 28Another configuration of the third optical element is shown;

[0107] Figure 29 shows the ray paths under different incidence conditions, and

[0108] Figure 30 Shows the angular range of the transmitted light compared to the incident light.

[0109] The accompanying drawings are not drawn to scale and are merely schematic representations. Furthermore, for the sake of greater clarity, only a few light rays are shown in each case, although in reality there are many more. DETAILED DESCRIPTION

[0110] An exemplary planarly extending first optical element 1 includes at least first regions B1 composed of a transparent first material having a first refractive index N1 and second regions B2 composed of a transparent second material having a second refractive index N2. The first and second regions alternate in a one- or two-dimensional periodic sequence across the surface of the first optical element 1. The first refractive index N1 is greater than the second refractive index N2 across the entire wavelength range visible to the human eye. The first optical element 1 also includes a first layer OB that is at least temporarily opaque on the underside of each second region B2 and a second layer AB that is at least temporarily opaque on the upper side of each second region B2. "At least temporarily" means that the layer is either permanently opaque or can be switched between an opaque and a transparent state. If the layer is permanently opaque, it need not be switchable. The upper side generally refers to the light exit side of the optical element 1, specifically the light exit surfaces of the first and second regions. Similarly, the lower side corresponds to the light entrance side of the optical element 1, specifically the light entrance surface of the first or second region. An observer or user of the optical element looks toward the upper side of the element, from which light exits.

[0111] Light incident on the light incident side of the optical element 1 enters the optical element 1 only through the light incident surface of the first region B1 due to the first layer OB when the first layer OB is in an opaque state, and there, depending on the angle of incidence, polarization and the ratio of the first refractive index N1 to the second refractive index N2: a) is totally reflected in the first region B1 or propagates unimpeded and then couples out again at the light exit surface of the corresponding first region B1, or b) penetrates from the first region B1 into the adjacent second region B2, propagates in the second region, and is finally absorbed on its light exit side if the second layer AB is in an opaque state, or is coupled out when the second layer AB is in a transparent state, or c) if the light penetrates from the first region (B1) into the adjacent second region (B2), it penetrates again into another adjacent first region (B1) and, depending on the propagation direction and polarization given at the time, is coupled out at the light exit surface or continues to propagate in the optical element (1) until it is coupled out or absorbed. Ultimately, the light emitted from the optical element (1) on the light exit side is limited in its propagation direction compared to the light incident on the optical element (1) on the light incident side. In principle, case c) should include all light rays that do not fall into cases a) or b). In practice, there are multiple first regions B1 and second regions B2 on the first optical element 1.

[0112] In this regard, Figure 1a A schematic diagram of such a first optical element 1 according to a first configuration is shown in a first state (i.e., the first layer OB and the second layer AB are opaque), wherein only the light from case a) is coupled out of the optical element 1. Compared to the light incident on the optical element 1 from below, the coupled-out light has a restricted propagation direction. The light from case b) is absorbed by the second layer AB. Light incident on the first layer OB from below is also absorbed. For dimensioning, D1 denotes the width of the first region B1, D2 denotes the width of the second region B2, and H denotes the same height of the two regions B1 and B2. For special applications, the first region B1 and the second region B2 can also have different heights within certain limits.

[0113] Figure 1b A schematic diagram of the first optical element 1 according to the first configuration is also shown in the second state, in which only the light of cases a) and b) is coupled out of the optical element 1. For this purpose, the upper second layer AB is in a transparent state (indicated by the dashed line). As a result, the angular range of the light emitted from the optical element 1 at the top is significantly wider than that according to the embodiment of the invention. Figure 1a The angular range of the conditions, in Figure 1a Only the light of case a) is emitted.

[0114] also, Figure 1cSchematic diagram of the first optical element 1 according to the first configuration in a third state, wherein no light is absorbed but only deflected and / or totally reflected. For this purpose, both the AB layer and the OB layer are in a transparent state (shown in dashed lines).

[0115] at last, Figure 1d A schematic diagram shows a first optical element 1 in a first state according to a second configuration (i.e., both layers AB and OB are opaque), wherein only light from cases a) and c) is coupled out of the optical element 1. Case c) is particularly useful in special applications for light that, after crossing the refractive index boundary from B1 to B2, crosses the next refractive index boundary B2 with the next adjacent region B1 and, depending on the propagation direction and polarization at that time, is coupled out or continues to propagate in the optical element 1 until it is coupled out or absorbed. This is, for example, when light propagation directions within an average angular range of approximately 30° to 50° are to be absorbed, but greater and smaller angles are to be exposed. The case described in c) can be included or excluded based on optical simulations of the optical element, by appropriately setting the first and second refractive indices N1 and N2, and by selecting the widths and heights of the first and second regions B1 and B2.

[0116] In order to achieve the preferred restriction on the propagation direction of the incident light (i.e. only the light of case a still exists), Figure 1a As shown in FIG. 1 , it is important that the two at least temporarily opaque first and second layers OB and AB are actually opaque. If one of the layers, for example, the second layer AB, is not opaque, oblique light rays penetrating into the second region B2 above the actual critical angle for total internal reflection at the interface B1-B2 can be emitted through the opaque second region AB layer at its upper edge.

[0117] Figure 2 The figure also shows a schematic diagram of first region B1 and second region B2 of the first optical element 1 when viewed in a parallel projection (i.e., a top view) perpendicular to the optical element 1. The first and second regions are arranged alternately in strips across the surface of the optical element. Therefore, the restriction of the light propagation direction is effective perpendicular to the strip-shaped first and second regions B1 and B2, but not in directions parallel thereto.

[0118] Instead, Figure 3aA schematic diagram shows a first region B1 and a second region B2 of a first optical element 1 when viewed in a parallel projection perpendicular to the optical element 1 (i.e., a top view). Here, the first region B1 is arranged rectangularly and distributed across the surface of the optical element 1 and is completely surrounded by a single second region B2 (black in the diagram). This means that the plurality of or a single second region B2 are each shaped complementary to the first region B2. Consequently, the direction of light propagation is restricted in at least two planes perpendicular to the surface of the optical element 1. In practice, the effect of such an optical element 1 is typically that the direction of light propagation is focused close to or parallel to the perpendicular bisector of the optical element at all angles. In this context, "close to" means that the deviation from the perpendicular bisector or a line parallel thereto is less than 25° or 30°, depending on the configuration.

[0119] Figure 3b Also shown is a schematic diagram of a plurality of regions B1 to B4 of the optical element 1 when viewed in a parallel projection perpendicular to the optical element, wherein the regions B1, B3 and B4 are distributed in a rectangular shape on the surface of the optical element and are completely surrounded by the region B2. In addition to the first region B1 and the second region B2, the optical element 1 also has further regions B3 and B4. The regions B1, B3 and B4 each have different parameters in shape and / or refractive index. Therefore, the light passing through these regions B3 and B4 and emitted from the optical element 1 is subject to different restrictions in the propagation direction than in the region B1. Therefore, it is possible to achieve regions distributed on the optical element 1 with different degrees of restriction in the light propagation direction, so to speak, with different degrees of focusing. According to Figure 2 、 Figure 3a and Figure 3b All variations can be easily combined with Figures 1a to 1d Other shapes of the first region B1 and the second region B2 are also possible. It is always important to maintain the function of the present invention that the first region B1 and the second region B2 are directly adjacent to each other optically, so that an optical step in the refractive index is present without any air gap as much as possible.

[0120] An advantageous configuration is designed such that each at least temporarily opaque first layer OB is formed on the underside of the second region B2, that is, on the light entrance surface, by a permanently absorbing layer and / or by at least one downwardly reflecting layer. If only one reflective layer is present, it naturally also has opaque properties. The reflective properties contribute to improved efficiency, for example, when the optical element 1 is incorporated into a lighting device, such as an LCD panel. Furthermore, it is possible that each at least temporarily opaque second layer AB can also be formed on the top side, that is, on the light exit surface of the second region B2, by a permanently absorbing layer. If both layers have permanently opaque properties in a defined static configuration and the first and second refractive indices N1 and N2 are unchangeable, the optical element 1 permanently restricts the propagation direction of light incident thereon.

[0121] On the contrary, if in other switchable configurations of the present invention, at least one of the two layers AB and / or OB of the first optical element 1 can be switched between an opaque and a transparent state, the property of limiting the propagation direction of incident light of the optical element 1 can be turned on and off in the following manner: the light propagation direction is limited only when both the AB layer and the OB layer are not transparent (case a) see FIG1 ). Once one of the two layers AB or OB is not opaque, the light propagation direction is no longer limited (cases a) and b), and, if necessary, case c), mainly in Figure 1b ) is shown. Thus, the optical element 1 is switchable. If even layers AB and OB are switched to transparent, as Figure 1c As shown, the optical element 1 only experiences light deflection and direction due to total internal reflection at the boundary between the first area B1 and the second area B2 according to the incident direction of the light, but no light is blocked as a whole.

[0122] In a preferred switchable configuration, only the upper second layer AB is designed to be switchable from opaque to transparent, while the lower first layer OB is designed to be permanently opaque (and optionally also reflective). This is sufficient to achieve the desired effect.

[0123] The switchability of the first or second layer OB or AB can preferably be based on one or more of the following principles: electrowetting, electrophoresis, electrochromism and / or liquid crystal cells. In the case of electrowetting, at least two states of the amount of opaque liquid that is subject to electrowetting are defined for the relevant first layer OB and / or second layer AB. To this end, Figure 23 As a detailed illustration, a modification of the first optical element 1 according to the first configuration to form a switchable twelfth configuration is shown, here in the first state, corresponding to Figure 1a In contrast, Figure 24 As a detailed illustration, the first optical element 1 according to the first configuration is modified to form a switchable twelfth configuration, here in the second state, corresponding to Figure 1b . In accordance with Figure 23 and Figure 24 In the configuration of the two figures, at least the following components are present: at least one planar indium tin oxide (ITO) electrode 4, a planar insulator layer 8, a planar electrode 9 (which extends beyond a thin electrode 9a extending from the surface into a droplet 10, and a controllable voltage source not shown in the figure is in contact with the planar ITO electrode 4 and the planar electrode 9), an opaque droplet 10, which is arranged between the insulator layer 8 and the electrode 9 and, if necessary, embedded in a gel matrix or a transparent liquid and subjected to the electrowetting effect.

[0124] In accordance with Figure 23 In the first operating state, the droplets 10 of the second layer AB will cover the corresponding surface of the second area B2 as completely as possible, i.e. be opaque (the propagation direction is then limited) and Figure 24 In the second operating state, the droplets 10 of the second layer AB will only cover the corresponding surface of the second region B2 over the smallest possible area, i.e., be largely transparent (the propagation direction is then not restricted). To this end, the voltage required for the above-mentioned state is adjusted at the voltage source.

[0125] In the case of electrophoresis, electrophoretically mobile opaque particles are provided in a liquid or gel matrix for the first layer OB and / or the second layer AB. Due to the action of an electric field that can be applied via a transparent electrode, in a first operating state, the electrode covers the corresponding surface of the second area B2 as completely as possible as the first or second layer OB or AB in question, so that the corresponding layer OB or AB behaves opaquely (the propagation direction is then restricted). In a second operating state with a different electric field distribution, the particles cover the corresponding surface of the second area B2 of the first layer OB or second layer AB to the smallest possible extent, or are transferred to a reservoir or distributed in a volume, so that the layer becomes transparent (the propagation direction is then not restricted).

[0126] In a modification of this, opaque, electrophoretically movable particles can also replace the two layers OB and / or AB. Such particles would then be located directly on the surface of the second region B2, i.e., at the locations of the two layers OB and / or AB, in order to disrupt total internal reflection and produce an opaque state, or, after electrophoretic movement, would be arranged at intervals of up to 100 micrometers to allow total internal reflection at these locations and thus allow the light to continue to propagate in the optical element until it is coupled out in the first region B1.

[0127] also, Figure 22A cross-sectional view according to the first configuration shows a modification of the first optical element 1 to form a switchable eleventh configuration. Here, to form the second layer AB, at least the following components are present: transparent electrodes 4 and 6, a controllable voltage source (not shown) in contact with the transparent electrodes 4 and 6, at least one electrochromic layer 5, and optionally also a protective layer 7, such as glass or a polymer. In the case of electrochromism, the layer 5 is constructed with an electrochromic material, for example a metal oxide (such as TiO2, NiO, Nb2O, MoO3, Ta2O5, WO3, IrO2, or Zr2O5), and corresponding transparent electrodes 4 and 6, such as ITO (indium-doped tin oxide), FTO (fluorine-doped tin oxide), or AZO (aluminum-doped zinc oxide), into which the electrochromic material 5 is embedded. Depending on the voltage applied to the electrodes 4 and 6, at least two states are defined for the electrochromic layer 5, and thus for the second layer AB. In a first operating state, the second layer AB is opaque (the propagation direction is then restricted) and in a second operating state, the second layer AB is transparent (the propagation direction is then unrestricted). This can be applied analogously to the first layer OB.

[0128] The first layer OB and / or the second layer AB can also be designed as a liquid crystal cell, for example, a TN cell (twisted nematic liquid crystal cell) with a corresponding pair of polarizers. The liquid crystal cell can then be made opaque (then the propagation direction is restricted) or transparent (then the propagation direction is unrestricted) by applying an appropriate electric field or voltage to the electrodes.

[0129] Furthermore, it may be advantageous if the first layer OB and / or the second layer AB is embedded in the material forming the first region B1 , wherein the material portion of the first region B1 of the optical element 1 preferably transitions seamlessly into the portion embedded in the relevant layer. Figure 4 Schematic diagram showing a first optical element according to a third configuration and a fourth configuration Figure 5 .like Figure 4 As shown, the material of the first region B1 having the first refractive index N1 may be the same as the material of the substrate formed as described above. Alternatively, it may be considered that the second region B2 is completely surrounded by the material of the first region B1 having the first refractive index N1, as shown in FIG. Figure 5 shown.

[0130] Another configuration is that, when viewed in a cutting direction perpendicular to the upper surface of the optical element 1, the first region B1 and the second region B2 are designed to be trapezoidal. Figures 6a to 6c Schematic diagrams of the first optical element 1 according to the fifth, sixth and seventh configurations are shown. By this configuration of the first area B1 and the second area B2, the propagation direction of the light emitted from the optical element 1 is specifically influenced: depending on the configuration, the light passes through this surface more intensely ( Figure 6a ) or weaker ( Figure 6b) is also possible, for example, by a parallelogram cross section ( Figure 6c ), a peak shift is achieved by means of a consequent tilting of the interface between the first region B1 and the second region B2.

[0131] It is also possible to apply a lens structure L, preferably a convex lens structure, to at least a portion of the first area B1 of the optical element 1, preferably to all of the first area B1, on its upper side, i.e., on the light exit surface. This helps to influence the propagation direction of the light emitted from the optical element 1 in a defined manner. To this end, Figure 7 A schematic diagram of the first optical element 1 according to the eighth configuration is shown. Alternatively or additionally, the lower side of the first area B1, i.e., the light entrance surface, may include a concave or convex lens structure (not shown) to influence the direction of light entering area B1 and, therefore, whether the light ultimately falls into the aforementioned scenarios a), b), or c). The terms "upper side" and "lower side" are used relative to a viewer who is mounted in an image reproduction device and who perceives only the light exit side of the first optical element 1, which faces the viewer and thus forms the upper side.

[0132] Figure 8 Simulation of the normalized brightness of the three sets of parameters reflecting the light emitted from the first optical element 1 according to the first configuration, plotted against the emission angle. Figure 1a and Figure 2 Here, it is assumed that the opacity of the first layer OB and the second layer AB is 100%. It can be easily seen that a flat top light distribution is achieved with a small difference of 0.01 in the refractive index between N1=1.6 and N2=1.59. In addition, it can be seen that extinction at a larger angle can be achieved with arbitrarily strong coefficients. In this calculation example, the height H of the first area B1 and the second area B2, which are identical for both, varies within the range of 32μm, 50μm and 65μm. The greater the height H, the narrower the angular range of the coupled-out light. The overall coupled-out light must belong to case a).

[0133] In other words, the mechanism works as follows: When light strikes the interface between first region B1 and second region B2 (i.e., transitioning from first refractive index N1 to second refractive index N2), depending on the angle of incidence, it is either completely reflected or enters second region B2 (with refractive index N2). If the subsequent light is now refracted into second region B2 (with second refractive index N2), a (small) portion is still reflected back into first region B1 (Fresnel reflection). The smaller the difference in refractive index N1-N2, the smaller this reflected portion. The higher the height H (subject to manufacturing limitations), the more this back-reflection effect is masked. Ideally, a nearly perfectly rectangular distribution is generated.

[0134] exist Figures 8 to 10 The back reflection mentioned above has been included. It should be noted that the logarithmic vertical axis in these figures. Figures 8 to 10 The same exemplary parameters are given for the technical optical dimensions of the basic parameters - width D1 of the first region, width D2 of the second region, identical height of the region H, first and second refractive indices N1 and N2.

[0135] As a supplement, Figure 9 Simulations based on the same assumptions show the normalized brightness of three additional sets of parameters for light emitted by the first optical element 1 in the first configuration. This time, at a fixed height H = 65 μm, the second refractive index N2 and the refractive index difference vary between the first refractive index N1 = 1.6 and the second refractive index N2 (N2 = 1.56 / 1.575 / 1.59). It can be seen here that the greater the difference in refractive index, the more light is coupled out at lateral angles. All the outcoupled light will fall into case a). Nevertheless, here too, a flat top light distribution is present. A comparison with conventional thin-film filters for limiting the direction of light is also shown. Figure 2 As can be clearly seen, the first optical element 1 according to the present invention exhibits significantly improved properties compared to prior art, laminar filters. Firstly, the visual protection effect improves by orders of magnitude from a certain angle of 25° to approximately 30°, depending on the design. Secondly, the present invention exhibits an ideal top-hat light distribution. In contrast, laminar filters, which typically do not exhibit a top-hat light distribution, can experience fluctuations in perceived brightness depending on the design and viewing position, even with deviations of only a few degrees from the midpoint. If measured at an angle exceeding 10° from the midpoint, the brightness can be reduced by half.

[0136] In contrast, Figure 10 A simulation shows the normalized brightness for a parameter set of light emitted from the first optical element 1 in a second configuration, plotted against the emission angle. The disruptive distribution of the propagation angles exposed to the light with side edges can be clearly seen. While the light rays belonging to case a) lie at angles between approximately 28° and +28°, additional light rays from case c) are present between approximately -50° and -77° and +50° and +77°.

[0137] also, Figure 11This figure reflects the simulated portion of the brightness outside the 25° and +25° range for light emitted from the first optical element 1 in the first configuration (i.e., the light from case a). The simulation is based on a first refractive index N1 = 1.6 and a second refractive index N2 = 1.59. The upper (bright) parameter window is visible, where the proportion of light coupled out within the aforementioned angular range is greatest. From this, one skilled in the art can derive the dimensional values ​​for the widths D1 and D2 and height H of the first and second regions B1 and B2 in order to optimize the optical element 1 for case a).

[0138] also, Figure 18 Given the first configuration (corresponding to Figure 1a ) and the eighth configuration (corresponding to Figure 7 ) of the first optical element 1 of the normalized brightness of the light emitted by the simulation, plotted against the emission angle. It can be seen that the use of lens L can significantly improve the angle limitation effect without destroying the flat top light distribution.

[0139] In a specific configuration of the optical element 1 according to the present invention, the first refractive index N1 of the material in the first region B1 and / or the second refractive index N2 of the material in the second region B2 can be switched between at least two states, so that the refractive index difference in the region from B1 to B2 and at the refractive index boundary can be modulated respectively, whereby the restriction on the propagation direction can be changed. Figure 12 A schematic diagram shows the first optical element 1 according to the ninth configuration in a first state, wherein only the light of case a) is coupled out of the optical element 1 within a narrow angular range. Here, with the corresponding orientation of the liquid crystal, the second refractive index N2 = 1.49 and the first refractive index N1 = 1.5.

[0140] Figure 13 A schematic diagram of the first optical element 1 according to the ninth configuration in the second state is shown, wherein there is also only light of case a), but at a ratio of Figure 12 The widened angle range of the conditions in the coupling-out of the optical element 1. Here, with the corresponding orientation of the liquid crystal, the second refractive index N2 = 1.49 and the first refractive index N1 = 1.6. For this purpose, Figure 19 Shown in the corresponding Figure 12 and 13 Comparison of optical simulations of the normalized brightness of light emitted from the first optical element 1 according to the ninth configuration in two states, plotted against the emission angle. It is clear that the angular limitation can be changed by the aforementioned switchable ninth configuration of the optical element 1.

[0141] For the aforementioned ninth configuration, at least one of the materials of the first region B1 and / or the second region B2 may be composed of liquid crystals in contact with electrodes so as to cause a change in the refractive index of linearly polarized light in the liquid crystals by changing the voltage on the electrodes. When the electrodes are arranged, for example, on the upper and lower sides, i.e., the light exit and light incident surfaces of the first region B1, the electrodes may be transparent, for example in the form of an ITO layer. For this configuration, it should be noted that the first layer OB and the second layer AB are preferably permanently opaque, and furthermore, generally only the light rays of case a) can leave the optical element 1 upward. However, depending on the refractive index difference at the interface between the first region B1 and the second region B2, these light rays in case a) have a narrower or wider range of propagation direction angles, such as Figure 12 、 Figure 13 and Figure 19 As shown. The greater the refractive index difference, the larger the angular range, and the smaller the refractive index difference, the smaller the angular range. In principle, according to the ninth configuration, the third, fourth, and other states can also be set, and if the application requires, these states also correspond to other refractive index values.

[0142] For special applications, at least one first region B1 can be formed on the optical element 1, wherein, when viewed in a parallel projection perpendicular to the optical element 1, the first region has its shortest extension at least 20 times larger than the shortest extension of all second regions B2 when viewed in a parallel projection perpendicular to the optical element 1, so that within the at least one first region B1, except at its edges and ignoring parallel offsets, there is essentially no restriction on the propagation direction of the light emerging from the optical element 1 compared to the light incident on the optical element 1. To this end, Figure 17 is a schematic diagram illustrating the first optical element 1 in such a tenth configuration. The unshaded left half corresponds to, for example, a single, complete first region B1, while the shaded right half has alternating first and second regions B1 and B2, corresponding to, for example, the first through ninth configurations of optical element 1. This means that the propagation direction of light penetrating optical element 1 is restricted not across the entire surface of optical element 1 but, in this example, only on the right half.

[0143] The invention obtains a particularly important element in the use of the above-mentioned first optical element 1 with an image reproduction unit (such as an LCD panel, OLED or micro LED or any other display technology) or with an illumination device for a transmissive image display. For this purpose, Figure 20A schematic diagram (cross-sectional view, outline) shows a first optical element 1 in a first configuration in a first state, particularly for use with a transmissive image reproduction unit (LCD) and a backlight (BLU). The optical element 1 is thus directly integrated into the backlight (BLU) of a transmissive image reproduction unit, such as an LCD module, particularly in a switchable configuration. Advantageously, the permanently opaque layer OB is reflective on the underside, so that light incident there is reflected back into the backlight (BLU) and recycled there, as shown in the figure. Consequently, light from the backlight (BLU) can penetrate only into the first region (B1), where, when the second layer (AB) is opaque, the light direction is limited according to the present invention in the first state of the optical element 1. The image reproduction unit (LCD) is then penetrated only by the light directed according to the present invention and, ignoring scattering losses, for example, due to the LCD panel itself, is visible only from a correspondingly limited angular range. If the optical element 1 is set to a second state (not shown in the figure), in which the second layer (AB) is switched to transparent, light can penetrate the image reproduction unit (LCD) over a wide angular range, making the light visible from a wide angular range.

[0144] In the above-described application method, a switchable eye protection for an image reproduction unit LCD is realized: in a first operating state, in which only the condition a) described above is retained for the light emerging from the optical element 1, the eye protection effect is achieved with a top-hat light distribution, depending on the configuration. For the observer, the top-hat light distribution is more pleasant than a typical light distribution based on a thin-film filter, because the thin-film filter severely restricts the freedom of movement: a head movement of a few centimeters to the side will produce a strong drop in the visible light brightness (see also Figure 9 (Compare) If the screen is large enough, the light can already be partially visible even when the head is at rest. A flat top light distribution effectively overcomes this. In the second operating state, if conditions a) and b) and possibly also condition c) apply to the light emanating from the optical element 1, a free viewing mode is achieved, in which the image reproduction unit LCD can be viewed freely from all directions.

[0145] Figure 21Also shown is a schematic diagram (partial cross-sectional view) of a first optical element 1 in a first configuration in a first state, in particular when used together with a self-luminous image reproduction unit 3. Here, the optical element 1 is arranged in the viewing direction in front of such an image reproduction unit 3, for example an OLED panel (however, LCD panels with backlight and any other screen technology are equally applicable), selectively or permanently limiting the direction of light propagation. In this context, there may also be an optical device on the image reproduction unit 3, which focuses the light emitted by the individual pixels of the image reproduction unit 3 essentially on a surface opposite the first area B1. This is feasible, for example, for a microlens grid or a biconvex lens with a period of approximately the pixel width (or possibly height). In the best case, the period of the first area B1 (i.e. the sum of the widths D2+D1) should match the period of the pixel width (or height if necessary) and be aligned with each other. The period of the pixel width of the image reproduction unit 3 is in the range Figure 21 A pixel is then, for example, approximately in the middle of the first region B1. For the sake of clarity, the previously described optical device with a microlens grid or a lenticular lens is not shown in FIG. Figure 21 Not shown, but may exist.

[0146] The present invention also includes a method for manufacturing a first optical element 1, referring to Figures 25a to 25f To explain the method, Figures 25a to 25f A simplified schematic diagram is shown. It comprises the following steps: First, a plurality of base blocks BL are produced, said base blocks comprising the following layers connected to each other in this order: a second layer AB serving as an absorption layer, a transparent second layer made of a material having a second refractive index N2, an opaque and optionally at the same time reflective first layer OB and a transparent first layer made of a material having a first refractive index N1 (see Figure 25a ). A plurality of base blocks BL are then stacked one on top of the other and connected, for example, by vulcanization or gluing, to obtain a first stacked block ST (see FIG. 25 b ). Slices SC with a layer thickness D2 are then cut from the stacked block ST, preferably perpendicular to the surface extension plane of the respective second layer AB (see FIG. 25 c ), wherein, as an alternative to perpendicular cutting, a cutting angle of approximately 60° to 120° can also be considered. The slices SC are then stacked together with a transparent first layer having a first refractive index N1 and a first layer thickness D1, and the slices are connected to the transparent first layer, for example, by vulcanization or gluing, to obtain a second stacked block SN (see FIG. Figure 25d Finally, the optical element 1 is cut out of the second stacked block SN, preferably perpendicular to the plane of extension of the individual slices SC (see Figure 25e ) cutting. Thus, there is a (first) optical element 1, such as Figure 25f Of course, other methods for manufacturing the optical element 1 are also feasible.

[0147] Figure 15 A second optical element 2 is shown, which is composed of a one-dimensional or two-dimensional periodic sequence of two transparent complementary shapes with a first area B1 and a second area B2, respectively having a first refractive index N1 and a second refractive index N2, wherein the shapes are optionally formed on a planar substrate S, so that each shape forms a plane in two directions. In this context, the second refractive index B2 can advantageously be equal to 1, i.e. the material of the shape of the second area B2 is, for example, air. This is in Figure 15 Schematic diagram of the second optical element 2 according to the first configuration is shown in FIG. Figure 16 An exemplary light path is shown. Therefore, light incident on such a second optical element 2 in a (narrow-angle) preferred direction is transmitted unimpeded (see the right figure, vertically, i.e., incident light in the preferred direction), while light with an angle greater than 15° from the preferred direction (see the oblique light on the left) is deflected by the second optical element 2 due to total internal reflection and / or Fresnel reflection. Here, the propagation direction of the outgoing light is also affected. The above configurations can be deduced by analogy and will not be described in detail here. The design variants and mean effect relationships specified above (Mittel- ) also applies here and should not be repeated here for redundancy reasons.

[0148] Finally, the present invention further includes a third optical element 10, which is planar and has a light incident side and a light exiting side. Figure 26 As shown (partial / cross-sectional view). The third optical element comprises at least a first region E1 composed of a transparent material having a first refractive index N1 and a second region E2 composed of an opaque material having a second refractive index N2. The first and second regions alternate in a one- or two-dimensional periodic sequence on the surface of the optical element 10. The first refractive index N1 is greater than the second refractive index N2 throughout the entire wavelength range visible to the human eye. Due to the opaque material of the second region E2, light incident on the first large surface of the optical element 10 enters the optical element 10 only through the light entrance surface of the first region E1. Depending on the geometric direction of incidence, polarization, and the ratio of the first refractive index N1 to the second refractive index N2, the light either propagates unimpeded within the first region E1 or is totally reflected. In either case, it is then coupled out again at the corresponding light exit surface of the first region E1. Alternatively, the light penetrates from the first region E1 into the adjacent second region E2 and is absorbed there due to the opaque material of the second region E2.

[0149] Due to the different first and second refractive indices N1 and N2, light penetrating the second region E2 is refracted more strongly away from the vertical. Consequently, light emitted from the second large surface of the optical element 10 is confined in its propagation direction compared to light incident on the first large surface. The opaque material having the second refractive index comprises a transparent portion corresponding to the second refractive index and an opaque portion composed of absorptive particles. The particles are preferably uniformly distributed throughout the opaque material, with their mass proportion typically not exceeding 50%.

[0150] The third optical element 10 improves the prior art, in particular achieving the following effects: first, a flat-top light distribution can also be achieved using a third optical element similar to a thin-layer filter, because due to total internal reflection, more useful light is transmitted into the required limited angular range, rather than without total internal reflection as in the prior art; second, the angular range of light penetrating the third optical element 10 is significantly more restricted, because not only does the opaque thin sheet ensure the restriction of the light direction, but the refractive index difference between areas E1 and E2 ensures that: the light penetrating into area E2 is refracted more strongly away from the plumb line and must therefore cover a longer optical path through an absorptive material, and therefore, stronger absorption occurs than without such a refractive index difference because it occurs over a longer optical path.

[0151] from Figures 8 to 10 In a similar manner, as can be seen in the explanation of , a slight refractive index difference of 0.01 is sufficient to achieve significant angular limitation. This slight refractive index difference can be achieved, for example, by doping a polymer or transparent silicon as the material for regions E1 or E2 of the third optical element 10. In the simplest case, all regions E1 and E2 of the third optical element 10 will be composed of the same material. However, in addition, region E1 may also be doped with transparent particles to increase the refractive index, and region E2 may be doped with, for example, opaque nanoparticles or microparticles to enhance opacity.

[0152] The aforementioned third optical element 10 may advantageously have a reflective portion on one of the large surfaces, preferably the first large surface, wherein the reflective portion is designed as an angle-dependent reflective portion of the entire large surface or a total reflective portion on the surface of the area E2 .

[0153] The third optical element 10 described above can advantageously be integrated into an illumination device for a transmissive image reproduction unit, such as an LCD panel. This illumination device can then be used permanently as a directional background illumination and can be used, for example, in a configuration according to the applicant's WO 2015 / 121398 or WO 2019 / 002496.

[0154] Figures 27a to 27c and Figure 28Various improvements of such a third optical element are shown, which is here respectively connected to the substrate M5 but is not part of the aforementioned optical element. As previously described, the third optical element 10 according to this configuration also has an area E1 made of a transparent first material M1 with a first refractive index N1 and a second area E2 made of an opaque second material M2 with a second refractive index N2. The opaque second material M2 is mixed with an absorptive material so that the light in the second area is absorbed in any case, even if the initial material is transparent. The second refractive index N2 corresponds to the transparent part. In addition to the first area and the second area, a third area made of an additional opaque material M3 with a third refractive index N3 is formed between each two second areas, specifically as shown in FIG. Figure 27c As shown. The third refractive index N3 is respectively greater than the first refractive index N1 and the second refractive index N2. The further opaque material M3 also has a transparent portion that determines the third refractive index N3 and a portion of absorbing particles that achieve opacity. The mass proportion of the absorbing particles in the opaque second material M2 and the further opaque material M3 can be as high as 50%, or even more in individual cases. When using the further opaque material M3, the mass fraction of the absorbing particles in the opaque second material M2 can also be significantly less than 50%. For example, the particles in Figure 28 The third material M3 is symbolized.

[0155] like Figure 27a and Figure 27b As shown, the second region E2 made of the opaque second material M2 having the second refractive index N2 can also be constructed between the light incident side of the optical element 10 and the third region made of another opaque material M3, and between the light exit side of the optical element 10 and the light exit surface of the first region E1 made of the transparent first material M1. This is easier to manufacture because it involves a layer made of another opaque material that is continuous and closed in the plane. The first region and the second region made of the transparent first material M1 and the opaque second material M2 can also be designed in cross section as follows: Figure 28 The trapezoidal shape of the first area E1 can also be used in a variant without further opaque material, with the advantage that the angular distribution is thus better focused and the privacy mode / view protection mode is further improved, in which case the third optical element Figure 10 Used in the corresponding image reproduction device. Figure 27a In addition, a light-reflecting layer M4 is applied to the substrate and arranged between the substrate and a second region, which is arranged between the substrate and a third region made of a third material M3, on the light entrance surface of the optical element 10. In this configuration, the second region can be formed, in particular, as a film, that is, significantly thinner than the first and third regions, in particular on the light exit surface of the first region.

[0156] The refractive indices N1, N2, and N3 are designed so that total internal reflection occurs at a specific small angle between a first material M1 having a first refractive index N1 and a second material M2 having a second refractive index N2. In other words, the second refractive index N2 is smaller than the first refractive index N1. The refractive index difference between the first refractive index N1 and the second refractive index N2 is preferably less than 0.1. A third refractive index N3 of a third material M3, which, like the second material M2, is doped with an absorptive material, has a third refractive index greater than or equal to the first and second refractive indices, but not less than the first and second refractive indices. This means that light that is not totally reflected at the interface between the first material M1 and the third material M3 is refracted at a larger angle at the interface between the third material and the second material.

[0157] This is Figure 29 and Figure 30 1 and 2 for different situations. In situation A, the light is reflected from the reflective layer and then recycled in the backlight unit (not shown). For situation B with light having a small incident angle, these light rays are either totally reflected at the interface between the first area and the second area, or pass through the first area unimpeded and pass through the optical element 10. Figure 30 In the example, this corresponds to the area between the origin and the first dotted line on the abscissa. The angles of incidence and reflection are the same.

[0158] For light rays entering the first region at an angle greater than the angle of total reflection at the interface between the first and second regions, two cases must be distinguished depending on the angle of incidence. In case C, shown with dashed lines only to distinguish the light guidance from case D, the light rays strike the interface between the first and second regions and are refracted at a smaller angle, leaving the optical element at the light exit surface of the second region. Depending on the thickness of the second region, this only affects a relatively small range of angles. In case D, the light rays with a larger angle of incidence first enter the second region from the first region, and from there into the third region, where they are refracted at a still larger angle upon reaching the interface between the second and third regions. Ideally, this creates an angle range in which no light or significantly less light is emitted compared to the case without the third region, thereby further improving the view protection mode.

[0159] Some of the modifications described above for the first optical element 1 may also be applied to the second optical element 2 and the third optical element 10 .

[0160] The optical element described above achieves the following objectives: an optical element has been described that influences the propagation direction of incident light in a defined manner and can be selectively switched between at least two operating states. Each optical element can be produced cost-effectively and can be used universally with various screen types, enabling switching between a protected viewing mode and a free viewing mode without substantially or only negligibly reducing the resolution of such screens. Furthermore, the optical element offers the possibility of achieving a flat top light distribution.

[0161] The advantages of the present invention are manifold. The aforementioned principle of action is thus achieved with a single optical element, which does not necessarily have to have a surface structure. Furthermore, the first region B1 and the second region B2 of the optical element can be embedded in a protective material, for example, in the material of the first region B1. Furthermore, a highly preferred flat-top light distribution is achieved for the emitted light, and an arbitrarily high level of privacy contrast is achieved in theoretical simulations. If the optical element according to the present invention is used for the backlighting of LCD panels, high brightness is achieved. Furthermore, light propagation limitation can be achieved in two planes, for example, simultaneously left / right and up / down, using only one optical element.

[0162] The invention described above can be advantageously used in conjunction with image reproduction devices, wherever confidential data is displayed and / or entered, for example, when entering a PIN, displaying data at an ATM or payment terminal, entering passwords, or reading emails on a mobile device. The invention can also be used in passenger vehicles, for example, when the driver is not allowed to view specific image content of the passengers, such as entertainment programs. Furthermore, the optical element according to the invention can be used for other technical and commercial purposes, such as for light alignment in darkfield illumination for microscopes and, more generally, for light shaping in lighting (e.g., in vehicle headlights and measurement technology).

Claims

1. A planar extended optical element having a light incident side and a light exiting side, the optical element comprising: At least a first region (B1) composed of a transparent first material having a first refractive index (N1) and a second region (B2) composed of a transparent second material having a second refractive index (N2), wherein the first region and the second region alternately appear in a one-dimensional or two-dimensional periodic sequence on the surface of the optical element, wherein the first refractive index (N1) is greater than the second refractive index (N2) in the entire wavelength range visible to the human eye, a first layer (OB) located on the light entrance surface of each second region (B2) and which is permanently opaque or switchable between a transparent state and an opaque state, a second layer (AB) located on the light exit surface of each second region (B2), which is permanently opaque or switchable between a transparent state and an opaque state, wherein each first layer (OB) or each second layer (AB) is permanently opaque, or each first layer (OB) and each second layer (AB) are permanently opaque, Such that: when the first layer (OB) is in an opaque state, light incident on the optical element at the light incident side enters the optical element only through the light incident surface of the first region (B1) based on the first layer (OB), and the light there is incident according to the incident angle, polarization, and the ratio of the first refractive index (N1) to the second refractive index (N2): a) propagates unimpeded within the first region (B1) or is totally reflected and then coupled out again at the light exit surface of the corresponding first region (B1), or b) penetrates from the first region (B1) into the adjacent second region (B2), propagates in said adjacent second region and is finally absorbed on the light exit side of the second layer (AB) when it is in the opaque state, or is coupled out when it is in the transparent state, or c) when light penetrates from a first region (B1) into an adjacent second region (B2), it then penetrates into another adjacent first region (B1) and, depending on the propagation direction and polarization then given, is coupled out at the light exit surface or further propagates in the optical element until the light is coupled out or absorbed, Thus, in the case where at least the first layer (OB) and / or the second layer (AB) is opaque, light emitted from the optical element on the light exit side is limited in its propagation direction compared to light incident on the optical element on the light entrance side, Each first layer (OB) on the light entry face of the second region (B2) consists of a permanently absorbing layer and / or of at least one layer that reflects away from the optical element, and / or, Each second layer (AB) on the light exit surface of the second region (B2) is composed of a permanent absorption layer.

2. The optical element according to claim 1, wherein The first refractive index (N1) of the material in the first region (B1) and / or the second refractive index (N2) of the material in the second region (B2) can be switched between at least two states, so that the ratio of the two refractive indices (N1, N2) at the boundary between the first region (B1) and the second region (B2) can be modulated separately, thereby changing the said restriction on the propagation direction.

3. The optical element according to claim 2, wherein At least one of the materials of the first region (B1) and / or the second region (B2) is composed of liquid crystal in contact with electrodes so that changing the voltage on the electrodes causes a change in the refractive index of linearly polarized light in the liquid crystal.

4. The optical element according to any one of claims 1 to 3, characterized in that The second layer (AB) and / or the first layer (OB) are switchable between an opaque state and a transparent state, this switchability being based on one or more of the following principles: electrowetting, electrophoresis, electrochromism and / or liquid crystal cells.

5. The optical element according to any one of claims 1 to 3, characterized in that The second layer (AB) and / or the first layer (OB) are embedded in the material constituting the first region (B1), wherein the material portion of the first region (B1) of the optical element seamlessly transitions into the portion embedded in the second layer (AB) and / or the first layer (OB).

6. The optical element according to any one of claims 1 to 3, characterized in that The first region and the second region are arranged alternately distributed in stripes on the surface of the optical element when viewed in a parallel projection perpendicular to the optical element.

7. The optical element according to any one of claims 1 to 3, characterized in that The first regions are arranged distributed on the surface of the optical element in a dot-like, circular, elliptical, rectangular or hexagonal shape when viewed in a parallel projection perpendicular to the optical element, and the second regions are each shaped complementary thereto.

8. The optical element according to any one of claims 1 to 3, characterized in that A lens structure (L) is applied to at least a portion of the first region on the light exit side of the first region.

9. The optical element according to any one of claims 1 to 3, characterized in that A lens structure (L) is applied to all first regions on the light exit side of the first regions.

10. The optical element according to any one of claims 1 to 3, characterized in that A polarizer is arranged on the light incident side and / or the light exit side of the optical element.

11. The optical element according to any one of claims 1 to 3, characterized in that At least one first region is formed on the optical element, the shortest extension of which, when viewed in a parallel projection perpendicular to the optical element, is at least twenty times larger than the shortest extension of all second regions when viewed in a parallel projection perpendicular to the optical element, so that within the at least one first region, except at its edges and disregarding parallel offsets, the propagation direction of light emerging from the optical element on the light exit side is unrestricted compared to light incident on the light entrance side toward the optical element.

12. The optical element according to any one of claims 1 to 3, characterized in that In addition to the first and second regions, further regions are constructed that have different parameters in shape and / or refractive index compared to the first and second regions, so that: compared to the first regions, the light that passes through these further regions and emerges from the optical element is subject to additional restrictions on the propagation direction.

13. A method for manufacturing an optical element according to any one of the preceding claims 1 to 5, the method comprising the following steps: manufacturing a mold with a positive structure of the first area (B1) and a negative structure of the carrier substrate, filling the mold with a first polymer having a first refractive index (N1) after curing, The first polymer is hardened by UV light or cooling, and the workpiece is then removed from the mold. The structure of filling a second region (B2) in the workpiece with a second polymer having a second refractive index (N2) after hardening, The second polymer is hardened by ultraviolet light or cooling.

14. The method according to claim 13, characterized in that After the first polymer or the second polymer is cured, an opaque material or a material switchable between transparent and opaque is evaporated or sputtered on the second area (B2) on the surface of the workpiece through a mask protecting the first area (B1).

15. A method for manufacturing an optical element according to any one of claims 1 to 5, the method comprising the following steps: producing a plurality of base blocks (BL) comprising the following layers connected to one another in order: a second layer (AB) serving as an absorption layer, a transparent second layer made of a material having a second refractive index (N2), an opaque first layer (OB) and a transparent first layer made of a material having a first refractive index (N1), stacking a plurality of base blocks (BL) on top of each other and connecting them to obtain a first stacking block (ST), Slices (SC) with a second layer thickness (D2) are cut from the stacked block (ST), stacking slices (SC) between which transparent first layers having a first refractive index (N1) and a first layer thickness (D1) are respectively arranged, and connecting the slices and the transparent first layers to obtain a second stacked block (SN), and Optical elements are cut out from the second stacked block (SN).

16. Use of an optical element according to any one of claims 1 to 5 for selectively limiting the viewing direction of an image reproduction unit, the optical element being used for an image reproduction unit (3) or for a backlighting unit (BLU) of a transmissive image reproduction unit (LCD).

17. A planar extended optical element, the optical element having a light incident side and a light exiting side, the optical element comprising: At least a first region (E1) composed of a transparent material having a first refractive index (N1) and a second region (E2) composed of an opaque material having a second refractive index (N2), wherein the first region and the second region alternately appear in a one-dimensional or two-dimensional periodic sequence on the surface of the optical element, and within the entire wavelength range visible to the human eye, the first refractive index (N1) is greater than the second refractive index (N2), The first region (E1) and the second region (E2) are constructed in a trapezoidal shape when viewed along a section direction perpendicular to the upper surface of the optical element, and at least the first region (E1) has an isosceles trapezoidal cross section, wherein the longer base of the trapezoid corresponds to the light exit surface of the corresponding first region (E1), and the shorter base of the trapezoid corresponds to the light incident surface of the corresponding first region (E1). Thus, on the first large surface of the optical element, light incident on the optical element enters the optical element only through the light incident surface of the first area (E1) due to the opaque material of the second area (E2), and the light there is incident according to the incident direction, polarization and the ratio of the first refractive index (N1) to the second refractive index (N2): a) propagates unimpeded within the first region (E1) or is totally reflected and then coupled out again at the light exit surface of the corresponding first region (E1), or b) penetrates from the first area (E1) into the adjacent second area (E2) and is absorbed there due to the opaque material of the second area (E2), Since the first refractive index (N1) and the second refractive index (N2) are different, the light penetrating into the second area (E2) will be refracted more strongly away from the plumb line. Thus, the light emitted from the optical element on the second large surface of the optical element is limited in its propagation direction compared to the light incident on the optical element on the first large surface. A third region composed of a further opaque material (M3) having a third refractive index (N3) is formed between each two second regions (E2), wherein the third refractive index (N3) is greater than the first refractive index (N1) and greater than the second refractive index (N2).

18. The optical element according to claim 17, wherein The opaque material is made of a transparent material having a second refractive index (N2), and the transparent material is doped with absorbent particles, thereby producing an overall opaque effect.

19. The optical element according to claim 17 or 18, characterized in that The opaque material consists of a paint or a polymer doped with graphite particles with a size of less than 500 nm, black carbon nanoparticles with a size of less than 200 nm, or a dye or a dye mixture as absorbing particles.

20. The optical element according to claim 17 or 18, characterized in that The optical element has a reflective portion on one of the two large surfaces. The reflective portion is designed as an angle-dependent reflective portion of the entire large surface or as a total reflective portion on the surface of the second area (E2).

21. The optical element according to claim 20, wherein The optical element has a reflective portion on the first large surface.

22. The optical element according to claim 17 or 18, characterized in that A second region (E2) is also formed between the light incident side of the optical element and the third region and between the light exit side of the optical element and the light exit surface of the first region (E1).

23. The optical element according to claim 17 or 18, characterized in that The first region and the second region are arranged alternately distributed in stripes on the surface of the optical element when viewed in a parallel projection perpendicular to the optical element.

24. The optical element according to claim 17 or 18, characterized in that The first regions are arranged distributed on the surface of the optical element in a dot-like, circular, elliptical, rectangular or hexagonal shape when viewed in a parallel projection perpendicular to the optical element, and the second regions are each shaped complementary thereto.

25. The optical element according to claim 17 or 18, characterized in that A lens structure (L) is applied to at least a portion of the first region on the light exit side of the first region.

26. The optical element according to claim 17 or 18, characterized in that A lens structure (L) is applied to all first regions on the light exit side of the first regions.

27. The optical element according to claim 25, wherein The lens structure (L) is a convex lens structure.

28. The optical element according to claim 17 or 18, characterized in that A polarizer is arranged on the light incident side and / or the light exit side of the optical element.

29. The optical element according to claim 28, wherein The polarizer is a reflective polarizer.

30. The optical element according to claim 17 or 18, characterized in that At least one first region is formed on the optical element, the shortest extension of which, when viewed in a parallel projection perpendicular to the optical element, is at least twenty times larger than the shortest extension of all second regions when viewed in a parallel projection perpendicular to the optical element, so that within the at least one first region, except at its edges and disregarding parallel offsets, the propagation direction of light emerging from the optical element on the light exit side is unrestricted compared to light incident on the light entrance side toward the optical element.

31. The optical element according to claim 17 or 18, characterized in that In addition to the first and second regions, further regions are constructed that have different parameters in shape and / or refractive index compared to the first and second regions, so that: compared to the first regions, the light that passes through these further regions and emerges from the optical element is subject to additional restrictions on the propagation direction.

32. A method for manufacturing an optical element according to any one of claims 17 to 19, the method comprising the steps of: Alternatingly stacking first layers made of a transparent material having a first refractive index (N1) and second layers made of an opaque material having a second refractive index (N2), wherein the first refractive index (N1) is greater than the second refractive index (N2), connecting the first layer and the second layer to each other, Optical elements are cut out of the layer composite.

33. Use of an optical element according to any one of claims 17 to 31 for selectively limiting the viewing direction of an image reproduction unit, the optical element being used for an image reproduction unit (3) or for a backlighting unit (BLU) of a transmissive image reproduction unit (LCD).

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