Screen with switchable light filter

Abstract

Screen with an image sensor (2) which uses a first grid of pixels P to display image content Bild exhibits, further comprising a first switchable light filter (5), in turn comprising - a first optical element (1), itself comprising • a multitude of light-absorbing transition dipole moments, • wherein the majority of the transition dipole moments are permanently or at least in a first state aligned with a tolerance of at most 20° parallel to a first preferred direction selectable for the first optical element (1) or vary around it, • so that light which enters the first optical element (1) is transmitted or at least partially absorbed depending on its polarization state and its direction of incidence relative to the first optical element (1), - Means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is directed into a second grid with pixels P LC are divided - a liquid crystal layer (3) arranged in front of or behind the first optical element (1), onto which the respective pixel P is applied LC The generated electric field acts, and depending on this, it influences the polarization state of light passing through it. - wherein the transmission properties of the switchable light filter (5) differ between a first operating mode B1 at corresponding pixels P LC , where the first electric field EF1 is applied, and a second operating mode B2 at corresponding pixels P LC , where the second electric field EF2 is applied, distinguish, - wherein the first and second rasters differ in at least one of the parameters resolution, pixel shape, pixel size, raster shape, base angle of the coordinate axes of both rasters, orientation of the coordinate axes and / or number of the respective pixels P LC or P Bild differ, and - where, in parallel projection of the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LC of the second grid on any edge of pixels P Bild of the first grid, thereby reducing visually visible overlaps of the image source (2) and other components of the screen.

Description

Technical field of the invention

[0001] Significant progress has been made in recent years in widening the viewing angle of LCDs. However, there are often situations where this very wide viewing area can be a disadvantage. Information such as banking details, personal information, and sensitive data is increasingly accessible on mobile devices like laptops and tablets. Consequently, people need control over who can see this sensitive data; they must be able to choose between a wide viewing angle—a public mode—to share information on their display with others, for example, when viewing vacation photos or for advertising purposes. Conversely, they need a narrow viewing angle—a private mode—when they want to keep the image information confidential.

[0002] A similar problem arises in vehicle manufacturing: The driver must not be distracted by visual content, such as digital entertainment programs, when the engine is running, while the passenger wants to consume these programs even while the vehicle is in motion. Therefore, a screen is needed that can switch between the corresponding display modes.

[0003] Additional films based on microlouvers have already been used for mobile displays to achieve visual privacy. However, these films were neither switchable nor reversible; they always had to be manually applied and then removed. They also had to be transported separately from the display when not in use. Furthermore, a significant disadvantage of using such lamellar films is the associated loss of light transmission.

[0004] US Patent 6,765,550 B2 describes such a privacy screen using micro-louvers. The biggest disadvantages are the mechanical removal and installation of the filter, as well as the light loss in the protected mode.

[0005] US Patent 5,993,940 A describes the use of a film with small, strip-shaped prisms evenly spaced across its surface to achieve a private mode, i.e., a restricted viewing mode with a small viewing angle. Development and manufacturing are technically quite complex.

[0006] In WO 2012 / 033583 A1, the switching between clear and restricted vision is achieved by controlling liquid crystals between so-called "chromonic" layers. This results in a loss of light and the technical effort is quite high.

[0007] US 2012 / 0235891 A1 describes a very complex backlight – a backlight – in a screen. According to this, Fig. 1 and Fig. 15 not only employ several light guides, but also other complex optical elements such as microlens elements 40 and prism structures 50, which reshape the light from the rear illumination on its way to the front illumination. This is expensive and technically complex to implement and also involves light loss. According to the variant according to Fig. In US patent 2012 / 0235891 A1, both light sources 4R and 18 produce light with a narrow illumination angle, whereby the light from the rear light source 18 is first converted into light with a wide illumination angle in a complex process. This complex conversion—as already noted above—significantly reduces brightness.

[0008] According to JP 2007-155783 A, special optical surfaces, which are complex to calculate and manufacture, are used to deflect light into different narrow or wide areas depending on the angle of incidence. These structures resemble Fresnel lenses. Furthermore, there are obstructions that deflect light in undesired directions. Therefore, it remains unclear whether truly useful light distributions can be achieved.

[0009] US patent 2013 / 0308185 A1 describes a special, stepped light guide that emits light in different directions across a large area, depending on the direction from which it is illuminated from one of its narrow sides. In conjunction with a transmissive display device, such as an LCD, this allows for the creation of a screen that can be switched between unobstructed and restricted viewing modes. A disadvantage of this design is that the restricted viewing effect can only be generated for either left / right or top / bottom, but not for left / right / top / bottom simultaneously, as is necessary for certain payment transactions. Furthermore, even in restricted viewing mode, some residual light remains visible from obstructed viewing angles.

[0010] WO 2015 / 121398 A1, filed by the applicant, describes a screen with two operating modes, in which scattering particles are present in the volume of the corresponding light guide for switching between the operating modes. However, the scattering particles chosen, made of a polymer, generally have the disadvantage that light is coupled out from both large areas, causing approximately half of the useful light to be emitted in the wrong direction, namely towards the backlight, where it cannot be sufficiently recycled due to the design. Furthermore, the scattering polymer particles distributed in the volume of the light guide can, under certain circumstances, especially at higher concentrations, lead to scattering effects that reduce the visual privacy effect in the protected operating mode.

[0011] The approach of "electrical birefringence (EDB)" technology is based on the idea of ​​using the switchable liquid crystals of an additionally applied LC panel to "filter" all light rays that do not exit the imaging layer at a specific viewing angle. Disadvantages of this technology include high additional energy and cost consumption and the difficulty in altering the + / -40° sweet spot, i.e., the optimal viewing position. The absorption coefficient of the LC structures is also insufficient, as the attenuation of light intensity increases again for viewing angles larger than the sweet spot, resulting in a light intensity of up to 3% of the maximum light intensity for viewing angles greater than + / -40°.

[0012] Furthermore, DE 10 2020 006 110 B3 of the applicant discloses a switchable light filter and a screen with such a switchable light filter. However, it does not provide any information on preventing possible moiré effects in configurations with partial switching.

[0013] Finally, a switchable light filter and a screen with such a switchable light filter are also described in the applicant's application DE 10 2023 114 957 B3. This application also provides no guidance on preventing potential moiré effects in configurations with partial switching.

[0014] The aforementioned methods and arrangements generally share the disadvantage that they significantly reduce the brightness of the main screen and / or require a complex and expensive optical element for mode switching and / or reduce the resolution in the freely viewable, public mode and / or exhibit visual artifacts on very high-resolution displays. Description of the invention

[0015] The object of the invention is therefore to describe a screen with a switchable light filter. The switchable light filter should be inexpensive to implement and, in particular, universally usable with various types of screens in order to enable switching between a visual barrier – e.g., in the horizontal direction relative to a standing or seated viewer – i.e., a restricted viewing mode, and an unobstructed viewing mode, without reducing the resolution of such a screen, even slightly. Good image quality should be achieved, especially with no or imperceptible moiré effects between the screen's image sensor and the switchable light filter, which is arranged in front of or behind such an image sensor.

[0016] In a first embodiment of the invention, this problem is solved by a screen with an image sensor which uses a first grid with pixels P to display image content. Bild exhibits, furthermore comprehensively a first switchable light filter, in turn comprehensively - a first optical element, itself comprehensive • a multitude of light-absorbing transition dipole moments, • wherein the majority of the transition dipole moments are permanently or at least in a first state aligned with a tolerance of a maximum of 20° parallel to a first preferred direction selectable for the first optical element or vary around it, • so that light entering the first optical element is transmitted or at least partially absorbed depending on its polarization state and direction of incidence relative to the first optical element, - Means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is directed into a second grid with pixels P LC are divided (this second grid is preferably, but not necessarily, structured in rows and columns; however, it could also be only rows or only columns), - a liquid crystal layer arranged in front of or behind the first optical element, onto which - usually pixel by pixel - the respective pixel P is deposited LC the generated electric field acts, and depending on this, it influences the polarization state of light passing through it - usually pixel by pixel - so that - the transmission properties of the first switchable light filter between a first operating mode B1 at corresponding pixels P LC , where the first electric field EF1 is applied, and a second operating mode B2 at corresponding pixels P LC, to which the second electric field EF2 is applied, distinguishing, explicitly also at all pixels P LC either the first or the second electric field, or another electric field, can be applied, which typically assumes a numerical value between the numerical values ​​of the first and second electric fields EF1 and EF2, - wherein the first and second grids differ in at least one of the parameters - preferably in at least two of the parameters, alternatively in at least three of the parameters - resolution, pixel shape, pixel size, grid shape, base angle of the coordinate axes of the grids, orientation of the coordinate axes (implementable, for example, in two 90° grids that are rotated relative to each other) and / or number of the respective pixels P LC or P Bild differ, and - where, in parallel projection of the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LCof the second grid on any edge of pixels P Bild of the first grid, thereby reducing visually noticeable overlaps of the image source and other components of the screen.

[0017] The first grid can be advantageously divided into rows and columns.

[0018] The grid shape (for the first and second grids) describes the entirety of all pixel positions within the grid. In display technology, grid shapes with perpendicular rows and columns are common in many cases. However, the grid shape can also deviate from this, for example, if the rows and / or columns are sinusoidal or stepped.

[0019] A first optical element can, for example, be formed as a laminate of layers of polymer film polarizers. Other manufacturing methods and material configurations are, of course, possible. Alternatively, or in combination, a first optical element can also be produced by photoalignment of molecules or particles.

[0020] The transition dipole moment – ​​also known as the transition matrix element – ​​is a quantum mechanical vector quantity associated with a specific transition between an initial state – usually the ground state – and a final state – usually an excited state – of a system, i.e., an atom, molecule, or solid. Macroscopically, it corresponds to the electric dipole moment associated with this transition. The direction of the vector defines the polarization of the transition, which in turn determines how the system interacts with an electromagnetic wave of a given polarization. For example, it absorbs light of the corresponding polarization direction during the transition from the ground state to the excited state. The magnitude of the vector corresponds to the strength of the interaction or the transition probability.

[0021] The first preferred direction corresponds to the orientation of the transition dipole moments for a given direction of propagation of light, where absorption is the same for any polarization directions of the light.

[0022] Materials within the meaning of the invention, which contain fixed or—for the second embodiment of second switchable light filters described below—alignable transition dipole moments, include, for example, dichroic dyes or dye mixtures combined with a support material that does not impair the properties, such as liquid crystals or polymers. The optical element may, for example, contain only one dye. However, it may also contain several dyes, i.e., dye mixtures, in a single optical element. The aforementioned materials relax essentially through non-radiative processes.

[0023] The extinction of light is essentially due to absorption and depends on the absolute number of transition dipole moments—and thus inherently also on the layer thickness in which the transition dipole moments are located—and on the alignment between the transition dipole moments and the polarization of the incident light. Depending on the implementation, the density, strength, or refractive index of these transition dipole moments can vary within the layers of the optical element. In a passive, i.e., non-switchable, first optical element, the volume density of the transition dipoles can approach 100%.

[0024] For simplified transmission modeling, it is assumed that the transition dipole moments in the relevant (first or second) optical element are oriented parallel to the plane of incidence of the light onto that optical element. The plane of incidence is defined as the plane in which the propagation direction of the light wave lies, with the surface of the optical element and the plane of incidence forming a right angle. As a transverse wave, the light wave exhibits a transverse magnetic component and a transverse electrical component, which—depending on the medium through which it is traversed—are generally at least approximately perpendicular to each other and to the direction of propagation. Light striking the optical element is initially unpolarized in its entirety, i.e.,The vibration directions of the transverse-electrical—and consequently also the transverse-magnetic—components are statistically distributed. Upon arrival at the surface of the optical element with transition dipole moments oriented perpendicular to the surface, the light interacts with the optical element or the transition dipole moments of the material it contains and is polarized. The vibrational components lying in the plane of incidence are absorbed. Light polarized parallel to the plane of incidence, i.e., transversely magnetic or p-polarized, is absorbed, whereas light polarized perpendicular to the plane of incidence—i.e., parallel to the surface of the optical element—i.e., transversely electric or s-polarized, is either completely transmitted or only significantly reduced in its absorption.Unpolarized light that does not pass through the optical element in question parallel to transition dipole moments will therefore be at least partially s-polarized when passing through the optical element in question with transition dipole moments that are aligned parallel to the plane of incidence of the light.

[0025] This property is essential in all embodiments of the invention. The following model describes the transmission of p-polarized light with an incident intensity I0(α). The transmission of light through an absorbing layer is described by the Lambert-Beer law: T(α)=e−d(α)N1 σabs(α).

[0026] Here, α is the angle between the propagation direction and the surface normal, d(α) is the optical path length as a function of the propagation direction, N1 is the number of absorbing molecules per volume, and σ abs(α) the absorption cross-section as a function of the angle of incidence. Using Snell's law of refraction, the propagation angle α in the medium can be calculated from the angle of incidence β. This results in: T(α)=e−dcos αN1 σabs(α).

[0027] The absorption cross-section for each molecule, or rather for each dipole moment, follows Malus's law; that is, the smaller the angle between the electric field and the dipole moment, the higher the absorption. Additionally, there is absorption by (undesirably) misaligned molecules that absorb light at perpendicular incidence and s-polarized light. The factor of 1 / 3 used below results from the arbitrary orientation of the dyes relative to the incident light. For the calculation, all possible orientations between the incident electric field and the molecule must be summed. Thus, the transmittance for p-polarized light with volume density N2 for the misaligned dyes is: T(α)=e−dcos α(N1 σabssin2α+N23σabs).

[0028] The equation can also be expressed as follows: T(α)=e−dcos α(γ1 sin2α+γ2)

[0029] This can be interpreted differently. For the transmission of s-polarized light, the term N1 or γ1 is omitted. Here, the parameter γ1 determines the optical filtering, and γ2 determines the transmission of s-polarized light as well as the transmission at perpendicular incidence. γ1 / γ2 is a measure of the orientation of the dyes and determines the performance of a first (or a second, defined in more detail below) optical element. Due to technological limitations, ratios of 10⁻¹⁰ are frequently achieved, but other values ​​are possible.

[0030] The object of the invention is further solved by a second embodiment of a screen with an image sensor which is used to display image content in a first grid with pixels P (e.g. arranged in rows and columns). Bild is divided, furthermore encompassing a second switchable light filter, in turn encompassing - a second optical element, which i. comprises a multitude of light-absorbing transition dipole moments, which are formed in the form of molecules of one and / or in the form of one or more dichroic dyes, ii. wherein the majority of the transition dipole moments are aligned parallel to or vary around a first preferred direction selectable for the second optical element with a tolerance of at most 20° in at least a first state, iii. so that light which enters the second optical element is transmitted or at least partially absorbed depending on its polarization state and its direction of incidence relative to the second optical element, iv. wherein the transition dipole moments are embedded in a liquid crystal layer, such that the transition dipole moments can be varied in their orientation and / or magnitude between the first and at least one second state in order to be able to alternatively put the second optical element into at least two different states, - Means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is directed into a second grid with pixels P LC are divided (this second grid is preferably, but not necessarily, structured in rows and columns; however, it could also be only rows or only columns), - the transmission properties of the second switchable light filter between a first operating mode B1 at corresponding pixels P LC, where the first electric field EF1 is applied to the liquid crystal layer, and a second operating mode B2 at corresponding pixels P LC , where the second electric field EF2 is applied to the liquid crystal layer, distinguishing, explicitly also at all pixels P LC either the first or the second electric field, or another electric field, can be applied, which typically assumes a numerical value between the numerical values ​​of the first and second electric fields EF1 and EF2, - wherein the first and second grids differ in at least one of the parameters - preferably in at least two of the parameters, alternatively in at least three of the parameters - resolution, pixel shape, pixel size, grid shape, base angle of the coordinate axes of the grids, orientation of the coordinate axes (implementable, for example, in two 90° grids that are rotated relative to each other) and / or number of the respective pixels P LC or P Bild differ, and - where, in parallel projection of the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LC of the second grid on any edge of pixels P Bild of the first grid, thereby reducing visually noticeable overlaps of the image source and other components of the screen.

[0031] The transition dipole moments can be formed—as described above—by a dichroic dye or by several dichroic dyes, i.e., by such dye molecules, which are integrated into the liquid crystals of the liquid crystal layer in a guest-host arrangement. In the second embodiment, the dye molecules then align themselves parallel to the liquid crystal molecules of the liquid crystal layer. The alignment of the liquid crystal molecules in the voltage-free electric field is, in turn, induced by the surfaces that bound them. One possible material for such surfaces is PMI.

[0032] Generally speaking, this refers to liquid crystal polymers doped with dye(s). Various approaches are known (e.g., thermosettling LCs and epoxy LCs), which will therefore not be discussed in detail here. The following publications serve as examples in this context:

[0033] N. Saba, M. Jawaid, O. Y. Alothman, M. T. Paridah, and A. Hassan, „Recent advances in epoxy resin, naturalfiber-reinforced epoxy composites and their applications,“ Journal of Reinforced Plasticsand Composites, vol. 35, no. 6, 2015.

[0034] C. Carfagna, E. Amendola, and M. Giamberini, „Liquid crystalline epoxy based thermosetting polymers,“ Progress in Polymer Science, vol. 22, pp. 1607-1647, 1997.

[0035] V. P. Shibaev and A. Yu. Bobrovsky, „Liquid crystalline polymers: development trends and photocontrollable materials,“ Russian Chemical Reviews, vol. 86, pp. 1024-1072, 2017.

[0036] T. Ikeda, J.-i. Mamiya, and Y. Yu, „Photomechanics of liquid-crystalline elastomers and other polymers,“ Angew. Chem. Int. Ed., vol. 46, pp. 506-528, 2007.

[0037] The at least one dye consists of dye molecules, wherein advantageously a transition dipole or transition dipole moment is associated with each dye molecule, i.e., each dye molecule corresponds to a transition dipole or transition dipole moment. Typically, a dye has a mass fraction of 0.01% to 10% (or possibly significantly more), preferably 0.1% to 5%, of the material of the respective layer(s) in the first or second optical element. The thickness of the layers is preferably in the range of 0.2 µm to 50 µm, more preferably in the range of 0.5 µm to 20 µm, including all extreme values. The dyes or dye mixtures in the first and second optical element can also be formed differently in their respective layers, if present.

[0038] In the second embodiment, a preferred configuration is a mixture of liquid crystals with at least one dye, particularly with at least one dichroic dye mixture, for each layer. Examples of suitable dichroic dyes or dye mixtures include azomethine dyes, indigoid and thioindigoid dyes, merocyanines, azulene, quinophthalone dyes, perylene dyes, phthaloperine dyes, dioxazine dyes, triphenodioxazine dyes, quinoxaline dyes, triazine dyes, tartrazine, azo dyes, and anthraquinone dyes. The preparation of a liquid crystal dye mixture is described, for example, in US 4,695,131A. Furthermore, the outer surfaces enclosing the layers are preferably treated, for example, by brushing, to achieve a homogeneous surface alignment of the transition dipole moments or, if present, of the liquid crystals.

[0039] The mode of operation of the measures according to the invention for all embodiments is explained in more detail below: By modifying the first and the second grid in at least one of the parameters - preferably in at least two of the parameters, alternatively in at least three of the parameters - resolution, pixel shape, pixel size, grid shape, base angle of the coordinate axes of the grids, orientation of the coordinate axes (implementable, for example, in two 90° grids that are rotated relative to each other) and / or number of the respective pixels P LC or P BildBy distinguishing between the two grids, the invention reduces or completely prevents the superposition of local or entire periods of the first and second grids. In this way, periodic brightness fluctuations are suppressed. In particular, visually perceptible superpositions of the image sensor and other components in the screen are reduced or even completely avoided. Thus, the invention helps to prevent moiré effects.

[0040] Alternatively, at least partial or complete non-periodicity of the respective pixels can be used in one or both grids. This is also useful for combating visually perceptible overlaps, but requires a corresponding transformation of the image geometry to the pixel geometry when addressing the respective grid or both grids, especially in the first grid, so that no distorted image content is perceptible.

[0041] Both the first and second configurations of the screen in question can also be implemented in such a way that the number of pixels P LC the second grid is smaller than the number of pixels P Bild of the first grid. The number of pixels P is advantageous. LC the second grid is even smaller by a factor of 2, 5, 10, 50 or more than 100 than the number of pixels P Bild of the first grid. This helps to avoid visually noticeable overlaps between the two grids, because as a result, the periods of the grids, if any, are usually different, and the period of the second grid is also usually not an integer multiple of the first grid.

[0042] Furthermore, it is possible for the first and second grids to differ at least in their base angle of the coordinate axes, such that the coordinate axes of the second grid have an angle between 45° and less than 88° (preferably between 60° and 85°) to each other, while the coordinate axes of the first grid have an angle between 88° and 92° inclusive. This defined rotation also helps to suppress visually perceptible overlaps between the two grids.

[0043] Furthermore, it can be advantageous if the pixel P LC The second grid is parallelogram-shaped or otherwise non-square (e.g., with rounded corners). If the meshes of the first grid correspond to pixels P, for example... Bild If such pixels correspond to a pixel P, then such a pixel P will be... BildTypically, they can be rectangular, square, parallelogram-shaped, or diamond-shaped. It should be noted here that, for the sake of simplicity, the term pixel refers to the smallest area (possibly separated by color, i.e., color subpixels) that can be addressed separately with a sub-image content, enclosing a non-luminous or non-transmitting area, e.g., a black matrix, so that the first grid is completely filled with the pixels (without holes). In the case that the actual light-emitting or light-transmitting aperture of such a pixel P Bild If this were taken into consideration, significantly more complex geometries would be conceivable, as documented, for example, at https: / / lcdtech.info / en / tests / Icd.pixels.structure.htm.

[0044] The Pixel P Bild The first raster can be configured, for example, as monochrome or as color subpixels (e.g., RGB or RGB white).

[0045] In accordance with the invention, it is also conceivable that at least two pixels P LC The second grid may have a different size and / or shape. This is also generally possible for the first grid. Furthermore, the second grid should be at least two pixels P apart. LC exhibit, so that the measures according to the invention can be implemented.

[0046] Preferably, when projecting the second raster onto the first raster along the perpendicular bisector of the first raster, less than 20%, and particularly preferably less than 5%, of the edges of pixels P are removed. LC of the second grid on any edge of pixels P Bild of the first grid. This geometric condition also helps to avoid moiré effects and any other visually noticeable overlaps.

[0047] In a preferred embodiment, a polarization filter is further provided, which can be positioned upstream or downstream of the first optical element in the direction of incidence. Such a polarization filter preferably transmits horizontally linearly polarized light.

[0048] The means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is fed into a second grid with pixels P LC The configuration can, in both embodiments, comprise at least two conductive layers (e.g., ITO layers) which are connected to a signal generator, wherein at least one of the two conductive layers corresponds to the second grid in pixel P. LC is divided.

[0049] Furthermore, it is advantageous to use the aforementioned screen of the first or second configuration in such a way that - at corresponding pixels P LC, to which the first electric field EF1 is applied, in a first operating mode B1, on the one hand, linearly or elliptically polarized light (in the case of elliptically polarized light, the ratios of the magnitudes of the semi-axes should be at least 1:4, preferably at least 1:10 or greater), which originates from the image sensor and occurs parallel to the first preferred direction into the (first or second) switchable light filter, is transmitted to a minimum of 24%, and on the other hand, linearly or elliptically polarized light, which originates from the image sensor and occurs at a minimum of a first angle of more than 35° to the first preferred direction, which lies in a first plane, is absorbed to a minimum of 85%, - at corresponding pixels P LC, to which the second electric field EF1 is applied, in a second operating mode B2, on the one hand, linearly or elliptically polarized light originating from the image sensor and incident parallel to the first preferred direction into the (first or second) switchable light filter is transmitted by at least 24%, and on the other hand, linearly or elliptically polarized light originating from the image sensor and incident at at least a second angle of more than 35° to the first preferred direction, which lies in a second plane, into the (first or second) switchable light filter is absorbed by at least 85%, wherein the first and the second plane intersect at an angle of 80° to 100°, so that the directions of (main) absorption for the first operating mode B1 and the second operating mode B2 differ by 80° to 100° each.

[0050] The aforementioned first preferred direction can advantageously include an angle between 0° and 45° inclusive with respect to a surface normal of the first or second optical element, respectively. Furthermore, in particular embodiments, the first preferred direction can vary across the surface of the first or second optical element. For the purposes of the invention, the first preferred direction that averages across the surface then applies.

[0051] In a preferred embodiment, a polarizing filter P is further provided, which can be positioned upstream or downstream of the first or second optical element in the direction of incidence. Alternatively, a λ / 4 delay layer can also be provided to generate linearly polarized light from circularly polarized light, depending on the properties of the light originating from a corresponding light source, i.e., the corresponding image source.

[0052] In the second embodiment of the invention, the optical effect of the second switchable light filter is switched by varying the orientation and / or magnitude of the transition dipole moments in each layer between the first and at least one second state, thus enabling the respective layer to be switched to at least two different states. Possible embodiments of a second optical element or of each layer therein are based, for example, on liquid crystals and / or dyes or dye mixtures, which are arranged in the liquid crystal cell with a homogeneous orientation on the surfaces and can be rotated therein between at least two states. In this process, the light-absorbing transition dipole moments are also rotated and can therefore assume at least two operating states. It is particularly conceivable in such embodiments that more than two states, e.g.,Three or eight states, each with different optical effects, can be achieved. Other configurations of the liquid crystal cells are also conceivable. For this purpose, electric fields EF1, EF2, etc., are used to rotate the liquid crystals. It is possible, for example, that either a first electric field or a second electric field describes a field-free state, with the other electric field having an absolute field strength greater than zero, e.g., 0.5 MV / m, and changing dynamically to prevent the liquid crystals from becoming charged.

[0053] In this case, a first such state corresponds to the conditions described above, and at least a second state differs from it, i.e., it has at least one other preferred direction.

[0054] In such active, i.e., second switchable, optical filters, volume densities of the transition dipole moments between 0.1% and 90% are conceivable, based on liquid crystals in the second optical element. Alternatively, configurations of a second optical element, or of each layer within it, are conceivable in which the transition dipole moments are embedded in a liquid subjected to an electro-wetting process. In this way, the density of the transition dipole moments can be varied, in particular, but not exclusively.

[0055] Furthermore, it is possible that the means for selectively generating at least one first electric field EF1 or one second electric field EF2 may also selectively generate different third, fourth or further electric fields at pixels P. LCof the second grid, so that third, fourth and possibly further states can be generated for the liquid crystal layer, which in turn can generate third, fourth and possibly further absorption or transmission characteristics of the (first or second) switchable light filter at locations of the pixel P LC of the second grid in previously described screens.

[0056] Furthermore, a first or second switchable light filter can be extended by a further first optical element that is identical in construction to the first optical element (or varied with respect to its preferred direction), between which the respective liquid crystal layer is located. This makes it possible, among other things, to selectively switch angular restrictions in the transmission between one direction (e.g., angular restrictions only horizontally) and two directions (e.g., angular restrictions horizontally and vertically).

[0057] Similarly, the second embodiment of a switchable light filter can also be supplemented by a second liquid crystal layer, structurally identical to the (first) liquid crystal layer. This makes it possible, for example, to selectively limit the transmission angle between no, one, and two directions.

[0058] For the first and second optical elements of the first and second embodiments, it can still be the case that the respective preferred direction of a transition dipole moment can be selected depending on its position on the respective optical element.

[0059] In this context, it can be particularly useful that each first and second optical element is divided into different regions (A1, A2, ...) along a selectable reference line on the respective first and second optical element, with a separate preferred direction selectable for each region (A1, A2, ...). This preferred direction applies to all transition dipole moments of the corresponding first and second optical element lying within that region (A1, A2, ...). All preferred directions are pairwise distinct and point towards the viewer with a maximum tolerance of + / -10 degrees. Within an optical element and within each applicable region, all transition dipole moments are therefore aligned parallel to the preferred direction within that region, with a maximum tolerance of + / -10°.

[0060] Advantageously, the image generator corresponds to an LCD panel whose polarizing filter matches the polarizing filter of the first or second switchable light filter. This can be the front or rear polarizer in the LCD assembly. Furthermore, the first or second switchable light filter can advantageously be positioned between the LCD panel and its backlight to achieve pixel-by-pixel (P) polarization. LC The system switches between a first operating state for an unobstructed view and a second operating state for a restricted view, because the backlight light, due to the switchable light filter, is sometimes focused and sometimes unfocused in the horizontal direction – for example, when switching horizontally. "Focusing" here does not refer to focusing as with lenses, but rather to a narrowing of the beam angle or transmission range.

[0061] In contrast, the first or second switchable light filter can also be positioned in front of the LCD panel in the viewing direction.

[0062] The image source can alternatively be an OLED, a SED screen, a field emission display (FED), a microLED panel, or a vacuum fluorescent display (VFD), in front of which a first or second switchable light filter is positioned. Since the described first and second switchable light filters of the screen are effective regardless of the type of image source, any other screen type is also suitable.

[0063] Such a screen is advantageously used in mobile devices, motor vehicles, aircraft or watercraft, payment terminals, or access control systems. It allows switching between the aforementioned operating modes across the entire screen or section by section or pixel by pixel, in order to protect sensitive data, i.e., to display it perceptibly to only one viewer, or alternatively, to display image content simultaneously to multiple viewers.

[0064] In principle, the performance of the invention is maintained if the parameters described above are varied within certain limits.

[0065] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations given, but also in other combinations or on their own, without leaving the scope of the present invention. Brief description of the drawings

[0066] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings, which also disclose essential features of the invention. These exemplary embodiments serve only for illustration and are not to be interpreted as limiting. For example, a description of an exemplary embodiment with a plurality of elements or components is not to be interpreted as meaning that all of these elements or components are necessary for implementation. Rather, other exemplary embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components from different exemplary embodiments may be combined with one another unless otherwise specified. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments.To avoid repetition, identical or corresponding elements in different figures are designated with the same reference symbols and are not explained multiple times. They show: Fig. 1. A schematic diagram of a first exemplary pixel arrangement of an image sensor in the prior art, Fig. 2. A schematic diagram for the subdivision of a first exemplary pixel arrangement of an image sensor into color subpixels in the prior art. Fig. 3 a schematic diagram of a second exemplary pixel arrangement of an image transmitter, Fig. 4 a schematic diagram of a third exemplary pixel arrangement of an image transmitter, Fig. 5 a schematic diagram of a fourth exemplary pixel arrangement of an image transmitter, Fig. 6. A schematic diagram illustrating an example of different orientations of the respective coordinate axes of the first and second grids. Fig. 7. A schematic diagram of an exemplary different design of the first and second grids, wherein the respective coordinate axes of the first and second grids are partially oriented differently. Fig. 8 an exemplary first setup of a screen, as well as Fig. 9 an exemplary second screen setup. Detailed description of the drawings

[0067] The drawings are not to scale and merely represent schematic diagrams. The following embodiments are only examples. Variations in the arrangement and geometry of the pixels are also covered by the invention.

[0068] The Fig. Figure 1 shows the schematic diagram of a first exemplary pixel arrangement of an image transmitter 2 for displaying image content, wherein a first grid with pixels P BildThe arrangement used is known from the prior art. In this pixel arrangement, the axes are perpendicular to each other, and the aspect ratio of the pixel size along the axes is 1, meaning the pixels have a height equal to their width. This configuration is found in most color liquid crystal displays in the prior art.

[0069] Furthermore, there Fig. 2. A schematic diagram for subdividing a first exemplary pixel arrangement, i.e., a first grid, an image transmitter (according to Fig. 1) in color subpixels in the prior art. Here, the pixels are themselves subdivided into color subpixels that separately emit or transmit red (R), green (G) and blue (B) light.

[0070] If a second optical grid, such as a monoLCD panel with the same pixel sizes as the first grid of the image source 2, were placed at a distance of a few hundred micrometers to a few millimeters above the image source 2, unpleasant moiré effects would generally occur due to optical superposition effects of similar (or identical) grids. With this in mind, the following describes a first design of a screen with an image source 2, which uses a first grid with pixels P to display image content. Bild exhibits, further comprising a first switchable light filter 5. The first switchable light filter 5 in turn comprises - a first optical element 1, itself comprising • a multitude of light-absorbing transition dipole moments, • wherein the majority of the transition dipole moments are permanently or at least in a first state aligned with a tolerance of a maximum of 20° parallel to a first preferred direction selectable for the first optical element 1 or vary around it, • so that light which enters the first optical element 1 is transmitted or at least partially absorbed depending on its polarization state and its direction of incidence relative to the first optical element 1, - Means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is directed into a second grid with pixels P LC are divided (this second grid is preferably, but not necessarily, structured in rows and columns; however, it could also be only rows or only columns), - a liquid crystal layer 3 arranged in front of or behind the first optical element 1, onto which - usually pixel by pixel - the respective pixel P is deposited LC the generated electric field acts, and depending on this, it influences the polarization state of light passing through it - usually pixel by pixel - so that - the transmission properties of the first switchable light filter 5 between a first operating mode B1 at corresponding pixels P LC , where the first electric field EF1 is applied, and a second operating mode B2 at corresponding pixels P LC , to which the second electric field EF2 is applied, distinguishing, explicitly also at all pixels P LC either the first or the second electric field, or another electric field, can be applied, which typically assumes a numerical value between the numerical values ​​of the first and second electric fields EF1 and EF2, - wherein the first and second grids differ in at least one of the parameters - preferably in at least two of the parameters, alternatively in at least three of the parameters - resolution, pixel shape, pixel size, grid shape, base angle of the coordinate axes of the grids, orientation of the coordinate axes (implementable, for example, in two 90° grids that are rotated relative to each other) and / or number of the respective pixels P LC or P Bild differ, and - where, in parallel projection of the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LC of the second grid on any edge of pixels P Bild of the first grid, thereby reducing visually visible overlaps of the image generator 2 and other components of the screen.

[0071] The first grid can be advantageously divided into rows and columns.

[0072] A first optical element 1 can be produced, for example, by photoalignment of molecules or particles. Materials within the meaning of the invention, which contain fixed or – for the second embodiment of second switchable light filters 1a described below – alignable transition dipole moments, include, for example, dichroic dyes or dye mixtures, which are combined with a support material that does not impair the properties, such as liquid crystals or polymers.

[0073] The Fig. Figure 3 shows a schematic diagram of a second exemplary pixel arrangement of an image sensor 2, first grid. Here, the pixels are P BildThe first raster (which in turn can be subdivided into color subpixels) is rectangular, but the angle between the axes deviates from 90°. Here, for example, it is 75°, but it can also take on other values, for example between 10° and 80°. A second raster with pixels P LC , which is used in a previously described screen, could, for example, have axes arranged rectangularly to each other, as (but for a first grid) in Fig. Figure 1 shows that the first and second grids differ in at least one of the parameters mentioned above, and visually perceptible overlaps of the image sensor 2 and other components of the screen are reduced or even avoided because the first and second grids differ. The larger center-to-center distance of the pixels P Bild is in Fig. 3. oriented along the vertical direction. However, in other configurations it can also be oriented along the other direction.

[0074] Furthermore, it shows Fig. 4. A schematic diagram of a third exemplary pixel arrangement for the first grid with pixels P Bild of an image transmitter 2. A second grid with pixels P LC , which is used in a previously described screen, could, for example, have axes arranged rectangularly to each other, as in Fig. Figure 1 shows that the axes of the first grid are rotated 45° relative to the second grid (not shown in the drawing). This means that the first and second grids differ in at least one of the parameters mentioned above, and visually perceptible overlaps of the image sensor 2 and other screen components are reduced or even avoided because the first and second grids are different.

[0075] In Fig. Figure 5 is a schematic diagram of a fourth exemplary pixel arrangement for the first grid with pixels P Bild Figure 2 shows a possible color subpixel arrangement for an image sensor. This is a possible arrangement of color subpixels, for example, for OLED image sensors. The first grid is rotated 45° relative to the second grid (not shown in the drawing). Furthermore, the number of each of the different subpixels R, G, B in the first grid is not the same; that is, there are as many green subpixels as red and blue subpixels combined. In addition, the green subpixels have a different size than the red and blue ones. A second grid with pixels P LC , which is used in a previously described screen, could, for example, have axes arranged rectangularly to each other, as in Fig. 1 shown. This means that the first and second grids differ in at least one of the parameters mentioned above, and visually visible overlaps of the image sensor 2 and other components of the screen are reduced or even avoided because the first and second grids differ.

[0076] Furthermore, there Fig. Figure 6 shows a schematic diagram illustrating an example of different orientations of the respective coordinate axes of the first and second grids. Here, the orthogonal axes indicated by solid lines represent the first grid, and the orthogonal axes indicated by dashed lines represent the second grid. However, the meaning can also be reversed without departing from the scope of the invention. The nearest adjacent axes of the first and second grids each form an angle of approximately 30°.

[0077] Furthermore, it shows Fig. Figure 7 shows a schematic diagram illustrating an exemplary different configuration of the first and second grids, where the respective coordinate axes of the first and second grids are partially oriented differently. The orthogonal axes indicated by solid lines represent the first grid with pixels P. Bild The pixels P are represented by dashed lines. LC of the second grid. The pixels P Bild The first raster is rectangular (square) in this example, while the pixels P LCThe second grid is parallelogram-shaped. One axis of each grid (here, from the viewer's perspective, the horizontal axes on the paper plane) is parallel to each other, while the other axis of each grid forms an angle greater than zero, here for example, 20° (other values ​​are possible). Thus, the first and second grids again differ in at least one of the parameters mentioned above, and visually perceptible overlaps of the image source 2 and other components of the screen are reduced or even avoided because the first and second grids differ. It is particularly evident here that when the second grid is projected parallel to the first grid along the perpendicular bisector of the first grid, less than 50% of the edges of pixels P are affected. LC of the second grid on any edge of pixels P Bild of the first grid.

[0078] Generally speaking, pixels used in all screen configurations are P Bild or P LC They can also take on non-rectangular shapes.

[0079] The Fig. Figure 8 shows an exemplary initial setup of a screen of the aforementioned first configuration. From the viewer's perspective, from back to front, such a screen comprises - an image generator 2 with pixels P Bild in a first grid, for example designed as for the Fig. 3, Fig. 4, Fig. 5 or Fig. 7 described, - optional: a linear polarization filter P - a first switchable light filter 5, in turn comprehensive i. a planar ITO layer ITO1, ii. a liquid crystal layer 3, iii. a planar, but structured ITO layer ITO2, which forms pixels P LCthe second grid is equipped with TFTs, as well as iv. a first optical element 1, as described above, wherein, by way of example, the first preferred direction is to be aligned approximately parallel to the perpendicular bisector on the first optical element 1.

[0080] The first and second ITO layers, ITO1 and ITO2, serve as the means for selectively generating at least one first electric field EF1 or one second electric field EF2. They are coupled to control electronics (including a signal generator), not shown in the diagram, which generates defined voltages. It is possible, for example, that either a first electric field EF1 or a second electric field EF2 describes a field-free state, with the other (usually dynamic) electric field having an absolute field strength greater than zero, e.g., 0.5 MV / m.

[0081] Additional layers and components, not shown in the drawing, may be present, such as protective or top layers made of glass and / or polymers. An example of such a screen according to... Fig. 8 functions as described at the beginning. Due to the measures taken, namely that the first and second grids differ in at least one of the parameters – preferably in at least two of the parameters, alternatively in at least three of the parameters – resolution, pixel shape, pixel size, grid shape, base angle of the coordinate axes of the grids, orientation of the coordinate axes (implementable, for example, in two 90° grids that are rotated relative to each other) and / or number of the respective pixels P. LC or P Bild By differentiating between the image sensor 2 and other components of the screen, visually visible overlaps are reduced or even completely prevented.

[0082] In the following, a second configuration of a screen with an image sensor 2, which is used to display image content in a first grid with pixels P (e.g. arranged in rows and columns), is described. Bild The system is further divided into two parts, including a second switchable light filter 5a, which is described. The second switchable light filter 5a in turn comprises: - a second optical element 1a, which i. comprises a multitude of light-absorbing transition dipole moments, which are formed in the form of molecules of one and / or in the form of one or more dichroic dyes, ii. wherein the majority of the transition dipole moments are aligned parallel to or vary around a first preferred direction selectable for the second optical element 1a with a tolerance of at most 20° in at least a first state, iii. such that light which enters the second optical element 1a is transmitted or at least partially absorbed depending on its polarization state and its direction of incidence relative to the second optical element 1a, iv. wherein the transition dipole moments are embedded in a liquid crystal layer 3a, such that the transition dipole moments can be varied in their orientation and / or magnitude between the first and at least one second state in order to be able to alternatively put the second optical element 1a into at least two different states, - Means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is directed into a second grid with pixels P LC are divided (this second grid is preferably, but not necessarily, structured in rows and columns; however, it could also be only rows or only columns), - the transmission properties of the second switchable light filter 5a between a first operating mode B1 at corresponding pixels P LC , where the first electric field EF1 is applied to the liquid crystal layer 3a, and a second operating mode B2 at corresponding pixels P LC , where the second electric field EF2 is applied to the liquid crystal layer 3a, distinguishing, explicitly also at all pixels P LC either the first or the second electric field, or another electric field, can be applied, which typically assumes a numerical value between the numerical values ​​of the first and second electric fields EF1 and EF2, - wherein the first and second grids differ in at least one of the parameters - preferably in at least two of the parameters, alternatively in at least three of the parameters - resolution, pixel shape, pixel size, grid shape, base angle of the coordinate axes of the grids, orientation of the coordinate axes (implementable, for example, in two 90° grids that are rotated relative to each other) and / or number of the respective pixels P LC or P Bild differ, and - where, in parallel projection of the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LC of the second grid on any edge of pixels P Bild of the first grid, thereby reducing visually visible overlaps of the image generator 2 and other components of the screen.

[0083] The transition dipole moments can be formed—as described above—by one or more dichroic dye(s), i.e., by such dye molecules, which are integrated into liquid crystals of the liquid crystal layer in a guest-host arrangement. In the second embodiment, the dye molecules then align themselves parallel to the liquid crystal molecules of the liquid crystal layer. The alignment of the liquid crystal molecules in the voltage-free electric field is, in turn, induced by the surfaces that bound them.

[0084] This shows the Fig. 9. An exemplary second screen setup. From the viewer's perspective, from back to front, such a screen comprises - an image generator 2 with pixels P Bild in a first grid, for example designed as for the Fig. 3, Fig. 4, Fig. 5 or Fig. 7 described, - optional: a linear polarization filter P, - a second switchable light filter 5a, itself comprising i. a planar first ITO layer ITO1, ii. a second optical element 1a with a liquid crystal layer 3a, as described above, as well as iii. a planar, but structured second ITO layer ITO2, which forms pixels P LC the second grid is equipped with TFTs.

[0085] The first and second ITO layers, ITO1 and ITO2, serve as the means for selectively generating at least one first electric field EF1 or one second electric field EF2, pixel by pixel. They are coupled to control electronics (not shown in the diagram) that generate defined voltages. It is possible, for example, that either a first electric field EF1 or a second electric field EF2 describes a field-free state, with the other (usually dynamic) electric field having an absolute field strength greater than zero, e.g., 0.5 MV / m.

[0086] Further, graphically in Fig. Nine layers and components not shown may be present, such as protective or cover layers made of glass and / or polymers. An example of such a screen according to... Fig. 9 functions as described above. Due to the measures taken, namely that the first and second grids differ in at least one of the parameters – preferably in at least two of the parameters, alternatively in at least three of the parameters – resolution, pixel shape, pixel size, grid shape, base angle of the coordinate axes of the grids, orientation of the coordinate axes (implementable, for example, in two 90° grids that are rotated relative to each other) and / or number of the respective pixels P. LC or P Bild By differentiating between the image sensor 2 and other components of the screen, visually visible overlaps are reduced or even completely prevented.

[0087] The at least one dye consists of dye molecules, wherein advantageously a transition dipole or transition dipole moment is associated with each dye molecule, i.e., each dye molecule corresponds to a transition dipole or transition dipole moment. Typically, a dye has a mass fraction of 0.01% to 10% (or possibly significantly more), preferably 0.1% to 5%, of the material of the respective layer(s) in the first or second optical element. The thickness of the layers is preferably in the range of 0.2 µm to 50 µm, more preferably in the range of 0.5 µm to 20 µm, including all extreme values. The dyes or dye mixtures in the first and second optical element can also be formed differently in their respective layers, if present.

[0088] In general, this can be described as dye-doped liquid crystal polymers. Various approaches are known in the field (e.g., thermosettling liquid crystals and epoxy liquid crystals), which have already been mentioned above as examples, but not exhaustively. In the second embodiment, a preferred configuration is a mixture of liquid crystals with at least one dye, particularly with at least one dichroic dye mixture, for each layer.

[0089] The mode of operation of the measures according to the invention in the first and second exemplary embodiments will be explained in more detail below using examples from Fig. 7 explains: Because the first and second rasters differ in several of the mentioned parameters, in this case in the parameters resolution, pixel shape, pixel size, raster shape, base angle of the coordinate axes of the rasters and number of the respective pixels P LC or P BildIn particular, the superposition of local or entire periods of the first and second rasters is reduced or completely prevented. In this way, periodic brightness fluctuations are suppressed. Specifically, visually perceptible superpositions of the image sensor 2 and other components in the screen are thus reduced or even completely suppressed. Therefore, the invention helps to avoid moiré effects.

[0090] Both the first and second configurations of the screen in question can also be implemented in such a way that the number of pixels P LC the second grid is smaller than the number of pixels P Bild of the first grid. This property is also shown in the example after Fig. 7. This helps avoid visually noticeable overlaps between the two rasters, because the periods of the rasters are usually different, and the period of the second raster is usually not an integer multiple of the first raster.

[0091] Furthermore, the example differs according to Fig. 7. The first and second grids are also rotated in their base angle of the coordinate axes, since the coordinate axes of the second grid are at an angle of approximately 75° to each other, while the coordinate axes of the first grid are at an angle of approximately 90° to each other. This defined rotation also helps to suppress visually perceptible overlaps between the two grids.

[0092] Furthermore, it can be advantageous if—as in Fig. 7 indicated - the pixel P LC the second grid is designed in a parallelogram shape.

[0093] The Pixel P BildThe first grid can be configured in all variations, for example as monochrome or as color subpixels (e.g. RGB or RGB white).

[0094] In the example according to Fig. 7 is also realized that when projecting the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LC of the second grid on any edge of pixels P Bild the first grid is projected. This geometric condition also helps to avoid moiré effects and any other visually noticeable overlaps.

[0095] The aforementioned first preferred direction can advantageously include an angle between 0° and 45° inclusive with respect to a surface normal of the first or second optical element, respectively. Furthermore, in particular embodiments, the first preferred direction can vary across the surface of the first or second optical element, i.e., the respective preferred direction of a transition dipole moment can be selected depending on its position on the respective optical element. For the purposes of the invention, the first preferred direction averaged over the surface then applies.

[0096] In this context, it can be particularly useful that each first and second optical element is divided into different regions (A1, A2, ...) along a selectable reference line on the respective first and second optical element, with a separate preferred direction selectable for each region (A1, A2, ...). This preferred direction applies to all transition dipole moments of the corresponding first and second optical element lying within that region (A1, A2, ...). All preferred directions are pairwise distinct and point towards the viewer with a maximum tolerance of + / -10 degrees. Within an optical element and within each applicable region, all transition dipole moments are therefore aligned parallel to the preferred direction within that region, with a maximum tolerance of + / -10°.

[0097] Furthermore, it is possible that the means for selectively generating at least one first electric field EF1 or one second electric field EF2 may also selectively generate different third, fourth or further electric fields at pixels P. LC of the second grid, so that third, fourth and possibly further states can be generated for the liquid crystal layer, which in turn can generate third, fourth and possibly further absorption or transmission characteristics of the (first or second) switchable light filter at locations of the pixel P LC of the second grid in previously described screens.

[0098] Advantageously, the image generator 2 corresponds to an LCD panel, one of whose polarization filters corresponds to the optional polarization filter P in the screen. This can be the front or rear polarizer in the LCD assembly.

[0099] The image source 2 can alternatively be an OLED, a SED screen, a field emission display (FED), a microLED panel, or a vacuum fluorescent display (VFD), in front of which a first or second switchable light filter 5, 5a is arranged. Since the described first and second switchable light filters 5, 5a of the screen are effective regardless of the type of image source 2, any other screen types are also suitable.

[0100] The invention described above solves the stated problem: A screen with a switchable light filter has been described. The switchable light filter can be implemented inexpensively and, in particular, is universally applicable with various types of screens to enable switching between a privacy mode, i.e., a restricted viewing mode, and an unobstructed viewing mode, without reducing the resolution of such a screen. This achieves good image quality, especially with no or imperceptible moiré effects between the screen's image sensor and the switchable light filter.

[0101] The invention described above can be advantageously applied wherever confidential data is displayed and / or entered, such as during PIN entry or data display at ATMs or payment terminals, or for password entry or reading emails on mobile devices. As described above, the invention can also be used in cars to selectively conceal distracting visual content from the driver or passenger. Reference symbol list 1. First optical element 1a second optical element 2 image sensors 3 Liquid crystal layer 3a Liquid crystal layer ITO1 ITO layer ITO2 ITO layer P Linear polarization filter P Bild Pixels in the first raster P LC Pixels in the second grid

Claims

[1] Screen with an image sensor (2) which displays image content using a first grid of pixels P Bild exhibits, further comprising a first switchable light filter (5), in turn comprising - a first optical element (1), itself comprising • a multitude of light-absorbing transition dipole moments, • wherein the majority of the transition dipole moments are permanently or at least in a first state aligned with a tolerance of at most 20° parallel to a first preferred direction selectable for the first optical element (1) or vary around it, • so that light which enters the first optical element (1) is transmitted or at least partially absorbed depending on its polarization state and its direction of incidence relative to the first optical element (1), - Means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is directed into a second grid with pixels P LC are divided - a liquid crystal layer (3) arranged in front of or behind the first optical element (1), onto which the respective pixel P is applied LC The generated electric field acts, and depending on this, it influences the polarization state of light passing through it. - wherein the transmission properties of the switchable light filter (5) differ between a first operating mode B1 at corresponding pixels P LC , where the first electric field EF1 is applied, and a second operating mode B2 at corresponding pixels P LC , where the second electric field EF2 is applied, distinguish, - wherein the first and second rasters differ in at least one of the parameters resolution, pixel shape, pixel size, raster shape, base angle of the coordinate axes of both rasters, orientation of the coordinate axes and / or number of the respective pixels P LC or P Bild differ, and - where, in parallel projection of the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LC of the second grid on any edge of pixels P Bild of the first grid, thereby reducing visually visible overlaps of the image source (2) and other components of the screen. [2] Screen with an image sensor (2) which is used to display image content in a first grid of pixels P Bild is divided, further comprising a second switchable light filter (5a), in turn comprising - a second optical element (1a), which • comprises a multitude of light-absorbing transition dipole moments, which are formed in the form of molecules of one and / or in the form of one or more dichroic dyes, • wherein the majority of the transition dipole moments are aligned parallel to or vary around a first preferred direction selectable for the second optical element (1a) with a tolerance of at most 20° in at least a first state, • so that light which enters the second optical element (1a) is transmitted or at least partially absorbed depending on its polarization state and its direction of incidence relative to the second optical element (1a), • wherein the transition dipole moments are embedded in a liquid crystal layer (3a) so that the transition dipole moments can be varied in their orientation and / or magnitude between the first and at least one second state in order to be able to switch the second optical element (1a) to at least two different states alternatively, - Means for selectively generating at least one first electric field EF1 or one second electric field EF2, which is directed into a second grid with pixels P LC are divided - wherein the transmission properties of the second switchable light filter (5a) differ between a first operating mode B1 at corresponding pixels P LC , where the first electric field EF1 is applied to the liquid crystal layer (3a), and a second operating mode B2 at corresponding pixels P LC , where the second electric field EF2 is applied to the liquid crystal layer (3a), distinguish, - wherein the first and second rasters differ in at least one of the parameters resolution, pixel shape, pixel size, raster shape, base angle of the coordinate axes of the two rasters, orientation of the coordinate axes and / or number of the respective pixels P LC or P Bild differ, and - where, in parallel projection of the second raster onto the first raster along the perpendicular bisector of the first raster, less than 50% of the edges of pixels P LC of the second grid on any edge of pixels P Bild of the first grid, thereby reducing visually visible overlaps of the image source (2) and other components of the screen. [3] Screen according to claim 1 or 2, characterized by , that - at corresponding pixels P LC, to which the first electric field EF1 is applied, in the first operating mode B1, on the one hand, linearly or elliptically polarized light which occurs parallel to the selectable first preferred direction into the first or second switchable light filter (5, 5a) is transmitted to at least 24% and on the other hand, linearly or elliptically polarized light which occurs at at least a first angle of more than 35° to the selectable first preferred direction, which lies in a first plane, into the first or second switchable light filter (5, 5a) is absorbed to at least 85%, - at corresponding pixels P LC, to which the second electric field EF2 is applied, in the second operating mode B2, on the one hand, linearly or elliptically polarized light which occurs parallel to the selectable first preferred direction into the first or second switchable light filter (5, 5a) is transmitted to at least 24% and on the other hand, linearly or elliptically polarized light which occurs at at least a second angle of more than 35° to the selectable first preferred direction, which lies in a second plane, into the first or second switchable light filter (5, 5a) is absorbed to at least 85%, wherein the first and the second plane intersect at an angle of 80° to 100°, so that the directions of absorption for the first operating mode B1 and the second operating mode B2 differ by 80° to 100° each. [4] Screen according to any of the aforementioned claims, characterized by , that the number of pixels P LCthe second grid is smaller than the number of pixels P Bild of the first grid. [5] Screen according to any of the aforementioned claims, characterized by , that the first and second grids differ at least in their base angle of the coordinate axes, in that the coordinate axes of the second grid have an angle between 45° and less than 88° to each other, while the coordinate axes of the first grid have an angle between 88° and 92° to each other. [6] Screen according to any of the aforementioned claims, characterized by that the pixel P Bild of the first grid rectangular and the pixels P LC The second grid is non-square, preferably parallelogram-shaped. [7] Screen according to any of the aforementioned claims, characterized by that at least two pixels P LC The second grid may have a different size and / or shape. [8] Screen according to any of the aforementioned claims, characterized by that the pixel P Bild of the first raster are formed as color subpixels. [9] Screen according to any of the aforementioned claims, characterized by , that when the second raster is projected parallel to the first raster along the perpendicular bisector of the first raster, less than 20%, preferably less than 5%, of the edges of pixels P LC of the second grid on any edge of pixels P Bild of the first grid. [10] Screen according to any of the aforementioned claims, characterized by , that the means for selectively generating at least one first electric field EF1 or one second electric field EF2, or optionally also third, fourth or further electric fields different from these, at pixels P LC of the second grid.

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