Screen

Abstract

The invention relates to a screen with pixels (P) and an optical element (1), wherein the pixels (P) emit light in at least two different wavelengths or wavelength ranges, in a first operating mode B1 at least a first part (P1) of the pixels (P) emits light, in a second operating mode B2 at least a second part (P2) of the pixels (P) emits light, wherein the optical element (1) includes at least one section (S1, S2, S3, ...) whose haze value for light with a first wavelength or a first wavelength range is greater than 15%, while for light with a second wavelength or a second wavelength range it is less than 12%, wherein each such section (S1, S2, S3, ...)) Light can enter a first part (P1) and a second part (P2) of the pixels, wherein the wavelengths or wavelength ranges of the incident light differ for each such section (S1, S2, S3, ..) at least in their peak wavelength, depending on whether it originates from the first part (P1) or the second part (P2) of the pixels (P), so that, depending on the wavelength or wavelength range of the light incident on such a section (S1, S2, S3, ..) this light is scattered more or less strongly.

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 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.

[0008] 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.

[0009] 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 beam angle. Disadvantages of this technology include high additional energy and cost consumption and the difficulty in adjusting 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°.

[0010] 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. Furthermore, most of the aforementioned methods are applicable to self-illuminating panels such as OLED or microLED in the prior art.

[0011] Patent 10 2004 044 802 A1 describes an arrangement for the selective display of images in either three-dimensional or two-dimensional terms. For 3D display, a barrier structure is used in the backlight, the light-structuring effect of which is selectively diffused for 2D display. With this setup, it is not possible, among other things, to selectively emit image content displayed on OLED panels into different angular ranges.

[0012] In DE 10 2021 000 968 B3, the applicant discloses a screen with a free and a restricted viewing mode. This involves the use of a component with variable transmission. However, even with this design, it is not possible, among other things, to selectively project image content displayed on OLED panels into different angular ranges.

[0013] US patent 2022 / 0107500 A1 describes a system for controlling the optical properties of a display. A disadvantage of this system is, among other things, the considerable effort required to implement the necessary setup.

[0014] US patent 2024 / 0272464 A1, filed by the applicant, discloses a screen with a free and a restricted viewing mode. This screen uses a switchable backlight. However, even with this design, it is not possible, among other things, to selectively project image content displayed on OLED panels into different viewing angles.

[0015] Finally, US patent 2007 / 0030240 A1 reveals a screen with a switchable viewing angle. This primarily utilizes GHLC or PDLC systems with backlighting. However, such a screen does not allow for the selective projection of image content displayed on OLED panels into different viewing angles. Description of the invention

[0016] The object of the invention is therefore to describe a screen that emits the displayed image content selectively into different angular ranges. The invention is intended to be applicable to common image sensor systems such as LCD, OLED or microLED.

[0017] This problem is solved according to the invention by a screen with pixels P for displaying image content, an electronic control of the pixels P and an optical element in front of the pixels P in the viewing direction of a viewer, wherein a. the pixels P emit light in at least two (preferably at least three) different wavelengths or wavelength ranges with different peak wavelengths (which can represent, for example, red, green and blue light, i.e., RGB subpixels), b. in at least one first operating mode B1 at least one first part P1 of the pixel P emits light, c. in at least one second operating mode B2 at least one second part P2 of the pixel P emits light, d. wherein the optical element contains at least one section S1, S2, S3, ... (preferably several or a plurality of such sections) whose haze value for light with a first wavelength or first wavelength range is greater than 15%, while for light with a second wavelength or second wavelength range it is less than 12%, e. wherein furthermore, light from a first part P1 and a second part P2 of the pixels can fall upon each such section S1, S2, S3, .., wherein the wavelengths or wavelength ranges of the respective incident light differ, depending on their origin from the first part P1 or the second part P2 of the pixels P for each such section S1, S2, S3, .. at least in their peak wavelength, f. so that, depending on the wavelength or wavelength range of the light incident on such a section S1, S2, S3, .. this light is scattered more or less strongly.

[0018] An optical element with sections S1, S2, S3, ... can, for example, be designed and manufactured based on metamaterials. Other wavelength-dependent diffusers are also suitable as optical elements, such as those based on liquid crystals.

[0019] It is advantageous that each of the pixels P comprises at least two subpixels, of which at least one belongs to the first part P1 and at least one to the second part P2.

[0020] One possibility is that the at least two subpixels of each pixel P, of which at least one belongs to the first part P1 and at least one to the second part P2, lie next to each other in the viewing direction of a viewer.

[0021] Alternatively, it is conceivable that the at least two subpixels of each pixel P, of which at least one belongs to the first part P1 and at least one to the second part P2, lie one behind the other in the viewing direction of a viewer.

[0022] In a broader embodiment, at least a portion of the pixels P is variable in the wavelength or wavelength range they emit or transmit, such that this portion of the pixels P belongs to the first part P1 in the first operating mode B1 and to the second part P2 in the second operating mode B2. It is explicitly possible for the pixels that can optionally belong to groups P1 and P2 to be identical, i.e., to comprise all pixels P.

[0023] The invention becomes particularly significant when at least the pixels of the second part P2, but preferably all pixels P, emit collimated light. Then, due to the different haze values ​​(corresponding to the strength of the scattering) of the optical element, the displayed image content is emitted into different angular ranges for the first part P1 of pixel P and for the second part P2 of pixel P. Thus, advantageously, in the first operating mode B1, the first part P1 of pixel P is visible from a wide angular range due to the scattering effect of the optical element 1, while in the second operating mode B2, the second part P2 of pixel P is visible from a narrower angular range due to the lower scattering effect of the optical element.

[0024] The aforementioned collimation of light can be implemented, for example, using collimated light sources, such as focused backlights, lens arrays in front of image sensors, the use of µ-lases, VCSELs, etc. Furthermore, the collimation can also be "off-axis", i.e., inclined relative to the perpendicular to the optical element.

[0025] It is also possible to simultaneously apply image content to the first and second parts P1, P2 of pixels P. Depending on the configuration, these pixels will then be visible from different angles. If the angles do not overlap, only a portion of pixels P will be visible at any given time.

[0026] Furthermore, a screen with pixels P for displaying image content, an electronic control of the pixels P, and an optical element in front of the pixels P in the viewing direction of a viewer is disclosed, wherein a. all pixels P emit collimated light, b. the optical element is provided with switchable meta-structures whose properties can be switched between a haze value less than 12% and greater than 15%, c. wherein furthermore in a first operating mode B1 the optical element contains at least one section whose haze value for the light emitted by the pixels P is greater than 15%, such that on this at least one section the pixels P behind it are visible from a wide (preferably unrestricted) angular range, d. and wherein in a second operating mode B2 the optical element contains at least one section whose haze value for the light emitted by the pixels P is less than 12%, such that on this at least one section the pixels P behind it are visible from a restricted angular range.

[0027] Advantageously, the switchable meta-structures of the optical element can be modified in their scattering properties by at least one of the following measures: a) pressure (change), b) temperature (change), c) application of an electric and / or a magnetic field, d) modification of a structure by rotation of a liquid crystal, e) modification of a structure by particle movement by means of electro-wetting and / or electrophoresis, or f) application of biological and / or chemical agents (e.g., change of the surrounding pH value).

[0028] The invention also comprises a screen with pixels P for displaying image content, an electronic control of the pixels P, and an optical element in front of the pixels P in the viewing direction of a viewer, wherein a. in at least one first operating mode B1 at least one first part P1 of the pixels P emits light of a first group of wavelengths or wavelength ranges, b. in at least one second operating mode B2 at least one second part P2 of the pixel P emits light of a second group of wavelengths or wavelength ranges, wherein the peak wavelengths of the first and second groups of wavelengths or wavelength ranges are each pairwise different, c. wherein the optical element further comprises at least one section whose haze value is greater than 15% for light with wavelengths or wavelength ranges of the first group, while it is less than 12% for light with wavelengths or wavelength ranges of the second group, such that the light of the first part P1 of the pixels P is scattered more strongly than the light of the second part P2 of the pixels P, whereby the image content displayed on the pixels P is selectively emitted into different angular ranges depending on the use of the first part P1 of the pixels P and / or the second part P2 of the pixels P.

[0029] The haze value is preferably measured according to ASTM D1003, where the measurement according to the more common procedure A is used as a reference with a hazemeter.

[0030] A screen as described above is advantageously used in a mobile device, a motor vehicle, aircraft or watercraft, a payment terminal, or an access control system. It is possible to switch between the aforementioned operating modes to protect sensitive data, i.e., to display it perceptible to only one viewer, or alternatively to display image content simultaneously to multiple viewers.

[0031] In principle, the performance of the invention is maintained if the parameters described above are varied within certain limits.

[0032] 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

[0033] 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 legend for the different pixels and sections on the optical element, Fig. 2. The schematic diagram of an exemplary screen in a first design, Fig. 3 the schematic diagram of an exemplary screen in a second embodiment, Fig. 4a the schematic diagram of an exemplary screen in a first operating mode B1 in a third embodiment, Fig. 4b the schematic diagram of an exemplary screen in a second operating mode B2 in a third embodiment, Fig. 5a the schematic diagram of an exemplary screen in a first operating mode B1 in a fourth embodiment, as well as Fig. 5b the schematic diagram of an exemplary screen in a second operating mode B2 in a fourth embodiment. Detailed description of the drawings

[0034] The drawings are not to scale and only represent schematic diagrams.

[0035] In Fig. Figure 1 is a legend for the various pixels and sections on the optical element 1. Here, λ1, λ2, and λ3 each represent peak wavelengths for the light emitted by pixels P and color subpixels, respectively. Sections S1, S2, and S3 are each configured to scatter light of a first peak wavelength (and adjacent wavelengths up to a selectable tolerance), to transmit light of a second peak wavelength (and adjacent wavelengths up to a selectable tolerance) (i.e., to have a haze value of at most 15%), and to transmit light of a second peak wavelength (and adjacent wavelengths up to a selectable tolerance) (i.e., to have a haze value of at most 12%). For example, each section S1 scatters light with peak wavelength λ1 and transmits light with peak wavelength λ2. Similarly, each section S2 scatters light with peak wavelength λ2 and transmits light with peak wavelength λ3. Finally, for example, section S3 scatters light of a second peak wavelength (and adjacent wavelengths up to a selectable tolerance).Each section S3 scatters light with peak wavelength λ3 and transmits light with peak wavelength λ1. The aforementioned scattering and transmission properties naturally also apply to light with wavelengths adjacent to the respective peak wavelengths, up to a selectable tolerance, i.e., for corresponding wavelength ranges. The sections S1, S2, and S3 can, for example, be formed by suitable metamaterials.

[0036] The Fig. Figure 2 shows a schematic diagram of an exemplary screen in a first embodiment. One or more viewers (not shown in the diagram) would be located in the plane of the drawing above the screen. Such a screen comprises pixels P for displaying image content, an electronic control unit for the pixels P (not shown in the diagram), and, in the viewing direction of a viewer, an optical element 1 in front of the pixels P, wherein a. the pixels P emit light in at least two different wavelengths or wavelength ranges with different peak wavelengths, (in Fig. 2ff there are three peak wavelengths λ1 to λ3, which can represent, for example, red, green and blue light (i.e., RGB subpixels) and b. in at least one first operating mode B1 at least one first part P1 of the pixel P emits light, c. in at least one second operating mode B2 at least one second part P2 of the pixel P emits light, d. wherein the optical element 1 contains several sections S1, S2, S3, ... (preferably a plurality of such sections), whose haze value for light with a first wavelength or first wavelength range is greater than 15%, while for light with a second wavelength or second wavelength range it is less than 12%, e. wherein furthermore, light from a first part P1 and a second part P2 of the pixels can fall upon each such section S1, S2, S3, .., wherein the wavelengths or wavelength ranges of the respective incident light differ, depending on their origin from the first part P1 or the second part P2 of the pixels P for each such section S1, S2, S3, .. at least in their peak wavelength, f. so that, depending on the wavelength or wavelength range of the light incident on such a section S1, S2, S3, ..., this light is scattered more or less strongly (strong scattering is in Fig. 2ff are represented with three outward-facing arrows each, while weak dispersion is indicated with only one directional arrow).

[0037] It is advantageous that each of the pixels P comprises at least two subpixels, of which at least one belongs to the first part P1 and at least one to the second part P2.

[0038] It is like in Fig. As shown in Figure 2, it is possible that the at least two subpixels of each pixel P, of which at least one belongs to the first part P1 and at least one to the second part P2, lie next to each other in the viewing direction of an observer. If the first and second parts P1, P2 of pixel P are switched on and emit light, then each of the sections S1, S2, S3 receives light from one subpixel of the first part P1 and from a second subpixel of the second part P2, with their peak wavelengths differing. Due to the different scattering properties of each of the sections S1, S2, S3, this light is scattered differently depending on the peak wavelength, as indicated by the arrows.

[0039] Alternatively, it is conceivable, as in Fig. Figure 3 is shown as a schematic diagram of an exemplary screen in a second embodiment, in which the at least two subpixels of each pixel P, of which at least one belongs to the first part P1 and at least one to the second part P2, lie one behind the other in the viewing direction of a viewer.

[0040] Furthermore, it shows Fig. 4a the schematic diagram of an exemplary screen in a first operating mode B1 in a third configuration and Fig. 4b the schematic diagram of an exemplary screen in a second operating mode B2 in a third embodiment. In this third embodiment, at least a part of the pixel P is variable in the wavelength range it emits or transmits, such that this part of the pixel P in the first operating mode B1 (see Fig. 4a) to the first part P1 and in the second operating mode B2 to the second part P2 (see Fig. 4b). It is explicitly possible here that the pixels which optionally belong to groups P1 and P2 are identical, i.e., encompass all pixels P.

[0041] The invention takes on particular significance if at least the pixels of the second part P2, but preferably all pixels P, emit collimated light, as shown in all drawings. Fig. 2 to Fig. Figure 5b illustrates this. Due to the different haze values ​​(corresponding to the strength of the scattering) of the optical element 1, the displayed image content is emitted into different angular ranges for the first part P1 of pixel P and for the second part P2 of pixel P. Thus, in the first operating mode B1, the first part P1 of pixel P is advantageously visible from a wide angular range due to the scattering effect of the optical element 1, while in the second operating mode B2, the second part P2 of pixel P is visible from a narrower angular range due to the lower scattering effect of the optical element 1.

[0042] It is also possible to simultaneously apply image content to the first and second parts P1, P2 of pixels P. Depending on the configuration, these pixels will then be visible from different angles. If the angles do not overlap, only a portion of pixels P will be visible at any given time.

[0043] Finally, it shows Fig. 5a the schematic diagram of an exemplary screen in a first operating mode B1 in a fourth embodiment as well as Fig. 5b the schematic diagram of an exemplary screen in a second operating mode B2 in a fourth embodiment. This is a screen with pixels P for displaying image content, an electronic control of the pixels P and, in the viewing direction of a viewer, an optical element 1 in front of the pixels P, wherein a. all pixels P emit collimated light, b. the optical element 1 is provided with switchable meta-structures whose properties can be switched between a haze value less than 12% and greater than 15%, c. furthermore, in a first operating mode B1 (see Fig. 5a) the optical element 1 contains at least one section whose haze value for the light emitted by the pixels P is greater than 15%, such that the pixels P behind it are visible from a wide (preferably unrestricted) angular range on this at least one section, d. and wherein in a second operating mode B2 (see Fig. 5b) the optical element 1 contains at least one section whose haze value for the light emitted by the pixels P is less than 12%, such that on this at least one section the pixels P behind it are visible from a restricted angular range.

[0044] Advantageously, the switchable meta-structures of the optical element 1 can be modified in their scattering properties by at least one of the following measures: a) pressure (change), b) temperature (change), c) application of an electric and / or a magnetic field, d) modification of a structure by rotation of a liquid crystal, e) modification of a structure by particle movement by means of electro-wetting and / or electrophoresis, or f) application of biological and / or chemical agents (e.g., change of the surrounding pH value).

[0045] Within the scope of the invention, and particularly with regard to the backlighting, the term "restricted angular range" means that the corresponding luminance is concentrated at least 80% or 90% within a defined angular range, while some residual light may still be present outside this restricted angular range, which is generally due to technical limitations. Ideally, this residual light is minimal and decreases with increasing angle. To achieve particularly strong minimization, a suitable light filter may be used in addition to any backlighting 8 that emits light within a restricted angular range.

[0046] The invention solves the stated problem: A screen was to be described that emits the displayed image content selectively into different angular ranges. The invention is applicable to common image generation systems such as LCD, OLED, or microLED.

[0047] The invention described above can be advantageously used in conjunction with an image display device wherever confidential data is displayed and / or entered, such as for PIN entry or data display at ATMs or payment terminals, for password entry, or when reading emails on mobile devices. As described above, the invention can also be used in cars to selectively shield the driver or passenger from distracting visual content.

Claims

[1] Screen with pixels (P) for displaying image content, an electronic control of the pixels (P) and an optical element (1) in front of the pixels (P) in the viewing direction of a viewer, wherein - the pixels (P) emit light in at least two different wavelengths or wavelength ranges with different peak wavelengths, - in at least one first operating mode B1 at least one first part (P1) of the pixels (P) emits light, - in at least one second operating mode B2 at least one second part (P2) of the pixels (P) emits light, , - wherein the optical element (1) contains at least one section (S1, S2, S3, ...) whose haze value is greater than 15% for light with a first wavelength or first wavelength range, while it is less than 12% for light with a second wavelength or second wavelength range, - wherein furthermore, light from a first part (P1) and a second part (P2) of the pixels can fall upon each such section (S1, S2, S3, ..), wherein the wavelengths or wavelength ranges of the respective incident light differ for each such section (S1, S2, S3, ..) at least in their peak wavelength, depending on whether it originates from the first part (P1) or the second part (P2) of the pixels (P). - so that, depending on the wavelength or wavelength range of the light incident on such a section (S1, S2, S3, ..), this light is scattered more or less strongly. [2] Screen according to claim 1, characterized by , that each of the pixels (P) comprises at least two subpixels, of which at least one belongs to the first part (P1) and at least one to the second part (P2). [3] Screen according to claim 2, characterized by, that the at least two subpixels of each pixel (P), of which at least one belongs to the first part (P1) and at least one to the second part (P2), lie next to each other in the viewing direction of a viewer. [4] Screen according to claim 2, characterized by , that the at least two subpixels of each pixel (P), of which at least one belongs to the first part (P1) and at least one to the second part (P2), lie one behind the other in the viewing direction of a viewer. [5] Screen according to claim 1, characterized by , that at least a part of the pixels (P) is variable in the wavelength range emitted or transmitted by them, such that this part of the pixels (P) belongs to the first part (P1) in the first operating mode B1 and to the second part (P2) in the second operating mode B2. [6] Screen according to any of the aforementioned claims, characterized by, that at least the second part (P2) of the pixels (P), preferably all pixels (P), emit collimated light. [7] Screen according to any of the aforementioned claims, characterized by , that in the first operating mode B1 the first part (P1) of the pixels are visible from a wide angular range due to the scattering effect of the optical element (1). [8] Screen according to one of claims 6 or 7, characterized by , that in the second operating mode B2 the second part (P2) of the pixels (P) are visible from a restricted angular range due to the lower scattering effect of the optical element (1). [9] Screen with pixels (P) for displaying image content, an electronic control of the pixels (P) and an optical element (1) in front of the pixels (P) in the viewing direction of a viewer, wherein - in at least one first operating mode B1 at least one first part (P1) of the pixels (P) emits light of a first group of wavelengths or wavelength ranges, - in at least one second operating mode B2 at least one second part (P2) of the pixels (P) emits light of a second group of wavelengths or wavelength ranges, wherein the peak wavelengths of the first and second groups of wavelengths or wavelength ranges are each pairwise different, - wherein the optical element (1) further comprises at least one section whose haze value is greater than 15% for light with wavelengths or wavelength ranges of the first group, while it is less than 12% for light with wavelengths or wavelength ranges of the second group.

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