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CN-121986295-A - Switchable filter, lighting device and screen

CN121986295ACN 121986295 ACN121986295 ACN 121986295ACN-121986295-A

Abstract

The invention relates to a switchable filter (5) comprising a first optical element (1) comprising a plurality of light-absorbing transition dipole moments, wherein the transition dipole moments of the relative proportion p (0.6≤p≤1.0) of all transition dipole moments are oriented with a tolerance of at most 15 DEG parallel to a first preferred direction selectable for the first optical element (1), means for selectively generating a first electric field (EF 1) or a second electric field (EF 2), a liquid crystal layer (3) arranged in the viewing direction behind or in front of the first optical element (1), the first electric field (EF 1) or the second electric field (EF 2) acting on the liquid crystal layer and influencing the polarization state of light penetrating the liquid crystal layer in dependence thereon, wherein the absolute values of the first electric field (EF 1) and the second electric field (EF 2) differ by at least 0.1 MV/m, such that the transmission characteristics of the switchable filter (5) differ between a first operating mode B1, in which the first electric field (EF 1) is applied, and a second operating mode (EF 2) in which the second electric field (EF 2) is applied.

Inventors

  • Andre Hiber
  • Marcus Klipstein

Assignees

  • 矽光学有限公司

Dates

Publication Date
20260505
Application Date
20240927
Priority Date
20231009

Claims (9)

  1. 1. A switchable filter (5) comprising: a first optical element (1) comprising: a plurality of light-absorbing transition dipole moments arranged in one layer of at least 0.1 μm, at most 40 μm, or in a plurality of individual layers of total thickness of the transition dipole moments at most 40 μm, Wherein the transition dipole moments of the relative proportion p of all transition dipole moments are permanently oriented or vary around a first preferred direction selectable for the first optical element (1) with a tolerance of at most 15 DEG or at least in a first state, wherein 0.6≤p≤1.0, the first preferred direction being arranged at a predetermined angle alpha to a central normal of the first optical element (1), wherein the angle alpha is measured in a selectable first plane comprising the central normal, So that light entering the first optical element (1) in an incident direction and in a polarization state is transmitted or at least partially absorbed depending on its incident direction with respect to the first optical element (1) and its polarization state, Means for selectively generating a first electric field (EF 1) or a second electric field (EF 2), A liquid crystal layer (3) arranged behind or in front of the first optical element (1) in a viewing direction, the first electric field (EF 1) or the second electric field (EF 2) acting on the liquid crystal layer and thereby influencing the polarization state of light penetrating the liquid crystal layer, wherein the absolute values of the first electric field (EF 1) and the second electric field (EF 2) differ by at least 0.1 MV/m, A first linear polarization filter (X) which is located in front of the liquid crystal layer (3) in the viewing direction if the liquid crystal layer (3) is arranged in front of the first optical element (1), So that the transmission characteristics of the switchable filter (5) differ between a first operating mode B1, to which the first electric field (EF 1) is applied, and a second operating mode B2, to which the second electric field (EF 2) is applied, wherein, at least one point on the switchable filter (5), except for a selectable tolerance, the respective relative transmission in the two operating modes B1 and B2 is described by a first transmission T B1 (beta) for the first operating mode B1 and a second transmission T B2 (beta) for the second operating mode B2, respectively, which are related to the angle beta and are normalized, respectively, so that the transmission values of a predetermined angle beta=alpha are applicable T B1 (alpha) =1 and T B2 (alpha) =1, Thus, if the ratio of the major half axis to the minor half axis is at least 4:1, the linearly polarized light or elliptically polarized light is: Injecting the switchable filter (5) at an angle (beta) of alpha-5 DEG≤beta≤alpha+5 DEG, the ratio of T B1 （β）/T B2 (beta) being greater than 0.9+log 10 (p) and less than 1.3-log 10 (p), Injecting the switchable filter (5) at an angle (beta) of alpha-30 DEG beta alpha-20 DEG or alpha +20 DEG beta alpha +30 DEG, the ratio of T B1 （β）/T B2 (beta) is greater than 2 DEG (1 + log 10 (p)), and The ratio of T B1 （β）/T B2 (beta) is greater than 9 DEG (1+2 log 10 (p)) when the switchable filter (5) is injected at an angle (beta) of alpha-45 DEG beta alpha-35 DEG or alpha+35 DEG beta alpha+45 deg.
  2. 2. Switchable filter (5) according to claim 1, wherein the first optical element (1) comprises a plurality of light absorbing transition dipole moments, the transition dipole moments being arranged in one layer at least 1 μm thick and at most 40 μm thick, or in a plurality of separate layers with a total thickness of the transition dipole moments at most 40 μm, Thus, if the ratio of the major half axis to the minor half axis is at least 4:1, the linearly polarized light or elliptically polarized light is: Injecting the switchable filter (5) at an angle (beta) of alpha-5 DEG≤beta≤alpha+5 DEG, the ratio of T B1 （β）/T B2 (beta) being greater than 1.0+log 10 (p) and less than 1.3-log 10 (p), Injecting the switchable filter (5) at an angle (beta) of alpha-30 DEG beta alpha-20 DEG or alpha +20 DEG beta alpha +30 DEG, the ratio of T B1 （β）/T B2 (beta) is greater than 3 DEG (1 + log 10 (p)), and The ratio of T B1 （β）/T B2 (beta) is greater than 16 DEG (1+2 log 10 (p)) when the switchable filter (5) is injected at an angle (beta) of alpha-45 DEG beta alpha-35 DEG or alpha+35 DEG beta alpha+45 deg.
  3. 3. Switchable filter (5) according to claim 1 or 2, wherein the first optical element (1) and/or the liquid crystal layer (3) and/or the means for selectively generating the first electric field EF1 or the second electric field EF2 are divided into a plurality of individually switchable sections in order to be able to locally switch between the respective possible modes of operation.
  4. 4. A lighting device for a screen operable in at least a first operating mode B1 for a free view mode and a second operating mode B2 for a restricted view mode in which light is emitted into a range of viewing angles that is more limited to an observer than the free view mode, the lighting device comprising: A planar extended backlight (8) which emits light, and A switchable filter (5) as claimed in any one of claims 1 to 3, which is arranged in front of the backlight (8) in the viewing direction.
  5. 5.A screen operable in at least a first operating mode B1 for a free view mode and a second operating mode B2 for a restricted view mode in which light is emitted into a range of viewing angles that are more limited to an observer than the free view mode, the screen comprising: the lighting device according to claim 4, A second linear polarizing filter (P) arranged in front of the backlight (8) in a viewing direction if the first linear polarizing filter (X) is not arranged in the switchable filter (5) of the lighting device, thereby limiting the propagation direction of light emitted from the backlight and penetrating the second linear polarizing filter (P), and A transmissive image reproduction device (11) arranged in front of the switchable filter (5) in the viewing direction, Wherein the second electric field (EF 2) is applied in the second operating mode B2, and wherein the first electric field (EF 1) is applied in the first operating mode B1.
  6. 6. The screen according to claim 5, wherein the first linear polarizing filter (X) is arranged in or part of the transmissive image reproduction device (11) if present, otherwise the second linear polarizing filter (P) is arranged in or part of the transmissive image reproduction device (11).
  7. 7. A screen operable in at least a first operating mode B1 for a free view mode and a second operating mode B2 for a restricted view mode in which light is emitted into a range of viewing angles that are more limited to an observer than the free view mode, the screen comprising: An image reproduction device (12), A switchable filter (5) as claimed in any one of claims 1 to 3, which is arranged in front of the image rendering device (12) in the viewing direction, Wherein the second electric field (EF 2) is applied in the second operating mode B2, and wherein the first electric field (EF 1) is applied in the first operating mode B1.
  8. 8. Screen according to claim 7, wherein the switchable filter (5) is subsequently mounted by the user and/or reversibly on the image reproduction device (12).
  9. 9. Screen according to any one of claims 7 to 8, wherein a second optical element (2) is arranged in front of the image reproduction device (12) in the viewing direction, said optical element comprising: a plurality of light absorption transition dipole moments, Wherein most of the transition dipole moments are permanently or at least in a first state oriented parallel to or fluctuate around a second preferred direction selectable for the second optical element (2) with a tolerance of at most 20 °, wherein the second preferred direction is arranged at a predetermined angle a 1 to a central normal of the second optical element (2), wherein the angle a 1 is measured in a selectable second plane containing the central normal, So that light entering the second optical element (2) is transmitted or at least partially absorbed, depending on its direction of incidence with respect to the second optical element (2) and its polarization state.

Description

Switchable filter, lighting device and screen Technical Field In recent years, significant progress has been made in the expansion of the viewing angle of LCDs. But there are often situations where the very large field of view of the screen constitutes a disadvantage. Increasingly, information, such as banking or other personal information, as well as sensitive data, may also be provided on mobile devices such as notebook and tablet computers. Accordingly, people need to control who can see these sensitive data, they need to be able to choose a wide view-public mode to share information on the display with others, for example when viewing holiday photos, even for advertising purposes. On the other hand, if it is desired to maintain the privacy of the image information, a smaller viewing angle-privacy mode is required. A similar problem exists in the automotive field in that the driver is not allowed to be distracted by the video content, such as digital entertainment after engine start, while the passenger wishes to be able to view the video content during driving. Thus, there is a need for a screen that can be switched between corresponding presentation modes. Additional films based on micro-blinds have been applied to mobile displays to achieve data protection in the visual sense. However, such films are not switchable or switchable and always have to be applied by hand and then removed. And when not in use, the display is also required to be transported separately from the display. Another major disadvantage of using such a ply film is light loss. Background US6,765,550 B2 describes such privacy protection through micro-blinds. The biggest disadvantage of this solution is the mechanical removal and mechanical attachment of the filter, as well as the loss of light in the protection mode. US 5,993,940A describes the use of a film whose surface is uniformly distributed with small stripe-shaped prisms to achieve a private mode, i.e. a limited viewing mode with a small viewing angle range. The technical difficulty in research and development and manufacturing is quite great. US 2013/0308185 A1 describes a special light guide provided with steps that emit light over a large surface in different directions, depending on which direction the light guide is illuminated in from the narrow face. By cooperating with a transmissive image reproduction device, such as an LC display, a screen is created that can be switched between a free viewing mode and a limited viewing mode. The disadvantage is mainly that limited viewing effects can only be produced left/right or up/down, but not simultaneously left/right/up/down, which is necessary for certain payment processes, for example. Furthermore, even in the limited viewing mode, residual light is visible from a blocked viewing angle. WO 2015/121398 A1 by the applicant describes a screen with two modes of operation, wherein, in order to effect a switching of the modes of operation, scattering particles are present in the volume of the respective light guides. However, the polymer scattering particles selected in this case generally have the disadvantage that light is outcoupled from both large surfaces, so that about half of the useful light is emitted in the wrong direction, i.e. in the direction of the backlight, and for structural reasons a sufficient degree of recycling cannot be obtained there. Furthermore, as the case may be, particularly in the case of higher concentrations, scattering particles composed of polymers distributed in the volume of the light guide may lead to scattering effects, which impair the privacy effect in the protected mode of operation. The above methods and arrangements generally have the disadvantage of significantly reducing the basic screen brightness and/or requiring complex and expensive optical elements for mode conversion and/or reducing the resolution in the public mode of free viewing and/or having visual artefacts in case of very high resolution displays and/or being unusable for self-luminous type screens, such as OLEDs. Disclosure of Invention The object of the invention is therefore to describe a filter with an optical element, in which light entering the optical element is transmitted or partially or completely absorbed, depending on its position, depending on its direction of incidence and polarization properties. By means of such a filter, the transmission of light can be influenced angularly dependent, optionally perpendicularly with respect to a sitting or standing observer, wherein a transition between at least two modes of operation can be made. In particular, the angle-dependent proportion of the transmission behavior between the two operating modes should be defined. In addition, the filter should also be applicable with self-luminous type screens (e.g. OLEDs). In a first aspect, the present invention provides a switchable filter for achieving the above object, comprising: A first optical element comprising A plurality of