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CN-121986291-A - Optical element, switchable filter, lighting device and screen

CN121986291ACN 121986291 ACN121986291 ACN 121986291ACN-121986291-A

Abstract

The invention relates to a first optical element (1) comprising a plurality of light-absorbing transition dipole moments. Most of the transition dipole moments are permanently oriented or vary around a first preferred direction selectable for the first optical element (1) with a tolerance τ of τ≤20° or at least in a first state, wherein the transition dipole moments oriented with the tolerance τ parallel to the first preferred direction have a density N 1 and the remaining transition dipole moments have a density N 2 , such that light incident into the first optical element (1) is transmitted or at least partially absorbed depending on its direction of incidence relative to the first optical element (1) and its polarization state. Permanently or at least in the first state described above, the ratio of the respective densities N 1 and N 2 satisfies the inequality on the optical element (1) (I) The larger tolerance value τ is thereby at least partially compensated by the ratio of the densities N 1 and N 2 of the correspondingly increased transition dipole moments, whereby the absorption of p-polarized light impinging on the optical element (1) at an angle greater than 45 ° is enhanced. The invention also discloses a first switchable filter (5), a second switchable filter (5 a), a lighting device and a screen.

Inventors

  • Andre Hiber
  • Marcus Klipstein

Assignees

  • 矽光学有限公司

Dates

Publication Date
20260505
Application Date
20240927
Priority Date
20231009

Claims (13)

  1. 1. A first optical element (1) comprising: A plurality of light absorption transition dipole moments, wherein the corresponding absorption cross-section is denoted by sigma abs and is selectively adapted to one wavelength, a plurality of selected wavelengths or, in general, to a plurality of wavelengths in the human visible spectrum, Wherein most of the transition dipole moments are permanently or at least in a first state oriented parallel to or varying around a first preferred direction selectable for the first optical element (1) with a tolerance τ of τ≤19 °, wherein the first preferred direction is arranged at an angle α with respect to a center normal of the first optical element (1), wherein the angle α is measured in a selectable first plane containing the center normal, and wherein the transition dipole moments oriented parallel to the first preferred direction with a tolerance τ have a density N 1 , the rest of the transition dipole moments have a density N 2 , So that light entering the first optical element (1) is transmitted or at least partially absorbed depending on its direction of incidence relative to the first optical element (1) and its polarization state, Characterized in that the ratio of the respective densities N 1 and N 2 for the transition dipole moment on the optical element (1) permanently or at least in the first state satisfies the inequality , The correspondingly increased ratio of the densities N 1 and N 2 of the transition dipole moments is thereby used to at least partially compensate for the larger tolerance value τ, whereby the absorption of p-polarized light incident on the optical element (1) in the first plane at an angle of more than 45 ° is enhanced.
  2. 2. A first switchable filter (5) comprising: the first optical element (1) according to claim 1, 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, A first linear polarizing filter (X) which is located in front of the liquid crystal layer (3) in the viewing direction in the case where the liquid crystal layer (3) is arranged in front of the first optical element (1) in the viewing direction, So that the transmission characteristics of the first 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 B2 in which the second electric field (EF 2) is applied.
  3. 3. A second switchable filter (5 a) comprising: a second optical element (2) comprising: A plurality of light absorption transition dipole moments, wherein the corresponding absorption cross-section is denoted by sigma abs and is selectively adapted to one wavelength, a plurality of selected wavelengths or, in general, to a plurality of wavelengths in the human visible spectrum, Wherein the transition dipole moment is composed of one or more dichroic dyes and is contained in the second liquid crystal layer (3 a) in a guest-host arrangement, respectively, Wherein most of the transition dipole moments are also oriented parallel to or vary around a second preferred direction selectable for the second optical element (2) with a tolerance τ of τ≤19° at least in a first state, wherein the second preferred direction is arranged at an angle α with respect to a center normal of the second optical element (2), wherein the angle α is measured in a selectable second plane containing the center normal, and wherein the transition dipole moments oriented parallel to the second preferred direction with a tolerance τ have a density N 1 , the rest of the transition dipole moments have a density N 2 , 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), its polarization state and the state of the second liquid crystal layer (3 a), Means for selectively generating at least a first electric field (EF 1) or a second electric field (EF 2), wherein the respective electric field acts on the second liquid crystal layer (3 a) such that the transmission characteristics of the second switchable filter (5 a) differ between a first operating mode B1 in which the first electric field (EF 1) is applied and the second liquid crystal layer (3 a) is in the first state and a second operating mode B2 in which the second electric field (EF 2) is applied and the second liquid crystal layer (3 a) is in the second state, Characterized in that the ratio of the respective densities N 1 and N 2 for the transition dipole moment over the second optical element (2) at least in the first state satisfies the inequality , The correspondingly increased ratio of the densities N 1 and N 2 of the transition dipole moments is thereby used to at least partially compensate for the larger tolerance value τ, whereby the absorption of p-polarized light incident on the second optical element (2) in the second plane at an angle of more than 45 ° is enhanced.
  4. 4. A second switchable filter (5 a) as claimed in claim 3, wherein the ratio of the respective densities N 1 and N 2 for the transition dipole moment over the second optical element (2) at least in the second state satisfies the inequality , Thereby, p-polarized light absorbed in the second plane and impinging on the second optical element (2) at an angle of more than 45 DEG is attenuated.
  5. 5. The first switchable filter (5) of claim 2 or the second switchable filter (5 a) of claim 3 or 4, wherein the potential difference of the electrodes for generating the first electric field (EF 1) and the second electric field (EF 2) differ by at least 2 volts.
  6. 6. The first switchable filter (5) according to claim 2, wherein the first optical element (1) and/or the liquid crystal layer (3) and/or the means for 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 operating states.
  7. 7. A lighting device for a screen operable in at least two modes of operation B1 and B2 for a free view mode and 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 is optionally configured in a direct-lit manner, and The first switchable filter (5) as claimed in claim 2, or the second switchable filter (5 a) as claimed in claim 3 or 4, which is arranged in front of the backlight (8) in the viewing direction.
  8. 8. A screen operable in at least two modes of operation B1 and B2 for a free view mode and 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 screen comprising: the lighting device according to claim 7, A second linear polarization filter (P) arranged in front of the backlight (8) in a viewing direction in a case where the first linear polarization filter (X) is not arranged in the first switchable filter (5) or the second switchable filter (5 a) of the illumination device, thereby restricting a propagation direction of light emitted from the backlight and penetrating the second linear polarization filter (P), and A transmissive image reproducing device (11) arranged in front of the first switchable filter (5) or the second switchable filter (5 a) in the viewing direction, Wherein the second electric field (EF 2) is applied in the operating mode B2, and wherein the first electric field (EF 1) is applied in the operating mode B1.
  9. 9. The screen according to claim 8, wherein the first (X) or second (P) linear polarizing filter is arranged in or is part of the transmissive image reproduction device (11).
  10. 10. A screen operable in at least two modes of operation B1 and B2 for a free view mode and 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 screen comprising: An image reproduction device (12), The first switchable filter (5) according to claim 2, or the second switchable filter (5 a) according to claim 3 or 4, being arranged in front of the image rendering device (12) in the viewing direction, Wherein the second electric field (EF 2) is applied in the operating mode B2, and wherein the first electric field (EF 1) is applied in the operating mode B1.
  11. 11. A lighting device for a screen operable in at least two modes of operation B1 and B2 for a free view mode and for a restricted view mode in which light is emitted into a more limited angular range than the free view mode, the lighting device comprising: A planar extended backlight (8 b) which emits light over a limited angular range and is optionally configured in a direct-lit manner, and A plate-shaped light guide (9) which is located in front of the backlight (8 b) in the viewing direction and which has a plurality of outcoupling components on at least one of a plurality of large surfaces and/or in its volume, A light emitting device (10) laterally arranged on at least one narrow side of the light guide body (9), and An optional linear polarizing filter (P), A first switchable filter (5) as claimed in claim 2, or a second switchable filter (5 a) as claimed in claim 3 or 4, which is arranged in front of the backlight (8 b) in the viewing direction, Wherein in the operating mode B2 the backlight (8B) is on and the light emitting means (10) is off, and wherein in the operating mode B1 at least the light emitting means (10) is on, and Wherein the second electric field (EF 2) is applied in the operating mode B2, and wherein the first electric field (EF 1) is applied in the operating mode B1.
  12. 12. A lighting device for a screen operable in at least two modes of operation B1 and B2 for a free view mode and for a restricted view mode in which light is emitted into a more limited angular range than the free view mode, the lighting device comprising: A planar extended backlight (8 c) which emits light over a non-limited angular range and is optionally configured in a direct-lit manner, and A plate-shaped light guide (9 c) located in front of the backlight (8 c) in the viewing direction, the light guide having a plurality of out-coupling components on at least one of a plurality of large surfaces and/or within its volume, wherein the out-coupling components out-couple a majority of light in at least one narrow face of the light guide (9 c) laterally in a limited angular range, A light-emitting device (10) arranged laterally on at least one narrow face of the light-guiding body (9 c), and An optional linear polarizing filter (P), A first switchable filter (5) as claimed in claim 2, or a second switchable filter (5 a) as claimed in claim 3 or 4, which is arranged in front of the backlight (8 c) in the viewing direction, Wherein in the operating mode B2 the backlight (8 c) is off and the light emitting means (10) is on, and wherein in the operating mode B1 at least the backlight (8 c) is on, and Wherein the second electric field (EF 2) is applied in the operating mode B2, and wherein the first electric field (EF 1) is applied in the operating mode B1.
  13. 13. A lighting device for a screen operable in at least two modes of operation B1 and B2 for a free view mode and for a restricted view mode in which light is emitted into a more limited angular range than the free view mode, the lighting device comprising: A planar extended backlight (8 b) which emits light over a limited angular range and comprises a first optical element (1) according to claim 1, and is optionally configured in a direct-lit manner, and A plate-shaped light guide (9) which is located in front of the backlight (8 b) in the viewing direction and which has a plurality of outcoupling components on at least one of a plurality of large surfaces and/or in its volume, A light emitting device (10) laterally arranged on at least one narrow side of the light guide body (9), and Wherein in the operating mode B2 the backlight (8B) is on and the light emitting means (10) is off, and wherein in the operating mode B1 at least the light emitting means (10) is on.

Description

Optical element, 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. In WO 2012/033583 A1, switching between a free viewing angle and a limited viewing angle is achieved by controlling the liquid crystal between so-called "chromonic" layers. Light losses occur during this and the technical difficulties are quite high. US 2012/0235891 A1 describes a very complex screen backlight. According to fig. 1 and 15 of the scheme, not only are multiple light guides used, but also other complex optical elements such as microlens assemblies 40 and prism structures 50, which shape the light originating from the back illumination on its way to the front illumination. The method has high realization cost and great technical difficulty, and can also bring light loss. According to a variant as shown in fig. 17 in US 2012/0235891 A1, both light sources 4R and 18 produce light with a narrow illumination angle, wherein the light from the rear light source 18 is converted into light with a large illumination angle after a complex process. As previously described, such complex conversion greatly reduces brightness. 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 present inventors describes a screen with two modes of operation, wherein, in order to achieve a switching of the modes of operation, scattering particles are present in the volume of the respective light conductors. 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 resolution in the public mode of free viewing and/