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US-20260126575-A1 - LENS, IMAGE DISPLAY DEVICE, AND VIRTUAL REALITY DISPLAY APPARATUS

US20260126575A1US 20260126575 A1US20260126575 A1US 20260126575A1US-20260126575-A1

Abstract

A lens, image display device, and virtual reality display apparatus are provided that suppress ghosting when used in a pancake-lens VR system. The lens includes a retardation layer that converts circularly polarized light into linearly polarized light. The retardation layer includes first and second optically anisotropic layers having reverse wavelength dispersibility, and at least one of these layers is formed by immobilizing a twistedly aligned liquid crystal compound with a helical axis in the thickness direction. The image display device includes an image display panel, an absorptive polarizer, and the retardation layer in this order. The virtual reality display apparatus includes the lens or the image display device.

Inventors

  • Naoyoshi Yamada
  • Shinpei YOSHIDA

Assignees

  • FUJIFILM CORPORATION

Dates

Publication Date
20260507
Application Date
20251205
Priority Date
20230710

Claims (20)

  1. 1 . A lens comprising: a retardation layer which converts circularly polarized light into linearly polarized light, wherein the retardation layer includes a first optically anisotropic layer and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersibility, and at least one of the first optically anisotropic layer or the second optically anisotropic layer is a layer obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction.
  2. 2 . The lens according to claim 1 , wherein both the first optically anisotropic layer and the second optically anisotropic layer are layers obtained by immobilizing a liquid crystal compound.
  3. 3 . The lens according to claim 2 , wherein an alignment direction of the liquid crystal compound contained in the first optically anisotropic layer and an alignment direction of the liquid crystal compound contained in the second optically anisotropic layer are continuous at an interface between the first optically anisotropic layer and the second optically anisotropic layer.
  4. 4 . The lens according to claim 1 , wherein the first optically anisotropic layer is a positive A-plate, and the second optically anisotropic layer is a layer obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction.
  5. 5 . The lens according to claim 1 , wherein both the first optically anisotropic layer and the second optically anisotropic layer are layers obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction, and a helical pitch of the first optically anisotropic layer is different from a helical pitch of the second optically anisotropic layer.
  6. 6 . The lens according to claim 1 , further comprising: a reflective linear polarizer.
  7. 7 . The lens according to claim 1 , further comprising: a reflective circular polarizer.
  8. 8 . The lens according to claim 7 , wherein the reflective circular polarizer has a cholesteric liquid crystal layer.
  9. 9 . The lens according to claim 6 , further comprising: an absorptive polarizer.
  10. 10 . A virtual reality display apparatus comprising: an image display device; and the lens according to claim 1 .
  11. 11 . An image display device comprising, in the following order: an image display panel; an absorptive polarizer; and a retardation layer which converts circularly polarized light into linearly polarized light, wherein the retardation layer includes a first optically anisotropic layer and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersibility, and at least one of the first optically anisotropic layer or the second optically anisotropic layer is a layer obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction.
  12. 12 . The image display device according to claim 11 , wherein both the first optically anisotropic layer and the second optically anisotropic layer are layers obtained by immobilizing a liquid crystal compound.
  13. 13 . The image display device according to claim 12 , wherein an alignment direction of the liquid crystal compound contained in the first optically anisotropic layer and an alignment direction of the liquid crystal compound contained in the second optically anisotropic layer are continuous at an interface between the first optically anisotropic layer and the second optically anisotropic layer.
  14. 14 . The image display device according to claim 11 , wherein the first optically anisotropic layer is a positive A-plate, and the second optically anisotropic layer is a layer obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction.
  15. 15 . The image display device according to claim 11 , wherein both the first optically anisotropic layer and the second optically anisotropic layer are layers obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction, and a helical pitch of the first optically anisotropic layer is different from a helical pitch of the second optically anisotropic layer.
  16. 16 . A virtual reality display apparatus comprising: a lens; and the image display device according to claim 11 .
  17. 17 . A virtual reality display apparatus comprising: the lens according to claim 1 ; and an image display device comprising, in the following order, an image display panel, an absorptive polarizer, and a retardation layer which converts circularly polarized light into linearly polarized light, wherein the retardation layer includes a first optically anisotropic layer and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersibility, and at least one of the first optically anisotropic layer or the second optically anisotropic layer is a layer obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction.
  18. 18 . The lens according to claim 2 , wherein the first optically anisotropic layer is a positive A-plate, and the second optically anisotropic layer is a layer obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction.
  19. 19 . The lens according to claim 2 , wherein both the first optically anisotropic layer and the second optically anisotropic layer are layers obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction, and a helical pitch of the first optically anisotropic layer is different from a helical pitch of the second optically anisotropic layer.
  20. 20 . The lens according to claim 2 , further comprising: a reflective linear polarizer.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Continuation of PCT International Application No. PCT/JP2024/022521 filed on Jun. 21, 2024, which claims priority under 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2023-113176 filed on Jul. 10, 2023 and Japanese Patent Application No. 2024-024329 filed on Feb. 21, 2024. The above applications are hereby expressly incorporated by reference, in their entirety, into the present application. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens, an image display device, and a virtual reality display apparatus. 2. Description of the Related Art A virtual reality display apparatus is a display device which can obtain a realistic effect as if entering a virtual world by wearing a dedicated headset on a head and visually recognizing a video displayed through a composite lens. It has been known that the virtual reality display apparatus includes an image display device and a Fresnel lens, but a distance from the image display device to the Fresnel lens is large, and thus a headset is thick and has poor wearability, which are problems. Therefore, as disclosed in JP2020-519964A and U.S. Pat. No. 10,394,040B, a lens configuration of a composite lens called a pancake lens has been proposed, the lens configuration including an image display device, a half mirror, a retardation layer, and a reflective polarizer, and causing rays emitted from the image display device to reciprocate between the half mirror and the reflective polarizer to reduce a thickness of the entire headset. The reflective polarizer herein is a polarizer having a function of reflecting one polarized light in incidence ray and transmitting the other polarized light. For example, reflected light and transmitted light by a reflective linear polarizer are linearly polarized light having polarization states orthogonal to each other. In addition, reflected light and transmitted light by a reflective circular polarizer are circularly polarized light in one turning direction and circularly polarized light in the opposite turning direction. As the reflective linear polarizer in which the transmitted light and the reflected light are linearly polarized, for example, a film in which a dielectric multi-layer film is stretched and a wire grid polarizer have been known. In addition, as the reflective circular polarizer in which the transmitted light and the reflected light are converted into circularly polarized light, for example, a cholesteric liquid crystal layer having a light reflective layer in which a cholesteric liquid crystalline phase is fixed has been known. SUMMARY OF THE INVENTION JP2020-519964A discloses a virtual reality display apparatus including an image display device, a half mirror, a first retardation layer, and a reflective linear polarizer, which are arranged in this order in a pancake lens, in order to obtain a wide field of view, low chromatic aberration, low distortion, and an excellent modulation transfer function (MTF). In addition, a configuration in which a second retardation layer is provided on a surface of the image display device is also disclosed. The present inventors have made a virtual reality display apparatus including the pancake lens with reference to JP2020-519964A and the like, and have made a detailed examination of the performance thereof, and as a result, have found that there is room for further improvement in occurrence of ghost (double image) due to leaked light. The present invention has been made in view of the above-described problem, and an object to be achieved by the present invention is to provide an image display device and a lens, which suppress occurrence of ghost in a case of being applied to a virtual reality display apparatus using a pancake lens. Another object to be achieved by the present invention is to provide a virtual reality display apparatus in which the occurrence of ghost is suppressed. As a result of intensive studies repeatedly conducted by the present inventors on the above-described object, it has been found that the above-described object can be achieved by the following configurations. [1] A lens comprising:a retardation layer which converts circularly polarized light into linearly polarized light,in which the retardation layer includes a first optically anisotropic layer and a second optically anisotropic layer,the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersibility, andat least one of the first optically anisotropic layer or the second optically anisotropic layer is a layer obtained by immobilizing a twistedly aligned liquid crystal compound with a helical axis in a thickness direction.[2] The lens according to [1],in which both the first optically anisotropic layer and the second optically anisotropic layer are layers obtained by immobilizing a liquid crystal compound.[3] The lens according to [2],in which an al