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EP-4737973-A1 - OPTICAL MODULE AND HEAD-MOUNTED DISPLAY DEVICE

EP4737973A1EP 4737973 A1EP4737973 A1EP 4737973A1EP-4737973-A1

Abstract

Embodiments of the present application provide an optical module and a head-mounted display device. The optical module comprises a lens group, and a light splitting element, a first phase retarder and a polarization reflector which are arranged between light paths of the lens group, and the first phase retarder is located between the light splitting element and the polarization reflector. The lens group is composed of a first lens and a second lens which are cemented with each other, and the first lens and the second lens are adjacently arranged along the same optical axis; and a ratio H/T 2 of the sag H of the surface of the second lens facing away from the first lens to the center thickness T 2 of the second lens satisfies: 0.38≤H/T 2 ≤0.82. The optical module provided by the embodiments of the present application has the characteristics of a small total track length and good imaging quality.

Inventors

  • SONG, Wenbao

Assignees

  • Goertek Optical Technology Co., Ltd.

Dates

Publication Date
20260506
Application Date
20231024

Claims (11)

  1. An optical module, comprising a lens group, and a light splitting element (11), a first phase retarder (10) and a polarization reflector (9) disposed between optical paths of the lens group, wherein the first phase retarder (10) is located between the light splitting element (11) and the polarization reflector (9); wherein the lens group comprises a first lens (3) and a second lens (4) adhered to each other, and the first lens (3) and the second lens (4) are disposed adjacent to each other along a same optical axis (1); and a ratio H/T 2 of a sagittal height H of a surface of the second lens (4) away from the first lens (3) to a center thickness T 2 of the second lens (4) satisfies: 0.38≤ H/T 2 ≤ 0.82.
  2. The optical module according to claim 1, wherein a surface of the second lens (4) adjacent to the first lens (3) is a concave surface or a reverse curved surface; and a surface of the first lens (3) adjacent to the second lens (4) is a convex surface or a reverse curved surface.
  3. The optical module according to claim 2, wherein a surface of the second lens (4) away from the first lens (3) is a convex surface.
  4. The optical module according to any one of claims 1-3, wherein the optical module further comprises a display screen (5), the display screen (5) is located on a side of the second lens (4) away from the first lens (3), and a ratio T 2 /L of the center thickness T 2 of the second lens (4) to an aperture L of a light emitting region of the display screen (5) satisfies: 0.2≤ T 2 /L ≤ 0.5.
  5. The optical module according to claim 1, wherein a total length TTL of the optical module is less than 25 mm, and a MTF value of the optical module is greater than 0.5.
  6. The optical module according to claim 1, wherein an effective focal length of the optical module is 13 mm to 23 mm.
  7. The optical module according to claim 4, wherein the light splitting element (11) is disposed on a surface of the second lens (4) close to the display screen (5); and the first phase retarder (10) is disposed on a surface of the second lens (4) away from the display screen (5), and the polarization reflector (9) is stacked on a side of the first phase retarder (10) away from the second lens (4).
  8. The optical module according to claim 7, wherein the optical module further comprises a first polarizer (8), and the first polarizer (8) is disposed on a side of the polarization reflector (9) away from the first phase retarder (10); and the first polarizer (8) is adhered to the first lens (3) through an adhesive layer (7).
  9. The optical module according to claim 4, wherein the display screen (5) is configured to be capable of emitting a circularly polarized light or a natural light; and when a light emitted by the display screen (5) is the natural light, a second polarizer (13) is disposed on a light emitting surface of the display screen (5), a second phase retarder (12) is stacked on a side of the second polarizer (13) away from the display screen (5), and the second polarizer (13) and the second phase retarder (12) form a stacked element for converting the natural light into the circularly polarized light.
  10. The optical module according to claim 9, wherein the light splitting element (11) is located between the first phase retarder (10) and the second phase retarder (12).
  11. A head-mounted display device, comprising: a housing; and the optical module according to any one of claims 1-10.

Description

Technical Field An embodiment of the present application relates to a technical field of optical imaging, and more specifically, to an optical module and a head-mounted display device. Description of Related Art A core component of the virtual reality technology is an optical module disposed therein, and the effect of the displayed image directly determines the quality of virtual reality products. As people's requirements for the comfort of wearing virtual reality products become increasingly higher, design requirements for lightening and thinning virtual reality products are put forward. However, the existing optical module applied in the virtual reality product cannot meet the requirement of considering the imaging quality in the case of a small volume. In order to ensure the imaging quality, it is impossible to achieve a miniaturized optical module design. SUMMARY An objective of the present application is to provide a new technical solution of an optical module and a head-mounted display device, which has the characteristics of small total length and good imaging image quality of the optical module. According to a first aspect, the present application provides an optical module. The optical module includes a lens group, and a light splitting element, a first phase retarder and a polarization reflector disposed between optical paths of the lens group, wherein the first phase retarder is located between the light splitting element and the polarization reflector; wherein the lens group includes a first lens and a second lens adhered to each other, and the first lens and the second lens are arranged adjacent to each other along a same optical axis;a ratio H/T2 of a sagittal height H of a surface of the second lens away from the first lens to a center thickness T2 of the second lens satisfies: 0.38≤ H/T2 ≤ 0.82. Optionally, a surface of the second lens adjacent to the first lens is a concave surface or a reverse curved surface; a surface of the first lens adjacent to the second lens is a convex surface or a reverse curved surface. Optionally, a surface of the second lens away from the first lens is a convex surface. Optionally, the optical module further includes a display screen, the display screen is located on a side of the second lens away from the first lens, and a ratio T2/L of a center thickness T2 of the second lens to an aperture L of a light emitting region of the display screen satisfies: 0.2≤ T2/L ≤ 0.5. Optionally, a total length TTL of the optical module is less than 25 mm, and a MTF (modulation transfer function) value of the optical module is greater than 0.5. Optionally, an effective focal length of the optical module is 13 mm to 23 mm. Optionally, the light splitting element is disposed on a surface of the second lens close to the display screen; the first phase retarder is disposed on a surface of the second lens away from the display screen, and the polarization reflector is stacked on a side of the first phase retarder away from the second lens. Optionally, the optical module further includes a first polarizer disposed on a side of the polarization reflector away from the first phase retarder; and the first polarizer is adhered to the first lens through an adhesive layer. Optionally, the display screen is configured to be capable of emitting a circularly polarized light or a natural light; when a light emitted by the display screen is the natural light, a second polarizer is disposed on a light emitting surface of the display screen, a second phase retarder is stacked on a side of the second polarizer away from the display screen, and the second polarizer and the second phase retarder form a stacked element to convert the natural light into the circularly polarized light. Optionally, the light splitting element is located between the first phase retarder and the second phase retarder. According to a second aspect, the present application provides a head-mounted display device. The head-mounted display device includes: a housing; andthe optical module according to the first aspect. The beneficial effects of the present application are as below: the optical module provided in the embodiment of the present application is a folded optical path solution, the optical module has a cemented lens group, and the cemented lens group includes two lenses. By designing the surface shape and center thickness parameters of the second lens, the total length of the optical module can be reduced while also considering the image quality of the imaging. Other features and advantages of the specification will become apparent from the following detailed description of exemplary embodiments of the specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.