Near-to-eye display module and wearable device

Abstract

The invention provides a near-to-eye display module and wearable equipment, and belongs to the technical field of XR. The near-to-eye display module comprises a display unit; the first optical element, the second optical element, the third optical element and the fourth optical element are sequentially arranged on a light emitting path of the display unit, the second optical element is of a prism structure and is provided with a first optical surface, a second optical surface and a third optical surface, the first optical surface faces the first optical element, and the third optical surface faces the side close to human eyes. A polarization beam splitting element is arranged on the third optical surface; a reflecting element is arranged on one side, far away from the third optical element, of the fourth optical element; the optical path of light transmitted from the second optical surface of the second optical element to the third optical surface after being reflected by the third optical element along the main optical axis in the system is defined as L, the focal length of the system is defined as F, and the relation between the optical path L and the focal length F of the system meets the condition that 0.5 < = L / F < = 0.9. The module is low in stray, good in imaging quality and large in field angle, and the user experience is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of XR technology, specifically relating to a near-eye display module and wearable device. Background Technology

[0002] Augmented reality (AR) optical display technology is a technology that can project and magnify display images. This technology not only expands upon traditional display technologies but also introduces entirely new experiences: merging the real and virtual worlds, making life more convenient and enriching entertainment. It is currently widely used in education, healthcare, aerospace, and many other fields.

[0003] With the continuous development of augmented reality display technology, related application areas are constantly expanding, and the requirements for display devices are becoming increasingly stringent. Current AR modules generally suffer from issues such as module thickness and a relatively small field of view, resulting in poor user satisfaction. Furthermore, while existing technologies utilize the reflective properties of prisms to expand the field of view, inherent problems with prism shape and stress can lead to image distortion, color cast, and reduced contrast. Summary of the Invention

[0004] The purpose of this invention is to provide a near-eye display module that is small in size, thin in thickness, has low stray light, low distortion, good imaging quality, and a large field of view, thereby greatly improving the user experience.

[0005] Another objective of the embodiments of the present invention is to provide a wearable device that is lightweight and easy to wear.

[0006] The embodiments of the present invention are implemented as follows: An embodiment of the present invention provides a near-eye display module, including a display unit; A first optical element is disposed in the light-emitting path of the display unit; The second optical element is disposed on the transmitted light path of the first optical element. The second optical element is a prism structure, which has a first optical surface, a second optical surface and a third optical surface. The first optical surface faces the first optical element, the second optical surface faces the side away from the human eye, and the third optical surface faces the side closer to the human eye. A third optical element is disposed on the second optical surface of the second optical element, and an anti-reflection coating is provided on the side of the third optical element away from the second optical element; A polarization beam splitter element, wherein the polarization beam splitter element is disposed on the third optical surface of the second optical element; A fourth optical element is disposed on the side of the third optical element away from the second optical element, and a reflective element is provided on the side of the fourth optical element away from the third optical element; The light emitted by the display unit is processed by the first optical element, enters the interior of the second optical element from the first optical surface of the second optical element, and propagates forward, passing through the second optical surface and entering the third optical element. It is reflected in the third optical element, and the light reflected by the third optical element enters the interior of the second optical element from the second optical surface of the second optical element and propagates toward the third optical surface of the second optical element. The optical path length of the light along the principal optical axis in the optical system from the second optical surface of the second optical element to the third optical surface after being reflected by the third optical element is defined as L, and the system focal length is F. Then the relationship between the optical path length L and the system focal length F satisfies: 0.5≤L / F≤0.9.

[0007] Furthermore, it also includes a fifth optical element, which is a prism structure and is disposed on the side of the polarizing beam splitter away from the second optical element.

[0008] Furthermore, the third optical element is a plane mirror with a thickness of 0.1-0.5 mm and a surface area PV < 15 μm.

[0009] Furthermore, the third optical element is a zero-phase optical film or a zero-phase optical lens, with an in-plane phase difference R01 = 0 ± 5 nm and a thickness direction phase difference Rth1 = 0 ± 5 nm.

[0010] Furthermore, the third optical element is a specially positioned phase difference optical film or a specially positioned phase difference optical lens, with an in-plane phase difference R02 = 0 ± 10 nm and a thickness direction phase difference of -200 nm < Rth2 < 200 nm.

[0011] Furthermore, the third optical element is a half-wave plate, or a combination of a quarter-wave plate and a half-wave plate.

[0012] Furthermore, the third optical element is any combination of two or more of the following: a plane mirror with an anti-reflection coating, a zero-position phase difference optical film, a zero-position phase difference optical lens, a specific phase difference optical film, a specific phase difference optical lens, a quarter-wave plate, and a half-wave plate.

[0013] Furthermore, the function of the third optical element is to guide light from the first optical surface of the second optical element to the third optical element, where it is reflected. Light with an incident angle greater than 40° is reflected by the third optical element, with an average reflectivity greater than 95% in the visible spectrum range of 380-780 nm. Light with an incident angle less than or equal to 25° is transmitted out of the third optical element, with an average transmittance greater than 97% in the visible spectrum range of 380-780 nm. When light propagates from the fourth optical element toward the third optical element, light with an incident angle less than or equal to 25° is transmitted through the third optical element and enters the second optical element, with an average transmittance greater than 97% in the visible spectrum range of 380-780 nm.

[0014] Furthermore, the system focal length of the near-eye display module is 10-20mm.

[0015] Embodiments of the present invention also provide a wearable device, including a wearable component and the aforementioned near-eye display module, wherein the near-eye display module is disposed on the wearable component.

[0016] The beneficial effects of this invention are as follows: The near-eye display module provided by this invention has a compact structure, small size, thin thickness, low stray light, low distortion, good imaging quality, and a large field of view, with a maximum field of view of over 70°, which can greatly improve the user experience. Furthermore, the light emitted from the display unit passes through the first optical element and then enters the second optical element. The light then needs to be transmitted from the second optical surface of the second optical element to enter the third optical element, where it undergoes total internal reflection. This allows the light to be modulated by the third optical element, ensuring flatness and making the light reflection surface smoother, thus significantly improving image flatness. The third optical element also provides specific phase difference compensation, improving color cast; or, under the action of an anti-reflection coating, improving stray light in the image.

[0017] The wearable device provided by the embodiments of the present invention has a simple manufacturing process, low cost, large field of view, high image quality reproduction, and is easy to wear, which greatly improves the user's wearing experience. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0019] Figure 1This is an architectural diagram of the near-eye display module in Embodiment 1; In the figure: 1-First optical element; 2-Second optical element; 21-First optical surface; 22-Second optical surface; 23-Third optical surface; 3-Third optical element; 31-Antireflective coating layer; 4-Fourth optical element; 41-Reflective element; 5-Fifth optical element; 6-Display unit; 7-Polarization beam splitter. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0023] In the description of this invention, it should be noted that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. Example 1

[0024] refer to Figure 1 As shown, Embodiment 1 of the present invention provides a near-eye display module, including a display unit 6, a first optical element 1, a second optical element 2, a third optical element 3 and a fourth optical element 4.

[0025] The display unit 6 mainly functions to emit light. The display unit 6 can display 2D or 3D images or videos, and can be an OLED display, LCD display, LCOS display, micro-LED display, or mini-LED display.

[0026] The first optical element 1 is disposed on the light output path of the display unit 6. The number of first optical elements 1 can be one piece or a lens group composed of multiple pieces.

[0027] The first optical element 1 is a transmission mirror, and its optical surface shape can be planar, spherical, or aspherical. The first optical element 1 is used to control light, improve image quality parameters such as image distortion and resolution, and reduce the module size.

[0028] The second optical element 2 is disposed on the transmitted light path of the first optical element 1. The second optical element 2 is a prism structure, which is a triangular prism structure in this embodiment. It has a first optical surface 21, a second optical surface 22 and a third optical surface 23. The first optical surface 21 faces the first optical element 1, the second optical surface 22 faces the side away from the human eye, and the third optical surface 23 faces the side closer to the human eye.

[0029] The first optical surface 21 of the second optical element 2 is a planar surface or a curved surface that is convex or concave.

[0030] The third optical element 3 is disposed on the second optical surface 22 of the second optical element 2.

[0031] The third optical element 3 can play a role in color adjustment and phase adjustment, as well as increasing light transmittance, reducing reflectivity and reducing stray light in the system, and can also adjust the flatness of the image.

[0032] The third optical element 3 has an anti-reflection coating 31 on the side away from the second optical element 2. The anti-reflection coating 31 is used to increase the transmittance of light and reduce the reflectance of light.

[0033] In this embodiment, the third optical element 3 is a plane mirror, and one side surface of the plane mirror is attached to the second optical surface 22 of the second optical element 2. The thickness of the plane mirror is 0.1mm-0.5mm, preferably 0.2mm, and the surface profile PV is <5μm. It should be noted that the surface profile PV value refers to the vertical distance difference between the highest and lowest points in the surface morphology of the lens. The smaller the PV value, the better the flatness.

[0034] Of course, in an optional embodiment, the third optical element 3 adopts a zero-phase optical film or a zero-phase optical lens, with an in-plane phase difference R01 = 0 ± 5 nm and a thickness-direction phase difference Rth1 = 0 ± 5 nm. Because this third optical element 3 does not have phase difference, it will not add additional color cast effects, and the anti-reflection and anti-reflection functions it provides can improve stray light in the image.

[0035] In an optional embodiment, the third optical element 3 may also employ a special phase difference optical film or a special phase difference optical lens, with a surface phase difference R02 = 0 ± 10 nm and a thickness phase difference of -200 nm < Rth2 < 200 nm. This third optical element 3 has a thickness direction phase difference correction function, improving the color cast problem in the image.

[0036] In an optional embodiment, the third optical element 3 may also employ any combination of two or more of the following: a plane mirror with an anti-reflection coating layer 31, a zero-position phase difference optical film, a zero-position phase difference optical lens, a specific phase difference optical film, a specific phase difference optical lens, a quarter-wave plate, and a half-wave plate.

[0037] In one optional embodiment, the third optical element 3 can be a half-wave plate, with an in-plane phase difference of 240nm ≤ R0 ≤ 320nm. The half-wave plate can change the vibration state of polarized light, working in conjunction with the quarter-wave plate in the subsequent optical path to improve the conversion rate of circularly polarized light, enhance image contrast, and reduce stray light. Alternatively, a combination of a half-wave plate and a quarter-wave plate can be used, with an in-plane phase difference of 120nm ≤ R0 ≤ 160nm for the quarter-wave plate.

[0038] The third optical surface 23 of the second optical element 2 is provided with a polarization beam splitter 7. The function of the polarization beam splitter 7 is to split transmitted and reflected light, control phase, and absorb stray light.

[0039] The fourth optical element 4 is disposed on the side of the third optical element 3 away from the second optical element 2. A reflective element 41 is provided on the side of the fourth optical element 4 away from the third optical element 3. The reflective element 41 is a reflective film or a reflective lens. When the reflective element 41 is a reflective film, the reflective film can be disposed on the surface of the fourth optical element 4 by means of bonding or coating. When the reflective element 41 is a reflective lens, the reflective lens and the fourth optical element 4 can be tightly attached or spaced apart.

[0040] A fifth optical element 5 can also be disposed on the side of the polarization beam splitter 7 away from the second optical element 2. The fifth optical element 5 is a prism structure, with its front surface attached to the polarization beam splitter 7 and its rear surface facing the human eye. The fifth optical element 5 mainly serves to compensate for the optical path.

[0041] In this embodiment, when light propagates from the first optical surface 21 toward the second optical surface 22 and enters the third optical element 3, light with an incident angle greater than 40° is reflected by the third optical element 3, and its average reflectivity in the visible spectrum range of 380-780 nm is greater than 95%. Light with an incident angle less than or equal to 25° is transmitted out of the third optical element 3, and its average transmittance in the visible spectrum range of 380-780 nm is greater than 97%. When light propagates from the fourth optical element 4 toward the third optical element 3, light with an incident angle less than or equal to 25° is transmitted through the third optical element 3 and enters the second optical element 2, and its average transmittance in the visible spectrum range of 380-780 nm is greater than 97%.

[0042] The system focal length of the near-eye display module can be designed to be 10mm-20mm. In this embodiment, the focal length of the near-eye display module is approximately 13mm.

[0043] The light emitted from display unit 6, after being processed by the first optical element 1, enters the interior of the second optical element 2 through the first optical surface 21, propagates forward, and is transmitted through the second optical surface 22 into the third optical element 3. It is reflected within the third optical element 3, and the reflected light enters the interior of the second optical element 2 through the second optical surface 22, propagating towards the third optical surface 23. Let L be the optical path length of the light along the principal optical axis in the optical system, after reflection by the third optical element, from the second optical surface 22 to the third optical surface 23. Let F be the focal length of the system. Then, the relationship between the optical path length L and the focal length F satisfies: 0.5 ≤ L / F ≤ 0.9.

[0044] It should be noted that the dashed arrows in the figure represent the propagation path of the imaging light rays.

[0045] The imaging principle of the near-eye display module provided in this embodiment is as follows: The light emitted from the display unit 6 is incident on the first optical element 1, processed, and then transmitted out. The light transmitted from the first optical element 1 enters the interior of the second optical element 2 through the first optical surface 21, then propagates inside to the second optical surface 22, and then is transmitted out from the second optical surface 22 into the third optical element 3. Within the third optical element 3, it is reflected, and the reflected light enters the second optical element 2 through the second optical surface 22, propagates inside to the third optical surface 23, and then is transmitted out from the third optical surface 23 to the polarization beam splitter 7, where it is reflected again. The reflected light enters the interior of the second optical element 2 again through the third optical surface 23 of the second optical element 2, and propagates inside the second optical element 2 to reach the second optical surface 22 again. Then it is transmitted out from the second optical surface 22 and enters the third optical element 3. It is then transmitted out from the third optical element 3 and enters the fourth optical element 4. It is transmitted out from the fourth optical element 4 and reaches the reflecting element 41, where it is reflected. The reflected light passes through the fourth optical element 4, the third optical element 3, the second optical element 2, the polarizing beam splitter 7, and the fifth optical element 5 in sequence before reaching the human eye, forming a virtual image with a specific magnification. Example 2

[0046] Embodiment 2 of the present invention also provides a wearable device, including a wearable component and a near-eye display module.

[0047] It should be noted that the near-eye display module in this embodiment can be the near-eye display module in Embodiment 1. Its structure, working principle and technical effects are the same as those in Embodiment 1, and will not be repeated here.

[0048] The near-eye display module is mounted on a wearable component. This component can be a helmet or eyeglass frame, making it convenient for people to wear on their heads. Wearable devices also include a control unit and a storage unit; the control unit controls the device, and the storage unit stores images, videos, etc.

[0049] It should be noted that this application does not limit the optical display system to wearable devices. The optical display system can also be used on other devices. In one possible application scenario, it can also be integrated into desktop optical display devices and automotive optical display devices. Its virtual image distance is relatively far, which can realize eye protection function and improve the viewing experience.

[0050] This invention is not limited to the optional embodiments described above, and anyone can derive other various forms of products based on the inspiration of this invention. The specific embodiments described above should not be construed as limiting the scope of protection of this invention; the scope of protection of this invention should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A near-eye display module, characterized in that: Includes a display unit; A first optical element is disposed in the light-emitting path of the display unit; The second optical element is disposed on the transmitted light path of the first optical element. The second optical element is a prism structure, which has a first optical surface, a second optical surface and a third optical surface. The first optical surface faces the first optical element, the second optical surface faces the side away from the human eye, and the third optical surface faces the side closer to the human eye. A third optical element is disposed on the second optical surface of the second optical element, and an anti-reflection coating is provided on the side of the third optical element away from the second optical element; A polarization beam splitter element, wherein the polarization beam splitter element is disposed on the third optical surface of the second optical element; A fourth optical element is disposed on the side of the third optical element away from the second optical element, and a reflective element is provided on the side of the fourth optical element away from the third optical element; The light emitted by the display unit is processed by the first optical element, enters the interior of the second optical element from the first optical surface of the second optical element, and propagates forward, passing through the second optical surface and entering the third optical element. It is reflected in the third optical element, and the light reflected by the third optical element enters the interior of the second optical element from the second optical surface of the second optical element and propagates toward the third optical surface of the second optical element. The optical path length of the light along the principal optical axis in the optical system from the second optical surface of the second optical element to the third optical surface after being reflected by the third optical element is defined as L, and the system focal length is F. Then the relationship between the optical path length L and the system focal length F satisfies: 0.5≤L / F≤0.

9.

2. The near-eye display module according to claim 1, characterized in that: It also includes a fifth optical element, which is a prism structure and is disposed on the side of the polarizing beam splitter away from the second optical element.

3. The near-eye display module according to claim 1, characterized in that: The third optical element is a plane mirror with a thickness of 0.1-0.5 mm and a surface area PV < 15 μm.

4. The near-eye display module according to claim 1, characterized in that: The third optical element is a zero-phase optical film or a zero-phase optical lens, with an in-plane phase difference R01 = 0 ± 5 nm and a thickness direction phase difference Rth1 = 0 ± 5 nm.

5. The near-eye display module according to claim 1, characterized in that: The third optical element is a specially positioned phase difference optical film or a specially positioned phase difference optical lens, with an in-plane phase difference R02 = 0 ± 10 nm and a thickness direction phase difference of -200 nm < Rth2 < 200 nm.

6. The near-eye display module according to claim 1, characterized in that: The third optical element is a half-wave plate, or a combination of a half-wave plate and a quarter-wave plate.

7. The near-eye display module according to claim 1, characterized in that: The third optical element is any combination of two or more of the following: a plane mirror with an anti-reflection coating, a zero-position phase difference optical film, a zero-position phase difference optical lens, a special position phase difference optical film, a special position phase difference optical lens, a quarter-wave plate, and a half-wave plate.

8. The near-eye display module according to claim 1, characterized in that: The function of the third optical element is to guide light from the first optical surface of the second optical element to the third optical element, where it is reflected. Light with an incident angle greater than 40° is reflected by the third optical element, and its average reflectivity in the visible spectrum range of 380-780 nm is greater than 95%. Light with an incident angle less than or equal to 25° is transmitted out of the third optical element, and its average transmittance in the visible spectrum range of 380-780 nm is greater than 97%. When light propagates from the fourth optical element toward the third optical element, light with an incident angle of less than or equal to 25° passes through the third optical element and enters the second optical element, with an average transmittance of more than 97% in the visible spectrum range of 380-780nm.

9. The near-eye display module according to claim 1, characterized in that: The system focal length of the near-eye display module is 10-20mm.

10. A wearable device, characterized in that: It includes a wearable component and a near-eye display module as described in any one of claims 1-9, wherein the near-eye display module is disposed on the wearable component.

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