Near-eye display module and wearable device

Abstract

The embodiment of the present application provides a near-eye display module and a wearable device; wherein the near-eye display module comprises an imaging lens group, and a light splitting element, a first phase retarder and a polarization reflection element; wherein the first phase retarder is located between the light splitting element and the polarization reflection element; the imaging lens group comprises at least two lenses, and at least two Fresnel surfaces are arranged in the imaging lens group, the Fresnel surfaces are located between the light splitting element and the polarization reflection element, and the absolute value of the ratio of the curvature radius of the Fresnel surface to the focal length of the near-eye display module satisfies: 1-20. The near-eye display module provided by the embodiment of the present application can improve the imaging quality while reducing the total length of the optical system.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of optical imaging technology, and more particularly, to a near-eye display module and a wearable device. BACKGROUND

[0002] In recent years, virtual reality (VR) technology has been applied in, for example, head-mounted display devices and has developed rapidly. The core component of virtual reality technology is an optical module. The quality of the image displayed by the optical module will directly determine the quality of the head-mounted display device.

[0003] With the continuous improvement of consumer demand, the size and imaging quality of virtual reality products are increasingly required to be smaller, thinner and higher definition. Specifically, reducing the size of the optical module, especially improving the imaging quality of the optical module under the premise of reducing the size of the optical module, is a problem to be solved. The total length of a conventional VR folded optical path system is generally greater than 15 mm. Once the total length of the optical system is reduced, the final imaging quality will be affected. SUMMARY

[0004] The purpose of the present application is to provide a new technical solution for a near-eye display module and a wearable device, which effectively shortens the total length of the optical system while improving the imaging quality.

[0005] In a first aspect, the present application provides a near-eye display module. The near-eye display module comprises an imaging lens group, and a light splitting element, a first phase retarder and a polarization reflection element; wherein the first phase retarder is located between the light splitting element and the polarization reflection element.

[0006] The imaging lens group comprises at least two lenses, and at least two Fresnel surfaces are arranged in the imaging lens group. The Fresnel surfaces are located between the light splitting element and the polarization reflection element, and the absolute value of the ratio of the radius of curvature of the Fresnel surface to the focal length of the near-eye display module satisfies 1-20.

[0007] Optionally, the near-eye display module further comprises a display assembly, and the display assembly comprises a support plate and a display screen embedded in the support plate.

[0008] The light splitting element is located between the support plate and the imaging lens group.

[0009] The height h1 of the light splitting element and the height h2 of the display screen satisfy h1>h2; wherein the height direction of the light splitting element and the display screen is perpendicular to the optical axis of the imaging lens group.

[0010] Optionally, the optical system total length TTL of the near-eye display module satisfies: TTL < 10 mm.

[0011] Optionally, the maximum incident angle of the incident light rays into the first phase retarder and the polarization reflection element is < 15°.

[0012] Optionally, the maximum incident angle of the incident light rays into the first phase retarder and the polarization reflection element is < 5°.

[0013] Optionally, the imaging lens group comprises a first lens and a second lens arranged adjacently and spaced apart, wherein the first lens is located between the display assembly and the second lens, and the first lens, the second lens and the display screen are located on the same optical axis.

[0014] The spacing L between the first lens and the second lens is set to: L > 0.2 mm.

[0015] Optionally, the two surfaces of the first lens adjacent to the second lens are set to Fresnel surfaces.

[0016] Optionally, the absolute value of the ratio of the radius of curvature of the Fresnel surface of the first lens to the focal length of the near-eye display module satisfies: 1-20.

[0017] The absolute value of the ratio of the radius of curvature of the Fresnel surface of the second lens to the focal length of the near-eye display module satisfies: 1-2.

[0018] Optionally, the support plate comprises a fifth surface and a sixth surface, the sixth surface is close to the first lens, and the light splitting element is arranged on the sixth surface.

[0019] The fifth surface is provided with a receiving groove recessed towards the sixth surface, and the display screen is located in the receiving groove; wherein the spacing l between the sixth surface and the bottom wall of the receiving groove is greater than 0.

[0020] Optionally, the near-eye display module further comprises a first polarization element, the first phase retarder, the polarization reflection element and the first polarization element are stacked to form a composite film, the composite film is arranged on the surface of the second lens away from the display assembly, and the surface of the second lens close to the display assembly is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure.

[0021] The surface of the first lens close to the display assembly is an aspherical surface, and the surface of the first lens away from the display assembly is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure.

[0022] Optionally, the optical power of the first lens and the second lens is set to be positive.

[0023] Optionally, an absolute value of a ratio of focal lengths of the second lens and the first lens satisfies 0.1-20.

[0024] Optionally, the display screen is configured to emit circularly polarized light or natural light.

[0025] When the light emitted by the display screen is natural light, a superposition sheet is arranged on a light emitting surface side of the display screen, and the superposition sheet is configured to convert the natural light emitted by the display screen into circularly polarized light; the superposition sheet comprises a second phase retarder, a third phase retarder, and a second polarizing element arranged between the second phase retarder and the third phase retarder.

[0026] In a second aspect, the present application provides a wearable device, the wearable device comprising:

[0027] a housing; and

[0028] The near-eye display module as described in the first aspect.

[0029] The near-eye display module as described in the first aspect.

[0030] The near-eye display module provided by the embodiments of the present application is a folded light path structure design, at least two Fresnel surfaces are introduced in the folded light path design, and the imaging quality of the near-eye display module can be improved while the total length of the optical system is reduced by cooperation of the folded light path design; the whole light path structure design is simple, and miniaturization, thinning and high-quality imaging of the near-eye display module are realized.

[0031] Other features of the present application and its advantages will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and together with the description, serve to explain the principles of the present application.

[0033] Figure 1 FIG. 1 is a structural schematic diagram of a near-eye display module provided by an embodiment of the present application;

[0034] Figure 2 FIG. 3 is a schematic diagram of a superposition sheet arranged on a surface of a second lens in the near-eye display module provided by the embodiment of the present application;

[0035] Figure 3 FIG. 4 is a point diagram of the near-eye display module shown in FIG. 1; Figure 1 FIG. 5 is an MTF curve diagram of the near-eye display module shown in FIG. 1; and

[0036] Figure 4 FIG. 4 is a point diagram of the near-eye display module shown in FIG. 1; Figure 1 FIG. 5 is an MTF curve diagram of the near-eye display module shown in FIG. 1; and

[0037] Figure 5 For Figure 1 The field curvature distortion map of the near-eye display module shown;

[0038] Figure 6 For Figure 1 The tangential chromatic aberration map of the near-eye display module shown;

[0039] Figure 7 For one of the structural schematic diagrams of the display assembly of the near-eye display module provided by the embodiments of the present application;

[0040] Figure 8 For the second structural schematic diagram of the display assembly of the near-eye display module provided by the embodiments of the present application;

[0041] Figure 9 For the second structural schematic diagram of the near-eye display module provided by the embodiments of the present application;

[0042] Figure 10 For Figure 9 The MTF curve diagram of the near-eye display module shown;

[0043] Figure 11 For Figure 9 The point spread diagram of the near-eye display module shown;

[0044] Figure 12 For Figure 9 The field curvature distortion map of the near-eye display module shown;

[0045] Figure 13 For Figure 9 The tangential chromatic aberration map of the near-eye display module shown;

[0046] Figure 14 For the third structural schematic diagram of the near-eye display module provided by the embodiments of the present application;

[0047] Figure 15 For Figure 14 The MTF curve diagram of the near-eye display module shown;

[0048] Figure 16 For Figure 14 The point spread diagram of the near-eye display module shown;

[0049] Figure 17 For Figure 14 The field curvature distortion map of the near-eye display module shown;

[0050] Figure 18 For Figure 14 The tangential chromatic aberration map of the near-eye display module shown.

[0051] Explanation of reference signs:

[0052] 10, first lens; 11, first surface; 12, second surface; 20, second lens; 21, third surface; 22, fourth surface; 30, display assembly; 31, support plate; 311, fifth surface; 312, sixth surface; 32, display screen; 40, light splitting element; 50, first phase retarder; 60, polarizing reflecting element; 70, first polarizing element; 80, anti-reflection film; 01, human eye. DETAILED DESCRIPTION

[0053] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of the components and steps set forth in the embodiments, as well as the numerical expressions and numerical values, are not limiting to the scope of the present application unless specifically stated otherwise.

[0054] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way limiting to the scope of the application or its applications or uses.

[0055] Techniques and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification where appropriate.

[0056] In all examples shown and discussed herein, any specific value should be interpreted as merely illustrative and not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0057] It should be noted that like numbers and letters refer to like items throughout the drawings, and that, once an item is defined in one drawing, it should not require further discussion in subsequent drawings.

[0058] The near-eye display module and wearable device according to the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0059] According to an aspect of the embodiments of the present application, a near-eye display module is provided, which can be suitable for wearable devices such as head-mounted displays (HMDs), for example, VR head-mounted displays.

[0060] The VR head-mounted display may, for example, include VR smart glasses or VR smart helmets, and the specific form of the wearable device is not limited in the embodiments of the present application.

[0061] The near-eye display module according to the embodiments of the present application is described below with reference to Figure 1 , Figure 9 and Figure 14The near-eye display module comprises an imaging lens group, and a light splitting element 40, a first phase retarder 50, and a polarization reflection element 60; wherein the first phase retarder 50 is located between the light splitting element 40 and the polarization reflection element 60; the imaging lens group comprises at least two lenses, and at least two Fresnel surfaces are arranged in the imaging lens group, the Fresnel surfaces are located between the light splitting element 40 and the polarization reflection element 60, and the absolute value of the ratio of the radius of curvature of the Fresnel surface to the focal length of the near-eye display module satisfies 1-20.

[0062] The near-eye display module provided in the above embodiments of the present application is a pancake-based optical module. Specifically, referring to Figure 1 The imaging lens group cooperates with the light splitting element 40, the first phase retarder 50, and the polarization reflection element 60 to form a pancake optical path for the near-eye display module; and the first phase retarder 50 is located between the light splitting element 40 and the polarization reflection element 60.

[0063] In the embodiments of the present application, the total length of the optical system of the near-eye display module can be shortened by introducing the Fresnel surface into the optical path and combining with the pancake optical path design.

[0064] Specifically, the number of Fresnel surfaces in the optical path is increased, for example, two or more Fresnel surfaces are arranged, so as to improve the imaging quality of the near-eye display module; and the absolute value of the ratio of the radius of curvature of the Fresnel surface in the optical path to the focal length of the near-eye display module satisfies 1-20, so that the total length of the optical system of the near-eye display module can be effectively shortened while the optical imaging quality is improved.

[0065] For example, the total length of the optical system of the near-eye display module can be less than 10 mm, and good imaging quality can be ensured. Compared with the traditional optical module, the total length of the optical system is significantly reduced.

[0066] The near-eye display module provided in the embodiments of the present application is beneficial to the miniaturization, thinness, and high-quality imaging requirements of virtual reality display devices (VR display devices), and can ensure high imaging quality in the case of small device size.

[0067] Since the total length of the optical system of the near-eye display module can be relatively small, the virtual reality display device using the near-eye display module can also have the feature of small size, which is more suitable for users to wear and use, and can improve the comfort of wearing.

[0068] According to the near-eye display module provided in the embodiment of the present application, a folding light path structure design is provided, at least two Fresnel surfaces are introduced in the folding light path design, and the imaging quality of the near-eye display module can be improved while the total length of the optical system is reduced; the whole light path structure design is simple, and miniaturization, thinness and high-quality imaging of the near-eye display module are realized.

[0069] The near-eye display module provided in the embodiment of the present application is a folding light path, in addition to containing an imaging lens group, the near-eye display module also contains a light splitting element, a phase retarder and a polarization reflection element and other optical elements for forming a folding light path.

[0070] The optical elements (optical films) described above can be used to form a folding light path in the near-eye display module, so that the light rays are folded therein to prolong the propagation path of the light rays, which is beneficial to the final clear imaging and also beneficial to reducing the volume of the whole near-eye display module.

[0071] In the near-eye display module provided in the embodiment of the present application, the number of lenses used can be flexibly adjusted according to specific needs, but considering that at least two Fresnel surfaces need to be designed in the light path, and one Fresnel surface should be arranged on each lens, otherwise the light reflection will be affected, therefore, at least two lenses are designed in the embodiment of the present application. Although the number of lenses used in the folding light path can improve the imaging quality of the near-eye display module, it will also affect the size of the near-eye display module along the optical axis direction (lateral direction), resulting in a larger volume and increased weight of the near-eye display module.

[0072] In the embodiment of the present application, considering many factors such as the volume, weight, imaging quality and production cost of the whole near-eye display module, two lenses are designed in the light path, as shown in Figure 1 , which realizes a better thin design of the near-eye display module. Of course, the near-eye display module provided in the embodiment of the present application is not limited to having two lenses inside, which is only an example.

[0073] The light splitting element 40 is, for example, a semi-transparent and semi-reflective film.

[0074] The light splitting element 40 can transmit a part of the light and reflect another part of the light.

[0075] It should be noted that the reflectivity and transmissivity of the light splitting element 40 can be flexibly adjusted according to specific needs, which is not limited in the embodiment of the present application.

[0076] Optionally, the reflectivity of the light splitting element 40 is 47% to 53%.

[0077] The first phase retarder 50 is, for example, a quarter-wave plate. Of course, the first phase retarder 50 can also be set as other phase retarders such as a half-wave plate according to requirements.

[0078] In the near-eye display module, the first phase retarder 50 is arranged in the folded light path close to the human eye 01, which can be used to change the polarization state of the light. For example, it is used to convert linearly polarized light into circularly polarized light, or to convert circularly polarized light into linearly polarized light.

[0079] The polarization reflection element 60 is, for example, a polarization reflection film.

[0080] The polarization reflection element 60 is a polarization reflector that reflects horizontally linearly polarized light and transmits vertically linearly polarized light, or a polarization reflector that reflects linearly polarized light at any specific angle and transmits linearly polarized light perpendicular to the angle.

[0081] In the embodiment of the present application, the first phase retarder 50 and the polarization reflection element 60 cooperate to analyze and transmit light. The polarization reflection element 60 has a transmission axis, and the angle between the transmission axis of the polarization reflection element 60 and the fast axis or slow axis of the first phase retarder 50 is, for example, 45°.

[0082] The three optical elements, the light splitting element 40, the first phase retarder 50, and the polarization reflection element 60, are arranged flexibly in the near-eye display module, but the first phase retarder 50 must be between the light splitting element 40 and the polarization reflection element 60.

[0083] The optical path diagram of the near-eye display module of the embodiment of the present application is shown in FIG. 4. Figure 1 The light propagation path is as follows: the incident light is, for example, circularly polarized light, which enters the light splitting element 40 and then enters the imaging lens group. The incident light can be folded back by the first phase retarder 50 and the polarization reflection element 60 in the imaging lens group, and finally exits through the lens close to the human eye 01. In this way, a high-quality imaging image can be presented in the human eye 01, and the image quality is better.

[0084] In some examples of the present application, the near-eye display module further includes a display assembly 30, which includes a support plate 31 and a display screen 32 embedded in the support plate 31. The light splitting element 40 is located between the support plate 31 and the imaging lens group, and the height h1 of the light splitting element 40 and the height h2 of the display screen 32 satisfy: h1>h2. The height direction of the light splitting element 40 and the display screen 32 is perpendicular to the optical axis of the imaging lens group.

[0085] In the above examples of the present application, the display screen 32 is supported in the optical path structure by the support plate 31, and the support plate 31 and the display screen 32 combine to form a display assembly 30. The support plate 31 can not only support the display screen 32, but also protect the display screen 32, for example, provide dust protection, and prevent the display screen 32 from breaking or being damaged when the near-eye display module falls.

[0086] The support plate 31 is, for example, a flat lens. Referring to Figure 1 , the display assembly 30 is located on the light-incoming side of the imaging lens group, and the human eye 01 is located on the light-outgoing side of the imaging lens group.

[0087] Specifically, referring to Figure 8 , the support plate 31 is provided with a recessed structure on the fifth surface 311 away from the imaging lens group, and the display screen 32 can be embedded in the recessed structure, so that the support plate 31 and the display screen 32 form an integral piece, which is beneficial to assembly in the optical path.

[0088] The light splitting element 40 is, for example, a half-mirror.

[0089] Optionally, the light splitting element 40 can be independently arranged between the display assembly 30 and the imaging lens group. Of course, referring to Figure 1 , the light splitting element 40 can also be arranged on a surface of the support plate 31, such as the sixth surface 312, which is not limited in the present application.

[0090] In the above examples of the present application, referring to Figure 7 and Figure 8 , since the display screen 32 is embedded in the support plate 31, the size of the support plate 31 is greater than the size of the display screen 32. In order to make the light emitted by the display screen 32 enter the light splitting element 40 as much as possible and improve the utilization rate of light energy, the size of the light splitting element 40 can also be designed to be larger.

[0091] For example, when the light splitting element 40 is arranged on the sixth surface 312 of the support plate 31 facing the imaging lens group, the size of the light splitting element 40 in the height direction should be greater than the size of the display screen 32 in the height direction, referring to Figure 8 , that is, the height h1 of the light splitting element 40 and the height h2 of the display screen 32 satisfy: h1>h2.

[0092] In addition, the size of the light splitting element 40 is designed to be larger than the size of the display screen 32 and to be adapted to the size of the support plate 31. In this way, the assembly of the light splitting element 40 on the support plate 31 is also facilitated.

[0093] The total length TTL of the optical system of the near-eye display module provided in the above embodiments satisfies TTL < 10 mm.

[0094] For the near-eye display module, reducing the size of the module and improving the imaging quality of the near-eye display module under the premise of reducing the size of the module are currently problems to be solved. The total length of the conventional VR folding light path system is generally greater than 15 mm. In the prior art, once the total length of the optical system is reduced, the final imaging quality is affected.

[0095] The optical technical solution provided in the embodiments of the present application can effectively reduce the total length of the optical system of the near-eye display module while improving the optical imaging quality by increasing the number of Fresnel surfaces in the folding light path, for example, by providing two or more Fresnel surfaces, and by designing the ratio of the absolute value of the radius of curvature of the Fresnel surface in the light path to the focal length of the near-eye display module to satisfy 1-20.

[0096] It should be noted that the total length of the optical system of the near-eye display module provided in the embodiments of the present application can be only 10 mm or even smaller, which is obviously further reduced in size compared with the existing 15 mm, and at the same time, the near-eye display module also has excellent imaging quality. When applied to a VR device, not only the comfort of the user wearing can be improved, but also the visual experience can be improved.

[0097] In some examples of the present application, the maximum incident angle of the incident light rays into the first phase retarder 50 and the polarization reflection element 60 is < 15°.

[0098] In the near-eye display module provided in the embodiments of the present application, at least two Fresnel surfaces are located in the folding light path, and such a design can effectively reduce the incident angle of the incident light rays into the first phase retarder 50 and the polarization reflection element 60 of the near-eye display module. When the incident angle is small, for example, less than 15° in the above example, the polarization state change of the incident light rays can be improved, and stray light can be reduced, which is beneficial to improve the imaging quality.

[0099] The incident light rays can be emitted by the display screen 32 on one side of the imaging lens group, for example.

[0100] More preferably, the maximum incident angle of the incident light rays into the first phase retarder 50 and the polarization reflection element 60 can be less than 5°.

[0101] That is, the near-eye display module provided by the embodiments of the present application can effectively control stray light and improve optical imaging quality by designing at least two Fresnel surfaces in the folded light path, so that the incident angle of the incident light (imaging light) emitted by the display screen 32 can be less than 15°, and even less than 5° after being incident on the first phase retarder 50 and the polarization reflection element 60.

[0102] In one example of the present application, referring to Figure 1 , the imaging lens group comprises a first lens 10 and a second lens 20 arranged adjacently and spaced apart, wherein the first lens 10 is located between the display assembly 30 and the second lens 20, and the first lens 10, the second lens 20 and the display screen 32 are located on the same optical axis; the spacing L between the first lens 10 and the second lens 20 is set as L>0.2mm.

[0103] In the above example, the imaging lens group can be designed to comprise two lenses, each of which has a Fresnel surface, so that two Fresnel surfaces are formed in the light path of the near-eye display module. This design is conducive to achieving the thin design of the entire near-eye display module.

[0104] Referring to Figure 1 , the second lens 20 is located, for example, on the side close to the eye 01, and the first lens 10 is located, for example, on the side close to the display assembly 30. The first lens 10 and the second lens 20 need to be spaced apart appropriately, for example, more than 0.2mm, to ensure that the lenses do not interfere with each other and do not affect the final imaging.

[0105] In the above example, optionally, the two surfaces of the first lens 10 and the second lens 20 adjacent to each other are designed as Fresnel surfaces.

[0106] Referring to Figure 1 , the first lens 10 comprises a first surface 11 and a second surface 12, wherein the first surface 11 is close to the display assembly 30, and the second surface 12 is away from the display assembly 30. The second lens 20 comprises a third surface 21 and a fourth surface 22, wherein the third surface 21 is close to the display assembly 30, and the fourth surface 22 is away from the display assembly 30. On this basis, the second surface 12 and the third surface 21 are arranged adjacently and spaced apart, and are located at a relatively central position of the imaging lens group. When the two surfaces are designed as Fresnel surfaces, this is conducive to making the two Fresnel surfaces completely located in the folded light path.

[0107] In the imaging lens, two Fresnel surfaces can be designed on other surfaces of the first lens 10 and the second lens 20 as needed, that is, including but not limited to the two adjacent surfaces described above. For example, when other lenses are also included in the imaging lens, the Fresnel surfaces can also be designed on the surfaces of the other lenses as needed, as long as at least two Fresnel surfaces are located in the folded optical path.

[0108] In the above example, the absolute value of the ratio of the radius of curvature of the Fresnel surface of the first lens 10 to the focal length of the near-eye display module satisfies 1-20; and the absolute value of the ratio of the radius of curvature of the Fresnel surface of the second lens 20 to the focal length of the near-eye display module satisfies 1-2.

[0109] In the embodiments of the present application, by adjusting the ratio of the focal length of the two lenses to the near-eye display module, the imaging quality of the near-eye display module and the control of the total length of the optical system are more beneficial.

[0110] In some examples of the present application, referring to Figure 7 and Figure 8 , the near-eye display module further includes the display assembly 30 described above, the display assembly 30 includes a support plate 31 and a display screen 32 embedded in the support plate 31; wherein the support plate 31 includes a fifth surface 311 and a sixth surface 312, the sixth surface 312 is close to the first lens 10, and the light splitting element 40 is arranged on the sixth surface 312; the fifth surface 311 is provided with a receiving groove recessed toward the sixth surface, and the display screen 32 is located in the receiving groove; wherein, referring to Figure 8 , the distance l between the sixth surface 312 of the support plate 31 and the bottom wall of the receiving groove is greater than 0 mm.

[0111] For example, the support plate 31 is provided with a recessed receiving groove on the fifth surface 311 away from the imaging lens, which forms a containing space on one side of the support plate 31, and the display screen 32 can be embedded in the receiving groove.

[0112] Specifically, the support plate 31 is, for example, a lens with a receiving groove on one side, and when assembled, the receiving groove of the support plate 31 is directly buckled on the display screen 32 opposite to the display screen 32, so that the assembly method is simple and stable.

[0113] Wherein, the size of the receiving groove is matched with the display screen 32, so as to facilitate the stable assembly of the display screen 32.

[0114] The support flat plate 31 can not only support the display screen 32, but also protect the display screen 32, for example, prevent dust, and prevent the display screen 32 from being broken or damaged when the near-eye display module falls.

[0115] Optionally, referring to Figure 1 and Figure 2 , the near-eye display module further comprises a first polarization element 70, the first phase retarder 50, the polarization reflection element 60 and the first polarization element 70 are stacked to form a composite film, the composite film is arranged on the surface (the fourth surface 22) of the second lens 20 away from the display assembly 30, and the surface (the third surface 21) of the second lens 20 close to the display assembly 30 is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure; the surface (the first surface 11) of the first lens 10 close to the display assembly 30 is an aspheric surface, and the surface (the second surface 12) of the first lens 10 away from the display assembly 30 is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure.

[0116] Among them, the introduction of the first polarization element 70 can be used to reduce stray light.

[0117] Referring to Figure 2 , the first phase retarder 50, the polarization reflection element 60 and the first polarization element 70 are stacked and form a composite film, and are arranged on the surface (the fourth surface 22) of the second lens 20 away from the display screen 32; in this way, there is enough space to arrange a Fresnel surface between the light splitting element 40 and the composite film, so that at least two Fresnel surfaces can be completely located in the formed folded light path.

[0118] Specifically, in the near-eye display module, one Fresnel surface and the composite film are located on two surfaces of the same lens, for example, the third surface 21 and the fourth surface 22 of the second lens 20 on the side of the near human eye 01.

[0119] In addition, optionally, an anti-reflection film 80 can also be introduced into the composite film, referring to Figure 2 , the anti-reflection film 80 is arranged on the side of the first polarization element 70 away from the polarization reflection element 60.

[0120] Optionally, an anti-reflection film is arranged on the third surface 21, i.e. the Fresnel surface, of the second lens 20.

[0121] The anti-reflection film can reduce reflection, reduce reflected energy, and improve light efficiency. The anti-reflection film can be formed on the optical component by pasting or plating to form an interface, increase the transmittance, reduce the reflectivity, thereby reducing image distortion, so that the user can enjoy clearer image quality, and the phenomenon of reducing glare is achieved.

[0122] The near-eye display module provided in the above examples refers to Figure 1 The propagation of light is as follows:

[0123] The display screen 32 emits incident light (circularly polarized light), which is transmitted through the light splitting element 40, the first lens 10, the third surface 21 (Fresnel surface) of the second lens 20, reflected by the fourth surface 22 of the second lens 20, transmitted through the third surface 21 (Fresnel surface) and the first lens 10, reflected by the light splitting element 40 again, and transmitted through the first lens 10 and the second lens 20 to enter the human eye 01 for imaging.

[0124] The fourth surface 22 is provided with a composite film, which includes a first phase retarder 50, a polarization reflection element 60, and a first polarization element 70; the first phase retarder 50 can change the incident light into linearly polarized light (P light), which is reflected by the polarization reflection element 60, and then changes into circularly polarized light after passing through the first phase retarder 50 again. The light is reflected by the light splitting element 40 again, and then changes into linearly polarized light (S light) after passing through the first phase retarder 50 again. Finally, the light is transmitted through the second lens 20 and enters the human eye 01 to display an image. The two Fresnel surfaces (the second surface 12 of the first lens 10 and the third surface of the second lens 20) are completely located in the folded optical path.

[0125] In some examples of the present application, the optical power of the first lens 10 and the second lens 20 is set to be positive.

[0126] Referring to Figure 1 The first lens 10 and the second lens 20 can form a lens group, and the optical elements forming the folded optical path are arranged on both sides of the two lenses. When the optical power of the second lens 20 and the first lens 10 is set to be positive, the angle of the incident light transmitted through the first lens 10 and the second lens 20 to the polarization reflection element 60 is small, which is beneficial to make a large amount of light enter the human eye 01 for imaging.

[0127] In some examples of the present application, the absolute value of the focal length ratio of the second lens 20 to the first lens 10 satisfies: 0.1-20.

[0128] The near-eye display module provided in the embodiments of the present application controls the focal length reasonably on the basis of small size, and within the above focal length range, different users can watch clear and complete pictures.

[0129] Optionally, the focal length of the near-eye display module is 15mm-25mm.

[0130] In some examples of the present application, the display screen 32 is configured to emit circularly polarized light or natural light; when the light emitted by the display screen 32 is natural light, a superposition sheet is arranged on the light emitting surface of the display screen 32, which can be used to convert the natural light emitted by the display screen 32 into circularly polarized light; wherein the superposition sheet comprises a second phase retarder, a third phase retarder and a second polarization element between the second phase retarder and the third phase retarder.

[0131] The incident light into the imaging lens group should be circularly polarized light. When the display screen 32 emits natural light, the polarization state of the natural light needs to be converted first, so that the natural light is first converted into circularly polarized light before entering the left imaging lens group, and finally the light emitted by the imaging lens group is imaged into the human eye 01.

[0132] Optionally, the superposition sheet comprises a second phase retarder, a third phase retarder and a second polarization element between the second phase retarder and the third phase retarder. The superposition sheet can be used to convert natural light into circularly polarized light.

[0133] The superposition sheet, for example, comprises two phase retarders and a polarization element arranged between the two phase retarders. Specifically, the display screen 32 emits natural light, the natural light still remains natural light after passing through a phase retarder, and becomes linearly polarized light after passing through the second polarization element, and becomes circularly polarized light after passing through another phase retarder.

[0134] In the superposition sheet, the two phase retarders are, for example, both set as quarter-wave plates; one of the quarter-wave plates can be used to adjust the polarization state of light, and the other quarter-wave plate is located at the outermost side and can be used to block a part of incident light. Specifically, this part of light is the light that is not wanted in imaging, and if this part of light is not blocked, it will be reflected back through the light emitting surface of the display screen 32 and hit the human eye 01, which is not conducive to the final imaging.

[0135] In some examples of the present application, the central thickness T1 of the first lens 10 ranges from 1mm to 5mm, which includes two optical surfaces, as shown in Figure 1, respectively, a first surface 11 close to the display screen 32 and a second surface 12 away from the display screen 32; wherein the first surface 11 is aspherical, and an anti-reflection film is arranged on the surface; the second surface 12 is a Fresnel surface, and the surface is a sawtooth structure; the absolute value of the ratio of the radius of curvature of the Fresnel surface of the first lens to the focal length of the near-eye display module satisfies: 0.6-14.

[0136] In some examples of the present application, the central thickness T2 of the second lens 20 ranges from 1mm Figure 1 , respectively, a third surface 21 close to the display screen 32 and a fourth surface 22 away from the display screen 32; wherein the third surface 21 is a Fresnel surface, and the surface is a sawtooth structure; the absolute value of the ratio of the radius of curvature of the Fresnel surface of the second lens to the focal length of the near-eye display module satisfies: 1-15; the fourth surface 22 is provided with a composite film including an anti-reflection film 80, a first polarizing element 70, the polarizing reflection element 60, and the first phase retarder 50.

[0137] The near-eye display module of the embodiment of the present application includes a first lens 10 and a second lens 20, and the refractive index n of the first lens 10 and the second lens 20 ranges from 1.4

[0138] In a specific example of the present application, the refractive index of the first lens 10 is 1.54, and the dispersion coefficient is 56.3; the refractive index of the second lens 20 is 1.54, and the dispersion coefficient is 56.3.

[0139] The near-eye display module provided by the embodiment of the present application is described in detail through Examples 1-3 below.

[0140] Example 1

[0141] Referring to Figure 1 and Figure 2 , the near-eye display module includes an imaging lens group and a display assembly 30, the imaging lens group includes a first lens 10 and a second lens 20 arranged adjacent to and spaced apart from each other, and the first lens 10 is located between the display assembly 30 and the second lens 20; the spacing L between the first lens 10 and the second lens 20 is 0.2mm; the display assembly 30 includes a support plate 31 and a display screen 32 embedded in the support plate 31; the first lens 10, the second lens 20, and the display screen 32 in the display assembly 30 are located on the same optical axis;

[0142] The second surface 12 of the first lens 10 and the third surface 21 of the second lens 20 are adjacent and are both Fresnel surfaces; the absolute value of the ratio of the curvature radius of the Fresnel surface of the first lens 10 to the focal length of the near-eye display module satisfies 1.52; the absolute value of the ratio of the curvature radius of the Fresnel surface of the second lens 20 to the focal length of the near-eye display module satisfies 1.83;

[0143] The support plate 31 includes a fifth surface 311 and a sixth surface 312, the sixth surface 312 is close to the first lens 10, and the light splitting element 40 is arranged on the sixth surface 312; the fifth surface 311 is provided with a receiving groove recessed towards the sixth surface, and the display screen 32 is located in the receiving groove; referring to Surface The distance l between the sixth surface 312 of the support plate 31 and the bottom wall of the receiving groove is greater than 0 mm; the height h1 of the light splitting element and the height h2 of the display screen 32 satisfy h1>h2, and the height direction of the light splitting element and the display screen is perpendicular to the optical axis of the imaging lens group;

[0144] The near-eye display module further includes a first phase retarder 50, a polarization reflection element 60 and a first polarization element 70, the first phase retarder 50, the polarization reflection element 60 and the first polarization element 70 are stacked to form a composite film, the composite film is arranged on the surface of the second lens 20 away from the display assembly 30, the surface of the second lens 20 close to the display assembly 30 is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure; the surface of the first lens 10 close to the display assembly 30 is an aspherical surface, and the surface of the first lens 10 away from the display assembly 30 is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure;

[0145] The optical power of the first lens 10 and the second lens 20 satisfies

[0146] The absolute value of the ratio of the focal length of the second lens 20 to the focal length of the first lens 10 satisfies 0.65, and the focal length of the near-eye display module is 15 mm to 25 mm;

[0147] The display screen 32 is configured to emit circularly polarized light or natural light; when the light emitted by the display screen 32 is natural light, a superposition sheet is arranged on the light emitting surface side of the display screen 32, which can be used to convert the natural light emitted by the display screen into circularly polarized light; the superposition sheet includes a second phase retarder, a third phase retarder and a second polarization element between the second phase retarder and the third phase retarder;

[0148] The maximum incident angle of the incident light rays into the first phase retarder 50 and the polarization reflection element 60 is < 15°.

[0149] The total length of the optical system of the near-eye display module is less than 10 mm.

[0150] Table 1 shows the specific optical parameters of each lens in the near-eye display module provided in Embodiment 1.

[0151] Table 1

[0152] Radius Center thickness Material Conic coefficient APEL A4 a6 a8 22 -481 2 APEL 0 2.303E-06 0 0 21 -29.5 0.2 / 0 1.602E-05 2.12E-09 8.33E-12 12 28.2 2 Figures 3 to 6 0 1.11E-06 7.63E-10 -1.42E-11 21 59.2 6 / 0 3.71E-06 0 0

[0153] For the near-eye display module provided in Embodiment 1, the optical performance can be as shown in Figure 3 Figure 4 is a schematic diagram of a spot diagram of a near-eye display module, Figure 5 is a curve diagram of MTF of a near-eye display module, Figure 6 is a distortion diagram of field curvature of a near-eye display module, Figure 3 is a diagram of the axial chromatic aberration of a near-eye display module.

[0154] The spot diagram refers to a diffused pattern formed by a plurality of light rays emitted from a point after passing through the near-eye display module, and the intersection points of the light rays with the image plane are no longer concentrated on the same point due to aberration. The spot diagram can be used to evaluate the imaging quality of the near-eye display module. Referring to Figure 4 , the maximum value of the image point in the spot diagram corresponds to the maximum field of view, and the maximum value of the image point in the spot diagram is less than 11 μm.

[0155] The MTF curve diagram is a modulation transfer function diagram, and the imaging clarity of the near-eye display module is represented by the contrast of black and white lines. Referring to Figure 5 , the MTF is > 0.3 at 60 lp / mm, and the imaging is clear.

[0156] The distortion diagram reflects the difference in the image plane position of clear images at different fields of view. Referring to Figure 5 , the maximum distortion occurs at 1 field of view, and the maximum value is less than 35%. The field curvature diagram reflects the difference in the image plane position of clear images at different fields of view. Referring to Figure 6 , the maximum field curvature occurs near 1 field of view, and the maximum value is less than 0.2 mm.

[0157] The axial chromatic aberration, also known as the magnification chromatic aberration, mainly refers to a principal ray of a complex color in the object side, which becomes a plurality of light rays when exiting the image side due to the dispersion of the refractive system. The difference in the focal point positions of blue light and red light on the image plane. Referring to Figure 9 , the maximum chromatic aberration value of the near-eye display module is less than 350 μm.

[0158] Embodiment 2

[0159] ​The near-eye display module provided in Embodiment 2 can refer to Figures 10 to 13 The difference between the near-eye display module provided in Embodiment 1 and the near-eye display module provided in Embodiment 2 is that:

[0160] The absolute value of the ratio of the radius of curvature of the Fresnel surface of the first lens 10 to the focal length of the near-eye display module satisfies 4.05; and the absolute value of the ratio of the radius of curvature of the Fresnel surface of the second lens 20 to the focal length of the near-eye display module satisfies 1.57.

[0161] The absolute value of the ratio of the focal length of the second lens 20 to the first lens 10 satisfies 0.16.

[0162] The distance L between the first lens 10 and the second lens 20 is set to 2.87mm.

[0163] Table 2 shows the specific optical parameters of each lens in the near-eye display module provided in Embodiment 2.

[0164] Table 2

[0165]

[0166] The optical performance of the near-eye display module provided in Embodiment 2 can be as shown in Figure 10 Figure 11 is a MTF curve diagram of the near-eye display module, Figure 12 is a point spread diagram of the near-eye display module, Figure 13 is a field curvature distortion diagram of the near-eye display module, Figure 10 is a sagittal chromatic aberration diagram of the near-eye display module.

[0167] The MTF curve diagram is a modulation transfer function diagram, which represents the imaging clarity of the near-eye display module through the contrast of black and white lines. Referring to Figure 11 , the MTF is greater than 0.4 at 60lp / mm, and the imaging is clear.

[0168] The point spread diagram refers to a dispersion diagram formed by a point emitting many light rays after passing through the near-eye display module, and the intersection points of the light rays with the image plane are no longer concentrated in the same point due to aberration, which can be used to evaluate the imaging quality of the near-eye display module. Referring to Figure 12 , the maximum value of the image point in the point spread diagram corresponds to the maximum field of view, and the maximum value of the image point in the point spread diagram is less than 10μm.

[0169] The distortion diagram reflects the difference in image plane position of different fields of view to form a clear image. Referring to Figure 12 , the maximum distortion occurs at 1 field of view, and the maximum value is less than 37%. The field curvature diagram reflects the difference in image plane position of different fields of view to form a clear image. Referring to Figure 13 ​The maximum field curvature occurs near 1 field, and the maximum value is less than 0.2 mm.

[0170] The axial chromatic aberration is also called the magnification chromatic aberration, and mainly refers to a complex color chief ray in the object side, which becomes multiple rays when exiting the image side due to the chromatic dispersion of the refractive system. The difference between the focal point positions of blue light and red light on the image plane is the axial chromatic aberration. For details, refer to Figure 14 As shown in FIG. 6, the maximum chromatic aberration of the near-eye display module is less than 400 μm.

[0171] Embodiment 3

[0172] The near-eye display module provided in Embodiment 3 is different from the near-eye display module provided in Embodiment 1 in that: Figures 15 to 18

[0173] The absolute value of the ratio of the curvature radius of the Fresnel surface of the first lens 10 to the focal length of the near-eye display module satisfies 14.53; and the absolute value of the ratio of the curvature radius of the Fresnel surface of the second lens 20 to the focal length of the near-eye display module satisfies 1.58.

[0174] The absolute value of the ratio of the focal length of the second lens 20 to the focal length of the first lens 10 satisfies 13.7.

[0175] The distance L between the first lens 10 and the second lens 20 is set to 0.81 mm.

[0176] Table 3 shows the specific optical parameters of each lens in the near-eye display module provided in Embodiment 3.

[0177] Table 3

[0178]

[0179] For the near-eye display module provided in Embodiment 3, the optical performance can be as shown in FIG. 7. Figure 15 Figure 16 is a MTF curve diagram of the near-eye display module, Figure 17 is a point array diagram of the near-eye display module, Figure 18 is a field curvature distortion diagram of the near-eye display module, Figure 15 is an axial chromatic aberration diagram of the near-eye display module.

[0180] The MTF curve diagram is a modulation transfer function diagram, and the imaging clarity of the near-eye display module is represented by the contrast of the black and white lines. For details, refer to Figure 16 As shown in FIG. 8, the MTF is greater than 0.45 at 60 lp / mm, and the imaging is clear.

[0181] ​​The point spread diagram refers to a dispersed diagram formed by a plurality of light rays emitted from a point and then passing through the near-eye display module, and the intersection points of the light rays with the image plane are no longer concentrated at the same point due to aberration. The point spread diagram can be used to evaluate the imaging quality of the near-eye display module. See Figure 17 As shown in FIG. 6, the maximum value of the image point in the point spread diagram corresponds to the maximum field of view, and the maximum value of the image point in the point spread diagram is less than 6 μm.

[0182] The distortion diagram reflects the difference in the image plane position of a clear image at different fields of view. See Figure 17 As shown in FIG. 7, the maximum distortion occurs at 1 field of view, and the maximum value is less than 35%. The field curvature diagram reflects the difference in the image plane position of a clear image at different fields of view. See Figure 18 The maximum field curvature occurs near 1 field of view, and the maximum value is less than 0.2 mm.

[0183] The axial chromatic aberration, also known as the magnification chromatic aberration, mainly refers to a primary light ray of a complex color in the object side, which becomes a plurality of light rays when exiting the image side due to the dispersion of the refractive system. The difference in the focal point position of the blue light and the red light on the image plane. See ​ As shown in FIG. 8, the maximum chromatic aberration of the near-eye display module is less than 400 μm.

[0184] According to another aspect of the embodiments of the present application, a wearable device is also provided, which includes a housing and the near-eye display module as described above.

[0185] The wearable device is, for example, a head-mounted display device.

[0186] The head-mounted display device is, for example, a VR head-mounted device, including a VR glasses or a VR helmet, and the like, and the embodiments of the present application do not specifically limit this.

[0187] The specific implementation of the wearable device of the embodiments of the present application can refer to the above-mentioned near-eye display module embodiments, and thus at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described here.

[0188] The above embodiments mainly describe the differences between the embodiments, and the optimization features different between the embodiments can be combined to form a more optimal embodiment as long as they are not contradictory. Considering the brevity of the writing, this will not be described here.

[0189] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, but not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A near-eye display module, comprising: The imaging lens group, a light splitting element (40), a first phase retarder (50), and a polarization reflection element (60) are included; the first phase retarder (50) is located between the light splitting element (40) and the polarization reflection element (60). The imaging lens group includes at least two lenses, and at least two Fresnel surfaces are arranged in the imaging lens group, the Fresnel surfaces are located between the light splitting element (40) and the polarization reflection element (60), and the absolute value of the ratio of the radius of curvature of the Fresnel surface to the focal length of the near-eye display module satisfies 1-20. The near-eye display module further includes a display assembly (30), and the display assembly (30) includes a support plate (31) and a display screen (32) embedded in the support plate (31). The light splitting element (40) is located between the support plate (31) and the imaging lens group. The height h1 of the light splitting element (40) and the height h2 of the display screen (32) satisfy h1>h2; wherein the height direction of the light splitting element (40) and the display screen (32) is perpendicular to the optical axis of the imaging lens group. The imaging lens group includes a first lens (10) and a second lens (20) arranged adjacent to and spaced apart, wherein the first lens (10) is located between the display assembly (30) and the second lens (20), the first lens (10), the second lens (20), and the display screen (32) are located on the same optical axis, and the distance L between the first lens (10) and the second lens (20) is set as L>0.2mm. The two surfaces of the first lens (10) and the second lens (20) adjacent to each other are set as Fresnel surfaces. The total length TTL of the optical system of the near-eye display module satisfies TTL<10mm.

2. The near-eye display module of claim 1, wherein, The maximum incident angle of the incident light rays into the first phase retarder (50) and the polarization reflection element (60) is <15°.

3. The near-eye display module of claim 1, wherein, The maximum incident angle of the incident light rays into the first phase retarder (50) and the polarization reflection element (60) is <5°.

4. The near-eye display module of claim 1, wherein, The absolute value of the ratio of the radius of curvature of the Fresnel surface of the first lens (10) to the focal length of the near-eye display module satisfies 1-20. The absolute value of the ratio of the radius of curvature of the Fresnel surface of the second lens (20) to the focal length of the near-eye display module satisfies 1-2.

5. The near-eye display module of claim 1, wherein, The support plate (31) includes a fifth surface (311) and a sixth surface (312), the sixth surface (312) is close to the first lens (10), and the light splitting element (40) is arranged on the sixth surface (312). The fifth surface (311) is provided with a containing groove recessed toward the sixth surface (312), and the display screen (32) is located in the containing groove; wherein the distance l between the sixth surface (312) and the bottom wall of the containing groove is greater than 0.

6. The near-eye display module of claim 1, wherein, The near-eye display module further comprises a first polarization element (70), the first phase retarder (50), the polarization reflection element (60) and the first polarization element (70) are stacked to form a composite film, the composite film is arranged on the surface of the second lens (20) away from the display assembly (30), and the surface of the second lens (20) close to the display assembly (30) is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure. The surface of the first lens (10) close to the display assembly (30) is aspherical, and the surface of the first lens (10) away from the display assembly (30) is a Fresnel surface, and the surface of the Fresnel surface has a tooth-shaped structure.

7. The near-eye display module of claim 1, wherein, The optical power of the first lens (10) and the second lens (20) is set to be positive.

8. The near-eye display module of claim 1, wherein, The absolute value of the ratio of the focal length of the second lens (20) to the first lens (10) satisfies 0.1-20.

9. The near-eye display module of claim 1, wherein, The display screen (32) is configured to emit circularly polarized light or natural light. When the light emitted by the display screen (32) is natural light, a superposition sheet is arranged on the light emitting surface of the display screen (32), which can be used to convert the natural light emitted by the display screen (32) into circularly polarized light; wherein the superposition sheet comprises a second phase retarder, a third phase retarder and a second polarization element between the second phase retarder and the third phase retarder.

10. A wearable device, comprising: Comprise: a housing; and The near-eye display module of any one of claims 1-9.

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