Lens assembly and near-eye display device

Abstract

The present application provides a lens assembly, comprising: a first lens, comprising a first surface and a second surface; a second lens, arranged on one side of the first lens, wherein the second lens comprises a third surface and a fourth surface, and the third surface is adjacent to the second surface; a semi-transmissive and semi-reflective film, attached to the third surface; a composite film layer, attached to the fourth surface; a third lens, arranged on the side of the composite film layer distant from the second lens, wherein the third lens comprises a fifth surface and a sixth surface, and the fifth surface is adjacent to the composite film layer; and a fourth lens, arranged on the side of the third lens distant from the composite film layer, wherein the fourth lens comprises a seventh surface and an eighth surface, and the seventh surface is adjacent to the sixth surface. The composite film layer comprises a phase retardation layer and a reflective polarization layer, and the phase retardation layer is close to the fourth surface. The present application further provides a near-eye display device comprising the lens assembly.

Description

Lens assembly and near-eye display device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to a Chinese patent filed with the China Patent Office on December 8, 2023, with application number 202311695784.X and application name “Lens group and near-eye display device,” the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to a lens assembly and a near-eye display device including the lens assembly. Background Art

[0004] The spatial resolution of near-eye display devices is usually judged by the number of pixels per unit field of view (Pixels Per Degree, PPD), that is, the angular resolution. Currently, near-eye display devices using folded optical path technology can only reach about 20PPD, while the resolution limit of human eye recognition is about 60PPD. Therefore, users will observe obvious pixel particles when using near-eye display devices. In order to achieve high resolution, while improving the resolution of the display screen, it is also necessary to improve the resolution of the lens group. Currently, near-eye display devices that use two to three lenses to form a lens group are usually unable to achieve high resolution due to the limitations of the curvature of a single lens and the bonding process between lenses.

[0005] Summary of the Invention

[0006] On one hand, the present application provides a lens assembly, comprising:

[0007] a first lens comprising a first surface and a second surface;

[0008] a second lens disposed on one side of the first lens, the second lens comprising a third surface and a fourth surface, the third surface being adjacent to the second surface;

[0009] a semi-transparent and semi-reflective membrane attached to the third surface;

[0010] a composite film layer adhered to the fourth surface;

[0011] a third lens disposed on a side of the composite film layer away from the second lens, the third lens comprising a fifth surface and a sixth surface, the fifth surface being adjacent to the composite film layer; and

[0012] a fourth lens, disposed on a side of the third lens away from the composite film layer, the fourth lens comprising a seventh surface and an eighth surface, the seventh surface being adjacent to the sixth surface;

[0013] The composite film layer includes a phase retardation layer and a reflective polarization layer, and the phase retardation layer is close to the fourth surface.

[0014] The lens group provided in the embodiment of the present application adopts four lenses, and a composite film layer is set on the fourth surface, and a semi-transparent and semi-reflective film is set on the third surface. It can make the light return between the third surface and the fourth surface, thereby expanding the total length of the optical path. At the same time, by setting the third lens and the fourth lens, the returned light can be further modulated, which is beneficial to achieving high resolution while reducing the lens curvature.

[0015] In one embodiment, the first surface is a plane, and the first surface is provided with a light-transmitting area and a light-shielding area, the light-transmitting area is used to transmit image light, and a light-shielding layer is provided on the light-shielding area.

[0016] In one embodiment, a first adhesive layer is provided between the first lens and the second lens, a second adhesive layer is provided between the composite film layer and the third lens, and a third adhesive layer is provided between the third lens and the fourth lens.

[0017] In one embodiment, the refractive indexes of the first lens, the second lens, the third lens, and the fourth lens are all 1.46-1.58; and the refractive indexes of the first adhesive layer, the second adhesive layer, and the third adhesive layer are all 1.45-1.7.

[0018] In one embodiment, optical coatings are provided on surfaces of the first lens, the third lens, and the fourth lens, and the refractive index of the optical coatings is between the refractive index of the first lens and the refractive index of the first adhesive layer.

[0019] In one embodiment, the lens assembly further includes a linear polarization layer, the linear polarization layer is adhered to the eighth surface, and a transmission axis of the linear polarization layer is in the same direction as a transmission axis of the reflective polarization layer.

[0020] In one embodiment, the eighth surface is a plane.

[0021] In one embodiment, the second surface, the third surface, the fourth surface, the fifth surface, the sixth surface, and the seventh surface are all curved surfaces that are bent toward the first surface.

[0022] Another aspect of the present application provides a near-eye display device, comprising:

[0023] The above-mentioned lens assembly; and

[0024] A display screen is arranged on a side of the first lens away from the second lens, and is used for incident image light onto the first surface.

[0025] In one embodiment, the image light incident on the first surface is circularly polarized light.

[0026] In one embodiment, the display screen is attached to the first surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic structural diagram of a lens assembly in one embodiment of the present application.

[0028] FIG2 is a schematic diagram of the optical path of a lens assembly in an embodiment of the present application.

[0029] FIG3 is a schematic diagram of the polarization direction of light on the eighth surface in one embodiment of the present application.

[0030] FIG4 is a schematic diagram of the polarization direction of light on the eighth surface in a pair of comparisons of the present application.

[0031] FIG5 is a diagram showing a resolution test of a lens assembly in an embodiment of the present application.

[0032] FIG6 is a resolution test diagram of a lens assembly in a pair of ratios of the present application.

[0033] FIG7 is a resolution test diagram of a lens assembly in another comparative example of the present application.

[0034] FIG8 is a schematic structural diagram of a near-eye display device in one embodiment of the present application.

[0035] Description of main component symbols:

[0036] Lens group 100

[0037] First lens 10

[0038] First surface 12

[0039] Light-transmitting area 121

[0040] Shade area 123

[0041] Second surface 14

[0042] First adhesive layer 21

[0043] Second adhesive layer 23

[0044] The third adhesive layer 25

[0045] Fourth adhesive layer 27

[0046] Second lens 30

[0047] Semi-transparent and semi-reflective membrane 31

[0048] Third surface 32

[0049] Fourth surface 34

[0050] Composite film layer 40

[0051] Phase retardation layer 41

[0052] Reflective polarizing layer 43

[0053] The third lens 50

[0054] Fifth surface 52

[0055] Sixth surface 54

[0056] Fourth lens 60

[0057] Seventh surface 62

[0058] Eighth surface 64

[0059] Linear polarization layer 65

[0060] Light shielding layer 70

[0061] Near-eye display device 200

[0062] Display 210

[0063] Polarizing film 211

[0064] Human Eye E

[0065] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0066] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0067] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0068] In order to further illustrate the technical means and effects adopted by this application to achieve the intended purpose, the following detailed description of this application is made in conjunction with the accompanying drawings and preferred implementation methods.

[0069] Referring to FIG. 1 , an embodiment of the present application provides a lens assembly 100 comprising a first lens 10, a semi-transparent and semi-reflective film 31, a second lens 30, a composite film layer 40, a third lens 50, and a fourth lens 60, arranged in sequence. The first lens 10 comprises a first surface 12 and a second surface 14, the second lens 30 comprises a third surface 32 and a fourth surface 34, the third surface 32 and the second surface 14 being adjacent, and the semi-transparent and semi-reflective film 31 is bonded to the third surface 32. The composite film layer 40 is bonded to the fourth surface 34, and the composite film layer 40 comprises a phase retardation layer 41 and a reflective polarization layer 43, wherein the phase retardation layer 41 is adjacent to the fourth surface. The third lens 50 comprises a fifth surface 52 and a sixth surface 54, wherein the fifth surface 52 is adjacent to the composite film layer 40. The fourth lens 60 comprises a seventh surface 62 and an eighth surface 64, wherein the seventh surface 62 is adjacent to the sixth surface 54.

[0070] Referring to Figures 1 and 2 , the lens assembly 100 provided in an embodiment of the present application has a first lens 10 configured to receive circularly polarized image light and direct the image light through the fourth lens to the human eye E. Specifically, the image light enters the lens assembly 100 from the first surface 12 . Upon entering the transflective film 31 , half of the image light's energy passes through the film 31 and enters the composite film layer 40 . The phase retarder layer 41 is configured to convert the circularly polarized image light into linearly polarized light. The image light, after passing through the phase retarder layer 41 for the first time, is reflected by the reflective polarizing layer 43 . After passing through the phase retarder layer 41 for the second time, the image light enters the transflective film 31 again. A portion of the image light (at this point, the image light's energy is one-quarter of what it was before entering the lens assembly 100 ) is reflected back to the composite film layer 40 by the transflective film 31 . After passing through the phase retarder layer 41 for the third time, the linearly polarized image light continues to pass through the reflective polarizing layer 43 , passes through the third lens 50 , and finally enters the human eye E.

[0071] Continuing with Figure 1 , in this embodiment, the first surface 12 is a planar surface. A light-transmitting region 121 and a light-shielding region 123 are provided on the first surface 12. The light-transmitting region 121 transmits image light, while the light-shielding region 123 is provided with a light-shielding layer 70 to block stray light. Specifically, the light-transmitting region 121 is located in the center of the first surface 12, while the light-shielding region 123 is located in the peripheral region of the first surface 12, surrounding the light-transmitting region 121. The light-shielding layer 70 may be a blackened metal or other black material to block stray light other than the image light.

[0072] In this embodiment, the refractive index of the first lens 10, the second lens 30, the third lens 50, and the fourth lens 60 are all 1.46-1.58. Specifically, they can be any value in the range of 1.46-1.48, 1.48-1.5, 1.5-1.52, 1.52-1.54, 1.54-1.56, or 1.56-1.58, and this application does not impose any limitation on this.

[0073] A first adhesive layer 21 is provided between the first lens 10 and the second lens 30 for bonding the first lens 10 to the second lens 30 coated with a semi-transparent and semi-reflective film 31. A second adhesive layer 23 is provided between the second lens 30 and the composite film layer 40, and a third adhesive layer 25 is provided between the third lens 50 and the fourth lens 60. The first adhesive layer 21, the second adhesive layer 23, and the third adhesive layer 25 can be transparent adhesive materials such as optical adhesive or liquid optical adhesive, and this application does not impose any restrictions on this. The first lens 10, the second lens 30, the third lens 50, and the fourth lens 60 bonded by the first adhesive layer 21, the second adhesive layer 23, and the third adhesive layer 25 can have inconsistent surface shapes between any two adjacent surfaces, and the gap between the two surfaces can be filled with adhesive.

[0074] The refractive index of the first adhesive layer 21, the second adhesive layer 23, and the third adhesive layer 25 are all 1.45-1.7. Specifically, the refractive index can be any value in the range of 1.45-1.46, 1.46-1.48, 1.48-1.5, 1.5-1.52, 1.52-1.54, 1.54-1.56, -1.56-1.58, 1.58-1.6, 1.6-1.62, 1.62-1.64, 1.64-1.66, 1.66-1.68, or 1.68-1.7, and the present application does not impose any limitation thereto.

[0075] In this embodiment, the surfaces of the first lens 10, the third lens 50, and the fourth lens 60 are all provided with an optical coating (not shown). The refractive index of the optical coating is between the refractive indices of the first lens 10, the third lens 50, and the fourth lens 60, and the refractive indices of the first adhesive layer 21, the second adhesive layer 23, and the third adhesive layer 25, thereby achieving a refractive index transition. In other embodiments, the optical coating may also be an anti-reflection layer, an anti-fouling layer, or the like, which is not limited in this application.

[0076] In this embodiment, the lens assembly 100 further includes a linear polarizing layer 65, which is attached to the eighth surface 64. The transmission axis of the linear polarizing layer 65 is aligned with the transmission axis of the reflective polarizing layer 43. Specifically, the linear polarizing layer 65 is configured to allow light of a specific polarization direction to pass therethrough. By aligning the transmission axis of the linear polarizing layer 65 with the transmission axis of the reflective polarizing layer 43, image light emitted from the reflective polarizing layer 43 can pass through the linear polarizing layer 65 before entering the human eye E, while filtering out other stray light.

[0077] In this embodiment, the eighth surface 64 is a plane. Specifically, please refer to Figures 3 and 4 , where the horizontal and vertical coordinates represent the coordinates of the lens cross section, and the line segments in the figures represent the polarization directions of the linearly polarized light. Due to limitations of the lens structure, when the eighth surface 64 is not a plane, distortion occurs at the edges. Specifically, when the linearly polarized light emitted from the reflective polarizing layer 43 passes through the third lens 50 and the fourth lens 60, polarization error occurs at the edges of the lens. This causes the polarization direction of the linearly polarized light to change, reducing the brightness of the light passing through the linear polarizing layer 65 and thus affecting the user's viewing experience. However, by making the eighth surface 64 a plane, it can be seen that the linearly polarized light emitted from the eighth surface does not experience polarization error, thereby ensuring the brightness of the image at the edges.

[0078] In this embodiment, the second surface 14, the third surface 32, the fourth surface 34, the fifth surface 52, the sixth surface 54, and the seventh surface 62 are all curved surfaces that are convex toward the first surface 12. That is, with the exception of the first surface 12 and the eighth surface 64, the other surfaces in the lens assembly 100 have the same curved surface orientation, facilitating the lamination process. In other embodiments, the eighth surface 64 may also be a surface that is convex toward the first surface 12, as shown in FIG2 , but this application is not limited thereto.

[0079] In this embodiment, the thickness of the first lens 10 at its center is 0.2-3 mm, the thickness of the second lens 30 at its center is 8-12 mm, the thickness of the third lens 50 at its center is 1-4 mm, and the thickness of the fourth lens 60 at its center is 1.5-4.5 mm. Since the image light is primarily folded in the second lens 30, the thickness of the second lens 30 is greater than that of the other lenses, thereby extending the overall optical path of the image light.

[0080] The lens assembly 100 provided in the embodiment of the present application is further described below in conjunction with specific embodiments and comparative examples.

[0081] Example 1

[0082] The lens assembly 100 provided in Example 1 has a third surface 32 with a radius of curvature ranging from -29 mm to -32 mm, a fourth surface 34 with a radius of curvature ranging from -20 mm to -35 mm, a sixth surface 54 with a radius of curvature ranging from -60 mm to -85 mm, and an eighth surface 64 with a radius of curvature ranging from -70 mm to -90 mm. Referring to FIG5 , the resolution test chart shows that the lens assembly 100 of Example 1 has a resolution greater than 0.6 at various field angles, tangential and sagittal directions, and at both center and edge positions, demonstrating high resolution. When used in near-eye display devices, it can achieve a resolution of 60 PPD.

[0083] Comparative Example 1

[0084] The lens group provided in Comparative Example 1 is different from the lens group 100 provided in Example 1 in that it only includes a first lens, a second lens and a third lens, a semi-transparent and semi-reflective film is arranged between the first lens and the second lens, and a composite film layer is arranged between the second lens and the third lens. Among them, the first surface of the first lens is a plane, the radius of curvature of the third surface is -29mm to -32mm, the radius of curvature of the fourth surface is -29mm to -32mm, and the radius of curvature of the sixth surface is -80mm to -84mm. Please refer to Figure 6. It can be seen from the resolution test chart that at a larger field of view angle, the resolution of the lens group at the edge position will be 0.6. Therefore, the lens group provided in Comparative Example 1 cannot achieve a resolution of 60PPD when applied to a near-eye display device.

[0085] Comparative Example 2

[0086] The lens assembly provided in Comparative Example 2 differs from the lens assembly in Example 1 in that a transflective film is positioned between the second and third lenses, and a composite film layer is positioned between the third and fourth lenses. Referring to Figure 7, the resolution test chart shows that at wider field angles, the resolution of the lens assembly drops below 0.6 at the edges. Therefore, the lens assembly provided in Comparative Example 2 cannot achieve a resolution of 60 PPD when used in near-eye displays.

[0087] Comparative Example 3

[0088] The lens group provided in Comparative Example 3 is a simulation test, which only includes the first lens, the second lens and the third lens. The semi-transparent and semi-reflective film is arranged between the first lens and the second lens, and the composite film layer is arranged between the second lens and the third lens, and the lens group can achieve a high-resolution situation. According to the simulation results, the radius of curvature of the third surface of the second lens is -10mm to -20mm, and the radius of curvature of the fourth surface of the second lens is -10mm to -20mm. Because the radius of curvature of the third surface and the fourth surface is too small, while causing the field of view angle to become smaller, in the actual production process, it is impossible to attach the semi-transparent and semi-reflective film and the composite film layer to the second lens. Therefore, the lens group of Comparative Example 3 cannot obtain an actual product and can only be simulated.

[0089] In summary, the lens assembly 100 provided in the embodiment of the present application, by arranging a first lens 10, a second lens 30, a third lens 50, and a fourth lens 60, with a transflective film 31 disposed between the first lens 10 and the second lens 30, and a composite film layer 40 disposed between the second lens 30 and the third lens 50, can achieve high resolution at a large radius of curvature. This not only meets the requirements of the near-eye display 60PPD, but also meets the process requirements of actual production.

[0090] Please refer to Figure 8. An embodiment of the present application also provides a near-eye display device 200, which includes the lens group 100 in the above embodiment and a display screen 210. The display screen 210 is arranged on the side of the first lens 10 away from the second lens 30, and is used to emit image light to the lens group 100.

[0091] The image light incident on the first surface 12 is circularly polarized. Specifically, in order to achieve the reversal of the image light path through the combination of the composite film layer 40 and the transflective film 31, the image light incident on the first surface 12 needs to be configured as circularly polarized light. In this embodiment, a polarizing film 211 can be provided on the light-emitting surface of the display screen 210 to convert the light emitted by the display screen 210 into circularly polarized light. In other embodiments, the structure of the display screen 210 can also be configured so that the display screen 210 directly emits circularly polarized light, which is not limited in this application.

[0092] In this embodiment, the display screen 210 is attached to the first surface 12. Specifically, a fourth adhesive layer 27 is disposed between the display screen 210 and the first surface 12. The fourth adhesive layer 27 may be optical adhesive, liquid optical adhesive, or other transparent adhesive material. In other embodiments, the display screen 210 may be fixed to the first lens 10 using other methods, which are not limited in this application.

[0093] In this embodiment, the resolution of the display screen 210 is 11264*6336, i.e., 11K resolution. When used with the lens assembly 100, the near-eye display device 200 can achieve a resolution of 60PPD, thereby reaching the retinal resolution. In other embodiments, the resolution of the display screen 210 can also be higher than 11K, and this application does not limit this.

[0094] The near-eye display device 200 provided in the embodiment of the present application can achieve a high resolution of 60PPD by setting a display screen 210 in combination with a lens group 100, and the bonding process of the lens group is simple and easy to assemble.

[0095] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. A lens group, characterized in that, it includes: A first lens, including a first surface and a second surface; A second lens, disposed on one side of the first lens, the second lens includes a third surface and a fourth surface, and the third surface is adjacent to the second surface; A semi-transmissive semi-reflective film, attached to the third surface; A composite film layer, attached to the fourth surface; A third lens, disposed on the side of the composite film layer away from the second lens, the third lens includes a fifth surface and a sixth surface, and the fifth surface is adjacent to the composite film layer; and A fourth lens, disposed on the side of the third lens away from the composite film layer, the fourth lens includes a seventh surface and an eighth surface, and the seventh surface is adjacent to the sixth surface; wherein, the composite film layer includes a phase retardation layer and a reflective polarization layer, and the phase retardation layer is close to the fourth surface.

2. The lens group according to claim 1, characterized in that, The first surface is a plane, and a light-transmitting area and a light-shielding area are provided on the first surface. The light-transmitting area is used for transmitting image light, and a light-shielding layer is provided on the light-shielding area.

3. The lens group according to claim 1, characterized in that, A first adhesive layer is provided between the first lens and the second lens, a second adhesive layer is provided between the composite film layer and the third lens, and a third adhesive layer is provided between the third lens and the fourth lens.

4. The lens group according to claim 3, characterized in that, The refractive indices of the first lens, the second lens, the third lens and the fourth lens are all 1.46 - 1.58; the refractive indices of the first adhesive layer, the second adhesive layer and the third adhesive layer are all 1.45 - 1.

7.

5. The lens group according to claim 4, characterized in that, Optical coatings are provided on the surfaces of the first lens, the third lens and the fourth lens, and the refractive index of the optical coating is between the refractive index of the first lens and the refractive index of the first adhesive layer.

6. The lens group according to claim 1, characterized in that, It further includes a linear polarization layer, the linear polarization layer is attached to the eighth surface, and the transmission axis of the linear polarization layer is in the same direction as the transmission axis of the reflective polarization layer.

7. The lens group according to claim 6, characterized in that, The eighth surface is a plane.

8. The lens group according to claim 1, characterized in that, The second surface, the third surface, the fourth surface, the fifth surface, the sixth surface and the seventh surface are all curved surfaces convex in the direction towards the first surface.

9. A near-eye display device, characterized in that, it includes: The lens group according to any one of claims 1 to 8; and A display screen, disposed on the side of the first lens away from the second lens, for incident image light on the first surface.

10. The near-eye display device according to claim 9, characterized in that, The image light incident on the first surface is circularly polarized light.

11. The near-eye display device according to claim 9, characterized in that, The display screen is attached to the first surface.

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