Optical system and VR device

Abstract

An optical system and a VR device. The optical system is a straight-through optical structure, and along the direction of line of sight of human eyes, the optical system comprises a first lens (1), a second lens (2) and a third lens (3) which are arranged in sequence. The first lens (1), the second lens (2) and the third lens (3) are coaxially arranged. The first lens (1) and the second lens (2) have positive focal power, and the third lens (3) has negative focal power. The surface of the first lens (1) facing away from the second lens (2) is a convex surface, a concave surface or an aspheric surface, the surface of the first lens (1) facing the second lens (2) is a Fresnel surface, and the surface of the second lens (2) facing the first lens (1) is a Fresnel surface; or the surface of the first lens (1) facing away from the second lens (2) is a concave surface or an aspheric surface, the surface of the first lens (1) facing the second lens (2) is a Fresnel surface, and the surface of the second lens (2) facing the first lens (1) is an aspheric surface.

Description

Optical systems and VR devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311621159.0 filed in China on November 30, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of display product manufacturing, and in particular to an optical system and VR equipment. Background Art

[0004] With the development of virtual reality (VR) technology, the forms and types of VR devices are becoming increasingly diverse, and their application fields are becoming more and more extensive. Current VR devices usually transmit and amplify the display screen in the device through an optical system, and then transmit the output image to the human eye. Therefore, the human eye receives the magnified virtual image of the display screen, thereby achieving the purpose of large-screen viewing through VR devices.

[0005] With the development of VR technology, the demand for thin and light optical machines with a wide viewing angle has become increasingly urgent. Although mainstream pancake optical machines can achieve thinness and lightness, the overall lighting efficiency is greatly reduced, theoretically no more than 25%, and actually less than 20%, so the power consumption of the optical machine increases.

[0006] Summary of the Invention

[0007] In order to solve the above technical problems, the present disclosure provides an optical system and a VR device, which can improve the light efficiency while achieving ultra-lightness and thinness.

[0008] To achieve the above objectives, the technical solution adopted in the embodiments of the present disclosure is: an optical system, comprising a first lens, a second lens, and a third lens arranged in sequence from the image side to the object side, the first lens, the second lens, and the third lens being coaxially arranged, the first lens and the second lens having positive optical power, and the third lens having negative optical power;

[0009] The surface of the first lens facing away from the second lens is a convex surface, a concave surface or an aspheric surface, the surface of the first lens facing the second lens is a Fresnel surface, and the surface of the second lens facing the first lens is a Fresnel surface; or

[0010] The surface of the first lens facing away from the second lens is a concave surface or an aspherical surface, the surface of the first lens facing the second lens is a Fresnel surface, and the surface of the second lens facing the first lens is an aspherical surface.

[0011] Optionally, a surface of the first lens facing away from the second lens is a concave surface or an aspherical surface, a surface of the first lens facing the second lens is a Fresnel surface, and a surface of the second lens facing the first lens is a Fresnel surface;

[0012] The aperture of the first lens is D1, the focal length of the first lens is f1, the aperture of the second lens is D2, the focal length of the second lens is f2, the aperture of the third lens is D3, the focal length of the third lens is f3, and the overall focal length of the optical system is f;

[0013] The first lens, the second lens and the third lens satisfy the following conditions: 0.7<D1 / f1<1, 2<D2 / f2<3.3, -2.5<D3 / f3<-1.8, wherein: -1<f2 / f3<-0.8, 3<f1 / f2<4, 2<(f1+f2+f3) / f<3.

[0014] Optionally, a surface of the first lens facing away from the second lens is a concave surface or an aspherical surface, a surface of the first lens facing the second lens is a Fresnel surface, and a surface of the second lens facing the first lens is an aspherical surface; the aperture of the first lens is D1, the focal length of the first lens is f1, the aperture of the second lens is D2, the focal length of the second lens is f2, the aperture of the third lens is D3, the focal length of the third lens is f3, and the overall focal length of the optical system is f;

[0015] The first lens, the second lens and the third lens satisfy the following conditions: 0.5<D1 / f1<0.8, 1<D2 / f2<2, -1<D3 / f3<-0.5, wherein: -1<f2 / f3<-0.5, 2<f1 / f2<3, 1<(f1+f2+f3) / f<2.

[0016] Optionally, a surface of the first lens facing away from the second lens is a convex surface, a surface of the first lens facing the second lens is a Fresnel surface, and a surface of the second lens facing the first lens is a Fresnel surface;

[0017] The aperture of the first lens is D1, the focal length of the first lens is f1, the aperture of the second lens is D2, the focal length of the second lens is f2, the aperture of the third lens is D3, and the focal length of the third lens is f3;

[0018] The first lens, the second lens and the third lens satisfy the following conditions: 0.7<D1 / f1<1, 1<D2 / f2<2, -1.5<D3 / f3<-1, wherein: -1<f2 / f3<-0.5, 1<f1 / f2<2.

[0019] Optionally, the overall aperture D of the optical system satisfies the following condition: D<35 mm.

[0020] Optionally, the aperture of the first lens is D1, the aperture of the third lens is D3, the curvature radius of a surface of the first lens facing away from the second lens is r11, the curvature radius of a surface of the third lens facing the second lens is r31, and the curvature radius of a surface of the third lens facing away from the second lens is r32, wherein the first lens and the third lens meet the following conditions:

[0021] -30mm<r11<-15mm, -2<D1 / r11<-1.5;

[0022] -2<D3 / r31<-1.7, 1.5<D3 / r32<2.

[0023] Optionally, the eyebox range is greater than 8*8mm and the pupil distance is greater than 11mm.

[0024] Optionally, the optical system further includes an adjustment structure for adjusting the distance between the third lens and the display screen, the adjustment structure being configured such that when the distance between the third lens and the display screen is a first distance, the myopia of the human eye is zero, and when the distance between the third lens and the display screen is reduced by a preset distance nΔx, the myopia of the human eye is n*100, where n is a positive integer and n≤6, f is the focal length of the entire optical system.

[0025] Optionally, a surface of the second lens facing the third lens is a convex spherical surface or an aspherical surface.

[0026] Optionally, the surface shape of the third lens is plano-concave, concave-plano, or bi-concave spherical or aspherical.

[0027] Optionally, an antireflection film is provided on at least one of the light incident surface and the light exit surface of the first lens, the light incident surface and the light exit surface of the second lens, and the light incident surface and the light exit surface of the third lens.

[0028] Optionally, the Fresnel surface of the first lens includes a plurality of saw teeth arranged along the radial direction of the first lens, the saw teeth include an effective light incident surface and an invalid surface, the top angle θ of the saw teeth is greater than 40°, and the inclination angle α of the invalid surface relative to the radial direction of the first lens is less than 90°.

[0029] Optionally, the Fresnel surface of the second lens includes a plurality of saw teeth arranged along the radial direction of the second lens, the saw teeth include an effective light incident surface and an invalid surface, the top angle θ of the saw teeth is greater than 40°, and the inclination angle α of the invalid surface relative to the radial direction of the second lens is less than 90°.

[0030] An embodiment of the present disclosure further provides a VR device, comprising the above-mentioned optical system and a display screen, wherein the optical system is arranged on the light-emitting side of the display screen.

[0031] The beneficial effect of the present disclosure is that the optical system in the embodiment of the present disclosure includes a first lens, a second lens and a third lens arranged in sequence along the line of sight of the human eye. The first lens, the second lens and the third lens are matched through specific surface shapes to achieve an ultra-light and high-light-efficiency effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a first structural diagram of an optical system in an embodiment of the present disclosure;

[0033] FIG2 shows a second structural diagram of the optical system in an embodiment of the present disclosure;

[0034] FIG3 shows a third structural diagram of the optical system in an embodiment of the present disclosure;

[0035] FIG4 shows a fourth structural diagram of the optical system in an embodiment of the present disclosure;

[0036] FIG5 is a schematic structural diagram of a Fresnel surface in an embodiment of the present disclosure;

[0037] FIG6 is a schematic diagram showing light distribution in an embodiment of the present disclosure;

[0038] FIG7 is a schematic diagram showing a light effect curve in an embodiment of the present disclosure;

[0039] FIG8 is a first schematic diagram showing a modulation transfer function curve of the optical system in an embodiment of the present disclosure;

[0040] FIG9 is a second schematic diagram showing a modulation transfer function curve of the optical system in an embodiment of the present disclosure;

[0041] FIG10 is a first schematic diagram showing a distortion curve of the optical system in an embodiment of the present disclosure;

[0042] FIG11 shows a second schematic diagram of a distortion curve of the optical system in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0043] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0044] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by people with ordinary skills in the field to which this disclosure belongs. The words "first", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one", "an" or "the" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0045] An embodiment of the present disclosure provides a straight-through optical system, which is applied to a VR device. The light transmission is as follows: the image on the display screen of the VR device is transmitted and amplified through the optical system described in the embodiment of the present disclosure and then transmitted to the human eye. At this time, what the human eye receives through the optical system is a magnified virtual image of the display screen; that is, light is emitted from the display screen, and after being transmitted through the optical system, what is viewed by the human eye is a magnified inverted virtual image.

[0046] The optical system adopts a straight-through structure, eliminating the need for light to fold back and forth multiple times within the system, instead transmitting light along a single straight line. This results in high optical efficiency and resolution. When used on AR devices, it effectively enhances user immersion and provides a better user experience. Referring to Figure 7, the horizontal axis represents the field of view angle, and the vertical axis represents the illuminance. As can be seen from Figure 7, using the straight-through optical system in this embodiment, the light efficiency at all field of view angles is above 70%.

[0047] With reference to FIG1-FIG4, in some embodiments, this embodiment provides an optical system having a straight-through optical structure, comprising a first lens 1, a second lens 2, and a third lens 3 arranged sequentially from the image side to the object side, wherein the first lens 1, the second lens 2, and the third lens 3 are coaxially arranged, the first lens 1 and the second lens 2 have positive optical power, and the third lens 3 has negative optical power;

[0048] The surface of the first lens 1 facing away from the second lens 2 (i.e., the first surface 11) is a convex, concave, or aspherical surface, the surface of the first lens 1 facing the second lens 2 (i.e., the second surface 12) is a Fresnel surface, and the surface of the second lens 2 facing the first lens 1 (i.e., the third surface 21) is a Fresnel surface; or

[0049] The surface of the first lens 1 facing away from the second lens 2 is a concave surface or an aspherical surface, the surface of the first lens 1 facing the second lens 2 is a Fresnel surface, and the surface of the second lens 2 facing the first lens 1 is an aspherical surface.

[0050] It should be noted that the image side is the side observed by the human eye. When a user uses a VR device with the above-mentioned optical system, along the line of sight of the human eye M, the optical system includes a first lens 1, a second lens 2 and a third lens 3 arranged in sequence.

[0051] It should be noted that the display screen 10 in the VR device has the following parameters: the display screen image source size is 1.3 inches, and the AA area is 22.38*24.19 mm (the display screen 10 in FIG1 only shows the AA area).

[0052] 1 , in an exemplary embodiment, a surface of the first lens 1 facing away from the second lens 2 (i.e., the first surface 11 ) is a concave or aspherical surface, a surface of the first lens 1 facing the second lens 2 (i.e., the second surface 12 ) is a Fresnel surface, and a surface of the second lens 2 facing the first lens 1 (i.e., the third surface 21 ) is a Fresnel surface.

[0053] The aperture of the first lens 1 is D1, the focal length of the first lens 1 is f1, the aperture of the second lens 2 is D2, the focal length of the second lens 2 is f2, the aperture of the third lens 3 is D3, the focal length of the third lens 3 is f3, and the overall focal length of the optical system is f;

[0054] The first lens 1, the second lens 2 and the third lens 3 satisfy the following conditions: 0.7<D1 / f1<1, 2<D2 / f2<3.3, -2.5<D3 / f3<-1.8, wherein: -1<f2 / f3<-0.8, 3<f1 / f2<4, 2<(f1+f2+f3) / f<3.

[0055] Through the above settings, a VR lens system with ultra-short optical length (optical length <21.5mm), ultra-light and thin (the weight of the entire optical system is <15g), large FOV (field of view angle FOV >100°) and high light efficiency (light efficiency greater than 60%) can be achieved.

[0056] The optical length is the distance between the center point of the first lens 1 and the display screen 10 .

[0057] 2 , in an exemplary embodiment, a surface of the first lens 1 facing away from the second lens 2 (i.e., the first surface 11) is a concave or aspherical surface, a surface of the first lens 1 facing the second lens 2 (i.e., the second surface 12) is a Fresnel surface, and a surface of the second lens 2 facing the first lens 1 (i.e., the third surface 21) is an aspherical surface; the aperture of the first lens 1 is D1, the focal length of the first lens 1 is f1, the aperture of the second lens 2 is D2, the focal length of the second lens 2 is f2, the aperture of the third lens 3 is D3, the focal length of the third lens 3 is f3, and the overall focal length of the optical system is f;

[0058] The first lens 1, the second lens 2 and the third lens 3 satisfy the following conditions: 0.5<D1 / f1<0.8, 1<D2 / f2<2, -1<D3 / f3<-0.5, wherein: -1<f2 / f3<-0.5, 2<f1 / f2<3, 1<(f1+f2+f3) / f<2.

[0059] Through the above settings, a VR lens system with ultra-short optical length (optical length <21.5mm), ultra-light and thin (the weight of the entire optical system is <15g), large FOV (field of view angle FOV >100°) and high light efficiency (light efficiency greater than 70%) can be achieved.

[0060] The optical length is the distance between the center point of the first lens 1 and the display screen.

[0061] 3 , in an exemplary embodiment, a surface of the first lens 1 facing away from the second lens 2 (i.e., the first surface 11 ) is a convex surface, a surface of the first lens 1 facing the second lens 2 (i.e., the second surface 12 ) is a Fresnel surface, and a surface of the second lens 2 facing the first lens 1 (i.e., the third surface 21 ) is a Fresnel surface.

[0062] The aperture of the first lens 1 is D1, and the focal length of the first lens 1 is f1; the aperture of the second lens 2 is D2, and the focal length of the second lens 2 is f2; the aperture of the third lens 3 is D3, and the focal length of the third lens 3 is f3;

[0063] The first lens 1, the second lens 2 and the third lens 3 meet the following conditions: 0.7<D1 / f1<1, 1<D2 / f2<2, -1.5<D3 / f3<-1, wherein: -1<f2 / f3<-0.5, 1<f1 / f2<2.

[0064] Through the above settings, a VR lens system with ultra-short optical length (optical length <21.5mm), ultra-light and thin (the weight of the entire optical system is <15g), large FOV (field of view angle FOV >100°) and high light efficiency (light efficiency greater than 60%) can be achieved.

[0065] The optical length is the distance between the center point of the first lens 1 and the display screen.

[0066] It should be noted that the surface of the first lens 1 facing the second lens 2 is a Fresnel surface, and the surface of the second lens 2 facing the first lens 1 is a Fresnel surface. The Fresnel surface of the first lens 1 and the Fresnel surface of the second lens 2 may be the same or different, but both the Fresnel surface of the first lens 1 and the Fresnel surface of the second lens 2 satisfy the following conditions:

[0067] The Fresnel surface includes multiple concentrically arranged wedge-shaped rings or saw teeth. The saw teeth of the Fresnel surface include an effective light incident surface 101 and an ineffective surface 102. The top angle θ of the saw teeth of the Fresnel surface is greater than 40°, and the inclination angle α of the ineffective surface 102 is less than 90°, where α is 85°-88°, so as to facilitate demolding during actual processing. The saw tooth depth h of the Fresnel surface is less than 0.5 mm, refer to Figure 5.

[0068] The first lens 1 and the second lens 2 are both provided with a Fresnel surface, or the first lens 1 is provided with a Fresnel surface only. Regardless of the configuration, the structures of the Fresnel surface on the first lens 1 and the Fresnel surface on the second lens 2 may be the same or different, but both meet the above conditions.

[0069] Exemplarily, the Fresnel surface of the first lens 1 includes a plurality of saw teeth arranged along the radial direction of the first lens 1, the saw teeth including an effective light incident surface 101 and an invalid surface 102, the vertex angle θ of the saw teeth is greater than 40°, and the inclination angle α of the invalid surface 102 relative to the radial direction of the first lens 1 is less than 90°.

[0070] Exemplarily, the Fresnel surface of the second lens 2 includes a plurality of saw teeth arranged along the radial direction of the second lens 2, the saw teeth including an effective light incident surface and an invalid surface, the top angle θ of the saw teeth is greater than 40°, and the inclination angle α of the invalid surface relative to the radial direction of the second lens 2 is less than 90°.

[0071] In some embodiments, the Fresnel surface on the first lens 1 and the Fresnel surface on the second lens 2 further have the following structural features.

[0072] Exemplarily, the serrations of the Fresnel surface in FIG. 5 are of equal height, but the present invention is not limited thereto.

[0073] Exemplarily, the widths of the multiple saw teeth in the Fresnel surface gradually decrease from the center to the edge.

[0074] Exemplarily, the width of the multiple saw teeth on the Fresnel surface is 0.2-1.4 mm.

[0075] Exemplarily, the effective light incident surface of the sawtooth is a curved surface.

[0076] In an exemplary embodiment, the overall aperture D of the optical system satisfies the following condition: D<35 mm, see FIG1 .

[0077] It should be noted that the aperture D2 of the second lens 2 in FIG. 1 is the largest, but the present invention is not limited thereto.

[0078] In an exemplary embodiment, the aperture of the first lens 1 is D1, the aperture of the third lens 3 is D3, the curvature radius of the surface of the first lens 1 facing away from the second lens 2 is r11, the curvature radius of the surface of the third lens 3 facing the second lens 2 is r31, and the curvature radius of the surface of the third lens 3 facing away from the second lens 2 is r32. The first lens 1 and the third lens 3 satisfy the following conditions:

[0079] -30mm<r11<-15mm, -2<D1 / r11<-1.5;

[0080] -2<D3 / r31<-1.7, 1.5<D3 / r32<2.

[0081] Through the above settings, different FOV angles are controlled at different positions on the display screen, so that when the field of view angle is 0-60°, the magnification of the image on the display screen is about 140, and the corresponding PPD (Pixels Per Degree (angular resolution, which refers to the average number of pixels filled within every 1° angle in the field of view) is about 43, and light with a field of view angle of 60° corresponds to about 8.01 mm on the display screen (as shown in point a of FIG6 , light with a field of view angle of 0-60° corresponds to the first area 1001 of the display screen, and the first area 1001 is an area with a radius of 8.01 mm centered on the center point of the display screen); when the field of view angle is 60-100°, the magnification of the image on the display screen is 210 (light with a field of view angle of 60-100° corresponds to the second area 1002 of the display screen, and the second area 1002 is arranged outside the first area 1001, that is, the annular area between the circular area with a radius of 11.9 mm and the first area 1001 with a radius of 8.01 mm), and the corresponding PPD is about 26. Light with a field of view angle of 100° corresponds to about 11.19 mm on the display screen (see point b of FIG6 ). To meet the high PPD requirements of the human eye within 60°.

[0082] It should be noted that FIG6 only illustrates the light rays of half the field of view.

[0083] In an exemplary embodiment, the eyebox is greater than 8*8 mm and the pupil distance is greater than 11 mm. The human eye M is at an appropriate distance from the first lens 1 of the optical system (i.e., the pupil distance), which can effectively enhance the user's sense of immersion and bring a better user experience.

[0084] In an exemplary embodiment, an antireflection coating is provided on at least one of the light incident surface (i.e., second surface 12) and light exit surface (i.e., first surface 11) of the first lens 1, the light incident surface (i.e., fourth surface 22) and light exit surface (i.e., third surface 21) of the second lens 2, and the light incident surface (i.e., sixth surface 32) and light exit surface (i.e., fifth surface 31) of the third lens 3. The provision of an antireflection coating can increase light transmittance.

[0085] FIG8 is a schematic diagram of the modulation transfer function curve of the optical system when the field of view angle is within 60 degrees. When the limit resolution is 79 lp / mm within the 60° range (half field of view 30°) where the human eye is sensitive, the MTF value is greater than 0.1.

[0086] In Figure 8, in the modulation transfer function curve of the light with a field of view angle of 0 degrees, the MTF value is >0.35, in the modulation function curve of the light with a half field of view angle of 7.5 degrees, the MTF value is >0.18, in the modulation function curve of the light with a half field of view angle of 15 degrees, the MTF value is >0.21, in the modulation function curve of the light with a half field of view angle of 20 degrees, the MTF value is >0.11, and in the modulation function curve of the light with a half field of view angle of 30 degrees, the MTF value is >0.1.

[0087] Figure 9 shows a schematic diagram of the modulation transfer function curve of the optical system when the field of view angle is within 60 degrees to 100 degrees. When the maximum resolution of 35 lp / mm is achieved within the range of 60 degrees (half field of view 30 degrees) to 100 degrees (half field of view 50 degrees), which is insensitive to the human eye, the MTF value is greater than 0.1.

[0088] In Figure 9, in the modulation function curve of the light with a half field of view angle of 30 degrees, the MTF value is >0.45, in the modulation function curve of the light with a half field of view angle of 35 degrees, the MTF value is >0.22, in the modulation function curve of the light with a half field of view angle of 40 degrees, the MTF value is >0.1, in the modulation function curve of the light with a half field of view angle of 45 degrees, the MTF value is >0.4, and in the modulation function curve of the light with a half field of view angle of 49 degrees, the MTF value is >0.1.

[0089] Refer to Figures 10 and 11. Figure 10 shows the distortion curves for the optical system within a field of view of 60 degrees or less, and Figure 10 shows the distortion curves for a field of view of 100 degrees or less. The horizontal axis represents the distortion percentage, and the vertical axis represents the field of view (unit: degrees). As can be seen from Figures 10 and 11, the distortion within the 60° field of view, which is sensitive to the human eye, is less than 12%, and within the 60-100° field of view, the distortion is less than 42%, indicating that the optical system's distortion is well corrected.

[0090] It should be noted that both FIG. 10 and FIG. 11 illustrate distortion curves under half the field of view.

[0091] In an exemplary embodiment, the optical system is located on the light-emitting side of the display screen of the VR device. The optical system also includes an adjustment structure for adjusting the distance between the third lens 3 and the display screen. The adjustment structure is configured so that when the distance between the third lens 3 and the display screen is a first distance X (refer to FIG1 ), the myopia of the human eye is zero, and the distance between the third lens 3 and the display screen is reduced by a preset distance nΔx. Then, the myopia of the human eye is n*100, that is, for every 100-degree increase in the myopia of the viewer, the preset distance Δx can be reduced by reducing the distance between the third lens 3 and the display screen to obtain a better image. Wherein, n is a positive integer, and n≤6, f is the focal length of the entire optical system.

[0092] The setting of the adjustment structure makes the optical system suitable for people with myopia and non-myopic eyes, so that both people with myopia and non-myopic eyes have a better usage experience.

[0093] It should be noted that the specific structural form of the adjustment structure can be various. For example, the optical system includes a shell, the first lens 1, the second lens 2 and the third lens 3 are spirally connected in the shell, and the display screen is located at one end of the shell, so that the distance between the third lens 3 and the display screen can be adjusted by rotating the shell.

[0094] It should be noted that the relative positions of the first lens 1 , the second lens 2 and the third lens 3 remain unchanged.

[0095] In an exemplary embodiment, a surface of the second lens 2 facing the third lens 3 (ie, the fourth surface 22 ) is a convex spherical surface or an aspherical surface.

[0096] In an exemplary embodiment, the surface shape of the third lens 3 is a plano-concave, concave-plano, bi-concave spherical or aspherical surface.

[0097] 4 , in an exemplary embodiment, the second lens 2 and the third lens 3 may be connected together by gluing, which further reduces the size while being relatively friendly in terms of assembly and tolerance.

[0098] Exemplarily, the second lens 2 and the third lens 3 are connected together by gluing, and the optical length of the optical system can be less than 20 mm.

[0099] An embodiment of the present disclosure further provides a VR device, comprising the above-mentioned optical system and a display screen 10 , wherein the optical system is arranged on the light-emitting side of the display screen 10 .

[0100] The display screen 10 is used to transmit light signals including image information. For example, the display screen 10 can be one of Micro LED, OLED, LCD, LCOS, and M-OLED, providing users with high-definition and realistic images.

[0101] The optical system is located between the human eye M and the display screen 10. The optical system is arranged in the light-emitting direction of the display screen 10, and the third lens 3 is arranged closer to the display screen 10 than the first lens 1. The optical system is used to modulate the light signal emitted by the display screen 10 and transmit it to the human eye M. Image information emitted from the display screen 10 enters the human eye M through the optical system for formation of an image. The user can observe a high-definition, magnified virtual image, providing an extremely realistic sensory experience.

[0102] The VR device provided in this embodiment includes an optical system. Since the optical system has the advantages of short optical length, large field of view, high light efficiency, adjustable diopter (that is, the distance between the third lens 3 and the display screen is adjustable), and small size, the VR device with this optical system can achieve the advantages of ultra-short optical length (optical length <21.5mm), ultra-light and thin (the weight of the entire optical system is <15g), large FOV (field of view FOV>100°) and high light efficiency (light efficiency greater than 60%), as well as ultra-high resolution (true 4K display imaging), and can provide a good sensory experience for both myopic and non-myopic users when wearing it.

[0103] There are a few points to note:

[0104] (1) The drawings of the embodiments of the present disclosure only relate to the structures related to the embodiments of the present disclosure. Other structures may refer to conventional designs.

[0105] (2) For the sake of clarity, the thickness of layers or regions in the drawings used to describe the embodiments of the present disclosure are exaggerated or reduced, i.e., these drawings are not drawn to scale. It is understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, the element may be "directly" "on" or "under" the other element or intervening elements may be present.

[0106] (3) In the absence of conflict, the embodiments of the present disclosure and the features therein may be combined with each other to form new embodiments.

[0107] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. An optical system, wherein, the optical system comprises a first lens, a second lens, and a third lens arranged in sequence from the image side to the object side, the first lens, the second lens, and the third lens are arranged coaxially, the first lens and the second lens have positive optical power, and the third lens has negative optical power; The surface of the first lens facing away from the second lens is a convex surface, a concave surface or an aspherical surface, the surface of the first lens facing the second lens is a Fresnel surface, and the surface of the second lens facing the first lens is a Fresnel surface; or, A surface of the first lens facing away from the second lens is a concave surface or an aspherical surface, a surface of the first lens facing the second lens is a Fresnel surface, and a surface of the second lens facing the first lens is an aspherical surface.

2. The optical system according to claim 1, wherein: A surface of the first lens facing away from the second lens is a concave surface or an aspherical surface, a surface of the first lens facing the second lens is a Fresnel surface, and a surface of the second lens facing the first lens is a Fresnel surface; The aperture of the first lens is D1, the focal length of the first lens is f1, the aperture of the second lens is D2, the focal length of the second lens is f2, the aperture of the third lens is D3, the focal length of the third lens is f3, and the overall focal length of the optical system is f; The first lens, the second lens and the third lens satisfy the following conditions: 0.7<D1 / f1<1, 2<D2 / f2<3.3, -2.5<D3 / f3<-1.8, wherein: -1<f2 / f3<-0.8, 3<f1 / f2<4, 2<(f1+f2+f3) / f<3.

3. The optical system according to claim 1, wherein: The surface of the first lens facing away from the second lens is a concave surface or an aspherical surface, the surface of the first lens facing the second lens is a Fresnel surface, and the surface of the second lens facing the first lens is an aspherical surface; the aperture of the first lens is D1, the focal length of the first lens is f1, the aperture of the second lens is D2, the focal length of the second lens is f2, the aperture of the third lens is D3, the focal length of the third lens is f3, and the overall focal length of the optical system is f; The first lens, the second lens and the third lens satisfy the following conditions: 0.5<D1 / f1<0.8, 1<D2 / f2<2, -1<D3 / f3<-0.5, wherein: -1<f2 / f3<-0.5, 2<f1 / f2<3, 1< (f1+f2+f3) / f<2.

4. The optical system according to claim 1, wherein: The surface of the first lens facing away from the second lens is a convex surface, the surface of the first lens facing the second lens is a Fresnel surface, and the surface of the second lens facing the first lens is a Fresnel surface; The aperture of the first lens is D1, and the focal length of the first lens is f1; the aperture of the second lens is D2, and the focal length of the second lens is f2; the aperture of the third lens is D3, and the focal length of the third lens is f3; The first lens, the second lens and the third lens satisfy the following conditions: 0.7<D1 / f1<1, 1<D2 / f2<2, -1.5<D3 / f3<-1, wherein: -1<f2 / f3<-0.5, 1<f1 / f2<2.

5. The optical system according to claim 1, wherein: The diameter D of the largest lens among the first lens, the second lens and the third lens satisfies the following condition: D<35 mm.

6. The optical system according to claim 1, wherein: The aperture of the first lens is D1, the aperture of the third lens is D3, the curvature radius of the first lens facing away from the second lens is r11, the curvature radius of the third lens facing the second lens is r31, and the curvature radius of the third lens facing away from the second lens is r32, wherein the first lens and the third lens meet the following conditions: -30mm<r11<-15mm, -2<D1 / r11<-1.5; -2<D3 / r31<-1.7, 1.5<D3 / r32<2.

7. The optical system according to claim 1, wherein: Eyebox range>8*8mm, pupil distance>11mm.

8. The optical system according to claim 1, wherein: The optical system further includes an adjustment structure for adjusting the distance between the third lens and the display screen, the adjustment structure being configured such that when the distance between the third lens and the display screen is a first distance, the myopia degree of the human eye is zero, and when the distance between the third lens and the display screen is reduced by a preset distance nΔx, the myopia degree of the human eye is n*100, where n is a positive integer and n≤6, f is the focal length of the entire optical system.

9. The optical system according to claim 1, wherein: A surface of the second lens facing the third lens is a convex spherical surface or an aspherical surface.

10. The optical system according to claim 1, wherein: The surface shape of the third lens is plano-concave, concave-planar or bi-concave spherical or aspherical.

11. The optical system according to claim 1, wherein: An antireflection film is disposed on at least one of the light incident surface and the light exit surface of the first lens, the light incident surface and the light exit surface of the second lens, and the light incident surface and the light exit surface of the third lens.

12. The optical system according to claim 1, wherein: The Fresnel surface of the first lens includes a plurality of saw teeth arranged along the radial direction of the first lens, the saw teeth include an effective light incident surface and an invalid surface, the top angle θ of the saw teeth is greater than 40°, and the inclination angle α of the invalid surface relative to the radial direction of the first lens is less than 90°.

13. The optical system according to claim 1, wherein: The Fresnel surface of the second lens includes a plurality of saw teeth arranged along the radial direction of the second lens, the saw teeth include an effective light incident surface and an invalid surface, the top angle θ of the saw teeth is greater than 40°, and the inclination angle α of the invalid surface relative to the radial direction of the second lens is less than 90°.

14. A VR device, wherein: It comprises the optical system according to any one of claims 1 to 13, and a display screen, wherein the optical system is arranged on the light emitting side of the display screen.

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