Optical system and VR device including the same

Abstract

The present application discloses an optical system, which includes a first element group, a second element group, and a third element group in sequence from the first side to the second side along the optical axis, wherein the first element group includes a filter and a reflective polarizing element; the second element group has positive optical power and includes a quarter-wave plate and a first lens; the third element group includes a second lens, and the second lens has positive optical power or negative optical power. The effective focal length FG2 of the second element group, the center thickness CTF of the filter on the optical axis, the center thickness CTR of the reflective polarizing element on the optical axis, the center thickness CTQ of the quarter-wave plate on the optical axis, and the center thickness CT1 of the first lens on the optical axis satisfy the following conditions: 1.5 <FG2 / (CTF+CTR+CTQ+CT1)<3.0。

Description

Technical Field

[0001] The present application relates to the field of optical elements, and more specifically, to an optical system and a VR device including the optical system. Background Art

[0002] With the increasing demand for remote work and teleconferencing, people are increasingly demanding more diverse methods and experiences for online interactions. For example, to reduce the sense of distance during online interactions and enhance the realism of meetings, head-mounted devices (HMDs) are becoming an option for many companies. Virtual reality (VR) technology is maturing, and pancake-shaped headsets, in particular, are gaining popularity among consumers due to their ability to significantly reduce the thickness of the device, making them thinner and lighter.

[0003] However, due to the limitations of current film lamination technology, the degree of freedom of curved surfaces in optical systems is low, resulting in limited room for performance improvement in conventional structural systems. Therefore, how to effectively improve system performance through design optimization is one of the issues that technical personnel in this field need to address. Summary of the Invention

[0004] The present application provides an optical system, which may include a first element group, a second element group, and a third element group in sequence from the first side to the second side along the optical axis, wherein the first element group includes a filter and a reflective polarizing element; the second element group has positive optical power and includes a quarter-wave plate and a first lens; the third element group includes a second lens, and the second lens has positive optical power or negative optical power. The effective focal length FG2 of the second element group, the center thickness CTF of the filter on the optical axis, the center thickness CTR of the reflective polarizing element on the optical axis, the center thickness CTQ of the quarter-wave plate on the optical axis, and the center thickness CT1 of the first lens on the optical axis may satisfy the following conditions: 1.5 <FG2 / (CTF+CTR+CTQ+CT1)<3.0。

[0005] In one embodiment, the curvature radius R3 of the first side surface of the second lens and the curvature radius R2 of the second side surface of the first lens may satisfy: 1.3 <R3 / R2<3.0。

[0006] In one embodiment, the distance TD from the first side surface of the first lens to the second side surface of the second lens on the optical axis and the entrance pupil diameter EPD of the optical system may satisfy: 2.4 <TD / EPD<3.8。

[0007] In one embodiment, the optical system further comprises an aperture and an image surface disposed on the second side, and a distance SL from the aperture to the image surface on the optical axis and a distance ER from the aperture to the first side surface of the first lens on the optical axis may satisfy: 2.0 <SL / ER<2.5。

[0008] In one embodiment, the optical system further comprises an aperture, and a distance SD from the aperture to the second side surface of the second lens on the optical axis and an effective focal length f of the optical system may satisfy: 1.0 <SD / f<1.4。

[0009] In one embodiment, the optical system further includes an image surface provided on the second side, and the center thickness CT2 of the second lens on the optical axis and the distance BFL from the second side surface of the second lens to the image surface on the optical axis may satisfy: 0.2 <CT2 / BFL<3.8。

[0010] In one embodiment, the refractive index N2 of the second lens, the refractive index N1 of the first lens, and the center thickness CTQ of the quarter-wave plate on the optical axis may satisfy: 0.1 mm<(N2 / N1)×CTQ<0.6 mm.

[0011] In one embodiment, the effective focal length FG2 of the second element group, the effective focal length f of the optical system, and the maximum field of view FOV of the optical system may satisfy: 0.6 <FG2 / (f×tan(FOV / 2))<0.9。

[0012] In one embodiment, the curvature radius R1 of the first side surface of the first lens, the Abbe number VF of the filter, and the Abbe number V1 of the first lens may satisfy the following: 1.1 mm<|R1| / (VF+V1)<2.1 mm.

[0013] In one embodiment, a center thickness CT1 of the first lens on the optical axis and an air interval T12 between the first lens and the second lens on the optical axis may satisfy the following: 1.0<(CT1+T12) / (CT1-T12)<6.1.

[0014] In one embodiment, the effective focal length f of the optical system and the distance TD from the first side surface of the first lens to the second side surface of the second lens on the optical axis may satisfy: 1.5 <f / TD<2.4。

[0015] In one embodiment, the second side surface of the first lens is convex, and the first side surface of the second lens is concave.

[0016] On the other hand, the present application also provides a VR device, which includes the optical system provided by at least one of the above-described embodiments. Here, the first side is the human eye side, and the second side is the display side.

[0017] The optical system disclosed in the present application sequentially includes a first element group, a second element group, and a third element group along the optical axis from the first side to the second side. Among them, the first element group includes a filter and a reflective polarizing element. The two sides of the filter are flat, which is beneficial for the attachment of the reflective polarizing element. The reflective polarizing element reflects light in one direction and transmits light orthogonal to it, which is beneficial for realizing the refraction and reflection of the optical path. The second element group has a positive optical power, which is convenient for converging light rays to reduce the screen height. At the same time, it includes a quarter-wave plate for converting circularly polarized light and linearly polarized light. The third element group includes a second lens, which is beneficial for compensating the aberration of the first lens. At the same time, by controlling the effective focal length of the second element group, the central thickness of the filter on the optical axis, the central thickness of the reflective polarizing element on the optical axis, the central thickness of the quarter-wave plate on the optical axis, and the central thickness of the first lens on the optical axis to satisfy the conditional formula 1.5 < FG2 / (CTF + CTR + CTQ + CT1) < 3.0, it is possible to reasonably control the incident angle of light on the flat plate and avoid light leakage at large angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In combination with the accompanying drawings, through the following detailed description of non-limiting embodiments, other features, objectives, and advantages of the present application will become more obvious. In the drawings:

[0019] Figure 1 Shows a schematic structural diagram of the optical system according to Embodiment 1 of the present application;

[0020] Figures 2A to 2C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 1;

[0021] Figure 3 Shows a schematic structural diagram of the optical system according to Embodiment 2 of the present application;

[0022] Figures 4A to 4C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 2;

[0023] Figure 5 Shows a schematic structural diagram of the optical system according to Embodiment 3 of the present application;

[0024] Figures 6A to 6C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 3;

[0025] Figure 7shows a schematic structural diagram of an optical system according to embodiment 4 of the present application; and

[0026] Figures 8A to 8C The axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Example 4 are respectively shown. DETAILED DESCRIPTION

[0027] For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely descriptions of exemplary embodiments of the present application and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0028] It should be noted that in this specification, the terms "first," "second," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, without departing from the teachings of this application, the first optical lens discussed below could also be referred to as the second optical lens, and the second optical lens could also be referred to as the first optical lens.

[0029] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical and aspherical surfaces shown in the drawings are provided by way of example. That is, the shapes of the spherical and aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0030] In this article, the paraxial region refers to the region near the optical axis. If a lens surface is convex and the location of the convex surface is undefined, it means that the lens surface is convex at least in the paraxial region; if a lens surface is concave and the location of the concave surface is undefined, it means that the lens surface is concave at least in the paraxial region.

[0031] It should also be understood that the terms "comprises," "including," "having," "includes," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application." And, the term "exemplary" is intended to refer to an example or illustration.

[0032] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0033] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] The features, principles and other aspects of the present application are described in detail below.

[0035] According to an exemplary embodiment of the present application, an optical system may include a first element group, a second element group, and a third element group arranged in sequence from a first side to a second side along an optical axis, wherein the first element group may include a filter and a reflective polarizing element, the second element group may include a quarter-wave plate and a first lens, and the third element group may include a second lens.

[0036] In an exemplary embodiment, the second element group may have positive optical power.

[0037] In example embodiments, the second lens in the third element group may have positive or negative power.

[0038] In an exemplary embodiment, the first side may be, for example, the eye side, and the second side may be, for example, the display side. The optical system may be used, for example, in a head-mounted device. The optical elements included in the optical system, such as the filter, reflective polarizer, quarter-wave plate, first lens, and second lens, may be arranged in order along the optical axis from the eye side to the display side.

[0039] The following will refer to Figure 1 An example description of the optical system is given below. Figure 1As shown, the optical system according to an exemplary embodiment of the present application may include a filter IR, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a partial reflection element BS, and a second lens E2 arranged in sequence from the first side to the second side. Among them, the filter IR and the reflective polarizing element RP form a first element group, the quarter-wave plate QWP and the first lens E1 form a second element group, and the partial reflection element BS and the second lens E2 form a third element group. In actual use, the optical system according to an exemplary embodiment of the present application can be used as a VR lens. At this time, the first side corresponds to the human eye side, and the second side corresponds to the display side. The optical system may further include an image plane IMG located on the display side. The light beam emitted from the image plane IMG can sequentially pass through the second lens E2 and the partial reflection element BS of the third element group, as well as the first lens E1 and the quarter-wave plate QWP of the second element group, and reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the quarter-wave plate QWP and the first lens E1 again to reach the partial reflection element BS. After that, the light beam is reflected again at the reflection element BS and sequentially passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizing element RP, and the filter IR to be emitted toward the human eye side. In the exemplary embodiment, the partial reflection element BS may be a semi-transmissive and semi-reflective film layer coated on the first side surface of the second lens E2.

[0040] In the exemplary embodiment, the optical system of the present application may satisfy the condition 1.5 < FG2 / (CTF + CTR + CTQ + CT1) < 3.0, where FG2 is the effective focal length of the second element group, CTF is the central thickness of the filter on the optical axis, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ is the central thickness of the quarter-wave plate on the optical axis, and CT1 is the central thickness of the first lens on the optical axis.

[0041] An optical system according to an exemplary embodiment of the present application sequentially arranges a first element group, a second element group, and a third element group along the optical axis from the first side to the second side. Specifically, by setting the first element group to include a filter and a reflective polarizing element, wherein both sides of the filter are flat, which is conducive to the attachment of the reflective polarizing element. The reflective polarizing element reflects light in one direction and transmits light orthogonal to it, which is conducive to realizing the refraction and reflection of the optical path. By setting the second element group to have a positive optical power, it is convenient for light to converge to reduce the screen height, and at the same time includes a quarter-wave plate for converting circular polarization and linear polarization. By setting the third element group to include a second lens, it is conducive to compensating for the aberration of the first lens. At the same time, by controlling the effective focal length of the second element group, the central thickness of the filter on the optical axis, the central thickness of the reflective polarizing element on the optical axis, the central thickness of the quarter-wave plate on the optical axis, and the central thickness of the first lens on the optical axis to satisfy the conditional formula 1.5 < FG2 / (CTF + CTR + CTQ + CT1) < 3.0, the incident angle of light on the flat plate can be reasonably controlled to avoid light leakage at large angles.

[0042] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.3 < R3 / R2 < 3.0, where R3 is the curvature radius of the first side surface of the second lens, and R2 is the curvature radius of the second side surface of the first lens. By controlling the ratio of the curvature radius of the first side surface of the second lens to the curvature radius of the second side surface of the first lens within this range, the air gap between the first lens and the second lens can be reasonably restricted to ensure the assembly and support of the first lens and the second lens.

[0043] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 2.4 < TD / EPD < 3.8, where TD is the distance on the optical axis from the first side surface of the first lens to the second side surface of the second lens, and EPD is the entrance pupil diameter of the optical system. By controlling the ratio of the distance on the optical axis from the first side surface of the first lens to the second side surface of the second lens to the entrance pupil diameter of the optical system within this range, on the premise that the entrance pupil diameter is constant, the length of the optical system can be indirectly restricted, which is conducive to the thinning and lightening of the head-mounted device.

[0044] In an exemplary embodiment, the optical system of the present application may further include an aperture stop and an image plane provided on the second side, and the optical system of the present application can satisfy the conditional formula 2.0 < SL / ER < 2.5, where SL is the distance on the optical axis from the aperture stop to the image plane, and ER is the distance on the optical axis from the aperture stop to the first side surface of the first lens. By controlling the ratio of the distance on the optical axis from the aperture stop to the image plane to the distance on the optical axis from the aperture stop to the first side surface of the first lens within this range, when the optical powers of the first lens and the second lens are constant, it is conducive to controlling the field angle of the system.

[0045] In an exemplary embodiment, the optical system of the present application may further include an aperture, and the optical system of the present application may satisfy the conditional formula 1.0 < SD / f < 1.4, where SD is the distance from the aperture to the second side surface of the second lens on the optical axis, and f is the effective focal length of the optical system. By controlling the ratio of the distance from the aperture to the second side surface of the second lens on the optical axis to the effective focal length of the optical system within this range, it is beneficial to control the TTL ratio of the optical system. When the screen size is determined, it is beneficial to shorten the total length of the optical system.

[0046] In an exemplary embodiment, the optical system of the present application may further include an image plane provided on the second side, and the optical system of the present application may satisfy the conditional formula 0.2 < CT2 / BFL < 3.8, where CT2 is the central thickness of the second lens on the optical axis, and BFL is the distance from the second side surface of the second lens to the image plane on the optical axis. By controlling the ratio of the central thickness of the second lens on the optical axis to the distance from the second side surface of the second lens to the image plane on the optical axis within this range, the medium thickness of the second lens can be ensured, which is beneficial to ensuring the molding of the second lens.

[0047] In an exemplary embodiment, the optical system of the present application may satisfy the conditional formula 0.1 mm < (N2 / N1) × CTQ < 0.6 mm, where N2 is the refractive index of the second lens, N1 is the refractive index of the first lens, and CTQ is the central thickness of the quarter-wave plate on the optical axis. By controlling the refractive index of the second lens, the refractive index of the first lens, and the central thickness of the quarter-wave plate on the optical axis to satisfy the conditional formula 0.1 mm < (N2 / N1) × CTQ < 0.6 mm, on the one hand, it is beneficial to the reasonable distribution of the system optical power, and on the other hand, it is beneficial to the curved surface attachment of the quarter-wave plate by reasonably controlling the medium thickness of the quarter-wave plate.

[0048] In an exemplary embodiment, the optical system of the present application may satisfy the conditional formula 0.6 < FG2 / (f × tan(FOV / 2)) < 0.9, where FG2 is the effective focal length of the second element group, f is the effective focal length of the optical system, and FOV is the maximum field of view angle of the optical system. By controlling the effective focal length of the second element group, the effective focal length of the optical system, and the maximum field of view angle of the optical system to satisfy 0.6 < FG2 / (f × tan(FOV / 2)) < 0.9, it is beneficial to control the lens shape of the first lens, thereby ensuring the molding of the first lens.

[0049] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.1 mm < |R1| / (VF + V1) < 2.1 mm, where R1 is the radius of curvature of the first side of the first lens, VF is the Abbe number of the filter, and V1 is the Abbe number of the first lens. By controlling the radius of curvature of the first side of the first lens, the Abbe number of the filter, and the Abbe number of the first lens to satisfy the conditional formula 1.1 mm < |R1| / (VF + V1) < 2.1 mm, it is beneficial to correct the chromatic aberration of the optical system and improve the wearing experience of consumers.

[0050] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.0 < (CT1 + T12) / (CT1 - T12) < 6.1, where CT1 is the central thickness of the first lens on the optical axis, and T12 is the air gap between the first lens and the second lens on the optical axis. By controlling the central thickness of the first lens on the optical axis and the air gap between the first lens and the second lens on the optical axis to satisfy the conditional formula 1.0 < (CT1 + T12) / (CT1 - T12) < 6.1, on the one hand, it is beneficial to restrict the total length of the optical system, and on the other hand, it is beneficial to ensure the strength of the first lens and the assembly stability.

[0051] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.5 < f / TD < 2.4, where f is the effective focal length of the optical system, and TD is the distance on the optical axis from the first side of the first lens to the second side of the second lens. By controlling the ratio of the effective focal length of the optical system to the distance on the optical axis from the first side of the first lens to the second side of the second lens within this range, the maximum field angle of the optical system can be indirectly controlled. By increasing the field angle, the wearing experience of consumers can be improved.

[0052] In an exemplary embodiment, the second side of the first lens can be convex. The first side of the second lens can be concave. By restricting the shape of the lens, the angle of light can be reasonably controlled, which is beneficial to reducing the screen height.

[0053] In an exemplary embodiment, the optical system of the present application can include at least one aperture stop. The aperture stop can restrict the light path and control the light intensity. The aperture stop can be set at an appropriate position in the optical system. For example, the aperture stop can be located between the human eye side and the first element group.

[0054] In an exemplary embodiment, optionally, the above optical system can further include a protective glass for protecting the photosensitive element located on the imaging surface.

[0055] In an exemplary embodiment, the effective focal length f of the optical system may be, for example, in the range of 28.00 mm to 29.50 mm, the effective focal length FG2 of the second element group may be, for example, in the range of 28.18 mm to 29.28 mm, and the effective focal length FG3 of the third element group may be, for example, in the range of -322.26 mm to 22323.94 mm.

[0056] For the optical system according to the above embodiment of the present application, by arranging the first element group to include a filter and a reflective polarizing element, where both sides of the filter are flat, which is beneficial for the attachment of the reflective polarizing element. The reflective polarizing element reflects light in one direction and transmits light orthogonal to it, which is beneficial for realizing the refraction and reflection of the optical path; by arranging the second element group to have a positive optical power, it is convenient for light rays to converge to reduce the screen height, and at the same time includes a quarter-wave plate, which can be used for the conversion between circular polarization and linear polarization; and by arranging the third element group to include a second lens, it is beneficial for compensating the aberration of the first lens. At the same time, by controlling the effective focal length of the second element group, the central thickness of the filter on the optical axis, the central thickness of the reflective polarizing element on the optical axis, the central thickness of the quarter-wave plate on the optical axis, and the central thickness of the first lens on the optical axis to satisfy the conditional formula 1.5 < FG2 / (CTF + CTR + CTQ + CT1) < 3.0, the incident angle of light on the flat plate can be reasonably controlled to avoid light leakage at large angles.

[0057] According to some embodiments of the present application, by reasonably setting the center thickness, curvature radius, refractive index, and Abbe number of the lens, as well as parameters such as the effective focal length of the optical system, the maximum field angle, the entrance pupil diameter, and the effective focal lengths of the second and third element groups, and by reasonably setting parameters such as the distance between the aperture stop, the lens, and the image plane, the molding of the lens can be ensured; it is beneficial to ensure the strength of the lens; it is beneficial for the assembly and support of the first lens and the second lens to ensure the assembly stability. It is also beneficial for the curved surface attachment of the quarter-wave plate. At the same time, by combining flat surface film and curved surface film, the system performance can be effectively improved. And it can restrict the length of the optical system, which is beneficial for the thinning of the head-mounted device; it can reasonably control the angle of light, which is beneficial for reducing the screen height, and at the same time can correct the chromatic aberration of the optical system to improve the wearing experience of consumers.

[0058] The following further describes specific embodiments of the optical system applicable to the above embodiments with reference to the drawings.

[0059] Example 1

[0060] The following refers to Figures 1 to 2C Describe the optical system according to Embodiment 1 of the present application. Figure 1 The structural schematic diagram of the optical system according to Embodiment 1 of the present application is shown.

[0061] like Figure 1 As shown, the optical system includes, in order from the human eye side to the display side along the optical axis: a filter IR, a reflective polarizer RP, a quarter-wave plate QWP, a first lens E1, a partially reflecting element BS and a second lens E2.

[0062] In this embodiment, the first optical lens E1 has positive refractive power, with its surface near the human eye being convex and its surface near the display being convex. The second optical lens E2 has negative refractive power, with its surface near the human eye being concave and its surface near the display being flat.

[0063] In this embodiment, the light beam emitted from the image surface IMG can pass through the second lens E2 and the partially reflecting element BS, as well as the first lens E1 and the quarter-wave plate QWP in sequence, and reach the reflective polarizer RP. After being reflected at the reflective polarizer RP, it passes through the quarter-wave plate QWP and the first lens E1 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the reflective element BS and passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizer RP, and the filter IR in sequence to be emitted toward the human eye.

[0064] In this embodiment, the partially reflective element BS may be a semi-transmissive and semi-reflective film layer coated on the first side surface (the surface close to the human eye) of the second lens E2.

[0065] Table 1 shows basic parameters of the optical system of Example 1, wherein the units of the curvature radius and thickness are both millimeters (mm).

[0066] surface element Surface type Radius of curvature thickness Refractive index Abbe number Refraction / Reflection S0 spherical surface endless endless refraction S1 Aperture (STO) spherical surface endless 15.0000 refraction S2 Filter (IR) spherical surface endless 0.8000 1.52 64.17 refraction S3 Reflective polarizer (RP) spherical surface endless 0.2000 1.52 64.17 refraction S4 spherical surface endless 0.1000 refraction S5 Quarter Wave Plate (QWP) spherical surface 140.3419 0.2000 1.54 56.00 refraction S6 First lens (E1) spherical surface 140.3419 8.9765 1.54 56.00 refraction S7 Aspheric -93.2267 6.4157 refraction S8 Partially reflective element (BS) spherical surface -131.7171 -6.4157 reflection S9 First lens (E1) Aspheric -93.2267 -8.9765 1.54 56.00 refraction S10 Quarter Wave Plate (QWP) spherical surface 140.3419 -0.2000 1.54 56.00 refraction S11 spherical surface 140.3419 -0.1000 refraction S12 Reflective polarizer (RP) spherical surface endless 0.1000 reflection S13 Quarter Wave Plate (QWP) spherical surface 140.3419 0.2000 1.54 56.00 refraction S14 First lens (E1) spherical surface 140.3419 8.9765 1.54 56.00 refraction S15 Aspheric -93.2267 6.4157 refraction S16 Second lens (E2) spherical surface -131.7171 2.5500 1.67 19.00 refraction S17 spherical surface endless 3.5591 refraction S18 Image surface (IMG) spherical surface endless 0.0000 refraction

[0067] Table 1

[0068] In Example 1, the surface S7 of the first optical lens E1 close to the display is an aspherical surface. The surface shape x of the aspherical lens can be defined by, but not limited to, the following aspherical surface formula:

[0069]

[0070] Wherein, x is the distance vector height of the aspheric surface from the vertex of the aspheric surface at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the curvature radius R in Table 1 above); k is the conic coefficient; Ai is the correction coefficient of the i-th order of the aspheric surface. Table 2 below lists the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, A44, A45, A46, A47, A50, A51, A52, A53, A54, A55, A56, A57, A58, A59, A60, A61, A71, A72, A73, A74, A75, A76, A8 10 、A 12 、A 14 、A 16 、A 18 and A20 .

[0071] Coefficient\Surface S7 A4 1.1746E-06 A6 -1.9180E-11 A8 1.9663E-13 A10 -1.6585E-16 A12 5.1303E-20 A14 0.0000E+00 A16 0.0000E+00 A18 0.0000E+00 A20 0.0000E+00

[0072] Table 2

[0073] Figure 2A The axial chromatic aberration curve of the optical system of Example 1 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 2B The astigmatism curve of the optical system of Example 1 is shown, which indicates meridional field curvature and sagittal field curvature. Figure 2C The distortion curve of the optical system of Example 1 is shown, which represents the distortion value corresponding to different field angles. Figures 2A to 2C It can be seen that the optical system provided in Example 1 can achieve good imaging quality.

[0074] Example 2

[0075] The following reference Figures 3 to 4C The optical system according to Example 2 of the present application is described. In this embodiment and the following embodiments, some descriptions similar to those in Example 1 will be omitted for the sake of brevity. Figure 3 A structural schematic diagram of an optical system according to Example 2 of the present application is shown.

[0076] like Figure 3 As shown, the optical system includes, in order from the human eye side to the display side along the optical axis: a filter IR, a reflective polarizer RP, a first lens E1, a quarter-wave plate QWP, a partially reflecting element BS and a second lens E2.

[0077] In this embodiment, the first optical lens E1 has positive optical power, with its surface near the human eye being concave and its surface near the display being convex. The second optical lens E2 has negative optical power, with its surface near the human eye being concave and its surface near the display being flat.

[0078] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the second lens E2 and the partially reflecting element BS, as well as the quarter-wave plate and the QWP first lens E1, to reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the first lens E1 and the quarter-wave plate QWP again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the reflective element BS and sequentially pass through the quarter-wave plate QWP, the first lens E1, the reflective polarizing element RP and the filter IR to be emitted toward the human eye side.

[0079] In this embodiment, the partially reflective element BS may be a semi-transmissive and semi-reflective film layer coated on the first side surface (the surface close to the human eye) of the second lens E2.

[0080] Table 3 shows the basic parameters of the optical system of Example 2, where the units of curvature radius and thickness are both millimeters (mm). In this embodiment, the surface S6 of the first optical lens E1 close to the display side and the surface S16 of the second optical lens E2 close to the human eye side are both aspherical. Table 4 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, A44, A45, A46, A47, A4 10 、A 12 、A 14 、A 16 、A 18 and A 20 , wherein each aspheric surface shape can be defined by formula (1) given in the above embodiment 1.

[0081]

[0082]

[0083] Table 3

[0084] Coefficient\Surface S6 S16 A4 2.8368E-06 2.5111E-01 A6 -1.3523E-10 1.9108E-01 A8 1.3075E-12 -3.2700E-02 A10 -1.7745E-15 5.6024E-03 A12 7.6890E-19 -1.7809E-03 A14 0.0000E+00 6.0608E-04 A16 0.0000E+00 -3.8751E-04 A18 0.0000E+00 0.0000E+00 A20 0.0000E+00 0.0000E+00

[0085] Table 4

[0086] Figure 4A The axial chromatic aberration curve of the optical system of Example 2 is shown, which indicates the deviation of the convergent focus of light of different wavelengths after passing through the lens. Figure 4B The astigmatism curve of the optical system of Example 2 is shown, which indicates meridional field curvature and sagittal field curvature. Figure 4C The distortion curve of the optical system of Example 2 is shown, which represents the distortion value corresponding to different field angles. Figures 4A to 4C It can be seen that the optical system provided in Example 2 can achieve good imaging quality.

[0087] Example 3

[0088] The following reference Figures 5 to 6C An optical system according to Example 3 of the present application is described. Figure 5 A structural schematic diagram of an optical system according to Example 3 of the present application is shown.

[0089] like Figure 5 As shown, the optical system includes, in order from the human eye side to the display side along the optical axis: a filter IR, a reflective polarizer RP, a quarter-wave plate QWP, a first lens E1, a second lens E2 and a partially reflecting element BS.

[0090] In this embodiment, the first optical lens E1 has positive refractive power, and its surface close to the human eye is convex, and its surface close to the display is also convex. The second optical lens E2 has positive refractive power, and its surface close to the human eye is concave, and its surface close to the display is convex.

[0091] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the partially reflecting element BS and the second lens E2, as well as the first lens E1 and the quarter-wave plate QWP, to reach the reflective polarizer RP, be reflected at the reflective polarizer RP and pass through the quarter-wave plate QWP, the first lens E1 and the second lens E2 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the reflective element BS and sequentially pass through the second lens E2, the first lens E1, the quarter-wave plate QWP, the reflective polarizer RP and the filter IR to be emitted toward the human eye side.

[0092] In this embodiment, the partially reflective element BS may be a semi-transmissive and semi-reflective film layer coated on the second side surface (the surface close to the display) of the second lens E2.

[0093] Table 5 shows the basic parameters of the optical system of Example 3, where the units of the curvature radius and thickness are both in millimeters (mm). In this embodiment, the surface S7 of the first optical lens E1 close to the display side is an aspherical surface. Table 6 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, A44, A45, A46, A47, A48, A49, A50, A51, A5 10 、A 12 、A 14 、A 16 、A 18 and A 20 , wherein each aspheric surface shape can be defined by formula (1) given in the above embodiment 1.

[0094] surface element Surface type Radius of curvature thickness Refractive index Abbe number Refraction / Reflection S0 spherical surface endless endless refraction S1 Aperture (STO) spherical surface endless 15.0000 refraction S2 Filter (IR) spherical surface endless 0.8000 1.52 64.17 refraction S3 Reflective polarizer (RP) spherical surface endless 0.2000 1.52 64.17 refraction S4 spherical surface endless 1.4998 refraction S5 Quarter Wave Plate (QWP) spherical surface 175.0000 0.5000 1.48 60.00 refraction S6 First lens (E1) spherical surface 175.0000 15.6448 1.48 60.00 refraction S7 Aspheric -82.4212 1.0000 refraction S8 Second lens (E2) spherical surface -113.1580 2.0956 1.67 19.00 refraction S9 Partially reflective element (BS) spherical surface -113.1580 -2.0956 1.67 19.00 reflection S10 spherical surface -113.1580 -1.0000 refraction S11 First lens (E1) Aspheric -82.4212 -15.6448 1.48 60.00 refraction S12 Quarter Wave Plate (QWP) spherical surface 175.0000 -0.5000 1.48 60.00 refraction S13 spherical surface 175.0000 -1.4998 refraction S14 Reflective polarizer (RP) spherical surface endless 1.4998 reflection S15 Quarter Wave Plate (QWP) spherical surface 175.0000 0.5000 1.48 60.00 refraction S16 First lens (E1) spherical surface 175.0000 15.6448 1.48 60.00 refraction S17 Aspheric -82.4212 1.0000 refraction S18 Second lens (E2) spherical surface -113.1580 2.0956 1.67 19.00 refraction S19 spherical surface -113.1580 0.5532 refraction S20 Image surface (IMG) spherical surface endless 0.0000 refraction

[0095] Table 5

[0096] Coefficient\Surface S7 A4 6.4273E-07 A6 1.2825E-10 A8 2.1014E-13 A10 -1.1885E-16 A12 2.7918E-20 A14 0.0000E+00 A16 0.0000E+00 A18 0.0000E+00 A20 0.0000E+00

[0097] Table 6

[0098] Figure 6A The axial chromatic aberration curve of the optical system of Example 3 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 6B The astigmatism curve of the optical system of Example 3 is shown, which indicates the meridional field curvature and the sagittal field curvature. Figure 6C The distortion curve of the optical system of Example 3 is shown, which represents the distortion value corresponding to different field angles. Figures 6A to 6C It can be seen that the optical system provided in Example 3 can achieve good imaging quality.

[0099] Example 4

[0100] The following reference Figures 7 to 8C An optical system according to Example 4 of the present application is described. Figure 7 A structural schematic diagram of an optical system according to Example 4 of the present application is shown.

[0101] like Figure 7 As shown, the optical system includes, in order from the human eye side to the display side along the optical axis: a filter IR, a reflective polarizer RP, a quarter-wave plate QWP, a first lens E1, a partially reflecting element BS and a second lens E2.

[0102] In this embodiment, the first optical lens E1 has positive refractive power, and its surface close to the human eye is convex, and its surface close to the display is also convex. The second optical lens E2 has positive refractive power, and its surface close to the human eye is concave, and its surface close to the display is convex.

[0103] In this embodiment, the light beam emitted from the image surface IMG can pass through the second lens E2, the partially reflecting element BS, the first lens E1, and the quarter-wave plate QWP in sequence to reach the reflective polarizer RP, be reflected at the reflective polarizer RP and pass through the quarter-wave plate QWP and the first lens E1 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the reflective element BS and passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizer RP, and the filter IR in sequence to be emitted toward the human eye.

[0104] In this embodiment, the partially reflective element BS may be a semi-transmissive and semi-reflective film layer coated on the second side surface (the surface close to the display) of the first lens E1 .

[0105] Table 7 shows the basic parameters of the optical system of Example 4, where the units of the curvature radius and thickness are both in millimeters (mm). In this embodiment, the surface S14 on the side close to the human eye and the surface S15 on the side close to the display of the second optical lens E2 are both aspherical. Table 8 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, A44, A45, A46, A47, A4 10 、A 12 、A 14 、A 16 、A 18 and A 20 , wherein each aspheric surface shape can be defined by formula (1) given in the above embodiment 1.

[0106] surface element Surface type Radius of curvature thickness Refractive index Abbe number Refraction / Reflection S0 spherical surface endless endless refraction S1 Aperture (STO) spherical surface endless 15.0000 refraction S2 Filter (IR) spherical surface endless 0.8000 1.52 64.17 refraction S3 Reflective polarizer (RP) spherical surface endless 0.2000 1.52 64.17 refraction S4 spherical surface endless 3.2678 refraction S5 Quarter Wave Plate (QWP) spherical surface 175.0000 0.3000 1.52 40.43 refraction S6 First lens (E1) spherical surface 175.0000 9.0945 1.52 40.43 refraction S7 Partially reflective element (BS) spherical surface -113.1580 -9.0945 1.52 40.43 reflection S8 Quarter Wave Plate (QWP) spherical surface 175.0000 -0.3000 1.52 40.43 refraction S9 spherical surface 175.0000 -3.2678 refraction S10 Reflective polarizer (RP) spherical surface endless 3.2678 reflection S11 Quarter Wave Plate (QWP) spherical surface 175.0000 0.3000 1.52 40.43 refraction S12 First lens (E1) spherical surface 175.0000 9.0945 1.52 40.43 refraction S13 spherical surface -113.1580 1.0537 refraction S14 Second lens (E2) Aspheric -285.3638 2.0000 1.67 19.00 refraction S15 Aspheric -196.9259 8.2840 refraction S16 Image surface (IMG) spherical surface endless 0.0000 refraction

[0107] Table 7

[0108]

[0109]

[0110] Table 8

[0111] Figure 8A The axial chromatic aberration curve of the optical system of Example 4 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 8B The astigmatism curve of the optical system of Example 4 is shown, which indicates the meridional field curvature and the sagittal field curvature. Figure 8C The distortion curve of the optical system of Example 4 is shown, which represents the distortion value corresponding to different field angles. Figures 8A to 8C It can be seen that the optical system provided in Example 4 can achieve good imaging quality.

[0112] In addition, in Examples 1 to 4, the effective focal length FG2 of the second element group, the effective focal length FG3 of the third element group, the effective focal length f of the optical system, the entrance pupil diameter EPD of the optical system, the distance SL on the optical axis from the aperture to the image plane of the optical system, the distance SD on the optical axis from the aperture to the surface of the second lens on the display side, the distance TD on the optical axis from the surface of the first lens on the human eye side to the surface of the second lens on the display side, the distance BFL on the optical axis from the surface of the second lens on the display side to the image plane of the optical system, the distance ER on the optical axis from the aperture to the surface of the first lens on the human eye side, the center thickness CTF of the filter on the optical axis, the center thickness CTR of the reflective polarizing element on the optical axis, the center thickness CTQ of the quarter-wave plate on the optical axis, and the maximum field of view FOV of the optical system are as shown in Table 9.

[0113] Parameters / Example 1 2 3 4 FG2(mm) 28.60 28.78 29.28 28.18 FG3(mm) -194.76 -322.26 22323.94 929.25 f(mm) 29.35 29.50 29.50 28.00 EPD(mm) 5.00 5.00 5.00 5.00 SL(mm) 37.80 40.00 37.29 40.00 SD(mm) 34.24 32.97 36.74 31.72 TD(mm) 17.94 14.35 18.74 12.15 BFL(mm) 3.56 7.03 0.55 8.28 ER(mm) 16.30 18.62 18.00 19.57 CTF(mm) 0.80 0.20 0.80 0.80 CTR(mm) 0.20 0.80 0.20 0.20 CTQ(mm) 0.20 0.20 0.50 0.30 FOV(°) 106.0 106.0 106.0 106.0

[0114] Table 9

[0115] Examples 1 to 4 respectively satisfy the conditions shown in Table 10.

[0116] Conditional formula / Example 1 2 3 4 FG2 / (CTF+CTR+CTQ+CT1) 2.81 2.09 1.71 2.71 R3 / R2 1.41 2.90 1.37 2.52 TD / EPD 3.59 2.87 3.75 2.43 SL / ER 2.32 2.15 2.07 2.04 SD / f 1.17 1.12 1.25 1.13 CT2 / BFL 0.72 0.21 3.79 0.24 (N2 / N1)×CTQ(mm) 0.22 0.20 0.56 0.33 FG2 / (f×tan(FOV / 2)) 0.73 0.74 0.75 0.76 |R1| / (VF+V1)(mm) 1.17 2.03 1.41 1.67 (CT1+T12) / (CT1-T12) 6.01 1.05 1.14 1.26 f / TD 1.64 2.06 1.57 2.30

[0117] Table 10

[0118] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of protection provided in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the concept of this application. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An optical system, characterized in that The optical axis includes a first element group, a second element group, a third element group and an image plane in sequence from the first side to the second side, wherein: The first element group includes a filter and a reflective polarizing element; The second element group has positive optical power and includes a quarter-wave plate and a first lens, wherein the second side surface of the first lens is convex; The third element group includes a second lens having positive or negative optical power and a first side surface thereof being concave; The optical system satisfies: 1.71≤FG2 / (CTF+CTR+CTQ+CT1)≤2.81, 0.2 <CT2 / BFL<3.8; 1.57≤f / TD≤2.30; Wherein, FG2 is the effective focal length of the second element group, CTF is the center thickness of the filter on the optical axis, CTR is the center thickness of the reflective polarizer on the optical axis, CTQ is the center thickness of the quarter-wave plate on the optical axis, CT1 is the center thickness of the first lens on the optical axis, CT2 is the center thickness of the second lens on the optical axis, BFL is the distance from the second side surface of the second lens to the image plane on the optical axis, f is the effective focal length of the optical system, and TD is the distance from the first side surface of the first lens to the second side surface of the second lens on the optical axis; The number of lenses having optical power in the optical system is two; The first side is a human eye side, and the second side is a display side.

2. The optical system according to claim 1, wherein: The curvature radius R3 of the first side surface of the second lens and the curvature radius R2 of the second side surface of the first lens satisfy: 1.37≤R3 / R2≤2.

90.

3. The optical system according to claim 1, wherein: The distance TD from the first side surface of the first lens to the second side surface of the second lens on the optical axis and the entrance pupil diameter EPD of the optical system satisfy: 2.43≤TD / EPD≤3.

75.

4. The optical system according to claim 1, wherein: The optical system further includes a stop, and a distance SL from the stop to the image plane on the optical axis and a distance ER from the stop to the first side surface of the first lens on the optical axis satisfy: 2.04≤SL / ER≤2.

32.

5. The optical system according to claim 1, wherein: The optical system further includes an aperture, and a distance SD from the aperture to the second side surface of the second lens on the optical axis satisfies the following relationship with the effective focal length f of the optical system: 1.12≤SD / f≤1.

25.

6. The optical system according to claim 1, wherein: The refractive index N2 of the second lens, the refractive index N1 of the first lens, and the center thickness CTQ of the quarter-wave plate on the optical axis satisfy: 0.20mm≤(N2 / N1)×CTQ≤0.56mm.

7. The optical system according to claim 1, wherein: The effective focal length FG2 of the second element group, the effective focal length f of the optical system, and the maximum field of view FOV of the optical system satisfy: 0.73≤FG2 / (f×tan(FOV / 2))≤0.

76.

8. The optical system according to claim 1, wherein: The curvature radius R1 of the first side surface of the first lens, the Abbe number VF of the filter, and the Abbe number V1 of the first lens satisfy: 1.17mm≤|R1| / (VF+V1)≤2.03mm.

9. The optical system according to claim 1, wherein: The center thickness CT1 of the first lens on the optical axis and the air interval T12 between the first lens and the second lens on the optical axis satisfy: 1.05≤(CT1+T12) / (CT1-T12)≤6.

01.

10. A VR device comprising the optical system according to any one of claims 1 to 9.

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