Optical system and VR device including the same

Abstract

The present application discloses an optical system, which includes a first element group and a second element group in sequence from the first side to the second side along the optical axis, wherein the first element group has positive optical power and includes a first lens, a reflective polarizing element, a quarter-wave plate, and a second lens; the second element group has negative optical power and includes a partially reflecting element and a third lens. The effective focal length FG1 of the first element group, the center thickness CT1 of the first lens 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 CT2 of the second lens on the optical axis satisfy: 1.4 <FG1 / (CT1+CTR+CTQ+CT2)<2.4。

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 continuous development and progress of computer technology and precision manufacturing, the concept of virtual reality (VR), which began in the 1980s, is now being used through various display devices, body tracking and information integration equipment to truly enable users to obtain binocular three-dimensional virtual immersive experience, and has become a technology gradually applied to education, military, leisure and other fields.

[0003] As the direct output of virtual images, various display devices are crucial for their performance in terms of compatibility between the visual optical system and human vision, imaging quality, and the portability of the lens structure. Currently, VR devices based on the principle of folding the optical path of a catadioptric optical system can effectively shorten the total optical length. However, there is still room for improvement in terms of compatibility with the human eye and optimization of aberrations and image quality. Therefore, based on the optical design of a catadioptric optical system, developing an optical system with higher compatibility with the human eye and better imaging quality, so that VR display devices with broad applications and development prospects can better meet people's needs, is one of the technical problems currently being addressed by those skilled in the art. Summary of the Invention

[0004] The present application provides an optical system, which may include a first element group and a second element group in sequence from the first side to the second side along the optical axis, wherein the first element group has positive optical power and includes a first lens, a reflective polarizing element, a quarter-wave plate, and a second lens; the second element group has negative optical power and includes a partially reflecting element and a third lens. The effective focal length FG1 of the first element group, the center thickness CT1 of the first lens 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 CT2 of the second lens on the optical axis may satisfy: 1.4 <FG1 / (CT1+CTR+CTQ+CT2)<2.4。

[0005] In one embodiment, the curvature radius R5 of the first side surface of the third lens and the curvature radius R4 of the second side surface of the second lens may satisfy: 1.4 <R5 / R4<1.9。

[0006] In one embodiment, the air gap T12 between the first lens and the second lens on the optical axis, the center thickness CTR of the reflective polarizing element on the optical axis, and the center thickness CTQ of the quarter-wave plate on the optical axis may satisfy: 1.2 <T12 / (CTR+CTQ)<4.2。

[0007] In one embodiment, the effective focal length f of the optical system and the entrance pupil diameter EPD of the optical system may satisfy: 6.0 <f / EPD<6.3。

[0008] 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 third lens on the optical axis may satisfy: 1.1 <f / TD<2.1。

[0009] In one embodiment, the optical system further includes an image plane disposed on the second side, and an air gap T23 between the second lens and the third lens on the optical axis, a center thickness CT3 of the third lens on the optical axis, and a distance BFL from the second side surface of the third lens to the image plane on the optical axis may satisfy the following conditions: 0.1<(T23+CT3) / BFL<1.3.

[0010] In one embodiment, the effective focal length f of the optical system, the refractive index N1 of the first lens, the refractive index N2 of the second lens, and the refractive index N3 of the third lens may satisfy: 6.3 mm <f / (N1+N2+N3)<6.6mm。

[0011] In one embodiment, the optical system further includes an aperture and an image surface disposed on the second side, and the effective focal length FG2 of the second element group, the distance SL from the aperture to the image surface on the optical axis, and the distance SD from the aperture to the second side surface of the third lens on the optical axis may satisfy: -3.8 <FG2 / (SL+SD)<-1.5。

[0012] In one embodiment, the curvature radius R1 of the first side surface of the first lens, the curvature radius R4 of the second side surface of the second lens, the Abbe number V1 of the first lens, and the Abbe number V2 of the second lens may satisfy: 1.3 mm<|R1+R4| / (V1+V2)<6.3 mm.

[0013] In one embodiment, the effective focal length FG2 of the second element group and the curvature radius R5 of the first side surface of the third lens can satisfy: 0.8 <FG2 / R5<2.4。

[0014] In one embodiment, the effective focal length FG1 of the first element group, the effective focal length FG2 of the second element group, and the effective focal length f of the optical system may satisfy the following: 4.8<(FG1-FG2) / f<11.5.

[0015] In one embodiment, a surface of a lens in the first element group is flat.

[0016] In one embodiment, the second side of the second lens is a convex surface, and the first side of the third lens is a concave surface.

[0017] 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 embodiments. Among them, the first side is the human eye side, and the second side is the display side.

[0018] The optical system disclosed in the present application sequentially includes a first element group and a second element group along the optical axis from the first side to the second side. By setting the first element group to include a first lens, a reflective polarizing element, a quarter-wave plate, and a second lens, the setting of the reflective polarizing element and the quarter-wave plate can perform semi-reflection and semi-transmission processing on the passing light and change the polarization state, which is beneficial to the folded transmission of the optical path; and the first element group is set to have a positive optical power to facilitate the convergence of light. The second element group is set to include a partially reflective element and a third lens, and the second element group has a negative optical power, which can meet the reflection and transmission requirements of different optical path conditions and is beneficial to compensating the aberration of the first element group and optimizing the imaging ability of the optical system. At the same time, controlling the effective focal length of the first element group, the central thickness of the first lens, the central thickness of the reflective polarizing element, the central thickness of the quarter-wave plate, and the central thickness of the second lens to satisfy the conditional formula 1.4 < FG1 / (CT1 + CTR + CTQ + CT2) < 2.4 is beneficial to controlling the shape of the lens and the field angle, facilitating the realization of a lightweight short-focus wide-angle design, and meeting the human eye vision and wearing requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In combination with the drawings, through the following detailed description of non-limiting embodiments, other features, objects, and advantages of the present application will become more obvious. In the drawings:

[0020] Figure 1 Shows a schematic structural diagram of the optical system according to Embodiment 1 of the present application;

[0021] Figures 2A to 2C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 1;

[0022] Figure 3 Shows a schematic structural diagram of the optical system according to Embodiment 2 of the present application;

[0023] Figures 4A to 4C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 2;

[0024] Figure 5 Shows a schematic structural diagram of the optical system according to Embodiment 3 of the present application;

[0025] Figures 6A to 6C axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Example 3 are respectively shown;

[0026] Figure 7 1 shows a schematic structural diagram of an optical system according to Example 4 of the present application;

[0027] Figures 8A to 8C The axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Example 4 are respectively shown;

[0028] Figure 9 1 shows a schematic structural diagram of an optical system according to Example 5 of the present application;

[0029] 10A to 10C The axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Example 5 are shown respectively;

[0030] Figure 11 shows a schematic structural diagram of an optical system according to Example 6 of the present application; and

[0031] 12A to 12C The axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Example 6 are respectively shown. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The features, principles and other aspects of the present application are described in detail below.

[0040] According to an exemplary embodiment of the present application, an optical system may include a first element group and a second 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 first lens, a reflective polarizing element, a quarter-wave plate and a second lens, and the second element group may include a partially reflective element and a third lens.

[0041] In an exemplary embodiment, the first element group may have positive optical power and the second element group may have negative optical power.

[0042] In an exemplary embodiment, the first side may be, for example, a human eye side, and the second side may be, for example, a display side. The optical system may be used in, for example, various VR display devices.

[0043] In an exemplary embodiment, the first side of the first lens may be the surface of the first lens closer to the human eye, and the second side of the first lens may be the surface of the first lens closer to the display. The first side of the second lens may be the surface of the second lens closer to the human eye, and the second side of the second lens may be the surface of the second lens closer to the display. The first side of the third lens may be the surface of the third lens closer to the human eye, and the second side of the third lens may be the surface of the third lens closer to the display.

[0044] A示例性 description of the optical system will be given below with reference to Figure 1 As shown in Figure 1 According to an exemplary embodiment of the present application, the optical system may include a first lens E1, a reflective polarizing element RP, a quarter-wave plate QWP, a second lens E2, a partial reflection element BS, and a third lens E3 arranged in sequence from the first side to the second side. Among them, the first lens E1, the reflective polarizing element RP, the quarter-wave plate QWP, and the second lens E2 form a first element group, and the partial reflection element BS and the third lens E3 form a second element group. In actual use, according to an exemplary embodiment of the present application, the optical system 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 on the display side. The light beam emitted from the image plane IMG may sequentially pass through the third lens E3 and the partial reflection element BS of the second element group, as well as the second lens E2 and the quarter-wave plate QWP of the first element group, reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the quarter-wave plate QWP and the second lens E2 again to reach the partial reflection element BS. After that, the light beam is reflected again at the partial reflection element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to exit toward the human eye side. In an exemplary embodiment, the partial reflection element BS may be a semi-transmissive and semi-reflective film layer coated on the first side of the third lens E3. In an exemplary embodiment, the reflective polarizing element RP may be attached to the second side of the first lens E1, and the quarter-wave plate QWP may be attached to the surface of the reflective polarizing element RP closer to the display side.

[0045] In an exemplary embodiment, the optical system of the present application may satisfy the condition 1.4 < FG1 / (CT1 + CTR + CTQ + CT2) < 2.4, where FG1 is the effective focal length of the first element group, CT1 is the central thickness of the first lens 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 CT2 is the central thickness of the second lens on the optical axis.

[0046] An optical system according to an exemplary embodiment of the present application includes a first element group and a second element group in sequence from the first side to the second side along the optical axis. By arranging the first element group to include a first lens, a reflective polarizing element, a quarter-wave plate, and a second lens, the reflective polarizing element and the quarter-wave plate can perform semi-reflection and semi-transmission processing on the passing light and change the polarization state, which is beneficial for folded optical path transmission. And the first element group is arranged to have a positive optical power to facilitate light convergence. The second element group is arranged to include a partial reflection element and a third lens, and the second element group has a negative optical power, which can meet the reflection and transmission requirements of different optical path conditions and is beneficial for compensating the aberration of the first element group and optimizing the imaging ability of the optical system. At the same time, controlling the effective focal length of the first element group, the central thickness of the first lens, the central thickness of the reflective polarizing element, the central thickness of the quarter-wave plate, and the central thickness of the second lens to satisfy the conditional formula 1.4 < FG1 / (CT1 + CTR + CTQ + CT2) < 2.4 is beneficial for controlling the shape of the lens and the field angle, facilitating the realization of a lightweight short-focus wide-angle design, and meeting the human eye vision and wearing requirements.

[0047] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.4 < R5 / R4 < 1.9, where R5 is the radius of curvature of the first side surface of the third lens, and R4 is the radius of curvature of the second side surface of the second lens. By controlling the ratio of the radius of curvature of the first side surface of the third lens to the radius of curvature of the second side surface of the second lens within this range, the surface shape of the lens can be constrained, the air gap between the lenses can be limited, and the assembly and support between the two lenses can be ensured.

[0048] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.2 < T12 / (CTR + CTQ) < 4.2, where T12 is the air gap between the first lens and the second lens on the optical axis, CTR is the central thickness of the reflective polarizing element on the optical axis, and CTQ is the central thickness of the quarter-wave plate on the optical axis. By controlling the air gap between the first lens and the second lens on the optical axis, the central thickness of the reflective polarizing element on the optical axis, and the central thickness of the quarter-wave plate on the optical axis to satisfy 1.2 < T12 / (CTR + CTQ) < 4.2, on the basis of ensuring the assembly requirements and avoiding assembly interference, it is beneficial to shorten the length of the first element group and thus constrain the total length of the optical system.

[0049] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 6.0 < f / EPD < 6.3, where f is the effective focal length of the optical system, and EPD is the entrance pupil diameter of the optical system. By controlling the ratio of the effective focal length of the optical system to the entrance pupil diameter of the optical system within this range, when the entrance pupil diameter is fixed, the size of the screen can be constrained and the selection direction of the screen can be clarified.

[0050] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.1 < f / TD < 2.1, where f is the effective focal length of the optical system, and TD is the distance on the optical axis from the first side surface of the first lens to the second side surface of the third 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 surface of the first lens to the second side surface of the third lens within this range, when the focal length is fixed, it is beneficial to control the overall optical length, thereby controlling the overall length of the device and improving the portability of the device; and it can indirectly control the maximum field angle of the optical system. By increasing the field angle, the wearing experience of consumers can be improved.

[0051] In an exemplary embodiment, the optical system of the present application further includes an image plane provided on the second side, and the optical system of the present application can satisfy the conditional formula 0.1 < (T23 + CT3) / BFL < 1.3, where T23 is the air gap on the optical axis between the second lens and the third lens, CT3 is the central thickness of the third lens on the optical axis, and BFL is the distance on the optical axis from the second side surface of the third lens to the image plane. By controlling the air gap on the optical axis between the second lens and the third lens, the central thickness of the third lens on the optical axis, and the distance on the optical axis from the second side surface of the third lens to the image plane to satisfy 0.1 < (T23 + CT3) / BFL < 1.3, on the one hand, it is beneficial to ensure the molding and strength of the third lens, and on the other hand, it can reasonably control the incident angle of light on the flat plate and avoid light leakage at large angles.

[0052] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 6.3 mm < f / (N1 + N2 + N3) < 6.6 mm, where f is the effective focal length of the optical system, N1 is the refractive index of the first lens, N2 is the refractive index of the second lens, and N3 is the refractive index of the third lens. By controlling the effective focal length of the optical system, the refractive index of the first lens, the refractive index of the second lens, and the refractive index of the third lens to satisfy 6.3 mm < f / (N1 + N2 + N3) < 6.6 mm, it is beneficial for the lens to select a low-stress material, thereby improving the polarization efficiency of the optical system and reducing the screen brightness loss caused by multiple light reflections.

[0053] In an exemplary embodiment, the optical system of the present application may further include an aperture stop and an image plane disposed on the second side, and the optical system of the present application may satisfy the conditional formula -3.8 < FG2 / (SL + SD) < -1.5, where FG2 is the effective focal length of the second lens group, SL is the distance from the aperture stop to the image plane on the optical axis, and SD is the distance from the aperture stop to the second side surface of the third lens on the optical axis. By controlling the effective focal length of the second lens group, the distance from the aperture stop to the image plane on the optical axis, and the distance from the aperture stop to the second side surface of the third lens on the optical axis to satisfy -3.8 < FG2 / (SL + SD) < -1.5, the total length of the folded optical path and the actual occupied axial length can be controlled, which is beneficial to ensuring TTL; at the same time, by controlling the focal length of the third lens to share the system focal length, the aberration generated by the first lens group can be adjusted.

[0054] In an exemplary embodiment, the optical system of the present application may satisfy the conditional formula 1.3 mm < |R1 + R4| / (V1 + V2) < 6.3 mm, where R1 is the radius of curvature of the first side surface of the first lens, R4 is the radius of curvature of the second side surface of the second lens, V1 is the Abbe number of the first lens, and V2 is the Abbe number of the second lens. By controlling the radius of curvature of the first side surface of the first lens, the radius of curvature of the second side surface of the second lens, the Abbe number of the first lens, and the Abbe number of the second lens to satisfy 1.3 mm < |R1 + R4| / (V1 + V2) < 6.3 mm, it is beneficial to correct the chromatic aberration of the optical system and improve the imaging effect.

[0055] In an exemplary embodiment, the optical system of the present application may satisfy the conditional formula 0.8 < FG2 / R5 < 2.4, where FG2 is the effective focal length of the second lens group and R5 is the radius of curvature of the first side surface of the third lens. By controlling the ratio of the effective focal length of the second lens group to the radius of curvature of the first side surface of the third lens within this range, the shape of the third lens can be restricted, which is beneficial to reducing the sensitivity of the third lens and facilitating the optical path connection between lens groups.

[0056] In an exemplary embodiment, the optical system of the present application may satisfy the conditional formula 4.8 < (FG1 - FG2) / f < 11.5, where FG1 is the effective focal length of the first lens group, FG2 is the effective focal length of the second lens group, and f is the effective focal length of the optical system. By controlling the effective focal length of the first lens group, the effective focal length of the second lens group, and the effective focal length of the optical system to satisfy 4.8 < (FG1 - FG2) / f < 11.5, the optical power of the system can be reasonably distributed, which is beneficial to ensuring the optical performance of the system.

[0057] In an exemplary embodiment, one surface of one lens in the first element group may have a planar shape, that is, one of the first lens and the second lens may have a surface with a planar shape. By restricting the lens surface shape to be planar, it is beneficial for the attachment of the reflective polarizing element and the quarter-wave plate.

[0058] In an exemplary embodiment, the second side surface of the second lens may be convex. The first side surface of the third lens may be concave. By constraining the lens shapes of the surface of the second lens close to the display side and the surface of the third lens away from the display side, the angle of light can be controlled, which is beneficial for reducing the screen height.

[0059] In an exemplary embodiment, the optical system of the present application may include at least one aperture stop. The aperture stop can restrict the optical path and control the light intensity. The aperture stop can be arranged at an appropriate position in the optical system. For example, the aperture stop can be located between the first side (the human eye side) and the first element group.

[0060] In an exemplary embodiment, optionally, the above optical system may further include a protective glass for protecting the photosensitive element located on the imaging surface.

[0061] In an exemplary embodiment, the effective focal length f of the optical system can be, for example, in the range of 30.18 mm to 30.88 mm, the effective focal length FG1 of the first element group can be, for example, in the range of 26.67 mm to 29.58 mm, and the effective focal length FG2 of the second element group can be, for example, in the range of -317.90 mm to -119.04 mm.

[0062] According to the optical system of the above embodiment of the present application, by sequentially arranging the first element group and the second element group along the optical axis from the first side to the second side, a total of three lenses are included. The first element group is set to include a first lens, a reflective polarizing element, a quarter-wave plate, and a second lens. The setting of the reflective polarizing element and the quarter-wave plate can perform semi-reflection and semi-transmission processing on the passing light and change the polarization state, which is beneficial for the folded transmission of the optical path. And the first element group is set to have a positive optical power to facilitate the convergence of light. The second element group is set to include a partially reflective element and a third lens, and the second element group has a negative optical power, which can meet the reflection and transmission requirements of different optical path conditions and is beneficial for compensating the aberration of the first element group and optimizing the imaging ability of the optical system. At the same time, controlling the effective focal length of the first element group, the central thickness of the first lens, the central thickness of the reflective polarizing element, the central thickness of the quarter-wave plate, and the central thickness of the second lens to satisfy the conditional formula 1.​​According to some embodiments of the present application, by reasonably setting the lens's radius of curvature, center thickness, surface shape, refractive index, and Abbe number, as well as parameters such as the effective focal length and entrance pupil diameter of the optical system, and by reasonably setting parameters such as the aperture, lens, and the distance between the image planes, it is beneficial to ensure the molding and strength of the lens, and to reduce the sensitivity of the lens; at the same time, it can ensure the support between the lens assemblies. It is beneficial to constrain the total length of the optical system; and when the entrance pupil diameter is constant, it can constrain the size of the screen and clarify the screen selection direction; it is beneficial to control the total length of the device and improve the device's portability. It can also increase the field of view and enhance the consumer's wearing experience. It can avoid light leakage at large angles; it is beneficial to improve the polarization efficiency of the optical system and reduce the loss of screen brightness caused by multiple returns of light; it is beneficial to improve the imaging effect and ensure the optical performance of the system.

[0064] Specific embodiments of the optical system applicable to the above-mentioned embodiments will be further described below with reference to the accompanying drawings.

[0065] Example 1

[0066] The following reference Figures 1 to 2C An optical system according to Example 1 of the present application is described. Figure 1 A structural schematic diagram of an optical system according to Example 1 of the present application is shown.

[0067] like Figure 1 As shown, the optical system includes, in order from the eye side to the display side along the optical axis: an aperture STO, a first lens E1, a reflective polarizer RP, a quarter-wave plate QWP, a second lens E2, a partially reflecting element BS, a third lens E3, and an image surface IMG. The first lens E1, reflective polarizer RP, quarter-wave plate QWP, and second lens E2 form a first element group, while the partially reflecting element BS and third lens E3 form a second element group.

[0068] In this embodiment, the first lens group has positive optical power. Surface S2 of the first lens element E1 on the eye side is convex, and surface S3 on the display side is flat. Surface S6 of the second lens element E2 on the eye side is convex, and surface S7 on the display side is convex. The second lens group has negative optical power. Surface S16 of the third lens element E3 on the eye side is concave, and surface S17 on the display side is concave.

[0069] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the third lens E3 and the partially reflecting element BS of the second element group, and the second lens E2 and the quarter-wave plate QWP of the first element group to reach the reflective polarizing element RP. After being reflected at the reflective polarizing element RP, it passes through the quarter-wave plate QWP and the second lens E2 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the partially reflecting element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to be emitted toward the human eye side.

[0070] In this embodiment, the partially reflective element BS may be a transflective film layer coated on the first side surface (the surface closest to the eye) of the third lens element E3. The reflective polarizer RP may be attached to the second side surface (the surface closest to the display) of the first lens element E1, and a quarter-wave plate QWP may be attached to the surface of the reflective polarizer RP closest to the display.

[0071] 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).

[0072] 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 First lens (E1) Aspheric 795.0596 2.4928 1.54 56.00 refraction S3 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 refraction S4 Quarter Wave Plate (QWP) spherical surface endless 0.2000 1.50 57.00 refraction S5 spherical surface endless 1.2410 refraction S6 Second lens (E2) Aspheric 187.2437 8.7654 1.54 56.00 refraction S7 Aspheric -94.3088 0.1000 refraction S8 Partially reflective element (BS) Aspheric -144.1146 -0.1000 reflection S9 Second lens (E2) Aspheric -94.3088 -8.7654 1.54 56.00 refraction S10 Aspheric 187.2437 -1.2410 refraction S11 Quarter Wave Plate (QWP) spherical surface endless -0.2000 1.50 57.00 refraction S12 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 reflection S13 spherical surface endless 1.2410 refraction S14 Second lens (E2) Aspheric 187.2437 8.7654 1.54 56.00 refraction S15 Aspheric -94.3088 0.1000 refraction S16 Third lens (E3) Aspheric -144.1146 2.0000 1.67 19.00 refraction S17 Aspheric 128.4419 14.9474 refraction S18 Image surface (IMG) spherical surface endless 0.0000 refraction

[0073] Table 1

[0074] In Example 1, the surface S2 of the first lens element E1 on the side closest to the human eye, the surface S6 and the surface S7 of the second lens element E2 on the side closest to the human eye, and the surface S16 and the surface S17 of the third lens element E3 on the side closest to the human eye are all aspherical surfaces. The surface shape x of the aspherical lenses can be defined by, but is not limited to, the following aspherical surface formula:

[0075]

[0076] 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 that can be used for the aspheric mirror surfaces S2, S6, S7, S16, and S17 in Example 1. 10 、A 12 、A 14 、A 16 、A 18 and A 20 .

[0077]

[0078]

[0079] Table 2

[0080] 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.

[0081] Example 2

[0082] 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.

[0083] like Figure 3 As shown, the optical system includes, in order from the eye side to the display side along the optical axis: an aperture STO, a first lens E1, a reflective polarizer RP, a quarter-wave plate QWP, a second lens E2, a partially reflecting element BS, a third lens E3, and an image surface IMG. The first lens E1, reflective polarizer RP, quarter-wave plate QWP, and second lens E2 form a first element group, while the partially reflecting element BS and third lens E3 form a second element group.

[0084] In this embodiment, the first lens group has positive optical power. Surface S2 of the first lens element E1 on the eye side is convex, and surface S3 on the display side is flat. Surface S6 of the second lens element E2 on the eye side is convex, and surface S7 on the display side is convex. The second lens group has negative optical power. Surface S16 of the third lens element E3 on the eye side is concave, and surface S17 on the display side is concave.

[0085] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the third lens E3 and the partially reflecting element BS of the second element group, and the second lens E2 and the quarter-wave plate QWP of the first element group to reach the reflective polarizing element RP. After being reflected at the reflective polarizing element RP, it passes through the quarter-wave plate QWP and the second lens E2 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the partially reflecting element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to be emitted toward the human eye side.

[0086] In this embodiment, the partially reflective element BS may be a transflective film layer coated on the first side surface (the surface closest to the eye) of the third lens element E3. The reflective polarizer RP may be attached to the second side surface (the surface closest to the display) of the first lens element E1, and a quarter-wave plate QWP may be attached to the surface of the reflective polarizer RP closest to the display.

[0087] Table 3 shows the basic parameters of the optical system of Example 2, where the units of the curvature radius and thickness are both in millimeters (mm). In this embodiment, the surface S2 of the first lens E1 near the human eye side, the surface S6 near the human eye side and the surface S7 near the display side of the second lens E2, and the surface S16 near the human eye side and the surface S17 near the display side of the third lens E3 are all aspherical surfaces. Table 4 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, 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, A52, A53, A54, A55, A56, A57, A58, A59, A60, A61, A71, A72, A73, A74, A75 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.

[0088]

[0089]

[0090] Table 3

[0091] Coefficient\Surface S2 S6 S7 S16 S17 A4 -3.2322E-01 3.4622E-01 -3.1006E-01 8.0621E-02 -2.9268E-01 A6 -1.5510E-02 7.4402E-02 -8.6134E-02 1.0801E-02 -4.0317E-01 A8 -1.4942E-02 -4.2540E-02 1.3720E-01 -6.4907E-02 8.5275E-02 A10 -2.0747E-03 -8.3050E-03 -5.3703E-02 2.0828E-02 -5.0634E-03 A12 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A14 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A16 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A18 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A20 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0092] Table 4

[0093] 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 4CThe 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.

[0094] Example 3

[0095] 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.

[0096] like Figure 5 As shown, the optical system includes, in order from the eye side to the display side along the optical axis: an aperture STO, a first lens E1, a reflective polarizer RP, a quarter-wave plate QWP, a second lens E2, a partially reflecting element BS, a third lens E3, and an image surface IMG. The first lens E1, reflective polarizer RP, quarter-wave plate QWP, and second lens E2 form a first element group, while the partially reflecting element BS and third lens E3 form a second element group.

[0097] In this embodiment, the first lens group has positive optical power. Surface S2 of the first lens element E1 on the eye side is convex, and surface S3 on the display side is flat. Surface S6 of the second lens element E2 on the eye side is convex, and surface S7 on the display side is convex. The second lens group has negative optical power. Surface S16 of the third lens element E3 on the eye side is concave, and surface S17 on the display side is convex.

[0098] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the third lens E3 and the partially reflecting element BS of the second element group, and the second lens E2 and the quarter-wave plate QWP of the first element group to reach the reflective polarizing element RP. After being reflected at the reflective polarizing element RP, it passes through the quarter-wave plate QWP and the second lens E2 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the partially reflecting element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to be emitted toward the human eye side.

[0099] In this embodiment, the partially reflective element BS may be a transflective film layer coated on the first side surface (the surface closest to the eye) of the third lens element E3. The reflective polarizer RP may be attached to the second side surface (the surface closest to the display) of the first lens element E1, and a quarter-wave plate QWP may be attached to the surface of the reflective polarizer RP closest to the display.

[0100] 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 S2 of the first lens E1 near the human eye side, the surface S6 near the human eye side and the surface S7 near the display side of the second lens E2, and the surface S16 near the human eye side and the surface S17 near the display side of the third lens E3 are all aspherical surfaces. Table 6 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, 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, A52, A53, A54, A55, A56, A57, A58, A59, A60, A61, A62, A63, A70, A71, A72, A73, A74, A75 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.

[0101] 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 First lens (E1) Aspheric 251.1249 2.8137 1.54 56.00 refraction S3 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 refraction S4 Quarter Wave Plate (QWP) spherical surface endless 0.2000 1.50 57.00 refraction S5 spherical surface endless 0.9786 refraction S6 Second lens (E2) Aspheric 322.8911 15.7317 1.54 56.00 refraction S7 Aspheric -94.1298 0.1543 refraction S8 Partially reflective element (BS) Aspheric -134.2108 -0.1543 reflection S9 Second lens (E2) Aspheric -94.1298 -15.7317 1.54 56.00 refraction S10 Aspheric 322.8911 -0.9786 refraction S11 Quarter Wave Plate (QWP) spherical surface endless -0.2000 1.50 57.00 refraction S12 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 reflection S13 spherical surface endless 0.9786 refraction S14 Second lens (E2) Aspheric 322.8911 15.7317 1.54 56.00 refraction S15 Aspheric -94.1298 0.1543 refraction S16 Third lens (E3) Aspheric -134.2108 5.3178 1.67 19.00 refraction S17 Aspheric -6098.8343 4.4574 refraction S18 Image surface (IMG) spherical surface endless 0.0000 refraction

[0102] Table 5

[0103] Coefficient\Surface S2 S6 S7 S16 S17 A4 -3.0080E-01 3.6982E-01 -3.0802E-01 8.2294E-02 -1.3435E-01 A6 -1.1303E-02 4.3705E-03 -1.3355E-01 3.8213E-03 -3.7569E-01 A8 -2.1150E-02 2.8420E-03 1.5724E-01 -5.5203E-02 1.1670E-01 A10 1.5462E-04 -1.5506E-02 -4.4261E-02 1.3099E-02 -3.7180E-02 A12 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A14 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A16 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A18 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A20 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0104] Table 6

[0105] 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.

[0106] Example 4

[0107] 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.

[0108] like Figure 7 As shown, the optical system includes, in order from the eye side to the display side along the optical axis: an aperture STO, a first lens E1, a reflective polarizer RP, a quarter-wave plate QWP, a second lens E2, a partially reflecting element BS, a third lens E3, and an image surface IMG. The first lens E1, reflective polarizer RP, quarter-wave plate QWP, and second lens E2 form a first element group, while the partially reflecting element BS and third lens E3 form a second element group.

[0109] In this embodiment, the first lens group has positive optical power. Surface S2 of the first lens element E1 on the eye side is concave, and surface S3 on the display side is convex. Surface S6 of the second lens element E2 on the eye side is flat, and surface S7 on the display side is convex. The second lens group has negative optical power. Surface S14 of the third lens element E3 on the eye side is concave, and surface S15 on the display side is concave.

[0110] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the third lens E3 and the partially reflecting element BS of the second element group, and the second lens E2 and the quarter-wave plate QWP of the first element group to reach the reflective polarizing element RP. After being reflected at the reflective polarizing element RP, it passes through the quarter-wave plate QWP and the second lens E2 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the partially reflecting element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to be emitted toward the human eye side.

[0111] In this embodiment, the partially reflective element BS may be a transflective coating layer coated on the first side surface (the surface closest to the eye) of the third lens element E3. A quarter-wave plate QWP may be attached to the first side surface (the surface closest to the eye) of the second lens element E2, and the reflective polarizer RP may be attached to the eye-facing surface of the quarter-wave plate QWP.

[0112] 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 S2 and surface S3 of the first lens E1 close to the human eye side, the surface S7 of the second lens E2 close to the display side, and the surface S14 and surface S15 of the third lens E3 close to the human eye side, are all aspherical surfaces. Table 8 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15 of the aspherical mirror surfaces S2, S3, S7, S14, and S15 that can be used in Example 4. 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.

[0113] 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 First lens (E1) Aspheric -285.7430 5.1234 1.54 56.00 refraction S3 Aspheric -68.0192 0.1000 refraction S4 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 refraction S5 Quarter Wave Plate (QWP) spherical surface endless 0.2000 1.50 57.00 refraction S6 Second lens (E2) spherical surface endless 9.8278 1.54 56.00 refraction S7 Aspheric -78.7963 2.4555 refraction S8 Partially reflective element (BS) Aspheric -145.6210 -2.4555 reflection S9 Second lens (E2) Aspheric -78.7963 -9.8278 1.54 56.00 refraction S10 Quarter Wave Plate (QWP) spherical surface endless -0.2000 1.50 57.00 refraction S11 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 reflection S12 Second lens (E2) spherical surface endless 9.8278 1.54 56.00 refraction S13 Aspheric -78.7963 2.4555 refraction S14 Third lens (E3) Aspheric -145.6210 2.0000 1.67 19.00 refraction S15 Aspheric 139.5727 10.2170 refraction S16 Image surface (IMG) spherical surface endless 0.0000 refraction

[0114] Table 7

[0115] Coefficient\Surface S2 S3 S7 S14 S15 A4 3.4766E-02 -2.9252E-01 -3.8223E-01 2.0754E-01 -2.4221E-01 A6 -4.3569E-02 1.3178E-01 -5.7302E-02 -2.1152E-02 -3.4737E-01 A8 -1.5011E-02 -1.1092E-02 7.8176E-02 -4.0106E-02 2.5224E-03 A10 -8.3303E-03 -9.0445E-03 -5.5907E-03 5.1680E-03 1.7444E-02 A12 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A14 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A16 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A18 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A20 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0116] Table 8

[0117] 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.

[0118] Example 5

[0119] The following reference Figures 9 to 10C An optical system according to Example 5 of the present application is described. Figure 9 A structural schematic diagram of an optical system according to Example 5 of the present application is shown.

[0120] like Figure 9 As shown, the optical system includes, in order from the eye side to the display side along the optical axis: an aperture STO, a first lens E1, a reflective polarizer RP, a quarter-wave plate QWP, a second lens E2, a partially reflecting element BS, a third lens E3, and an image surface IMG. The first lens E1, reflective polarizer RP, quarter-wave plate QWP, and second lens E2 form a first element group, while the partially reflecting element BS and third lens E3 form a second element group.

[0121] In this embodiment, the first lens group has positive optical power. Surface S2 of the first lens element E1 on the eye side is concave, and surface S3 on the display side is convex. Surface S6 of the second lens element E2 on the eye side is flat, and surface S7 on the display side is convex. The second lens group has negative optical power. Surface S14 of the third lens element E3 on the eye side is concave, and surface S15 on the display side is concave.

[0122] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the third lens E3 and the partially reflecting element BS of the second element group, and the second lens E2 and the quarter-wave plate QWP of the first element group to reach the reflective polarizing element RP. After being reflected at the reflective polarizing element RP, it passes through the quarter-wave plate QWP and the second lens E2 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the partially reflecting element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to be emitted toward the human eye side.

[0123] In this embodiment, the partially reflective element BS may be a transflective coating layer coated on the first side surface (the surface closest to the eye) of the third lens element E3. A quarter-wave plate QWP may be attached to the first side surface (the surface closest to the eye) of the second lens element E2, and the reflective polarizer RP may be attached to the eye-facing surface of the quarter-wave plate QWP.

[0124] Table 9 shows the basic parameters of the optical system of Example 5, where the units of the curvature radius and thickness are both in millimeters (mm). In this embodiment, the surface S2 and surface S3 of the first lens E1 close to the human eye side, the surface S7 of the second lens E2 close to the display side, and the surface S14 and surface S15 of the third lens E3 close to the human eye side, are all aspherical surfaces. Table 10 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15 of the aspherical mirror surfaces S2, S3, S7, S14, and S15 that can be used in Example 5. 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.

[0125]

[0126]

[0127] Table 9

[0128] Coefficient\Surface S2 S3 S7 S14 S15 A4 6.0484E-02 -2.1612E-01 -3.6641E-01 2.1855E-01 1.6958E-03 A6 1.2179E-02 2.2124E-01 -6.0207E-02 -3.5156E-02 -4.3990E-01 A8 -9.5218E-03 -8.1644E-03 6.9891E-02 -3.3330E-02 4.8405E-02 A10 -3.1446E-03 -5.8450E-03 -1.5079E-02 7.0510E-03 2.2722E-02 A12 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A14 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A16 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A18 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A20 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0129] Table 10

[0130] Figure 10A The axial chromatic aberration curve of the optical system of Example 5 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 10B The astigmatism curve of the optical system of Example 5 is shown, which indicates the meridional field curvature and the sagittal field curvature. Figure 10C The distortion curve of the optical system of Example 5 is shown, which represents the distortion value corresponding to different field angles. 10A to 10C It can be seen that the optical system provided in Example 5 can achieve good imaging quality.

[0131] Example 6

[0132] The following reference Figures 11 to 12C An optical system according to Example 6 of the present application is described. Figure 11 A structural schematic diagram of an optical system according to Example 6 of the present application is shown.

[0133] like Figure 11 As shown, the optical system includes, in order from the eye side to the display side along the optical axis: an aperture STO, a first lens E1, a reflective polarizer RP, a quarter-wave plate QWP, a second lens E2, a partially reflecting element BS, a third lens E3, and an image surface IMG. The first lens E1, reflective polarizer RP, quarter-wave plate QWP, and second lens E2 form a first element group, while the partially reflecting element BS and third lens E3 form a second element group.

[0134] In this embodiment, the first lens group has positive optical power. Surface S2 of the first lens element E1 on the eye side is concave, and surface S3 on the display side is convex. Surface S6 of the second lens element E2 on the eye side is flat, and surface S7 on the display side is convex. The second lens group has negative optical power. Surface S14 of the third lens element E3 on the eye side is concave, and surface S15 on the display side is concave.

[0135] In this embodiment, the light beam emitted from the image surface IMG can sequentially pass through the third lens E3 and the partially reflecting element BS of the second element group, and the second lens E2 and the quarter-wave plate QWP of the first element group to reach the reflective polarizing element RP. After being reflected at the reflective polarizing element RP, it passes through the quarter-wave plate QWP and the second lens E2 again to reach the partially reflecting element BS. Thereafter, the light beam is reflected again at the partially reflecting element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to be emitted toward the human eye side.

[0136] In this embodiment, the partially reflective element BS may be a transflective coating layer coated on the first side surface (the surface closest to the eye) of the third lens element E3. A quarter-wave plate QWP may be attached to the first side surface (the surface closest to the eye) of the second lens element E2, and the reflective polarizer RP may be attached to the eye-facing surface of the quarter-wave plate QWP.

[0137] Table 11 shows the basic parameters of the optical system of Example 6, where the units of the curvature radius and thickness are both in millimeters (mm). In this embodiment, the surface S2 and surface S3 of the first lens E1 near the human eye side, the surface S7 of the second lens E2 near the display side, and the surface S14 and surface S15 of the third lens E3 near the human eye side, are all aspherical surfaces. Table 12 shows the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15 of the aspherical mirror surfaces S2, S3, S7, S14, and S15 that can be used in Example 6. 10 、A 12 、A 14 、A 16 、A18 and A 20 , wherein each aspheric surface shape can be defined by formula (1) given in the above embodiment 1.

[0138] 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 First lens (E1) Aspheric -264.9633 6.2107 1.54 56.00 refraction S3 Aspheric -53.4711 0.1000 refraction S4 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 refraction S5 Quarter Wave Plate (QWP) spherical surface endless 0.2000 1.50 57.00 refraction S6 Second lens (E2) spherical surface endless 6.9708 1.54 56.00 refraction S7 Aspheric -85.5070 3.5638 refraction S8 Partially reflective element (BS) Aspheric -145.7175 -3.5638 reflection S9 Second lens (E2) Aspheric -85.5070 -6.9708 1.54 56.00 refraction S10 Quarter Wave Plate (QWP) spherical surface endless -0.2000 1.50 57.00 refraction S11 Reflective polarizer (RP) spherical surface endless 0.2000 1.50 57.00 reflection S12 Second lens (E2) spherical surface endless 6.9708 1.54 56.00 refraction S13 Aspheric -85.5070 3.5638 refraction S14 Third lens (E3) Aspheric -145.7175 2.0000 1.67 19.00 refraction S15 Aspheric 133.6482 10.8970 refraction S16 Image surface (IMG) spherical surface endless 0.0000 refraction

[0139] Table 11

[0140] Coefficient\Surface S2 S3 S7 S14 S15 A4 1.9046E-01 -2.0987E-01 -3.6637E-01 2.9035E-01 -2.0171E-01 A6 -2.7750E-02 2.2832E-01 -7.6890E-04 -6.6431E-02 -3.4099E-01 A8 -1.1090E-03 3.5757E-03 2.8548E-02 -2.0791E-02 3.2601E-02 A10 -1.0703E-03 -4.5181E-03 -1.8886E-02 8.2119E-03 2.0471E-02 A12 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A14 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A16 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A18 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 A20 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0141] Table 12

[0142] Figure 12A The axial chromatic aberration curve of the optical system of Example 6 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 12B The astigmatism curve of the optical system of Example 6 is shown, which indicates the meridional field curvature and the sagittal field curvature. Figure 12C The distortion curve of the optical system of Example 6 is shown, which represents the distortion value corresponding to different field angles. 12A to 12C It can be seen that the optical system provided in Example 6 can achieve good imaging quality.

[0143] In addition, in Examples 1 to 6, the effective focal length FG1 of the first element group, the effective focal length FG2 of the second 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 third 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 third lens on the display side, the distance BFL on the optical axis from the surface of the third lens on the display side to the image plane, the center thickness CTR of the reflective polarizer on the optical axis, and the center thickness CTQ of the quarter-wave plate on the optical axis are as shown in Table 13.

[0144] Parameters / Example 1 2 3 4 5 6 FG1(mm) 26.67 29.18 29.58 28.38 28.89 27.97 FG2(mm) -119.04 -215.96 -317.90 -134.13 -140.34 -126.00 f(mm) 30.18 30.44 30.47 30.72 30.88 30.55 EPD(mm) 5.00 5.00 5.00 5.00 5.00 5.00 SL(mm) 44.95 44.96 44.85 45.12 45.12 45.14 SD(mm) 30.00 38.70 40.40 34.91 36.26 34.25 TD(mm) 15.00 23.70 25.40 19.91 21.26 19.25 BFL(mm) 14.95 6.26 4.46 10.22 8.86 10.90 CTR(mm) 0.20 0.20 0.20 0.20 0.20 0.20 CTQ(mm) 0.20 0.20 0.20 0.20 0.20 0.20

[0145] Table 13

[0146] Examples 1 to 6 respectively satisfy the conditions shown in Table 14.

[0147] Conditional formula / Example 1 2 3 4 5 6 FG1 / (CT1+CTR+CTQ+CT2) 2.29 1.66 1.56 1.85 1.71 2.06 R5 / R4 1.53 1.45 1.43 1.85 1.78 1.70 T12 / (CTR+CTQ) 4.10 3.99 3.45 1.25 1.25 1.25 f / EPD 6.04 6.09 6.09 6.14 6.18 6.11 f / TD 2.01 1.28 1.20 1.54 1.45 1.59 (T23+CT3) / BFL 0.14 0.79 1.23 0.44 0.49 0.51 f / (N1+N2+N3)(mm) 6.35 6.41 6.41 6.47 6.50 6.43 FG2 / (SL+SD) -1.59 -2.58 -3.73 -1.68 -1.72 -1.59 |R1+R4| / (V1+V2)(mm) 6.26 1.42 1.40 3.25 3.44 3.13 FG2 / R5 0.83 1.56 2.37 0.92 0.97 0.86 (FG1-FG2) / f 4.83 8.05 11.40 5.29 5.48 5.04

[0148] Table 14

[0149] 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 first element group and the second element group are sequentially included from the first side to the second side along the optical axis, wherein: The first element group has positive optical power and is composed of, in order from the first side to the second side along the optical axis, a first lens with positive optical power, a reflective polarizing element, a quarter-wave plate, and a second lens with positive optical power; the second side surface of the second lens is convex; The second element group has negative optical power and is composed of a partially reflecting element and a third lens having negative optical power, wherein the partially reflecting element is located on a first side surface of the third lens; and the first side surface of the third lens is a concave surface; The number of lenses having optical power in the optical system is three; The optical system satisfies: 1.56≤FG1 / (CT1+CTR+CTQ+CT2)≤2.29, Among them, FG1 is the effective focal length of the first element group, CT1 is the center thickness of the first lens on the optical axis, CTR is the center thickness of the reflective polarizing element on the optical axis, CTQ is the center thickness of the quarter-wave plate on the optical axis, and CT2 is the center thickness of the second lens on the optical axis.

2. The optical system according to claim 1, wherein: The curvature radius R5 of the first side surface of the third lens and the curvature radius R4 of the second side surface of the second lens satisfy: 1.4<R5 / R4≤1.

85.

3. The optical system according to claim 1, wherein: The air gap T12 between the first lens and the second lens on the optical axis, the center thickness CTR of the reflective polarizing element on the optical axis, and the center thickness CTQ of the quarter-wave plate on the optical axis satisfy the following conditions: 1.25≤T12 / (CTR+CTQ)≤4.

10.

4. The optical system according to claim 1, wherein: The effective focal length f of the optical system and the entrance pupil diameter EPD of the optical system satisfy: 6.0<f / EPD≤6.

18.

5. The optical system according to claim 1, wherein: 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 third lens on the optical axis satisfy: 1.20≤f / TD≤2.

01.

6. The optical system according to claim 1, wherein: The optical system further includes an image plane disposed on the second side, and an air gap T23 between the second lens and the third lens on the optical axis, a center thickness CT3 of the third lens on the optical axis, and a distance BFL from the second side surface of the third lens to the image plane on the optical axis satisfy the following conditions: 0.1<(T23+CT3) / BFL≤1.

23.

7. The optical system according to claim 1, wherein: The effective focal length f of the optical system, the refractive index N1 of the first lens, the refractive index N2 of the second lens, and the refractive index N3 of the third lens satisfy: 6.35mm≤f / (N1+N2+N3)≤6.50mm.

8. The optical system according to any one of claims 1 to 7, characterized in that The optical system further includes an aperture and an image surface disposed on the second side, wherein the effective focal length FG2 of the second element group, the distance SL from the aperture to the image surface on the optical axis, and the distance SD from the aperture to the second side surface of the third lens on the optical axis satisfy: -3.73≤FG2 / (SL+SD)≤-1.

59.

9. The optical system according to any one of claims 1 to 7, characterized in that The curvature radius R1 of the first side surface of the first lens, the curvature radius R4 of the second side surface of the second lens, the Abbe number V1 of the first lens, and the Abbe number V2 of the second lens satisfy: 1.40mm≤ R1+R4 / (V1+V2)<6.3mm.

10. The optical system according to any one of claims 1 to 7, characterized in that The effective focal length FG2 of the second lens element group and the curvature radius R5 of the first side surface of the third lens satisfy: 0.8<FG2 / R5<2.

4.

11. The optical system according to any one of claims 1 to 7, characterized in that The effective focal length FG1 of the first element group, the effective focal length FG2 of the second element group and the effective focal length f of the optical system satisfy: 4.8<(FG1-FG2) / f≤11.

40.

12. The optical system according to any one of claims 1 to 7, characterized in that The second side surface of the first lens or the first side surface of the second lens is a plane.

13. A VR device comprising the optical system according to any one of claims 1 to 12, wherein: The first side is a human eye side, and the second side is a display side.

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