CN116107071A

CN116107071A - Optical system and VR device including the same

Info

Publication number: CN116107071A
Application number: CN202310167648.7A
Authority: CN
Inventors: 戴付建; 梁宁; 张晓彬; 金银芳; 赵烈烽
Original assignee: Zhejiang Sunny Optics Co Ltd
Current assignee: Zhejiang Sunny Optics Co Ltd
Priority date: 2023-02-17
Filing date: 2023-02-17
Publication date: 2023-05-12

Abstract

The application discloses an optical system, which sequentially comprises a first element group and a second element group from a first side to a second side along an optical axis, wherein the first element group has positive focal power and comprises a reflective polarizing element, a first lens, a quarter wave plate and a second lens; the second element group has positive or negative optical power and includes a third lens and a partially reflecting element. The effective focal length FG1 of the first element group and the effective focal length FG2 of the second element group satisfy: 0.5< (FG2+FG1)/(FG2-FG1) <1.6.

Description

Optical system and VR device including the same

Technical Field

The present application relates to the field of optical elements, and more particularly, to an optical system and VR device including the same.

Background

In recent years, with the rapid increase of the number of users in the field related to VR devices, higher demands are also being made on hardware upgrades of VR devices, especially on the improvement of the portability and the visual efficiency of the devices, and the development of a "catadioptric optical system ultra-short focal optical scheme" has become a popular choice.

The refraction and reflection type optical system scheme is based on the polarized light principle, utilizes the characteristic that the reflection polaroid selectively reflects and projects different polarized lights, and is matched with a 1/4 phase delay sheet to adjust the polarized light form, so that the folding effect of an optical path is realized, the thickness of an optical module can be greatly reduced, and the volume of VR equipment is obviously compressed. However, the 2-piece type scheme is generally adopted in the refraction and reflection type optical system scheme in the market at present, the scheme has serious ghost image problem, and the angle of view is limited, so that the optical performance and the application range of the refraction and reflection type optical system are affected to a certain extent. Therefore, how to improve the design scheme of the present catadioptric optical system, for example, by adjusting the folded light path structure, so as to attempt to solve the ghost problem and further increase the field angle is one of the technical problems that needs to be solved by those skilled in the art.

Disclosure of Invention

The application provides an optical system, which sequentially comprises a first element group and a second element group from a first side to a second side along an optical axis, wherein the first element group has positive optical power and comprises a reflective polarizing element, a first lens, a quarter wave plate and a second lens; the second element group has positive optical power or negative optical power and comprises a third lens and a partial reflecting element; and the effective focal length FG1 of the first element group and the effective focal length FG2 of the second element group may satisfy: 0.5< (FG2+FG1)/(FG2-FG1) <1.6.

In one embodiment, the radius of curvature R2 of the second side of the first lens and the radius of curvature R1 of the first side of the first lens may satisfy: 0.4< R2/R1<1.7.

In one embodiment, the radius of curvature R3 of the first side of the second lens and the radius of curvature R4 of the second side of the second lens may satisfy: -0.9< (r3—r4)/(r3+r4) <0.7.

In one embodiment, the refractive index N1 of the first lens, the refractive index N2 of the second lens, and the central thickness CTR of the reflective polarizing element on the optical axis and the central thickness CTQ of the quarter-wave plate on the optical axis may satisfy: 1.2mm < (N1+N2) × (CTR+CTQ) <1.6mm.

In one embodiment, the effective focal length f of the optical system and the entrance pupil diameter EPD of the optical system may satisfy: 5.3< f/EPD <6.0.

In one embodiment, the effective focal length FG1 of the first element group, the center thickness CT1 of the first lens on the optical axis, and the center thickness CT2 of the second lens on the optical axis may satisfy: 2< FG1/(CT1+CT2) <8.

In one embodiment, the optical system further includes a diaphragm and an image surface disposed on the second side, and a distance SL between the diaphragm and the image surface on the optical axis and a distance TD between the first side surface of the first lens and the second side surface of the third lens on the optical axis may satisfy: 2.5< SL/TD <3.3.

In one embodiment, the optical system further includes a stop, and the distance SD of the stop to the second side of the third lens and the distance ER of the stop to the first side of the first lens on the optical axis may satisfy: 1.6< SD/ER <2.0.

In one embodiment, the radius of curvature R1 of the first side surface of the first lens, the radius of curvature R3 of the first side surface of the second lens, and the abbe number V1 of the first lens and the abbe number V2 of the second lens may satisfy: 2.0mm < |R1+R3|/(V1+V2) <6.9mm.

In one embodiment, the center thickness CTQ of the quarter-wave plate on the optical axis, the air interval T23 of the second lens and the third lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, and the abbe number V3 of the third lens may satisfy: 0.05mm < (CTQ+T23+CT3)/V3 <0.35mm.

In one embodiment, the first side of the first lens is concave and the second side is convex.

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

In another aspect, the present application further provides a VR device, where the VR device includes an optical system provided in at least one of the foregoing embodiments, and the first side is a human eye side and the second side is a display side.

The optical system sequentially comprises a first element group and a second element group from a first side to a second side along an optical axis, wherein the first element group comprises a reflective polarizing element, a first lens, a quarter wave plate and a second lens, and the first element group has positive focal power; providing a second element group comprising a third lens and a partially reflecting element; meanwhile, the effective focal lengths of the first element group and the second element group are controlled to meet the condition that (FG2+FG1)/(FG2-FG1) <1.6, so that the spherical aberration can be reduced and the chromatic aberration can be reduced; the method is beneficial to the increase of the angle of view and the improvement of ghost images; and the system focal power distribution can be met, and meanwhile, the light design of the system is facilitated.

Drawings

Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, taken in conjunction with the accompanying drawings. In the drawings:

fig. 1 shows a schematic configuration diagram of an optical system according to embodiment 1 of the present application;

fig. 2A to 2C show an on-axis chromatic aberration curve, an astigmatism curve, and a distortion curve, respectively, of the optical system of embodiment 1;

fig. 3 shows a schematic structural view of an optical system according to embodiment 2 of the present application;

fig. 4A to 4C show an on-axis chromatic aberration curve, an astigmatism curve, and a distortion curve of the optical system of embodiment 2, respectively;

fig. 5 shows a schematic structural view of an optical system according to embodiment 3 of the present application;

fig. 6A to 6C show an on-axis chromatic aberration curve, an astigmatism curve, and a distortion curve of the optical system of embodiment 3, respectively;

fig. 7 shows a schematic structural view of an optical system according to embodiment 4 of the present application;

fig. 8A to 8C show an on-axis chromatic aberration curve, an astigmatism curve, and a distortion curve of the optical system of embodiment 4, respectively;

fig. 9 shows a schematic structural view of an optical system according to embodiment 5 of the present application;

fig. 10A to 10C show an on-axis chromatic aberration curve, an astigmatism curve, and a distortion curve of the optical system of embodiment 5, respectively;

Fig. 11 shows a schematic structural view of an optical system according to embodiment 6 of the present application; and

fig. 12A to 12C show an on-axis chromatic aberration curve, an astigmatism curve, and a distortion curve of the optical system of embodiment 6, respectively.

Detailed Description

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 description are merely illustrative of exemplary embodiments of the application and are not intended to limit the scope of the application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that in this specification, the expressions first, second, etc. are only used to distinguish one feature from another feature, and do not represent any limitation of the feature. Accordingly, a first optical lens discussed below may also be referred to as a second optical lens, and a second optical lens may also be referred to as a first optical lens, without departing from the teachings of the present application.

In the drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for convenience of explanation. In particular, the spherical or aspherical shape shown in the drawings is shown by way of example. That is, the shape of the spherical or aspherical surface is not limited to the shape of the spherical or aspherical surface shown in the drawings. The figures are merely examples and are not drawn to scale.

Herein, the paraxial region refers to a region near the optical axis. If the lens surface is convex and the convex position is not defined, then the lens surface is convex at least in the paraxial region; if the lens surface is concave and the concave position is not defined, it means that the lens surface is concave at least in the paraxial region.

It will be further understood that the terms "comprises," "comprising," "includes," "including," "having," "containing," and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Furthermore, when a statement such as "at least one of the following" appears after a list of features that are listed, the entire listed feature is modified instead of modifying a separate element in the list. Furthermore, when describing embodiments of the present application, use of "may" means "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.

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

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

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

The optical system according to the exemplary embodiment of the present application may include a first element group and a second element group sequentially arranged from a first side to a second side along the optical axis, wherein the first element group may include a reflective polarizing element, a first lens, a quarter wave plate, and a second lens, and the second element group may include a third lens and a partially reflective element.

In an exemplary embodiment, the first element group may have positive optical power. The second element group may have positive or negative optical power.

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, for example, in a variety of VR display devices.

In an exemplary embodiment, the first side of the first lens may be a surface of the first lens on a side close to the human eye, and the second side of the first lens may be a surface of the first lens on a side close to the display. The first side of the second lens may be a surface of the second lens close to the human eye side, and the second side of the second lens may be a surface of the second lens close to the display side. The first side of the third lens may be a surface of the third lens close to the human eye side, and the second side of the third lens may be a surface of the third lens close to the display side.

An optical system will be exemplarily described below with reference to fig. 1. As shown in fig. 1, the optical system according to the exemplary embodiment of the present application may include a reflective polarizing element RP, a first lens E1, a second lens E2, a quarter wave plate QWP, a partially reflective element BS, and a third lens E3, which are sequentially arranged from a first side to a second side, wherein the reflective polarizing element RP, the first lens E1, the second lens E2, and the quarter wave plate QWP constitute a first element group, and the partially reflective element BS and the third lens E3 constitute a second element group. In actual use, the optical system according to the exemplary embodiment of the present application may be used as a VR lens, in which case the first side corresponds to the human eye side and the second side corresponds to the display side. The optical system may further comprise an image plane IMG located at the display side. The light beam emitted from the image plane IMG may sequentially pass through the third lens E3 and the partial reflecting element BS of the second element group, and the quarter-wave plate QWP, the second lens E2 and the first lens E1 of the first element group, reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the first lens E1, the second lens E2 and the quarter-wave plate QWP again to reach the partial reflecting element BS, and then be reflected again at the partial reflecting element BS and sequentially pass through the quarter-wave plate QWP, the second lens E2, the first lens E1 and the reflective polarizing element RP to exit toward the human eye side. In an exemplary embodiment, the partially reflective element BS may be a semi-transparent and semi-reflective film layer plated on the first side of the third lens E3. In an exemplary embodiment, the reflective polarizing element RP may be attached to the first side of the first lens E1. In an exemplary embodiment, a quarter wave plate QWP may be attached on the second side of the second lens E2.

In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 0.5< (FG 2+fg 1)/(FG 2-FG 1) <1.6, where FG1 is an effective focal length of the first element group and FG2 is an effective focal length of the second element group.

According to the optical system of the exemplary embodiment of the present application, a first element group and a second element group are sequentially arranged from a first side to a second side along an optical axis, and include three lenses in total, specifically, the first element group is arranged to include a reflective polarizing element, a first lens, a quarter wave plate, and a second lens, and the second element group includes a third lens and a partially reflective element; the surface shapes of the first lens and the third lens are reasonably controlled, so that the spherical aberration can be reduced and the chromatic aberration can be reduced; attaching a reflective polarizing element to, for example, the eye side surface of the first lens, reasonably attaching a quarter-wave plate to the eye side surface of the second lens or the display side surface, and reasonably plating a partial reflective layer on the eye side surface of the third lens or the display side surface, thereby being beneficial to the increase of the angle of view and the improvement of ghost images; meanwhile, the effective focal length of the first element group and the effective focal length of the second element group are controlled to meet the condition of 0.5< (FG2+FG1)/(FG2-FG1) <1.6, and the light design of the system can be facilitated while the system focal power distribution is met.

In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 0.4< R2/R1<1.7, where R2 is a radius of curvature of the second side surface of the first lens and R1 is a radius of curvature of the first side surface of the first lens. By controlling the ratio of the radius of curvature of the second side surface of the first lens to the radius of curvature of the first side surface of the first lens within this range, the optical power of the first lens can be controlled, and the first lens can be made to have good manufacturability.

In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression-0.9 < (R3-R4)/(r3+r4) <0.7, where R3 is a radius of curvature of the first side of the second lens and R4 is a radius of curvature of the second side of the second lens. By controlling the radius of curvature of the first side of the second lens and the radius of curvature of the second side of the second lens to satisfy-0.9 < (R3-R4)/(R3+R4) <0.7, the optical power of the second lens can be controlled, and the light ray trend can be controlled to be more optimal, thereby being beneficial to improving the image quality and the relative illuminance of the system.

In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 1.2mm < (n1+n2) × (ctr+ctq) <1.6mm, where N1 is the refractive index of the first lens, N2 is the refractive index of the second lens, CTR is the center thickness of the reflective polarizing element on the optical axis, and CTQ is the center thickness of the quarter-wave plate on the optical axis. By controlling the refractive index of the first lens, the refractive index of the second lens, 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 1.2mm < (n1+n2) × (ctr+ctq) <1.6mm, the optical path of light passing through the reflective polarizing element and the quarter-wave plate can be controlled, reducing the introduction of additional system aberrations by both.

In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 5.3< f/EPD <6.0, where f is an effective focal length of the optical system and EPD is an 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 in the range, the aperture of the system can be controlled, so that the aperture of the system is larger, and the light entering quantity of the system is increased.

In an exemplary embodiment, the optical system of the present application may satisfy the condition 2< fg1/(CT 1+ct 2) <8, where FG1 is the effective focal length of the first element group, CT1 is the center thickness of the first lens on the optical axis, and CT2 is the center thickness of the second lens on the optical axis. The effective focal length of the first element group, the central thickness of the first lens on the optical axis and the central thickness of the second lens on the optical axis are controlled to be 2< FG1/(CT1+CT2) <8, so that the miniaturization of the system is facilitated, and the ghost image risk caused by the reflection of the lens is avoided.

In an exemplary embodiment, the optical system of the present application may further include a stop and an image surface disposed at the second side, and the optical system of the present application may satisfy conditional expression 2.5< SL/TD <3.3, where SL is a distance on the optical axis from the stop to the image surface, and TD is a 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 distance from the diaphragm to the image surface on the optical axis to the distance from the first side surface of the first lens to the second side surface of the third lens on the optical axis within the range, the position of the diaphragm of the system can be adjusted, the off-axis aberration of the system can be improved, the total length of the system can be controlled, and the light and small design of the system can be realized.

In an exemplary embodiment, the optical system of the present application may further include a stop, and the optical system of the present application may satisfy a conditional expression 1.6< SD/ER <2.0, where SD is a distance on the optical axis of the stop to the second side of the third lens, and ER is a distance on the optical axis of the stop to the first side of the first lens. By controlling the ratio of the distance from the diaphragm to the second side of the third lens on the optical axis to the distance from the diaphragm to the first side of the first lens on the optical axis within this range, the aperture position of the system can be controlled, which is advantageous for adjusting the exit pupil position of the optical system, and the system throughput can be controlled.

In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 2.0mm < |r1+r3|/(v1+v2) <6.9mm, where R1 is a radius of curvature of the first side surface of the first lens, R3 is a radius of curvature of the first side surface of the second lens, V1 is an abbe number of the first lens, and V2 is an abbe number of the second lens. By controlling the radius of curvature of the first side of the first lens, the radius of curvature of the first side of the second lens, the abbe number of the first lens, and the abbe number of the second lens to satisfy 2.0mm < |r1+r3|/(v1+v2) <6.9mm, it is advantageous to optimize the light ray direction, and the amount of system dispersion introduced by the first and second lenses can be further controlled.

In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 0.05mm < (ctq+t23+ct3)/V3 <0.35mm, where CTQ is a center thickness of the quarter wave plate on the optical axis, T23 is an air space of the second lens and the third lens on the optical axis, CT3 is a center thickness of the third lens on the optical axis, and V3 is an abbe number of the third lens. The dispersion amount introduced by the third lens and the quarter wave plate can be controlled by controlling the center thickness of the quarter wave plate on the optical axis, the air interval of the second lens and the third lens on the optical axis, the center thickness of the third lens on the optical axis and the Abbe number of the third lens to be 0.05mm < (CTQ+T23+CT3)/V3 <0.35mm, which is beneficial to the optimization of the chromatic aberration of the system.

In an exemplary embodiment, the first side of the first lens may be concave and the second side may be convex. By controlling the surface shape of the first lens, the outgoing angle of the light is favorably controlled, and the improvement of the angle of view is favorably realized.

In an exemplary embodiment, the first side of the second lens may be concave and the second side may be convex. The first side of the third lens may be concave. The surface shapes of the second lens and the third lens are reasonably controlled, so that the trend of light rays can be further optimized, the image quality of a system is improved, the incidence angle of marginal light rays is restrained, and chip matching is facilitated.

In an exemplary embodiment, the optical system of the present application may include at least one aperture. The diaphragm can restrict the light path and control the intensity of light. The diaphragm may be arranged in a suitable position of the optical system, for example, the diaphragm may be located between the first side (the eye side) and the first element group.

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

In an exemplary embodiment, the effective focal length f of the optical system may be, for example, in the range of 27.33mm to 29.05mm, the effective focal length FG1 of the first element group may be, for example, in the range of 25.58mm to 29.93mm, and the effective focal length FG2 of the second element group may be, for example, in the range of-258.94 mm to 1718.66 mm.

According to the optical system of the above embodiment of the present application, by disposing a first element group and a second element group sequentially from a first side to a second side along an optical axis, the first element group includes a reflective polarizing element, a first lens, a quarter wave plate, and a second lens, and the second element group includes a third lens and a partially reflective element; simultaneously controlling the effective focal length of the first element group and the effective focal length of the second element group to meet the condition of 0.5< (FG2+FG1)/(FG2-FG1) <1.6, which can be beneficial to reducing spherical aberration and chromatic aberration; the method is beneficial to the increase of the angle of view and the improvement of ghost images; and the system focal power distribution can be met, and meanwhile, the light design of the system is facilitated.

According to some embodiments of the present application, the lens may have good processing manufacturability by reasonably setting parameters such as a radius of curvature, a surface shape, a refractive index, a center thickness, an abbe number, an effective focal length, an entrance pupil diameter, and the like of the lens, and by reasonably setting parameters such as a diaphragm, a lens, and a distance between image surfaces; the light direction can be controlled to be better, and the improvement of the system image quality and the relative illumination is facilitated; additional system aberrations introduced by the element can be reduced; the system dispersion quantity introduced by the element can be controlled, which is favorable for optimizing the chromatic aberration of the system. The light inlet amount of the system can be increased; the system is beneficial to light and miniaturization, and meanwhile, the risk of ghost images caused by self-reflection of the lens is avoided; it is also advantageous to improve the off-axis aberrations of the system. In addition, the system view angle is improved; is beneficial to chip matching and the like.

Specific examples of the optical system applicable to the above-described embodiments are further described below with reference to the drawings.

Example 1

An optical system according to embodiment 1 of the present application is described below with reference to fig. 1 to 2C. Fig. 1 shows a schematic configuration of an optical system according to embodiment 1 of the present application.

As shown in fig. 1, the optical system sequentially includes, along the optical axis from the human eye side to the display side: stop STO, reflective polarizer RP, first lens E1, second lens E2, quarter wave plate QWP, partial reflector BS, third lens E3 and image plane IMG. Wherein the reflective polarizing element RP, the first lens E1, the second lens E2 and the quarter wave plate QWP constitute a first element group, and the partially reflective element BS and the third lens E3 constitute a second element group.

In this embodiment, the first element group has positive optical power, wherein the surface of the first lens E1 near the human eye side is concave, and the surface near the display side is convex; the surface of the second lens E2 near the human eye side is concave, and the surface near the display side is convex. The second element group has positive optical power, wherein the surface of the third lens E3 close to the human eye side is concave, and the surface close to the display side is convex.

In this embodiment, the light beam emitted from the image plane IMG may sequentially pass through the third lens E3 and the partially reflective element BS of the second element group, and the quarter-wave plate QWP, the second lens E2 and the first lens E1 of the first element group, reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the first lens E1, the second lens E2 and the quarter-wave plate QWP again to reach the partially reflective element BS, and then be reflected again at the partially reflective element BS and sequentially pass through the quarter-wave plate QWP, the second lens E2, the first lens E1 and the reflective polarizing element RP to exit toward the human eye side.

In this embodiment, the partially reflecting element BS may be a semi-transparent and semi-reflecting film layer plated on the first side surface (surface near the human eye side) of the third lens E3. The reflective polarizing element RP may be attached to the first side surface (surface near the human eye side) of the first lens E1. A quarter wave plate QWP may be attached to the second side surface (surface near the display side) of the second lens E2.

Table 1 shows basic parameters of the optical system of example 1, in which the unit of radius of curvature and thickness are both millimeters (mm).

TABLE 1

In embodiment 1, the surface S3 near the human eye side, the surface S4 near the display side, the surface S5 near the human eye side, the surface S6 near the display side, and the surface S18 near the human eye side, the surface S19 near the display side of the first lens E1, the surface pattern x of the aspherical lens are all aspherical, and the surface pattern x of the aspherical lens can be defined by, but not limited to, the following aspherical formula:

wherein x is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at the position with the height h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c=1/R (i.e., paraxial curvature c is the inverse of radius of curvature R in table 1 above); k is a conic coefficient; ai is the correction coefficient of the aspherical i-th order. Table 2 below shows the higher order coefficients A that can be used for the aspherical mirrors S3-S6, S18 and S19 in example 1 ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ 、A ₁₆ 、A ₁₈ And A ₂₀ 。

Coefficient/surface

S3

S4

S5

S6

S18

S19

A4

-2.8936E-01

-1.5113E-01

1.3327E-01

-4.8905E-03

-2.8988E-01

2.6714E-01

A6

1.9843E-01

-2.6197E-01

-2.7377E-01

3.2017E-01

8.8077E-02

-2.4404E-02

A8

-7.2904E-03

3.0361E-02

-4.9264E-03

-1.2643E-01

5.3540E-03

-1.8751E-01

A10

-1.6157E-03

5.3787E-03

-1.1425E-02

2.2082E-02

-7.6645E-03

9.1382E-03

A12

0.0000E+00

A14

0.0000E+00

A16

0.0000E+00

A18

0.0000E+00

A20

0.0000E+00

TABLE 2

Fig. 2A shows an on-axis chromatic aberration curve of the optical system of embodiment 1, which represents the focus deviation of light rays of different wavelengths after passing through the lens. Fig. 2B shows an astigmatism curve of the optical system of embodiment 1, which represents meridional image plane curvature and sagittal image plane curvature. Fig. 2C shows a distortion curve of the optical system of embodiment 1, which represents distortion magnitude values corresponding to different angles of view. As can be seen from fig. 2A to 2C, the optical system of embodiment 1 can achieve good imaging quality.

Example 2

An optical system according to embodiment 2 of the present application is described below with reference to fig. 3 to 4C. In this embodiment and the following embodiments, descriptions of portions similar to embodiment 1 will be omitted for brevity. Fig. 3 shows a schematic configuration of an optical system according to embodiment 2 of the present application.

As shown in fig. 3, the optical system sequentially includes, along the optical axis from the human eye side to the display side: stop STO, reflective polarizer RP, first lens E1, quarter wave plate QWP, second lens E2, partial reflector BS, third lens E3 and image plane IMG. Wherein the reflective polarizing element RP, the first lens E1, the quarter-wave plate QWP and the second lens E2 constitute a first element group, and the partially reflective element BS and the third lens E3 constitute a second element group.

In this embodiment, the first element group has positive optical power, wherein the surface of the first lens E1 near the human eye side is concave, and the surface near the display side is convex; the surface of the second lens E2 near the human eye side is concave, and the surface near the display side is convex. The second element group has negative focal power, wherein the surface of the third lens E3 close to the human eye side is a concave surface, and the surface close to the display side is a concave surface.

In this embodiment, the light beam emitted from the image plane IMG may sequentially pass through the third lens E3 and the partially reflective element BS of the second element group, and the second lens E2, the quarter-wave plate QWP and the first lens E1 of the first element group, reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the first lens E1, the quarter-wave plate QWP and the second lens E2 again to reach the partially reflective element BS, and then be reflected again at the partially reflective element BS and sequentially pass through the second lens E2, the quarter-wave plate QWP, the first lens E1 and the reflective polarizing element RP to exit toward the human eye side.

In this embodiment, the partially reflecting element BS may be a semi-transparent and semi-reflecting film layer plated on the first side surface (surface near the human eye side) of the third lens E3. The reflective polarizing element RP may be attached to the first side surface (surface near the human eye side) of the first lens E1. A quarter wave plate QWP may be attached to the first side (the surface near the human eye side) of the second lens E2.

Table 3 shows basic parameters of the optical system of example 2, in which the unit of radius of curvature and thickness are both millimeters (mm). In this embodiment, the surface S3 near the human eye side, the surface S4 near the display side, the surface S6 near the human eye side, the surface S7 near the display side, and the surface S18 near the human eye side, the surface S19 near the display side, of the first lens E1, the surface S18 near the human eye side, the surface S19 near the display side, of the third lens E3 are all aspherical surfaces, and Table 4 shows the higher order coefficients A that can be used for the aspherical mirror surfaces S3, S4, S6, S7, S18, and S19 in embodiment 2 ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ 、A ₁₆ 、A ₁₈ And A ₂₀ Wherein each aspherical surface profile can be defined by the formula (1) given in the above-described embodiment 1.

TABLE 3 Table 3

Coefficient/surface

S3

S4

S6

S7

S18

S19

A4

1.9887E-01

-1.9268E-01

2.3843E-01

-5.2062E-02

2.7880E-01

-2.3371E-01

A6

1.4662E-01

-4.2712E-02

-1.4118E-01

2.9558E-01

7.2087E-02

-1.6573E-01

A8

-3.8664E-02

-1.4715E-01

2.1236E-02

9.3743E-02

-2.4548E-02

-7.1272E-02

A10

-6.5591E-03

-3.1046E-03

1.4213E-04

3.0666E-04

-2.9853E-03

7.2500E-03

A12

0.0000E+00

A14

0.0000E+00

A16

0.0000E+00

A18

0.0000E+00

A20

0.0000E+00

TABLE 4 Table 4

Fig. 4A shows an on-axis chromatic aberration curve of the optical system of embodiment 2, which represents the focus deviation of light rays of different wavelengths after passing through the lens. Fig. 4B shows an astigmatism curve of the optical system of embodiment 2, which represents meridional image plane curvature and sagittal image plane curvature. Fig. 4C shows a distortion curve of the optical system of embodiment 2, which represents distortion magnitude values corresponding to different angles of view. As can be seen from fig. 4A to 4C, the optical system of embodiment 2 can achieve good imaging quality.

Example 3

An optical system according to embodiment 3 of the present application is described below with reference to fig. 5 to 6C. Fig. 5 shows a schematic structural view of an optical system according to embodiment 3 of the present application.

As shown in fig. 5, the optical system sequentially includes, along the optical axis from the human eye side to the display side: stop STO, reflective polarizer RP, first lens E1, quarter-wave plate QWP, second lens E2, third lens E3, partially reflective element BS and image plane IMG. Wherein the reflective polarizing element RP, the first lens E1, the quarter-wave plate QWP and the second lens E2 constitute a first element group, and the third lens E3 and the partially reflective element BS constitute a second element group.

In this embodiment, the first element group has positive optical power, wherein the surface of the first lens E1 near the human eye side is concave, and the surface near the display side is convex; the surface of the second lens E2 near the human eye side is concave, and the surface near the display side is convex. The second element group has negative focal power, wherein the surface of the third lens E3 close to the human eye side is concave, and the surface close to the display side is convex.

In this embodiment, the light beam emitted from the image plane IMG may sequentially pass through the partial reflection element BS and the third lens E3 of the second element group, and the second lens E2, the quarter wave plate QWP and the first lens E1 of the first element group, reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the first lens E1, the quarter wave plate QWP, the second lens E2 and the third lens E3 again to reach the partial reflection element BS, and then be reflected again at the partial reflection element BS and sequentially pass through the third lens E3, the second lens E2, the quarter wave plate QWP, the first lens E1 and the reflective polarizing element RP to exit toward the human eye side.

In this embodiment, the partially reflecting element BS may be a semi-transparent and semi-reflecting film layer plated on the second side surface (surface near the display side) of the third lens E3. The reflective polarizing element RP may be attached to the first side surface (surface near the human eye side) of the first lens E1. A quarter wave plate QWP may be attached to the first side (the surface near the human eye side) of the second lens E2.

Table 5 shows basic parameters of the optical system of example 3, in which the unit of radius of curvature and thickness are both millimeters (mm). In this embodiment, the surface S3 near the human eye side, the surface S4 near the display side, the surface S6 near the human eye side, the surface S7 near the display side, and the surface S8 near the human eye side, the surface S9 near the display side, of the third lens E3 are all aspherical surfaces, and Table 6 shows the higher order coefficients A that can be used for the aspherical mirror surfaces S3, S4, S6, S7, S8 and S9 in embodiment 3 ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ 、A ₁₆ 、A ₁₈ And A ₂₀ Wherein each aspherical surface profile can be defined by the formula (1) given in the above-described embodiment 1.

Surface of the body	Element	Surface type	Radius of curvature	Thickness of (L)	Refractive index	Abbe number	Refraction/reflection
								S0		Spherical surface	Infinity is provided	Infinity is provided			Refraction by refraction
S1	Diaphragm (STO)	Spherical surface	Infinity is provided	18.5927			Refraction by refraction
								S2	Reflective polarizing element (RP)	Aspherical surface	-71.7746	0.2000	1.50	57.00	Refraction by refraction
S3	First lens (E1)	Aspherical surface	-71.7746	1.9700	1.60	26.13	Refraction by refraction
								S4		Aspherical surface	-95.9737	0.1000			Refraction by refraction
S5	Quarter Wave Plate (QWP)	Aspherical surface	-140.7247	0.3000	1.50	57.00	Refraction by refraction
								S6	Second lens (E2)	Aspherical surface	-140.7247	11.2197	1.56	46.39	Refraction by refraction
S7		Aspherical surface	-40.0554	0.1000			Refraction by refraction
								S8	Third lens (E3)	Aspherical surface	-42.1444	2.0000	1.64	21.46	Refraction by refraction
S9	Partial reflecting member (BS)	Aspherical surface	-56.3156	-2.0000	1.64	21.46	Reflection of
								S10		Aspherical surface	-42.1444	-0.1000			Refraction by refraction
S11	Second lens (E2)	Aspherical surface	-40.0554	-11.2197	1.56	46.39	Refraction by refraction
								S12	Quarter Wave Plate (QWP)	Aspherical surface	-140.7247	-0.3000	1.50	57.00	Refraction by refraction
S13		Aspherical surface	-140.7247	-0.1000			Refraction by refraction
								S14	First lens (E1)	Aspherical surface	-95.9737	-1.9700	1.60	26.13	Refraction by refraction
S15	Reflective polarizing element (RP)	Aspherical surface	-71.7746	1.9700	1.60	26.13	Reflection of
								S16		Aspherical surface	-95.9737	0.1000			Refraction by refraction
S17	Quarter Wave Plate (QWP)	Aspherical surface	-140.7247	0.3000	1.50	57.00	Refraction by refraction
								S18	Second pass throughMirror (E2)	Aspherical surface	-140.7247	11.2197	1.56	46.39	Refraction by refraction
S19		Aspherical surface	-40.0554	0.1000			Refraction by refraction
								S20	Third lens (E3)	Aspherical surface	-42.1444	2.0000	1.64	21.46	Refraction by refraction
S21		Aspherical surface	-56.3156	5.3777			Refraction by refraction
								S22	Image plane (IMG)	Spherical surface	Infinity is provided	0.0000			Refraction by refraction

TABLE 5

Coefficient/surface

S3

S4

S6

S7

S8

S9

A4

-3.9844E-02

-1.5037E-01

2.5695E-01

5.9157E-02

-1.4120E-01

-2.9627E-02

A6

1.1446E-01

-2.1338E-01

1.3168E-02

2.5578E-01

-2.0257E-01

-1.6513E-03

A8

-2.8323E-02

1.3476E-01

7.5666E-02

-9.2370E-02

1.2953E-01

-1.2735E-02

A10

-4.4345E-03

-2.4579E-03

-3.4733E-02

-5.1424E-03

8.8666E-03

1.4788E-02

A12

0.0000E+00

A14

0.0000E+00

A16

0.0000E+00

A18

0.0000E+00

A20

0.0000E+00

TABLE 6

Fig. 6A shows an on-axis chromatic aberration curve of the optical system of embodiment 3, which indicates the focus deviation of light rays of different wavelengths after passing through the lens. Fig. 6B shows an astigmatism curve of the optical system of embodiment 3, which represents meridional image plane curvature and sagittal image plane curvature. Fig. 6C shows a distortion curve of the optical system of example 3, which represents distortion magnitude values corresponding to different angles of view. As can be seen from fig. 6A to 6C, the optical system provided in embodiment 3 can achieve good imaging quality.

Example 4

An optical system according to embodiment 4 of the present application is described below with reference to fig. 7 to 8C. Fig. 7 shows a schematic structural diagram of an optical system according to embodiment 4 of the present application.

As shown in fig. 7, the optical system sequentially includes, along the optical axis from the human eye side to the display side: stop STO, reflective polarizer RP, first lens E1, quarter-wave plate QWP, second lens E2, third lens E3, partially reflective element BS and image plane IMG. Wherein the reflective polarizing element RP, the first lens E1, the quarter-wave plate QWP and the second lens E2 constitute a first element group, and the third lens E3 and the partially reflective element BS constitute a second element group.

Table 7 shows basic parameters of the optical system of example 4, in which the unit of radius of curvature and thickness are both millimeters (mm). In this embodiment, the surface S3 near the human eye side, the surface S4 near the display side, the surface S6 near the human eye side, the surface S7 near the display side, and the surface S8 near the human eye side, the surface S9 near the display side, of the third lens E3 are all aspherical surfaces, and Table 8 shows the higher order coefficients A that can be used for the aspherical mirror surfaces S3, S4, S6, S7, S8 and S9 in embodiment 4 ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ 、A ₁₆ 、A ₁₈ And A ₂₀ Wherein each aspherical surface profile can be defined by the formula (1) given in the above-described embodiment 1.

TABLE 7

Coefficient/surface

S3

S4

S6

S7

S8

S9

A4

-8.4010E-02

-7.8546E-02

1.9036E-01

-2.1572E-02

5.2745E-02

-1.3152E-01

A6

2.2228E-01

1.1684E-02

1.6292E-01

2.4958E-01

-2.4073E-01

1.4465E-01

A8

-2.7025E-02

-4.2279E-02

1.1215E-01

3.7177E-02

5.8821E-02

-2.5503E-02

A10

-2.2199E-03

8.6666E-02

6.9469E-02

5.8298E-02

8.0173E-02

-2.5179E-03

A12

0.0000E+00

A14

0.0000E+00

A16

0.0000E+00

A18

0.0000E+00

A20

0.0000E+00

TABLE 8

Fig. 8A shows an on-axis chromatic aberration curve of the optical system of embodiment 4, which indicates the focus deviation of light rays of different wavelengths after passing through the lens. Fig. 8B shows an astigmatism curve of the optical system of embodiment 4, which represents meridional image plane curvature and sagittal image plane curvature. Fig. 8C shows a distortion curve of the optical system of example 4, which represents distortion magnitude values corresponding to different angles of view. As can be seen from fig. 8A to 8C, the optical system of embodiment 4 can achieve good imaging quality.

Example 5

An optical system according to embodiment 5 of the present application is described below with reference to fig. 9 to 10C. Fig. 9 shows a schematic structural view of an optical system according to embodiment 5 of the present application.

As shown in fig. 9, the optical system sequentially includes, along the optical axis from the human eye side to the display side: stop STO, reflective polarizer RP, first lens E1, quarter-wave plate QWP, second lens E2, third lens E3, partially reflective element BS and image plane IMG. Wherein the reflective polarizing element RP, the first lens E1, the quarter-wave plate QWP and the second lens E2 constitute a first element group, and the third lens E3 and the partially reflective element BS constitute a second element group.

Table 9 shows basic parameters of the optical system of example 5, in which the unit of radius of curvature and thickness are both millimeters (mm). In this embodiment, the surface S3 near the human eye side, the surface S4 near the display side, the surface S6 near the human eye side, the surface S7 near the display side, and the surface S8 near the human eye side, the surface S9 near the display side, of the third lens E3 are all aspherical surfaces, and Table 10 shows the higher order coefficients A that can be used for the aspherical mirror surfaces S3, S4, S6, S7, S8 and S9 in embodiment 5 ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ 、A ₁₆ 、A ₁₈ And A ₂₀ Wherein each aspherical surface profile can be defined by the formula (1) given in the above-described embodiment 1.

Surface of the body	Element	Surface type	Radius of curvature	Thickness of (L)	Refractive index	Abbe number	Refraction/reflection
								S0		Spherical surface	Infinity is provided	Infinity is provided			Refraction by refraction
S1	Diaphragm (STO)	Spherical surface	Infinity is provided	18.5927			Refraction by refraction
								S2	Reflective polarizing element (RP)	Aspherical surface	-71.7746	0.2000	1.60	26.13	Refraction by refraction
S3	First lens (E1)	Aspherical surface	-71.7746	1.9700	1.60	26.13	Refraction by refraction
								S4		Aspherical surface	-95.9737	0.1000			Refraction by refraction
S5	Quarter Wave Plate (QWP)	Aspherical surface	-140.7247	0.2000	1.50	57.00	Refraction by refraction
								S6	Second lens (E2)	Aspherical surface	-140.7247	11.3197	1.56	46.39	Refraction by refraction
S7		Aspherical surface	-40.0554	0.1000			Refraction by refraction
								S8	Third lens (E3)	Aspherical surface	-42.1444	2.0000	1.64	21.46	Refraction by refraction
S9	Partial reflecting member (BS)	Aspherical surface	-56.3156	-2.0000	1.64	21.46	Reflection of
								S10		Aspherical surface	-42.1444	-0.1000			Refraction by refraction
S11	Second lens (E2)	Aspherical surface	-40.0554	-11.3197	1.56	46.39	Refraction by refraction
								S12	Quarter Wave Plate (QWP)	Aspherical surface	-140.7247	-0.2000	1.50	57.00	Refraction by refraction
S13		Aspherical surface	-140.7247	-0.1000			Refraction by refraction
								S14	First lens (E1)	Aspherical surface	-95.9737	-1.9700	1.60	26.13	Refraction by refraction
S15	Reflective polarizing element (RP)	Aspherical surface	-71.7746	1.9700	1.60	26.13	Reflection of
								S16		Aspherical surface	-95.9737	0.1000			Refraction by refraction
S17	Quarter Wave Plate (QWP)	Aspherical surface	-140.7247	0.2000	1.50	57.00	Refraction by refraction
								S18	Second lens (E2)	Aspherical surface	-140.7247	11.3197	1.56	46.39	Refraction by refraction
S19		Aspherical surface	-40.0554	0.1000			Refraction by refraction
								S20	Third lens (E3)	Aspherical surface	-42.1444	2.0000	1.64	21.46	Refraction by refraction
S21		Aspherical surface	-56.3156	5.3828			Refraction by refraction
								S22	Image plane (IMG)	Spherical surface	Infinity is provided	0.0000			Refraction by refraction

TABLE 9

Coefficient/surface

S3

S4

S6

S7

S8

S9

A4

-3.9844E-02

-1.5037E-01

2.5695E-01

5.9157E-02

-1.4120E-01

-2.9627E-02

A6

1.1446E-01

-2.1338E-01

1.3168E-02

2.5578E-01

-2.0257E-01

-1.6513E-03

A8

-2.8323E-02

1.3476E-01

7.5666E-02

-9.2370E-02

1.2953E-01

-1.2735E-02

A10

-4.4345E-03

-2.4579E-03

-3.4733E-02

-5.1424E-03

8.8666E-03

1.4788E-02

A12

0.0000E+00

A14

0.0000E+00

A16

0.0000E+00

A18

0.0000E+00

A20

0.0000E+00

Table 10

Fig. 10A shows an on-axis chromatic aberration curve of the optical system of embodiment 5, which indicates the focus deviation of light rays of different wavelengths after passing through the lens. Fig. 10B shows an astigmatism curve of the optical system of embodiment 5, which represents meridional image plane curvature and sagittal image plane curvature. Fig. 10C shows a distortion curve of the optical system of example 5, which represents distortion magnitude values corresponding to different angles of view. As can be seen from fig. 10A to 10C, the optical system provided in embodiment 5 can achieve good imaging quality.

Example 6

An optical system according to embodiment 6 of the present application is described below with reference to fig. 11 to 12C. Fig. 11 shows a schematic structural view of an optical system according to embodiment 6 of the present application.

As shown in fig. 11, the optical system sequentially includes, along the optical axis from the human eye side to the display side: stop STO, reflective polarizer RP, first lens E1, second lens E2, quarter-wave plate QWP, third lens E3, partially reflective element BS and image plane IMG. Wherein the reflective polarizing element RP, the first lens E1, the second lens E2 and the quarter-wave plate QWP constitute a first element group, and the third lens E3 and the partially reflective element BS constitute a second element group.

In this embodiment, the light beam emitted from the image plane IMG may sequentially pass through the partially reflective element BS and the third lens E3 of the second element group, and the quarter-wave plate QWP, the second lens E2, and the first lens E1 of the first element group, reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP, and again pass through the first lens E1, the second lens E2, the quarter-wave plate QWP, and the third lens E3 to reach the partially reflective element BS, and then be reflected again at the partially reflective element BS and sequentially pass through the third lens E3, the quarter-wave plate QWP, the second lens E2, the first lens E1, and the reflective polarizing element RP to exit toward the human eye side.

In this embodiment, the partially reflecting element BS may be a semi-transparent and semi-reflecting film layer plated on the second side surface (surface near the display side) of the third lens E3. The reflective polarizing element RP may be attached to the first side surface (surface near the human eye side) of the first lens E1. A quarter wave plate QWP may be attached to the second side surface (surface near the display side) of the second lens E2.

Table 11 shows basic parameters of the optical system of example 6, in which the unit of the radius of curvature and the thickness are both millimeters (mm). In this embodiment, a surface S3 of the first lens E1 near the human eye side, a surface S4 near the display side, a surface S5 of the second lens E2 near the human eye side, a surface S6 near the display side, andthe surface S8 of the three lenses E3 near the human eye and the surface S9 near the display are aspherical, and Table 12 shows the higher order coefficients A that can be used for the aspherical mirror surfaces S3-S6, S8 and S9 in example 6 ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ 、A ₁₆ 、A ₁₈ And A ₂₀ Wherein each aspherical surface profile can be defined by the formula (1) given in the above-described embodiment 1.

TABLE 11

Coefficient/surface

S3

S4

S5

S6

S8

S9

A4

1.0585E-01

-2.5138E-02

-1.5441E-01

-8.0549E-03

2.4021E-01

6.2176E-02

A6

1.6102E-01

-2.9134E-01

6.4997E-03

2.1074E-01

-1.0945E-01

9.0487E-02

A8

-1.1245E-02

-3.0654E-02

1.0340E-01

1.0632E-01

-4.7500E-02

-1.5944E-03

A10

-8.2352E-03

-6.0035E-03

6.4735E-02

4.0456E-02

-1.5822E-02

4.0798E-03

A12

0.0000E+00

A14

0.0000E+00

A16

0.0000E+00

A18

0.0000E+00

A20

0.0000E+00

Table 12

Fig. 12A shows an on-axis chromatic aberration curve of the optical system of embodiment 6, which indicates the focus deviation of light rays of different wavelengths after passing through the lens. Fig. 12B shows an astigmatism curve of the optical system of embodiment 6, which represents meridional image plane curvature and sagittal image plane curvature. Fig. 12C shows a distortion curve of the optical system of example 6, which represents distortion magnitude values corresponding to different angles of view. As can be seen from fig. 12A to 12C, the optical system provided in embodiment 6 can achieve good imaging quality.

Further, in embodiments 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 of the stop to the image plane of the optical system on the optical axis, the distance SD of the stop to the surface of the third lens on the display side, the distance TD of the surface of the first lens on the human eye side to the surface of the third lens on the display side, the distance ER of the stop to the surface of the first lens on the human eye side, 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 are shown in table 13.

Parameters/embodiments	1	2	3	4	5	6
							FG1(mm)	26.83	25.58	27.34	27.92	27.34	29.93
FG2(mm)	1186.53	-98.95	-258.94	1718.66	-258.94	131.04
							f(mm)	27.33	29.05	28.43	28.44	28.43	28.40
EPD(mm)	5.00	5.00	5.00	5.00	5.00	5.00
							SL(mm)	38.91	41.81	39.86	40.62	39.87	40.34
SD(mm)	35.71	29.26	34.48	32.70	34.48	32.88
							TD(mm)	15.31	12.71	15.69	14.27	15.69	14.81
ER(mm)	20.40	16.55	18.79	18.43	18.79	18.07
							CTR(mm)	0.20	0.20	0.20	0.20	0.20	0.20
CTQ(mm)	0.20	0.20	0.30	0.20	0.20	0.20

Examples 1 to 6 each satisfy the conditions shown in table 14.

TABLE 14

The foregoing description is only of the preferred embodiments of the present application and is presented as a description of the principles of the technology being utilized. It should be understood by those skilled in the art that the scope of protection referred to in this application is not limited to the specific combination of the above technical features, but also encompasses other technical solutions formed by any combination of the above technical features or their equivalents without departing from the spirit of the application. Such as the above-described features and technical features having similar functions (but not limited to) disclosed in the present application are replaced with each other.

Claims

1. An optical system, comprising a first element group and a second element group in order from a first side to a second side along an optical axis, wherein,

the first element group has positive focal power and comprises a reflective polarizing element, a first lens, a quarter wave plate and a second lens;

the second element group has positive optical power or negative optical power and comprises a third lens and a partial reflecting element; and

the effective focal length FG1 of the first element group and the effective focal length FG2 of the second element group satisfy:

0.5<(FG2+FG1)/(FG2-FG1)<1.6。

2. the optical system of claim 1, wherein the radius of curvature R2 of the second side of the first lens and the radius of curvature R1 of the first side of the first lens satisfy:

0.4<R2/R1<1.7。

3. the optical system of claim 1, wherein the radius of curvature R3 of the first side of the second lens and the radius of curvature R4 of the second side of the second lens satisfy:

-0.9<(R3-R4)/(R3+R4)<0.7。

4. the optical system according to claim 1, wherein a refractive index N1 of the first lens, a refractive index N2 of the second lens, and a center thickness CTR of the reflective polarizing element on the optical axis and a center thickness CTQ of the quarter-wave plate on the optical axis satisfy:

1.2mm<(N1+N2)×(CTR+CTQ)<1.6mm。

5. The optical system of claim 1, wherein an effective focal length f of the optical system and an entrance pupil diameter EPD of the optical system satisfy:

5.3<f/EPD<6.0。

6. the optical system according to claim 1, wherein an effective focal length FG1 of the first element group, a center thickness CT1 of the first lens on the optical axis, and a center thickness CT2 of the second lens on the optical axis satisfy:

2<FG1/(CT1+CT2)<8。

7. the optical system according to any one of claims 1 to 6, further comprising a stop and an image surface provided on the second side, a distance SL of the stop to the image surface on the optical axis and a distance TD of the first side surface of the first lens to the second side surface of the third lens on the optical axis satisfying:

2.5<SL/TD<3.3。

8. the optical system according to any one of claims 1 to 6, further comprising a stop, a distance SD of the stop to the second side of the third lens on the optical axis and a distance ER of the stop to the first side of the first lens on the optical axis satisfying:

1.6<SD/ER<2.0。

9. the optical system according to any one of claims 1 to 6, wherein a radius of curvature R1 of the first side surface of the first lens, a radius of curvature R3 of the first side surface of the second lens, and an abbe number V1 of the first lens and an abbe number V2 of the second lens satisfy:

2.0mm<|R1+R3|/(V1+V2)<6.9mm。

10. VR device comprising an optical system according to at least one of the claims 1 to 9, wherein the first side is the human eye side and the second side is the display side.