Optical system and optical apparatus comprising the same

Abstract

The application discloses an optical system and an optical device comprising the same. The optical system comprises a first element group and a second element group in sequence from a first side to a second side along an optical axis. The first element group comprises a reflective polarizing element, a first quarter-wave plate, a first lens and a partially reflective element. The second element group comprises a second lens, a second quarter-wave plate, a polarizer and a display. The optical system satisfies 0.5 < fz1 / fz2 < 1.4 and 5.30 <= (CT2+CTQ2+CTL) / AL <= 7.71, wherein fz1 is a combined focal length of the reflective polarizing element, the first quarter-wave plate and the first lens, fz2 is a combined focal length of the second lens, the second quarter-wave plate and the polarizer, CT2 is a central thickness of the second lens along the optical axis, CTQ2 is a central thickness of the second quarter-wave plate along the optical axis, CTL is a central thickness of the polarizer along the optical axis, and AL is a change in a distance between the first element group and the second element group along the optical axis when the optical system is in a first state and in a second state.

Description

Technical Field

[0001] The present application relates to the field of optical elements, and more particularly, to an optical system and an optical device comprising the optical system. Background Art

[0002] With the continuous development of virtual reality technology, the mainstream solution for the visual system of VR head-mounted display devices has shifted from the Fresnel solution to the reentrant solution. The reentrant solution has the advantages of shorter system length, better display performance, and diopter adjustment function. However, the optical path of the reentrant optical system is relatively complex, and the different assembly positions of the lenses and reflective elements will lead to different performance of the optical system. The visual system of the current reentrant solution VR head-mounted display device still has some shortcomings. First, the existing design usually uses a large number of lenses or a thicker lens, which will increase the size and weight of the system, thereby affecting the user's wearing comfort. Secondly, although the existing design can achieve the diopter adjustment function, it is often difficult to achieve a compact structure and lightweight design while ensuring image quality.

[0003] Therefore, one of the current research hotspots for those skilled in the art is to rationally design the structural arrangement of lenses, reflective elements, and displays to obtain a catadioptric optical system with a compact structure and a diopter adjustment function. Summary of the Invention

[0004] The first aspect of the present application provides 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. The first element group includes a reflective polarizing element, a first quarter wave plate, a first lens and a partially reflecting element. The second element group includes a second lens, a second quarter wave plate, a polarizer and a display. Among them, the reflective polarizing element, the first quarter wave plate, the first lens and the partially reflecting element are glued in sequence from the first side to the second side; the second lens, the second quarter wave plate, the polarizer and the display are glued in sequence from the first side to the second side. The first lens has positive optical power, its first side is a plane, and its second side is a convex surface; the second lens has positive optical power, its first side is a convex surface, and its second side is a plane. The second element group moves between the first side and the second side along the optical axis to adjust the spacing distance between the first element group and the second element group on the optical axis, so that the optical system switches between the first state and the second state. The optical system satisfies: 0.5 <fz1 / fz2<1.4及5.30≤(CT2+CTQ2+CTL) / ΔL≤7.71,其中,fz1为反射式偏光元件、第一四分之一波片和第一透镜的组合焦距,fz2为第二透镜、第二四分之一波片和偏振片的组合焦距,CT2为第二透镜在光轴上的中心厚度,CTQ2为第二四分之一波片在光轴上的中心厚度,CTL为偏振片在光轴上的中心厚度,ΔL为光学系统在第一状态时与第二状态时第一元件组与第二元件组在光轴上的间隔距离的变化量。

[0005] In one embodiment, the optical system satisfies: 0.15 mm < (f2 / f1) × Δf < 0.35 mm, where f2 is the effective focal length of the second lens, f1 is the effective focal length of the first lens, and Δf is the change in the effective focal length of the optical system between the first state and the second state.

[0006] In one embodiment, the optical system satisfies the following condition: -2.15 mm < (R2 / R3) × ΔL < -1.30 mm, where R2 is the radius of curvature of the second side surface of the first lens, R3 is the radius of curvature of the first side surface of the second lens, and ΔL is the change in the spacing between the first element group and the second element group on the optical axis between the first state and the second state of the optical system.

[0007] In one embodiment, the optical system satisfies: 5.66≤fm / T12m≤5.95, where fm is the effective focal length of the optical system in the first state, and T12m is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in the first state.

[0008] In one embodiment, the optical system satisfies: 2.21≤R3 / TDn≤4.80, where R3 is the radius of curvature of the first side surface of the second lens, and TDn is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the second state.

[0009] In one embodiment, the optical system satisfies: 1.87≤fn / (CT1+CTR+CTQ1)≤2.50, where fn is the effective focal length of the optical system in the second state, 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, and CTQ1 is the center thickness of the first quarter-wave plate on the optical axis.

[0010] In one embodiment, the optical system satisfies the following: 3.65≤T12n / Δf≤6.16, where T12n is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in the second state, and Δf is the change in the effective focal length of the optical system between the first state and the second state.

[0011] In one embodiment, the optical system satisfies the following condition: 6.95<(TDm+TDn) / EPD<9.45, where TDm is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the first state, TDn is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the second state, and EPD is the entrance pupil diameter of the optical system.

[0012] In one embodiment, the optical system satisfies the following: 1.93≤CT2 / (T12m+T12n)≤2.82, where CT2 is the center thickness of the second lens on the optical axis, T12m is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in a first state, and T12n is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in a second state.

[0013] In one embodiment, the optical system satisfies the following: 2.30≤(f1 / N1) / TDm≤3.16, where f1 is the effective focal length of the first lens, N1 is the refractive index of the first lens, and TDm is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the first state.

[0014] In one embodiment, the optical system satisfies: 0.85≤(f2 / V2) / ΔL≤1.63, where f2 is the effective focal length of the second lens, V2 is the dispersion coefficient of the second lens, and ΔL is the change in the spacing between the first element group and the second element group on the optical axis when the optical system is in the first state and the second state.

[0015] In one embodiment, the optical system satisfies the following condition: 1.67 mm ≤ (fz1 / CT1) × Δf ≤ 3.58 mm, where fz1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the first lens, CT1 is the center thickness of the first lens on the optical axis, and Δf is the change in the effective focal length of the optical system between the first state and the second state.

[0016] In one embodiment, the optical system satisfies: 2.0 mm < (fz2 / R3) × ΔL < 3.2 mm, where fz2 is the combined focal length of the second lens, the second quarter-wave plate, and the polarizer, R3 is the radius of curvature of the first side surface of the second lens, and ΔL is the change in the spacing distance between the first element group and the second element group on the optical axis between the first state and the second state of the optical system.

[0017] In one embodiment, the optical system satisfies: 2.20≤f2 / (fm+fn)≤5.01, where f2 is the effective focal length of the second lens, fm is the effective focal length of the optical system in the first state, and fn is the effective focal length of the optical system in the second state.

[0018] The second aspect of the present application provides 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. The first element group includes a reflective polarizing element, a first quarter wave plate, a first lens and a partially reflecting element. The second element group includes a second lens, a second quarter wave plate, a polarizer and a display. Among them, the reflective polarizing element, the first quarter wave plate, the first lens and the partially reflecting element are glued in sequence from the first side to the second side; the second lens, the second quarter wave plate, the polarizer and the display are glued in sequence from the first side to the second side. The first lens has positive optical power, its first side is a plane, and its second side is a convex surface; the second lens has positive optical power, its first side is a convex surface, and its second side is a plane. The second element group moves between the first side and the second side along the optical axis to adjust the spacing distance between the first element group and the second element group on the optical axis, so that the optical system switches between the first state and the second state. The optical system satisfies: 0.5 <fz1 / fz2<1.4及0.85≤(f2 / V2) / ΔL≤1.63,其中,fz1为反射式偏光元件、第一四分之一波片和第一透镜的组合焦距,fz2为第二透镜、第二四分之一波片和偏振片的组合焦距,f2为第二透镜的有效焦距,V2为第二透镜的色散系数,ΔL为光学系统在第一状态时与第二状态时第一元件组与第二元件组在光轴上的间隔距离的变化量。

[0019] The third aspect of the present application also provides an optical device comprising the optical system provided by any one of the above embodiments.

[0020] The optical system provided by the present application is a catadioptric optical system, comprising a first element group and a second element group, the second element group moves between the first side and the second side along the optical axis to switch the optical system between the first state and the second state, which means that the optical system can realize the diopter adjustment function. The optical system provided by the present application also satisfies 0.5 < fz1 / fz2 < 1.4 and 5.30 ≤ (CT2+CTQ2+CTL) / ΔL ≤ 7.71, which reasonably allocates the optical power of the two lenses, controls the diopter adjustment range of the optical system within a reasonable range, ensures its processability, and improves the optical imaging performance. The optical system with the diopter adjustment function can adopt a smaller exit pupil distance, which is beneficial to further reducing the length of the optical system. BRIEF DESCRIPTION OF DRAWINGS

[0021] Other characteristics, objects and advantages of the present application will become more apparent from the following detailed description of non-restrictive embodiments made with reference to the attached drawings. In the drawings:

[0022] Figure 1 A structural schematic diagram of an optical system according to Embodiment 1 of the present application in a +2D state is shown;

[0023] Figure 2 A modulation transfer function curve of the optical system according to Embodiment 1 of the present application in a +2D state is shown;

[0024] Figure 3 A structural schematic diagram of an optical system according to Embodiment 1 of the present application in a -5D state is shown;

[0025] Figure 4 A modulation transfer function curve of the optical system according to Embodiment 1 of the present application in a -5D state is shown;

[0026] Figure 5 A structural schematic diagram of an optical system according to Embodiment 2 of the present application in a +2D state is shown;

[0027] Figure 6 A modulation transfer function curve of the optical system according to Embodiment 2 of the present application in a +2D state is shown;

[0028] Figure 7 A structural schematic diagram of an optical system according to Embodiment 2 of the present application in a -5D state is shown;

[0029] Figure 8 A modulation transfer function curve of the optical system according to Embodiment 2 of the present application in a -5D state is shown;

[0030] Figure 9 1 shows a schematic structural diagram of an optical system in a +2D state according to Example 3 of the present application;

[0031] Figure 10 shows a modulation transfer function curve of the optical system in the +2D state according to Example 3 of the present application;

[0032] Figure 11 Schematic diagram showing the structure of the optical system in -5D state according to Example 3 of the present application;

[0033] Figure 12 shows a modulation transfer function curve of the optical system in -5D state according to Example 3 of the present application;

[0034] Figure 13 2. A schematic structural diagram of an optical system in a +2D state according to Example 4 of the present application is shown;

[0035] Figure 14 shows a modulation transfer function curve of the optical system in the +2D state according to Example 4 of the present application;

[0036] Figure 15 Schematic diagram showing the structure of the optical system in -5D state according to Example 4 of the present application;

[0037] Figure 16 shows a modulation transfer function curve of the optical system in -5D state according to Example 4 of the present application;

[0038] Figure 17 2. A schematic structural diagram of an optical system in a +2D state according to Embodiment 5 of the present application is shown;

[0039] Figure 18 shows a modulation transfer function curve of the optical system in the +2D state according to Example 5 of the present application;

[0040] Figure 19 1 shows a schematic structural diagram of an optical system in a -5D state according to Example 5 of the present application;

[0041] Figure 20 The modulation transfer function curve of the optical system according to Example 5 of the present application in the -5D state is shown. DETAILED DESCRIPTION

[0042] For a better understanding of the present application, various aspects of the present application will be described in greater detail below with reference to the accompanying drawings. It is to be noted that these detailed descriptions are merely descriptive of exemplary embodiments of the present application and are not intended in any way to limit the scope of the present application. Throughout the specification, like drawing reference numerals will be understood to refer to like parts throughout the specification and the claims. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0043] It is to be noted that the expressions first, second, and so on in the present specification are used merely to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, the first lens discussed below can also be referred to as the second lens, and the second lens can also be referred to as the first lens without departing from the teachings of the present application.

[0044] In the drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for the sake of explanation. Specifically, the shape of the spherical surface or aspherical surface shown in the drawings is shown by way of example. That is, the shape of the spherical surface or aspherical surface is not limited to the shape of the spherical surface or aspherical surface shown in the drawings. The drawings are merely examples and are not drawn to scale.

[0045] In the present specification, the paraxial region refers to a region near the optical axis. If the lens surface is convex and the position of the convex surface is not specified, it means that the lens surface is convex at least in the paraxial region. If the lens surface is concave and the position of the concave surface is not specified, it means that the lens surface is concave at least in the paraxial region. The judgment of the shape of the surface in the paraxial region can be made in accordance with a general method in the art, for example, judging convexity or concavity by the sign of the R value (R refers to the radius of curvature in the paraxial region). In the present specification, with respect to the first side, when the R value is positive, it is judged to be convex, and when the R value is negative, it is judged to be concave. With respect to the second side, when the R value is positive, it is judged to be concave, and when the R value is negative, it is judged to be convex.

[0046] It is also to be understood that the use of the terms "including", "including having", "having", "containing", and / or "containing having", when used in this specification, signify 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 groups thereof. In addition, when expressions such as "at least one of... " appear after a list of items, it is meant to refer to any and all combinations of one or more of the listed items. Furthermore, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Also, the expression "exemplary" is intended to mean example or illustrative.

[0047] 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 overly literal or overly formal sense unless expressly so defined herein.

[0048] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0049] The optical system according to the exemplary embodiments of the present application comprises, in order from the first side to the second side along the optical axis, a first element group and a second element group. The first element group comprises a reflective polarizing element, a first quarter-wave plate, a first lens, and a partially reflective element. The second element group comprises a second lens, a second quarter-wave plate, a polarizer, and a display. The display can be used to provide an image or image light.

[0050] In the exemplary embodiments, the reflective polarizing element, the first quarter-wave plate, the first lens, and the partially reflective element are glued in order from the first side to the second side. That is, the second side of the reflective polarizing element is attached to the first side of the first quarter-wave plate, the second side of the first quarter-wave plate is attached to the first side of the first lens. The partially reflective element is attached to the second side of the first lens.

[0051] In the exemplary embodiments, the second lens, the second quarter-wave plate, the polarizer, and the display are glued in order from the first side to the second side. That is, the second side of the second lens is attached to the first side of the second quarter-wave plate, the second side of the second quarter-wave plate is attached to the first side of the polarizer.

[0052] When the object distance changes, by adjusting the interval distance between the first element group and the second element group along the optical axis, the optical system can be switched between the first state and the second state, i.e. the optical power adjustment function of the optical system is realized. For example, the first state can be a +2D state, and the second state can be a -5D state, where D represents diopter. More specifically, the optical power adjustment function of the optical system is realized by moving the second element group along the optical axis between the first side and the second side to approach or move away from the first element group. When the second element group moves away from the first element group, the optical system is in the first state (+2D state), and when the second element group approaches the first element group, the optical system is in the second state (-5D state).

[0053] Those skilled in the art will understand that a reflective polarizer can reflect polarized light in a certain direction while also transmitting light polarized orthogonally to that direction, and a quarter-wave plate can change the polarization state of light. By combining light reflection and refraction using a reflective polarizer and a quarter-wave plate, the desired optical path can be folded, effectively shortening the optical system.

[0054] In an exemplary embodiment, the optical system according to the present application can be applied to, for example, a VR device, the first side can be, for example, the human eye side, the second side can be, for example, the display side (or screen side), the surface of each lens closest to the human eye side is called the near-human eye side of the lens, and the surface of each lens closest to the display is called the near-display side (or near-screen side) of the lens. Figure 1 As shown, the optical system comprises, in order from the eye side to the screen side along the optical axis, a first element group G1 and a second element group G2. The first element group G1 comprises a reflective polarizer RP, a first quarter-wave plate QWP1, a first lens E1, and a partially reflective element BS. The second element group G2 comprises a second lens E2, a second quarter-wave plate QWP2, a polarizer LP, and a display IMG. The reflective polarizer RP is attached to the eye-side of the first quarter-wave plate QWP1, which is attached to the eye-side of the first lens E1. The partially reflective element BS, which may have a semi-transmissive and semi-reflective function, is attached to the screen-side of the first lens E1. The second quarter-wave plate QWP2 is attached to the screen-side of the second lens E2, the polarizer LP is attached to the screen-side of the second quarter-wave plate QWP2, and the display IMG is attached to the screen-side of the polarizer LP.

[0055] like Figure 1 As shown, the optical system according to the present application may further include an aperture STO disposed on the side of the human eye. The user's eyes can view the image projected by the display IMG at the position of the aperture STO. Specifically, Figure 1 A schematic diagram of the light path reversal of the optical system according to the present application is also shown. The light emitted by the display IMG passes through the polarizer LP, the second quarter-wave plate QWP2, the second lens E2, the first lens E1, the first quarter-wave plate QWP1 in sequence to reach the reflective polarizing element RP, is reflected at the reflective polarizing element RP and passes through the first quarter-wave plate QWP1 and the first lens E1 again. The light beam is reflected again at the partially reflecting element BS on the near-screen side of the first lens E1 and passes through the first lens E1, the first quarter-wave plate QWP1 and the reflective polarizing element RP in sequence, then passes through the aperture STO and is finally emitted toward the human eye side.

[0056] In an exemplary embodiment, the first lens may have positive optical power, a first side surface thereof being planar, and a second side surface thereof being convex;

[0057] In an exemplary embodiment, the second lens may have positive optical power, a convex first side, and a flat second side.

[0058] In an exemplary embodiment, the optical system of the present application may satisfy: 0.5 <fz1 / fz2<1.4,其中,fz1为反射式偏光元件、第一四分之一波片和第一透镜的组合焦距,fz2为第二透镜、第二四分之一波片和偏振片的组合焦距。满足0.5<fz1 / fz2<1.4,有助于合理分配第一透镜和第二透镜的光焦度,使光学系统的屈光度调节范围控制在合理的范围内,提高光学成像性能。光学系统具备屈光度调节功能可以采用更小的出瞳距离,有利于更进一步缩小光学系统长度。

[0059] In an exemplary embodiment, the optical system of the present application may satisfy the following condition: 5.30 ≤ (CT2 + CTQ2 + CTL) / ΔL ≤ 7.71, where CT2 is the center thickness of the second lens on the optical axis, CTQ2 is the center thickness of the second quarter-wave plate on the optical axis, CTL is the center thickness of the polarizer on the optical axis, and ΔL is the change in the separation distance between the first and second element groups on the optical axis between the first and second states of the optical system. Meeting the condition 5.30 ≤ (CT2 + CTQ2 + CTL) / ΔL ≤ 7.71 helps control the overall length of the second element group and maintains a reasonable range of movement for the second element group. This condition also ensures the workability of the second element group and improves optical imaging performance.

[0060] In an exemplary embodiment, the optical system of the present application may satisfy the following conditions: 0.15 mm < (f2 / f1) × Δf < 0.35 mm, where f2 is the effective focal length of the second lens, f1 is the effective focal length of the first lens, and Δf is the difference in effective focal length between the first and second states of the optical system. This condition allows the optical system to adjust its diopter from the first to the second state, or vice versa, for example, from a +2D state to a -5D state.

[0061] In the example embodiment, the optical system of the present application can satisfy: -2.15mm < (R2 / R3) x AL < -1.30mm, where R2 is the curvature radius of the second side surface of the first lens, R3 is the curvature radius of the first side surface of the second lens, and AL is the change in the distance between the first element group and the second element group on the optical axis when the optical system is in the first state and in the second state. Satisfying -2.15mm < (R2 / R3) x AL < -1.30mm can ensure the processability of the first lens and the second lens, while controlling the moving range of the second element group within a reasonable range and improving the imaging quality of the system.

[0062] In the example embodiment, the optical system of the present application can satisfy: 5.66 ≤ fm / T12m ≤ 5.95, where fm is the effective focal length of the optical system in the first state, and T12m is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in the first state. Satisfying 5.66 ≤ fm / T12m ≤ 5.95 helps to ensure that the second element group can move when the system is adjusted in diopter.

[0063] In the example embodiment, the optical system of the present application can satisfy: 2.21 ≤ R3 / TDn ≤ 4.80, where R3 is the curvature radius of the first side surface of the second lens, and TDn is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the second state. Satisfying 2.21 ≤ R3 / TDn ≤ 4.80 can improve the clarity and accuracy of imaging and reduce optical distortion. At the same time, it reduces the focal point change of the system in different states, ensuring the stability and consistency of the focal point adjustment of the system.

[0064] In the example embodiment, the optical system of the present application can satisfy: 1.87 ≤ fn / (CT1+CTR+CTQ1) ≤ 2.50, where fn is the effective focal length of the optical system in the second state, 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, and CTQ1 is the center thickness of the first quarter-wave plate on the optical axis. Satisfying 1.87 ≤ fn / (CT1+CTR+CTQ1) ≤ 2.50 can ensure that the optical system can achieve -5D diopter function in the second state by reasonably designing the effective focal length of the optical system in the second state and the sum of the thicknesses of the first lens, the reflective polarizing element, and the first quarter-wave plate in the first element group.

[0065] In an exemplary embodiment, the optical system of the present application can satisfy: 3.65≤T12n / Δf≤6.16, where T12n is the distance between the second side of the first lens and the first side of the second lens on the optical axis of the optical system in the second state, and Δf is the change in effective focal length of the optical system between the first state and the second state. Satisfying 3.65≤T12n / Δf≤6.16 ensures that the first lens and the second lens do not interfere in the second state (-5D state).

[0066] In an exemplary embodiment, the optical system of the present application can satisfy: 6.95<(TDm+TDn) / EPD<9.45, where TDm is the distance between the first side of the first lens and the second side of the second lens on the optical axis of the optical system in the first state, TDn is the distance between the first side of the first lens and the second side of the second lens on the optical axis of the optical system in the second state, and EPD is the entrance pupil diameter of the optical system. Satisfying 6.95<(TDm+TDn) / EPD<9.45 can control the overall length of the optical system, making the product more lightweight.

[0067] In an exemplary embodiment, the optical system of the present application can satisfy: 1.93≤CT2 / (T12m+T12n)≤2.82, where CT2 is the center thickness of the second lens on the optical axis, T12m is the distance between the second side of the first lens and the first side of the second lens on the optical axis of the optical system in the first state, and T12n is the distance between the second side of the first lens and the first side of the second lens on the optical axis of the optical system in the second state. Satisfying 1.93≤CT2 / (T12m+T12n)≤2.82 can limit the spacing distance between the first lens and the second lens, making the overall length of the optical system shorter and the product more lightweight.

[0068] In an exemplary embodiment, the optical system of the present application can satisfy: 2.30≤(f1 / N1) / TDm≤3.16, where f1 is the effective focal length of the first lens, N1 is the refractive index of the first lens, and TDm is the distance between the first side of the first lens and the second side of the second lens on the optical axis of the optical system in the first state. Satisfying 2.30≤(f1 / N1) / TDm≤3.16 is conducive to improving system imaging performance while controlling the cost of the first lens material.

[0069] In exemplary embodiments, the optical system of the present application can satisfy: 0.85≤(f2 / V2) / AL≤1.63, where f2 is the effective focal length of the second lens, V2 is the dispersion coefficient of the second lens, and AL is the change in the interval distance of the first element group and the second element group on the optical axis when the optical system is in the first state and in the second state. Satisfying 0.85≤(f2 / V2) / AL≤1.63 is conducive to reducing the system chromatic aberration while controlling the cost of the second lens material, and improving the system imaging performance.

[0070] In exemplary embodiments, the optical system of the present application can satisfy: 1.67mm≤(fz1 / CT1) x Af≤3.58mm, where fz1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate and the first lens, CT1 is the center thickness of the first lens on the optical axis, and Af is the change in the effective focal length of the optical system when the optical system is in the first state and in the second state. Satisfying 1.67mm≤(fz1 / CT1) x Af≤3.58mm is conducive to reducing the total length of the system by reducing the thickness of the first lens while ensuring the processability of the lens.

[0071] In exemplary embodiments, the optical system of the present application can satisfy: 2.0mm<(fz2 / R3) x AL<3.2mm, where fz2 is the combined focal length of the second lens, the second quarter-wave plate and the polarizer, R3 is the radius of curvature of the first side of the second lens, and AL is the change in the interval distance of the first element group and the second element group on the optical axis when the optical system is in the first state and in the second state. Satisfying 2.0mm<(fz2 / R3) x AL<3.2mm allows the light to be better converged, meeting the imaging requirements while reducing the lens sensitivity tolerance.

[0072] In exemplary embodiments, the optical system of the present application can satisfy: 2.20≤f2 / (fm+fn)≤5.01, where f2 is the effective focal length of the second lens, fm is the effective focal length of the optical system in the first state, and fn is the effective focal length of the optical system in the second state. Satisfying 2.20≤f2 / (fm+fn)≤5.01 can allow the optical system to meet the requirements of different diopters in the first state (+2D state) and the second state (-5D state).

[0073] In exemplary embodiments, the optical system of the present application can include at least one diaphragm. The diaphragm can constrain the light path and control the light intensity. The diaphragm can be arranged at an appropriate position of the optical system, for example, the diaphragm can be located on the first side of the first lens.

[0074] In an exemplary embodiment, the effective focal length fm of the optical system in the first state may be, for example, in the range of 12.49 mm to 15.94 mm, and the effective focal length fn of the optical system in the second state may be, for example, in the range of 12.26 mm to 15.77 mm. The combined focal length fz1 of the reflective polarizing element, the first quarter-wave plate, and the first lens (i.e., the effective focal length f1 of the first lens) may be, for example, in the range of 73.59 mm to 86.41 mm, and the combined focal length fz2 of the second lens, the second quarter-wave plate, and the polarizer (i.e., the effective focal length f2 of the second lens) may be, for example, in the range of 54.40 mm to 158.73 mm.

[0075] According to some embodiments of the present application, the optical system of the present application is a compact optical system with high-definition imaging quality. In applications, the optical system according to the exemplary embodiments of the present application can be applied to VR devices. By rationally designing the structural arrangement of the lens, reflective polarizer, quarter-wave plate, partial reflective layer, and display, the system's volume and weight are reduced while ensuring diopter adjustment, and light energy utilization efficiency is improved, thereby providing users with a more comfortable and high-quality virtual reality experience.

[0076] In an embodiment of the present application, at least one of the mirror surfaces of each lens is an aspherical mirror surface. The characteristic of an aspherical lens is that the curvature changes continuously from the center of the lens to the periphery. Unlike a spherical lens with a constant curvature from the center of the lens to the periphery, an aspherical lens has a better curvature radius characteristic, with the advantages of improving distortion aberration and improving astigmatism aberration. After using an aspherical lens, the aberration that occurs during imaging can be eliminated as much as possible, thereby improving imaging quality. Optionally, the second side surface of the first lens and the first side surface of the second lens are both aspherical mirror surfaces.

[0077] The following further describes a specific embodiment of the optical system applicable to the above-mentioned embodiment with reference to the accompanying drawings. Specifically, the optical system is applied to a VR device, for example, with the first side being the human eye side and the second side being the screen side.

[0078] Example 1

[0079] The following reference Figures 1 to 4 An optical system according to Example 1 of the present application is described. Figure 1 Schematic diagram of the structure of the optical system in +2D state according to Example 1 of the present application. Figure 3 This is a structural diagram of the optical system in -5D state according to Example 1 of the present application.

[0080] like Figure 1 and Figure 3As shown, the optical system of Example 1 includes an aperture STO, a first element group G1, and a second element group G2. The first element group G1 includes a reflective polarizer RP, a first quarter-wave plate QWP1, a first lens E1, and a partially reflective element BS. The second element group G2 includes a second lens E2, a second quarter-wave plate QWP2, a polarizer LP, and a display IMG. The reflective polarizer RP is attached to the side of the first quarter-wave plate QWP1 closest to the eye, and the first quarter-wave plate QWP1 is attached to the side of the first lens E1 closest to the eye. The partially reflective element BS, which may have a semi-transmissive and semi-reflective function, is attached to the side of the first lens E1 closest to the screen. The second quarter-wave plate QWP2 is attached to the side of the second lens E2 closest to the screen, the polarizer LP is attached to the side of the second quarter-wave plate QWP2 closest to the screen, and the display IMG is attached to the side of the polarizer LP closest to the screen.

[0081] The first lens E1 has positive refractive power, its side closest to the human eye is flat, and its side closest to the screen is convex. The second lens E2 has positive refractive power, its side closest to the human eye is convex, and its side closest to the screen is flat.

[0082] In this example, the light emitted by the display IMG passes through the polarizer LP, the second quarter-wave plate QWP2, the second lens E2, the first lens E1, the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, is reflected at the reflective polarizer RP and passes through the first quarter-wave plate QWP1 and the first lens E1 again. The light beam is reflected again at the partially reflecting element BS on the near-screen side of the first lens E1 and passes through the first lens E1, the first quarter-wave plate QWP1 and the reflective polarizer RP in sequence, then passes through the aperture STO and is finally emitted toward the human eye side.

[0083] Table 1 shows the basic parameters of the optical system of Example 1, where the units of curvature radius and thickness / distance are all in millimeters (mm). Table 1 only lists the correspondence between the surface numbers of some surfaces and some components. Due to the problem of shared surfaces between adjacent components, it is not convenient to mark the locations of all components with shared surfaces in Table 1.

[0084] Table 1

[0085] Serial number Component Name Surface type Radius of curvature Thickness / distance Refractive index Abbe number Refraction / Reflection Cone coefficient 0 spherical surface endless D1 refraction 1 Aperture (STO) spherical surface endless 10.0000 refraction 2 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 refraction 3 First quarter wave plate (QWP1) spherical surface endless 0.1000 1.517 64.17 refraction 4 First lens (E1) spherical surface endless 6.3697 1.639 23.52 refraction 5 Partially reflective element (BS) Aspheric -47.9562 -6.3697 1.639 23.52 reflection 2.7419 6 spherical surface endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 reflection 8 First lens (E1) spherical surface endless 6.3697 1.639 23.52 refraction 9 Aspheric -47.9562 D2 refraction 2.7419 10 Second lens (E2) Aspheric 29.5910 6.0000 1.544 55.92 refraction 4.5442 11 Second Quarter Wave Plate (QWP2) spherical surface endless 0.1000 1.517 64.17 refraction 12 Polarizer (LP) spherical surface endless 0.1000 1.517 64.17 refraction 13 spherical surface endless 0.0000 refraction 14 Display (IMG) spherical surface endless 0.0000 refraction

[0086] In this example, as object distance D1 changes, the second element group G2 of the optical system moves along the optical axis to perform a diopter adjustment function. Table 2 shows the air spacing D2 between the first and second lenses on the optical axis of the optical system of Example 1 at different object distances D1. When object distance D1 = 500 mm, the optical system is in the first state (+2D state), and when object distance D1 = -200 mm, the optical system is in the second state (-5D state). All values ​​in Table 2 are in millimeters (mm).

[0087] Table 2

[0088] D1 D2 +2D status 500.0000 2.1069 -5D state -200.0000 1.0000

[0089] In Example 1, the side surface of the first lens E1 near the screen and the side surface of the second lens E2 near the human eye are both aspherical surfaces. The surface shape of each aspherical lens can be defined by, but not limited to, the following aspherical surface formula:

[0090]

[0091] Where x is the distance vector 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 i-th order correction coefficient of the aspheric surface. Table 3 below lists the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, and A18 that can be used for each aspheric mirror surface in Example 1.

[0092] Table 3

[0093] Component Name surface A4 A6 A8 A10 A12 A14 A16 A18 First lens Near the side of the screen 4.3568E-06 3.8240E-09 1.3745E-11 2.7647E-14 -7.3707E-17 0.0000E+00 0.0000E+00 0.0000E+00 Second lens Side view of human eye 1.6544E-05 -8.1139E-07 3.2323E-09 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0094] Figure 2 is the modulation transfer function curve of the optical system of Example 1 in the +2D state, Figure 4 is the modulation transfer function curve of the optical system of Example 1 in -5D state. Figure 2 and Figure 4 It can be seen that the optical system provided in Example 1 can achieve good imaging quality under different diopter states.

[0095] Example 2

[0096] The following reference Figures 5 to 8 An optical system according to Example 2 of the present application is described. Figure 5 This is a structural schematic diagram of the optical system in the +2D state according to Example 2 of the present application. Figure 7 Schematic diagram of the structure of the optical system in -5D state according to Example 2 of the present application. In this embodiment and the following embodiments, for the sake of brevity, some descriptions similar to those in Example 1 will be omitted.

[0097] As shown in Figure 5 and Figure 7 , the optical system of Example 2 includes a stop STO, a first element group G1 and a second element group G2. The first element group G1 includes a reflective polarizing element RP, a first quarter-wave plate QWP1, a first lens E1 and a partially reflective element BS, and the second element group G2 includes a second lens E2, a second quarter-wave plate QWP2, a polarizer LP and a display IMG. Among them, the reflective polarizing element RP is attached to the near-eye side of the first quarter-wave plate QWP1, and the first quarter-wave plate QWP1 is attached to the near-eye side of the first lens E1; the partially reflective element BS can have a semi-transparent and semi-reflective function, and is attached to the near-screen side of the first lens E1. The second quarter-wave plate QWP2 is attached to the near-screen side of the second lens E2, the polarizer LP is attached to the near-screen side of the second quarter-wave plate QWP2, and the display IMG is attached to the near-screen side of the polarizer LP.

[0098] The first lens E1 has a positive focal power, and its near-eye side is a plane and its near-screen side is a convex surface. The second lens E2 has a positive focal power, and its near-eye side is a convex surface and its near-screen side is a plane.

[0099] In this example, the light emitted by the display IMG sequentially passes through the polarizer LP, the second quarter-wave plate QWP2, the second lens E2, the first lens E1, the first quarter-wave plate QWP1, and reaches the reflective polarizing element RP, is reflected at the reflective polarizing element RP and again passes through the first quarter-wave plate QWP1, the first lens E1, the light beam is again reflected at the partially reflective element BS on the near-screen side of the first lens E1 and sequentially passes through the first lens E1, the first quarter-wave plate QWP1 and the reflective polarizing element RP, and then passes through the stop STO and finally exits towards the eye side.

[0100] Table 4 shows the basic parameters of the optical system of Example 2, wherein the units of the curvature radius and the thickness / distance are millimeters (mm).

[0101] Table 4

[0102] Serial number Component Name Surface type Radius of curvature Thickness / distance Refractive index Abbe number Refraction / Reflection Cone coefficient 0 spherical surface endless D1 refraction 1 Aperture (STO) spherical surface endless 12.0000 refraction 2 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 refraction 3 First quarter wave plate (QWP1) spherical surface endless 0.1000 1.517 64.17 refraction 4 First lens (E1) spherical surface endless 6.6172 1.639 23.52 refraction 5 Partially reflective element (BS) Aspheric -55.2294 -6.6172 1.639 23.52 reflection 2.8059 6 spherical surface endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 reflection 8 First lens (E1) spherical surface endless 6.6172 1.639 23.52 refraction 9 Aspheric -55.2294 D2 refraction 2.8059 10 Second lens (E2) Aspheric 39.2193 8.0000 1.544 55.92 refraction 7.2329 11 Second Quarter Wave Plate (QWP2) spherical surface endless 0.1000 1.517 64.17 refraction 12 Polarizer (LP) spherical surface endless 0.1000 1.517 64.17 refraction 13 spherical surface endless 0.0000 refraction 14 Display (IMG) spherical surface endless 0.0000 refraction

[0103] In this example, when the object distance D1 changes, the second element group G2 of the optical system moves along the optical axis to perform the diopter adjustment function, and Table 5 shows the air separation D2 of the first lens and the second lens on the optical axis of the optical system of Example 2 under different object distances D1. When the object distance D1 = 500 mm, the optical system is in the first state (+2D state), and when the object distance D1 = -200 mm, the optical system is in the second state (-5D state), and the units in Table 5 are millimeters (mm).

[0104] Table 5

[0105] D1 D2 +2D status 500.0000 2.5181 -5D state -200.0000 1.0000

[0106] Table 6 shows the high-order coefficients of each aspheric mirror surface that can be used in Example 2, wherein the surface shape of each aspheric surface can be defined by formula (1) given in Example 1 above.

[0107] Table 6

[0108] Component Name surface A4 A6 A8 A10 A12 A14 A16 A18 First lens Near the side of the screen 3.2268E-06 1.4104E-09 1.7916E-11 -2.2793E-14 -3.9628E-18 0.0000E+00 0.0000E+00 0.0000E+00 Second lens Side view of human eye 1.0535E-05 -2.6024E-07 1.3695E-09 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0109] Figure 6 is the modulation transfer function curve of the optical system of Example 2 in the +2D state, Figure 8 is the modulation transfer function curve of the optical system of Example 2 in -5D state. Figure 6 and Figure 8 It can be seen that the optical system provided in Example 2 can achieve good imaging quality under different diopter states.

[0110] Example 3

[0111] The following reference Figures 9 to 12 An optical system according to Example 3 of the present application is described. Figure 9 This is a structural schematic diagram of the optical system in the +2D state according to Example 3 of the present application. Figure 11 This is a structural diagram of the optical system in -5D state according to Example 3 of the present application.

[0112] like Figure 9 and Figure 11 As shown, the optical system of Example 3 includes an aperture STO, a first element group G1, and a second element group G2. The first element group G1 includes a reflective polarizer RP, a first quarter-wave plate QWP1, a first lens E1, and a partially reflective element BS. The second element group G2 includes a second lens E2, a second quarter-wave plate QWP2, a polarizer LP, and a display IMG. The reflective polarizer RP is attached to the side of the first quarter-wave plate QWP1 closest to the eye, and the first quarter-wave plate QWP1 is attached to the side of the first lens E1 closest to the eye. The partially reflective element BS, which may have a semi-transmissive and semi-reflective function, is attached to the side of the first lens E1 closest to the screen. The second quarter-wave plate QWP2 is attached to the side of the second lens E2 closest to the screen, the polarizer LP is attached to the side of the second quarter-wave plate QWP2 closest to the screen, and the display IMG is attached to the side of the polarizer LP closest to the screen.

[0113] The first lens E1 has positive focal power, its proximal human eye side is a plane, and its proximal screen side is a convex surface. The second lens E2 has positive focal power, its proximal human eye side is a convex surface, and its proximal screen side is a plane.

[0114] In this example, the light emitted by the display IMG sequentially passes through the polarizer LP, the second quarter-wave plate QWP2, the second lens E2, the first lens E1, the first quarter-wave plate QWP1, and reaches the reflective polarizing element RP, is reflected at the reflective polarizing element RP and again passes through the first quarter-wave plate QWP1, the first lens E1, is again reflected at the partial reflecting element BS on the proximal screen side of the first lens E1 and sequentially passes through the first lens E1, the first quarter-wave plate QWP1 and the reflective polarizing element RP, then passes through the stop STO and finally exits towards the human eye side.

[0115] Table 7 shows the basic parameters of the optical system of Example 3, wherein the units of the radius of curvature and the thickness / distance are millimeters (mm).

[0116] Table 7

[0117]

[0118]

[0119] In this example, when the object distance D1 changes, the second element group G2 of the optical system moves along the optical axis to perform the diopter adjustment function, and Table 8 shows the air separation D2 of the first lens and the second lens on the optical axis of the optical system of Example 3 at different object distances D1. When the object distance D1 = 500 mm, the optical system is in the first state (+2D state), and when the object distance D1 = -200 mm, the optical system is in the second state (-5D state), and the units in Table 8 are millimeters (mm).

[0120] 5Table 8

[0121] D1 D2 +2D status 500.0000 2.3864 -5D state -200.0000 1.0000

[0122] Table 9 shows the high-order term coefficients of the aspherical mirrors that can be used in Example 3, wherein each aspherical surface type can be defined by the formula (1) given in Example 1 above.

[0123] Table 9

[0124] Component Name surface A4 A6 A8 A10 A12 A14 A16 A18 First lens Near the side of the screen 2.8933E-06 -2.2868E-09 2.9192E-11 -4.7550E-14 1.9262E-17 0.0000E+00 0.0000E+00 0.0000E+00 Second lens Side view of human eye 1.8973E-05 -2.9308E-07 1.2936E-09 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0125] Figure 10 is the modulation transfer function curve of the optical system of Example 3 in the +2D state, Figure 12 is the modulation transfer function curve of the optical system of Example 3 in the -5D state. According to Figure 10 and Figure 12 It can be seen that the optical system provided in Example 3 can achieve good imaging quality under different diopter states.

[0126] Example 4

[0127] The following reference Figures 13 to 16 An optical system according to Example 4 of the present application is described. Figure 13 This is a structural schematic diagram of the optical system in the +2D state according to Example 4 of the present application. Figure 15 This is a structural schematic diagram of the optical system in -5D state according to Example 4 of the present application.

[0128] like Figure 13 and Figure 15 As shown, the optical system of Example 4 includes an aperture STO, a first element group G1, and a second element group G2. The first element group G1 includes a reflective polarizer RP, a first quarter-wave plate QWP1, a first lens E1, and a partially reflective element BS. The second element group G2 includes a second lens E2, a second quarter-wave plate QWP2, a polarizer LP, and a display IMG. The reflective polarizer RP is attached to the side of the first quarter-wave plate QWP1 closest to the eye, and the first quarter-wave plate QWP1 is attached to the side of the first lens E1 closest to the eye. The partially reflective element BS, which may have a semi-transmissive and semi-reflective function, is attached to the side of the first lens E1 closest to the screen. The second quarter-wave plate QWP2 is attached to the side of the second lens E2 closest to the screen, the polarizer LP is attached to the side of the second quarter-wave plate QWP2 closest to the screen, and the display IMG is attached to the side of the polarizer LP closest to the screen.

[0129] The first lens E1 has positive refractive power, its side closest to the human eye is flat, and its side closest to the screen is convex. The second lens E2 has positive refractive power, its side closest to the human eye is convex, and its side closest to the screen is flat.

[0130] In this example, the light emitted by the display IMG passes through the polarizer LP, the second quarter-wave plate QWP2, the second lens E2, the first lens E1, the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, is reflected at the reflective polarizer RP and passes through the first quarter-wave plate QWP1 and the first lens E1 again. The light beam is reflected again at the partially reflecting element BS on the near-screen side of the first lens E1 and passes through the first lens E1, the first quarter-wave plate QWP1 and the reflective polarizer RP in sequence, then passes through the aperture STO and is finally emitted toward the human eye side.

[0131] Table 10 shows basic parameters of the optical system of Example 4, where the units of curvature radius and thickness / distance are all millimeters (mm).

[0132] Table 10

[0133] Serial number Component Name Surface type Radius of curvature Thickness / distance Refractive index Abbe number Refraction / Reflection Cone coefficient 0 spherical surface endless D1 refraction 1 Aperture (STO) spherical surface endless 9.0000 refraction 2 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 refraction 3 First quarter wave plate (QWP1) spherical surface endless 0.1000 1.517 64.17 refraction 4 First lens (E1) spherical surface endless 4.7897 1.639 23.52 refraction 5 Partially reflective element (BS) Aspheric -50.3037 -4.7897 1.639 23.52 reflection 2.9593 6 spherical surface endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 reflection 8 First lens (E1) spherical surface endless 4.7897 1.639 23.52 refraction 9 Aspheric -50.3037 D2 refraction 2.9593 10 Second lens (E2) Aspheric 39.5956 9.0000 1.544 55.92 refraction 8.3873 11 Second Quarter Wave Plate (QWP2) spherical surface endless 0.1000 1.517 64.17 refraction 12 Polarizer (LP) spherical surface endless 0.1000 1.517 64.17 refraction 13 spherical surface endless 0.0000 refraction 14 Display (IMG) spherical surface endless 0.0000 refraction

[0134] In this example, as object distance D1 changes, the second element group G2 of the optical system moves along the optical axis to perform diopter adjustment. Table 11 shows the optical axis air gap D2 between the first and second lenses of the optical system of Example 4 at different object distances D1. When object distance D1 = 500 mm, the optical system is in the first state (+2D state), and when object distance D1 = -200 mm, the optical system is in the second state (-5D state). All values ​​in Table 11 are in millimeters (mm).

[0135] Table 11

[0136] D1 D2 +2D status 500.0000 2.1933 -5D state -200.0000 1.0000

[0137] Table 12 shows the high-order coefficients of each aspheric mirror surface that can be used in Example 4, wherein the surface shape of each aspheric surface can be defined by the formula (1) given in the above Example 1.

[0138] Table 12

[0139] Component Name surface A4 A6 A8 A10 A12 A14 A16 A18 First lens Near the side of the screen 5.7070E-06 -7.2912E-09 1.2163E-10 -4.1072E-13 5.2266E-16 0.0000E+00 0.0000E+00 0.0000E+00 Second lens Side view of human eye 3.3403E-05 -2.6483E-07 1.6918E-09 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0140] Figure 14 is the modulation transfer function curve of the optical system of Example 4 in the +2D state, Figure 16 is the modulation transfer function curve of the optical system of Example 4 in -5D state. Figure 14 and Figure 16 It can be seen that the optical system provided in Example 4 can achieve good imaging quality under different diopter states.

[0141] Example 5

[0142] The following reference Figures 17 to 20 An optical system according to Example 5 of the present application is described. Figure 17 This is a structural schematic diagram of the optical system in the +2D state according to Example 5 of the present application. Figure 19 This is a structural schematic diagram of the optical system in -5D state according to Example 5 of the present application.

[0143] like Figure 17 and Figure 19As shown, the optical system of Example 5 includes an aperture STO, a first element group G1, and a second element group G2. The first element group G1 includes a reflective polarizer RP, a first quarter-wave plate QWP1, a first lens E1, and a partially reflective element BS. The second element group G2 includes a second lens E2, a second quarter-wave plate QWP2, a polarizer LP, and a display IMG. The reflective polarizer RP is attached to the side of the first quarter-wave plate QWP1 closest to the eye, and the first quarter-wave plate QWP1 is attached to the side of the first lens E1 closest to the eye. The partially reflective element BS, which may have a semi-transmissive and semi-reflective function, is attached to the side of the first lens E1 closest to the screen. The second quarter-wave plate QWP2 is attached to the side of the second lens E2 closest to the screen, the polarizer LP is attached to the side of the second quarter-wave plate QWP2 closest to the screen, and the display IMG is attached to the side of the polarizer LP closest to the screen.

[0144] The first lens E1 has positive refractive power, its side closest to the human eye is flat, and its side closest to the screen is convex. The second lens E2 has positive refractive power, its side closest to the human eye is convex, and its side closest to the screen is flat.

[0145] In this example, the light emitted by the display IMG passes through the polarizer LP, the second quarter-wave plate QWP2, the second lens E2, the first lens E1, the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, is reflected at the reflective polarizer RP and passes through the first quarter-wave plate QWP1 and the first lens E1 again. The light beam is reflected again at the partially reflecting element BS on the near-screen side of the first lens E1 and passes through the first lens E1, the first quarter-wave plate QWP1 and the reflective polarizer RP in sequence, then passes through the aperture STO and is finally emitted toward the human eye side.

[0146] Table 13 shows basic parameters of the optical system of Example 5, where the units of the curvature radius and thickness / distance are all millimeters (mm).

[0147] Table 13

[0148] Serial number Component Name Surface type Radius of curvature Thickness / distance Refractive index Abbe number Refraction / Reflection Cone coefficient 0 spherical surface endless D1 refraction 1 Aperture (STO) spherical surface endless 13.0000 refraction 2 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 refraction 3 First quarter wave plate (QWP1) spherical surface endless 0.1000 1.517 64.17 refraction 4 First lens (E1) spherical surface endless 7.9973 1.810 41.00 refraction 5 Partially reflective element (BS) Aspheric -66.6356 -7.9973 1.810 41.00 reflection 3.5114 6 spherical surface endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) spherical surface endless 0.1000 1.517 64.17 reflection 8 First lens (E1) spherical surface endless 7.9973 1.810 41.00 refraction 9 Aspheric -66.6356 D2 refraction 3.5114 10 Second lens (E2) Aspheric 86.3340 9.0000 1.544 55.92 refraction 25.3678 11 Second Quarter Wave Plate (QWP2) spherical surface endless 0.1000 1.517 64.17 refraction 12 Polarizer (LP) spherical surface endless 0.1000 1.517 64.17 refraction 13 spherical surface endless 0.0000 refraction 14 Display (IMG) spherical surface endless 0.0000 refraction

[0149] In this example, as object distance D1 changes, the second element group G2 of the optical system moves along the optical axis to perform a diopter adjustment function. Table 14 shows the optical axis air gap D2 between the first and second lenses of the optical system of Example 5 at different object distances D1. When object distance D1 = 500 mm, the optical system is in the first state (+2D state), and when object distance D1 = -200 mm, the optical system is in the second state (-5D state). All values ​​in Table 14 are in millimeters (mm).

[0150] Table 14

[0151] D1 D2 +2D status 500.0000 2.7364 -5D state -200.0000 1.0000

[0152] Table 15 shows the high-order coefficients of each aspheric mirror surface that can be used in Example 5, wherein the surface shape of each aspheric surface can be defined by formula (1) given in Example 1 above.

[0153] Table 15

[0154] Component Name surface A4 A6 A8 A10 A12 A14 A16 A18 First lens Near the side of the screen 2.8237E-06 -4.0411E-09 2.4381E-11 -3.7137E-14 2.1215E-17 0.0000E+00 0.0000E+00 0.0000E+00 Second lens Side view of human eye 2.8805E-05 -2.3764E-07 7.0914E-10 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00

[0155] Figure 18 is the modulation transfer function curve of the optical system of Example 5 in the +2D state, Figure 20 is the modulation transfer function curve of the optical system of Example 5 in -5D state. Figure 18 and Figure 20 It can be seen that the optical system provided in Example 5 can achieve good imaging quality under different diopter states.

[0156] Table 16 shows some parameter values ​​of the optical systems of Examples 1 to 5, all in millimeters (mm).

[0157] Table 16

[0158] Parameters / Example 1 2 3 4 5 fm(mm) 12.49 14.26 14.20 12.64 15.94 fn(mm) 12.26 13.99 14.04 12.45 15.77 f1(mm) 75.03 86.41 73.95 78.70 82.27 f2(mm) 54.40 72.10 114.71 72.80 158.73 fz1(mm) 75.03 86.41 73.95 78.70 82.27 fz2(mm) 54.40 72.10 114.71 72.80 158.73 EPD(mm) 4.00 4.00 4.00 4.00 4.00 TDm(mm) 14.48 17.14 17.58 15.98 19.73 TDn(mm) 13.37 15.62 16.19 14.79 18.00 T12m(mm) 2.11 2.52 2.39 2.19 2.74 T12n(mm) 1.00 1.00 1.00 1.00 1.00 ΔL(mm) 1.11 1.52 1.39 1.19 1.74 Δf(mm) 0.23 0.27 0.16 0.19 0.17 fm(mm) 12.49 14.26 14.20 12.64 15.94 fn(mm) 12.26 13.99 14.04 12.45 15.77

[0159] In summary, the optical systems of Examples 1 to 9 satisfy the relationship shown in Table 17.

[0160] Table 17

[0161] Conditional formula / Example 1 2 3 4 5 fz1 / fz2 1.38 1.20 0.64 1.08 0.52 (CT2+CTQ2+CTL) / ΔL 5.60 5.40 5.91 7.71 5.30 (f2 / f1)×Δf(mm) 0.17 0.23 0.25 0.17 0.32 (R2 / R3)×ΔL(mm) -1.79 -2.14 -1.33 -1.52 -1.34 fm / T12m 5.93 5.66 5.95 5.76 5.82 R3 / TDn 2.21 2.51 3.85 2.68 4.80 fn / (CT1+CTR+CTQ1) 1.87 2.05 1.90 2.50 1.92 T12n / Δf 4.31 3.65 6.16 5.32 6.00 (TDm+TDn) / EPD 6.96 8.19 8.44 7.69 9.43 CT2 / (T12m+T12n) 1.93 2.27 2.36 2.82 2.41 (f1 / N1) / TDm 3.16 3.08 2.32 3.00 2.30 (f2 / V2) / ΔL 0.88 0.85 1.48 1.09 1.63 (fz1 / CT1)×Δf(mm) 2.73 3.58 1.67 3.09 1.71 (fz2 / R3)×ΔL(mm) 2.03 2.79 2.55 2.19 3.19 f2 / (fm+fn) 2.20 2.55 4.06 2.90 5.01

[0162] The present application also provides an optical device, which can be an independent projection device such as a projector, or a projection module integrated into a mobile electronic device such as a VR device. The optical device is equipped with the optical system described above.

[0163] 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 It sequentially includes, from the first side to the second side along the optical axis: The first element group, including: a reflective polarizing element, a first quarter-wave plate, a first lens, and a partial reflection element; The second element group, including: a second lens, a second quarter-wave plate, a polarizer, and a display; Wherein, The reflective polarizing element, the first quarter-wave plate, the first lens, and the partial reflection element are sequentially glued from the first side to the second side; The second lens, the second quarter-wave plate, the polarizer, and the display are sequentially glued from the first side to the second side; The first lens has a positive optical power, its first side is a plane, and its second side is a convex surface; The second lens has a positive optical power, its first side is a convex surface, and its second side is a plane; The second element group moves along the optical axis between the first side and the second side to adjust the spacing distance between the first element group and the second element group on the optical axis, so that the optical system switches between a first state and a second state; The optical system satisfies: \(0.5 < f_{z1} / f_{z2}<1.4\) and \(5.30\leq(CT2 + CTQ2 + CTL) / \Delta L\leq7.71\), where \(f_{z1}\) is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the first lens, \(f_{z2}\) is the combined focal length of the second lens, the second quarter-wave plate, and the polarizer, \(CT2\) is the central thickness of the second lens on the optical axis, \(CTQ2\) is the central thickness of the second quarter-wave plate on the optical axis, \(CTL\) is the central thickness of the polarizer on the optical axis, and \(\Delta L\) is the change amount of the spacing distance between the first element group and the second element group on the optical axis when the optical system is in the first state and the second state.

2. The optical system according to claim 1, wherein The optical system satisfies: \(0.15\mathrm{mm}<(f2 / f1)\times\Delta f<0.35\mathrm{mm}\), where \(f2\) is the effective focal length of the second lens, \(f1\) is the effective focal length of the first lens, and \(\Delta f\) is the change amount of the effective focal length when the optical system is in the first state and the second state.

3. The optical system according to claim 1, wherein: The optical system satisfies: \(-2.15\mathrm{mm}<(R2 / R3)\times\Delta L<-1.30\mathrm{mm}\), where \(R2\) is the radius of curvature of the second side of the first lens, and \(R3\) is the radius of curvature of the first side of the second lens.

4. The optical system according to claim 1, wherein: The optical system satisfies: \(5.66\leq f_m / T_{12m}\leq5.95\), where \(f_m\) is the effective focal length of the optical system in the first state, and \(T_{12m}\) is the distance on the optical axis between the second side of the first lens and the first side of the second lens when the optical system is in the first state.

5. The optical system according to claim 1, wherein The optical system satisfies: \(2.21\leq R3 / TD_n\leq4.80\), where \(R3\) is the radius of curvature of the first side of the second lens, and \(TD_n\) is the distance on the optical axis between the first side of the first lens and the second side of the second lens when the optical system is in the second state.

6. The optical system according to claim 1, wherein: The optical system satisfies the following: 1.87≤fn / (CT1+CTR+CTQ1)≤2.50, where fn is the effective focal length of the optical system in the second state, 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, and CTQ1 is the center thickness of the first quarter-wave plate on the optical axis.

7. The optical system according to claim 1, wherein: The optical system satisfies the following: 3.65≤T12n / Δf≤6.16, where T12n is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in the second state, and Δf is the change in the effective focal length of the optical system between the first state and the second state.

8. The optical system according to claim 1, wherein: The optical system satisfies the following: 6.95<(TDm+TDn) / EPD<9.45, where TDm is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the first state, TDn is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the second state, and EPD is the entrance pupil diameter of the optical system.

9. The optical system according to any one of claims 1 to 8, wherein: The optical system satisfies the following: 1.93≤CT2 / (T12m+T12n)≤2.82, where CT2 is the center thickness of the second lens on the optical axis, T12m is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in a first state, and T12n is the distance between the second side surface of the first lens and the first side surface of the second lens on the optical axis when the optical system is in a second state.

10. The optical system according to any one of claims 1 to 8, wherein: The optical system satisfies the following condition: 2.30≤(f1 / N1) / TDm≤3.16, where f1 is the effective focal length of the first lens, N1 is the refractive index of the first lens, and TDm is the distance between the first side surface of the first lens and the second side surface of the second lens on the optical axis when the optical system is in the first state.

11. The optical system according to any one of claims 1 to 8, wherein: The optical system satisfies the following: 0.85≤(f2 / V2) / ΔL≤1.63, where f2 is the effective focal length of the second lens, and V2 is the dispersion coefficient of the second lens.

12. The optical system according to any one of claims 1 to 8, wherein: The optical system satisfies the following: 1.67 mm ≤ (fz1 / CT1) × Δf ≤ 3.58 mm, where CT1 is the center thickness of the first lens on the optical axis, and Δf is the change in the effective focal length of the optical system between the first state and the second state.

13. The optical system according to any one of claims 1 to 8, wherein: The optical system satisfies: 2.0 mm<(fz2 / R3)×ΔL<3.2 mm, where R3 is the curvature radius of the first side surface of the second lens.

14. The optical system according to any one of claims 1 to 8, wherein: The optical system satisfies: 2.20≤f2 / (fm+fn)≤5.01, wherein f2 is the effective focal length of the second lens, fm is the effective focal length of the optical system in the first state, and fn is the effective focal length of the optical system in the second state.

15. An optical device, characterized in that: Comprising the optical system according to any one of claims 1 to 14.

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