Optical system and optical apparatus including the same

Abstract

The invention discloses an optical system and optical equipment comprising the same. 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. The first element group comprises a reflective polarization element, a first quarter-wave plate, a first lens and a partial reflection element. And the second element group comprises a second lens, a second quarter-wave plate, a polaroid and a display. The optical system satisfies: 0.5 lt; fz1 / fz2lt; 1.4 and 5.30 < = (CT2 + CTQ2 + CTL) / deltaL < = 7.71, fz1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate and the first lens, fz2 is the combined focal length of the second lens, the second quarter-wave plate and the polarizing film, 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 polarizing film on the optical axis, and deltaL is the center thickness of the polarizing film on the optical axis. And delta L is the variable quantity 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.

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 changed 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. There are still some shortcomings in the visual system of the current reentrant solution VR head-mounted display device. First, the existing design usually uses a large number of lenses or a large lens thickness, which will increase the volume and weight of the system, thereby affecting the user's wearing comfort. Secondly, although the existing design can realize the diopter adjustment function, it is often difficult to achieve a compact structure and lightweight design while ensuring image quality.

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

[0004] The first aspect of the present application provides an optical system. The optical system sequentially includes a first element group and a second element group along the optical axis from the first side to the second side. The first element group includes a reflective polarizing element, a first quarter-wave plate, a first lens, and a partial reflection 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 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 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 and 5.30 ≤ (CT2 + CTQ2 + CTL) / ΔL ≤ 7.71, where fz1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the first lens, fz2 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 ΔL 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 the second state.

[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 when the optical system is in the first state and the second state.

[0006] In one embodiment, the optical system satisfies: -2.15 mm < (R2 / R3) × ΔL < -1.30 mm, where R2 is the radius of curvature of the second side of the first lens, R3 is the radius of curvature of the first side of the second lens, and ΔL 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 the second state.

[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 of the first lens and the first side 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, wherein 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, wherein 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: 3.65≤T12n / Δf≤6.16, wherein 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: 6.95<(TDm+TDn) / EPD<9.45, wherein 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: 1.93≤CT2 / (T12m+T12n)≤2.82, wherein 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 the 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 the second state.

[0013] In one embodiment, the optical system satisfies: 2.30≤(f1 / N1) / TDm≤3.16, wherein 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, wherein 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 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.

[0015] In one embodiment, the optical system satisfies: 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 central 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 distance between the first element group and the second element group on the optical axis of the optical system between the first state and the second state.

[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 sequentially includes a first element group and a second element group along the optical axis from the first side to the second side. The first element group includes a reflective polarizing element, a first quarter-wave plate, a first lens, and a partial reflection 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 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 surface is a plane, and its second side surface 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 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 and 0.85 ≤ (f2 / V2) / ΔL ≤ 1.63, where fz1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the first lens, fz2 is the combined focal length of the second lens, the second quarter-wave plate, and the polarizer, 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 distance between the first element group and the second element group on the optical axis of the optical system between the first state and the second state.

[0019] The third aspect of the present application also provides an optical device, which includes 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, which includes a first element group and a second element group. The second element group moves along the optical axis between a first side and a second side, so that the optical system switches between a first state and a second state, which means that the optical system can achieve a 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, reasonably distributing the optical powers of two lenses, controlling the diopter adjustment range of the optical system within a reasonable range, while ensuring its processability and improving the optical imaging performance. The optical system with a 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 THE DRAWINGS

[0021] Other features, objects, and advantages of the present application will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings. In the drawings:

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

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

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

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

[0030] Fig. 9 A schematic structural diagram of an optical system in a +2D state according to Embodiment 3 of the present application is shown;

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

[0032] Fig.11 A schematic diagram showing the structure of an optical system in a -5D state according to Embodiment 3 of the present application is shown;

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

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

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

[0036] Fig.15 A schematic diagram showing the structure of an optical system in a -5D state according to Embodiment 4 of the present application is shown;

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

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

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

[0040] Fig.19 A schematic diagram showing the structure of an optical system in a -5D state according to Embodiment 5 of the present application is shown;

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

[0042] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present application, and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0043] It should be noted that in this specification, the expressions of first, second, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present application, the first lens discussed below may also be referred to as the second lens, and the second lens may also be referred to as the first lens.

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

[0045] In this article, the paraxial area refers to the area near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial area; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial area. The judgment of the surface type in the paraxial area can be judged according to the general method in this field, for example, judging the convexity and concavity by the positive and negative R value (R refers to the radius of curvature of the paraxial area). In this article, for the first side, when the R value is positive, it is judged as a convex surface, and when the R value is negative, it is judged as a concave surface; for the second side, when the R value is positive, it is judged as a concave surface, and when the R value is negative, it is judged as a convex surface.

[0046] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0047] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0048] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0049] The optical system according to the exemplary embodiment of the present application includes: a first element group and a second element group in order 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. The display can be used to provide an image or video light.

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

[0051] In an exemplary embodiment, 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, that is, the second side surface of the second lens is bonded to the first side surface of the second quarter wave plate, and the second side surface of the second quarter wave plate is bonded to the first side surface of the polarizer.

[0052] When the object distance changes, by adjusting the spacing between the first element group and the second element group on the optical axis, the optical system can be switched between the first state and the second state, that is, the diopter adjustment function of the optical system can be 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 diopter 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 is away from the first element group, the optical system is in the first state (+2D state), and when the second element group is close to the first element group, the optical system is in the second state (-5D state).

[0053] Those skilled in the art should understand that the reflective polarizing element can reflect polarized light in a certain direction and can also transmit polarized light orthogonal to the polarization direction, and the quarter wave plate can change the state of polarized light. The combination of light reflection and refraction using the reflective polarizing element and the quarter wave plate can fold the required optical path, effectively shortening the length of 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 includes the following in order from the human 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 includes a reflective polarizing element RP, a first quarter wave plate QWP1, a first lens E1 and a partially reflecting element BS, and the second element group G2 includes a second lens E2, a second quarter wave plate QWP2, a polarizing plate LP and a display IMG. Among them, the reflective polarizing element RP is attached to the side of the first quarter wave plate QWP1 near the human eye, and the first quarter wave plate QWP1 is attached to the side of the first lens E1 near the human eye; the partially reflecting element BS may have a semi-transmissive and semi-reflective function, and is attached to the side of the first lens E1 near the screen. The second quarter wave plate QWP2 is attached to the side of the second lens E2 near the screen, the polarizing plate LP is attached to the side of the second quarter wave plate QWP2 near the screen, and the display IMG is attached to the side of the polarizing plate LP near the screen.

[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 may 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, where 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, and the light beam is reflected again at the partial reflection 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 finally emerges toward the human eye side.

[0056] In an exemplary embodiment, the first lens may have positive optical power, a first side surface of which is flat and a second side surface of which is convex;

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

[0058] In an exemplary embodiment, the optical system of the present application may satisfy: 0.5 < fz1 / fz2 < 1.4, where fz1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the first lens, and fz2 is the combined focal length of the second lens, the second quarter-wave plate, and the polarizer. Satisfying 0.5 < fz1 / fz2 < 1.4 helps to reasonably distribute the optical powers of the first lens and the second lens, control the diopter adjustment range of the optical system within a reasonable range, and improve the optical imaging performance. Having a diopter adjustment function in the optical system allows for a smaller exit pupil distance, which is beneficial for further reducing the length of the optical system.

[0059] In an exemplary embodiment, the optical system of the present application may satisfy: 5.30 ≤ (CT2 + CTQ2 + CTL) / ΔL ≤ 7.71, where 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 ΔL is the change in the 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. Satisfying 5.30 ≤ (CT2 + CTQ2 + CTL) / ΔL ≤ 7.71 helps to control the overall length of the second element group, control the movement range of the second element group within a reasonable range, ensure the processability of the second element group, and improve the optical imaging performance.

[0060] In an exemplary embodiment, the optical system of the present application may satisfy: 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 between the first state and the second state of the optical system. Satisfying 0.15 mm < (f2 / f1) × Δf < 0.35 mm can achieve the diopter adjustment function of the optical system from the first state to the second state or from the second state to the first state. For example, it can achieve the diopter adjustment function from the +2D state to the -5D state.

[0061] In an exemplary embodiment, the optical system of the present application may satisfy: -2.15mm<(R2 / R3)×ΔL<-1.30mm, 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 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. Satisfying -2.15mm<(R2 / R3)×ΔL<-1.30mm can ensure the machinability of the first lens and the second lens, and at the same time, the movement range of the second element group is controlled within a reasonable range, thereby improving the imaging quality of the system.

[0062] In an exemplary embodiment, the optical system of the present application may satisfy: 5.66≤fm / T12m≤5.95, wherein 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 diopter of the system is adjusted.

[0063] In an exemplary embodiment, the optical system of the present application may satisfy: 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. Satisfying 2.21≤R3 / TDn≤4.80 can improve the clarity and accuracy of imaging and reduce optical distortion. At the same time, the focus change of the system in different states is reduced to ensure the stability and consistency of the focus adjustment of the system.

[0064] In an exemplary embodiment, the optical system of the present application may satisfy: 1.87≤fn / (CT1+CTR+CTQ1)≤2.50, wherein 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, and 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, can ensure that the optical system can achieve a -5D diopter function in the second state.

[0065] In an exemplary embodiment, the optical system of the present application may satisfy: 3.65≤T12n / Δf≤6.16, wherein 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. Satisfying 3.65≤T12n / Δf≤6.16 ensures that in the second state (-5D state), the first lens and the second lens do not interfere with each other.

[0066] In an exemplary embodiment, the optical system of the present application may satisfy: 6.95<(TDm+TDn) / EPD<9.45, wherein 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. When 6.95<(TDm+TDn) / EPD<9.45 is satisfied, the overall length of the optical system can be controlled, making the product thinner and lighter.

[0067] In an exemplary embodiment, the optical system of the present application may satisfy: 1.93≤CT2 / (T12m+T12n)≤2.82, wherein 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 the 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 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 thinner and lighter.

[0068] In an exemplary embodiment, the optical system of the present application may satisfy: 2.30≤(f1 / N1) / TDm≤3.16, wherein 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. Satisfying 2.30≤(f1 / N1) / TDm≤3.16 is conducive to improving the imaging performance of the system while controlling the material cost of the first lens.

[0069] In an exemplary embodiment, the optical system of the present application may satisfy: 0.85≤(f2 / V2) / ΔL≤1.63, wherein 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 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. Satisfying 0.85≤(f2 / V2) / ΔL≤1.63 is conducive to reducing system chromatic aberration and improving system imaging performance while controlling the material cost of the second lens.

[0070] In an exemplary embodiment, the optical system of the present application may satisfy: 1.67mm≤(fz1 / CT1)×Δf≤3.58mm, wherein 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. Satisfying 1.67mm≤(fz1 / CT1)×Δf≤3.58mm is conducive to reducing the overall length of the system by reducing the thickness of the first lens while ensuring the processability of the lens.

[0071] In an exemplary embodiment, the optical system of the present application may satisfy: 2.0mm<(fz2 / R3)×ΔL<3.2mm, wherein 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 when the optical system is in the first state and the second state. Satisfying 2.0mm<(fz2 / R3)×ΔL<3.2mm allows light to converge better, meeting imaging requirements while reducing lens sensitivity tolerance.

[0072] In an exemplary embodiment, the optical system of the present application may satisfy: 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. Satisfying 2.20≤f2 / (fm+fn)≤5.01 can enable the optical system to meet different diopter requirements in the first state (+2D state) and the second state (-5D state).

[0073] In an exemplary embodiment, the optical system of the present application may include at least one aperture. The aperture may constrain the optical path and control the light intensity. The aperture may be set at an appropriate position of the optical system, for example, the aperture may 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 polarizing plate (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 small-volume optical system with high-definition imaging quality. In application, the optical system according to the exemplary embodiment of the present application can be applied to VR equipment. By rationally designing the structural arrangement of the lens, reflective polarizing element, quarter-wave plate, partial reflection layer and display, the volume and weight of the system are reduced while ensuring the diopter adjustment function, and the efficiency of light energy utilization is improved, thereby providing users with a more comfortable and high-quality virtual reality experience.

[0076] In the embodiments of the present application, at least one of the mirror surfaces of each lens is an aspherical mirror surface. The characteristic of the aspherical lens is that the curvature changes continuously from the center of the lens to the periphery of the lens. Unlike a spherical lens having a constant curvature from the center of the lens to the periphery of the lens, an aspherical lens has a better curvature radius characteristic, and has the advantages of improving distortion aberration and improving astigmatism aberration. After adopting an aspherical lens, the aberration occurring during imaging can be eliminated as much as possible, thereby improving the 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 Embodiment 1 of the present application is described. Figure 1 It is a structural schematic diagram of the optical system in +2D state according to Example 1 of the present application. Figure 3 It is a structural schematic 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 polarizing element RP, a first quarter wave plate QWP1, a first lens E1 and a partially reflecting element BS, and the second element group G2 includes a second lens E2, a second quarter wave plate QWP2, a polarizing plate LP and a display IMG. Among them, the reflective polarizing element RP is attached to the side of the first quarter wave plate QWP1 near the human eye, and the first quarter wave plate QWP1 is attached to the side of the first lens E1 near the human eye; the partially reflecting element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the first lens E1 near the screen. The second quarter wave plate QWP2 is attached to the side of the second lens E2 near the screen, the polarizing plate LP is attached to the side of the second quarter wave plate QWP2 near the screen, and the display IMG is attached to the side of the polarizing plate LP near the screen.

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

[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 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, and 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 finally exits toward the human eye side.

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

[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 endless D1 refraction 1 Aperture (STO) Spherical endless 10.0000 refraction 2 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 refraction 3 First Quarter Wave Plate (QWP1) Spherical endless 0.1000 1.517 64.17 refraction 4 First lens (E1) Spherical 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 endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 reflection 8 First lens (E1) Spherical 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 endless 0.1000 1.517 64.17 refraction 12 Polarizer(LP) Spherical endless 0.1000 1.517 64.17 refraction 13 Spherical endless 0.0000 refraction 14 Display (IMG) Spherical endless 0.0000 refraction

[0086] 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. Table 2 shows the air interval D2 between the first lens and the second lens on the optical axis at different object distances D1 of the optical system of Example 1. 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). The units in Table 2 are all 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, and the surface shape of each aspherical lens can be defined by but not limited to the following aspherical surface formula:

[0090]

[0091] Wherein, x is the distance vector height from the vertex of the aspheric surface when the aspheric surface is 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 cone coefficient; Ai is the correction coefficient of the i-th order of the aspheric surface. Table 3 below gives the high-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 the -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 Embodiment 2 of the present application is described. Figure 5 It is a structural schematic diagram of the optical system in +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 Embodiment 2 of the present application. In this embodiment and the following embodiments, for the sake of brevity, some descriptions similar to Embodiment 1 will be omitted.

[0097] like Figure 5 and Figure 7 As shown, the optical system of Example 2 includes an aperture 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 reflecting element BS, and the second element group G2 includes a second lens E2, a second quarter wave plate QWP2, a polarizing plate LP and a display IMG. Among them, the reflective polarizing element RP is attached to the side of the first quarter wave plate QWP1 near the human eye, and the first quarter wave plate QWP1 is attached to the side of the first lens E1 near the human eye; the partially reflecting element BS may have a semi-transmissive and semi-reflective function, and is attached to the side of the first lens E1 near the screen. The second quarter wave plate QWP2 is attached to the side of the second lens E2 near the screen, the polarizing plate LP is attached to the side of the second quarter wave plate QWP2 near the screen, and the display IMG is attached to the side of the polarizing plate LP near the screen.

[0098] The first lens E1 has positive refractive power, its side surface near the human eye is a flat surface, and its side surface near the screen is a convex surface. The second lens E2 has positive refractive power, its side surface near the human eye is a convex surface, and its side surface near the screen is a flat surface.

[0099] 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 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, and 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 finally exits toward the human eye side.

[0100] Table 4 shows basic parameters of the optical system of Example 2, wherein the units of the radius of curvature and thickness / distance are both 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 endless D1 refraction 1 Aperture (STO) Spherical endless 12.0000 refraction 2 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 refraction 3 First Quarter Wave Plate (QWP1) Spherical endless 0.1000 1.517 64.17 refraction 4 First lens (E1) Spherical 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 endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 reflection 8 First lens (E1) Spherical 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 endless 0.1000 1.517 64.17 refraction 12 Polarizer(LP) Spherical endless 0.1000 1.517 64.17 refraction 13 Spherical endless 0.0000 refraction 14 Display (IMG) Spherical 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. Table 5 shows the air interval D2 on the optical axis between the first lens and the second lens of the optical system of Example 2 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). The units in Table 5 are all 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 aspherical mirror surface that can be used in Example 2, wherein each aspherical surface shape can be defined by the formula (1) given in the above Example 1.

[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 the -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. Fig. 9 It is a structural schematic diagram of the optical system in the +2D state according to Example 3 of the present application. Fig.11 It is a structural schematic diagram of the optical system in -5D state according to Example 3 of the present application.

[0112] like Fig. 9 and Fig.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 polarizing element RP, a first quarter wave plate QWP1, a first lens E1 and a partially reflecting element BS, and the second element group G2 includes a second lens E2, a second quarter wave plate QWP2, a polarizing plate LP and a display IMG. Among them, the reflective polarizing element RP is attached to the side of the first quarter wave plate QWP1 near the human eye, and the first quarter wave plate QWP1 is attached to the side of the first lens E1 near the human eye; the partially reflecting element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the first lens E1 near the screen. The second quarter wave plate QWP2 is attached to the side of the second lens E2 near the screen, the polarizing plate LP is attached to the side of the second quarter wave plate QWP2 near the screen, and the display IMG is attached to the side of the polarizing plate LP near the screen.

[0113] The first lens E1 has positive refractive power, its side surface near the human eye is a flat surface, and its side surface near the screen is a convex surface. The second lens E2 has positive refractive power, its side surface near the human eye is a convex surface, and its side surface near the screen is a flat surface.

[0114] 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 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, and 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 finally exits toward the human eye side.

[0115] Table 7 shows basic parameters of the optical system of Example 3, wherein the units of the radius of curvature and thickness / distance are both 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. Table 8 shows the air interval D2 between the first lens and the second lens on the optical axis at different object distances D1 of the optical system of Example 3. 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). The units in Table 8 are all millimeters (mm).

[0120] 5 Table 8

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

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

[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] Fig.10 is the modulation transfer function curve of the optical system of Example 3 in the +2D state, Fig.12 is the modulation transfer function curve of the optical system of Example 3 in the -5D state. Fig.10 and Fig.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. Fig.13 It is a structural schematic diagram of the optical system in the +2D state according to Example 4 of the present application. Fig.15 It is a structural schematic diagram of the optical system in -5D state according to Example 4 of the present application.

[0128] like Fig.13 and Fig.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 polarizing element RP, a first quarter wave plate QWP1, a first lens E1 and a partially reflecting element BS, and the second element group G2 includes a second lens E2, a second quarter wave plate QWP2, a polarizing plate LP and a display IMG. Among them, the reflective polarizing element RP is attached to the side of the first quarter wave plate QWP1 near the human eye, and the first quarter wave plate QWP1 is attached to the side of the first lens E1 near the human eye; the partially reflecting element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the first lens E1 near the screen. The second quarter wave plate QWP2 is attached to the side of the second lens E2 near the screen, the polarizing plate LP is attached to the side of the second quarter wave plate QWP2 near the screen, and the display IMG is attached to the side of the polarizing plate LP near the screen.

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

[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 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, and 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 finally exits toward the human eye side.

[0131] Table 10 shows basic parameters of the optical system of Example 4, wherein the units of the radius of curvature and thickness / distance are both 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 endless D1 refraction 1 Aperture (STO) Spherical endless 9.0000 refraction 2 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 refraction 3 First Quarter Wave Plate (QWP1) Spherical endless 0.1000 1.517 64.17 refraction 4 First lens (E1) Spherical 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 endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 reflection 8 First lens (E1) Spherical 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 endless 0.1000 1.517 64.17 refraction 12 Polarizer(LP) Spherical endless 0.1000 1.517 64.17 refraction 13 Spherical endless 0.0000 refraction 14 Display (IMG) Spherical endless 0.0000 refraction

[0134] 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. Table 11 shows the air interval D2 between the first lens and the second lens on the optical axis at different object distances D1 of the optical system of Example 4. 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). The units in Table 11 are all 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 aspherical mirror surface that can be used in Example 4, wherein each aspherical surface shape 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] Fig.14 is the modulation transfer function curve of the optical system of Example 4 in the +2D state, Fig.16 is the modulation transfer function curve of the optical system of Example 4 in the -5D state. Fig.14 and Fig.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. Fig.17 It is a structural schematic diagram of the optical system in the +2D state according to Example 5 of the present application. Fig.19 It is a structural schematic diagram of the optical system in -5D state according to Example 5 of the present application.

[0143] like Fig.17 and Fig.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 polarizing element RP, a first quarter wave plate QWP1, a first lens E1 and a partially reflecting element BS, and the second element group G2 includes a second lens E2, a second quarter wave plate QWP2, a polarizing plate LP and a display IMG. Among them, the reflective polarizing element RP is attached to the side of the first quarter wave plate QWP1 near the human eye, and the first quarter wave plate QWP1 is attached to the side of the first lens E1 near the human eye; the partially reflecting element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the first lens E1 near the screen. The second quarter wave plate QWP2 is attached to the side of the second lens E2 near the screen, the polarizing plate LP is attached to the side of the second quarter wave plate QWP2 near the screen, and the display IMG is attached to the side of the polarizing plate LP near the screen.

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

[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 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, and 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 finally exits toward the human eye side.

[0146] Table 13 shows basic parameters of the optical system of Example 5, wherein the units of the radius of curvature and thickness / distance are both 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 endless D1 refraction 1 Aperture (STO) Spherical endless 13.0000 refraction 2 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 refraction 3 First Quarter Wave Plate (QWP1) Spherical endless 0.1000 1.517 64.17 refraction 4 First lens (E1) Spherical 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 endless -0.1000 1.517 64.17 refraction 7 Reflective polarizer (RP) Spherical endless 0.1000 1.517 64.17 reflection 8 First lens (E1) Spherical 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 endless 0.1000 1.517 64.17 refraction 12 Polarizer(LP) Spherical endless 0.1000 1.517 64.17 refraction 13 Spherical endless 0.0000 refraction 14 Display (IMG) Spherical endless 0.0000 refraction

[0149] 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. Table 14 shows the air interval D2 between the first lens and the second lens on the optical axis at different object distances D1 of the optical system of Example 5. 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). The units in Table 14 are all 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 aspherical mirror surface that can be used in Example 5, wherein each aspherical surface shape can be defined by the formula (1) given in the above Example 1.

[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] Fig.18 is the modulation transfer function curve of the optical system of Example 5 in the +2D state, Fig. 20 is the modulation transfer function curve of the optical system of Example 5 in the -5D state. Fig.18 and Fig. 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 / Examples 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 / 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 may be an independent projection device such as a projector, or a projection module integrated in a mobile electronic device such as a VR. The optical device is equipped with the optical system described above.

[0163] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of protection involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the concept of the present application. For example, the above features are replaced with the technical features with similar functions disclosed in the present application (but not limited to) by each other.

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 < fz1 / fz2 < 1.4 and 5.30 ≤ (CT2 + CTQ2 + CTL) / ΔL ≤ 7.71, where fz1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the first lens, fz2 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 ΔL is the change amount of the spacing distance between the first element group and the second element group on the optical axis of the optical system in the first state and the second state.

2. The optical system according to claim 1, wherein: 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 amount of the effective focal length of the optical system in the first state and the second state.

3. The optical system according to claim 1, wherein: The optical system satisfies: -2.15 mm < (R2 / R3)×ΔL < -1.30 mm, where R2 is the curvature radius of the second side of the first lens, and R3 is the curvature radius of the first side of the second lens.

4. The optical system according to claim 1, wherein: 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 on the optical axis between the second side of the first lens and the first side of the second lens of the optical system in the first state.

5. The optical system according to claim 1, wherein: The optical system satisfies: 2.21 ≤ R3 / TDn ≤ 4.80, where R3 is the curvature radius of the first side of the second lens, and TDn is the distance on the optical axis between the first side of the first lens and the second side of the second lens of the optical system in the second state.

6. The optical system according to claim 1, wherein: The optical system satisfies: 1.87≤fn / (CT1+CTR+CTQ1)≤2.50, wherein 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: 3.65≤T12n / Δf≤6.16, wherein 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: 6.95<(TDm+TDn) / EPD<9.45, wherein 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: 1.93≤CT2 / (T12m+T12n)≤2.82, wherein 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 the 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 the second state.

10. The optical system according to any one of claims 1 to 8, wherein: The optical system satisfies: 2.30≤(f1 / N1) / TDm≤3.16, wherein 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: 0.85≤(f2 / V2) / ΔL≤1.63, wherein 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: 1.67 mm ≤ (fz1 / CT1) × Δf ≤ 3.58 mm, wherein 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, wherein R3 is the radius of curvature 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 an optical system as claimed in any one of claims 1 to 14.

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