Optical system

Abstract

The utility model discloses an optical system. The utility model relates to an optical lens which comprises a first lens with positive focal power and a convex plane type, a reflective polarizing element, a first quarter-wave plate, a second lens with negative focal power and a concave second side, a third lens with positive focal power and a convex surface type, and a partial reflection element in sequence from a first side to a second side along an optical axis, the fourth lens has negative focal power and is of a concave plane type; the second quarter-wave plate and the polarizing film are arranged in the concave plane type; the reflective polarizing element and the second side face of the first lens, the first quarter-wave plate and the second side face of the reflective polarizing element, the second quarter-wave plate and the second side face of the fourth lens, and the polarizing film and the second side face of the second quarter-wave plate are at least partially attached respectively. The effective focal lengths f1 and f3 of the first lens and the third lens satisfy 0.75 lt; f1 / f3lt; 1.15, the effective focal lengths f2 and f4 of the second lens and the fourth lens satisfy 0.2 lt; f2 / f4lt; 1.4, the combined focal length fz1 of the first lens, the reflective polarizing element and the first quarter-wave plate and the curvature radius R1 of the first side surface of the first lens satisfy 1.96 lt; fz1 / R1lt; and 2.13.

Description

Technical Field

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

[0002] In recent years, VR (Virtual Reality) and AR (Augmented Reality) technologies have developed rapidly. VR / AR can provide an immersive environment with high precision and realism, so it has been widely used in many fields such as education, medical care, and industry, which can not only improve work efficiency, but also enrich people's life and work experiences.

[0003] Optical systems applicable to VR / AR devices, after the development of aspherical lenses, Fresnel lenses and other solutions, are currently developing in the direction of a catadioptric structure. The catadioptric structure can significantly compress the length of the system through the folding of the optical path, which is beneficial to the miniaturization and thinness of the device, so it is widely favored. However, the current catadioptric optical system still has problems of relatively large volume and weight, is not very suitable for users to wear and use for a long time, and has poor comfort. In addition, people's requirements for the imaging quality of the system are also getting higher and higher, and an optical system is required to provide clearer and more realistic images and reduce distortion, etc. Summary of the Utility Model

[0004] This application provides an optical system, which may sequentially include, along the optical axis from the first side to the second side: a first lens with positive optical power, whose first side is convex and the second side is flat; a reflective polarizing element; a first quarter-wave plate; a second lens with negative optical power, whose second side is concave; a third lens with positive optical power, whose first side is convex and the second side is convex; a partial reflection element; a fourth lens with negative optical power, whose first side is concave and the second side is flat; a second quarter-wave plate; and a polarizer. Among them, the reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens; the first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate. The optical system can satisfy: 0.75 < f1 / f3 < 1.15, 0.2 < f2 / f4 < 1.4, and 1.96 < fz1 / R1 < 2.13, where f1 is the effective focal length of the first lens, f3 is the effective focal length of the third lens, f2 is the effective focal length of the second lens, f4 is the effective focal length of the fourth lens, fz1 is the combined focal length of the first lens, the reflective polarizing element and the first quarter-wave plate, and R1 is the radius of curvature of the first side of the first lens.

[0005] In one embodiment, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis, and the distance T12 on the optical axis from the second side surface of the first lens to the first side surface of the second lens satisfy: 0.05 < (CTR + CTQ1) / T12 < 0.4.

[0006] In one embodiment, the radius of curvature R5 of the first side surface of the third lens and the central thickness CT3 of the third lens on the optical axis satisfy: 2.2 < R5 / CT3 < 4.5.

[0007] In one embodiment, the combined focal length fz2 of the fourth lens, the second quarter-wave plate, and the polarizer and the radius of curvature R7 of the first side surface of the fourth lens satisfy: 1.2 ≤ fz2 / R7 < 2.1.

[0008] In one embodiment, the effective focal length f1 of the first lens and the central thickness CT1 of the first lens on the optical axis satisfy: 5.6 < f1 / CT1 < 7.2.

[0009] In one embodiment, the effective focal length f2 of the second lens, the central thickness CT2 of the second lens on the optical axis, and the distance T23 on the optical axis from the second side surface of the second lens to the first side surface of the third lens satisfy: -8.6 < f2 / (CT2 + T23) < -5.7.

[0010] In one embodiment, the dispersion coefficient V1 of the first lens and the refractive index N1 of the first lens satisfy: 41.8 ≤ V1 / N1 < 47.2.

[0011] In one embodiment, the effective focal length f of the optical system, the dispersion coefficient V2 of the second lens, and the refractive index N2 of the second lens satisfy: 1.55 mm < f / (V2 / N2) < 2.15 mm.

[0012] In one embodiment, the central thickness CT1 of the first lens on the optical axis and the axial distance SAG11 from the intersection of the first side surface of the first lens and the optical axis to the vertex of the effective radius of the first side surface of the first lens satisfy: 1.29 ≤ CT1 / SAG11 < 1.55.

[0013] In one embodiment, the optical system may further include a diaphragm located on the first side of the first lens. The sum ∑CT of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis and the distance SR on the optical axis from the diaphragm to the first side surface of the first lens satisfy: 0.95 < ∑CT / SR ≤ 1.3.

[0014] In one embodiment, the distance T34 on the optical axis from the second side surface of the third lens to the first side surface of the fourth lens and the axial distance SAG41 from the intersection of the first side surface of the fourth lens and the optical axis to the vertex of the effective radius of the first side surface of the fourth lens may satisfy: -1.55 < T34 / SAG41 < -0.9.

[0015] In one embodiment, the effective focal length f1 of the first lens and the entrance pupil diameter EPD of the optical system may satisfy: 1.65 < f1 / EPD < 1.79.

[0016] The optical system disclosed in this application sequentially includes a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer along the optical axis from the first side to the second side. Among them, the first lens has a positive optical power, its first side surface is convex, and its second side surface is flat; the second lens has a negative optical power, and its second side surface is concave; the third lens has a positive optical power, its first side surface is convex, and its second side surface is convex; the fourth lens has a negative optical power, its first side surface is concave, and its second side surface is flat; the reflective polarizing element is placed on the second side surface of the first lens and at least partially adheres to the second side surface of the first lens; the first quarter-wave plate is placed on the second side surface of the reflective polarizing element and at least partially adheres to the second side surface of the reflective polarizing element; the second quarter-wave plate is placed on the second side surface of the fourth lens and at least partially adheres to the second side surface of the fourth lens; the polarizer is placed on the second side surface of the second quarter-wave plate and at least partially adheres to the second side surface of the second quarter-wave plate. Moreover, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: 0.75 < f1 / f3 < 1.15, the effective focal length f2 of the second lens and the effective focal length f4 of the fourth lens satisfy: 0.2 < f2 / f4 < 1.4, and the combined focal length fz1 of the first lens, the reflective polarizing element, and the first quarter-wave plate and the radius of curvature R1 of the first side surface of the first lens satisfy: 1.96 < fz1 / R1 < 2.13. This optical system adopts a polarization folding optical path. By reasonably configuring the optical system and the film pasting method, and through the above settings of the optical system, while f1 and f3, f2 and f4 respectively satisfy 0.75 < f1 / f3 < 1.15 and 0.2 < f2 / f4 < 1.4, controlling fz1 and R1 to satisfy 1.96 < fz1 / R1 < 2.13 can reasonably distribute the optical power of the optical system. At the same time, by using the aberration correction ability of the spherical or aspherical surfaces of the lenses, the performance of the optical system can be improved. Description of the Drawings

[0017] Combined with the drawings, through the following detailed description of non-limiting embodiments, other features, purposes, and advantages of this application will become more obvious. In the drawings:

[0018] Figure 1 Shows a schematic structural diagram of an optical system according to Embodiment 1 of the present application;

[0019] Figure 2 、 Figure 3 and Figure 4 respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 1;

[0020] Figure 5 Shows the modulation transfer function (MTF) curve of the optical system of Embodiment 1;

[0021] Figure 6 Shows a schematic structural diagram of an optical system according to Embodiment 2 of the present application;

[0022] Figure 7 、 Figure 8 and Figure 9 respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 2;

[0023] Figure 10 Shows the modulation transfer function (MTF) curve of the optical system of Embodiment 2;

[0024] Figure 11 Shows a schematic structural diagram of an optical system according to Embodiment 3 of the present application;

[0025] Figure 12 、 Figure 13 and Figure 14 respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 3;

[0026] Figure 15 Shows the modulation transfer function (MTF) curve of the optical system of Embodiment 3;

[0027] Figure 16 Shows a schematic structural diagram of an optical system according to Embodiment 4 of the present application;

[0028] Figure 17 、 Figure 18 and Figure 19 respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Embodiment 4;

[0029] Figure 20 Shows the modulation transfer function (MTF) curve of the optical system of Embodiment 4;

[0030] Figure 21 Shows a schematic structural diagram of an optical system according to Embodiment 5 of the present application;

[0031] Figure 22 、 Figure 23 andFigure 24 The axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system of Example 5 are respectively shown; and

[0032] Figure 25 The modulation transfer function (MTF) curve of the optical system of Example 5 is shown. Detailed implementation mode

[0033] To better understand the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the exemplary embodiments of the present application and do not 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.

[0034] It should be noted that in this specification, the expressions such as first, second, etc. are only used to distinguish one feature from another feature and do not represent any limitation on the feature. Therefore, without departing from the teachings 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.

[0035] In the drawings, for ease of illustration, the thickness, size, and shape of the lens have been slightly exaggerated. 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 spherical or aspherical shapes shown in the drawings. The drawings are for illustration only and are not drawn to an exact scale.

[0036] In this article, the paraxial region refers to the region 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 region; 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 region.

[0037] It should also be understood that the terms "comprises", "comprising", "has", "including" and / or "including having", when used in this specification, mean 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 an expression such as "at least one of..." appears after the list of listed features, it modifies the entire list of listed features rather than individual elements in the list. In addition, when describing the embodiments of the present application, the use of "may" means "one or more embodiments of the present application". And the term "exemplary" is intended to refer to an example or illustration.

[0038] 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 should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formalized sense unless expressly so defined herein.

[0039] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will detail this application with reference to the drawings and in conjunction with the embodiments.

[0040] The features, principles, and other aspects of this application will be described in detail below.

[0041] The optical system according to an exemplary embodiment of this application may include a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer. In the exemplary embodiment, the first lens, the reflective polarizing element, the first quarter-wave plate, the second lens, the third lens, the partial reflection element, the fourth lens, the second quarter-wave plate, and the polarizer may be arranged in sequence from the first side to the second side along the optical axis.

[0042] In the exemplary embodiment, the first lens may have a positive focal power, its first side may be convex, and its second side may be flat. The second lens may have a negative focal power, its first side may be concave or convex, and its second side may be concave. The third lens may have a positive focal power, its first side may be convex, and its second side may be convex. The fourth lens may have a negative focal power, its first side may be concave, and its second side may be flat.

[0043] In the exemplary embodiment, the reflective polarizing element may be disposed on the second side of the first lens, and the first side of the reflective polarizing element may at least partially conform to the second side of the first lens. The first quarter-wave plate may be disposed on the second side of the reflective polarizing element, and the first side of the first quarter-wave plate may at least partially conform to the second side of the reflective polarizing element. The second quarter-wave plate may be disposed on the second side of the fourth lens, and the first side of the second quarter-wave plate may at least partially conform to the second side of the fourth lens. The polarizer may be disposed on the second side of the second quarter-wave plate, and the first side of the polarizer may at least partially conform to the second side of the second quarter-wave plate.

[0044] In the exemplary embodiment, the partial reflection element may be a semi-transmissive and semi-reflective film layer coated on the second side of the third lens.

[0045] In an exemplary embodiment, the first side may be, for example, a human eye side, and the second side may be, for example, an image surface side. The optical system may be used in, for example, VR / AR devices and the like.

[0046] The following will refer to Figure 1 An example description of the optical system is given below. Figure 1 As shown, the optical system according to the exemplary embodiment of the present application may include a first lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter wave plate QWP2 and a polarizer LP arranged in sequence from the first side to the second side, wherein the reflective polarizing element RP is arranged on the second side of the first lens E1, the first quarter wave plate QWP1 is arranged on the second side of the reflective polarizing element RP, the partial reflection element BS is arranged on the second side of the third lens E3, the second quarter wave plate QWP2 is arranged on the second side of the fourth lens E4, and the polarizer LP is arranged on the second side of the second quarter wave plate QWP2. In actual use, the optical system according to the exemplary embodiment of the present application can be used as a VR / AR lens, for example, in which case the first side corresponds to the human eye side and the second side corresponds to the image surface side. The optical system may also include, for example, an image surface IMG located on the second side of the polarizer LP. The light beam emitted from the image plane IMG can sequentially pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2, the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the first quarter-wave plate QWP1, the second lens E2 and the third lens E3 again to reach the partial reflection element BS, and then, the light beam is reflected again at the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP and the first lens E1 to be emitted toward the first side (e.g., the human eye side).

[0047] In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 0.75 <f1 / f3<1.15,其中,f1为第一透镜的有效焦距,f3为第三透镜的有效焦距。

[0048] In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 0.2 <f2 / f4<1.4,其中,f2为第二透镜的有效焦距,f4为第四透镜的有效焦距。

[0049] In an exemplary embodiment, the optical system of the present application may satisfy the conditional expression 1.96 <fz1 / R1<2.13,其中,fz1为第一透镜、反射式偏光元件和第一四分之一波片的组合焦距,R1为第一透镜的第一侧面的曲率半径。

[0050] An optical system according to an exemplary embodiment of the present application sequentially includes a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer along the optical axis from the first side to the second side. Among them, the first lens has a positive optical power, its first side is convex, and its second side is flat; the second lens has a negative optical power, and its second side is concave; the third lens has a positive optical power, its first side is convex, and its second side is convex; the fourth lens has a negative optical power, its first side is concave, and its second side is flat; the reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens; the first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate. Moreover, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: 0.75 < f1 / f3 < 1.15, the effective focal length f2 of the second lens and the effective focal length f4 of the fourth lens satisfy: 0.2 < f2 / f4 < 1.4, and the combined focal length fz1 of the first lens, the reflective polarizing element, and the first quarter-wave plate and the radius of curvature R1 of the first side of the first lens satisfy: 1.96 < fz1 / R1 < 2.13. This optical system adopts a polarization folding optical path. By reasonably configuring the optical system and the film pasting method, and through the above settings of the optical system, while f1 and f3, f2 and f4 respectively satisfy 0.75 < f1 / f3 < 1.15 and 0.2 < f2 / f4 < 1.4, controlling fz1 and R1 to satisfy 1.96 < fz1 / R1 < 2.13 can reasonably distribute the optical power of the optical system. At the same time, by using the aberration correction ability of the spherical or aspherical surface of the lens, the performance of the optical system can be improved. The optical system according to an exemplary embodiment of the present application adopts a four-piece catadioptric structure. While achieving a reduction in the overall optical length of the system and making the device more portable and comfortable, it can also provide clearer and more realistic images and reduce distortion, etc.

[0051] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 0.05 < (CTR + CTQ1) / T12 < 0.4, where CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ1 is the central thickness of the first quarter-wave plate on the optical axis, and T12 is the distance on the optical axis from the second side of the first lens to the first side of the second lens. By controlling the system to satisfy the conditional formula 0.05 < (CTR + CTQ1) / T12 < 0.4, it is possible to reduce the length of the optical system while ensuring the lens forming, which is beneficial for the device to meet the requirements of being thin and light.

[0052] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 2.2 < R5 / CT3 < 4.5, where R5 is the radius of curvature of the first side surface of the third lens, and CT3 is the central thickness of the third lens on the optical axis. By controlling the ratio of the radius of curvature of the first side surface of the third lens to the central thickness of the third lens on the optical axis within this range, it is beneficial to the shaping of the lens and to reducing the difficulty of the process; at the same time, it can also effectively control the refraction angle of the system light beam, thereby meeting the CRA requirements of the optical system.

[0053] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.2 ≤ fz2 / R7 < 2.1, where fz2 is the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer, and R7 is the radius of curvature of the first side surface of the fourth lens. By controlling the system to satisfy the conditional formula 1.2 ≤ fz2 / R7 < 2.1, the shape of the fourth lens can be reasonably restricted, which is beneficial to reducing the sensitivity of the fourth lens and the difficulty of film pasting, thereby improving the yield of assembly.

[0054] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 5.6 < f1 / CT1 < 7.2, where f1 is the effective focal length of the first lens, and CT1 is the central thickness of the first lens on the optical axis. The focal length and thickness of the lens directly affect the complexity and performance of the optical path design. By reasonably controlling the range of this conditional formula, the focusing position of the light can be adjusted to achieve precise control of imaging. Reasonably designing the thickness of the lens can make the optical system more compact, reduce the volume and weight, and improve the portability and practicality.

[0055] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula -8.6 < f2 / (CT2 + T23) < -5.7, where f2 is the effective focal length of the second lens, CT2 is the central thickness of the second lens on the optical axis, and T23 is the distance on the optical axis from the second side surface of the second lens to the first side surface of the third lens. By controlling the system to satisfy the conditional formula -8.6 < f2 / (CT2 + T23) < -5.7, it ensures that the optical performance of the second lens remains stable within a certain range, ensures that the lens system can correctly focus light, reduces the generation of aberration and other optical distortions. Reasonably designing the thickness of the lens and the distance between the lenses can reduce the difficulty of forming and processing on the premise of meeting the imaging requirements, and can also make the optical system more compact, reduce the volume and weight, and improve the portability and practicality.

[0056] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 41.8 ≤ V1 / N1 < 47.2, where V1 is the dispersion coefficient of the first lens and N1 is the refractive index of the first lens. By controlling the refractive index and dispersion coefficient of the first lens, it can help optimize the refraction effect of the optical system, control the propagation speed and refraction angle of light in the system, contribute to achieving the desired optical imaging effect, and contribute to improving the clarity and contrast of the image; at the same time, satisfying the dispersion coefficient condition can reduce the dispersion effect and improve the color accuracy and imaging quality of the image.

[0057] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.55 mm < f / (V2 / N2) < 2.15 mm, where f is the effective focal length of the optical system, V2 is the dispersion coefficient of the second lens, and N2 is the refractive index of the second lens. By controlling the optical system to satisfy the conditional formula 1.55 mm < f / (V2 / N2) < 2.15 mm, the imaging quality of the system can be optimized, the clarity and contrast of the image can be improved, and the aberrations of the system, such as chromatic aberration and distortion, can also be reduced, thereby improving the performance and stability of the optical system.

[0058] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.29 ≤ CT1 / SAG11 < 1.55, where CT1 is the central thickness of the first lens on the optical axis, and SAG11 is the axial distance from the intersection of the first side of the first lens and the optical axis to the vertex of the effective radius of the first side of the first lens. By controlling the system to satisfy the conditional formula 1.29 ≤ CT1 / SAG11 < 1.55, the lens thickness can be reasonably controlled, which can avoid the difficulty of processing and forming due to being too thin, and can also avoid being too thick resulting in a large and heavy volume. The control of this conditional formula is beneficial to ensuring the lightness of the lens and the system, facilitating carrying, and enhancing the user experience.

[0059] In an exemplary embodiment, the optical system of the present application further includes a diaphragm located on the first side of the first lens, and the optical system of the present application can satisfy the conditional formula 0.95 < ∑CT / SR ≤ 1.3, where ∑CT is the sum of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis, and SR is the distance from the diaphragm to the first side of the first lens on the optical axis. By controlling the proportional relationship between the lens thickness and the diaphragm position parameter so that the system satisfies the conditional formula 0.95 < ∑CT / SR ≤ 1.3, the aberrations in the system can be reduced, and the clarity and accuracy of imaging can be improved; at the same time, it is also beneficial to the forming of the lens and to making the optical system more compact, shortening the length of the optical system, and meeting the requirements of the virtual device being thin and light.

[0060] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula -1.55 < T34 / SAG41 < -0.9, where T34 is the distance on the optical axis from the second side of the third lens to the first side of the fourth lens, and SAG41 is the axial distance from the intersection point of the first side of the fourth lens and the optical axis to the vertex of the effective radius of the first side of the fourth lens. By controlling the system to satisfy the conditional formula -1.55 < T34 / SAG41 < -0.9, optical properties such as the focal length, aberration, and distortion of the system can be adjusted.

[0061] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 1.65 < f1 / EPD < 1.79, where f1 is the effective focal length of the first lens and EPD is the entrance pupil diameter of the optical system. By controlling the ratio of the effective focal length of the first lens to the entrance pupil diameter of the optical system within this range, the optical power of the system is reasonably controlled, which is beneficial to reducing the spherical aberration of the system and can effectively reduce the sensitivity of the system.

[0062] In an exemplary embodiment, the optical system of the present application can include at least one aperture stop. The aperture stop can restrict the light path and control the light intensity. The aperture stop can be set at an appropriate position in the optical system. For example, the aperture stop can be located between the first side (such as the human eye side) and the first lens.

[0063] In an exemplary embodiment, optionally, the optical system of the present application can further include a protective glass for protecting the photosensitive element located on the imaging surface.

[0064] On the one hand, the optical system according to an exemplary embodiment of the present application sequentially includes, along the optical axis from the first side to the second side, a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer. Among them, the first lens has a positive optical power, its first side is convex, and its second side is flat; the second lens has a negative optical power, and its second side is concave; the third lens has a positive optical power, its first side is convex, and its second side is convex; the fourth lens has a negative optical power, its first side is concave, and its second side is flat; the reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens; the first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate. Moreover, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: 0.75 < f1 / f3 < 1.15, the effective focal length f2 of the second lens and the effective focal length f4 of the fourth lens satisfy: 0.2 < f2 / f4 < 1.4, and the combined focal length fz1 of the first lens, the reflective polarizing element, and the first quarter-wave plate and the radius of curvature R1 of the first side of the first lens satisfy: 1.96 < fz1 / R1 < 2.13. This optical system adopts a polarization folding optical path. By reasonably configuring the optical system and the film pasting method, and through the above settings of the optical system, while f1 and f3, f2 and f4 respectively satisfy 0.75 < f1 / f3 < 1.15 and 0.2 < f2 / f4 < 1.4, controlling fz1 and R1 to satisfy 1.96 < fz1 / R1 < 2.13 can reasonably distribute the optical power of the optical system. At the same time, by using the aberration correction ability of the spherical or aspherical surface of the lens, the performance of the optical system can be improved. While achieving the reduction of the overall optical length of the system and making the device more portable and comfortable, it can also provide clearer and more realistic images and reduce distortion, etc.

[0065] On the other hand, the optical system according to an exemplary embodiment of the present application sequentially includes a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer along the optical axis from the first side to the second side. Among them, the first lens has a positive optical power, its first side is convex, and its second side is flat; the second lens has a negative optical power, and its second side is concave; the third lens has a positive optical power, its first side is convex, and its second side is convex; the fourth lens has a negative optical power, its first side is concave, and its second side is flat; the reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens; the first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate. Moreover, the combined focal length fz2 of the fourth lens, the second quarter-wave plate, and the polarizer and the radius of curvature R7 of the first side of the fourth lens satisfy the conditional formula 1.2 ≤ fz2 / R7 < 2.1. By the above setting of the optical system and the control of this conditional formula, the shape of the fourth lens can be reasonably restricted, which is beneficial to reducing the sensitivity and the film sticking difficulty of the fourth lens and is beneficial to improving the yield of assembly.

[0066] On the other hand, the optical system according to an exemplary embodiment of the present application sequentially includes, along the optical axis from the first side to the second side, a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer. Among them, the first lens has a positive optical power, its first side is convex, and its second side is flat; the second lens has a negative optical power, and its second side is concave; the third lens has a positive optical power, its first side is convex, and its second side is convex; the fourth lens has a negative optical power, its first side is concave, and its second side is flat; the reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens; the first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate. Moreover, the effective focal length f2 of the second lens, the central thickness CT2 of the second lens on the optical axis, and the distance T23 on the optical axis from the second side of the second lens to the first side of the third lens satisfy the conditional formula -8.6 < f2 / (CT2 + T23) < -5.7. Through the above settings of the optical system and the control of this conditional formula, the optical performance of the second lens is ensured to be stable within a certain range, ensuring that the lens system can correctly focus light, reducing the generation of aberrations and other optical distortions. Reasonably designing the thickness of the lens and the distance between the lenses can reduce the difficulty of molding and processing on the premise of meeting the imaging requirements, and can also make the optical system more compact, reducing the volume and weight, and improving the portability and practicality.

[0067] On the other hand, an optical system according to an exemplary embodiment of the present application sequentially includes, along the optical axis from the first side to the second side, a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer. Among them, the first lens has a positive optical power, its first side is convex, and its second side is flat; the second lens has a negative optical power, its second side is concave; the third lens has a positive optical power, its first side is convex, and its second side is convex; the fourth lens has a negative optical power, its first side is concave, and its second side is flat; the reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens; the first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate. Moreover, the optical system further includes a diaphragm located on the first side of the first lens, and the distance SR on the optical axis from the diaphragm to the first side of the first lens and the sum ∑CT of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis satisfy the conditional formula 0.95 < ∑CT / SR ≤ 1.3. By reasonably controlling the proportional relationship between the thickness of the lens and the position parameter of the diaphragm, making the system satisfy the conditional formula 0.95 < ∑CT / SR ≤ 1.3, the aberration in the system can be reduced, and the clarity and accuracy of imaging can be improved; at the same time, it is also beneficial to the molding of the lens, and it is beneficial to make the optical system more compact, shorten the length of the optical system, and meet the requirements of the virtual device being thinner and lighter.

[0068] In addition, the present application also provides a VR / AR device, which may include the optical system provided by any one of the above various embodiments. Among them, the first side is the human eye side, and the second side is the image plane side. The VR / AR device can provide clearer and more real images, reduce distortion, and at the same time, it can also have a smaller total optical length, making the device lighter and more comfortable, which is beneficial to improving the user experience.

[0069] The following further describes specific embodiments of the optical system applicable to the above embodiments with reference to the accompanying drawings.

[0070] Example 1

[0071] The following refers to Figures 1 to 5 Describe the optical system according to Embodiment 1 of the present application. Figure 1 The structural schematic diagram of the optical system according to Embodiment 1 of the present application is shown.

[0072] As Figure 1As shown, the optical system sequentially includes, along the optical axis from the first side to the second side: a stop STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image plane IMG.

[0073] In this embodiment, the first lens E1 has a positive focal power, its first side is convex, and its second side is flat. The second lens E2 has a negative focal power, its first side is concave, and its second side is concave. The third lens E3 has a positive focal power, its first side is convex, and its second side is convex. The fourth lens E4 has a negative focal power, its first side is concave, and its second side is flat.

[0074] In this embodiment, the light beam emitted from the image plane IMG can sequentially pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again to reach the partial reflection element BS. Then, the light beam is reflected again at the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1 to be emitted towards the first side (such as the human eye side).

[0075] In this embodiment, the reflective polarizing element RP can be disposed on the second side of the first lens E1, and the first side of the reflective polarizing element RP can at least partially fit with the second side of the first lens E1. The first quarter-wave plate QWP1 can be disposed on the second side of the reflective polarizing element RP, and the first side of the first quarter-wave plate QWP1 can at least partially fit with the second side of the reflective polarizing element RP. The partial reflection element BS can be a semi-transmissive and semi-reflective film layer deposited on the second side of the third lens E3. The second quarter-wave plate QWP2 can be disposed on the second side of the fourth lens E4, and the first side of the second quarter-wave plate QWP2 can at least partially fit with the second side of the fourth lens E4. The polarizer LP can be disposed on the second side of the second quarter-wave plate QWP2, and the first side of the polarizer LP can at least partially fit with the second side of the second quarter-wave plate QWP2.

[0076] Table 1 shows the basic parameters of the optical system of Embodiment 1, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0077]

[0078]

[0079] Table 1

[0080] In this embodiment, the first side surface S6 and the second side surface S7 of the second lens E2 and the first side surface S22 of the fourth lens E4 are all aspherical surfaces. The surface profile x of the aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0081]

[0082] where x is the sagitta, which is the distance from the vertex of the aspherical surface to the aspherical surface along the optical axis at a position with a height of h; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic constant; Ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 below gives the higher-order term coefficients A4, A6, A8, A 10 , A 12 , A 14 , A 16 , A 18 and A 20 for the aspherical surfaces S6 - S7 and S22 in this embodiment.

[0083] Coefficient / Surface S6 S7 S22 A4 -2.6840E-06 1.1428E-05 1.0665E-01 A6 -2.0575E-08 2.8625E-09 -1.1264E-02 A8 1.3665E-10 1.7689E-10 2.0564E-03 A10 -6.1688E-13 -4.5242E-13 -7.0976E-04 A12 0.0000E+00 0.0000E+00 -3.8235E-05 A14 0.0000E+00 0.0000E+00 -2.0845E-04 A16 0.0000E+00 0.0000E+00 -2.2913E-04 A18 0.0000E+00 0.0000E+00 -8.2067E-05 A20 0.0000E+00 0.0000E+00 0.0000E+00

[0084] Table 2

[0085] Figure 2 shows the axial chromatic aberration curve of the optical system of Embodiment 1, which represents the deviation of the converging focal points of light rays with different wavelengths after passing through the lens. Figure 3 shows the astigmatism curve of the optical system of Embodiment 1, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 4 shows the distortion curve of the optical system of Embodiment 1, which represents the distortion magnitude values corresponding to different field angles. Figure 5 shows the modulation transfer function (MTF) curve of the optical system of Embodiment 1, which represents the optical modulation function values corresponding to different cut-off frequencies. According to Figures 2 to 5 it can be seen that the optical system given in Embodiment 1 can achieve good imaging quality.

[0086] Example 2

[0087] The following refers to Figures 6 to 10 to describe the optical system according to Embodiment 2 of the present application. Figure 6 shows a schematic structural diagram of the optical system according to Embodiment 2 of the present application.

[0088] As Figure 6As shown, the optical system sequentially includes, along the optical axis, from the first side to the second side: a stop STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image plane IMG.

[0089] In this embodiment, the first lens E1 has a positive focal power, its first side is convex, and its second side is flat. The second lens E2 has a negative focal power, its first side is convex, and its second side is concave. The third lens E3 has a positive focal power, its first side is convex, and its second side is convex. The fourth lens E4 has a negative focal power, its first side is concave, and its second side is flat.

[0090] In this embodiment, the light beam emitted from the image plane IMG can sequentially pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again to reach the partial reflection element BS. Then, the light beam is reflected again at the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1 to be emitted towards the first side (such as the human eye side).

[0091] In this embodiment, the reflective polarizing element RP can be disposed on the second side of the first lens E1, and the first side of the reflective polarizing element RP can at least partially conform to the second side of the first lens E1. The first quarter-wave plate QWP1 can be disposed on the second side of the reflective polarizing element RP, and the first side of the first quarter-wave plate QWP1 can at least partially conform to the second side of the reflective polarizing element RP. The partial reflection element BS can be a semi-transmissive and semi-reflective film layer coated on the second side of the third lens E3. The second quarter-wave plate QWP2 can be disposed on the second side of the fourth lens E4, and the first side of the second quarter-wave plate QWP2 can at least partially conform to the second side of the fourth lens E4. The polarizer LP can be disposed on the second side of the second quarter-wave plate QWP2, and the first side of the polarizer LP can at least partially conform to the second side of the second quarter-wave plate QWP2.

[0092] Table 3 shows the basic parameters of the optical system of this embodiment, where the unit of the radius of curvature and the thickness is millimeter (mm). In this embodiment, the first side S6 and the second side S7 of the second lens E2 and the first side S22 of the fourth lens E4 are all aspherical surfaces, and Table 4 shows the high-order term coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 for each of the aspherical surfaces S6 - S7 and S22 that can be used in this embodiment, where the aspherical surface profiles can be defined by formula (1) given in Embodiment 1 above

[0093]

[0094]

[0095] Table 3

[0096] Coefficient / Surface S6 S7 S22 A4 -2.8843E-06 1.0282E-05 1.0193E-01 A6 -1.5545E-08 8.6242E-09 -8.4111E-03 A8 8.8648E-11 1.4916E-10 1.8924E-03 A10 -4.1001E-13 -1.8055E-13 -5.0204E-04 A12 0.0000E+00 0.0000E+00 1.9465E-04 A14 0.0000E+00 0.0000E+00 -1.6507E-04 A16 0.0000E+00 0.0000E+00 -8.6062E-05 A18 0.0000E+00 0.0000E+00 -8.2474E-05 A20 0.0000E+00 0.0000E+00 0.0000E+00

[0097] Table 4

[0098] Figure 7 shows the axial chromatic aberration curve of the optical system of Embodiment 2, which represents the deviation of the convergence focal points of light rays with different wavelengths after passing through the lens. Figure 8 shows the astigmatism curve of the optical system of Embodiment 2, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 9 shows the distortion curve of the optical system of Embodiment 2, which represents the distortion magnitude values corresponding to different field angles. Figure 10 shows the modulation transfer function (MTF) curve of the optical system of Embodiment 2, which represents the optical modulation function values corresponding to different cut-off frequencies. According to Figures 7 to 10 it can be known that the optical system given in Embodiment 2 can achieve good imaging quality.

[0099] Example 3

[0100] The following refers to Figures 11 to 15 to describe the optical system according to Embodiment 3 of the present application. Figure 11 shows the structural schematic diagram of the optical system according to Embodiment 3 of the present application.

[0101] As Figure 11 shown, the optical system sequentially includes, along the optical axis from the first side to the second side: a diaphragm STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image plane IMG.

[0102] In this embodiment, the first lens E1 has a positive optical power, its first side is convex, and its second side is flat. The second lens E2 has a negative optical power, its first side is concave, and its second side is concave. The third lens E3 has a positive optical power, its first side is convex, and its second side is convex. The fourth lens E4 has a negative optical power, its first side is concave, and its second side is flat.

[0103] In this embodiment, the light beam emitted from the image plane IMG can sequentially pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again to reach the partial reflection element BS. After that, the light beam is reflected again at the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1 to be emitted toward the first side (e.g., the human eye side).

[0104] In this embodiment, the reflective polarizing element RP can be disposed on the second side of the first lens E1, and the first side of the reflective polarizing element RP can at least partially conform to the second side of the first lens E1. The first quarter-wave plate QWP1 can be disposed on the second side of the reflective polarizing element RP, and the first side of the first quarter-wave plate QWP1 can at least partially conform to the second side of the reflective polarizing element RP. The partial reflection element BS can be a semi-transmissive and semi-reflective film layer deposited on the second side of the third lens E3. The second quarter-wave plate QWP2 can be disposed on the second side of the fourth lens E4, and the first side of the second quarter-wave plate QWP2 can at least partially conform to the second side of the fourth lens E4. The polarizer LP can be disposed on the second side of the second quarter-wave plate QWP2, and the first side of the polarizer LP can at least partially conform to the second side of the second quarter-wave plate QWP2.

[0105] Table 5 shows the basic parameters of the optical system of this embodiment. Among them, the units of the radius of curvature and the thickness are both millimeters (mm). In this embodiment, the first side S6 and the second side S7 of the second lens E2 and the first side S22 of the fourth lens E4 are all aspherical surfaces. Table 6 shows the higher-order term coefficients A4, A6, A8, A 10 , A 12 , A 14 , A 16 , A 18 and A 20, wherein each aspherical surface type can be defined by formula (1) given in Embodiment 1 above.

[0106]

[0107]

[0108] Table 5

[0109] Coefficient / Surface S6 S7 S22 A4 2.0128E-05 3.6106E-05 -3.1127E-03 A6 -8.7777E-08 -5.4935E-08 7.4536E-04 A8 2.6728E-10 2.7301E-10 4.3113E-04 A10 -4.5967E-13 2.0452E-13 4.0675E-05 A12 0.0000E+00 0.0000E+00 2.1830E-04 A14 0.0000E+00 0.0000E+00 -1.0501E-05 A16 0.0000E+00 0.0000E+00 3.4150E-05 A18 0.0000E+00 0.0000E+00 -3.6096E-05 A20 0.0000E+00 0.0000E+00 0.0000E+00

[0110] Table 6

[0111] Figure 12 shows the axial chromatic aberration curve of the optical system of Embodiment 3, which represents the deviation of the convergence focal points of light rays of different wavelengths after passing through the lens. Figure 13 shows the astigmatism curve of the optical system of Embodiment 3, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 14 shows the distortion curve of the optical system of Embodiment 3, which represents the distortion magnitude values corresponding to different field angles. Figure 15 shows the modulation transfer function (MTF) curve of the optical system of Embodiment 3, which represents the optical modulation function values corresponding to different cut-off frequencies. According to Figures 12 to 15 it can be known that the optical system given in Embodiment 3 can achieve good imaging quality.

[0112] Example 4

[0113] The following refers to Figures 16 to 20 to describe the optical system according to Embodiment 4 of the present application. Figure 16 shows a schematic structural diagram of the optical system according to Embodiment 4 of the present application.

[0114] As Figure 16 shown, the optical system sequentially includes, along the optical axis from the first side to the second side: a diaphragm STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image plane IMG.

[0115] In this embodiment, the first lens E1 has a positive optical power, its first side is convex, and its second side is flat. The second lens E2 has a negative optical power, its first side is concave, and its second side is concave. The third lens E3 has a positive optical power, its first side is convex, and its second side is convex. The fourth lens E4 has a negative optical power, its first side is concave, and its second side is flat.

[0116] In this embodiment, the light beam emitted from the image plane IMG can sequentially pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again to reach the partial reflection element BS. After that, the light beam is reflected again at the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1 to be emitted toward the first side (such as the human eye side).

[0117] In this embodiment, the reflective polarizing element RP can be disposed on the second side surface of the first lens E1, and the first side surface of the reflective polarizing element RP can at least partially adhere to the second side surface of the first lens E1. The first quarter-wave plate QWP1 can be disposed on the second side surface of the reflective polarizing element RP, and the first side surface of the first quarter-wave plate QWP1 can at least partially adhere to the second side surface of the reflective polarizing element RP. The partial reflection element BS can be a semi-transmissive and semi-reflective film layer coated on the second side surface of the third lens E3. The second quarter-wave plate QWP2 can be disposed on the second side surface of the fourth lens E4, and the first side surface of the second quarter-wave plate QWP2 can at least partially adhere to the second side surface of the fourth lens E4. The polarizer LP can be disposed on the second side surface of the second quarter-wave plate QWP2, and the first side surface of the polarizer LP can at least partially adhere to the second side surface of the second quarter-wave plate QWP2.

[0118] Table 7 shows the basic parameters of the optical system of this embodiment. Among them, the units of the radius of curvature and the thickness are both millimeters (mm). In this embodiment, the first side surface S6 and the second side surface S7 of the second lens E2 and the first side surface S22 of the fourth lens E4 are all aspherical surfaces. Table 8 shows the higher-order term coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 of the aspherical surfaces S6 - S7 and S22 that can be used in this embodiment. Among them, each aspherical surface type can be defined by the formula (1) given in the above Embodiment 1.

[0119] Surface Element Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / Reflection Conic coefficient S0 Spherical surface Infinity -100000.0000 Refraction S1 Aperture stop (STO) Spherical surface Infinity 20.0000 Refraction S2 First lens (E1) Spherical surface 21.0000 6.1309 1.489 70.24 Refraction S3 Reflective polarizing element (RP) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S4 First quarter-wave plate (QWP1) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S5 Spherical surface Infinity 1.2068 Refraction S6 Second lens (E2) Aspherical surface -37.3080 4.4683 1.755 43.08 Refraction 0.0000 S7 Aspherical surface 2496787.9254 2.7019 Refraction 0.0000 S8 Third lens (E3) Spherical surface 28.2937 8.2719 1.489 70.24 Refraction S9 Partial reflection element (BS) Spherical surface -402.9896 -8.2719 1.489 70.24 Reflection S10 Spherical surface 28.2937 -2.7019 Refraction S11 Aspherical surface 2496787.9254 -4.4683 1.755 43.08 Refraction 0.0000 S12 Aspherical surface -37.3080 -1.2068 Refraction 0.0000 S13 Spherical surface Infinity -0.1100 1.502 57.00 Refraction S14 Spherical surface Infinity -0.1100 1.502 57.00 Refraction S15 Reflective polarizing element (RP) Spherical surface Infinity 0.1100 1.502 57.00 Reflection S16 First quarter-wave plate (QWP1) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S17 Spherical surface Infinity 1.2068 Refraction S18 Second lens (E2) Aspherical surface -37.3080 4.4683 1.755 43.08 Refraction 0.0000 S19 Aspherical surface 2496787.9254 2.7019 Refraction 0.0000 S20 Third lens (E3) Spherical surface 28.2937 8.2719 1.489 70.24 Refraction S21 Spherical surface -402.9896 0.7902 Refraction S22 Fourth lens (E4) Aspherical surface -26.3424 1.4000 1.489 70.24 Refraction 0.0000 S23 Second quarter-wave plate (QWP2) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S24 Polarizer (LP) Spherical surface Infinity 0.1500 1.502 57.00 Refraction S25 Spherical surface Infinity 0.5400 Refraction S26 Spherical surface Infinity 0.7100 1.519 64.17 Refraction S27 Spherical surface Infinity 0.3000 Refraction S28 Image plane (IMG) Spherical surface Infinity 0.0000 Refraction

[0120] Table 7

[0121] Coefficient / Surface S6 S7 S22 A4 6.5208E-05 7.0848E-05 -1.6894E-03 A6 -1.9828E-07 -1.0062E-07 1.6654E-03 A8 4.5948E-10 1.8760E-10 4.4506E-04 A10 -5.8432E-13 4.7151E-13 -3.6966E-04 A12 0.0000E+00 0.0000E+00 1.2433E-04 A14 0.0000E+00 0.0000E+00 -9.4879E-05 A16 0.0000E+00 0.0000E+00 3.9927E-05 A18 0.0000E+00 0.0000E+00 7.3139E-05 A20 0.0000E+00 0.0000E+00 0.0000E+00

[0122] Table 8

[0123] Figure 17 Shows the axial chromatic aberration curve of the optical system of Embodiment 4, which represents the deviation of the convergence focal points of light rays of different wavelengths after passing through the lens. Figure 18 Shows the astigmatism curve of the optical system of Embodiment 4, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 19 Shows the distortion curve of the optical system of Embodiment 4, which represents the distortion magnitude values corresponding to different field angles. Figure 20 Shows the modulation transfer function (MTF) curve of the optical system of Embodiment 4, which represents the optical modulation function values corresponding to different cut-off frequencies. According to Figures 17 to 20 It can be seen that the optical system given in Embodiment 4 can achieve good imaging quality.

[0124] Example 5

[0125] The following refers to Figures 21 to 25 Describe the optical system according to Embodiment 5 of the present application. Figure 21 Shows a schematic structural diagram of the optical system according to Embodiment 5 of the present application.

[0126] As Figure 21 Shown, the optical system sequentially includes, along the optical axis from the first side to the second side: a diaphragm STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image plane IMG.

[0127] In this embodiment, the first lens E1 has a positive optical power, its first side is convex, and its second side is flat. The second lens E2 has a negative optical power, its first side is concave, and its second side is concave. The third lens E3 has a positive optical power, its first side is convex, and its second side is convex. The fourth lens E4 has a negative optical power, its first side is concave, and its second side is flat.

[0128] In this embodiment, the light beam emitted from the image plane IMG can sequentially pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, and is reflected at the reflective polarizing element RP and then passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again to reach the partial reflection element BS. After that, the light beam is reflected again at the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1 to be emitted toward the first side (such as the human eye side).

[0129] In this embodiment, the reflective polarizing element RP can be disposed on the second side surface of the first lens E1, and the first side surface of the reflective polarizing element RP can be at least partially attached to the second side surface of the first lens E1. The first quarter-wave plate QWP1 can be disposed on the second side surface of the reflective polarizing element RP, and the first side surface of the first quarter-wave plate QWP1 can be at least partially attached to the second side surface of the reflective polarizing element RP. The partial reflection element BS can be a semi-transmissive and semi-reflective film layer deposited on the second side surface of the third lens E3. The second quarter-wave plate QWP2 can be disposed on the second side surface of the fourth lens E4, and the first side surface of the second quarter-wave plate QWP2 can be at least partially attached to the second side surface of the fourth lens E4. The polarizer LP can be disposed on the second side surface of the second quarter-wave plate QWP2, and the first side surface of the polarizer LP can be at least partially attached to the second side surface of the second quarter-wave plate QWP2.

[0130] Table 9 shows the basic parameters of the optical system of this embodiment. Among them, the units of the radius of curvature and the thickness are both millimeters (mm). In this embodiment, the first side surface S6 and the second side surface S7 of the second lens E2 and the first side surface S22 of the fourth lens E4 are all aspherical surfaces. Table 10 shows the higher-order term coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 of the aspherical surfaces S6 - S7 and S22 that can be used in this embodiment. Among them, each aspherical surface type can be defined by the formula (1) given in the above Embodiment 1.

[0131] Surface Element Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / Reflection Conic coefficient S0 Spherical surface Infinity -100000.0000 Refraction S1 Aperture stop (STO) Spherical surface Infinity 20.0000 Refraction S2 First lens (E1) Spherical surface 21.0000 7.4340 1.502 62.77 Refraction S3 Reflective polarizing element (RP) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S4 First quarter-wave plate (QWP1) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S5 Spherical surface Infinity 0.3491 Refraction S6 Second lens (E2) Aspherical surface -199.2720 5.9701 1.734 45.80 Refraction 0.0000 S7 Aspherical surface 30.7267 0.2224 Refraction 0.0000 S8 Third lens (E3) Spherical surface 24.7575 11.0765 1.520 62.95 Refraction S9 Partial reflection element (BS) Spherical surface -200.0000 -11.0765 1.520 62.95 Reflection S10 Spherical surface 24.7575 -0.2224 Refraction S11 Aspherical surface 30.7267 -5.9701 1.734 45.80 Refraction 0.0000 S12 Aspherical surface -199.2720 -0.3491 Refraction 0.0000 S13 Spherical surface Infinity -0.1100 1.502 57.00 Refraction S14 Spherical surface Infinity -0.1100 1.502 57.00 Refraction S15 Reflective polarizing element (RP) Spherical surface Infinity 0.1100 1.502 57.00 Reflection S16 First quarter-wave plate (QWP1) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S17 Spherical surface Infinity 0.3491 Refraction S18 Second lens (E2) Aspherical surface -199.2720 5.9701 1.734 45.80 Refraction 0.0000 S19 Aspherical surface 30.7267 0.2224 Refraction 0.0000 S20 Third lens (E3) Spherical surface 24.7575 11.0765 1.520 62.95 Refraction S21 Spherical surface -200.0000 0.3043 Refraction S22 Fourth lens (E4) Aspherical surface -126.0328 1.6137 1.834 24.13 Refraction -99.0000 S23 Second quarter-wave plate (QWP2) Spherical surface Infinity 0.1100 1.502 57.00 Refraction S24 Polarizer (LP) Spherical surface Infinity 0.1500 1.502 57.00 Refraction S25 Spherical surface Infinity 0.5400 Refraction S26 Spherical surface Infinity 0.7100 1.519 64.17 Refraction S27 Spherical surface Infinity 0.3000 Refraction S28 Image plane (IMG) Spherical surface Infinity 0.0000 Refraction

[0132] Table 9

[0133] Coefficient / Surface S6 S7 S22 A4 1.6050E-05 3.0510E-05 1.3130E+01 A6 -5.7994E-08 -4.1185E-08 4.0010E+00 A8 1.6522E-10 2.8205E-10 -2.5704E+00 A10 -2.7434E-13 -3.2717E-13 -3.2979E+00 A12 0.0000E+00 0.0000E+00 -1.4078E+00 A14 0.0000E+00 0.0000E+00 -1.1709E-01 A16 0.0000E+00 0.0000E+00 1.2098E-01 A18 0.0000E+00 0.0000E+00 3.4903E-02 A20 0.0000E+00 0.0000E+00 0.0000E+00

[0134] Table 10

[0135] Figure 22 shows the axial chromatic aberration curve of the optical system of Embodiment 5, which represents the deviation of the convergence focal points of light rays with different wavelengths after passing through the lens. Figure 23 shows the astigmatism curve of the optical system of Embodiment 5, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 24 shows the distortion curve of the optical system of Embodiment 5, which represents the distortion magnitude values corresponding to different field angles. Figure 25 shows the modulation transfer function (MTF) curve of the optical system of Embodiment 5, which represents the optical modulation function values corresponding to different cut-off frequencies. According to Figures 22 to 25It can be seen that the optical system given in Embodiment 5 can achieve good imaging quality.

[0136] In Embodiments 1 to 5, the effective focal length f of the optical system, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens, the effective focal length f4 of the fourth lens, the entrance pupil diameter EPD of the optical system, the combined focal length fz1 of the first lens, the reflective polarizing element and the first quarter-wave plate, the combined focal length fz2 of the fourth lens, the second quarter-wave plate and the polarizer, the axial distance SAG11 from the intersection of the first side surface of the first lens and the optical axis to the vertex of the effective radius of the first side surface of the first lens, the axial distance SAG41 from the intersection of the first side surface of the fourth lens and the optical axis to the vertex of the effective radius of the first side surface of the fourth lens, the distance SR on the optical axis from the aperture stop to the first side surface of the first lens, and the sum ∑CT of the central thicknesses of the first lens, the second lens, the third lens and the fourth lens on the optical axis are shown in Table 11 respectively.

[0137] Parameter / Example Example 1 Example 2 Example 3 Example 4 Example 5 f (mm) 42.00 42.00 42.00 42.00 42.00 f1 (mm) 44.48 42.93 41.44 42.93 41.85 f2 (mm) -42.72 -45.89 -42.65 -49.40 -35.86 f3 (mm) 39.81 45.27 45.36 54.39 43.12 f4 (mm) -31.31 -33.65 -39.20 -53.85 -151.16 EPD (mm) 25.00 25.00 25.00 25.00 25.00 fz1 (mm) 44.48 42.93 41.44 42.93 41.85 fz2 (mm) -31.31 -33.65 -39.20 -53.85 -151.16 SAG11 (mm) 4.79 4.73 4.80 4.73 4.85 SAG41 (mm) -1.17 -1.20 -0.85 -0.84 -0.21 SR (mm) 20.00 20.00 20.00 20.00 20.00 ∑CT (mm) 19.37 19.98 22.41 20.27 26.09

[0138] Table 11

[0139] In addition, Embodiments 1 to 5 respectively satisfy the conditions shown in Table 12.

[0140] Conditional formula / Example Example 1 Example 2 Example 3 Example 4 Example 5 f1 / f3 1.12 0.95 0.91 0.79 0.97 f2 / f4 1.36 1.36 1.09 0.92 0.24 fz1 / R1 2.12 2.04 1.97 2.04 1.99 (CTR + CTQ1) / T12 0.06 0.11 0.27 0.15 0.39 R5 / CT3 4.44 3.90 2.21 3.42 2.24 fz2 / R7 1.83 2.00 1.55 2.04 1.20 f1 / CT1 7.18 7.00 6.41 7.00 5.63 f2 / (CT2 + T23) -6.81 -6.32 -8.54 -6.89 -5.79 V1 / N1 45.43 47.16 46.78 47.16 41.80 f / (V2 / N2) (mm) 2.11 2.02 1.85 1.71 1.59 CT1 / SAG11 1.29 1.30 1.35 1.30 1.53 ∑CT / SR 0.97 1.00 1.12 1.01 1.30 T34 / SAG41 -1.27 -1.53 -0.95 -0.94 -1.43 f1 / EPD 1.78 1.72 1.66 1.72 1.67

[0141] Table 12

[0142] The above description is only the preferred embodiments of the present application and the description of the applied technical principles. Those skilled in the art should understand that the protection scope involved in the present application is not limited to the technical solutions formed by the 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 technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. An optical system, characterized in that, It sequentially includes from the first side to the second side along the optical axis: A first lens with positive optical power, whose first side is convex and the second side is flat; A reflective polarizing element; A first quarter-wave plate; A second lens with negative optical power, whose second side is concave; A third lens with positive optical power, whose first side is convex and the second side is convex; A partial reflection element; A fourth lens with negative optical power, whose first side is concave and the second side is flat; A second quarter-wave plate; and A polarizer; The reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens; the first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate; The number of lenses with optical power in the optical system is four; The optical system satisfies: 0.75 < f1 / f3 < 1.15, 0.2 < f2 / f4 < 1.4, 1.96 < fz1 / R1 < 2.13, wherein, f1 is the effective focal length of the first lens, f3 is the effective focal length of the third lens, f2 is the effective focal length of the second lens, f4 is the effective focal length of the fourth lens, fz1 is the combined focal length of the first lens, the reflective polarizing element and the first quarter-wave plate, and R1 is the radius of curvature of the first side of the first lens.

2. The optical system according to claim 1, wherein, The central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis and the distance T12 on the optical axis from the second side of the first lens to the first side of the second lens satisfy: 0.05 < (CTR + CTQ1) / T12 < 0.

4.

3. The optical system according to claim 1, characterized in that, The radius of curvature R5 of the first side of the third lens and the central thickness CT3 of the third lens on the optical axis satisfy: 2.2 < R5 / CT3 ≤ 4.

44.

4. The optical system according to claim 1, wherein The combined focal length fz2 of the fourth lens, the second quarter-wave plate and the polarizer and the radius of curvature R7 of the first side of the fourth lens satisfy: 1.2 ≤ fz2 / R7 ≤ 2.

04.

5. The optical system according to claim 1, characterized in that, The effective focal length f1 of the first lens and the central thickness CT1 of the first lens on the optical axis satisfy: 5.6 < f1 / CT1 < 7.

2.

6. The optical system according to claim 1, wherein The effective focal length f2 of the second lens, the central thickness CT2 of the second lens on the optical axis and the distance T23 on the optical axis from the second side of the second lens to the first side of the third lens satisfy: -8.54 ≤ f2 / (CT2 + T23) ≤ -5.

79.

7. The optical system according to any one of claims 1 to 6, characterized in that, The dispersion coefficient V1 of the first lens and the refractive index N1 of the first lens satisfy: 41.8 ≤ V1 / N1 < 47.

2.

8. The optical system according to any one of claims 1 to 6, characterized in that The effective focal length f of the optical system, the dispersion coefficient V2 of the second lens, and the refractive index N2 of the second lens satisfy: 1.55 mm < f / (V2 / N2) < 2.15 mm.

9. The optical system according to any one of claims 1 to 6, characterized in that, The central thickness CT1 of the first lens on the optical axis and the axial distance SAG11 from the intersection of the first side surface of the first lens and the optical axis to the vertex of the effective radius of the first side surface of the first lens satisfy: 1.29 ≤ CT1 / SAG11 < 1.

55.

10. The optical system according to any one of claims 1 to 6, characterized in that, The optical system further includes a diaphragm located on the first side of the first lens. The sum ∑CT of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis and the distance SR from the diaphragm to the first side surface of the first lens on the optical axis satisfy: 0.95 < ∑CT / SR ≤ 1.

3.

11. The optical system according to any one of claims 1 to 6, characterized in that, The distance T34 on the optical axis from the second side surface of the third lens to the first side surface of the fourth lens and the axial distance SAG41 from the intersection of the first side surface of the fourth lens and the optical axis to the vertex of the effective radius of the first side surface of the fourth lens satisfy: -1.55 < T34 / SAG41 < -0.

9.

12. The optical system according to any one of claims 1 to 6, characterized in that, The effective focal length f1 of the first lens and the entrance pupil diameter EPD of the optical system satisfy: 1.65 < f1 / EPD < 1.79.

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