An optical system

Abstract

The present invention discloses an optical system, comprising: a first element group, a second element group and a third lens; the first element group has a positive optical power, the first element group includes a reflective polarizing element, a first lens and a quarter-wave plate; the second element group has a positive optical power, the second element group includes a second lens and a partial reflection element; the third lens has a positive or negative optical power; wherein, for the effective focal length f of the optical system and the effective focal length FG1 of the first element group, 1 < FG1 / f < 2.5. This optical system can reduce the aperture and screen size of the display device, is beneficial to ensuring the focal length of the system, and simultaneously improves the optical performance of the system.

Description

Technical Field

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

[0002] In recent years, VR display devices have developed rapidly. Especially VR display devices using a folded optical path structure have received extensive attention in the industry due to their advantages. The folded optical path structure utilizes the polarization characteristics of light, combines a quarter-wave plate and a reflective polarizer to deflect the optical path and compress the optical path, thereby achieving the goal of making the display device thinner.

[0003] Based on the above principle, how to further reduce the height of the display device and improve the system performance by using the curved surface laminating technology to enhance the consumer experience is the problem that this application aims to solve. Summary of the Invention

[0004] This application aims to provide an optical system that can reduce the aperture and screen size of the display device, is beneficial to ensuring the focal length of the system, and at the same time improves the optical performance of the system.

[0005] This application provides an optical system, including: a first element group, a second element group, and a third lens;

[0006] The first element group has a positive optical power. The first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate;

[0007] The second element group has a positive optical power. The second element group includes a second lens and a partial reflection element;

[0008] The third lens has a positive optical power or a negative optical power;

[0009] Wherein, for the effective focal length f of the optical system and the effective focal length FG1 of the first element group, it satisfies: 1 < FG1 / f < 2.5.

[0010] According to an embodiment provided by this application, for the effective focal length f of the optical system and the focal length f2 of the second lens, it satisfies: 2 < f2 / f < 5.

[0011] According to an embodiment provided by this application, the surface of the second lens away from the display is concave, and the surface close to the display is convex.

[0012] According to an embodiment provided by this application, the refractive indices of the first lens, the second lens, and the third lens are all greater than 1.50.

[0013] According to an embodiment provided by the present application, the reflective polarizing element and the quarter-wave plate are disposed between the first lens and the second lens, and at least a part of the side surface of the reflective polarizing element away from the display contacts at least a part of the side surface of the first lens close to the display.

[0014] According to an embodiment provided by the present application, the reflective polarizing element and the quarter-wave plate are disposed between the first lens and the second lens, and at least a part of the side surface of the quarter-wave plate close to the display contacts at least a part of the side surface of the second lens away from the display.

[0015] According to an embodiment provided by the present application, the radius of curvature R3 of the side surface of the second lens away from the display and the radius of curvature R4 of the side surface of the second lens close to the display satisfy: 0.5 < R3 / R4 < 1.5.

[0016] According to an embodiment provided by the present application, the Abbe number V1 of the first lens, the Abbe number V2 of the second lens, the central thickness CT1 of the first lens on the optical axis, the central thickness CT2 of the second lens on the optical axis, and the interval distance T12 on the optical axis between the side surface of the first lens close to the display and the side surface of the second lens away from the display satisfy: 0 < (V1*CT1 + V2*CT2) / (CT1 + T12 + CT2) < 2.5.

[0017] According to an embodiment provided by the present application, the interval distance T23 on the optical axis between the side surface of the second lens close to the display and the side surface of the third lens away from the display, the central thickness CT3 of the third lens on the optical axis, and the effective focal length f of the optical system satisfy: 0 < f / CT3*T23 < 1.

[0018] According to an embodiment provided by the present application, the effective focal length f of the optical system and the entrance pupil diameter EPD of the optical system satisfy: 5.2 < f / EPD < 5.7.

[0019] According to an embodiment provided by the present application, when CT2 < 1 mm, the interval distance T12 on the optical axis between the side surface of the first lens close to the display and the side surface of the second lens away from the display, and the axial distance TD from the side surface of the first lens away from the display to the side surface of the third lens close to the display satisfy: 3 < TD / T12 < 4.

[0020] According to an embodiment provided by the present application, when CT2 > 7 mm, the interval distance T12 on the optical axis between the side surface of the first lens close to the display and the side surface of the second lens away from the display, and the axial distance TD from the side surface of the first lens away from the display to the side surface of the third lens close to the display satisfy: 8 < TD / T12 < 14.

[0021] According to an embodiment provided by the present application, the radius of curvature R2 of the surface of the first lens close to the display side, and the effective focal length f of the optical system satisfy: -3.5 < R2 / f < -1.

[0022] According to an embodiment provided by the present application, the axial distance SAG31 between the intersection of the surface of the third lens far from the display side and the optical axis and the vertex of the effective radius of the surface of the third lens far from the display side, and the axial distance SAG22 between the intersection of the surface of the second lens close to the display side and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display side satisfy: -2.2 < SAG31 / SAG22 < 0.

[0023] According to an embodiment provided by the present application, the axial distance TD from the surface of the first lens far from the display side to the surface of the third lens close to the display side, and half of the maximum field of view angle Semi-FOV of the optical system satisfy: 25 < TD * tan(Semi-FOV) < 45.

[0024] Advantages of the present invention:

[0025] The optical system of the present invention is composed of three lenses, a reflective polarizing element, a quarter-wave plate, and a partial reflection element. Among them, the first element group has a positive optical power, which is beneficial to the convergence of light rays, thereby reducing the aperture of the display device. At the same time, the first element group includes a reflective polarizing element and a quarter-wave plate, and the two polarizing elements are combined together, reducing the difficulty of element attachment. The second element group has a positive optical power, further compressing the light ray height, which is beneficial to reducing the screen size. At the same time, the second element group includes a partial reflection element, which is convenient for the refraction and reflection of the optical path, and is beneficial to reducing the height of the display device. The third lens has a positive or negative optical power. Combining with the optical powers of the first two lenses, the optical power is reasonably distributed, which is beneficial to ensuring the focal length of the system and improving the optical performance of the system. The ratio of the focal length of the first element group to the focal length of the optical system is conditionally controlled. On the one hand, it ensures the positive optical power of the first element group, and on the other hand, makes the first lens bear a larger optical power, which is more beneficial to the convergence of light rays and reduces the aperture of the display device. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a schematic diagram of the lens group structure of the optical system of the present invention;

[0028] Figure 2 isFigure 1 Partial enlarged view;

[0029] Figure 3 Schematic diagram of the lens group structure of Embodiment 1 of the optical system of the present invention;

[0030] Figure 4a 、 Figure 4b and Figure 4c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 1 of the optical system of the present invention;

[0031] Figure 5 Schematic diagram of the lens group structure of Embodiment 2 of the optical system of the present invention;

[0032] Figure 6a 、 Figure 6b and Figure 6c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 2 of the optical system of the present invention;

[0033] Figure 7 Schematic diagram of the lens group structure of Embodiment 3 of the optical system of the present invention;

[0034] Figure 8a 、 Figure 8b and Figure 8c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 3 of the optical system of the present invention;

[0035] Figure 9 Schematic diagram of the lens group structure of Embodiment 4 of the optical system of the present invention;

[0036] Figure 10a 、 Figure 10b and Figure 10c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 4 of the optical system of the present invention;

[0037] Figure 11 Schematic diagram of the lens group structure of Embodiment 5 of the optical system of the present invention;

[0038] Figure 12a 、 Figure 12b and Figure 12c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 5 of the optical system of the present invention;

[0039] Figure 13 Schematic diagram of the lens group structure of Embodiment 6 of the optical system of the present invention;

[0040] Figure 14a 、 Figure 14b and Figure 14c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 6 of the optical system of the present invention;

[0041] Figure 15 Schematic diagram of the lens group structure of Embodiment 7 of the optical system of the present invention;

[0042] Figure 16a 、 Figure 16b and Figure 16c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 7 of the optical system of the present invention;

[0043] Figure 17 Schematic diagram of the lens group structure of Embodiment 8 of the optical system of the present invention;

[0044] Figure 18a 、 Figure 18b and Figure 18c are respectively the axial chromatic aberration curve, astigmatism curve and distortion curve of Embodiment 8 of the optical system of the present invention. Detailed implementation manners

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0046] It should be noted that in this specification, the expressions such as first, second, and third 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 invention, the first lens discussed below can also be referred to as the second lens or the third lens.

[0047] It should also be understood that the terms "include", "include having", "have", "contain" and / or "contain 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 listed features, rather than modifying the 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.

[0048] In the drawings, for the sake of clarity, the thickness, size and shape of the lens have been slightly exaggerated. Specifically, the shape of the spherical or aspherical surface shown in the drawings is shown by way of example. That is, the shape of the spherical or aspherical surface is not limited to the spherical or aspherical surface shown in the drawings. The drawings are only for example and are not drawn strictly to scale.

[0049] In the description of the present invention, 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. The surface of each lens closest to the object being photographed is called the side of the lens away from the display, and the surface of each lens closest to the imaging surface is called the side of the lens close to the display.

[0050] 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 formal manner unless expressly so defined herein.

[0051] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The features, principles and other aspects of the present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0052] Exemplary embodiments

[0053] Such as Figure 1 And Figure 2As shown in the figure, this exemplary embodiment provides an optical system, including: a first element group, a second element group, and a third lens; the first element group has a positive optical power, and the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, and the second element group includes a second lens and a partial reflection element; the third lens has a positive or negative optical power; wherein, for the effective focal length f of the optical system and the effective focal length FG1 of the first element group, it satisfies: 1 < FG1 / f < 2.5. The optical system is composed of three lenses, a reflective polarizing element, a quarter-wave plate, and a partial reflection element. Among them, the first element group has a positive optical power, which is conducive to the convergence of light rays, thereby reducing the aperture of the display device; at the same time, the first element group includes a reflective polarizing element and a quarter-wave plate, combining the two polarizing elements together, reducing the difficulty of element attachment; the second element group has a positive optical power, further compressing the light height, which is conducive to reducing the screen size; at the same time, the second element group includes a partial reflection element, facilitating the refraction and reflection of the optical path, which is conducive to reducing the height of the display device. The third lens has a positive or negative optical power. Combining with the optical powers of the first two lenses, the optical power is reasonably distributed, which is conducive to ensuring the focal length of the system and improving the optical performance of the system; the ratio of the focal length of the first element group to the focal length of the optical system is conditionally controlled. On the one hand, it ensures the positive optical power of the first element group, and on the other hand, it enables the first lens to bear a large optical power, thus being more conducive to the convergence of light rays and reducing the aperture of the display device.

[0054] In this exemplary embodiment, for the effective focal length f of the optical system and the focal length f2 of the second lens, it satisfies: 2 < f2 / f < 5. By controlling the ratio of the focal length of the second lens to the focal length of the optical system, on the one hand, it ensures the positive optical power of the second lens, and on the other hand, it enables the second lens to bear part of the optical power, which is conducive to further reducing the light height of the light rays passing through the first lens, thereby reducing the screen size.

[0055] In this exemplary embodiment, the surface of the second lens away from the display is concave, and the surface close to the display is convex. By controlling the bending directions of the two surfaces of the second lens, it is conducive to controlling the incident angles of light rays on the two surfaces, thereby reducing the aberration introduced due to the large incident angle, which is conducive to ensuring the performance of the optical system.

[0056] In this exemplary embodiment, the refractive indices of the first lens, the second lens, and the third lens are all greater than 1.50. By controlling the refractive indices of the first lens to the third lens, on the one hand, making the refractive index greater than 1.5 is conducive to improving the system performance, and on the other hand, making the refractive index not too large is convenient for selecting materials with small stress.

[0057] In the present exemplary embodiment, the reflective polarizing element and the quarter-wave plate are disposed between the first lens and the second lens, and the side surface of the reflective polarizing element away from the display is at least partially in contact with the side surface of the first lens close to the display. By controlling the positions of the reflective polarizing element and the quarter-wave plate such that they are between the first lens and the second lens, and the reflective polarizing element is away from the display, the length of the optical path folding and reflection is ensured.

[0058] In the present exemplary embodiment, the reflective polarizing element and the quarter-wave plate are disposed between the first lens and the second lens, and the side surface of the quarter-wave plate close to the display is at least partially in contact with the side surface of the second lens away from the display. By controlling the positions of the reflective polarizing element and the quarter-wave plate such that they are between the first lens and the second lens, the first lens does not participate in the folding and reflection of the optical path, increasing the selection range of the material of the first lens, which is beneficial to reducing the chromatic aberration of the system through material matching.

[0059] In the present exemplary embodiment, for the radius of curvature R3 of the side surface of the second lens away from the display and the radius of curvature R4 of the side surface of the second lens close to the display, it satisfies: 0.5 < R3 / R4 < 1.5. By controlling the radii of curvature of the two surfaces of the second lens, it is beneficial to control the shape of the second lens. On the one hand, it is beneficial to control the molding of the second lens, and on the other hand, it is beneficial to control the exit angle of the light passing through the second lens to reduce the height of the display.

[0060] In the present exemplary embodiment, for the Abbe number V1 of the first lens, the Abbe number V2 of the second lens, the central thickness CT1 of the first lens on the optical axis, the central thickness CT2 of the second lens on the optical axis, and the spacing distance T12 on the optical axis between the side surface of the first lens close to the display and the side surface of the second lens away from the display, it satisfies: 0 < (V1*CT1 + V2*CT2) / (CT1 + T12 + CT2) < 2.5. By controlling the Abbe numbers of the first lens and the second lens, as well as the central thicknesses and the gap between the two lenses, on the one hand, the chromatic aberration of the system is restricted, and on the other hand, the strength of the lenses and the bearing between the lenses are restricted, which is beneficial to the resistance stability.

[0061] In this exemplary embodiment, the spacing distance T23 on the optical axis between the side surface of the second lens close to the display and the side surface of the third lens far from the display, the central thickness CT3 of the third lens on the optical axis, and the effective focal length f of the optical system satisfy: 0 < f / CT3 * T23 < 1. By controlling the gap between the second lens and the third lens, the central thickness of the third lens, and the spacing of the optical system, the distribution of the optical power of the third lens in the optical system is constrained, which is beneficial to the selection of the optical system architecture. In this exemplary embodiment, the effective focal length f of the optical system and the entrance pupil diameter EPD of the optical system satisfy: 5.2 < f / EPD < 5.7. By controlling the focal length and the entrance pupil diameter of the optical system, with a certain focal length of the optical system, a larger entrance pupil diameter is obtained, taking into account the attenuation of performance during eye rotation and making the display device have better effects. In this exemplary embodiment, when CT2 < 1 mm, the spacing distance T12 on the optical axis between the side surface of the first lens close to the display and the side surface of the second lens far from the display, and the axial distance TD from the side surface of the first lens far from the display to the side surface of the third lens close to the display satisfy: 3 < TD / T12 < 4. Through the above conditional formula, when the second lens is thinner, a larger gap in front of the second lens is obtained, which is beneficial to increasing the distance of light refraction, thereby compensating for the disadvantage of the smaller optical path of light in the second lens.

[0062] In this exemplary embodiment, when CT2 > 7 mm, the spacing distance T12 on the optical axis between the side surface of the first lens close to the display and the side surface of the second lens far from the display, and the axial distance TD from the side surface of the first lens far from the display to the side surface of the third lens close to the display satisfy: 8 < TD / T12 < 14. Through the above conditional formula, when the second lens is thicker, a smaller gap in front of the second lens is obtained, ensuring the reliability of the second lens assembly.

[0063] In this exemplary embodiment, the radius of curvature R2 of the side surface of the first lens close to the display and the effective focal length f of the optical system satisfy: -3.5 < R2 / f < -1. By controlling the ratio of the radius of curvature of the first lens to the effective focal length of the optical system, the shape of the first lens is constrained. On the one hand, it is beneficial to the forming of the first lens, and on the other hand, it is beneficial to the surface film pasting.

[0064] In the present exemplary embodiment, the axial distance SAG31 between the intersection of the side surface of the third lens away from the display and the optical axis and the vertex of the effective radius of the side surface of the third lens away from the display, and the axial distance SAG22 between the intersection of the side surface of the second lens close to the display and the optical axis and the vertex of the effective radius of the side surface of the second lens close to the display satisfy: -2.2 < SAG31 / SAG22 < 0. By controlling the sagittal heights of the third lens and the second lens, the bending degrees of the two lenses are reduced. On the one hand, it is beneficial to the molding of the two lenses, and on the other hand, the risk of large-angle ghost images is reduced. In the present exemplary embodiment, the axial distance TD from the side surface of the first lens away from the display to the side surface of the third lens close to the display, and half of the maximum field of view angle Semi-FOV of the optical system satisfy: 25 < TD*tan(Semi-FOV) < 45. By controlling the field of view angle and the axial distance from the first lens to the third lens, on the one hand, the length of the display device is restricted, and on the other hand, on the premise of a certain length, the system field of view is increased, improving the user experience of consumers.

[0065] In the present exemplary embodiment, both the side surface of any one of the first lens E1 to the third lens E3 away from the display and the side surface close to the display are aspherical surfaces, and the surface shape x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0066]

[0067] Wherein, x is the sagittal height of the distance from the vertex of the aspherical surface when the aspherical surface is along the optical axis direction at a position with a height of h; c is the paraxial curvature of the aspherical surface, c = 1 / R (that is, the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1); k is the conic coefficient; Ai is the correction coefficient of the i-th order of the aspherical surface.

[0068] In the present exemplary embodiment, the above optical system may further include a diaphragm. The diaphragm can be set at an appropriate position as needed. For example, the diaphragm can be set in front of the first lens. Optionally, the above optical system may further include a filter for correcting color deviation and / or a protective glass for protecting the photosensitive element located on the imaging surface.

[0069] The optical system according to the above embodiment of the present invention can adopt multiple lenses, such as the three lenses mentioned above. By reasonably distributing the optical power, surface shape, central thickness of each lens, and the axial spacing between each lens, etc., the optical system has a large imaging surface, has the characteristics of a wide imaging range and high imaging quality, and ensures the ultra-thinness of the mobile phone.

[0070] In an exemplary embodiment, at least one of the mirror surfaces of each lens is an aspherical mirror surface, that is, at least one of the mirror surfaces from the side of the first lens away from the display to the side of the third lens close to the display is an aspherical mirror surface. The characteristics of an aspherical lens are as follows: from the center of the lens to the periphery of the lens, the curvature changes continuously. Different from a spherical lens with a constant curvature from the center of the lens to the periphery of the lens, an aspherical lens has better curvature radius characteristics and has the advantages of improving distortion aberration and improving astigmatism aberration. After using an aspherical lens, it is possible to eliminate as much as possible the aberration that appears during imaging, thereby improving the imaging quality. Optionally, at least one of the surfaces of each of the first lens, the second lens, and the third lens is an aspherical mirror surface.

[0071] However, those skilled in the art should understand that without departing from the technical solutions claimed in the present application, the number of lenses constituting the optical system can be changed to obtain the various results and advantages described in this specification. For example, although three lenses are described as an example in the embodiment, the optical system is not limited to including three lenses. If necessary, the optical system may further include other numbers of lenses.

[0072] The display device including the optical system of the present application may further include at least one storage mechanism, where the storage mechanism is used to compress the volume of the display device. For example, the storage mechanism enables the user to compress the volume of the display device (for example, fold the display device) when the display device is not in use.

[0073] The display device may further include at least one autofocus device, where the autofocus device is arranged corresponding to the optical system, and the autofocus device is used to move the optical lens of the optical system. Thereby, the autofocus device can provide a focusing function for the optical system and can adjust the focal length according to the vision of different users. In some embodiments, the number of autofocus devices is one, which can adjust the focal lengths of two optical systems simultaneously. Additionally, in some embodiments, the number of autofocus devices is two to adjust the focal lengths of two optical systems respectively.

[0074] It should be noted that the communication connection mentioned herein refers to a connection method in which two components exchange signals with each other, for example, by wired or wireless transmission.

[0075] The above technical features in the optical system and the display device of the present application can be combined and configured to achieve corresponding effects.

[0076] In the optical system disclosed in the present application, the material of the lens can be glass or plastic. If the material of the lens is glass, the degree of freedom in configuring the refractive power of the optical system can be increased, and the influence of external environmental temperature changes on imaging can be reduced. The glass lens can be fabricated by techniques such as grinding or molding. If the material of the lens is plastic, the production cost can be effectively reduced. In addition, a spherical or aspherical surface (ASP) can be provided on the lens surface. Among them, the spherical lens can reduce the manufacturing difficulty. If an aspherical surface is provided on the lens surface, more control variables can be obtained thereby to reduce aberration, reduce the number of lenses, and effectively reduce the total length of the optical system of the present application. Further, the aspherical surface can be fabricated by methods such as plastic injection molding or molding of glass lenses.

[0077] In the optical system disclosed in the present application, if the lens surface is aspherical, it means that all or a part of the optically effective area of the lens surface is aspherical.

[0078] In the optical system disclosed in the present application, if the lens surface is convex and the position of the convex surface is not defined, it means that the convex surface can be located near the optical axis of the lens surface; if the lens surface is concave and the position of the concave surface is not defined, it means that the concave surface can be located near the optical axis of the lens surface. If the refractive power or focal length of the lens is not defined in terms of its regional position, it means that the refractive power or focal length of the lens can be the refractive power or focal length of the lens near the optical axis.

[0079] In the optical system disclosed in the present application, the inflection point of the lens surface refers to the intersection point where the sign of the lens surface curvature changes. The critical point of the lens surface refers to the tangent point on the tangent line where the plane perpendicular to the optical axis is tangent to the lens surface, and the critical point is not located on the optical axis.

[0080] In the optical system disclosed in the present application, depending on the corresponding display, the image plane of the optical system can be a plane or a curved surface with any curvature, especially a curved surface with a concave surface facing the human eye side.

[0081] In the optical system disclosed in the present application, at least one aperture stop can be provided, which can be located in front of the first optical lens, between each optical lens, or behind the last optical lens. The types of the aperture stop such as a glare stop or a field stop can be used to reduce stray light and help improve the image quality.

[0082] The present application may appropriately provide a variable aperture element, which may be a mechanical component or a light control element, and its aperture size and shape can be controlled by electricity or electrical signals. The mechanical component may include movable parts such as a blade group and a shielding plate; the light control element may include shielding materials such as a filter element, an electrochromic material, and a liquid crystal layer. The variable aperture element can enhance the image adjustment ability by controlling the light incident amount or exposure time of the image. In addition, the variable aperture element may also be the aperture of the present application, and the image quality can be adjusted by changing the aperture value, such as the depth of field or the exposure speed.

[0083] The following further describes specific embodiments of the optical system applicable to the above embodiments with reference to the accompanying drawings. Specific Embodiment 1

[0085] Figure 3 It is a schematic structural diagram of a lens group of Embodiment 1 of the optical system of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, and the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, and the second element group includes a second lens and a partial reflection element; the third lens has a positive optical power or a negative optical power.

[0086] The first optical lens E1 has a positive refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical.

[0087] The second optical lens E2 has a negative refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical.

[0088] The third optical lens E3 has a positive refractive power. Its surface away from the display side is convex, and its surface close to the display side is concave; and both of its surfaces are aspherical.

[0089] A partial reflection layer is plated on the surface of the first lens E1 close to the display side, and the partial reflection layer has an average light reflectivity of 50%.

[0090] As shown in Table 1, it is the basic parameter table of the optical system of Embodiment 1, where the units of the radius of curvature, thickness, and focal length are all millimeters (mm).

[0091] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / Reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -185.4349 10.5671 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -40.1359 0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -40.1359 0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -40.1359 7.2398 Refraction S5 Partial reflection layer (BS) Aspherical surface -37.6333 -7.2398 Reflection S4 Reflective polarizing element (RP) Aspherical surface -40.1359 -0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -40.1359 7.2398 1.5000 57.0000 Reflection S4 Aspherical surface -40.1359 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -37.6333 0.6000 1.6700 19.0000 Refraction S6 Aspherical surface -44.0072 0.1000 Refraction S7 Third lens (E3) Aspherical surface 102.7091 8.7016 1.5447 56.0000 Refraction S8 Aspherical surface 430.0430 3.3744 Refraction S9 Light source Spherical surface Infinity Refraction

[0092] Table 1

[0093] As shown in Table 2, in Embodiment 1, the total effective focal length f of the optical system is 27.00 mm, and the effective focal length FG1 of the first element group is 47.19 mm.

[0094]

[0095] Table 2

[0096] The optical system in Example 1 satisfies:

[0097] FG1 / f = 1.75; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0098] f2 / f = 3.44; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0099] TD * tan(Semi - FOV) = 36.64; where TD is the axial distance from the surface of the first lens away from the display to the surface of the third lens close to the display, and Semi - FOV is half of the maximum field of view angle of the optical system.

[0100] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 0.92; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the axial distance between the surface of the first lens close to the display and the surface of the second lens away from the display.

[0101] R3 / R4 = 0.86; where R3 is the radius of curvature of the surface of the second lens away from the display, and R4 is the radius of curvature of the surface of the second lens close to the display.

[0102] f / CT3 * T23 = 0.31; where T23 is the axial distance between the surface of the second lens close to the display and the surface of the third lens away from the display, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0103] TD / T12 = 3.61; where T12 is the axial distance between the surface of the first lens close to the display and the surface of the second lens away from the display, and TD is the axial distance from the surface of the first lens away from the display to the surface of the third lens close to the display.

[0104] R2 / f = -1.49; where R2 is the radius of curvature of the surface of the first lens close to the display, and f is the effective focal length of the optical system.

[0105] SAG31 / SAG22 = -1.38; where SAG31 is the axial distance between the intersection of the surface of the third lens away from the display side and the optical axis and the vertex of the effective radius of the surface of the third lens away from the display side, and SAG22 is the axial distance between the intersection of the surface of the second lens close to the display side and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display side.

[0106] In Embodiment 1, Table 3 shows the high-order term coefficients A4, A6, A8, A 10 .

[0107]

[0108]

[0109] Table 3

[0110] Figure 4a shows the axial chromatic aberration curve of the optical system of Embodiment 1, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the lens. Figure 4b shows the astigmatism curve of the optical system of Embodiment 1, which represents the curvature of the meridional image plane and the sagittal image plane. Figure 4c shows the distortion curve of the optical system of Embodiment 1, which represents the distortion magnitude values in different viewing angle cases. According to Figures 4a to 4c as shown, the optical system given in Embodiment 1 can achieve good imaging quality. Specific Embodiment 2

[0112] Figure 5 This is a schematic structural diagram of the lens group of Embodiment 2 of the optical system of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, and the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, and the second element group includes a second lens and a partial reflection element; the third lens has a positive or negative optical power.

[0113] The first optical lens E1 has a positive refractive power, its surface away from the display side is concave, and its surface close to the display side is convex;; and both of its surfaces are aspherical surfaces.

[0114] The second optical lens E2 has a negative refractive power, its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0115] The third optical lens E3 has a positive refractive power, its surface away from the display side is convex, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0116] The partial reflective layer is deposited on the surface of the first lens E1 near the display side, and the partial reflective layer has an average light reflectivity of 50%.

[0117] As shown in Table 4, it is the basic parameter table of the optical system of Example 2. Among them, the units of the radius of curvature, thickness, and focal length are all millimeters (mm).

[0118] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / Reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -93.0221 8.2579 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -46.9337 0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -46.9337 0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -46.9337 7.5150 Refraction S5 Partial reflection layer (BS) Aspherical surface -37.4230 -7.5150 Reflection S4 Reflective polarizing element (RP) Aspherical surface -46.9337 -0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -46.9337 7.5150 1.5000 57.0000 Reflection S4 Aspherical surface -46.9337 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -37.4230 0.6000 1.6700 19.0000 Refraction S6 Aspherical surface -46.9689 0.1000 Refraction S7 Third lens (E3) Aspherical surface 73.8318 11.8967 1.5447 56.0000 Refraction S8 Aspherical surface -123.4279 2.2204 Refraction S9 Light source Spherical surface Infinity Refraction

[0119] Table 4

[0120] As shown in Table 5, in Example 2, the total effective focal length f of the optical system is 27.00 mm, and the effective focal length FG1 of the first element group is 49.36 mm.

[0121]

[0122] Table 5

[0123] The optical system in Example 2 satisfies:

[0124] FG1 / f = 1.83; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0125] f2 / f = 3.80; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0126] TD * tan(Semi - FOV) = 38.18; where TD is the on - axis distance from the surface of the first lens far from the display side to the surface of the third lens near the display side, and Semi - FOV is half of the maximum field - of - view angle of the optical system.

[0127] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 0.82; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the interval distance on the optical axis between the surface of the first lens near the display side and the surface of the second lens far from the display side.

[0128] R3 / R4 = 0.80; where R3 is the radius of curvature of the surface of the second lens far from the display side, and R4 is the radius of curvature of the surface of the second lens near the display side.

[0129] f / CT3 * T23 = 0.23; where T23 is the interval distance on the optical axis between the surface of the second lens near the display side and the surface of the third lens far from the display side, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0130] TD / T12 = 3.63; where T12 is the axial distance between the surface of the first lens close to the display and the surface of the second lens far from the display on the optical axis, and TD is the axial distance from the surface of the first lens far from the display to the surface of the third lens close to the display.

[0131] R2 / f = -1.74; where R2 is the radius of curvature of the surface of the first lens close to the display, and f is the effective focal length of the optical system.

[0132] SAG31 / SAG22 = -1.28; where SAG31 is the axial distance between the intersection point of the surface of the third lens far from the display and the optical axis and the vertex of the effective radius of the surface of the third lens far from the display, and SAG22 is the axial distance between the intersection point of the surface of the second lens close to the display and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display.

[0133] In Embodiment 2, Table 6 shows the higher-order term coefficients A4, A6, A8, A 10 .

[0134] Surface number A4 A6 A8 A10 S1 5.9815E-01 9.9465E-02 -3.3426E-02 1.1841E-02 S2 -9.7650E-01 -7.3581E-02 -7.3884E-03 -2.3946E-02 S5 -3.7875E-01 -1.3330E-02 -4.2261E-03 -1.2727E-03 S6 3.4658E+00 -5.9000E-01 1.6824E-01 -6.0425E-02 S7 1.5686E+00 1.1875E-01 -7.7953E-02 -9.3928E-02 S8 -2.9334E+00 2.4824E+00 -7.0666E-01 3.3920E-01

[0135] Table 6

[0136] Figure 6a shows the axial chromatic aberration curve of the optical system of Embodiment 2, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the lens. Figure 6b shows the astigmatism curve of the optical system of Embodiment 2, which represents the curvature of the meridional image plane and the sagittal image plane. Figure 6c shows the distortion curve of the optical system of Embodiment 2, which represents the distortion magnitude values in different viewing angle cases. According to Figures 6a to 6c as shown, the optical system given in Embodiment 2 can achieve good imaging quality. Specific Embodiment 3

[0138] Figure 7 This is a schematic structural diagram of the lens group of Embodiment 3 of the optical system of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, the second element group includes a second lens and a partial reflection element; the third lens has a positive or negative optical power.

[0139] The first optical lens E1 has a positive refractive power, its surface far from the display is concave, and its surface close to the display is convex; and both of its surfaces are aspherical surfaces.

[0140] The second optical lens E2 has a negative refractive power, with its surface away from the display side being concave and its surface close to the display side being convex; and both of its surfaces are aspherical surfaces.

[0141] The third optical lens E3 has a positive refractive power, with its surface away from the display side being convex and its surface close to the display side being concave; and both of its surfaces are aspherical surfaces.

[0142] The partial reflection layer is plated on the surface of the first lens E1 close to the display side, and the partial reflection layer has an average light reflectivity of 50%.

[0143] As shown in Table 7, it is the basic parameter table of the optical system of Example 3, where the units of the radius of curvature, thickness, and focal length are all millimeters (mm).

[0144] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / Reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -200.0376 10.7749 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -40.1470 0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -40.1470 0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -40.1470 7.2131 Refraction S5 Partial reflection layer (BS) Aspherical surface -37.5983 -7.2131 Reflection S4 Reflective polarizing element (RP) Aspherical surface -40.1470 -0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -40.1470 7.2131 1.5000 57.0000 Reflection S4 Aspherical surface -40.1470 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -37.5983 0.6000 1.6700 19.0000 Refraction S6 Aspherical surface -44.5752 0.1000 Refraction S7 Third lens (E3) Aspherical surface 105.0618 8.3903 1.5447 56.0000 Refraction S8 Aspherical surface 384.4029 3.5046 Refraction S9 Light source Spherical surface Infinity Refraction

[0145] Table 7

[0146] As shown in Table 8, in Example 3, the total effective focal length f of the optical system is 27.00 mm, and the effective focal length FG1 of the first element group is 46.94 mm.

[0147]

[0148]

[0149] Table 8

[0150] The optical system in Example 3 satisfies:

[0151] FG1 / f = 1.74; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0152] f2 / f = 3.51; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0153] TD * tan(Semi - FOV) = 36.46; where TD is the axial distance from the surface of the first lens away from the display side to the surface of the third lens close to the display side, and Semi - FOV is half of the maximum field - of - view angle of the optical system.

[0154] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 0.93; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the interval distance on the optical axis between the surface of the first lens close to the display side and the surface of the second lens away from the display side.

[0155] R3 / R4 = 0.84; where R3 is the radius of curvature of the second lens surface away from the display side, and R4 is the radius of curvature of the second lens surface close to the display side.

[0156] f / CT3*T23 = 0.32; where T23 is the axial distance between the second lens surface close to the display side and the third lens surface away from the display side, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0157] TD / T12 = 3.61; where T12 is the axial distance between the first lens surface close to the display side and the second lens surface away from the display side, and TD is the axial distance from the first lens surface away from the display side to the third lens surface close to the display side.

[0158] R2 / f = -1.49; where R2 is the radius of curvature of the first lens surface close to the display side, and f is the effective focal length of the optical system.

[0159] SAG31 / SAG22 = -1.38; where SAG31 is the axial distance between the intersection of the third lens surface away from the display side and the optical axis and the vertex of the effective radius of the third lens surface away from the display side, and SAG22 is the axial distance between the intersection of the second lens surface close to the display side and the optical axis and the vertex of the effective radius of the second lens surface close to the display side.

[0160] In Example 3, Table 9 shows the higher-order term coefficients A4, A6, A8, A 10 .

[0161] Surface number A4 A6 A8 A10 S1 6.1373E-01 -4.1371E-02 -1.1401E-03 2.1686E-03 S2 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 S5 -2.4514E-01 -2.1558E-02 -6.4670E-03 -2.2224E-03 S6 4.6069E+00 -7.2000E-01 2.5341E-01 -7.5126E-02 S7 3.0090E+00 -5.8004E-01 2.8263E-01 -1.0853E-01 S8 -5.0533E+00 1.1790E+00 -1.9952E-01 5.2915E-02

[0162] Table 9

[0163] Figure 8a shows the axial chromatic aberration curve of the optical system of Example 3, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the lens. Figure 8b shows the astigmatism curve of the optical system of Example 3, which represents the curvature of the meridional image plane and the curvature of the sagittal image plane. Figure 8c shows the distortion curve of the optical system of Example 3, which represents the distortion magnitude values under different viewing angles. According to Figures 8a to 8c shown, the optical system given in Example 3 can achieve good imaging quality. Specific Example 4

[0165] Figure 9Schematic diagram of the lens group structure of Embodiment 4 of the optical system of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, the second element group includes a second lens and a partial reflection element; the third lens has a positive or negative optical power.

[0166] The first optical lens E1 has a positive refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0167] The second optical lens E2 has a negative refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0168] The third optical lens E3 has a positive refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0169] The partial reflection layer is plated on the surface of the first lens E1 close to the display side, and the partial reflection layer has an average light reflectivity of 50%.

[0170] As shown in Table 10, it is the basic parameter table of the optical system of Embodiment 4. Among them, the units of the radius of curvature, thickness, and focal length are all millimeters (mm).

[0171] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / Reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -576.0593 13.5083 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -42.8292 0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -42.8292 0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -42.8292 7.5524 Refraction S5 Partial reflection layer (BS) Aspherical surface -37.5026 -7.5524 Reflection S4 Reflective polarizing element (RP) Aspherical surface -42.8292 -0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -42.8292 7.5524 1.5000 57.0000 Reflection S4 Aspherical surface -42.8292 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -37.5026 0.6000 1.6700 19.0000 Refraction S6 Aspherical surface -39.8355 0.1000 Refraction S7 Third lens (E3) Aspherical surface -143.5985 5.6229 1.5447 56.0000 Refraction S8 Aspherical surface -439.7386 3.2006 Refraction S9 Light source Spherical surface Infinity Refraction

[0172] Table 10

[0173] As shown in Table 11, in Embodiment 4, the total effective focal length f of the optical system is 27.00 mm, and the effective focal length FG1 of the first element group is 43.24 mm.

[0174]

[0175] Table 11

[0176] The optical system in Embodiment 4 satisfies:

[0177] FG1 / f = 1.60; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0178] f2 / f = 3.00; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0179] TD * tan(Semi - FOV) = 36.87; where TD is the axial distance from the surface of the first lens away from the display to the surface of the third lens close to the display, and Semi - FOV is half of the maximum field of view angle of the optical system.

[0180] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 0.99; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the axial distance between the surface of the first lens close to the display and the surface of the second lens away from the display on the optical axis.

[0181] R3 / R4 = 0.94; where R3 is the radius of curvature of the surface of the second lens away from the display, and R4 is the radius of curvature of the surface of the second lens close to the display.

[0182] f / CT3 * T23 = 0.48; where T23 is the axial distance between the surface of the second lens close to the display and the surface of the third lens away from the display on the optical axis, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0183] TD / T12 = 3.49; where T12 is the axial distance between the surface of the first lens close to the display and the surface of the second lens away from the display on the optical axis, and TD is the axial distance from the surface of the first lens away from the display to the surface of the third lens close to the display.

[0184] R2 / f = -1.59; where R2 is the radius of curvature of the surface of the first lens close to the display, and f is the effective focal length of the optical system.

[0185] SAG31 / SAG22 = -1.32; where SAG31 is the axial distance between the intersection point of the surface of the third lens away from the display and the optical axis and the vertex of the effective radius of the surface of the third lens away from the display, and SAG22 is the axial distance between the intersection point of the surface of the second lens close to the display and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display.

[0186] In Example 4, Table 12 shows the high - order term coefficients A4, A6, A8, A 10 .

[0187] Surface number A4 A6 A8 A10 S1 3.0990E-01 1.1498E-02 -7.4793E-03 9.8268E-04 S2 -3.0816E-01 4.8814E-02 -2.3980E-03 -1.5764E-02 S5 -2.0112E-01 -1.7421E-02 -3.9245E-03 -1.1372E-03 S6 8.5883E+00 -1.4112E+00 5.4352E-01 -1.8695E-01 S7 8.4866E+00 -1.7106E+00 4.1044E-01 -1.4416E-01 S8 -1.4574E+00 3.2459E-01 -2.6493E-01 1.4297E-01

[0188] Table 12

[0189] Figure 10aThe axial chromatic aberration curve of the optical system of Embodiment 4 is shown, which represents the deviation of the focusing points of light rays of different wavelengths after passing through the lens. Figure 10b The astigmatism curve of the optical system of Embodiment 4 is shown, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 10c The distortion curve of the optical system of Embodiment 4 is shown, which represents the distortion magnitude values under different viewing angles. According to Figures 10a to 10c As can be seen from the figure, the optical system given in Embodiment 4 can achieve good imaging quality. Specific Embodiment 5

[0191] Figure 11 This is a schematic structural diagram of the lens group of Embodiment 5 of the optical system of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, and the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, and the second element group includes a second lens and a partially reflective element; the third lens has a positive or negative optical power.

[0192] The first optical lens E1 has a positive refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical.

[0193] The second optical lens E2 has a negative refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical.

[0194] The third optical lens E3 has a positive refractive power. Its surface away from the display side is convex, and its surface close to the display side is concave; and both of its surfaces are aspherical.

[0195] A partially reflective layer is deposited on the surface of the first lens E1 close to the display side, and the partially reflective layer has an average light reflectivity of 50%.

[0196] As shown in Table 13, it is the basic parameter table of the optical system of Embodiment 5. Among them, the units of the radius of curvature, thickness, and focal length are all millimeters (mm).

[0197] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / Reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -188.1443 10.6399 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -40.1486 0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -40.1486 0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -40.1486 7.1452 Refraction S5 Partial reflection layer (BS) Aspherical surface -37.4238 -7.1452 Reflection S4 Reflective polarizing element (RP) Aspherical surface -40.1486 -0.2000 1.5000 57.0000 Refraction S3 Quarter-wave plate (QWP) Aspherical surface -40.1486 7.1452 1.5000 57.0000 Reflection S4 Aspherical surface -40.1486 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -37.4238 0.6000 1.6700 19.0000 Refraction S6 Aspherical surface -43.9273 0.1000 Refraction S7 Third lens (E3) Aspherical surface 97.6028 8.5337 1.5447 56.0000 Refraction S8 Aspherical surface 261.1100 3.5812 Refraction S9 Light source Spherical surface Infinity Refraction

[0198] Table 13

[0199] As shown in Table 14, in Embodiment 5, the total effective focal length f of the optical system is 27.00 mm, and the effective focal length FG1 of the first element group is 47.24 mm.

[0200]

[0201] Table 14

[0202] The optical system in Embodiment 5 satisfies:

[0203] FG1 / f = 1.75; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0204] f2 / f = 3.44; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0205] TD * tan(Semi - FOV) = 36.39; where TD is the on - axis distance from the surface of the first lens away from the display to the surface of the third lens close to the display, and Semi - FOV is half of the maximum field of view angle of the optical system.

[0206] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 0.93; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the on - axis distance between the surface of the first lens close to the display and the surface of the second lens away from the display.

[0207] R3 / R4 = 0.85; where R3 is the radius of curvature of the surface of the second lens away from the display, and R4 is the radius of curvature of the surface of the second lens close to the display.

[0208] f / CT3 * T23 = 0.32; where T23 is the on - axis distance between the surface of the second lens close to the display and the surface of the third lens away from the display, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0209] TD / T12 = 3.63; where T12 is the on - axis distance between the surface of the first lens close to the display and the surface of the second lens away from the display, and TD is the on - axis distance from the surface of the first lens away from the display to the surface of the third lens close to the display.

[0210] R2 / f = - 1.49; where R2 is the radius of curvature of the surface of the first lens close to the display, and f is the effective focal length of the optical system.

[0211] SAG31 / SAG22 = - 1.43; where SAG31 is the on - axis distance between the intersection of the surface of the third lens away from the display and the optical axis and the vertex of the effective radius of the surface of the third lens away from the display, and SAG22 is the on - axis distance between the intersection of the surface of the second lens close to the display and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display.

[0212] In Example 5, Table 15 shows the higher-order coefficients A4, A6, A8, A that can be used for each aspherical mirror surface S1, S2, S5-8 in Example 5 10 .

[0213] Surface number A4 A6 A8 A10 S1 7.1205E-01 -5.6187E-02 1.1369E-03 2.2369E-03 S2 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 S5 -2.3494E-01 -1.9351E-02 -6.6792E-03 -2.2171E-03 S6 4.6247E+00 -7.4878E-01 2.5255E-01 -7.2874E-02 S7 1.7742E+00 -3.9153E-01 1.1762E-01 -1.1317E-02 S8 -3.6759E+00 6.3639E-01 -8.3000E-02 8.9885E-03

[0214] Table 15

[0215] Figure 12a shows the axial chromatic aberration curve of the optical system of Example 5, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the lens Figure 12b shows the astigmatism curve of the optical system of Example 5, which represents the curvature of the meridional image plane and the curvature of the sagittal image plane Figure 12c shows the distortion curve of the optical system of Example 5, which represents the distortion magnitude values in different viewing angle cases. According to Figures 12a to 12c as shown, the optical system given in Example 5 can achieve good imaging quality Specific Example 6

[0217] Figure 13 This is a schematic structural diagram of the lens group of the optical system according to Example 6 of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, the second element group includes a second lens and a partial reflection element; the third lens has a positive optical power or a negative optical power

[0218] The first optical lens E1 has a positive refractive power, its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical

[0219] The second optical lens E2 has a positive refractive power, its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical

[0220] The third optical lens E3 has a positive refractive power, its surface away from the display side is convex, and its surface close to the display side is arranged to be concave; and both of its surfaces are aspherical

[0221] A partial reflection layer is coated on the surface of the first lens E1 close to the display side, and the partial reflection layer has an average light reflectivity of 50%

[0222] As shown in Table 16, it is the basic parameter table of the optical system of Example 6, where the units of the radius of curvature, thickness, and focal length are all millimeters (mm)

[0223] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -4398.8568 6.9496 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -80.2302 0.2000 1.5000 57.0000 Refraction S3 Aspherical surface -80.2302 1.5914 Refraction S4 Quarter-wave plate (QWP) Aspherical surface -63.8359 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -63.8359 9.3772 1.5447 56.0000 Refraction S6 Partial reflection layer (BS) Aspherical surface -54.9165 -9.3772 1.5447 56.0000 Reflection S5 Quarter-wave plate (QWP) Aspherical surface -63.8359 -0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -63.8359 -1.5914 Refraction S3 Reflective polarizing element (RP) Aspherical surface -80.2302 1.5914 Reflection S4 Quarter-wave plate (QWP) Aspherical surface -63.8359 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -63.8359 9.3772 1.5447 56.0000 Refraction S6 Aspherical surface -54.9165 0.1000 Refraction S7 Third lens (E3) Aspherical surface 58.3430 6.1384 1.5447 56.0000 Refraction S8 Aspherical surface 476.1250 5.4328 Refraction S9 Light source Spherical surface Refraction

[0224] Table 16

[0225] As shown in Table 17, in Example 6, the total effective focal length f of the optical system is 27.00 mm, and the effective focal length FG1 of the first element group is 49.79 mm.

[0226]

[0227] Table 17

[0228] The optical system in Example 6 satisfies:

[0229] FG1 / f = 1.80; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0230] f2 / f = 3.90; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0231] TD * tan(Semi - FOV) = 32.59; where TD is the on - axis distance from the surface of the first lens away from the display to the surface of the third lens close to the display, and Semi - FOV is half of the maximum field - of - view angle of the optical system.

[0232] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 1.38; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the on - axis distance between the surface of the first lens close to the display and the surface of the second lens away from the display.

[0233] R3 / R4 = 1.16; where R3 is the radius of curvature of the surface of the second lens away from the display, and R4 is the radius of curvature of the surface of the second lens close to the display.

[0234] f / CT3 * T23 = 0.45; where T23 is the on - axis distance between the surface of the second lens close to the display and the surface of the third lens away from the display, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0235] TD / T12 = 12.33; where T12 is the on - axis distance between the surface of the first lens close to the display and the surface of the second lens away from the display, and TD is the on - axis distance from the surface of the first lens away from the display to the surface of the third lens close to the display.

[0236] R2 / f = - 2.91; where R2 is the radius of curvature of the surface of the first lens close to the display, and f is the effective focal length of the optical system.

[0237] SAG31 / SAG22 = -0.88; where SAG31 is the axial distance between the intersection of the surface of the third lens away from the display side and the optical axis and the vertex of the effective radius of the surface of the third lens away from the display side, and SAG22 is the axial distance between the intersection of the surface of the second lens close to the display side and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display side.

[0238] In Embodiment 6, Table 18 shows the higher-order term coefficients A4, A6, A8, A 10 .

[0239] Surface number A4 A6 A8 A10 S1 3.1296E-04 1.3384E-01 -4.5427E-02 1.8491E-03 S2 -6.0585E-01 1.0661E-01 -2.8579E-02 -1.0820E-02 S5 -7.7691E-01 5.0961E-02 -2.9737E-02 2.0523E-02 S6 -4.0192E-01 6.7556E-02 -1.5481E-02 1.1809E-03 S7 -4.7932E-01 8.2422E-02 5.4738E-02 -2.7049E-02 S8 1.3041E+00 -2.8592E-01 1.1392E-01 -6.1476E-02

[0240] Table 18

[0241] Figure 14a shows the axial chromatic aberration curve of the optical system of Embodiment 6, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the lens. Figure 14b shows the astigmatism curve of the optical system of Embodiment 6, which represents the curvature of the meridional image plane and the curvature of the sagittal image plane. Figure 14c shows the distortion curve of the optical system of Embodiment 6, which represents the distortion magnitude values in different viewing angle cases. According to Figures 14a to 14c as shown, the optical system given in Embodiment 6 can achieve good imaging quality. Specific Embodiment 7

[0243] Figure 15 This is a schematic structural diagram of the lens group of Embodiment 7 of the optical system of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, and the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, and the second element group includes a second lens and a partial reflection element; the third lens has a positive optical power or a negative optical power.

[0244] The first optical lens E1 has a positive refractive power, its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0245] The second optical lens E2 has a positive refractive power, its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0246] The third optical lens E3 has a positive refractive power, its surface away from the display side is convex, and its surface close to the display side is concave; and both of its surfaces are aspherical surfaces.

[0247] The partial reflective layer is deposited on the surface of the first lens E1 near the display side, and the partial reflective layer has an average light reflectivity of 50%.

[0248] As shown in Table 19, it is the basic parameter table of the optical system of Example 7. Among them, the units of the radius of curvature, thickness, and focal length are all millimeters (mm).

[0249] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -6900.2663 7.0487 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -80.8247 0.2000 1.5000 57.0000 Refraction S3 Aspherical surface -80.8247 1.9655 Refraction S4 Quarter-wave plate (QWP) Aspherical surface -64.2406 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -64.2406 8.6640 1.5447 56.0000 Refraction S6 Partial reflection layer (BS) Aspherical surface -54.7212 -8.6640 1.5447 56.0000 Reflection S5 Quarter-wave plate (QWP) Aspherical surface -64.2406 -0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -64.2406 -1.9655 Refraction S3 Reflective polarizing element (RP) Aspherical surface -80.8247 1.9655 Reflection S4 Quarter-wave plate (QWP) Aspherical surface -64.2406 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -64.2406 8.6640 1.5447 56.0000 Refraction S6 Aspherical surface -54.7212 0.1000 Refraction S7 Third lens (E3) Aspherical surface 59.6313 6.6238 1.5447 56.0000 Refraction S8 Aspherical surface 678.0661 5.1869 Refraction S9 Light source Spherical surface Refraction

[0250] Table 19

[0251] As shown in Table 20, in Example 7, the total effective focal length f of the optical system is 27.51 mm, and the effective focal length FG1 of the first element group is 49.71 mm.

[0252]

[0253] Table 20

[0254] The optical system in Example 7 satisfies:

[0255] FG1 / f = 1.81; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0256] f2 / f = 3.90; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0257] TD * tan(Semi - FOV) = 32.91; where TD is the axial distance from the surface of the first lens far from the display side to the surface of the third lens near the display side, and Semi - FOV is half of the maximum field of view angle of the optical system.

[0258] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 1.35; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the interval distance on the optical axis between the surface of the first lens near the display side and the surface of the second lens far from the display side.

[0259] R3 / R4 = 1.17; where R3 is the radius of curvature of the surface of the second lens far from the display side, and R4 is the radius of curvature of the surface of the second lens near the display side.

[0260] f / CT3 * T23 = 0.42; where T23 is the interval distance on the optical axis between the surface of the second lens near the display side and the surface of the third lens far from the display side, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0261] TD / T12 = 10.48; where T12 is the axial distance between the surface of the first lens near the display and the surface of the second lens away from the display on the optical axis, and TD is the axial distance from the surface of the first lens away from the display to the surface of the third lens near the display.

[0262] R2 / f = -2.94; where R2 is the radius of curvature of the surface of the first lens near the display, and f is the effective focal length of the optical system.

[0263] SAG31 / SAG22 = -0.88; where SAG31 is the axial distance between the intersection of the surface of the third lens away from the display and the optical axis and the vertex of the effective radius of the surface of the third lens away from the display, and SAG22 is the axial distance between the intersection of the surface of the second lens near the display and the optical axis and the vertex of the effective radius of the surface of the second lens near the display.

[0264] In Example 7, Table 21 shows the higher-order term coefficients A4, A6, A8, A of the aspherical mirrors S1, S2, S5-8 that can be used in Example 7. 10 .

[0265] Surface number A4 A6 A8 A10 S1 -2.5866E-02 1.4594E-01 -5.0118E-02 2.1660E-03 S2 -6.8550E-01 1.1878E-01 -2.9378E-02 -1.1070E-02 S5 -1.0563E+00 1.0448E-01 -4.4675E-02 2.5793E-02 S6 -5.1840E-01 8.5787E-02 -1.9550E-02 1.8048E-03 S7 -2.6342E-01 3.6010E-02 5.2245E-02 -1.6028E-02 S8 1.0006E+00 -1.9397E-01 6.3733E-02 -4.4766E-02

[0266] Table 21

[0267] Figure 16a shows the axial chromatic aberration curve of the optical system of Example 7, which represents the deviation of the focusing points of light rays of different wavelengths after passing through the lens. Figure 16b shows the astigmatism curve of the optical system of Example 7, which represents the curvature of the meridional image plane and the curvature of the sagittal image plane. Figure 16c shows the distortion curve of the optical system of Example 7, which represents the distortion magnitude values in different viewing angle cases. According to Figures 16a to 16c as shown, the optical system given in Example 7 can achieve good imaging quality. Specific Example 8

[0269] Figure 17 is a schematic structural diagram of the lens group of the optical system of Example 8 of the present invention. The optical system includes: a first element group, a second element group, and a third lens; the first element group has a positive optical power, and the first element group includes a reflective polarizing element, a first lens, and a quarter-wave plate; the second element group has a positive optical power, and the second element group includes a second lens and a partial reflection element; the third lens has a positive optical power or a negative optical power.

[0270] The first optical lens E1 has a positive refractive power, its surface away from the display is concave, and its surface near the display is convex; and both of its surfaces are aspherical.

[0271] The second optical lens E2 has a positive refractive power. Its surface away from the display side is concave, and its surface close to the display side is convex; and both of its surfaces are aspherical surfaces.

[0272] The third optical lens E3 has a positive refractive power. Its surface away from the display side is convex, and its surface close to the display side is concave; and both of its surfaces are aspherical surfaces.

[0273] The partial reflection layer is plated on the surface of the first lens E1 close to the display side, and the partial reflection layer has an average light reflectivity of 50%.

[0274] As shown in Table 22, it is the basic parameter table of the optical system of Example 8. Among them, the units of the radius of curvature, thickness, and focal length are all millimeters (mm).

[0275] Surface number Surface type Radius of curvature Thickness Refractive index Dispersion coefficient Refraction / reflection Spherical surface Infinity Infinity Refraction STO Aperture stop (STO) Spherical surface Infinity 15.0000 Refraction S1 First lens (E1) Aspherical surface -4387.5280 7.1728 1.5447 56.0000 Refraction S2 Reflective polarizing element (RP) Aspherical surface -80.5898 0.2000 1.5000 57.0000 Refraction S3 Aspherical surface -80.5898 2.0209 Refraction S4 Quarter-wave plate (QWP) Aspherical surface -64.2999 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -64.2999 8.6412 1.5447 56.0000 Refraction S6 Partial reflection layer (BS) Aspherical surface -54.6012 -8.6412 1.5447 56.0000 Reflection S5 Quarter-wave plate (QWP) Aspherical surface -64.2999 -0.2000 1.5000 57.0000 Refraction S4 Aspherical surface -64.2999 -2.0209 Refraction S3 Reflective polarizing element (RP) Aspherical surface -80.5898 2.0209 Reflection S4 Quarter-wave plate (QWP) Aspherical surface -64.2999 0.2000 1.5000 57.0000 Refraction S5 Second lens (E2) Aspherical surface -64.2999 8.6412 1.5447 56.0000 Refraction S6 Aspherical surface -54.6012 0.1000 Refraction S7 Third lens (E3) Aspherical surface 62.2089 6.5811 1.5447 56.0000 Refraction S8 Aspherical surface 671.5306 5.0725 Refraction S9 Light source Spherical surface Refraction

[0276] Table 22

[0277] As shown in Table 23, in Example 8, the total effective focal length f of the optical system is 27.54 mm, and the effective focal length FG1 of the first element group is 49.42 mm.

[0278]

[0279] Table 23

[0280] The optical system in Example 8 satisfies:

[0281] FG1 / f = 1.79; where f is the effective focal length of the optical system, and FG1 is the effective focal length of the first element group.

[0282] f2 / f = 3.88; where f is the effective focal length of the optical system, and f2 is the focal length of the second lens.

[0283] TD * tan(Semi - FOV) = 33.06; where TD is the on - axis distance from the surface of the first lens away from the display side to the surface of the third lens close to the display side, and Semi - FOV is half of the maximum field - of - view angle of the optical system.

[0284] (V1 * CT1 + V2 * CT2) / (CT1 + T12 + CT2) = 1.34; where V1 is the dispersion coefficient of the first lens, V2 is the dispersion coefficient of the second lens, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the interval distance on the optical axis between the surface of the first lens close to the display side and the surface of the second lens away from the display side.

[0285] R3 / R4 = 1.18; where R3 is the radius of curvature of the second lens on the side away from the display surface, and R4 is the radius of curvature of the second lens on the side close to the display surface.

[0286] f / CT3*T23 = 0.42; where T23 is the axial distance between the surface of the second lens close to the display and the surface of the third lens away from the display on the optical axis, CT3 is the central thickness of the third lens on the optical axis, and f is the effective focal length of the optical system.

[0287] TD / T12 = 10.29; where T12 is the axial distance between the surface of the first lens close to the display and the surface of the second lens away from the display on the optical axis, and TD is the axial distance from the surface of the first lens away from the display to the surface of the third lens close to the display.

[0288] R2 / f = -2.93; where R2 is the radius of curvature of the first lens on the side close to the display surface, and f is the effective focal length of the optical system.

[0289] SAG31 / SAG22 = -0.84; where SAG31 is the axial distance between the intersection of the surface of the third lens away from the display and the optical axis and the vertex of the effective radius of the surface of the third lens away from the display, and SAG22 is the axial distance between the intersection of the surface of the second lens close to the display and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display.

[0290] In Example 8, Table 24 shows the higher-order term coefficients A4, A6, A8, A 10 .

[0291] Surface number A4 A6 A8 A10 S1 1.6751E-03 1.3867E-01 -4.8530E-02 2.2835E-03 S2 -6.9388E-01 1.2023E-01 -3.0506E-02 -1.0282E-02 S5 -1.0983E+00 1.1265E-01 -4.6296E-02 2.6141E-02 S6 -5.1616E-01 8.6208E-02 -1.9697E-02 1.9283E-03 S7 -1.9129E-01 2.1281E-02 4.7592E-02 -9.7776E-03 S8 7.6300E-01 -1.3875E-01 2.9929E-02 -3.0214E-02

[0292] Table 24

[0293] Figure 18a shows the axial chromatic aberration curve of the optical system of Example 8, which represents the deviation of the focusing points of light rays of different wavelengths after passing through the lens. Figure 18b shows the astigmatism curve of the optical system of Example 8, which represents the curvature of the meridional image plane and the curvature of the sagittal image plane. Figure 18c shows the distortion curve of the optical system of Example 8, which represents the distortion magnitude values in different viewing angle cases. According to Figures 18a to 18c as shown, the optical system given in Example 8 can achieve good imaging quality.

[0294] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, improvements, equivalent replacements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optical system, characterized in that, The optical system consists of a first element group, a second element group, and a third lens in sequence from the near-eye side to the display side along the optical axis; The first element group has a positive optical power, and the first element group consists of a first lens, a reflective polarizing element, and a quarter-wave plate in sequence from the near-eye side to the display side along the optical axis; The second element group has a positive optical power, and the second element group consists of a partially reflective element and a second lens in sequence from the near-eye side to the display side along the optical axis; Among them, for the effective focal length f of the optical system and the effective focal length FG1 of the first element group, it satisfies: 1.6 ≤ FG1 / f ≤ 1.83; The first lens has a positive optical power, with its near-eye side being concave and its display side being convex; For the second lens, its near-eye side is concave and its display side is convex; The second lens has a negative optical power and the third lens has a positive optical power; or the second lens has a negative optical power and the third lens has a negative optical power; or the second lens has a positive optical power and the third lens has a positive optical power; The reflective polarizing element is attached to the display side of the first lens; the quarter-wave plate is attached to the outside of the reflective polarizing element; the partially reflective element is attached to the near-eye side of the second lens.

2. The optical system according to claim 1, characterized in that The refractive indices of the first lens, the second lens, and the third lens are all greater than 1.

50.

3. The optical system according to claim 1, characterized in that, The reflective polarizing element and the quarter-wave plate are placed between the first lens and the second lens, and at least part of the surface of the reflective polarizing element away from the display side is in contact with at least part of the surface of the first lens close to the display side.

4. The optical system according to claim 1, characterized in that The reflective polarizing element and the quarter-wave plate are placed between the first lens and the second lens, and at least part of the surface of the quarter-wave plate close to the display side is in contact with at least part of the surface of the second lens away from the display side.

5. The optical system according to claim 1, characterized in that, For the radius of curvature R3 of the surface of the second lens away from the display side and the radius of curvature R4 of the surface of the second lens close to the display side, it satisfies: 0.8 ≤ R3 / R4 ≤ 1.

18.

6. The optical system according to claim 1, characterized in that, For the Abbe number V1 of the first lens, the Abbe number V2 of the second lens, the central thickness CT1 of the first lens on the optical axis, the central thickness CT2 of the second lens on the optical axis, and the axial distance T12 between the surface of the first lens close to the display side and the surface of the second lens away from the display side on the optical axis, it satisfies: 0.82 ≤ (V1*CT1 + V2*CT2) / (CT1 + T12 + CT2) ≤ 1.

38.

7. The optical system according to claim 1, characterized in that For the axial distance T23 between the surface of the second lens close to the display side and the surface of the third lens away from the display side on the optical axis, the central thickness CT3 of the third lens on the optical axis, and the effective focal length f of the optical system, it satisfies: 0.23 ≤ f / CT3*T23 ≤ 0.

48.

8. The optical system according to claim 1, wherein For the effective focal length f of the optical system and the entrance pupil diameter EPD of the optical system, it satisfies: 5.2 < f / EPD < 5.

7.

9. The optical system according to claim 1, wherein When CT2 < 1 mm, for the axial distance T12 between the surface of the first lens close to the display side and the surface of the second lens away from the display side on the optical axis, and the axial distance TD from the surface of the first lens away from the display side to the surface of the third lens close to the display side on the optical axis, it satisfies: 3.49 ≤ TD / T12 ≤ 3.

63.

10. The optical system according to claim 1, characterized in that, When CT2 > 7mm, the axial distance T12 between the surface of the first lens close to the display and the surface of the second lens away from the display on the optical axis, and the axial distance TD from the surface of the first lens away from the display to the surface of the third lens close to the display satisfy: 10.29 ≤ TD / T12 ≤ 12.

33.

11. The optical system according to claim 1, characterized in that, The radius of curvature R2 of the surface of the first lens close to the display, and the effective focal length f of the optical system satisfy: -2.94 ≤ R2 / f ≤ -1.

49.

12. The optical system according to claim 1, characterized in that, The axial distance SAG31 between the intersection point of the surface of the third lens away from the display and the optical axis and the vertex of the effective radius of the surface of the third lens away from the display, and the axial distance SAG22 between the intersection point of the surface of the second lens close to the display and the optical axis and the vertex of the effective radius of the surface of the second lens close to the display satisfy: -1.43 ≤ SAG31 / SAG22 ≤ -0.

84.

13. The optical system according to claim 1, characterized in that, The axial distance TD from the surface of the first lens away from the display to the surface of the third lens close to the display, and the half of the maximum field of view Semi-FOV of the optical system satisfy: 32.59 ≤ TD * tan(Semi-FOV) ≤ 38.18.

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