Optical system

Abstract

The application discloses an optical system, which comprises a first element group and a second element group in sequence from a first side to a second side along an optical axis; the first element group has positive focal power and comprises a reflective polarizing element, a quarter-wave plate, a first lens, a partially reflective element and a second lens; the second element group has positive focal power and comprises a third lens; wherein the first lens and the second lens form a cemented lens; the effective focal length FG1 of the first element group, the effective focal length FG2 of the second element group and the total effective focal length f of the optical system satisfy: 3.2<(FG1+FG2) / f<4.2.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical devices, in particular, to an optical system. BACKGROUND

[0002] In a virtual reality system, high-performance display and light weight of an optical system are one of the performances that consumers focus on. A foldable optical system relying on the principle of polarization can effectively compress the distance between a display and a human eye, thereby reducing the total length of the optical system. However, for the foldable optical system, on the one hand, multiple fold of light rays will cause loss of light energy; on the other hand, compared with a conventional pair of glasses, the foldable optical system still has a significantly thick and heavy body, so that there is a large optimization space in the manufacturing process and wearing experience. SUMMARY

[0003] An optical system is provided in the embodiments of the present application, which comprises a first element group and a second element group in sequence from a first side to a second side along an optical axis; the first element group has a positive focal power and comprises a reflective polarizing element, a quarter-wave plate, a first lens, a partially reflective element and a second lens; the second element group has a positive focal power and comprises a third lens; wherein the first lens and the second lens form a cemented lens; an effective focal length FG1 of the first element group, an effective focal length FG2 of the second element group and a total effective focal length f of the optical system satisfy: 3.2<(FG1+FG2) / f<4.2.

[0004] In some embodiments, a central thickness CT1 of the first lens on the optical axis and a central thickness CT2 of the second lens on the optical axis satisfy: 1.7<FG1 / (CT1+CT2)<2.9.

[0005] In some embodiments, a separation distance T23 of the second lens and the third lens on the optical axis, a central thickness CT3 of the third lens on the optical axis and a central thickness CT2 of the second lens on the optical axis satisfy: 2.2<(T23+CT3) / CT2<6.6.

[0006] In some embodiments, a distance TD of the first side of the first lens to the second side of the third lens on the optical axis and a sum ∑CT of the central thicknesses of the first lens, the second lens and the third lens on the optical axis satisfy: 0.9<TD / ∑CT<1.3.

[0007] In some embodiments, a refractive index N1 of the first lens, a refractive index N2 of the second lens and an entrance pupil diameter EPD of the optical system satisfy: 14<(N1+N2)×(f / EPD)<17.3.

[0008] In some embodiments, the radius of curvature R1 of the first side of the first lens and the radius of curvature R4 of the second side of the second lens satisfy: 0.1 < 10 x FG1 / |R1 + R4| < 1.1.

[0009] In some embodiments, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ of the quarter-wave plate on the optical axis, and the separation distance T23 of the second lens and the third lens on the optical axis satisfy: 0.05 < (CTR + CTQ) / T23 < 2.1.

[0010] In some embodiments, the radius of curvature R4 of the second side of the second lens and the radius of curvature R6 of the second side of the third lens satisfy: -1.5 < (R4 + R6) / (R4 - R6) < 3.0.

[0011] In some embodiments, the maximum field of view angle FOV of the optical system, the distance TD of the first side of the first lens to the second side of the third lens on the optical axis satisfy: 0.9 < (f x tan(FOV / 2)) / TD < 1.4.

[0012] In some embodiments, the refractive index N3 of the third lens, the central thickness CT3 of the third lens on the optical axis satisfy: 0.1 < N3 x (CT3 / FG2) < 0.4.

[0013] In some embodiments, the Abbe number V1 of the first lens and the Abbe number of the second lens satisfy: 0.2 mm < FG1 / (V1 + V2) < 0.7 mm.

[0014] In some embodiments, the separation distance T12 of the first lens and the second lens on the optical axis is 0.

[0015] In some embodiments, the quarter-wave plate is attached to the first side of the first lens, and the reflective polarizing element is attached to the first side of the quarter-wave plate.

[0016] In some embodiments, the partially reflective element is attached to the second side of the first lens, or the first side of the second lens.

[0017] The optical system provided by the embodiment of the present application realizes the design of the light returning type by the combination of the reflective polarizing element, the quarter-wave plate, the partial reflecting element and the lens. By forming the first lens and the second lens into the cemented lens, the transmittance in the light propagation process can be improved, the light energy loss can be reduced, the brightness of the light into the pupil can be improved, the limitation of the actual production and manufacturing due to the demand of the high brightness screen can be avoided, in other words, the demand threshold of the high brightness screen can be reduced, and the flexibility of the screen selection can be improved. The cemented lens can also eliminate the air gap between the two lenses, avoid the total reflection stray light ghost image due to the difference in refractive index when the light passes through the air gap between the lenses, and affect the visual effect into the eye. In addition, the combination of the second element group is beneficial to realize the distribution and control of the focal length of the optical system, indirectly control the total length of each element group and the optical system, help to realize the actual design requirement of light weight, and improve the wearing experience. BRIEF DESCRIPTION OF DRAWINGS

[0018] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments thereof as read in conjunction with the accompanying drawings:

[0019] Figure 1 A structure schematic diagram of an optical system according to Embodiment 1 of the present application is shown;

[0020] Figures 2A to 2C An on-axis chromatic aberration curve, an astigmatism curve and a distortion curve of the optical system according to Embodiment 1 of the present application are shown respectively;

[0021] Figure 3 A structure schematic diagram of an optical system according to Embodiment 2 of the present application is shown;

[0022] Figures 4A to 4C An on-axis chromatic aberration curve, an astigmatism curve and a distortion curve of the optical system according to Embodiment 2 of the present application are shown respectively;

[0023] Figure 5 A structure schematic diagram of an optical system according to Embodiment 3 of the present application is shown;

[0024] Figures 6A to 6C An on-axis chromatic aberration curve, an astigmatism curve and a distortion curve of the optical system according to Embodiment 3 of the present application are shown respectively;

[0025] Figure 7 A structure schematic diagram of an optical system according to Embodiment 4 of the present application is shown;

[0026] Figures 8A to 8C An on-axis chromatic aberration curve, an astigmatism curve and a distortion curve of the optical system according to Embodiment 4 of the present application are shown respectively;

[0027] Figure 9A structural diagram of an optical system according to Embodiment 5 of the present application is shown; and

[0028] Figures 10A to 10C An on-axis chromatic aberration curve, an astigmatism curve, and a distortion curve of the optical system according to Embodiment 5 of the present application are shown, respectively. DETAILED DESCRIPTION

[0029] For a better understanding of the present application, various aspects of the present application will be described in greater detail below with reference to the accompanying drawings. It is to be understood that the detailed description is merely exemplary of the application and is not intended to limit the scope of the application in any way. Throughout the specification, like reference numerals refer to like elements, and across various embodiments.

[0030] It is to be noted that the terms first, second, third, etc. in the present specification are used only for distinguishing one feature from another, and do not denote any limitation. Thus, a first lens discussed below can also be termed as a second lens or a third lens without departing from the teaching of the present application.

[0031] In the drawings, the thickness, size, and shape of lenses have been exaggerated slightly for the sake of explanation. Specifically, the shape of a spherical surface or an aspherical surface shown in the drawings is shown by way of example. That is, the shape of a spherical surface or an aspherical surface is not limited to the shape of a spherical surface or an aspherical surface shown in the drawings. The drawings are merely examples and are not drawn to scale.

[0032] In the present specification, a paraxial region refers to a region near an optical axis. If a lens surface is convex and the position of the convex surface is not specified, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the position of the concave surface is not specified, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to a first side (e.g., a human eye side) is referred to as a first side surface of the lens, and the surface of each lens closest to a second side (e.g., an image plane side) is referred to as a second side surface of the lens.

[0033] It is also to be understood that the terms "comprise", "comprising", "have", "having", "include" and / or "including" when used in this specification, specify the presence of stated features, elements and / or components, but do not preclude the presence or addition of one or more other features, elements, components and / or groups thereof. Furthermore, when describing the embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Also, the term "exemplary" is intended to mean an example or an illustration.

[0034] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0035] It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0036] The features, principles and other aspects of the present application are described in detail below.

[0037] In an example embodiment, the optical system includes a first element group and a second element group arranged in sequence along a first optical axis from a first side to a second side. The first element group has a positive focal power and includes a reflective polarizing element, a quarter-wave plate, a first lens, a partially reflective element, and a second lens. The second element group has a positive focal power and includes a third lens. The first lens and the second lens form a cemented lens. For example, the quarter-wave plate is attached to a first side of the first lens, and the reflective polarizing element is attached to a first side of the quarter-wave plate. The partially reflective element is attached to a second side of the first lens or a first side of the second lens.

[0038] In the optical system, the turn-back light design is achieved by the combination of the reflective polarizing element, the quarter-wave plate, the partially reflective element, and the lenses. By forming the first lens and the second lens into a cemented lens, the transmittance in the light propagation process can be improved, the light energy loss can be reduced, the brightness of the entrance pupil light can be improved, the limitation of actual production and manufacturing due to the demand for high-brightness screens can be avoided, in other words, the demand threshold for high-brightness screens can be reduced, and the flexibility of screen selection can be improved. The cemented lens can also eliminate the air gap between the two, avoid total reflection stray light ghost images due to the difference in refractive index, and affect the visual effect of the eye.

[0039] In an example embodiment, the optical system according to the present application can satisfy: 3.2<(FG1+FG2) / f<4.2, where FG1 is the effective focal length of the first element group, FG2 is the effective focal length of the second element group, and f is the total effective focal length of the optical system. The optical system satisfies 3.2<(FG1+FG2) / f<4.2, which is conducive to the allocation and control of the focal length of the optical system, indirectly controls the total length of each element group and the optical system, helps to achieve the actual design requirement of light weight, and improves the wearing experience.

[0040] In the example embodiment, the optical system according to the present application can satisfy: 1.7 < FG1 / (CT1+CT2) < 2.9, where FG1 is the effective focal length of the first element group, CT1 is the center thickness of the first lens on the optical axis, and CT2 is the center thickness of the second lens on the optical axis. The optical system satisfying 1.7 < FG1 / (CT1+CT2) < 2.9, on the one hand, is conducive to controlling the strength of the two cemented lenses to ensure the forming and processing strength; on the other hand, is conducive to indirectly constraining the field of view angle of the first element group and the size of the lens to improve the flexibility of the overall size design of the optical system and the screen selection.

[0041] In the example embodiment, the optical system according to the present application can satisfy: 2.2 < (T23+CT3) / CT2 < 6.6, where T23 is the spacing distance of the second lens and the third lens on the optical axis, CT3 is the center thickness of the third lens on the optical axis, and CT2 is the center thickness of the second lens on the optical axis. The optical system satisfying 2.2 < (T23+CT3) / CT2 < 6.6 is conducive to the strength and assembly distribution control of the lens, avoids processing problems such as cracking or assembly interference, and can improve the feasibility of mass production.

[0042] In the example embodiment, the optical system according to the present application can satisfy: 0.9 < TD / ∑CT < 1.3, where TD is the distance from the first side of the first lens to the second side of the third lens on the optical axis, and ∑CT is the sum of the center thicknesses of the first lens, the second lens, and the third lens on the optical axis. The optical system satisfying 0.9 < TD / ∑CT < 1.3 can reasonably distribute the optical axis proportion of each lens on the basis of ensuring the basic lens forming and assembly strength, thereby further controlling and compressing the total length of the optical system to achieve the goal of lightweight design and improve the wearing experience.

[0043] In the example embodiment, the optical system according to the present application can satisfy: 14 < (N1+N2)×(f / EPD) < 17.3, where N1 is the refractive index of the first lens, N2 is the refractive index of the second lens, f is the total effective focal length of the optical system, and EPD is the entrance pupil diameter of the optical system. The optical system satisfying 14 < (N1+N2)×(f / EPD) < 17.3 can control the width, brightness, and refraction angle of the entrance pupil light. Combining the high transmittance mode of the cemented lens with reasonable entrance pupil design can further improve the brightness of the entrance pupil light, reduce the demand threshold for high-brightness screens, improve the flexibility of screen selection, reduce the production cost and energy consumption of the optical system, and is conducive to actual processing and manufacturing.

[0044] In an example embodiment, the optical system according to the present application can satisfy: 0.1 < 10 x FG1 / |R1 + R4| < 1.1, where FG1 is the effective focal length of the first element group, R1 is the curvature radius of the first side surface of the first lens, and R4 is the curvature radius of the second side surface of the second lens. The optical system satisfying 0.1 < 10 x FG1 / |R1 + R4| < 1.1 is conducive to controlling the shape of the outer surface of the cemented lens, conducive to processing and manufacturing, and conducive to realizing edge ray control of the cemented lens to optimize edge ray aberration.

[0045] In an example embodiment, the optical system according to the present application can satisfy: 0.05 < (CTR + CTQ) / T23 < 2.1, where CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ is the central thickness of the quarter-wave plate on the optical axis, and T23 is the interval distance of the second lens and the third lens on the optical axis. The optical system satisfying 0.05 < (CTR + CTQ) / T23 < 2.1 is conducive to controlling the turnaround distance of the turnaround optical system to further compress the overall length of the optical system while avoiding assembly interference.

[0046] In an example embodiment, the optical system according to the present application can satisfy: -1.5 < (R4 + R6) / (R4 - R6) < 3.0, where R4 is the curvature radius of the second side surface of the second lens, and R6 is the curvature radius of the second side surface of the third lens. The optical system satisfying -1.5 < (R4 + R6) / (R4 - R6) < 3.0 is conducive to reasonably constraining the surface shape of the second lens and the second lens to balance the edge aberration and improve the outer field performance.

[0047] In an example embodiment, the optical system according to the present application can satisfy: 0.9 < (f x tan(FOV / 2)) / TD < 1.4, where f is the total effective focal length of the optical system, FOV is the maximum field angle of the optical system, and TD is the distance from the first side surface of the first lens to the second side surface of the third lens on the optical axis. The optical system satisfying 0.9 < (f x tan(FOV / 2)) / TD < 1.4 can effectively control the image height and the object height. In addition, satisfying the above condition, on the one hand, it can ensure the basic visual immersion experience; on the other hand, it is convenient for feedback screen selection for actual production and processing. At the same time, it is conducive to the balance between the main value parameters such as the field angle and the overall length of the machine, and realizes the actual use demand of performance experience and equipment light weight.

[0048] In an example embodiment, the optical system according to the present application can satisfy: 0.1 < N3 x (CT3 / FG2) < 0.4, where N3 is the refractive index of the third lens, CT3 is the center thickness of the third lens on the optical axis, and FG2 is the effective focal length of the second element group. The optical system satisfying 0.1 < N3 x (CT3 / FG2) < 0.4, on the one hand, is conducive to ensuring the forming strength of the third lens, facilitating actual assembly; on the other hand, can indirectly control the material selection of the third lens, facilitating the convergence and regulation of screen light.

[0049] In an example embodiment, the optical system according to the present application can satisfy: 0.2 mm < FG1 / (V1+V2) < 0.7 mm, where FG1 is the effective focal length of the first element group, V1 is the Abbe number of the first lens, and V2 is the Abbe number of the second lens. The optical system satisfying 0.2 mm < FG1 / (V1+V2) < 0.7 mm facilitates the selection of Abbe number complementary materials, and is conducive to controlling the dispersion of the cemented lens. In addition, in combination with the effective focal length setting of the first element group, it is conducive to the control of the exit pupil light and the optimization of the in-eye visual experience.

[0050] In an example embodiment, at least one of the surfaces of each of the first lens to the third lens is an aspherical surface. The aspherical lens has the characteristic that the curvature is continuously changed from the center of the lens to the periphery of the lens. Unlike the spherical lens having a constant curvature from the center of the lens to the periphery of the lens, the aspherical lens has better curvature radius characteristics, and has the advantages of improving the distortion aberration and improving the astigmatism aberration. After using the aspherical lens, the aberration that occurs during imaging can be eliminated as much as possible, thereby improving the imaging quality.

[0051] In an example embodiment, the optical system can be applied to a virtual reality system. For example, the optical system can be used as a visual optical system in the virtual reality system. Optionally, the virtual reality system can further include a positioning optical system. In the virtual reality system, the image of the external environment captured by the positioning optical system can be calculated by a visual algorithm (for example, a SLAM algorithm) to obtain the spatial position of the virtual reality system, thereby realizing the positioning of human-computer interaction. Based on the above positioning result, the visual optical system can dynamically adjust the virtual image content of the image plane (for example, a display), and project the virtual image into the user's eyes to make the user feel as if he or she were in the scene. The virtual immersion of the visual optical system combined with the positioning function of the positioning optical system can break through the spatial limitation of the virtual reality system, and realize the interaction between the real world and the virtual world of the virtual optical system.

[0052] However, those skilled in the art will appreciate that the number of lenses comprising the optical system can be varied to achieve the various results and advantages described herein without departing from the technical solutions claimed in this application. For example, while the optical system is described in the embodiments using three lenses as an example, the optical system is not limited to including three lenses. If desired, the optical system can also include other numbers of lenses.

[0053] Specific embodiments of the optical system applicable to the above-mentioned embodiments will be further described below with reference to the accompanying drawings.

[0054] Example 1

[0055] The following reference Figures 1 to 2C An optical system according to Example 1 of the present application is described.

[0056] like Figure 1 As shown, the optical system includes a stop STO, a first element group G1, a second element group G2, and an image surface IMG (eg, a display) arranged in sequence from the first side to the second side along the optical axis. The first element group G1 has positive refractive power, and the second element group G2 has positive refractive power.

[0057] The first element group G1 includes a reflective polarizer RP, a quarter-wave plate QWP, a first lens E1, a partially reflecting element BS, and a second lens E2. In the first element group G1, the reflective polarizer RP and the quarter-wave plate QWP are bonded together, with the quarter-wave plate QWP attached to the first side surface S1 of the first lens E1. The first lens E1 and the second lens E2 form a cemented lens, with the second side surface S2 of the first lens E1 and the first side surface S3 of the second lens E2 bonded together. The partially reflecting element BS is attached between the first lens E1 and the second lens E2. For example, the partially reflecting element BS is attached to the second side surface S2 of the first lens E1 or the first side surface S3 of the second lens E2. The first side surface S1 of the first lens E1 is concave, and the second side surface S2 is convex. The first side surface S3 of the second lens E2 is concave, and the second side surface S4 is convex. The second element group G2 includes a third lens E3. The first side surface S5 of the third lens E3 is convex, and the second side surface S6 is convex.

[0058] In Embodiment 1, the light from the image plane IMG sequentially passes through the third lens E3, the second lens E2, the first lens E1, and the quarter-wave plate QWP, and reaches the reflective polarizing element RP, and a first reflection occurs at the reflective polarizing element RP. The light after the first reflection sequentially passes through the quarter-wave plate QWP and the first lens E1, and reaches the partially reflective element BS, and a second reflection occurs at the partially reflective layer BS. The light after the second reflection sequentially passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizing element PR, and the stop STO, and reaches the human eye. The optical system projects the light from the image plane IMG into the human eye through two reflections.

[0059] Table 1 shows a basic parameter table of the optical system of Embodiment 1, where the units of the radius of curvature, the thickness / distance are millimeters (mm). The light from the image plane IMG passes through each element in the order of No. 13 to No. 1 and is projected into the human eye.

[0060]

[0061] Table 1

[0062] In Embodiment 1, the first side surface S3 of the second lens E2 (i.e., the second side surface S2 of the first lens E1) and the first side surface S5 of the third lens E3 are both aspherical surfaces, and the surface shape x of each aspherical surface can be defined by, but not limited to, the following aspherical surface formula:

[0063]

[0064] where x is the sag of the aspherical surface at a position along the optical axis at a height h from the vertex of the aspherical surface; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the inverse of the radius of curvature R in Table 1 above); k is the conic coefficient; and Ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 shows the high-order term coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for the aspherical surfaces S3 and S5 in Embodiment 1.

[0065]

[0066]

[0067] Table 2

[0068] The effective focal length FG1 of the first element group G1 is 30.85 mm, the effective focal length FG2 of the second element group G2 is 74.12 mm, the total effective focal length f of the optical system is 27.00 mm, the entrance pupil diameter EPD of the optical system is 5.00 mm, the maximum field of view FOV of the optical system is 100.00°, the distance TD of the first side S1 of the first lens E1 to the second side S6 of the third lens E3 on the optical axis is 29.733 mm, the central thickness CTR of the reflective polarizing element RP on the optical axis is 0.02 mm, the central thickness CTQ of the quarter-wave plate QWP on the optical axis is 0.02 mm, and the sum ∑CT of the central thicknesses of the first lens E1, the second lens E2 and the third lens E3 on the optical axis is 29.53 mm.

[0069] Figure 2A An on-axis chromatic aberration curve of the optical system of Embodiment 1 is shown, which represents the convergence focal point deviation of light rays of different wavelengths after passing through the optical system. Figure 2B An astigmatism curve of the optical system of Embodiment 1 is shown, which represents the meridional image surface curvature and sagittal image surface curvature corresponding to different field angles. Figure 2C A distortion curve of the optical system of Embodiment 1 is shown, which represents the distortion size value corresponding to different field angles. Figures 2A to 2C It can be seen that the optical system given in Embodiment 1 can achieve good imaging quality.

[0070] Example 2

[0071] The following refers to Figures 3 to 4C An optical system according to Embodiment 2 of the present application is described.

[0072] As shown in Figure 3 , the optical system includes, in order from a first side to a second side along an optical axis, a stop STO, a first element group G1, a second element group G2, and an image plane IMG (e.g., a display). The first element group G1 has positive refractive power, and the second element group G2 has positive refractive power.

[0073] The first element group G1 includes a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a partially reflective element BS, and a second lens E2. In the first element group G1, the reflective polarizing element RP and the quarter-wave plate QWP are attached to each other, and the quarter-wave plate QWP is attached to the first side S1 of the first lens E1. The first lens E1 and the second lens E2 form a cemented lens, and the second side S2 of the first lens E1 and the first side S3 of the second lens E2 are attached to each other. The partially reflective element BS is attached between the first lens E1 and the second lens E2. For example, the partially reflective element BS is attached to the second side S2 of the first lens E1 or the first side S3 of the second lens E2. In the first lens E1, the first side S1 is a convex surface, and the second side S2 is a concave surface. In the second lens E2, the first side S3 is a convex surface, and the second side S4 is a convex surface. The second element group G2 includes a third lens E3. In the third lens E3, the first side S5 is a convex surface, and the second side S6 is a convex surface.

[0074] In the embodiment 2, the light from the image plane IMG sequentially passes through the third lens E3, the second lens E2, the first lens E1, and the quarter-wave plate QWP, and reaches the reflective polarizing element RP, and a first reflection occurs at the reflective polarizing element RP. The light after the first reflection sequentially passes through the quarter-wave plate QWP and the first lens E1, and reaches the partially reflective element BS, and a second reflection occurs at the partially reflective layer BS. The light after the second reflection sequentially passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizing element PR, and the stop STO, and reaches the human eye. The optical system projects the light from the image plane IMG into the human eye through two reflections.

[0075] The effective focal length FG1 of the first element group G1 is 32.16 mm, the effective focal length FG2 of the second element group G2 is 77.64 mm, the total effective focal length f of the optical system is 27.00 mm, the entrance pupil diameter EPD of the optical system is 5.00 mm, the maximum field of view FOV of the optical system is 100.00°, the distance TD of the first side S1 of the first lens E1 to the second side S6 of the third lens E3 on the optical axis is 24.500 mm, the central thickness CTR of the reflective polarizing element RP on the optical axis is 0.02 mm, the central thickness CTQ of the quarter-wave plate QWP on the optical axis is 0.02 mm, and the sum ∑CT of the central thicknesses of the first lens E1, the second lens E2, and the third lens E3 on the optical axis is 19.95 mm.

[0076] Table 3 shows the basic parameters of the optical system of Example 2, where the units of the radius of curvature, thickness / distance are millimeters (mm). The light from the image plane IMG passes through each element in the order of No. 13 to No. 1 and is projected into the human eye. Table 4 shows the high-order term coefficients of each aspherical surface in Example 2, where each aspherical surface can be defined by the formula (1) given in Example 1 above.

[0077]

[0078] Table 3

[0079] Coefficient / Face Number S1 S6 A4 -2.8155E-07 -1.8183E+00 A6 1.6555E-10 -3.0514E+00 A8 -1.0445E-13 1.7378E+00 A10 3.0836E-17 -1.5057E+00 A12 -6.6579E-21 1.4156E+00 A14 0.0000E+00 -1.0787E+00 A16 0.0000E+00 5.7436E-01 A18 0.0000E+00 -1.9407E-01 A20 0.0000E+00 3.1183E-02

[0080] Table 4

[0081] Figure 4A The on-axis chromatic aberration curve of the optical system of Example 2 is shown, which represents the convergence point deviation of light rays of different wavelengths after passing through the optical system. Figure 4B The astigmatism curve of the optical system of Example 2 is shown, which represents the meridional image surface curvature and sagittal image surface curvature corresponding to different field angles. Figure 4C The distortion curve of the optical system of Example 2 is shown, which represents the distortion size value corresponding to different field angles. According to the formula (2) given above, the distortion value of the optical system of Example 2 is 0.0003, which is very small. Figures 4A to 4C It can be seen that the optical system given in Example 2 can achieve good imaging quality.

[0082] Example 3

[0083] The following refers to Figures 5 to 6C An optical system according to Example 3 of the present application is described.

[0084] As shown in Figure 5 , the optical system includes, in order along the optical axis from the first side to the second side, a stop STO, a first element group G1, a second element group G2, and an image plane IMG (e.g., a display). The first element group G1 has positive optical power, and the second element group G2 has positive optical power.

[0085] The first element group G1 includes a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a partial reflection element BS, and a second lens E2. In the first element group G1, the reflective polarizing element RP and the quarter-wave plate QWP are attached to each other, and the quarter-wave plate QWP is attached to the first side surface S1 of the first lens E1. The first lens E1 and the second lens E2 form a cemented lens, and the second side surface S2 of the first lens E1 and the first side surface S3 of the second lens E2 are attached to each other. The partial reflection element BS is attached between the first lens E1 and the second lens E2. For example, the partial reflection element BS is attached to the second side surface S2 of the first lens E1 or the first side surface S3 of the second lens E2. Among them, the first side surface S1 of the first lens E1 is a convex surface, and the second side surface S2 is a convex surface. The first side surface S3 of the second lens E2 is a concave surface, and the second side surface S4 is a concave surface. The second element group G2 includes a third lens E3. Among them, the first side surface S5 of the third lens E3 is a convex surface, and the second side surface S6 is a concave surface.

[0086] In the embodiment 3, the light from the image surface IMG sequentially passes through the third lens E3, the second lens E2, the first lens E1, and the quarter-wave plate QWP and reaches the reflective polarizing element RP, and the first reflection occurs at the reflective polarizing element RP. The light after the first reflection sequentially passes through the quarter-wave plate QWP and the first lens E1 and reaches the partial reflection element BS, and the second reflection occurs at the partial reflection layer BS. The light after the second reflection sequentially passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizing element PR, and the stop STO and reaches the human eye. The optical system projects the light of the image surface IMG into the human eye through two reflections.

[0087] The effective focal length FG1 of the first element group G1 is 26.96 mm, the effective focal length FG2 of the second element group G2 is 43.20 mm, the total effective focal length f of the optical system is 21.70 mm, the entrance pupil diameter EPD of the optical system is 5.00 mm, the maximum field of view FOV of the optical system is 100.00°, the distance TD of the first side surface S1 of the first lens E1 to the second side surface S6 of the third lens E3 on the optical axis is 26.157 mm, the central thickness CTR of the reflective polarizing element RP on the optical axis is 0.02 mm, the central thickness CTQ of the quarter-wave plate QWP on the optical axis is 0.02 mm, and the sum ∑CT of the central thicknesses of the first lens E1, the second lens E2, and the third lens E3 on the optical axis is 24.15 mm.

[0088] Table 5 lists the basic parameters of the optical system of Example 3, where the units of curvature radius and thickness / distance are all in millimeters (mm). Light from the image surface IMG passes through the various components in the order of sequence numbers 13 to 1 and is projected into the human eye. Table 6 shows the high-order coefficients of the various aspheric mirror surfaces that can be used in Example 3, where the surface shapes of the various aspheric surfaces can be defined by formula (1) given in Example 1 above.

[0089]

[0090]

[0091] Table 5

[0092] Coefficient / Face Number S1 S6 A4 -4.9887E-08 -1.1749E+01 A6 4.5501E-11 -9.5487E+00 A8 -2.6136E-13 3.7213E+00 A10 2.9233E-16 -1.8997E+00 A12 -1.2043E-19 2.3213E+00 A14 0.0000E+00 -2.3703E+00 A16 0.0000E+00 -1.3237E+00 A18 0.0000E+00 3.0258E+00 A20 0.0000E+00 -1.3789E+00

[0093] Table 6

[0094] Figure 6A The axial chromatic aberration curve of the optical system of Example 3 is shown, which indicates the deviation of the convergence point of light of different wavelengths after passing through the optical system. Figure 6B The astigmatism curve of the optical system of Example 3 is shown, which represents the meridional field curvature and sagittal field curvature corresponding to different field angles. Figure 6C The distortion curve of the optical system of Example 3 is shown, which represents the distortion value corresponding to different field angles. Figures 6A to 6C It can be seen that the optical system provided in Example 3 can achieve good imaging quality.

[0095] Example 4

[0096] The following reference Figures 7 to 8C An optical system according to Example 4 of the present application is described.

[0097] like Figure 7 As shown, the optical system includes a stop STO, a first element group G1, a second element group G2, and an image surface IMG (eg, a display) arranged in sequence from the first side to the second side along the optical axis. The first element group G1 has positive refractive power, and the second element group G2 has positive refractive power.

[0098] The first element group G1 includes a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a partial reflection element BS, and a second lens E2. In the first element group G1, the reflective polarizing element RP and the quarter-wave plate QWP are attached to each other, and the quarter-wave plate QWP is attached to the first side surface S1 of the first lens E1. The first lens E1 and the second lens E2 form a cemented lens, and the second side surface S2 of the first lens E1 and the first side surface S3 of the second lens E2 are attached to each other. The partial reflection element BS is attached between the first lens E1 and the second lens E2. For example, the partial reflection element BS is attached to the second side surface S2 of the first lens E1 or the first side surface S3 of the second lens E2. Among them, the first side surface S1 of the first lens E1 is a convex surface, and the second side surface S2 is a flat surface. The first side surface S3 of the second lens E2 is a flat surface, and the second side surface S4 is a concave surface. The second element group G2 includes a third lens E3. Among them, the first side surface S5 of the third lens E3 is a convex surface, and the second side surface S6 is a concave surface.

[0099] In embodiment 4, the light from the image surface IMG sequentially passes through the third lens E3, the second lens E2, the first lens E1, and the quarter-wave plate QWP and reaches the reflective polarizing element RP, and the first reflection occurs at the reflective polarizing element RP. The light after the first reflection sequentially passes through the quarter-wave plate QWP and the first lens E1 and reaches the partial reflection element BS, and the second reflection occurs at the partial reflection layer BS. The light after the second reflection sequentially passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizing element PR, and the stop STO and reaches the human eye. The optical system projects the light of the image surface IMG into the human eye through two reflections.

[0100] The effective focal length FG1 of the first element group G1 is 27.38 mm, the effective focal length FG2 of the second element group G2 is 51.54 mm, the total effective focal length f of the optical system is 23.06 mm, the entrance pupil diameter EPD of the optical system is 5.00 mm, the maximum field of view FOV of the optical system is 106.00°, the distance TD of the first side surface S1 of the first lens E1 to the second side surface S6 of the third lens E3 on the optical axis is 27.259 mm, the central thickness CTR of the reflective polarizing element RP on the optical axis is 0.02 mm, the central thickness CTQ of the quarter-wave plate QWP on the optical axis is 0.02 mm, and the sum ∑CT of the central thicknesses of the first lens E1, the second lens E2, and the third lens E3 on the optical axis is 23.55 mm.

[0101] Table 7 lists the basic parameters of the optical system of Example 4, where the units of curvature radius and thickness / distance are all in millimeters (mm). Light from the image surface IMG passes through the various components in the order of sequence numbers 13 to 1 and is projected into the human eye. Table 8 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 4, where the surface shapes of the various aspherical surfaces can be defined by formula (1) given in Example 1 above.

[0102]

[0103] Table 7

[0104]

[0105]

[0106] Table 8

[0107] Figure 8A The axial chromatic aberration curve of the optical system of Example 4 is shown, which indicates the deviation of the focal point of light of different wavelengths after passing through the optical system. Figure 8B The astigmatism curve of the optical system of Example 4 is shown, which represents the meridional field curvature and sagittal field curvature corresponding to different field angles. Figure 8C The distortion curve of the optical system of Example 4 is shown, which represents the distortion value corresponding to different field angles. Figures 8A to 8C It can be seen that the optical system provided in Example 4 can achieve good imaging quality.

[0108] Example 5

[0109] The following reference Figures 9 to 10C An optical system according to Example 5 of the present application is described.

[0110] like Figure 9 As shown, the optical system includes a stop STO, a first element group G1, a second element group G2, and an image surface IMG (eg, a display) arranged in sequence from the first side to the second side along the optical axis. The first element group G1 has positive refractive power, and the second element group G2 has positive refractive power.

[0111] The first element group G1 includes a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a partial reflection element BS, and a second lens E2. In the first element group G1, the reflective polarizing element RP and the quarter-wave plate QWP are attached to each other, and the quarter-wave plate QWP is attached to the first side surface S1 of the first lens E1. The first lens E1 and the second lens E2 form a cemented lens, and the second side surface S2 of the first lens E1 and the first side surface S3 of the second lens E2 are attached to each other. The partial reflection element BS is attached between the first lens E1 and the second lens E2. For example, the partial reflection element BS is attached to the second side surface S2 of the first lens E1 or the first side surface S3 of the second lens E2. Among them, the first side surface S1 of the first lens E1 is a convex surface, and the second side surface S2 is a flat surface. The first side surface S3 of the second lens E2 is a flat surface, and the second side surface S4 is a convex surface. The second element group G2 includes a third lens E3. Among them, the first side surface S5 of the third lens E3 is a flat surface, and the second side surface S6 is a convex surface.

[0112] In embodiment 5, the light from the image plane IMG sequentially passes through the third lens E3, the second lens E2, the first lens E1, and the quarter-wave plate QWP and reaches the reflective polarizing element RP, and the first reflection occurs at the reflective polarizing element RP. The light after the first reflection sequentially passes through the quarter-wave plate QWP and the first lens E1 and reaches the partial reflection element BS, and the second reflection occurs at the partial reflection layer BS. The light after the second reflection sequentially passes through the first lens E1, the quarter-wave plate QWP, the reflective polarizing element PR, and the stop STO and reaches the human eye. The optical system projects the light of the image plane IMG into the human eye through two reflections.

[0113] The effective focal length FG1 of the first element group G1 is 25.22 mm, the effective focal length FG2 of the second element group G2 is 56.30 mm, the total effective focal length f of the optical system is 22.00 mm, the entrance pupil diameter EPD of the optical system is 5.00 mm, the maximum field of view FOV of the optical system is 100.00°, the distance TD of the first side surface S1 of the first lens E1 to the second side surface S6 of the third lens E3 on the optical axis is 23.474 mm, the central thickness CTR of the reflective polarizing element RP on the optical axis is 0.02 mm, the central thickness CTQ of the quarter-wave plate QWP on the optical axis is 0.02 mm, and the sum ∑CT of the central thicknesses of the first lens E1, the second lens E2, and the third lens E3 on the optical axis is 21.15 mm.

[0114] Table 9 shows the basic parameters of the optical system of Example 5, wherein the units of the radius of curvature, thickness / distance are millimeters (mm). The light from the image plane IMG passes through each element in the order of No. 13 to No. 1 and is projected into the human eye. Table 10 shows the high-order term coefficients of each aspherical mirror surface that can be used in Example 5, wherein each aspherical surface can be defined by the formula (1) given in Example 1 above.

[0115]

[0116] Table 9

[0117] Coefficient / Face Number S1 S6 A4 -7.2127E-07 1.0289E+00 A6 3.8838E-10 -2.7662E+00 A8 -1.8007E-13 5.9907E-01 A10 -7.8446E-17 -5.8467E-01 A12 -1.0694E-19 3.7037E-01 A14 0.0000E+00 -3.0558E-01 A16 0.0000E+00 1.1025E-01 A18 0.0000E+00 -3.4189E-02 A20 0.0000E+00 -2.8275E-03

[0118] Table 10

[0119] Figure 10A The on-axis chromatic aberration curve of the optical system of Example 5 is shown, which represents the deviation of the convergent focal points of light rays of different wavelengths after passing through the positioning optical system. Figure 10B The astigmatism curve of the optical system of Example 5 is shown, which represents the meridional image surface curvature and sagittal image surface curvature corresponding to different field angles. Figure 10C The distortion curve of the optical system of Example 5 is shown, which represents the distortion size values corresponding to different field angles. According to the formula (2) given above, the distortion size values of the optical system of Example 5 are shown in Table 11. Figures 10A to 10C It can be seen that the optical system given in Example 5 can achieve good imaging quality.

[0120] In summary, Examples 1 to 5 respectively satisfy the relationships shown in Table 11.

[0121]

[0122] Table 11

[0123] The above description is merely preferred embodiments of the present application and a principle of applied technologies. It should be understood by those skilled in the art that the scope of the application involved in the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combinations of the above technical features or equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features and the technical features disclosed in the present application (but not limited to) having similar functions.

Claims

1. An optical system, characterized in that: The optical system comprises a first element group, a second element group, and an image plane in sequence from the first side to the second side along the optical axis, wherein the image plane is disposed on the second side of the optical system; The first element group has positive optical power and includes a reflective polarizing element, a quarter-wave plate, a first lens, a partially reflecting element, and a second lens, wherein the first lens has positive optical power; The second element group has positive optical power and includes a third lens; wherein the number of lenses having optical power in the optical system is three; The first lens and the second lens form a cemented lens; The quarter-wave plate is attached to the first side surface of the first lens, and the reflective polarizing element is attached to the first side surface of the quarter-wave plate; The partially reflective element is attached to the second side surface of the first lens or the first side surface of the second lens; The effective focal length FG1 of the first element group, the effective focal length FG2 of the second element group, and the total effective focal length f of the optical system satisfy the following: 3.2<(FG1+FG2) / f≤4.

07.

2. The optical system according to claim 1, wherein A center thickness CT1 of the first lens on the optical axis and a center thickness CT2 of the second lens on the optical axis satisfy the following: 1.76≤FG1 / (CT1+CT2)≤2.

81.

3. The optical system according to claim 1, wherein: A distance T23 between the second lens and the third lens on the optical axis, a center thickness CT3 of the third lens on the optical axis, and a center thickness CT2 of the second lens on the optical axis satisfy: 2.2<(T23+CT3) / CT2≤6.

52.

4. The optical system according to claim 1, wherein A distance TD from the first side surface of the first lens to the second side surface of the third lens on the optical axis and a sum ΣCT of the center thicknesses of the first lens, the second lens, and the third lens on the optical axis respectively satisfy the following: 1.01≤TD / ΣCT≤1.

23.

5. The optical system according to claim 1, wherein: A refractive index N1 of the first lens, a refractive index N2 of the second lens, and an entrance pupil diameter EPD of the optical system satisfy: 14.09≤(N1+N2)×(f / EPD)<17.

3.

6. The optical system according to claim 1, wherein: A curvature radius R1 of the first side surface of the first lens and a curvature radius R4 of the second side surface of the second lens satisfy: 0.1<10×FG1 / |R1+R4|≤0.

99.

7. The optical system according to claim 1, wherein: The center thickness CTR of the reflective polarizer on the optical axis, the center thickness CTQ of the quarter-wave plate on the optical axis, and the spacing T23 between the second lens and the third lens on the optical axis satisfy the following: 0.05<(CTR+CTQ) / T23≤2.

00.

8. The optical system according to claim 1, wherein: A curvature radius R4 of the second side surface of the second lens and a curvature radius R6 of the second side surface of the third lens satisfy: -1.40≤(R4+R6) / (R4-R6)≤2.

90.

9. The optical system according to claim 1, wherein: The maximum field of view FOV of the optical system and the distance TD from the first side surface of the first lens to the second side surface of the third lens on the optical axis satisfy the following conditions: 0.99≤(f×tan(FOV / 2)) / TD≤1.

31.

10. The optical system according to claim 1, wherein: A refractive index N3 of the third lens and a center thickness CT3 of the third lens on the optical axis satisfy the following conditions: 0.17≤N3×(CT3 / FG2)<0.

4.

11. The optical system according to claim 1, wherein: The Abbe number V1 of the first lens and the Abbe number V2 of the second lens satisfy the following: 0.25 mm≤FG1 / (V1+V2)≤0.63 mm.

12. The optical system according to any one of claims 1 to 11, characterized in that A distance T12 between the first lens and the second lens on the optical axis is 0.

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