Optical system and optical apparatus comprising the same

Abstract

The application discloses an optical system and an optical device comprising the same. The optical system comprises, in order from a first side to a second side along an optical axis, a first lens, a second lens, a reflective polarizing element, a quarter-wave plate, and a third lens. The second side of the second lens is a plane. The second side of the third lens is provided with a partial reflection layer. The radius of curvature R1 of the first side of the first lens, the central thickness CT1 of the first lens along the optical axis, and the Abbe number V1 of the first lens satisfy 55.0 < R1 / CT1+R1 / V1 < 221.

Description

Technical Field

[0001] This application relates to the field of optical components, and more specifically, to an optical system and an optical device including the optical system. Background Technology

[0002] Since the concept of the "metaverse" was proposed, AR / VR has ushered in its second opportunity for development. Optical systems, as the entry point for human-computer interaction in AR / VR devices, play a crucial role. Among them, virtual reality head-mounted displays, or VR glasses, are devices based on human-computer interaction and offer a certain degree of immersive experience. When worn, users see a magnified virtual image formed by the screen, and the parallax between the two eyes increases the sense of depth in the image.

[0003] Traditional Fresnel optical paths use large displays and thicker lenses, resulting in bulky and heavy VR devices that significantly reduce the user experience. However, the emergence of catadioptric optical solutions has changed the structure of Fresnel lens optical paths, shortening the overall length of the optical path, saving assembly space, and reducing weight, making it the main direction for VR devices.

[0004] The optical path of a catadioptric optical system is relatively complex. Different lens shapes and lens assembly positions will lead to different performance of the optical system. Therefore, designing the arrangement of lenses and reflective elements in a reasonable way to obtain a catadioptric optical system with good imaging quality is one of the current research hotspots. Summary of the Invention

[0005] This application provides an optical system comprising, in sequence along the optical axis from a first side to a second side: a first lens, a second lens, a reflective polarizing element, a quarter-wave plate, and a third lens, wherein the second side of the second lens is a plane; the second side of the third lens is provided with a partially reflective layer; and the radius of curvature R1 of the first side of the first lens, the center thickness CT1 of the first lens on the optical axis, and the Abbe number V1 of the first lens satisfy: 55.0 < R1 / CT1 + R1 / V1 < 221.

[0006] In one embodiment, the effective focal length f1 of the first lens, the refractive index N1 of the first lens, and the radius of curvature R2 of the second side surface of the first lens satisfy: -12.0 < f1 × N1 / R2 < -2.0.

[0007] In one embodiment, the effective focal length f2 of the second lens, the refractive index N2 of the second lens, and the radius of curvature R3 of the first side surface of the second lens satisfy: 2.0 < f2 × N2 / R3 < 3.0.

[0008] In one embodiment, the center thickness CT1 of the first lens on the optical axis and the air gap T12 between the first lens and the second lens on the optical axis satisfy: 6.0 < CT1 / T12 < 20.0.

[0009] In one embodiment, the effective focal length f3 of the third lens, the refractive index N3 of the third lens, and the radius of curvature R6 of the second side surface of the third lens satisfy: -2.5 < f3 × N3 / R6 < -1.5.

[0010] In one embodiment, the radius of curvature R5 of the first side of the third lens, the radius of curvature R6 of the second side of the third lens, the center thickness CT3 of the third lens on the optical axis, and the air gap T23 between the second and third lenses on the optical axis satisfy: 4.0 < |R5 / R6| + CT3 / T23 < 5.0.

[0011] In one embodiment, the center thickness dqwp of the quarter-wave plate on the optical axis, the air gap T23 between the second and third lenses on the optical axis, the center thickness CT3 of the third lens on the optical axis, and the distance TD between the first side of the first lens and the second side of the third lens on the optical axis satisfy: 1.5 < 3 × (dqwp + T23 + CT3) / TD < 2.5.

[0012] In one embodiment, the center thickness CT1 of the first lens on the optical axis, the center thickness CT2 of the second lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, the center thickness dqwp of the quarter-wave plate on the optical axis, and the center thickness drp of the reflective polarizing element on the optical axis satisfy: 0.5 < CT3 / (CT1+CT2+drp+dqwp) < 2.0.

[0013] In one embodiment, the effective focal length f3 of the third lens, the maximum semi-FOV of the optical system, and the radius of curvature R6 of the second side surface of the third lens satisfy: -2.5 < f3 × tan(Semi-FOV) / R6 < -1.5.

[0014] In one embodiment, the radius of curvature R1 of the first side surface of the first lens, the radius of curvature R3 of the first side surface of the second lens, the Abbe number V2 of the second lens and the Abbe number V1 of the first lens satisfy: 4.0 < |R1 / R3| + V2 / V1 < 7.0.

[0015] In one embodiment, the effective focal length f2 of the second lens, the Abbe number Vrp of the reflective polarizing element, and the Abbe number Vqwp of the quarter-wave plate satisfy: 1.0 < |f2| / (Vrp+Vqwp) < 2.5.

[0016] On the other hand, this application also provides an optical device that includes the optical system provided in at least one of the above embodiments.

[0017] The optical system provided in this application is a three-piece catadioptric optical system. On the one hand, by utilizing the phase-adding function of the quarter-wave plate, the beam-splitting function of the reflective polarizing element, and the reflection function of the partial reflective layer, the optical path is refracted, which can better compress the body height and improve the imaging quality. On the other hand, controlling the radius of curvature of the first side of the first lens, as well as the center thickness and Abbe number of the first lens, is beneficial to the processing and shaping of the lens, as well as to the correction of chromatic aberration of the system, thereby improving system performance and enhancing the consumer experience. Attached Figure Description

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments, taken in conjunction with the accompanying drawings. In the drawings:

[0019] Figure 1A This is a diagram showing the positional distribution of the aperture, first lens, second lens, reflective polarizing element, quarter-wave plate, third lens, and partial reflective layer in an optical system according to an embodiment of this application, as well as a schematic diagram of the optical path.

[0020] Figure 1B This is a schematic diagram of ghost images produced by optical systems in the prior art;

[0021] Figure 1C A schematic diagram showing some parameters of an optical system according to this application is provided;

[0022] Figure 2 A schematic diagram of the structure of the optical system according to Embodiment 1 of this application is shown;

[0023] Figures 3A to 3C The on-axis chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 1 of this application are shown respectively.

[0024] Figure 4 A schematic diagram of the structure of the optical system according to Embodiment 2 of this application is shown;

[0025] Figures 5A to 5C The on-axis chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 2 of this application are shown respectively.

[0026] Figure 6 A schematic diagram of the structure of the optical system according to Embodiment 3 of this application is shown;

[0027] Figures 7A to 7C The on-axis chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 3 of this application are shown respectively.

[0028] Figure 8 A schematic diagram of the structure of the optical system according to Embodiment 4 of this application is shown;

[0029] Figures 9A to 9C The on-axis chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 4 of this application are shown respectively.

[0030] Figure 10 A schematic diagram of the structure of the optical system according to Embodiment 5 of this application is shown;

[0031] Figures 11A to 11C The on-axis chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 5 of this application are shown respectively.

[0032] Figure 12 A schematic diagram of the structure of the optical system according to Embodiment 6 of this application is shown; and

[0033] Figures 13A to 13C The on-axis chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 6 of this application are shown respectively. Detailed Implementation

[0034] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0035] It should be noted that in this specification, the terms "first," "second," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of this application, the first lens discussed below may also be referred to as the second lens, and the second lens may also be referred to as the first lens.

[0036] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0037] In this paper, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity 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 location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region.

[0038] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0039] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formalized sense, unless expressly so specified herein.

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] The features, principles and other aspects of this application will be described in detail below with reference to the accompanying drawings and embodiments.

[0042] An optical system according to an exemplary embodiment of this application includes, in sequence along the optical axis from the first side to the second side: a first lens, a second lens, a reflective polarizing element, a quarter-wave plate, and a third lens.

[0043] In an exemplary embodiment, the first side of the reflective polarizing element is attached to the second side of the second lens, and the second side of the reflective polarizing element is attached to the first side of the quarter-wave plate.

[0044] In an exemplary embodiment, the reflective polarizing element and the quarter-wave plate are combined, and the desired structure can be obtained in a single bonding operation, instead of bonding in two steps. This reduces the angular position error caused by bonding and improves the imaging quality.

[0045] In an exemplary implementation, such as Figure 1AAs shown, the optical system according to this application can be applied to, for example, VR devices. The first side can be, for example, the human eye side, and the second side can be, for example, the screen side. The optical system, along the optical axis from the human eye side to the screen side, sequentially includes: a first lens E1, a second lens E2, a reflective polarizing element RP, a quarter-wave plate QWP, a third lens E3, and a partial reflective layer BS. The reflective polarizing element RP can be attached to the near-screen side of the second lens E2, and the quarter-wave plate QWP can be attached to the near-screen side of the reflective polarizing element RP. The partial reflective layer BS can have a semi-transparent, semi-reflective function. The partial reflective layer BS is, for example, but not limited to, a mirror, capable of reflecting a portion of the light. For example, in some cases, the partial reflective layer BS can be configured to allow a portion of the light to pass through while another portion is reflected.

[0046] In an exemplary implementation, such as Figure 1A As shown, the optical system according to this application also includes an aperture STO disposed on the side of the human eye and a display screen E4 disposed on the side of the screen. The user's eye can view the image projected by the display screen E4 at the position of the aperture STO. That is, the image light on the display screen E4 is finally projected to the user's eye after multiple refractions and reflections through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1.

[0047] Figure 1A A schematic diagram of the optical path refraction of the optical system according to this application is also shown. Light emitted from the display screen E4 sequentially passes through the third lens E3, the quarter-wave plate QWP, and reaches the reflective polarizing element RP. It is reflected at the reflective polarizing element RP and passes again through the quarter-wave plate QWP and the third lens E3. The beam is reflected again at the partial reflective layer BS on the near-screen side of the third lens E3 and sequentially passes through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1, passing through the aperture STO and finally exiting towards the viewer's eye. Compared to... Figure 1B The optical system described in the prior art produces ghosting, while the optical system provided in this application can significantly reduce ghosting. Furthermore, this application can fold the required optical path using a combination of light reflection and refraction, effectively shortening the length of the optical system.

[0048] To facilitate a better understanding of the present invention, Figure 1C A schematic diagram showing some parameters of an optical system according to this application is provided, as follows: Figure 1CAs shown, CT1 represents the center thickness of the first lens on the optical axis, CT2 represents the center thickness of the second lens on the optical axis, CT3 represents the center thickness of the third lens on the optical axis, T12 represents the air gap between the first and second lenses on the optical axis, T23 represents the air gap between the second and third lenses on the optical axis, R1 represents the radius of curvature of the first side of the first lens, R2 represents the radius of curvature of the second side of the first lens, R3 represents the radius of curvature of the first side of the second lens, R4 represents the radius of curvature of the second side of the second lens, R5 represents the radius of curvature of the first side of the third lens, and R6 represents the radius of curvature of the second side of the third lens.

[0049] An optical system according to an exemplary embodiment of this application includes, in sequence along the optical axis from the first side to the second side: a first lens, a second lens, a reflective polarizing element, a quarter-wave plate, and a third lens. The second side of the second lens is planar; the second side of the third lens has a partially reflective layer; and the radius of curvature R1 of the first side of the first lens, the center thickness CT1 of the first lens on the optical axis, and the Abbe number V1 of the first lens satisfy: 55.0 < R1 / CT1 + R1 / V1 < 221. The combination of the first lens, the second lens, and the third lens can converge light. Coating or applying a film to the lens surface can reverse the light path, shortening the length of the optical system. Specifically, the reflective polarizing element can reflect polarized light in a certain direction while also transmitting polarized light orthogonal to that polarization direction. The quarter-wave plate can change the state of polarized light. The partially reflective layer on the second side of the third lens can transmit half of the light and reflect the other half. Furthermore, by controlling the radius of curvature of the first side of the first lens, as well as the center thickness and Abbe number of the first lens, it is beneficial to the processing and shaping of the lens on the one hand, and to correct the chromatic aberration of the system on the other hand, thereby improving system performance and enhancing the consumer experience.

[0050] In an exemplary embodiment, the optical system of this application satisfies: -12.0 < f1 × N1 / R2 < -2.0, where f1 is the effective focal length of the first lens, N1 is the refractive index of the first lens, and R2 is the radius of curvature of the second side surface of the first lens. Satisfying -12.0 < f1 × N1 / R2 < -2.0, by controlling the effective focal length and refractive index of the first lens, as well as the radius of curvature of the second side surface of the lens, facilitates the rational allocation of optical power, enabling light convergence and improving image quality; it also helps correct system aberrations.

[0051] In an exemplary embodiment, the optical system of this application satisfies: 2.0 < f2 × N2 / R3 < 3.0, where f2 is the effective focal length of the second lens, N2 is the refractive index of the second lens, and R3 is the radius of curvature of the first side surface of the second lens. Satisfying 2.0 < f2 × N2 / R3 < 3.0 allows for the rational allocation of optical power by controlling the effective focal length of the second lens. Simultaneously, controlling the refractive index of the second lens optimizes the optical path and improves image quality. Furthermore, controlling the radius of curvature of the first side surface of the second lens reduces the height of the light rays, thereby reducing the size of the optical system.

[0052] In an exemplary embodiment, the optical system of this application satisfies: 6.0 < CT1 / T12 < 20.0, where CT1 is the center thickness of the first lens on the optical axis, and T12 is the air gap between the first and second lenses on the optical axis. Satisfying 6.0 < CT1 / T12 < 20.0, by controlling the ratio of the center thickness of the first lens to the air gap between the first and second lenses on the optical axis, is beneficial for the molding of the first lens, reducing processing difficulty; on the other hand, it effectively limits the overall length of the optical system, making the optical device more miniaturized.

[0053] In an exemplary embodiment, the optical system of this application satisfies the condition -2.5 < f3 × N3 / R6 < -1.5, where f3 is the effective focal length of the third lens, N3 is the refractive index of the third lens, and R6 is the radius of curvature of the second side surface of the third lens. By satisfying -2.5 < f3 × N3 / R6 < -1.5, and controlling the effective focal length, refractive index, and radius of curvature of the second side surface of the third lens, the optical power of the system is reasonably controlled, reducing the height of the light rays and thus minimizing ghosting caused by edge reflections of the lens; it also improves the shapeability of the third lens.

[0054] In an exemplary embodiment, the optical system of this application satisfies: 4.0 < |R5 / R6| + CT3 / T23 < 5.0, where R5 is the radius of curvature of the first side of the third lens, R6 is the radius of curvature of the second side of the third lens, CT3 is the center thickness of the third lens on the optical axis, and T23 is the air gap between the second and third lenses on the optical axis. Satisfying 4.0 < |R5 / R6| + CT3 / T23 < 5.0, by controlling the ratio of the radius of curvature of the first side of the third lens to the radius of curvature of the second side of the third lens, the center thickness of the lens, and the air gap between the second and third lenses, facilitates a more compact system, reduces the overall length of the optical system, makes the optical device lighter, and improves the user experience; furthermore, it also facilitates the processing and shaping of the third lens.

[0055] In an exemplary embodiment, the optical system of this application satisfies: 1.5 < 3 × (dqwp + T23 + CT3) / TD < 2.5, where dqwp is the center thickness of the quarter-wave plate on the optical axis, T23 is the air gap between the second and third lenses on the optical axis, CT3 is the center thickness of the third lens on the optical axis, and TD is the distance on the optical axis from the first side of the first lens to the second side of the third lens. By satisfying 1.5 < 3 × (dqwp + T23 + CT3) / TD < 2.5, and by controlling the center thickness of the quarter-wave plate, the air gap between the second and third lenses, the center thickness of the third lens, and the distance on the optical axis from the first side of the first lens to the second side of the third lens, the tolerances in the lens assembly process are reasonably allocated, effectively limiting the total length of the system's optical path, making the system more compact, and reducing the weight of the equipment; at the same time, it facilitates the attachment or coating of the quarter-wave plate onto the lens, reducing the difficulty of the coating or coating process.

[0056] In an exemplary embodiment, the optical system of this application satisfies: 0.5 < CT3 / (CT1+CT2+drp+dqwp) < 2.0, where CT1 is the center thickness of the first lens on the optical axis, CT2 is the center thickness of the second lens on the optical axis, CT3 is the center thickness of the third lens on the optical axis, dqwp is the center thickness of the quarter-wave plate on the optical axis, and drp is the center thickness of the reflective polarizing element on the optical axis. By satisfying 0.5 < CT3 / (CT1+CT2+drp+dqwp) < 2.0, and by controlling the center thicknesses of the first and second lenses, as well as the center thicknesses of the quarter-wave plate and the reflective polarizing element, the lens thickness is effectively allocated, making the system more compact and optimizing the light path, while also improving the shapeability of the first and second lenses.

[0057] In an exemplary embodiment, the optical system of this application satisfies: -2.5 < f3 × tan(Semi-FOV) / R6 < -1.5, where f3 is the effective focal length of the third lens, Semi-FOV is the maximum half-field-of-view of the optical system, and R6 is the radius of curvature of the second side surface of the third lens. By satisfying -2.5 < f3 × tan(Semi-FOV) / R6 < -1.5, and by controlling the tangent of the effective focal length and maximum half-field-of-view of the third lens, as well as the radius of curvature of the second side surface of the third lens, the height of the light rays can be further constrained while maintaining the field of view, thereby reducing the size of the display screen and, on the other hand, reducing ghosting introduced by reflections from the display screen and lens.

[0058] In an exemplary embodiment, the optical system of this application satisfies: 4.0 < |R1 / R3| + V2 / V1 < 7.0, where R1 is the radius of curvature of the first side surface of the first lens, R3 is the radius of curvature of the first side surface of the second lens, V2 is the Abbe number of the second lens, and V1 is the Abbe number of the first lens. Satisfying 4.0 < |R1 / R3| + V2 / V1 < 7.0, by controlling the radius of curvature of the first side surfaces of the first and second lenses, as well as the Abbe numbers of the first and second lenses, helps to reduce chromatic aberration and improve the relative illumination and imaging quality of the system; furthermore, it also ensures good manufacturability of the lenses.

[0059] In an exemplary embodiment, the optical system of this application satisfies: 1.0 < |f2| / (Vrp+Vqwp) < 2.5, where f2 is the effective focal length of the second lens, Vrp is the Abbe number of the reflective polarizing element, and Vqwp is the Abbe number of the quarter-wave plate. By satisfying 1.0 < |f2| / (Vrp+Vqwp) < 2.5, and controlling the effective focal length of the second lens, the Abbe number of the reflective polarizing element, and the Abbe number of the quarter-wave plate, the optical power of the second lens is made more reasonable, while reducing the chromatic aberration introduced by the reflective polarizing element and the quarter-wave plate, thus improving the imaging quality of the system.

[0060] In an exemplary embodiment, the effective focal length f1 of the first lens may be in the range of -1167.0 mm to 78.0 mm, the effective focal length f2 of the second lens may be in the range of -158.0 mm to 230.0 mm, and the effective focal length f3 of the third lens may be in the range of 146.0 mm to 212.0 mm.

[0061] According to some embodiments of this application, the optical system of this application is a small-volume optical system with high-definition imaging quality. In application, the optical system according to exemplary embodiments of this application can be applied to VR devices. By reasonably setting the effective focal length, maximum field of view, entrance pupil diameter, and lens parameters such as center thickness, refractive index, Abbe number, and radius of curvature of the optical system, and by reasonably setting the aperture stop parameters, the wide-angle purpose of the VR device can be met, as well as the chromatic aberration of the system can be corrected, thereby improving the system's imaging quality.

[0062] In an exemplary embodiment, the optical system provided in this application can be applied to, for example, VR devices, with the first side being, for example, the human eye side, and the second side being, for example, the screen side.

[0063] Specific embodiments of the optical system applicable to the above-described embodiments are further described below with reference to the accompanying drawings.

[0064] Example 1

[0065] The following is for reference Figures 2 to 3C The optical system according to Embodiment 1 of this application is described. Figure 2 A schematic diagram of the structure of an optical system according to Embodiment 1 of this application is shown.

[0066] like Figure 2 As shown, the optical system, from the human eye side to the screen side, includes, in sequence: aperture STO, first lens E1, second lens E2, reflective polarizing element RP, quarter-wave plate QWP, third lens E3, partial reflective layer BS, and display screen E4.

[0067] The first lens E1 has positive optical power, with a convex surface near both the human eye and the screen. The second lens E2 has negative optical power, with a concave surface near the human eye and a flat surface near the screen. The third lens E3 has positive optical power, with a convex surface near both the human eye and the screen. A reflective polarizing element RP is attached to the screen side of the second lens E2, and a quarter-wave plate QWP is attached to the screen side of the reflective polarizing element RP. A partial reflective layer BS is attached to the screen side of the third lens E3.

[0068] In this example, a light source may be provided on the display screen E4. The image light from the display screen E4 passes sequentially through the third lens E3, the quarter-wave plate QWP, and reaches the reflective polarizing element RP. It is reflected for the first time at the reflective polarizing element RP and passes through the quarter-wave plate QWP and the third lens E3 again. The light beam is reflected for the second time at the partial reflective layer BS on the near-screen side of the third lens E3 and passes sequentially through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1. It passes through the aperture STO and finally exits towards the human eye.

[0069] In this example, the effective focal length f1 of the first lens is 75.94 mm, the effective focal length f2 of the second lens is -153.86 mm, the effective focal length f3 of the third lens is 211.87 mm, and the maximum semi-field of view (Semi-FOV) of the optical system is 53.0°.

[0070] Table 1 shows the basic parameters of the optical system of Embodiment 1, where the units for radius of curvature and thickness are millimeters (mm). Image light from display screen E4 passes through each component in the order of number 16 to number 1 and is finally projected onto the target object in space, such as the human eye.

[0071]

[0072] Table 1

[0073] In Example 1, the near-eye side and near-screen side of the first lens E1, the near-eye side of the second lens E2, and the near-eye side and near-screen side of the third lens E3 are all aspherical. The surface shape of each aspherical lens is... The following aspherical formulas can be used for limitation:

[0074] (1)

[0075] in, For an aspherical surface along the optical axis at a height of h When the position is such that the distance from the vertex of the aspherical surface is the height vector; 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 above); k is the conic coefficient, which is 0 in this embodiment and the following embodiments; Ai is the i-th order correction coefficient of the aspherical surface. Table 2 below gives the higher-order coefficients A4, A6, A8 and A10 that can be used for each aspherical mirror in Embodiment 1.

[0076]

[0077] Table 2

[0078] Figure 3A The on-axis chromatic aberration curve of the optical system of Embodiment 1 is shown, which represents the deviation of light of different wavelengths from the convergence focal point after passing through the lens. Figure 3B The astigmatism curves of the optical system of Embodiment 1 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 3C The distortion curves of the optical system of Example 1 are shown, representing the distortion magnitude values ​​corresponding to different half-field angles. According to... Figures 3A to 3C It can be seen that the optical system given in Example 1 can achieve good imaging quality.

[0079] Example 2

[0080] The following is for reference Figures 4 to 5C An optical system according to Embodiment 2 of this application is described. In this embodiment and the following embodiments, for the sake of brevity, descriptions similar to those in Embodiment 1 will be omitted. Figure 4 A schematic diagram of the structure of an optical system according to Embodiment 2 of this application is shown.

[0081] like Figure 4 As shown, the optical system, from the human eye side to the screen side, includes, in sequence: aperture STO, first lens E1, second lens E2, reflective polarizing element RP, quarter-wave plate QWP, third lens E3, partial reflective layer BS, and display screen E4.

[0082] The first lens E1 has negative optical power, with a convex surface near the human eye and a concave surface near the screen. The second lens E2 has positive optical power, with a convex surface near the human eye and a flat surface near the screen. The third lens E3 has positive optical power, with a convex surface near both the human eye and screen. A reflective polarizing element RP is attached to the near-screen side of the second lens E2, and a quarter-wave plate QWP is attached to the near-screen side of the reflective polarizing element RP. A partial reflective layer BS is attached to the near-screen side of the third lens E3.

[0083] In this example, a light source may be provided on the display screen E4. The image light from the display screen E4 passes sequentially through the third lens E3, the quarter-wave plate QWP, and reaches the reflective polarizing element RP. It is reflected for the first time at the reflective polarizing element RP and passes through the quarter-wave plate QWP and the third lens E3 again. The light beam is reflected for the second time at the partial reflective layer BS on the near-screen side of the third lens E3 and passes sequentially through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1. It passes through the aperture STO and finally exits towards the human eye.

[0084] In this example, the effective focal length f1 of the first lens is -732.57mm, the effective focal length f2 of the second lens is 209.72mm, the effective focal length f3 of the third lens is 158.04mm, and the maximum semi-FOV of the optical system is 53.0°.

[0085] Table 3 shows the basic parameters of the optical system of Embodiment 2, where the units for radius of curvature and thickness are millimeters (mm). Image light from display screen E4 passes through each component in the order of number 16 to number 1 and is finally projected onto the target object in space, such as the human eye. Table 4 shows the higher-order coefficients that can be used for each aspherical mirror in Embodiment 2, where each aspherical surface shape can be defined by formula (1) given in Embodiment 1 above.

[0086]

[0087] Table 3

[0088]

[0089] Table 4

[0090] Figure 5A The on-axis chromatic aberration curve of the optical system of Embodiment 2 is shown, which represents the deviation of light of different wavelengths from the convergence focal point after passing through the lens. Figure 5B The astigmatism curves of the optical system of Embodiment 2 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 5CThe distortion curves of the optical system in Example 2 are shown, representing the distortion magnitudes corresponding to different half-field angles. According to... Figures 5A to 5C It can be seen that the optical system given in Example 2 can achieve good imaging quality.

[0091] Example 3

[0092] The following is for reference Figures 6 to 7C An optical system according to Embodiment 3 of this application is described. Figure 6 A schematic diagram of the structure of an optical system according to Embodiment 3 of this application is shown.

[0093] like Figure 6 As shown, the optical system, from the human eye side to the screen side, includes, in sequence: aperture STO, first lens E1, second lens E2, reflective polarizing element RP, quarter-wave plate QWP, third lens E3, partial reflective layer BS, and display screen E4.

[0094] The first lens E1 has negative optical power, with a convex surface near the human eye and a concave surface near the screen. The second lens E2 has positive optical power, with a convex surface near the human eye and a flat surface near the screen. The third lens E3 has positive optical power, with a convex surface near both the human eye and screen. A reflective polarizing element RP is attached to the near-screen side of the second lens E2, and a quarter-wave plate QWP is attached to the near-screen side of the reflective polarizing element RP. A partial reflective layer BS is attached to the near-screen side of the third lens E3.

[0095] In this example, a light source may be provided on the display screen E4. The image light from the display screen E4 passes sequentially through the third lens E3, the quarter-wave plate QWP, and reaches the reflective polarizing element RP. It is reflected for the first time at the reflective polarizing element RP and passes through the quarter-wave plate QWP and the third lens E3 again. The light beam is reflected for the second time at the partial reflective layer BS on the near-screen side of the third lens E3 and passes sequentially through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1. It passes through the aperture STO and finally exits towards the human eye.

[0096] In this example, the effective focal length f1 of the first lens is -1077.83mm, the effective focal length f2 of the second lens is 229.74mm, the effective focal length f3 of the third lens is 147.17mm, and the maximum semi-field of view (Semi-FOV) of the optical system is 53.0°.

[0097] Table 5 shows the basic parameters of the optical system of Embodiment 3, where the units for radius of curvature and thickness are millimeters (mm). Image light from display screen E4 passes through each component in the order of number 16 to number 1 and is finally projected onto the target object in space, such as the human eye. Table 6 shows the higher-order coefficients that can be used for each aspherical mirror in Embodiment 3, where each aspherical surface shape can be defined by formula (1) given in Embodiment 1 above.

[0098]

[0099] Table 5

[0100]

[0101] Table 6

[0102] Figure 7A The on-axis chromatic aberration curve of the optical system of Embodiment 3 is shown, which represents the deviation of light of different wavelengths from the convergence focal point after passing through the lens. Figure 7B The astigmatism curves of the optical system of Embodiment 3 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 7C The distortion curves of the optical system in Example 3 are shown, representing the distortion magnitudes corresponding to different half-field angles. According to... Figures 7A to 7C It can be seen that the optical system given in Example 3 can achieve good imaging quality.

[0103] Example 4

[0104] The following is for reference Figures 8 to 9C An optical system according to Embodiment 4 of this application is described. Figure 8 A schematic diagram of the structure of an optical system according to Embodiment 4 of this application is shown.

[0105] like Figure 8 As shown, the optical system, from the human eye side to the screen side, includes, in sequence: aperture STO, first lens E1, second lens E2, reflective polarizing element RP, quarter-wave plate QWP, third lens E3, partial reflective layer BS, and display screen E4.

[0106] The first lens E1 has positive optical power, with a convex surface near both the human eye and the screen. The second lens E2 has negative optical power, with a concave surface near the human eye and a flat surface near the screen. The third lens E3 has positive optical power, with a convex surface near both the human eye and the screen. A reflective polarizing element RP is attached to the screen side of the second lens E2, and a quarter-wave plate QWP is attached to the screen side of the reflective polarizing element RP. A partial reflective layer BS is attached to the screen side of the third lens E3.

[0107] In this example, a light source may be provided on the display screen E4. The image light from the display screen E4 passes sequentially through the third lens E3, the quarter-wave plate QWP, and reaches the reflective polarizing element RP. It is reflected for the first time at the reflective polarizing element RP and passes through the quarter-wave plate QWP and the third lens E3 again. The light beam is reflected for the second time at the partial reflective layer BS on the near-screen side of the third lens E3 and passes sequentially through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1. It passes through the aperture STO and finally exits towards the human eye.

[0108] In this example, the effective focal length f1 of the first lens is 77.45 mm, the effective focal length f2 of the second lens is -157.47 mm, the effective focal length f3 of the third lens is 210.41 mm, and the maximum semi-field of view (Semi-FOV) of the optical system is 53.0°.

[0109] Table 7 shows the basic parameters of the optical system of Embodiment 4, where the units for radius of curvature and thickness are millimeters (mm). Image light from display screen E4 passes through each component in the order of number 16 to number 1 and is finally projected onto the target object in space, such as the human eye. Table 8 shows the higher-order coefficients that can be used for each aspherical mirror in Embodiment 4, where each aspherical surface shape can be defined by formula (1) given in Embodiment 1 above.

[0110]

[0111] Table 7

[0112]

[0113] Table 8

[0114] Figure 9A The on-axis chromatic aberration curve of the optical system of Embodiment 4 is shown, which represents the deviation of light of different wavelengths from the convergence focal point after passing through the lens. Figure 9B The astigmatism curves of the optical system of Example 4 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 9C The distortion curves of the optical system in Example 4 are shown, representing the distortion magnitudes corresponding to different half-field angles. According to... Figures 9A to 9C It can be seen that the optical system given in Example 4 can achieve good imaging quality.

[0115] Example 5

[0116] The following is for reference Figures 10 to 11C An optical system according to Embodiment 5 of this application is described. Figure 10 A schematic diagram of the structure of an optical system according to Embodiment 5 of this application is shown.

[0117] like Figure 10 As shown, the optical system, from the human eye side to the screen side, includes, in sequence: aperture STO, first lens E1, second lens E2, reflective polarizing element RP, quarter-wave plate QWP, third lens E3, partial reflective layer BS, and display screen E4.

[0118] The first lens E1 has negative optical power, with a convex surface near the human eye and a concave surface near the screen. The second lens E2 has positive optical power, with a convex surface near the human eye and a flat surface near the screen. The third lens E3 has positive optical power, with a convex surface near both the human eye and screen. A reflective polarizing element RP is attached to the near-screen side of the second lens E2, and a quarter-wave plate QWP is attached to the near-screen side of the reflective polarizing element RP. A partial reflective layer BS is attached to the near-screen side of the third lens E3.

[0119] In this example, a light source may be provided on the display screen E4. The image light from the display screen E4 passes sequentially through the third lens E3, the quarter-wave plate QWP, and reaches the reflective polarizing element RP. It is reflected for the first time at the reflective polarizing element RP and passes through the quarter-wave plate QWP and the third lens E3 again. The light beam is reflected for the second time at the partial reflective layer BS on the near-screen side of the third lens E3 and passes sequentially through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1. It passes through the aperture STO and finally exits towards the human eye.

[0120] In this example, the effective focal length f1 of the first lens is -1166.01mm, the effective focal length f2 of the second lens is 223.01mm, the effective focal length f3 of the third lens is 146.73mm, and the maximum semi-FOV of the optical system is 53.0°.

[0121] Table 9 shows the basic parameters of the optical system of Embodiment 5, where the units for radius of curvature and thickness are millimeters (mm). Image light from display screen E4 passes through each component in the order of number 16 to number 1 and is finally projected onto the target object in space, such as the human eye. Table 10 shows the higher-order coefficients that can be used for each aspherical mirror in Embodiment 5, where each aspherical surface shape can be defined by formula (1) given in Embodiment 1 above.

[0122]

[0123] Table 9

[0124]

[0125] Table 10

[0126] Figure 11AThe on-axis chromatic aberration curve of the optical system of Embodiment 5 is shown, which represents the deviation of light of different wavelengths from the convergence focal point after passing through the lens. Figure 11B The astigmatism curves of the optical system of Example 5 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 11C The distortion curves of the optical system in Example 5 are shown, representing the distortion magnitudes corresponding to different half-field angles. According to... Figures 11A to 11C It can be seen that the optical system given in Example 5 can achieve good imaging quality.

[0127] Example 6

[0128] The following is for reference Figures 12 to 13C An optical system according to Embodiment 6 of this application is described. Figure 12 A schematic diagram of the structure of an optical system according to Embodiment 6 of this application is shown.

[0129] like Figure 12 As shown, the optical system, from the human eye side to the screen side, includes, in sequence: aperture STO, first lens E1, second lens E2, reflective polarizing element RP, quarter-wave plate QWP, third lens E3, partial reflective layer BS, and display screen E4.

[0130] The first lens E1 has negative optical power, with a convex surface near the human eye and a concave surface near the screen. The second lens E2 has positive optical power, with a convex surface near the human eye and a flat surface near the screen. The third lens E3 has positive optical power, with a convex surface near both the human eye and screen. A reflective polarizing element RP is attached to the near-screen side of the second lens E2, and a quarter-wave plate QWP is attached to the near-screen side of the reflective polarizing element RP. A partial reflective layer BS is attached to the near-screen side of the third lens E3.

[0131] In this example, a light source may be provided on the display screen E4. The image light from the display screen E4 passes sequentially through the third lens E3, the quarter-wave plate QWP, and reaches the reflective polarizing element RP. It is reflected for the first time at the reflective polarizing element RP and passes through the quarter-wave plate QWP and the third lens E3 again. The light beam is reflected for the second time at the partial reflective layer BS on the near-screen side of the third lens E3 and passes sequentially through the third lens E3, the quarter-wave plate QWP, the reflective polarizing element RP, the second lens E2, and the first lens E1. It passes through the aperture STO and finally exits towards the human eye.

[0132] In this example, the effective focal length f1 of the first lens is -603.37mm, the effective focal length f2 of the second lens is 210.55mm, the effective focal length f3 of the third lens is 156.54mm, and the maximum semi-field of view (Semi-FOV) of the optical system is 53.0°.

[0133] Table 11 shows the basic parameters of the optical system of Embodiment 6, where the units for radius of curvature and thickness are millimeters (mm). Image light from display screen E4 passes through each component in the order of number 16 to number 1 and is finally projected onto a target object in space, such as a human eye. Table 12 shows the higher-order coefficients that can be used for each aspherical mirror in Embodiment 6, where each aspherical surface shape can be defined by formula (1) given in Embodiment 1 above.

[0134]

[0135] Table 11

[0136]

[0137] Table 12

[0138] Figure 13A The on-axis chromatic aberration curve of the optical system of Embodiment 6 is shown, which represents the deviation of light of different wavelengths from the convergence focal point after passing through the lens. Figure 13B The astigmatism curves of the optical system of Embodiment 6 are shown, representing the meridional image plane curvature and the sagittal image plane curvature. Figure 13C The distortion curves of the optical system in Example 6 are shown, representing the distortion magnitudes corresponding to different half-field angles. According to... Figures 13A to 13C It can be seen that the optical system given in Example 6 can achieve good imaging quality.

[0139] In summary, the relationships of the optical systems in Examples 1 to 6 are shown in Table 13.

[0140]

[0141] Table 13

[0142] This application also provides an optical device, which can be a stand-alone projection device such as a projector, or a projection module integrated into a mobile electronic device such as a VR device. The optical device is equipped with the optical system described above.

[0143] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of protection involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the concept of this application. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An optical system, characterized in that, Along the optical axis, from the first side to the second side, it sequentially includes: a first lens, a second lens, a reflective polarizing element, a quarter-wave plate, and a third lens, wherein... The first side surface of the first lens is a convex surface; The second side surface of the second lens is a plane; The third lens has positive optical power, and both its first and second sides are convex surfaces, with a partial reflective layer disposed on its second side; and The reflective polarizing element is disposed on the second side of the second lens, and the quarter-wave plate is disposed on the second side of the reflective polarizing element; The optical system has three lenses with optical power. The radius of curvature R1 of the first side surface of the first lens, the center thickness CT1 of the first lens on the optical axis and the Abbe number V1 of the first lens satisfy: 55.10≤R1 / CT1+R1 / V1≤220.17; The center thickness CT1 of the first lens on the optical axis and the air gap T12 between the first lens and the second lens on the optical axis satisfy: 6.0 < CT1 / T12 ≤ 19.

48.

2. The optical system according to claim 1, characterized in that, The effective focal length f1 of the first lens, the refractive index N1 of the first lens, and the radius of curvature R2 of the second side surface of the first lens satisfy the following: -11.18≤f1×N1 / R2≤-2.

81.

3. The optical system according to claim 1, characterized in that, The effective focal length f2 of the second lens, the refractive index N2 of the second lens, and the radius of curvature R3 of the first side surface of the second lens satisfy the following: 2.47≤f2×N2 / R3<3.

0.

4. The optical system according to claim 1, characterized in that, The effective focal length f3 of the third lens, the refractive index N3 of the third lens, and the radius of curvature R6 of the second side surface of the third lens satisfy the following: -2.34≤f3×N3 / R6≤-1.

84.

5. The optical system according to claim 1, characterized in that, The radius of curvature R5 of the first side surface of the third lens, the radius of curvature R6 of the second side surface of the third lens, the center thickness CT3 of the third lens on the optical axis, and the air gap T23 between the second lens and the third lens on the optical axis satisfy the following: 4.11≤|R5 / R6|+CT3 / T23≤4.

46.

6. The optical system according to claim 1, characterized in that, The center thickness dqwp of the quarter-wave plate on the optical axis, the air gap T23 between the second lens and the third lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, and the distance TD from the first side of the first lens to the second side of the third lens on the optical axis satisfy: 1.84≤3×(dqwp+T23+CT3) / TD≤2.

14.

7. The optical system according to claim 1, characterized in that, The center thickness CT1 of the first lens on the optical axis, the center thickness CT2 of the second lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, the center thickness dqwp of the quarter-wave plate on the optical axis, and the center thickness drp of the reflective polarizing element on the optical axis satisfy: 0.86≤CT3 / (CT1+CT2+drp+dqwp)≤1.

62.

8. The optical system according to any one of claims 1 to 7, characterized in that, The effective focal length f3 of the third lens, the maximum semi-FOV of the optical system, and the radius of curvature R6 of the second side surface of the third lens satisfy: -2.10≤f3×tan(Semi-FOV) / R6≤-1.

58.

9. The optical system according to any one of claims 1 to 7, characterized in that, The radius of curvature R1 of the first side surface of the first lens, the radius of curvature R3 of the first side surface of the second lens, the Abbe number V2 of the second lens and the Abbe number V1 of the first lens satisfy: 4.37≤|R1 / R3|+V2 / V1≤6.

50.

10. The optical system according to any one of claims 1 to 7, characterized in that, The effective focal length f2 of the second lens, the Abbe number Vrp of the reflective polarizing element, and the Abbe number Vqwp of the quarter-wave plate satisfy the following: 1.35≤|f2| / (Vrp+Vqwp)≤2.

02.

11. An optical device comprising the optical system as described in any one of claims 1 to 10.

Images