Optical system and optical apparatus including the same
By designing an optical system with polarization reversal optical path, the problem of long and complex optical paths in traditional VR/AR headset optical systems is solved, and better imaging quality and polarization performance are achieved, improving user experience.
Patent Information
- Application Number
- CN202421866752.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-02
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2034-08-02
AI Technical Summary
The optical system of traditional VR/AR headsets has optical distortion and large volume due to the long optical path. The optical path of the foldback optical system is complex. The different assembly positions of the lens and reflective elements lead to different performances, making it difficult to design an optical system with good imaging quality.
An optical system with a polarization reversing optical path is designed. By reasonably configuring the spatial arrangement and filming of lenses, reflective polarization elements and quarter-wave plates, the polarization performance of the optical system is controlled and the polarization characteristics of the optical system is controlled.
The balance of imaging quality, polarization performance and design complexity of the optical system is achieved, optical distortion is reduced, image clarity and stability is improved, and users have a better sense of immersion and user experience.
Smart Images
Figure CN222994757U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of optical elements, and more particularly, to an optical system and an optical device including the optical system. Background Art
[0002] VR (Virtual Reality) and AR (Augmented Reality) headsets are interactive devices based on optical and computer technologies, which can immerse users in virtual or augmented reality environments. With the continuous progress of technology, VR / AR headsets have been widely used in fields such as entertainment, education, and healthcare. In order to provide a more real and vivid virtual experience with VR / AR headsets, higher requirements are placed on the optical systems in the headsets.
[0003] The optical systems of traditional VR / AR headsets usually adopt a straight optical path, that is, light directly enters the user's eyes from the display screen through a lens. The optical path of this structure is relatively long, which easily leads to problems such as optical distortion and large volume. To solve these problems, the folded optical system has become one of the research hotspots for current VR / AR headsets. The folded optical system has the advantages of shortening the total length of the optical path, saving assembly space, and reducing weight. However, the optical path of the folded optical system is relatively complex, and different assembly positions of the lens and the reflecting element will result in different performances of the optical system. Therefore, reasonably designing the arrangement of the lens and the reflecting element to obtain a folded optical system with good imaging quality is one of the important research topics for those skilled in the art at present. Summary of the Utility Model
[0004] A first aspect of the present application provides an optical system. The optical system sequentially includes, from a first side to a second side along the optical axis: a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer. Among them, the first lens has a positive optical power, and its first side is convex; the second lens has a negative optical power, its first side is flat, and its second side is concave; the third lens has a positive optical power, and its first side is convex; the first quarter-wave plate is placed on the first side of the second lens and at least partially adheres to the first side of the second lens; the reflective polarizing element is placed on the first side of the first quarter-wave plate and at least partially adheres to the first side of the first quarter-wave plate; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate; the effective focal length f of the optical system and the effective focal length f2 of the second lens satisfy: -0.8 < f / f2 < -0.2; and the combined focal length FG1 of the reflective polarizing element, the first quarter-wave plate, and the second lens and the radius of curvature R4 of the second side of the second lens satisfy: -1.5 < FG1 / R4 < -1.1.
[0005] In one embodiment, the optical system satisfies: 0.3 < f1 / f3 < 0.5, where f1 is the effective focal length of the first lens and f3 is the effective focal length of the third lens.
[0006] In one embodiment, the optical system satisfies: 1.4 < (CT1 + T12) / (CTR + CTQ1 + CT2) < 2.1, where CT1 is the central thickness of the first lens on the optical axis, T12 is the axial distance from the second side of the first lens to the first side of the second lens, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ1 is the central thickness of the first quarter-wave plate on the optical axis, and CT2 is the central thickness of the second lens on the optical axis.
[0007] In one embodiment, the optical system satisfies: 2.0 < f / R1 < 2.4, where f is the effective focal length of the optical system and R1 is the radius of curvature of the first side of the first lens.
[0008] In one embodiment, the optical system satisfies: 0.45 < N4 / (NQ2 + NL) < 0.65, where N4 is the refractive index of the fourth lens, NQ2 is the refractive index of the second quarter-wave plate, and NL is the refractive index of the polarizer.
[0009] In one embodiment, the optical system satisfies: 5.2 ≤ CT4 / (CTQ2 + CTL) < 6.9, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, and CTL is the central thickness of the polarizer on the optical axis.
[0010] In one embodiment, the optical system satisfies: 0.4 < R5 / R4 < 1.7, where R5 is the radius of curvature of the first side surface of the third lens, and R4 is the radius of curvature of the second side surface of the second lens.
[0011] In one embodiment, the optical system satisfies: 1.68 < N2 < 1.86 and 23.7 < V2 < 31.2, where N2 is the refractive index of the second lens, and V2 is the dispersion coefficient of the second lens.
[0012] In one embodiment, the optical system satisfies: 3.0 < TD / CT3 < 3.5, where TD is the distance on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens, and CT3 is the central thickness of the third lens on the optical axis.
[0013] In one embodiment, the optical system satisfies: 0.4 < EPD / f1 < 0.8, where EPD is the entrance pupil diameter of the optical system, and f1 is the effective focal length of the first lens.
[0014] In one embodiment, the optical system satisfies: 1.1 < FG2 / R7 < 2.1, where FG2 is the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer, and R7 is the radius of curvature of the first side surface of the fourth lens.
[0015] In one embodiment, the optical system satisfies: 0.7 < SAG11 / CT1 < 1.1, where SAG11 is the axial distance between the intersection point of the first side surface of the first lens and the optical axis and the vertex of the effective radius of the first side surface of the first lens, and CT1 is the central thickness of the first lens on the optical axis.
[0016] In one embodiment, the optical system satisfies: 1.2 < T34 / |SAG41| < 1.6, where T34 is the axial distance from the second side surface of the third lens to the first side surface of the fourth lens, and SAG41 is the axial distance between the intersection point of the first side surface of the fourth lens and the optical axis and the vertex of the effective radius of the first side surface of the fourth lens.
[0017] In one embodiment, the optical system satisfies: 1.8 < f / ∑CT < 2.6, where f is the effective focal length of the optical system, and ∑CT is the sum of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis.
[0018] A second aspect of the present application provides an optical system. Along the optical axis, the optical system sequentially includes, from the first side to the second side: a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer. The first lens has a positive optical power, and its first side is convex; the second lens has a negative optical power, its first side is flat, and its second side is concave; the third lens has a positive optical power, and its first side is convex; the first quarter-wave plate is placed on the first side of the second lens and at least partially adheres to the first side of the second lens; the reflective polarizing element is placed on the first side of the first quarter-wave plate and at least partially adheres to the first side of the first quarter-wave plate; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate; the effective focal length f of the optical system and the effective focal length f2 of the second lens satisfy: -0.8 < f / f2 < -0.2; and the refractive index N4 of the fourth lens, the refractive index NQ2 of the second quarter-wave plate, and the refractive index NL of the polarizer satisfy: 0.45 < N4 / (NQ2 + NL) < 0.65.
[0019] A third aspect of the present application further provides an optical device, which includes the optical system provided by any one of the above-described embodiments.
[0020] The optical system provided by the present application adopts a polarization folding optical path design. By reasonably configuring the spatial arrangement and film attachment method of the lens, the reflective polarizing element, and the quarter-wave plate, on the premise of satisfying -0.8 < f / f2 < -0.2, the ratio of the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the second lens to the curvature radius of the second side of the second lens is controlled to satisfy -1.5 < FG1 / R4 < -1.1, which helps to control the polarization performance of the optical system, can realize the control of the polarization characteristics of the optical system, and is very beneficial for applications in the folding optical path that requires a specific polarization state. At the same time, it can also balance the imaging quality, polarization performance, and design complexity of the optical system, thereby achieving better overall performance, and helping the VR / AR head-mounted device to achieve better immersion and user experience. Description of the Drawings
[0021] In combination with the drawings, through the following detailed description of non-limiting embodiments, other features, purposes, and advantages of the present application will become more obvious. In the drawings:
[0022] Figure 1 A schematic structural diagram of the optical system according to Embodiment 1 of the present application is shown;
[0023] Figures 2A to 2Drespectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical system according to Embodiment 1 of the present application;
[0024] Figure 3 shows a schematic structural diagram of the optical system according to Embodiment 2 of the present application;
[0025] Figures 4A to 4D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical system according to Embodiment 2 of the present application;
[0026] Figure 5 shows a schematic structural diagram of the optical system according to Embodiment 3 of the present application;
[0027] Figures 6A to 6D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical system according to Embodiment 3 of the present application;
[0028] Figure 7 shows a schematic structural diagram of the optical system according to Embodiment 4 of the present application;
[0029] Figures 8A to 8D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical system according to Embodiment 4 of the present application;
[0030] Figure 9 shows a schematic structural diagram of the optical system according to Embodiment 5 of the present application; and
[0031] Figures 10A to 10D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical system according to Embodiment 5 of the present application. Detailed implementation manners
[0032] To better understand the present application, more detailed descriptions of various aspects of the present application will be made with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the exemplary embodiments of the present application and do not limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.
[0033] It should be noted that in this specification, the expressions such as first and second are only used to distinguish one feature from another feature and do not represent any limitation on the feature. Therefore, without departing from the teachings of the present application, the first lens discussed below may also be referred to as the second lens, and the second lens may also be referred to as the first lens.
[0034] In the drawings, for the sake of clarity, the thickness, dimensions, and shape of the lenses have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are presented by way of example. That is, the spherical or aspherical shapes are not limited to those shown in the drawings. The drawings are provided by way of example and are not drawn to an exact scale.
[0035] In this document, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region.
[0036] It should also be understood that the terms "comprises," "comprising," "has," "including," and / or "containing," when used in this specification, denote the presence of the stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Further, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of listed features rather than individual elements in the list. Additionally, when describing embodiments of the present application, the use of "may" indicates "one or more embodiments of the present application." And the term "exemplary" is intended to refer to an example or illustration.
[0037] Unless otherwise defined, all terms used herein (including technical and scientific terms) 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 (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formalized sense unless expressly so defined herein.
[0038] It should be noted that, without conflict, the embodiments and features in the embodiments of the present application may be combined with each other. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.
[0039] The features, principles, and other aspects of the present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.
[0040] An optical system according to an exemplary embodiment of the present application sequentially includes, along the optical axis from a first side to a second side: a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partially reflective element, a fourth lens, a second quarter-wave plate, and a polarizer.
[0041] Those skilled in the art should understand that a reflective polarizing element can reflect polarized light in a certain direction and also transmit polarized light orthogonal to that polarization direction. A quarter-wave plate can change the state of polarized light. By using the combination of light reflection and refraction of a reflective polarizing element and a quarter-wave plate, the required optical path can be folded, effectively shortening the length of the optical system.
[0042] In an exemplary embodiment, the first quarter-wave plate is disposed on the first side of the second lens and at least partially attached to the first side of the second lens; the reflective polarizing element is disposed on the first side of the first quarter-wave plate and at least partially attached to the first side of the first quarter-wave plate. Exemplarily, the reflective polarizing element and the first quarter-wave plate can be compounded and attached to the first side of the second lens through a single attachment process, rather than attaching them separately in two times, reducing the angular position error caused by attachment and improving the imaging quality.
[0043] In an exemplary embodiment, the second quarter-wave plate is disposed on the second side of the fourth lens and at least partially attached to the second side of the fourth lens; the polarizer is disposed on the second side of the second quarter-wave plate and at least partially attached to the second side of the second quarter-wave plate. Exemplarily, the second quarter-wave plate and the polarizer can be compounded and attached to the second side of the fourth lens through a single attachment process, rather than attaching them separately in two times, reducing the angular position error caused by attachment and improving the imaging quality.
[0044] In an exemplary embodiment, the optical system according to the present application can be applied to, for example, a VR device. The first side can be, for example, the human eye side, and the second side can be, for example, the screen side. As Figure 1 shown, the optical system along the optical axis from the human eye side to the screen side sequentially includes: a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, and a polarizer LP. Among them, the reflective polarizing element RP is attached to the human eye side surface of the first quarter-wave plate QWP1, and the first quarter-wave plate QWP1 is attached to the human eye side surface of the second lens E2; the second quarter-wave plate QWP2 is attached to the screen side surface of the fourth lens E4, and the polarizer LP is attached to the screen side surface of the second quarter-wave plate QWP2. The partial reflection element BS can have a semi-transmissive and semi-reflective function and is attached to the screen side surface of the third lens E3.
[0045] In an exemplary embodiment, as Figure 1 shown, the optical system according to the present application further includes a diaphragm STO disposed on the human eye side and an image plane IMG disposed on the screen side. Optionally, Figure 1The optical system shown may further include a protective glass GL for protecting the light-emitting element located on the image plane IMA. The user's eyes can view the image projected by the image plane IMG at the position of the aperture STO, that is, the image light on the image plane IMG passes through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, etc., and is finally projected onto the user's eyes after multiple refractions and reflections. Specifically, Figure 1 A schematic diagram of the optical path folding-back of the optical system according to the present application is also shown. The light emitted from the image plane IMG sequentially passes through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, where it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The part of the light beam on the near-screen side of the third lens E3 is reflected again by the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, then passes through the aperture STO and finally exits toward the human eye side.
[0046] In an exemplary embodiment, the first lens has a positive optical power, and its first side is a convex surface; the second lens has a negative optical power, its first side is a flat surface, and its second side is a concave surface; the third lens has a positive optical power, and its first side is a convex surface.
[0047] In an exemplary embodiment, the effective focal length f of the optical system and the effective focal length f2 of the second lens satisfy: -0.8 < f / f2 < -0.2.
[0048] In an exemplary embodiment, the combined focal length FG1 of the reflective polarizing element, the first quarter-wave plate, and the second lens and the radius of curvature R4 of the second side of the second lens satisfy: -1.5 < FG1 / R4 < -1.1.
[0049] The optical system provided by the present application can use four lenses, and the positive and negative optical powers of the four lenses are arranged alternately, which is beneficial to reducing the sensitivity of the optical system to environmental conditions and improving the stability and reliability of the system. A reflective polarizing element and a quarter-wave plate are attached to the first side of the second lens, and a reflective polarizing element and a polarizer are attached to the second side of the fourth lens. Such a design can convert the natural light emitted from the image plane into polarized light and realize the folding-back of the optical path. In addition to reducing the overall optical length, the optical system provided by the present application can also effectively reduce optical distortion, improve the clarity and stability of the image, and enable users to obtain a better visual experience.
[0050] One aspect of the present application provides an optical system which sequentially includes, along the optical axis from the first side to the second side: a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer. Among them, the first lens has a positive optical power, and its first side is a convex surface; the second lens has a negative optical power, its first side is a plane, and its second side is a concave surface; the third lens has a positive optical power, and its first side is a convex surface; the first quarter-wave plate is placed on the first side of the second lens and at least partially adheres to the first side of the second lens; the reflective polarizing element is placed on the first side of the first quarter-wave plate and at least partially adheres to the first side of the first quarter-wave plate; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate; the effective focal length f of the optical system and the effective focal length f2 of the second lens satisfy: -0.8 < f / f2 < -0.2; and the combined focal length FG1 of the reflective polarizing element, the first quarter-wave plate, and the second lens and the radius of curvature R4 of the second side of the second lens satisfy: -1.5 < FG1 / R4 < -1.1. The optical system provided by the present application adopts a polarization folding optical path design. By reasonably configuring the spatial arrangement and film attachment method of the lens, the reflective polarizing element, and the quarter-wave plate, on the premise of a reasonable range of f / f2, controlling the ratio of the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the second lens to the radius of curvature of the second side of the second lens within a certain range helps to control the polarization performance of the optical system, can achieve the control of the polarization characteristics of the optical system, and is very beneficial for applications in the folding optical path that requires a specific polarization state. At the same time, it can also balance the imaging quality, polarization performance, and design complexity of the optical system, thereby achieving better overall performance. This is particularly important for VR / AR head-mounted devices because users need to view clear and real images in the device to obtain a better sense of immersion and user experience.
[0051] In an exemplary embodiment, the optical system of the present application may satisfy: 0.3 < f1 / f3 < 0.5, where f1 is the effective focal length of the first lens and f3 is the effective focal length of the third lens. Controlling the ratio of the effective focal length of the first lens to the effective focal length of the third lens within a certain range can adjust the magnification of the system to meet specific application requirements, which helps to achieve the required magnification and field of view, and can also optimize the aberration and distortion of the optical system, improving the clarity, contrast, and accuracy of the image.
[0052] In an exemplary embodiment, the optical system of the present application may satisfy: 1.4 < (CT1 + T12) / (CTR + CTQ1 + CT2) < 2.1, where CT1 is the central thickness of the first lens on the optical axis, T12 is the on-axis distance from the second side of the first lens to the first side of the second lens, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ1 is the central thickness of the first quarter-wave plate on the optical axis, and CT2 is the central thickness of the second lens on the optical axis. Satisfying 1.4 < (CT1 + T12) / (CTR + CTQ1 + CT2) < 2.1 can avoid the lens being too thin by restricting the central thicknesses of the first lens, the second lens, the reflective polarizing element, and the first quarter-wave plate, as well as the air gap between the first lens and the second lens, ensuring the strength of the lens; and can also avoid the lens being too thick. At the same time, by restricting the air gap between the first lens and the second lens, the overall optical length of the system can be reduced, which is beneficial to the thinning and lightening of the head-mounted device.
[0053] In an exemplary embodiment, the optical system of the present application may satisfy: 2.0 < f / R1 < 2.4, where f is the effective focal length of the optical system and R1 is the radius of curvature of the first side of the first lens. By controlling the ratio of the effective focal length of the optical system to the radius of curvature of the first side of the first lens within a certain range, light can be effectively focused on the image plane, and at the same time, the shape of the first lens is restricted, which is beneficial to reducing the sensitivity of the first lens, thereby improving the assembly yield.
[0054] In an exemplary embodiment, the optical system of the present application may satisfy: 0.45 < N4 / (NQ2 + NL) < 0.65, where N4 is the refractive index of the fourth lens, NQ2 is the refractive index of the second quarter-wave plate, and NL is the refractive index of the polarizer. Controlling the ratio of the refractive index of the fourth lens to the sum of the refractive indices of the second quarter-wave plate and the polarizer and satisfying 0.45 < N4 / (NQ2 + NL) < 0.65 can reduce the reflection and refraction losses in the optical system, improve the light transmission efficiency, and thus enhance the brightness and clarity of the image. At the same time, satisfying 0.45 < N4 / (NQ2 + NL) < 0.65 is also helpful for controlling the dispersion effect of the optical system. Dispersion is the phenomenon that light rays of different wavelengths have different degrees of refraction when passing through a lens or other optical elements. By reasonably selecting the refractive index of the fourth lens, the dispersion effect can be reduced, thereby improving the color accuracy and imaging quality of the image; restricting the material selection of the fourth lens is beneficial to reducing the stress of the lens material, thereby improving the polarization efficiency of the optical system.
[0055] In an exemplary embodiment, the optical system of the present application can satisfy: 5.2 ≤ CT4 / (CTQ2 + CTL) < 6.9, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, and CTL is the central thickness of the polarizer on the optical axis. By satisfying 5.2 ≤ CT4 / (CTQ2 + CTL) < 6.9 and reasonably controlling the ratio of the central thicknesses of the fourth lens, the second quarter-wave plate, and the polarization element, the optical system can maintain a relatively thin design. A thinner design means using less material, thereby reducing the weight of the optical system. This is particularly important for VR / AR head-mounted devices because users need to wear the device for a long time, and a lighter weight can reduce the burden on the neck and head and improve wearing comfort.
[0056] In an exemplary embodiment, the optical system of the present application can satisfy: 0.4 < R5 / R4 < 1.7, where R5 is the radius of curvature of the first side surface of the third lens and R4 is the radius of curvature of the second side surface of the second lens. By satisfying 0.4 < R5 / R4 < 1.7 and controlling the radii of curvature of the first side surface of the third lens and the second side surface of the second lens, the light rays in the marginal field of view can be controlled, which helps to control the aberration of the optical system and improve the imaging quality of the marginal field of view.
[0057] In an exemplary embodiment, the optical system of the present application can satisfy: 1.68 < N2 < 1.86 and 23.7 < V2 < 31.2, where N2 is the refractive index of the second lens and V2 is the dispersion coefficient of the second lens. By satisfying 1.68 < N2 < 1.86 and 23.7 < V2 < 31.2 and controlling the refractive index and dispersion coefficient of the second lens, the refraction effect of the optical system can be optimized, and the propagation speed and refraction angle of light rays in the system can be controlled. This helps to achieve the required optical imaging effect and improve the clarity and contrast of the image. At the same time, satisfying 1.68 < N2 < 1.86 can reduce the dispersion effect and improve the color accuracy and imaging quality of the image.
[0058] In an exemplary embodiment, the optical system of the present application can satisfy: 3.0 < TD / CT3 < 3.5, where TD is the distance on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens, and CT3 is the central thickness of the third lens on the optical axis. By satisfying 3.0 < TD / CT3 < 3.5 and limiting the ratio of the distance on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens to the central thickness of the third lens within a certain range, it is beneficial to improve the formability of the lens and reduce the process difficulty on the premise of ensuring that the overall optical length is within a reasonable range.
[0059] In an exemplary embodiment, the optical system of the present application may satisfy: 0.4 < EPD / f1 < 0.8, where EPD is the entrance pupil diameter of the optical system and f1 is the effective focal length of the first lens. Satisfying 0.4 < EPD / f1 < 0.8 helps to control the light flux of the optical system and can also ensure that sufficient light passes through the system and is correctly focused to obtain a clear and sharp image. This helps to improve the contrast, details, and accuracy of the image.
[0060] In an exemplary embodiment, the optical system of the present application may satisfy: 1.1 < FG2 / R7 < 2.1, where FG2 is the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer, and R7 is the radius of curvature of the first side surface of the fourth lens. Satisfying 1.1 < FG2 / R7 < 2.1, by controlling the ratio of the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer to the radius of curvature of the first side surface of the fourth lens within a certain range, the shape of the fourth lens is constrained, which is beneficial to reducing the sensitivity of the fourth lens and thus improving the yield of assembly.
[0061] In an exemplary embodiment, the optical system of the present application may satisfy: 0.7 < SAG11 / CT1 < 1.1, where SAG11 is the axial distance between the intersection of the first side surface of the first lens and the optical axis and the vertex of the effective radius of the first side surface of the first lens, and CT1 is the central thickness of the first lens on the optical axis. Satisfying 0.7 < SAG11 / CT1 < 1.1 can adjust the curvature and bending degree of the system and reduce the difficulty of lens forming. At the same time, the size of the optical system can be reduced to make it more compact. This is very beneficial for portable devices or application scenarios with limited space.
[0062] In an exemplary embodiment, the optical system of the present application may satisfy: 1.2 < T34 / |SAG41| < 1.6, where T34 is the axial distance from the second side surface of the third lens to the first side surface of the fourth lens, and SAG41 is the axial distance between the intersection of the first side surface of the fourth lens and the optical axis and the vertex of the effective radius of the first side surface of the fourth lens. Satisfying 1.2 < T34 / |SAG41| < 1.6 can help to control the axial position of the optical system. Appropriately selecting the range of the conditional expression T34 / |SAG41| can adjust the axial position of the system to meet specific application requirements and help to achieve the desired optical effect and imaging quality.
[0063] In an exemplary embodiment, the optical system of the present application may satisfy: 1.8 < f / ∑CT < 2.6, where f is the effective focal length of the optical system, and ∑CT is the sum of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis. By satisfying 1.8 < f / ∑CT < 2.6 and controlling the ratio of the effective focal length to the sum of the central thicknesses of the lenses, the aberration and distortion of the optical system can be optimized, the clarity, contrast, and accuracy of the image can be improved, and it is also helpful to achieve the required imaging distance and focusing range.
[0064] In an exemplary embodiment, the optical system according to the present application may further include a protective glass for protecting the light-emitting element located on the image plane.
[0065] In an exemplary embodiment, the optical system of the present application may include at least one aperture stop. The aperture stop can constrain the light path and control the light intensity. The aperture stop can be set at an appropriate position in the optical system. For example, the aperture stop can be located on the first side of the first lens.
[0066] In an embodiment of the present application, at least one of the surfaces of each of the first lens to the fourth lens is an aspherical surface. The characteristic of an aspherical lens is that the curvature changes continuously from the center of the lens to the periphery of the lens. Different from a spherical lens with a constant curvature from the center of the lens to the periphery of the lens, an aspherical lens has better curvature radius characteristics and has the advantages of improving distortion aberration and astigmatism aberration. After using an aspherical lens, it is possible to eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality. Optionally, the first side and the second side of the third lens, and the first side of the fourth lens can be aspherical surfaces. Optionally, the first side and the second side of the first lens, the second side of the second lens, the first side and the second side of the third lens, and the first side of the fourth lens can be aspherical surfaces.
[0067] On the other hand, the present application also provides an optical system which sequentially includes, along the optical axis from the first side to the second side: a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partially reflective element, a fourth lens, a second quarter-wave plate, and a polarizer. Among them, the first lens has a positive optical power, and its first side is convex; the second lens has a negative optical power, its first side is flat, and its second side is concave; the third lens has a positive optical power, and its first side is convex; the first quarter-wave plate is placed on the first side of the second lens and at least partially adheres to the first side of the second lens; the reflective polarizing element is placed on the first side of the first quarter-wave plate and at least partially adheres to the first side of the first quarter-wave plate; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate; the effective focal length f of the optical system and the effective focal length f2 of the second lens satisfy: -0.8 < f / f2 < -0.2; and the refractive index N4 of the fourth lens, the refractive index NQ2 of the second quarter-wave plate, and the refractive index NL of the polarizer satisfy: 0.45 < N4 / (NQ2 + NL) < 0.65. The optical system provided by the present application adopts a polarization folding optical path design. By reasonably configuring the spatial arrangement and film attachment method of the lens, the reflective polarizing element, and the quarter-wave plate, on the premise of a reasonable range of f / f2, controlling the refractive index N4 of the fourth lens, the refractive index NQ2 of the second quarter-wave plate, and the refractive index NL of the polarizer to satisfy 0.45 < N4 / (NQ2 + NL) < 0.65 can reduce the reflection and refraction losses in the optical system, improve the light transmission efficiency, and thus enhance the brightness and clarity of the image. At the same time, it also helps to control the chromatic dispersion effect of the optical system. By reasonably selecting the refractive index of the fourth lens, the chromatic dispersion effect can be reduced, thereby improving the color accuracy and imaging quality of the image; restricting the material selection of the fourth lens is beneficial to reducing the stress of the lens material, and thus improving the polarization efficiency of the optical system.
[0068] According to some embodiments of the present application, the optical system of the present application has advantages such as small volume, small optical distortion, clear and stable image, etc., and can provide a better virtual reality experience for users. In applications, the optical system according to the exemplary embodiments of the present application can be applied to VR devices. By reasonably setting parameters such as the optical power, entrance pupil diameter, and the central thickness, refractive index, Abbe number, and curvature radius of the lens of the optical system, the purpose of a wide angle of the VR device can be achieved, as well as correcting the chromatic aberration of the system, reducing optical distortion, and improving the imaging quality and reliability of the system.
[0069] The following further describes specific embodiments of the optical system applicable to the above embodiments with reference to the accompanying drawings.
[0070] Example 1
[0071] Refer to the following Figures 1 to 2D to describe the optical system according to Embodiment 1 of the present application. Figure 1 FIG. shows a schematic structural diagram of the optical system according to Embodiment 1 of the present application.
[0072] As Figure 1 shown, the optical system sequentially includes, from the human eye side to the screen side: a stop STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.
[0073] The first lens E1 has a positive optical power, its side near the human eye is convex, and its side near the screen is concave. The second lens E2 has a negative optical power, its side near the human eye is flat, and its side near the screen is concave. The third lens E3 has a positive optical power, its side near the human eye is convex, and its side near the screen is convex. The fourth lens E4 has a positive optical power, its side near the human eye is convex, and its side near the screen is flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 near the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 near the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 near the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 near the screen. The partial reflection element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 near the screen.
[0074] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, where it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the side of the third lens E3 near the screen and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, and then passes through the stop STO and finally exits toward the human eye side.
[0075] Table 1 shows the basic parameters of the optical system of Embodiment 1, where the units of the radius of curvature and the thickness are both millimeters (mm).
[0076] Table 1
[0077]
[0078]
[0079] In Embodiment 1, the near-eye side and the near-screen side of the third lens, and the near-eye side of the fourth lens are all aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:
[0080]
[0081] where x is the sagitta, which is the distance from the vertex of the aspherical surface along the optical axis at a position with a height of h; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic constant; and Ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 below gives the higher-order term coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for each aspherical mirror surface in Embodiment 1.
[0082] Table 2
[0083]
[0084] Table 3 shows some basic parameters of the optical system of Embodiment 1, such as f, f1, f2, f3, f4, EPD, TD, FG1, FG2, SAG11, and SAG41.
[0085] Table 3
[0086]
[0087] Figure 2A shows the axial chromatic aberration curve of the optical system of Embodiment 1, which represents the deviation of the convergence points of light rays with different wavelengths after passing through the lens. Figure 2B shows the astigmatism curve of the optical system of Embodiment 1, which represents the curvature of the meridional image plane and the curvature of the sagittal image plane. Figure 2C shows the distortion curve of the optical system of Embodiment 1, which represents the distortion magnitude values corresponding to different field angles. Figure 2D shows the modulation transfer function (MTF) curve of the optical system of Embodiment 1. According to Figures 2A to 2D it can be seen that the optical system given in Embodiment 1 can achieve good imaging quality.
[0088] Example 2
[0089] The following refers to Figures 3 to 4D to describe the optical system according to Embodiment 2 of the present application. In this embodiment and the following embodiments, for the sake of brevity, some descriptions similar to those in Embodiment 1 will be omitted. Figure 3 shows a schematic structural diagram of the optical system according to Embodiment 2 of the present application.
[0090] As shown Figure 3 in FIG. 1, the optical system sequentially includes, from the human eye side to the screen side: a diaphragm STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.
[0091] The first lens E1 has a positive focal power, with its side near the human eye being convex and its side near the screen being convex. The second lens E2 has a negative focal power, with its side near the human eye being flat and its side near the screen being concave. The third lens E3 has a positive focal power, with its side near the human eye being convex and its side near the screen being concave. The fourth lens E4 has a negative focal power, with its side near the human eye being concave and its side near the screen being flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 near the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 near the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 near the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 near the screen. The partial reflection element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 near the screen.
[0092] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, where it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the side of the third lens E3 near the screen and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, then passes through the diaphragm STO and finally exits toward the human eye side.
[0093] Table 4 shows the basic parameters of the optical system of Example 2, where the units of the radius of curvature and the thickness are both millimeters (mm). Table 5 shows the higher-order term coefficients of the aspherical mirrors that can be used in Example 2, where each aspherical surface type can be defined by the formula (1) given in the above Example 1.
[0094] Table 4
[0095]
[0096]
[0097] Table 5
[0098]
[0099] Table 6 shows some basic parameters of the optical system of Example 2, such as f, f1, f2, f3, f4, EPD, TD, FG1, FG2, SAG11, and SAG41.
[0100] Table 6
[0101]
[0102] Figure 4A shows the axial chromatic aberration curve of the optical system of Example 2, which represents the deviation of the focusing points of light rays with different wavelengths after passing through the lens. Figure 4B shows the astigmatism curve of the optical system of Example 2, which represents the curvature of the meridional image plane and the sagittal image plane. Figure 4C shows the distortion curve of the optical system of Example 2, which represents the distortion magnitude values corresponding to different field angles. Figure 4D shows the modulation transfer function (MTF) curve of the optical system of Example 2. According to Figures 4A to 4D it can be seen that the optical system given in Example 2 can achieve good imaging quality.
[0103] Example 3
[0104] The following refers to Figures 5 to 6D describes the optical system according to Embodiment 3 of the present application. Figure 5 shows a schematic structural diagram of the optical system according to Embodiment 3 of the present application.
[0105] As Figure 5 shown, the optical system sequentially includes, from the human eye side to the screen side: a diaphragm STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.
[0106] The first lens E1 has a positive optical power, with its side closer to the human eye being convex and its side closer to the screen being concave. The second lens E2 has a negative optical power, with its side closer to the human eye being flat and its side closer to the screen being concave. The third lens E3 has a positive optical power, with its side closer to the human eye being convex and its side closer to the screen being convex. The fourth lens E4 has a negative optical power, with its side closer to the human eye being concave and its side closer to the screen being flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 closer to the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 closer to the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 closer to the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 closer to the screen. The partial reflection element BS can have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 closer to the screen.
[0107] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, the first quarter-wave plate QWP1 and reaches the reflective polarizing element RP. It is reflected at the reflective polarizing element RP and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the side of the third lens E3 closer to the screen and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP and the first lens E1, and then passes through the aperture stop STO and finally exits toward the human eye side.
[0108] Table 7 shows the basic parameters of the optical system of Example 3, where the units of the radius of curvature and the thickness are both millimeters (mm). Table 8 shows the higher-order term coefficients of the aspherical mirrors that can be used in Example 3, where each aspherical surface type can be defined by the formula (1) given in the above Example 1.
[0109] Table 7
[0110]
[0111] Table 8
[0112]
[0113] Table 9 shows some basic parameters of the optical system of Example 3, such as f, f1, f2, f3, f4, EPD, TD, FG1, FG2, SAG11, SAG41.
[0114] Table 9
[0115]
[0116] Figure 6AShows the axial chromatic aberration curve of the optical system of Embodiment 3, which represents the deviation of the focusing points of light rays of different wavelengths after passing through the lens. Figure 6B Shows the astigmatism curve of the optical system of Embodiment 3, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 6C Shows the distortion curve of the optical system of Embodiment 3, which represents the distortion magnitude values corresponding to different field angles. Figure 6D Shows the modulation transfer function (MTF) curve of the optical system of Embodiment 3. According to Figures 6A to 6D It can be seen that the optical system given in Embodiment 3 can achieve good imaging quality.
[0117] Example 4
[0118] The following refers to Figures 7 to 8D Describes the optical system according to Embodiment 4 of the present application. Figure 7 Shows the structural schematic diagram of the optical system according to Embodiment 4 of the present application.
[0119] As Figure 7 Shown, the optical system sequentially includes, from the human eye side to the screen side: a diaphragm STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.
[0120] The first lens E1 has a positive optical power, its side near the human eye is convex, and its side near the screen is convex. The second lens E2 has a negative optical power, its side near the human eye is flat, and its side near the screen is concave. The third lens E3 has a positive optical power, its side near the human eye is convex, and its side near the screen is concave. The fourth lens E4 has a negative optical power, its side near the human eye is concave, and its side near the screen is flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 near the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 near the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 near the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 near the screen. The partial reflection element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 near the screen.
[0121] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, polarizer LP, second quarter-wave plate QWP2, fourth lens E4, third lens E3, second lens E2, first quarter-wave plate QWP1 and reaches the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, second lens E2, and third lens E3 again. The partial reflection element BS on the near-screen side of the third lens E3 reflects the light again, and the light sequentially passes through the third lens E3, second lens E2, first quarter-wave plate QWP1, reflective polarizing element RP, and first lens E1, then passes through the aperture STO and finally exits toward the human eye side.
[0122] Table 10 shows the basic parameters of the optical system of Example 4, where the units of the radius of curvature and thickness are both millimeters (mm). Table 11 shows the higher-order term coefficients of the aspherical mirrors that can be used in Example 4, where each aspherical surface type can be defined by formula (1) given in the above Example 1.
[0123] Table 10
[0124]
[0125] Table 11
[0126]
[0127]
[0128] Table 12 shows some basic parameters of the optical system of Example 4, such as f, f1, f2, f3, f4, EPD, TD, FG1, FG2, SAG11, SAG41.
[0129] Table 12
[0130]
[0131] Figure 8A shows the axial chromatic aberration curve of the optical system of Example 4, which represents the deviation of the focusing points of light rays of different wavelengths after passing through the lens. Figure 8B shows the astigmatism curve of the optical system of Example 4, which represents the meridional image plane curvature and sagittal image plane curvature. Figure 8C shows the distortion curve of the optical system of Example 4, which represents the distortion magnitude values corresponding to different field angles. Figure 8D shows the modulation transfer function (MTF) curve of the optical system of Example 4. According to Figures 8A to 8D it can be seen that the optical system given in Example 4 can achieve good imaging quality.
[0132] Example 5
[0133] The following is a reference to Figures 9 to 10D an optical system according to Embodiment 5 of the present application is described. Figure 9 A schematic structural diagram of the optical system according to Embodiment 5 of the present application is shown.
[0134] As Figure 9 shown, the optical system sequentially includes, from the human eye side to the screen side: a stop STO, a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.
[0135] The first lens E1 has a positive optical power, its side near the human eye is convex, and its side near the screen is convex. The second lens E2 has a negative optical power, its side near the human eye is flat, and its side near the screen is concave. The third lens E3 has a positive optical power, its side near the human eye is convex, and its side near the screen is concave. The fourth lens E4 has a negative optical power, its side near the human eye is concave, and its side near the screen is flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 near the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 near the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 near the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 near the screen. The partial reflection element BS can have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 near the screen.
[0136] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, where it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the side of the third lens E3 near the screen and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, then passes through the stop STO and finally exits towards the human eye side.
[0137] Table 13 shows the basic parameters of the optical system of Embodiment 5, where the units of the radius of curvature and the thickness are both millimeters (mm). Table 14 shows the higher-order term coefficients of the aspherical mirror surfaces that can be used in Embodiment 5, where each aspherical surface type can be defined by the formula (1) given in Embodiment 1 above.
[0138] Table 13
[0139]
[0140] Table 14
[0141]
[0142] Table 15 shows some basic parameters of the optical system of Example 5, such as f, f1, f2, f3, f4, EPD, TD, FG1, FG2, SAG11, SAG41.
[0143] Table 15
[0144]
[0145] Figure 10A Shows the axial chromatic aberration curve of the optical system of Example 5, which represents the deviation of the focusing points of light rays of different wavelengths after passing through the lens. Figure 10B Shows the astigmatism curve of the optical system of Example 5, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 10C Shows the distortion curve of the optical system of Example 5, which represents the distortion magnitude values corresponding to different field angles. Figure 10D Shows the modulation transfer function (MTF) curve of the optical system of Example 5. According to Figures 10A to 10D It can be seen that the optical system given in Example 5 can achieve good imaging quality.
[0146] In summary, the optical systems of Examples 1 to 5 have the relationships shown in Table 16.
[0147] Table 16
[0148] Conditional / Example 1 2 3 4 5 f / f2 -0.41 -0.76 -0.29 -0.49 -0.44 FG1 / R4 -1.38 -1.44 -1.17 -1.17 -1.17 f1 / f3 0.40 0.44 0.38 0.37 0.33 (CT1 + T12) / (CTR + CTQ1 + CT2) 2.01 1.60 1.92 1.46 1.64 f / R1 2.06 2.33 2.06 2.30 2.29 N4 / (NQ2 + NL) 0.62 0.50 0.58 0.58 0.58 CT4 / (CTQ2 + CTL) 6.03 5.20 5.20 6.82 5.20 R5 / R4 1.65 1.03 0.69 0.51 0.49 N2 1.723 1.694 1.855 1.855 1.855 V2 29.51 31.18 23.83 23.80 23.77 TD / CT3 3.45 3.09 3.16 3.42 3.27 EPD / f1 0.43 0.71 0.45 0.77 0.77 FG2 / R7 1.17 2.04 1.33 1.34 1.34 SAG11 / CT1 1.07 0.78 0.95 0.80 0.71 T34 / |SAG41| 1.44 1.47 1.52 1.23 1.23 f / ∑CT 2.56 1.89 2.37 1.88 1.83
[0149] This application also provides an optical device, which can be an independent projection device such as a projector, or a projection module integrated on a mobile electronic device such as VR. The optical device is equipped with the optical system described above.
[0150] The above description is only the preferred embodiments of this application and the description of the applied technical principles. Those skilled in the art should understand that the protection scope involved in this application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the concept of this application. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) having similar functions disclosed in this application.
Claims
1. An optical system, characterized in that In sequence from the first side to the second side along the optical axis, it includes: a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter-wave plate, and a polarizer, where, The first lens has a positive optical power, and its first side is convex; The second lens has a negative optical power, its first side is flat, and its second side is concave; The third lens has a positive optical power, and its first side is convex; The second side of the fourth lens is flat; The first quarter-wave plate is placed on the first side of the second lens and at least partially adheres to the first side of the second lens; The reflective polarizing element is placed on the first side of the first quarter-wave plate and at least partially adheres to the first side of the first quarter-wave plate; The second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; The polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate; The effective focal length f of the optical system and the effective focal length f2 of the second lens satisfy: -0.8 < f / f2 ≤ -0.29; and The combined focal length FG1 of the reflective polarizing element, the first quarter-wave plate, and the second lens and the radius of curvature R4 of the second side of the second lens satisfy: -1.44 ≤ FG1 / R4 ≤ -1.17; The number of lenses with optical power in the optical system is four.
2. The optical system according to claim 1, characterized in that The optical system satisfies: 0.3 < f1 / f3 ≤ 0.44, where f1 is the effective focal length of the first lens and f3 is the effective focal length of the third lens.
3. The optical system according to claim 1, characterized in that The optical system satisfies: 1.46 ≤ (CT1 + T12) / (CTR + CTQ1 + CT2) ≤ 2.01, where CT1 is the central thickness of the first lens on the optical axis, T12 is the axial distance from the second side of the first lens to the first side of the second lens, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ1 is the central thickness of the first quarter-wave plate on the optical axis, and CT2 is the central thickness of the second lens on the optical axis.
4. The optical system according to claim 1, characterized in that The optical system satisfies: 2.06 ≤ f / R1 ≤ 2.33, where f is the effective focal length of the optical system and R1 is the radius of curvature of the first side of the first lens.
5. The optical system according to claim 1, characterized in that The optical system satisfies: 0.45 < N4 / (NQ2 + NL) < 0.65, where N4 is the refractive index of the fourth lens, NQ2 is the refractive index of the second quarter-wave plate, and NL is the refractive index of the polarizer.
6. The optical system according to claim 1, characterized in that The optical system satisfies: 5.2 ≤ CT4 / (CTQ2 + CTL) ≤ 6.82, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, and CTL is the central thickness of the polarizer on the optical axis.
7. The optical system according to claim 1, characterized in that The optical system satisfies: 0.49 ≤ R5 / R4 < 1.7, where R5 is the radius of curvature of the first surface of the third lens and R4 is the radius of curvature of the second surface of the second lens.
8. The optical system according to claim 1, characterized in that The optical system satisfies: 1.694 ≤ N2 < 1.86 and 23.77 ≤ V2 < 31.2, where N2 is the refractive index of the second lens and V2 is the Abbe number of the second lens.
9. The optical system according to any one of claims 1 to 8, characterized in that: The optical system satisfies: 3.09 ≤ TD / CT3 < 3.5, where TD is the distance on the optical axis from the first surface of the first lens to the second surface of the fourth lens, and CT3 is the central thickness of the third lens on the optical axis.
10. The optical system according to any one of claims 1 to 8, characterized in that: The optical system satisfies: 0.4 < EPD / f1 < 0.8, where EPD is the entrance pupil diameter of the optical system and f1 is the effective focal length of the first lens.
11. The optical system according to any one of claims 1 to 8, characterized in that: The optical system satisfies: 1.17 ≤ FG2 / R7 ≤ 2.04, where FG2 is the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer, and R7 is the radius of curvature of the first surface of the fourth lens.
12. The optical system according to any one of claims 1 to 8, characterized in that: The optical system satisfies: 0.7 < SAG11 / CT1 < 1.1, where SAG11 is the axial distance between the intersection of the first surface of the first lens and the optical axis and the vertex of the effective radius of the first surface of the first lens, and CT1 is the central thickness of the first lens on the optical axis.
13. The optical system according to any one of claims 1 to 8, characterized in that: The optical system satisfies: 1.2 < T34 / |SAG41| ≤ 1.52, where T34 is the axial distance from the second surface of the third lens to the first surface of the fourth lens, and SAG41 is the axial distance between the intersection of the first surface of the fourth lens and the optical axis and the vertex of the effective radius of the first surface of the fourth lens.
14. The optical system according to any one of claims 1 to 8, characterized in that: The optical system satisfies: 1.8 < f / ∑CT < 2.6, where f is the effective focal length of the optical system and ∑CT is the sum of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis.
15. An optical device, characterized in that: Comprising the optical system according to any one of claims 1 to 14.