Optical system
By designing an optical system including four lenses, using polarization foldback optical path and reasonable lens configuration, the problems of low imaging clarity, poor image stability and insufficient compactness in the optical system of AR/VR equipment are solved, and higher imaging quality, better vibration resistance and more compact equipment design are achieved.
Patent Information
- Application Number
- CN202421870858.9
- 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 existing head-mounted optical systems suitable for AR/VR devices have problems such as low imaging clarity, poor image stability, and insufficient system compactness.
An optical system including four lenses was designed. By reasonably configuring the focal length, surface shape, center thickness and on-axis spacing of the lens, the polarization folding optical path is adopted to optimize aberration performance, improve imaging clarity and vibration resistance, and reduce the equipment volume and weight by controlling the size and layout of the lens.
The compact design of the optical system is realized, the clarity and accuracy of imaging is improved, the vibration resistance is enhanced, the volume and weight of the equipment are reduced, and the convenience and comfort of wearing are improved.
Smart Images
Figure CN222994758U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of optical elements, and in particular, to an optical system including a four-piece lens. Background Art
[0002] In recent years, with the concept of "metaverse" being proposed, augmented reality (AR) and virtual reality (VR) for human-computer interaction have ushered in a second opportunity for development. The head-mounted device of AR / VR equipment can make the wearer feel as if he is in a different environment, bringing great changes in the fields of social interaction, entertainment, medical treatment and education.
[0003] The reentrant optical system can compress the optical path through the characteristics of polarized light. It also has the functions and advantages of providing a larger field of view and reducing glare and scattering. It is often used in optical system solutions for AR / VR devices. The reentrant optical system is a complex system composed of multiple lenses and optical elements, which is used to control and manipulate the propagation and imaging of light. When designing and optimizing optical systems, many factors need to be considered, such as aberrations, resolution, focusing ability, light transmittance, etc.
[0004] However, the optical systems of current head-mounted devices suitable for AR / VR equipment often have at least one problem, such as low imaging clarity, poor image stability, and insufficient system compactness. Utility Model Content
[0005] According to an embodiment of the present application, an optical system is provided, which includes, in order from the first side to the second side along the optical axis direction: a first lens with positive focal power, whose first side surface is convex and whose second side surface is flat; a reflective polarizing element; a first quarter wave plate; a second lens with positive focal power, whose first side surface is convex; a third lens with negative focal power, whose first side surface is concave and whose second side surface is flat; a partial reflection element; a second quarter wave plate; a polarizer; and a fourth lens with negative focal power; wherein the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: -1.5 <f3 / f1<-1.0;以及第三透镜在光轴上的中心厚度CT3、偏振片在光轴上的中心厚度CTL、第二四分之一波片在光轴上的中心厚度CTQ2、第一透镜在光轴上的中心厚度CT1、反射式偏光元件在光轴上的中心厚度CTR,以及第一四分之一波片在光轴上的中心厚度CTQ1满足:2≤(CT3+CTQ2+CTL) / (CT1+CTR+CTQ1)<2.9。
[0006] In some embodiments, the effective focal length f2 of the second lens and the radius of curvature R3 of the first side surface of the second lens satisfy: 1 ≤ f2 / R3 < 1.8.
[0007] In some embodiments, the distance TD on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens and the effective focal length f of the optical system satisfy: 0.5 < TD / f < 0.6.
[0008] In some embodiments, the effective focal length f4 of the fourth lens and the effective focal length f of the optical system satisfy: -1.4 < f4 / f ≤ -0.7.
[0009] In some embodiments, the refractive index N3 of the third lens, the refractive index N1 of the first lens, the Abbe number V3 of the third lens, and the Abbe number V1 of the first lens satisfy: 1.0 < N3 / N1 < 1.2; 0.4 < V3 / V1 < 0.7.
[0010] In some embodiments, the effective focal length f of the optical system, the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, and the central thickness CTQ1 of the first quarter-wave plate on the optical axis satisfy: 11 < f / (CT1 + CTR + CTQ1) < 12.4.
[0011] In some embodiments, the effective focal length f1 of the first lens and the radius of curvature R1 of the first side surface of the first lens satisfy: 1.3 < f1 / R1 < 2.1.
[0012] In some embodiments, the central thickness CT3 of the third lens on the optical axis and the sum ∑CT of the central thicknesses of the first lens to the fourth lens on the optical axis satisfy: 0.35 < CT3 / ∑CT < 0.55.
[0013] In some embodiments, the entrance pupil diameter EPD of the optical system and the distance TD on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens satisfy: 0.9 < EPD / TD < 1.0.
[0014] In some embodiments, the effective focal length f3 of the third lens and the radius of curvature R5 of the first side surface of the third lens satisfy: 1.3 < f3 / R5 < 1.5.
[0015] In some embodiments, the combined focal length FG1 of the first lens, the reflective polarizing element, and the first quarter-wave plate and the effective focal length f2 of the second lens satisfy: 0.6 < FG1 / f2 < 1.4.
[0016] In some embodiments, the combined focal length FG2 of the third lens, the second quarter-wave plate, and the polarizer and the effective focal length f4 of the fourth lens satisfy: 1.3 < FG2 / f4 < 3.2.
[0017] In some embodiments, the axial distance SAG21 between the intersection of the first side surface of the second lens and the optical axis and the vertex of the effective radius of the first side surface of the second lens satisfies 0.4 < SAG21 / SAG11 < 1.0 with the axial distance SAG11 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.
[0018] In some embodiments, the axial distance SAG41 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, the axial distance SAG42 between the intersection of the second side surface of the fourth lens and the optical axis and the vertex of the effective radius of the second side surface of the fourth lens, and the central thickness CT4 of the fourth lens on the optical axis satisfy 0.2 < (|SAG41| + |SAG42|) / CT4 < 1.9.
[0019] In some embodiments, the reflective polarizing element is disposed on the second side surface of the first lens and at least partially adheres to the second side surface of the first lens; the first quarter-wave plate is disposed on the second side surface of the reflective polarizing element and at least partially adheres to the second side surface of the reflective polarizing element; and the partial reflective element is disposed on the second side surface of the third lens and at least partially adheres to the second side surface of the third lens; the second quarter-wave plate is disposed on the second side surface of the partial reflective element and at least partially adheres to the second side surface of the partial reflective element; the polarizer is disposed on the second side surface of the second quarter-wave plate and at least partially adheres to the second side surface of the second quarter-wave plate.
[0020] According to the optical system provided by the embodiments of the present application, a four-lens polarization folding optical path is adopted. By reasonably configuring the focal lengths, surface profiles, and central thicknesses on the optical axis of the lenses of the optical system, the body height can be better compressed and a compact design of the optical system can be achieved. On the premise that f3 / f1 satisfies a reasonable range, by precisely controlling the axial distance and thickness ratio between the lenses, the aberration performance of the optical system can be optimized, and the clarity and accuracy of imaging can be improved; at the same time, it helps to improve the anti-vibration ability of the optical system, making the image more stable and clear; in addition, by controlling the size and layout of the lenses, the volume and weight of the device can be reduced, and the portability and comfort of carrying can be improved. In summary, the optical system provided by the embodiments of the present application can optimize the aberration performance of the optical system, improve the clarity and accuracy of imaging, and thus achieve at least one of the effects of optimizing the imaging performance, anti-vibration ability, and compactness of the optical system through optical design and optimization, such as by controlling the axial distance or thickness ratio between the lenses. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments read in conjunction with the accompanying drawings:
[0022] Figure 1 Shows a schematic structural diagram of an optical system according to Embodiment 1 of the present application;
[0023] Figure 2A 、 Figure 2B and Figure 2C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 1 of the present application;
[0024] Figure 3 Shows the MTF curve of the optical system according to Embodiment 1 of the present application;
[0025] Figure 4 Shows a schematic structural diagram of an optical system according to Embodiment 2 of the present application;
[0026] Figure 5A 、 Figure 5B and Figure 5C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 2 of the present application;
[0027] Figure 6 Shows the MTF curve of the optical system according to Embodiment 2 of the present application;
[0028] Figure 7 Shows a schematic structural diagram of an optical system according to Embodiment 2 of the present application;
[0029] Figure 8A 、 Figure 8B and Figure 8C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 3 of the present application;
[0030] Figure 9 Shows the MTF curve of the optical system according to Embodiment 3 of the present application;
[0031] Figure 10 Shows a schematic structural diagram of an optical system according to Embodiment 4 of the present application;
[0032] Figure 11A 、 Figure 11B and Figure 11C Respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical system according to Embodiment 4 of the present application;
[0033] Figure 12 Shows the MTF curve of the optical system according to Embodiment 4 of the present application;
[0034] Figure 13 Shows a schematic structural diagram of an optical system according to Embodiment 5 of the present application;
[0035] Figure 14A 、 Figure 14B and Figure 14C respectively show the axial chromatic aberration curve, astigmatism curve and distortion curve of the optical system according to Embodiment 5 of the present application; and
[0036] Figure 15 Shows the MTF curve of the optical system according to Embodiment 5 of the present application. Detailed implementation manners
[0037] To better understand the present application, more detailed descriptions will be made on various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of 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.
[0038] It should be noted that in this specification, the expressions such as first, second, third, fourth, etc. are only used to distinguish one feature from another feature and do not represent any limitation on the features. Therefore, without departing from the teachings of the present application, the first lens discussed below may also be referred to as the second lens or the third lens.
[0039] In the accompanying drawings, for the sake of convenience of illustration, the thickness, size and shape of the lens have been slightly exaggerated. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the spherical or aspherical surfaces shown in the drawings. The drawings are only for illustration and are not drawn strictly to scale.
[0040] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region.
[0041] It should also be understood that the terms "comprising", "comprises", "having", "includes" and / or "including", 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. Further, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Also, the term "exemplary" is intended to refer to an example or illustration.
[0042] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0043] 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 following embodiments only represent several implementation manners of the present application, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these all belong to the protection scope of the present application. For example, the lens groups (i.e., the first lens to the fourth lens), the barrel structure and the spacer elements in the embodiments of the present application can be arbitrarily combined, and it is not limited that the lens group in one embodiment can only be combined with the barrel structure, the spacer element, etc. in that embodiment.
[0044] The features, principles and other aspects of the present application will be described in detail below.
[0045] Refer to Figure 1 As shown, a first aspect of the present application provides an optical system, which may include, arranged in sequence along the optical axis from the first side to the second side: 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 second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. An air gap may be provided between any adjacent lenses. In an exemplary embodiment, the second side of the optical system may further include a display screen.
[0046] In an exemplary embodiment, the first side of the optical system may be, for example, the side closer to the human eye, and the second side may be, for example, the side closer to the display. Correspondingly, each optical element (the first lens, the reflective polarizing element, the first quarter-wave plate, the second lens, the third lens, the partial reflection element, the second quarter-wave plate, the polarizer, the fourth lens, etc.) has at least one first side relatively closer to the human eye side and at least one second side relatively closer to the display side.
[0047] In an exemplary embodiment, the first lens E1 may have a positive optical power. The second lens E2 may have a positive optical power. The third lens E3 may have a negative optical power. The fourth lens E4 may have a negative optical power.
[0048] In an exemplary embodiment, the first side of the first lens E1 may be convex, and the second side may be flat. The reflective polarizing element RP may be disposed on the second side (the surface closer to the display side) of the first lens E1 and at least partially adhered to the second side of the first lens E1. The first quarter-wave plate QWP1 may be disposed on the second side (the surface closer to the display side) of the reflective polarizing element RP and at least partially adhered to the second side of the reflective polarizing element RP. Exemplarily, the reflective polarizing element RP and the first quarter-wave plate QWP1 may be sequentially adhered to the second side of the first lens E1, or the two may be compounded together to achieve a single adhesion, thereby improving production efficiency and reducing costs; at the same time, compounding the two together can also avoid the angular deviation between the optical axis of the reflective polarizing element and the optical axis of the first quarter-wave plate caused by the adhesion process, and improve the imaging quality.
[0049] In an exemplary embodiment, the first side of the second lens E2 may be convex, and the second side may be convex or concave.
[0050] In an exemplary embodiment, the first side of the third lens E3 may be concave, and the second side may be flat. The partial reflection element BS may be disposed on the second side of the third lens E3 and at least partially adhered to the second side of the third lens E3. The second quarter-wave plate QWP2 may be disposed on the second side of the partial reflection element BS and at least partially adhered to the second side of the partial reflection element BS. The polarizer LP may be disposed on the second side of the second quarter-wave plate QWP2 and at least partially adhered to the second side of the second quarter-wave plate QWP2. Exemplarily, the partial reflection element BS, the second quarter-wave plate QWP2, and the polarizer LP may be sequentially adhered to the second side of the third lens E3.
[0051] In an exemplary embodiment, the first side of the fourth lens E4 may be convex or concave, and the second side may be concave or convex.
[0052] For the optical system according to an exemplary embodiment of the present application, when light passes through a reflective polarizing element, the reflective polarizing element can reflect light in a certain direction and transmit light orthogonal to the reflected light. A quarter-wave plate can be used to convert between circularly polarized light and linearly polarized light to achieve the folding back of the optical path. The partial reflection element can be a partial reflection layer (such as a semi-transmissive and semi-reflective film) attached or deposited on the second side surface of the second lens, and the partial reflection layer has a semi-transmissive and semi-reflective effect on light. The function of the polarizer is to convert the natural light emitted by the screen into linearly polarized light. The image light from the display screen is finally projected onto the user's eyes after multiple refractions and reflections by the visual optical system.
[0053] The optical system provided according to the embodiment of the present application can be applied to the head-mounted device of an AR device or a VR device. Specifically, it can be used as the visual optical system of the head-mounted device. By folding the optical path, the body length of the lens can be compressed, so that the center of gravity of the head-mounted device moves backward, increasing the consumer experience.
[0054] In the exemplary embodiment, the effective focal length f1 of the first lens, the effective focal length f3 of the third lens, the central thickness CT3 of the third lens on the optical axis, the central thickness CTL of the polarizer on the optical axis, the central thickness CTQ2 of the second quarter-wave plate on the optical axis, the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, and the central thickness CTQ1 of the first quarter-wave plate on the optical axis satisfy: -1.5 < f3 / f1 < -1.0; 2 ≤ (CT3 + CTQ2 + CTL) / (CT1 + CTR + CTQ1) < 2.9. By designing and optimizing the optical system, on the premise that the ratio of f3 / f1 is within a reasonable range, by controlling the thickness ratio of relevant optical elements within a certain range, the transmittance of light can be optimized. Specifically, adjusting the thickness ratio within the appropriate range of 2 ≤ (CT3 + CTQ2 + CTL) / (CT1 + CTR + CTQ1) < 2.9 can minimize the loss and reflection of light, thereby improving the transmittance and efficiency of the optical system. Among them, the thickness ratio of the optical elements plays an important role in the balance of the optical path. By reasonably adjusting the thickness ratio, the balanced transmission of light between different elements can be achieved, avoiding excessive scattering and diffraction of light, thereby maintaining the clarity and quality of the image; in addition, when light propagates through elements with different thicknesses, refraction and deflection will occur, and by controlling the appropriate thickness ratio, these aberrations can be corrected, thereby contributing to correcting the aberrations in the optical system and improving the geometric shape and accuracy of the image.
[0055] In an exemplary embodiment, the effective focal length f2 of the second lens and the radius of curvature R3 of the first side surface of the second lens satisfy: 1 ≤ f2 / R3 < 1.8. By controlling the ratio between the focal length and the radius of curvature of the lens within a certain range, the generation of astigmatism can be effectively reduced. Astigmatism is a common aberration in optical systems, which can cause image distortion and blurring. Satisfying this conditional expression can reduce astigmatism and improve the clarity and accuracy of imaging.
[0056] In an exemplary embodiment, the distance TD on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens and the effective focal length f of the optical system satisfy: 0.5 < TD / f < 0.6. By satisfying this conditional expression, the ratio between the focal length of the optical system and the distance between the lenses can be optimized, improving the clarity, sharpness, and resolution of the image, making the imaging result more accurate and real, thereby achieving the best imaging quality; at the same time, the layout and structure of the lenses can also be optimized, making the optical system more stable and enhancing its anti-vibration ability, which helps to maintain the stability of the image and reduce the impact of vibration on imaging, especially in application scenarios where movement or vibration is required.
[0057] In an exemplary embodiment, the effective focal length f4 of the fourth lens and the effective focal length f of the optical system satisfy: -1.4 < f4 / f ≤ -0.7. The ratio of the focal lengths of the lenses is a key parameter in the design of optical systems. By satisfying -1.4 < f4 / f ≤ -0.7, the performance of the optical system can be optimized, including improving the imaging quality, enhancing the light focusing ability, and reducing aberrations, etc.
[0058] In an exemplary embodiment, the refractive index N3 of the third lens, the refractive index N1 of the first lens, the dispersion coefficient V3 of the third lens, and the dispersion coefficient V1 of the first lens satisfy: 1.0 < N3 / N1 < 1.2; 0.4 < V3 / V1 < 0.7. The refractive index and dispersion coefficient of the lenses are important factors affecting the image quality. By selecting the ratio of the refractive indices and the ratio of the dispersion coefficients of the lenses, color correction of the optical system can be achieved, which helps to reduce chromatic aberration and dispersion phenomena, and improve the color accuracy and clarity of the image. Satisfying these conditional expressions can optimize the performance of the optical system, including improving the imaging quality, reducing chromatic aberration and dispersion phenomena, making the image clearer and more real, and better reproducing the colors of the real world; in addition, by optimizing the color correction and image quality of the optical system, the occurrence of visual fatigue can also be reduced, and the visual burden on the user can be alleviated.
[0059] In an exemplary embodiment, the effective focal length f of the optical system, the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, and the central thickness CTQ1 of the first quarter-wave plate on the optical axis satisfy: 11 < f / (CT1 + CTR + CTQ1) < 12.4. Satisfying this conditional expression can achieve a compact design of the optical system, reduce the volume and weight of the device, improve the wearing convenience, and can effectively reduce astigmatism and improve the clarity and accuracy of imaging.
[0060] In an exemplary embodiment, the effective focal length f1 of the first lens and the curvature radius R1 of the first side surface of the first lens satisfy: 1.3 < f1 / R1 < 2.1. Satisfying this conditional expression, by reasonably configuring the ratio of the lens curvature radius and the focal length, the distortion in the optical system can be reduced, and the accuracy and authenticity of imaging can be improved; at the same time, the performance of the optical system can also be optimized, including improving the imaging quality and enhancing the light focusing ability, etc.
[0061] In an exemplary embodiment, the central thickness CT3 of the third lens on the optical axis and the sum ∑CT of the central thicknesses of the first lens to the fourth lens on the optical axis satisfy: 0.35 < CT3 / ∑CT < 0.55. Satisfying this conditional expression can optimize the performance of the optical system, including improving the imaging quality, enhancing the light focusing ability and reducing distortion, and also helps to achieve a lightweight design of the optical system.
[0062] In an exemplary embodiment, the entrance pupil diameter EPD of the optical system and the distance TD on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens satisfy: 0.9 < EPD / TD < 1.0. The brightness of the optical system is directly related to the light transmittance. The ratio of the entrance pupil diameter EPD and the optical axis distance (TD) can affect the light transmittance of the optical system. By satisfying this conditional expression, the light transmittance can be maximized, the energy loss can be reduced, and thus the brightness of the optical system can be increased and the efficiency of the optical system can be improved. This is particularly important for virtual reality devices, which can provide brighter and clearer images and enhance the user's visual experience. In addition, by adjusting the ratio of the entrance pupil diameter and the optical axis distance, the field of view angle of the optical system can also be increased. This is equally important for virtual reality devices, which can provide a wider field of view and enhance the immersion and realism.
[0063] In an exemplary embodiment, the effective focal length f3 of the third lens and the curvature radius R5 of the first side surface of the third lens satisfy: 1.3 < f3 / R5 < 1.5. Satisfying this conditional expression, by configuring an appropriate ratio of the lens focal length and the curvature radius, the aberration in the optical system can be reduced, and the clarity of imaging and the optical performance of the optical system can be improved.
[0064] In an exemplary embodiment, the combined focal length FG1 of the first lens, the reflective polarizing element, and the first quarter-wave plate satisfies 0.6 < FG1 / f2 < 1.4 with the effective focal length f2 of the second lens. Satisfying this conditional expression can maximize the light transmittance, reduce energy loss, and improve the efficiency of the optical system; at the same time, it can improve the resolution of the optical system, making the image clearer and more delicate; in addition, it can also optimize the chromatic aberration performance of the optical system, improving the accuracy and authenticity of imaging.
[0065] In an exemplary embodiment, the combined focal length FG2 of the third lens, the second quarter-wave plate, and the polarizer satisfies 1.3 < FG2 / f4 < 3.2 with the effective focal length f4 of the fourth lens. Satisfying this conditional expression can optimize the chromatic aberration of the optical system, avoid the appearance of colored edges or chromatic aberration in the image, and can also improve the resolution of the optical system, more clearly restoring the clarity and more details of the image.
[0066] In an exemplary embodiment, the axial distance SAG21 between the intersection of the first side surface of the second lens and the optical axis and the effective radius vertex of the first side surface of the second lens satisfies 0.4 < SAG21 / SAG11 < 1.0 with the axial distance SAG11 between the intersection of the first side surface of the first lens and the optical axis and the effective radius vertex of the first side surface of the first lens. Satisfying this conditional expression can reduce the axial distance ratio between the lenses, thereby reducing the generation of aberration and improving the clarity and accuracy of imaging.
[0067] In an exemplary embodiment, the axial distance SAG41 between the intersection of the first side surface of the fourth lens and the optical axis and the effective radius vertex of the first side surface of the fourth lens, the axial distance SAG42 between the intersection of the second side surface of the fourth lens and the optical axis and the effective radius vertex of the second side surface of the fourth lens, and the central thickness CT4 of the fourth lens on the optical axis satisfy 0.2 < (|SAG41| + |SAG42|) / CT4 < 1.9. Considering that the optical system may be affected by vibration during use, which can cause image blurring or distortion. By satisfying this conditional expression, the structure and stability of the lens can be optimized, the anti-vibration ability of the optical system can be improved, making the image more stable and clear; and by controlling the ratio of the axial distance and the central thickness of the fourth lens, a compact design of the optical system can also be achieved.
[0068] Reference Figure 1As shown, a second aspect of the present application provides an optical system, which may include, arranged in sequence along the optical axis from the first side to the second side: 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 second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. There may be an air gap between any adjacent lenses. In an exemplary embodiment, the second side of the optical system may further include a display screen.
[0069] Wherein, the effective focal length f1 of the first lens, the effective focal length f3 of the third lens, the entrance pupil diameter EPD of the optical system, and the distance TD on the optical axis from the first side of the first lens to the second side of the fourth lens satisfy: -1.5 < f3 / f1 < -1.0; 0.9 < EPD / TD < 1.0. By designing and optimizing the optical system, on the premise that the ratio of f3 / f1 is within a reasonable range, by controlling the ratio of the entrance pupil diameter EPD and the optical axis distance (TD) within a certain range, the light transmittance can be optimized. Among them, the brightness of the optical system is directly related to the light transmittance, and the ratio of the entrance pupil diameter and the optical axis distance can affect the light transmittance of the optical system. By satisfying the conditional formula 0.9 < EPD / TD < 1.0, the light transmittance can be maximized, the energy loss can be reduced, and thus the brightness of the optical system can be increased and the efficiency of the optical system can be improved. This is particularly important for virtual reality devices, which can provide brighter and clearer images and enhance the user's visual experience. In addition, by adjusting the ratio of the entrance pupil diameter and the optical axis distance, the field of view angle of the optical system can also be increased. This is also particularly important for virtual reality devices, which can provide a wider field of view and enhance the immersion and realism.
[0070] According to the optical system of the above embodiment of the present application, a four-lens catadioptric scheme can be adopted, and by adopting a polarized catadioptric optical path method, the body height can be better compressed and the imaging quality can be improved; in addition, by reasonably distributing the focal lengths, surface shapes, central thicknesses of each lens, and the on-axis spacings between each lens, etc., the incident light can be effectively converged, the total optical length can be reduced, and the processability can be improved, making the optical system more conducive to production and processing.
[0071] In an embodiment of the present application, the first side or the second side of any one lens of the optical system may be an aspherical surface. The aspherical lens has better curvature radius characteristics and has the advantages of improving distortion aberration and astigmatism aberration. By using an aspherical lens, the aberration that appears during imaging can be eliminated as much as possible, thereby improving the imaging quality.
[0072] Embodiments 1 to 5 of the optical system applicable to the above exemplary embodiments will be further described below with reference to the drawings and in conjunction with the embodiments.
[0073] Example 1
[0074] Figure 1 The structural schematic diagram of the optical system according to Embodiment 1 of the present application is shown.
[0075] As Figure 1 shown, the optical system includes, in order along the optical axis from the side close to the human eye to the side close to the display: 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 second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4.
[0076] The optical system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.
[0077] In this embodiment, the first lens E1 has a positive optical power. The first side surface of the first lens E1 is convex, and the second side surface is flat. The reflective polarizing element RP and the first quarter-wave plate QWP1 are sequentially attached to the second side surface. The second lens E2 has a positive optical power. The first side surface is convex, and the second side surface is concave. The first side surface of the third lens E3 is concave, and the second side surface is flat. The partial reflection element BS, the second quarter-wave plate QWP2, and the polarizer LP are sequentially attached to the second side surface. The fourth lens E4 has a negative optical power. The first side surface is convex, and the second side surface is concave. An optical element may also be provided between the fourth lens E4 and the image plane (IMA), and the optical element may be a filter or a protective glass, etc.
[0078] Table 1 shows the basic parameter table of the optical system of Embodiment 1, where the unit of the radius of curvature and the thickness / distance is millimeter (mm). The image light rays from the display screen sequentially pass through the optical surfaces of each element and are finally projected into the human eye.
[0079]
[0080]
[0081] Table 1
[0082] In this embodiment, both the first side surface and the second side surface of the fourth lens E4 are aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:
[0083]
[0084] Wherein, x is the sagitta, which is the distance from the vertex of the aspheric surface to the position along the optical axis at a height of h; c is the paraxial curvature of the aspheric 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 aspheric surface.
[0085] Table 2 shows the higher-order coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16 , A 18 and A 20 that can be used for the aspheric mirrors S24 and S25 in Example 1.
[0086] Coefficient / Plane Number S24 S25 A4 -7.9931E-01 -6.3669E-01 A6 -3.9385E-02 -4.2803E-01 A8 -1.7119E-03 -6.1338E-02 A10 -1.3914E-03 -4.4223E-02 A12 6.7489E-04 -2.3695E-02 A14 6.5301E-05 -1.7514E-02 A16 -6.2995E-06 -6.3956E-03 A18 5.8711E-05 -1.4767E-03 A20 0.0000E+00 0.0000E+00
[0087] Table 2
[0088] Figure 2A shows the axial chromatic aberration curve of the optical system of Example 1, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the optical system. Figure 2B shows the astigmatism curve of the optical system of Example 1, which represents the meridional image plane curvature and sagittal image plane curvature corresponding to different field angles. Figure 2C shows the distortion curve of the optical system of Example 1, which represents the distortion magnitude values corresponding to different field angles. According to Figures 2A to 2C it can be seen that the optical system given in Example 1 can achieve good imaging quality.
[0089] Figure 3 shows the MTF curve of the optical imaging system of Example 1. From Figure 3 it can be seen that the optical system of this embodiment has good contrast within a spatial frequency of 30 lp / mm and clear imaging.
[0090] Example 2
[0091] Figure 4 shows the schematic structural diagram of the optical system according to Embodiment 2 of the present application. In this embodiment and the following embodiments, for the sake of simplicity, some descriptions similar to those in Example 1 will be omitted.
[0092] As Figure 4 shown, the optical system includes, in order from the side close to the human eye to the side close to the display along the optical axis: 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 second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4.
[0093] The optical system may further include a stop STO disposed near the human eye side. The stop STO may be disposed on the first side of the first lens E1.
[0094] In this embodiment, the first lens E1 has a positive optical power. The first side surface of the first lens E1 is a convex surface, and the second side surface is a flat surface. A reflective polarizing element RP and a first quarter-wave plate QWP1 are sequentially attached to the second side surface. The second lens E2 has a positive optical power. The first side surface is a convex surface, and the second side surface is a convex surface. The first side surface of the third lens E3 is a concave surface, and the second side surface is a flat surface. A partial reflection element BS, a second quarter-wave plate QWP2, and a polarizer LP are sequentially attached to the second side surface. The fourth lens E4 has a negative optical power. The first side surface is a convex surface, and the second side surface is a concave surface.
[0095] Table 3 shows the basic parameter table of the optical system of Embodiment 2, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).
[0096]
[0097]
[0098] Table 3
[0099] In this embodiment, both the first side surface and the second side surface of the fourth lens E4 are aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but is not limited to, the formula (1) given in the foregoing Embodiment 1.
[0100] Table 4 shows the higher-order term coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16 , A 18 and A 20 .
[0101] Coefficient / Plane Number S24 S25 A4 -1.5200E+00 -5.4807E+00 A6 1.4310E-02 -8.5773E-01 A8 6.2137E-02 -1.9172E+00 A10 4.3495E-02 -2.4615E+00 A12 2.8231E-02 -1.9482E+00 A14 1.1967E-02 -1.0110E+00 A16 2.6612E-03 -3.2794E-01 A18 1.3535E-04 -5.0105E-02 A20 0.0000E+00 0.0000E+00
[0102] Table 4
[0103] Figure 5A shows the axial chromatic aberration curve of the optical system of Embodiment 2, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the optical system. Figure 5B shows the astigmatism curve of the optical system of Embodiment 2, which represents the meridional image plane curvature and the sagittal image plane curvature corresponding to different field angles. Figure 5C shows the distortion curve of the optical system of Embodiment 2, which represents the distortion magnitude values corresponding to different field angles. According to Figures 5A to 5C it can be known that the optical system given in Embodiment 2 can achieve good imaging quality.
[0104] Figure 6 The MTF curve of the optical imaging system of Embodiment 2 is shown. It can be seen from Figure 6 that the optical system of this embodiment has good contrast within the spatial frequency of 30 lp / mm and the imaging is clear.
[0105] Example 3
[0106] Figure 7 The structural schematic diagram of the optical system according to Embodiment 3 of the present application is shown.
[0107] As Figure 7 shown, the optical system includes, in order along the optical axis from the side close to the human eye to the side close to the display: 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 second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4.
[0108] The optical system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.
[0109] In this embodiment, the first lens E1 has a positive optical power. The first side surface of the first lens E1 is a convex surface, and the second side surface is a flat surface. The reflective polarizing element RP and the first quarter-wave plate QWP1 are sequentially attached to the second side surface. The second lens E2 has a positive optical power. The first side surface is a convex surface, and the second side surface is a convex surface. The first side surface of the third lens E3 is a concave surface, and the second side surface is a flat surface. The partial reflection element BS, the second quarter-wave plate QWP2, and the polarizer LP are sequentially attached to the second side surface. The fourth lens E4 has a negative optical power. The first side surface is a convex surface, and the second side surface is a concave surface.
[0110] Table 5 shows the basic parameter table of the optical system of Embodiment 3, where the unit of the radius of curvature and the thickness / distance is millimeter (mm).
[0111]
[0112] Table 5
[0113] In this embodiment, both the first side surface and the second side surface of the fourth lens E4 are aspherical surfaces. The surface shape x of each aspherical lens can be defined by, but not limited to, the formula (1) given in the foregoing Embodiment 1.
[0114] Table 6 shows the higher-order term coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16, A 18 and A 20 .
[0115] Coefficient / Plane Number S24 S25 A4 -1.1342E+00 -1.4002E+00 A6 7.2212E-03 8.6453E-02 A8 8.8705E-03 9.8141E-02 A10 3.7541E-03 8.4787E-02 A12 6.3881E-03 5.2505E-02 A14 2.5120E-03 2.2854E-02 A16 9.3741E-04 7.7876E-03 A18 2.8491E-04 2.0627E-03 A20 0.0000E+00 0.0000E+00
[0116] Table 6
[0117] Figure 8A shows the axial chromatic aberration curve of the optical system of Embodiment 3, which represents the deviation of the focusing points of light rays with different wavelengths after passing through the optical system. Figure 8B shows the astigmatism curve of the optical system of Embodiment 3, which represents the meridional image plane curvature and sagittal image plane curvature corresponding to different field angles. Figure 8C shows the distortion curve of the optical system of Embodiment 3, which represents the distortion magnitude values corresponding to different field angles. According to Figures 8A to 8C it can be seen that the optical system given in Embodiment 3 can achieve good imaging quality.
[0118] Figure 9 shows the MTF curve of the optical imaging system of Embodiment 3. From Figure 9 it can be seen that the optical system of this embodiment has good contrast within the spatial frequency of 30 lp / mm and the imaging is clear.
[0119] Example 4
[0120] Figure 10 shows a schematic structural diagram of the optical system according to Embodiment 4 of the present application.
[0121] As Figure 10 shown, the optical system includes, in order along the optical axis from the side close to the human eye to the side close to the display: 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 second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4.
[0122] The optical system may further include a diaphragm STO disposed on the side close to the human eye. The diaphragm STO may be disposed on the first side of the first lens E1.
[0123] In this embodiment, the first lens E1 has a positive optical power. The first side surface of the first lens E1 is a convex surface, and the second side surface is a flat surface. The reflective polarizing element RP and the first quarter-wave plate QWP1 are sequentially attached to the second side surface. The second lens E2 has a positive optical power. The first side surface is a convex surface, and the second side surface is a convex surface. The first side surface of the third lens E3 is a concave surface, and the second side surface is a flat surface. The partial reflection element BS, the second quarter-wave plate QWP2, and the polarizer LP are sequentially attached to the second side surface. The fourth lens E4 has a negative optical power. The first side surface is a concave surface, and the second side surface is a concave surface.
[0124] Table 7 shows the basic parameter table of the optical system of Example 4, where the unit of the radius of curvature and the thickness / distance is millimeter (mm).
[0125]
[0126]
[0127] Table 7
[0128] In this embodiment, both the first side and the second side of the fourth lens E4 are aspherical surfaces, and the surface profile x of each aspherical lens can be defined by, but not limited to, the formula (1) given in the foregoing Example 1.
[0129] Table 8 shows the high-order term coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16 , A 18 and A 20 .
[0130]
[0131]
[0132] Table 8
[0133] Figure 11A shows the axial chromatic aberration curve of the optical system of Example 4, which represents the deviation of the convergence points of light rays with different wavelengths after passing through the optical system. Figure 11B shows the astigmatism curve of the optical system of Example 4, which represents the meridional image plane curvature and the sagittal image plane curvature corresponding to different field angles. Figure 11C shows the distortion curve of the optical system of Example 4, which represents the distortion magnitude values corresponding to different field angles. According to Figures 11A to 11C , it can be known that the optical system given in Example 4 can achieve good imaging quality.
[0134] Figure 12 shows the MTF curve of the optical imaging system of Example 4. It can be seen from Figure 12 that the optical system of this embodiment has better contrast within the spatial frequency of 30 lp / mm and the imaging is clear.
[0135] Example 5
[0136] Figure 13 shows the structural schematic diagram of the optical system according to Embodiment 5 of the present application.
[0137] AsFigure 13 As shown, the optical system includes, in order along the optical axis from the side close to the human eye to the side close to the display: 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 second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4.
[0138] The optical system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.
[0139] In this embodiment, the first lens E1 has a positive optical power. The first side surface of the first lens E1 is convex, and the second side surface is flat. The reflective polarizing element RP and the first quarter-wave plate QWP1 are sequentially attached to the second side surface. The second lens E2 has a positive optical power. The first side surface is convex, and the second side surface is convex. The first side surface of the third lens E3 is concave, and the second side surface is flat. The partial reflection element BS, the second quarter-wave plate QWP2, and the polarizer LP are sequentially attached to the second side surface. The fourth lens E4 has a negative optical power. The first side surface is concave, and the second side surface is convex.
[0140] Table 9 shows the basic parameter table of the optical system of Embodiment 5, where the unit of the radius of curvature and the thickness / distance is millimeter (mm).
[0141]
[0142]
[0143] Table 9
[0144] In this embodiment, both the first side surface and the second side surface of the fourth lens E4 are aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the formula (1) given in the foregoing Embodiment 1.
[0145] Table 10 shows the high-order term coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16 , A 18 and A 20 .
[0146] Coefficient / Plane Number S24 S25 A4 -5.6635E-01 -1.9809E-01 A6 1.4571E-02 -3.1399E-01 A8 -1.1511E-02 -2.4986E-01 A10 -3.4113E-02 1.0909E-01 A12 -5.4541E-03 1.9584E-01 A14 -1.1154E-02 -1.7031E-02 A16 1.6867E-03 -7.5399E-02 A18 -1.1201E-03 -5.8405E-02 A20 0.0000E+00 0.0000E+00
[0147] Table 10
[0148] Figure 14A shows the axial chromatic aberration curve of the optical system of Embodiment 5, which represents the deviation of the convergence points of light rays of different wavelengths after passing through the optical system. Figure 14BThe astigmatism curve of the optical system of Embodiment 5 is shown, which represents the meridional image plane curvature and sagittal image plane curvature corresponding to different field angles. Figure 14C The distortion curve of the optical system of Embodiment 5 is shown, which represents the distortion magnitude values corresponding to different field angles. According to Figures 14A to 14C it can be known that the optical system given in Embodiment 5 can achieve good imaging quality.
[0149] Figure 15 The MTF curve of the optical imaging system of Embodiment 5 is shown. From Figure 15 it can be seen that the optical system of this embodiment has good contrast within the spatial frequency of 30 lp / mm and the imaging is clear.
[0150] Table 11 shows the optical parameters of the optical systems of the above-mentioned Embodiments 1 to 5 respectively, such as the entrance pupil diameter EPD of the optical system, the effective focal length f of the optical system, and the effective focal lengths and combined focal lengths of each lens and other related parameters. The unit of each optical parameter is millimeter (mm).
[0151] Parameter / Example 1 2 3 4 5 f (mm) 42.00 42.00 42.00 42.00 42.00 f1 (mm) 64.76 45.35 73.87 63.58 76.19 f2 (mm) 70.44 66.90 56.51 64.47 61.07 f3 (mm) -88.59 -67.79 -76.17 -88.38 -93.33 f4 (mm) -55.05 -49.84 -37.66 -30.48 -29.43 EPD (mm) 23.00 23.00 23.00 23.00 23.00 TD (mm) 23.62 23.80 23.64 24.60 24.51 FG1 (mm) 64.76 45.35 73.87 63.58 76.19 FG2 (mm) -88.59 -67.79 -76.17 -88.38 -93.33 SAG11 (mm) 1.98 2.29 2.00 2.10 1.87 SAG21 (mm) 1.65 1.03 1.61 1.67 1.70 SAG41 (mm) 0.43 0.0012 -0.03 -0.81 -1.64 SAG42 (mm) 1.08 0.90 0.84 0.11 -0.72
[0152] Table 11
[0153] In summary, in Embodiments 1 to 5, the optical systems respectively satisfy the conditional expressions shown in Table 12 below.
[0154]
[0155]
[0156] Table 12
[0157] The above description is only the preferred embodiments of the present application and the description of the applied technical principles. Those skilled in the art should understand that the scope of the utility model involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. 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 the present application.
Claims
1. An optical system, characterized in that: In the direction of the optical axis, from the first side to the second side in sequence, it includes: A first lens with positive optical power, whose first side is convex and the second side is flat; A reflective polarizing element; A first quarter-wave plate; A second lens with positive optical power, whose first side is convex; A third lens with negative optical power, whose first side is concave and the second side is flat; A partial reflection element; A second quarter-wave plate; A polarizer; and A fourth lens with negative optical power; Among them, the number of lenses with optical power in the optical system is four; The effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: -1.5 < f3 / f1 < -1.0; and The central thickness CT3 of the third lens on the optical axis, the central thickness CTL of the polarizer on the optical axis, the central thickness CTQ2 of the second quarter-wave plate on the optical axis, the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, and the central thickness CTQ1 of the first quarter-wave plate on the optical axis satisfy: 2 ≤ (CT3 + CTQ2 + CTL) / (CT1 + CTR + CTQ1) ≤ 2.
81.
2. The optical system according to claim 1, characterized in that The effective focal length f2 of the second lens and the curvature radius R3 of the first side of the second lens satisfy: 1 ≤ f2 / R3 ≤ 1.
73.
3. The optical system according to claim 1, characterized in that The distance TD on the optical axis from the first side of the first lens to the second side of the fourth lens and the effective focal length f of the optical system satisfy: 0.56 ≤ TD / f < 0.
6.
4. The optical system according to claim 1, characterized in that The effective focal length f4 of the fourth lens and the effective focal length f of the optical system satisfy: -1.31 ≤ f4 / f ≤ -0.
7.
5. The optical system according to claim 1, characterized in that The refractive index N3 of the third lens, the refractive index N1 of the first lens, the dispersion coefficient V3 of the third lens, and the dispersion coefficient V1 of the first lens satisfy: 1.0 < N3 / N1 ≤ 1.14; 0.4 < V3 / V1 ≤ 0.
61.
6. The optical system according to claim 1, characterized in that The effective focal length f of the optical system, the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, and the central thickness CTQ1 of the first quarter-wave plate on the optical axis satisfy: 11 < f / (CT1 + CTR + CTQ1) < 12.
4.
7. The optical system according to claim 1, characterized in that The effective focal length f1 of the first lens and the curvature radius R1 of the first side of the first lens satisfy: 1.3 < f1 / R1 ≤ 2.
04.
8. The optical system according to claim 1, wherein: The central thickness CT3 of the third lens on the optical axis and the sum ∑CT of the central thicknesses of the first lens to the fourth lens on the optical axis satisfy: 0.35 < CT3 / ∑CT < 0.
55.
9. The optical system according to claim 1, characterized in that The entrance pupil diameter EPD of the optical system and the distance TD on the optical axis from the first side of the first lens to the second side of the fourth lens satisfy: 0.9 < EPD / TD < 1.
0.
10. The optical system according to claim 1, characterized in that The effective focal length f3 of the third lens and the curvature radius R5 of the first side of the third lens satisfy: 1.3 < f3 / R5 ≤ 1.
43.
11. The optical system according to any one of claims 1 to 10, characterized in that: The combined focal length FG1 of the first lens, the reflective polarizing element and the first quarter-wave plate and the effective focal length f2 of the second lens satisfy the following: 0.68≤FG1 / f2≤1.
31.
12. The optical system according to any one of claims 1 to 10, characterized in that: The combined focal length FG2 of the third lens, the second quarter wave plate and the polarizer, and the effective focal length f4 of the fourth lens satisfy the following: 1.36≤FG2 / f4<3.
2.
13. The optical system according to any one of claims 1 to 10, characterized in that: The on-axis distance SAG21 between the intersection of the first side surface of the second lens and the optical axis to the effective radius vertex of the first side surface of the second lens and the on-axis distance SAG11 between the intersection of the first side surface of the first lens and the optical axis to the effective radius vertex of the first side surface of the first lens satisfy: 0.4 <SAG21 / SAG11≤0.91。 14. The optical system according to any one of claims 1 to 10, characterized in that: An on-axis distance SAG41 between the intersection of the first side surface of the fourth lens and the optical axis to the effective radius vertex of the first side surface of the fourth lens, an on-axis distance SAG42 between the intersection of the second side surface of the fourth lens and the optical axis to the effective radius vertex of the second side surface of the fourth lens, and a center thickness CT4 of the fourth lens on the optical axis satisfy: 0.26≤(|SAG41|+|SAG42|) / CT4≤1.
82.
15. The optical system according to any one of claims 1 to 10, characterized in that: The reflective polarizing element is disposed on the second side surface of the first lens and is at least partially attached to the second side surface of the first lens; the first quarter-wave plate is disposed on the second side surface of the reflective polarizing element and is at least partially attached to the second side surface of the reflective polarizing element; and The partially reflecting element is arranged on the second side surface of the third lens and is at least partially in contact with the second side surface of the third lens; the second quarter-wave plate is arranged on the second side surface of the partially reflecting element and is at least partially in contact with the second side surface of the partially reflecting element; the polarizer is arranged on the second side surface of the second quarter-wave plate and is at least partially in contact with the second side surface of the second quarter-wave plate.
16. The optical system according to any one of claims 1 to 10, characterized in that: The second side surface of the second lens is a convex surface or a concave surface; The first side surface of the fourth lens is convex, and the second side surface is concave; or the first side surface is concave, and the second side surface is concave; or the first side surface is concave, and the second side surface is convex.