Optical system
By adopting four lenses in the folding and trans optical system, the power is reasonably configured, and the polarization performance is controlled, the problem of poor imaging quality in the prior art is solved, and better imaging quality and overall performance are achieved.
Patent Information
- Application Number
- CN202421871050.2
- 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 fold-trans optical systems have poor imaging quality, resulting in blurred pictures.
The optical system using four-piece lenses is reasonably configured, and the polarization performance of the optical system is controlled by limiting the ratio of the combined focal length of the reflective polarization element, the first quarter wave plate and the second lens to the radius of curvature of the second lens.
The imaging quality of the optical system is improved, the imaging quality, polarization performance and design complexity are balanced, and the overall performance is achieved.
Smart Images
Figure CN222994759U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical devices, and particularly to a catadioptric optical system. Background Art
[0002] The catadioptric optical system utilizes the characteristics of polarized light to shorten the body length of the optical system, effectively reduce the volume of the optical system, and reserve space for the overall design of electronic devices including the optical system. Therefore, the catadioptric optical system has been widely used in fields such as virtual reality technology or augmented reality technology.
[0003] However, the existing catadioptric optical systems usually adopt two lenses, which results in a relatively blurred image and poor imaging quality of the catadioptric optical system. Summary of the Utility Model
[0004] This application provides an optical system that can at least solve or partially solve at least one problem or other problems existing in the prior art.
[0005] On the one hand, this application provides such an optical system, which sequentially includes a first lens, a second lens, a third lens, and a fourth lens along the optical axis from the first side to the second side. The first lens has a positive optical power, its first side is a convex surface, and its second side is a concave surface. The second lens has a positive optical power, its first side is a plane, and its second side is a convex surface. The third lens has a negative optical power, its first side is a concave surface, and its second side is a convex surface. The fourth lens has a positive optical power, its first side is a plane, and its second side is a convex surface. Among them, the optical system further includes a first quarter-wave plate, a reflective polarizing element, a partial reflection element, a polarizer, and a second quarter-wave plate; the first quarter-wave plate is disposed on the first side of the second lens; the reflective polarizing element is disposed on the first side of the first quarter-wave plate; the partial reflection element is disposed on the second side of the third lens; the polarizer is disposed on the first side of the fourth lens; the second quarter-wave plate is disposed on the first side of the polarizer. The effective focal length f1 of the first lens and the effective focal length f2 of the second lens satisfy: 0.05 < f1 / f2 < 0.5; the combined focal length fz1 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: -2.1 < fz1 / R4 < -1.9.
[0006] According to an exemplary embodiment of this application, the refractive index NQ1 of the first quarter-wave plate and the refractive index N2 of the second lens satisfy: 0.95 < N2 / NQ1 < 1.05.
[0007] According to an exemplary embodiment of this application, the Abbe number V1 of the first lens and the Abbe number V3 of the third lens satisfy: 2.0 < V1 / V3 < 2.5.
[0008] According to an exemplary embodiment of the present application, the effective focal length f1 of the first lens, the radius of curvature R1 of the first side surface of the first lens, and the radius of curvature R2 of the second side surface of the first lens satisfy: 0.4 < f1 / (R1 + R2) < 1.0.
[0009] According to an exemplary embodiment of the present application, the radius of curvature R5 of the first side surface of the third lens and the radius of curvature R6 of the second side surface of the third lens satisfy: 0.2 < R5 / R6 < 0.6.
[0010] According to an exemplary embodiment of the present application, the total effective focal length f of the optical system and the effective focal length f3 of the third lens satisfy: -0.55 < f / f3 < -0.15.
[0011] According to an exemplary embodiment of the present application, the central thickness CT3 of the third lens on the optical axis, the central thickness CTQ2 of the second quarter-wave plate on the optical axis, the central thickness CTL of the polarizer on the optical axis, and the central thickness CT4 of the fourth lens on the optical axis satisfy: 2.5 < CT3 / (CTQ2 + CTL + CT4) < 4.4.
[0012] According to an exemplary embodiment of the present application, the on-axis distance T12 from the second side surface of the first lens to the first side surface of the second lens, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis, and the central thickness CT2 of the second lens on the optical axis satisfy: 0.2 < T12 / (CTR + CTQ1 + CT2) < 1.4.
[0013] According to an exemplary embodiment of the present application, the effective focal length f4 of the fourth lens and the radius of curvature R8 of the second side surface of the fourth lens satisfy: -0.9 < R8 / f4 < -0.5.
[0014] According to an exemplary embodiment of the present application, the Abbe number VR of the reflective polarizing element, the Abbe number VQ1 of the first quarter-wave plate, and the Abbe number V2 of the second lens satisfy: 1.6 < (VR + VQ1) / V2 < 2.0.
[0015] According to an exemplary embodiment of the present application, the optical system further includes a diaphragm disposed between the first side and the first lens. Wherein, the on-axis distance SR from the diaphragm to the first side surface of the first lens and the central thickness CT1 of the first lens on the optical axis satisfy: 3.3 < SR / CT1 < 4.2.
[0016] According to an exemplary embodiment of the present application, 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 semi-aperture of the first side surface of the first lens and the axial distance SAG12 between the intersection of the second side surface of the first lens and the optical axis and the vertex of the effective semi-aperture of the second side surface of the first lens satisfy: 0.1 < SAG12 / SAG11 < 0.4.
[0017] According to an exemplary embodiment of the present application, the axial distance SAG31 between the intersection of the first side surface of the third lens and the optical axis and the vertex of the effective semi-aperture of the first side surface of the third lens, the axial distance SAG32 between the intersection of the second side surface of the third lens and the optical axis and the vertex of the effective semi-aperture of the second side surface of the third lens, and the central thickness CT3 of the third lens on the optical axis satisfy: 6.3 < CT3 / |SAG31 + SAG32| < 10.9.
[0018] The optical system provided by the present application uses four lenses, rationally configures the optical powers of the four lenses, and makes the optical system satisfy "0.05 < f1 / f2 < 0.5", which is beneficial to improving the imaging quality of the optical system; at the same time, by restricting 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 surface of the second lens, it is beneficial to control the polarization performance of the optical system, realize the constraint of the polarization characteristics of the optical system, and can also balance the imaging quality, polarization performance and design complexity of the optical system, so as to ensure that the optical system achieves better overall performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other features, objects and advantages of the present application will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Among them:
[0020] Figure 1 shows a schematic structural diagram of the optical system according to Embodiment 1 of the present application;
[0021] Figures 2A to 2D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve and modulation transfer function (MTF) curve of the optical system according to Embodiment 1 of the present application;
[0022] Figure 3 shows a schematic structural diagram of the optical system according to Embodiment 2 of the present application;
[0023] 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;
[0024] Figure 5Shows a schematic structural diagram of an optical system according to Embodiment 3 of the present application;
[0025] 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;
[0026] Figure 7 Shows a schematic structural diagram of an optical system according to Embodiment 4 of the present application;
[0027] 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;
[0028] Figure 9 Shows a schematic structural diagram of an optical system according to Embodiment 5 of the present application; and
[0029] 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
[0030] 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 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.
[0031] 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.
[0032] In the 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 shapes shown in the drawings. The drawings are only examples and are not drawn strictly to scale.
[0033] 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. The surface of each lens closest to the first side (such as the human eye side) is called the first side surface of the lens, and the surface of each lens closest to the second side (such as the display screen side) is called the second side surface of the lens.
[0034] 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. In addition, when describing the embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Also, the term "exemplary" is intended to refer to an example or illustration.
[0035] 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.
[0036] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.
[0037] The features, principles and other aspects of the present application will be described in detail below.
[0038] Referring to Figure 1 , Figure 3 , Figure 5 , Figure 7 and Figure 9 , a first aspect of the present application provides an optical system that may include a first lens, a second lens, a third lens, and a fourth lens arranged in sequence along the optical axis from a first side to a second side.
[0039] In an exemplary embodiment, the first lens may have a positive focal power. The second lens may have a positive focal power. The third lens may have a negative focal power. The fourth lens may have a positive focal power. Reasonably configuring the focal powers of the respective lenses is beneficial to improving the imaging quality of the optical system.
[0040] In an exemplary embodiment, the first side of the first lens may be convex, and the second side may be concave.
[0041] In an exemplary embodiment, the first side of the second lens may be planar, and the second side may be convex.
[0042] In an exemplary embodiment, the first side of the third lens may be concave, and the second side may be convex.
[0043] In an exemplary embodiment, the first side surface of the fourth lens may be a plane, and the second side surface may be a convex surface.
[0044] In an exemplary embodiment, the optical system may further include a first quarter-wave plate. The first quarter-wave plate is used to change the polarization state of light. For example, it can convert circularly polarized light into linearly polarized light, or convert linearly polarized light into circularly polarized light. The circularly polarized light may include right-handed circularly polarized light or left-handed circularly polarized light. The linearly polarized light may include S linearly polarized light or P linearly polarized light.
[0045] In an exemplary embodiment, the optical system may further include a reflective polarizing element. The reflective polarizing element is used to reflect linearly polarized light in a predetermined direction and transmit linearly polarized light orthogonal to the predetermined direction. For example, the reflective polarizing element may reflect S linearly polarized light and transmit P linearly polarized light, or the reflective polarizing element may reflect P linearly polarized light and transmit S linearly polarized light.
[0046] In an exemplary embodiment, the first quarter-wave plate may be disposed on the first side surface of the second lens and at least partially adhered to the first side surface of the second lens. The reflective polarizing element may be disposed on the first side surface of the first quarter-wave plate and at least partially adhered to the first side surface of the first quarter-wave plate.
[0047] In an exemplary embodiment, the first side surface of the second lens may be a plane. The reflective polarizing element and the first quarter-wave plate are adhered and attached to the first side surface of the second lens, wherein the first quarter-wave plate is closer to the second lens than the reflective polarizing element. By combining the reflective polarizing element and the first quarter-wave plate together and then attaching them to the first side plane of the second lens, the difficulty of the attaching process can be reduced, the attaching quality can be improved, and thus the performance of the optical system can be improved.
[0048] In an exemplary embodiment, the optical system may further include a partial reflection element. The partial reflection element may be disposed on the second side surface of the third lens and at least partially adhered to the second side surface of the third lens. The partial reflection element may have a semi-transmissive and semi-reflective effect on light. By disposing the partial reflection element on the second side surface of the third lens and combining it with the reflective polarizing element and the first quarter-wave plate, the light can be refracted and reflected multiple times, effectively reducing the overall length of the optical system.
[0049] In an exemplary embodiment, the optical system may further include a second quarter-wave plate and a polarizer. The polarizer may be disposed on the first side surface of the fourth lens and at least partially adhered to the first side surface of the fourth lens. The second quarter-wave plate may be disposed on the first side surface of the polarizer and at least partially adhered to the first side surface of the polarizer. The polarizer is configured to convert natural light emitted from the display screen on the second side into linearly polarized light, and the second quarter-wave plate is configured to convert the linearly polarized light from the polarizer into circularly polarized light (e.g., right-handed circularly polarized light or left-handed circularly polarized light). By using the second quarter-wave plate and the polarizer, the natural light emitted from the display screen can be converted into circularly polarized light, reducing the influence of material stress of the components between the display screen and the polarizer, and improving the contrast of the optical system.
[0050] In an exemplary embodiment, the first side surface of the fourth lens may be a plane. The second quarter-wave plate and the polarizer are adhered and attached to the first side surface of the fourth lens, wherein the polarizer is closer to the fourth lens than the second quarter-wave plate. By combining the second quarter-wave plate and the polarizer together and then attaching them to the first side surface of the fourth lens, the difficulty of the attaching process can be reduced, the attaching quality can be improved, and thus the performance of the optical system can be improved.
[0051] In an exemplary embodiment, the optical system may further include a diaphragm, and the diaphragm may be disposed between the first side and the first lens. The image light from the second side passes through the fourth lens, the polarizer, the second quarter-wave plate, the third lens, the second lens, the first quarter-wave plate, the reflective polarizing element, the first lens, etc., and is finally projected onto the eyes of the user on the first side after multiple refractions and reflections.
[0052] In an exemplary embodiment, the first side may be, for example, the human eye side, and the second side may be, for example, the display screen side. Correspondingly, the first side surfaces of the respective components (the first lens, the second lens, the third lens, the fourth lens, the first quarter-wave plate, the polarizer) may be referred to as the near-eye side surfaces, and the second side surfaces may be referred to as the near-screen side surfaces.
[0053] In an exemplary embodiment, an image plane may be provided on the second side of the optical system. A display screen may be provided on the image plane. Image light from the display screen may sequentially pass through a fourth lens, a polarizer, a second quarter-wave plate, a third lens, a second lens, and a first quarter-wave plate, and reach a reflective polarizing element, and then be reflected at the reflective polarizing element to form first reflected image light. The first reflected image light passes through the first quarter-wave plate, the second lens, and the third lens and reaches a partial reflection element on the second side surface of the third lens, and then is reflected at the partial reflection element to form second reflected image light. The second reflected image light sequentially passes through the third lens, the second lens, the first quarter-wave plate, the reflective polarizing element, the first lens to the aperture stop and finally projects into the user's eyes. The optical system provided in this application folds the required optical path in a manner of combining light reflection and refraction without affecting the projection quality, effectively shortening the body length of the optical system.
[0054] In an exemplary embodiment, the effective focal length f1 of the first lens and the effective focal length f2 of the second lens may satisfy: 0.05 < f1 / f2 < 0.5; the combined focal length fz1 of the reflective polarizing element, the first quarter-wave plate, and the second lens and the radius of curvature R4 of the second side surface of the second lens may satisfy: -2.1 < fz1 / R4 < -1.9. By controlling the optical system to satisfy "0.05 < f1 / f2 < 0.5", it is beneficial to improve the imaging quality of the optical system; at the same time, by restricting 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 surface of the second lens, it is beneficial to control the polarization performance of the optical system, realize the constraint on the polarization characteristics of the optical system, and balance the imaging quality, polarization performance, and design complexity of the optical system, so as to ensure that the optical system achieves better overall performance.
[0055] In an exemplary embodiment, the refractive index NQ1 of the first quarter-wave plate and the refractive index N2 of the second lens may satisfy: 0.95 < N2 / NQ1 < 1.05. Reasonably configuring the ratio of the refractive index of the second lens to the refractive index of the first quarter-wave plate can avoid total internal reflection of light caused by too large a difference in the refractive indices of the first quarter-wave plate and the second lens, reduce light reflection and refraction losses in the optical system, and improve the light transmission efficiency; at the same time, it is also beneficial to improve the dispersion effect of the optical system.
[0056] In an exemplary embodiment, the Abbe number V1 of the first lens and the Abbe number V3 of the third lens may satisfy: 2.0 < V1 / V3 < 2.5. The chromatic dispersion effect of the optical system will cause the focusing positions of light rays of different wavelengths to be different, thereby affecting the imaging quality of the optical system. Reasonably configuring the ratio of the Abbe number of the first lens to the Abbe number of the third lens can effectively reduce the chromatic dispersion effect of the optical system, improve the performance of the optical system such as resolution, contrast, and imaging quality, making the optical system more stable and reliable; at the same time, it can also simplify the design and manufacturing process of the optical system, reduce costs and time, and improve production efficiency.
[0057] In an exemplary embodiment, the effective focal length f1 of the first lens, the curvature radius R1 of the first side surface of the first lens, and the curvature radius R2 of the second side surface of the first lens may satisfy: 0.4 < f1 / (R1 + R2) < 1.0. Reasonably configuring the ratio of the effective focal length of the first lens to the sum of the curvature radii of the first side surface and the second side surface of the first lens can reduce aberrations such as spherical aberration and astigmatism of the optical system, improve the imaging quality of the optical system, and make the image formed by the optical system clearer and more accurate; at the same time, it can also simplify the manufacturing process of the optical system, reduce the process difficulty and cost.
[0058] In an exemplary embodiment, the curvature radius R5 of the first side surface of the third lens and the curvature radius R6 of the second side surface of the third lens may satisfy: 0.2 < R5 / R6 < 0.6. Reasonably configuring the ratio of the curvature radius of the first side surface of the third lens to the curvature radius of the second side surface of the third lens can constrain the shape of the third lens, better control the focusing and transmission of light rays, reduce the aberrations of the optical system, and improve the optical performance of the optical system.
[0059] In an exemplary embodiment, the total effective focal length f of the optical system and the effective focal length f3 of the third lens may satisfy: -0.55 < f / f3 < -0.15. Reasonably configuring the ratio of the total effective focal length of the optical system to the effective focal length of the third lens can improve the imaging quality of the optical system, enhance the light focusing ability, and reduce the distortion of the optical system.
[0060] In an exemplary embodiment, the central thickness CT3 of the third lens on the optical axis, the central thickness CTQ2 of the second quarter-wave plate on the optical axis, the central thickness CTL of the polarizer on the optical axis, and the central thickness CT4 of the fourth lens on the optical axis may satisfy: 2.5 < CT3 / (CTQ2 + CTL + CT4) < 4.4. By controlling the above conditional expression, a compact design of the optical system can be achieved, thereby reducing the volume and weight of the electronic device including the optical system and improving the convenience of wearing the electronic device; at the same time, it can also avoid the thickness of the fourth lens being too thin, reduce the processing, shaping, and assembly difficulty of the fourth lens, and is beneficial to the attachment of the polarizer and the second quarter-wave plate.
[0061] In an exemplary embodiment, the on-axis distance T12 from the second side surface of the first lens to the first side surface of the second lens, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis, and the central thickness CT2 of the second lens on the optical axis may satisfy: 0.2 < T12 / (CTR + CTQ1 + CT2) < 1.4. By controlling the above conditional expression, a compact design of the optical system can be achieved, thereby reducing the volume and weight of the electronic device including the optical system and improving the convenience of wearing the electronic device; at the same time, it can also prevent the thickness of the second lens from being too thin, reducing the difficulty of processing, forming, and assembling the second lens, and being beneficial to the attachment of the reflective polarizing element and the first quarter-wave plate.
[0062] In an exemplary embodiment, the effective focal length f4 of the fourth lens and the radius of curvature R8 of the second side surface of the fourth lens may satisfy: -0.9 < R8 / f4 < -0.5. By reasonably configuring the ratio of the radius of curvature of the second side surface of the fourth lens to the effective focal length of the fourth lens, the shape of the fourth lens can be constrained, making the propagation of light inside the fourth lens more appropriate and effective, thereby ensuring the refraction and focusing effects of light inside the fourth lens.
[0063] In an exemplary embodiment, the Abbe number VR of the reflective polarizing element, the Abbe number VQ1 of the first quarter-wave plate, and the Abbe number V2 of the second lens may satisfy: 1.6 < (VR + VQ1) / V2 < 2.0. The chromatic dispersion effect of the optical system will cause the focusing positions of light rays of different wavelengths to be different, thus affecting the imaging quality of the optical system. By reasonably configuring the ratio of the sum of the Abbe numbers of the reflective polarizing element and the first quarter-wave plate to the Abbe number of the second lens, the chromatic dispersion effect of the optical system can be effectively reduced, the resolution, contrast, and imaging quality of the optical system can be improved, and the optical system can be made more stable and reliable.
[0064] In an exemplary embodiment, the on-axis distance SR from the aperture stop to the first side surface of the first lens and the central thickness CT1 of the first lens on the optical axis may satisfy: 3.3 < SR / CT1 < 4.2. By reasonably configuring the ratio of the on-axis distance from the aperture stop to the first side surface of the first lens to the central thickness of the first lens on the optical axis, it is beneficial to constrain the angle and position of the incident light rays, reduce the defocusing and astigmatism phenomena of the optical system, improve the clarity and accuracy of the imaging of the optical system, and improve the imaging effect of the optical system.
[0065] In an exemplary embodiment, 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 semi-aperture of the first side surface of the first lens and the axial distance SAG12 between the intersection of the second side surface of the first lens and the optical axis and the vertex of the effective semi-aperture of the second side surface of the first lens may satisfy: 0.1 < SAG12 / SAG11 < 0.4. By controlling the above conditional expression, a compact design of the optical system can be achieved, thereby reducing the volume and weight of the electronic device including the optical system and improving the convenience of wearing the electronic device; at the same time, it can also prevent the thickness of the first lens from being too thin and reduce the difficulty of processing, forming, and assembling the first lens.
[0066] In an exemplary embodiment, the axial distance SAG31 between the intersection of the first side surface of the third lens and the optical axis and the vertex of the effective semi-aperture of the first side surface of the third lens, the axial distance SAG32 between the intersection of the second side surface of the third lens and the optical axis and the vertex of the effective semi-aperture of the second side surface of the third lens, and the central thickness CT3 of the third lens on the optical axis may satisfy: 6.3 < CT3 / |SAG31 + SAG32| < 10.9. By controlling the above conditional expression, a compact design of the optical system can be achieved, thereby reducing the volume and weight of the electronic device including the optical system and improving the convenience of wearing the electronic device; at the same time, it can also prevent the thickness of the third lens from being too thin and reduce the difficulty of processing, forming, and assembling the third lens.
[0067] The optical system according to the above embodiment of the present application may employ multiple lenses, such as the four lenses described above. By reasonably allocating the parameters of the reflective polarizing element, the first quarter-wave plate, the second quarter-wave plate, the polarizer, and each lens, the body length of the optical system can be reduced and the imaging quality of the optical system can be improved. The optical system configured as above has characteristics such as miniaturization and good imaging quality, and can well meet the usage requirements of various portable electronic products in a projection scenario.
[0068] In an embodiment of the present application, at least one of the surfaces of the second lens, the third lens, and the fourth lens is an aspherical surface. The characteristics of an aspherical lens are 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.
[0069] Reference Figure 1 、 Figure 3 、 Figure 5 、 Figure 7 and Figure 9, a second aspect of the present application provides an optical system which sequentially includes a first lens, a second lens, a third lens, and a fourth lens along the optical axis from the first side to the second side. The first lens has a positive optical power, its first side is convex, and its second side is concave. The second lens has a positive optical power, its first side is flat, and its second side is convex. The third lens has a negative optical power, its first side is concave, and its second side is convex. The fourth lens has a positive optical power, its first side is flat, and its second side is convex. Wherein, the optical system further includes a first quarter-wave plate, a reflective polarizing element, a partial reflection element, a polarizer, and a second quarter-wave plate; the first quarter-wave plate is disposed on the first side of the second lens; the reflective polarizing element is disposed on the first side of the first quarter-wave plate; the partial reflection element is disposed on the second side of the third lens; the polarizer is disposed on the first side of the fourth lens; the second quarter-wave plate is disposed on the first side of the polarizer. The optical system further includes a diaphragm disposed between the first side and the first lens.
[0070] Wherein, the effective focal length f1 of the first lens and the effective focal length f2 of the second lens can satisfy: 0.05 < f1 / f2 < 0.5; the axial distance SR from the diaphragm to the first side of the first lens and the central thickness CT1 of the first lens on the optical axis can satisfy: 3.3 < SR / CT1 < 4.2. The optical system provided by the present application uses four lenses, reasonably configures the optical powers of the four lenses and enables the optical system to satisfy "0.05 < f1 / f2 < 0.5", which is beneficial to improving the imaging quality of the optical system; at the same time, by restricting the ratio of the axial distance from the diaphragm to the first side of the first lens to the central thickness of the first lens on the optical axis, it is beneficial to constrain the angle and position of the incident light, reduce the defocusing and astigmatism phenomena of the optical system, improve the clarity and accuracy of the imaging of the optical system, and improve the imaging effect of the optical system.
[0071] However, those skilled in the art should understand that without departing from the technical solutions claimed in the present application, the number of lenses constituting the optical system can be changed to obtain the various results and advantages described in this specification.
[0072] The following further describes specific embodiments of the optical system applicable to the above embodiments with reference to the accompanying drawings.
[0073] Example 1
[0074] The following refers to Figure 1 , Figure 2A , Figure 2B , Figure 2C and Figure 2D to describe the optical system of Embodiment 1 of the present application.
[0075] As Figure 1As shown, the optical system may include 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 arranged in sequence along the optical axis from the first side to the second side. The aperture STO may be disposed between the first side and the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side. The first side surfaces of each element are all referred to as the near-eye side surfaces, and the second side surfaces are all referred to as the near-screen side surfaces.
[0076] The first lens E1 has a positive focal power. Its near-eye side surface S1 is convex, and its near-screen side surface S2 is concave. The second lens E2 has a positive focal power. Its near-eye side surface S3 is flat, and its near-screen side surface S4 is convex. The third lens E3 has a negative focal power. Its near-eye side surface S5 is concave, and its near-screen side surface S6 is convex. The fourth lens E4 has a positive focal power. Its near-eye side surface S7 is flat, and its near-screen side surface S8 is convex. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the near-eye side surface S3 of the second lens E2. The partial reflection element BS is attached to the near-screen side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the near-eye side surface S7 of the fourth lens E4. It should be noted that the surfaces S1 - S8 are not shown in Figure 1 this figure.
[0077] In this example, an image plane IMG may be provided on the second side of the optical system. The image plane IMG may be provided with a display screen, for example. The image light from the image plane IMG sequentially passes through the fourth lens E4, the polarizer LP, the second quarter-wave plate QWP2, the third lens E3, the second lens E2, the first quarter-wave plate QWP1 and reaches the reflective polarizing element RP, where the first reflection occurs. The light after the first reflection passes through the first quarter-wave plate QWP1, the second lens E2, the third lens E3 and reaches the partial reflection element BS located on the near-screen side surface of the third lens E3, where the second reflection occurs. The light after the second reflection sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and finally projects into the user's eye. For example, the light after two reflections of this optical system finally projects into the user's eye. A protective glass (not shown) may also be provided between the image plane IMG and the fourth lens E4.
[0078] Table 1 shows the basic parameter table of the optical system of Embodiment 1. Among them, the units of the radius of curvature and the thickness / distance are both millimeters (mm). The image light from the image plane IMG passes through each element in the order from No. 23 to No. 1 and finally projects into the human eye.
[0079]
[0080]
[0081] Table 1
[0082] In this embodiment, the near-eye side S5 and the near-screen side S6 of the third lens E3, and the near-screen side S8 of the fourth lens E4 are all aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:
[0083]
[0084] where x is the sagitta, the distance from the vertex of the aspherical surface to 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 (that is, the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic constant; Ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 gives the higher-order term coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 .
[0085] Plane number A4 A6 A8 A10 A12 A14 A16 A18 A20 S5 -1.1484E-01 -4.3240E-02 -1.8153E-01 -9.0684E-02 -3.6076E-02 -1.0030E-02 -1.4527E-03 0.0000E+00 0.0000E+00 S6 2.8668E-01 -1.4136E-02 -1.1010E-01 -7.0024E-02 -3.0565E-02 -8.7823E-03 -1.3157E-03 0.0000E+00 0.0000E+00 S8 -7.4713E-02 2.2604E-02 -1.0719E-03 -7.8212E-04 5.5282E-04 -2.7132E-04 -5.0273E-05 0.0000E+00 0.0000E+00
[0086] Table 2
[0087] Figure 2A shows the axial chromatic aberration curve of the optical system of Embodiment 1, which represents the deviation of the focusing points of light rays with different wavelengths after passing through the optical system. Figure 2B shows the astigmatism curve of the optical system of Embodiment 1, which represents the meridional image plane curvature and the sagittal image plane curvature corresponding to different field angles. 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 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 describes the optical system of Embodiment 2 of the present application with reference to Figure 3 、 Figure 4A 、 Figure 4B 、 Figure 4C and Figure 4D .
[0090] As shown Figure 3 in the figure, the optical system may include 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 arranged in sequence along the optical axis from the first side to the second side. An aperture STO may be disposed between the first side and the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side. The first side surfaces of the respective elements are all referred to as the near-eye side surfaces, and the second side surfaces are all referred to as the near-screen side surfaces.
[0091] The first lens E1 has a positive optical power. Its near-eye side surface S1 is convex, and its near-screen side surface S2 is concave. The second lens E2 has a positive optical power. Its near-eye side surface S3 is flat, and its near-screen side surface S4 is convex. The third lens E3 has a negative optical power. Its near-eye side surface S5 is concave, and its near-screen side surface S6 is convex. The fourth lens E4 has a positive optical power. Its near-eye side surface S7 is flat, and its near-screen side surface S8 is convex. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the near-eye side surface S3 of the second lens E2. The partial reflection element BS is attached to the near-screen side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the near-eye side surface S7 of the fourth lens E4. It should be noted that the surfaces S1 - S8 are not shown in Figure 3 the figure.
[0092] In this example, an image plane IMG may be disposed on the second side of the optical system. The image plane IMG may be provided with a display screen, for example. The image light from the image plane IMG sequentially passes through the fourth lens E4, the polarizer LP, the second quarter-wave plate QWP2, the third lens E3, the second lens E2, the first quarter-wave plate QWP1 and reaches the reflective polarizing element RP, where the first reflection occurs. The light after the first reflection passes through the first quarter-wave plate QWP1, the second lens E2, the third lens E3 and reaches the partial reflection element BS located on the near-screen side surface of the third lens E3, where the second reflection occurs. The light after the second reflection sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and finally projects into the user's eye. For example, the light of the optical system after two reflections finally projects into the user's eye. A protective glass (not shown) may also be disposed between the image plane IMG and the fourth lens E4.
[0093] Table 3 shows the basic parameter table of the optical system of Example 2, where the unit of the radius of curvature and the thickness / distance is millimeter (mm). The image light from the image plane IMG passes through each element in the order of No. 23 to No. 1 and is finally projected into the human eye.
[0094]
[0095]
[0096] Table 3
[0097] In this embodiment, the side S5 of the third lens E3 close to the human eye and the side S6 close to the screen, and the side S8 of the fourth lens E4 close to the screen are all aspherical surfaces. Table 4 gives the higher-order coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 .
[0098] Plane number A4 A6 A8 A10 A12 A14 A16 A18 A20 S5 -4.3410E-01 1.1114E-01 -4.1613E-02 -2.5404E-04 3.3580E-03 1.8738E-03 4.9089E-04 0.0000E+00 0.0000E+00 S6 3.8184E-01 1.5502E-01 1.8114E-02 4.7055E-03 4.4412E-04 -3.0054E-05 1.8337E-06 0.0000E+00 0.0000E+00 S8 -1.2977E-01 2.3621E-02 -1.3190E-03 -1.4779E-04 1.3903E-04 -1.7295E-04 -7.2783E-05 0.0000E+00 0.0000E+00
[0099] Table 4
[0100] 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 optical system. Figure 4B shows the astigmatism curve of the optical system of Example 2, which represents the meridional image plane curvature and the sagittal image plane curvature corresponding to different field angles. 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 curve of the optical system of Example 2. According to Figures 4A to 4D it can be known that the optical system given in Example 2 can achieve good imaging quality.
[0101] Example 3
[0102] The following will describe the optical system of Embodiment 3 of the present application with reference to Figure 5 、 Figure 6A 、 Figure 6B 、 Figure 6C and Figure 6D .
[0103] As Figure 5As shown, the optical system may include 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 arranged in sequence along the optical axis from the first side to the second side. The aperture STO may be disposed between the first side and the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side. The first side surfaces of each element are all referred to as the near-human-eye side surfaces, and the second side surfaces are all referred to as the near-screen side surfaces.
[0104] The first lens E1 has a positive focal power. Its near-human-eye side surface S1 is convex, and its near-screen side surface S2 is concave. The second lens E2 has a positive focal power. Its near-human-eye side surface S3 is flat, and its near-screen side surface S4 is convex. The third lens E3 has a negative focal power. Its near-human-eye side surface S5 is concave, and its near-screen side surface S6 is convex. The fourth lens E4 has a positive focal power. Its near-human-eye side surface S7 is flat, and its near-screen side surface S8 is convex. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the near-human-eye side surface S3 of the second lens E2. The partial reflection element BS is attached to the near-screen side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the near-human-eye side surface S7 of the fourth lens E4. It should be noted that the surfaces S1 - S8 are not shown in Figure 5 this figure.
[0105] In this example, an image plane IMG may be provided on the second side of the optical system. The image plane IMG may be provided with a display screen, for example. The image light from the image plane IMG sequentially passes through the fourth lens E4, the polarizer LP, the second quarter-wave plate QWP2, the third lens E3, the second lens E2, the first quarter-wave plate QWP1 and reaches the reflective polarizing element RP, where the first reflection occurs. The light reflected for the first time passes through the first quarter-wave plate QWP1, the second lens E2, the third lens E3 and reaches the partial reflection element BS located on the near-screen side surface of the third lens E3, where the second reflection occurs. The light reflected for the second time sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and finally projects into the user's eyes. For example, the light after two reflections of this optical system finally projects into the user's eyes. A protective glass (not shown) may also be provided between the image plane IMG and the fourth lens E4.
[0106] Table 5 shows the basic parameter table of the optical system of Embodiment 3. Among them, the units of the radius of curvature and the thickness / distance are both millimeters (mm). The image light from the image plane IMG passes through each element in the order from No. 23 to No. 1 and finally projects into the human eyes.
[0107]
[0108] Table 5
[0109] In this embodiment, the near-screen side surface S4 of the second lens E2, the near-eye side surface S5 and the near-screen side surface S6 of the third lens E3, and the near-screen side surface S8 of the fourth lens E4 are all aspherical surfaces. Table 6 gives the higher-order term coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 .
[0110] Plane number A4 A6 A8 A10 A12 A14 A16 A18 A20 S4 3.2530E-02 -2.7702E-03 -1.9171E-04 2.0197E-04 -2.9287E-05 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 S5 -3.5666E-01 3.8444E-02 -4.2280E-02 -2.2584E-02 -8.0897E-03 -4.3337E-04 -1.5128E-04 0.0000E+00 0.0000E+00 S6 1.5672E-01 6.3412E-02 -1.4093E-03 -4.7976E-03 -2.8644E-03 -5.9418E-04 -1.3646E-04 0.0000E+00 0.0000E+00 S8 -7.5675E-02 1.3219E-02 -2.0133E-04 -2.0736E-04 1.0836E-04 -5.7616E-05 -5.4961E-05 0.0000E+00 0.0000E+00
[0111] Table 6
[0112] Figure 6A shows 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 optical system. 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 corresponding to different field angles. 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 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.
[0113] Example 4
[0114] The following describes the optical system of Embodiment 4 of the present application with reference to Figure 7 、 Figure 8A 、 Figure 8B 、 Figure 8C and Figure 8D .
[0115] As Figure 7As shown, the optical system may include 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 arranged in sequence along the optical axis from the first side to the second side. The aperture STO may be disposed between the first side and the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side. The first side surfaces of all the elements are referred to as the near-eye side surfaces, and the second side surfaces are referred to as the near-screen side surfaces.
[0116] The first lens E1 has a positive optical power. Its near-eye side surface S1 is convex, and its near-screen side surface S2 is concave. The second lens E2 has a positive optical power. Its near-eye side surface S3 is flat, and its near-screen side surface S4 is convex. The third lens E3 has a negative optical power. Its near-eye side surface S5 is concave, and its near-screen side surface S6 is convex. The fourth lens E4 has a positive optical power. Its near-eye side surface S7 is flat, and its near-screen side surface S8 is convex. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the near-eye side surface S3 of the second lens E2. The partial reflection element BS is attached to the near-screen side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the near-eye side surface S7 of the fourth lens E4. It should be noted that the surfaces S1 - S8 are not shown in Figure 7 the figure.
[0117] In this example, an image plane IMG may be provided on the second side of the optical system. The image plane IMG may be provided with a display screen, for example. The image light from the image plane IMG sequentially passes through the fourth lens E4, the polarizer LP, the second quarter-wave plate QWP2, the third lens E3, the second lens E2, the first quarter-wave plate QWP1 and reaches the reflective polarizing element RP, where the first reflection occurs. The light after the first reflection passes through the first quarter-wave plate QWP1, the second lens E2, the third lens E3 and reaches the partial reflection element BS located on the near-screen side surface of the third lens E3, where the second reflection occurs. The light after the second reflection sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and finally projects into the user's eyes. For example, the light of the optical system after two reflections finally projects into the user's eyes. A protective glass (not shown) may also be provided between the image plane IMG and the fourth lens E4.
[0118] Table 7 shows the basic parameter table of the optical system of Embodiment 4. Among them, the units of the radius of curvature and the thickness / distance are both millimeters (mm). The image light from the image plane IMG passes through each element in the order from No. 23 to No. 1 and finally projects into the human eyes.
[0119]
[0120] Table 7
[0121] In this embodiment, the near-eye side surface S5 and the near-screen side surface S6 of the third lens E3, and the near-screen side surface S8 of the fourth lens E4 are all aspherical surfaces. Table 8 gives the higher-order coefficients A4, A6, A8, A 10 , A 12 , A 14 , A 16 , A 18 , and A 20 .
[0122] Plane number A4 A6 A8 A10 A12 A14 A16 A18 A20 S5 -1.2655E+00 -6.7949E-01 -5.3222E-01 -2.6516E-01 -1.0177E-01 -2.6735E-02 -3.6799E-03 0.0000E+00 0.0000E+00 S6 -3.7357E-01 -5.0463E-01 -3.8787E-01 -1.9594E-01 -7.2611E-02 -1.8009E-02 -2.3212E-03 0.0000E+00 0.0000E+00 S8 -6.1539E-02 1.5299E-02 1.8727E-03 -6.5188E-04 4.1568E-04 -1.2510E-04 1.3397E-04 0.0000E+00 0.0000E+00
[0123] Table 8
[0124] Figure 8A shows the axial chromatic aberration curve of the optical system of Embodiment 4, which represents the deviation of the convergence 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 4, which represents the meridional image plane curvature and the sagittal image plane curvature corresponding to different field angles. Figure 8C shows the distortion curve of the optical system of Embodiment 4, which represents the distortion magnitude values corresponding to different field angles. Figure 8D shows the modulation transfer function curve of the optical system of Embodiment 4. According to Figures 8A to 8D , it can be known that the optical system given in Embodiment 4 can achieve good imaging quality.
[0125] Example 5
[0126] The following describes the optical system of Embodiment 5 of the present application with reference to Figure 9 , Figure 10A , Figure 10B , Figure 10C and Figure 10D .
[0127] As Figure 9 shown, the optical system may include 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 arranged in sequence along the optical axis from the first side to the second side. The aperture stop STO may be disposed between the first side and the first lens E1. In this embodiment, the first side refers to the eye side, and the second side refers to the display screen side. The first side surfaces of all elements are referred to as the near-eye side surfaces, and the second side surfaces are referred to as the near-screen side surfaces.
[0128] The first lens E1 has a positive focal power, with its side S1 close to the human eye being convex and its side S2 close to the screen being concave. The second lens E2 has a positive focal power, with its side S3 close to the human eye being flat and its side S4 close to the screen being convex. The third lens E3 has a negative focal power, with its side S5 close to the human eye being concave and its side S6 close to the screen being convex. The fourth lens E4 has a positive focal power, with its side S7 close to the human eye being flat and its side S8 close to the screen being convex. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the side S3 of the second lens E2 close to the human eye. The partial reflection element BS is attached to the side S6 of the third lens E3 close to the screen. The second quarter-wave plate QWP2 and the polarizer LP are attached to the side S7 of the fourth lens E4 close to the human eye. It should be noted that the surfaces S1 - S8 are not shown in Figure 9 the figure.
[0129] In this example, an image plane IMG can be provided on the second side of the optical system, and the image plane IMG can be provided with a display screen, for example. The image light from the image plane IMG sequentially passes through the fourth lens E4, the polarizer LP, the second quarter-wave plate QWP2, the third lens E3, the second lens E2, the first quarter-wave plate QWP1 and reaches the reflective polarizing element RP, where the first reflection occurs. The light reflected for the first time passes through the first quarter-wave plate QWP1, the second lens E2, the third lens E3 and reaches the partial reflection element BS located on the side S6 of the third lens E3 close to the screen, where the second reflection occurs. The light reflected for the second time sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and finally projects into the user's eye. For example, the light after two reflections of this optical system finally projects into the user's eye. A protective glass (not shown) can also be provided between the image plane IMG and the fourth lens E4.
[0130] Table 9 shows the basic parameter table of the optical system of Example 5, where the units of the radius of curvature and the thickness / distance are both millimeters (mm). The image light from the image plane IMG passes through each element in the order from No. 23 to No. 1 and finally projects into the human eye.
[0131]
[0132]
[0133] Table 9
[0134] In this embodiment, the near-eye side surface S5 and the near-screen side surface S6 of the third lens E3, and the near-screen side surface S8 of the fourth lens E4 are all aspherical surfaces. Table 10 gives the higher-order term coefficients A4, A6, A8, A 10 , A 12 , A 14 , A 16 , A 18 and A 20 for the aspherical surfaces S5, S6, and S8 that can be used in Embodiment 5.
[0135] Plane number A4 A6 A8 A10 A12 A14 A16 A18 A20 S5 -1.5837E+00 -6.4837E-01 -6.2169E-01 -2.9333E-01 -1.0731E-01 -2.6438E-02 -2.9174E-03 0.0000E+00 0.0000E+00 S6 -1.7603E-01 -2.7204E-01 -2.8992E-01 -1.5499E-01 -6.0855E-02 -1.5901E-02 -2.0740E-03 0.0000E+00 0.0000E+00 S8 -3.4819E-02 2.7662E-03 4.0296E-03 -2.3324E-03 1.2051E-03 -4.8623E-04 7.0302E-05 0.0000E+00 0.0000E+00
[0136] Table 10
[0137] Figure 10A 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 10B shows the astigmatism curve of the optical system of Embodiment 5, which represents the meridional image plane curvature and the sagittal image plane curvature corresponding to different field angles. Figure 10C shows the distortion curve of the optical system of Embodiment 5, which represents the distortion magnitude values corresponding to different field angles. Figure 10D shows the modulation transfer function curve of the optical system of Embodiment 5. According to Figures 10A to 10D , it can be seen that the optical system given in Embodiment 5 can achieve good imaging quality.
[0138] Table 11 gives the basic parameters of each of Embodiments 1 to 5, such as the values of f, f1, f2, f3, f4, SR, fz1, SAG11, SAG12, SAG31, and SAG32.
[0139]
[0140]
[0141] Table 11
[0142] In summary, Table 12 shows the conditional values of each of Embodiments 1 to 5.
[0143] Conditional / Example 1 2 3 4 5 f1 / f2 0.10 0.33 0.45 0.45 0.32 fz1 / R4 -1.99 -2.00 -2.04 -1.91 -1.91 N2 / NQ1 1.00 1.00 0.99 1.01 1.01 V1 / V3 2.47 2.26 2.18 2.09 2.09 f1 / (R1+R2) 0.98 0.61 0.75 0.45 0.90 R5 / R6 0.57 0.31 0.31 0.21 0.35 f / f3 -0.19 -0.40 -0.35 -0.50 -0.38 CT3 / (CTQ2+CTL+CT4) 2.94 3.20 4.25 4.36 2.52 T12 / (CTR+CTQ1+CT2) 1.38 0.37 0.49 0.21 0.93 R8 / f4 -0.55 -0.67 -0.86 -0.55 -0.85 (VR+VQ1) / V2 1.73 1.99 1.62 1.83 1.83 SR / CT1 4.11 3.35 3.85 3.39 3.68 SAG12 / SAG11 0.38 0.23 0.29 0.18 0.32 CT3 / |SAG31+SAG32| 10.82 8.21 10.51 9.13 6.34
[0144] Table 12
[0145] 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 a virtual reality device. The optical device is equipped with the optical system described above.
[0146] The above description is only a preferred embodiment of the present application and an explanation of the technical principles applied. 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) disclosed in the present application that have similar functions.
Claims
1. An optical system, characterized in that The method comprises, in order from the first side to the second side along the optical axis: A first lens having positive optical power, wherein the first side surface is convex and the second side surface is concave; a second lens having positive optical power, wherein the first side surface is a flat surface and the second side surface is a convex surface; a third lens element having negative optical power, wherein the first side surface is concave and the second side surface is convex; and a fourth lens having positive power, wherein the first side surface is a flat surface and the second side surface is a convex surface; Wherein, the optical system further comprises: A first quarter wave plate, disposed on a first side surface of the second lens; a reflective polarizing element, disposed on a first side surface of the first quarter-wave plate; A partial reflective element, disposed on the second side surface of the third lens; a polarizer, disposed on a first side surface of the fourth lens; and A second quarter wave plate, disposed on the first side of the polarizer; The number of lenses having optical power in the optical system is four; The effective focal length f1 of the first lens and the effective focal length f2 of the second lens satisfy: 0.05 <f1 / f2<0.5; The combined focal length fz1 of the reflective polarizing element, the first quarter-wave plate and the second lens and the curvature radius R4 of the second side surface of the second lens satisfy: -2.04≤fz1 / R4<-1.
9.
2. The optical system according to claim 1, characterized in that The refractive index NQ1 of the first quarter wave plate and the refractive index N2 of the second lens satisfy: 0.95 <N2 / NQ1<1.05。 3. The optical system according to claim 1, characterized in that The Abbe number V1 of the first lens and the Abbe number V3 of the third lens satisfy: 2.09≤V1 / V3<2.
5.
4. The optical system according to claim 1, characterized in that The effective focal length f1 of the first lens, the curvature radius R1 of the first side surface of the first lens, and the curvature radius R2 of the second side surface of the first lens satisfy: 0.4 <f1 / (R1+R2)<1.0。 5. The optical system according to claim 1, characterized in that The curvature radius R5 of the first side surface of the third lens and the curvature radius R6 of the second side surface of the third lens satisfy: 0.2 <R5 / R6<0.6。 6. The optical system according to claim 1, characterized in that The total effective focal length f of the optical system and the effective focal length f3 of the third lens satisfy: -0.55 <f / f3<-0.15。 7. The optical system according to any one of claims 1 to 6, characterized in that: The center thickness CT3 of the third lens on the optical axis, the center thickness CTQ2 of the second quarter wave plate on the optical axis, the center thickness CTL of the polarizer on the optical axis and the center thickness CT4 of the fourth lens on the optical axis satisfy: 2.5 <CT3 / (CTQ2+CTL+CT4)<4.4。 8. The optical system according to any one of claims 1 to 6, characterized in that: The on-axis distance T12 from the second side surface of the first lens to the first side surface of the second lens, the center thickness CTR of the reflective polarizing element on the optical axis, the center thickness CTQ1 of the first quarter wave plate on the optical axis, and the center thickness CT2 of the second lens on the optical axis satisfy: 0.2 <T12 / (CTR+CTQ1+CT2)<1.4。 9. The optical system according to any one of claims 1 to 6, characterized in that: The effective focal length f4 of the fourth lens and the curvature radius R8 of the second side surface of the fourth lens satisfy: -0.9 <R8 / f4<-0.5。 10. The optical system according to any one of claims 1 to 6, characterized in that: The Abbe number VR of the reflective polarizing element, the Abbe number VQ1 of the first quarter wave plate, and the Abbe number V2 of the second lens satisfy: 1.6<(VR+VQ1) / V2<2.
0.
11. The optical system according to any one of claims 1 to 6, characterized in that: The optical system further includes a stop disposed between the first side and the first lens; The on-axis distance SR from the aperture to the first side surface of the first lens and the center thickness CT1 of the first lens on the optical axis satisfy: 3.3 <SR / CT1≤4.11。 12. The optical system according to any one of claims 1 to 6, characterized in that: An on-axis distance SAG11 between the intersection of the first side surface of the first lens and the optical axis to the effective half-aperture vertex of the first side surface of the first lens and an on-axis distance SAG12 between the intersection of the second side surface of the first lens and the optical axis to the effective half-aperture vertex of the second side surface of the first lens satisfy: 0.18≤SAG12 / SAG11<0.
4.
13. The optical system according to any one of claims 1 to 6, characterized in that: The on-axis distance SAG31 between the intersection of the first side surface of the third lens and the optical axis and the effective half-diameter vertex of the first side surface of the third lens, the on-axis distance SAG32 between the intersection of the second side surface of the third lens and the optical axis and the effective half-diameter vertex of the second side surface of the third lens, and the center thickness CT3 of the third lens on the optical axis satisfy: 6.3 <CT3 / |SAG31+SAG32|≤10.82。