Optical system
Through the optical system design of polarization foldback optical path and glued lens, the overall length and performance improvement of the optical system in VR/AR devices is solved, and lightweight and high imaging quality is achieved, reducing production costs and difficulty.
Patent Information
- Application Number
- CN202421829487.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-30
- Publication Date
- 2025-08-19
- Estimated Expiration
- 2034-07-30
AI Technical Summary
The optical systems of existing VR/AR devices have challenges in reducing the overall system length, improving the optical performance of the system, reducing production costs and improving production yield.
The optical system design adopts polarization foldback optical path and glued lens. By reasonably configuring the system architecture and filming method, light is reflected first and then projected, and the screen size and field of view of the optical system are controlled, meeting the conditions of 0.15
It realizes the lightweight and high performance of the optical system, reduces the overall system length, and improves the processability and productivity of the lens.
Smart Images
Figure CN223244894U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical elements, and more specifically, to an optical system. Background Art
[0002] With the continuous development of virtual reality technology, people's requirements for the imaging effect of devices such as VR glasses are getting higher and higher. At the same time, the gluing technology of large-aperture optical lenses is becoming more and more mature. After the development and iteration of technical solutions such as aspherical lenses and Fresnel lenses, the current catadioptric structure solution is favored among many solutions because it can greatly compress the system size through the folding of the optical path, and has gradually become the mainstream design solution for such optical systems.
[0003] In view of the current development status of the catadioptric structure solution and devices such as VR / AR, reducing the total system length and improving the optical performance of the system are still the main development trends. At the same time, reducing production costs, reducing production difficulty, and improving production yield are also technical problems that need to be solved urgently in this field. Utility Model Content
[0004] This application provides an optical system, which may sequentially include, along the optical axis from the first side to the second side: a first lens with positive optical power; a reflective polarizing element; a first quarter-wave plate; a second lens with positive optical power; a third lens with negative optical power; a partially reflective element; a fourth lens with positive or negative optical power; a second quarter-wave plate; and a polarizer. Among them, the reflective polarizing element is placed on the second side surface of the first lens, and the first side surface of the reflective polarizing element is at least partially in contact with the second side surface of the first lens; the first quarter-wave plate is placed on the second side surface of the reflective polarizing element, the first side surface of the first quarter-wave plate is at least partially in contact with the second side surface of the reflective polarizing element, and the second side surface of the first quarter-wave plate is at least partially in contact with the first side surface of the second lens; the second lens and the third lens are glued; the third lens and the fourth lens are glued. The optical system satisfies: 0.15 < f2 / f1 < 1.6 and 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05, where f2 is the effective focal length of the second lens, f1 is the effective focal length of the first lens, CT1 is the central thickness of the first lens on the optical axis, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ1 is the central thickness of the first quarter-wave plate on the optical axis, and CT2 is the central thickness of the second lens on the optical axis.
[0005] In one embodiment, the optical system further includes an aperture located on the first side of the first lens, and the effective focal length f of the optical system and the distance SR from the aperture to the first side surface of the first lens on the optical axis may satisfy: 1.45 < f / SR < 1.8.
[0006] In one embodiment, the effective focal length f2 of the second lens, the refractive index N2 of the second lens, the effective focal length f3 of the third lens, and the refractive index N3 of the third lens may satisfy: -0.7<(f2×N2) / (f3×N3)<-0.3.
[0007] In one embodiment, the center thickness CT2 of the second lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, and the curvature radius R4 of the second side surface of the second lens may satisfy: -0.4<(CT2+CT3) / R4<-0.15.
[0008] In one embodiment, the center thickness CT3 of the third lens on the optical axis, the chromatic aberration coefficient V3 of the third lens, the center thickness CT4 of the fourth lens on the optical axis, and the chromatic aberration coefficient V4 of the fourth lens may satisfy: 0.5<(CT3×V3) / (CT4×V4)<1.75.
[0009] In one embodiment, the distance TD from the first side surface of the first lens to the second side surface of the fourth lens on the optical axis, the center thickness CTR of the reflective polarizer 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 may satisfy: 2.8 <TD / (CTR+CTQ1+CT2)<3.2。
[0010] In one embodiment, the curvature radius R6 of the second side surface of the third lens and the curvature radius R5 of the first side surface of the third lens may satisfy: 1.2 <R6 / R5<1.6。
[0011] In one embodiment, the effective focal length f of the optical system, the refractive index NR of the reflective polarizer, the refractive index NQ1 of the first quarter wave plate, the refractive index NQ2 of the second quarter wave plate, and the refractive index NL of the polarizer may satisfy: 3.7 mm <f / (NR+NQ1+NQ2+NL)<4.4mm。
[0012] In one embodiment, the center thickness CT1 of the first lens on the optical axis, the dispersion coefficient V1 of the first lens, and the dispersion coefficient VR of the reflective polarizing element can satisfy the following conditions: 2.5 mm <CT1 / (V1 / VR)<6.5mm。
[0013] In one embodiment, the effective focal length f2 of the second lens, the dispersion coefficient VQ1 of the first quarter wave plate, and the dispersion coefficient V2 of the second lens may satisfy: 0.9 mm <f2 / (VQ1+V2)<1.4mm。
[0014] In one embodiment, the sum of the center thicknesses ΣCT of the first lens, the second lens, the third lens, and the fourth lens on the optical axis and the entrance pupil diameter EPD of the optical system may satisfy: 4.4<ΣCT / EPD<5.15.
[0015] In one embodiment, the curvature radius R7 of the first side surface of the fourth lens, the Abbe number V3 of the third lens, and the Abbe number V4 of the fourth lens may satisfy: -1.25 mm <R7 / (V3+V4)<-0.5mm。
[0016] In one embodiment, the effective focal length f of the optical system and the center thickness CT2 of the second lens on the optical axis may satisfy: 3.7 <f / CT2<4.2。
[0017] In one embodiment, the distance TD from the first side surface of the first lens to the second side surface of the fourth lens on the optical axis, the refractive index N1 of the first lens, and the refractive index N4 of the fourth lens may satisfy: 5.5 mm <TD / (N1+N4)<6.8mm。
[0018] In one embodiment, the first lens, the second lens, the third lens, and the fourth lens may all be made of plastic.
[0019] In one embodiment, the first side surface and the second side surface of each of the first lens, the second lens, the third lens, and the fourth lens may be spherical surfaces.
[0020] The optical system disclosed in this application sequentially includes, along the optical axis from the first side to the second side, a first lens with positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with positive optical power, a third lens with negative optical power, a partial reflection element, a fourth lens with positive or negative optical power, a second quarter-wave plate, and a polarizer. Among them, the reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens. The first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element. The first side of the second lens at least partially adheres to the second side of the first quarter-wave plate; the second lens and the third lens are cemented; the third lens and the fourth lens are cemented; and the effective focal length f2 of the second lens and the effective focal length f1 of the first lens satisfy the conditional formula 0.15 < f2 / f1 < 1.6. The central thicknesses CT1, CTR, CTQ1, and CT2 of the first lens, the reflective polarizing element, the first quarter-wave plate, and the second lens on the optical axis respectively satisfy the conditional formula 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05. This optical system adopts a polarization folding optical path and cemented lenses. Through the above settings of the optical system, the system architecture and film pasting method are reasonably configured, enabling the light to be reflected first and then projected, meeting the requirement of light folding. On the one hand, the screen size of the optical system is controlled, and on the other hand, the field of view of the optical system is controlled; while f2 and f1 satisfy the conditional formula 0.15 < f2 / f1 < 1.6, the control system satisfies the conditional formula 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05, which is beneficial to controlling the overall thickness of the first lens and the second lens. While ensuring the processability of the two lenses, the thickness of the second lens is controlled to be larger, making the optical path of the light refolded in the second lens longer, improving the performance of the optical system while reducing the total length of the optical system. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Combined with the accompanying drawings, through the detailed description of the following non-restrictive embodiments, other features, objectives, and advantages of this application will become more obvious. In the drawings:
[0022] Figure 1 Shows a schematic structural diagram of the optical system according to Embodiment 1 of this application;
[0023] Figure 2 and Figure 3 Respectively show the axial chromatic aberration curve and distortion curve of the optical system of Embodiment 1;
[0024] Figure 4 Shows the modulation transfer function (MTF) curve of the optical system of Embodiment 1;
[0025] Figure 51 shows a schematic structural diagram of an optical system according to Example 2 of the present application;
[0026] Figure 6 and Figure 7 axial chromatic aberration curve and distortion curve of the optical system of Example 2 are shown respectively;
[0027] Figure 8 shows a modulation transfer function (MTF) curve of the optical system of Example 2;
[0028] Figure 9 1 shows a schematic structural diagram of an optical system according to Example 3 of the present application;
[0029] Figure 10 and Figure 11 axial chromatic aberration curve and distortion curve of the optical system of Example 3 are shown respectively;
[0030] Figure 12 shows a modulation transfer function (MTF) curve of the optical system of Example 3;
[0031] Figure 13 1 shows a schematic structural diagram of an optical system according to Example 4 of the present application;
[0032] Figure 14 and Figure 15 The axial chromatic aberration curve and the distortion curve of the optical system of Example 4 are shown respectively;
[0033] Figure 16 shows a modulation transfer function (MTF) curve of the optical system of Example 4;
[0034] Figure 17 1 shows a schematic structural diagram of an optical system according to Example 5 of the present application;
[0035] Figure 18 and Figure 19 axial chromatic aberration curve and distortion curve of the optical system of Example 5 are respectively shown; and
[0036] Figure 20 A modulation transfer function (MTF) curve of the optical system of Example 5 is shown. DETAILED DESCRIPTION
[0037] For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely descriptions of exemplary embodiments of the present application and are not intended to 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 terms "first," "second," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, without departing from the teachings of this application, the first lens discussed below could also be referred to as the second lens, and the second lens could also be referred to as the first lens.
[0039] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical and aspherical surfaces shown in the drawings are provided by way of example. That is, the shapes of the spherical and aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.
[0040] In this article, the paraxial region refers to the region near the optical axis. If a lens surface is convex and the location of the convex surface is undefined, it means that the lens surface is convex at least in the paraxial region; if a lens surface is concave and the location of the concave surface is undefined, it means that the lens surface is concave at least in the paraxial region.
[0041] It should also be understood that the terms "comprises," "including," "having," "includes," and / or "comprising," when used in this specification, indicate 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 expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application." And, the term "exemplary" is intended to refer to an example or illustration.
[0042] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.
[0043] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0044] The features, principles and other aspects of the present application are described in detail below.
[0045] An optical system according to an exemplary embodiment of the present application may include a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partially reflecting element, a fourth lens, a second quarter-wave plate, and a polarizer. In an exemplary embodiment, the first lens, the reflective polarizing element, the first quarter-wave plate, the second lens, the third lens, the partially reflecting element, the fourth lens, the second quarter-wave plate, and the polarizer may be arranged in sequence from a first side to a second side along an optical axis.
[0046] In an exemplary embodiment, the first lens may have positive optical power. The second lens may have positive optical power. The third lens may have negative optical power. The fourth lens may have positive optical power or negative optical power.
[0047] In an exemplary embodiment, the first side surface of the first lens may be concave or convex, and the second side surface may be convex or concave. The first side surface of the second lens may be concave or convex, and the second side surface may be convex. The first side surface of the third lens may be concave, and the second side surface may be convex. The first side surface of the fourth lens may be concave, and the second side surface may be convex or concave.
[0048] In an exemplary embodiment, a reflective polarizing element may be disposed on the second side surface of the first lens, and the first side surface of the reflective polarizing element may at least partially overlap with the second side surface of the first lens. A first quarter-wave plate may be disposed on the second side surface of the reflective polarizing element, and the first side surface of the first quarter-wave plate may at least partially overlap with the second side surface of the reflective polarizing element. The second side surface of the first quarter-wave plate may at least partially overlap with the first side surface of the second lens.
[0049] In an exemplary embodiment, the second lens may be cemented to the third lens, for example, the second side surface of the second lens may be cemented to the first side surface of the third lens. The third lens may be cemented to the fourth lens, for example, the second side surface of the third lens may be cemented to the first side surface of the fourth lens.
[0050] In an exemplary embodiment, the partially reflective element may be a semi-transparent and semi-reflective film layer coated on the second side surface of the third lens. In an exemplary embodiment, the first side surface of the fourth lens may be glued to the second side surface of the third lens coated with the partially reflective element.
[0051] In an exemplary embodiment, the partially reflective element may be a semi-transmissive and semi-reflective film layer coated on the first side surface of the fourth lens. In an exemplary embodiment, the second side surface of the third lens may be glued to the first side surface of the fourth lens coated with the partially reflective element.
[0052] In an exemplary embodiment, the optical system may further include an image plane located on the second side of the polarizer. The polarizer may be disposed, for example, on the first side of the image plane. The second quarter-wave plate may be disposed, for example, on the first side of the polarizer, and the second side of the second quarter-wave plate may be at least partially adhered to the first side of the polarizer.
[0053] In an exemplary embodiment, the first side may be, for example, the human eye side, and the second side may be, for example, the image plane side. The optical system may be used, for example, in VR / AR devices, etc.
[0054] The following will refer to Figure 1 to make an exemplary description of the optical system. As Figure 1 shown, the optical system according to an exemplary embodiment of the present application 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 fourth lens E4, a second quarter-wave plate QWP2, and a polarizer LP arranged in sequence from the first side to the second side. Among them, the reflective polarizing element RP is disposed on the second side of the first lens E1, the first quarter-wave plate QWP1 is disposed on the second side of the reflective polarizing element RP, the first side of the second lens E2 is adhered to the second side of the first quarter-wave plate QWP1, the third lens E3 is glued to the second lens E2, the fourth lens E4 is glued to the third lens E3, and a partial reflection element BS is disposed between the third lens E3 and the fourth lens E4. In actual use, the optical system according to an exemplary embodiment of the present application may be used as a VR lens, for example. At this time, the first side corresponds to the human eye side, and the second side corresponds to the image plane side. The optical system may further include an image plane IMG located on the second side of the polarizer LP. The light beam emitted from the image plane IMG may sequentially pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again to reach the partial reflection element BS. Then, the light beam is reflected again at the partial reflection element BS and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1 to be emitted toward the first side (such as the human eye side).
[0055] In an exemplary embodiment, the optical system of the present application may satisfy the condition 0.15 < f2 / f1 < 1.6, where f2 is the effective focal length of the second lens and f1 is the effective focal length of the first lens.
[0056] In an exemplary embodiment, the optical system of the present application can satisfy the conditional expression 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05, where CT1 is the central thickness of the first lens on the optical axis, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ1 is the central thickness of the first quarter-wave plate on the optical axis, and CT2 is the central thickness of the second lens on the optical axis.
[0057] The optical system according to an exemplary embodiment of the present application sequentially includes, along the optical axis from the first side to the second side, a first lens with a positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with a positive optical power, a third lens with a negative optical power, a partial reflection element, a fourth lens with a positive or negative optical power, a second quarter-wave plate, and a polarizer. The reflective polarizing element is placed on the second side of the first lens and at least partially adheres to the second side of the first lens. The first quarter-wave plate is placed on the second side of the reflective polarizing element and at least partially adheres to the second side of the reflective polarizing element. The first side of the second lens at least partially adheres to the second side of the first quarter-wave plate. The second lens and the third lens are cemented together. The third lens and the fourth lens are cemented together. Moreover, the effective focal length f2 of the second lens and the effective focal length f1 of the first lens satisfy the conditional expression 0.15 < f2 / f1 < 1.6. The central thicknesses CT1, CTR, CTQ1, and CT2 of the first lens, the reflective polarizing element, the first quarter-wave plate, and the second lens on the optical axis respectively satisfy the conditional expression 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05. This optical system adopts a polarization folding optical path and cemented lenses. By setting the optical system as described above, the system architecture and film pasting method are reasonably configured, enabling the light to be reflected first and then projected, meeting the requirement of light folding. On the one hand, the screen size of the optical system is controlled, and on the other hand, the field of view of the optical system is controlled. While f2 and f1 satisfy the conditional expression 0.15 < f2 / f1 < 1.6, the control system satisfies the conditional expression 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05, which is beneficial to controlling the overall thickness of the first lens and the second lens, ensuring the processability of the two lenses while controlling the second lens to have a greater thickness, making the optical path of the light refolded in the second lens longer, improving the performance of the optical system while reducing the total length of the optical system.
[0058] In an exemplary embodiment, the optical system of the present application may further include an aperture located on the first side of the first lens and can satisfy the conditional expression 1.45 < f / SR < 1.8, where f is the effective focal length of the optical system and SR is the distance from the aperture to the first side of the first lens on the optical axis. By reasonably controlling the ratio of the effective focal length of the optical system to the distance from the aperture to the first side of the first lens on the optical axis within this range, the total length of the optical system can be controlled within a smaller range.
[0059] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula -0.7 < (f2 × N2) / (f3 × N3) < -0.3, where f2 is the effective focal length of the second lens, N2 is the refractive index of the second lens, f3 is the effective focal length of the third lens, and N3 is the refractive index of the third lens. By controlling the optical system to satisfy the conditional formula -0.7 < (f2 × N2) / (f3 × N3) < -0.3, the surface profiles of the second lens and the third lens can meet the processing requirements, and at the same time, it can also contribute to the system performance to a certain extent.
[0060] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula -0.4 < (CT2 + CT3) / R4 < -0.15, where CT2 is the central thickness of the second lens on the optical axis, CT3 is the central thickness of the third lens on the optical axis, and R4 is the radius of curvature of the second side surface of the second lens. By controlling the system to satisfy the conditional formula -0.4 < (CT2 + CT3) / R4 < -0.15, large surface profile fluctuations of the second lens and the third lens can be avoided, which is beneficial to improving the processability of the lenses.
[0061] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 0.5 < (CT3 × V3) / (CT4 × V4) < 1.75, where CT3 is the central thickness of the third lens on the optical axis, V3 is the dispersion coefficient of the third lens, CT4 is the central thickness of the fourth lens on the optical axis, and V4 is the dispersion coefficient of the fourth lens. By controlling the system to satisfy the conditional formula 0.5 < (CT3 × V3) / (CT4 × V4) < 1.75, the third lens and the fourth lens can respectively承担部分降低色差的功能,有利于提高光学系统性能。
[0062] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 2.8 < TD / (CTR + CTQ1 + CT2) < 3.2, where TD is the distance on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ1 is the central thickness of the first quarter-wave plate on the optical axis, and CT2 is the central thickness of the second lens on the optical axis. By controlling the optical system to satisfy the conditional formula 2.8 < TD / (CTR + CTQ1 + CT2) < 3.2, it is beneficial to reduce the total length of the optical system, increase the optical path, and improve the performance of the optical system.
[0063] It should be noted that there is an unclear expression in the translation of . It is recommended to check and correct the original text for a more accurate translation. The corrected translation of is as follows: In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 0.5 < (CT3 × V3) / (CT4 × V4) < 1.75, where CT3 is the central thickness of the third lens on the optical axis, V3 is the dispersion coefficient of the third lens, CT4 is the central thickness of the fourth lens on the optical axis, and V4 is the dispersion coefficient of the fourth lens. By controlling the system to satisfy the conditional formula 0.5 < (CT3 × V3) / (CT4 × V4) < 1.75, the third lens and the fourth lens can respectively assume part of the function of reducing chromatic aberration, which is beneficial to improving the performance of the optical system.In an exemplary embodiment, the optical system of the present application can satisfy the conditional expression 1.2 < R6 / R5 < 1.6, where R6 is the radius of curvature of the second side surface of the third lens, and R5 is the radius of curvature of the first side surface of the third lens. By controlling the ratio of the radius of curvature of the second side surface of the third lens to the radius of curvature of the first side surface of the third lens within this range, it is beneficial to control the overall shape of the third lens, thereby controlling the thickness ratio of the lens, etc., and is beneficial to improving the processability of the lens.
[0064] In an exemplary embodiment, the optical system of the present application can satisfy the conditional expression 3.7 mm < f / (NR + NQ1 + NQ2 + NL) < 4.4 mm, where f is the effective focal length of the optical system, NR is the refractive index of the reflective polarizing element, NQ1 is the refractive index of the first quarter-wave plate, NQ2 is the refractive index of the second quarter-wave plate, and NL is the refractive index of the polarizing plate. By controlling the relationship between the effective focal length of the optical system and the refractive indices of each film layer to satisfy the conditional expression 3.7 mm < f / (NR + NQ1 + NQ2 + NL) < 4.4 mm, it is beneficial to reduce the chromatic aberration of the optical system and improve the performance of the optical system.
[0065] In an exemplary embodiment, the optical system of the present application can satisfy the conditional expression 2.5 mm < CT1 / (V1 / VR) < 6.5 mm, where CT1 is the central thickness of the first lens on the optical axis, V1 is the dispersion coefficient of the first lens, and VR is the dispersion coefficient of the reflective polarizing element. By controlling the optical system to satisfy the conditional expression 2.5 mm < CT1 / (V1 / VR) < 6.5 mm, it is beneficial to reduce the thickness of the first lens, reduce the overall length of the optical system, and is beneficial to achieving thin and light.
[0066] In an exemplary embodiment, the optical system of the present application can satisfy the conditional expression 0.9 mm < f2 / (VQ1 + V2) < 1.4 mm, where f = 2 is the effective focal length of the second lens, VQ1 is the dispersion coefficient of the first quarter-wave plate, and V2 is the dispersion coefficient of the second lens. By controlling the optical system to satisfy the conditional expression 0.9 mm < f2 / (VQ1 + V2) < 1.4 mm, it is beneficial to improve the converging ability of the system for light rays of different wavelengths and improve the performance of the optical system.
[0067] In an exemplary embodiment, the optical system of the present application can satisfy the conditional expression 4.4 < ∑CT / EPD < 5.15, where ∑CT is the sum of the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis respectively, and EPD is the entrance pupil diameter of the optical system. By controlling the optical system to satisfy the conditional expression 4.4 < ∑CT / EPD < 5.15, it is beneficial to reduce the overall length of the optical system when the system has a certain entrance pupil diameter.
[0068] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula -1.25 mm < R7 / (V3 + V4) < -0.5 mm, where R7 is the radius of curvature of the first side surface of the fourth lens, V3 is the dispersion coefficient of the third lens, and V4 is the dispersion coefficient of the fourth lens. By controlling the optical system to satisfy the conditional formula -1.25 mm < R7 / (V3 + V4) < -0.5 mm, it is beneficial to control the angle when the peripheral field of view passes through the polarization reflection sheet, which is beneficial to reducing the polarization angle effect and the risk of ghost images.
[0069] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 3.7 < f / CT2 < 4.2, where f is the effective focal length of the optical system and CT2 is the central thickness of the second lens on the optical axis. By controlling the ratio of the effective focal length of the optical system to the central thickness of the second lens on the optical axis within this range, the thickness of the second lens can be better controlled, which is beneficial to improving the processability of the lens.
[0070] In an exemplary embodiment, the optical system of the present application can satisfy the conditional formula 5.5 mm < TD / (N1 + N4) < 6.8 mm, where TD is the distance on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens, N1 is the refractive index of the first lens, and N4 is the refractive index of the fourth lens. By controlling the relationship between the total length of the center of the system lenses and the refractive indices of the first and fourth lenses to satisfy the conditional formula 5.5 mm < TD / (N1 + N4) < 6.8 mm, it is beneficial to reduce the total length of the optical system and the overall thickness of devices such as VR glasses.
[0071] In an exemplary embodiment, the materials of the first lens, the second lens, the third lens, and the fourth lens of the optical system of the present application can all be plastics. By using plastic materials, the lenses can be better formed during processing, and at the same time, the weight of the lenses can be reduced to achieve the purpose of light weight. In other exemplary embodiments, the first lens, the second lens, the third lens, and the fourth lens of the optical system of the present application can also partially use plastic materials.
[0072] In an exemplary embodiment, the first side surface and the second side surface of each of the first lens, the second lens, the third lens, and the fourth lens of the optical system of the present application can all be spherical surfaces. The surface type of the spherical surface is easier to process than the aspherical surface type, which is beneficial to improving the overall tolerance and sensitivity of the system, and at the same time, it is beneficial to reducing the difficulty of lens gluing. In other exemplary embodiments, the first side surface and the second side surface included in the first lens, the second lens, the third lens, and the fourth lens of the optical system of the present application can also be partially spherical surfaces.
[0073] In an exemplary embodiment, the optical system of the present application may include at least one aperture stop. The aperture stop can restrict the optical path and control the light intensity. The aperture stop can be disposed at an appropriate position of the optical system. For example, the aperture stop can be located between the first side (such as the human eye side) and the first lens.
[0074] On the one hand, the optical system according to an exemplary embodiment of the present application sequentially includes, along the optical axis from the first side to the second side, a first lens with positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with positive optical power, a third lens with negative optical power, a partially reflective element, a fourth lens with positive or negative optical power, a second quarter-wave plate, and a polarizer. Among them, the reflective polarizing element is disposed on the second side surface of the first lens, and the first side surface of the reflective polarizing element is at least partially adhered 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, the first side surface of the first quarter-wave plate is at least partially adhered to the second side surface of the reflective polarizing element, and the second side surface of the first quarter-wave plate is at least partially adhered to the first side surface of the second lens; the second lens and the third lens are cemented; the third lens and the fourth lens are cemented; and the effective focal length f2 of the second lens and the effective focal length f1 of the first lens satisfy the conditional formula 0.15 < f2 / f1 < 1.6. The central thicknesses CT1, CTR, CTQ1, and CT2 of the first lens, the reflective polarizing element, the first quarter-wave plate, and the second lens on the optical axis respectively satisfy the conditional formula 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05. The optical system adopts a polarization folding optical path and cemented lenses. By the above settings of the optical system, the system architecture and film pasting method are reasonably configured, so that the light is first reflected and then projected, meeting the requirement of light folding. On the one hand, the screen size of the optical system is controlled, and on the other hand, the field of view of the optical system is controlled; while f2 and f1 satisfy the conditional formula 0.15 < f2 / f1 < 1.6, the control system satisfies the conditional formula 0.35 < (CT1 + CTR) / (CTQ1 + CT2) < 1.05, which is beneficial to controlling the overall thickness of the first lens and the second lens, ensuring the processability of the two lenses, while controlling the second lens to have a greater thickness, making the optical path of the light refolded in the second lens longer, improving the performance of the optical system while reducing the total length of the optical system.
[0075] On the other hand, the optical system according to the exemplary embodiment of the present application sequentially includes, along the optical axis from the first side to the second side, a first lens with a positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with a positive optical power, a third lens with a negative optical power, a partial reflection element, a fourth lens with a positive or negative optical power, a second quarter-wave plate, and a polarizer. The reflective polarizing element is disposed on the second side surface of the first lens, and the first side surface of the reflective polarizing element is at least partially adhered 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, the first side surface of the first quarter-wave plate is at least partially adhered to the second side surface of the reflective polarizing element, and the second side surface of the first quarter-wave plate is at least partially adhered to the first side surface of the second lens; the second lens and the third lens are cemented; the third lens and the fourth lens are cemented; and the effective focal length f2 of the second lens and the effective focal length f1 of the first lens satisfy the conditional expression 0.15 < f2 / f1 < 1.6, and the effective focal length f of the optical system and the refractive index NR of the reflective polarizing element, the refractive index NQ1 of the first quarter-wave plate, the refractive index NQ2 of the second quarter-wave plate, and the refractive index NL of the polarizer satisfy the conditional expression 3.7 mm < f / (NR + NQ1 + NQ2 + NL) < 4.4 mm. The optical system adopts a polarization folding optical path and cemented lenses. By the above settings of the optical system, the system architecture and film pasting method are reasonably configured, so that the light is first reflected and then projected, meeting the requirement of light folding. On the one hand, the screen size of the optical system is controlled, and on the other hand, the field of view of the optical system is controlled; while f2 and f1 satisfy the conditional expression 0.15 < f2 / f1 < 1.6, the control system satisfies the conditional expression 3.7 mm < f / (NR + NQ1 + NQ2 + NL) < 4.4 mm, which is beneficial to reducing the chromatic aberration of the optical system and improving the performance of the optical system.
[0076] The optical system according to the exemplary embodiment of the present application can reduce the total length of the optical system, improve the performance of the optical system, reduce the molding difficulty of the lens, and the spherical design can also reduce the cementing difficulty of the lens, which is beneficial to improving the production yield and reducing the production cost by adopting a spherical cemented folding optical system architecture and reasonably configuring the optical power of each lens and the film pasting method of the system.
[0077] In addition, the present application also provides a VR / AR device, which may include the optical system provided in any one of the above embodiments. The first side is the human eye side, and the second side is the image plane side. The VR / AR device can have characteristics such as miniaturization, light weight, and high imaging quality, enabling users to obtain a better application experience.
[0078] The following further describes specific embodiments of the optical system applicable to the above embodiments with reference to the drawings.
[0079] Example 1
[0080] The following reference Figures 1 to 4 An optical system according to Example 1 of the present application is described. Figure 1 A structural schematic diagram of an optical system according to Example 1 of the present application is shown.
[0081] like Figure 1 As shown, the optical system includes, from the first side to the second side along the optical axis, a first lens E1, a reflective polarizer RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partially reflecting element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image surface IMG. The first side surface of the reflective polarizer RP is bonded to the second side surface of the first lens E1; the first side surface of the first quarter-wave plate QWP1 is bonded to the second side surface of the reflective polarizer RP; the first side surface of the second lens E2 is bonded to the second side surface of the first quarter-wave plate QWP1; the second side surface of the second lens E2 is cemented to the first side surface of the third lens E3; the third lens E3 is cemented to the fourth lens E4, with the partially reflecting element BS located between the third lens E3 and the fourth lens E4; the second side surface of the second quarter-wave plate QWP2 is bonded to the first side surface of the polarizer LP; and the second side surface of the polarizer LP is disposed on the first side of the image surface IMG.
[0082] In this embodiment, the first lens E1 has positive optical power, its first side surface is concave, and its second side surface is convex. The second lens E2 has positive optical power, its first side surface is concave, and its second side surface is convex. The third lens E3 has negative optical power, its first side surface is concave, and its second side surface is convex. The fourth lens E4 has positive optical power, its first side surface is concave, and its second side surface is convex.
[0083] In this embodiment, the light beam emitted from the image surface IMG located on the second side of the system can pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2 and the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, be reflected at the reflective polarizer RP and pass through the first quarter-wave plate QWP1, the second lens E2 and the third lens E3 again to reach the partially reflection element BS, and then the light beam is reflected again at the partially reflection element BS and passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizer RP and the first lens E1 in sequence to be emitted toward the first side, for example, the aperture STO.
[0084] Table 1 shows basic parameters of the optical system of Example 1, wherein the units of the curvature radius and thickness are both millimeters (mm).
[0085]
[0086]
[0087] Table 1
[0088] Figure 2 The axial chromatic aberration curve of the optical system of Example 1 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 3 The distortion curve of the optical system of Example 1 is shown, which represents the distortion magnitude values corresponding to different field angles. Figure 4 The modulation transfer function (MTF) curve of the optical system of Example 1 is shown, which represents the optical modulation function values corresponding to different cut-off frequencies. Figures 2 to 4 It can be seen that the optical system provided in Example 1 can achieve good imaging quality.
[0089] Example 2
[0090] The following reference Figures 5 to 8 An optical system according to Example 2 of the present application is described. Figure 5 A structural schematic diagram of an optical system according to Example 2 of the present application is shown.
[0091] like Figure 5 As shown, the optical system includes, from the first side to the second side along the optical axis, a first lens E1, a reflective polarizer RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partially reflecting element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image surface IMG. The first side surface of the reflective polarizer RP is bonded to the second side surface of the first lens E1; the first side surface of the first quarter-wave plate QWP1 is bonded to the second side surface of the reflective polarizer RP; the first side surface of the second lens E2 is bonded to the second side surface of the first quarter-wave plate QWP1; the second side surface of the second lens E2 is cemented to the first side surface of the third lens E3; the third lens E3 is cemented to the fourth lens E4, with the partially reflecting element BS located between the third lens E3 and the fourth lens E4; the second side surface of the second quarter-wave plate QWP2 is bonded to the first side surface of the polarizer LP; and the second side surface of the polarizer LP is disposed on the first side of the image surface IMG.
[0092] In this embodiment, the first lens E1 has positive optical power, with its first and second side surfaces being convex. The second lens E2 has positive optical power, with its first and second side surfaces being concave and convex. The third lens E3 has negative optical power, with its first and second side surfaces being concave and convex. The fourth lens E4 has negative optical power, with its first and second side surfaces being concave and convex.
[0093] In this embodiment, the light beam emitted from the image surface IMG located on the second side of the system can pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2 and the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, be reflected at the reflective polarizer RP and pass through the first quarter-wave plate QWP1, the second lens E2 and the third lens E3 again to reach the partially reflection element BS, and then the light beam is reflected again at the partially reflection element BS and passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizer RP and the first lens E1 in sequence to be emitted toward the first side, for example, the aperture STO.
[0094] Table 2 shows the basic parameters of the optical system of this embodiment, wherein the units of the curvature radius and thickness are both millimeters (mm).
[0095]
[0096]
[0097] Table 2
[0098] Figure 6 The axial chromatic aberration curve of the optical system of Example 2 is shown, which indicates the deviation of the convergent focus of light of different wavelengths after passing through the lens. Figure 7 The distortion curve of the optical system of Example 2 is shown, which represents the distortion magnitude values corresponding to different field angles. Figure 8 The modulation transfer function (MTF) curve of the optical system of Example 2 is shown, which represents the optical modulation function values corresponding to different cut-off frequencies. Figures 6 to 8 It can be seen that the optical system provided in Example 2 can achieve good imaging quality.
[0099] Example 3
[0100] The following reference Figures 9 to 12 An optical system according to Example 3 of the present application is described. Figure 9 A structural schematic diagram of an optical system according to Example 3 of the present application is shown.
[0101] like Figure 9As shown, the optical system includes, from the first side to the second side along the optical axis, a first lens E1, a reflective polarizer RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partially reflecting element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image surface IMG. The first side surface of the reflective polarizer RP is bonded to the second side surface of the first lens E1; the first side surface of the first quarter-wave plate QWP1 is bonded to the second side surface of the reflective polarizer RP; the first side surface of the second lens E2 is bonded to the second side surface of the first quarter-wave plate QWP1; the second side surface of the second lens E2 is cemented to the first side surface of the third lens E3; the third lens E3 is cemented to the fourth lens E4, with the partially reflecting element BS located between the third lens E3 and the fourth lens E4; the second side surface of the second quarter-wave plate QWP2 is bonded to the first side surface of the polarizer LP; and the second side surface of the polarizer LP is disposed on the first side of the image surface IMG.
[0102] In this embodiment, the first lens E1 has positive optical power, with its first side surface being convex and its second side surface being concave. The second lens E2 has positive optical power, with its first side surface being convex and its second side surface being convex. The third lens E3 has negative optical power, with its first side surface being concave and its second side surface being convex. The fourth lens E4 has negative optical power, with its first side surface being concave and its second side surface being convex.
[0103] In this embodiment, the light beam emitted from the image surface IMG located on the second side of the system can pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2 and the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, be reflected at the reflective polarizer RP and pass through the first quarter-wave plate QWP1, the second lens E2 and the third lens E3 again to reach the partially reflection element BS, and then the light beam is reflected again at the partially reflection element BS and passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizer RP and the first lens E1 in sequence to be emitted toward the first side, for example, the aperture STO.
[0104] Table 3 shows the basic parameters of the optical system of this embodiment, wherein the units of the curvature radius and thickness are both millimeters (mm).
[0105]
[0106]
[0107] Table 3
[0108] Figure 10The axial chromatic aberration curve of the optical system of Example 3 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 11 The distortion curve of the optical system of Example 3 is shown, which represents the distortion magnitude values corresponding to different field angles. Figure 12 The modulation transfer function (MTF) curve of the optical system of Example 3 is shown, which represents the optical modulation function values corresponding to different cut-off frequencies. Figures 10 to 12 It can be seen that the optical system provided in Example 3 can achieve good imaging quality.
[0109] Example 4
[0110] The following reference Figures 13 to 16 An optical system according to Example 4 of the present application is described. Figure 13 A structural schematic diagram of an optical system according to Example 4 of the present application is shown.
[0111] like Figure 13 As shown, the optical system includes, from the first side to the second side along the optical axis, a first lens E1, a reflective polarizer RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partially reflecting element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image surface IMG. The first side surface of the reflective polarizer RP is bonded to the second side surface of the first lens E1; the first side surface of the first quarter-wave plate QWP1 is bonded to the second side surface of the reflective polarizer RP; the first side surface of the second lens E2 is bonded to the second side surface of the first quarter-wave plate QWP1; the second side surface of the second lens E2 is cemented to the first side surface of the third lens E3; the third lens E3 is cemented to the fourth lens E4, with the partially reflecting element BS located between the third lens E3 and the fourth lens E4; the second side surface of the second quarter-wave plate QWP2 is bonded to the first side surface of the polarizer LP; and the second side surface of the polarizer LP is disposed on the first side of the image surface IMG.
[0112] In this embodiment, the first lens E1 has positive optical power, with its first and second side surfaces being convex. The second lens E2 has positive optical power, with its first and second side surfaces being concave and convex. The third lens E3 has negative optical power, with its first and second side surfaces being concave and convex. The fourth lens E4 has negative optical power, with its first and second side surfaces being concave and concave.
[0113] In this embodiment, the light beam emitted from the image surface IMG located on the second side of the system can pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2 and the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, be reflected at the reflective polarizer RP and pass through the first quarter-wave plate QWP1, the second lens E2 and the third lens E3 again to reach the partially reflection element BS, and then the light beam is reflected again at the partially reflection element BS and passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizer RP and the first lens E1 in sequence to be emitted toward the first side, for example, the aperture STO.
[0114] Table 4 shows the basic parameters of the optical system of this embodiment, wherein the units of the curvature radius and thickness are both millimeters (mm).
[0115] surface element Surface type Radius of curvature thickness Refractive index dispersion coefficient Refraction / Reflection S0 spherical surface endless -1300.0000 refraction S1 Aperture (STO) spherical surface endless 15.0000 refraction S2 First lens (E1) spherical surface 104.8000 6.2945 1.538 55.71 refraction S3 Reflective polarizer (RP) spherical surface -128.6177 0.1100 1.503 57.00 refraction S4 First quarter wave plate (QWP1) spherical surface -128.6177 0.1100 1.503 57.00 refraction S5 Second lens (E2) spherical surface -128.6177 6.4535 1.538 55.71 refraction S6 Third lens (E3) spherical surface -45.8194 5.4640 1.644 23.98 refraction S7 Partially reflective element (BS) spherical surface -60.9221 -5.4640 1.644 23.98 reflection S8 spherical surface -45.8194 -6.4535 1.538 55.71 refraction S9 spherical surface -128.6177 -0.1100 1.503 57.00 refraction S10 Reflective polarizer (RP) spherical surface -128.6177 0.1100 1.503 57.00 reflection S11 Second lens (E2) spherical surface -128.6177 6.4535 1.538 55.71 refraction S12 Third lens (E3) spherical surface -45.8194 5.4640 1.644 23.98 refraction S13 Fourth lens (E4) spherical surface -60.9221 1.5360 1.538 55.71 refraction S14 spherical surface 200.0000 5.0622 refraction S15 Second Quarter Wave Plate (QWP2) spherical surface endless 0.1100 1.503 57.00 refraction S16 Polarizer (LP) spherical surface endless 0.1500 1.503 57.00 refraction S17 spherical surface endless 0.0000 refraction S18 Image surface (IMG) spherical surface endless 0.0000 refraction
[0116] Table 4
[0117] Figure 14 The axial chromatic aberration curve of the optical system of Example 4 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 15 The distortion curve of the optical system of Example 4 is shown, which represents the distortion magnitude values corresponding to different field angles. Figure 16 The modulation transfer function (MTF) curve of the optical system of Example 4 is shown, which represents the optical modulation function values corresponding to different cut-off frequencies. Figures 14 to 16 It can be seen that the optical system provided in Example 4 can achieve good imaging quality.
[0118] Example 5
[0119] The following reference Figures 17 to 20 An optical system according to Example 5 of the present application is described. Figure 17 A structural schematic diagram of an optical system according to Example 5 of the present application is shown.
[0120] like Figure 17As shown, the optical system includes, from the first side to the second side along the optical axis, a first lens E1, a reflective polarizer RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partially reflecting element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, and an image surface IMG. The first side surface of the reflective polarizer RP is bonded to the second side surface of the first lens E1; the first side surface of the first quarter-wave plate QWP1 is bonded to the second side surface of the reflective polarizer RP; the first side surface of the second lens E2 is bonded to the second side surface of the first quarter-wave plate QWP1; the second side surface of the second lens E2 is cemented to the first side surface of the third lens E3; the third lens E3 is cemented to the fourth lens E4, with the partially reflecting element BS located between the third lens E3 and the fourth lens E4; the second side surface of the second quarter-wave plate QWP2 is bonded to the first side surface of the polarizer LP; and the second side surface of the polarizer LP is disposed on the first side of the image surface IMG.
[0121] In this embodiment, the first lens E1 has positive optical power, with its first side surface being concave and its second side surface being convex. The second lens E2 has positive optical power, with its first side surface being concave and its second side surface being convex. The third lens E3 has negative optical power, with its first side surface being concave and its second side surface being convex. The fourth lens E4 has negative optical power, with its first side surface being concave and its second side surface being convex.
[0122] In this embodiment, the light beam emitted from the image surface IMG located on the second side of the system can pass through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the partial reflection element BS, the third lens E3, the second lens E2 and the first quarter-wave plate QWP1 in sequence to reach the reflective polarizer RP, be reflected at the reflective polarizer RP and pass through the first quarter-wave plate QWP1, the second lens E2 and the third lens E3 again to reach the partially reflection element BS, and then the light beam is reflected again at the partially reflection element BS and passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizer RP and the first lens E1 in sequence to be emitted toward the first side, for example, the aperture STO.
[0123] Table 5 shows the basic parameters of the optical system of this embodiment, wherein the units of the curvature radius and thickness are both millimeters (mm).
[0124] surface element Surface type Radius of curvature thickness Refractive index dispersion coefficient Refraction / Reflection S0 spherical surface endless -1300.0000 refraction S1 Aperture (STO) spherical surface endless 15.0000 refraction S2 First lens (E1) spherical surface -250.5385 6.0098 1.547 56.14 refraction S3 Reflective polarizer (RP) spherical surface -45.4795 0.1100 1.503 57.00 refraction S4 First quarter wave plate (QWP1) spherical surface -45.4795 0.1100 1.503 57.00 refraction S5 Second lens (E2) spherical surface -45.4795 6.0109 1.547 56.14 refraction S6 Third lens (E3) spherical surface -31.1752 3.6196 1.672 20.37 refraction S7 Partially reflective element (BS) spherical surface -38.8975 -3.6196 1.672 20.37 reflection S8 spherical surface -31.1752 -6.0109 1.547 56.14 refraction S9 spherical surface -45.4795 -0.1100 1.503 57.00 refraction S10 Reflective polarizer (RP) spherical surface -45.4795 0.1100 1.503 57.00 reflection S11 Second lens (E2) spherical surface -45.4795 6.0109 1.547 56.14 refraction S12 Third lens (E3) spherical surface -31.1752 3.6196 1.672 20.37 refraction S13 Fourth lens (E4) spherical surface -38.8975 1.9958 1.661 21.52 refraction S14 spherical surface -41.2873 4.7464 refraction S15 Second Quarter Wave Plate (QWP2) spherical surface endless 0.1100 1.503 57.00 refraction S16 Polarizer (LP) spherical surface endless 0.1500 1.503 57.00 refraction S17 spherical surface endless 0.0000 refraction S18 Image surface (IMG) spherical surface endless 0.0000 refraction
[0125] Table 5
[0126] Figure 18 The axial chromatic aberration curve of the optical system of Example 5 is shown, which indicates the deviation of the convergent focus of light of different wavelengths passing through the lens. Figure 19The distortion curve of the optical system of Example 5 is shown, which represents the distortion magnitude values corresponding to different field angles. Figure 20 The modulation transfer function (MTF) curve of the optical system of Example 5 is shown, which represents the optical modulation function values corresponding to different cut-off frequencies. Figures 18 to 20 It can be seen that the optical system provided in Example 5 can achieve good imaging quality.
[0127] In Examples 1 to 5, the effective focal length f of the optical system, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens, the effective focal length f4 of the fourth lens, the entrance pupil diameter EPD of the optical system, 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, the distance SR on the optical axis from the aperture to the first side surface of the first lens, and the sum ΣCT of the center thicknesses of the first to fourth lenses on the optical axis are shown in Table 6.
[0128]
[0129]
[0130] Table 6
[0131] In addition, Examples 1 to 5 respectively satisfy the conditions shown in Table 7.
[0132] Conditional formula / Example Example 1 Example 2 Example 3 Example 4 Example 5 f2 / f1 1.06 1.09 0.16 1.19 1.57 (CT1+CTR) / (CTQ1+CT2) 0.83 0.97 0.40 0.98 1.00 f / SR 1.68 1.69 1.75 1.74 1.50 (f2×N2) / (f3×N3) -0.65 -0.38 -0.33 -0.36 -0.51 (CT2+CT3) / R4 -0.39 -0.26 -0.19 -0.26 -0.31 (CT3×V3) / (CT4×V4) 0.87 0.85 0.52 1.53 1.72 TD / (CTR+CTQ1+CT2) 3.15 3.06 2.82 2.99 2.87 R6 / R5 1.40 1.37 1.54 1.33 1.25 f / (NR+NQ1+NQ2+NL)(mm) 4.20 4.22 4.36 4.35 3.73 CT1 / (V1 / VR)(mm) 5.11 6.47 2.60 6.44 6.10 f2 / (VQ1+V2)(mm) 1.26 1.06 0.91 1.14 1.39 ∑CT / EPD 4.89 5.10 4.66 4.94 4.41 R7 / (V3+V4)(mm) -0.53 -0.77 -1.20 -0.76 -0.93 f / CT2 4.17 3.89 4.06 4.05 3.73 TD / (N1+N4)(mm) 6.43 6.71 6.13 6.49 5.57
[0133] Table 7
[0134] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of protection provided in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the concept of this application. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.
Claims
1. An optical system, characterized in that The optical axis includes, in order from the first side to the second side: a first lens having positive optical power; Reflective polarizing element; First quarter wave plate; a second lens having positive optical power; a third lens having negative optical power; Partially reflective elements; a fourth lens element having positive or negative optical power; a second quarter-wave plate; and Polarizer; The reflective polarizing element is placed on the second side surface of the first lens, and the first side surface of the reflective polarizing element is at least partially in contact with the second side surface of the first lens; the first quarter-wave plate is placed on the second side surface of the reflective polarizing element, and the first side surface of the first quarter-wave plate is at least partially in contact with the second side surface of the reflective polarizing element, and the second side surface of the first quarter-wave plate is at least partially in contact with the first side surface of the second lens; The second lens is cemented to the third lens; the third lens is cemented to the fourth lens; The number of lenses having optical power in the optical system is four; The optical system satisfies: 0.15 <f2 / f1<1.6, 0.40≤(CT1+CTR) / (CTQ1+CT2)≤1.00, Among them, f2 is the effective focal length of the second lens, f1 is the effective focal length of the first lens, CT1 is the center thickness of the first lens on the optical axis, CTR is the center thickness of the reflective polarizing element on the optical axis, CTQ1 is the center thickness of the first quarter-wave plate on the optical axis, and CT2 is the center thickness of the second lens on the optical axis.
2. The optical system according to claim 1, wherein: The optical system further includes a stop located on a first side of the first lens, and an effective focal length f of the optical system and a distance SR from the stop to a first side surface of the first lens on the optical axis satisfy: 1.50≤f / SR<1.
8.
3. The optical system according to claim 1, wherein: The effective focal length f2 of the second lens, the refractive index N2 of the second lens, the effective focal length f3 of the third lens, and the refractive index N3 of the third lens satisfy: -0.7<(f2×N2) / (f3×N3)<-0.
3.
4. The optical system according to claim 1, wherein The center thickness CT2 of the second lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, and the curvature radius R4 of the second side surface of the second lens satisfy: -0.4<(CT2+CT3) / R4<-0.
15.
5. The optical system according to claim 1, wherein: The center thickness CT3 of the third lens on the optical axis, the Abbe coefficient V3 of the third lens, the center thickness CT4 of the fourth lens on the optical axis, and the Abbe coefficient V4 of the fourth lens satisfy: 0.5<(CT3×V3) / (CT4×V4)<1.
75.
6. The optical system according to claim 1, wherein: The distance TD from the first side surface of the first lens to the second side surface of the fourth lens on the optical axis, 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 the following conditions: 2.8 <TD / (CTR+CTQ1+CT2)<3.2。 7. The optical system according to claim 1, wherein: The curvature radius R6 of the second side surface of the third lens and the curvature radius R5 of the first side surface of the third lens satisfy: 1.25≤R6 / R5≤1.
54.
8. The optical system according to claim 1, wherein: The effective focal length f of the optical system, the refractive index NR of the reflective polarizing element, the refractive index NQ1 of the first quarter-wave plate, the refractive index NQ2 of the second quarter-wave plate, and the refractive index NL of the polarizer satisfy: 3.7mm <f / (NR+NQ1+NQ2+NL)<4.4mm。 9. The optical system according to any one of claims 1 to 8, characterized in that The central thickness CT1 of the first lens on the optical axis, the Abbe coefficient V1 of the first lens, and the Abbe coefficient VR of the reflective polarizing element satisfy: 2.60mm≤CT1 / (V1 / VR)<6.5mm.
10. The optical system according to any one of claims 1 to 8, characterized in that The effective focal length f2 of the second lens, the dispersion coefficient VQ1 of the first quarter-wave plate, and the dispersion coefficient V2 of the second lens satisfy: 0.9mm <f2 / (VQ1+V2)<1.4mm。 11. The optical system according to any one of claims 1 to 8, characterized in that The sum of the center thicknesses ΣCT of the first lens, the second lens, the third lens, and the fourth lens on the optical axis and the entrance pupil diameter EPD of the optical system satisfy the following: 4.4<∑CT / EPD≤5.
10.
12. The optical system according to any one of claims 1 to 8, characterized in that The curvature radius R7 of the first side surface of the fourth lens, the Abbe coefficient V3 of the third lens, and the Abbe coefficient V4 of the fourth lens satisfy: -1.20mm≤R7 / (V3+V4)<-0.5mm.
13. The optical system according to any one of claims 1 to 8, characterized in that The effective focal length f of the optical system and the center thickness CT2 of the second lens on the optical axis satisfy: 3.7 <f / CT2<4.2。 14. The optical system according to any one of claims 1 to 8, characterized in that 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, the refractive index N1 of the first lens, and the refractive index N4 of the fourth lens satisfy: 5.57mm≤TD / (N1+N4)≤6.71mm.
15. The optical system according to any one of claims 1 to 8, characterized in that The first lens, the second lens, the third lens and the fourth lens are all made of plastic.
16. The optical system according to any one of claims 1 to 8, characterized in that The first side surface and the second side surface of each lens of the first lens, the second lens, the third lens and the fourth lens are all spherical surfaces.
17. The optical system according to any one of claims 1 to 8, characterized in that The second side surface of the second lens is a convex surface; The first side surface of the third lens is concave, and the second side surface is convex; The first side surface of the fourth lens is a concave surface.