Optical system and optical apparatus including the same

Abstract

The utility model discloses an optical system and optical equipment comprising the same. The optical system sequentially comprises a first lens with positive focal power, a reflective polarizing element, a first quarter-wave plate, a second lens with negative focal power, a third lens with positive focal power, a partial reflection element, a fourth lens with negative focal power, a second quarter-wave plate and a polarizing film from a first side to a second side along an optical axis, the optical system further comprises a first spacing element and a second spacing element; the optical system satisfies 0.05 lt; cP1 / CP2lt; 0.75 [mu] m and-2.6 [mu] m; fG1 / (d1m + d2s) lt; cP1 is the maximum thickness of the first spacing element in the optical axis direction, CP2 is the maximum thickness of the second spacing element in the optical axis direction, FG1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate and the second lens, d1m is the inner diameter of the second side face of the first spacing element, and d2s is the inner diameter of the first side face of the second spacing element.

Description

Technical Field

[0001] This application relates to the field of optical elements, and more particularly, to an optical system and an optical device including the optical system. Background Art

[0002] With the continuous progress of technology, VR (Virtual Reality) and AR (Augmented Reality) headsets have been widely used in fields such as entertainment, education, and healthcare.

[0003] The optical systems of traditional VR / AR headsets usually adopt a straight optical path, that is, light rays enter the user's eyes directly from the display screen through lenses. The optical path of this structure is relatively long, which easily leads to problems such as optical distortion and large volume. To solve these problems, a folding optical system has been proposed and has become one of the research hotspots of current VR / AR headsets.

[0004] The folding optical system has the advantages of shortening the total optical path length, saving assembly space, and reducing the weight of the device. However, due to the relatively complex optical path of the folding optical system, there are many challenges in its structural layout design, assembly stability, and imaging quality. At present, folding devices based on optical path folding have been released. From the user experience, the outer field of view image is relatively blurred, and the imaging quality of the lens needs to be improved. Therefore, reasonably designing the layout of lenses, reflecting elements, and spacer elements to obtain a folding optical system with good imaging quality is one of the important research topics for those skilled in the art at present. Summary of the Utility Model

[0005] The first aspect of the present application provides an optical system, which sequentially includes, along the optical axis, from the first side to the second side: a first lens with positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with negative optical power, a third lens with positive optical power, a partial reflection element, a fourth lens with negative optical power, a second quarter-wave plate, and a polarizer. Among them, the first quarter-wave plate is placed on the first side surface of the second lens and at least partially adheres to the first side surface of the second lens; the reflective polarizing element is placed on the first side surface of the first quarter-wave plate and at least partially adheres to the first side surface of the first quarter-wave plate; the second quarter-wave plate is placed on the second side surface of the fourth lens and at least partially adheres to the second side surface of the fourth lens; the polarizer is placed on the second side surface of the second quarter-wave plate and at least partially adheres to the second side surface of the second quarter-wave plate; the optical system further includes a first spacer element and a second spacer element. Among them, the first spacer element is placed between the first lens and the second lens and abuts against the second side surface of the first lens, and the second spacer element is placed between the second lens and the third lens and abuts against the second side surface of the second lens; the optical system satisfies 0.05 < CP1 / CP2 < 0.75 and -2.6 < FG1 / (d1m + d2s) < -0.9, where CP1 is the maximum thickness of the first spacer element along the optical axis direction, CP2 is the maximum thickness of the second spacer element along the optical axis direction, FG1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the second lens, d1m is the inner diameter of the second side surface of the first spacer element, and d2s is the inner diameter of the first side surface of the second spacer element.

[0006] In one embodiment, the optical system satisfies: 0.7 < CT2 / EP12 < 0.9, where CT2 is the central thickness of the second lens on the optical axis, and EP12 is the distance along the optical axis from the second side surface of the first spacer element to the first side surface of the second spacer element.

[0007] In one embodiment, the optical system satisfies: 1.0 < f1 / d1s < 1.75, where f1 is the effective focal length of the first lens, and d1s is the inner diameter of the first side surface of the first spacer element.

[0008] In one embodiment, the optical system further includes a lens barrel and satisfies: 2.0 < f / (d0s - d0m) ≤ 2.4, where f is the effective focal length of the optical system, d0s is the inner diameter of the first side end face of the lens barrel, and d0m is the inner diameter of the second side end face of the lens barrel.

[0009] In one embodiment, the optical system further includes a fourth spacer element placed on the second side of the fourth lens and abutting against the second side surface of the fourth lens; the optical system satisfies: 1.5 ≤ D1s / D4s < 1.7, where D1s is the outer diameter of the first side surface of the first spacer element, and D4s is the outer diameter of the first side surface of the fourth spacer element.

[0010] In one embodiment, the optical system satisfies: 0.2 ≤ D2m / f3 < 0.4, where D2m is the outer diameter of the second side surface of the second spacer element, and f3 is the effective focal length of the third lens.

[0011] In one embodiment, the optical system satisfies: 3.9 < D1m / CT1 < 6.0, where D1m is the outer diameter of the second side surface of the first spacer element, and CT1 is the central thickness of the first lens on the optical axis.

[0012] In one embodiment, the optical system satisfies: -0.55 < D2s / f2 < -0.15, where D2s is the outer diameter of the first side surface of the second spacer element, and f2 is the effective focal length of the second lens.

[0013] In one embodiment, the optical system further includes a third spacer element and a fourth spacer element. The third spacer element is disposed between the third lens and the fourth lens and abuts against the second side surface of the third lens. The fourth spacer element is disposed on the second side of the fourth lens and abuts against the second side surface of the fourth lens. The optical system satisfies: 0.8 < (CT4 + CTQ2 + CTL) / EP34 < 1.2, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, CTL is the central thickness of the polarizer on the optical axis, and EP34 is the distance along the optical axis from the second side surface of the third spacer element to the first side surface of the fourth spacer element.

[0014] In one embodiment, the optical system further includes a third spacer element disposed between the third lens and the fourth lens and abutting against the second side surface of the third lens. The optical system satisfies: 3.2 ≤ TD / (EP23 + CP3) < 3.7, where TD is the distance along the optical axis from the first side surface of the first lens to the second side surface of the fourth lens, EP23 is the distance along the optical axis from the second side surface of the second spacer element to the first side surface of the third spacer element, and CP3 is the maximum thickness of the third spacer element along the optical axis.

[0015] In one embodiment, the optical system further includes a third spacer element disposed between the third lens and the fourth lens and abutting against the second side surface of the third lens. The optical system satisfies: -2.5 < R7 / d3m < -0.5, where R7 is the radius of curvature of the first side surface of the fourth lens, and d3m is the inner diameter of the second side surface of the third spacer element.

[0016] In one embodiment, the optical system further includes a third spacer element disposed between the third lens and the fourth lens and abutted against the second side surface of the third lens; the optical system further includes a lens barrel, and satisfies: 1.5 ≤ D0s / D3s < 1.7, where D0s is the outer diameter of the first side end surface of the lens barrel, and D3s is the outer diameter of the first side surface of the third spacer element.

[0017] In one embodiment, the optical system further includes a fourth spacer element disposed on the second side of the fourth lens and abutted against the second side surface of the fourth lens; the optical system satisfies: -1.2 < d4s / FG2 < -0.2, where d4s is the inner diameter of the first side surface of the fourth spacer element, and FG2 is the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer.

[0018] In one embodiment, the optical system further includes a third spacer element disposed between the third lens and the fourth lens and abutted against the second side surface of the third lens; the optical system satisfies: -1.5 < D3m / f4 < -0.3, where D3m is the outer diameter of the second side surface of the third spacer element, and f4 is the effective focal length of the fourth lens.

[0019] In one embodiment, the optical system further includes a lens barrel, and satisfies: 1.6 < EP01 / T12 < 4.9, where EP01 is the distance along the optical axis from the first side end surface of the lens barrel to the first side surface of the first spacer element, and T12 is the on-axis distance from the second side surface of the first lens to the first side surface of the second lens.

[0020] In one embodiment, the optical system further includes a lens barrel, and a fourth spacer element disposed on the second side of the fourth lens and abutted against the second side surface of the fourth lens; the optical system satisfies: 1.5 ≤ D0m / D4m ≤ 1.6, where D0m is the outer diameter of the second side end surface of the lens barrel, and D4m is the outer diameter of the second side surface of the fourth spacer element.

[0021] A second aspect of the present application provides an optical system, which sequentially includes, along the optical axis, from the first side to the second side: a first lens with positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with negative optical power, a third lens with positive optical power, a partial reflection element, a fourth lens with negative optical power, a second quarter-wave plate, and a polarizer. Among them, the first quarter-wave plate is placed on the first side surface of the second lens and at least partially adheres to the first side surface of the second lens; the reflective polarizing element is placed on the first side surface of the first quarter-wave plate and at least partially adheres to the first side surface of the first quarter-wave plate; the second quarter-wave plate is placed on the second side surface of the fourth lens and at least partially adheres to the second side surface of the fourth lens; the polarizer is placed on the second side surface of the second quarter-wave plate and at least partially adheres to the second side surface of the second quarter-wave plate; the optical system further includes a first spacer element and a second spacer element. Among them, the first spacer element is placed between the first lens and the second lens and abuts against the second side surface of the first lens, and the second spacer element is placed between the second lens and the third lens and abuts against the second side surface of the second lens; the optical system satisfies 0.05 < CP1 / CP2 < 0.75 and 1.0 < f1 / d1s < 1.75, where CP1 is the maximum thickness of the first spacer element along the optical axis direction, CP2 is the maximum thickness of the second spacer element along the optical axis direction, f1 is the effective focal length of the first lens, and d1s is the inner diameter of the first side surface of the first spacer element.

[0022] A third aspect of the present application further provides an optical device, which includes the optical system provided by any one of the above-mentioned embodiments.

[0023] The optical system provided by the present application adopts a polarization folding optical path design, arranging the optical powers of 4 lenses alternately positive and negative, which is beneficial to reducing the sensitivity of the optical system to environmental conditions and improving the stability and reliability of the system. The optical system provided by the present application reasonably designs the spatial arrangement of the lenses, the reflective polarizing element, and the quarter-wave plate, as well as the parameters of the spacer element, and satisfies 0.05 < CP1 / CP2 < 0.75 and -2.6 < FG1 / (d1m + d2s) < -0.9. By controlling the thicknesses of the first spacer element and the second spacer element and controlling FG1 / (d1m + d2s) within a certain range, the processability of the first spacer element and the second spacer element can be ensured, and the edge thickness of the second lens can be restricted, effectively solving the problem that due to the unreasonable edge thickness of the second lens, the assembly bearing stability becomes poor, resulting in poor field curvature and affecting the imaging quality. That is, the assembly stability of the second lens is improved, the lens deformation is reduced, the field curvature is reduced, and the on-axis imaging quality of the optical system is improved. Description of the Drawings

[0024] In conjunction with the accompanying drawings, through the following detailed description of non-limiting embodiments, other features, objectives, and advantages of the present application will become more apparent. In the drawings:

[0025] Figure 1A shows a schematic structural diagram of an optical system according to Embodiment 1 of the present application;

[0026] Figure 1B shows a schematic structural diagram of an optical system according to Embodiment 2 of the present application;

[0027] Figure 1C shows a schematic structural diagram of an optical system according to Embodiment 3 of the present application;

[0028] FIG. 2A to FIG. 2D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical systems according to Embodiments 1 to 3 of the present application;

[0029] Figure 3A shows a schematic structural diagram of an optical system according to Embodiment 4 of the present application;

[0030] Figure 3B shows a schematic structural diagram of an optical system according to Embodiment 5 of the present application;

[0031] Figure 3C shows a schematic structural diagram of an optical system according to Embodiment 6 of the present application;

[0032] FIG. 4A to FIG. 4D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical systems according to Embodiments 4 to 6 of the present application;

[0033] Figure 5A shows a schematic structural diagram of an optical system according to Embodiment 7 of the present application;

[0034] Figure 5B shows a schematic structural diagram of an optical system according to Embodiment 8 of the present application;

[0035] Figure 5C shows a schematic structural diagram of an optical system according to Embodiment 9 of the present application;

[0036] FIG. 6A to FIG. 6D respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and modulation transfer function curve of the optical systems according to Embodiments 7 to 9 of the present application; and

[0037] Figure 7 shows a schematic structural diagram of the optical system according to the present application and a schematic diagram of some parameters. Detailed implementation manners

[0038] To better understand 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 only descriptions of exemplary embodiments of the present application and do not limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0039] It should be noted that in this specification, the expressions such as first, second, etc. are only used to distinguish one feature from another feature and do not represent any limitation on the feature. Therefore, without departing from the teachings of the present application, the first lens discussed below may also be referred to as the second lens, and the second lens may also be referred to as the first lens.

[0040] In the drawings, for ease of illustration, the thickness, size, and shape of the lens have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are shown by way of example. That is, the spherical or aspherical shapes are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are only examples and are not drawn to an exact scale.

[0041] In this document, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region.

[0042] It should also be understood that the terms "comprise", "comprising", "have", "include", and / or "including", when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. In addition, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of listed features rather than an individual element in the list. In addition, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". And the term "exemplary" is intended to refer to an example or illustration.

[0043] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application 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 formalized sense unless expressly so defined herein.

[0044] 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 accompanying drawings and in combination with the embodiments.

[0045] The features, principles and other aspects of the present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0046] According to an exemplary embodiment of the present application, the optical system sequentially includes, along the optical axis from the first side to the second side: a first lens, a reflective polarizing element, a first quarter-wave plate, a second lens, a third lens, a partially reflective element, a fourth lens, a second quarter-wave plate, and a polarizer.

[0047] In the exemplary embodiment, the first lens has a positive optical power, the second lens has a negative optical power, the third lens has a positive optical power, and the fourth lens has a negative optical power. Alternating the positive and negative optical powers of the four lenses is beneficial to reducing the sensitivity of the optical system to environmental conditions and improving the stability and reliability of the system.

[0048] Those skilled in the art should understand that the reflective polarizing element can reflect polarized light in a certain direction and can also transmit polarized light orthogonal to the polarization direction. The quarter-wave plate can change the state of polarized light. By using the combination of light reflection and refraction of the reflective polarizing element and the quarter-wave plate, the required optical path can be folded, effectively shortening the length of the optical system.

[0049] In the exemplary embodiment, the first quarter-wave plate is placed on the first side of the second lens and at least partially adheres to the first side of the second lens; the reflective polarizing element is placed on the first side of the first quarter-wave plate and at least partially adheres to the first side of the first quarter-wave plate. Exemplarily, the reflective polarizing element and the first quarter-wave plate can be compounded and attached to the first side of the second lens through a single attachment process instead of two separate attachments, reducing the angular position error caused by the attachment and improving the imaging quality.

[0050] In the exemplary embodiment, the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate. Exemplarily, the second quarter-wave plate and the polarizer can be compounded and attached to the second side of the fourth lens through a single attachment process instead of two separate attachments, reducing the angular position error caused by the attachment and improving the imaging quality.

[0051] In the exemplary embodiment, the optical system according to the present application can be applied to, for example, a VR device. The first side can be, for example, the human eye side, and the second side can be, for example, the screen side, as Figure 1AAs shown, the optical system sequentially includes, along the optical axis from the human eye side to the screen side: a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown), a fourth lens E4, a second quarter-wave plate QWP2, and a polarizer LP. Among them, the reflective polarizing element RP is attached to the human-eye side surface of the first quarter-wave plate QWP1, and the first quarter-wave plate QWP1 is attached to the human-eye side surface of the second lens E2; the second quarter-wave plate QWP2 is attached to the screen side surface of the fourth lens E4, and the polarizer LP is attached to the screen side surface of the second quarter-wave plate QWP2. The partial reflection element BS can have a semi-transmissive and semi-reflective function and is attached to the screen side surface of the third lens E3.

[0052] Figure 1A The optical system shown further includes an image plane IMG provided on the screen side and a protective glass GL for protecting the light-emitting element located on the image plane IMA. The optical system may further include a diaphragm STO (not shown) provided on the human eye side. The user's eyes can view the image projected by the image plane IMG at the position of the aperture STO, that is, the image light on the image plane IMG passes through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, etc., and is finally projected onto the user's eyes after multiple refractions and reflections. More specifically, Figure 1A The light path of the optical system in [description] is as follows: The light emitted from the image plane IMG sequentially passes through the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP, where it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the screen side surface of the third lens E3 and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, then passes through the diaphragm STO and finally exits toward the human eye side.

[0053] In an exemplary embodiment, the optical system may include at least one of a first spacer element, a second spacer element, a third spacer element, and a fourth spacer element. The first spacer element is placed between the first lens and the second lens and abuts against the second side surface of the first lens. The second spacer element is placed between the second lens and the third lens and abuts against the second side surface of the second lens. The third spacer element is placed between the third lens and the fourth lens and abuts against the second side surface of the third lens. The fourth spacer element is placed on the second side surface of the fourth lens and abuts against the second side surface of the fourth lens.

[0054] In an exemplary embodiment, the optical system may include a first spacer element and a second spacer element. The first spacer element is disposed between the first lens and the second lens and abuts against the second side surface of the first lens. The second spacer element is disposed between the second lens and the third lens and abuts against the second side surface of the second lens.

[0055] It should be understood that the present application does not specifically limit the number of spacer elements. Any number of spacer elements may be included between any two lenses, and any number of spacer elements may also be included in the entire imaging system. The spacer elements help the imaging system intercept redundant catadioptric light paths, reducing the generation of stray light and ghost images. The spacer elements also help increase the auxiliary support between the lens and the lens barrel, which is beneficial to improving problems such as poor assembly stability and low performance yield caused by large step differences between lenses.

[0056] Figure 7 A schematic structural diagram of the optical system according to the present application and a schematic diagram of some parameters are shown. As Figure 7 shown, CP1 is the maximum thickness of the first spacer element along the optical axis direction, CP2 is the maximum thickness of the second spacer element along the optical axis direction, CP3 is the maximum thickness of the third spacer element along the optical axis direction, CP4 is the maximum thickness of the fourth spacer element along the optical axis direction, EP01 is the distance along the optical axis direction from the first side end face of the lens barrel to the first side surface of the first spacer element, EP12 is the distance along the optical axis direction from the second side surface of the first spacer element to the first side surface of the second spacer element, EP23 is the distance along the optical axis direction from the second side surface of the second spacer element to the first side surface of the third spacer element, EP34 is the distance along the optical axis direction from the second side surface of the third spacer element to the first side surface of the fourth spacer element, and L is the distance along the optical axis direction from the first side end face of the lens barrel to the second side end face. D0s is the outer diameter of the first side end face of the lens barrel, d0s is the inner diameter of the first side end face of the lens barrel, D1s is the outer diameter of the first side surface of the first spacer element, d1s is the inner diameter of the first side surface of the first spacer element, D2s is the outer diameter of the first side surface of the second spacer element, d2s is the inner diameter of the first side surface of the second spacer element, D3s is the outer diameter of the first side surface of the third spacer element, D4s is the outer diameter of the first side surface of the fourth spacer element, d4s is the inner diameter of the first side surface of the fourth spacer element, d3s is the inner diameter of the first side surface of the third spacer element, d0m is the inner diameter of the second side end face of the lens barrel, d4m is the inner diameter of the second side surface of the fourth spacer element, d3m is the inner diameter of the second side surface of the third spacer element, D4m is the outer diameter of the second side surface of the fourth spacer element, D3m is the outer diameter of the second side surface of the third spacer element, d2m is the inner diameter of the second side surface of the second spacer element, D2m is the outer diameter of the second side surface of the second spacer element, D0m is the outer diameter of the second side end face of the lens barrel, d1m is the inner diameter of the second side surface of the first spacer element, and D1m is the outer diameter of the second side surface of the first spacer element.

[0057] Those skilled in the art should understand that some parameters of the lenses often used in the art (such as the central thickness CT2 of the second lens on the optical axis) are not shown in Figure 7 the text, Figure 7 and only some parameters of the lens barrel and the spacer elements of an imaging system of the present application are exemplarily shown for better understanding of the present invention.

[0058] On the one hand, the present application provides such an optical system, which 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 negative optical power, a third lens with positive optical power, a partially reflective element, a fourth lens with negative optical power, a second quarter-wave plate, and a polarizer. The optical system further includes a first spacer element and a second spacer element, wherein the first spacer element is disposed between the first lens and the second lens and abuts against the second side surface of the first lens, and the second spacer element is disposed between the second lens and the third lens and abuts against the second side surface of the second lens. The optical system satisfies 0.05 < CP1 / CP2 < 0.75 and -2.6 < FG1 / (d1m + d2s) < -0.9, where CP1 is the maximum thickness of the first spacer element along the optical axis direction, CP2 is the maximum thickness of the second spacer element along the optical axis direction, FG1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the second lens, d1m is the inner diameter of the second side surface of the first spacer element, and d2s is the inner diameter of the first side surface of the second spacer element. Satisfying 0.05 < CP1 / CP2 < 0.75 and -2.6 < FG1 / (d1m + d2s) < -0.9 can ensure the processability of the first spacer element and the second spacer element, and at the same time can also restrict the edge thickness of the second lens, avoiding the problem that the assembly bearing stability becomes poor due to the unreasonable edge thickness of the second lens, resulting in the deterioration of the field curvature and affecting the imaging quality. Further, by controlling FG1 / (d1m + d2s) within a certain range, the above problem of the deterioration of the field curvature is effectively solved, and the assembly stability of the second lens can also be improved, reducing deformation, thereby reducing the field curvature and improving the imaging quality of the optical system on the axis.

[0059] In an exemplary embodiment, the optical system satisfies 0.7 < CT2 / EP12 < 0.9, where CT2 is the central thickness of the second lens on the optical axis, and EP12 is the distance along the optical axis from the second side of the first spacer element to the first side of the second spacer element. Since the thicknesses of the first spacer element and the second spacer element are relatively large, more stray light will be generated. Satisfying 0.7 < CT2 / EP12 < 0.9 and controlling the central thickness of the second lens on the optical axis within a certain range are beneficial to reducing the reflection of redundant light and improving the imaging quality. In addition, controlling EP12 helps to control the edge thickness of the second lens. Satisfying this conditional expression can also control the ratio of the central thickness to the edge thickness of the second lens and ensure the processability of the second lens.

[0060] In an exemplary embodiment, the optical system satisfies: 1.0 < f1 / d1s < 1.75, where f1 is the effective focal length of the first lens, and d1s is the inner diameter of the first side of the first spacer element. By controlling the effective focal length of the first lens, the field of view angle of the optical system is effectively constrained, which is beneficial for the optical system to meet the characteristics of a large field of view of a VR lens. At the same time, restricting the inner diameter of the first side of the first spacer element can effectively control the light input amount of the optical system and utilize light to participate in imaging with higher efficiency. Controlling the inner diameter size of the first side of the first spacer element can better change the reflection route of redundant light, reduce the generation of stray light, and improve the imaging clarity.

[0061] In an exemplary embodiment, the optical system satisfies: 2.0 < f / (d0s - d0m) ≤ 2.4, where f is the effective focal length of the optical system, d0s is the inner diameter of the first side end face of the lens barrel, and d0m is the inner diameter of the second side end face of the lens barrel. Controlling the inner diameter of the second side end face of the lens barrel can effectively control the light input amount and utilize light to participate in imaging with higher efficiency. Controlling the inner diameter sizes of the first side end face and the second side end face of the lens barrel can better change the reflection route of redundant light, reduce the generation of stray light, and improve the imaging clarity.

[0062] In an exemplary embodiment, the optical system satisfies: 1.5 ≤ D1s / D4s < 1.7, where D1s is the outer diameter of the first side of the first spacer element, and D4s is the outer diameter of the first side of the fourth spacer element. Satisfying 1.5 ≤ D1s / D4s < 1.7 can limit the processing outer shape sizes of the first spacer element and the fourth spacer element to meet the processing feasibility, and can also limit the bearing misalignment amount of each lens between the first spacer element and the fourth spacer element, making the lens assembly more stable and having a smaller deformation amount.

[0063] In an exemplary embodiment, the optical system satisfies: 0.8 < (CT4 + CTQ2 + CTL) / EP34 < 1.2, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, CTL is the central thickness of the polarizer on the optical axis, and EP34 is the distance along the optical axis from the second side surface of the third spacer element to the first side surface of the fourth spacer element. By controlling EP34, the edge thickness of the fourth lens is controlled, and further, the ratio of the central thickness of the fourth lens to the edge thickness of the fourth lens is controlled within a certain range, which helps to control the shape and processability of the fourth lens; further, by combining the control of the central thickness of the second quarter-wave plate and the central thickness of the polarizer, it is beneficial to ensure that the second quarter-wave plate is smoothly attached to the second side surface of the fourth lens, and it is also beneficial to ensure that the polarizer is well attached to the second quarter-wave plate.

[0064] In an exemplary embodiment, the optical system satisfies: 0.2 ≤ D2m / f3 < 0.4, where D2m is the outer diameter of the second side surface of the second spacer element, and f3 is the effective focal length of the third lens. Controlling the ratio of the outer diameter of the second side surface of the second spacer element to the effective focal length of the third lens can effectively control the trend of light passing through the third lens, and avoid the problem of excessive sensitivity of the lens caused by too steep light.

[0065] In an exemplary embodiment, the optical system satisfies: 3.2 ≤ TD / (EP23 + CP3) < 3.7, where TD is the distance along the optical axis from the first side surface of the first lens to the second side surface of the fourth lens, EP23 is the distance along the optical axis from the second side surface of the second spacer element to the first side surface of the third spacer element, and CP3 is the maximum thickness of the third spacer element along the optical axis. Controlling the distance TD along the optical axis from the first side surface of the first lens to the second side surface of the fourth lens overall limits the length of the optical system, which is of great significance for reducing the size of the whole machine; at the same time, by controlling EP23, the edge thickness of the third lens is limited, ensuring the processability of the third lens, and by controlling the thickness of the third spacer element, it is beneficial to the processing and forming of the third spacer element.

[0066] In an exemplary embodiment, the optical system satisfies: -2.5 < R7 / d3m < -0.5, where R7 is the radius of curvature of the first side surface of the fourth lens, and d3m is the inner diameter of the second side surface of the third spacer element. By controlling the ratio of the radius of curvature of the second side surface of the fourth lens to the inner diameter of the second side surface of the third spacer element within a certain range, the refraction angle of light passing through the fourth lens can be reasonably controlled, making the cooperation between the lenses more compact. Controlling the size of the inner diameter of the second side surface of the third spacer element is beneficial to blocking the optical path reflected between the mechanism part at the effective diameter edge of the first side surface of the fourth lens and the small inclined surface of the third spacer element, and avoiding the stray light generated by the reflected light reaching the inside of the lens.

[0067] In an exemplary embodiment, the optical system satisfies: 1.5 ≤ D0s / D3s < 1.7, where D0s is the outer diameter of the first side end face of the lens barrel, and D3s is the outer diameter of the first side surface of the third spacer element. Reasonably setting the outer diameter of the lens barrel and the outer diameter of the first side surface of the third spacer element effectively restricts the overall size of the optical system, which is beneficial for later matching with the module; at the same time, by restricting the outer shape size of the lens barrel, on the premise of ensuring the processability of the lens barrel, the outer shape size of the lens barrel is made as small as possible, thereby reducing the size of the whole machine.

[0068] In an exemplary embodiment, the optical system satisfies: 3.9 < D1m / CT1 < 6.0, where D1m is the outer diameter of the second side surface of the first spacer element, and CT1 is the central thickness of the first lens on the optical axis. Since the central thickness of the first lens is relatively large, the thickness ratio of the first lens is relatively small. By controlling the central thickness of the first lens on the optical axis, it is beneficial for the processing and forming of the first lens; secondly, controlling the outer diameter of the second side surface of the first spacer element is beneficial to improving the processability of the first spacer element on the basis of ensuring its supporting function.

[0069] In an exemplary embodiment, the optical system satisfies: -1.2 < d4s / FG2 < -0.2, where d4s is the inner diameter of the first side surface of the fourth spacer element, and FG2 is the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer. Controlling the combined focal length of the fourth lens, the second quarter-wave plate, and the polarizer within a certain range is beneficial for making the combined component of the fourth lens, the second quarter-wave plate, and the polarizer generate positive spherical aberration and balance the negative spherical aberration generated by other lenses in the system, so that the imaging quality of the system on the axis is good; secondly, controlling the inner diameter of the first side surface of the fourth spacer element is beneficial to improving the processability of the fourth spacer element on the basis of ensuring its supporting function.

[0070] In an exemplary embodiment, the optical system satisfies: -0.55 < D2s / f2 < -0.15, where D2s is the outer diameter of the first side surface of the second spacer element, and f2 is the effective focal length of the second lens. Satisfying -0.55 < D2s / f2 < -0.15 can effectively control the trend of light passing through the second lens and avoid the problem of excessive sensitivity of the lens caused by too steep light rays.

[0071] In an exemplary embodiment, the optical system satisfies: -1.5 < D3m / f4 < -0.3, where D3m is the outer diameter of the second side surface of the third spacer element, and f4 is the effective focal length of the fourth lens. Satisfying -1.5 < D3m / f4 < -0.3 can effectively control the trend of light passing through the fourth lens and avoid the problem of excessive sensitivity of the lens caused by too steep light rays.

[0072] In an exemplary embodiment, the optical system satisfies: 1.6 < EP01 / T12 < 4.9, where EP01 is the distance along the optical axis from the first side end face of the lens barrel to the first side surface of the first spacer element, and T12 is the on-axis distance from the second side surface of the first lens to the first side surface of the second lens. Reasonably setting the distance along the optical axis from the first side end face of the lens barrel to the first side surface of the first spacer element indirectly ensures the edge thickness of the first lens, which is beneficial to the molding of parts. In addition, it also ensures the dispensing space of the first lens and indirectly ensures the reliability.

[0073] In an exemplary embodiment, the optical system satisfies: 1.5 ≤ D0m / D4m ≤ 1.6, where D0m is the outer diameter of the second side end face of the lens barrel, and D4m is the outer diameter of the second side surface of the fourth spacer element. Reasonably setting the outer diameters of the lens barrel and the fourth spacer element makes the bearing misalignment amount of each element in the lens barrel appropriate, and the assembly is more stable, which is beneficial to the later matching with the module; by restricting the outer dimension of the lens barrel, on the premise of ensuring the machinability of the lens barrel, the outer dimension of the lens barrel is made as small as possible, thereby reducing the overall size of the machine.

[0074] On the other hand, the present application also provides an optical system, which sequentially includes, from the first side to the second side along the optical axis: a first lens with a positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with a negative optical power, a third lens with a positive optical power, a partial reflection element, a fourth lens with a negative optical power, a second quarter-wave plate, and a polarizer. Among them, the first quarter-wave plate is placed on the first side of the second lens and at least partially adheres to the first side of the second lens; the reflective polarizing element is placed on the first side of the first quarter-wave plate and at least partially adheres to the first side of the first quarter-wave plate; the second quarter-wave plate is placed on the second side of the fourth lens and at least partially adheres to the second side of the fourth lens; the polarizer is placed on the second side of the second quarter-wave plate and at least partially adheres to the second side of the second quarter-wave plate; the optical system further includes a first spacer element and a second spacer element. Among them, the first spacer element is placed between the first lens and the second lens and abuts against the second side of the first lens, and the second spacer element is placed between the second lens and the third lens and abuts against the second side of the second lens; the optical system satisfies 0.05 < CP1 / CP2 < 0.75 and 1.0 < f1 / d1s < 1.75, where CP1 is the maximum thickness of the first spacer element along the optical axis direction, CP2 is the maximum thickness of the second spacer element along the optical axis direction, f1 is the effective focal length of the first lens, and d1s is the inner diameter of the first side of the first spacer element. By controlling the thicknesses of the first spacer element and the second spacer element, the processability of the first spacer element and the second spacer element can be ensured. At the same time, the edge thickness of the second lens can be restricted, avoiding the problem that the assembly bearing stability deteriorates due to the unreasonable edge thickness of the second lens, resulting in the deterioration of the field curvature and affecting the imaging quality. By controlling the effective focal length of the first lens, the field of view angle of the optical system is effectively restricted, which is beneficial to making the optical system meet the characteristics of a large field of view of a VR lens; at the same time, by restricting the inner diameter of the first side of the first spacer element, the light input amount of the optical system can be effectively controlled, and the light can be utilized more efficiently to participate in imaging. By controlling the inner diameter size of the first side of the first spacer element, the reflection route of the redundant light can be better changed, the generation of stray light can be reduced, and the imaging clarity can be improved.

[0075] 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 set at an appropriate position of the optical system. For example, the aperture stop can be located on the first side of the first lens.

[0076] In an embodiment of the present application, at least one of the surfaces of each of the first lens to the fourth lens is an aspherical surface. The characteristic of an aspherical lens is that the curvature continuously changes 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, 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 as much as possible the aberration that appears during imaging, thereby improving the imaging quality. Optionally, the first side and the second side of the third lens, and the first side of the fourth lens can be aspherical surfaces. Optionally, the first side and the second side of the first lens, the second side of the second lens, the first side and the second side of the third lens, and the first side of the fourth lens can be aspherical surfaces.

[0077] The optical system provided by the present application can use four lenses. A reflective polarizing element and a quarter-wave plate are attached to the first side of the second lens, and a reflective polarizing element and a polarizer are attached to the second side of the fourth lens. Such a design can convert the natural light emitted from the image plane into polarized light and realize the refolding of the optical path. In addition to reasonably arranging the lenses and reflective elements, the optical system provided by the present application can also reasonably design the size of the spacer element, improve the assembly stability of the optical system, reduce the stray light interference, and improve the imaging quality of the system.

[0078] According to some embodiments of the present application, the optical system of the present application has the advantages of small volume, small optical distortion, clear and stable image, etc., and can provide a better virtual reality experience for users. In applications, the optical system according to the exemplary embodiments of the present application can be applied to VR devices. By reasonably setting parameters such as the optical power, entrance pupil diameter, and the center thickness, refractive index, Abbe number, and curvature radius of the lens of the optical system, the purpose of wide angle of the VR device can be achieved, the chromatic aberration of the system can be corrected, the optical distortion can be reduced, and the imaging quality and reliability of the system can be improved.

[0079] Next, taking the optical system applied to, for example, a VR device, with the first side being the human eye side and the second side being the screen side, and referring to the accompanying drawings, a specific embodiment of the optical system applicable to the above embodiments will be further described.

[0080] Example 1

[0081] Figure 1A FIG. 16 shows a schematic structural diagram of an optical system 1001 according to Embodiment 1 of the present application.

[0082] As Figure 1AAs shown, the optical system 1001 includes a lens barrel P0 and various components disposed within the lens barrel. The optical system 1001 includes, in sequence from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.

[0083] The first lens E1 has a positive focal power. Its side near the human eye is convex, and its side near the screen is convex. The second lens E2 has a negative focal power. Its side near the human eye is flat, and its side near the screen is concave. The third lens E3 has a positive focal power. Its side near the human eye is convex, and its side near the screen is concave. The fourth lens E4 has a negative focal power. Its side near the human eye is concave, and its side near the screen is flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 near the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 near the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 near the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 near the screen. The partial reflection element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 near the screen.

[0084] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the side of the third lens E3 near the screen and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, and then passes through the diaphragm STO and finally exits toward the human eye side.

[0085] Table 1 shows the basic parameters of the optical system of Example 1, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0086] Table 1

[0087]

[0088]

[0089] In Example 1, the surfaces of the side of the third lens near the human eye and the side near the screen, and the surface of the side of the fourth lens near the human eye are all aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0090]

[0091] Wherein, x is the sagitta, which is the distance from the vertex of the aspheric surface to the position along the optical axis at a height of h; c is the paraxial curvature of the aspheric surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic coefficient; Ai is the correction coefficient of the i-th order of the aspheric surface. Table 2 below gives the higher-order term coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for each aspheric mirror surface in Example 1.

[0092] Table 2

[0093]

[0094] Table 3 shows some basic parameters of the optical system of Example 1, such as f, f1, f2, f3, f4, TD, FG1, and FG2. The units of each parameter in Table 3 are all millimeters (mm).

[0095] Table 3

[0096] f f1 f2 f3 f4 TD FG1 FG2 42.00 32.21 -55.39 72.39 -56.20 24.74 -55.39 -56.20

[0097] As Figure 1A shown, the optical system 1001 further includes 4 spacer elements, namely the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The first spacer element P1 is placed between the first lens and the second lens and abuts against the near-screen side surface of the first lens. The second spacer element P2 is placed between the second lens and the third lens and abuts against the near-screen side surface of the second lens; the third spacer element P3 is placed between the third lens and the fourth lens and abuts against the near-screen side surface of the third lens; the fourth spacer element P4 is placed on the second side of the fourth lens and abuts against the near-screen side surface of the fourth lens. Table 4 shows the basic parameter table of the spacer elements of the imaging system 1001. The units of each parameter in Table 4 are all millimeters (mm). The above spacer elements can block external redundant light from entering, enable the lens and the lens barrel to be better supported, and enhance the structural stability of the imaging system 1001.

[0098] Table 4

[0099] parameter d1s d1m D1s D1m d2s D2s D2m d3m Numeric 29.592 30.291 31.459 31.494 26.250 28.231 28.161 19.170 parameter D3s D3m d4s D4s D4m d0s d0m D0s Numeric 22.622 21.671 19.921 21.013 19.375 35.078 16.953 36.863 parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Numeric 29.579 2.384 0.986 6.756 1.436 5.848 0.931 1.394

[0100] Example 2

[0101] Figure 1B shows a schematic structural diagram of the optical system 1002 according to Embodiment 2 of the present application. In this embodiment and the following embodiments, for the sake of simplicity, some descriptions similar to those in Embodiment 1 will be omitted.

[0102] As Figure 1B shown in the figure, the optical system 1002 includes a lens barrel P0 and various components placed inside the lens barrel. The optical system 1002 sequentially includes, from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG. These components are exactly the same as those in Embodiment 1 and will not be elaborated here. The basic parameters of the optical system 1002 are shown in detail in Tables 1 to 3 and will not be elaborated here.

[0103] As Figure 1B shown in the figure, the optical system 1002 further includes 4 spacer elements, namely a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The first spacer element P1 is placed between the first lens and the second lens and abuts against the near-screen side surface of the first lens. The second spacer element P2 is placed between the second lens and the third lens and abuts against the near-screen side surface of the second lens. The third spacer element P3 is placed between the third lens and the fourth lens and abuts against the near-screen side surface of the third lens. The fourth spacer element P4 is placed on the second side of the fourth lens and abuts against the near-screen side surface of the fourth lens. Table 5 shows the basic parameter table of the spacer elements of the imaging system 1002. The unit of each parameter in Table 5 is millimeter (mm). The above spacer elements can block external redundant light from entering, enable the lens and the lens barrel to abut better, and enhance the structural stability of the imaging system 1002.

[0104] Table 5

[0105] parameter d1s d1m D1s D1m d2s D2s D2m d3m Numeric 29.592 30.291 31.459 31.494 26.250 28.231 28.161 19.170 parameter D3s D3m d4s D4s D4m d0s d0m D0s Numeric 22.622 21.671 19.921 21.013 19.375 34.987 16.953 36.161 parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Numeric 29.579 1.416 0.986 6.756 1.436 5.848 0.931 1.394

[0106] Example 3

[0107] Figure 1C shows a schematic structural diagram of an imaging system 1003 according to Embodiment 3 of the present application.

[0108] As Figure 1C shown in the figure, the optical system 1003 includes a lens barrel P0 and various components placed inside the lens barrel. The optical system 1003 sequentially includes, from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG. These components are exactly the same as those in Embodiment 1 and will not be elaborated here. The basic parameters of the optical system 1003 are shown in detail in Tables 1 to 3 and will not be elaborated here.

[0109] As Figure 1C As shown, the optical system 1003 further includes four spacer elements, namely the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The first spacer element P1 is disposed between the first lens and the second lens and abuts against the near-screen side of the first lens. The second spacer element P2 is disposed between the second lens and the third lens and abuts against the near-screen side of the second lens. The third spacer element P3 is disposed between the third lens and the fourth lens and abuts against the near-screen side of the third lens. The fourth spacer element P4 is disposed on the second side of the fourth lens and abuts against the near-screen side of the fourth lens. Table 6 shows the basic parameter table of the spacer elements of the imaging system 1003, and the unit of each parameter in Table 5 is millimeter (mm). The above spacer elements can block the entry of excess external light, enable the lens and the lens barrel to bear against each other better, and enhance the structural stability of the imaging system 1003.

[0110] Table 6

[0111] parameter d1s d1m D1s D1m d2s D2s D2m d3m Numeric 29.293 30.109 31.786 31.796 25.501 28.871 28.418 18.700 parameter D3s D3m d4s D4s D4m d0s d0m D0s Numeric 21.893 21.039 19.739 20.673 19.095 34.842 16.441 36.665 parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Numeric 29.579 1.305 0.986 6.756 1.436 5.848 0.931 1.394

[0112] Figure 2A shows the axial chromatic aberration curves of the imaging system 1001 of Embodiment 1, the imaging system 1002 of Embodiment 2, and the imaging system 1003 of Embodiment 3, which represent the deviation of the convergence points of light rays of different wavelengths after passing through the lens. Figure 2B shows the astigmatism curves of the imaging system 1001 of Embodiment 1, the imaging system 1002 of Embodiment 2, and the imaging system 1003 of Embodiment 3, which represent the curvature of the meridional image plane and the curvature of the sagittal image plane. Figure 2C shows the distortion curves of the imaging system 1001 of Embodiment 1, the imaging system 1002 of Embodiment 2, and the imaging system 1003 of Embodiment 3, which represent the distortion magnitude values corresponding to different field angles. Figure 2D shows the modulation transfer function (MTF) curves of the imaging system 1001 of Embodiment 1, the imaging system 1002 of Embodiment 2, and the imaging system 1003 of Embodiment 3. According to FIG. 2A to FIG. 2D it can be known that the imaging systems 1001 of Embodiment 1, 1002 of Embodiment 2, and 1003 of Embodiment 3 can all achieve good imaging quality.

[0113] Example 4

[0114] Figure 3A shows the structural schematic diagram of the optical system 2001 according to Embodiment 4 of the present application.

[0115] As Figure 3AAs shown, the optical system 2001 includes a lens barrel P0 and various components placed inside the lens barrel. The optical system 2001 sequentially includes, from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.

[0116] The first lens E1 has a positive optical power. Its side near the human eye is convex, and its side near the screen is concave. The second lens E2 has a negative optical power. Its side near the human eye is flat, and its side near the screen is concave. The third lens E3 has a positive optical power. Its side near the human eye is convex, and its side near the screen is convex. The fourth lens E4 has a negative optical power. Its side near the human eye is concave, and its side near the screen is flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 near the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 near the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 near the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 near the screen. The partial reflection element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 near the screen.

[0117] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the side of the third lens E3 near the screen and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, and then passes through the diaphragm STO and finally exits towards the human eye side.

[0118] Table 7 shows the basic parameters of the optical system of Example 4. Among them, the units of the radius of curvature and the thickness are both millimeters (mm). Table 8 shows the high-order term coefficients of the aspherical mirror surfaces that can be used in Example 4. Among them, each aspherical surface type can be defined by the formula (1) given in the above Example 1.

[0119] Table 7

[0120] Serial number Part Name Surface type Radius of curvature thickness Refractive Index Abbe number Refraction / Reflection Cone coefficient 0 Spherical endless -100000.0000 refraction 1 Aperture (STO) Spherical endless 20.0000 refraction 2 First lens (E1) Spherical 20.4339 5.2553 1.520 63.50 refraction 3 Spherical 82.3466 1.3496 refraction 4 Reflective polarizer (RP) Spherical endless 0.1100 1.502 57.00 refraction 5 First Quarter Wave Plate (QWP1) Spherical endless 0.1100 1.502 57.00 refraction 6 Second lens (E2) Spherical endless 3.3361 1.855 23.83 refraction 7 Spherical 123.4815 4.7788 refraction 8 Third lens (E3) Aspheric 85.6895 7.8248 1.500 57.28 refraction 0.0000 9 Partially reflective element (BS) Aspheric -296.7258 -7.8248 1.500 57.28 reflection 0.0000 10 Aspheric 85.6895 -4.7788 refraction 0.0000 11 Spherical 123.4815 -3.3361 1.855 23.83 refraction 12 Spherical endless -0.1100 1.502 57.00 refraction 13 Reflective polarizer (RP) Spherical endless 0.1100 1.502 57.00 reflection 14 Second lens (E2) Spherical endless 3.3361 1.855 23.83 refraction 15 Spherical 123.4815 4.7788 refraction 16 Third lens (E3) Aspheric 85.6895 7.8248 1.500 57.28 refraction 0.0000 17 Aspheric -296.7258 0.6754 refraction 0.0000 18 Fourth lens (E4) Aspheric -50.2343 1.3000 1.755 35.02 refraction 0.0000 19 Second Quarter Wave Plate (QWP2) Spherical endless 0.1000 1.502 57.00 refraction 20 Polarizer(LP) Spherical endless 0.1500 1.502 57.00 refraction 21 Spherical endless 1.2000 refraction 22 Protective glass (GL) Spherical endless 0.7100 1.519 64.17 refraction 23 Spherical endless 0.1000 refraction 24 Image surface (IMG) Spherical endless 0.0000 refraction

[0121] Table 8

[0122]

[0123] Table 9 shows some basic parameters of the optical system of Example 4, such as f, f1, f2, f3, f4, TD, FG1, and FG2. The unit of each parameter in Table 9 is millimeter (mm).

[0124] Table 9

[0125] f f1 f2 f3 f4 TD FG1 FG2 42.00 50.84 -144.42 133.84 -66.57 24.74 -144.42 -66.57

[0126] As Figure 3A shown, the optical system 2001 further includes four spacer elements, namely the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The first spacer element P1 is placed between the first lens and the second lens and abuts against the near-screen side of the first lens. The second spacer element P2 is placed between the second lens and the third lens and abuts against the near-screen side of the second lens. The third spacer element P3 is placed between the third lens and the fourth lens and abuts against the near-screen side of the third lens. The fourth spacer element P4 is placed on the second side of the fourth lens and abuts against the near-screen side of the fourth lens. Table 10 shows the basic parameter table of the spacer elements of the imaging system 2001. The unit of each parameter in Table 10 is millimeter (mm). The above spacer elements can block the entry of excess external light, enable the lens and the lens barrel to better abut, and enhance the structural stability of the imaging system 2001.

[0127] Table 10

[0128] parameter d1s d1m D1s D1m d2s D2s D2m d3m Numeric 29.356 29.639 32.195 31.424 26.905 28.793 27.537 20.776 parameter D3s D3m d4s D4s D4m d0s d0m D0s Numeric 24.446 22.256 18.143 19.821 19.493 34.811 16.686 36.596 parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Numeric 29.312 2.630 0.453 4.016 4.808 6.937 0.805 1.349

[0129] Example 5

[0130] Figure 3B shows a schematic structural diagram of the optical system 2002 according to Embodiment 5 of the present application. In this embodiment and the following embodiments, for the sake of simplicity, some descriptions similar to those in Embodiment 4 will be omitted.

[0131] As Figure 3B shown, the optical system 2002 includes a lens barrel P0 and various elements placed inside the lens barrel. The optical system 2002 includes, in sequence from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG. These elements are exactly the same as those in Embodiment 4 and will not be described in detail. The basic parameters of the optical system 2002 are shown in Tables 7 to 9 and will not be described in detail.

[0132] As Figure 3BAs shown, the optical system 2002 further includes four spacer elements, namely the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The first spacer element P1 is disposed between the first lens and the second lens and abuts against the screen-side surface of the first lens. The second spacer element P2 is disposed between the second lens and the third lens and abuts against the screen-side surface of the second lens. The third spacer element P3 is disposed between the third lens and the fourth lens and abuts against the screen-side surface of the third lens. The fourth spacer element P4 is disposed on the second side of the fourth lens and abuts against the screen-side surface of the fourth lens. Table 11 shows the basic parameter table of the spacer elements of the imaging system 2002. The unit of each parameter in Table 11 is millimeter (mm). The above spacer elements can block the entry of excess external light, enable the lens and the lens barrel to better abut, and enhance the structural stability of the imaging system 2002.

[0133] Table 11

[0134]

[0135]

[0136] Example 6

[0137] Figure 3C Shows a schematic structural diagram of the imaging system 2003 according to Embodiment 6 of the present application.

[0138] As Figure 3C shown, the optical system 2003 includes a lens barrel P0 and various elements disposed inside the lens barrel. The optical system 2003 includes, in sequence from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG. These elements are exactly the same as those in Embodiment 4 and will not be described in detail. The basic parameters of the optical system 2003 are shown in detail in Tables 7 to 9 and will not be described in detail.

[0139] As Figure 3CAs shown, the optical system 2003 further includes four spacer elements, namely the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The first spacer element P1 is disposed between the first lens and the second lens and abuts against the near-screen side of the first lens. The second spacer element P2 is disposed between the second lens and the third lens and abuts against the near-screen side of the second lens. The third spacer element P3 is disposed between the third lens and the fourth lens and abuts against the near-screen side of the third lens. The fourth spacer element P4 is disposed on the second side of the fourth lens and abuts against the near-screen side of the fourth lens. Table 12 shows the basic parameter table of the spacer elements of the imaging system 2003. The unit of each parameter in Table 12 is millimeter (mm). The above spacer elements can block the entry of excess external light, enable the lens and the lens barrel to abut better, and enhance the structural stability of the imaging system 2003.

[0140] Table 12

[0141] parameter d1s d1m D1s D1m d2s D2s D2m d3m Numeric 29.743 29.738 31.698 31.039 26.398 28.257 27.014 20.215 parameter D3s D3m d4s D4s D4m d0s d0m D0s Numeric 23.877 22.590 18.376 19.324 18.321 35.066 15.835 37.039 parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Numeric 29.312 2.961 0.453 4.016 4.808 6.937 0.805 1.349

[0142] Figure 4A shows the axial chromatic aberration curves of the imaging system 2001 of Embodiment 4, the imaging system 2002 of Embodiment 5, and the imaging system 2003 of Embodiment 6, which represent the deviation of the convergence points of light rays of different wavelengths after passing through the lens. Figure 4B shows the astigmatism curves of the imaging system 2001 of Embodiment 4, the imaging system 2002 of Embodiment 5, and the imaging system 2003 of Embodiment 6, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 4C shows the distortion curves of the imaging system 2001 of Embodiment 4, the imaging system 2002 of Embodiment 5, and the imaging system 2003 of Embodiment 6, which represent the distortion magnitude values corresponding to different field angles of view. Figure 4D shows the modulation transfer function (MTF) curves of the imaging system 2001 of Embodiment 4, the imaging system 2002 of Embodiment 5, and the imaging system 2003 of Embodiment 6. According to FIG. 4A to FIG. 4D it can be known that the imaging system 2001 of Embodiment 4, the imaging system 2002 of Embodiment 5, and the imaging system 2003 of Embodiment 6 can all achieve good imaging quality.

[0143] Example 7

[0144] Figure 5A shows the structural schematic diagram of the optical system 3001 according to Embodiment 7 of the present application.

[0145] As Figure 5AAs shown, the optical system 3001 includes a lens barrel P0 and various components disposed within the lens barrel. The optical system 3001 includes, in sequence from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG.

[0146] The first lens E1 has a positive optical power. Its side near the human eye is convex, and its side near the screen is convex. The second lens E2 has a negative optical power. Its side near the human eye is flat, and its side near the screen is concave. The third lens E3 has a positive optical power. Its side near the human eye is convex, and its side near the screen is concave. The fourth lens E4 has a negative optical power. Its side near the human eye is concave, and its side near the screen is flat. Among them, the reflective polarizing element RP is attached to the side of the first quarter-wave plate QWP1 near the human eye, and the first quarter-wave plate QWP1 is attached to the side of the second lens E2 near the human eye; the second quarter-wave plate QWP2 is attached to the side of the fourth lens E4 near the screen, and the polarizer LP is attached to the side of the second quarter-wave plate QWP2 near the screen. The partial reflection element BS may have a semi-transmissive and semi-reflective function and is attached to the side of the third lens E3 near the screen.

[0147] In this example, the light emitted from the image plane IMG sequentially passes through the protective glass GL, the polarizer LP, the second quarter-wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, and the first quarter-wave plate QWP1 to reach the reflective polarizing element RP. At the reflective polarizing element RP, it is reflected and passes through the first quarter-wave plate QWP1, the second lens E2, and the third lens E3 again. The light beam is reflected again at the partial reflection element BS on the side of the third lens E3 near the screen and sequentially passes through the third lens E3, the second lens E2, the first quarter-wave plate QWP1, the reflective polarizing element RP, and the first lens E1, and then passes through the diaphragm STO and finally exits toward the human eye side.

[0148] Table 13 shows the basic parameters of the optical system of Example 7, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0149] Table 14 shows the higher-order term coefficients of the aspherical mirror surfaces that can be used in Example 7, where each aspherical surface type can be defined by the formula (1) given in the above Example 1.

[0150] Table 13

[0151] Serial number Part Name Surface type Radius of curvature thickness Refractive Index Abbe number Refraction / Reflection Cone coefficient 0 Spherical endless -100000.0000 refraction 1 Aperture (STO) Spherical endless 20.0000 Refraction 2 First lens (E1) Aspherical surface 18.0080 7.7182 1.591 61.16 Refraction -0.0100 3 Aspherical surface -1100.0889 0.3608 Refraction -99.0000 4 Reflective polarizing element (RP) Spherical surface Infinity 0.1100 1.502 57.00 Refraction 5 First quarter-wave plate (QWP1) Spherical surface Infinity 0.1100 1.502 57.00 Refraction 6 Second lens (E2) Spherical surface Infinity 5.4796 1.855 23.80 Refraction 7 Aspherical surface 72.1236 0.2680 Refraction 2.1699 8 Third lens (E3) Aspherical surface 36.7287 7.2025 1.546 56.14 Refraction 0.0000 9 Partial reflection element (BS) Aspherical surface 193.2815 -7.2025 1.546 56.14 Reflection 0.0000 10 Aspherical surface 36.7287 -0.2680 Refraction 0.0000 11 Aspherical surface 72.1236 -5.4796 1.855 23.80 Refraction 2.1699 12 Spherical surface Infinity -0.1100 1.502 57.00 Refraction 13 Reflective polarizing element (RP) Spherical surface Infinity 0.1100 1.502 57.00 Reflection 14 Second lens (E2) Spherical surface Infinity 5.4796 1.855 23.80 Refraction 15 Aspherical surface 72.1236 0.2680 Refraction 2.1699 16 Third lens (E3) Aspherical surface 36.7287 7.2025 1.546 56.14 Refraction 0.0000 17 Aspherical surface 193.2815 1.6638 Refraction 0.0000 18 Fourth lens (E4) Aspherical surface -11.7501 1.7052 1.747 27.74 Refraction 0.0000 19 Second quarter-wave plate (QWP2) Spherical surface Infinity 0.1000 1.502 57.00 Refraction 20 Polarizer (LP) Spherical surface Infinity 0.1500 1.502 57.00 Refraction 21 Spherical surface Infinity 1.0000 Refraction 22 Protective glass (GL) Spherical surface Infinity 0.7100 1.519 64.17 Refraction 23 Spherical surface Infinity 0.1000 Refraction 24 Image plane (IMG) Spherical surface Infinity 0.0000 Refraction

[0152] Table 14

[0153]

[0154]

[0155] Table 15 shows some basic parameters of the optical system of Example 7, such as f, f1, f2, f3, f4, TD, FG1, and FG2. The unit of each parameter in Table 15 is millimeter (mm).

[0156] Table 15

[0157] f f1 f2 f3 f4 TD FG1 FG2 41.50 30.03 -84.35 81.66 -15.73 24.62 -84.35 -15.73

[0158] As Figure 5A shown, the optical system 3001 further includes four spacer elements, namely the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The first spacer element P1 is placed between the first lens and the second lens and abuts against the near-screen side of the first lens. The second spacer element P2 is placed between the second lens and the third lens and abuts against the near-screen side of the second lens. The third spacer element P3 is placed between the third lens and the fourth lens and abuts against the near-screen side of the third lens. The fourth spacer element P4 is placed on the second side of the fourth lens and abuts against the near-screen side of the fourth lens. Table 16 shows the basic parameter table of the spacer elements of the imaging system 3001. The unit of each parameter in Table 16 is millimeter (mm). The above spacer elements can block the entry of excess external light, enable the lens and the lens barrel to abut better, and enhance the structural stability of the imaging system 3001.

[0159] Table 16

[0160] Parameter d1s d1m D1s D1m d2s D2s D2m d3m Value 29.756 29.314 31.640 31.099 26.255 29.026 28.197 20.269 Parameter D3s D3m d4s D4s D4m d0s d0m D0s Value 23.603 22.427 17.545 19.857 19.211 35.168 16.405 36.953 Parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Value 29.031 2.682 0.595 6.438 0.808 6.009 0.848 2.217

[0161] Example 8

[0162] Figure 5B shows a schematic structural diagram of the optical system 3002 according to Embodiment 8 of the present application. In this embodiment and the following embodiments, for the sake of simplicity, some descriptions similar to those in Embodiment 7 will be omitted.

[0163] As Figure 5B shown, the optical system 3002 includes a lens barrel P0 and the elements placed inside the lens barrel. The optical system 3002 includes, in sequence from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG. These elements are exactly the same as those in Embodiment 7 and will not be described in detail. The basic parameters of the optical system 3002 can be found in Tables 13 to 15 and will not be described in detail.

[0164] As Figure 5B shown, the optical system 3002 further includes four spacer elements, namely a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The first spacer element P1 is disposed between the first lens and the second lens and abuts against the near-screen side of the first lens. The second spacer element P2 is disposed between the second lens and the third lens and abuts against the near-screen side of the second lens. The third spacer element P3 is disposed between the third lens and the fourth lens and abuts against the near-screen side of the third lens. The fourth spacer element P4 is disposed on the second side of the fourth lens and abuts against the near-screen side of the fourth lens. Table 17 shows the basic parameter table of the spacer elements of the imaging system 3002. The unit of each parameter in Table 17 is millimeter (mm). The above spacer elements can block the entry of excess external light, enable the lens and the lens barrel to abut better, and enhance the structural stability of the imaging system 3002.

[0165] Table 17

[0166] Parameter d1s d1m D1s D1m d2s D2s D2m d3m Value 29.756 29.314 31.640 31.099 26.255 29.026 28.913 20.269 Parameter D3s D3m d4s D4s D4m d0s d0m D0s Value 23.603 22.427 17.545 19.857 19.211 34.607 17.308 36.542 Parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Value 29.031 2.564 0.595 6.438 0.808 6.009 0.848 2.217

[0167] Example 9

[0168] Figure 5C shows a schematic structural diagram of an imaging system 3003 according to Embodiment 9 of the present application.

[0169] As Figure 5C shown, the optical system 3003 includes a lens barrel P0 and various elements disposed within the lens barrel. The optical system 3003 includes, in sequence from the human eye side to the screen side: a diaphragm STO (not shown), a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter-wave plate QWP2, a polarizer LP, a protective glass GL, and an image plane IMG. These elements are exactly the same as those in Embodiment 7 and will not be described in detail. The basic parameters of the optical system 3003 are shown in detail in Tables 13 to 15 and will not be described in detail.

[0170] As Figure 5CAs shown, the optical system 3003 further includes four spacer elements, namely the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The first spacer element P1 is placed between the first lens and the second lens and abuts against the near-screen side of the first lens. The second spacer element P2 is placed between the second lens and the third lens and abuts against the near-screen side of the second lens. The third spacer element P3 is placed between the third lens and the fourth lens and abuts against the near-screen side of the third lens. The fourth spacer element P4 is placed on the second side of the fourth lens and abuts against the near-screen side of the fourth lens. Table 18 shows the basic parameter table of the spacer elements of the imaging system 3003. The unit of each parameter in Table 18 is millimeter (mm). The above spacer elements can block the entry of excess external light, enable the lens and the lens barrel to better abut, and enhance the structural stability of the imaging system 3003.

[0171] Table 18

[0172] Parameter d1s d1m D1s D1m d2s D2s D2m d3m Value 29.350 29.502 31.360 30.690 25.498 28.316 28.315 20.899 Parameter D3s D3m d4s D4s D4m d0s d0m D0s Value 22.834 21.787 17.327 19.238 18.821 35.453 15.548 37.562 Parameter D0m EP01 CP1 EP12 CP2 EP23 CP3 EP34 Value 29.031 2.827 0.595 6.438 0.808 6.009 0.847 2.217

[0173] Figure 6A Shows the axial chromatic aberration curves of the imaging system 3001 of Embodiment 7, the imaging system 3002 of Embodiment 8, and the imaging system 3003 of Embodiment 9, which represent the deviation of the converging points of light rays of different wavelengths after passing through the lens. Figure 6B Shows the astigmatism curves of the imaging system 3001 of Embodiment 7, the imaging system 3002 of Embodiment 8, and the imaging system 3003 of Embodiment 9, which represent the curvature of the meridional image plane and the curvature of the sagittal image plane. Figure 6C Shows the distortion curves of the imaging system 3001 of Embodiment 7, the imaging system 3002 of Embodiment 8, and the imaging system 3003 of Embodiment 9, which represent the distortion magnitude values corresponding to different field angles. Figure 6D Shows the modulation transfer function (MTF) curves of the imaging system 3001 of Embodiment 7, the imaging system 3002 of Embodiment 8, and the imaging system 3003 of Embodiment 9. According to Figures 6A to 6D it can be known that the imaging systems 3001 of Embodiment 7, 3002 of Embodiment 8, and 3003 of Embodiment 9 can all achieve good imaging quality.

[0174] In summary, the optical systems of Embodiments 1 to 9 have the relationships shown in Table 19.

[0175] Table 19

[0176] Conditional / Example 1 2 3 4 5 6 7 8 9 CP1 / CP2 0.69 0.69 0.69 0.09 0.09 0.09 0.74 0.74 0.74 FG1 / (d1m + d2s) -0.98 -0.98 -1.00 -2.55 -2.55 -2.57 -1.52 -1.52 -1.53 CT2 / EP12 0.74 0.74 0.74 0.83 0.83 0.83 0.85 0.85 0.85 f1 / d1s 1.09 1.09 1.10 1.73 1.73 1.71 1.01 1.01 1.02 f / (d0s - d0m) 2.32 2.33 2.28 2.32 2.32 2.18 2.21 2.40 2.08 D1s / D4s 1.50 1.50 1.54 1.62 1.62 1.64 1.59 1.59 1.63 (CT4 + CTQ2 + CTL) / EP34 1.11 1.11 1.11 1.15 1.15 1.15 0.88 0.88 0.88 D2m / f3 0.39 0.39 0.39 0.21 0.21 0.20 0.35 0.35 0.35 TD / (EP23 + CP3) 3.65 3.65 3.65 3.20 3.20 3.20 3.59 3.59 3.59 R7 / d3m -1.43 -1.43 -1.47 -2.42 -2.42 -2.49 -0.58 -0.58 -0.56 D0s / D3s 1.63 1.60 1.67 1.50 1.50 1.55 1.57 1.55 1.65 D1m / CT1 4.01 4.01 4.05 5.98 5.98 5.91 4.03 4.03 3.98 d4s / FG2 -0.35 -0.35 -0.35 -0.27 -0.27 -0.28 -1.12 -1.12 -1.10 D2s / f2 -0.51 -0.51 -0.52 -0.20 -0.20 -0.20 -0.34 -0.34 -0.34 D3m / f4 -0.39 -0.39 -0.37 -0.33 -0.33 -0.34 -1.43 -1.43 -1.39 EP01 / T12 4.58 2.72 2.51 1.68 1.68 1.89 4.62 4.41 4.87 D0m / D4m 1.53 1.53 1.55 1.50 1.50 1.60 1.51 1.51 1.54

[0177] The present 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 VR device. The optical device is equipped with the optical system described above.

[0178] 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 protection involved in the present application is not limited to the technical solution 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 concept of the present application. For example, the technical solution 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 It sequentially includes, from the first side to the second side along the optical axis: a first lens with positive optical power, a reflective polarizing element, a first quarter-wave plate, a second lens with negative optical power, a third lens with positive optical power, a partial reflection element, a fourth lens with negative optical power, a second quarter-wave plate, and a polarizer, where the first quarter-wave plate is placed on the first side surface of the second lens and at least partially adheres to the first side surface of the second lens; the reflective polarizing element is placed on the first side surface of the first quarter-wave plate and at least partially adheres to the first side surface of the first quarter-wave plate; the second quarter-wave plate is placed on the second side surface of the fourth lens and at least partially adheres to the second side surface of the fourth lens; the polarizer is placed on the second side surface of the second quarter-wave plate and at least partially adheres to the second side surface of the second quarter-wave plate; the optical system further includes a first spacer element and a second spacer element, where the first spacer element is placed between the first lens and the second lens and abuts against the second side surface of the first lens, and the second spacer element is placed between the second lens and the third lens and abuts against the second side surface of the second lens; the optical system satisfies 0.05 < CP1 / CP2 < 0.75 and -2.6 < FG1 / (d1m + d2s) ≤ -0.98, where CP1 is the maximum thickness of the first spacer element along the optical axis direction, CP2 is the maximum thickness of the second spacer element along the optical axis direction, FG1 is the combined focal length of the reflective polarizing element, the first quarter-wave plate, and the second lens, d1m is the inner diameter of the second side surface of the first spacer element, and d2s is the inner diameter of the first side surface of the second spacer element; the number of lenses with optical power in the optical system is four.

2. The optical system according to claim 1, characterized in that the optical system satisfies: 0.7 < CT2 / EP12 < 0.9, where CT2 is the central thickness of the second lens on the optical axis, and EP12 is the distance along the optical axis from the second side surface of the first spacer element to the first side surface of the second spacer element.

3. The optical system according to claim 1, characterized in that the optical system satisfies: 1.0 < f1 / d1s < 1.75, where f1 is the effective focal length of the first lens, and d1s is the inner diameter of the first side surface of the first spacer element.

4. The optical system according to claim 1, characterized in that the optical system further includes a lens barrel and satisfies: 2.08 ≤ f / (d0s - d0m) ≤ 2.4, where f is the effective focal length of the optical system, d0s is the inner diameter of the first side end face of the lens barrel, and d0m is the inner diameter of the second side end face of the lens barrel.

5. The optical system according to claim 1, characterized in that the optical system further includes a fourth spacer element placed on the second side of the fourth lens and abutting against the second side surface of the fourth lens; the optical system satisfies: 1.5 ≤ D1s / D4s ≤ 1.64, where D1s is the outer diameter of the first side surface of the first spacer element, and D4s is the outer diameter of the first side surface of the fourth spacer element.

6. The optical system according to claim 1, characterized in that The optical system satisfies: 0.2 ≤ D2m / f3 < 0.4, where D2m is the outer diameter of the second side surface of the second spacer element, and f3 is the effective focal length of the third lens.

7. The optical system according to claim 1, characterized in that The optical system satisfies: 3.98 ≤ D1m / CT1 < 6.0, where D1m is the outer diameter of the second side surface of the first spacer element, and CT1 is the central thickness of the first lens on the optical axis.

8. The optical system according to claim 1, characterized in that The optical system satisfies: -0.55 < D2s / f2 < -0.15, where D2s is the outer diameter of the first side surface of the second spacer element, and f2 is the effective focal length of the second lens.

9. The optical system according to any one of claims 1 to 8, characterized in that: The optical system further includes a third spacer element and a fourth spacer element. The third spacer element is disposed between the third lens and the fourth lens and abuts against the second side surface of the third lens. The fourth spacer element is disposed on the second side of the fourth lens and abuts against the second side surface of the fourth lens. The optical system satisfies: 0.88 ≤ (CT4 + CTQ2 + CTL) / EP34 < 1.2, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, CTL is the central thickness of the polarizer on the optical axis, and EP34 is the distance along the optical axis from the second side surface of the third spacer element to the first side surface of the fourth spacer element.

10. The optical system according to any one of claims 1 to 8, characterized in that: The optical system further includes a third spacer element disposed between the third lens and the fourth lens and abutting against the second side surface of the third lens. The optical system satisfies: 3.2 ≤ TD / (EP23 + CP3) < 3.7, 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, EP23 is the distance along the optical axis from the second side surface of the second spacer element to the first side surface of the third spacer element, and CP3 is the maximum thickness of the third spacer element along the optical axis.

11. The optical system according to any one of claims 1 to 8, characterized in that: The optical system further includes a third spacer element disposed between the third lens and the fourth lens and abutting against the second side surface of the third lens. The optical system satisfies: -2.5 < R7 / d3m ≤ -0.56, where R7 is the radius of curvature of the first side surface of the fourth lens, and d3m is the inner diameter of the second side surface of the third spacer element.

12. The optical system according to any one of claims 1 to 8, characterized in that: The optical system further includes a third spacer element disposed between the third lens and the fourth lens and abutting against the second side surface of the third lens. The optical system further includes a lens barrel and satisfies: 1.5 ≤ D0s / D3s < 1.7, where D0s is the outer diameter of the first side end face of the lens barrel, and D3s is the outer diameter of the first side surface of the third spacer element.

13. The optical system according to any one of claims 1 to 8, characterized in that: The optical system further includes a fourth spacer element disposed on the second side of the fourth lens and abutting against the second side surface of the fourth lens. The optical system satisfies: -1.12≤d4s / FG2≤-0.27, wherein d4s is the inner diameter of the first side surface of the fourth spacing element, and FG2 is the combined focal length of the fourth lens, the second quarter wave plate, and the polarizer.

14. The optical system according to any one of claims 1 to 8, characterized in that: The optical system further comprises a third spacing element disposed between the third lens and the fourth lens and abutting against a second side surface of the third lens; The optical system satisfies: -1.43≤D3m / f4<-0.3, wherein D3m is the outer diameter of the second side surface of the third spacing element, and f4 is the effective focal length of the fourth lens.

15. The optical system according to any one of claims 1 to 8, characterized in that: The optical system also includes a lens barrel and satisfies: 1.68≤EP01 / T12<4.9, wherein EP01 is the distance from the first side end surface of the lens barrel to the first side surface of the first spacing element along the optical axis direction, and T12 is the on-axis distance from the second side surface of the first lens to the first side surface of the second lens.

16. The optical system according to any one of claims 1 to 8, characterized in that: The optical system further comprises a lens barrel and a fourth spacing element disposed on a second side of the fourth lens and abutting against a second side surface of the fourth lens; The optical system satisfies: 1.5≤D0m / D4m≤1.6, wherein D0m is the outer diameter of the second side end surface of the lens barrel, and D4m is the outer diameter of the second side surface of the fourth spacing element.

17. The optical system according to any one of claims 1 to 8, characterized in that: The first side surface of the first lens is a convex surface; The first side surface of the second lens is a plane surface, and the second side surface is a concave surface; The first side surface of the third lens is a convex surface; The first side surface of the fourth lens is a concave surface, and the second side surface is a flat surface.

18. An optical device, characterized in that: Comprising an optical system as claimed in any one of claims 1 to 17.

Images