Visual system

Abstract

The utility model discloses a visual system which comprises a lens cone, a lens group and a spacing element group, wherein the lens group and the spacing element group are assembled in the lens cone; the lens group comprises a first lens with positive focal power, a reflective polarization element, a first quarter-wave plate, a second lens with positive focal power, a third lens with negative focal power, a partial reflection element and a second quarter-wave plate which are sequentially arranged from the first side to the second side along the optical axis. The fourth lens has negative focal power; the spacing element group comprises a first spacing element, a second spacing element, a third spacing element and a fourth spacing element; wherein the number of the lenses with focal power in the lens group is four; the effective focal length f1 of the first lens and the effective focal length f of the visual system satisfy 1.5 lt; f1 / flt; 1.9); the combined focal length FG1 of the first lens, the reflective polarizing element and the first quarter-wave plate and the inner diameter d1s of the first side surface of the first spacing element meet the following conditions: 2.35 lt; fG1 / d1slt, FG1 / d1slt; and 2.75%.

Description

Technical Field

[0001] This application relates to the field of optical devices, and more particularly, to a visual system. Background Art

[0002] With the continuous development of VR (Virtual Reality) technology, more and more optical lenses are applied to various devices of virtual reality technology. As the entrance of human-computer interaction, VR imaging lenses play an important role. On the one hand, the imaging quality of VR imaging lenses needs to meet the resolution requirements of the human eye; on the other hand, the early aspherical or Fresnel lenses had a relatively long body, and the center of gravity was forward when worn on the head, resulting in a poor experience, which urgently needed to be improved. Based on the above requirements, a catadioptric scheme was proposed. By folding the optical path, the body length of the lens was compressed to half of the original, so that the center of gravity of the head-mounted device was moved backward, increasing the consumer experience.

[0003] Combined with the above development status of virtual reality devices, immersive experience and seamless interaction between virtual and real have become one of the key development directions of virtual reality devices. And how to enhance the immersion and further improve the user experience has always been the goal pursued in this field.

[0004] In summary, how to design and optimize optical lenses such as the visual system included in virtual reality devices to ensure good imaging quality while meeting the stability requirements of system assembly and optical performance, so as to further improve the user experience, has become one of the technical problems that those skilled in the art are committed to solving. Utility Model Content

[0005] This application provides a visual system that can at least solve or partially solve at least one problem or other problems existing in the prior art.

[0006] A first aspect of the present application provides a visual system, which may include a lens barrel, and a lens group and a spacer element group assembled in the lens barrel. The lens group includes, in order 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 positive optical power, a third lens with a negative optical power, a partially reflective element, a second quarter-wave plate, a polarizer, and a fourth lens with a negative optical power; the spacer element group includes: a first spacer element located between the first lens and the second lens and abutting against the second side surface of the first lens, a second spacer element located between the second lens and the third lens and abutting against the second side surface of the second lens, a third spacer element located between the third lens and the fourth lens and abutting against the second side surface of the third lens, and a fourth spacer element located between the fourth lens and the lens barrel and abutting against the second side surface of the fourth lens; wherein, the number of lenses with optical power in the lens group is four; the effective focal length f1 of the first lens and the effective focal length f of the visual system satisfy: 1.5 < f1 / f < 1.9; the combined focal length FG1 of the first lens, the reflective polarizing element and the first quarter-wave plate and the inner diameter d1s of the first side surface of the first spacer element satisfy: 2.35 < FG1 / d1s < 2.75.

[0007] According to an exemplary embodiment of the present application, the maximum thickness CP1 of the first spacer element, the maximum thickness CP2 of the second spacer element, and the central thickness CT2 of the second lens on the optical axis satisfy: 1.0 < (CP1 + CP2) / CT2 < 2.8.

[0008] According to an exemplary embodiment of the present application, the curvature radius R3 of the first side surface of the second lens and the inner diameter d1m of the second side surface of the first spacer element satisfy: 1.5 < R3 / d1m < 1.7.

[0009] According to an exemplary embodiment of the present application, the inner diameter d0s of the first side end surface of the lens barrel and the curvature radius R1 of the first side surface of the first lens satisfy: 0.8 < d0s / R1 < 1.0.

[0010] According to an exemplary embodiment of the present application, the effective focal length f2 of the second lens and the outer diameter D2s of the first side surface of the second spacer element satisfy: 2.1 < f2 / D2s < 2.6.

[0011] According to an exemplary embodiment of the present application, the distance TD on the optical axis from the first side surface of the first lens to the second side surface of the fourth lens and the interval EP23 along the optical axis from the second side surface of the second spacer element to the first side surface of the third spacer element satisfy: 2.3 ≤ TD / EP23 < 3.2.

[0012] According to an exemplary embodiment of the present application, the combined focal length FG2 of the third lens, the second quarter-wave plate, and the polarizer, the inner diameter d3s of the first side surface of the third spacer element, and the inner diameter d3m of the second side surface of the third spacer element satisfy: -2.1 < FG2 / (d3s + d3m) < -1.6.

[0013] According to an exemplary embodiment of the present application, the inner diameter d2s of the first side surface of the second spacer element, the central thickness CT2 of the second lens on the optical axis, and the axial distance T23 from the second side surface of the second lens to the first side surface of the third lens satisfy: 3.0 < d2s / (CT2 + T23) < 3.4.

[0014] According to an exemplary embodiment of the present application, the axial spacing EP34 from the second side surface of the third spacer element to the first side surface of the fourth spacer element and the central thickness CT4 of the fourth lens on the optical axis satisfy: 1.2 < EP34 / CT4 < 1.4.

[0015] According to an exemplary embodiment of the present application, the maximum thickness CP3 of the third spacer element and the maximum thickness CP4 of the fourth spacer element satisfy: 1.6 < CP4 / CP3 < 2.8.

[0016] According to an exemplary embodiment of the present application, the outer diameter D0s of the first side end surface of the lens barrel and the inner diameter d0m of the second side end surface of the lens barrel satisfy: 1.8 < D0s / d0m < 2.4.

[0017] According to an exemplary embodiment of the present application, the effective focal length f4 of the fourth lens, the inner diameter d4s of the first side surface of the fourth spacer element, and the inner diameter d4m of the second side surface of the fourth spacer element satisfy: -1.4 < f4 / (d4s + d4m) ≤ -0.8.

[0018] According to an exemplary embodiment of the present application, the outer diameter D3s of the first side surface of the third spacer element and the D4s of the first side surface of the fourth spacer element satisfy: 1.1 < D3s / D4s < 1.2.

[0019] According to an exemplary embodiment of the present application, the radius of curvature R5 of the first side surface of the third lens, the inner diameter d2m of the second side surface of the second spacer element, and the outer diameter D2m of the second side surface of the second spacer element satisfy: -1.4 < R5 / (d2m + D2m) < -1.0.

[0020] According to an exemplary embodiment of the present application, the outer diameter D1s of the first side surface of the first spacer element and the entrance pupil diameter EPD of the visual system satisfy: 1.2 < D1s / EPD < 1.4.

[0021] According to an exemplary embodiment of the present application, the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis, and the spacing EP01 along the optical axis from the first side end face of the lens barrel to the first side face of the first spacer element satisfy: 0.9 < (CT1 + CTR + CTQ1) / EP01 < 1.1.

[0022] A second aspect of the present application provides a visual system, which may include a lens barrel and a lens group and a spacer element group assembled in the lens barrel. The lens group includes, in order 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 positive optical power, a third lens with a negative optical power, a partially reflective element, a second quarter-wave plate, a polarizer, and a fourth lens with a negative optical power; the spacer element group includes: a first spacer element located between the first lens and the second lens and abutting against the second side face of the first lens, a second spacer element located between the second lens and the third lens and abutting against the second side face of the second lens, a third spacer element located between the third lens and the fourth lens and abutting against the second side face of the third lens, and a fourth spacer element located between the fourth lens and the lens barrel and abutting against the second side face of the fourth lens; wherein, the number of lenses with optical power in the lens group is four; the effective focal length f1 of the first lens and the effective focal length f of the visual system satisfy: 1.5 < f1 / f < 1.9; the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis, and the spacing EP01 along the optical axis from the first side end face of the lens barrel to the first side face of the first spacer element satisfy: 0.9 < (CT1 + CTR + CTQ1) / EP01 < 1.1.

[0023] The visual system according to the exemplary embodiment of the present application can satisfy the conditional expressions 1.5 < f1 / f < 1.9 and 2.35 < FG1 / d1s < 2.75. On the premise that the ratio of f1 / f is within a reasonable range, by controlling FG1 / d1s within a reasonable range, the refraction angle of light when passing through the corresponding lens can be reasonably controlled; and by controlling the inner diameter size of the first side face of the first spacer element, the light path reflected by the small inclined plane of the effective diameter edge mechanism part near the second side face of the fourth lens reaching the inside of the lens can be blocked, thereby improving the imaging quality and clarity and enhancing the visual experience.

[0024] The visual system according to an exemplary embodiment of the present application can satisfy the conditions of 1.5 < f1 / f < 1.9 and 0.9 < (CT1 + CTR + CTQ1) / EP01 < 1.1. On the premise that the ratio of f1 / f is within a reasonable range, by reasonably distributing the thicknesses of the components inside the lens barrel, it is beneficial to the assembly of the lens; at the same time, by reasonably setting the distance on the optical axis from the first end face of the lens barrel to the first side face of the first spacer element, the edge thickness of the lens is indirectly ensured, which is beneficial to the molding of the parts; in addition, the dispensing space of the first lens is ensured, indirectly ensuring the reliability of the visual system and improving the assembly stability and imaging quality of the visual system.

[0025] The visual system according to the above embodiment of the present application adopts a catadioptric scheme including four lenses, and by adopting a polarized catadioptric optical path method, it can better compress the body height and improve the imaging quality; at the same time, by adopting at least one spacer element and reasonably distributing the parameters of each lens and each spacer element, it is possible to achieve at least one of reducing the stray light risk of the visual system, improving the processing formability, assembly stability and imaging quality of the visual system. Brief Description of the Drawings

[0026] Other features, objects and advantages of the present application will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Among them:

[0027] Figure 1 Shows the structure and partial parameter schematic diagram of the visual system according to an exemplary embodiment of the present application;

[0028] Figure 2 Shows the structural schematic diagram of the visual system according to Embodiment 1 of the present application;

[0029] Figure 3 Shows the structural schematic diagram of the visual system according to Embodiment 2 of the present application;

[0030] Figure 4 Shows the structural schematic diagram of the visual system according to Embodiment 3 of the present application;

[0031] Figure 5A 、 Figure 5B and Figure 5C Respectively show the axial chromatic aberration curve, astigmatism curve and distortion curve of the visual system according to Embodiment 1, 2 or 3 of the present application;

[0032] Figure 6 Shows the MTF curve of the visual system according to Embodiment 1, 2 or 3 of the present application;

[0033] Figure 7 Shows the structural schematic diagram of the visual system according to Embodiment 4 of the present application;

[0034] Figure 8 Shows a schematic structural diagram of the visual system according to Embodiment 5 of the present application;

[0035] Figure 9 Shows a schematic structural diagram of the visual system according to Embodiment 6 of the present application;

[0036] Figure 10A 、 Figure 10B and Figure 10C respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the visual system according to Embodiment 4, 5, or 6 of the present application;

[0037] Figure 11 Shows the MTF curve of the visual system according to Embodiment 4, 5, or 6 of the present application;

[0038] Figure 12 Shows a schematic structural diagram of the visual system according to Embodiment 7 of the present application;

[0039] Figure 13 Shows a schematic structural diagram of the visual system according to Embodiment 8 of the present application;

[0040] Figure 14 Shows a schematic structural diagram of the visual system according to Embodiment 9 of the present application;

[0041] Figure 15A 、 Figure 15B and Figure 15C respectively show the axial chromatic aberration curve, astigmatism curve, and distortion curve of the visual system according to Embodiment 7, 8, or 9 of the present application; and

[0042] Figure 16 Shows the MTF curve of the visual system according to Embodiment 7, 8, or 9 of the present application. Detailed implementation manners

[0043] To better understand the present application, more detailed descriptions of various aspects of the present application will be made with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present application and do not limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0044] It should be noted that in this specification, the expressions such as first, second, third, fourth, etc. are only used to distinguish one feature from another feature and do not represent any limitation on the 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 or the third lens.

[0045] In the drawings, for the sake of clarity, the thickness, dimensions, and shape of the lenses have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are presented by way of example. That is, the spherical or aspherical shapes are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not drawn to an exact scale.

[0046] 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.

[0047] It should also be understood that the terms "comprises," "comprising," "has," "including," and / or "including having," when used in this specification, denote the presence of the stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. In addition, when 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 a single 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.

[0048] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0049] It should be noted that, without conflict, the embodiments and features in the embodiments of the present application may be combined with each other. The following embodiments merely represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but should not be construed as a limitation on the patent scope of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can be made, and these all belong to the protection scope of the present application. For example, the lens groups (i.e., the first lens to the fourth lens), the barrel structure, and the spacer elements in the embodiments of the present application can be combined arbitrarily, and it is not limited that the lens group in one embodiment can only be combined with the barrel structure, spacer elements, etc. in that embodiment.

[0050] The features, principles, and other aspects of the present application are described in detail below.

[0051] Figure 1Schematic diagrams of the structural layout and partial parameters of the visual system according to an exemplary embodiment of the present application. Refer to Figure 1 , CP1 represents the maximum thickness of the first spacer element, CP2 represents the maximum thickness of the second spacer element, CP3 represents the maximum thickness of the third spacer element, CP4 represents the maximum thickness of the fourth spacer element, EP01 represents the distance along the optical axis from the first side end face of the lens barrel to the first side face of the first spacer element, EP12 represents the distance along the optical axis from the second side face of the first spacer element to the first side face of the second spacer element, EP23 represents the distance along the optical axis from the second side face of the second spacer element to the first side face of the third spacer element, EP34 represents the distance along the optical axis from the second side face of the third spacer element to the first side face of the fourth spacer element, D0s represents the outer diameter of the first side end face of the lens barrel, d0s represents the inner diameter of the first side end face of the lens barrel, D1s represents the outer diameter of the first side face of the first spacer element, d1s represents the inner diameter of the first side face of the first spacer element, D2s represents the outer diameter of the first side face of the second spacer element, d2s represents the inner diameter of the first side face of the second spacer element, D3s represents the outer diameter of the first side face of the third spacer element, d3s represents the inner diameter of the first side face of the third spacer element, D4s represents the outer diameter of the first side face of the fourth spacer element, d4s represents the inner diameter of the first side face of the fourth spacer element, d0m represents the inner diameter of the second side end face of the lens barrel, d4m represents the inner diameter of the second side face of the fourth spacer element, D4m represents the outer diameter of the second side face of the fourth spacer element, and so on.

[0052] Refer to Figures 2 to 4 , Figures 7 to 9 and Figures 12 to 14 , a first aspect of the present application provides a visual system, which may include a lens group, a spacer element group, and a lens barrel, wherein both the lens group and the spacer element group are assembled within the lens barrel.

[0053] In an exemplary embodiment, the lens barrel P0 may include a first side end face, a second side end face, an outer ring face, and an inner ring face. Among them, the first side end face of the lens barrel may be, for example, the end face closest to the first side, and the second side end face of the lens barrel may be, for example, the end face closest to the second side; in a direction perpendicular to the optical axis, the surface of the lens barrel farthest from the optical axis is the outer ring face, and the surface of the lens barrel closest to the optical axis is the inner ring face.

[0054] In an exemplary embodiment, the lens group may be a four-piece lens group, which may include, in order from the first side to the second side along the optical axis: a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. An air gap may be provided between any adjacent lenses. In an exemplary embodiment, the second side of the visual system may further include a display screen.

[0055] In an exemplary embodiment, the first side of the visual system may be, for example, the side close to the human eye, and the second side may be, for example, the side close to the display. Correspondingly, each optical element (the first lens, the reflective polarizing element, the first quarter-wave plate, the second lens, the third lens, the partial reflection element, the second quarter-wave plate, the polarizer, the fourth lens, etc.) has at least one first side surface relatively close to the human eye side and at least one second side surface relatively close to the display side.

[0056] In an exemplary embodiment, the first lens E1 may have a positive optical power. The second lens E2 may have a positive optical power. The third lens E3 may have a negative optical power. The fourth lens E4 may have a negative optical power.

[0057] In an exemplary embodiment, the first side surface of the first lens E1 may be convex, and the second side surface may be flat. The reflective polarizing element RP may be disposed on the second side surface (the surface close to the display side) of the first lens E1 and at least partially adhered to the second side surface of the first lens E1. The first quarter-wave plate QWP1 may be disposed on the second side surface (the surface close to the display side) of the reflective polarizing element RP and at least partially adhered to the second side surface of the reflective polarizing element RP. Exemplarily, the reflective polarizing element RP and the first quarter-wave plate QWP1 may be sequentially attached to the second side surface of the first lens E1, or they may be combined together to achieve a single attachment, thereby improving production efficiency and reducing costs. At the same time, combining the two together can also avoid the angular deviation between the optical axis of the reflective polarizing element and the optical axis of the first quarter-wave plate caused by the attachment process, and improve the imaging quality.

[0058] In an exemplary embodiment, the first side surface of the second lens E2 may be convex, and the second side surface may be convex or concave.

[0059] In an exemplary embodiment, the first side surface of the third lens E3 may be concave, and the second side surface may be flat. The partial reflection element BS may be disposed on the second side surface of the third lens E3 and at least partially adhered to the second side surface of the third lens E3. The second quarter-wave plate QWP2 may be disposed on the second side surface of the partial reflection element BS and at least partially adhered to the second side surface of the partial reflection element BS. The polarizer LP may be disposed on the second side surface of the second quarter-wave plate QWP2 and at least partially adhered to the second side surface of the second quarter-wave plate QWP2. Exemplarily, the partial reflection element BS, the second quarter-wave plate QWP2, and the polarizer LP may be sequentially attached to the second side surface of the third lens E3.

[0060] In an exemplary embodiment, the first side surface of the fourth lens E4 may be convex or concave, and the second side surface may be concave or convex.

[0061] In the visual system according to the exemplary embodiment of the present application, when light passes through the reflective polarizing element, the reflective polarizing element can reflect light in a certain direction and transmit light orthogonal to the reflected light. The quarter-wave plate can be used to convert between circularly polarized light and linearly polarized light to achieve the refolding of the optical path. The partial reflection element may be a partial reflection layer (such as a semi-transmissive and semi-reflective film) attached or deposited on the second side surface of the second lens, and the partial reflection layer has a semi-transmissive and semi-reflective effect on light. The function of the polarizer is to convert the natural light emitted by the screen into linearly polarized light. The image light from the display screen is finally projected onto the user's eyes after multiple refractions and reflections by the visual system.

[0062] The visual system provided according to the embodiment of the present application can be applied to the head-mounted device of virtual reality devices such as VR or AR (Augmented Reality) devices. Specifically, it can be used as the visual system of the head-mounted device. By refolding the optical path, the body length of the lens can be compressed, so that the center of gravity of the head-mounted device moves backward, increasing the user experience.

[0063] In an exemplary embodiment, the spacer element group may include one or more of a first spacer element, a second spacer element, a third spacer element, and a fourth spacer element. The first spacer element may be located between the first lens and the second lens and abuts against the second side surface of the first lens. The second spacer element may be located between the second lens and the third lens and abuts against the second side surface of the second lens. The third spacer element may be located between the third lens and the fourth lens and abuts against the second side surface of the third lens. The fourth spacer element may be located between the fourth lens and the lens barrel and abuts against the second side surface of the fourth lens. Reasonable use of the spacer element can effectively avoid the risk of stray light, reduce the interference with the image quality, and thus improve the imaging quality of the visual system; it is also beneficial to improve the assembly stability of the system, thereby ensuring that the system has good structural performance.

[0064] In an exemplary embodiment, there may be at least one beveled lens in the lens group. The outer peripheral surface of the beveled lens may have a beveled portion and a non-beveled portion, and the outer diameter of the beveled portion of the lens is smaller than the outer diameter of the non-beveled portion of the lens. When the outer peripheral surface of the lens has a beveled portion, the outer diameter of the lens generally refers to the outer diameter of the non-beveled portion of the lens, and the outer diameter of the spacer element generally refers to the maximum outer diameter of the non-beveled portion.

[0065] In an exemplary embodiment, the effective focal length f1 of the first lens and the effective focal length f of the visual system may satisfy: 1.5 < f1 / f < 1.9; the combined focal length FG1 of the first lens, the reflective polarizing element, and the first quarter-wave plate and the inner diameter d1s of the first side surface of the first spacer element may satisfy: 2.35 < FG1 / d1s < 2.75. By designing and optimizing the visual system to satisfy the conditional expressions 1.5 < f1 / f < 1.9 and 2.35 < FG1 / d1s < 2.75, on the premise that the ratio of f1 / f is within a reasonable range, by controlling FG1 / d1s within a reasonable range, the refraction angle of light when passing through the corresponding lens can be reasonably controlled; and, by controlling the inner diameter size of the first side surface of the first spacer element, the stray light generated by the light path reflected by the small inclined surface of the part near the effective diameter edge of the second side of the fourth lens reaching the inside of the lens can be blocked, thereby improving the imaging quality and clarity and enhancing the visual experience.

[0066] In an exemplary embodiment, the maximum thickness CP1 of the first spacer element, the maximum thickness CP2 of the second spacer element, and the central thickness CT2 of the second lens on the optical axis may satisfy: 1.0 < (CP1 + CP2) / CT2 < 2.8. Satisfying this conditional expression, by controlling the ratio of the sum of the maximum thicknesses of the first spacer element and the second spacer element to the central thickness of the second lens, it is beneficial to ensure the assembly of the first lens and the second lens, reduce the deformation after the lens and the spacer element are assembled, and thus is beneficial to improving the overall assembly stability of the system.

[0067] In an exemplary embodiment, the curvature radius R3 of the first side surface of the second lens and the inner diameter d1m of the second side surface of the first spacer element may satisfy: 1.5 < R3 / d1m < 1.7. Satisfying this conditional expression, by controlling the ratio of the curvature radius of the first side surface of the second lens and the inner diameter of the second side surface of the first spacer element within a certain range, the refraction angle of light can be reasonably controlled, making the cooperation of each lens of the lens more compact, and at the same time, the stray light generated by the light path reflected by the small inclined surface of the part near the effective diameter edge of the first side of the fourth lens reaching the inside of the lens can be blocked, improving the imaging quality.

[0068] In an exemplary embodiment, the inner diameter d0s of the first side end face of the lens barrel and the curvature radius R1 of the first side face of the first lens may satisfy: 0.8 < d0s / R1 < 1.0. By satisfying this conditional expression and controlling the relationship between the curvature radius of the first side face of the first lens with a relatively small absolute value of the focal length and the inner diameter of the light exit hole of the lens barrel, the light blocking area can be increased to reduce stray light, which helps to improve the overall stray light of the lens.

[0069] In an exemplary embodiment, the effective focal length f2 of the second lens and the outer diameter D2s of the first side face of the second spacer element may satisfy: 2.1 < f2 / D2s < 2.6. By satisfying this conditional expression and controlling the ratio range of the effective focal length value of the second lens to the outer diameter of the second side face of the second spacer element, the trend of light passing through the second lens can be effectively controlled, and the problem of excessive sensitivity of the second lens caused by too steep light can be avoided.

[0070] In an exemplary embodiment, the distance TD on the optical axis from the first side face of the first lens to the second side face of the fourth lens and the interval EP23 along the optical axis from the second side face of the second spacer element to the first side face of the third spacer element may satisfy: 2.3 ≤ TD / EP23 < 3.2. By satisfying this conditional expression and controlling the distance on the optical axis from the first lens to the fourth lens and the interval between the second side face of the second spacer element and the first side face of the third spacer element, on the one hand, it is beneficial to the processing and imaging of the second lens, and on the other hand, it is beneficial to shortening the height of the system and realizing miniaturization of the visual system.

[0071] In an exemplary embodiment, the combined focal length FG2 of the third lens, the second quarter-wave plate and the polarizer, the inner diameter d3s of the first side face of the third spacer element, and the inner diameter d3m of the second side face of the third spacer element may satisfy: -2.1 < FG2 / (d3s + d3m) < -1.6. By satisfying this conditional expression, the effective focal length of the third lens can be controlled within a certain range, enabling it to generate positive spherical aberration and balance the negative spherical aberration generated by other lenses in the system, so that the on-axis imaging quality of the system is good; secondly, by controlling the outer diameter and inner diameter of the third spacer element away from the light source surface, on the basis of ensuring its supporting effect, it is beneficial to improve the processability of the third spacer element.

[0072] In an exemplary embodiment, the inner diameter d2s of the first side surface of the second spacer element, the central thickness CT2 of the second lens on the optical axis, and the on-axis distance T23 from the second side surface of the second lens to the first side surface of the third lens may satisfy: 3.0 < d2s / (CT2 + T23) < 3.4. By satisfying this conditional expression, by controlling the ratio of the center thickness of the second lens and the sum of the air gaps between the second lens and the third lens to the inner diameter of the first side surface of the second spacer element, on the one hand, it is beneficial to the molding and strength of the second lens, and on the other hand, it limits the air gap specification between the second lens and the third lens, which is beneficial to controlling the total length of the optical module and standardizing the assembly and abutment between the two; in addition, controlling the inner diameter of the first side surface of the second spacer element can also limit the transmission of excess light and reduce the generation of stray light.

[0073] In an exemplary embodiment, the on-axis spacing EP34 from the second side surface of the third spacer element to the first side surface of the fourth spacer element and the central thickness CT4 of the fourth lens on the optical axis may satisfy: 1.2 < EP34 / CT4 < 1.4. By satisfying this conditional expression, controlling the central thickness of the fourth lens on the optical axis and the on-axis distance between the third spacer and the first side surface of the fourth spacer within a certain range can avoid the generation of more stray light due to the relatively large thicknesses of the third and fourth spacer elements, which is beneficial to improving stray light and reducing the reflection of excess light, thereby improving the imaging quality; in addition, it also limits the ratio of the edge thickness to the center thickness of the fourth lens within a certain range, which is beneficial to the processing and molding of the fourth lens.

[0074] In an exemplary embodiment, the maximum thickness CP3 of the third spacer element and the maximum thickness CP4 of the fourth spacer element may satisfy: 1.6 < CP4 / CP3 < 2.8. By satisfying this conditional expression, by controlling the ratio of the maximum thickness of the fourth spacer element to the maximum thickness of the third spacer element, the edge thickness of the third lens can be controlled within a certain range, which is beneficial to the processing and molding of the third lens.

[0075] In an exemplary embodiment, the outer diameter D0s of the first side end surface of the lens barrel and the inner diameter d0m of the second side end surface of the lens barrel may satisfy: 1.8 < D0s / d0m < 2.4. By satisfying this conditional expression, reasonably setting the inner and outer diameters of the two side end surfaces of the lens barrel effectively restricts the overall size of the visual system, which is beneficial to subsequent matching with other modules; 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 minimized as much as possible, thereby reducing the overall size of the machine.

[0076] In an exemplary embodiment, the effective focal length f4 of the fourth lens, the inner diameter d4s of the first side surface of the fourth spacer element, and the inner diameter d4m of the second side surface of the fourth spacer element may satisfy: -1.4 < f4 / (d4s + d4m) ≤ -0.8. By satisfying this conditional expression, the field of view angle of the system is effectively constrained by controlling the effective focal length of the fourth lens, thereby enabling the system to meet the characteristics of a large field of view of a VR lens; at the same time, by restricting the inner diameter of the far-light surface of the fourth spacer element that is farthest from the light source and the inner diameter of the near-light surface that is closest to the light source, the light incident amount can be effectively controlled, and the light can be utilized more efficiently to participate in imaging; in addition, by controlling the inner diameter size, 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.

[0077] In an exemplary embodiment, the outer diameter D3s of the first side surface of the third spacer element and the D4s of the first side surface of the fourth spacer element may satisfy: 1.1 < D3s / D4s < 1.2. By satisfying this conditional expression, the processing outer shape dimensions of the third spacer element and the fourth spacer element can be restricted to meet the processing feasibility. In addition, the abutting misalignment amount can be restricted, making the lens assembly more stable and having a smaller deformation amount.

[0078] In an exemplary embodiment, the radius of curvature R5 of the first side surface of the third lens, the inner diameter d2m of the second side surface of the second spacer element, and the outer diameter D2m of the second side surface of the second spacer element may satisfy: -1.4 < R5 / (d2m + D2m) < -1.0. By satisfying this conditional expression, by restricting the radius of curvature of the far-light surface of the third lens, it is beneficial to reduce the sensitivity of the third lens, thereby improving the yield of assembly; secondly, the outer diameter of the far-light surface and the inner diameter of the near-light surface of the second spacer element can be restricted to ensure its processability.

[0079] In an exemplary embodiment, the outer diameter D1s of the first side surface of the first spacer element and the entrance pupil diameter EPD of the visual system may satisfy: 1.2 < D1s / EPD < 1.4. By satisfying this conditional expression, by controlling the ratio range of the outer diameter of the first spacer element to the entrance pupil diameter of the system, it is beneficial to the processing and forming of the first spacer element, ensuring the stability of the assembly abutment and reducing the impact on the system performance.

[0080] In an exemplary embodiment, the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis, and the distance EP01 along the optical axis from the first side end face of the lens barrel to the first side face of the first spacer element satisfy: 0.9 < (CT1 + CTR + CTQ1) / EP01 < 1.1. Satisfying this conditional expression is conducive to the assembly of the lens by reasonably distributing the thicknesses of the components inside the lens barrel; at the same time, by reasonably setting the distance along the optical axis from the first side end face of the lens barrel to the first side face of the first spacer element, the edge thickness of the lens is indirectly ensured, which is conducive to the molding of components; in addition, the dispensing space of the first lens is ensured, indirectly ensuring the reliability of the visual system and improving the assembly stability and imaging quality of the visual system.

[0081] In an embodiment of the present application, the visual system may further include a diaphragm STO disposed near the human eye side. The diaphragm STO may be disposed, for example, on the first side of the first lens E1.

[0082] In an embodiment of the present application, at least one of the surfaces of each lens among the first lens to the fourth lens is an aspherical surface. The aspherical lens has better curvature radius characteristics and has the advantages of improving distortion aberration and astigmatism aberration. By using an aspherical lens, it is possible to eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality.

[0083] A second aspect of the present application provides a visual system, which includes a lens barrel and a four-piece lens group and a spacer element group assembled in the lens barrel. The four-piece lens group includes, in order from the first side to the second side along the optical axis: a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group may include one or more of a first spacer element, a second spacer element, a third spacer element, and a fourth spacer element. The first spacer element may be located between the first lens and the second lens and abut against the second side face of the first lens. The second spacer element may be located between the second lens and the third lens and abut against the second side face of the second lens. The third spacer element may be located between the third lens and the fourth lens and abut against the second side face of the third lens. The fourth spacer element may be located between the fourth lens and the lens barrel and abut against the second side face of the fourth lens.

[0084] In an exemplary embodiment, the effective focal length f1 of the first lens and the effective focal length f of the visual system may satisfy: 1.5 < f1 / f < 1.9; the central thickness CT1 of the first lens on the optical axis, the central thickness CTR of the reflective polarizing element on the optical axis, the central thickness CTQ1 of the first quarter-wave plate on the optical axis, and the interval EP01 along the optical axis from the first side end face of the lens barrel to the first side face of the first spacer element may satisfy: 0.9 < (CT1 + CTR + CTQ1) / EP01 < 1.1. By making the visual system satisfy the conditional expressions 1.5 < f1 / f < 1.9 and 0.9 < (CT1 + CTR + CTQ1) / EP01 < 1.1, on the premise that the ratio of f1 / f is within a reasonable range, by reasonably distributing the thicknesses of the components inside the lens barrel, it is beneficial to the assembly of the lens; at the same time, by reasonably setting the distance on the optical axis from the first side end face of the lens barrel to the first side face of the first spacer element, the edge thickness of the lens is indirectly ensured, which is beneficial to the molding of the parts; in addition, the dispensing space of the first lens is ensured, indirectly ensuring the reliability of the visual system and improving the assembly stability and imaging quality of the visual system.

[0085] The visual system according to the above embodiment of the present application adopts a catadioptric scheme including four lenses, and by adopting a polarized catadioptric optical path method, the body height can be better compressed and the imaging quality can be improved; at the same time, by adopting at least one spacer element and reasonably distributing the parameters of each lens and each spacer element, at least one aspect such as reducing the stray light risk of the visual system, improving the processing formability, assembly stability and imaging quality of the visual system can be achieved.

[0086] Those skilled in the art should understand that without departing from the technical solutions claimed in the present application, the number of lenses and spacer elements constituting the visual system can be changed to obtain the various results and advantages described in this specification.

[0087] The following further describes specific embodiments of the visual system applicable to the above embodiments with reference to the drawings.

[0088] Example 1

[0089] The following refers to Figure 2 Describe the visual system according to Embodiment 1 of the present application.

[0090] As Figure 2 shown, the visual system includes a lens barrel P0 and a four-lens group and a spacer element group assembled in the lens barrel P0.

[0091] Among them, the four-piece lens group sequentially includes, along the optical axis, from the first side (e.g., the side close to the human eye) to the second side (e.g., the side close to the display): the first lens E1, the reflective polarizing element RP, the first quarter-wave plate QWP1, the second lens E2, the third lens E3, the partially reflective element BS (not shown in the figure), the second quarter-wave plate QWP2, the polarizer LP, and the fourth lens E4.

[0092] The spacer element group includes the first spacer element P1, the second spacer element P2, the third spacer element P3, and the fourth spacer element P4. The spacer elements can block the excess light during the imaging process from entering the next lens, and at the same time enable the lens to better rest against the lens barrel, enhancing the structural stability of the visual system.

[0093] The visual system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.

[0094] In this embodiment, the first lens E1 has a positive optical power. Its first side is convex, and its second side is flat. The reflective polarizing element RP and the first quarter-wave plate QWP1 are sequentially attached to the second side. The second lens E2 has a positive optical power. Its first side is convex, and its second side is concave. The third lens E3 has a negative optical power. Its first side is concave, and its second side is flat. The partially reflective element BS, the second quarter-wave plate QWP2, and the polarizer LP are sequentially attached to the second side. The fourth lens E4 has a negative optical power. Its first side is convex, and its second side is concave. There may also be an optical element between the fourth lens E4 and the image plane (IMG), and this optical element may be a filter or a protective glass, etc.

[0095] Table 1 shows the basic parameter table of the visual system of Embodiment 1. Among them, the units of the radius of curvature and the thickness / distance are both millimeters (mm). The image light rays from the display screen sequentially pass through the optical surfaces of each element and are finally projected into the human eye.

[0096]

[0097]

[0098] Table 1

[0099] In this embodiment, both the first side and the second side of the fourth lens E4 are aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0100]

[0101] Wherein, x is the sagitta, which is the distance from the vertex of the aspheric surface to the position along the optical axis at a height of h; c is the paraxial curvature of the aspheric surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic constant; Ai is the correction coefficient of the i-th order of the aspheric surface.

[0102] Table 2 shows the higher-order coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16 , A 18 and A 20 that can be used for the aspheric mirrors S24 and S25 in Example 1.

[0103] Coefficient / Face number S24 S25 A4 -7.9931E-01 -6.3669E-01 A6 -3.9385E-02 -4.2803E-01 A8 -1.7119E-03 -6.1338E-02 A10 -1.3914E-03 -4.4223E-02 A12 6.7489E-04 -2.3695E-02 A14 6.5301E-05 -1.7514E-02 A16 -6.2995E-06 -6.3956E-03 A18 5.8711E-05 -1.4767E-03 A20 0.0000E+00 0.0000E+00

[0104] Table 2

[0105] Example 2

[0106] The following refers to Figure 3 to describe the visual system according to Embodiment 2 of the present application.

[0107] As Figure 3 shown, the visual system includes a lens barrel P0 and a four-lens group and a spacer element group assembled in the lens barrel P0. Among them, the four-lens group includes, in order from the first side (e.g., the side close to the human eye) to the second side (e.g., the side close to the display) along the optical axis: a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.

[0108] The structures of the lenses in this embodiment are the same as those of the lenses in Embodiment 1, that is, the basic parameter table of the visual system in this embodiment is the same as Table 1, and the aspheric coefficient table is the same as Table 2. In addition, the spacer elements included in the spacer element group of the visual system in this embodiment are the same as those in Embodiment 1, and the difference is only that at least one of the parameters such as the lens barrel, the thickness of the spacer element, the inner diameter of the spacer element, the outer diameter of the spacer element, and the distance between the spacer elements is different.

[0109] Example 3

[0110] The following refers to Figure 4 to describe the visual system according to Embodiment 3 of the present application.

[0111] As shown Figure 4 in the figure, the visual system includes a lens barrel P0, a four-piece lens group and a spacer element group assembled in the lens barrel P0. Among them, the four-piece lens group includes, in sequence along the optical axis from the first side (e.g., the side close to the human eye) to the second side (e.g., the side close to the display): a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a diaphragm STO disposed on the side close to the human eye. The diaphragm STO may be disposed on the first side of the first lens E1.

[0112] The structures of the lenses in this embodiment are the same as those of the lenses in Embodiment 1, that is, the basic parameter table of the visual system in this embodiment is the same as Table 1, and the aspheric coefficient table is the same as Table 2. In addition, the spacer elements included in the spacer element group of the visual system in this embodiment are the same as those in Embodiment 1, and the difference lies only in that at least one of the parameters such as the lens barrel, the thickness of the spacer element, the inner diameter of the spacer element, the outer diameter of the spacer element, and the distance between the spacer elements is different.

[0113] Figure 5A The axial chromatic aberration curves of the visual systems of Embodiments 1, 2, and 3 are shown, which represent the deviation of the convergence points of light rays of different wavelengths after passing through the visual system. Figure 5B The astigmatism curves of the visual systems of Embodiments 1, 2, and 3 are shown, which represent the meridional image plane curvature and sagittal image plane curvature corresponding to different field angles. Figure 5C The distortion curves of the visual systems of Embodiments 1, 2, and 3 are shown, which represent the distortion magnitude values corresponding to different field angles. According to Figures 5A to 5C it can be seen that the visual systems given in Embodiments 1, 2, and 3 can achieve good imaging quality.

[0114] Figure 6 The MTF curves of the visual systems of Embodiments 1, 2, and 3 are shown. From Figure 6 it can be seen that the visual systems of Embodiments 1, 2, and 3 have good contrast within a spatial frequency of 30 lp / mm and clear imaging.

[0115] Example 4

[0116] The following refers to Figure 7 to describe the visual system according to Embodiment 4 of the present application.

[0117] As Figure 7As shown in the figure, the visual system includes a lens barrel P0, and a four-piece lens group and a spacer element group assembled in the lens barrel P0. Among them, the four-piece lens group includes, in order along the optical axis from the first side (e.g., the side close to the human eye) to the second side (e.g., the side close to the display): a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a diaphragm STO disposed on the side close to the human eye. The diaphragm STO may be disposed on the first side of the first lens E1.

[0118] In this embodiment, the first lens E1 has a positive optical power. Its first side is convex, and its second side is flat. The reflective polarizing element RP and the first quarter-wave plate QWP1 are sequentially attached to the second side. The second lens E2 has a positive optical power. Its first side is convex, and its second side is convex. The third lens E3 has a negative optical power. Its first side is concave, and its second side is flat. The partial reflection element BS, the second quarter-wave plate QWP2, and the polarizer LP are sequentially attached to the second side. The fourth lens E4 has a negative optical power. Its first side is convex, and its second side is concave. An optical element may also be provided between the fourth lens E4 and the image plane (IMG), and the optical element may be a filter or a protective glass, etc.

[0119] Table 3 shows the basic parameter table of the visual system of Embodiment 4, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0120]

[0121]

[0122] Table 3

[0123] In this embodiment, both the first side and the second side of the fourth lens E4 are aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the formula (1) given in the aforementioned Embodiment 1.

[0124] Table 4 shows the higher-order term coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16 , A 18 and A 20 that can be used for the aspherical surfaces S24 and S25 in Embodiment 4.

[0125] Coefficient / Face number S24 S25 A4 -1.1342E+00 -1.4002E+00 A6 7.2212E-03 8.6453E-02 A8 8.8705E-03 9.8141E-02 A10 3.7541E-03 8.4787E-02 A12 6.3881E-03 5.2505E-02 A14 2.5120E-03 2.2854E-02 A16 9.3741E-04 7.7876E-03 A18 2.8491E-04 2.0627E-03 A20 0.0000E+00 0.0000E+00

[0126] Table 4

[0127] Example 5

[0128] Refer to the following Figure 8 to describe the visual system according to Embodiment 5 of the present application.

[0129] As Figure 8 shown, the visual system includes a lens barrel P0, and a four-piece lens group and a spacer element group assembled in the lens barrel P0. Among them, the four-piece lens group includes, in order along the optical axis from the first side (for example, the side close to the human eye) to the second side (for example, the side close to the display): a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.

[0130] The structure of each lens in this embodiment is the same as that of each lens in Embodiment 4, that is, the basic parameter table of the visual system in this embodiment is the same as Table 3, and the aspherical coefficient table is the same as Table 4. In addition, the spacer elements included in the spacer element group of the visual system in this embodiment are also the same as those in Embodiment 4, and the difference lies only in that at least one of the parameters such as the lens barrel, the thickness of the spacer element, the inner diameter of the spacer element, the outer diameter of the spacer element, and the distance between the spacer elements is different.

[0131] Example 6

[0132] Refer to the following Figure 9 to describe the visual system according to Embodiment 6 of the present application.

[0133] As Figure 9 shown, the visual system includes a lens barrel P0, and a four-piece lens group and a spacer element group assembled in the lens barrel P0. Among them, the four-piece lens group includes, in order along the optical axis from the first side (for example, the side close to the human eye) to the second side (for example, the side close to the display): a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.

[0134] The structures of the lenses in this embodiment are the same as those of the lenses in Embodiment 4. That is, the basic parameter table of the visual system in this embodiment is the same as Table 3, and the aspheric coefficient table is the same as Table 4. In addition, the spacer elements included in the spacer element group of the visual system in this embodiment are also the same as those in Embodiment 4, except that at least one of the parameters such as the lens barrel, the thickness of the spacer element, the inner diameter of the spacer element, the outer diameter of the spacer element, and the distance between the spacer elements is different.

[0135] Figure 10A The axial chromatic aberration curves of the visual systems of Embodiments 4, 5, and 6 are shown, which represent the deviation of the convergence points of light rays of different wavelengths after passing through the visual system. Figure 10B The astigmatism curves of the visual systems of Embodiments 4, 5, and 6 are shown, which represent the meridional image plane curvature and sagittal image plane curvature corresponding to different field angles. Figure 10C The distortion curves of the visual systems of Embodiments 4, 5, and 6 are shown, which represent the distortion magnitude values corresponding to different field angles. According to Figures 10A to 10C it can be known that the visual systems given in Embodiments 4, 5, and 6 can achieve good imaging quality.

[0136] Figure 11 The MTF curves of the visual systems of Embodiments 4, 5, and 6 are shown. From Figure 11 it can be seen that the visual systems of Embodiments 4, 5, and 6 have good contrast within a spatial frequency of 30 lp / mm and the imaging is clear.

[0137] Example 7

[0138] The following will refer to Figure 12 to describe the visual system according to Embodiment 7 of the present application.

[0139] As Figure 12 shown, the visual system includes a lens barrel P0 and a four-lens group and a spacer element group assembled in the lens barrel P0. Among them, the four-lens group includes, in order from the first side (e.g., the side close to the human eye) to the second side (e.g., the side close to the display) along the optical axis: a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a diaphragm STO disposed on the side close to the human eye. The diaphragm STO may be disposed on the first side of the first lens E1.

[0140] In this embodiment, the first lens E1 has a positive optical power. Its first side is convex, and its second side is flat. A reflective polarizing element RP and a first quarter-wave plate QWP1 are successively attached to the second side. The second lens E2 has a positive optical power. Its first side is convex, and its second side is convex. The third lens E3 has a negative optical power. Its first side is concave, and its second side is flat. A partial reflection element BS, a second quarter-wave plate QWP2, and a polarizer LP are successively attached to the second side. The fourth lens E4 has a negative optical power. Its first side is concave, and its second side is convex. An optical element may also be provided between the fourth lens E4 and the image plane (IMG), and the optical element may be a filter or a protective glass, etc.

[0141] Table 5 shows the basic parameter table of the visual system of Embodiment 7, where the unit of the radius of curvature and the thickness / distance is millimeter (mm).

[0142]

[0143]

[0144] Table 5

[0145] In this embodiment, both the first side and the second side of the fourth lens E4 are aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the formula (1) given in the foregoing Embodiment 1.

[0146] Table 6 shows the higher-order term coefficients A4, A6, A8, A 10 , A 12 and A 14 , A 16 , A 18 and A 20 .

[0147] Coefficient / Face number S24 S25 A4 -5.6635E-01 -1.9809E-01 A6 1.4571E-02 -3.1399E-01 A8 -1.1511E-02 -2.4986E-01 A10 -3.4113E-02 1.0909E-01 A12 -5.4541E-03 1.9584E-01 A14 -1.1154E-02 -1.7031E-02 A16 1.6867E-03 -7.5399E-02 A18 -1.1201E-03 -5.8405E-02 A20 0.0000E+00 0.0000E+00

[0148] Table 6

[0149] Example 8

[0150] The following refers to Figure 13 to describe the visual system according to Embodiment 8 of the present application.

[0151] As Figure 13As shown, the visual system includes a lens barrel P0, a four-piece lens group, and a spacer element group assembled in the lens barrel P0. Among them, the four-piece lens group sequentially includes, along the optical axis, from the first side (e.g., the side close to the human eye) to the second side (e.g., the side close to the display): a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.

[0152] The structures of the lenses in this embodiment are the same as those of the lenses in Embodiment 7. That is, the basic parameter table of the visual system in this embodiment is the same as Table 5, and the aspherical coefficient table is the same as Table 6. In addition, the spacer elements included in the spacer element group of the visual system in this embodiment are the same as those in Embodiment 7, and the difference lies only in that at least one of the parameters such as the lens barrel, the thickness of the spacer element, the inner diameter of the spacer element, the outer diameter of the spacer element, and the distance between the spacer elements is different.

[0153] Example 9

[0154] The following refers to Figure 14 Describe the visual system according to Embodiment 9 of the present application.

[0155] As Figure 14 As shown, the visual system includes a lens barrel P0, a four-piece lens group, and a spacer element group assembled in the lens barrel P0. Among them, the four-piece lens group sequentially includes, along the optical axis, from the first side (e.g., the side close to the human eye) to the second side (e.g., the side close to the display): a first lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS (not shown in the figure), a second quarter-wave plate QWP2, a polarizer LP, and a fourth lens E4. The spacer element group includes a first spacer element P1, a second spacer element P2, a third spacer element P3, and a fourth spacer element P4. The visual system may further include a stop STO disposed on the side close to the human eye. The stop STO may be disposed on the first side of the first lens E1.

[0156] The structures of the lenses in this embodiment are the same as those of the lenses in Embodiment 7. That is, the basic parameter table of the visual system in this embodiment is the same as Table 5, and the aspheric coefficient table is the same as Table 6. Additionally, the spacer elements included in the spacer element group of the visual system in this embodiment are the same as those in Embodiment 7, with the only difference being that at least one of the parameters such as the lens barrel, the thickness of the spacer element, the inner diameter of the spacer element, the outer diameter of the spacer element, and the distance between the spacer elements is different.

[0157] Figure 15A The axial chromatic aberration curves of the visual systems of Embodiments 7, 8, and 9 are shown, which represent the deviation of the convergence points of light rays of different wavelengths after passing through the visual systems. Figure 15B The astigmatism curves of the visual systems of Embodiments 7, 8, and 9 are shown, which represent the meridional image plane curvature and sagittal image plane curvature corresponding to different field angles. Figure 15C The distortion curves of the visual systems of Embodiments 7, 8, and 9 are shown, which represent the distortion magnitude values corresponding to different field angles. According to Figures 15A to 15C It can be seen that the visual systems given in Embodiments 7, 8, and 9 can achieve good imaging quality.

[0158] Figure 16 The MTF curves of the visual systems of Embodiments 7, 8, and 9 are shown. From Figure 16 it can be seen that the visual systems of Embodiments 7, 8, and 9 have good contrast within a spatial frequency of 30 lp / mm and clear imaging.

[0159] Table 7 shows some optical parameters of the visual systems of the embodiments in Embodiments 1 - 9, such as the entrance pupil diameter EPD of the visual system, the distance TD on the optical axis from the first side of the first lens to the second side of the fourth lens, the effective focal length f of the visual system, and related parameters such as the effective focal lengths and combined focal lengths of each lens. The unit of each optical parameter is millimeter (mm).

[0160] Parameter / Example 1 2 3 4 5 6 7 8 9 f (mm) 42.00 42.00 42.00 42.00 42.00 42.00 42.00 42.00 42.00 f1 (mm) 64.76 64.76 64.76 73.87 73.87 73.87 76.19 76.19 76.19 f2 (mm) 70.44 70.44 70.44 56.51 56.51 56.51 61.07 61.07 61.07 f3 (mm) -88.59 -88.59 -88.59 -76.17 -76.17 -76.17 -93.33 -93.33 -93.33 f4 (mm) -55.05 -55.05 -55.05 -37.66 -37.66 -37.66 -29.43 -29.43 -29.43 EPD (mm) 23.00 23.00 23.00 23.00 23.00 23.00 23.00 23.00 23.00 TD (mm) 23.62 23.62 23.62 23.64 23.64 23.64 24.51 24.51 24.51 FG1 (mm) 64.76 64.76 64.76 73.87 73.87 73.87 76.19 76.19 76.19 FG2 (mm) -88.59 -88.59 -88.59 -76.17 -76.17 -76.17 -93.33 -93.33 -93.33

[0161] Table 7

[0162] Table 8 shows the values of some parameters of the embodiments in Embodiments 1 - 9, such as the values of parameters d1s, d1m, D1s, d2s, d2m, D2s, D2m, d3s, d3m, ……, D0s, EP01, EP23, EP34, CP1, CP2, CP3, CP4, etc. Among them, the above parameters can be measured according to the Figure 1 indicated marking method, and the units of the parameters listed in Table 8 are all mm.

[0163]

[0164]

[0165] Table 8 In summary, in Examples 1 to 9, the visual system satisfies each conditional expression shown in Table 9 below.

[0166] Condition formula / Example 1 2 3 4 5 6 7 8 9 f1 / f 1.54 1.54 1.54 1.76 1.76 1.76 1.81 1.81 1.81 FG1 / d1s 2.40 2.40 2.42 2.66 2.66 2.68 2.74 2.74 2.71 (CT1 + CTR + CTQ1) / EP01 0.98 0.98 0.98 1.03 1.03 1.03 1.00 1.00 1.00 (CP1 + CP2) / CT2 2.73 2.73 2.73 1.44 1.44 1.44 1.09 1.09 1.09 R3 / d1m 1.52 1.52 1.59 1.61 1.61 1.59 1.59 1.59 1.57 d0s / R1 0.94 0.91 0.91 0.96 0.96 0.94 0.90 0.90 0.88 f2 / D2s 2.58 2.58 2.53 2.14 2.14 2.12 2.30 2.30 2.36 TD / EP23 3.11 3.11 3.11 2.30 2.30 2.30 2.42 2.42 2.42 FG2 / (d3s + d3m) -1.86 -1.86 -1.88 -1.65 -1.65 -1.68 -2.06 -2.06 -2.07 d2s / (CT2 + T23) 3.39 3.39 3.26 3.26 3.26 3.20 3.05 3.05 3.10 EP34 / CT4 1.21 1.21 1.21 1.28 1.28 1.28 1.37 1.37 1.37 CP4 / CP3 1.66 1.66 1.66 1.87 1.87 1.87 2.73 2.73 2.73 D0s / d0m 1.88 1.87 1.87 2.27 2.27 2.38 2.27 2.27 2.22 f4 / (d4s + d4m) -1.34 -1.34 -1.36 -1.05 -1.05 -1.05 -0.81 -0.81 -0.80 D3s / D4s 1.17 1.17 1.17 1.17 1.17 1.18 1.16 1.16 1.18 R5 / (d2m + D2m) -1.24 -1.24 -1.27 -1.06 -1.06 -1.06 -1.33 -1.33 -1.34 D1s / EPD 1.29 1.29 1.30 1.30 1.30 1.28 1.31 1.31 1.29

[0167] Table 9

[0168] The above description is only for the preferred embodiments of the present application and the explanation of the technical principles applied. Those skilled in the art should understand that the scope of the utility model involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) having similar functions disclosed in the present application.

Claims

1. A visual system, characterized in that: The invention comprises a lens barrel and a lens group and a spacer element group assembled in the lens barrel. The lens group includes: a first lens with positive power, a reflective polarizing element, a first quarter wave plate, a second lens with positive power, a third lens with negative power, a partial reflective element, a second quarter wave plate, a polarizing plate, and a fourth lens with negative power, which are arranged in sequence from the first side to the second side along the optical axis; The spacer element group includes: a first spacer element located between the first lens and the second lens and abutting against the second side surface of the first lens, a second spacer element located between the second lens and the third lens and abutting against the second side surface of the second lens, a third spacer element located between the third lens and the fourth lens and abutting against the second side surface of the third lens, and a fourth spacer element located between the fourth lens and the lens barrel and abutting against the second side surface of the fourth lens; Wherein, the number of lenses having optical power in the lens group is four; The effective focal length f1 of the first lens and the effective focal length f of the visual system satisfy: 1.5 <f1 / f≤1.81; The combined focal length FG1 of the first lens, the reflective polarizing element and the first quarter-wave plate and the inner diameter d1s of the first side surface of the first spacing element satisfy: 2.35 <FG1 / d1s<2.75。 2. The visual system according to claim 1, characterized in that: The maximum thickness CP1 of the first spacing element, the maximum thickness CP2 of the second spacing element, and the center thickness CT2 of the second lens on the optical axis satisfy: 1.09≤(CP1+CP2) / CT2≤2.

73.

3. The visual system according to claim 1, characterized in that: The curvature radius R3 of the first side surface of the second lens and the inner diameter d1m of the second side surface of the first spacing element satisfy: 1.5 <R3 / d1m≤1.61。 4. The visual system according to claim 1, characterized in that: An inner diameter d0s of the first side end surface of the lens barrel and a curvature radius R1 of the first side surface of the first lens satisfy the following relationship: 0.88≤d0s / R1<1.

0.

5. The visual system according to claim 1, characterized in that: The effective focal length f2 of the second lens and the outer diameter D2s of the first side surface of the second spacing element satisfy: 2.1 <f2 / D2s<2.6。 6. The visual system according to claim 1, characterized in that: A distance TD from the first side surface of the first lens to the second side surface of the fourth lens on the optical axis and an interval EP23 from the second side surface of the second spacing element to the first side surface of the third spacing element along the optical axis satisfy: 2.3≤TD / EP23≤3.

11.

7. The visual system according to claim 1, characterized in that: The combined focal length FG2 of the third lens, the second quarter wave plate and the polarizer, the inner diameter d3s of the first side surface of the third spacing element and the inner diameter d3m of the second side surface of the third spacing element satisfy: -2.1 <FG2 / (d3s+d3m)<-1.6。 8. The visual system according to claim 1, characterized in that: The inner diameter d2s of the first side surface of the second spacer element, the center thickness CT2 of the second lens on the optical axis, and the axial distance T23 from the second side surface of the second lens to the first side surface of the third lens satisfy: 3.0 <d2s / (CT2+T23)<3.4。 9. The visual system according to claim 1, characterized in that: The interval EP34 from the second side surface of the third spacing element to the first side surface of the fourth spacing element along the optical axis and the center thickness CT4 of the fourth lens on the optical axis satisfy: 1.2 <EP34 / CT4<1.4。 10. The visual system according to claim 1, characterized in that: The maximum thickness CP3 of the third spacer element and the maximum thickness CP4 of the fourth spacer element satisfy: 1.66≤CP4 / CP3≤2.

73.

11. The visual system according to any one of claims 1 to 10, characterized in that: An outer diameter D0s of the first side end surface of the lens barrel and an inner diameter d0m of the second side end surface of the lens barrel satisfy the following: 1.87≤D0s / d0m<2.

4.

12. The visual system according to any one of claims 1 to 10, characterized in that: The effective focal length f4 of the fourth lens, the inner diameter d4s of the first side surface of the fourth spacing element, and the inner diameter d4m of the second side surface of the fourth spacing element satisfy: -1.4 <f4 / (d4s+d4m)≤-0.8。 13. The visual system according to any one of claims 1 to 10, characterized in that: An outer diameter D3s of the first side surface of the third spacing element and an outer diameter D4s of the first side surface of the fourth spacing element satisfy the following: 1.16≤D3s / D4s<1.

2.

14. The visual system according to any one of claims 1 to 10, characterized in that: The curvature radius R5 of the first side surface of the third lens, the inner diameter d2m of the second side surface of the second spacing element, and the outer diameter D2m of the second side surface of the second spacing element satisfy: -1.34≤R5 / (d2m+D2m)≤-1.

06.

15. The visual system according to any one of claims 1 to 10, characterized in that: An outer diameter D1s of the first side surface of the first spacing element and an entrance pupil diameter EPD of the visual system satisfy the following: 1.28≤D1s / EPD≤1.

31.

16. The visual system according to any one of claims 1 to 10, characterized in that: The center thickness CT1 of the first lens on the optical axis, the center thickness CTR of the reflective polarizing element on the optical axis, the center thickness CTQ1 of the first quarter-wave plate on the optical axis, and the interval EP01 from the first side end surface of the lens barrel to the first side surface of the first spacing element along the optical axis satisfy: 0.98≤(CT1+CTR+CTQ1) / EP01≤1.

03.

17. The visual system according to any one of claims 1 to 10, characterized in that: The first side surface of the first lens is a convex surface, and the second side surface is a flat surface; The first side surface of the second lens is a convex surface, and the second side surface is a convex surface or a concave surface; The first side surface of the third lens is a concave surface, and the second side surface is a flat surface; The first side surface of the fourth lens is convex, and the second side surface is concave; or the first side surface of the fourth lens is concave, and the second side surface is convex.

Images