Visual system

Abstract

The invention discloses a visual system which sequentially comprises a first lens group and a second lens group from a first side to a second side along an optical axis, the first lens group comprises a first lens with positive focal power, a reflective polarization element and a quarter-wave plate, and the second lens group comprises a second lens with positive focal power, a partial reflection element and a third lens. The second lens and the third lens are glued; the second lens group is movable along the optical axis to switch the visual system between a first state and a second state. The combined focal length fz of the first lens group and the focal length fm of the system in the first state meet the condition that fz / fm is more than or equal to 5.69 and less than or equal to 8.09; the combined focal length f23 of the second lens and the third lens and the axial distances TDm and TDn from the first side face of the first lens to the second side face of the third lens meet the condition that f23 / (TDm + TDn) is larger than or equal to 1.78 and smaller than or equal to 7.01 when the system is in the first state and the second state respectively. When the system is in the first state, the air interval T12m between the first lens and the second lens and the variable quantity delta f of the effective focal length of the system switched from the first state to the second state meet the condition that T12m / delta f is larger than or equal to 2.00 and smaller than or equal to 4.70.

Description

Technical Field

[0001] The present application relates to the field of optical elements, and more specifically, to a visual system. Background Art

[0002] With the continuous development of virtual reality (VR) technology, the mainstream solution for the visual system of various VR devices has changed from the Fresnel solution to the reentrant solution. The reentrant solution can significantly shorten the total length of the system, have better display performance, and can also provide functions such as diopter adjustment, which has many advantages. However, the reentrant solution, especially when using multiple lenses, will also cause more ghost images and stray light in the final image due to reflections between the lenses, affecting the image quality; in addition, the system is still developing in the direction of miniaturization and lightness, and the system's processability still needs to be continuously improved. Summary of the invention

[0003] The present application provides a visual system, which may include a first lens group and a second lens group in sequence from the first side to the second side along the optical axis; the first lens group includes a first lens, a reflective polarizing element and a quarter wave plate, wherein the first lens has positive optical focal length, its first side surface is convex, and the second side surface is flat; the second lens group includes a second lens, a partial reflecting element and a third lens, wherein the second lens has positive optical focal length, and its second side surface is convex; the third lens has positive optical focal length or negative optical focal length, its first side surface is concave, and the second side surface is convex; and the second lens and the third lens are double-cemented lenses glued to each other; the second lens group is configured to be able to move along the optical axis to approach or move away from a display located on the second side, and enable the visual system to switch between a first state and a second state. The visual system can satisfy the following conditional expressions: 5.69≤fz / fm≤8.09, 1.78≤f23 / (TDm+TDn)≤7.01 and 2.00≤T12m / Δf≤4.70, wherein fz is the combined focal length of the first lens, the reflective polarizing element and the quarter wave plate, fm is the effective focal length of the visual system in the first state, f23 is the combined focal length of the second lens and the third lens, TDm is the distance on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the first state, TDn is the distance on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the second state, T12m is the distance on the optical axis from the second side surface of the first lens to the first side surface of the second lens when the visual system is in the first state, and Δf is the change in the effective focal length when the visual system switches from the first state to the second state.

[0004] In one embodiment, the center thickness CT2 of the second lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, and the distance ΔL that the second lens group moves along the optical axis when the visual system switches from the first state to the second state may satisfy: 3.55<(CT2+CT3) / ΔL<3.95.

[0005] In one embodiment, the radius of curvature R1 of the first side surface of the first lens and the effective focal length fn of the visual system in the second state may satisfy: 3.45≤R1 / fn≤4.52.

[0006] In one embodiment, 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 CTQ of the quarter-wave plate on the optical axis, and the distance T12n from the second side surface of the first lens to the first side surface of the second lens on the optical axis when the visual system is in the second state may satisfy: 4.7<(CT1+CTR+CTQ) / T12n<6.65.

[0007] In one embodiment, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens, and the change Δf of the effective focal length when the visual system switches from the first state to the second state may satisfy: 0.38mm≤|f2 / f3|×Δf≤2.08mm.

[0008] In one embodiment, when the visual system is in the second state, the distance TDn on the optical axis from the first side surface of the first lens to the second side surface of the third lens, the effective focal length f1 of the first lens, and the dispersion coefficient V1 of the first lens may satisfy: 5.0 <TDn / (f1 / V1)<7.9。

[0009] In one embodiment, when the visual system is in the second state, the distance BFLn from the second side surface of the third lens to the display on the optical axis and the distance T12n from the second side surface of the first lens to the first side surface of the second lens on the optical axis when the visual system is in the second state may satisfy: 3.75 <BFLn / T12n<6.95。

[0010] In one embodiment, the center thickness CT3 of the third lens on the optical axis and the distance BFLm from the second side surface of the third lens to the display on the optical axis when the visual system is in the first state may satisfy: 1.05 <CT3 / BFLm<1.45。

[0011] In one embodiment, the effective focal length f2 of the second lens, the curvature radius R4 of the second side surface of the second lens, and the distance T12m from the second side surface of the first lens to the first side surface of the second lens on the optical axis when the visual system is in the first state may satisfy: -6.81mm≤(f2 / R4)×T12m≤-3.74mm.

[0012] In one embodiment, the effective focal length f3 of the third lens, the curvature radius R5 of the first side surface of the third lens, and the distance BFLm from the second side surface of the third lens to the display on the optical axis when the visual system is in the first state may satisfy: 3.12 mm≤|f3 / R5|×BFLm≤6.12 mm.

[0013] In one embodiment, the effective focal length fn of the visual system in the second state and the distance ΔL that the second lens group moves along the optical axis during the process of switching the visual system from the first state to the second state may satisfy: 7.10≤fn / ΔL≤7.58.

[0014] In one embodiment, the entrance pupil diameter EPD of the visual system and the change Δf of the effective focal length when the visual system switches from the first state to the second state may satisfy: 4.82≤EPD / Δf≤12.15.

[0015] In one embodiment, the curvature radius R1 of the first side surface of the first lens, the curvature radius R6 of the second side surface of the third lens, and the distance ΔL that the second lens group moves along the optical axis when the visual system switches from the first state to the second state may satisfy: -4.33mm≤(R1 / R6)×ΔL≤-0.34mm.

[0016] In one embodiment, the combined focal length f23 of the second lens and the third lens, the effective focal length fm of the visual system in the first state, and the effective focal length fn of the visual system in the second state may satisfy: 1.61≤f23 / (fm+fn)≤5.84.

[0017] In one embodiment, the effective focal length f3 of the third lens and the distance TDm on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the first state may satisfy: 5.90≤|f3| / TDm≤12.19.

[0018] The visual system disclosed in the present application includes a first lens group and a second lens group in sequence from the first side to the second side along the optical axis, the first lens group includes a first lens, a reflective polarizing element and a quarter wave plate, the second lens group includes a second lens, a partial reflecting element and a third lens, wherein the first lens has positive optical focal length, the first side surface is a convex surface, and the second side surface is a plane; the second lens has positive optical focal length, and the second side surface is a convex surface; the third lens has positive optical focal length or negative optical focal length, the first side surface is a concave surface, and the second side surface is a convex surface; and the second lens and the third lens are double-cemented lenses glued to each other; the second lens group is configured to be able to move along the optical axis to approach or move away from a display located on the second side, and enable the visual system to switch between a first state and a second state; through reasonable configuration of the visual system, and the combined focal length fz of the first lens group and the visual system in the first When the effective focal length fm in one state satisfies the conditional expression 5.69≤fz / fm≤8.09, the combined focal length f23 of the second lens and the third lens and the distances TDm and TDn on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the first state and the second state respectively are controlled to satisfy the conditional expression 1.78≤f23 / (TDm+TDn)≤7.01, and the air gap T12m between the first lens and the second lens when the visual system is in the first state and the change Δf of the effective focal length when the visual system switches from the first state to the second state are controlled to satisfy the conditional expression 2.00≤T12m / Δf≤4.70. This can enable the optical system to realize the diopter adjustment function while reducing the total length of the system, ensuring the air gap between lenses, ensuring the overall processability of the system, and reducing the system stray light. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, purposes and advantages of the present application will become more apparent through the following detailed description of non-limiting embodiments in conjunction with the accompanying drawings. In the accompanying drawings: Figure 1 A schematic diagram showing the structure of the visual system according to Embodiment 1 of the present application when it is in the first state (+2D state); Figure 2 shows the MTF (Modulation Transfer Function) curve when the visual system of Example 1 is in the first state (+2D state); Figure 3 A schematic diagram showing the structure of the visual system according to Embodiment 1 of the present application when it is in the second state (-5D state); Figure 4 shows the MTF curve when the visual system of Example 1 is in the second state (-5D state); Figure 5 A schematic diagram showing the structure of the visual system according to Embodiment 2 of the present application when it is in the first state (+2D state); Figure 6 shows the MTF curve when the visual system of Example 2 is in the first state (+2D state); Figure 7 A schematic diagram of the structure of the visual system according to Embodiment 2 of the present application when it is in the second state (-5D state); Figure 8 shows the MTF curve when the visual system of Example 2 is in the second state (-5D state); Fig. 9 A schematic diagram of the structure of the visual system according to Embodiment 3 of the present application when it is in the first state (+2D state); Fig.10 shows the MTF curve when the visual system of Example 3 is in the first state (+2D state); Fig.11 A schematic diagram of the structure of the visual system according to Embodiment 3 of the present application when it is in the second state (-5D state); Fig.12 shows the MTF curve when the visual system of Example 3 is in the second state (-5D state); Fig.13 A schematic diagram of the structure of the visual system according to Embodiment 4 of the present application when it is in the first state (+2D state); Fig.14 shows the MTF curve when the visual system of Example 4 is in the first state (+2D state); Fig.15 A schematic diagram of the structure of the visual system according to Embodiment 4 of the present application when it is in the second state (-5D state); Fig.16 shows the MTF curve when the visual system of Example 4 is in the second state (-5D state); Fig.17 A schematic diagram of the structure of the visual system according to Embodiment 5 of the present application when it is in the first state (+2D state); Fig.18 shows the MTF curve when the visual system of Example 5 is in the first state (+2D state); Fig.19 A schematic diagram of the structure of the visual system according to Embodiment 5 of the present application when in the second state (-5D state); Fig. 20 The MTF curve of Example 5 when the visual system is in the second state (-5D state) is shown. DETAILED DESCRIPTION

[0020] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present application, and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0021] It should be noted that in this specification, the expressions of first, second, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching 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.

[0022] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0023] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the convex position 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 concave position is not defined, it means that the lens surface is concave at least in the paraxial region.

[0024] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0025] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0026] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] The features, principles and other aspects of the present application are described in detail below.

[0028] The visual system according to an exemplary embodiment of the present application may include a first lens group and a second lens group, wherein the first lens group may include a first lens, a reflective polarizing element and a quarter wave plate, and the second lens group may include a second lens, a partially reflecting element and a third lens. In an exemplary embodiment, the first lens group and the second lens group may be arranged in sequence from the first side to the second side along the optical axis. In an exemplary embodiment, the first lens, the reflective polarizing element, the quarter wave plate, the second lens, the partially reflecting element and the third lens may be arranged in sequence from the first side to the second side along the optical axis.

[0029] In an exemplary embodiment, the first lens may have positive optical power, its first side surface may be convex, and its second side surface may be flat.

[0030] In an exemplary embodiment, the second lens may have positive optical power, and the second side surface thereof may be convex.

[0031] In an exemplary embodiment, it may have positive optical power or negative optical power, its first side may be concave, and its second side may be convex.

[0032] In an exemplary embodiment, the second lens and the third lens may be double-cemented lenses that are bonded to each other. The bonding of the second lens and the third lens can reduce the total length of the system, which is conducive to miniaturization; can reduce the sensitivity of tolerance between lenses, which is conducive to ensuring production yield; can help balance various aberrations and improve resolution; and can also reduce reflection between lenses, reduce stray light ghost images, and help improve relative illumination.

[0033] In an exemplary embodiment, the reflective polarizing element may be disposed on or attached to the second side surface of the first lens; the quarter wave plate may be disposed on or attached to the second side surface of the reflective polarizing element. Exemplarily, the first side surface of the reflective polarizing element may at least partially conform to the second side surface of the first lens; the first side surface of the quarter wave plate may at least partially conform to the second side surface of the reflective polarizing element.

[0034] In an exemplary embodiment, the partial reflective element may be disposed between the second lens and the third lens, and the partial reflective element may be disposed on the second side surface of the second lens or may be disposed on the first side surface of the third lens. Exemplarily, the partial reflective element may be a semi-transparent and semi-reflective film layer coated on the second side surface of the second lens or the first side surface of the third lens.

[0035] By reasonably setting the structure of the visual system, the light path can be refracted, which can effectively shorten the length of the visual system body, reduce the volume and weight of the visual system, and realize the lightness of the visual system.

[0036] In an exemplary embodiment, the first side may be, for example, a human eye side, and the second side may be, for example, a display side. The visual system may be used in, for example, VR equipment, etc.

[0037] In an exemplary embodiment, the distance on the optical axis of the first lens group including the first lens, the reflective polarizing element and the quarter wave plate relative to the display or the image surface on the second side of the visual system can be fixed. The second lens group including the second lens, the partial reflective element and the third lens can be configured to be able to move along the optical axis to approach or move away from the display or the image surface on the second side of the visual system, and enable the visual system to switch between the first state and the second state. Specifically, when the second lens group moves to the position closest to the display or the image surface, the distance between the second lens group and the first lens group on the optical axis is the largest, and the visual system can be in the +2D state, that is, the first state; when the second lens group moves to the position farthest from the display or the image surface, the distance between the second lens group and the first lens group on the optical axis is the smallest, and the visual system can be in the -5D state, that is, the second state.

[0038] Exemplarily, when the visual system is in the first state, the diopter of the visual system is +2D, for example, it is applicable to users with a diopter of +2D; when the visual system is in the second state, the diopter of the visual system is -5D, for example, it is applicable to users with a diopter of -5D. Wherein, when the sign of the diopter is a negative sign, it may indicate that the user is a myopic user; when the sign of the diopter is a positive sign, it may indicate that the user is a hyperopic user; the specific value of the diopter may indicate the diopter of the user. For example, a diopter of +1D may indicate that the user's hyperopia is approximately 100 degrees, and a diopter of -1D may indicate that the user's myopia is approximately 100 degrees.

[0039] It should be understood that, in addition to the first state and the second state, the visual system according to the embodiment of the present application may also have other states, for example, between -5D and +2D. The visual system according to the embodiment of the present application can achieve continuous zooming within the range of -5D to +2D, which can meet the needs of users with different vision, so that users can enjoy the VR experience without wearing glasses.

[0040] In an exemplary embodiment, the visual system of the present application may include at least one aperture. The aperture may constrain the optical path and control the light intensity. The aperture may be set at an appropriate position of the visual system, for example, the aperture may be located between the first side (e.g., the human eye side) and the first lens.

[0041] In an exemplary embodiment, the visual system has different virtual image distances VID in the first state and the second state, and the virtual image distance may be, for example, the distance from the virtual image formed by the image light from the second side at a predetermined position to the aperture on the optical axis, wherein VID=1000 / diopter.

[0042] Reference below Figure 1 Give an example description of the visual system. Figure 1 As shown, the visual system according to the exemplary embodiment of the present application may include a first lens group G1 and a second lens group G2 arranged in sequence from the first side to the second side along the optical axis, the first lens group G1 includes a first lens E1, a reflective polarizing element RP and a quarter wave plate QWP arranged in sequence from the first side to the second side along the optical axis, wherein the reflective polarizing element RP is arranged on the second side of the first lens E1, and the quarter wave plate QWP is arranged on the second side of the reflective polarizing element RP; the second lens group G2 includes a second lens E2, a partial reflective element BS and a third lens E3 arranged in sequence from the first side to the second side along the optical axis, the second lens E2 and the third lens E3 are glued to each other, and the partial reflective element BS is arranged between the second lens E2 and the third lens E3. In actual use, the visual system according to the exemplary embodiment of the present application can be used as a VR lens, for example, in which case the first side corresponds to the human eye side, and the second side corresponds to the display or image surface side. The second side of the visual system has, for example, a display or an image surface IMG. The light beam emitted from IMG can sequentially pass through the third lens E3, the partial reflection element BS, the second lens E2, and the quarter-wave plate QWP to reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the quarter-wave plate QWP and the second lens E2 again to reach the partial reflection element BS. Afterwards, the light beam is reflected again at the partial reflection element BS and sequentially passes through the second lens E2, the quarter-wave plate QWP, the reflective polarizing element RP, and the first lens E1 to be directed toward the first side (for example Figure 1 The visual system provided by the present application folds the required optical path without affecting the projection quality by combining light reflection and refraction, thereby effectively shortening the main body length of the visual system.

[0043] In an exemplary embodiment, the visual system of the present application may satisfy the condition 5.69≤fz / fm≤8.09, wherein fz is the combined focal length of the first lens group, that is, the combined focal length of the first lens, the reflective polarizing element, and the quarter-wave plate; and fm is the effective focal length of the visual system in the +2D state.

[0044] In an exemplary embodiment, the visual system of the present application may satisfy the condition 1.78≤f23 / (TDm+TDn)≤7.01, wherein f23 is the combined focal length of the second lens and the third lens, TDm is the distance on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the +2D state, and TDn is the distance on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the -5D state.

[0045] In an exemplary embodiment, the visual system of the present application may satisfy the conditional formula 2.00≤T12m / Δf≤4.70, wherein T12m is the distance on the optical axis from the second side of the first lens to the first side of the second lens when the visual system is in the +2D state, that is, the air gap between the first lens and the second lens; Δf is the change in the effective focal length of the visual system when switching from the +2D state to the -5D state, that is, the difference between the effective focal length fm of the visual system in the +2D state and the effective focal length fn of the visual system in the -5D state.

[0046] According to the visual system of the exemplary embodiment of the present application, the first lens group and the second lens group are sequentially included from the first side to the second side along the optical axis, the first lens group includes a first lens, a reflective polarizing element and a quarter wave plate, the second lens group includes a second lens, a partial reflecting element and a third lens, wherein the first lens has positive optical focal length, the first side surface is convex, and the second side surface is flat; the second lens has positive optical focal length, and the second side surface is convex; the third lens has positive optical focal length or negative optical focal length, the first side surface is concave, and the second side surface is convex; and the second lens and the third lens are double-cemented lenses glued to each other; the second lens group is configured to be able to move along the optical axis to approach or move away from the display located on the second side, and enable the visual system to switch between the first state and the second state; through the reasonable configuration of the visual system, and the combined focal length fz of the first lens group and the visual When the effective focal length fm of the system in the first state satisfies the conditional expression 5.69≤fz / fm≤8.09, the combined focal length f23 of the second lens and the third lens and the distances TDm and TDn on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the first state and the second state respectively are controlled to satisfy the conditional expression 1.78≤f23 / (TDm+TDn)≤7.01, and the air gap T12m between the first lens and the second lens when the visual system is in the first state and the change Δf of the effective focal length when the visual system switches from the first state to the second state are controlled to satisfy the conditional expression 2.00≤T12m / Δf≤4.70. This can enable the optical system to realize the diopter adjustment function while reducing the total length of the system, ensuring the air gap between the lenses, ensuring the overall processability of the system, and reducing the system stray light.

[0047] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 3.55 < (CT2 + CT3) / ΔL < 3.95, where CT2 is the central thickness of the second lens on the optical axis, CT3 is the central thickness of the third lens on the optical axis, and ΔL is the distance that the second lens group moves along the optical axis during the process of the visual system switching from the +2D state to the -5D state. By controlling this conditional expression, while ensuring the processability of the lens, the overall length of the system can be reduced by reducing the total thickness of the two lenses.

[0048] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 3.45 ≤ R1 / fn ≤ 4.52, where R1 is the radius of curvature of the first side of the first lens, and fn is the effective focal length of the visual system in the -5D state. By controlling this conditional expression, the contribution of the first lens to the overall imaging of the system can be ensured, and the imaging performance of the system can be improved.

[0049] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 4.7 < (CT1 + CTR + CTQ) / T12n < 6.65, where CT1 is the central thickness of the first lens on the optical axis, CTR is the central thickness of the reflective polarizing element on the optical axis, CTQ is the central thickness of the quarter-wave plate on the optical axis, and T12n is the distance on the optical axis from the second side of the first lens to the first side of the second lens when the visual system is in the -5D state. By controlling this conditional expression, while ensuring the processability of components such as the lens, the overall length of the system can be reduced by reducing the thickness.

[0050] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 0.38 mm ≤ |f2 / f3| × Δf ≤ 2.08 mm, where f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and Δf is the change in the effective focal length of the visual system when switching from the +2D state to the -5D state. By reasonably controlling the range of this conditional expression, it can be ensured that when the second and third lenses move, the change in diopter meets the requirements.

[0051] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 5.0 < TDn / (f1 / V1) < 7.9, where TDn is the distance on the optical axis from the first side of the first lens to the second side of the third lens when the visual system is in the -5D state, f1 is the effective focal length of the first lens, and V1 is the dispersion coefficient of the first lens. By reasonably controlling the range of this conditional expression, the overall space occupied by the system can be reduced, making the product thinner and lighter.

[0052] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 3.75 < BFLn / T12n < 6.95, where BFLn is the distance from the second side of the third lens to the display on the optical axis in the -5D state of the visual system, and T12n is the distance from the second side of the first lens to the first side of the second lens on the optical axis in the -5D state of the visual system. By reasonably controlling the range of this conditional formula, it can be ensured that when the optical system performs diopter adjustment, the second lens and the third lens have sufficient moving space, so that the system can meet the requirements of adjustment in the range of -5D to +2D.

[0053] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 1.05 < CT3 / BFLm < 1.45, where CT3 is the central thickness of the third lens on the optical axis, and BFLm is the distance from the second side of the third lens to the display on the optical axis in the +2D state of the visual system. By reasonably controlling the range of this conditional formula, it can be ensured that when the optical system performs diopter adjustment, the third lens and the display do not interfere, and the processability of the system can be ensured.

[0054] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula -6.81 mm ≤ (f2 / R4) × T12m ≤ -3.74 mm, where f2 is the effective focal length of the second lens, R4 is the curvature radius of the second side of the second lens, and T12m is the distance from the second side of the first lens to the first side of the second lens on the optical axis in the +2D state of the visual system. By reasonably controlling the range of this conditional formula, it can be ensured that when the optical system performs diopter adjustment, the second lens and the third lens have sufficient moving space, so that the system can meet the requirements of adjustment in the range of -5D to +2D.

[0055] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 3.12 mm ≤ |f3 / R5| × BFLm ≤ 6.12 mm, where f3 is the effective focal length of the third lens, R5 is the curvature radius of the first side of the third lens, and BFLm is the distance from the second side of the third lens to the display on the optical axis in the +2D state of the visual system. By reasonably controlling the range of this conditional formula, the bonding yield of the third lens and the second lens can be increased while ensuring the system performance.

[0056] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 7.10≤fn / ΔL≤7.58, wherein fn is the effective focal length of the visual system in the -5D state, and ΔL is the distance that the second lens group moves along the optical axis during the process of the visual system switching from the +2D state to the -5D state. By reasonably controlling the range of this conditional expression, it can be ensured that there is enough space for each state of the visual system in the range of -5D to +2D, so that users can find the state that suits them more quickly when using it.

[0057] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 4.82≤EPD / Δf≤12.15, where EPD is the entrance pupil diameter of the visual system, and Δf is the change in effective focal length when the visual system switches from a +2D state to a -5D state. By reasonably controlling the range of this conditional expression, when the user uses the visual system, the entrance pupil diameter of the system can be larger than the pupil diameter of the human eye, thereby ensuring the performance of imaging of light emitted by the display screen in the human eye.

[0058] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula -4.33mm≤(R1 / R6)×ΔL≤-0.34mm, where R1 is the radius of curvature of the first side surface of the first lens, R6 is the radius of curvature of the second side surface of the third lens, and ΔL is the distance that the second lens group moves along the optical axis during the process of the visual system switching from the +2D state to the -5D state. By reasonably controlling the range of this conditional formula, while ensuring the imaging performance of the system, the first lens and the third lens will not be difficult to process due to excessive curvature, thereby improving the processability of the first lens and the third lens.

[0059] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 1.61≤f23 / (fm+fn)≤5.84, wherein f23 is the combined focal length of the second lens and the third lens, fm is the effective focal length of the visual system in the +2D state, and fn is the effective focal length of the visual system in the -5D state. By reasonably controlling the range of this conditional formula, light can be better converged and the imaging performance of the system can be improved.

[0060] In an exemplary embodiment, the visual system of the present application can satisfy the conditional expression 5.90≤|f3| / TDm≤12.19, wherein f3 is the effective focal length of the third lens, and TDm is the distance on the optical axis from the first side of the first lens to the second side of the third lens when the visual system is in the +2D state. By reasonably controlling the range of this conditional expression, the light can be better converged, and the lens sensitivity tolerance can be reduced while meeting the imaging requirements.

[0061] In the visual system according to the implementation mode of the present application, there may be one or more aspherical lenses among the first lens, the second lens and the third lens. The aspherical lens has a better curvature radius characteristic and has the advantages of improving distortion aberration and improving astigmatism aberration. After using the aspherical lens, the aberration occurring during imaging can be eliminated as much as possible, thereby improving the imaging quality.

[0062] On the one hand, according to the visual system of the exemplary embodiment of the present application, a first lens group and a second lens group are sequentially included from the first side to the second side along the optical axis, the first lens group includes a first lens, a reflective polarizing element and a quarter wave plate, and the second lens group includes a second lens, a partial reflective element and a third lens, wherein the first lens has positive optical focal length, the first side surface is convex, and the second side surface is flat; the second lens has positive optical focal length, and the second side surface is convex; the third lens has positive optical focal length or negative optical focal length, the first side surface is concave, and the second side surface is convex; and the second lens and the third lens are double-cemented lenses glued to each other; the second lens group is configured to be able to move along the optical axis to approach or move away from the display located on the second side, and enable the visual system to switch between the first state and the second state; through the reasonable configuration of the visual system, and when the combined focal length fz of the first lens group is When the effective focal length fm of the visual system in the first state satisfies the conditional expression 5.69≤fz / fm≤8.09, the combined focal length f23 of the second lens and the third lens and the distances TDm and TDn on the optical axis from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the first state and the second state respectively are controlled to satisfy the conditional expression 1.78≤f23 / (TDm+TDn)≤7.01, and the air gap T12m between the first lens and the second lens when the visual system is in the first state and the change Δf of the effective focal length of the visual system when it switches from the first state to the second state are controlled to satisfy the conditional expression 2.00≤T12m / Δf≤4.70. This can enable the optical system to realize the diopter adjustment function while reducing the total length of the system, ensuring the air gap between lenses, ensuring the overall processability of the system, and reducing the system stray light.

[0063] On the other hand, according to the visual system of the exemplary embodiment of the present application, the first lens group and the second lens group are sequentially included from the first side to the second side along the optical axis, the first lens group includes a first lens, a reflective polarizing element and a quarter wave plate, the second lens group includes a second lens, a partial reflecting element and a third lens, wherein the first lens has positive optical focal length, the first side surface is convex, and the second side surface is flat; the second lens has positive optical focal length, and the second side surface is convex; the third lens has positive optical focal length or negative optical focal length, the first side surface is concave, and the second side surface is convex; and the second lens and the third lens are double-cemented lenses glued to each other; the second lens group is configured to be able to move along the optical axis to approach or move away from the display located on the second side, and enable the visual system to switch between the first state and the second state; through the reasonable configuration of the visual system, and when the combined focal length fz of the first lens group and the effective focal length fm of the visual system in the first state satisfy the condition When the formula 5.69≤fz / fm≤8.09 is used, the combined focal length f23 of the second lens and the third lens is controlled to satisfy the condition 1.78≤f23 / (TDm+TDn)≤7.01 from the first side surface of the first lens to the second side surface of the third lens when the visual system is in the first state and the second state, respectively. The curvature radius R1 of the first side surface of the first lens, the curvature radius R6 of the second side surface of the third lens, and the distance ΔL moved by the second lens group along the optical axis during the switching of the visual system from the first state to the second state satisfy the condition -4.33mm≤(R1 / R6)×ΔL≤-0.34mm. This enables the optical system to realize the diopter adjustment function, reduces the total length of the system, ensures the imaging performance of the system, and prevents the first lens and the third lens from being difficult to process due to excessive curvature, thereby improving the machinability of the first lens and the third lens.

[0064] According to the visual system of the exemplary embodiment of the present application, a three-piece glued folding optical solution is adopted, for example. Through the reasonable configuration of the system structure and parameters, it is possible to reduce the total optical length and the total amount of the system, realize the miniaturization and lightweight of the system, and improve the user comfort; the system can also achieve zoom in the range of -5D to +2D through the movement of the second lens group to meet the needs of users with different vision, and users can enjoy the VR experience without wearing glasses; at the same time, it can also effectively reduce the reflected stray light between the lenses, reduce the risk of ghost images in the imaging, and is conducive to improving the imaging quality of the system.

[0065] In addition, the present application also provides a VR device, which may include the visual system provided by any of the above-mentioned embodiments, wherein the first side may be the human eye side, and the second side may be the display / image surface side. The VR device may have the characteristics of miniaturization, lightness, and high imaging quality, and may achieve zooming within the range of -5D to +2D, so that users with different vision conditions can clearly enjoy the VR experience without wearing glasses, thereby enabling users to obtain a better application experience.

[0066] Specific embodiments of the visual system applicable to the above-mentioned embodiments are further described below with reference to the accompanying drawings.

[0067] Example 1

[0068] The following reference Figures 1 to 4 Describe the visual system according to Example 1 of the present application.

[0069] The visual system according to Example 1 of the present application includes, in sequence from the first side to the second side along the optical axis: a first lens group G1 and a second lens group G2, wherein the first lens group G1 includes a first lens E1, a reflective polarizing element RP and a quarter-wave plate QWP arranged in sequence from the first side to the second side along the optical axis, the reflective polarizing element RP is disposed on the second side of the first lens E1, and the quarter-wave plate QWP is disposed on the second side of the reflective polarizing element RP; the second lens group G2 includes a second lens E2, a partial reflection element BS and a third lens E3 arranged in sequence from the first side to the second side along the optical axis, the second lens E2 and the third lens E3 are glued to each other, and the partial reflection element BS is disposed between the second lens E2 and the third lens E3.

[0070] In this example, the first lens E1 has positive optical power, its first side surface is convex, and its second side surface is flat; the second lens E2 has positive optical power, its first side surface is convex, and its second side surface is convex; the third lens E3 has negative optical power, its first side surface is concave, and its second side surface is convex.

[0071] In this example, a stop STO may be provided on the first side of the visual system, and a display / image surface IMG may be provided on the second side of the visual system. The first lens group G1: the first lens E1, the reflective polarizing element RP and the quarter-wave plate QWP are relatively fixed in distance from the display / image surface IMG along the optical axis; the second lens group G2: the second lens E2, the partial reflection element BS and the third lens E3 can move along the optical axis to approach or move away from the display / image surface IMG, and in this process the visual system can achieve zooming in the range of -5D to +2D. Figure 1 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the position closest to the display / image plane IMG, and at this time the visual system is in a +2D state. Figure 3 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the farthest position from the display / image plane IMG, and at this time the visual system is in a -5D state.

[0072] like Figure 1 and Figure 3 As shown, in a specific application of the visual system according to this example, for example, image light from the display / image surface IMG can sequentially pass through the third lens E3, the partial reflection element BS, the second lens E2 and the quarter wave plate QWP to reach the reflective polarizing element RP, be reflected at the reflective polarizing element RP and pass through the quarter wave plate QWP and the second lens E2 again to reach the partial reflection element BS, and then the light beam is reflected again at the partial reflection element BS and sequentially passes through the second lens E2, the quarter wave plate QWP, the reflective polarizing element RP and the first lens E1 to the aperture and finally forms an image at a predetermined position. For example, the light of the visual system after two reflections can finally be projected to the user's pupil.

[0073] Table 1 shows the basic parameters of the visual system of Example 1, wherein the units of the radius of curvature and thickness / distance are both millimeters (mm).

[0074] Table 1

[0075] The parameters D1 to D5 in Table 1 can be understood as follows: D5 can be understood as the value taken along the optical axis from the display / image surface IMG to the second side surface of the third lens E3; D4 can be understood as the value taken along the optical axis from the first side surface of the second lens E2 to the second side surface of the quarter-wave plate QWP; D3 can be understood as the value taken along the optical axis from the second side surface of the quarter-wave plate QWP to the first side surface of the second lens E2; D2 can be understood as the value taken along the optical axis from the first side surface of the second lens E2 to the second side surface of the quarter-wave plate QWP; D1 can be understood as the value of the virtual image distance of the visual system according to this embodiment. In the process of realizing zooming by moving the second lens group G2 along the optical axis of the visual system according to this embodiment, the values ​​of the above parameters D1 to D5 will change accordingly. The visual system is Figure 1 The +2D state shown and Figure 3 The values ​​of parameters D1 to D5 in the -5D state are shown in Table 2 below.

[0076] Table 2

[0077] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the bonding surface S14 of the second lens E2 and the third lens E3, and the second side surface S15 of the third lens E3 are all aspherical surfaces. The surface shape of each aspherical lens can be defined by but not limited to the following aspherical surface formula: (1) in, The aspheric surface is at a height of h When the position is , the distance vector height from the vertex of the aspherical surface; c is the paraxial curvature of the aspheric surface, c =1 / R (i.e., paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the cone coefficient; Ai Aspheric i Table 3 below lists the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, 10 , A 12 , A 14 , A 16 , A 18 and A 20 .

[0078] Table 3

[0079] Figure 2 It shows that the visual system according to this embodiment is in Figure 1 The MTF curve in the +2D state is shown. Figure 4 It shows that the visual system according to this embodiment is in Figure 3 The MTF curve in the -5D state shown in the figure can represent the optical modulation function values ​​corresponding to different spatial frequencies. Figure 2 and Figure 4 It can be seen that the visual system provided in this embodiment can achieve good imaging quality in two different focal length states of +2D and -5D.

[0080] Example 2

[0081] The following reference Figures 5 to 8 The visual system according to Embodiment 2 of the present application is described. In this embodiment and the following embodiments, for the sake of brevity, some descriptions similar to Embodiment 1 will be omitted.

[0082] In this embodiment, the visual system also includes a first lens group G1 and a second lens group G2 arranged in sequence from the first side to the second side along the optical axis. The first lens group G1 includes a first lens E1, a reflective polarizing element RP and a quarter wave plate QWP arranged in sequence from the first side to the second side along the optical axis, the reflective polarizing element RP is arranged on the second side of the first lens E1, and the quarter wave plate QWP is arranged on the second side of the reflective polarizing element RP; the second lens group G2 includes a second lens E2, a partial reflection element BS and a third lens E3 arranged in sequence from the first side to the second side along the optical axis, the second lens E2 and the third lens E3 are glued to each other, and the partial reflection element BS is arranged between the second lens E2 and the third lens E3.

[0083] In this embodiment, the first lens E1 has positive power, its first side surface is convex, and its second side surface is flat; the second lens E2 has positive power, its first side surface is convex, and its second side surface is convex; the third lens E3 has negative power, its first side surface is concave, and its second side surface is convex.

[0084] Table 4 shows basic parameters of the visual system according to this embodiment.

[0085] Table 4

[0086] In this example, a stop STO may be provided on the first side of the visual system, and a display / image surface IMG may be provided on the second side of the visual system. The first lens group G1: the first lens E1, the reflective polarizing element RP and the quarter-wave plate QWP are relatively fixed in distance from the display / image surface IMG along the optical axis; the second lens group G2: the second lens E2, the partial reflection element BS and the third lens E3 can move along the optical axis to approach or move away from the display / image surface IMG, and in this process the visual system can achieve zooming in the range of -5D to +2D. Figure 5 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the position closest to the display / image plane IMG, and at this time the visual system is in a +2D state. Figure 7 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the farthest position from the display / image plane IMG, and at this time the visual system is in a -5D state.

[0087] According to the visual system of this embodiment, Figure 5 The +2D state shown and Figure 7 In the -5D state shown, the values ​​of parameters D1 to D5 in Table 4 are respectively shown in Table 5 below.

[0088] Table 5

[0089] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the bonding surface S14 of the second lens E2 and the third lens E3, and the second side surface S15 of the third lens E3 are all aspherical surfaces. The surface shape of each aspherical surface can be calculated using the formula (1) in Example 1. The following Table 6 lists the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, A 10 , A 12 , A 14 , A 16 , A 18 and A 20 .

[0090] Table 6

[0091] Figure 6 It shows that the visual system according to this embodiment is in Figure 5 The MTF curve in the +2D state is shown. Figure 8 It shows that the visual system according to this embodiment is in Figure 7 The MTF curve in the -5D state is shown by Figure 6 and Figure 8 It can be seen that the visual system provided in this embodiment can achieve good imaging quality in two different focal length states of +2D and -5D.

[0092] Example 3

[0093] The following reference Figures 9 to 12 Describe the visual system according to Example 3 of the present application.

[0094] In this embodiment, the visual system also includes a first lens group G1 and a second lens group G2 arranged in sequence from the first side to the second side along the optical axis. The first lens group G1 includes a first lens E1, a reflective polarizing element RP and a quarter wave plate QWP arranged in sequence from the first side to the second side along the optical axis, the reflective polarizing element RP is arranged on the second side of the first lens E1, and the quarter wave plate QWP is arranged on the second side of the reflective polarizing element RP; the second lens group G2 includes a second lens E2, a partial reflection element BS and a third lens E3 arranged in sequence from the first side to the second side along the optical axis, the second lens E2 and the third lens E3 are glued to each other, and the partial reflection element BS is arranged between the second lens E2 and the third lens E3.

[0095] In this embodiment, the first lens E1 has positive power, its first side surface is convex, and its second side surface is flat; the second lens E2 has positive power, its first side surface is convex, and its second side surface is convex; the third lens E3 has negative power, its first side surface is concave, and its second side surface is convex.

[0096] Table 7 shows basic parameters of the visual system according to this embodiment.

[0097] Table 7

[0098] In this example, a stop STO may be provided on the first side of the visual system, and a display / image surface IMG may be provided on the second side of the visual system. The first lens group G1: the first lens E1, the reflective polarizing element RP and the quarter-wave plate QWP are relatively fixed in distance from the display / image surface IMG along the optical axis; the second lens group G2: the second lens E2, the partial reflection element BS and the third lens E3 can move along the optical axis to approach or move away from the display / image surface IMG, and in this process the visual system can achieve zooming in the range of -5D to +2D. Fig. 9 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the position closest to the display / image plane IMG, and at this time the visual system is in a +2D state. Fig.11 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the farthest position from the display / image plane IMG, and at this time the visual system is in a -5D state.

[0099] According to the visual system of this embodiment, Fig. 9 The +2D state shown and Fig.11 In the -5D state shown, the values ​​of parameters D1 to D5 in Table 7 are respectively shown in Table 8 below.

[0100] Table 8

[0101] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the bonding surface S14 of the second lens E2 and the third lens E3, and the second side surface S15 of the third lens E3 are all aspherical surfaces. The surface shape of each aspherical surface can be calculated using the formula (1) in Example 1. The following Table 9 lists the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, A 10 , A 12 , A 14 , A 16 , A 18 and A 20 .

[0102] Table 9

[0103] Fig.10 It shows that the visual system according to this embodiment is in Fig. 9 The MTF curve in the +2D state is shown. Fig.12 It shows that the visual system according to this embodiment is in Fig.11 The MTF curve in the -5D state is shown by Fig.10 and Fig.12 It can be seen that the visual system provided in this embodiment can achieve good imaging quality in two different focal length states of +2D and -5D.

[0104] Example 4

[0105] The following reference Figures 13 to 16 Describe the visual system according to Example 4 of the present application.

[0106] In this example, the visual system also includes a first lens group G1 and a second lens group G2 arranged in sequence from the first side to the second side along the optical axis. The first lens group G1 includes a first lens E1, a reflective polarizing element RP and a quarter wave plate QWP arranged in sequence from the first side to the second side along the optical axis, the reflective polarizing element RP is arranged on the second side of the first lens E1, and the quarter wave plate QWP is arranged on the second side of the reflective polarizing element RP; the second lens group G2 includes a second lens E2, a partial reflection element BS and a third lens E3 arranged in sequence from the first side to the second side along the optical axis, the second lens E2 and the third lens E3 are glued to each other, and the partial reflection element BS is arranged between the second lens E2 and the third lens E3.

[0107] In this embodiment, the first lens E1 has positive power, its first side surface is convex, and its second side surface is flat; the second lens E2 has positive power, its first side surface is convex, and its second side surface is convex; the third lens E3 has positive power, its first side surface is concave, and its second side surface is convex.

[0108] Table 10 shows basic parameters of the visual system according to this embodiment.

[0109] Table 10

[0110] In this example, a stop STO may be provided on the first side of the visual system, and a display / image surface IMG may be provided on the second side of the visual system. The first lens group G1: the first lens E1, the reflective polarizing element RP and the quarter-wave plate QWP are relatively fixed in distance from the display / image surface IMG along the optical axis; the second lens group G2: the second lens E2, the partial reflection element BS and the third lens E3 can move along the optical axis to approach or move away from the display / image surface IMG, and in this process the visual system can achieve zooming in the range of -5D to +2D. Fig.13 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the position closest to the display / image plane IMG, and at this time the visual system is in a +2D state. Fig.15 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the farthest position from the display / image plane IMG, and at this time the visual system is in a -5D state.

[0111] According to the visual system of this embodiment, Fig.13 The +2D state shown and Fig.15 In the -5D state shown, the values ​​of parameters D1 to D5 in Table 10 are respectively shown in Table 11 below.

[0112] Table 11

[0113] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the bonding surface S14 of the second lens E2 and the third lens E3, and the second side surface S15 of the third lens E3 are all aspherical surfaces. The surface shape of each aspherical surface can be calculated using the formula (1) in Example 1. The following Table 12 lists the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, 10 , A 12 , A 14 , A 16 , A 18 and A 20 .

[0114] Table 12

[0115] Fig.14 It shows that the visual system according to this embodiment is in Fig.13 The MTF curve in the +2D state is shown. Fig.16 It shows that the visual system according to this embodiment is in Fig.15 The MTF curve in the -5D state is shown by Fig.14 and Fig.16It can be seen that the visual system provided in this embodiment can achieve good imaging quality in two different focal length states of +2D and -5D.

[0116] Example 5

[0117] The following reference Figures 17 to 20 Describe the visual system according to Example 5 of the present application.

[0118] In this example, the visual system also includes a first lens group G1 and a second lens group G2 arranged in sequence from the first side to the second side along the optical axis. The first lens group G1 includes a first lens E1, a reflective polarizing element RP and a quarter wave plate QWP arranged in sequence from the first side to the second side along the optical axis, the reflective polarizing element RP is arranged on the second side of the first lens E1, and the quarter wave plate QWP is arranged on the second side of the reflective polarizing element RP; the second lens group G2 includes a second lens E2, a partial reflection element BS and a third lens E3 arranged in sequence from the first side to the second side along the optical axis, the second lens E2 and the third lens E3 are glued to each other, and the partial reflection element BS is arranged between the second lens E2 and the third lens E3.

[0119] In this embodiment, the first lens E1 has positive optical power, its first side surface is convex, and its second side surface is flat; the second lens E2 has positive optical power, its first side surface is concave, and its second side surface is convex; the third lens E3 has positive optical power, its first side surface is concave, and its second side surface is convex.

[0120] Table 13 shows basic parameters of the visual system according to this embodiment.

[0121] Table 13

[0122] In this example, a stop STO may be provided on the first side of the visual system, and a display / image surface IMG may be provided on the second side of the visual system. The first lens group G1: the first lens E1, the reflective polarizing element RP and the quarter-wave plate QWP are relatively fixed in distance from the display / image surface IMG along the optical axis; the second lens group G2: the second lens E2, the partial reflection element BS and the third lens E3 can move along the optical axis to approach or move away from the display / image surface IMG, and in this process the visual system can achieve zooming in the range of -5D to +2D. Fig.17 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the position closest to the display / image plane IMG, and at this time the visual system is in a +2D state. Fig.19 It shows a schematic diagram of the structure of the visual system when the second lens group G2 moves along the optical axis to the farthest position from the display / image plane IMG, and at this time the visual system is in a -5D state.

[0123] According to the visual system of this embodiment, Fig.17 The +2D state shown and Fig.19 In the -5D state shown, the values ​​of parameters D1 to D5 in Table 13 are respectively shown in Table 14 below.

[0124] Table 14

[0125] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the bonding surface S14 of the second lens E2 and the third lens E3, and the second side surface S15 of the third lens E3 are all aspherical surfaces. The surface shape of each aspherical surface can be calculated using the formula (1) in Example 1. The following Table 15 lists the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, 10 , A 12 , A 14 , A 16 , A 18 and A 20 .

[0126] Table 15

[0127] Fig.18 It shows that the visual system according to this embodiment is in Fig.17 The MTF curve in the +2D state is shown. Fig. 20 It shows that the visual system according to this embodiment is in Fig.19 The MTF curve in the -5D state is shown by Fig.18 and Fig. 20 It can be seen that the visual system provided in this embodiment can achieve good imaging quality in two different focal length states of +2D and -5D.

[0128] In summary, in Examples 1 to 5, the effective focal length fm of the visual system in the +2D state, the effective focal length fn of the visual system in the -5D state, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens, the combined focal length f23 of the second lens and the third lens, the combined focal length fz of the first lens, the reflective polarizing element and the quarter-wave plate, the entrance pupil diameter EPD of the visual system, the distance TDm on the optical axis from the first side surface of the first lens to the second side surface of the third lens in the +2D state of the visual system, the distance TDn on the optical axis from the first side surface of the first lens to the second side surface of the third lens in the -5D state of the visual system, the distance TDn on the optical axis from the first side surface of the first lens to the second side surface of the third lens in the +2D state of the visual system, and the distance TDn on the optical axis from the first side surface of the first lens to the second side surface of the third lens in the -5D state of the visual system The distance T12m from the second side surface of the first lens to the first side surface of the second lens on the optical axis in the D state, the distance T12n from the second side surface of the first lens to the first side surface of the second lens on the optical axis in the visual system in the -5D state, the distance BFLm from the second side surface of the third lens to the display / image plane on the optical axis in the +2D state of the visual system, the distance BFLn from the second side surface of the third lens to the display / image plane on the optical axis in the -5D state of the visual system, the distance ΔL that the second lens group moves along the optical axis when the visual system switches from the +2D state to the -5D state, and the change Δf in the effective focal length of the system when the visual system switches from the +2D state to the -5D state are shown in Table 16 below.

[0129] Table 16

[0130] In addition, Example 1 to Example 5 respectively satisfy the conditions shown in Table 17 below.

[0131] Table 17

[0132] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. 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 a specific combination of the above technical features, but 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 above features are replaced with the technical features with similar functions disclosed in the present application (but not limited to) to form a technical solution.

Claims

1. A visual system, characterized in that: The lens comprises a first lens group and a second lens group in order from the first side to the second side along the optical axis; The first lens group includes a first lens, a reflective polarizing element and a quarter wave plate, wherein the first lens has positive optical power, a first side surface is a convex surface, and a second side surface is a flat surface; The second lens group includes a second lens, a partial reflection element and a third lens, wherein the second lens has positive optical power, and its second side surface is a convex surface; the third lens has positive optical power or negative optical power, its first side surface is a concave surface, and its second side surface is a convex surface; and the second lens and the third lens are a cemented lens; The second lens group is configured to be movable along the optical axis to be closer to or farther from the display located at the second side, and to switch the visual system between a first state and a second state; and The visual system meets the following requirements: 5.69≤fz / fm≤8.09; 1.78≤f23 / (TDm+TDn)≤7.01; 2.00≤T12m / Δf≤4.70; Among them, fz is the combined focal length of the first lens, the reflective polarizing element and the quarter-wave plate, fm is the effective focal length of the visual system in the first state, f23 is the combined focal length of the second lens and the third lens, TDm is the distance from the first side of the first lens to the second side of the third lens on the optical axis when the visual system is in the first state, TDn is the distance from the first side of the first lens to the second side of the third lens on the optical axis when the visual system is in the second state, T12m is the distance from the second side of the first lens to the first side of the second lens on the optical axis when the visual system is in the first state, and Δf is the change in the effective focal length of the visual system when it switches from the first state to the second state.

2. The visual system according to claim 1, characterized in that: The center thickness CT2 of the second lens on the optical axis, the center thickness CT3 of the third lens on the optical axis, and the distance ΔL moved by the second lens group along the optical axis during the process of the visual system switching from the first state to the second state satisfy: 3.55<(CT2+CT3) / ΔL<3.

95.

3. The visual system according to claim 1, characterized in that: The curvature radius R1 of the first side surface of the first lens and the effective focal length fn of the visual system in the second state satisfy: 3.45≤R1 / fn≤4.

52.

4. The visual system according to claim 1, 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 CTQ of the quarter-wave plate on the optical axis, and the distance T12n from the second side surface of the first lens to the first side surface of the second lens on the optical axis when the visual system is in the second state satisfy: 4.7<(CT1+CTR+CTQ) / T12n<6.

65.

5. The visual system according to claim 1, characterized in that: The effective focal length f2 of the second lens and the effective focal length f3 of the third lens satisfy: 0.38mm≤|f2 / f3|×Δf≤2.08mm.

6. The visual system according to claim 1, characterized in that: The effective focal length f1 of the first lens and the dispersion coefficient V1 of the first lens satisfy: 5.0 <TDn / (f1 / V1)<7.9。 7. The visual system according to claim 1, characterized in that: When the visual system is in the second state, the distance BFLn from the second side surface of the third lens to the display on the optical axis and the distance T12n from the second side surface of the first lens to the first side surface of the second lens on the optical axis when the visual system is in the second state satisfy: 3.75 <BFLn / T12n<6.95。 8. The visual system according to claim 1, characterized in that: The center thickness CT3 of the third lens on the optical axis and the distance BFLm from the second side surface of the third lens to the display on the optical axis when the visual system is in the first state satisfy: 1.05 <CT3 / BFLm<1.45。 9. The visual system according to claim 1, characterized in that: The effective focal length f2 of the second lens and the curvature radius R4 of the second side surface of the second lens satisfy: -6.81mm≤(f2 / R4)×T12m≤-3.74mm.

10. The visual system according to claim 1, characterized in that: The effective focal length f3 of the third lens, the curvature radius R5 of the first side surface of the third lens, and the distance BFLm from the second side surface of the third lens to the display on the optical axis when the visual system is in the first state satisfy: 3.12mm≤|f3 / R5|×BFLm≤6.12mm.

11. The visual system according to claim 1, characterized in that: The effective focal length fn of the visual system in the second state and the distance ΔL moved by the second lens group along the optical axis during the process of switching the visual system from the first state to the second state satisfy: 7.10≤fn / ΔL≤7.

58.

12. The visual system according to claim 1, characterized in that: The entrance pupil diameter EPD of the visual system satisfies: 4.82≤EPD / Δf≤12.

15.

13. The visual system according to claim 1, characterized in that: The curvature radius R1 of the first side surface of the first lens, the curvature radius R6 of the second side surface of the third lens, and the distance ΔL that the second lens group moves along the optical axis during the process of switching the visual system from the first state to the second state satisfy: -4.33mm≤(R1 / R6)×ΔL≤-0.34mm.

14. The visual system according to claim 1, characterized in that: The effective focal length fn of the visual system in the second state satisfies: 1.61≤f23 / (fm+fn)≤5.

84.

15. The visual system according to claim 1, characterized in that: The effective focal length f3 of the third lens satisfies: 5.90≤|f3| / TDm≤12.19.

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