Visual system

Abstract

The present application discloses a visual system, which sequentially includes a first lens group and a second lens group along the optical axis from a first side to a second side. The first lens group includes a first lens with a positive optical power, a reflective polarizing element, and a quarter-wave plate. The second lens group includes a second lens with a positive optical power, a partially reflective element, and a third lens, and the second and third lenses are cemented together. 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 satisfy 5.69 ≤ fz / fm ≤ 8.09. The combined focal length f23 of the second and third lenses and the axial distances TDm and TDn from the first side of the first lens to the second side of the third lens when the system is in the first state and the second state respectively satisfy 1.78 ≤ f23 / (TDm + TDn) ≤ 7.01. The air gap T12m between the first and second lenses when the system is in the first state and the change amount Δf of the effective focal length of the system when switching from the first state to the second state satisfy 2.00 ≤ T12m / Δf ≤ 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 visual systems of various VR devices has changed from the Fresnel solution to the catadioptric solution. The catadioptric solution can significantly shorten the total length of the system, and can have better display performance, and can also provide functions such as diopter adjustment, having advantages in many aspects. However, for the catadioptric solution, especially when using multiple lenses, reflections between the lenses will also cause more problems such as ghosts and stray light in the final image, affecting the imaging quality; in addition, the system is still continuously developing towards miniaturization and light weight, and the processability of the system still needs to be continuously improved. Summary of the Invention

[0003] The present application provides a visual system, which may sequentially include a first lens group and a second lens group along the optical axis from the first side to the second side; the first lens group includes a first lens, a reflective polarizing element, and a quarter-wave plate, wherein the first lens has a positive optical power, its first side is convex, and its second side is flat; the second lens group includes a second lens, a partial reflection element, and a third lens, wherein the second lens has a positive optical power, its second side is convex; the third lens has a positive or negative optical power, its first side is concave, and its second side is convex; and the second lens and the third lens are a cemented doublet lens; 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 to switch the visual system between a first state and a second state. The visual system can satisfy the conditions: 5.69 ≤ fz / fm ≤ 8.09, 1.78 ≤ f23 / (TDm + TDn) ≤ 7.01, and 2.00 ≤ T12m / Δf ≤ 4.70, where 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 of the first lens to the second side 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 of the first lens to the second side 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 of the first lens to the first side of the second lens when the visual system is in the first state, and Δf is the change in the effective focal length of the visual system when switching from the first state to the second state.

[0004] In one embodiment, the central thickness CT2 of the second lens on the optical axis, the central thickness CT3 of the third lens on the optical axis, and the distance ΔL that the second lens group moves 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.

[0005] In one embodiment, the radius of curvature R1 of the first side 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.

[0006] In one 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 CTQ of the quarter-wave plate on the optical axis, and the distance T12n 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 second state 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 amount Δf of the effective focal length of the visual system when switching from the first state to the second state satisfy: 0.38 mm ≤ |f2 / f3|×Δf ≤ 2.08 mm.

[0008] In one embodiment, the distance TDn 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 second state, 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.

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

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

[0011] In one embodiment, the effective focal length f2 of the second lens, the radius of curvature R4 of the second side of the second lens, and the distance T12m 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 first state satisfy: -6.81 mm ≤ (f2 / R4)×T12m ≤ -3.74 mm.

[0012] In one embodiment, the effective focal length f3 of the third lens, the radius of curvature 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 the visual system switching 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 amount Δf of the effective focal length of the visual system during the process of switching from the first state to the second state may satisfy: 4.82 ≤ EPD / Δf ≤ 12.15.

[0015] In one embodiment, the radius of curvature R1 of the first side surface of the first lens, the radius of curvature 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 the visual system switching from the first state to the second state may satisfy: -4.33 mm ≤ (R1 / R6) × ΔL ≤ -0.34 mm.

[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 from the first side surface of the first lens to the second side surface of the third lens on the optical axis when the visual system is in the first state may satisfy: 5.90 ≤ |f3| / TDm ≤ 12.19.

[0018] The visual system disclosed in this application sequentially includes a first lens group and a second lens group along the optical axis from the first side to the second side. 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 partially reflective element, and a third lens. Among them, the first lens has a positive optical power, the first side is convex, and the second side is flat; the second lens has a positive optical power, and the second side is convex; the third lens has a positive or negative optical power, the first side is concave, and the second side is convex; and the second lens and the third lens are a cemented doublet lens; the second lens group is configured to be movable along the optical axis to approach or move away from the display located on the second side, and to switch the visual system between a first state and a 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 conditional formula 5.69 ≤ fz / fm ≤ 8.09, at the same time, controlling 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 of the first lens to the second side of the third lens when the visual system is in the first state and the second state respectively to satisfy the conditional formula 1.78 ≤ f23 / (TDm + TDn) ≤ 7.01, and controlling the air gap T12m between the first lens and the second lens when the visual system is in the first state and the change amount Δf of the effective focal length when the visual system switches from the first state to the second state to satisfy the conditional formula 2.00 ≤ T12m / Δf ≤ 4.70, it is possible to realize the diopter adjustment function of the optical system while reducing the overall length of the system, ensuring the air gap between the lenses, guaranteeing the overall processability of the system, and reducing the stray light of the system. Description of the Drawings

[0019] Combined with the drawings, through the detailed description of the following non-limiting embodiments, other features, purposes, and advantages of this application will become more obvious. In the drawings:

[0020] Figure 1 The structural schematic diagram of the visual system according to Embodiment 1 of this application in the first state (+2D state) is shown;

[0021] Figure 2 The MTF (Modulation Transfer Function) curve of the visual system according to Embodiment 1 in the first state (+2D state) is shown;

[0022] Figure 3 The structural schematic diagram of the visual system according to Embodiment 1 of this application in the second state (-5D state) is shown;

[0023] Figure 4 The MTF curve of the visual system according to Embodiment 1 in the second state (-5D state) is shown;

[0024] Figure 5 Shows the schematic structural diagram of the visual system according to Embodiment 2 of the present application when in the first state (+2D state);

[0025] Figure 6 Shows the MTF curve of the visual system according to Embodiment 2 when in the first state (+2D state);

[0026] Figure 7 Shows the schematic structural diagram of the visual system according to Embodiment 2 of the present application when in the second state (-5D state);

[0027] Figure 8 Shows the MTF curve of the visual system according to Embodiment 2 when in the second state (-5D state);

[0028] Figure 9 Shows the schematic structural diagram of the visual system according to Embodiment 3 of the present application when in the first state (+2D state);

[0029] Figure 10 Shows the MTF curve of the visual system according to Embodiment 3 when in the first state (+2D state);

[0030] Figure 11 Shows the schematic structural diagram of the visual system according to Embodiment 3 of the present application when in the second state (-5D state);

[0031] Figure 12 Shows the MTF curve of the visual system according to Embodiment 3 when in the second state (-5D state);

[0032] Figure 13 Shows the schematic structural diagram of the visual system according to Embodiment 4 of the present application when in the first state (+2D state);

[0033] Figure 14 Shows the MTF curve of the visual system according to Embodiment 4 when in the first state (+2D state);

[0034] Figure 15 Shows the schematic structural diagram of the visual system according to Embodiment 4 of the present application when in the second state (-5D state);

[0035] Figure 16 Shows the MTF curve of the visual system according to Embodiment 4 when in the second state (-5D state);

[0036] Figure 17 Shows the schematic structural diagram of the visual system according to Embodiment 5 of the present application when in the first state (+2D state);

[0037] Figure 18Shows the MTF curve of the visual system of Embodiment 5 when in the first state (+2D state);

[0038] Figure 19 Shows a schematic structural diagram of the visual system according to Embodiment 5 of the present application when in the second state (-5D state);

[0039] Figure 20 Shows the MTF curve of the visual system of Embodiment 5 when in the second state (-5D state). Detailed implementation manners

[0040] 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 the 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.

[0041] It should be noted that in this specification, the expressions such as first and second are only used to distinguish one feature from another feature and do not represent any limitation on the feature. Therefore, without departing from the teachings of the present application, the first lens discussed below may also be referred to as the second lens, and the second lens may also be referred to as the first lens.

[0042] In the drawings, for the sake of clarity, the thickness, dimensions and shapes of the lenses have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are shown by way of example. That is, the spherical or aspherical shapes are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are only examples and are not drawn to an exact scale.

[0043] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region.

[0044] It should also be understood that the terms "comprises", "comprising", "has", "including" and / or "including having", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of listed features rather than individual elements in the list. In addition, when describing the 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.

[0045] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formalized sense unless expressly so defined herein.

[0046] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The following will describe this application in detail with reference to the drawings and in combination with the embodiments.

[0047] The features, principles, and other aspects of this application will be described in detail below.

[0048] The visual system according to an exemplary embodiment of this application may include a first lens group and a second lens group. Among them, 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 reflective element, and a third lens. In the exemplary embodiment, the first lens group and the second lens group may be arranged in sequence along the optical axis from the first side to the second side. In the exemplary embodiment, the first lens, the reflective polarizing element, the quarter-wave plate, the second lens, the partially reflective element, and the third lens may be arranged in sequence along the optical axis from the first side to the second side.

[0049] In the exemplary embodiment, the first lens may have a positive focal power, its first side may be convex, and its second side may be flat.

[0050] In the exemplary embodiment, the second lens may have a positive focal power, and its second side may be convex.

[0051] In the exemplary embodiment, it may have a positive or negative focal power, its first side may be concave, and its second side may be convex.

[0052] In the exemplary embodiment, the second lens and the third lens may be a cemented doublet lens. The cementing of the second lens and the third lens can reduce the overall system length, which is beneficial to miniaturization; it can reduce the tolerance sensitivity between lenses, which is beneficial to ensuring the production yield; it is beneficial to balance various aberrations and improve the resolution; at the same time, it can also reduce the reflection between lenses, reduce stray light ghosts, and is beneficial to the improvement of relative illumination.

[0053] In an exemplary embodiment, the reflective polarizing element may be disposed on or attached to the second side of the first lens; the quarter-wave plate may be disposed on or attached to the second side of the reflective polarizing element. Exemplarily, the first side of the reflective polarizing element may at least partially conform to the second side of the first lens; the first side of the quarter-wave plate may at least partially conform to the second side of the reflective polarizing element.

[0054] In an exemplary embodiment, the partial reflection element may be disposed between the second lens and the third lens, and the partial reflection element may be disposed on the second side of the second lens or may be disposed on the first side of the third lens. Exemplarily, the partial reflection element may be a semi-transmissive and semi-reflective film layer coated on the second side of the second lens or the first side of the third lens.

[0055] By reasonably setting the structure of the visual system, the refraction and reflection of the optical path can be achieved, effectively shortening the body length of the visual system, reducing the volume and weight of the visual system, and realizing the light weight of the visual system.

[0056] In an exemplary embodiment, the first side may be, for example, the human eye side, and the second side may be, for example, the display side. The visual system may be used in, for example, VR devices.

[0057] In an exemplary embodiment, the distance of the first lens group including the first lens, the reflective polarizing element, and the quarter-wave plate from the display or image plane on the optical axis with respect to the second side of the visual system may be fixed. The second lens group including the second lens, the partial reflection element, and the third lens may be configured to be movable along the optical axis to approach or move away from the display or image plane located on the second side of the visual system, and to switch the visual system between a first state and a second state. Specifically, when the second lens group moves to the position closest to the display or image plane, at this time, the distance between the second lens group and the first lens group on the optical axis is the largest, and the visual system may be in the +2D state, that is, the first state; when the second lens group moves to the position farthest from the display or image plane, at this time, the distance between the second lens group and the first lens group on the optical axis is the smallest, and the visual system may be in the -5D state, that is, the second state.

[0058] Exemplarily, when the visual system is in the first state, the diopter of the visual system is +2D, and it may be applicable to users with a diopter of +2D, for example; when the visual system is in the second state, the diopter of the visual system is -5D, and it may be applicable to users with a diopter of -5D, for example. Among them, when the sign of the diopter is negative, it may indicate that the user is a myopic user; when the sign of the diopter is positive, it may indicate that the user is a hyperopic user; the specific value of the diopter may represent the refractive power of the user. For example, a diopter of +1D may indicate that the user's hyperopia degree is about 100 degrees, and a diopter of -1D may indicate that the user's myopia degree is about 100 degrees.

[0059] It should be understood that, in addition to the first state and the second state, the visual system according to the embodiments of the present application may also have other states, for example, between -5D and +2D. The visual system according to the embodiments of the present application can achieve continuous zoom within the range of -5D to +2D, which can meet the needs of users with different visual acuities, enabling users to enjoy the VR experience without wearing glasses.

[0060] In an exemplary embodiment, the visual system of the present application may include at least one aperture. The aperture can constrain the light path and control the light intensity. The aperture can be set at an appropriate position of the visual system. For example, the aperture can be located between the first side (such as the human eye side) and the first lens.

[0061] In an exemplary embodiment, the virtual image distances (VIDs) of the visual system in the first state and the second state are different. The virtual image distance can 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.

[0062] The following refers to Figure 1 for an exemplary description of the visual system. As Figure 1 shown, the visual system according to an 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 disposed on the second side surface of the first lens E1, and the quarter-wave plate QWP is disposed on the second side surface 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. In actual use, the visual system according to an exemplary embodiment of the present application can be used as a VR lens, for example. At this time, the first side corresponds to the human eye side, and the second side corresponds to the display or image plane side. The second side of the visual system has, for example, a display or an image plane IMG. The light beam emitted from the 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, and is reflected at the reflective polarizing element RP and then passes through the quarter-wave plate QWP, the second lens E2 again to reach the partial reflection element BS. After that, 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 face the first side (such as Figure 1It exits at the stop STO in [the figure]. The visual system provided by this application folds the required optical path through a combination of light reflection and refraction, effectively shortening the body length of the visual system without affecting the projection quality.

[0063] In an exemplary embodiment, the visual system of this application can satisfy the conditional formula 5.69 ≤ fz / fm ≤ 8.09, where 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; fm is the effective focal length of the visual system in the +2D state.

[0064] In an exemplary embodiment, the visual system of this application can satisfy the conditional formula 1.78 ≤ f23 / (TDm + TDn) ≤ 7.01, where 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 of the first lens to the second side 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 of the first lens to the second side of the third lens when the visual system is in the -5D state.

[0065] In an exemplary embodiment, the visual system of this application can satisfy the conditional formula 2.00 ≤ T12m / Δf ≤ 4.70, where 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 when the visual system switches 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.

[0066] According to the visual system of an exemplary embodiment of the present application, along the optical axis from the first side to the second side, it sequentially includes a first lens group and a second lens group. 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 partially reflective element, and a third lens. Among them, the first lens has a positive optical power, the first side is convex, and the second side is flat; the second lens has a positive optical power, and the second side is convex; the third lens has a positive or negative optical power, the first side is concave, and the second side is convex; and the second lens and the third lens are a cemented doublet lens; 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 a first state and a second state; through a 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 conditional formula 5.69≤fz / fm≤8.09, while controlling 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 of the first lens to the second side of the third lens when the visual system is in the first state and the second state respectively to satisfy the conditional formula 1.78≤f23 / (TDm+TDn)≤7.01, and controlling the air gap T12m between the first lens and the second lens when the visual system is in the first state and the change amount Δf of the effective focal length of the visual system when switching from the first state to the second state to satisfy the conditional formula 2.00≤T12m / Δf≤4.70, it is possible to realize the diopter adjustment function of the optical system while reducing the overall length of the system, ensuring the air gap between the lenses, guaranteeing the overall processability of the system, and reducing the stray light of the system.

[0067] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 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 formula, 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.

[0068] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 3.45≤R1 / fn≤4.52, where R1 is the curvature radius 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 formula, the contribution of the first lens to the overall imaging of the system can be guaranteed, and the imaging performance of the system can be improved.

[0069] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 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 formula, while ensuring the processability of components such as lenses, the overall length of the system can be reduced by decreasing the thickness.

[0070] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 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 formula, it can be ensured that when the second and third lenses move, the change in diopter meets the requirements.

[0071] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 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 formula, the overall space occupied by the system can be reduced, making the product thinner and lighter.

[0072] 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 on the optical axis from the second side of the third lens to the display when the visual system is in the -5D state, 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 reasonably controlling the range of this conditional formula, it can be ensured that when the optical system adjusts the diopter, the second lens and the third lens have sufficient movement space, so that the system can meet the requirements for adjustment in the range of -5D to +2D.

[0073] 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 on the optical axis from the second side of the third lens to the display when the visual system is in the +2D state. By reasonably controlling the range of this conditional formula, it can be ensured that when the optical system adjusts the diopter, the third lens and the display do not interfere, and the processability of the system can be guaranteed.

[0074] 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 radius of curvature of the second side of the second lens, and 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. 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.

[0075] 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 radius of curvature of the first side of the third lens, and BFLm is the distance on the optical axis from the second side of the third lens to the display when the visual system is in the +2D state. By reasonably controlling the range of this conditional formula, while ensuring the system performance, the bonding yield of the third lens and the second lens can be increased.

[0076] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 7.10 ≤ fn / ΔL ≤ 7.58, where 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 formula, it can be ensured that each state within the range of -5D to +2D of the visual system has sufficient space, facilitating the user to more quickly find a suitable state when using it.

[0077] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 4.82 ≤ EPD / Δf ≤ 12.15, where EPD is the entrance pupil diameter of the visual system, 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 formula, when the user uses the visual system, the entrance pupil diameter of the system is larger than the pupil diameter of the human eye, ensuring the imaging performance of the light emitted by the display screen in the human eye.

[0078] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula -4.33 mm ≤ (R1 / R6) × ΔL ≤ -0.34 mm, where R1 is the radius of curvature of the first side of the first lens, R6 is the radius of curvature of the second side 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 are not difficult to process due to excessive curvature, improving the processability of the first lens and the third lens.

[0079] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 1.61 ≤ f23 / (fm + fn) ≤ 5.84, where 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, the light can be better converged, improving the imaging performance of the system.

[0080] In an exemplary embodiment, the visual system of the present application can satisfy the conditional formula 5.90 ≤ |f3| / TDm ≤ 12.19, where 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 formula, the light can be better converged, and while meeting the imaging requirements, the lens sensitivity tolerance can be reduced.

[0081] In the visual system according to the embodiment of the present application, one or more of the first lens, the second lens, and the third lens can be aspherical lenses. The aspherical lens has better curvature radius characteristics and has the advantages of improving distortion aberration and astigmatism aberration; after using the aspherical lens, the aberration that appears during imaging can be eliminated as much as possible, thereby improving the imaging quality.

[0082] On the one hand, the visual system according to an exemplary embodiment of the present application sequentially includes a first lens group and a second lens group along the optical axis from the first side to the second side. 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 partially reflective element, and a third lens. Among them, the first lens has a positive optical power, the first side surface is convex, and the second side surface is flat; the second lens has a positive optical power, and the second side surface is convex; the third lens has a positive or negative optical power, the first side surface is concave, and the second side surface is convex; and the second lens and the third lens are a cemented doublet lens; the second lens group is configured to be movable along the optical axis to approach or move away from a display located on the second side, and to switch the visual system between a first state and a second state; through a 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 conditional formula 5.69 ≤ fz / fm ≤ 8.09, at the same time, controlling 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 to satisfy the conditional formula 1.78 ≤ f23 / (TDm + TDn) ≤ 7.01, and controlling the air gap T12m between the first lens and the second lens when the visual system is in the first state and the change amount Δf of the effective focal length when the visual system is switched from the first state to the second state to satisfy the conditional formula 2.00 ≤ T12m / Δf ≤ 4.70, it is possible to realize the diopter adjustment function of the optical system while reducing the overall length of the system, ensuring the air gap between the lenses, ensuring the overall processability of the system, and reducing the stray light of the system.

[0083] On the other hand, the visual system according to the exemplary embodiment of the present application sequentially includes a first lens group and a second lens group along the optical axis from the first side to the second side. 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 partially reflective element, and a third lens. Among them, the first lens has a positive optical power, the first side is convex, and the second side is flat; the second lens has a positive optical power, and the second side is convex; the third lens has a positive or negative optical power, the first side is concave, and the second side is convex; and the second lens and the third lens are a cemented doublet lens; the second lens group is configured to be movable along the optical axis to approach or move away from the display located on the second side, and to switch the visual system between a first state and a 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 conditional formula 5.69 ≤ fz / fm ≤ 8.09, while controlling 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 of the first lens to the second side of the third lens when the visual system is in the first state and the second state respectively to satisfy the conditional formula 1.78 ≤ f23 / (TDm + TDn) ≤ 7.01, and controlling the curvature radius R1 of the first side of the first lens, the curvature radius R6 of the second side of the third lens, and the distance ΔL that the second lens group moves along the optical axis during the process of the visual system switching from the first state to the second state to satisfy the conditional formula -4.33 mm ≤ (R1 / R6)×ΔL ≤ -0.34 mm, the optical system can realize the diopter adjustment function, reduce the overall length of the system, ensure the imaging performance of the system, and at the same time, the first lens and the third lens are not difficult to process due to excessive curvature, improving the processability of the first lens and the third lens.

[0084] The visual system according to the exemplary embodiment of the present application adopts, for example, a cemented three-mirror folded optical scheme. Through the reasonable configuration of the system structure and parameters, it can not only reduce the overall optical length, reduce the total weight of the system, realize the miniaturization and light weight of the system, and improve the user's comfort; but also realize the zoom of the system in the range of -5D to +2D through the movement of the second lens group, meet the needs of users with different visual acuities, 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 beneficial to the improvement of the system imaging quality.

[0085] In addition, the present application also provides a VR device, which may include the visual system provided in any one of the above embodiments. Among them, the first side may be the human eye side, and the second side may be the display / image plane side. The VR device may have characteristics such as miniaturization, light weight, and high imaging quality, and may achieve zooming in 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.

[0086] The following further describes specific embodiments of the visual system applicable to the above embodiments with reference to the accompanying drawings.

[0087] Embodiment 1

[0088] The following refers to Figures 1 to 4 Describe the visual system according to Embodiment 1 of the present application.

[0089] The visual system according to Embodiment 1 of the present application sequentially includes, along the optical axis, from the first side to the second side: a first lens group G1 and a second lens group G2. Among them, the first lens group G1 includes a first lens E1, a reflective polarizing element RP, and a quarter-wave plate QWP arranged in sequence along the optical axis from the first side to the second side. The reflective polarizing element RP is disposed on the second side surface of the first lens E1, and the quarter-wave plate QWP is disposed on the second side surface 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 along the optical axis from the first side to the second side. The second lens E2 and the third lens E3 are adhesively bonded to each other, and the partial reflection element BS is disposed between the second lens E2 and the third lens E3.

[0090] In this example, the first lens E1 has a positive optical power, its first side surface is convex, and its second side surface is flat; the second lens E2 has a positive optical power, its first side surface is convex, and its second side surface is convex; the third lens E3 has a negative optical power, its first side surface is concave, and its second side surface is convex.

[0091] In this example, a stop STO may be disposed on the first side of the visual system, and a display / image plane IMG may be disposed on the second side of the visual system. For the first lens group G1: the distances of the first lens E1, the reflective polarizing element RP, and the quarter-wave plate QWP from the display / image plane IMG along the optical axis direction are relatively fixed; for the second lens group G2: the second lens E2, the partial reflection element BS, and the third lens E3 may move along the optical axis direction to approach or move away from the display / image plane IMG. During this process, the visual system may achieve zooming in the range of -5D to +2D. Figure 1 Fig. shows a schematic structural diagram 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. At this time, the visual system is in the +2D state.Figure 3 FIG. 1 shows a schematic structural diagram of the visual system when the second lens group G2 is moved along the optical axis to the position farthest from the display / image plane IMG. At this time, the visual system is in the -5D state.

[0092] As Figure 1 and Figure 3 shown, in the specific application of the visual system according to this example, image light from the display / image plane IMG, for example, 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. At the reflective polarizing element RP, it is reflected and then passes through the quarter-wave plate QWP and the second lens E2 again to reach the partial reflection element BS. After that, 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 rays after two reflections of the visual system can finally be projected onto the user's pupil.

[0093] Table 1 shows the basic parameters of the visual system of Example 1, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0094] Table 1

[0095]

[0096] The parameters D1 to D5 in Table 1 can be understood as follows: D5 can be understood as the value along the optical axis from the second side of the third lens E3 to the display / image plane IMG; D4 can be understood as the value along the optical axis from the first side of the second lens E2 to the second side of the quarter-wave plate QWP; D3 can be understood as the value along the optical axis from the second side of the quarter-wave plate QWP to the first side of the second lens E2; D2 can be understood as the value along the optical axis from the first side of the second lens E2 to the second side 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. During the process of zooming by moving the second lens group G2 along the optical axis in the visual system according to this embodiment, the values of the above parameters D1 to D5 will all change accordingly. The visual system is in Figure 1 the +2D state shown in Figure 3 and the values of the parameters D1 to D5 in the -5D state shown in

[0097] Table 2

[0098]

[0099] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the cemented surface S14 between 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 profiles of the aspherical lenses can be defined by, but are not limited to, the following aspherical formula:

[0100] (1)

[0101] wherein, is the sagitta, which is the distance from the vertex of the aspherical surface to the aspherical surface along the optical axis at a position with a height of h ; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic coefficient; Ai is the correction coefficient of the i -th order of the aspherical surface. Table 3 below gives the high-order coefficients A4, A6, A8, A 10 , A 12 , A 14 , A 16 , A 18 and A 20 that can be used for the aspherical surfaces S3 and S13 - S15 in this embodiment.

[0102] Table 3

[0103]

[0104] Figure 2 shows the MTF curve of the visual system according to this embodiment in the Figure 1 shown +2D state, Figure 4 shows the MTF curve of the visual system according to this embodiment in the Figure 3 shown -5D state. The MTF curve can represent the optical modulation function values corresponding to different spatial frequencies. As can be seen from Figure 2 and Figure 4 , the visual system given in this embodiment can achieve good imaging quality in both the +2D and -5D different focal length states.

[0105] Embodiment 2

[0106] The following describes the visual system according to Embodiment 2 of the present application with reference to Figures 5 to 8 . In this embodiment and the following embodiments, for the sake of simplicity, some descriptions similar to those in Embodiment 1 will be omitted.

[0107] In this embodiment, the visual system along the optical axis from the first side to the second side also includes a first lens group G1 and a second lens group G2 arranged in sequence. Among them, the first lens group G1 includes a first lens E1, a reflective polarizing element RP, and a quarter-wave plate QWP arranged in sequence along the optical axis from the first side to the second side. The reflective polarizing element RP is disposed on the second side surface of the first lens E1, and the quarter-wave plate QWP is disposed on the second side surface 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 along the optical axis from the first side to the second side. 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.

[0108] In this embodiment, the first lens E1 has a positive focal power, its first side surface is convex, and its second side surface is flat; the second lens E2 has a positive focal power, its first side surface is convex, and its second side surface is convex; the third lens E3 has a negative focal power, its first side surface is concave, and its second side surface is convex.

[0109] Table 4 shows the basic parameters of the visual system according to this embodiment.

[0110] Table 4

[0111]

[0112] In this example, a stop STO can be provided on the first side of the visual system, and a display / image plane IMG can be provided on the second side of the visual system. For the first lens group G1: the distances of the first lens E1, the reflective polarizing element RP, and the quarter-wave plate QWP from the display / image plane IMG in the optical axis direction are relatively fixed; for the second lens group G2: the second lens E2, the partial reflection element BS, and the third lens E3 can move in the optical axis direction to approach or move away from the display / image plane IMG. During this process, the visual system can achieve zooming in the range of -5D to +2D. Figure 5 Fig. shows the structural schematic diagram 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. At this time, the visual system is in the +2D state. Figure 7 Fig. shows the structural schematic diagram of the visual system when the second lens group G2 moves along the optical axis to the position farthest from the display / image plane IMG. At this time, the visual system is in the -5D state.

[0113] For the visual system according to this embodiment in Figure 5 the +2D state shown in Figure 7 and the -5D state shown in

[0114] Table 5

[0115]

[0116] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the cemented surface S14 between 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 profiles of the aspherical surfaces can be calculated using the formula (1) in Embodiment 1. Table 6 below gives the higher-order term coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 .

[0117] Table 6

[0118]

[0119] Figure 6 shows the MTF curve of the visual system according to this embodiment when it is in the Figure 5 shown +2D state, Figure 8 shows the MTF curve of the visual system according to this embodiment when it is in the Figure 7 shown -5D state. As can be seen from Figure 6 and Figure 8 , the visual system given in this embodiment can achieve good imaging quality in both the +2D and -5D different focal length states.

[0120] Embodiment 3

[0121] The following describes the visual system according to Embodiment 3 of the present application with reference to Figures 9 to 12 .

[0122] In this embodiment, the visual system along the optical axis from the first side to the second side also includes a first lens group G1 and a second lens group G2 arranged in sequence. Among them, the first lens group G1 includes a first lens E1, a reflective polarizing element RP, and a quarter-wave plate QWP arranged in sequence along the optical axis from the first side to the second side. The reflective polarizing element RP is disposed on the second side surface of the first lens E1, and the quarter-wave plate QWP is disposed on the second side surface 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 along the optical axis from the first side to the second side. The second lens E2 and the third lens E3 are cemented to each other, and the partial reflection element BS is disposed between the second lens E2 and the third lens E3.

[0123] In this embodiment, the first lens E1 has a positive optical power, its first side is convex, and its second side is flat; 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 convex.

[0124] Table 7 shows the basic parameters of the visual system according to this embodiment.

[0125] Table 7

[0126]

[0127] In this example, a diaphragm STO can be provided on the first side of the visual system, and a display / image plane IMG can be provided on the second side of the visual system. First lens group G1: The distances of the first lens E1, the reflective polarizing element RP, and the quarter-wave plate QWP from the display / image plane IMG along the optical axis direction are relatively fixed; second lens group G2: The second lens E2, the partial reflection element BS, and the third lens E3 can move along the optical axis direction to approach or move away from the display / image plane IMG. During this process, the visual system can achieve zooming within the range of -5D to +2D. Figure 9 Fig. shows the structural schematic diagram 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. At this time, the visual system is in the +2D state. Figure 11 Fig. shows the structural schematic diagram of the visual system when the second lens group G2 moves along the optical axis to the position farthest from the display / image plane IMG. At this time, the visual system is in the -5D state.

[0128] For the visual system according to this embodiment, in Figure 9 the +2D state shown in Figure 11 and the -5D state shown in

[0129] Table 8

[0130]

[0131] In this embodiment, the first side S3 of the first lens E1, the first side S13 of the second lens E2, the cemented surface S14 between the second lens E2 and the third lens E3, and the second side S15 of the third lens E3 are all aspherical surfaces. The surface profiles of the aspherical surfaces can be calculated using the formula (1) in Embodiment 1. Table 9 below gives the higher-order term coefficients A4, A6, A8, A 10 , A 12 , A 14 , A 16 , A 18 and A20 。

[0132] Table 9

[0133]

[0134] Figure 10 shows the MTF curve of the visual system according to this embodiment when it is in the Figure 9 shown +2D state, Figure 12 shows the MTF curve of the visual system according to this embodiment when it is in the Figure 11 shown -5D state. As can be seen from Figure 10 and Figure 12 , the visual system given in this embodiment can achieve good imaging quality in both +2D and -5D different focal length states.

[0135] Embodiment 4

[0136] The following refers to Figures 13 to 16 to describe the visual system according to Embodiment 4 of the present application.

[0137] In this example, the visual system along the optical axis from the first side to the second side also includes a first lens group G1 and a second lens group G2 arranged in sequence. Among them, the first lens group G1 includes a first lens E1, a reflective polarizing element RP, and a quarter-wave plate QWP arranged in sequence along the optical axis from the first side to the second side. The reflective polarizing element RP is disposed on the second side surface of the first lens E1, and the quarter-wave plate QWP is disposed on the second side surface 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 along the optical axis from the first side to the second side. 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.

[0138] In this embodiment, the first lens E1 has a positive optical power, its first side surface is convex, and its second side surface is flat; the second lens E2 has a positive optical power, its first side surface is convex, and its second side surface is convex; the third lens E3 has a positive optical power, its first side surface is concave, and its second side surface is convex.

[0139] Table 10 shows the basic parameters of the visual system according to this embodiment.

[0140] Table 10

[0141]

[0142] In this example, a diaphragm STO can be provided on the first side of the visual system, and a display / image plane IMG can be provided on the second side of the visual system. First lens group G1: The first lens E1, the reflective polarizing element RP, and the quarter-wave plate QWP are relatively fixed in distance along the optical axis direction from the display / image plane IMG; Second lens group G2: The second lens E2, the partially reflective element BS, and the third lens E3 can move along the optical axis direction to approach or move away from the display / image plane IMG. During this process, the visual system can achieve zooming in the range of -5D to +2D. Figure 13 Fig. shows the schematic structural diagram 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. At this time, the visual system is in the +2D state. Figure 15 Fig. shows the schematic structural diagram of the visual system when the second lens group G2 moves along the optical axis to the position farthest from the display / image plane IMG. At this time, the visual system is in the -5D state.

[0143] According to the visual system of this embodiment Figure 13 in the +2D state shown in Figure 15 and the -5D state shown in

[0144] Table 11

[0145]

[0146] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the cemented surface S14 between 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 profiles of each aspherical surface can be calculated using formula (1) in Embodiment 1. Table 12 below gives the higher-order term coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 that can be used for each aspherical mirror surface S3 and S13 - S15 in this embodiment.

[0147] Table 12

[0148]

[0149] Figure 14 Fig. shows the MTF curve of the visual system according to this embodiment when it is in Figure 13 the +2D state shown in Figure 16 Fig. shows the MTF curve of the visual system according to this embodiment when it is in Figure 15 the -5D state shown in Figure 14 andFigure 16 It can be seen that the visual system provided in this embodiment can achieve good imaging quality at two different focal lengths of +2D and -5D.

[0150] Embodiment 5

[0151] The following refers to Figures 17 to 20 Describe the visual system according to Embodiment 5 of the present application.

[0152] In this example, the visual system also includes a first lens group G1 and a second lens group G2 arranged in sequence along the optical axis from the first side to the second side. Among them, the first lens group G1 includes a first lens E1, a reflective polarizing element RP, and a quarter-wave plate QWP arranged in sequence along the optical axis from the first side to the second side. The reflective polarizing element RP is disposed on the second side surface of the first lens E1, and the quarter-wave plate QWP is disposed on the second side surface 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 along the optical axis from the first side to the second side. The second lens E2 and the third lens E3 are glued together, and the partial reflection element BS is disposed between the second lens E2 and the third lens E3.

[0153] In this embodiment, the first lens E1 has a positive optical power, its first side surface is convex, and its second side surface is flat; the second lens E2 has a positive optical power, its first side surface is concave, and its second side surface is convex; the third lens E3 has a positive optical power, its first side surface is concave, and its second side surface is convex.

[0154] Table 13 shows the basic parameters of the visual system according to this embodiment.

[0155] Table 13

[0156]

[0157] In this example, a stop STO can be provided on the first side of the visual system, and a display / image plane IMG can be provided on the second side of the visual system. For the first lens group G1: the distances of the first lens E1, the reflective polarizing element RP, and the quarter-wave plate QWP along the optical axis direction from the display / image plane IMG are relatively fixed; for 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 direction to approach or move away from the display / image plane IMG. During this process, the visual system can achieve zooming within the range of -5D to +2D. Figure 17 Shows a schematic structural diagram 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. At this time, the visual system is in the +2D state. Figure 19Fig. shows the schematic structural diagram of the visual system when the second lens group G2 is moved along the optical axis to the position farthest from the display / image plane IMG. At this time, the visual system is in the -5D state.

[0158] For the visual system according to this embodiment, at Figure 17 the +2D state shown in Figure 19 and the -5D state shown in

[0159] Table 14

[0160]

[0161] In this embodiment, the first side surface S3 of the first lens E1, the first side surface S13 of the second lens E2, the cemented surface S14 between 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 profiles of the aspherical surfaces can be calculated using the formula (1) in Embodiment 1. Table 15 below gives the higher-order coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 .

[0162] Table 15

[0163]

[0164] Figure 18 Fig. shows the MTF curve of the visual system according to this embodiment when it is in Figure 17 the +2D state shown in Figure 20 Fig. shows the MTF curve of the visual system according to this embodiment when it is in Figure 19 the -5D state shown in Figure 18 and Figure 20 As can be seen from

[0165] In summary, in Embodiments 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 and 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 of the first lens to the second side of the third lens of the visual system in the +2D state, the distance TDn on the optical axis from the first side of the first lens to the second side of the third lens of the visual system in the -5D state, the distance T12m on the optical axis from the second side of the first lens to the first side of the second lens of the visual system in the +2D state, the distance T12n on the optical axis from the second side of the first lens to the first side of the second lens of the visual system in the -5D state, the distance BFLm on the optical axis from the second side of the third lens to the display / image plane of the visual system in the +2D state, the distance BFLn on the optical axis from the second side of the third lens to the display / image plane of the visual system in the -5D state, the distance ΔL 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, and the change amount Δf of the effective focal length of the system when the visual system switches from the +2D state to the -5D state are respectively shown in Table 16 below.

[0166] Table 16

[0167]

[0168] In addition, Embodiments 1 to 5 respectively satisfy the conditions shown in Table 17 below.

[0169] Table 17

[0170]

[0171] The above description is only the preferred embodiments of the present application and the description of the applied technical principles. Those skilled in the art should understand that the scope of protection involved in the present application is not limited to the technical solutions formed by the 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 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 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; The number of lenses having optical power in the visual system is three; 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: <h2 style=";text-align:left;direction:ltr">0.38mm≤<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> f2 / f3<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> ×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, a distance BFLn from the second side surface of the third lens to the display on the optical axis and a 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 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: -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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