Visual system

Abstract

The present application discloses a visual system, which includes, from the first side to the second side of the optical axis, a first lens with positive focal length, a second lens, a third lens, a partial reflection element, a fourth lens with negative focal length, a second quarter wave plate, and a polarizer; the visual system also includes a reflective polarizing element and a first quarter wave plate attached to each other, the first quarter wave plate is located on the first side surface of the second lens, or the reflective polarizing element is located on the second side surface of the second lens; the angle β between the tangent line of the second side surface of the third lens at the intersection of the main light of the 1.0 field of view reflected by the partial reflection element and the optical axis 1.0 Satisfies: 80.5°<β 1.0 <83.2°; Angle β between the tangent line of the second side surface of the third lens at the intersection of the main light of the 0.8 field of view after being reflected by the partial reflective element and the optical axis 0.8 Satisfies: 81.85°<β 0.8 <83.85°.

Description

Technical Field

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

[0002] The visual systems of virtual reality devices are mainly divided into three types: visual systems using aspherical lenses, visual systems using Fresnel lenses, and catadioptric visual systems. Among them, the catadioptric visual system is a major innovation in the visual system itself and reserves space for the overall design of virtual reality devices, and has become the mainstream trend of research and development.

[0003] The catadioptric visual system shortens the body length of the visual system by folding the optical path, thereby shifting the center of gravity of the virtual reality device backward and enhancing the user experience. However, the catadioptric visual system usually has a relatively serious ghost image problem, which affects the imaging effect of the visual system. Summary of the Invention

[0004] On the one hand, this application provides such a visual system, which sequentially includes a first lens with positive optical power, a second lens with positive or negative optical power, a third lens with positive or negative optical power, a partial reflection element, a fourth lens with negative optical power, a second quarter-wave plate, and a polarizer along the optical axis from the first side to the second side. The first side of the first lens is convex. The second side of the third lens is convex. The first side of the fourth lens is concave. The partial reflection element is located on the second side of the third lens. The number of lenses with optical power in the visual system is four. The visual system further includes a reflective polarizing element and a first quarter-wave plate arranged in sequence and attached to each other from the first side to the second side. The first quarter-wave plate is located on the first side of the second lens, or the reflective polarizing element is located on the second side of the second lens. The visual system satisfies: 80.5° < β 1.0 < 83.2°, 81.85° < β 0.8 < 83.85°, where β 1.0 is the angle between the tangent line of the second side of the third lens at the intersection position of the chief ray of the 1.0 field of view after being reflected by the partial reflection element and the optical axis, and β 0.8 is the angle between the tangent line of the second side of the third lens at the intersection position of the chief ray of the 0.8 field of view after being reflected by the partial reflection element and the optical axis.

[0005] According to an exemplary embodiment of the present application, the visual system further satisfies: -92.1 mm < R6 < -68.25 mm, where R6 is the radius of curvature of the second side of the third lens.

[0006] According to an exemplary embodiment of the present application, the visual system further satisfies: -2.2 < f3 / fz < 3.5, where f3 is the effective focal length of the third lens, and fz is the combined focal length of the second lens, the reflective polarizing element, and the first quarter-wave plate.

[0007] According to an exemplary embodiment of the present application, the visual system further satisfies: 3.0 < CT4 / (CTQ2 + CTL) < 3.85, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, and CTL is the central thickness of the polarizer on the optical axis.

[0008] According to an exemplary embodiment of the present application, the visual system further satisfies: 1.7 < R1 / f < 3.7, where R1 is the radius of curvature of the first side of the first lens, and f is the total effective focal length of the visual system.

[0009] According to an exemplary embodiment of the present application, the visual system further satisfies: -1.9 < f4 / f1 < -0.8, where f4 is the effective focal length of the fourth lens, and f1 is the effective focal length of the first lens.

[0010] According to an exemplary embodiment of the present application, the visual system further satisfies: 0.3 < tan(β 0.3 ) / tan(β 0.1 ) < 0.4, where β 0.3 is the angle between the tangent of the second side of the third lens at the intersection position of the chief ray of the 0.3 field of view after being reflected by the partial reflection element and the optical axis, and β 0.1 is the angle between the tangent of the second side of the third lens at the intersection position of the chief ray of the 0.1 field of view after being reflected by the partial reflection element and the optical axis.

[0011] According to an exemplary embodiment of the present application, the visual system further satisfies: 168.15° < β 0.5 +β 0.6 < 170.35°, where β 0.5 is the angle between the tangent of the second side of the third lens at the intersection position of the chief ray of the 0.5 field of view after being reflected by the partial reflection element and the optical axis, and β 0.6 is the angle between the tangent of the second side of the third lens at the intersection position of the chief ray of the 0.6 field of view after being reflected by the partial reflection element and the optical axis.

[0012] According to an exemplary embodiment of the present application, the visual system further satisfies: 17.2 mm < f×(N3 / N1) < 21.8 mm, where f is the total effective focal length of the visual system, N1 is the refractive index of the first lens, and N3 is the refractive index of the third lens.

[0013] According to an exemplary embodiment of the present application, the visual system further satisfies: 0.05 < TD / |f4| < 0.25, where TD is the on-axis distance from the first side surface of the first lens to the second side surface of the fourth lens, and f4 is the effective focal length of the fourth lens.

[0014] According to an exemplary embodiment of the present application, the visual system further satisfies: 0.08 < (CTR + CTQ1) / T12 < 0.25, where T12 is the on-axis distance from the second side surface of the first lens to the first side surface of the second lens, CTR is the central thickness of the reflective polarizing element on the optical axis, and CTQ1 is the central thickness of the first quarter-wave plate on the optical axis.

[0015] According to an exemplary embodiment of the present application, the visual system further satisfies: 81.2° < β 0.9 < 83.5°, where β 0.9 is the angle between the tangent line of the second side surface of the third lens at the intersection position of the chief ray of the 0.9 field of view after being reflected by the partial reflection element and the optical axis.

[0016] According to an exemplary embodiment of the present application, the visual system further satisfies: 21.5 < Vmin < 24.0, where Vmin is the Abbe number of the lens with the smallest Abbe number among the first lens to the fourth lens.

[0017] According to an exemplary embodiment of the present application, the visual system further satisfies: 0.45 < R7 / R6 < 1.55, where R6 is the radius of curvature of the second side surface of the third lens, and R7 is the radius of curvature of the first side surface of the fourth lens.

[0018] The intersection position of the chief ray of the 1.0 field of view after being reflected by the partial reflection element and the second side surface of the third lens may be A 1.0 , and the intersection position of the chief ray of the 0.8 field of view after being reflected by the partial reflection element and the second side surface of the third lens may be A 0.8 . By controlling the angle between the tangent line of the second side surface of the third lens at the intersection position A 1.0 and the optical axis and the angle between the tangent line of the second side surface of the third lens at the intersection position A 0.8 and the optical axis, the present application can constrain the slopes of the tangent lines of the partial reflection element at the intersection position A 1.0 and the intersection position A 0.8 , so that the light passes through the first quarter-wave plate and the reflective polarizing element in a manner approaching parallel light during the folding and reflection process, reducing the polarization angle effect, and thus reducing the ghost image formed by the light directly passing through the reflective polarizing element. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings, in which:

[0020] Figure 1 A schematic diagram of the structure of a visual system according to Example 1 of the present application is shown;

[0021] Figure 2 shows a modulation transfer function curve of a visual system according to Example 1 of the present application;

[0022] Figure 3 A schematic diagram of the structure of a visual system according to Embodiment 2 of the present application is shown;

[0023] Figure 4 shows a modulation transfer function curve of a visual system according to Example 2 of the present application;

[0024] Figure 5 A schematic structural diagram of a visual system according to Embodiment 3 of the present application is shown;

[0025] Figure 6 shows a modulation transfer function curve of a visual system according to Example 3 of the present application;

[0026] Figure 7 A schematic diagram of the structure of a visual system according to Embodiment 4 of the present application is shown;

[0027] Figure 8 shows a modulation transfer function curve of a visual system according to Example 4 of the present application;

[0028] Fig. 9 A schematic diagram of the structure of a visual system according to Embodiment 5 of the present application is shown;

[0029] Fig.10 shows a modulation transfer function curve of a visual system according to Example 5 of the present application;

[0030] Fig.11 A schematic diagram of the structure of a visual system according to Example 6 of the present application is shown;

[0031] Fig.12 shows a modulation transfer function curve of a visual system according to Example 6 of the present application;

[0032] Fig.13 FIG. 1 shows a β diagram of a visual system according to an exemplary embodiment of the present application. 1.0 , β 0.9 , β 0.8 , β 0.6 , β 0.5 , β 0.3 , β 0.1 Schematic diagram of

[0033] Fig.14 It shows that the visual system satisfies β 1.0 =73.5°, β 0.8 =75° when the ghost image is displayed;

[0034] Fig.15 It shows that the visual system satisfies β 1.0 =84.6°, β 0.8 =86° when the ghost image is displayed;

[0035] Fig.16 It shows that the visual system satisfies β 1.0 =82.25°, β 0.8 =82.76° ghost image effect. DETAILED DESCRIPTION

[0036] 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 do not limit the scope of the present application in any way. Throughout the specification, the same figure numerals refer to the same elements.

[0037] 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 can also be referred to as the second lens.

[0038] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of illustration. 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 for illustration only and are not drawn strictly to scale.

[0039] 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. The surface of each lens closest to the first side (e.g., the human eye side) is called the first side surface of the lens, and the surface of each lens closest to the second side (e.g., the display screen side) is called the second side surface of the lens.

[0040] It should also be understood that the terms "include", "comprising", "having", "including" 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 describing embodiments of the present application, the term "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.

[0041] 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 the same meaning as 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.

[0042] 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.

[0043] The features, principles and other aspects of the present application are described in detail below.

[0044] A first aspect of the present application provides a visual system that may include a first lens, a second lens, a third lens, a partial reflection element, a fourth lens, a second quarter wave plate, and a polarizer arranged in sequence from a first side to a second side along an optical axis.

[0045] In an exemplary embodiment, the first lens may have positive optical power. The first side surface of the first lens may be a convex surface, and the second side surface may be a convex surface or a concave surface.

[0046] In an exemplary embodiment, the second lens may have positive power or negative power. The first side surface of the second lens may be a plane surface or a convex surface or a concave surface, and the second side surface may be a convex surface or a plane surface.

[0047] In an exemplary embodiment, the third lens may have positive power or negative power. The first side surface of the third lens may be a convex surface or a concave surface, and the second side surface may be a convex surface.

[0048] In an exemplary embodiment, the fourth lens may have negative optical power. A first side surface of the fourth lens may be a concave surface, and a second side surface may be a flat surface or a convex surface.

[0049] In an exemplary embodiment, the visual system may further include a reflective polarizing element and a first quarter wave plate arranged in sequence from the first side to the second side. The first quarter wave plate is used to change the polarization state of the light, for example, converting circularly polarized light into linearly polarized light, or converting linearly polarized light into circularly polarized light. Circularly polarized light may include right-handed circularly polarized light or left-handed circularly polarized light. Linearly polarized light may include S-linearly polarized light or P-linearly polarized light. The reflective polarizing element is used to reflect linearly polarized light in a predetermined direction and transmit linearly polarized light orthogonal to the predetermined direction. For example, the reflective polarizing element may reflect S-linearly polarized light and transmit P-linearly polarized light, or the reflective polarizing element may reflect P-linearly polarized light and transmit S-linearly polarized light.

[0050] In an exemplary embodiment, the reflective polarizing element and the first quarter wave plate may be bonded to each other. The first quarter wave plate may be located on the first side of the second lens, or the reflective polarizing element may be located on the second side of the second lens. For example, the first quarter wave plate may be at least partially bonded to the first side of the second lens, and the reflective polarizing element may be at least partially bonded to the first side of the first quarter wave plate. For another example, the reflective polarizing element may be at least partially bonded to the second side of the second lens, and the first quarter wave plate may be at least partially bonded to the second side of the reflective polarizing element. As an example, the surface of the second lens on which the reflective polarizing element and the first quarter wave plate are disposed may be a plane.

[0051] In an exemplary embodiment, the partial reflective element may be located on the second side surface of the third lens and at least partially adhered to the second side surface of the third lens. The partial reflective element may have a semi-transmissive and semi-reflective effect on the light. By arranging the partial reflective element on the second side surface of the third lens and combining the reflective polarizing element and the first quarter wave plate, the light can be refracted multiple times, effectively reducing the main body length of the visual system.

[0052] In an exemplary embodiment, the second quarter wave plate and the polarizer may be attached to each other. The second quarter wave plate may be located on the second side of the fourth lens, or the second quarter wave plate and the polarizer may be located between the fourth lens and the image surface on the second side of the visual system. As an example, the surface of the fourth lens on which the second quarter wave plate and the polarizer are disposed may be a plane.

[0053] In an exemplary embodiment, the visual system may further include an aperture, which may be disposed between the first side and the first lens. As an example, the aperture may be, for example, a pupil of the user. The image light from the second side is refracted and reflected multiple times by the polarizer, the second quarter wave plate, the fourth lens, the partial reflection element, the third lens, the second lens, the first quarter wave plate, the reflective polarizing element, the first lens, etc., and is finally projected to the user's eye on the first side.

[0054] 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 screen side. Accordingly, the first side of each element (first lens, reflective polarizing element, first quarter wave plate, second lens, third lens, partially reflecting element, fourth lens, second quarter wave plate, polarizing plate) may be referred to as a side near the human eye, and the second side may be referred to as a side near the screen.

[0055] In an exemplary embodiment, an image surface may be provided on the second side of the visual system. A display screen may be provided on the image surface. The image light from the display screen may sequentially pass through a polarizer, a second quarter wave plate, a fourth lens, a third lens, a second lens, a first quarter wave plate, and reach a reflective polarizing element, and then be reflected at the reflective polarizing element to form a first reflected image light. The first reflected image light passes through the first quarter wave plate, the second lens, the third lens, and reaches a partially reflective element on the second side of the third lens, and then is reflected at the partially reflective element to form a second reflected image light. The second reflected image light sequentially passes through the third lens, the second lens, the first quarter wave plate, the reflective polarizing element, the first lens to the aperture and is finally projected to the user's eyes.

[0056] In other examples, the image light from the display screen may sequentially pass through the polarizer, the second quarter wave plate, the fourth lens, the third lens, the first quarter wave plate, reach the reflective polarizing element, and then be reflected at the reflective polarizing element to form the first reflected image light. The first reflected image light passes through the first quarter wave plate, the third lens, and reaches the partially reflective element on the second side of the third lens, and then is reflected at the partially reflective element to form the second reflected image light. The second reflected image light sequentially passes through the third lens, the first quarter wave plate, the reflective polarizing element, the second lens, the first lens to the aperture and is finally projected to the user's eyes.

[0057] The visual system provided in 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.

[0058] In an exemplary embodiment, the visual system may satisfy: 80.5°<β 1.0 <83.2°, 81.85°<β 0.8 <83.85°, where β 1.0 is the angle between the tangent line of the second side surface of the third lens and the optical axis at the intersection of the principal ray of the 1.0 field of view after being reflected by the partial reflective element, β 0.8 is the angle between the tangent line of the second side surface of the third lens at the intersection of the main light of 0.8 field of view after being reflected by the partial reflective element and the optical axis. Fig.13As shown in Figure a in FIG. 1 , the intersection position of the main light of the 1.0 field of view after being reflected by the partial reflection element and the second side surface of the third lens can be, for example, A 1.0 , the second side surface of the third lens is at the intersection position A 1.0 The angle between the tangent line at and the optical axis can be, for example, β 1.0 .like Fig.13 As shown in Figure c in FIG. 1 , the intersection position of the main light of the 0.8 field of view after being reflected by the partial reflection element and the second side surface of the third lens can be, for example, A 0.8 , the second side surface of the third lens is at the intersection position A 0.8 The angle between the tangent line at and the optical axis can be, for example, β 0.8 By controlling the second side surface of the third lens at the intersection position A 1.0 The angle between the tangent line at and the optical axis and the second side surface of the third lens at the intersection position A 0.8 The angle between the tangent line at the intersection and the optical axis can be used to determine the angle between the tangent line at the intersection and the optical axis. 1.0 , intersection position A 0.8 The slope of the tangent at the position is constrained, so that the light passes through the first quarter wave plate and the reflective polarizing element in a manner close to parallel light during the refraction process, thereby reducing the polarization angle effect, thereby reducing the ghost image formed by the light directly passing through the reflective polarizing element.

[0059] Combine the following Fig.14 , Fig.15 and Fig.16 To describe the imaging effect of the visual system. Among them, Fig.14 For the visual system to meet β 1.0 =73.5°, β 0.8 =75° when the ghost image is displayed; Fig.15 For the visual system to meet β 1.0 =84.6°, β 0.8 =86° when the ghost image is displayed; Fig.16 For the visual system to satisfy β 1.0 =82.25°, β 0.8 =82.76° ghost image effect.

[0060] from Fig.14 From the perspective of 1.0 =73.5°, β 0.8 =75°, the ghost image of the direct optical path of the visual system is larger. In this case, the ratio of the power of the direct optical path to the power of the main optical path is 3.57%. Fig.15 From the perspective of 1.0 =84.6°, β 0.8When β = 86°, the ghost image of the direct optical path of the visual system is relatively large. In this case, the ratio of the power of the direct optical path to the power of the main optical path is 1.47%. However, when the visual system satisfies β 1.0 = 82.25° and β 0.8 = 82.76°, the ghost image of the direct optical path of the visual system is significantly reduced ( Fig.16 ). In this case, the ratio of the power of the direct optical path to the power of the main optical path is 0.06%. It can be seen that by controlling the visual system to satisfy "80.5° < β 1.0 < 83.2°, 81.85° < β 0.8 < 83.85°", the ghost image formed by the light directly passing through the reflective polarizing element can be reduced. It should be noted that the direct optical path here can be the optical path formed by the light directly passing through the reflective polarizing element, and the main optical path can be the optical path formed by the light being reflected twice by the reflective polarizing element and the partial reflection element.

[0061] In an exemplary embodiment, the visual system can satisfy: -92.1 mm < R6 < -68.25 mm, where R6 is the radius of curvature of the second side surface of the third lens. Reasonably configuring the radius of curvature of the second side surface of the third lens can improve the processability of the third lens, and control the curvature of the partial reflection element on the second side surface of the third lens, thereby constraining the slope of the tangent line at the intersection position corresponding to the chief ray of different fields of view of the partial reflection element, so that the reflection angle of the light after being reflected by the partial reflection element is within an appropriate range, reducing the ghost image of the visual system.

[0062] In an exemplary embodiment, the visual system can satisfy: -2.2 < f3 / fz < 3.5, where f3 is the effective focal length of the third lens, and fz is the combined focal length of the second lens, the reflective polarizing element, and the first quarter-wave plate. Reasonably configuring the ratio of the effective focal length of the third lens to the combined focal length of the second lens, the reflective polarizing element, and the first quarter-wave plate can distribute the optical power of the second lens and the third lens, so that the light is incident on these two elements at an angle close to perpendicular when passing through the first quarter-wave plate and the reflective polarizing element for the first time, thereby reducing the ghost image of the visual system.

[0063] In an exemplary embodiment, the visual system may satisfy: 3.0 < CT4 / (CTQ2 + CTL) < 3.85, where CT4 is the central thickness of the fourth lens on the optical axis, CTQ2 is the central thickness of the second quarter-wave plate on the optical axis, and CTL is the central thickness of the polarizer on the optical axis. By controlling the relationship among the central thickness of the fourth lens on the optical axis, the central thickness of the second quarter-wave plate on the optical axis, and the central thickness of the polarizer on the optical axis, the body length of the visual system can be reduced while ensuring the processability of the fourth lens, achieving the thinning and lightening of the visual system.

[0064] In an exemplary embodiment, the visual system may satisfy: 1.7 < R1 / f < 3.7, where R1 is the radius of curvature of the first side surface of the first lens and f is the total effective focal length of the visual system. By reasonably configuring the ratio of the radius of curvature of the first side surface of the first lens to the total effective focal length of the visual system, the first side surface of the first lens can converge light better, while meeting the imaging requirements, reducing the sensitivity tolerance of the visual system.

[0065] In an exemplary embodiment, the visual system may satisfy: -1.9 < f4 / f1 < -0.8, where f4 is the effective focal length of the fourth lens and f1 is the effective focal length of the first lens. By reasonably configuring the ratio of the effective focal length of the fourth lens to the effective focal length of the first lens, the exit angle of the light from the display screen after exiting the fourth lens can be made smaller, facilitating the subsequent parallel folding and reflection of the light.

[0066] In an exemplary embodiment, the visual system may satisfy: 0.3 < tan(β 0.3 ) / tan(β 0.1 ) < 0.4, where β 0.3 is the angle between the tangent of the main ray of the 0.3 field of view after being reflected by the partial reflection element and the optical axis at the intersection position of the second side surface of the third lens, and β 0.1 is the angle between the tangent of the main ray of the 0.1 field of view after being reflected by the partial reflection element and the optical axis at the intersection position of the second side surface of the third lens. As shown in the f diagram in Fig.13 , the intersection position of the main ray of the 0.3 field of view after being reflected by the partial reflection element and the second side surface of the third lens may be, for example, A 0.3 , and the angle between the tangent of the second side surface of the third lens at the intersection position A 0.3 and the optical axis may be, for example, β 0.3 . As shown in the g diagram in Fig.13 , the intersection position of the main ray of the 0.1 field of view after being reflected by the partial reflection element and the second side surface of the third lens may be, for example, A 0.1 , and the angle between the tangent of the second side surface of the third lens at the intersection position A 0.1 and the optical axis may be, for example, β0.1 By controlling the above conditional expressions, the slope of the tangent line of the second side surface of the third lens at the intersection position A 0.3 can be made smaller than the slope of the tangent line of the second side surface of the third lens at the intersection position A 0.1 . While ensuring the imaging quality of the visual system, the processability of the third lens is improved.

[0067] In an exemplary embodiment, the visual system can satisfy: 168.15° < β 0.5 + β 0.6 < 170.35°, where β 0.5 is the angle between the tangent line of the second side surface of the third lens at the intersection position of the chief ray of the 0.5 field of view after being reflected by the partial reflection element and the optical axis, and β 0.6 is the angle between the tangent line of the second side surface of the third lens at the intersection position of the chief ray of the 0.6 field of view after being reflected by the partial reflection element and the optical axis. As shown in the d diagram of Fig.13 , the intersection position of the chief ray of the 0.6 field of view after being reflected by the partial reflection element and the second side surface of the third lens can be, for example, A 0.6 , and the angle between the tangent line of the second side surface of the third lens at the intersection position A 0.6 and the optical axis can be, for example, β 0.6 . As shown in the e diagram of Fig.13 , the intersection position of the chief ray of the 0.5 field of view after being reflected by the partial reflection element and the second side surface of the third lens can be, for example, A 0.5 , and the angle between the tangent line of the second side surface of the third lens at the intersection position A 0.5 and the optical axis can be, for example, β 0.5 . By controlling the above conditional expressions, the slopes of the tangent lines of the second side surface of the third lens at the intersection position A 0.5 and the intersection position A 0.6 can be constrained within a reasonable range, so that the reflection angle of the reflected light when the light is refracted and reflected at these two intersection positions and the region between these two intersection positions is not too large, facilitating subsequent parallel refraction and reflection of the light, and the processability of the third lens can be improved.

[0068] In an exemplary embodiment, the visual system can satisfy: 17.2 mm < f×(N3 / N1) < 21.8 mm, where f is the total effective focal length of the visual system, N1 is the refractive index of the first lens, and N3 is the refractive index of the third lens. By controlling the relationship between the total effective focal length of the visual system, the refractive index of the first lens, and the refractive index of the third lens, the imaging performance of the visual system can be improved, and the material costs of the first lens and the third lens can be reduced.

[0069] In an exemplary embodiment, the visual system may satisfy: 0.05 < TD / |f4| < 0.25, where TD is the on-axis distance from the first side surface of the first lens to the second side surface of the fourth lens, and f4 is the effective focal length of the fourth lens. By reasonably configuring the ratio of the on-axis distance from the first side surface of the first lens to the second side surface of the fourth lens to the effective focal length of the fourth lens, the body length of the visual system can be reduced, and the visual system can be made thinner and lighter.

[0070] In an exemplary embodiment, the visual system may satisfy: 0.08 < (CTR + CTQ1) / T12 < 0.25, where T12 is the on-axis distance from the second side surface of the first lens to the first side surface of the second lens, CTR is the central thickness of the reflective polarizing element on the optical axis, and CTQ1 is the central thickness of the first quarter-wave plate on the optical axis. By controlling the above conditional expression, the on-axis distance from the second side surface of the first lens to the first side surface of the second lens can be constrained within a reasonable range, so that there is sufficient installation space between the first lens and the second lens, facilitating the assembly of the reflective polarizing element and the first quarter-wave plate, and preventing interference between the reflective polarizing element and the first quarter-wave plate.

[0071] In an exemplary embodiment, the visual system may satisfy: 81.2° < β 0.9 < 83.5°, where β 0.9 is the angle between the tangent line of the second side surface of the third lens at the intersection position of the chief ray of the 0.9 field of view after being reflected by the partial reflection element and the optical axis. As Fig.13 shown in Figure b of 0.9 , the intersection position of the chief ray of the 0.9 field of view after being reflected by the partial reflection element and the second side surface of the third lens may be, for example, A 0.9 , and the angle between the tangent line of the second side surface of the third lens at the intersection position A 0.9 and the optical axis may be, for example, β 0.9 . By controlling the above conditional expression, the slope of the tangent line of the second side surface of the third lens at the intersection position A

[0072] can be constrained within a reasonable range, so that the reflection angle of the light when it is refracted and reflected at the intersection position and its nearby areas is not too large, facilitating subsequent parallel refraction and reflection of the light, and improving the processability of the third lens.

[0073] In an exemplary embodiment, the visual system may satisfy: 0.45 < R7 / R6 < 1.55, where R6 is the radius of curvature of the second surface of the third lens and R7 is the radius of curvature of the first surface of the fourth lens. By reasonably configuring the ratio of the radius of curvature of the first surface of the fourth lens to the radius of curvature of the second surface of the third lens, the angular change of light passing through these two surfaces can be within a certain range, improving the relative illuminance of the light in the large field of view of the visual system.

[0074] The visual system according to the above embodiment of the present application may employ multiple lenses, such as the four lenses described above. By reasonably allocating the parameters of the reflective polarizing element, the first quarter-wave plate, the second quarter-wave plate, the polarizer, and each lens, the body length of the visual system can be reduced and the imaging quality of the visual system can be improved. The visual system configured as above has the characteristics of being thin and light and having good imaging quality, and can well meet the usage requirements of various portable electronic products in the projection scenario.

[0075] In an embodiment of the present application, at least one of the surfaces of the first lens, the second lens, the third lens, and the fourth lens is an aspherical surface. The characteristic of an aspherical lens is that the curvature continuously changes from the center of the lens to the periphery of the lens. Different from a spherical lens with a constant curvature from the center of the lens to the periphery, an aspherical lens has better radius of curvature characteristics and has the advantages of improving distortion aberration and astigmatism aberration. After using an aspherical lens, it is possible to eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality.

[0076] The second aspect of the present application provides such a visual system that sequentially includes a first lens with a positive optical power, a second lens with a positive or negative optical power, a third lens with a positive or negative optical power, a partial reflection element, a fourth lens with a negative optical power, a second quarter-wave plate, and a polarizer along the optical axis from the first side to the second side. The first surface of the first lens is a convex surface. The second surface of the third lens is a convex surface. The first surface of the fourth lens is a concave surface. The partial reflection element is located on the second surface of the third lens. The number of lenses with optical power in the visual system is four. The visual system further includes a reflective polarizing element and a first quarter-wave plate that are sequentially arranged and adhered to each other from the first side to the second side, and the first quarter-wave plate is located on the first surface of the second lens, or the reflective polarizing element is located on the second surface of the second lens.

[0077] The visual system may satisfy: 80.5° < β 1.0 < 83.2°, -92.1 mm < R6 < -68.25 mm, where β 1.0is the angle between the tangent line of the second side surface of the third lens and the optical axis at the intersection of the main light of the 1.0 field of view after being reflected by the partial reflective element, and R6 is the radius of curvature of the second side surface of the third lens. Fig.13 As shown in Figure a in FIG. 1 , the intersection position of the main light of the 1.0 field of view after being reflected by the partial reflection element and the second side surface of the third lens can be, for example, A 1.0 , the second side surface of the third lens is at the intersection position A 1.0 The angle between the tangent line at and the optical axis can be, for example, β 1.0 By controlling the second side surface of the third lens at the intersection position A 1.0 By taking into account the angle between the tangent at the optical axis and the radius of curvature of the second side surface of the third lens, while ensuring the machinability of the third lens, the slope of the tangent of the partial reflective element at the intersection position corresponding to the main light of different fields of view can be constrained, so that the angle of the reflected light after the light is reflected by the partial reflective element is in an appropriate range, and the light passes through the first quarter wave plate and the reflective polarizing element in a manner close to parallel light during the refraction process, thereby reducing the polarization angle effect, thereby reducing the ghost image formed by the light directly passing through the reflective polarizing element.

[0078] However, those skilled in the art should understand that, without departing from the technical solution claimed in the present application, the number of lenses constituting the visual system can be changed to obtain the various results and advantages described in this specification.

[0079] Specific embodiments of the visual system applicable to the above-mentioned embodiments are further described below with reference to the accompanying drawings. Example 1

[0080] The following reference Figure 1 and Figure 2 Describe the visual system of Example 1 of the present application. Figure 1 This is a schematic diagram of the structure of the visual system of Example 1. Figure 2 is the modulation transfer function curve of the visual system of Example 1, wherein, Figure 2 The OTF in is the optical transfer function.

[0081] like Figure 1 As shown, the visual system may include a first lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter wave plate QWP2 and a polarizing plate LP arranged in sequence from the first side to the second side along the optical axis. The aperture STO may be located on the object side of the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side.

[0082] The first lens E1 has positive focal power, and its first side surface S1 is convex, and the second side surface S2 is concave. The second lens E2 has positive focal power, and its first side surface S3 is a plane, and the second side surface S4 is a convex surface. The third lens E3 has negative focal power, and its first side surface S5 is a concave surface, and the second side surface S6 is a convex surface. The fourth lens E4 has negative focal power, and its first side surface S7 is a concave surface, and the second side surface S8 is a plane. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the first side surface S3 of the second lens E2. The partially reflecting element BS is attached to the second side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the second side surface S8 of the fourth lens E4. It should be noted that surfaces S1, S2, S3, S4, S5, S6, S7 and S8 are Figure 1 Not shown.

[0083] In this example, an image surface IMG may be provided on the second side of the visual system, and the image surface IMG may be provided with a display screen, for example. The image light from the image surface IMG sequentially passes through the polarizer LP, the second quarter wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, the first quarter wave plate QWP1 and reaches the reflective polarizing element RP, and then the first reflection occurs at the reflective polarizing element RP. The light reflected for the first time passes through the first quarter wave plate QWP1, the second lens E2, the third lens E3 and reaches the partially reflective element BS located on the second side of the third lens, and then the second reflection occurs at the partially reflective element BS. The light reflected for the second time sequentially passes through the third lens E3, the second lens E2, the first quarter wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and is finally projected to the user's eyes. For example, the light of the visual system after two reflections is finally projected to the user's eyes.

[0084] 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 all millimeters (mm). The image light from the image surface IMG passes through the components in the order of sequence number 21 to sequence number 1 and is finally projected to the user's eyes.

[0085] Table 1

[0086]

[0087] In this embodiment, the first side surface S1 of the first lens E1, the second side surface S4 of the second lens E2, the first side surface S5 and the second side surface S6 of the third lens E3, and the first side surface S7 of the fourth lens E4 are aspherical surfaces, and the second side surface S2 of the first lens E1 is a thin Fresnel surface. The surface shape of each aspherical surface or thin Fresnel surface can be defined by but not limited to the following formula:

[0088] (1)

[0089] Wherein, is the distance vector height from the vertex of the aspherical surface (or thin Fresnel surface) when the aspherical surface (or thin Fresnel surface) is at a height of h along the optical axis; c is the paraxial curvature of the aspherical surface (or thin Fresnel surface), c=1 / R (i.e., the paraxial curvature c is the reciprocal of the curvature radius R in Table 1 above); k is the cone coefficient; Ai is the i-th order correction coefficient of the aspherical surface (or thin Fresnel surface). Table 2 shows the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the surfaces S1, S2, S4, S5, S6 and S7 that can be used in Example 1.

[0090] Table 2

[0091] Example 2

[0092] The following reference Figure 3 and Figure 4 Describe the visual system of Example 2 of the present application. Figure 3 This is a schematic diagram of the structure of the visual system of Example 2. Figure 4 is the modulation transfer function curve of the visual system of Example 2, wherein, Figure 4 The OTF in is the optical transfer function.

[0093] like Figure 3 As shown, the visual system may include a first lens E1, a second lens E2, a reflective polarizing element RP, a first quarter wave plate QWP1, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter wave plate QWP2 and a polarizing plate LP arranged in sequence from the first side to the second side along the optical axis. The aperture STO may be located on the object side of the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side.

[0094] The first lens E1 has positive focal power, and its first side surface S1 is convex, and the second side surface S2 is concave. The second lens E2 has positive focal power, its first side surface S3 is convex, and the second side surface S4 is a plane. The third lens E3 has positive focal power, its first side surface S5 is concave, and the second side surface S6 is convex. The fourth lens E4 has negative focal power, its first side surface S7 is concave, and the second side surface S8 is convex. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the second side surface S4 of the second lens E2. The partially reflecting element BS is attached to the second side surface S6 of the third lens E3. It should be noted that surfaces S1, S2, S3, S4, S5, S6, S7 and S8 are Figure 3 Not shown.

[0095] In this example, an image surface IMG may be provided on the second side of the visual system, and the image surface IMG may be provided with a display screen, for example. The image light from the image surface IMG sequentially passes through the polarizer LP, the second quarter wave plate QWP2, the fourth lens E4, the third lens E3, the first quarter wave plate QWP1 and reaches the reflective polarizing element RP, and then the first reflection occurs at the reflective polarizing element RP. The light reflected for the first time passes through the first quarter wave plate QWP1, the third lens E3 and reaches the partially reflective element BS located on the second side of the third lens, and then the second reflection occurs at the partially reflective element BS. The light reflected for the second time sequentially passes through the third lens E3, the first quarter wave plate QWP1, the reflective polarizing element RP, the second lens E2, the first lens E1 to the aperture and is finally projected to the user's eyes. For example, the light of the visual system after two reflections is finally projected to the user's eyes.

[0096] Table 3 shows the basic parameters of the visual system of Example 2, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm). The image light from the image surface IMG passes through the components in the order of sequence number 20 to sequence number 1 and is finally projected to the user's eyes.

[0097] Table 3

[0098]

[0099] In this embodiment, the first side surface S1 of the first lens E1, the first side surface S3 of the second lens E2, the first side surface S5 and the second side surface S6 of the third lens E3, the first side surface S7 and the second side surface S8 of the fourth lens E4 are aspherical surfaces, and the second side surface S2 of the first lens E1 is a thin Fresnel surface. Table 4 lists the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the surfaces S1, S2, S3, S5, S6, S7 and S8 that can be used in Embodiment 2.

[0100] Table 4

[0101] Example 3

[0102] The following reference Figure 5 and Figure 6 Describe the visual system of Example 3 of the present application. Figure 5 This is a schematic diagram of the structure of the visual system of Example 3. Figure 6 is the modulation transfer function curve of the visual system of Example 3, wherein, Figure 6 The OTF in is the optical transfer function.

[0103] like Figure 5As shown, the visual system may include a first lens E1, a second lens E2, a reflective polarizing element RP, a first quarter wave plate QWP1, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter wave plate QWP2 and a polarizing plate LP arranged in sequence from the first side to the second side along the optical axis. The aperture STO may be located on the object side of the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side.

[0104] The first lens E1 has positive focal power, and its first side surface S1 is convex, and the second side surface S2 is concave. The second lens E2 has negative focal power, its first side surface S3 is concave, and the second side surface S4 is a plane. The third lens E3 has positive focal power, its first side surface S5 is convex, and the second side surface S6 is convex. The fourth lens E4 has negative focal power, its first side surface S7 is concave, and the second side surface S8 is convex. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the second side surface S4 of the second lens E2. The partially reflecting element BS is attached to the second side surface S6 of the third lens E3. It should be noted that surfaces S1, S2, S3, S4, S5, S6, S7 and S8 are Figure 5 Not shown.

[0105] In this example, an image surface IMG may be provided on the second side of the visual system, and the image surface IMG may be provided with a display screen, for example. The image light from the image surface IMG sequentially passes through the polarizer LP, the second quarter wave plate QWP2, the fourth lens E4, the third lens E3, the first quarter wave plate QWP1 and reaches the reflective polarizing element RP, and then the first reflection occurs at the reflective polarizing element RP. The light reflected for the first time passes through the first quarter wave plate QWP1, the third lens E3 and reaches the partially reflective element BS located on the second side of the third lens, and then the second reflection occurs at the partially reflective element BS. The light reflected for the second time sequentially passes through the third lens E3, the first quarter wave plate QWP1, the reflective polarizing element RP, the second lens E2, the first lens E1 to the aperture and is finally projected to the user's eyes. For example, the light of the visual system after two reflections is finally projected to the user's eyes.

[0106] Table 5 shows the basic parameters of the visual system of Example 3, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm). The image light from the image surface IMG passes through the components in the order of sequence number 20 to sequence number 1 and is finally projected to the user's eyes.

[0107] Table 5

[0108]

[0109] In this embodiment, the first side surface S1 of the first lens E1, the first side surface S3 of the second lens E2, the first side surface S5 and the second side surface S6 of the third lens E3, the first side surface S7 and the second side surface S8 of the fourth lens E4 are aspherical surfaces, and the second side surface S2 of the first lens E1 is a thin Fresnel surface. Table 6 lists the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the surfaces S1, S2, S3, S5, S6, S7 and S8 that can be used in Embodiment 3.

[0110] Table 6

[0111] Example 4

[0112] The following reference Figure 7 and Figure 8 Describe the visual system of Example 4 of the present application. Figure 7 This is a schematic diagram of the structure of the visual system of Example 4. Figure 8 is the modulation transfer function curve of the visual system of Example 4, wherein, Figure 8 The OTF in is the optical transfer function.

[0113] like Figure 7 As shown, the visual system may include a first lens E1, a second lens E2, a reflective polarizing element RP, a first quarter wave plate QWP1, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter wave plate QWP2 and a polarizing plate LP arranged in sequence from the first side to the second side along the optical axis. The aperture STO may be located on the object side of the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side.

[0114] The first lens E1 has positive focal power, and its first side surface S1 is convex, and the second side surface S2 is concave. The second lens E2 has negative focal power, and its first side surface S3 is concave, and the second side surface S4 is a plane. The third lens E3 has positive focal power, and its first side surface S5 is convex, and the second side surface S6 is convex. The fourth lens E4 has negative focal power, and its first side surface S7 is concave, and the second side surface S8 is a plane. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the second side surface S4 of the second lens E2. The partially reflecting element BS is attached to the second side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the second side surface S8 of the fourth lens E4. It should be noted that surfaces S1, S2, S3, S4, S5, S6, S7 and S8 are Figure 7 Not shown.

[0115] In this example, an image surface IMG may be provided on the second side of the visual system, and the image surface IMG may be provided with a display screen, for example. The image light from the image surface IMG sequentially passes through the polarizer LP, the second quarter wave plate QWP2, the fourth lens E4, the third lens E3, the first quarter wave plate QWP1 and reaches the reflective polarizing element RP, and then the first reflection occurs at the reflective polarizing element RP. The light reflected for the first time passes through the first quarter wave plate QWP1, the third lens E3 and reaches the partially reflective element BS located on the second side of the third lens, and then the second reflection occurs at the partially reflective element BS. The light reflected for the second time sequentially passes through the third lens E3, the first quarter wave plate QWP1, the reflective polarizing element RP, the second lens E2, the first lens E1 to the aperture and is finally projected to the user's eyes. For example, the light of the visual system after two reflections is finally projected to the user's eyes.

[0116] Table 7 shows the basic parameters of the visual system of Example 4, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm). The image light from the image surface IMG passes through the components in the order of sequence number 19 to sequence number 1 and is finally projected to the user's eyes.

[0117] Table 7

[0118]

[0119] In this embodiment, the first side surface S1 and the second side surface S2 of the first lens E1, the first side surface S3 of the second lens E2, the first side surface S5 and the second side surface S6 of the third lens E3, and the first side surface S7 of the fourth lens E4 are aspherical surfaces. Table 8 shows the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the surfaces S1, S2, S3, S5, S6 and S7 that can be used in Embodiment 4.

[0120] Table 8

[0121] Example 5

[0122] The following reference Fig. 9 and Fig.10 Describe the visual system of Example 5 of the present application. Fig. 9 This is a schematic diagram of the structure of the visual system of Example 5. Fig.10 is the modulation transfer function curve of the visual system of Example 5, wherein, Fig.10 The OTF in is the optical transfer function.

[0123] like Fig. 9As shown, the visual system may include a first lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter wave plate QWP2 and a polarizing plate LP arranged in sequence from the first side to the second side along the optical axis. The aperture STO may be located on the object side of the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side.

[0124] The first lens E1 has positive focal power, and its first side surface S1 is convex, and the second side surface S2 is convex. The second lens E2 has positive focal power, and its first side surface S3 is a plane, and the second side surface S4 is a convex surface. The third lens E3 has negative focal power, and its first side surface S5 is a concave surface, and the second side surface S6 is a convex surface. The fourth lens E4 has negative focal power, and its first side surface S7 is a concave surface, and the second side surface S8 is a plane. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the first side surface S3 of the second lens E2. The partially reflecting element BS is attached to the second side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the second side surface S8 of the fourth lens E4. It should be noted that surfaces S1, S2, S3, S4, S5, S6, S7 and S8 are Fig. 9 Not shown.

[0125] In this example, an image surface IMG may be provided on the second side of the visual system, and the image surface IMG may be provided with a display screen, for example. The image light from the image surface IMG sequentially passes through the polarizer LP, the second quarter wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, the first quarter wave plate QWP1 and reaches the reflective polarizing element RP, and then the first reflection occurs at the reflective polarizing element RP. The light reflected for the first time passes through the first quarter wave plate QWP1, the second lens E2, the third lens E3 and reaches the partially reflective element BS located on the second side of the third lens, and then the second reflection occurs at the partially reflective element BS. The light reflected for the second time sequentially passes through the third lens E3, the second lens E2, the first quarter wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and is finally projected to the user's eyes. For example, the light of the visual system after two reflections is finally projected to the user's eyes.

[0126] Table 9 shows the basic parameters of the visual system of Example 5, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm). The image light from the image surface IMG passes through the components in the order of sequence number 21 to sequence number 1 and is finally projected to the user's eyes.

[0127] Table 9

[0128]

[0129] In this embodiment, the first side surface S1 of the first lens E1, the second side surface S4 of the second lens E2, the first side surface S5 and the second side surface S6 of the third lens E3, and the first side surface S7 of the fourth lens E4 are aspherical surfaces, and the second side surface S2 of the first lens E1 is a thin Fresnel surface. Table 10 lists the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the surfaces S1, S2, S4, S5, S6 and S7 that can be used in Embodiment 5.

[0130] Table 10

[0131] Example 6

[0132] The following reference Fig.11 and Fig.12 Describe the visual system of Example 6 of the present application. Fig.11 This is a schematic diagram of the structure of the visual system of Example 6. Fig.12 is the modulation transfer function curve of the visual system of Example 6, wherein, Fig.12 The OTF in is the optical transfer function.

[0133] like Fig.11 As shown, the visual system may include a first lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second lens E2, a third lens E3, a partial reflection element BS, a fourth lens E4, a second quarter wave plate QWP2 and a polarizing plate LP arranged in sequence from the first side to the second side along the optical axis. The aperture STO may be located on the object side of the first lens E1. In this embodiment, the first side refers to the human eye side, and the second side refers to the display screen side.

[0134] The first lens E1 has positive focal power, and its first side surface S1 is convex, and the second side surface S2 is convex. The second lens E2 has positive focal power, and its first side surface S3 is a plane, and the second side surface S4 is a convex surface. The third lens E3 has negative focal power, and its first side surface S5 is a concave surface, and the second side surface S6 is a convex surface. The fourth lens E4 has negative focal power, and its first side surface S7 is a concave surface, and the second side surface S8 is a plane. The reflective polarizing element RP and the first quarter-wave plate QWP1 are attached to the first side surface S3 of the second lens E2. The partially reflecting element BS is attached to the second side surface S6 of the third lens E3. The second quarter-wave plate QWP2 and the polarizer LP are attached to the second side surface S8 of the fourth lens E4. It should be noted that surfaces S1, S2, S3, S4, S5, S6, S7 and S8 are Fig.11 Not shown.

[0135] In this example, an image surface IMG may be provided on the second side of the visual system, and the image surface IMG may be provided with a display screen, for example. The image light from the image surface IMG sequentially passes through the polarizer LP, the second quarter wave plate QWP2, the fourth lens E4, the third lens E3, the second lens E2, the first quarter wave plate QWP1 and reaches the reflective polarizing element RP, and then the first reflection occurs at the reflective polarizing element RP. The light reflected for the first time passes through the first quarter wave plate QWP1, the second lens E2, the third lens E3 and reaches the partially reflective element BS located on the second side of the third lens, and then the second reflection occurs at the partially reflective element BS. The light reflected for the second time sequentially passes through the third lens E3, the second lens E2, the first quarter wave plate QWP1, the reflective polarizing element RP, the first lens E1 to the aperture and is finally projected to the user's eyes. For example, the light of the visual system after two reflections is finally projected to the user's eyes.

[0136] Table 11 shows the basic parameter table of the visual system of Example 6, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm). The image light from the image surface IMG passes through the components in the order of sequence number 21 to sequence number 1 and is finally projected to the user's eyes.

[0137] Table 11

[0138]

[0139] In this embodiment, the first side surface S1 of the first lens E1, the second side surface S4 of the second lens E2, the first side surface S5 and the second side surface S6 of the third lens E3, and the first side surface S7 of the fourth lens E4 are aspherical surfaces, and the second side surface S2 of the first lens E1 is a thin Fresnel surface. Table 12 lists the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the surfaces S1, S2, S4, S5, S6 and S7 that can be used in Embodiment 6.

[0140] Table 12

[0141]

[0142] Table 13 gives the basic parameters of each embodiment in embodiments 1 to 6, such as f, f1, f2, f3, f4, fz, CTR, CTQ1, CTQ2, CTL, TD, β 1.0 , β 0.9 , β 0.8 , β 0.6 , β 0.5 , β 0.3 and β 0.1 The value of .

[0143] Table 13

[0144]

[0145] Table 14 shows the values ​​of the conditional expressions of each of Examples 1 to 6.

[0146] Table 14

[0147]

[0148] The present application also provides an optical device, which may be an independent projection device such as a projector, or a projection module integrated in a mobile electronic device such as a virtual reality device. The optical device is equipped with the visual system described above.

[0149] 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 the invention 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 inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A visual system, characterized in that: The method comprises, in order from the first side to the second side along the optical axis: A first lens having positive optical power, wherein the first side surface of the first lens is convex; a second lens having positive or negative optical power; a third lens element having positive or negative optical power, wherein the second side surface of the third lens element is a convex surface; a partial reflective element, located on the second side surface of the third lens; a fourth lens element having negative optical power, wherein the first side surface of the fourth lens element is concave; a second quarter wave plate; and Polarizer; The number of lenses with optical power in the visual system is four; the first side is the human eye side, and the second side is the display screen side; The visual system further comprises a reflective polarizing element and a first quarter wave plate which are sequentially arranged from the first side to the second side and attached to each other, wherein the first quarter wave plate is located on the first side of the second lens, or the reflective polarizing element is located on the second side of the second lens; Wherein, the visual system satisfies: 80.5°<β 1.0 <83.2°, 81.85°<β 0.8 <83.85°, β 1.0 is the angle between the tangent line of the second side surface of the third lens at the intersection of the principal ray of the 1.0 field of view after being reflected by the partial reflective element and the optical axis, β 0.8 is the angle between the tangent line of the second side surface of the third lens at the intersection of the main light of 0.8 field of view after being reflected by the partial reflection element and the optical axis.

2. The visual system according to claim 1, wherein: The visual system also meets the following requirements: -92.1mm <R6<-68.25mm, Wherein, R6 is the radius of curvature of the second side surface of the third lens.

3. The visual system according to claim 1, wherein: The visual system also meets the following requirements: -2.2 <f3 / fz<3.5, Wherein, f3 is the effective focal length of the third lens, and fz is the combined focal length of the second lens, the reflective polarizing element and the first quarter-wave plate.

4. The visual system according to claim 1, wherein: The visual system also meets the following requirements: 3.0 <CT4 / (CTQ2+CTL)<3.85, Wherein, CT4 is the center thickness of the fourth lens on the optical axis, CTQ2 is the center thickness of the second quarter wave plate on the optical axis, and CTL is the center thickness of the polarizer on the optical axis.

5. The visual system according to claim 1, wherein: The visual system also meets the following requirements: 1.7 <R1 / f<3.7, Wherein, R1 is the radius of curvature of the first side surface of the first lens, and f is the total effective focal length of the visual system.

6. The visual system according to claim 1, wherein: The visual system also meets the following requirements: -1.9 <f4 / f1<-0.8, Wherein, f4 is the effective focal length of the fourth lens, and f1 is the effective focal length of the first lens.

7. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 0.3 <tan(β 0.3 ) / tan(β 0.1 )<0.4, Among them, β 0.3 is the angle between the tangent line of the second side surface of the third lens at the intersection of the principal ray of 0.3 field of view after being reflected by the partial reflective element and the optical axis, β 0.1 is the angle between the tangent line of the second side surface of the third lens at the intersection of the main light of 0.1 field of view after being reflected by the partial reflection element and the optical axis.

8. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 168.15°<β 0.5 +β 0.6 <170.35°， Among them, β 0.5 is the angle between the tangent line of the second side surface of the third lens at the intersection of the principal ray of 0.5 field of view after being reflected by the partial reflective element and the optical axis, β 0.6 is the angle between the tangent line of the second side surface of the third lens at the intersection of the main light of 0.6 field of view after being reflected by the partial reflection element and the optical axis.

9. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 17.2mm <f×(N3 / N1)<21.8mm, Wherein, f is the total effective focal length of the visual system, N1 is the refractive index of the first lens, and N3 is the refractive index of the third lens.

10. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 0.05 <TD / |f4|<0.25, Wherein, TD is the on-axis distance from the first side surface of the first lens to the second side surface of the fourth lens, and f4 is the effective focal length of the fourth lens.

11. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 0.08<(CTR+CTQ1) / T12<0.25, Among them, T12 is the on-axis distance from the second side surface of the first lens to the first side surface of the second lens, CTR is the center thickness of the reflective polarizing element on the optical axis, and CTQ1 is the center thickness of the first quarter wave plate on the optical axis.

12. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 81.2°<β 0.9 <83.5°， Among them, β 0.9 is the angle between the tangent line of the second side surface of the third lens at the intersection of the main light of 0.9 field of view after being reflected by the partial reflection element and the optical axis.

13. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 21.5 <Vmin<24.0, Wherein, Vmin is the Abbe number of the lens with the smallest Abbe number among the first lens to the fourth lens.

14. The visual system according to any one of claims 1 to 6, wherein: The visual system also meets the following requirements: 0.45 <R7 / R6<1.55, Wherein, R6 is the curvature radius of the second side surface of the third lens, and R7 is the curvature radius of the first side surface of the fourth lens.

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