Optical system and display device

Abstract

The invention provides an optical system and a display device. The optical system includes a lens assembly, a transflective film, a reflective polarization layer, and a phase retardation film. The lens assembly comprises at least two lenses, and each lens comprises a first surface, a second surface, a third surface and a fourth surface which are sequentially arranged in the optical axis direction of the lens assembly; the transflective film is located between the second surface and the third surface; the reflective polarization layer is located on one side of the fourth surface away from the first surface. The absolute value of the curvature radius of the fourth surface is larger than that of the first surface, the ratio of the curvature radius of the third surface to the curvature radius of the fourth surface is 0.3-0.8, and the ratio of the cone coefficient of the third surface to the absolute value of the cone coefficient of the fourth surface is not larger than 0.2. The optical system provided by the invention has the characteristics of ultra-short focus and large field of view.

Description

Technical Field

[0001] The present disclosure relates to an optical system and a display device. Background Art

[0002] Virtual reality (VR) devices use computer technology and photoelectric sensing technology to generate a virtual three-dimensional environment that users can interact with. The virtual reality device includes glasses and a display screen. The glasses use a catadioptric optical path (Pancake), and Pancake is gradually used in head-mounted display systems due to its compact structure and thinness. Summary of the invention

[0003] Embodiments of the present disclosure provide an optical system and a display device.

[0004] The optical system provided by the embodiment of the present disclosure includes: a lens assembly, a transflective film, a reflective polarizing layer, and a phase delay film. The lens assembly includes at least two lenses, the at least two lenses include a first surface, a second surface, a third surface, and a fourth surface arranged in sequence along the optical axis direction of the lens assembly, the second surface and the third surface have the same surface parameters; the transflective film is located between the second surface and the third surface of the lens assembly; the reflective polarizing layer is located on the side of the fourth surface of the lens assembly away from the first surface; the phase delay film is located on the side of the transflective film away from the first surface. The light incident on the lens assembly after being transmitted through the transflective film is configured to be reflected between the transflective film and the reflective polarizing layer and to be emitted from the reflective polarizing layer; the first surface and the second surface are two surfaces of the same lens, the first surface is a convex surface, the second surface is a concave surface, the third surface is a convex surface, and the fourth surface is a concave surface, the absolute value of the radius of curvature of the fourth surface is greater than the absolute value of the radius of curvature of the first surface, the ratio of the radius of curvature of the third surface to the radius of curvature of the fourth surface is 0.3 to 0.8, and the absolute value ratio of the cone coefficient of the third surface to the cone coefficient of the fourth surface is not greater than 0.2.

[0005] For example, according to an embodiment of the present disclosure, the distance between the two intersection points where the first surface and the second surface intersect the optical axis is a first distance, the distance between the two intersection points where the third surface and the fourth surface intersect the optical axis is a second distance, the first distance is smaller than the second distance, and the ratio of the second distance to the focal length of the optical system is 0.45 to 0.7.

[0006] For example, according to an embodiment of the present disclosure, the ratio of the radius of curvature of the first surface to the focal length is -1.5 to -2.5, the cone coefficient of the first surface is close to negative infinity, or the radius of curvature of the first surface is a negative value infinitely close to zero, and the cone coefficient of the first surface is -15 to -25; the ratio of the radius of curvature of the second surface and the third surface to the focal length is -1.75 to -2.5, and the cone coefficients of the second surface and the third surface are both -10 to 10; the ratio of the radius of curvature of the fourth surface to the focal length is -3.5 to -5, and the cone coefficient of the fourth surface is -100 to -50.

[0007] For example, according to an embodiment of the present disclosure, a ratio of the first distance to the focal length is 0.15 to 0.25.

[0008] For example, according to an embodiment of the present disclosure, the ratio of the aperture of the lens assembly to the focal length is 2 to 3.

[0009] For example, according to an embodiment of the present disclosure, the ratio of the total optical length of the optical system to the focal length is 0.8-1.

[0010] For example, according to an embodiment of the present disclosure, the phase delay film is located between the reflective polarizing layer and the transflective film, or is located on a side of the reflective polarizing layer away from the transflective film.

[0011] For example, according to an embodiment of the present disclosure, the optical system further includes: a linear polarization film located on a side of the reflective polarization layer away from the transflective film.

[0012] For example, according to an embodiment of the present disclosure, the lens assembly includes a first lens, a second lens and a third lens arranged in sequence along the optical axis direction, the first lens includes the first surface and the second surface, the second lens includes the third surface, the third lens includes the fourth surface, the second lens also includes a fifth surface opposite to the third surface, the third lens also includes a sixth surface located on the side of the fourth surface close to the fifth surface, the fifth surface and the sixth surface are both planes, or the fifth surface and the sixth surface have the same surface shape, and the absolute value of the curvature radius of the fifth surface in at least one direction is greater than the absolute values ​​of the curvature radius of other surfaces; the phase delay film is located on the fifth surface or the sixth surface.

[0013] For example, according to an embodiment of the present disclosure, the absolute value of the radius of curvature of the fifth surface is greater than 100 mm.

[0014] For example, according to an embodiment of the present disclosure, the distance between the two intersection points where the two surfaces of the first lens intersect the optical axis is the first distance, the distance between the two intersection points where the two surfaces of the second lens intersect the optical axis is the third distance, and the distance between the two intersection points where the two surfaces of the third lens intersect the optical axis is the fourth distance, and both the first distance and the fourth distance are smaller than the third distance.

[0015] For example, according to an embodiment of the present disclosure, the ratio of the sum of the third distance and the fourth distance to the second distance is 0.9 to 1.1.

[0016] For example, according to an embodiment of the present disclosure, the ratio of the first distance to the focal length is 0.15 to 0.25, the ratio of the third distance to the focal length is 0.3 to 0.45, and the ratio of the fourth distance to the focal length is 0.15 to 0.25.

[0017] For example, according to an embodiment of the present disclosure, the ratio of the center thickness to the edge thickness of the second lens is greater than or equal to 0.5 and not greater than 3, and the ratio of the edge thickness to the center thickness of the third lens is greater than or equal to 0.5 and not greater than 2.

[0018] For example, according to an embodiment of the present disclosure, the exit pupil distance of the optical system is 12 to 20 mm.

[0019] For example, according to an embodiment of the present disclosure, the material of the second lens is the same as that of the third lens, and the material of the first lens is different from that of the second lens.

[0020] For example, according to an embodiment of the present disclosure, the lens assembly includes a first lens and a second lens arranged in sequence along the optical axis direction, the first lens includes the first surface and the second surface, the second lens includes the third surface and the fourth surface; the phase delay film is located between the reflective polarizing layer and the transflective film, or is located on the side of the reflective polarizing layer away from the fourth surface.

[0021] For example, according to an embodiment of the present disclosure, the phase retardation film is located between the reflective polarization layer and the transflective film, and the reflective polarization layer is configured to reflect linear polarized light of one characteristic and transmit linear polarized light of another characteristic; or, the phase retardation film is located on the side of the reflective polarization layer away from the fourth surface, and the reflective polarization layer includes a cholesteric liquid crystal layer.

[0022] An embodiment of the present disclosure provides a display device, including a display screen and any one of the above optical systems, wherein the optical system is located on a display side of the display screen, and the second surface is located on a side of the first surface away from the display screen.

[0023] For example, according to an embodiment of the present disclosure, the display screen includes a plurality of sub-pixels and a micro-lens array located on the light-emitting side of the plurality of sub-pixels. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present disclosure, but are not intended to limit the present disclosure.

[0025] Figure 1 A cross-sectional view of an optical system provided according to an example of an embodiment of the present disclosure.

[0026] Figure 2 for Figure 1 Light path diagram when the optical system is applied to a display device.

[0027] Figure 3 for Figure 1 Spot diagram of the optical system shown.

[0028] Figure 4 for Figure 1 Plot of the diffuse spot size as a function of gaze point for the optical system shown.

[0029] Figure 5 for Figure 1 Distortion diagram of the optical system shown.

[0030] Figure 6 and Figure 7 Cross-sectional views of optical structures provided according to different examples of embodiments of the present disclosure.

[0031] Figure 8 and Fig. 9 for Figure 7 Schematic diagrams of different shapes of the fifth surface shown.

[0032] Figures 10 to 12 Schematic diagram of the cross-sectional structure of an optical structure provided according to different examples of an embodiment of the present disclosure.

[0033] Fig.13 It is a schematic diagram of a partial structure of a display device provided according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0035] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The words "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. The words "include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0036] The present disclosure provides an optical system and a display device. The optical system includes a lens assembly, a transflective film, a reflective polarizing layer, and a phase delay film. The lens assembly includes at least two lenses, and the at least two lenses include a first surface, a second surface, a third surface, and a fourth surface arranged in sequence along the optical axis direction of the lens assembly, and the second surface and the third surface have the same surface parameters; the transflective film is located between the second surface and the third surface of the lens assembly; the reflective polarizing layer is located on the side of the fourth surface of the lens assembly away from the first surface; and the phase delay film is located on the side of the transflective film away from the first surface. The light incident on the lens assembly after being transmitted through the transflective film is configured to be reflected between the transflective film and the reflective polarizing layer and to be emitted from the reflective polarizing layer; the first surface and the second surface are two surfaces of the same lens, the first surface is a convex surface, the second surface is a concave surface, the third surface is a convex surface, and the fourth surface is a concave surface, the absolute value of the radius of curvature of the fourth surface is greater than the absolute value of the radius of curvature of the first surface, the ratio of the radius of curvature of the third surface to the radius of curvature of the fourth surface is 0.3 to 0.8, and the absolute value ratio of the cone coefficient of the third surface to the cone coefficient of the fourth surface is not greater than 0.2.

[0037] The optical system provided by the present disclosure is provided by configuring a lens component to include at least four surfaces, wherein two surfaces are respectively provided with a transflective film and a reflective polarizing layer to realize the reflection of light, and the relationship between the curvature radii of the first surface, the second surface, the third surface and the fourth surface is configured, and the relationship between the cone coefficients of the third surface and the fourth surface is configured, thereby providing an optical system with ultra-short focus and large field of view characteristics.

[0038] The optical system and display device provided by the embodiments of the present disclosure are described below in conjunction with the accompanying drawings.

[0039] Figure 1 A cross-sectional view of an optical system provided according to an example of an embodiment of the present disclosure. Figure 2 for Figure 1 Light path diagram when the optical system is applied to a display device.

[0040] like Figure 1As shown, the optical system includes a lens assembly 10 , a transflective film 200 , a reflective polarizing layer 300 , and a phase delay film 400 .

[0041] like Figure 1 As shown, the lens assembly 10 includes at least two lenses, and the at least two lenses include a first surface 101, a second surface 102, a third surface 103 and a fourth surface 104 arranged in sequence along the optical axis OA direction of the lens assembly 10, and the second surface 102 and the third surface 103 have the same surface parameters. The first surface 101 and the second surface 102 are two surfaces of the same lens, the first surface 101 is a convex surface, the second surface 102 is a concave surface, the third surface 103 is a convex surface, and the fourth surface 104 is a concave surface. For example, the lens including the first surface 101 and the second surface 102 can be a negative lens. For example, at least one of the first surface 101, the second surface 102, the third surface 103 and the fourth surface 104 includes a spherical surface, an aspherical surface and a free-form surface. For example, the first surface 101 is an aspherical surface. For example, the second surface 102, the third surface 103 and the fourth surface 104 are all aspherical surfaces. The second surface 102 and the third surface 103 having the same surface parameters means that the second surface can be substantially completely attached to the third surface regardless of the presence of other film layers between the two.

[0042] For example, the optical axis OA is parallel to the X direction shown in the figure. Figure 1 The schematic diagram shows that the second surface 102 and the third surface 103 are glued together to alleviate the ghost problem and improve the compactness of the optical system. However, it is not limited thereto, and an air gap can be provided between the second surface and the third surface to improve the design freedom of the optical system.

[0043] like Figure 1 As shown, the transflective film 200 is located between the second surface 102 and the third surface 103 of the lens assembly 10. For example, the transflective film 200 can be disposed on the third surface 103. For example, the transflective film 200 can be plated on the third surface 103. For example, the transflective film 200 can be disposed on the second surface 102.

[0044] For example, Figure 1 As shown, the transflective film 200 is configured to transmit part of the light and reflect another part of the light. For example, the transflective film 200 may include at least one film layer, such as each film layer may have a thickness of 10 to 200 nanometers. For example, the transmittance of the transflective film 200 may be 50%, and the reflectivity may be 50%. For example, the transmittance of the transflective film 200 may be 60%, and the reflectivity may be 40%. For example, the transmittance of the transflective film 200 may be 65%, and the reflectivity may be 35%. The optical system provided by the present disclosure is not limited thereto, and the transmittance and reflectivity of the transflective film may be set according to product requirements.

[0045] like Figure 1 As shown, the reflective polarizing layer 300 is located on the side of the fourth surface 104 of the lens assembly 10 away from the first surface 101. For example, the reflective polarizing layer 300 can be disposed on the fourth surface 104. For example, the reflective polarizing layer 300 can be a polarizing reflective film, and the reflective polarizing layer 300 is configured to reflect linear polarized light of one characteristic and transmit linear polarized light of another characteristic.

[0046] For example, Figure 1 As shown, the functions of the reflective polarizing layer 300 are as follows: there is a light transmission axis direction in the plane of the film layer, the transmittance of the polarization component of the incident light parallel to the light transmission axis direction (such as s-linear polarized light) is greater than the transmittance of the polarization component perpendicular to the light transmission axis direction (such as p-linear polarized light), and the reflectivity of the polarization component parallel to the light transmission axis direction (such as s-linear polarized light) is less than the reflectivity of the polarization component perpendicular to the light transmission axis direction (such as p-linear polarized light). For example, the reflective polarizing layer 300 can also be called a polarization beam splitter film. For example, the transmittance of polarized light parallel to the light transmission axis direction of the reflective polarizing layer 300 is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%; the reflectivity of polarized light perpendicular to the light transmission axis direction of the reflective polarizing layer 300 is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%. For example, the reflective polarizing layer 300 may include a reflective dual brightness enhancement film (DBEF).

[0047] like Figure 1 As shown, the phase delay film 400 is located on the side of the transflective film 200 away from the first surface 100. For example, the phase delay film 400 is located between the reflective polarization layer 300 and the transflective film 200. For example, the phase delay film 400 is configured to enable the transmitted light to achieve a conversion between a circular polarization state and a linear polarization state. For example, the phase delay film 400 can be a 1 / 4 wave plate. For example, the material of the phase delay film 400 can include liquid crystal polymer or polycarbonate. For example, the phase delay film 400 has the following characteristics: there is a direction with the lowest refractive index and a direction with the highest refractive index in the plane of the film layer, which are the fast axis and the slow axis respectively, and the phase of the polarized light parallel to the slow axis after passing through the phase delay film 400 is delayed by 1 / 4 wavelength compared with the polarized light parallel to the fast axis after passing through the phase delay film 400.

[0048] For example, Figure 1 As shown, the angle between the slow axis of the phase retarder film 400 and the light transmission axis of the reflective polarizing layer 300 is 45 degrees.

[0049] In some examples, such as Figure 1As shown, the optical system further includes a linear polarization film 500 located on a side of the reflective polarization layer 300 away from the transflective film 200 .

[0050] For example, Figure 1 As shown, the light transmission axis of the linear polarizing film 500 coincides with the light transmission axis of the reflective polarizing layer 300, and the linear polarizing film 500 can be used to further filter other stray light, and only polarized light (such as s-linear polarized light) passing through the linear polarizing film 500 is allowed to enter the human eye. For example, the linear polarizing film 500 can adopt a three-layer laminated structure, the middle layer in the three-layer laminated structure can be polyvinyl alcohol (PVA) added with dichroic molecules, at least one layer on both sides of the middle layer in the three-layer laminated structure can be triacetate (TAC), and the total thickness of the three-layer laminated structure can be 40 to 200 microns.

[0051] For example, Figure 1 As shown, the reflective polarizing layer 300 is attached to the fourth surface 104, and the linear polarizing film 500 is attached to the surface of the reflective polarizing layer 300. For example, the surface of the linear polarizing film 500 facing the air is anti-reflective treated. For example, the surface of the linear polarizing film 500 facing the air can be attached with a moth-eye film.

[0052] like Figure 1 and Figure 2 As shown, light, such as light emitted from the display panel 20, is configured to be folded back between the transflective film 200 and the reflective polarizing layer 300 after being transmitted through the transflective film 200 and incident on the lens assembly 10, and to be emitted from the reflective polarizing layer 300 to achieve an ultra-short focus folded light path (Pancake).

[0053] For example, Figure 1 and Figure 2 As shown, the principle of the folded optical path is as follows: a wave plate can be provided on the light-emitting side of the display screen 20 located on the side of the first surface 101 away from the second surface 102. The image light emitted from the display screen is converted into right-handed circularly polarized light after passing through the wave plate. The right-handed circularly polarized light is refracted at the first surface 101 of the lens assembly 10 and incident on the transflective film 200. The polarization state of the right-handed circularly polarized light remains unchanged after passing through the transflective film 200. The right-handed circularly polarized light reaches the phase delay film 400. The right-handed circularly polarized light incident on the phase delay film 400 is converted into p-linear polarized light. The p-linear polarized light is reflected back to the phase delay film 400 by the reflective polarization layer 300, where the first reflection occurs. Then, the p-linear polarized light is converted into right-handed circularly polarized light after passing through the phase delay film 400. The right-handed circularly polarized light reaches the transflective film 200 and is reflected at the transflective film 200, where the second reflection occurs. Due to the half-wave loss, the reflected light changes from right-handed circularly polarized light to left-handed circularly polarized light. The left-handed circularly polarized light is converted into s-linearly polarized light by the phase delay film 400, and then the s-linearly polarized light is transmitted through the reflective polarizing layer 300 and the linear polarizing film 500 and then emitted to the human eye.

[0054] The above-mentioned folded optical path can change the polarization state of the light propagating between the reflective polarizing layer and the transflective film, thereby realizing the folding of the light, so that the original focal length of the optical system is folded due to, for example, two reflections added by setting the above-mentioned reflective polarizing layer, phase delay film and transflective film, thereby greatly compressing the space required between the human eye and the optical system, thereby making the optical system smaller and thinner.

[0055] For example, Figure 2 As shown, the light emitted by the display screen 20 is refracted or reflected by the optical surfaces in the optical system, and finally forms an upright and enlarged image at a fixed distance in front of the human eye. Since the image is not formed by the convergence of actual light rays, but by the light rays refracted to the human eye end and then extended in the reverse direction and converged, it is called a virtual image.

[0056] like Figure 1 As shown, the absolute value of the radius of curvature of the fourth surface 104 is greater than the absolute value of the radius of curvature of the first surface 101, the ratio of the radius of curvature of the third surface 103 to the radius of curvature of the fourth surface 104 is 0.3-0.8, and the absolute value ratio of the cone coefficient of the third surface 103 to the cone coefficient of the fourth surface 104 is not greater than 0.2.

[0057] In some examples, such as Figure 1 As shown, the distance between the two intersection points where the first surface 101 and the second surface 102 intersect the optical axis OA is a first distance D1, the distance between the two intersection points where the third surface 103 and the fourth surface 104 intersect the optical axis OA is a second distance D2, the first distance D1 is smaller than the second distance D2, and the ratio of the second distance D2 to the focal length of the optical system is 0.45 to 0.7.

[0058] The optical system provided by the embodiment of the present disclosure is an optical system using a folded optical path (Pancake), in which a lens component is arranged to include at least four surfaces, two of which are respectively provided with a transflective film and a reflective polarization layer to realize the reflection of light, and the relationship between the curvature radii of the first surface, the second surface, the third surface and the fourth surface, the relationship between the cone coefficients of the third surface and the fourth surface are arranged, and at the same time, the relationship between the distances between the surfaces and the proportional relationship with the focal length of the optical system are arranged, thereby providing an optical system with ultra-short focus and large field of view characteristics.

[0059] Compared with a single lens having only two surfaces, the optical system provided by the present disclosure has at least four surfaces, which is beneficial to increasing the degree of freedom in the design of the surface parameters of the optical system, so as to improve display performance including clarity, correction of aberrations, and increase of field of view angle.

[0060] By arranging the transflective film between the second surface and the third surface, the light emitted from the display panel is refracted by at least one air-medium interface before entering the transflective film, which is beneficial to deflecting the light and improving the viewing angle.

[0061] For example, Figure 1 As shown, the ratio of the radius of curvature of the third surface 103 to the radius of curvature of the fourth surface 104 may be 0.5 to 0.7, and the absolute value ratio of the cone coefficient of the third surface 103 to the cone coefficient of the fourth surface 104 is not greater than 0.18. For example, the ratio of the radius of curvature of the third surface 103 to the radius of curvature of the fourth surface 104 may be 0.4 to 0.6, and the absolute value ratio of the cone coefficient of the third surface 103 to the cone coefficient of the fourth surface 104 is not greater than 0.15. For example, the ratio of the radius of curvature of the third surface 103 to the radius of curvature of the fourth surface 104 may be 0.35 to 0.55, and the absolute value ratio of the cone coefficient of the third surface 103 to the cone coefficient of the fourth surface 104 is not greater than 0.12. For example, the ratio of the curvature radius of the third surface 103 to the curvature radius of the fourth surface 104 may be 0.45-0.75, and the absolute value ratio of the cone coefficient of the third surface 103 to the cone coefficient of the fourth surface 104 is not greater than 0.1.

[0062] For example, Figure 1 As shown, the ratio of the second distance D2 to the focal length of the optical system is 0.5 to 0.6. For example, the ratio of the second distance D2 to the focal length of the optical system is 0.48 to 0.65. For example, the ratio of the second distance D2 to the focal length of the optical system is 0.55 to 0.68.

[0063] In some examples, such as Figure 1 and Figure 2 As shown, the ratio of the radius of curvature of the first surface 101 to the focal length is -1.5 to -2.5, the cone coefficient of the first surface 101 is close to negative infinity, or the radius of curvature of the first surface 101 is a negative value infinitely close to zero, and the cone coefficient of the first surface is -15 to -25; the ratio of the radius of curvature of the second surface 102 and the third surface 103 to the focal length is -1.75 to -2.5, and the cone coefficient of the second surface 102 and the third surface 103 is -10 to 10; the ratio of the radius of curvature of the fourth surface 104 to the focal length is -3.5 to -5, and the cone coefficient of the fourth surface 104 is -100 to -50.

[0064] In some examples, such as Figure 1 As shown, the ratio of the first distance D1 to the focal length is 0.15-0.25.

[0065] In some examples, such as Figure 1 and Figure 2As shown, the ratio of the total optical length (TTL) of the optical system to the focal length is 0.8 to 1.

[0066] In some examples, such as Figure 1 As shown, the ratio of the aperture of the lens assembly 10 to the focal length of the optical system is 2 to 3. The aperture of the lens assembly 10 refers to the effective aperture, such as the maximum aperture through which light can pass, which is determined by the maximum luminous flux of the lens assembly 10.

[0067] For example, Figure 1 As shown, the exit pupil distance of the optical system is 12 to 20 mm.

[0068] By setting the ratio of the curvature radius of each surface to the focal length of the optical system, setting the cone coefficient of each surface, setting the ratio of the distance between different surfaces to the focal length, setting the ratio of the total optical length to the focal length, and setting the ratio of the aperture of the lens assembly to the focal length of the optical system, the optical system can have an ultra-short focal length, a large field of view display effect, and a more suitable exit pupil distance, thereby improving the user experience.

[0069] For example, Figure 1 As shown, the ratio of the curvature radius of the first surface 101 to the focal length is -1.7 to -2, and the conic coefficient of the first surface 101 approaches negative infinity. For example, the curvature radius of the first surface 101 is a negative value infinitely close to zero, and the conic coefficient of the first surface is -20.

[0070] For example, Figure 1 As shown, for example, the ratio of the radius of curvature of the second surface 102 and the third surface 103 to the focal length is -1.8 to -2, and the cone coefficients of the second surface 102 and the third surface 103 are both 0 to 1. For example, the ratio of the radius of curvature of the second surface 102 and the third surface 103 to the focal length is -1.85 to -2.3, and the cone coefficients of the second surface 102 and the third surface 103 are both -10 to 0. For example, the ratio of the radius of curvature of the second surface 102 and the third surface 103 to the focal length is -1.9 to -1.95, and the cone coefficients of the second surface 102 and the third surface 103 are both -8 to -5.

[0071] For example, Figure 1 As shown, the ratio of the curvature radius of the fourth surface 104 to the focal length is -3.8 to -4.5, and the conic coefficient of the fourth surface 104 is -90 to -60. For example, the ratio of the curvature radius of the fourth surface 104 to the focal length is -4 to -4.8, and the conic coefficient of the fourth surface 104 is -80 to -70.

[0072] For example, Figure 1As shown, the ratio of the first distance D1 to the focal length is 0.18 to 0.2. For example, the ratio of the first distance D1 to the focal length is 0.17 to 0.22. For example, the ratio of the first distance D1 to the focal length is 0.16 to 0.21. For example, the ratio of the first distance D1 to the focal length is 0.19 to 0.24.

[0073] For example, Figure 1 As shown, the first distance D1 may be the central thickness of the lens including the first surface 101 and the second surface 102 .

[0074] For example, Figure 1 As shown, the ratio of the total optical length (TTL) of the optical system to the focal length can be 0.85 to 1. For example, the ratio of the total optical length of the optical system to the focal length can be 0.8 to 0.95. For example, the ratio of the total optical length of the optical system to the focal length can be 0.89 to 0.9. For example, the above-mentioned total optical length can refer to the axial distance between the highest point of the fourth surface closest to the human eye in the optical system and the display surface of the display panel. The highest point on the fourth surface includes the edge sagittal height of the lens structure 10 on the fourth surface side.

[0075] For example, Figure 1 As shown, the ratio of the aperture of the lens assembly 10 to the focal length is 2.2 to 2.5. For example, the ratio of the aperture of the lens assembly 10 to the focal length is 2.4 to 2.8. For example, the ratio of the aperture of the lens assembly 10 to the focal length is 2.2 to 2.5. For example, the ratio of the aperture of the lens assembly 10 to the focal length is 2.3 to 2.7.

[0076] For example, Figure 1 As shown, the ratio of the total optical length of the optical system to the aperture of the lens assembly 10 is 35%.

[0077] For example, Figure 1 As shown, the pupil distance of the optical system is 13 to 18 mm. For example, the pupil distance of the optical system is 15 to 17 mm. For example, the pupil distance of the optical system is 16 to 19 mm.

[0078] For example, Figure 1 As shown, the field of view of the optical system may be 90 to 110 degrees. For example, the field of view of the optical system may be greater than 100 degrees.

[0079] For example, Figure 1 As shown, the curvature radius of the above-mentioned surface in the lens assembly 10 is the curvature radius of the base spherical surface of the surface. The above-mentioned "base spherical surface" means that the aspherical surface is further deformed based on the spherical surface, and the spherical surface serving as the basis of the aspherical surface is the base spherical surface of the aspherical surface. For example, the third surface 103 and the fourth surface 104 can both be aspherical surfaces, such as even aspherical surfaces (EVENASPH).

[0080] For example, the aspheric surface shape is expressed by the following numerical formula:

[0081]

[0082] For example, in the above formula, the height of the aspheric surface along the direction perpendicular to the optical axis is Y, the distance from the aspheric vertex to the projection of the aspheric surface at a height of Y on the optical axis is z, that is, z is the coordinate along the optical axis; C is the curvature (the inverse of the radius of curvature R), k is the conic constant, α i is the coefficient of each high-order term, and 2i is the order of Aspherical Coefficient.

[0083] When actually optimizing the reasonable configuration of the surface parameters of the lens structure 10, the curvature radius, cone coefficient, height and aspheric coefficient of the surface of the lens structure 10 are placed in the above numerical formula, and optical simulation calculations are performed to obtain various optimization parameters that can correct the aberrations of the optical structure.

[0084] For example, the high-order coefficients of the third surface 103 satisfy: α4=6.0e-005, α6=-1e-010, α8=-2e-011. For example, the high-order coefficients of the fourth surface 104 satisfy: α4=5.3e-007, α6=8e-010, α8=8e-012.

[0085] In some examples, such as Figure 1 As shown, the lens assembly 10 includes a first lens 110, a second lens 120, and a third lens 130 arranged in sequence along the optical axis OA direction, the first lens 110 includes a first surface 101 and a second surface 102, the second lens 120 includes a third surface 103, the third lens 130 includes a fourth surface 104, the second lens 120 also includes a fifth surface 105 opposite to the third surface 103, the third lens 130 also includes a sixth surface 106 located on the side of the fourth surface 104 close to the fifth surface 105, the fifth surface 105 and the sixth surface 106 are both planes, and the phase delay film 400 is located on the fifth surface 105 or the sixth surface 106. For example, the phase delay film 400 is attached to the fifth surface 105 or the sixth surface 106.

[0086] The phase delay film includes birefringent materials. Laminating the phase delay film to a flat surface with a flat shape can improve the flatness of the film material, overcome the process challenges caused by curved lamination, avoid the softening and stretching process of the above-mentioned film material which affects the deviation of its birefringent properties such as the optical axis angle and phase delay, and make it easy to maintain a fixed phase delay, which is beneficial to improving the comprehensive optical performance of the optical system such as clarity, stray light, and field of view to ensure imaging quality.

[0087] For example, Figure 1 As shown, the transflective film 200 is plated on the third surface of the second lens 120, the first lens 110 is bonded to the transflective film 200, the phase delay film 400 is bonded to the fifth surface 105 of the second lens 120, and the sixth surface 106 is bonded to the phase delay film 400. For example, the first lens 110 is bonded to the second lens 120, and the second lens 120 is bonded to the third lens 130.

[0088] For example, Figure 1 As shown, the apertures of the first lens 110 , the second lens 120 , and the third lens 130 may be substantially equal, such as the ratios of the apertures of the three lenses to the focal length of the optical system are all 2 to 3.

[0089] In some examples, such as Figure 1 As shown, the distance between the two intersection points where the two surfaces of the first lens 110 intersect the optical axis OA is a first distance D1, the distance between the two intersection points where the two surfaces of the second lens 120 intersect the optical axis OA is a third distance D3, and the distance between the two intersection points where the two surfaces of the third lens 130 intersect the optical axis OA is a fourth distance D4. Both the first distance D1 and the fourth distance D4 are smaller than the third distance D3.

[0090] For example, Figure 1 As shown, the center thickness of the second lens 120 is the third distance D3, and the center thickness of the third lens 130 is the fourth distance D4. For example, the second lens 120 can be a positive lens. For example, the second lens 120 can be a plano-convex lens. For example, the third lens 130 can be a negative lens. For example, the third lens 130 can be a plano-concave lens.

[0091] In some examples, such as Figure 1 As shown, the ratio of the first distance D1 to the focal length is 0.15-0.25, the ratio of the third distance D3 to the focal length is 0.3-0.45, and the ratio of the fourth distance D4 to the focal length is 0.15-0.25.

[0092] For example, Figure 1 As shown, the ratio of the first distance D1 to the focal length is 0.18-0.2, the ratio of the third distance D3 to the focal length is 0.35-0.4, and the ratio of the fourth distance D4 to the focal length is 0.18-0.2. For example, the ratio of the first distance D1 to the focal length is 0.17-0.23, the ratio of the third distance D3 to the focal length is 0.33-0.42, and the ratio of the fourth distance D4 to the focal length is 0.17-0.22. For example, the ratio of the first distance D1 to the focal length is 0.19-0.24, the ratio of the third distance D3 to the focal length is 0.38-0.43, and the ratio of the fourth distance D4 to the focal length is 0.16-0.24.

[0093] In some examples, such as Figure 1 As shown, the ratio of the sum of the third distance D3 and the fourth distance D4 to the second distance D2 is 0.9 to 1.1. Figure 1 The effect of each film layer on the distance between different surfaces of the lens assembly is schematically shown. When the thickness of each film layer is relatively thin, the thickness of the film layer can be ignored. In this case, the sum of the center thickness of the second lens and the center thickness of the third lens can be the above-mentioned second distance.

[0094] In some examples, such as Figure 1 As shown, the second lens 120 and the third lens 130 are made of the same material, and the material of the first lens 110 is different from that of the second lens 120, which is beneficial to correcting chromatic aberration. For example, the refractive index of the second lens 120 and the third lens 130 can be 1.45 to 1.75. By selecting a larger refractive index for the second lens and the third lens, it is beneficial to obtain a larger curvature radius.

[0095] By using the same material for the second lens and the third lens, the manufacture of the optical system can be facilitated.

[0096] For example, Figure 1 As shown, the Abbe numbers of the second lens 120 and the third lens 130 are both greater than 50. For example, the Abbe number of the first lens 110 is different from the Abbe numbers of the second lens 120 and the third lens 130.

[0097] For example, Figure 1 As shown, the material of the second lens 120 and the third lens 130 may be cycloolefin copolymer (COC), such as resin, with a refractive index of 1.54 and an Abbe number vd of 56. For example, the material of the first lens 110 may be polymethyl methacrylate (PMMA), such as organic glass, with a refractive index of 1.49 and an Abbe number of 57.2. For example, the material of the first lens 110 may be polystyrene (PS), with a refractive index of 1.59 and an Abbe number of 30.8. Of course, the embodiments of the present disclosure are not limited thereto, and the material of the first lens may be the same as that of the second lens and the third lens, or the materials of the second lens and the third lens may be different.

[0098] For example, Figure 1 As shown, when the aperture of the optical system satisfies the field of view angle of not less than 100 degrees, the thickness of the edge (outside the effective aperture) of at least one lens can be thinned to reduce the weight of the optical system. For example, when the optical system provided by the present disclosure is applied to a display device, the weight of the binocular lens is not more than 30 grams.

[0099] For example, Figure 1 As shown, an anti-reflective film may be provided on a surface of the first lens 110 that is away from the second lens 120 .

[0100] Figure 3 for Figure 1 Spot diagram of the optical system shown. Figure 4 for Figure 1 The speckle size of the optical system shown is a graph of the root mean square (RMS) of the speckle diameter as a function of gaze point. Figure 3 The normalized field of view in the X direction, the normalized field of view in the Y direction, the field of view angle in the X direction, the field of view angle in the Y direction, and the root mean square (RMS) of the diffuse spot diameter at different field of view angles are shown.

[0101] A point diagram refers to a diffuse pattern formed when many light rays emitted from one point pass through the optical system and their intersection with the image plane is no longer concentrated at the same point due to aberrations, but are spread over a certain range. This pattern can be used to evaluate the imaging quality of the optical system. Figure 3 It is usually used to evaluate the full field of view clarity of the optical system, that is, the image clarity of the full field of view that can be covered by the peripheral vision when the human pupil is at the entrance pupil position on the optical axis and the center of the optical system (i.e., zero field of view), also known as the transient mode. In addition to the full field of view clarity in this mode, the gaze point clarity is also a more important optical indicator for the wearer of the headset, such as the image clarity within a certain angle range that can be directly seen (not seen by the peripheral vision) when the eyes move up, down, left, and right.

[0102] In the gaze point mode, the eyeball rotates a certain angle, the pupil deviates from the center of the optical axis, and there is a certain deviation in the Z and Y directions of the optical axis, and the main light passing through the center of the pupil has a certain angle with the Z axis. For example, the range of the angle is ±35 degrees to take into account the observation habits of the human eye. For example, in order to see the front object that is more than 35 degrees beyond the center of the human eye, people will actively turn their heads instead of moving their eyeballs.

[0103] Figure 4 The figure shows the relationship between the clarity of the gaze point and the gaze angle. The diffuse spot in the central field of view is much smaller than a pixel. When the optical system provided in the present invention images the gaze point at an angle of 25 degrees, the diameter of the diffuse spot is 22 microns, and the clarity is relatively high.

[0104] Figure 5 for Figure 1 Distortion diagram of the optical system shown. For example, Figure 5 As shown in the figure, distortion is a parameter in the optical system and one of the important factors limiting the accuracy of optical measurement. It is the degree of distortion of the image formed by the optical system on the object relative to the object itself. Figure 5 The distortion degree of the optical system is shown. At a half field of view of 45°, the relative distortion of the optical system is not less than -35%, so the optical system meets the distortion requirements of imaging in general virtual reality products, and the distortion degree of the image is low. In addition, distortion correction can be pre-processed in the software.

[0105] Figure 6 A cross-sectional view of an optical structure provided according to another example of an embodiment of the present disclosure. Figure 6 and Figure 1 The difference between the optical structures shown is the different apertures of the first lens 110. For example, the aperture of the first lens 110 can be adjusted as long as it is larger than the effective aperture of the optical system.

[0106] Figure 7 A cross-sectional view of an optical structure provided according to another example of an embodiment of the present disclosure. Figure 7 The optical structure shown is Figure 1 The optical structures shown are different in that the fifth surface and the sixth surface have different surface shapes.

[0107] In some examples, such as Figure 7 As shown, the fifth surface 105 and the sixth surface 106 have the same surface parameters, and the absolute value of the radius of curvature of the fifth surface 105 in at least one direction is greater than the absolute value of the radius of curvature of other surfaces. For example, the fifth surface 105 and the sixth surface 106 are both curved toward the side close to the first surface 101. For example, without considering the film layer disposed between the fifth surface and the sixth surface, the fifth surface can be substantially completely attached to the sixth surface.

[0108] In some examples, such as Figure 7 As shown, the absolute value of the curvature radius of the fifth surface 105 and the sixth surface 106 is not less than 100 mm. For example, the fifth surface 105 and the sixth surface 106 may be micro-curved surfaces.

[0109] For example, Figure 7 As shown, the ratio of the curvature radius of the fifth surface 105 and the sixth surface 106 to the focal length of the optical system is -8 to -10.

[0110] For example, Figure 7As shown, when the fifth surface 105 (or the sixth surface 106) for setting the phase delay film 400 in the lens assembly 10 is a curved surface, in the process of bonding the phase delay film 400 to the lens assembly 100, the flat-shaped phase delay film 400 needs to be properly stretched first, and then completely bonded to the curved surface of the fifth surface 105. If the radius of curvature of the fifth surface 105 of the lens assembly 10 is small, for example, its absolute value is less than 100 microns and the cone coefficient is greater than or equal to zero, wrinkles may be generated when the phase delay film 400 is stretched and bonded to the fifth surface 105. The excessive stretching of the phase delay film 400 and the wrinkles generated during bonding may affect the phase delay accuracy of the phase delay film, thereby affecting the optical performance. In the optical system provided by the present disclosure, by setting the absolute value of the radius of curvature of the fifth surface for bonding the phase delay film to be larger, the influence of the curved surface of the fifth surface on the performance of the phase delay film can be reduced.

[0111] Figure 8 and Fig. 9 for Figure 7 Schematic diagrams of different shapes of the fifth surface shown.

[0112] For example, Figure 7 and Figure 8 As shown, the fifth surface 105 may be a curved surface with rotational symmetry. For example, the surface shapes of the fifth surface 105 in the X1 direction and the Y1 direction are consistent, and the curvature radius Rx of the fifth surface in the X1 direction is equal to the curvature radius Ry in the Y1 direction, such as both less than -100 microns. For example, the fifth surface 105 may be an aspherical surface.

[0113] For example, Figure 7 and Fig. 9 As shown, the fifth surface 105 can be a curved surface with axial symmetry. For example, the surface shape of the fifth surface 105 in the X1 direction is different from the surface shape in the Y1 direction, and the curvature radius Rx of the fifth surface in the X1 direction is different from the curvature radius Ry in the Y1 direction, such as one of them is less than -100 microns. For example, the fifth surface 105 can be an ellipsoidal surface. For example, the fifth surface 105 can be a cylindrical surface, that is, the fifth surface 105 is a curved surface in one of the X1 direction and the Y1 direction, and the other direction is a plane, that is, a cylindrical surface, Rx 1 0, Ry = 0.

[0114] By setting the shape of the fifth surface to Figure 8 The shape shown is helpful to prevent the shape of the phase delay film from being greatly affected during the process of stretching and bonding the phase delay film.

[0115] In some examples, such as Figure 7As shown, the ratio of the center thickness to the edge thickness of the second lens 120 is greater than or equal to 0.5 and not greater than 3, and the ratio of the edge thickness to the center thickness of the third lens 130 is greater than or equal to 0.5 and not greater than 2. By reasonably setting the ratio of the center thickness to the edge thickness of different lenses, it is beneficial to ensure the injection molding of different lenses, such as the second lens and the third lens, reduce stress, and facilitate processing.

[0116] For example, Figure 7 As shown, the ratio of the center thickness to the edge thickness of the second lens 120 is not greater than 2.8, and the ratio of the edge thickness to the center thickness of the third lens 130 is not greater than 1.5. For example, the ratio of the center thickness to the edge thickness of the second lens 120 is not greater than 2.5, and the ratio of the edge thickness to the center thickness of the third lens 130 is not greater than 1.7. For example, the ratio of the center thickness to the edge thickness of the second lens 120 is not greater than 2.3, and the ratio of the edge thickness to the center thickness of the third lens 130 is not greater than 1.4. For example, the ratio of the center thickness to the edge thickness of the second lens 120 is not greater than 2, and the ratio of the edge thickness to the center thickness of the third lens 130 is not greater than 1.2.

[0117] Fig.10 A schematic diagram of the cross-sectional structure of an optical structure provided according to another example of an embodiment of the present disclosure. Fig.10 The optical structure shown is Figure 1 The optical structures shown are different in that the number of lenses included in the lens assembly 10 is different, and the position of the phase delay film 400 is different.

[0118] In some examples, such as Fig.10 As shown, the lens assembly 10 includes a first lens 110 and a second lens 120 arranged in sequence along the optical axis direction, the first lens 110 includes a first surface 101 and a second surface 102, and the second lens 120 includes a third surface 103 and a fourth surface 104. The first surface, the second surface, the third surface and the fourth surface in this example have the same features as the first surface, the second surface, the third surface and the fourth surface in the lens assembly provided in the above example, and will not be repeated here.

[0119] By only providing the first lens and the second lens in the lens assembly, the manufacture of the lens assembly can be facilitated.

[0120] For example, Fig.10 As shown, the center thickness of the first lens 110 is the first distance D1, and the center thickness of the second lens 120 is the second distance D2. The first distance and the second distance in this example may have the same characteristics as the first distance and the second distance in the above example, and will not be repeated here.

[0121] For example, Fig.10As shown, the phase delay film 400 is located between the transflective film 200 and the third surface 103. For example, the transflective film 200 can be plated on the second surface 102, the phase delay film 400 can be attached to the third surface 103, and the first lens 110 and the second lens 120 are glued. The transflective film in this example has the same features as the transflective film in the above example, and will not be repeated here.

[0122] For example, Fig.10 As shown, the material of the phase delay film 400 can be liquid crystal polymer, which can achieve the same performance as traditional optical film materials such as quarter wave plates (conventional thickness is about 50 μm) at a very thin film thickness (1-5 μm); because of its thin film thickness, it has a high degree of adaptability to different curved surfaces and is easy to shape according to the curved surface. In addition, liquid crystal polymer is a cross-linked system, and the molecules are linked by chemical bonds, and the modulus is relatively high. When stretched after bonding, only elastic deformation occurs, and no molecular stretching, rearrangement, and other effects that strongly affect optical anisotropy will occur. Therefore, the optical displacement after the phase delay film of liquid crystal polymer is used for curved surface bonding is small. The phase delay film using the above-mentioned liquid crystal polymer can be bonded to a surface with a smaller absolute value of the radius of curvature, such as less than 100 microns, thereby increasing the degree of freedom of the radius of curvature of the surface in the lens assembly, which is beneficial to improving the image quality of the optical system, such as including indicators such as clarity, distortion, and dispersion.

[0123] The reflective polarizing layer and the linear polarizing film in the optical structure provided in this example may have the same characteristics as the reflective polarizing layer and the linear polarizing film in the optical structure provided in the above examples, and will not be described in detail here.

[0124] Fig.11 A schematic diagram of the cross-sectional structure of an optical structure provided according to another example of an embodiment of the present disclosure. Fig.11 The optical structure shown is Fig.10 The difference between the optical structures shown is the position of the phase delay film 400. Fig.11 As shown, the phase delay film 400 is located between the reflective polarizing layer 300 and the fourth surface 104 .

[0125] Figures 1 to 11 In the optical structures of the different examples shown, the phase delay film 400 is located between the reflective polarization layer 300 and the transflective film 200. Figures 1 to 11 The reflective polarizing layer 300 in each of the illustrated examples may be made of the same material.

[0126] Fig.12 A schematic diagram of the cross-sectional structure of an optical structure provided according to another example of an embodiment of the present disclosure. Fig.12 The optical structure shown is Fig.11The differences between the optical structures shown are that the positional relationship between the phase retardation film 400 and the reflective polarizing layer 300 is different, and the characteristics of the reflective polarizing layer 300 are different.

[0127] In some examples, such as Fig.12 As shown, the phase delay film 400 is located on a side of the reflective polarizing layer 300 away from the transflective film 200. For example, the phase delay film 400 is located on a side of the reflective polarizing layer 300 away from the fourth surface 104.

[0128] For example, Fig.12 As shown, the reflective polarizing layer 300 includes a cholesteric liquid crystal layer. The cholesteric liquid crystal layer can reflect circularly polarized light and transmit circularly polarized light. Referring to the aforementioned folded optical path principle, the cholesteric liquid crystal layer 300 is disposed between the phase delay film 400 and the transflective film 200. A wave plate can be disposed on the light-emitting surface of the display screen located on the side of the first lens 110 away from the second lens 120. The image light emitted from the display screen is converted into right-handed circularly polarized light after passing through the wave plate. The right-handed circularly polarized light is incident on the transflective film 200. The polarization state of the right-handed circularly polarized light remains unchanged after passing through the transflective film 200. The right-handed circularly polarized light is reflected back to the transflective film 200 after passing through the cholesteric liquid crystal layer 300, where the first reflection occurs; the right-handed circularly polarized light is reflected at the transflective film 200, where the second reflection occurs. Due to the half-wave loss, the reflected light changes from right circularly polarized light to left circularly polarized light. The left circularly polarized light reaches the phase delay film 400 after passing through the cholesteric liquid crystal layer 300, and is converted into s polarized light by the phase delay film 400. Then, the s linearly polarized light is transmitted through the linear polarization film 500 and emitted to the human eye.

[0129] Fig.13 It is a schematic diagram of a partial structure of a display device provided according to another embodiment of the present disclosure.

[0130] like Fig.13 As shown, the display device includes a display screen 20 and an optical system in any of the above examples. Fig.13 The optical system is schematically shown as Figure 1 The optical system shown, but not limited thereto, can also be Figure 6 , Figure 7 , Figures 10 to 12 An optical system is provided in any one of the examples.

[0131] like Fig.13 As shown, the optical system is located on the display side of the display screen 20 , and the second surface 102 is located on a side of the first surface 101 away from the display screen 20 .

[0132] For example, Fig.13 As shown, the display surface of the display screen 20 is located at the focal plane of the light incident side of the optical system.

[0133] In some examples, such as Fig.13 As shown, the display screen 20 includes a plurality of sub-pixels 21 and a microlens array 22 located on the light-emitting side of the plurality of sub-pixels 21. For example, the microlens array 22 includes a plurality of microlenses, such as a spherical lens or an aspherical lens. For example, the surface curvature radius of each microlens may be the same, but at least some of the microlenses may be eccentric microlenses, such as the convex surface vertex deviates from the center of the sub-pixel corresponding thereto, such as the angles between the optical axes of different microlenses and the normals of the light-emitting surface of the display screen are different, so that the light intensity of the light emitted by the sub-pixel is redistributed after passing through the microlens, so that the maximum value of the light intensity is consistent with the direction of the main light in different fields of view in the optical system.

[0134] For example, Fig.13 As shown, when the display screen is small, in order to obtain a larger field of view and a larger optical magnification, the light emitted from the edge of the display screen needs to maintain a larger inclination angle with the normal of the display screen surface, such as using a microlens array, so that the user can get a better viewing experience. For example, when the display screen is large in size and the field of view is medium, the microlens array may not be set in the display screen.

[0135] For example, Fig.13 As shown, the display screen 20 can be a silicon-based organic light-emitting diode display screen with extremely high pixel density. The optical system has the performance of high definition and large field of view. The diffuse spot of the optical system in the central field of view is smaller than the size of a sub-pixel (micrometer level), and the full field of view can exceed 100 degrees.

[0136] For example, Fig.13 As shown, the display screen 20 may be other types of display screens, such as a liquid crystal display screen, an inorganic light emitting diode display screen, a quantum dot display screen, a projector (such as an LCOS micro-projector), and the like.

[0137] For example, the display device may be a virtual reality (VR) display device. For example, the virtual reality display device may be a display device using an ultra-short-throw folded optical path.

[0138] For example, the display device may be a near-eye display device, and the near-eye display device may be a wearable VR helmet, VR glasses, etc., but the embodiments of the present disclosure are not limited thereto.

[0139] There are a few points to note:

[0140] (1) In the drawings of the embodiments of the present disclosure, only the structures related to the embodiments of the present disclosure are involved, and other structures can refer to the general design.

[0141] (2) In the absence of conflict, features in the same embodiment or in different embodiments of the present disclosure may be combined with each other.

[0142] The above description is merely an exemplary embodiment of the present disclosure and is not intended to limit the protection scope of the present disclosure. The protection scope of the present disclosure is determined by the appended claims.

Claims

1. An optical system, comprising: A lens assembly, comprising at least two lenses, wherein the at least two lenses comprise a first surface, a second surface, a third surface and a fourth surface arranged in sequence along an optical axis direction of the lens assembly, wherein the second surface and the third surface have the same surface parameters; a transflective film, located between the second surface and the third surface of the lens assembly; a reflective polarizing layer, located on a side of a fourth surface of the lens assembly away from the first surface; A phase delay film, located on a side of the transflective film away from the first surface; Wherein, the light incident on the lens assembly after being transmitted through the transflective film is configured to be folded back between the transflective film and the reflective polarizing layer, and to be emitted from the reflective polarizing layer; The first surface and the second surface are two surfaces of the same lens, the first surface is a convex surface, the second surface is a concave surface, the third surface is a convex surface, and the fourth surface is a concave surface. The absolute value of the radius of curvature of the fourth surface is greater than the absolute value of the radius of curvature of the first surface, the ratio of the radius of curvature of the third surface to the radius of curvature of the fourth surface is 0.3 to 0.8, and the ratio of the absolute value of the cone coefficient of the third surface to the cone coefficient of the fourth surface is not greater than 0.

2.

2. The optical system according to claim 1, wherein: The distance between two intersection points where the first surface and the second surface intersect the optical axis is a first distance, the distance between two intersection points where the third surface and the fourth surface intersect the optical axis is a second distance, the first distance is smaller than the second distance, and a ratio of the second distance to the focal length of the optical system is 0.45 to 0.

7.

3. The optical system according to claim 1, wherein: The ratio of the radius of curvature of the first surface to the focal length of the optical system is -1.5 to -2.5, and the conic coefficient of the first surface is close to negative infinity, or the radius of curvature of the first surface is a negative value infinitely close to zero, and the conic coefficient of the first surface is -15 to -25; The ratios of the curvature radii of the second surface and the third surface to the focal length of the optical system are both -1.75 to -2.5, and the conic coefficients of the second surface and the third surface are both -10 to 10; The ratio of the radius of curvature of the fourth surface to the focal length is -3.5 to -5, and the cone coefficient of the fourth surface is -100 to -50.

4. The optical system according to claim 2, wherein: The ratio of the first distance to the focal length of the optical system is 0.15-0.

25.

5. The optical system according to claim 1, wherein: The ratio of the aperture of the lens assembly to the focal length of the optical system is 2-3.

6. The optical system according to claim 1, wherein: The ratio of the total optical length of the optical system to the focal length of the optical system is 0.8-1.

7. The optical system according to any one of claims 1 to 6, wherein: The phase delay film is located between the reflective polarizing layer and the transflective film, or is located on a side of the reflective polarizing layer away from the transflective film.

8. The optical system according to any one of claims 1 to 6, further comprising: The linear polarizing film is located on a side of the reflective polarizing layer away from the transflective film.

9. The optical system according to claim 2, wherein: The lens assembly comprises a first lens, a second lens and a third lens arranged in sequence along the optical axis direction, the first lens comprises the first surface and the second surface, the second lens comprises the third surface, the third lens comprises the fourth surface, the second lens further comprises a fifth surface opposite to the third surface, the third lens further comprises a sixth surface located on a side of the fourth surface close to the fifth surface, the fifth surface and the sixth surface are both planes, or the fifth surface and the sixth surface have the same surface shape, and the absolute value of the curvature radius of the fifth surface in at least one direction is greater than the absolute values ​​of the curvature radius of other surfaces; The phase delay film is located on the fifth surface or the sixth surface.

10. The optical system according to claim 9, wherein: The absolute value of the radius of curvature of the fifth surface is greater than 100 mm.

11. The optical system according to claim 9, wherein: The distance between the two intersection points where the two surfaces of the first lens intersect the optical axis is the first distance, the distance between the two intersection points where the two surfaces of the second lens intersect the optical axis is the third distance, and the distance between the two intersection points where the two surfaces of the third lens intersect the optical axis is the fourth distance, and both the first distance and the fourth distance are smaller than the third distance.

12. The optical system according to claim 11, wherein: The ratio of the sum of the third distance and the fourth distance to the second distance is 0.9 to 1.

1.

13. The optical system according to claim 11, wherein: The ratio of the third distance to the focal length is 0.3 to 0.45, and the ratio of the fourth distance to the focal length is 0.15 to 0.

25.

14. The optical system according to claim 10, wherein: The ratio of the center thickness to the edge thickness of the second lens is greater than or equal to 0.5 and not greater than 3, and the ratio of the edge thickness to the center thickness of the third lens is greater than or equal to 0.5 and not greater than 2.

15. The optical system according to any one of claims 1 to 6, wherein: The exit pupil distance of the optical system is 12 to 20 mm.

16. The optical system according to any one of claims 9 to 14, wherein: The second lens and the third lens are made of the same material, and the first lens is made of a material different from that of the second lens.

17. The optical system according to any one of claims 1 to 6, wherein: The lens assembly comprises a first lens and a second lens sequentially arranged along the optical axis direction, the first lens comprises the first surface and the second surface, and the second lens comprises the third surface and the fourth surface; The phase delay film is located between the reflective polarizing layer and the transflective film, or is located on a side of the reflective polarizing layer away from the fourth surface.

18. The optical system according to claim 17, wherein: The phase delay film is located between the reflective polarizing layer and the transflective film, and the reflective polarizing layer is configured to reflect linear polarized light of one characteristic and transmit linear polarized light of another characteristic; or, The phase delay film is located on a side of the reflective polarizing layer away from the fourth surface, and the reflective polarizing layer includes a cholesteric liquid crystal layer.

19. A display device comprising a display screen and the optical system according to any one of claims 1 to 18, in, The optical system is located on a display side of the display screen, and the second surface is located on a side of the first surface away from the display screen.

20. The display device according to claim 19, wherein: The display screen includes a plurality of sub-pixels and a micro-lens array located on the light-emitting side of the plurality of sub-pixels.

Images