Optical system and display apparatus

Abstract

Provided are an optical system and a display apparatus. The optical system comprises: a lens structure, comprising a convex surface and a concave surface that are arranged opposite to each other, wherein the side of the concave surface distant from the convex surface is the light-emitting side of the lens structure; a polarizing reflective layer, arranged on the side of the concave surface of the lens structure distant from the convex surface; a phase delay film, arranged on the side of the concave surface of the lens structure distant from the convex surface; and a transmissive and reflective film, arranged on the side of the convex surface distant from the concave surface, wherein the ratio of the radius of curvature of the convex surface to the effective focal length of the optical system is -1.2 to -2.5, the ratio of the radius of curvature of the concave surface to the radius of curvature of the convex surface is 0.8-2, and in the direction parallel to the optical axis of the lens structure, the ratio of the thickness of the center of the lens structure to the effective focal length is 0.4-0.6.

Description

Optical system and display device

[0001] This application claims priority to Chinese Patent Application No. 202311006667.8 filed on August 10, 2023, and the contents of the above-mentioned Chinese patent application disclosure are hereby incorporated by reference in their entirety as part of this application. Technical Field

[0002] At least one embodiment of the present disclosure relates to an optical system and a display device. Background Art

[0003] Virtual Reality (VR) technology is a computer simulation technology that allows users to create and experience a virtual world. It uses computers to generate interactive, dynamic three-dimensional visuals, immersing users in the environment. To enhance the user experience, products using VR technology are becoming increasingly lightweight.

[0004] Summary of the Invention

[0005] At least one embodiment of the present disclosure provides an optical system, comprising: a lens structure, comprising a convex surface and a concave surface arranged opposite to each other, the side of the concave surface away from the convex surface being the light-emitting side of the lens structure; a polarizing reflection layer, arranged on the side of the concave surface of the lens structure away from the convex surface; a phase delay film, arranged on the side of the concave surface of the lens structure away from the convex surface; and a transflective film, arranged on the side of the convex surface away from the concave surface; wherein the ratio of the radius of curvature of the convex surface to the effective focal length of the optical system is -1.2 to -2.5, and the ratio of the radius of curvature of the concave surface to the radius of curvature of the convex surface is 0.8 to 2; along the direction parallel to the optical axis of the lens structure, the ratio of the center thickness of the lens structure to the effective focal length is 0.4 to 0.6.

[0006] For example, according to an embodiment of the present disclosure, the absolute value of the cone coefficient of the convex surface is less than or equal to the absolute value of the cone coefficient of the concave surface.

[0007] For example, according to an embodiment of the present disclosure, the cone coefficient of the convex surface is greater than or equal to -20 and less than 0, and the cone coefficient of the concave surface is greater than or equal to -50 and less than or equal to the cone coefficient of the convex surface.

[0008] For example, according to an embodiment of the present disclosure, at least one of the convex surface and the concave surface is an aspherical surface or a free-form surface.

[0009] For example, according to an embodiment of the present disclosure, the ratio of the total optical length of the optical system to the effective focal length is 0.8 to 1.2.

[0010] For example, according to an embodiment of the present disclosure, the ratio of the effective aperture of the lens structure to the effective focal length is greater than or equal to 2.

[0011] For example, according to an embodiment of the present disclosure, the exit pupil distance of the optical system is 12 to 18 mm.

[0012] For example, according to an embodiment of the present disclosure, the field of view angle of the optical system is 90° to 110°.

[0013] For example, according to an embodiment of the present disclosure, the lens structure is an integrated lens, and the convex surface and the concave surface are located on opposite sides of the integrated lens.

[0014] For example, according to an embodiment of the present disclosure, the polarized reflective layer is configured to reflect linearly polarized light of one characteristic and transmit linearly polarized light of another characteristic; the phase delay film is arranged on the side of the concave surface away from the convex surface, and the polarized reflective layer is arranged on the side of the phase delay film away from the convex surface; or the polarized reflective layer is a cholesteric liquid crystal layer; the cholesteric liquid crystal layer is arranged on the side of the concave surface away from the convex surface, and the phase delay film is arranged on the side of the cholesteric liquid crystal layer away from the convex surface.

[0015] For example, according to an embodiment of the present disclosure, the optical system further includes a linear polarization film; the linear polarization film is disposed on a side of the polarizing reflective layer away from the transflective film.

[0016] For example, according to an embodiment of the present disclosure, the lens structure includes a first lens and a second lens; the first lens has a first surface and a second surface arranged opposite to each other, the first surface is the convex surface of the lens structure, and the second surface is a plane; the second lens has a third surface and a fourth surface arranged opposite to each other, the third surface is a plane, and the fourth surface is the concave surface of the lens structure.

[0017] For example, according to an embodiment of the present disclosure, the phase delay film is disposed between the second surface and the third surface, and the polarized reflective layer is disposed on the fourth surface.

[0018] For example, according to an embodiment of the present disclosure, the lens structure includes a first lens and a second lens; the first lens has a first surface and a second surface arranged opposite to each other, the first surface is the convex surface of the lens structure, and the second surface is a curved surface; the second lens has a third surface and a fourth surface arranged opposite to each other, the third surface is a curved surface, and the fourth surface is the concave surface of the lens structure; the second surface has the same surface shape as the third surface, the absolute value of the curvature radius of at least one direction of the second surface is greater than the absolute value of the curvature radius of the first surface, and the absolute value of the curvature radius of at least one direction of the third surface is greater than the absolute value of the curvature radius of the fourth surface.

[0019] For example, according to an embodiment of the present disclosure, the absolute values ​​of the curvature radius of the second surface and the curvature radius of the third surface are both greater than 100 mm.

[0020] For example, according to an embodiment of the present disclosure, the second surface has a curved surface with rotational symmetry or a curved surface with axial symmetry.

[0021] For example, according to an embodiment of the present disclosure, the phase delay film is disposed between the second surface and the third surface, and the polarized reflective layer is disposed on the fourth surface.

[0022] For example, according to an embodiment of the present disclosure, the ratio of the center thickness to the edge thickness of the first lens is greater than or equal to 0.5 and less than 3; the ratio of the edge thickness to the center thickness of the second lens is greater than or equal to 0.5 and less than or equal to 2.

[0023] At least one embodiment of the present disclosure provides a display device, comprising a display screen and the optical system described in any of the above embodiments, wherein the display screen is located on a side of the convex surface of the lens structure away from the concave surface. 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, rather than limiting the present disclosure.

[0025] FIG1 is a schematic diagram of an optical system provided by at least one embodiment of the present disclosure.

[0026] FIG2 is a simplified diagram of the optical path of an optical system provided by at least one embodiment of the present disclosure.

[0027] FIG3 is a schematic diagram of an optical system provided by at least another embodiment of the present disclosure.

[0028] FIG4 is a point diagram of the optical system shown in FIG1 .

[0029] FIG5 is a graph showing how the diffuse spot size of the optical system shown in FIG1 changes with the field of view angle.

[0030] FIG6 is a distortion diagram of the optical system shown in FIG1 .

[0031] FIG7 is a schematic diagram of an optical system provided by at least another embodiment of the present disclosure.

[0032] FIG8 is a schematic diagram of an optical system provided by at least another embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not 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.

[0034] Unless otherwise defined, technical or scientific terms used in this disclosure should have the ordinary meanings understood by people with ordinary skills in the field to which this disclosure belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are simply used to distinguish different components. The words "include" or "comprising" and similar terms mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0035] The features such as "perpendicular", "parallel" and "same" used in the embodiments of the present disclosure include the features such as "perpendicular", "parallel" and "same" in the strict sense, as well as the cases where "approximately perpendicular", "approximately parallel" and "approximately the same" contain certain errors, taking into account the errors associated with the measurement and the measurement of specific quantities (that is, the limitations of the measurement system), and are expressed as being within the acceptable deviation range for a specific value determined by a person of ordinary skill in the art. The "center" in the embodiments of the present disclosure can include a position strictly at the geometric center and a position approximately at the center of a small area around the geometric center. For example, "approximately" can mean within one or more standard deviations, or within 10% or 5% of the value.

[0036] Virtual reality devices, such as head-mounted displays, often utilize pancake technology to reduce their size, making them compact and lightweight. This opens up new avenues for mobile, wearable, and consumer electronics. Products utilizing pancake technology can include single, double, or multiple lenses. These lenses can be either separate, with air spaces between them, or glued together.

[0037] During the research, the inventors of this application found that the current folded optical path products often find it difficult to take into account the requirements of optical parameters such as imaging clarity, field of view, distortion, chromatic aberration, etc., which affects the user experience.

[0038] At least one embodiment of the present disclosure provides an optical system and a display device. The optical system includes: a lens structure, a polarizing reflection layer, a phase delay film, and a transflective film. The lens structure includes a convex surface and a concave surface arranged opposite to each other, and the side of the concave surface away from the convex surface is the light-emitting side of the lens structure; the polarizing reflection layer is arranged on the side of the concave surface of the lens structure away from the convex surface; the phase delay film is arranged on the side of the concave surface of the lens structure away from the convex surface; and the transflective film is arranged on the side of the convex surface away from the concave surface. The ratio of the radius of curvature of the convex surface to the effective focal length of the optical system is -1.2 to -2.5, and the ratio of the radius of curvature of the concave surface to the radius of curvature of the convex surface is 0.8 to 2; along the direction parallel to the optical axis of the lens structure, the ratio of the center thickness of the lens structure to the effective focal length is 0.4 to 0.6.

[0039] The optical system provided by at least one embodiment of the present disclosure may be an optical system using a folded optical path (Pancake). While providing a polarizing reflection layer, a phase delay film, and a transflective film on both sides of the lens structure, parameters such as the curvature radius and the center thickness of the concave and convex surfaces of the lens structure are set and optimized. This enables the optical system to be thinner and lighter while achieving a larger full field of view, a larger exit pupil distance, and a smaller holographic height.

[0040] The optical system and the display device are described below with reference to the accompanying drawings and through some embodiments.

[0041] FIG1 is a schematic diagram of an optical system 100 provided in at least one embodiment of the present disclosure, and FIG2 is a simplified diagram of an optical path of the optical system 100 provided in at least one embodiment of the present disclosure.

[0042] 1 and 2 , optical system 100 includes a lens structure 110, a polarizing reflective layer 120, a phase retarder film 130, and a transflective film 140. Lens structure 110 includes a convex surface 111 and a concave surface 112 disposed opposite each other. The side of concave surface 112 facing away from convex surface 111 serves as the light-emitting side of lens structure 110. For example, when optical system 100 is used in a display device, display screen 400 is located on the side of convex surface 111 of lens structure 110 facing away from concave surface 112. Light emitted from display screen 400 passes through convex surface 111, enters lens structure 110, and then exits through concave surface 112.

[0043] As shown in Figure 1, the polarizing reflective layer 120 is disposed on the concave surface 112 of the lens structure 110, away from the convex surface 111. For example, the polarizing reflective film functions as follows: A transmission axis exists within the film plane, and the transmittance of the polarization component of incident light parallel to the transmission axis (e.g., s-polarized light) is greater than the transmittance of the polarization component perpendicular to the transmission axis (e.g., p-polarized light), and the reflectivity of the polarization component parallel to the transmission axis (e.g., s-polarized light) is less than the reflectivity of the polarization component perpendicular to the transmission axis (e.g., p-polarized light). For example, the polarizing reflective layer 120 may also be referred to as a polarizing beam splitter film. For example, the transmittance of polarized light parallel to the transmission axis of the polarizing reflective layer 120 is no less than 85%, such as no less than 90%, such as no less than 95%, or no less than 98%. The reflectivity of polarized light perpendicular to the transmission axis of the polarizing reflective layer 120 is no less than 85%, such as no less than 90%, such as no less than 95%, or no less than 98%.

[0044] As shown in FIG1 , a phase retarder film 130 is disposed on the side of the concave surface 112 of the lens structure 110 away from the convex surface 111. For example, the phase retarder film 130 is configured to convert the transmitted light between a circular polarization state and a linear polarization state. For example, the phase retarder film 130 may be a quarter-wave plate.

[0045] For example, the phase delay film 130 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. The phase of the polarized light parallel to the slow axis after passing through the phase delay film 130 is delayed by 1 / 4 wavelength compared with the polarized light parallel to the fast axis after passing through the phase delay film 130.

[0046] For example, the angle between the slow axis of the phase retardation film 130 and the transmission axis of the polarizing reflective film is 45 degrees.

[0047] For example, the phase retarder film 130 can be made of polycarbonate. The polycarbonate phase retarder film 130 is typically a planar film layer with a thickness of approximately 50 μm. When attaching the phase retarder film 130 to the concave surface 112 of the lens structure 110, the polycarbonate phase retarder film 130 can be appropriately stretched to fully conform to the concave surface 112, to accommodate the aspheric or free-form surface of the concave surface 112. Of course, in conjunction with some embodiments described below, when attaching the phase retarder film 130 to a surface such as a plane or a cylinder, it is not necessary to stretch it.

[0048] For example, the phase retarder film 130 can be made of a liquid crystal polymer. Because the phase retarder film 130 made of liquid crystal polymer is a polymer, its film thickness can be relatively thin, ranging from 1μm to 5μm. A thinner phase retarder film 130 is more adaptable to curved surfaces and can more easily be shaped to the surface's shape, reducing the possibility of wrinkles when attached to the curved surface, which could affect phase retardation accuracy and optical performance. Furthermore, the phase retarder film 130 made of liquid crystal polymer experiences less optical shift when attached to a curved surface. Liquid crystal polymer is a cross-linked system, with molecules linked by chemical bonds and a high modulus. When the phase retarder film 130 made of liquid crystal polymer is stretched after attachment, it only undergoes elastic deformation, without experiencing strong optical anisotropy effects such as molecular stretching or rearrangement. Therefore, the phase retarder film 130 made of liquid crystal polymer is suitable for attachment to surfaces with a small radius of curvature. This flexibility in the radius of curvature also makes it easier to meet requirements for clarity, distortion, and dispersion, facilitating better image quality for the optical system 100.

[0049] As shown in FIG1 , a transflective film 140 is disposed on the side of the convex surface 111 away from the concave surface 112 . For example, the transflective film 140 is configured to transmit some light and reflect another portion. For example, the transflective film 140 may have a transmittance of 50% and a reflectance of 50%. For example, the transflective film 140 may have a transmittance of 60% and a reflectance of 40%. For example, the transflective film 140 may have a transmittance of 65% and a reflectance of 35%. The optical system 100 provided herein is not limited to this embodiment; the transmittance and reflectance of the transflective film 140 may be configured to meet product requirements. For example, the transflective film 140 may be coated on the convex surface 111.

[0050] For example, the polarizing reflective layer 120 is configured to reflect linearly polarized light of one characteristic and transmit linearly polarized light of another characteristic; the phase delay film 130 is arranged on the side of the concave surface 112 away from the convex surface 111, and the polarizing reflective layer 120 is arranged on the side of the phase delay film 130 away from the convex surface 111.

[0051] For example, as shown in Figures 1 and 2, a folded optical path is formed using the aforementioned polarizing reflective layer 120, phase retarder film 130, and transflective film 140, each capable of reflecting linearly polarized light of one characteristic and transmitting linearly polarized light of another characteristic. The principle is as follows: a wave plate can be disposed on the display surface 400a of the display screen 400, located on the side of the convex surface 111 away from the concave surface 112. Image light emitted from the display surface 400a is converted to right-handed circularly polarized light after passing through the wave plate. The polarization state of the right-handed circularly polarized light remains unchanged after passing through the transflective film 140. This light enters the lens structure 110, transmits through the lens structure 110, and reaches the phase retarder film 130. The right-handed circularly polarized light incident on the phase retarder film 130 is converted to p-linearly polarized light. The p-linearly polarized light is reflected by the polarizing reflective layer 120 back to the phase retarder film 130, where the first reflection occurs. The p-linearly polarized light then passes through the phase retarder film 130 and is converted to right-handed circularly polarized light. This right-handed circularly polarized light then passes through the lens structure 110 and reaches the transflective film 140, where it is reflected, undergoing a second reflection. Due to 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 then passes through the lens structure 110 and reaches the phase retarder film 130, where it becomes s-linearly polarized light. This s-linearly polarized light then passes through the polarizing reflective layer 120 and is emitted toward the exit pupil, such as the human eye.

[0052] FIG3 is a schematic diagram of an optical system 100 provided in accordance with at least another embodiment of the present disclosure. Referring to FIG3 , for example, the polarizing reflective layer 120 is a cholesteric liquid crystal layer 120a. The cholesteric liquid crystal layer 120a is disposed on the side of the concave surface 112 away from the convex surface 111, and the phase retarder film 130 is disposed on the side of the cholesteric liquid crystal layer 120a away from the convex surface 111. Cholesteric liquid crystals can reflect and transmit circularly polarized light. Referring to the aforementioned principle of folded optical paths, the cholesteric liquid crystal layer 120a is disposed between the phase retarder film 130 and the concave surface 112 of the lens structure 110. Circularly polarized light is first reflected by the cholesteric liquid crystal layer 120a, transmitted by the lens structure 110, and reflected by the transflective film 140. It is then transmitted by the lens structure 110 and the cholesteric liquid crystal layer 120a to the phase retarder film 130, becoming linearly polarized light before being emitted toward the exit pupil.

[0053] The folded optical path can change the polarization state of light propagating between the polarizing reflective layer 120 and the transflective film 140, thereby folding the light. This causes the original effective focal length of the optical system 100 to be folded due to, for example, two additional reflections caused by the provision of the polarizing reflective layer 120, the phase delay film 130, and the transflective film 140. This greatly reduces the space required between the human eye and the optical system 100, thereby making the optical system 100 smaller and thinner.

[0054] For example, as shown in FIG1 , the optical system 100 further includes a linear polarizing film 150 . The linear polarizing film 150 is disposed on a side of the polarizing reflective layer 120 away from the transflective film 140 . For example, the transmission axis of the linear polarizing film 150 coincides with the transmission axis of the polarizing reflective layer 120 . The linear polarizing film 150 further filters out stray light, allowing only polarized light (e.g., s-polarized light) that passes through the linear polarizing film 150 to enter the human eye. For example, the material of the linear polarizing film 150 may include polyvinyl alcohol (PVA) with added dichroic molecules, a liquid crystal polymer film with added dichroic molecules, or the like.

[0055] For example, the optical system 100 further includes an anti-reflection film 160, which is disposed on a side of the linear polarizing film 150 away from the polarizing reflective layer 120. For example, the anti-reflection film 160 is helpful in reducing stray light caused by reflection.

[0056] For example, at least one of the convex surface 111 and the concave surface 112 is an aspheric surface or a free-form surface. The aspheric surface can be an even-order aspheric surface (EVENASPH), where the radius of curvature of the aspheric surface is the radius of curvature of the base spherical surface of its surface. The "base spherical surface" mentioned above refers to an aspheric surface that is further deformed from a spherical surface. The spherical surface that serves as the basis of the aspheric surface is the base spherical surface of the aspheric surface. A free-form surface is, for example, a complex, unconventional, continuous surface without an axis of rotational symmetry.

[0057] For example, as shown in FIG1 , the ratio of the radius of curvature of the convex surface 111 to the effective focal length of the optical system 100 is -1.2 to -2.5. The effective focal length refers to the distance from the rear main image plane to the paraxial image plane. The effective focal length is, for example, the effective focal length after coating the surface of the lens structure 110. For example, the ratio of the radius of curvature of the convex surface 111 to the effective focal length of the optical system 100 is -1.4 to -2.3. For example, the ratio of the radius of curvature of the convex surface 111 to the effective focal length of the optical system 100 is -1.6 to -2.1. For example, the ratio of the radius of curvature of the convex surface 111 to the effective focal length of the optical system 100 is -1.8 to -1.9.

[0058] As shown in FIG1 , the ratio of the radius of curvature of the concave surface 112 to the radius of curvature of the convex surface 111 is 0.8 to 2. For example, the ratio of the radius of curvature of the concave surface 112 to the radius of curvature of the convex surface 111 is 1.0 to 1.8. For example, the ratio of the radius of curvature of the concave surface 112 to the radius of curvature of the convex surface 111 is 1.2 to 1.6.

[0059] As shown in Figure 1 , the absolute value of the conic coefficient of the convex surface 111 is less than or equal to the absolute value of the conic coefficient of the concave surface 112. It can be understood that the curvature of the convex surface 111 is greater than that of the concave surface 112, ensuring that the lens structure 110 is thicker at the center and thinner at the edges, forming a convex lens structure overall.

[0060] For example, the conic coefficient of the convex surface 111 is greater than or equal to -20 and less than 0. For example, the conic coefficient of the convex surface 111 may be, but is not limited to, -20, -18, -16, -14, -12, -10, -8, -6, -4, -2, -1, -0.5, -0.3, -0.1, etc. For example, the conic coefficient of the concave surface 112 is greater than or equal to -50 and less than or equal to the conic coefficient of the convex surface 111. For example, the conic coefficient of the concave surface 112 is less than or equal to the conic coefficient of the convex surface 111, and may be, but is not limited to, -50, -40, -30, -20, -10, -9, -7, -5, etc.

[0061] As shown in FIG1 , along a direction parallel to the optical axis of lens structure 110, the ratio of the center thickness of lens structure 110 to the effective focal length is 0.4 to 0.6. The center thickness of lens structure 110 refers to the dimension of lens structure 110 intercepted by its optical axis. For example, the center thickness is the distance between two points where the optical axis of lens structure 110 passes through concave surface 112 and convex surface 111. For example, the center thickness is the maximum thickness of lens structure 110. For example, the ratio of the center thickness of lens structure 110 to the effective focal length is 0.45 to 0.55. For example, the ratio of the center thickness of lens structure 110 to the effective focal length is 0.5.

[0062] For example, the ratio of the effective aperture of the lens structure 110 to the effective focal length is greater than or equal to 2. The effective aperture of the lens structure 110 refers to the maximum aperture through which light can pass, and is determined by the maximum luminous flux of the lens structure 110. For example, the ratio of the effective aperture to the effective focal length is 2 to 2.75. It is understood that this ratio can be, but is not limited to, 2, 2.25, 2.5, or 2.75.

[0063] For example, the refractive index of the lens structure 110 is 1.45 to 1.75, and selecting a larger refractive index is more conducive to obtaining a larger radius of curvature. For example, the refractive index of the lens structure 110 is 1.5 to 1.7. For example, the refractive index of the lens structure 110 is 1.55 to 1.65. For example, the refractive index of the lens structure 110 is 1.6.

[0064] For example, the ratio of the total optical length to the effective focal length of the optical system 100 is 0.8 to 1.2. The total optical length refers to the distance along the optical axis from the highest point on the concave surface 112 of the lens structure 110 in the optical system 100 to the center of the display screen 400. The highest point on the concave surface 112 includes the edge sagittal height of the lens structure 110 on the concave surface 112 side. The ratio of the total optical length to the effective focal length can be, but is not limited to, 0.8, 0.9, 1.0, 1.1, or 1.2.

[0065] For example, the Abbe number of the lens structure 110 is 30 to 60. For example, the Abbe number of the lens structure 110 can be, but is not limited to, 30, 35, 40, 45, 50, 55, or 60.

[0066] For example, the exit pupil distance of optical system 100 is 12 to 18 mm. For example, the exit pupil distance is the distance between concave surface 112 and the exit pupil along the optical axis. The exit pupil is, for example, a human eye. For example, the exit pupil distance can be, but is not limited to, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, or 18 mm.

[0067] For example, the field of view of the optical system 100 is 90° to 110°. For example, the field of view is the full field of view. For example, the field of view of the optical system 100 can be, but is not limited to, 90°, 95°, 100°, 105°, or 110°. For example, based on an effective aperture capable of achieving a field of view of 100°, the weight of the binocular lens is approximately 20g.

[0068] For example, the ratio of the image height to the effective aperture of the optical system 100 is 0.5 to 0.6. For example, the image height is the full image height. For example, the ratio of the image height to the effective aperture is 0.55.

[0069] The optical system 100 provided by the present disclosure, by coordinating the lens structure 110 with the above-mentioned folded optical path, setting one side of the lens structure 110 as an aspheric convex surface 111 and the other side as an aspheric concave surface 112, setting the effective focal length and total optical length of the optical system 100, and setting parameters such as the curvature radius, cone coefficient, center thickness, effective aperture of the two aspheric surfaces in the lens structure 110, and the refractive index of the lens structure 110. On the basis of the optical system 100 having a smaller size, the full field of view angle of the optical system 100 can reach 90° to 110°, and the exit pupil distance can reach 12 to 18 mm, which is beneficial to improving the user experience, for example, it can meet the needs of myopic users wearing glasses.

[0070] For example, the surface shape of an aspheric surface is expressed by the following numerical formula:

[0071] 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 the height 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 curvature radius R), k is the cone constant, and α i is the coefficient of each higher-order term, and 2i is the order of Aspherical Coefficient.

[0072] When optimizing the proper configuration of the various parameters of the lens structure 110, the values ​​of the curvature radius, conic coefficient, height, and aspheric coefficient of the lens structure 110 are entered into the above numerical formulas, and optical simulation calculations are performed to obtain the optimized parameters that can correct the aberrations of the lens structure 110. The optimization process yields the preferred values ​​of the curvature radius, thickness along the optical axis, effective aperture, and conic coefficient of the lens structure 110.

[0073] For example, the higher-order coefficients of the convex surface 111 and the concave surface 112 are shown in Table 1.

[0074] For example, the lens structure 110 is an integrated lens, and the convex surface 111 and the concave surface 112 are located on opposite sides of the integrated lens. For example, the integrated lens can be called a single lens. For example, the integrated lens can be a convex lens.

[0075] Figure 4 is a spot diagram for the optical system 100 shown in Figure 1. A spot diagram refers to the distribution of light rays emitted from a single point through the optical system 100. Due to aberrations, their intersections with the image plane no longer converge at the same point, but rather form a diffuse pattern scattered across a certain range. This pattern can be used to evaluate the imaging quality of the optical system 100. In Figure 4, taking the first set of values ​​on the left vertical axis as an example, 0.00 represents the normalized field of view in the X direction, 1.00 represents the normalized field of view in the Y direction, 0.000 represents the field of view angle in the X direction, and 48.00 represents the field of view angle in the Y direction. Figure 4 is typically used to evaluate the full-field-of-view clarity of the optical system. This refers to the image clarity across the entire field of view covered by the peripheral vision when the human pupil is at the entrance pupil position on the optical axis and looking at the center of the lens (i.e., zero field of view), also known as transient mode. In addition to considering full-field-of-view clarity in transient mode, gaze point clarity is a more important optical metric for wearers, such as those wearing head-mounted displays. The focus point clarity refers to the clarity of the image within a certain angle range that can be seen directly (not seen by peripheral vision) when the eyes move up, down, left, and right. In the focus point mode, the eyeball rotates a certain angle, and the pupil deviates from the center of the optical axis. It has 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. The range of the angle is set taking into account the observation habits of the human eye. In order to see the objects in front that are more than 35 degrees beyond the center of the human eye, people will actively turn their heads instead of laboriously turning their eyeballs. Referring to Figure 5, Figure 5 shows the relationship between the focus point clarity and the focus angle. The diffuse spot of the central field of view is much smaller than a pixel. The diameter of the diffuse spot when the human eye rotates to 25 degrees is 10 microns. As can be seen from Figure 5, the diffuse spot of the optical system of the present application is small and the resolution of the optical system is high. In summary, it can be seen that the optical system 100 provided by at least one embodiment of the present disclosure can form clear images.

[0076] Figure 6 is a distortion diagram of the optical system 100 shown in Figure 1. This distortion diagram reflects the differences in image plane position for sharp images at different fields of view. As shown in Figure 6, the maximum absolute value of distortion is within 50%. This demonstrates that the optical system 100 provided in at least one embodiment of the present disclosure can effectively correct distortion and meet high-quality imaging requirements. Furthermore, distortion correction can be pre-processed in software.

[0077] Figure 7 is a schematic diagram of an optical system 200 provided by at least another embodiment of the present disclosure. Referring to Figure 7, for example, a lens structure 210 includes a first lens 211 and a second lens 212. The first lens 211 has a first surface 211a and a second surface 211b disposed opposite each other. The first surface 211a is a convex surface of the lens structure 210, and the second surface 211b is a flat surface. The second lens 212 has a third surface 212a and a fourth surface 212b disposed opposite each other. The third surface 212a is a flat surface, and the fourth surface 212b is a concave surface of the lens structure 210. For example, the first surface 211a is curved away from the flat surface to form the convex surface of the lens structure 210. For example, the fourth surface 212b is curved toward the flat surface to form a concave surface. For example, the second surface 211b and the third surface 212a are glued together. However, this embodiment is not limited to this embodiment. For example, an air gap may be provided between the second surface 211b and the third surface 212a, thereby increasing the design flexibility of the optical system. The lens structure 210 composed of the first lens 211 and the second lens 212 has a thinner thickness of a single lens, which can reduce the difficulty of processing.

[0078] For example, as shown in FIG7 , the first lens 211 may be a plano-convex lens, and the second lens 212 may be a plano-concave lens.

[0079] The first surface and the fourth surface in the lens structure provided in this example may have the same surface features as the convex surface and the concave surface in the lens structure shown in FIG1 , and will not be described in detail here.

[0080] For example, the first lens 211 and the second lens 212 can be made of different optical materials, so that the first lens 211 and the second lens 212 have different Abbe numbers, thereby compensating for dispersion. For example, the material of the first lens 211 is polystyrene (PS), which has a refractive index of 1.59 and an Abbe number of 30.8, and the material of the second lens 212 is optical-grade polymethyl methacrylate (PMMA), which has a refractive index of 1.49 and an Abbe number of 57.2. For example, the material of the first lens 211 is polycarbonate (PC), which has a refractive index of 1.58 and an Abbe number of 34, and the material of the second lens 212 is optical-grade polymethyl methacrylate (PMMA), which has a refractive index of 1.49 and an Abbe number of 57.2.

[0081] For example, the first lens 211 and the second lens 212 can be made of the same optical material. When the first lens 211 and the second lens 212 are made of the same optical material, optical properties such as spectral transmittance, refractive index, and Abbe number can be considered. Processability such as material fluidity, thermal shrinkage, stress, and cost can also be considered. For example, optical-grade polymethyl methacrylate (PMMA), polycarbonate (PC), cyclic olefin copolymer (COC), cyclic olefin homopolymer (COP), and polyethylene terephthalate (PET) can be used.

[0082] For example, the phase retarder film 230 is disposed between the second surface 211b and the third surface 212a, and the polarizing reflective layer 220 is disposed on the fourth surface 212b. Since both the second surface 211b and the third surface 212a are planar, disposing the phase retarder film 230 on a plane can reduce the difficulty of lamination and meet the requirements for clarity, distortion, color shift, and other indicators.

[0083] The polarizing reflective layer, transflective film and linear polarizing film in the optical structure provided in this example may have the same features as those in the optical structure shown in FIG1 , and are not described in detail here.

[0084] FIG8 is a schematic diagram of an optical system 300 provided in at least one further embodiment of the present disclosure. For example, a lens structure 310 includes a first lens 311 and a second lens 312. The first lens 311 has a first surface 311a and a second surface 311b disposed opposite to each other, wherein the first surface 311a is a convex surface of the lens structure 310 and the second surface 311b is a curved surface. The second lens 312 has a third surface 312a and a fourth surface 312b disposed opposite to each other, wherein the third surface 312a is a curved surface and the fourth surface 312b is a concave surface of the lens structure 310. The second surface 311b and the third surface 312a have the same surface shape. The same surface shape means that the second surface 311b and the third surface 312a can be completely aligned. Of course, the second surface 311b and the third surface 312a can be glued together or have an air gap therebetween.

[0085] The first surface and the fourth surface in the lens structure provided in this example may have the same surface features as the convex surface and the concave surface in the lens structure shown in FIG1 , and will not be described in detail here.

[0086] For example, the absolute value of the radius of curvature of the second surface 311b is greater than the absolute value of the radius of curvature of the first surface 311a, and the absolute value of the radius of curvature of the third surface 312a is greater than the absolute value of the radius of curvature of the fourth surface 312b. By making the second surface 311b and the third surface 312a as curved surfaces, the center thickness and edge thickness of the first lens 311 and the second lens 312 can be easily adjusted, reducing the difficulty of processing.

[0087] For example, the second surface 311b is a concave surface formed by curving toward the first surface 311a, thereby minimizing the difference between the center thickness and the edge thickness of the first lens 311. For example, the third surface 312a is a convex surface formed by curving away from the fourth surface 312b, thereby minimizing the difference between the center thickness and the edge thickness of the second lens 312.

[0088] For example, the absolute values ​​of the curvature radii of the second surface 311b and the curvature radii of the third surface 312a are both greater than 100 mm. The curvature radii of the second surface 311b and the third surface 312a are set to be relatively large, that is, the second surface 311b and the third surface 312a are configured as slightly curved surfaces that approach a plane. For example, the curvature radii of the second surface 311b and the curvature radii of the third surface 312a are both less than -100 mm.

[0089] For example, the second surface 311b is a surface with rotational symmetry or an axisymmetry. A surface with rotational symmetry refers to a surface formed by a curve rotating around a straight line, wherein the plane curve is the generatrix of the surface of rotation, and the straight line is the axis of rotation of the surface of rotation. A surface with rotational symmetry has the same radius of curvature and conic coefficient in different directions. A surface with axisymmetry refers to a surface that is symmetrical along an axis of symmetry, for example, a surface has different radii of curvature or conic coefficients in different directions. For example, a surface with axisymmetry can be a cylinder, which refers to a surface formed by a straight line moving parallel to a fixed curve. When the surface is a cylinder, it is a curved surface in one direction and a plane in another direction.

[0090] For example, the phase retarder film 330 is disposed between the second surface 311b and the third surface 312a, and the polarizing reflective layer 320 is disposed on the fourth surface 312b. Thus, the second surface 311b and the third surface 312a have a larger radius of curvature, which can provide a better bonding surface for the phase retarder film 330 and reduce bonding difficulty.

[0091] For example, the ratio of the center thickness to the edge thickness of the first lens 311 is greater than or equal to 0.5 and less than or equal to 3. For example, the ratio of the center thickness to the edge thickness of the first lens 311 is 2.9, 2.7, 2.5, 2.3, 2, 1.5, 1, 0.7, and 0.5. In this way, a more reasonable ratio can ensure the injection molding of the first lens 311.

[0092] For example, the ratio of the edge thickness to the center thickness of the second lens 312 is greater than or equal to 0.5 and less than or equal to 2. For example, the ratio of the edge thickness to the center thickness of the second lens 312 is 2, 1.8, 1.6, 1.4, 1.2, 1, 0.8, or 0.5. In this way, a more reasonable ratio can ensure the injection molding of the second lens 312.

[0093] The polarizing reflective layer, transflective film and linear polarizing film in the optical structure provided in this example may have the same features as those in the optical structure shown in FIG1 , and are not described in detail here.

[0094] With reference to FIG2 , at least one embodiment of the present disclosure provides a display device comprising a display screen 400 and an optical system 100 according to any of the aforementioned embodiments. The display screen 400 is located on a side of the convex surface 111 of the lens structure 110 that is away from the concave surface 112. Since the display device according to an embodiment of the present disclosure includes at least one of the aforementioned optical systems 100, it also has corresponding beneficial technical effects, which will not be further described here.

[0095] For example, the display surface 400 a of the display screen 400 is located at the focal plane on the light incident side of the optical system 100 .

[0096] For example, the display screen 400 may be any type of display screen, such as a liquid crystal display screen, an organic light emitting diode display screen, an inorganic light emitting diode display screen, a quantum dot display screen, a projector (such as an LCOS micro projector), etc.

[0097] For example, if the display screen is a liquid crystal display screen, the pixel size is about twenty micrometers. For example, if the display screen is an organic light emitting diode display screen, the pixel size is about several micrometers.

[0098] For example, the display device may be a virtual reality display device. For example, the virtual reality display device may be a display device using an ultra-short-throw folded optical path.

[0099] 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.

[0100] There are a few points to note:

[0101] (1) The drawings of the embodiments of the present disclosure only involve structures related to the embodiments of the present disclosure, and other structures can refer to general designs.

[0102] (2) In the absence of conflict, features in the same embodiment and different embodiments of the present disclosure may be combined with each other.

[0103] The foregoing description is merely an exemplary embodiment of the present disclosure and is not intended to limit the scope of protection of the present disclosure. The scope of protection of the present disclosure is determined by the appended claims.

Claims

1. An optical system, comprising: A lens structure, comprising a convex surface and a concave surface arranged opposite to each other, wherein a side of the concave surface away from the convex surface is a light emitting side of the lens structure; A polarized reflection layer is arranged on a side of the concave surface of the lens structure away from the convex surface; A phase delay film is arranged on a side of the concave surface of the lens structure away from the convex surface; A transflective film is arranged on a side of the convex surface away from the concave surface; Among them, the ratio of the curvature radius of the convex surface to the effective focal length of the optical system is -1.2 to -2.5, and the ratio of the curvature radius of the concave surface to the curvature radius of the convex surface is 0.8 to 2; along the direction parallel to the optical axis of the lens structure, the ratio of the center thickness of the lens structure to the effective focal length is 0.4 to 0.

6.

2. The optical system of claim 1, wherein: The absolute value of the cone coefficient of the convex surface is less than or equal to the absolute value of the cone coefficient of the concave surface.

3. The optical system of claim 2, wherein: The cone coefficient of the convex surface is greater than or equal to -20 and less than 0, and the cone coefficient of the concave surface is greater than or equal to -50 and less than or equal to the cone coefficient of the convex surface.

4. The optical system according to any one of claims 1 to 3, wherein: At least one of the convex surface and the concave surface is an aspherical surface or a free-form surface.

5. The optical system according to any one of claims 1 to 4, wherein: The ratio of the total optical length of the optical system to the effective focal length is 0.8 to 1.

2.

6. The optical system according to any one of claims 1 to 5, wherein: The ratio of the effective aperture of the lens structure to the effective focal length is greater than or equal to 2.

7. An optical system according to any one of claims 1 to 6, wherein: The exit pupil distance of the optical system is 12 to 18 mm.

8. An optical system according to any one of claims 1 to 7, wherein: The field of view angle of the optical system is 90° to 110°.

9. The optical system according to any one of claims 1 to 8, wherein: The lens structure is an integrated lens, and the convex surface and the concave surface are located on two opposite sides of the integrated lens.

10. The optical system according to any one of claims 1 to 9, wherein: The polarizing reflective layer is configured to reflect linear polarized light of one characteristic and transmit linear polarized light of another characteristic; the phase delay film is arranged on a side of the concave surface away from the convex surface, and the polarizing reflective layer is arranged on a side of the phase delay film away from the convex surface; or The polarized reflection layer is a cholesteric liquid crystal layer; the cholesteric liquid crystal layer is arranged on a side of the concave surface away from the convex surface, and the phase delay film is arranged on a side of the cholesteric liquid crystal layer away from the convex surface.

11. The optical system of claim 10, wherein: The optical system further comprises a linear polarization film; The linear polarization film is arranged on a side of the polarization reflection layer away from the transflective film.

12. The optical system according to any one of claims 1 to 8, wherein: The lens structure comprises a first lens and a second lens; The first lens has a first surface and a second surface that are oppositely disposed, the first surface is the convex surface of the lens structure, and the second surface is a plane; The second lens has a third surface and a fourth surface that are arranged opposite to each other, the third surface is a plane, and the fourth surface is the concave surface of the lens structure.

13. The optical system of claim 12, wherein: The phase delay film is disposed between the second surface and the third surface, and the polarized reflective layer is disposed on the fourth surface.

14. The optical system according to any one of claims 1 to 8, wherein: The lens structure comprises a first lens and a second lens; The first lens has a first surface and a second surface that are oppositely disposed, the first surface is the convex surface of the lens structure, and the second surface is a curved surface; The second lens has a third surface and a fourth surface that are arranged opposite to each other, the third surface is a curved surface, and the fourth surface is the concave surface of the lens structure; The second surface has the same surface shape as the third surface, the absolute value of the radius of curvature in at least one direction of the second surface is greater than the absolute value of the radius of curvature of the first surface, and the absolute value of the radius of curvature in at least one direction of the third surface is greater than the absolute value of the radius of curvature of the fourth surface.

15. The optical system of claim 14, wherein: The absolute values ​​of the curvature radius of the second surface and the curvature radius of the third surface are both greater than 100 mm.

16. An optical system according to claim 14 or 15, wherein: The second surface is a curved surface with rotational symmetry or a curved surface with axial symmetry.

17. An optical system according to any one of claims 14 to 16, wherein: The phase delay film is disposed between the second surface and the third surface, and the polarized reflective layer is disposed on the fourth surface.

18. An optical system according to any one of claims 14 to 17, wherein: The ratio of the center thickness to the edge thickness of the first lens is greater than or equal to 0.5 and less than 3; The ratio of the edge thickness to the center thickness of the second lens is greater than or equal to 0.5 and less than or equal to 2.

19. A display device comprising a display screen and the optical system according to any one of claims 1 to 18, wherein: The display screen is located on a side of the convex surface of the lens structure away from the concave surface.

Images