Optical system and display device

Abstract

The invention provides an optical system and a display device. The optical system comprises a lens structure which comprises a convex surface and a concave surface which are oppositely arranged, and the side, away from the convex surface, of the concave surface is the light emitting side of the lens structure; the polarization reflection layer is arranged on one side, far away from the convex surface, of the concave surface of the lens structure; the phase delay film is arranged on one side, far away from the convex surface, of the concave surface of the lens structure; the transflective film is arranged on one side, far away from the concave surface, of the convex surface; wherein 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 0.8-2; in 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 0.4-0.6.

Description

Technical Field

[0001] At least one embodiment of the present disclosure relates to an optical system and a display device. Background Art

[0002] Virtual Reality (VR) technology is a computer simulation technology that can create and experience a virtual world. It uses computers to generate an interactive three-dimensional dynamic view, allowing users to immerse themselves in the environment. In order to improve user experience, products using virtual reality technology are developing in the direction of being lighter and thinner. Summary of the invention

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] For example, according to an embodiment of the present disclosure, the exit pupil distance of the optical system is 12 to 18 mm.

[0010] For example, according to an embodiment of the present disclosure, the field of view angle of the optical system is 90° to 110°.

[0011] 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.

[0012] For example, according to an embodiment of the present disclosure, the polarized 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 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.

[0013] 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 polarization reflection layer away from the transflective film.

[0014] 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.

[0015] 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.

[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 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 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.

[0017] For example, according to an embodiment of the present disclosure, the absolute values ​​of the radius of curvature of the second surface and the radius of curvature of the third surface are both greater than 100 mm.

[0018] For example, according to an embodiment of the present disclosure, the second surface has a curved surface with rotational symmetry characteristics or a curved surface with axial symmetry characteristics.

[0019] 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.

[0020] 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.

[0021] 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

[0022] 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.

[0023] Figure 1 A schematic diagram of an optical system provided for at least one embodiment of the present disclosure.

[0024] Figure 2 A simplified optical path diagram of an optical system provided by at least one embodiment of the present disclosure.

[0025] Figure 3 A schematic diagram of an optical system provided according to at least another embodiment of the present disclosure.

[0026] Figure 4 for Figure 1 Spot diagram of the optical system shown.

[0027] Figure 5 for Figure 1 A graph showing the variation of the diffuse spot size with the field of view angle for the optical system shown.

[0028] Figure 6 for Figure 1 Distortion diagram of the optical system shown.

[0029] Figure 7 A schematic diagram of an optical system provided according to at least another embodiment of the present disclosure.

[0030] Figure 8 A schematic diagram of an optical system provided by at least another embodiment of the present disclosure. DETAILED DESCRIPTION

[0031] 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.

[0032] 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.

[0033] The features such as "vertical", "parallel" and "same" used in the embodiments of the present disclosure include the features such as "vertical", "parallel" and "same" in a strict sense, as well as the cases where "approximately vertical", "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 within the acceptable deviation range for a specific value determined by ordinary technicians in this field. The "center" in the embodiments of the present disclosure can include a position strictly located at the geometric center and a position approximately centered within 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.

[0034] For example, in virtual reality devices such as head mounted display devices, folded optical path (Pancake) technology is mostly used to compress the volume of virtual reality devices, making them compact and thin, creating more space for the application of mobile wearable civilian electronic devices. Products using folded optical path technology may include single lens, double lens or multiple lenses. The combination of different numbers of lenses can be separated from each other, that is, there is an air gap between the lenses, or they can be glued together.

[0035] During the research, the inventors of the present 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.

[0036] At least one embodiment of the present disclosure provides an optical system and a display device. The optical system includes: a lens structure, a polarized 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 polarized 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; the transflective film is arranged on the side of the convex surface away from the concave surface of the lens structure. 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.

[0037] The optical system provided by at least one embodiment of the present disclosure may be an optical system using a folded optical path (Pancake), in which a polarized reflection layer, a phase delay film, and a transflective film are arranged on both sides of the lens structure, and parameters such as the curvature radius of the concave and convex surfaces of the lens structure and the center thickness 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 total image height.

[0038] The optical system and the display device are described below with reference to the accompanying drawings and through some embodiments.

[0039] Figure 1 A schematic diagram of an optical system 100 provided by at least one embodiment of the present disclosure, Figure 2 A simplified optical path diagram of an optical system 100 provided in at least one embodiment of the present disclosure.

[0040] refer to Figure 1 and Figure 2 , the optical system 100 includes a lens structure 110, a polarizing reflection layer 120, a phase delay film 130, and a transflective film 140. The lens structure 110 includes a convex surface 111 and a concave surface 112 that are arranged opposite to each other, and the side of the concave surface 112 away from the convex surface 111 is the light-emitting side of the lens structure 110. For example, when the optical system 100 is applied to a display device, the display screen 400 is located on the side of the convex surface 111 of the lens structure 110 away from the concave surface 112, and the light emitted by the display screen 400 enters the lens structure 110 after passing through the convex surface 111, and then the light is emitted from the concave surface 112.

[0041] like Figure 1As shown, the polarizing reflective layer 120 is disposed on the side of the concave surface 112 of the lens structure 110 away from the convex surface 111. For example, the function of the polarizing reflective film is 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 polarizing reflective layer 120 can also be called a polarizing beam splitting film. For example, the transmittance of the polarized light parallel to the light transmission axis direction of the polarizing reflective layer 120 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 the polarized light perpendicular to the light transmission axis direction of the polarizing reflective layer 120 is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%.

[0042] like Figure 1 As shown, the phase delay 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 delay film 130 is configured to enable the transmitted light to achieve conversion between a circular polarization state and a linear polarization state. For example, the phase delay film 130 can be a 1 / 4 wave plate.

[0043] 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.

[0044] For example, the angle between the slow axis of the phase retardation film 130 and the light transmission axis of the polarization reflection film is 45 degrees.

[0045] For example, the material of the phase delay film 130 may include polycarbonate. The phase delay film 130 made of polycarbonate material is generally a planar film layer with a film thickness of about 50 μm. When the phase delay film 130 is attached to the concave surface 112 of the lens structure 110, in order to match the aspherical surface or free-form surface of the concave surface 112, the phase delay film 130 made of polycarbonate material may be appropriately stretched to completely fit the concave surface 112. Of course, in combination with some embodiments described later, when the phase delay film 130 is attached to a surface such as a plane or a cylinder, it is not necessary to stretch it.

[0046] For example, the material of the phase delay film 130 may include a liquid crystal polymer. Since the phase delay film 130 of the liquid crystal polymer material is a polymer, its film thickness is relatively thinner, which can reach 1μm to 5μm. The thinner phase delay film 130 has a higher degree of adaptability to the curved surface, and can be more easily shaped according to the surface shape of the curved surface, reducing the possibility of wrinkles when fitting with the curved surface and affecting the phase delay accuracy and optical performance. Moreover, the optical deviation of the phase delay film 130 of the liquid crystal polymer material after being attached to the curved surface is smaller. Liquid crystal polymer is a cross-linked system, and the molecules are connected by chemical bonds, and the modulus is relatively high. When the phase delay film 130 of this material is stretched after being attached, only elastic deformation occurs, and no strong optical anisotropy effects such as molecular stretching and rearrangement occur. Therefore, the phase delay film 130 made of liquid crystal polymer material is suitable for fitting with a surface shape with a small radius of curvature. Such a curvature radius freedom is also easier to meet the index requirements of clarity, distortion, dispersion, etc., which is conducive to the optical system 100 to obtain better image quality.

[0047] like Figure 1 As shown, the 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 part of the light and reflect another part of the light. For example, the transmittance of the transflective film 140 can be 50%, and the reflectance can be 50%. For example, the transmittance of the transflective film 140 can be 60%, and the reflectance can be 40%. For example, the transmittance of the transflective film 140 can be 65%, and the reflectance can be 35%. The optical system 100 provided in the present disclosure is not limited thereto, and the transmittance and reflectance of the transflective film 140 can be set according to product requirements. For example, the transflective film 140 can be plated on the convex surface 111.

[0048] For example, the polarizing reflective layer 120 is configured to reflect linear polarized light of one characteristic and transmit linear polarized light of another characteristic; the phase delay film 130 is disposed on the side of the concave surface 112 away from the convex surface 111 , and the polarizing reflective layer 120 is disposed on the side of the phase delay film 130 away from the convex surface 111 .

[0049] For example, Figure 1 and Figure 2As shown, the polarizing reflection layer 120, the phase delay film 130 and the transflective film 140 that can reflect linear polarized light of one characteristic and transmit linear polarized light of another characteristic are used to form a folded optical path. The principle is as follows: a wave plate can be set on the display surface 400a side of the display screen 400 located on the side of the convex surface 111 away from the concave surface 112. The image light emitted from the display surface 400a is converted into 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. The light enters the lens structure 110, and after being transmitted through the lens structure 110, it reaches the phase delay film 130. The right-handed circularly polarized light incident on the phase delay film 130 is converted into p-linear polarized light. The p-linear polarized light is reflected back to the phase delay film 130 by the polarizing reflection layer 120, and the first reflection occurs here. Then, the p-linear polarized light is converted into right-handed circularly polarized light after passing through the phase delay film 130. The right-handed circularly polarized light is transmitted through the lens structure 110 and reaches the transflective film 140, and is reflected at the transflective film 140, where a second reflection occurs. Due to the half-wave loss, the reflected light is converted from right-handed circularly polarized light to left-handed circularly polarized light. The left-handed circularly polarized light is transmitted through the lens structure 110 and reaches the phase delay film 130, and is converted into s-linear polarized light after passing through the phase delay film 130. Then, the s-linear polarized light is transmitted through the polarizing reflective layer 120 and is emitted to the exit pupil, such as the human eye.

[0050] Figure 3 A schematic diagram of an optical system 100 provided in at least another embodiment of the present disclosure. Figure 3 For example, the polarized reflection 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 delay film 130 is disposed on the side of the cholesteric liquid crystal layer 120a away from the convex surface 111. Cholesteric liquid crystal can reflect circularly polarized light and transmit circularly polarized light. Referring to the aforementioned folded optical path principle, the cholesteric liquid crystal layer 120a is disposed between the phase delay film 130 and the concave surface 112 of the lens structure 110. The 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, and then transmitted by the lens structure 110 and the cholesteric liquid crystal layer 120a to reach the phase delay film 130 to become linearly polarized light, and then emitted to the exit pupil.

[0051] The folded optical path can change the polarization state of the light propagating between the polarized reflective layer 120 and the transflective film 140, thereby realizing the folding of the light, so that the original effective focal length of the optical system 100 is folded due to, for example, two reflections added by setting the polarized reflective layer 120, the phase delay film 130 and the transflective film 140, thereby greatly compressing the space required between the human eye and the optical system 100, thereby making the optical system 100 smaller and thinner.

[0052] For example, Figure 1 As shown, the optical system 100 further includes a linear polarization film 150; the linear polarization film 150 is disposed on a side of the polarization reflection layer 120 away from the transflective film 140. For example, the light transmission axis of the linear polarization film 150 coincides with the light transmission axis of the polarization reflection layer 120. The linear polarization film 150 is used to further filter other stray light, and only polarized light (such as s-polarized light) passing through the linear polarization film 150 is allowed to enter the human eye. For example, the material of the linear polarization film 150 may include polyvinyl alcohol (PVA) added with dichroic molecules, a liquid crystal polymer film added with dichroic molecules, etc.

[0053] For example, the optical system 100 further includes an anti-reflection film 160; the anti-reflection film 160 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.

[0054] 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 may be an even aspheric surface (EVENASPH), and the radius of curvature of the aspheric surface is the radius of curvature of the base spherical surface of its surface. The above-mentioned "base spherical surface" means that the aspheric surface is further deformed based on the spherical surface, and the spherical surface serving 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 a rotational symmetry axis.

[0055] For example, Figure 1 As shown, 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 the surface of the lens structure 110 is coated. 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.

[0056] like Figure 1 As shown, the ratio of the curvature radius of the concave surface 112 to the curvature radius of the convex surface 111 is 0.8 to 2. For example, the ratio of the curvature radius of the concave surface 112 to the curvature radius of the convex surface 111 is 1.0 to 1.8. For example, the ratio of the curvature radius of the concave surface 112 to the curvature radius of the convex surface 111 is 1.2 to 1.6.

[0057] like Figure 1 As shown, the absolute value of the cone coefficient of the convex surface 111 is less than or equal to the absolute value of the cone 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 center of the lens structure 110 is thicker and the edges are thinner, and the overall structure is a convex lens.

[0058] For example, the cone coefficient of the convex surface 111 is greater than or equal to -20 and less than 0. For example, the cone 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 cone coefficient of the concave surface 112 is greater than or equal to -50 and less than or equal to the cone coefficient of the convex surface 111. For example, the cone coefficient of the concave surface 112 is less than or equal to the cone coefficient of the convex surface 111, and may be, but is not limited to, -50, -40, -30, -20, -10, -9, -7, -5, etc.

[0059] like Figure 1 As shown, along the direction parallel to the optical axis of the lens structure 110, the ratio of the center thickness of the lens structure 110 to the effective focal length is 0.4 to 0.6. The center thickness of the lens structure 110 refers to the dimension of the lens structure 110 intercepted by its optical axis. For example, the center thickness is the distance between two points where the optical axis of the lens structure 110 passes through the concave surface 112 and the convex surface 111. For example, the center thickness is the maximum thickness of the lens structure 110. For example, the ratio of the center thickness of the lens structure 110 to the effective focal length is 0.45 to 0.55. For example, the ratio of the center thickness of the lens structure 110 to the effective focal length is 0.5.

[0060] 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 through the lens structure 110, which 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, and it can be understood that the ratio can be, but is not limited to, 2, 2.25, 2.5, and 2.75.

[0061] For example, the refractive index of the lens structure 110 is 1.45-1.75, and 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 1.5-1.7. For example, the refractive index of the lens structure 110 is 1.55-1.65. For example, the refractive index of the lens structure 110 is 1.6.

[0062] 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 from the highest point on the concave surface 112 of the lens structure 110 in the optical system 100 along the optical axis 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 side of the concave surface 112. 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, 1.2.

[0063] For example, the Abbe number of the lens structure 110 is 30 to 60. For example, the Abbe number of the lens structure 110 may be, but is not limited to, 30, 35, 40, 45, 50, 55, or 60.

[0064] For example, the exit pupil distance of the optical system 100 is 12 to 18 mm. For example, the exit pupil distance is the distance between the concave surface 112 and the exit pupil in the direction of 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.

[0065] For example, the field of view of the optical system 100 is 90° to 110°. For example, the field of view is a full field of view. For example, the field of view of the optical system 100 may be, but is not limited to, 90°, 95°, 100°, 105°, and 110°. For example, based on the effective aperture that can achieve a field of view of 100°, the weight of the binocular lens is approximately 20 g.

[0066] 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.

[0067] The optical system 100 provided by the present disclosure cooperates with the above-mentioned folded optical path by setting one side of the lens structure 110 as an aspheric convex surface 111 and the other side as an aspheric concave surface 112, thereby setting the effective focal length and the total optical length of the optical system 100, and setting the 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, such as satisfying the use of myopic users wearing glasses.

[0068] For example, the surface shape of an aspheric surface is expressed by the following numerical formula:

[0069]

[0070] 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 cone constant, α i is the coefficient of each high-order term, and 2i is the order of Aspherical Coefficient.

[0071] When optimizing the reasonable configuration of the parameters of the lens structure 110, the values ​​of the curvature radius, cone coefficient, height and aspheric coefficient of the lens structure 110 are put into the above numerical formula, and the optical simulation calculation is performed to obtain the various optimized parameters that can correct the aberration of the lens structure 110. The preferred values ​​of the curvature radius, thickness along the optical axis, effective aperture and cone coefficient of the lens structure 110 are obtained through the optimization process.

[0072] For example, the high-order coefficients of the convex surface 111 and the concave surface 112 are shown in Table 1.

[0073] a4 a6 a8 Convex -4.0174e-5 2.5787e-7 -1.6641e-9 Concave 2.0173e-5 -1.2634e-7 5.2608e-10

[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 for Figure 1 The point diagram of the optical system 100 is shown. The point diagram refers to a diffuse pattern formed in a certain range because the intersection points of many light rays emitted from one point with the image plane are no longer concentrated at the same point after passing through the optical system 100 due to aberration. The point diagram can be used to evaluate the imaging quality of the optical system 100. Figure 4 In the figure, taking the first group of values ​​in the vertical direction on the left 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 It is usually used to evaluate the full-field clarity of the optical system, that is, 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), the imaging clarity of the full field of view that can be covered by the peripheral vision is also called the transient mode. In addition to considering the full-field clarity in transient mode, for wearers wearing head-mounted displays, for example, the gaze point clarity is one of the more important optical indicators. The gaze point clarity refers to the clarity of the image 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. In the gaze point mode, the eyeball rotates a certain angle, the pupil deviates from the center of the optical axis, and 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 turning their eyes with effort. Reference Figure 5 , Figure 5The figure shows the relationship between the gaze point clarity and the gaze angle. The diffuse spot in the center field of view is much smaller than a pixel. When the human eye rotates to 25 degrees, the diffuse spot diameter is 10 microns. Figure 5 It can be seen that the optical system of the present application has a smaller diffuse spot and a higher resolution. In summary, it can be seen that the optical system 100 provided by at least one embodiment of the present disclosure can form a clear image.

[0076] Figure 6 for Figure 1 The distortion diagram of the optical system 100 is shown. The distortion diagram reflects the difference in the image plane position of the clear image in different fields of view, see Figure 6 As shown, the absolute value of the maximum distortion is within 50%. It can be seen that the optical system 100 provided by at least one embodiment of the present disclosure can well correct the distortion and meet the requirements of high-quality imaging. In addition, the distortion correction can be pre-processed in the software.

[0077] Figure 7 A schematic diagram of an optical system 200 provided in at least one embodiment of the present disclosure. Figure 7 For example, the 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 arranged opposite to each other, the first surface 211a is a convex surface of the lens structure 210, and the second surface 211b is a plane; the second lens 212 has a third surface 212a and a fourth surface 212b arranged opposite to each other, the third surface 212a is a plane, and the fourth surface 212b is a concave surface of the lens structure 210. For example, the first surface 211a is bent in a direction away from the plane to form a convex surface of the lens structure 210. For example, the fourth surface 212b is bent in a direction close to the plane to form a concave surface. For example, the second surface 211b and the third surface 212a are glued together. However, the present solution is not limited to this, for example, there can also be an air gap between the second surface 211b and the third surface 212a, thereby improving the design freedom 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, Figure 7 As shown, 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 of the lens structure provided in this example can be Figure 1 The convex surface and the concave surface in the lens structure shown have the same surface characteristics, which will not be described in detail here.

[0080] For example, different optical materials may be used to make the first lens 211 and the second lens 212, 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), with 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), with 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), with 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), with 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 may also 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 may be considered, and processability such as material fluidity, thermal shrinkage, stress, and cost may also be considered. For example, optical grade polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin copolymer (COC), cycloolefin homopolymer (COP), polyethylene terephthalate (PET), and other materials may be used.

[0082] For example, the phase delay 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 the second surface 211b and the third surface 212a are both planes, disposing the phase delay film 230 on the plane can reduce the difficulty of bonding and meet the requirements of clarity, distortion, color shift and other indicators.

[0083] The polarized reflective layer, the transflective film and the linear polarization film in the optical structure provided in this example can be Figure 1 The polarized reflective layer, the transflective film and the linear polarization film in the optical structure shown have the same features, which will not be described in detail here.

[0084] Figure 8A schematic diagram of an optical system 300 provided for at least one more embodiment of the present disclosure. For example, the 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 arranged opposite to each other, 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 arranged opposite to each other, 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 fitted. Of course, the second surface 311b and the third surface 312a can be glued or have an air gap therebetween.

[0085] The first surface and the fourth surface of the lens structure provided in this example can be Figure 1 The convex surface and the concave surface in the lens structure shown have the same surface characteristics, which 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 bending toward the first surface 311a, so that the difference between the center thickness and the edge thickness of the first lens 311 is small. For example, the third surface 312a is a convex surface formed by bending away from the fourth surface 312b, so that the difference between the center thickness and the edge thickness of the second lens 312 is small.

[0088] For example, the absolute values ​​of the curvature radius of the second surface 311b and the curvature radius 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 larger, that is, the second surface 311b and the third surface 312a are constructed as micro-curved surfaces approaching a plane. For example, the curvature radius of the second surface 311b and the curvature radius of the third surface 312a are both less than -100 mm.

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

[0090] For example, the phase delay film 330 is disposed between the second surface 311b and the third surface 312a, and the polarized 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 shape for the phase delay film 330 and reduce the 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, 0.5. In this way, the injection molding of the first lens 311 can be guaranteed by a more reasonable ratio.

[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, 0.5. In this way, the injection molding of the second lens 312 can be guaranteed by a more reasonable ratio.

[0093] The polarized reflective layer, the transflective film and the linear polarization film in the optical structure provided in this example can be Figure 1 The polarized reflective layer, the transflective film and the linear polarization film in the optical structure shown have the same features, which will not be described in detail here.

[0094] refer to Figure 2 At least one embodiment of the present disclosure provides a display device, including a display screen 400 and an optical system 100 of any of the above embodiments, wherein the display screen 400 is located on a side of the convex surface 111 of the lens structure 110 away from the concave surface 112. Since the display device according to the embodiment of the present disclosure includes at least one of the above optical systems 100, it also has corresponding beneficial technical effects, which will not be described in detail here.

[0095] For example, a display surface 400 a of the display screen 400 is located at a 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, the display screen is a liquid crystal display screen, and the pixel size is about twenty micrometers. For example, the display screen is an organic light emitting diode display screen, and 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) 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.

[0102] (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.

[0103] 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 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 of claim 1, 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 4, wherein: The ratio of the effective aperture of the lens structure to the effective focal length is greater than or equal to 2.

7. The optical system according to any one of claims 1 to 4, wherein: The exit pupil distance of the optical system is 12 to 18 mm.

8. The optical system according to any one of claims 1 to 4, 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 4, 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 4, 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 4, 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 4, 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. The optical system of claim 14, wherein: The second surface is a curved surface with rotational symmetry or a curved surface with axial symmetry.

17. The optical system of claim 14, 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. The optical system of claim 14, 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.

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