Optical system and display device

Abstract

An optical system and a display device. The optical system comprises a lens assembly, a transmissive-reflection film, a reflective polarizing layer and a phase retardation film. The lens assembly comprises at least two lenses, comprising a first surface, a second surface, a third surface and a fourth surface arranged in sequence; the transmissive-reflection film is located on the side of the first surface away from the second surface; the reflective polarizing layer is located on the side of the second surface away from the first surface; the absolute value of the curvature radius of the first surface and the absolute value of the curvature radius of the second surface are both smaller than the absolute value of the curvature radius of the fourth surface, the ratio of the curvature radius of the first surface to the curvature radius of the second surface is 0.5-1.25, and the absolute value ratio of the conic constant of the first surface to the conic constant of the second surface is not greater than 0.4, so as to provide an optical system with ultra-short focal length and large field of view characteristics.

Description

Technical Field

[0001] This disclosure relates to an optical system and a display device. Background Technology

[0002] The imaging principle of a head-mounted display optical system is similar to that of a magnifying glass. The object (such as an image or video source) is located at the object-side focal plane of the optical lens (e.g., within one focal length), and the human eye, located on the other side of the lens, can observe an upright and magnified virtual image through the lens. Generally, the closer the object is to the focal plane of the lens, or the shorter the focal length of the lens, the greater the magnification; in addition, a shorter focal length allows for a shorter lens barrel length.

[0003] A single convex lens is the simplest magnifying glass and was first used in head-mounted display systems for imaging. Subsequently, the need for weight reduction and tube length reduction, the development of optical manufacturing technology, and the advancement of optical materials technology promoted the application of Fresnel lenses and refractive optical structures (pancakes) in head-mounted display optical systems. Summary of the Invention

[0004] This disclosure provides an optical system and a display device.

[0005] This disclosure provides an optical system including: a lens assembly, a transflective coating, a reflective polarizing layer, and a phase retardation film. The lens assembly includes at least two lenses, each including a first surface, a second surface, a third surface, and a fourth surface arranged sequentially along the optical axis of the lens assembly. The second surface and the third surface have the same surface profile parameters. The transflective coating is located on the side of the first surface of the lens assembly away from the second surface. The reflective polarizing layer is located between the second and third surfaces of the lens assembly. The phase retardation film is located on the side of the transflective coating facing the second surface. Light rays incident on the lens assembly after being transmitted through the transflective coating are configured to be reflected back between the transflective coating and the reflective polarizing layer, and then exit from the reflective polarizing layer. The third surface and the fourth surface are two surfaces of the same lens. The first surface is convex and the second surface is concave. The third surface is convex and the fourth surface is concave. The absolute values ​​of the radii of curvature of the first surface and the second surface are both smaller than the absolute value of the radii of curvature of the fourth surface. The ratio of the radii of curvature of the first surface to the radii of curvature of the second surface is 0.5 to 1.25. The ratio of the absolute values ​​of the conic coefficients of the first surface and the second surface is not greater than 0.4.

[0006] For example, according to an embodiment of this disclosure, the distance between the two intersection points of the first surface and the second surface with the optical axis is a first distance, the distance between the two intersection points of the third surface and the fourth surface with the optical axis is a second distance, the first distance is greater than the second distance, and the ratio of the first distance to the focal length is 0.45 to 0.8.

[0007] For example, according to an embodiment of this disclosure, the ratio of the radius of curvature of the first surface to the focal length is -1.5 to -2.5, and the conic coefficient of the first surface is -10 to 10; the ratio of the radius of curvature of the second surface and the third surface to the focal length is -2 to -3, and the conic coefficient of the second surface and the third surface is -50 to -30; the ratio of the radius of curvature of the fourth surface to the focal length is -4.5 to -6.5, and the conic coefficient of the fourth surface is 15 to 35.

[0008] For example, according to an embodiment of this disclosure, the ratio of the second distance to the focal length is 0.12 to 0.25.

[0009] For example, according to an embodiment of this disclosure, the ratio of the aperture of the lens assembly to the focal length is 2 to 3.

[0010] For example, according to an embodiment of this disclosure, the ratio of the total optical length of the optical system to the focal length is 0.8 to 0.1.

[0011] For example, according to an embodiment of this disclosure, the phase retardation film is located between the reflective polarization layer and the transmissive film, or on the side of the reflective polarization layer away from the transmissive film.

[0012] For example, according to an embodiment of this disclosure, the optical system further includes a linear polarizing film located on the side of the reflective polarizing layer away from the transflective film.

[0013] For example, according to an embodiment of this disclosure, the lens assembly includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis. The first lens includes a first surface, the second lens includes a second surface, and the third lens includes the third surface and the fourth surface. The first lens also includes a fifth surface opposite to the first surface, and the second lens also includes a sixth surface opposite to the second surface. The fifth surface and the sixth surface have the same surface profile parameters. Both the fifth surface and the sixth surface are planar, or the absolute value of the radius of curvature of the fifth surface in at least one direction is greater than the absolute value of the radius of curvature of the other surfaces. The phase retardation film is located on the fifth surface or the sixth surface.

[0014] For example, according to an embodiment of this disclosure, the absolute value of the radius of curvature of the fifth surface is greater than 100 mm.

[0015] For example, according to an embodiment of this disclosure, the distance between the two intersection points of the two surfaces of the first lens and the optical axis is a third distance, the distance between the two intersection points of the two surfaces of the second lens and the optical axis is a fourth distance, and the distance between the two intersection points of the two surfaces of the third lens and the optical axis is a second distance. Both the second distance and the fourth distance are less than the third distance.

[0016] For example, according to an embodiment of this disclosure, the ratio of the sum of the third distance and the fourth distance to the first distance is 0.9 to 1.1.

[0017] For example, according to embodiments of this disclosure, the ratio of the third distance to the focal length is 0.35 to 0.5, and the ratio of the fourth distance to the focal length is 0.1 to 0.3.

[0018] For example, according to an embodiment of this disclosure, the ratio of the center thickness to the edge thickness of the first lens is not less than 0.5 and not greater than 3, and the ratio of the edge thickness to the center thickness of the second lens is not less than 0.5 and not greater than 2.

[0019] For example, according to an embodiment of this disclosure, the exit pupil distance of the optical system is 12 to 20 millimeters.

[0020] For example, according to an embodiment of this disclosure, the first lens and the second lens are made of the same material, and the third lens is made of a different material than the second lens.

[0021] For example, according to an embodiment of this disclosure, the lens assembly includes a first lens and a second lens arranged sequentially along the optical axis, the first lens including a first surface and a second surface, and the second lens including a third surface and a fourth surface; the phase retardation film is located between the reflective polarization layer and the transflective film, or on the side of the reflective polarization layer away from the second surface.

[0022] For example, according to an embodiment of this disclosure, the phase retardation film is located between the reflective polarization layer and the transmissive film, and the reflective polarization layer is configured to reflect linearly polarized light of one characteristic and transmit linearly polarized light of another characteristic; or, the phase retardation film is located on the side of the reflective polarization layer away from the second surface, and the reflective polarization layer comprises cholesteric liquid crystal.

[0023] Another embodiment of this disclosure provides a display device including a display screen and any of the aforementioned optical systems, wherein the optical system is located on the display side of the display screen, and the second surface is located on the side of the first surface away from the display screen. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

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

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

[0027] Figure 3 for Figure 1 The diagram shows a dot matrix representation of the optical system.

[0028] Figure 4 for Figure 1 The graph shows the size of the blur spot of the optical system as a function of the gaze point.

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

[0030] Figures 6 to 9 Cross-sectional views of optical structures provided according to different examples of embodiments of this disclosure. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the described embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0032] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0033] This disclosure provides an optical system and a display device. The optical system includes a lens assembly, a transflective coating, a reflective polarizing layer, and a phase retardation film. The lens assembly includes at least two lenses, each lens including a first surface, a second surface, a third surface, and a fourth surface arranged sequentially along the optical axis of the lens assembly, the second surface and the third surface having the same surface profile parameters; the transflective coating is located on the side of the first surface of the lens assembly away from the second surface; the reflective polarizing layer is located on the side of the second surface of the lens assembly away from the first surface; and the phase retardation film is located on the side of the transflective coating facing the second surface. The light rays incident on the lens assembly after being reflected by the reflective coating are configured to be refracted between the reflective coating and the reflective polarizing layer, and then exit from the reflective polarizing layer. The third and fourth surfaces are two surfaces of the same lens. The first surface is convex and the second surface is concave. The absolute values ​​of the radii of curvature of the first and second surfaces are both smaller than the absolute value of the radii of curvature of the fourth surface. The ratio of the radii of curvature of the first surface to the radii of curvature of the second surface is 0.5 to 1.25. The absolute value of the conicity coefficient of the first surface to the conicity coefficient of the second surface is not greater than 0.4.

[0034] The optical system provided in this disclosure provides an optical system with ultra-short focal length and wide field of view by configuring the lens assembly to include at least four surfaces, wherein two surfaces are respectively provided with a transflective coating and a reflective polarizing layer to achieve light reflection, and setting the relationship between the radii of curvature of the first, second, third and fourth surfaces, and setting the relationship between the conic coefficients of the first and second surfaces.

[0035] The optical system and display device provided in the embodiments of this disclosure are described below with reference to the accompanying drawings.

[0036] Figure 1 This is a cross-sectional view of an optical system provided according to an example embodiment of the present disclosure. Figure 2 for Figure 1 The optical path diagram shown is when the optical system is applied to a display device.

[0037] like Figure 1 As shown, the optical system includes a lens assembly 10, a transflective coating 200, a reflective polarizing layer 300, and a phase retardation film 400.

[0038] like Figure 1As shown, the lens assembly 10 includes at least two lenses, each comprising a first surface 101, a second surface 102, a third surface 103, and a fourth surface 104 arranged sequentially along the optical axis OA of the lens assembly 10. The second surface 102 and the third surface 103 have the same surface profile parameters. The third surface 103 and the fourth surface 104 are two surfaces of the same lens, where the first surface 101 is convex, the second surface 102 is concave, the third surface 103 is convex, and the fourth surface 104 is concave. For example, the lens including the third surface 103 and the fourth surface 104 can be a convex lens. For example, at least one of the first surface 101, the second surface 102, the third surface 103, and the fourth surface 104 includes a spherical surface, an aspherical surface, and a freeform surface. For example, the first surface 101 is an aspherical surface. For example, both the second surface 102 and the third surface 103 are aspherical surfaces. For example, the fourth surface 104 is an aspherical surface. The second surface 102 and the third surface 103 have the same surface parameters, meaning that the second surface and the third surface can be basically completely bonded together when the film layer between them is not considered.

[0039] For example, the optical axis OA is parallel to the X direction shown in the figure. Figure 1 The diagram schematically illustrates that the second surface 102 can be bonded to the third surface 103 to alleviate ghosting issues while improving the compactness of the optical system. However, it is not limited to this; an air gap can also be provided between the second and third surfaces to increase the design freedom of the optical system.

[0040] like Figure 1 As shown, the reflective coating 200 is located on the side of the first surface 101 of the lens assembly 10 away from the second surface 102. For example, the reflective coating 200 may be disposed on the first surface 101. For example, the reflective coating 200 may be deposited on the first surface 101.

[0041] For example, such as Figure 1 As shown, the transflective film 200 is configured to transmit part of the light and reflect another part of the light. For example, the transflective film 200 may include at least one film layer, such as each film layer having a thickness of 10 to 200 nanometers. For example, the transflective film 200 may have a transmittance of 50% and a reflectance of 50%. For example, the transflective film 200 may have a transmittance of 60% and a reflectance of 40%. For example, the transflective film 200 may have a transmittance of 65% and a reflectance of 35%. The optical system provided in this disclosure is not limited thereto; the transmittance and reflectance of the transflective film can be set according to product requirements.

[0042] like Figure 1As shown, the reflective polarizing layer 300 is located between the second surface 102 and the third surface 103 of the lens assembly 10. For example, the reflective polarizing layer 300 can be disposed on the second surface 102. For example, the reflective polarizing layer 300 can be a polarizing reflective film, which is configured to reflect linearly polarized light with one characteristic and transmit linearly polarized light with another characteristic.

[0043] For example, such as Figure 1 As shown, the reflective polarization layer 300 functions as follows: Within the plane of the film layer, there exists a transmission axis direction. The transmittance of the polarization component of incident light parallel to this transmission axis direction (e.g., s-polarized light) is greater than the transmittance of the polarization component perpendicular to this transmission axis direction (e.g., p-polarized light), and the reflectance of the polarization component parallel to this transmission axis direction (e.g., s-polarized light) is less than the reflectance of the polarization component perpendicular to this transmission axis direction (e.g., p-polarized light). For example, the reflective polarization layer 300 can also be called a polarization beam splitter. For example, the transmittance of polarized light parallel to the transmission axis direction of the reflective polarization layer 300 is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%; the reflectance of polarized light perpendicular to the transmission axis direction of the reflective polarization layer 300 is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%. For example, the reflective polarization layer 300 may include a reflective dual brightness enhancement film (DBEF).

[0044] like Figure 1 As shown, the phase retardation film 400 is located on the side of the transflective film 200 facing the second surface 102. For example, the phase retardation film 400 is located between the reflective polarizing layer 300 and the transflective film 200. For example, the phase retardation film 400 is configured such that transmitted light achieves a conversion between circularly polarized and linearly polarized states. For example, the phase retardation film 400 can be a quarter-wave plate. For example, the material of the phase retardation film 400 can include a liquid crystal polymer or polycarbonate. For example, the phase retardation film 400 has the following characteristics: there is a direction with the lowest refractive index and a direction with the highest refractive index within the film plane, which are the fast axis and the slow axis, respectively; the phase of polarized light parallel to the slow axis after passing through the phase retardation film 400 is delayed by 1 / 4 wavelength compared to the phase of polarized light parallel to the fast axis after passing through the phase retardation film 400.

[0045] For example, such as Figure 1 As shown, the angle between the slow axis of the phase retardation film 400 and the transmission axis of the reflective polarization layer 300 is 45 degrees.

[0046] In some examples, such as Figure 1 As shown, the optical system also includes a linear polarizing film 500 located on the side of the reflective polarizing layer 300 away from the transflective film 200.

[0047] For example, such as Figure 1 As shown, the transmission axis of the linear polarizing film 500 coincides with the transmission axis of the reflective polarizing layer 300. The linear polarizing film 500 can be used to further filter other stray light, allowing only polarized light (such as S-polarized light) passing through the linear polarizing film 500 to enter the human eye. For example, the linear polarizing film 500 can adopt a three-layer stacked structure. The middle layer in the three-layer stacked structure can be polyvinyl alcohol (PVA) with added dichroic molecules, and at least one layer located on either side of the middle layer can be triacetate cellulose (TAC). The total thickness of the three-layer stacked structure can be 40–200 micrometers.

[0048] For example, such as Figure 1 As shown, the reflective polarizing layer 300 is attached to the second surface 102, and the linear polarizing film 500 is attached to the surface of the reflective polarizing layer 300 or to the third surface 103. For example, an anti-reflection film can be provided on the side of the fourth surface 104 away from the first surface 101.

[0049] like Figure 1 and Figure 2 As shown, light rays, such as those emitted from the display panel 20, are incident on the lens assembly 10 after passing through the transflective film 200. They are then configured to be reflected back between the transflective film 200 and the reflective polarization layer 300 and exit from the reflective polarization layer 300 to achieve an ultra-short focal length folded optical path (Pancake).

[0050] For example, such as Figure 1 and Figure 2 As shown, the principle of the folded optical path is as follows: A waveplate can be set on the light-emitting side of the display screen 20 located on the side of the first surface 101 away from the second surface 102. The image light emitted from the display screen is converted into right-hand circularly polarized light after passing through the waveplate. The right-hand circularly polarized light is incident on the transmission-reflection film 200. After being transmitted through the transmission-reflection film 200, the polarization state of the right-hand circularly polarized light remains unchanged. This right-hand circularly polarized light reaches the phase retardation film 400, where it is converted into p-linearly polarized light. The p-linearly polarized light is reflected back to the phase retardation film 400 by the reflective polarization layer 300, where the first reflection occurs. Then, the p-linearly polarized light is converted into right-hand circularly polarized light after passing through the phase retardation film 400. This right-hand circularly polarized light reaches the transmission-reflection film 200 and is reflected at the transmission-reflection film 200, where the second reflection occurs. Due to half-wave loss, the reflected light changes from right-hand circularly polarized light to left-hand circularly polarized light. Left-handed circularly polarized light is converted into s-linearly polarized light by phase retardation film 400, and then the s-linearly polarized light is transmitted through reflective polarization layer 300 and linear polarization film 500 before reaching the human eye.

[0051] The aforementioned folded optical path can change the polarization state of light propagating between the reflective polarization layer and the transflective coating, thereby achieving light folding. This folds the focal length of the optical system, which would otherwise be increased by two reflections due to the addition of the reflective polarization layer, phase retardation film, and transflective coating, thus greatly compressing the space required between the human eye and the optical system, making the optical system smaller and thinner.

[0052] like Figure 1 As shown, the absolute values ​​of the radius of curvature of the first surface 101 and the third surface 103 are both smaller than the absolute value of the radius of curvature of the fourth surface 104. The ratio of the radius of curvature of the first surface 101 to the radius of curvature of the second surface 102 is 0.5 to 1.25, and the ratio of the absolute values ​​of the conic coefficient of the first surface 101 to the conic coefficient of the second surface 102 is not greater than 0.4.

[0053] In some examples, such as Figure 1 As shown, the distance between the two intersection points of the first surface 101 and the second surface 102 with the optical axis OA is the first distance D1, and the distance between the two intersection points of the third surface 103 and the fourth surface 104 with the optical axis OA is the second distance D2. The first distance D1 is greater than the second distance D2, and the ratio of the first distance D1 to the focal length is 0.45 to 0.8.

[0054] The optical system provided in this disclosure is an optical system employing a folded optical path (Pancake). This optical system configures the lens assembly to include at least four surfaces, with two surfaces respectively provided with a transflective coating and a reflective polarizing layer to achieve light reflection. The system also sets the relationship between the radii of curvature of the first, second, third, and fourth surfaces, the relationship between the conic coefficients of the first and second surfaces, the relationship between the distances between the surfaces, and the relationship with the focal length ratio of the optical system. This provides an optical system with ultra-short focal length and a large field of view.

[0055] Compared to a single lens with only two surfaces, the optical system provided in this disclosure has at least four surfaces, which is beneficial to increasing the degree of freedom in designing the surface parameters of the optical system, thereby improving display performance, including sharpness, aberration correction, and increased field of view.

[0056] By placing the reflective polarizing layer between the second and fourth surfaces, the light emitted from the reflective polarizing layer is refracted through at least one medium-air interface before entering the human eye, which helps to deflect the light and increase the field of view.

[0057] For example, such as Figure 1As shown, the ratio of the radius of curvature of the first surface 101 to the radius of curvature of the second surface 102 is 0.7 to 1, and the absolute ratio of the conic coefficient of the first surface 101 to the conic coefficient of the second surface 102 is not greater than 0.35. For example, the ratio of the radius of curvature of the first surface 101 to the radius of curvature of the second surface 102 is 0.6 to 1.2, and the absolute ratio of the conic coefficient of the first surface 101 to the conic coefficient of the second surface 102 is not greater than 0.3. For example, the ratio of the radius of curvature of the first surface 101 to the radius of curvature of the second surface 102 is 0.8 to 1.1, and the absolute ratio of the conic coefficient of the first surface 101 to the conic coefficient of the second surface 102 is not greater than 0.25.

[0058] For example, such as Figure 1 As shown, the ratio of the first distance D1 to the focal length is 0.5 to 0.6. For example, the ratio of the first distance D1 to the focal length is 0.55 to 0.75. For example, the ratio of the first distance D1 to the focal length is 0.48 to 0.7.

[0059] In some examples, such as Figure 1 and Figure 2 As shown, the ratio of the radius of curvature to the focal length of the first surface 101 is -1.5 to -2.5, and the conic coefficient of the first surface 101 is -10 to 10; the ratio of the radius of curvature to the focal length of the second surface 102 and the third surface 103 is -2 to -3, and the conic coefficient of the second surface 102 and the third surface 103 is -50 to -30; the ratio of the radius of curvature to the focal length of the fourth surface 104 is -4.5 to -6.5, and the conic coefficient of the fourth surface 104 is 15 to 35.

[0060] In some examples, such as Figure 1 and Figure 2 As shown, the ratio of the second distance D2 to the focal length is 0.12 to 0.25.

[0061] In some examples, such as Figure 1 and Figure 2 As shown, the ratio of the total optical length (TTL) to the focal length of the optical system is 0.8 to 1.

[0062] In some examples, such as Figure 1 As shown, the ratio of the aperture of the lens assembly 10 to the focal length of the optical system is 2 to 3. The aperture of the lens assembly 10 refers to the effective light-transmitting aperture, which is the maximum aperture through which light can pass. This aperture is determined by the maximum light throughput of the lens assembly 10.

[0063] For example, such as Figure 1 As shown, the exit pupil distance of the optical system is 12–20 mm.

[0064] By setting the ratio of the curvature radius of each surface to the focal length of the optical system, the conic coefficient of each surface, the ratio of the distance between different surfaces to the focal length, the ratio of the total optical length to the focal length, and the ratio of the aperture of the lens assembly to the focal length of the optical system, the optical system can achieve an ultra-short focal length and wide field of view display effect while also having a large exit pupil distance, thus improving the user experience.

[0065] For example, such as Figure 1 As shown, the ratio of the radius of curvature of the first surface 101 to the focal length is -1.8 to -2, and the conic coefficient of the first surface 101 is -5 to 5. For example, the ratio of the radius of curvature of the first surface 101 to the focal length is -1.6 to -2.3, and the conic coefficient of the first surface 101 is -7 to 1. For example, the ratio of the radius of curvature of the first surface 101 to the focal length is -1.9 to -2.4, and the conic coefficient of the first surface 101 is -1 to 8. The ratio of the radius of curvature of the first surface 101 to the focal length is -1.7 to -2.2, and the conic coefficient of the first surface 101 is -3 to 7.

[0066] For example, such as Figure 1 As shown, the ratio of the radius of curvature to the focal length of both the second surface 102 and the third surface 103 is -2.5 to -2.8, and the conic coefficient of both surfaces is -40 to -35. For example, the ratio of the radius of curvature to the focal length of both surfaces is -2.3 to -2.7, and the conic coefficient of both surfaces is -45 to -37. For example, the ratio of the radius of curvature to the focal length of both surfaces is -2.2 to -2.6, and the conic coefficient of both surfaces is -48 to -32.

[0067] For example, such as Figure 1 As shown, the ratio of the radius of curvature to the focal length of the fourth surface 104 is -5 to -6, and the conic coefficient of the fourth surface 104 is 20 to 30. For example, the ratio of the radius of curvature to the focal length of the fourth surface 104 is -4.8 to -5.5, and the conic coefficient of the fourth surface 104 is 18 to 25. For example, the ratio of the radius of curvature to the focal length of the fourth surface 104 is -4.8 to -6.2, and the conic coefficient of the fourth surface 104 is 22 to 33.

[0068] For example, such as Figure 1 As shown, the ratio of the second distance D2 to the focal length is 0.15 to 0.2. The ratio of the second distance D2 to the focal length is 0.18 to 0.24. The ratio of the second distance D2 to the focal length is 0.17 to 0.23.

[0069] For example, such as Figure 1As shown, the second distance D2 can be the center thickness of the lens including the third surface 103 and the fourth surface 104.

[0070] For example, such as Figure 1 As shown, the ratio of the total optical length (TTL) to the focal length of the optical system can be 0.85 to 1. For example, the ratio can be 0.8 to 0.95. For example, the ratio can be 0.89 to 0.9. For example, the aforementioned total optical length can refer to the axial distance between the highest point of the fourth surface closest to the human eye and the display surface of the display panel. The highest point on the fourth surface includes the edge sagitta of the lens structure 10 on the fourth surface side.

[0071] For example, such as Figure 1 As shown, the ratio of the aperture to the focal length of the lens assembly 10 is 2.2 to 2.5. For example, the ratio of the aperture to the focal length of the lens assembly 10 is 2.4 to 2.8. For example, the ratio of the aperture to the focal length of the lens assembly 10 is 2.2 to 2.5. For example, the ratio of the aperture to the focal length of the lens assembly 10 is 2.3 to 2.7.

[0072] For example, such as Figure 1 As shown, the ratio of the total optical length of the optical system to the aperture of the lens assembly 10 is 35%.

[0073] For example, such as Figure 1 As shown, the exit pupil distance of the optical system is 13–18 mm. For example, the exit pupil distance of the optical system is 15–17 mm. For example, the exit pupil distance of the optical system is 16–19 mm.

[0074] For example, such as Figure 1 As shown, the field of view of the optical system can be 90 to 110 degrees. For example, the field of view of the optical system can be more than 100 degrees.

[0075] For example, such as Figure 1 As shown, the radius of curvature of the aforementioned surface in the lens assembly 10 is the radius of curvature of its base spherical surface. The aforementioned "base spherical surface" refers to an aspherical surface formed by further deformation based on a sphere, and the sphere that forms the basis of the aspherical surface is the base spherical surface of the aspherical surface. For example, the first surface 101 and the second surface 102 can both be aspherical surfaces, such as both being even-order aspherical surfaces (EVENASPH).

[0076] For example, aspherical surface types are represented by the following numerical formulas:

[0077]

[0078] For example, in the above formula, the height of the aspherical surface along the direction perpendicular to the optical axis is Y, and the distance from the vertex of the aspherical surface to the projection of the point at height Y on the aspherical surface onto the optical axis is z. That is, z is the coordinate along the optical axis; C is the curvature (the reciprocal of the radius of curvature R), k is the conic constant, and α... i These are the coefficients of the higher-order terms, and 2i represents the higher power of the aspherical coefficient.

[0079] When optimizing the surface parameters of the lens structure 10, the values ​​of the radius of curvature, conic coefficient, height, and aspheric coefficient of the surface of the lens structure 10 are put into the above numerical formula, and the optimized parameters that can correct the aberrations of the optical structure are obtained through optical simulation calculation.

[0080] For example, the higher-order coefficients of the first surface 101 satisfy: α4 = -1.4e-006, α6 = 8e-010, α8 = -8e-011. For example, the higher-order coefficients of the second surface 102 satisfy: α4 = -2e-005, α6 = -1.2e-007, α8 = -3.0e-010.

[0081] In some examples, such as Figure 1 As shown, the lens assembly 10 includes a first lens 110, a second lens 120, and a third lens 130 arranged sequentially along the optical axis OA. The first lens 110 includes a first surface 101, the second lens 120 includes a second surface 102, and the third lens 130 includes a third surface 103 and a fourth surface 104. The first lens 110 also includes a fifth surface 105 opposite to the first surface 101, and the second lens 120 also includes a sixth surface 106 opposite to the second surface 102. The fifth surface 105 and the sixth surface 106 have the same surface profile parameters. Both the fifth surface 105 and the sixth surface 106 are planar, and the phase retardation film 400 is located on either the fifth surface 105 or the sixth surface 106. For example, the phase retardation film 400 is bonded to either the fifth surface 105 or the sixth surface 106. For example, the fifth surface 105 and the sixth surface 106 having the same surface profile parameters means that, without considering the film layer between them, the fifth surface and the sixth surface can be substantially completely bonded.

[0082] Phase retardation films include birefringent materials. Laminating phase retardation films onto a flat plate surface with a planar shape can improve the flatness of the film material, overcome the process challenges caused by curved lamination, and avoid the softening and stretching process of the film material, which would affect the shift of its birefringent properties such as optical axis angle and phase retardation. It is easy to maintain a fixed phase retardation, which is beneficial to improving the overall optical performance of the optical system, such as sharpness, stray light, and field of view, in order to ensure imaging quality.

[0083] For example, such as Figure 1 As shown, a reflective coating 200 is deposited on the first surface 101 of the first lens 110, a phase retardation film 400 is attached to the sixth surface 106 of the second lens 120, and the first lens 110 is attached to the phase retardation film 400. For example, the phase retardation film 400 is attached to the fifth surface 105 of the first lens 110, and the first lens 110 is attached to the sixth surface 106 of the second lens 120. For example, a reflective polarizing layer 300 and a linear polarizing film 500 are attached to the second surface 102 of the second lens 120, and a third lens 130 is attached to the linear polarizing film 500. For example, the first lens 110 is bonded to the second lens 120, and the second lens 120 is bonded to the third lens 130.

[0084] For example, such as Figure 1 As shown, the apertures of the first lens 110, the second lens 120, and the third lens 130 can be basically equal, such that the ratio of the aperture of the three lenses to the focal length of the optical system is 2 to 3.

[0085] In some examples, such as Figure 1 As shown, the distance between the two intersection points of the two surfaces of the first lens 110 and the optical axis OA is the third distance D3; the distance between the two intersection points of the two surfaces of the second lens 120 and the optical axis OA is the fourth distance D4; and the distance between the two intersection points of the two surfaces of the third lens 130 and the optical axis OA is the second distance D2. Both the second distance D2 and the fourth distance D4 are less than the third distance D3.

[0086] For example, such as Figure 1 As shown, the center thickness of the first lens 110 is a third distance D3, and the center thickness of the second lens 120 is a fourth distance D4. For example, the first lens 110 can be a positive lens. For example, the first lens 110 can be a plano-convex lens. For example, the second lens 120 can be a negative lens. For example, the second lens 120 can be a plano-concave lens.

[0087] In some examples, such as Figure 1 As shown, the ratio of the third distance D3 to the focal length is 0.35 to 0.5, the ratio of the fourth distance D4 to the focal length is 0.1 to 0.3, and the ratio of the second distance D2 to the focal length is 0.12 to 0.25.

[0088] For example, such as Figure 1 As shown, the ratio of the third distance D3 to the focal length is 0.4–0.48, the ratio of the fourth distance D4 to the focal length is 0.15–0.25, and the ratio of the second distance D2 to the focal length is 0.15–0.2. For example, the ratio of the third distance D3 to the focal length is 0.37–0.45, the ratio of the fourth distance D4 to the focal length is 0.12–0.2, and the ratio of the second distance D2 to the focal length is 0.2–0.23.

[0089] In some examples, such as Figure 1 As shown, the ratio of the sum of the third distance D3 and the fourth distance D4 to the first distance D1 is 0.9 to 1.1. For example, Figure 1 The diagram illustrates the effect of each coating layer on the distance between different surfaces of the lens assembly. For example, when the thickness of each coating layer is thin, the coating layer thickness can be ignored. In this case, the sum of the center thickness of the first lens and the center thickness of the second lens can be the aforementioned first distance.

[0090] In some examples, such as Figure 1 As shown, the first lens 110 and the second lens 120 are made of the same material, while the third lens 130 is made of a different material than the second lens 120, which is beneficial for correcting chromatic aberration. For example, the refractive index of the first lens 110 and the second lens 120 can be between 1.45 and 1.75. By selecting a larger refractive index for the first and second lenses, it is beneficial to obtain a larger radius of curvature.

[0091] By using the same material for the first and second lenses, the fabrication of the optical system can be made easier.

[0092] For example, such as Figure 1 As shown, the Abbe numbers of both the first lens 110 and the second lens 120 are greater than 50. For example, the Abbe number of the third lens 130 is different from that of the first lens 110 and the second lens 120.

[0093] For example, such as Figure 1 As shown, the first lens 110 and the second lens 120 can be made of cyclic olefin copolymers (COC), such as resin, with a refractive index of 1.54 and an Abbe number vd of 56. For example, the third lens 130 can be made of polymethyl methacrylate (PMMA), such as plexiglass, with a refractive index of 1.49 and an Abbe number of 57.2. For example, the third lens 130 can be made of polystyrene (PS), with a refractive index of 1.59 and an Abbe number of 30.8. Of course, the embodiments disclosed herein are not limited to these; the material of the third lens can be the same as that of the first and second lenses, or the materials of the first and second lenses can be different.

[0094] For example, such as Figure 1 As shown, when the aperture of the optical system satisfies a field of view of not less than 100 degrees, the thickness of at least one lens edge (such as the thickness at a location other than the effective light-transmitting aperture) can be reduced to decrease the weight of the optical system. For example, the weight of the binocular lens of the optical system provided in this disclosure when applied to a display device is no more than 30 grams.

[0095] Figure 3 for Figure 1 The diagram shows a dot matrix representation of the optical system. Figure 4 for Figure 1 The diagram shows the size of the blur spot in the optical system, such as the root mean square (RMS) of the blur spot diameter as a function of the fixation point. Figure 3 The normalized field of view in the X direction, the normalized field of view in the Y direction, the field of view angle in the X direction, and the field of view angle in the Y direction are shown, as well as the root mean square (RMS) of the speckle diameter at different field of view angles.

[0096] A dot pattern refers to a diffuse pattern formed by many rays emitted from a point, which, after passing through an optical system, no longer converge at a single point due to aberrations, and instead create a pattern scattered over a certain range. This pattern can be used to evaluate the imaging quality of an optical system. Figure 3 The term "transient mode" is typically used to evaluate the full field-of-view sharpness of an optical system. It refers to the image sharpness covering the entire field of view when the pupil is at the entrance pupil position on the optical axis and the viewer is fixating on the center of the lens (i.e., zero field of view). Besides the full field-of-view sharpness in this mode, fixational sharpness is also a more important optical indicator for the wearer of the head-mounted display. This refers to the image sharpness within a specific angular range that the eye can directly see (rather than through peripheral vision) when moving up, down, left, and right.

[0097] In fixation mode, when the eyeball rotates at a certain angle, the pupil deviates from the center of the optical axis, exhibiting a certain deviation in both the Z and Y directions. Furthermore, the principal ray passing through the center of the pupil forms a certain angle with the Z-axis. For example, this angle ranges from ±35 degrees to account for human eye observation habits. To clearly see objects more than 35 degrees away from the center of the eye, a person will actively turn their head rather than laboriously rotating their eyeballs. Figure 4 The diagram shows the relationship between the sharpness of the fixation point and the fixation angle. The blur spot in the central field of view is much smaller than a pixel. The diameter of the blur spot is 16 micrometers when the human eye is rotated to 25 degrees.

[0098] Figure 5 for Figure 1 The distortion diagram of the optical system shown.

[0099] For example, such as Figure 5 As shown, distortion is a parameter in an optical system and one of the important factors limiting the accuracy of optical measurements. It is the degree of distortion of the image formed by an optical system relative to the object itself. Figure 5 The distortion level of the optical system is shown. At a 48° half-field angle, the relative distortion of the optical system is no less than -35%, thus meeting the distortion requirements of imaging in general virtual reality products, resulting in low image distortion. In addition, distortion correction can be pre-processed in the software.

[0100] Figure 6 This is a cross-sectional view of an optical structure provided according to another example of an embodiment of this disclosure. Figure 6 and Figure 1The difference in the optical structures shown lies in the position of the linear polarizing film 500. For example, as... Figure 6 As shown, the linear polarizing film 500 is located on the fourth surface 104. For example, the linear polarizing film 500 is adhered to the fourth surface. For example, the surface of the linear polarizing film 500 facing the air is treated with anti-reflective coating. For example, a moth-eye membrane can be adhered to the surface of the linear polarizing film 500 facing the air. Figure 6 The characteristics of each lens and each coating layer in the optical structure shown can be compared with... Figure 1 The corresponding lenses and corresponding films in the optical structures shown have the same characteristics, which will not be described again here.

[0101] For example, such as Figure 6 As shown, by attaching the reflective polarizing film 300 to the second surface 102 or the third surface 103, and attaching the linear polarizing film 500 to the fourth surface 104, problems such as wrinkles, film cracks or tension caused by thicker film layers can be avoided.

[0102] Figure 7 This is a cross-sectional view of an optical structure provided according to another example of an embodiment of this disclosure. Figure 7 The optical structure shown is Figure 1 The difference in the optical structure shown lies in the different surface shapes of the fifth and sixth surfaces.

[0103] In some examples, such as Figure 7 As shown, the absolute value of the radius of curvature of the fifth surface 105 in at least one direction is greater than the absolute value of the radius of curvature of the other surfaces, and the phase retardation film 400 is located on the fifth surface 105 or the sixth surface 106. For example, both the fifth surface 105 and the sixth surface 106 are curved toward the side closer to the first surface 101.

[0104] In some examples, such as Figure 7 As shown, the absolute values ​​of the radii of curvature of the fifth surface 105 and the sixth surface 106 are greater than 100 mm. For example, the fifth surface 105 and the sixth surface 106 can be micro-curved surfaces.

[0105] For example, such as Figure 7 As shown, the ratio of the radius of curvature of the fifth surface 105 and the sixth surface 106 to the focal length of the optical system is -8 to -10.

[0106] For example, such as Figure 7As shown, when the sixth surface 106 (or fifth surface 105) of the lens assembly 10 used to set the phase retardation film 400 is curved, during the process of bonding the phase retardation film 400 to the lens assembly 100, the planar phase retardation film 400 needs to be appropriately stretched first, and then fully bonded to the curved sixth surface 106. If the radius of curvature of the sixth surface 106 of the lens assembly 10 is small, for example, its absolute value is less than 100 micrometers and its conicity is greater than or equal to zero, wrinkles may occur when the phase retardation film 400 is stretched and bonded to the sixth surface 106. Both the excessive stretching of the phase retardation film 400 and the wrinkles generated during bonding may affect the accuracy of the phase retardation of the phase retardation film, thereby affecting the optical performance. In the optical system provided in this disclosure, by setting a larger absolute value of the radius of curvature of the sixth surface used to bond the phase retardation film, the influence of the curved surface shape of the sixth surface on the performance of the phase retardation film can be reduced.

[0107] For example, such as Figure 7 As shown, the sixth surface 106 can be a curved surface with rotational symmetry. For example, the sixth surface 106 has the same surface shape in two different directions, and the radii of curvature of the sixth surface 106 in the two different directions are equal, such as both being less than -100 micrometers. For example, the sixth surface 106 can be an aspherical surface.

[0108] For example, such as Figure 7 As shown, the sixth surface 106 can be a curved surface with axisymmetric properties. For example, the surface shape of the sixth surface 106 in one direction is different from that in another direction, and the radii of curvature of the sixth surface 106 in the two directions are different, such as one of them being less than -100 micrometers. For example, the sixth surface 106 can be an ellipsoid. For example, the sixth surface 106 can be a cylinder, that is, the sixth surface 106 is a curved surface in one of the two directions, and a plane in the other direction, i.e., a cylinder, with a radius of curvature of 0 in one of the two directions and a non-zero radius of curvature in the other direction.

[0109] By setting the shape of the sixth surface to a curved surface with axisymmetric properties, it is beneficial to prevent the shape of the phase retardation film from being greatly affected during the stretching and bonding process.

[0110] In some examples, such as Figure 7 As shown, the ratio of the center thickness to the edge thickness of the first lens 110 is not less than 0.5 and not greater than 3, and the ratio of the edge thickness to the center thickness of the second lens 120 is not less than 0.5 and not greater than 2. Therefore, both the first and second lenses achieve a reasonable center-to-edge thickness ratio, which is beneficial for ensuring the injection molding of both lenses, reducing stress, and facilitating processing.

[0111] For example, such as Figure 7As shown, the ratio of the center thickness to the edge thickness of the first lens 110 is no greater than 2.8, and the ratio of the edge thickness to the center thickness of the second lens 120 is no greater than 1.5. For example, the ratio of the center thickness to the edge thickness of the first lens 110 is no greater than 2.5, and the ratio of the edge thickness to the center thickness of the second lens 120 is no greater than 1.7. For example, the ratio of the center thickness to the edge thickness of the first lens 110 is no greater than 2.3, and the ratio of the edge thickness to the center thickness of the second lens 120 is no greater than 1.4. For example, the ratio of the center thickness to the edge thickness of the first lens 110 is no greater than 2, and the ratio of the edge thickness to the center thickness of the second lens 120 is no greater than 1.2.

[0112] Figure 8 This is a cross-sectional schematic diagram of an optical structure provided according to another example of an embodiment of the present disclosure. Figure 8 The optical structure shown is Figure 1 The difference in the optical structures shown is that the number of lenses included in the lens assembly 10 is different, and the position of the phase retardation film 400 is different.

[0113] In some examples, such as Figure 8 As shown, the lens assembly 10 includes a first lens 110 and a second lens 120 arranged sequentially along the optical axis. The first lens 110 includes a first surface 101 and a second surface 102, and the second lens 120 includes a third surface 103 and a fourth surface 104. The first, second, third, and fourth surfaces in this example have the same characteristics as the first, second, third, and fourth surfaces in the lens assembly provided in the above example, and will not be described again here.

[0114] By setting only the first and second lenses in the lens assembly, the manufacturing of the lens assembly can be simplified.

[0115] For example, such as Figure 8 As shown, the center thickness of the first lens 110 is a first distance D1, and the center thickness of the second lens 120 can be a second distance D2. The first and second distances in this example can have the same characteristics as the first and second distances in the examples above, and will not be repeated here.

[0116] For example, such as Figure 8 As shown, the transflective coating 200 can be deposited on the first surface 101, and the phase retardation film 400, the reflective polarizing layer 300, and the linear polarizing film 500 can be bonded between the second surface 102 and the third surface 103. The first lens 110 and the second lens 120 are cemented together. The transflective coating in this example has the same characteristics as the transflective coating in the examples above, and will not be described again here.

[0117] For example, such as Figure 8As shown, the phase retardation film 400 can be made of a liquid crystal polymer. This polymer can achieve the same performance as traditional optical films such as quarter-wave plates (typically about 50 μm thick) with a very thin film thickness (1-5 μm). Because of its thinness, it is highly adaptable to different curved surfaces and easy to shape according to the surface. In addition, liquid crystal polymers are cross-linked systems with molecules linked by chemical bonds, resulting in a high modulus. When stretched after bonding, they only undergo elastic deformation without molecular stretching or rearrangement, which strongly affects optical anisotropy. Therefore, the optical shift is small after bonding a phase retardation film made of liquid crystal polymer to a curved surface. The phase retardation film made of the above-mentioned liquid crystal polymer can be bonded to surfaces with smaller absolute values ​​of curvature radii, such as less than 100 micrometers, thereby increasing the degree of freedom of curvature radius of the surface in the lens assembly, which is beneficial to improving the image quality of the optical system, including indicators such as sharpness, distortion, and dispersion.

[0118] The reflective polarizing layer and linear polarizing film in the optical structure provided in this example can have the same characteristics as the reflective polarizing layer and linear polarizing film in the optical structure provided in the above examples, and will not be described again here.

[0119] Figures 1 to 8 In the optical structures shown in the different examples, the phase retardation film 400 is located between the reflective polarization layer 300 and the transmissive film 200. Figures 1 to 8 The reflective polarizing layer 300 in each of the examples shown can be made of the same material.

[0120] Figure 9 This is a cross-sectional schematic diagram of an optical structure provided according to another example of an embodiment of the present disclosure. Figure 9 The optical structure shown is Figure 8 The difference in the optical structure shown is that the phase retardation film 400 and the reflective polarization layer 300 have different positional relationships, and the reflective polarization layer 300 has different characteristics.

[0121] In some examples, such as Figure 9 As shown, the phase retardation film 400 is located on the side of the reflective polarization layer 300 away from the transmissive film 200.

[0122] For example, such as Figure 9As shown, the reflective polarization layer 300 includes a cholesteric liquid crystal layer. The cholesteric liquid crystal layer can reflect and transmit circularly polarized light. Referring to the aforementioned folded light path principle, the cholesteric liquid crystal layer 300 is disposed between the phase retardation film 400 and the transflective film 200. A waveplate can be disposed on the light-emitting side of the display screen located on the side of the first lens 110 away from the second lens 120. The image light emitted from the display screen is converted into right-hand circularly polarized light after passing through the waveplate. The right-hand circularly polarized light is incident on the transflective film 200, and its polarization state remains unchanged after transmission through the transflective film 200. This right-hand circularly polarized light is reflected back to the transflective film 200 after passing through the cholesteric liquid crystal layer 300, where the first reflection occurs; the right-hand circularly polarized light is reflected again at the transflective film 200, where the second reflection occurs. Due to half-wave loss, the reflected light changes from right-handed circularly polarized light to left-handed circularly polarized light. This left-handed circularly polarized light is transmitted through the cholesteric liquid crystal layer 300 and reaches the phase retardation film 400, where it is converted into s-polarized light. This s-polarized light is then transmitted through the linear polarization film 500 and directed toward the human eye.

[0123] Figure 2 A schematic diagram of a partial structure of a display device provided in another embodiment of this disclosure is shown.

[0124] like Figure 2 As shown, the display device includes a display screen 20 and an optical system as described in any of the above examples. Figure 2 The optical system is shown schematically as follows: Figure 1 The optical system shown is not limited to this; it can also be used for... Figures 7 to 9 The optical system provided in any of the examples.

[0125] like Figure 2 As shown, the optical system is located on the display side of the display screen 20, and the second surface 102 is located on the side of the first surface 101 away from the display screen 20.

[0126] For example, such as Figure 2 As shown, the display surface of the display screen 20 is located on the focal plane of the light-incident side of the optical system.

[0127] For example, such as Figure 2 As shown, the display screen 20 may further include multiple sub-pixels (not shown) and a microlens array (not shown) located on the light-emitting side of the multiple sub-pixels. For example, the microlens array includes multiple microlenses, such as spherical lenses or aspherical lenses. For example, the surface curvature radius of each microlens may be the same, but at least some microlenses may be eccentric microlenses, such as the vertex of the convex surface being offset from the center of its corresponding sub-pixel, or the angle between the optical axis of different microlenses and the normal of the light-emitting surface of the display screen being different, so that the light intensity emitted by the sub-pixel is redistributed after passing through the microlenses, so that the maximum light intensity is consistent with the direction of the principal rays of different fields of view in the optical system.

[0128] For example, such as Figure 2 As shown, the display screen 20 can be a silicon-based organic light-emitting diode display screen with extremely high pixel density. The optical system has high definition and a large field of view. The blur spot of the optical system in the center field of view is smaller than the size of a sub-pixel (micrometer level), and the full field of view can exceed 100 degrees.

[0129] For example, such as Figure 2 As shown, the display screen 20 can be any type of display screen, such as a liquid crystal display screen, an inorganic light-emitting diode display screen, a quantum dot display screen, a projector (such as an LCOS micro projector), etc.

[0130] For example, the display device can be a virtual reality (VR) display device. For instance, a virtual reality display device can be a display device employing an ultra-short-throw folded optical path.

[0131] For example, the display device can be a near-eye display device, such as a wearable VR helmet or VR glasses, but the embodiments disclosed herein are not limited thereto.

[0132] The following points need to be explained:

[0133] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure, and other structures can be referred to the general design.

[0134] (2) Where there is no conflict, features of the same embodiment and different embodiments of this disclosure may be combined with each other.

[0135] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.

Claims

1. An optical system, comprising: A lens assembly includes at least two lenses, which may be two or three lenses. The at least two lenses include a first surface, a second surface, a third surface, and a fourth surface arranged sequentially along the optical axis of the lens assembly. The second surface and the third surface have the same surface profile parameters. A transflective coating is located on the side of the first surface of the lens assembly away from the second surface; A reflective polarizing layer is located between the second and third surfaces of the lens assembly; A phase retardation film is located on the side of the transmissive and reflective film facing the second surface; The light rays that are transmitted through the transflective film and incident on the lens assembly are configured to be reflected back between the transflective film and the reflective polarization layer, and then exit from the reflective polarization layer. The third and fourth surfaces are two surfaces of the same lens. The first surface is convex, and the second surface is concave. The third surface is convex, and the fourth surface is concave. The absolute values ​​of the radii of curvature of the first and second surfaces are both smaller than the absolute value of the radii of curvature of the fourth surface. The ratio of the radii of curvature of the first surface to that of the second surface is 0.5 to 1.

25. The ratio of the absolute values ​​of the conic coefficients of the first and second surfaces is not greater than 0.

4. The ratio of the radii of curvature of the second and third surfaces to the focal length of the optical system is -2 to -3, and the conic coefficients of the second and third surfaces are -50 to -30. The ratio of the radii of curvature of the fourth surface to the focal length of the optical system is -4.5 to -6.5, and the conic coefficient of the fourth surface is 15 to 35. The field of view of the optical system is 90 to 110 degrees.

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

8.

3. The optical system according to claim 1, wherein, The ratio of the radius of curvature of the first surface to the focal length of the optical system is -1.5 to -2.5, and the conicity of the first surface is -10 to 10.

4. The optical system according to claim 2, wherein, The ratio of the second distance to the focal length of the optical system is 0.12 to 0.

25.

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

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

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

8. The optical system according to claim 1, further comprising: A linear polarizing film is located on the side of the reflective polarizing layer away from the transflective film.

9. The optical system according to claim 2, wherein, The lens assembly includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis. The first lens includes a first surface, the second lens includes a second surface, and the third lens includes the third surface and the fourth surface. The first lens also includes a fifth surface opposite to the first surface, and the second lens also includes a sixth surface opposite to the second surface. The fifth surface and the sixth surface have the same surface shape parameters. The fifth surface and the sixth surface are both planar, or the absolute value of the radius of curvature of the fifth surface in at least one direction is greater than the absolute value of the radius of curvature of the other surfaces, and the fifth surface is curved toward the side closer to the first surface. The phase retardation film is located on the fifth surface or the sixth surface.

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

11. The optical system according to claim 9, wherein, The distance between the two intersection points of the two surfaces of the first lens and the optical axis is the third distance; the distance between the two intersection points of the two surfaces of the second lens and the optical axis is the fourth distance; and the distance between the two intersection points of the two surfaces of the third lens and the optical axis is the second distance. Both the second distance and the fourth distance are less than the third distance.

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

1.

13. The optical system according to claim 11, wherein, The ratio of the third distance to the focal length is 0.35 to 0.5, and the ratio of the fourth distance to the focal length is 0.1 to 0.

3.

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

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

16. The optical system according to claim 9, wherein, The first lens and the second lens are made of the same material, and the third lens is made of a different material than the second lens.

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

18. The optical system according to claim 17, wherein, The phase retardation film is located between the reflective polarization layer and the transmissive film, and the reflective polarization layer is configured to reflect linearly polarized light of one characteristic and transmit linearly polarized light of another characteristic; or, The phase retardation film is located on the side of the reflective polarization layer away from the second surface, and the reflective polarization layer comprises cholesteric liquid crystal.

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

Images