Optical system and display device

Abstract

The invention provides an optical system and a display device. The optical system includes a lens assembly, a transflective film, a reflective polarization layer, and a phase retardation film. The lens assembly comprises at least two lenses, and each lens comprises a first surface, a second surface, a third surface and a fourth surface which are arranged in sequence; the transflective film is located on one side of the first surface away from the second surface; the reflective polarization layer is located on one 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 ratio of the absolute value of the cone coefficient of the first surface to the absolute value of the cone coefficient of the second surface is not larger than 0.4. The optical system has the characteristics of ultra-short focus and large field of view.

Description

Technical Field

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

[0002] The imaging principle of the head-mounted display optical system is equivalent to a magnifying glass. The object (such as a picture source or a video source) is in the object focal plane of the optical lens (such as within one focal length), and the human eye on the other side of the lens can observe the upright and enlarged 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, the shorter the focal length of the lens, the shorter the tube length can be.

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

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

[0005] The embodiment of the present disclosure provides an optical system, including: a lens assembly, a transflective film, a reflective polarizing layer, and a phase delay film. The lens assembly includes at least two lenses, the at least two lenses include a first surface, a second surface, a third surface, and a fourth surface arranged in sequence along the optical axis direction of the lens assembly, the second surface and the third surface have the same surface parameters; the transflective film is located 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 surface and the third surface of the lens assembly; the phase delay film is located on the side of the transflective film facing the second surface. The light incident on the lens assembly after being transmitted through the transflective film is configured to be reflected between the transflective film and the reflective polarizing layer and to be emitted from the reflective polarizing layer; the third surface and the fourth surface are two surfaces of the same lens, the first surface is a convex surface, the second surface is a concave surface, the third surface is a convex surface, and the fourth surface is a concave surface, the absolute value of the radius of curvature of the first surface and the absolute value of the radius of curvature of the second surface are both smaller than the absolute value of the radius of curvature of the fourth surface, the ratio of the radius of curvature of the first surface to the radius of curvature of the second surface is 0.5 to 1.25, and the absolute value ratio of the cone coefficient of the first surface to the cone coefficient of the second surface is not greater than 0.4.

[0006] For example, according to an embodiment of the present disclosure, the distance between the two intersection points where the first surface and the second surface intersect the optical axis is a first distance, the distance between the two intersection points where the third surface and the fourth surface intersect the optical axis is a second distance, the first distance is 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 the present disclosure, the ratio of the radius of curvature of the first surface to the focal length is -1.5 to -2.5, and the cone 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 cone coefficients of the second surface and the third surface are -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 cone coefficient of the fourth surface is 15 to 35.

[0008] For example, according to an embodiment of the present 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 the present 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 the present 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 the present disclosure, the phase delay film is located between the reflective polarizing layer and the transflective film, or is located on a side of the reflective polarizing layer away from the transflective film.

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

[0013] For example, according to an embodiment of the present disclosure, the lens assembly includes a first lens, a second lens and a third lens arranged in sequence along the optical axis direction, the first lens includes the first surface, the second lens includes the second surface, the third lens includes the third surface and the fourth surface, the first lens also includes a fifth surface opposite to the first surface, the second lens also includes a sixth surface opposite to the second surface, the fifth surface and the sixth surface have the same surface parameters, the fifth surface and the sixth surface are both planes, or the absolute value of the curvature radius of the fifth surface in at least one direction is greater than the absolute values ​​of the curvature radii of other surfaces; the phase delay film is located on the fifth surface or the sixth surface.

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

[0015] For example, according to an embodiment of the present disclosure, the distance between the two intersection points where the two surfaces of the first lens intersect the optical axis is the third distance, the distance between the two intersection points where the two surfaces of the second lens intersect the optical axis is the fourth distance, and the distance between the two intersection points where the two surfaces of the third lens intersect the optical axis is the second distance, and both the second distance and the fourth distance are smaller than the third distance.

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

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

[0018] 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 not less than 0.5 and not more 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 more than 2.

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

[0020] For example, according to an embodiment of the present disclosure, the material of the first lens and the second lens is the same, and the material of the third lens is different from that of the second lens.

[0021] For example, according to an embodiment of the present disclosure, the lens assembly includes a first lens and a second lens arranged in sequence along the optical axis direction, the first lens includes the first surface and the second surface, and the second lens includes the third surface and the fourth surface; the phase delay film is located between the reflective polarizing layer and the transflective film, or is located on the side of the reflective polarizing layer away from the second surface.

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

[0023] Another embodiment of the present disclosure provides a display device, including a display screen and any one of the above optical systems, wherein the optical system is located on a display side of the display screen, and the second surface is located on a side of the first surface away from the display screen. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

[0030] Figures 6 to 9 Cross-sectional views of optical structures provided according to different examples of embodiments 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 present disclosure provides an optical system and a display device. The optical system includes a lens assembly, a transflective film, a reflective polarizing layer, and a phase delay film. The lens assembly includes at least two lenses, and the at least two lenses include a first surface, a second surface, a third surface, and a fourth surface arranged in sequence along the optical axis direction of the lens assembly, and the second surface and the third surface have the same surface parameters; the transflective film is located 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 delay film is located on the side of the transflective film facing the second surface. The light incident on the lens assembly after being reflected by the transflective film is configured to be turned back between the transflective film and the reflective polarizing layer and to be emitted from the reflective polarizing layer; the third surface and the fourth surface are two surfaces of the same lens, the first surface is a convex surface, the second surface is a concave surface, the third surface is a convex surface, the fourth surface is a concave surface, the absolute value of the radius of curvature of the first surface and the absolute value of the radius of curvature of the second surface are both smaller than the absolute value of the radius of curvature of the fourth surface, the ratio of the radius of curvature of the first surface to the radius of curvature of the second surface is 0.5 to 1.25, and the ratio of the absolute value of the cone coefficient of the first surface to the cone coefficient of the second surface is not greater than 0.4.

[0034] The optical system provided by the present disclosure is provided by configuring a lens component to include at least four surfaces, wherein two surfaces are respectively provided with a transflective film and a reflective polarizing layer to realize the reflection of light, and the relationship between the curvature radii of the first surface, the second surface, the third surface and the fourth surface is configured, and the relationship between the cone coefficients of the first surface and the second surface is configured, thereby providing an optical system with ultra-short focus and large field of view characteristics.

[0035] The optical system and display device provided by the embodiments of the present disclosure are described below in conjunction with the accompanying drawings.

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

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

[0038] like Figure 1As shown, the lens assembly 10 includes at least two lenses, and the at least two lenses include a first surface 101, a second surface 102, a third surface 103 and a fourth surface 104 arranged in sequence along the optical axis OA direction of the lens assembly 10, and the second surface 102 and the third surface 103 have the same surface parameters. The third surface 103 and the fourth surface 104 are two surfaces of the same lens, the first surface 101 is a convex surface, the second surface 102 is a concave surface, the third surface 103 is a convex surface, and the fourth surface 104 is a concave surface. For example, the lens including the 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 free-form surface. For example, the first surface 101 is an aspherical surface. For example, the second surface 102 and the third surface 103 are both aspherical surfaces. For example, the fourth surface 104 is an aspherical surface. The second surface 102 and the third surface 103 having the same surface parameters means that the second surface and the third surface can be substantially completely attached to each other without considering the film layer therebetween.

[0039] For example, the optical axis OA is parallel to the X direction shown in the figure. Figure 1 It is schematically shown that the second surface 102 can be glued to the third surface 103 to alleviate the ghost problem and improve the compactness of the optical system. However, it is not limited to this, and an air gap can be set between the second surface and the third surface to improve the design freedom of the optical system.

[0040] like Figure 1 As shown, the transflective film 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 transflective film 200 can be disposed on the first surface 101. For example, the transflective film 200 can be plated on the first surface 101.

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

[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, and the reflective polarizing layer 300 is configured to reflect linear polarized light of one characteristic and transmit linear polarized light of another characteristic.

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

[0044] like Figure 1 As shown, the phase delay film 400 is located on the side of the transflective film 200 facing the second surface 102. For example, the phase delay film 400 is located between the reflective polarization layer 300 and the transflective film 200. For example, the phase delay film 400 is configured to enable the transmitted light to achieve a conversion between a circular polarization state and a linear polarization state. For example, the phase delay film 400 can be a 1 / 4 wave plate. For example, the material of the phase delay film 400 can include liquid crystal polymer or polycarbonate. For example, the phase delay film 400 has the following characteristics: there is a direction with the lowest refractive index and a direction with the highest refractive index in the plane of the film layer, which are the fast axis and the slow axis respectively, and the phase of the polarized light parallel to the slow axis after passing through the phase delay film 400 is delayed by 1 / 4 wavelength compared with the polarized light parallel to the fast axis after passing through the phase delay film 400.

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

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

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

[0048] For example, 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-reflective film may be disposed on the side of the fourth surface 104 away from the first surface 101.

[0049] like Figure 1 and Figure 2 As shown, light, such as light emitted from the display panel 20, is configured to be folded back between the transflective film 200 and the reflective polarizing layer 300 after entering the lens assembly 10 through the transflective film 200, and emitted from the reflective polarizing layer 300 to achieve an ultra-short focus folded light path (Pancake).

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

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

[0052] like Figure 1 As shown, the absolute value of the radius of curvature of the first surface 101 and the absolute value of the radius of curvature of 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 absolute value ratio of the cone coefficient of the first surface 101 to the cone 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 where the first surface 101 and the second surface 102 intersect the optical axis OA is a first distance D1, the distance between the two intersection points where the third surface 103 and the fourth surface 104 intersect the optical axis OA is a second distance D2, the first distance D1 is 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 by the embodiment of the present disclosure is an optical system using a folded optical path (Pancake), in which a lens component is arranged to include at least four surfaces, two of which are respectively provided with a transflective film and a reflective polarization layer to realize the reflection of light, and the relationship between the curvature radius of the first surface, the second surface, the third surface and the fourth surface is arranged, the relationship between the cone coefficient of the first surface and the second surface is arranged, and at the same time, the relationship between the distances between the surfaces and the proportional relationship with the focal length of the optical system are arranged, thereby providing an optical system with ultra-short focus and large field of view characteristics.

[0055] Compared with a single lens having only two surfaces, the optical system provided by the present disclosure has at least four surfaces, which is beneficial to increasing the degree of freedom in the design of the surface parameters of the optical system, so as to improve display performance including clarity, correction of aberrations, and increase of field of view angle.

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

[0057] For example, 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 value ratio of the cone coefficient of the first surface 101 to the cone 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 value ratio of the cone coefficient of the first surface 101 to the cone 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 value ratio of the cone coefficient of the first surface 101 to the cone coefficient of the second surface 102 is not greater than 0.25.

[0058] For example, 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 of the first surface 101 to the focal length is -1.5 to -2.5, and the cone coefficient of the first surface 101 is -10 to 10; the ratio of the radius of curvature of the second surface 102 and the third surface 103 to the focal length is -2 to -3, and the cone coefficients of the second surface 102 and the third surface 103 are -50 to -30; the ratio of the radius of curvature of the fourth surface 104 to the focal length is -4.5 to -6.5, and the cone 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 0.12-0.25.

[0061] In some examples, such as Figure 1 and Figure 2 As shown, the ratio of the total optical length (TTL) of the optical system to the focal length 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 aperture, such as the maximum aperture through which light can pass, which is determined by the maximum luminous flux of the lens assembly 10.

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

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

[0065] For example, 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 cone 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 cone 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 cone 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 cone coefficient of the first surface 101 is -3 to 7.

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

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

[0068] For example, 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, Figure 1As shown, the second distance D2 may be the central thickness of the lens including the third surface 103 and the fourth surface 104 .

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

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

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

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

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

[0075] For example, Figure 1 As shown, the curvature radius of the above-mentioned surface in the lens assembly 10 is the curvature radius of the base spherical surface of the surface. The above-mentioned "base spherical surface" means that the aspherical surface is further deformed based on the spherical surface, and the spherical surface serving as the basis of the aspherical surface is the base spherical surface of the aspherical surface. For example, the first surface 101 and the second surface 102 can both be aspherical surfaces, such as even aspherical surfaces (EVENASPH).

[0076] For example, the aspheric surface shape is expressed by the following numerical formula:

[0077]

[0078] For example, in the above formula, the height of the aspheric surface along the direction perpendicular to the optical axis is Y, the distance from the aspheric vertex to the projection of the aspheric surface at a height of Y on the optical axis is z, that is, z is the coordinate along the optical axis; C is the curvature (the inverse of the radius of curvature R), k is the conic constant, α i is the coefficient of each high-order term, and 2i is the order of Aspherical Coefficient.

[0079] When actually optimizing the reasonable configuration of the surface parameters of the lens structure 10, the curvature radius, cone coefficient, height and aspheric coefficient of the surface of the lens structure 10 are placed in the above numerical formula, and optical simulation calculations are performed to obtain various optimization parameters that can correct the aberrations of the optical structure.

[0080] For example, the high-order coefficients of the first surface 101 satisfy: α 4 =-1.4e-006, α 6 =8e-010,α 8 =-8e-011. For example, the high-order coefficients of the second surface 102 satisfy: α 4 =-2e-005, α 6 =-1.2e-007, α 8 =-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 in sequence along the optical axis OA direction, the first lens 110 includes a first surface 101, the second lens 120 includes a second surface 102, 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, 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 parameters, the fifth surface 105 and the sixth surface 106 are both planes, and the phase delay film 400 is located on the fifth surface 105 or the sixth surface 106. For example, the phase delay film 400 is bonded to the fifth surface 105 or the sixth surface 106. For example, the fifth surface 105 and the sixth surface 106 have the same surface parameters, which means that the fifth surface and the sixth surface can be substantially completely bonded without considering the film layer between the two.

[0082] The phase delay film includes birefringent materials. Laminating the phase delay film to a flat surface with a flat shape can improve the flatness of the film material, overcome the process challenges caused by curved lamination, avoid the softening and stretching process of the above-mentioned film material which affects the deviation of its birefringent properties such as the optical axis angle and phase delay, and make it easy to maintain a fixed phase delay, which is beneficial to improving the comprehensive optical performance of the optical system such as clarity, stray light, and field of view to ensure imaging quality.

[0083] For example, Figure 1 As shown, the transflective film 200 is plated on the first surface 101 of the first lens 110, the phase delay film 400 is bonded to the sixth surface 106 of the second lens 120, and the first lens 110 is bonded to the phase delay film 400. For example, the phase delay film 400 is bonded to the fifth surface 105 of the first lens 110, and the first lens 110 is bonded to the sixth surface 106 of the second lens 120. For example, the reflective polarizing layer 300 and the linear polarizing film 500 are bonded to the second surface 102 of the second lens 120, and the third lens 130 is bonded to the linear polarizing film 500. For example, the first lens 110 is glued to the second lens 120, and the second lens 120 is glued to the third lens 130.

[0084] For example, Figure 1 As shown, the apertures of the first lens 110 , the second lens 120 , and the third lens 130 may be substantially equal, such as the ratios of the apertures of the three lenses to the focal length of the optical system are all 2 to 3.

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

[0086] For example, Figure 1 As shown, the center thickness of the first lens 110 is the third distance D3, and the center thickness of the second lens 120 is the 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 0.35-0.5, the ratio of the fourth distance D4 to the focal length is 0.1-0.3, and the ratio of the second distance D2 to the focal length is 0.12-0.25.

[0088] For example, 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. Figure 1 The effect of each film layer on the distance between different surfaces of the lens assembly is schematically shown. When the thickness of each film layer is relatively thin, the thickness of the film layer can be ignored. At this time, the sum of the center thickness of the first lens and the center thickness of the second lens can be the above-mentioned 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, and the third lens 130 is made of a material different from that of 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 may be 1.45 to 1.75. By selecting a larger refractive index for the first lens and the second lens, a larger radius of curvature may be obtained.

[0091] By using the same material for the first lens and the second lens, the manufacture of the optical system can be facilitated.

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

[0093] For example, Figure 1 As shown, the material of the first lens 110 and the second lens 120 may be cycloolefin copolymer (COC), such as resin, with a refractive index of 1.54 and an Abbe number vd of 56. For example, the material of the third lens 130 may be polymethyl methacrylate (PMMA), such as organic glass, with a refractive index of 1.49 and an Abbe number of 57.2. For example, the material of the third lens 130 may be polystyrene (PS), with a refractive index of 1.59 and an Abbe number of 30.8. Of course, the embodiments of the present disclosure are not limited thereto, and the material of the third lens may be the same as that of the first lens and the second lens, or the materials of the first lens and the second lens may be different.

[0094] For example, Figure 1As shown, when the aperture of the optical system satisfies the field of view angle of not less than 100 degrees, the thickness of the edge of at least one lens (such as the thickness outside the effective aperture) can be thinned to reduce the weight of the optical system. For example, the weight of the binocular lens of the optical system provided by the present disclosure when applied to a display device is not more than 30 grams.

[0095] Figure 3 for Figure 1 Spot diagram of the optical system shown. Figure 4 for Figure 1 The speckle size of the optical system shown is a graph of the root mean square (RMS) of the speckle diameter as a function of gaze point. Figure 3 The normalized field of view in the X direction, the normalized field of view in the Y direction, the field of view angle in the X direction, the field of view angle in the Y direction, and the root mean square (RMS) of the diffuse spot diameter at different field of view angles are shown.

[0096] A point diagram refers to a diffuse pattern formed when many light rays emitted from one point pass through the optical system and their intersection with the image plane is no longer concentrated at the same point due to aberrations, but are spread over a certain range. This pattern can be used to evaluate the imaging quality of the optical system. Figure 3 It is usually used to evaluate the full field of view clarity of the optical system, that is, the image clarity of the full field of view that can be covered by the peripheral vision when the human pupil is at the entrance pupil position on the optical axis and the human eye is looking at the center of the lens (i.e., zero field of view). It is also called transient mode. In addition to the full field of view clarity in this mode, for the wearer of the headset, the gaze point clarity is also a more important optical indicator, such as the image clarity within a certain angle range that can be directly seen (not seen by the peripheral vision) when the eyes move up, down, left, and right.

[0097] In the gaze point mode, the eyeball rotates a certain angle, the pupil deviates from the center of the optical axis, and there is a certain deviation in the Z and Y directions of the optical axis, and the main light passing through the center of the pupil has a certain angle with the Z axis. For example, the range of the angle is ±35 degrees to take into account the observation habits of the human eye. For example, in order to see the front object that is more than 35 degrees beyond the center of the human eye, people will actively turn their heads instead of moving their eyeballs. Figure 4 The figure shows the relationship between the clarity of the gaze point and the gaze angle. The diffuse spot in the central field of view is much smaller than a pixel. When the human eye rotates to 25 degrees, the diameter of the diffuse spot is 16 microns.

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

[0099] For example, Figure 5 As shown in the figure, distortion is a parameter in the optical system and one of the important factors limiting the accuracy of optical measurement. It is the degree of distortion of the image formed by the optical system on the object relative to the object itself. Figure 5The distortion degree of the optical system is shown. At a half field of view angle of 48°, the relative distortion of the optical system is not less than -35%. Therefore, the optical system meets the distortion requirements of imaging in general virtual reality products, and the distortion degree of the imaging is low. In addition, the distortion correction can be pre-processed in the software.

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

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

[0102] Figure 7 A cross-sectional view of an optical structure provided according to another example of an embodiment of the present disclosure. Figure 7 The optical structure shown is Figure 1 The optical structures shown are different in that the fifth surface and the sixth surface have different surface shapes.

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

[0104] In some examples, such as Figure 7 As shown, the absolute value of the curvature radius of the fifth surface 105 and the sixth surface 106 is greater than 100 mm. For example, the fifth surface 105 and the sixth surface 106 may be micro-curved surfaces.

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

[0106] For example, Figure 7 As shown, when the sixth surface 106 (or the fifth surface 105) for setting the phase delay film 400 in the lens assembly 10 is a curved surface, in the process of bonding the phase delay film 400 to the lens assembly 100, the flat-shaped phase delay film 400 needs to be properly stretched first, and then completely bonded to the curved surface shape of the 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 microns and the cone coefficient is greater than or equal to zero, wrinkles may be generated when the phase delay film 400 is stretched and bonded to the sixth surface 106. The excessive stretching of the phase delay film 400 and the wrinkles generated during bonding may affect the phase delay accuracy of the phase delay film, thereby affecting the optical performance. In the optical system provided by the present disclosure, by setting the absolute value of the radius of curvature of the sixth surface for bonding the phase delay film to be larger, the influence of the curved surface of the sixth surface on the performance of the phase delay film can be reduced.

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

[0108] For example, Figure 7 As shown, the sixth surface 106 may be a curved surface with an axisymmetric property. For example, the surface shape of the sixth surface 106 in one direction is different from the surface shape in another direction, and the curvature radius of the sixth surface 106 in the above two directions is different, such as one of the two is less than -100 microns. For example, the sixth surface 106 may be an ellipsoidal surface. For example, the sixth surface 106 may be a cylindrical surface, that is, the sixth surface 106 is a curved surface in one of the above two directions, and a plane in the other direction, that is, a cylindrical surface, and the curvature radius in one of the above two directions is 0, and the curvature radius in the other direction is not 0.

[0109] By setting the shape of the sixth surface to be a curved surface with an axially symmetrical characteristic, it is advantageous to prevent the shape of the phase retardation film from being greatly affected during the process of stretching and bonding the phase retardation film.

[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 more 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 more than 2. Thus, both the first lens and the second lens achieve a reasonable thickness ratio of the center thickness to the edge thickness, which is beneficial to ensure the injection molding of the first lens and the second lens, reduce stress, and facilitate processing.

[0111] For example, Figure 7 As shown, the ratio of the center thickness to the edge thickness of the first lens 110 is not greater than 2.8, and the ratio of the edge thickness to the center thickness of the second lens 120 is not greater than 1.5. For example, the ratio of the center thickness to the edge thickness of the first lens 110 is not greater than 2.5, and the ratio of the edge thickness to the center thickness of the second lens 120 is not greater than 1.7. For example, the ratio of the center thickness to the edge thickness of the first lens 110 is not greater than 2.3, and the ratio of the edge thickness to the center thickness of the second lens 120 is not greater than 1.4. For example, the ratio of the center thickness to the edge thickness of the first lens 110 is not greater than 2, and the ratio of the edge thickness to the center thickness of the second lens 120 is not greater than 1.2.

[0112] Figure 8 A schematic diagram of the cross-sectional structure 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 optical structures shown are different in that the number of lenses included in the lens assembly 10 is different, and the position of the phase delay film 400 is different.

[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 in sequence along the optical axis direction, the first lens 110 includes a first surface 101 and a second surface 102, and the second lens 120 includes a third surface 103 and a fourth surface 104. The first surface, the second surface, the third surface and the fourth surface in this example have the same features as the first surface, the second surface, the third surface and the fourth surface in the lens assembly provided in the above example, and will not be repeated here.

[0114] By only providing the first lens and the second lens in the lens assembly, the manufacture of the lens assembly can be facilitated.

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

[0116] For example, Figure 8 As shown, the transflective film 200 can be plated on the first surface 101, the phase delay film 400, the reflective polarizing layer 300 and the linear polarizing film 500 can be attached between the second surface 102 and the third surface 103, and the first lens 110 is glued to the second lens 120. The transflective film in this example has the same features as the transflective film in the above examples, which will not be repeated here.

[0117] For example, Figure 8 As shown, the material of the phase delay film 400 can be liquid crystal polymer, which can achieve the same performance as traditional optical film materials such as quarter wave plates (conventional thickness is about 50 μm) at a very thin film thickness (1-5 μm); because of its thin film thickness, it has a high degree of adaptability to different curved surfaces and is easy to shape according to the curved surface. In addition, liquid crystal polymer is a cross-linked system, and the molecules are linked by chemical bonds, and the modulus is relatively high. When stretched after bonding, only elastic deformation occurs, and no molecular stretching, rearrangement, and other effects that strongly affect optical anisotropy will occur. Therefore, the optical displacement after the phase delay film of liquid crystal polymer is used for curved surface bonding is small. The phase delay film using the above-mentioned liquid crystal polymer can be bonded to a surface with a smaller absolute value of the radius of curvature, such as less than 100 microns, thereby increasing the degree of freedom of the radius of curvature of the surface in the lens assembly, which is beneficial to improving the image quality of the optical system, such as including indicators such as clarity, distortion, and dispersion.

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

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

[0120] Fig. 9 A schematic diagram of the cross-sectional structure of an optical structure provided according to another example of an embodiment of the present disclosure. Fig. 9 The optical structure shown is Figure 8 The differences between the optical structures shown are that the positional relationship between the phase retardation film 400 and the reflective polarizing layer 300 is different, and the characteristics of the reflective polarizing layer 300 are different.

[0121] In some examples, such as Fig. 9 As shown, the phase delay film 400 is located on a side of the reflective polarizing layer 300 away from the transflective film 200 .

[0122] For example, Fig. 9As shown, the reflective polarizing layer 300 includes a cholesteric liquid crystal layer. The cholesteric liquid crystal layer can reflect circularly polarized light and transmit circularly polarized light. Referring to the aforementioned folded optical path principle, the cholesteric liquid crystal layer 300 is disposed between the phase delay film 400 and the transflective film 200. A wave plate can be disposed on the light-emitting 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-handed circularly polarized light after passing through the wave plate. The right-handed circularly polarized light is incident on the transflective film 200. The polarization state of the right-handed circularly polarized light remains unchanged after passing through the transflective film 200. The right-handed circularly polarized light is reflected back to the transflective film 200 after passing through the cholesteric liquid crystal layer 300, where the first reflection occurs; the right-handed circularly polarized light is reflected at the transflective film 200, where the second reflection occurs. Due to the half-wave loss, the reflected light changes from right circularly polarized light to left circularly polarized light. The left circularly polarized light reaches the phase delay film 400 after passing through the cholesteric liquid crystal layer 300, and is converted into s polarized light by the phase delay film 400. Then, the s linearly polarized light is transmitted through the linear polarization film 500 and emitted to the human eye.

[0123] Figure 2 A partial structural diagram of a display device provided in another embodiment of the present disclosure is schematically shown.

[0124] like Figure 2 As shown, the display device includes a display screen 20 and an optical system in any of the above examples. Figure 2 The optical system is schematically shown as Figure 1 The optical system shown, but not limited thereto, can also be Figures 7 to 9 An optical system is provided in any one 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 a side of the first surface 101 away from the display screen 20 .

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

[0127] For example, Figure 2 As shown, the display screen 20 may also include a plurality of sub-pixels (not shown) and a microlens array (not shown) located on the light-emitting side of the plurality of sub-pixels. For example, the microlens array includes a plurality of microlenses, such as a microlens that may be a spherical lens or an aspherical lens. For example, the surface curvature radius of each microlens may be the same, but at least some of the microlenses may be eccentric microlenses, such as the convex surface vertex deviates from the center of the sub-pixel corresponding thereto, such as the angles between the optical axes of different microlenses and the normals of the light-emitting surface of the display screen are different, so that the light intensity of the light emitted by the sub-pixel is redistributed after passing through the microlens, so that the maximum value of the light intensity is consistent with the direction of the main light in different fields of view in the optical system.

[0128] For example, 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 the performance of high definition and large field of view. The diffuse spot of the optical system in the central field of view is smaller than the size of a sub-pixel (micrometer level), and the full field of view can exceed 100 degrees.

[0129] For example, 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 may be a virtual reality (VR) display device. For example, the virtual reality display device may be a display device using an ultra-short-throw folded optical path.

[0131] 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.

[0132] There are a few points to note:

[0133] (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.

[0134] (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.

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

Claims

1. An optical system, comprising: A lens assembly, comprising at least two lenses, wherein the at least two lenses comprise a first surface, a second surface, a third surface and a fourth surface arranged in sequence along an optical axis direction of the lens assembly, wherein the second surface and the third surface have the same surface parameters; A transflective film is located on a side of the first surface of the lens assembly away from the second surface; a reflective polarizing layer disposed between the second surface and the third surface of the lens assembly; A phase delay film, located on a side of the transflective film facing the second surface; Wherein, the light incident on the lens assembly after being transmitted through the transflective film is configured to be folded back between the transflective film and the reflective polarizing layer, and to be emitted from the reflective polarizing layer; The third surface and the fourth surface are two surfaces of the same lens, the first surface is a convex surface, the second surface is a concave surface, the third surface is a convex surface, and the fourth surface is a concave surface, the absolute value of the radius of curvature of the first surface and the absolute value of the radius of curvature of the second surface are both smaller than the absolute value of the radius of curvature of the fourth surface, the ratio of the radius of curvature of the first surface to the radius of curvature of the second surface is 0.5 to 1.25, and the ratio of the absolute value of the cone coefficient of the first surface to the cone coefficient of the second surface is not greater than 0.

4.

2. The optical system according to claim 1, wherein: The distance between two intersection points where the first surface and the second surface intersect the optical axis is a first distance, the distance between two intersection points where the third surface and the fourth surface intersect the optical axis is a second distance, the first distance is greater than the second distance, and a 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 conic coefficient of the first surface is -10 to 10; The ratios of the curvature radii of the second surface and the third surface to the focal length are both -2 to -3, and the conic coefficients of the second surface and the third surface are both -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 cone coefficient of the fourth surface is 15 to 35.

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 2-3.

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 0.

1.

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

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

9. The optical system according to claim 2, wherein: The lens assembly comprises a first lens, a second lens and a third lens arranged in sequence along the optical axis direction, the first lens comprises the first surface, the second lens comprises the second surface, the third lens comprises the third surface and the fourth surface, the first lens further comprises a fifth surface opposite to the first surface, the second lens further comprises a sixth surface opposite to the second surface, the fifth surface and the sixth surface have the same surface parameters, the fifth surface and the sixth surface are both planes, or the absolute value of the curvature radius of the fifth surface in at least one direction is greater than the absolute values ​​of the curvature radius of other surfaces; The phase 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 where the two surfaces of the first lens intersect the optical axis is the third distance, the distance between the two intersection points where the two surfaces of the second lens intersect the optical axis is the fourth distance, and the distance between the two intersection points where the two surfaces of the third lens intersect the optical axis is the second distance, and both the second distance and the fourth distance are smaller than the third distance.

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

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 more 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 more than 2.

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

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

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

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

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

Images