Optical System and Display Device

Abstract

Embodiments of the present disclosure provide an optical system and a display device. The optical system includes a lens, a polarization transmission and reflection film, a phase retardation film, and a transmission and reflection film. The lens includes a planar surface and an aspherical surface, and the aspherical surface is a convex surface. The phase retardation film and the transmission and reflection film are disposed on the side away from the aspherical surface of the planar surface of the lens, and the transmission and reflection film is disposed on the side away from the planar surface of the aspherical surface of the lens. The lens is an integral lens, the planar surface and the aspherical surface are located on opposite sides of the integral lens, the focal length of the optical system is 26 to 28 millimeters, the effective aperture of the lens is 50 to 52 millimeters, and the radius of curvature of the aspherical surface is -93 to -97 millimeters. The optical system according to the present disclosure uses a folded optical path, and at the same time, sets the lens as an integral lens including an aspherical surface, and optimizes parameters such as the focal length of the optical system, the effective aperture of the integral lens, and the radius of curvature of the aspherical surface. By doing so, the optical system can achieve a large viewing angle display and at the same time have a large exit pupil distance, improving the user experience.

Description

Technical Field

[0001] Cross - reference to related applications This application claims the priority of Chinese Patent Application No. 202210714718.1, filed on June 22, 2022, and the entire content disclosed in the above - mentioned Chinese patent application is incorporated herein by reference in its entirety.

[0002] Embodiments of the present disclosure relate to an optical system and a display device.

Background Art

[0003] Virtual Reality (VR) products are human - computer interaction products created using computers and the latest sensor technologies. They comprehensively utilize computer graphics systems and various interface devices such as reality and control, and provide an immersive experience in an interactive three - dimensional environment generated on a computer.

[0004] With the popularization of virtual reality products, the usage requirements of users for virtual reality products are increasing. Currently, since the number of users who watch movies by selecting and using virtual reality products is increasing, virtual reality display devices with a large field - of - view (FOV) display effect have become the mainstream.

Summary of the Invention

[0005] Embodiments of the present disclosure relate to an optical system and a display device.

[0006] Embodiments of the present disclosure provide an optical system, including a lens, a polarization transmission and reflection film, a phase retardation film, and a transmission and reflection film. The lens includes a planar surface and an aspherical surface, the aspherical surface is a convex surface, the side away from the aspherical surface of the planar surface is the light-emitting side of the lens, the polarization transmission and reflection film is installed on the side away from the aspherical surface of the planar surface of the lens, the phase retardation film is installed between the polarization transmission and reflection film and the planar surface of the lens, and the transmission and reflection film is installed on the side away from the planar surface of the aspherical surface of the lens. The lens is an integrated lens, the planar surface and the aspherical surface are located on opposite sides of the integrated lens, the focal length of the optical system is 26 to 28 millimeters, the effective aperture of the lens is 50 to 52 millimeters, and the radius of curvature of the aspherical surface is -93 to -97 millimeters.

[0007] For example, according to an embodiment of the present disclosure, the focal length of the lens is 160 to 180 millimeters.

[0008] For example, according to an embodiment of the present disclosure, the maximum thickness of the lens is 6 to 8 millimeters.

[0009] For example, according to an embodiment of the present disclosure, the exit pupil distance of the optical system is 13 to 21 millimeters.

[0010] For example, according to an embodiment of the present disclosure, the exit pupil distance of the optical system is 15 millimeters or more.

[0011] For example, according to an embodiment of the present disclosure, the maximum field of view angle of the optical system is 100° to 110°.

[0012] For example, according to an embodiment of the present disclosure, the modulation transfer function value at the maximum field of view angle of the optical system is 0.7 or more at a position where the spatial frequency is 20 line pairs / mm.

[0013] For example, according to an embodiment of the present disclosure, the modulation transfer function value at the maximum field of view angle of the optical system is 0.8 or more at a position where the spatial frequency is 15 line pairs / mm.

[0014] For example, according to an embodiment of the present disclosure, the refractive index of the lens is 1.5 to 1.6.

[0015] For example, according to an embodiment of the present disclosure, the phase retardation film and the polarization transmission reflection film are in close contact with the plane.

[0016] Embodiments of the present disclosure provide a display device, including a display screen and any one of the above optical systems. The display screen is located on the side away from the plane of the aspherical surface of the lens, and the display surface of the display screen is located on the focal plane of the light incident side of the optical system.

[0017] For example, according to an embodiment of the present disclosure, the distance between the aspherical surface and the display surface of the display screen is 26 to 28 millimeters.

[0018] For example, according to an embodiment of the present disclosure, the maximum size of the display surface of the display screen is 2 to 3 inches.

[0019] The optical system according to the embodiment of the present disclosure uses a folded optical path. At the same time, the lens is set as an integrated lens including an aspherical surface, and parameters such as the focal length of the optical system, the effective aperture of the integrated lens, and the radius of curvature of the aspherical surface are set. Thereby, the optical system can realize a large viewing angle display and at the same time have a large exit pupil distance, and can improve the user experience.

Brief Description of the Drawings

[0020] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below. Of course, the drawings in the following description are not limitations to the present disclosure, but are only related to some embodiments of the present disclosure.

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0022] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, hereinafter, with reference to the drawings of the embodiments of the present disclosure, the technical solutions of the embodiments of the present disclosure will be clearly and completely described. Of course, the described embodiments are only a part of the embodiments of the present disclosure, not all of the embodiments. All other embodiments obtained by those skilled in the art based on the described embodiments of the present disclosure without creative labor shall fall within the protection scope of the present disclosure.

[0023] Unless otherwise defined, technical terms or scientific terms used in the present disclosure should have the ordinary meaning understood by those skilled in the art. The "first", "second" and similar words used in the present disclosure do not represent any order, quantity or importance, but are only used to distinguish different components. Similar terms such as "comprising" or "including" mean that the elements or members described before "comprising" or "including" cover the elements or members listed after "comprising" or "including" and their equivalents, and do not exclude other elements or members.

[0024] In the research, the inventors of the present application discovered that in order to realize the viewing effect of a large field of view (FOV), the eye relief (ERF) of the current folded optical path (Pancake) products of virtual reality is generally 13 to 15 millimeters. However, the eye relief distance makes it difficult to satisfy the use of myopic users wearing glasses, and further affects the user experience.

[0025] Embodiments of the present disclosure provide an optical system and a display device. The optical system includes a lens, a polarization transmission and reflection film, a phase retardation film, and a transmission and reflection film. The lens includes a planar surface and an aspherical surface, the aspherical surface is a convex surface, and the side away from the planar aspherical surface is the light-emitting side of the lens. The polarization transmission and reflection film is installed on the side away from the planar aspherical surface of the lens, the phase retardation film is installed between the polarization transmission and reflection film and the planar surface of the lens, and the transmission and reflection film is installed on the side away from the planar surface of the aspherical surface of the lens. The lens is an integral lens, the planar surface and the aspherical surface are located on opposite sides of the integral lens, the focal length of the optical system is 26 to 28 millimeters, the effective aperture of the lens is 50 to 52 millimeters, and the radius of curvature of the aspherical surface is -93 to -97 millimeters. The optical system according to the embodiments of the present disclosure may be an optical system using a folded optical path (Pancake). While installing the polarization transmission and reflection film, the phase retardation film, and the transmission and reflection film on both sides of the lens, setting the lens as an integral lens including an aspherical surface, setting the focal length of the optical system, and setting and optimizing parameters such as the effective aperture of the integral lens and the radius of curvature of the aspherical surface, the optical system can achieve an ultra-short focal length and a large viewing angle display, and at the same time has a large exit pupil distance, improving the user experience.

[0026] Hereinafter, the optical system and the display device according to the embodiments of the present disclosure will be described with reference to the drawings.

[0027] FIG. 1 is a schematic structural diagram of a lens according to an embodiment of the present disclosure, and FIG. 2 is a schematic optical path diagram of an optical system including the lens shown in FIG. 1. As shown in FIGS. 1 and 2, the optical system includes a lens 100. The lens 100 includes a planar surface 110 and an aspherical surface 120. The aspherical surface 120 is a convex surface, and the side away from the aspherical surface 120 of the planar surface 110 is the light-emitting side of the lens 100. As shown in FIG. 1, the optical system further includes a polarization transmission and reflection film 500 installed on the side away from the aspherical surface 120 of the planar surface 110, and a phase retardation film 600 installed between the polarization transmission and reflection film 500 and the planar surface 110. As shown in FIG. 1, the optical system further includes a transmission and reflection film 700 installed on the side away from the planar surface 110 of the aspherical surface 120.

[0028] As shown in FIG. 1, the lens 100 is an integrated lens. The plane 110 and the aspherical surface 120 are located on opposite sides of the integrated lens 100. The focal length of the optical system is 26 to 28 millimeters, the effective aperture of the lens 100 is 50 to 52 millimeters, and the radius of curvature of the aspherical surface 120 is -93 to -97 millimeters.

[0029] The optical system according to an embodiment of the present disclosure may be an optical system using a folded optical path (Pancake). A polarization transmission reflection film and a phase retardation film are installed on one side of the lens, and at the same time, a transmission reflection film is installed on the other side of the lens. At the same time, the lens is set as an integrated lens including an aspherical surface, the focal length of the optical system is set, and parameters such as the effective aperture of the integrated lens and the radius of curvature of the aspherical surface are set and optimized. Thereby, the optical system can achieve an ultra-short focal length, a large viewing angle display, and at the same time has a large exit pupil distance, improving the user experience.

[0030] For example, the plane 110 and the aspherical surface 120 included in the integrated lens 100 are two surfaces of the lens 100. For example, the integrated lens 100 may be called a single lens. For example, the integrated lens 100 may be a plano-convex lens.

[0031] For example, the aspherical surface 120 curves away from the plane 110 to form a convex surface.

[0032] For example, the focal length of the optical system may be 26.5 to 27.5 millimeters. For example, the focal length of the optical system may be 27 to 27.3 millimeters.

[0033] In some examples, the focal length of the lens 100 is 160 to 180 millimeters. For example, the focal length of the lens 100 may be 162 to 178 millimeters. For example, the focal length of the lens 100 may be 165 to 175 millimeters. For example, the focal length of the lens 100 may be 167 to 172 millimeters. For example, the focal length of the lens 100 may be 169 to 170 millimeters. The focal length of the above lens refers to the focal length when the lens surface is not coated.

[0034] For example, as shown in FIG. 1, the polarization transmission reflection film 500 and the phase retardation film 600 are located on the myopia side of the lens 100, and the transmission reflection film 700 is located on the near image source side of the lens 100. For example, the polarization transmission reflection film 500 and the phase retardation film 600 are installed on the side away from the aspherical surface 120 of the plane 110, and the transmission reflection film 700 is installed on the side away from the plane 110 of the aspherical surface 120.

[0035] In some examples, the phase retardation film 600 and the polarization transmission reflection film 500 can be in close contact with the plane 110 of the lens 100 as a composite film layer. For example, the transmission reflection film 700 can be coated or plated on the aspherical surface 120.

[0036] For example, as shown in FIGS. 1 and 2, the polarization transmission reflection film 500 can include a polarization transmission film and a reflection polarization film, and the polarization transmission film is located on the side away from the phase retardation film 600 of the reflection polarization film.

[0037] For example, the polarization transmission reflection film 500 and the phase retardation film 600 constitute a folded optical path polarization device, which is also called a composite film. For example, the composite film is in close contact with the plane 110 of the lens 100.

[0038] For example, the function of a reflective polarizing film is to reflect polarized light in one direction (e.g., p linearly polarized light) while transmitting polarized light in the other direction (e.g., s linearly polarized light). For example, a reflective polarizing film (also referred to as a polarization separation film) has the following characteristics. There is a specific optical axis direction in the plane of the film material, and the transmittance (parallel transmittance) of the polarized light component parallel to this direction of the incident light > 80%. For example, the parallel transmittance > 85%. At the same time, the reflectance (parallel reflectance) of this component < 5%. For example, the parallel reflectance < 1%. The transmittance (orthogonal transmittance) of the polarized light component perpendicular to this direction of the incident light < 0.5%. For example, the orthogonal transmittance < 0.1%. At the same time, the reflectance (orthogonal reflectance) of this component > 80%. For example, the orthogonal reflectance > 85%. For example, the reflective polarizing film may be a plastic reflective film.

[0039] For example, the polarization axis of the polarization transmission film is parallel to the polarization axis of the reflective polarizing film. For example, the polarization transmission film may be a linear polarizing film and is used to further filter other stray light, allowing only the polarized light (e.g., s linearly polarized light) passing through the polarization transmission reflective film to enter the human eye.

[0040] For example, as shown in FIGS. 1 and 2, the phase retardation film 600 is configured to realize the conversion of the transmitted light between the circularly polarized state and the linearly polarized state. For example, the phase retardation film 600 may be a quarter-wave plate.

[0041] For example, as shown in FIGS. 1 and 2, the transmissive reflective film 700 can be configured to reflect a part of the light and transmit another part of the light. For example, the transmissive reflective film 700 can reflect 50% of the light rays and transmit 50% of the light rays.

[0042] As shown in FIGS. 1 and 2, the folded optical path is formed using the above-mentioned polarization transmission reflection film 500, phase retardation film 600, and transmission reflection film 700, and the principle of the folded optical path is as follows. A wave plate can be installed on the display surface 300 side of the display screen located on the side away from the plane 110 of the aspherical surface 120. The image light emitted from the display surface 300 passes through the wave plate and is converted into right-circularly polarized light. The right-circularly polarized light passes through the transmission reflection film 700 without changing its polarization state. The light ray enters the lens 100, passes through the lens 100, and reaches the phase retardation film 600. The right-circularly polarized light incident on the phase retardation film 600 is converted into p-linearly polarized light. The p-linearly polarized light is reflected by the polarization transmission reflection film 500 back to the phase retardation film 600, where the first reflection occurs. Then, the p-linearly polarized light passes through the phase retardation film 600 and is converted into right-circularly polarized light. The right-circularly polarized light passes through the lens 100 and reaches the transmission reflection film 700, and is reflected by the transmission reflection film 700, where the second reflection occurs. Due to the half-wave loss, the reflected light is converted from right-circularly polarized light to left-circularly polarized light. The left-circularly polarized light passes through the lens 100 and reaches the phase retardation film 600, passes through the phase retardation film 600 and is converted into s-linearly polarized light, and then the s-linearly polarized light passes through the polarization transmission reflection film 500 and is emitted to the exit pupil 200, for example, a person's eye.

[0043] The above-mentioned folded optical path can change the polarization state of the light ray propagated between the polarization transmission reflection film and the transmission reflection film, and can realize the folding of the light ray. Originally, the focal length of the lens is increased by the installation of the above-mentioned polarization transmission reflection film, phase retardation film, and transmission reflection film. For example, the light ray is folded by two reflections, thereby greatly compressing the required space between the person's eye and the optical system, and making the volume of the optical system smaller and thinner.

[0044] For example, the effective aperture of the lens 100 refers to the maximum aperture through which the light ray can pass through the lens 100, and the effective aperture is determined by the maximum light beam of the lens 100. For example, the effective aperture of the lens 100 may be 50.5 - 51.5 microns. For example, the effective aperture of the lens 100 may be 51 - 51.8 microns.

[0045] For example, the values of the effective aperture in each direction perpendicular to the optical axis of the lens 100 may all be the same, may be different, and can be set according to the requirements of the product.

[0046] Setting the size of the effective aperture of the above lens can ensure that the size in the direction perpendicular to the optical axis is small and can meet the requirements of the viewing range.

[0047] For example, the radius of curvature of the aspherical surface 120 may be -95 to -95.8 microns. For example, the radius of curvature of the aspherical surface 120 may be -93 to -95.5 microns. For example, the radius of curvature of the aspherical surface 120 may be -94 to -95 microns.

[0048] For example, as shown in FIGS. 1 and 2, the aspherical surface 120 may be an even aspherical surface (EVENASPH), and the radius of curvature of the aspherical surface 120 is the radius of curvature of the reference spherical surface of its surface. The above "reference spherical surface" is formed by further deforming the aspherical surface based on the spherical surface, and refers to the spherical surface serving as the reference for the aspherical surface being the reference spherical surface of the aspherical surface.

[0049] For example, the side of the plane 110 of the lens 100 away from the aspherical surface 120 includes the exit pupil 200. For example, the diameter of the exit pupil may be 4 millimeters.

[0050] For example, in the process of optimizing the parameters of the optical system, the imaging surface 300 of the optical system is located on the side away from the plane 110 of the aspherical surface 120, and the above imaging surface 300 is the position of the display surface of the display screen when the optical system is used in the display device. For example, a display surface 300 for displaying an image can be installed on the side of the lens 100 away from the plane 110 of the aspherical surface 120. For example, the image distance of the virtual image formed by the optical system may be 1200 to 2000 millimeters.

[0051] In some examples, as shown in FIGS. 1 and 2, the maximum thickness of the lens 100 is 6 to 8 millimeters. For example, the maximum thickness in the extending direction along the optical axis of the lens 100 (e.g., the X direction shown in FIG. 1) is 6 to 8 millimeters. For example, the distance between the intersection of the plane 110 and the optical axis and the intersection of the aspherical surface 120 and the optical axis is 6 to 8 millimeters. For example, the size of the lens 100 cut by its optical axis is 6 to 8 millimeters. For example, the maximum thickness of the lens 100 may be 6.5 to 7.5 millimeters. For example, the maximum thickness of the lens 100 may be 7 millimeters.

[0052] In the optical system according to this embodiment, the size of the lens in the optical axis direction is small, whereby the size of the optical system can be reduced and the compactness of the display device including the optical system can be improved.

[0053] In some examples, as shown in FIGS. 1 and 2, the exit pupil distance of the optical system is 13 to 21 millimeters. For example, the distance between the plane 110 of the lens 100 and the exit pupil 200 may be 13 to 21 millimeters.

[0054] In some examples, the exit pupil distance of the optical system is 15 millimeters or more. For example, the exit pupil distance of the optical system may be 16 to 21 millimeters. For example, the exit pupil distance of the optical system may be 17 to 19 millimeters. For example, the exit pupil distance of the optical system may be 18 to 20 millimeters. The optical system according to the present disclosure has a large exit pupil distance and can satisfy the use of myopic users wearing glasses.

[0055] In some examples, as shown in FIGS. 1 and 2, the maximum field of view angle of the optical system is 100° to 110°. For example, the maximum field of view angle of the optical system may be 100° to 103°. For example, the maximum field of view angle of the optical system may be 104° to 109°. For example, the maximum field of view angle of the optical system may be 105° to 108°. For example, the maximum field of view angle of the optical system may be 101° to 102°. For example, the maximum field of view angle of the optical system may be 100.5° to 101.5°.

[0056] In some examples, the refractive index of lens 10 is 1.5 to 1.6. For example, the refractive index of lens 10 may be 1.52 to 1.58. For example, the refractive index of lens 10 may be 1.53 to 1.57. For example, the refractive index of lens 10 may be 1.54 to 1.56. For example, the refractive index of lens 10 may be 1.55.

[0057] For example, the material of lens 10 includes an optical resin. For example, the material of the optical resin can include a cycloolefin copolymer (APL5014XH) with a refractive index of 1.555.

[0058] The optical system according to the present disclosure, while aligning the lens with the above-mentioned folded optical path, sets the lens as an integrated lens including an aspherical surface, sets the focal length of the optical system, and sets parameters such as the focal length, effective aperture, curvature radius of the aspherical surface, thickness of the lens, and refractive index of the integrated lens. By doing so, the optical system has a small size, and at the same time, the maximum field of view angle of the optical system reaches 100° to 110°, and the exit pupil distance reaches 13 to 21 millimeters, and even reaches 15 millimeters or more, which is advantageous for improving the user experience and can satisfy the use of myopic users wearing glasses, for example.

[0059] For example, the aspherical type is represented by the following numerical formula.

Number

[0060] For example, the height in the direction perpendicular to the optical axis of the aspherical surface in the above formula is Y, the distance from the vertex of the aspherical surface to the projection on the optical axis at the height Y on the aspherical surface is z. That is, z is the coordinate in the optical axis direction, C is the curvature (the reciprocal of the radius of curvature R), k is the conic constant, and α i is the coefficient of each higher-order term, and 2i is the order of the aspherical surface (the order of Aspherical Coefficient).

[0061] When actually optimizing the reasonable configuration of each parameter of the lens, substitute the values of the radius of curvature, conic constant, height, aspherical coefficient, etc. of the lens into the above numerical formula, and calculate by optical simulation to obtain each optimization parameter that can correct the aberration of the lens. Through the optimization process, the optimized values of the radius of curvature, thickness along the optical axis, effective aperture, and conic constant of the lens are obtained.

Table 1

[0062] For example, Table 1 above exemplifies the optical surface number (Surface) numbered sequentially from the human eye (aperture STOP) to the display screen, the radius of curvature (R) of each optical surface on the optical axis, and the distance (T) between each surface on the optical axis from the human eye (aperture) to the display screen and the next optical surface. Optical surface 2 represents the flat surface 110 of the lens 100, and optical surface 3 represents the aspherical surface 120 of the lens 100. For example, the aspherical surface 120 may be an even aspherical surface.

[0063] For example, the conic constant of the even aspherical surface may be -5 to -0.5. For example, the conic constant may be -3 to -0.8. For example, the conic constant may be -2 to -1.

[0064] For example, as shown in Table 1, the radius of curvature of the aspherical surface 120 is -95.657 millimeters, the image distance of the virtual image formed by the optical system is 2000 millimeters, the exit pupil distance is 17 millimeters, the thickness of the lens 100 is 7 millimeters, that is, the distance between the plane and the aspherical surface is 7 millimeters, the distance between the aspherical surface 120 and the display surface 300 of the display screen is 18.9 millimeters, the material of the lens 10 is a cycloolefin copolymer (APL5014XH), half of the exit pupil diameter is 2 microns, half of the effective aperture of the lens 100 is 26 microns, half of the size of the imaging surface is 23 millimeters, half of the virtual image size is 2514.344597837911 millimeters, and the conic coefficient of the aspherical surface 120 is -1.

[0065] By optimizing the exit pupil distance, the thickness of the lens, the distance between the lens and the display surface of the display screen, the refractive index of the lens, the radius of curvature of the aspherical surface, the conic coefficient, and the even aspherical coefficients, the optical system according to the present disclosure can obtain an optical system with good imaging effects at a large viewing angle and a long exit pupil distance.

[0066] FIG. 3 is a modulation transfer function (MTF) curve when the cut-off frequency of the optical system according to the embodiment of the present disclosure is 20 line pairs / mm. For example, FIG. 3 shows the modulation transfer function values at different spatial frequencies of the meridional lines 403, 406, 407, 409, and 411 (shown as solid lines in the figure) in different fields of view of the optical system and the modulation transfer function values at different spatial frequencies of the sagittal lines 402, 404, 405, 408, and 410 (shown as dashed lines in the figure) in different fields of view of the optical system. For example, MTF values are included. For example, curve 401 represents the diffraction limit. For example, meridional line 403 is the meridional line when the half field angle is 51°, meridional line 406 is the meridional line when the half field angle is 5°, meridional line 407 is the meridional line when the half field angle is 10°, meridional line 409 is the meridional line when the half field angle is 45°, and meridional line 411 is the meridional line when the half field angle is 20°. For example, sagittal line 402 is the sagittal line when the half field angle is 20°, sagittal line 404 is the sagittal line when the half field angle is 10°, sagittal line 405 is the sagittal line when the half field angle is 5°, sagittal line 408 is the sagittal line when the half field angle is 45°, and sagittal line 410 is the sagittal line when the half field angle is 51°.

[0067] For example, the above modulation transfer function value is also called the resolution. The resolution is the ability to resolve the details of the subject and is a physical quantity for describing the ability of the microscopic photography system to reproduce the fine parts of the subject.

[0068] The modulation transfer function (MTF) curve can comprehensively reflect the imaging quality of an optical system. The shape of the curve is smooth, and the higher the MTF value, the better the imaging quality of the optical system. Figure 3 shows the modulation transfer function curve when the cut-off frequency is 20 line pairs / mm (lp / mm), and the figure shows the modulation transfer function curves corresponding to multiple field rays. As shown in Figure 3, the overall modulation transfer function curve is smooth, and the modulation transfer function value in the edge field (for example, 102°) can reach 0.7 or more.

[0069] In some examples, as shown in Figure 3, the modulation transfer function value at the maximum field angle of the optical system is 0.7 or more at the spatial frequency position of 20 line pairs / mm. For example, the modulation transfer function value in the 102° field of the optical system is 0.7 or more at the spatial frequency position of 20 line pairs / mm. For example, the modulation function curve in the 102° field of the optical system is 0.72 or more at the spatial frequency position of 20 line pairs / mm.

[0070] For example, each of the above meridional line and sagittal line may be the meridional line and sagittal line of green light (for example, the central wavelength is 550 nm).

[0071] The optical system according to the present disclosure combines a lens with a folded optical path. At the same time, the lens is set as an integrated lens. Based on a plano-convex lens, the convex surface is changed from a spherical surface to an aspherical surface, the focal length of the optical system is set, and parameters such as the focal length, effective aperture, curvature radius of the aspherical surface, thickness of the lens, and refractive index of the lens of the integrated lens are set and optimized. As a result, the optical system has an ultra-short focal length, the maximum field of view angle of the optical system reaches 100° or more, the exit pupil distance reaches 17 millimeters or more, and the image distance of the formed virtual image can reach 2000 millimeters. At the same time, by optimizing the aspherical high-order term coefficient, the modulation transfer function value (MTF value) of the edge field of view of the optical system can reach 0.7 or more at a spatial frequency position of 20 line pairs / mm. The optical system has a good imaging effect and can satisfy the viewing use of myopic users wearing glasses.

[0072] For example, as shown in FIG. 3, the modulation transfer function value in the 40° field of view of the optical system is 0.8 or more at a spatial frequency position of 20 line pairs / mm.

[0073] For example, as shown in FIG. 3, the modulation transfer function value in the 20° field of view of the optical system is 0.5 or more at a spatial frequency position of 20 line pairs / mm.

[0074] FIG. 4 is a modulation transfer function curve when the cut-off frequency of the optical system according to the embodiment of the present disclosure is 15 line pairs / mm.

[0075] For example, as shown in FIG. 4, curve 401 represents the diffraction limit. For example, the meridional line 403 is the meridional line when the semi-field angle is 51°, the meridional line 406 is the meridional line when the semi-field angle is 5°, the meridional line 407 is the meridional line when the semi-field angle is 10°, the meridional line 409 is the meridional line when the semi-field angle is 45°, and the meridional line 411 is the meridional line when the semi-field angle is 20°. For example, the sagittal line 402 is the sagittal line when the semi-field angle is 20°, the sagittal line 404 is the sagittal line when the semi-field angle is 10°, the sagittal line 405 is the sagittal line when the semi-field angle is 5°, the sagittal line 408 is the sagittal line when the semi-field angle is 45°, and the sagittal line 410 is the sagittal line when the semi-field angle is 51°.

[0076] In some examples, as shown in FIG. 4, the modulation transfer function value at the maximum field angle of the optical system is 0.8 or more at a spatial frequency position of 15 line pairs / mm. For example, the modulation transfer function value in the 102° field of the optical system is 0.8 or more at a spatial frequency position of 15 line pairs / mm. For example, the modulation transfer function value in the 102° field of the optical system is 0.82 or more at a spatial frequency position of 15 line pairs / mm.

[0077] For example, as shown in FIG. 4, the modulation transfer function value in the 40° field of the optical system is 0.85 or more at a spatial frequency position of 15 line pairs / mm.

[0078] For example, as shown in FIG. 4, the modulation transfer function value in the 20° field of the optical system is 0.65 or more at a spatial frequency position of 15 line pairs / mm.

[0079] For example, as shown in FIG. 4, the modulation transfer function value in the 10° field of the optical system is 0.5 or more at a spatial frequency position of 15 line pairs / mm.

[0080] The optical system according to the present disclosure aligns the lens with the folded optical path. At the same time, the lens is set as an integrated lens. Based on a plano-convex lens, the convex surface is changed from a spherical surface to an aspherical surface, and parameters such as the focal length, effective aperture, radius of curvature of the aspherical surface, thickness of the lens, and refractive index of the lens of the integrated lens are set and optimized. As a result, the optical system has an ultra-short focal length, the maximum field of view angle of the optical system reaches 100° or more, the exit pupil distance reaches 17 millimeters or more, and the image distance of the virtual image formed can reach 2000 millimeters. At the same time, by optimizing the aspherical higher-order term coefficients, the modulation transfer function value (MTF value) of the edge field of view of the optical system can be 0.8 or more at a spatial frequency position of 15 line pairs / mm. The optical system has a good imaging effect and can satisfy the viewing use of myopic users wearing glasses.

[0081] For example, the aspherical surface 120 of the lens 100 can be manufactured into an aspherical surface by polishing or machining. The glass mold that forms the glass into an aspherical shape by a mold can be a type of composite aspherical surface that forms a resin on the surface of the glass into an aspherical shape.

[0082] FIG. 5 is a schematic structural diagram of a display device according to an embodiment of the present disclosure. As shown in FIG. 5, the display device includes a display screen 20 and the optical system 10 shown in the above embodiment. The display screen 20 is located on the side away from the plane 110 of the aspherical surface 120, and the display surface of the display screen 20 is located on the focal plane on the incident light side of the optical system 10.

[0083] In some examples, as shown in FIG. 5, the distance between the aspherical surface 120 and the display surface of the display screen 20 is 26 to 28 millimeters. For example, the distance between the aspherical surface 120 and the display surface of the display screen 20 is 27 millimeters. For example, the distance between the aspherical surface 120 and the display surface of the display screen 20 is 26.5 to 27.5 millimeters. For example, the distance between the aspherical surface 120 and the display surface of the display screen 20 is 26.2 to 27.8 millimeters. For example, the distance between the aspherical surface 120 and the display surface of the display screen 20 is 26.4 to 27.6 millimeters. For example, the distance between the aspherical surface 120 and the display surface of the display screen 20 is 26.8 to 27.2 millimeters.

[0084] The display device according to the present disclosure sets the lens as an integrated lens including an aspherical surface, and sets parameters such as the focal length, effective aperture, curvature radius of the aspherical surface, thickness of the lens, and refractive index of the lens of the integrated lens. At the same time, a polarization transmission reflection film and a phase retardation film are installed on one side of the lens, and a transmission reflection film is installed on the other side of the lens, so as to realize the folding of light rays, greatly reduce the focal length of the optical system, enable the optical system to have a small size, and at the same time, the maximum viewing angle of the optical system reaches 100° or more, and the exit pupil distance reaches 17 millimeters or more, and the image distance of the virtual image formed can reach 2000 millimeters. Thereby, the distance between the lens and the display surface of the display screen is shortened to 27 millimeters, which is advantageous for reducing the volume of the display device while improving the viewing experience of myopic users wearing glasses.

[0085] In some examples, the maximum size of the display surface of the display screen 20 is 2 to 3 inches. For example, the maximum size of the display surface of the display screen 20 is 2.5 inches. For example, the shape of the display surface of the display screen 20 may be rectangular, and the size of the diagonal of the rectangle may be 2.5 inches.

[0086] For example, the display screen 20 may be any type of display screen such as a liquid crystal display screen, an organic light emitting diode display screen, an inorganic light emitting diode display screen, a quantum dot display screen, a projector (e.g., an LCOS micro projector), etc.

[0087] For example, the display device may be a virtual reality display device. For example, the virtual reality display device may be a display device using an ultra-short focal length folded optical path.

[0088] 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., and the embodiments of the present disclosure are not limited thereto.

[0089] The following points need to be explained. (1) In the drawings of the embodiments of the present disclosure, only the structures according to the embodiments of the present disclosure are mentioned, and other structures can refer to normal designs. (2) When there is no conflict, the features in the same embodiment and different embodiments of the present disclosure can be combined with each other.

[0090] The above are only exemplary embodiments of the present disclosure and are 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 including a planar surface and an aspherical surface, wherein the aspherical surface is a convex surface, and the side of the planar surface away from the aspherical surface is the light-emitting side of the lens; a polarization-transmissive reflective film disposed on the side of the planar surface of the lens away from the aspherical surface; a phase retardation film disposed between the polarization-transmissive reflective film and the planar surface of the lens; a transmissive reflective film disposed on the side of the aspherical surface of the lens away from the planar surface, wherein the lens is an integral lens, the planar surface and the aspherical surface are located on opposite sides of the integral lens, the focal length of the optical system is 26 to 28 millimeters, the effective aperture of the lens is 50 to 52 millimeters, and the radius of curvature of the aspherical surface is -93 to -97 millimeters.

2. The optical system according to claim 1, wherein the focal length of the lens is 160 to 180 millimeters.

3. The optical system according to claim 1 or 2, wherein the maximum thickness of the lens is 6 to 8 millimeters.

4. The optical system according to any one of claims 1 to 3, wherein the exit pupil distance of the optical system is 13 to 21 millimeters.

5. The optical system according to claim 4, wherein the exit pupil distance of the optical system is 15 millimeters or more.

6. The optical system according to claim 4 or 5, wherein the maximum field angle of the optical system is 100° to 110°.

7. The optical system according to claim 6, wherein the modulation transfer function value at the maximum field angle of the optical system is 0.7 or more at a position where the spatial frequency is 20 line pairs / mm.

8. The optical system according to claim 6 or 7, wherein the modulation transfer function value at the maximum field angle of the optical system is 0.8 or more at a position where the spatial frequency is 15 line pairs / mm.

9. The optical system according to any one of claims 1 to 8, wherein the refractive index of the lens is 1.5 to 1.

6.

10. The optical system according to any one of claims 1 to 9, wherein the phase retardation film and the polarization-transmissive reflective film are in close contact with the planar surface.

11. A display device, comprising a display screen and the optical system according to any one of claims 1 to 10, wherein the display screen is located on the side of the aspherical surface of the lens away from the planar surface, and the display surface of the display screen is located on the focal plane on the light-incident side of the optical system.

12. The distance between the aspherical surface and the display surface of the display screen is 26 to 28 millimeters. The display device according to claim 11.

13. The maximum size of the display surface of the display screen is 2 to 3 inches. The display device according to claim 11 or 12.

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