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 priority from Chinese Patent Application No. 202210714718.1, filed on June 22, 2022, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to optical systems and display devices. [Background technology]

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

[0004] With the popularity of virtual reality products, users' requirements for using virtual reality products are becoming increasingly higher. Currently, more and more users choose to use virtual reality products to watch movies, so virtual reality display devices with a large viewing angle (FOV) display effect have become mainstream. Summary of the Invention

[0005] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to optical systems and display devices.

[0006] An embodiment of the present disclosure provides an optical system, including a lens, a polarized light transmission / reflection film, a phase retardation film, and a transmission / reflection film. The lens includes a flat surface and an aspherical surface, the aspherical surface is convex, the side of the flat surface away from the aspherical surface is the light exit side of the lens, the polarized light transmission / reflection film is disposed on the side of the flat surface away from the aspherical surface of the lens, the phase retardation film is disposed between the polarized light transmission / reflection film and the flat surface of the lens, and the transmission / reflection film is disposed on the side of the aspherical surface away from the flat surface of the lens. The lens is an integrated lens, the flat 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 mm, the effective aperture of the lens is 50 to 52 mm, and the radius of curvature of the aspherical surface is -93 to -97 mm.

[0007] For example, according to an embodiment of the present disclosure, the focal length of the lens is 160-180 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 optical system has an exit pupil distance of 13 to 21 millimeters.

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

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

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

[0013] For example, according to an embodiment of the present disclosure, the modulation transfer function value of the optical system at the maximum field of view is greater than or equal to 0.8 at a spatial frequency of 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 polarized light transmission / reflection film are in close contact with the plane.

[0016] An embodiment of the present disclosure provides a display device, including a display screen and any of the optical systems described above, wherein the display screen is located on a side of the aspherical surface of the lens away from the flat surface, and a display surface of the display screen is located on a focal plane on a light-entering 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, and at the same time, the lens is configured as an integrated lens including an aspherical surface. By setting 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, the optical system can achieve a wide viewing angle display and have a large exit pupil distance, thereby improving the user experience. [Brief explanation of the drawings]

[0020] In order to more clearly describe 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 on the present disclosure, but only relate to some embodiments of the present disclosure.

[0021] [Figure 1] 1 is a structural schematic diagram of a lens according to an embodiment of the present disclosure. [Figure 2] 2 is a schematic diagram of the optical path of an optical system including the lens shown in FIG. 1. [Figure 3]10 is a modulation transfer function curve of an optical system according to an embodiment of the present disclosure when the cutoff frequency is 20 line pairs / millimeter. [Figure 4] 10 is a modulation transfer function curve of an optical system according to an embodiment of the present disclosure when the cutoff frequency is 15 line pairs / millimeter. [Figure 5] 1 is a structural schematic diagram of a display device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings of the embodiments of the present disclosure. Of course, the described embodiments are only a part of the embodiments of the present disclosure, but not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments that a person skilled in the art can obtain without creative work fall within the scope of protection of the present disclosure.

[0023] Unless otherwise defined, technical or scientific terms used in this disclosure should have the ordinary meaning understood by those skilled in the art. The words "first," "second," and similar words used in this disclosure do not denote any order, quantity, or importance, but are merely used to distinguish different components. Similar terms such as "comprise" or "include" mean that the element or component listed before "comprise" or "include" covers the element or component listed after "comprise" or "include" and their equivalents, and does not exclude other elements or components.

[0024] Through research, the inventors of the present application found that to achieve a wide field of view (FOV) viewing effect, the eye relief (ERF) of current virtual reality folded optical path (Pancake) products is generally 13-15 mm, which makes it difficult for myopic users who wear glasses to use the product, further affecting the user experience.

[0025] An embodiment of the present disclosure provides an optical system and a display device. The optical system includes a lens, a polarized light transmission / reflection film, a phase retardation film, and a transmission / reflection film. The lens includes a flat surface and an aspherical surface, the aspherical surface being convex, and the side of the flat surface away from the aspherical surface is the light exit side of the lens. The polarized light transmission / reflection film is disposed on the side of the flat surface of the lens away from the aspherical surface, the phase retardation film is disposed between the polarized light transmission / reflection film and the flat surface of the lens, and the transmission / reflection film is disposed on the side of the aspherical surface of the lens away from the flat surface. The lens is an integrated lens, and the flat 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 mm, the effective aperture of the lens is 50 to 52 mm, and the radius of curvature of the aspherical surface is -93 to -97 mm. The optical system according to the embodiments of the present disclosure may be an optical system that uses a folded optical path (pancake), in which a polarized transmission-reflection film, a phase retardation film, and a transmission-reflection film are installed on both sides of the lens, and the lens is configured 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, so that the optical system can achieve an ultra-short focal length and a wide viewing angle display, and at the same time, has a large exit pupil distance, improving the user experience.

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

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

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

[0029] The optical system according to the embodiments of the present disclosure may be an optical system that uses a folded optical path (pancake), in which a polarized light 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. At the same time, the lens is configured as an integrated lens including an aspherical surface, and the focal length of the optical system is set. By setting and optimizing parameters such as the effective aperture of the integrated lens and the radius of curvature of the aspherical surface, the optical system can achieve an ultra-short focal length and a wide viewing angle display, and at the same time have a large exit pupil distance, thereby improving the user experience.

[0030] For example, the flat surface 110 and the aspherical surface 120 included in the integrated lens 100 are two surfaces of the lens 100, and 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, aspheric surface 120 curves away from planar surface 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 lens 100 is 160 to 180 mm. For example, the focal length of lens 100 may be 162 to 178 mm. For example, the focal length of lens 100 may be 165 to 175 mm. For example, the focal length of lens 100 may be 167 to 172 mm. For example, the focal length of lens 100 may be 169 to 170 mm. The focal lengths of the lenses mentioned above refer to the focal lengths when the lens surface is not coated.

[0034] 1, the polarizing transmission-reflection film 500 and the phase retardation film 600 are positioned on the near eye side of the lens 100, and the transmission-reflection film 700 is positioned on the near image source side of the lens 100. For example, the polarizing transmission-reflection film 500 and the phase retardation film 600 are disposed on the side of the flat surface 110 away from the aspheric surface 120, and the transmission-reflection film 700 is disposed on the side of the aspheric surface 120 away from the flat surface 110.

[0035] In some examples, the phase retardation film 600 and the polarizing transflective film 500 can be adhered as a composite film layer to the planar surface 110 of the lens 100. For example, the transflective film 700 can be painted or plated onto the aspheric surface 120.

[0036] For example, as shown in FIGS. 1 and 2, the polarized light transmitting and reflective film 500 may include a polarized light transmitting film and a reflective polarizer, and the polarized light transmitting film is located on the side of the reflective polarizer away from the phase retardation film 600 .

[0037] For example, the polarized light transmitting and reflecting film 500 and the phase retardation film 600 constitute a folded optical path deflecting device, also called a composite film, which is intimately attached to the plane 110 of the lens 100 .

[0038] For example, the function of a reflective polarizing film is to transmit light polarized in one direction (for example, s-linearly polarized light) while reflecting light polarized in the other direction (for example, p-linearly polarized light). For example, a reflective polarizing film (also called a polarization splitting film) has the following properties: There is a specific optical axis direction in the film material plane, and the transmittance (parallel transmittance) of the polarization component of incident light parallel to that direction is >80%. For example, the parallel transmittance is >85%. At the same time, the reflectance (parallel reflectance) of that component is <5%. For example, the parallel reflectance is <1%. The transmittance (orthogonal transmittance) of the polarization component perpendicular to the direction of incident light is <0.5%. For example, the orthogonal transmittance is <0.1%. At the same time, the reflectance (orthogonal reflectance) of that component is >80%. For example, the orthogonal reflectance is >85%. For example, the reflective polarizing film may be a plastic reflective film.

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

[0040] 1 and 2, the phase retardation film 600 is configured to convert the transmitted light between a circular polarization state and a linear polarization state, and may be, for example, a quarter wave plate.

[0041] 1 and 2, the transflective film 700 can be configured to reflect some light and transmit other light, for example, the transflective film 700 can reflect 50% of light and transmit 50% of light.

[0042] 1 and 2, the polarized light transmission / reflection film 500, the phase retardation film 600, and the transmission / reflection film 700 form a folded optical path. The principle of the folded optical path is as follows: A wave plate can be installed on the display surface 300 of the display screen, which is located away from the flat surface 110 of the aspheric surface 120. The image light emitted from the display surface 300 passes through the wave plate and is converted into right-handed circularly polarized light, and the polarization state of the right-handed circularly polarized light remains unchanged even after passing through the transmission / reflection film 700. The light enters the lens 100 and passes through the lens 100 to the phase retardation film 600. The right-handed circularly polarized light that enters the phase retardation film 600 is converted into p-linear polarized light, and the p-linear polarized light is reflected by the polarized light transmission / reflection film 500 to the phase retardation film 600, where it undergoes a first reflection. The p-linearly polarized light then passes through the phase retardation film 600 and is converted into right-handed circularly polarized light. The right-handed circularly polarized light then passes through the lens 100 to the transflective film 700 and is reflected by the transflective film 700, where it undergoes a second reflection. Due to a half-wave loss, the reflected light is converted from right-handed circularly polarized light to left-handed circularly polarized light. The left-handed circularly polarized light then passes through the lens 100 to the phase retardation film 600, where it is converted into s-linearly polarized light. The s-linearly polarized light then passes through the polarizing transflective film 500 and is emitted into the exit pupil 200, such as the human eye.

[0043] The folded optical path can change the polarization state of the light beam propagating between the polarized transmission-reflection film and the transmission-reflection film, thereby realizing the folding of the light beam. The focal length of the lens is originally increased by the installation of the polarized transmission-reflection film, phase retardation film and transmission-reflection film. For example, the light beam is folded by two reflections, which greatly reduces the space required between the human eye and the optical system, making the volume of the optical system smaller and thinner.

[0044] For example, the effective aperture of lens 100 refers to the largest diameter through which light can pass through lens 100, and the effective aperture is determined by the maximum luminous flux of lens 100. For example, the effective aperture of lens 100 may be 50.5 to 51.5 microns. For example, the effective aperture of lens 100 may be 51 to 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 be the same or different, and can be set according to the requirements of the product.

[0046] The size of the effective aperture of the lens is set to ensure that the size perpendicular to the optical axis is small, and the requirement of the field of view can be met.

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

[0048] 1 and 2, the aspherical surface 120 may be an even aspherical surface, and the radius of curvature of the aspherical surface 120 is the radius of curvature of the reference spherical surface of that surface. The "reference spherical surface" refers to an aspherical surface formed by further modifying a spherical surface as a reference, and the spherical surface that serves as the reference for the aspherical surface is the reference spherical surface for the aspherical surface.

[0049] For example, the side of the planar surface 110 of the lens 100 away from the aspheric surface 120 includes an 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 image plane 300 of the optical system is located on the side away from the flat surface 110 of the aspheric surface 120, and the image plane 300 corresponds to the position of the display surface of the display screen when the optical system is used in a display device. For example, the display surface 300 for displaying an image can be located on the side away from the flat surface 110 of the aspheric surface 120 of the lens 100. For example, the image distance of the virtual image formed by the optical system may be 1200 to 2000 mm.

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

[0052] The size of the lens in the optical system according to this embodiment in the optical axis direction is small, which reduces the size of the optical system and improves the compactness of the display device including the optical system.

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

[0054] In some examples, the optical system has an exit pupil distance of 15 millimeters or greater. For example, the optical system may have an exit pupil distance of 16 to 21 millimeters. For example, the optical system may have an exit pupil distance of 17 to 19 millimeters. For example, the optical system may have an exit pupil distance of 18 to 20 millimeters. The optical system according to the present disclosure has a large exit pupil distance and can be used satisfactorily by myopic users who wear eyeglasses.

[0055] In some examples, as shown in Figures 1 and 2, the maximum field of view of the optical system is between 100° and 110°. For example, the maximum field of view of the optical system may be between 100° and 103°. For example, the maximum field of view of the optical system may be between 104° and 109°. For example, the maximum field of view of the optical system may be between 105° and 108°. For example, the maximum field of view of the optical system may be between 101° and 102°. For example, the maximum field of view of the optical system may be between 100.5° and 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 the lens 10 includes an optical resin, and the material of the optical resin may include, for example, a cycloolefin copolymer (APL5014XH) having a refractive index of 1.555.

[0058] The optical system of the present disclosure aligns a lens with the folded optical path, and simultaneously configures the lens as an integrated lens including an aspherical surface, and sets the focal length of the optical system. Additionally, parameters such as the focal length of the integrated lens, the effective aperture, the radius of curvature of the aspherical surface, the lens thickness, and the lens refractive index are also configured. This allows the optical system to have a small size, a maximum field of view of 100° to 110°, and an exit pupil distance of 13 to 21 mm, or even 15 mm or more, which is beneficial to improving the user experience and can satisfy, for example, myopic users who wear glasses.

[0059] For example, the aspherical type is expressed by the following numerical formula:

number

[0060] For example, in the above formula, the height of the aspherical surface in the direction perpendicular to the optical axis is Y, and the distance from the vertex of the aspherical surface to the projection of the height Y on the aspherical surface on the optical axis is z. In other words, z is the coordinate in the optical axis direction, C is the curvature (the inverse 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 aspherical coefficient.

[0061] When actually optimizing the reasonable configuration of each parameter of the lens, values ​​such as the radius of curvature, conic coefficient, height, and aspheric coefficient of the lens are substituted into the above numerical formula, and calculated through optical simulation to obtain each optimized parameter that can correct the lens aberration. Through the optimization process, the optimized values ​​of the radius of curvature, thickness along the optical axis, clear aperture, and conic coefficient of the lens are obtained. [Table 1]

[0062] For example, Table 1 above exemplifies the optical surface numbers (Surfaces) sequentially numbered 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 lens 100, and optical surface 3 represents the aspherical surface 120 of lens 100. For example, aspherical surface 120 may be an even aspherical surface.

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

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

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

[0066] Figure 3 shows modulation transfer function (MTF) curves for an optical system according to an embodiment of the present disclosure when the cutoff frequency is 20 line pairs per millimeter. For example, Figure 3 shows modulation transfer function values ​​at different spatial frequencies for meridional line 403, meridional line 406, meridional line 407, meridional line 409, and meridional line 411 (shown as solid lines in the figure) in different fields of view of the optical system, and modulation transfer function values ​​at different spatial frequencies for sagittal line 402, sagittal line 404, sagittal line 405, sagittal line 408, and sagittal line 410 (shown as dashed lines in the figure) in different fields of view of the optical system, including MTF values. For example, curve 401 represents the diffraction limit. For example, meridional line 403 is the meridional line when the half field of view angle is 51°, meridional line 406 is the meridional line when the half field of view angle is 5°, meridional line 407 is the meridional line when the half field of view angle is 10°, meridional line 409 is the meridional line when the half field of view angle is 45°, and meridional line 411 is the meridional line when the half field of view angle is 20°. For example, sagittal line 402 is the sagittal line when the half field of view angle is 20°, sagittal line 404 is the sagittal line when the half field of view angle is 10°, sagittal line 405 is the sagittal line when the half field of view angle is 5°, sagittal line 408 is the sagittal line when the half field of view angle is 45°, and sagittal line 410 is the sagittal line when the half field of view angle is 51°.

[0067] For example, the modulation transfer function value is also called resolving power, which is the ability to resolve details of an object, and is a physical quantity that describes the ability of a microscopic system to reproduce minute details of an object.

[0068] The modulation transfer function (MTF) curve can comprehensively reflect the imaging quality of an optical system. The smoother the curve, and the higher the MTF value, the better the imaging quality of the optical system. Figure 3 shows the MTF curve when the cutoff frequency is 20 line pairs per millimeter (lp / mm), which shows the MTF curves corresponding to multiple field rays. As shown in Figure 3, the overall MTF curve is smooth, and the MTF value at the edge of the field (e.g., 102°) can reach 0.7 or more.

[0069] In some examples, the modulation transfer function value of the optical system at the maximum field of view is greater than or equal to 0.7 at a spatial frequency of 20 line pairs / millimeter, as shown in Figure 3. For example, the modulation transfer function value of the optical system at a 102° field of view is greater than or equal to 0.7 at a spatial frequency of 20 line pairs / millimeter. For example, the modulation transfer function curve of the optical system at a 102° field of view is greater than or equal to 0.72 at a spatial frequency of 20 line pairs / millimeter.

[0070] For example, the meridional and sagittal lines may be those of green light (for example, having a central wavelength of 550 nm).

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

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

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

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

[0075] For example, as shown in Figure 4, 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 of view angle is 20°, sagittal line 404 is the sagittal line when the half field of view angle is 10°, sagittal line 405 is the sagittal line when the half field of view angle is 5°, sagittal line 408 is the sagittal line when the half field of view angle is 45°, and sagittal line 410 is the sagittal line when the half field of view angle is 51°.

[0076] In some examples, the modulation transfer function value of the optical system at the maximum field of view is greater than or equal to 0.8 at a spatial frequency of 15 line pairs / millimeter, as shown in Figure 4. For example, the modulation transfer function value of the optical system at a 102° field of view is greater than or equal to 0.8 at a spatial frequency of 15 line pairs / millimeter. For example, the modulation transfer function value of the optical system at a 102° field of view is greater than or equal to 0.82 at a spatial frequency of 15 line pairs / millimeter.

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

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

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

[0080] The optical system of the present disclosure combines a lens with a folded optical path, and configures the lens as an integrated lens. Based on a plano-convex lens, the convex surface is changed from spherical to aspherical. Parameters such as the focal length, effective aperture, radius of curvature of the aspherical surface, lens thickness, and lens refractive index of the integrated lens are set and optimized, so that the optical system has an ultra-short focal length, and the maximum field of view of the optical system can reach 100° or more, the exit pupil distance can reach 17 mm or more, and the image distance of the formed virtual image can reach 2000 mm. At the same time, by optimizing the aspherical high-order term coefficients, the modulation transfer function value (MTF value) of the edge field of the optical system can be 0.8 or more at a spatial frequency of 15 line pairs / mm. This optical system has good imaging effect and can meet the viewing needs of myopic users who wear eyeglasses.

[0081] For example, aspherical surface 120 of lens 100 can be manufactured aspherically by polishing or machining, or the glass mold used to form glass into an aspherical shape using a mold may be aspherical, or a type of hybrid aspherical surface may be formed by forming resin onto the surface of glass into an aspherical shape.

[0082] 5 is a structural schematic 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 flat surface 110 of the aspherical surface 120, and the display surface of the display screen 20 is located on the focal plane of the light-entering 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] In the display device of the present disclosure, the lens is configured as an integrated lens including an aspherical surface, and parameters such as the focal length, effective aperture, radius of curvature of the aspherical surface, lens thickness, and lens refractive index of the integrated lens are configured. At the same time, a polarized transflective film and a phase retardation film are installed on one side of the lens, and a transflective film is installed on the other side of the lens, thereby realizing light folding and significantly reducing the focal length of the optical system. The optical system has a small size, and the maximum viewing angle of the optical system can reach 100° or more, with an exit pupil distance of 17 mm or more, and the image distance of the formed virtual image can reach 2000 mm. This reduces the distance between the lens and the display surface of the display screen to 27 mm, which is advantageous for reducing the volume of the display device while improving the viewing experience of myopic users who wear eyeglasses.

[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 diagonal size 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 (eg, an LCOS microprojector), etc.

[0087] For example, the display device may be a virtual reality display device, for example a virtual reality display device that uses an ultra-short throw 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 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 related to the embodiments of the present disclosure are referred to, and other structures may refer to conventional designs. (2) Features in the same and different embodiments of the present disclosure may be combined with each other if they do not conflict.

[0090] The above are only exemplary embodiments of the present disclosure, and are not intended to limit the protection scope of the present disclosure, which is determined by the appended claims.

Claims

1. 1. An optical system comprising: a lens including a flat surface and an aspherical surface, the aspherical surface being convex, and the side of the flat surface away from the aspherical surface being the light exit side of the lens; a polarized light transmitting and reflective film disposed on the plane of the lens on a side away from the aspherical surface; a phase retardation film disposed between the polarized light transmitting and reflective film and the plane of the lens; a transflective film disposed on a side of the aspherical surface of the lens away from the flat surface, the lens is an integrated lens, the flat 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.

2. 10. The optical system of claim 1, wherein the focal length of the lens is between 160 and 180 millimeters.

3. 10. The optical system of claim 1, wherein the maximum thickness of the lens is between 6 and 8 millimeters.

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

5. The optical system of claim 4 , wherein the optical system has an exit pupil distance of 15 millimeters or greater.

6. The optical system of claim 4, wherein the maximum viewing angle of the optical system is between 100° and 110°.

7. 7. The optical system of claim 6, wherein the modulation transfer function value of the optical system at the maximum field of view is 0.7 or greater at a spatial frequency of 20 line pairs / millimeter.

8. 7. The optical system of claim 6, wherein the modulation transfer function value of the optical system at the maximum field of view is 0.8 or greater at a spatial frequency of 15 line pairs / millimeter.

9. 4. The optical system according to claim 1, wherein the refractive index of the lens is between 1.5 and 1.

6.

10. 4. The optical system according to claim 1, wherein the phase retardation film and the polarized light transmission / reflection film are in close contact with the flat surface.

11. A display device comprising: a display screen; and the optical system according to any one of claims 1 to 3, wherein the display screen is located on a side away from the flat surface of the aspherical surface of the lens, and a display surface of the display screen is located on a focal plane on a light-entering side of the optical system.

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

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

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