Directive display sheet adapting to different pupil distances, manufacturing method thereof and display system

Abstract

The application discloses a directional display sheet suitable for different pupil distances, which is used for coupling out image light projected by a projection device to human eyes, and comprises a base and a structure layer with light guiding and converging functions. The structure layer comprises micro-nano structures in a pixel type distribution, and is directly etched on the base or arranged on the surface of the base. The image light propagates in the structure layer, changes directions through the micro-nano structures, and forms at least two view points at a single human eye. The application further discloses a display system comprising the directional display sheet suitable for different pupil distances. The application further discloses a manufacturing method of the directional display sheet suitable for different pupil distances, which is used for the directional display sheet suitable for different pupil distances. Through the above structure, the image light does not need to conduct by total reflection in the base, so that the thickness of the base is reduced, and the thickness of the directional display sheet suitable for different pupil distances is reduced, the display brightness is improved, and the paper sheet of the directional display sheet suitable for different pupil distances can be realized.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a directional display sheet adapted to different interpupillary distances, its manufacturing method, and a display system. Background Technology

[0002] Augmented Reality (AR) near-eye display industry is an important cutting-edge direction of next-generation information technology. It integrates technological innovations such as digital technology, new mobile communication technology, cloud technology, and display technology, giving rise to numerous new products, new business models, and new formats, bringing profound changes and impacts to the economy, science and technology, culture, and daily life. With the arrival of the 5G era, AR application scenarios will continue to expand, and AR technology will usher in large-scale marketization and commercialization. The AR industry is currently in a strategic window of explosive growth, with enormous development potential.

[0003] With the rapid development of the internet, people live in an information-overloaded society, making convenient and real-time access to information a crucial issue. Augmented Reality (AR) near-eye display technology undoubtedly offers a solution. AR technology seamlessly integrates real-world and virtual-world information, displaying not only real-world information but also virtual information simultaneously, with the two types of information complementing and overlaying each other. This eliminates the need for large flat-panel displays; instead, users only need a highly portable, stand-alone, or embedded miniature display system, resolving the contradiction between the decreasing size of current internet personal communication terminal hardware and the increasing volume of displayed information. Ultimately, this enables convenient and real-time information exchange between the real and virtual worlds.

[0004] In visual augmented reality, users utilize head-mounted displays to superimpose the real world with computer graphics, allowing them to see the real world surrounding them. Currently, most mainstream near-eye augmented reality display devices employ the waveguide principle. For example, HoloLens couples the image from the LCOS (Liquid Crystal Optical System) to waveguides via three holographic gratings, transmits the image through each waveguide, and finally outputs it through corresponding holographic gratings directly in front of the user's eye, projecting it onto the eye. It achieves color projection through a multi-layered waveguide design. Lumus uses an arrayed grating waveguide design, performing several semi-transparent and semi-reflective processes on the coupled light, allowing the transmitted light to enter the eye and achieve augmented reality display. In these examples, light transmission within the waveguide must meet the condition of total internal reflection, requiring a certain thickness and a high refractive index, meaning the material also has requirements, making it impossible to achieve sufficiently thinness. Furthermore, existing waveguides are limited by the pupil dilation principle; the light transmitted within the waveguide undergoes multiple grating diffractions during its journey from the coupling region to the coupling region, resulting in light energy loss. This means the overall efficiency is fragmented multiple times, leading to lower viewing brightness.

[0005] The preceding description is intended to provide general background information and does not necessarily constitute prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a directional display sheet with reduced thickness that adapts to different interpupillary distances, as well as its manufacturing method and display system.

[0007] This invention provides a directional display sheet adapted to different interpupillary distances, used to couple the image light projected by a projection device to the human eye to achieve augmented reality display. It includes a substrate and a structural layer with light guiding and converging functions. The structural layer includes micro-nano structures distributed in a pixel-like pattern. The structural layer is directly etched onto the substrate and integral with the substrate, or the structural layer is disposed on the surface of the substrate. The image light projected by the projection device propagates in the structural layer and, after being changed in direction by the pixel-like micro-nano structures, forms at least two viewpoints at a single human eye.

[0008] In one embodiment, the scale of the structural layer corresponds to the size of the light field projected by the projection device onto the directional display sheet adapted to different interpupillary distances, and the pixel distribution of the micro-nano structure corresponds one-to-one with the pixels of the light field.

[0009] In one embodiment, the size and orientation of the micro / nano structure depend on the projection angle, projection distance, viewpoint position, and number of viewpoints of the projection device.

[0010] In one embodiment, the micro / nano structure is a grating, a harmonic diffraction lens, or a Fresnel lens.

[0011] In one embodiment, when the micro / nano structure is a grating, the period and orientation angle of the grating can be determined according to the following grating equation:

[0012] tanφ1=sinφ / (cosφ-nsinθ(Λ / λ)),

[0013] sin 2 (θ1)=(λ / Λ) 2 +(nsinθ) 2 -2nsinθcosφ(λ / Λ);

[0014] Where θ1 and φ1 represent the diffraction angle and azimuth angle of the diffracted light, respectively; θ and λ represent the incident angle and wavelength of the light source, respectively; Λ and φ represent the period and orientation angle of the nano-diffraction grating, respectively; and n represents the refractive index of the light wave in the medium.

[0015] In one embodiment, the substrate has a transmittance of more than 80% in the visible light band, and the thickness of the substrate is no more than 1 mm.

[0016] In one embodiment, the substrate is made of resin or glass.

[0017] The present invention also provides a display system, including a directional display sheet adapted to different interpupillary distances and a micro-projection device. The micro-projection device includes an image source and a lens group. Image light emitted from the image source is projected onto the directional display sheet adapted to different interpupillary distances through the lens group. The directional display sheet adapted to different interpupillary distances is the aforementioned directional display sheet adapted to different interpupillary distances.

[0018] In one embodiment, the image source is a transmissive liquid crystal display (LCD), a digital light processor (DLP), a digital micromirror device (DMD), a liquid crystal on silicon (LCOS), a microelectromechanical scanning mirror (MEMS), or an organic light-emitting diode (OLED).

[0019] In one embodiment, a mounting bracket is also included, which secures the directional display sheet adapted to different interpupillary distances and the microprojection device, respectively.

[0020] The present invention also provides a method for manufacturing a directional display sheet adaptable to different interpupillary distances, the method comprising the following steps:

[0021] S1: Provides the substrate;

[0022] S2: Fabricate a structural layer with micro-nano structures on the substrate, wherein the micro-nano structures are distributed in a pixel-like manner, and the structural layer is directly etched onto the substrate or disposed on the surface of the substrate;

[0023] In one embodiment, step S2 further includes the following specific steps:

[0024] S21: A layer of photoresist is coated on one side of the substrate;

[0025] S22: Using interference lithography, holographic exposure, or overlay processes, micro-nano structures with pixel-like distributions are fabricated on the photoresist, and multiple such pixel-like micro-nano structures form a structural layer.

[0026] In one embodiment, step S2 further includes the following specific steps:

[0027] S21: A layer of photoresist is coated on one side of the substrate to form a photoresist layer;

[0028] S22: Select a region on the surface of the photoresist layer and pattern the region to obtain patterned photoresist and patterned grooves exposing the substrate surface;

[0029] S23: Etch the exposed substrate surface;

[0030] S24: Remove the patterned photoresist to obtain a structural layer integral with the substrate, the structural layer having a pixel-distributed micro / nano structure.

[0031] The present invention provides a directional display sheet adapted to different interpupillary distances. The structural layer is directly etched onto the substrate and integrated with the substrate, or the structural layer is disposed on the surface of the substrate. The image light projected by the projection device propagates in the structural layer. A pixel-distributed micro-nano structure is used to achieve viewpoint convergence, forming at least two viewpoints at a single human eye. This ensures that each eye receives at least one viewpoint image when the human eyeball rotates or the interpupillary distance changes due to different wearers. At the same time, the image light does not need to undergo total internal reflection within the substrate, greatly reducing light energy loss, improving display brightness, and reducing the necessary thickness of the substrate. This, in turn, reduces the thickness of the directional display sheet adapted to different interpupillary distances, enabling the paper-like fabrication of the directional display sheet adapted to different interpupillary distances. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a directional display panel adapted to different interpupillary distances according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of light transmission through a directional display sheet adapted to different interpupillary distances, representing an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram illustrating the multi-viewpoint implementation of the pixel distribution in the functional film layer of the present invention.

[0035] Figure 4 This is a schematic diagram of the structure of the display system according to an embodiment of the present invention;

[0036] Figure 5 This is a diagram showing the location of the micro-projection device in the display system according to an embodiment of the present invention;

[0037] Figure 6 This is another location diagram of the micro-projection device in the display system according to an embodiment of the present invention;

[0038] Figure 7 This is a flowchart illustrating the steps of a method for manufacturing a directional display sheet adapted to different interpupillary distances according to an embodiment of the present invention.

[0039] Figure 8 for Figure 7 A flowchart of the specific steps of step S2 in one embodiment;

[0040] Figure 9 for Figure 7 A flowchart illustrating the specific steps of step S2 in another embodiment. Detailed Implementation

[0041] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0042] Please refer to Figure 1 This invention provides a directional display sheet adapted to different interpupillary distances, used to couple the image light projected by a micro-projection device to the human eye for augmented reality display. It includes a substrate 11 and a structural layer 12 that guides and converges light; the structural layer 12 includes pixel-distributed micro / nano structures 121. The structural layer 12 is either directly etched onto the substrate 11 and integral with it, or disposed on the surface of the substrate 11. The image light projected by the projection device propagates in the structural layer 12, and after being redirected by the pixel-distributed micro / nano structures 121, forms at least two viewpoints at a single human eye.

[0043] Since the image light propagates within the structural layer 12, there is no need for total internal reflection within the substrate 11. Therefore, the substrate 11 does not need to be a high-refractive-index material, thus reducing costs and technological barriers. Simultaneously, the substrate 11 serves to support the structural layer 12 and transmit ambient light. Therefore, the substrate 11 only needs to support the structural layer 12 and transmit a certain amount of ambient light, allowing for a reduction in the thickness of the substrate 11, achieving an ultra-thin substrate. This, in turn, reduces the thickness of the directional display sheet adapting to different interpupillary distances, enabling a paper-like design for such directional displays. Furthermore, since multiple total internal reflections and diffraction emissions are not required within the substrate 11, light energy loss is significantly reduced. The ultra-thin substrate 11 also increases the brightness of the directional display sheet adapting to different interpupillary distances. Specifically, the substrate 11 is a transparent substrate with a transmittance of more than 80% in the visible light band and a thickness of no more than 1 mm. The substrate 11 can be made of a flexible substrate or a rigid substrate. However, in order to avoid deformation in actual use, which would cause the pixel distribution of the light field projected by the micro-projection device onto the directional display 1 adapted to different interpupillary distances to not correspond to the pixel distribution of the structural layer 12, the substrate 11 is preferably made of a rigid substrate, such as resin or glass.

[0044] In this embodiment, the structural layer 12 is directly etched onto the substrate 11. That is, etching technology is used to etch the surface of one side of the substrate 11 to form multiple micro / nano structures 121 on the substrate 11. The multiple micro / nano structures 121 are distributed in a pixel-like manner to form the structural layer 12. The size of this structural layer 12 corresponds to the size of the light field projected by the micro-projection device onto the directional display 1 adapted to different interpupillary distances. The micro / nano structures 121 have diffraction, refraction, or a combination of refraction and diffraction effects on light.

[0045] In other embodiments, a structural layer 12 with pixel-type distributed micro / nano structures 121 can be prepared first, and then the structural layer 12 can be attached to the substrate 11; alternatively, a structural layer 12 with pixel-type distributed micro / nano structures 121 can be directly prepared on the photoresist by coating the surface of the substrate 11 with photoresist.

[0046] The pixel size of the micro / nano structure 121 corresponds to the pixel size of the light field projected by the micro-projection device onto the directional display panel 1, which adapts to different interpupillary distances. In other words, the pixel distribution of the micro / nano structure 121 must correspond one-to-one with the pixels of the light field. Specifically, the size and orientation of the micro / nano structure 121 depend on the projection angle, projection distance, viewpoint position, and number of viewpoints of the projection device. In this embodiment, the pixel-distributed micro / nano structure 121 is directional, forming at least two viewpoints at a single human eye, thus achieving multi-viewpoint convergence at the target human eye. Based on the required number of viewpoints, the scale and orientation of its internal pixel structure are adjusted, allowing the human eye to achieve augmented reality optical information display at the viewpoint.

[0047] The micro-nano structures on directional display panels adapted to different interpupillary distances are distributed in a pixel-like pattern, such as... Figure 3As shown, the directional display panel adapted to different interpupillary distances contains four volume pixels, and each volume pixel contains four sub-pixels. The sub-pixels in the same volume pixel correspond to different viewpoints. Taking the number of target viewpoints as an example, each volume pixel has four sub-pixels. Sub-pixels 1a, 2a, 3a, and 4a together form volume pixel 1; sub-pixels 1b, 2b, 3b, and 4b together form volume pixel 2; sub-pixels 1c, 2c, 3c, and 4c together form volume pixel 3; and sub-pixels 1d, 2d, 3d, and 4d together form volume pixel 4. Each subpixel contains gratings with different periods and orientations, which can focus the outgoing light to the corresponding target viewpoint. Light rays passing through subpixels 1a, 1b, 1c, and 1d are directed towards viewpoint 1; those passing through subpixels 2a, 2b, 2c, and 2d are directed towards viewpoint 2; those passing through subpixels 3a, 3b, 3c, and 3d are directed towards viewpoint 3; and those passing through subpixels 4a, 4b, 4c, and 4d are directed towards viewpoint 4. Light passing through the substrate is redirected after passing through the gratings. Information with the number '1' is focused at viewpoint 1, while information with other numbers is focused at the corresponding viewpoint position. The micro-nano structures on the directional display sheet adapted to different interpupillary distances are distributed in a pixel-like manner. Therefore, the directional display sheet adapted to different interpupillary distances corresponding to a single human eye contains multiple volume pixels, and each volume pixel contains at least two sub-pixels, so that at least two viewpoints are formed at a single human eye. When the human eyeball moves or the interpupillary distance changes due to different people wearing it, each eye can receive at least one viewpoint image.

[0048] At least two viewpoints are formed at each individual eye to ensure that each eye receives at least one viewpoint image when the eyeball rotates or when the interpupillary distance changes due to different wearers. The directional display panel surface, adapted to different interpupillary distances, employs a pixel-distributed directional micro / nano structure to achieve viewpoint convergence. Compared to existing near-eye display technologies based on pupil expansion principles, this avoids the drawbacks of total internal reflection propagation and energy loss caused by multiple diffraction exits in optical waveguide technology. Increasing the number of viewpoints to expand the exit pupil further enhances energy convergence and improves efficiency. Simultaneously, because energy is concentrated at the viewpoint, observation brightness and efficiency are significantly improved, thereby reducing energy consumption and facilitating size reduction.

[0049] The micro / nano structure 121 is a grating, a harmonic diffraction lens, or a Fresnel lens.

[0050] In this embodiment, the micro / nano structure 121 is a grating. The grating period and orientation angle of the micro / nano structure 121 can be determined according to the following grating equation:

[0051] tanφ1=sinφ / (cosφ-nsinθ(Λ / λ)),

[0052] sin 2 (θ1)=(λ / Λ) 2 +(nsinθ) 2 -2nsinθcosφ(λ / Λ).

[0053] like Figure 2 As shown, A represents the incident ray from the light source, and A1 represents the diffracted ray after diffraction by a directional display panel adapted to different interpupillary distances. θ1 represents the diffraction angle of the diffracted light, i.e., the angle between the diffracted ray and the positive Z-axis; φ1 represents the azimuth angle of the diffracted light, i.e., the angle between the diffracted ray and the positive X-axis; θ represents the incident angle of the light source, i.e., the angle between the incident ray and the positive Z-axis; λ represents the wavelength of the light source; Λ represents the period of the nano-diffraction grating; φ represents the orientation angle of the nano-diffraction grating, i.e., the angle between the grating and the positive Y-axis; and n represents the refractive index of the light wave in the medium. Based on the above grating equations, it can be seen that once the incident ray wavelength, incident angle, diffraction angle, and diffraction azimuth angle are determined, the required grating period and orientation angle can be calculated.

[0054] Please refer to Figure 6 The present invention also provides a display system, including a directional display panel 1 adapted to different interpupillary distances and a micro-projection device 2. The micro-projection device 2 includes an image source 4 and a lens group, wherein image light emitted from the image source 4 is projected onto the directional display panel 1 adapted to different interpupillary distances via the lens group. The directional display panel 1 adapted to different interpupillary distances is the aforementioned directional display panel adapted to different interpupillary distances.

[0055] Image source 4 is a transmissive liquid crystal display (LCD), a digital light processor (DLP), a digital micromirror device (DMD), a liquid crystal on silicon (LCOS), a microelectromechanical scanning mirror (MEMS), or an organic light-emitting diode (OLED).

[0056] The micro-projection device 2 can be positioned in multiple ways relative to the directional display panel 1, which adapts to different interpupillary distances. Specifically, the micro-projection device 2 can project above, below, to the left, or to the right of the directional display panel 1, or it can project from inside or outside the human eye. Figure 5 The micro-projection device 2 is located outside the human eye, and the directional display 1, which is adapted to different interpupillary distances, is located above the directional display 1, which is adapted to different interpupillary distances. Figure 6 The micro-projection device 2 is located outside the human eye, and the directional display 1, which is adapted to different interpupillary distances, is located to the right of the directional display 1, which is adapted to different interpupillary distances.

[0057] The display system also includes a mounting bracket 3, which fixes a directional display panel 1 and a micro-projection device 2 adapted to different interpupillary distances.

[0058] Furthermore, the fixing frame 3 is an eyeglass frame. The fixing frame 3 fixes two directional display panels 1 that are adapted to different interpupillary distances. The left and right micro-projection devices 2 refresh the different parallax maps corresponding to the left and right eyes. That is, the left and right eyes simultaneously receive their respective parallax maps, which are then synthesized by the brain to form a three-dimensional image, thereby achieving a 3D near-eye display effect.

[0059] Please refer to Figure 1 and Figure 7 The present invention also provides a method for manufacturing a directional display sheet adaptable to different interpupillary distances, used to manufacture the aforementioned directional display sheet adaptable to different interpupillary distances. The specific steps of the method are as follows:

[0060] S1: Provides substrate 11;

[0061] S2: A structural layer 12 with micro-nano structures 121 is fabricated on the substrate 11. The micro-nano structures 121 are distributed in a pixel-like manner. The structural layer 12 is directly etched onto the substrate 11 or disposed on the surface of the substrate 11.

[0062] In step S1, the substrate 11 is a transparent substrate with a transmittance of more than 80% in the visible light band and a thickness of no more than 1 mm. The substrate 11 can be made of a flexible substrate or a rigid substrate. However, in order to avoid deformation in actual use, which would cause the pixel distribution of the light field projected by the micro-projection device onto the directional display 1 adapted to different interpupillary distances to not correspond to the pixel distribution of the structural layer 12, the substrate 11 is preferably made of a rigid substrate. For example, the material of the substrate 11 can be resin or glass.

[0063] In this embodiment, in step S2, as Figure 9 As shown, the following specific steps are also included.

[0064] S21: A layer of photoresist is coated on one side of the substrate 11 to form a photoresist layer.

[0065] S22: Select a region on the surface of the substrate and pattern the region to obtain patterned photoresist and patterned grooves exposing the substrate surface. Since the surface of the substrate is covered by a photoresist layer, the selected region is the area on the surface of the photoresist layer.

[0066] Specifically, the photoresist layer is exposed and developed according to the desired pattern to obtain patterned photoresist with the desired pattern morphology in the selected area, as well as patterned grooves on the exposed substrate 11 surface (i.e., the bottom of the patterned grooves is the exposed substrate surface). To ensure that the exposed part and the parts outside the area are cleaner, oxygen bombardment can also be performed directly after exposure and development using equipment such as a plasma stripper.

[0067] S23: Etch the exposed substrate surface. This results in a structural layer 12 integral with the substrate 11, the structural layer 12 having a pixel-like micro / nano structure.

[0068] Specifically, etching is performed according to the depth of the micro-nano structure to be distributed in a pixel-like manner. During etching, the difference in etching rate between the capping layer and the substrate 11, as well as the thickness of the capping layer, can be used to determine whether the patterned photoresist needs to be etched.

[0069] S24: Remove remaining patterned photoresist.

[0070] Specifically, the image photoresist can be removed using a removal solution.

[0071] The directional display panels made using the above method, which are adapted to different interpupillary distances, have characteristics such as anti-aging and durability.

[0072] In one embodiment, in step S2, as Figure 8 As shown, the following specific steps are also included:

[0073] S21: A layer of photoresist is coated on one side of the substrate 11;

[0074] S22: Using interference lithography, holographic exposure, or overlay processes, micro-nano structures with pixel-like distributions are fabricated on photoresist, and multiple such pixel-like micro-nano structures 121 form a structural layer 12.

[0075] Furthermore, to mass-produce display panels, pattern transfer and replication can be achieved through imprinting, enabling the mass production of high-fidelity display panels. Specifically, a directional display panel adapted to different interpupillary distances can be used as a master template. Imprinting adhesive is applied to a blank substrate, and the pattern is transferred by imprinting using an imprinting device.

[0076] In the accompanying drawings, the dimensions and relative dimensions of layers and regions are exaggerated for clarity. It should be understood that when an element, such as a layer, region, or substrate, is referred to as "formed on," "disposed on," or "located on" another element, the element may be directly disposed on said other element, or there may be intermediate elements present. Conversely, when an element is referred to as "directly formed on" or "directly disposed on" another element, there are no intermediate elements.

[0077] In this document, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art will understand the specific meaning of these terms based on the specific circumstances.

[0078] In this document, the terms "upper," "lower," "front," "back," "left," "right," "top," "bottom," "inner," "outer," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used for the clarity of expressing the technical solution and for the convenience of description, and therefore should not be construed as limiting the present invention.

[0079] In this document, unless otherwise stated, “multiple” or “several” means two or more.

[0080] In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0081] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A display system, characterized by, The fixed frame and two directional display pieces for different pupil distances and two micro projection devices are mounted on the fixed frame, the micro projection device includes an image source and a lens group, the image light emitted by the image source is projected to the directional display piece for different pupil distances through the lens group, the directional display piece for different pupil distances is used to couple out the image light projected by the projection device to the human eye, the two micro projection devices refresh different parallax maps corresponding to the left and right eyes, and the different parallax maps pass through the two directional display pieces for different pupil distances respectively; the directional display piece for different pupil distances includes a substrate and a structure layer with light guiding and converging functions, the structure layer includes micro-nano structures in a pixel type distribution, the structure layer is directly etched on the substrate and integrated with the substrate or is arranged on the surface of the substrate, the image light projected by the projection device propagates in the structure layer, changes the direction through the pixel type micro-nano structures, and forms at least two view points at a single human eye; the directional display piece for different pupil distances includes a plurality of volume pixels, each volume pixel includes at least two sub-pixels, so that at least two view points are formed at a single human eye, when the eyeball rotates or the pupil distance changes due to different people wearing, each eye can receive at least one view point image, the left eye and the right eye receive the parallax maps corresponding to each other at the same time, and a three-dimensional image is formed through the brain synthesis.

2. The display system of claim 1, wherein, The image source is a transmissive liquid crystal display (LCD), a digital light processor (DLP), a digital micro-mirror device (DMD), a liquid crystal on silicon (LCOS), a micro-electro-mechanical scanning mirror (MEMS) or an organic light-emitting diode (OLED).

3. The display system of claim 1, wherein, The fixed frame is further included, and the fixed frame respectively fixes the directional display piece for different pupil distances and the micro projection device.

4. The display system of claim 1, wherein, The size of the structure layer corresponds to the size of the light field surface of the projection device projected on the directional display piece for different pupil distances, and the pixel distribution of the micro-nano structure corresponds to the pixels of the light field surface one by one.

5. The display system of claim 1, wherein, The size and orientation of the micro-nano structure are determined according to the projection angle, projection distance, view point position and view point quantity of the projection device.

6. The display system of claim 1, wherein, When the micro-nano structure is a grating, the period and orientation angle of the grating can be determined according to the following grating equation: tanφ1=sinφ / (cosφ-nsinθ(Λ / λ)), sin 2 (θ1) = (λ / Λ) 2 + (nsinθ) 2 - 2nsinθcosφ(λ / Λ); wherein θ1 and φ1 represent the diffraction angle and azimuth angle of the diffracted light respectively, θ and λ represent the incident angle and wavelength of the light source respectively, Λ and φ represent the period and orientation angle of the nano-diffraction grating respectively, and n represents the refractive index of the light wave in the medium.

7. The display system of claim 1, wherein, The transmittance of the substrate in the visible light wave band is greater than 80%, and the thickness of the substrate is not greater than 1 mm.

8. The display system of claim 1 or 7, wherein, The material of the substrate is resin or glass.

9. The display system of claim 1, wherein, The micro-nano structure is a harmonic diffraction lens or a Fresnel lens.

10. A method of making a directional display sheet that accommodates different interpupillary distances, the method comprising: The method is used for manufacturing the directional display piece for different pupil distances in any one of claims 1 to 9, and the method includes the following steps: S1: providing a substrate; S2: a structure layer with micro-nano structures is made on the substrate, the micro-nano structures are distributed in a pixel type, the structure layer is etched directly on the substrate or arranged on the surface of the substrate; the micro-nano structures are harmonic diffraction lenses or Fresnel lenses, the micro-nano structures have diffraction, refraction or diffractive-refractive mixed effects on light, the light does not conduct by total reflection inside the substrate, and the thickness of the substrate is not greater than 1 mm.

11. The method of claim 10, wherein the step of forming the directional display sheet having a variable eye relief comprises the step of: In step S2, the following specific steps are further included: ​ S21: a photoresist layer is coated on one side of the surface of the substrate; S22: micro-nano structures in a pixel type are made on the photoresist layer by using an interference lithography or a holographic exposure or a lithography process, and a plurality of the micro-nano structures in a pixel type form a structure layer.

12. The method of claim 10, wherein the step of forming the directional display sheet having a variable eye relief comprises the step of: In step S2, the following specific steps are further included: ​ S21: a photoresist layer is coated on one side of the surface of the substrate to form a photoresist layer; S22: an area is selected on the surface of the photoresist layer, and the area is subjected to a patterning treatment to obtain a patterned photoresist and a patterned groove of the exposed substrate surface; S23: the exposed substrate surface is etched; S24: the patterned photoresist is removed to obtain a structure layer integrated with the substrate, and the structure layer has micro-nano structures in a pixel type.

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