System and method for realizing large-view-angle super-multi-view three-dimensional display

Abstract

The invention provides a system and a method for realizing large-view-angle super-multi-view three-dimensional display, and the system comprises a backlight module which is used for generating multi-directional collimation backlight; and the display panel is used for loading the coded viewpoint image sequence and the metasurface array with multi-angle polarization response and / or multi-angle incidence response, receiving intensity information of each viewpoint image, and performing phase and / or amplitude modulation on the linear polarization components with different polarization angles and / or the light rays with different incidence angles, so as to obtain the image intensity information of each viewpoint image. And finally, the light rays are diffracted, propagated and converged to different viewpoints through the metasurface array. Wherein the size of the metasurface nanostructure is matched according to a phase-amplitude-nanostructure size lookup table (LUT) method. Compared with cylindrical lens type super multi-view three-dimensional display, the system can control the phase and the direction of light with high precision; compared with a metasurface array responded by a single polarization angle or a single incidence angle, the metasurface array has the advantages that the flexibility and the degree of freedom of design are improved, and three-dimensional display with higher resolution and larger visual angle can be realized.

Description

Technical Field

[0001] The present invention relates to a system and method for realizing large-viewing-angle and ultra-multi-viewpoint three-dimensional display, belonging to the field of display technology. Background Art

[0002] Super Multi-view Display (SMD) is a technology that uses dense viewpoint arrangement to allow two or more viewpoint images to enter the human eye pupil at the same time for imaging.

[0003] Ultra-multi-viewpoint 3D display technology has become one of the research hotspots in the display field. Ultra-multi-viewpoint 3D display technology includes parallax barrier method, cylindrical lens method and diffraction element method, etc. By controlling the light or light field of the light source, dense arrangement of images from different viewpoints is achieved, achieving a realistic 3D effect that approximates the restoration of a continuous light field.

[0004] For example, patent CN1893672B discloses a three-dimensional display device based on a parallax barrier, and the three-dimensional display device includes an image display unit. The image display unit includes a pixel having a first sub-pixel corresponding to a left-eye image and a second sub-pixel corresponding to a right-eye image. The three-dimensional display device also includes a parallax barrier located near the image display unit. The parallax barrier includes a light blocking portion and a light transmitting portion arranged alternately and repeatedly in one direction. The parallax barrier also includes a color filter arranged between the light blocking portion and the light transmitting portion. The color filter controls the path of light from the pixel. The present invention can improve the quality of the three-dimensional image and improve the user's freedom of movement by reducing or minimizing dispersion.

[0005] For example, patent CN110262050A proposes a LED stereoscopic display device with super multi-viewpoints based on cylindrical gratings, wherein the LED stereoscopic display includes an LED flat screen and a human eye viewing viewpoint, and an arc cylindrical grating is arranged between the LED flat screen and the human eye viewing viewpoint. Each LED screen image in the LED flat screen is composed of RGB sub-pixels, which are magnified and projected into the human eye under the action of the cylindrical grating; one side of the arc cylindrical grating is highly precisely coupled with the LED flat screen, and the other side is a periodically undulating arc cylindrical surface. Among them, the LED display is placed on the focal plane of the cylindrical grating, and each sub-pixel of the viewpoint on the focal plane is magnified and projected to the left and right eyes of the viewer under the action of the cylindrical grating, forming a stereoscopic visual effect. However, the cylindrical grating in this system is a geometric optical element with limited light modulation capability, and the obtained image has problems such as limited viewing distance and large crosstalk. In addition, the use of cylindrical gratings in this system greatly limits the reduction and integration of optical devices.

[0006] For example, patent CN112255820A provides a naked-eye three-dimensional display device, including: a display component, which includes a display unit array formed by a plurality of display unit arrays; a viewing angle control device, which includes a harmonic diffraction lens array formed by a plurality of harmonic diffraction lens subunit arrays, wherein each harmonic diffraction lens subunit corresponds to a display unit, and the harmonic diffraction lens subunits of the harmonic diffraction lens array are divided into multiple groups, and the light emitted by the same group of harmonic diffraction lens subunits will converge into the same viewpoint, and the light emitted by different groups of harmonic diffraction lens subunits will converge into different viewpoints. However, the harmonic diffraction lens is a special diffraction lens, which has low diffraction efficiency, poor tunability, and is usually limited to a narrow bandwidth range. In addition, the manufacturing process of the harmonic diffraction lens array is complicated and time-consuming.

[0007] For example, patent CN116600097A provides a system and method for realizing ultra-multi-viewpoint three-dimensional display, which includes a display panel for loading a coded viewpoint image sequence, and a single-layer coded or double-layer coded or multi-layer coded metasurface array for receiving the image intensity information of each viewpoint, and performing phase and / or amplitude modulation on the light, and finally the metasurface array transmits light and converges it to different viewpoints. Among them, the size of the metasurface nanostructure is matched according to the pre-designed phase-amplitude-nanostructure size lookup table method (LUT). The system uses a metasurface array instead of a lens array and a cylindrical lens array, which can control the phase and direction of light with high precision, improve the flexibility and freedom of design, and realize a three-dimensional display with higher resolution, wide viewing angle, and low crosstalk; at the same time, the thin and light characteristics of the metasurface further compress the system volume; in addition, compared with the diffraction grating type three-dimensional display, the metasurface remains stable in a wide bandwidth and there is no dispersion effect.

[0008] In view of the above, the present invention aims to provide a system and method for realizing large-viewing-angle and ultra-multi-viewpoint three-dimensional display to solve one or more of the above-mentioned technical problems. Summary of the invention

[0009] In order to solve one or more technical problems in the prior art, according to one aspect of the present invention, a system and method for realizing large-viewing angle ultra-multi-viewpoint 3D display is provided. The ultra-multi-viewpoint 3D display system comprises:

[0010] A backlight module is used to generate time-division and / or space-division multi-directional backlight; a display panel is used to load a coded viewpoint image sequence, and a metasurface array with multi-angle polarization response and / or multi-angle incidence response is used to receive the image intensity information of each viewpoint and perform phase and / or amplitude modulation on the linear polarization components of different polarization angles and / or light at different incident angles. Finally, the light is diffracted and propagated through the metasurface array to converge to different viewpoints.

[0011] According to another aspect of the present invention, the multi-directional backlight module emits light to reach the display panel, and a viewpoint image display unit of the display panel corresponds one-to-one to an array subunit of the metasurface array; the same group of viewpoint image display units converge to the same viewpoint after being phase modulated by the corresponding metasurface array subunits, and different groups of viewpoint image display units converge to different viewpoints after being phase modulated by the corresponding metasurface array subunits, and linear polarized light components with different polarization angles or light with different incident angles converge to different angles through diffraction propagation of the metasurface array, ultimately forming a three-dimensional reconstructed image with a large viewing angle.

[0012] According to another aspect of the present invention, the display panel includes LCD, LED, DMD or LPD; preferably, the viewpoint image display unit includes but is not limited to an element image unit based on an integrated imaging display mode, a viewpoint image sub-pixel unit based on a cylindrical lens array display mode or a sub-pixel unit based on a diffraction grating display mode; optionally, the metasurface array has multi-angle polarization response characteristics or multi-angle incidence response characteristics; optionally, an array sub-unit of the metasurface array is a periodic structure or a non-periodic structure; optionally, a single nanostructure of the metasurface array is a multi-layer transmission type or a single-layer transmission type; optionally, a single nanostructure of the metasurface array includes but is not limited to nano-column type, nano-ring type, open resonant ring type, fan type, V-type, U-type, cylindrical type and other nanostructures.

[0013] According to another aspect of the present invention, preferably, the viewpoint image sequence encoding method loaded by the display panel includes but is not limited to a sub-pixel viewpoint encoding method based on a cylindrical lens array, a viewpoint encoding method based on an element image, or a sub-pixel viewpoint encoding method based on a diffraction grating.

[0014] According to another aspect of the present invention, the nanostructure size design of the metasurface array depends on the phase mutation of light before and after passing through the nanostructure of the metasurface array; characterized in that the phase shift depends on the incident light wave vector incident on the metasurface and the outgoing light wave vector emitted from the metasurface to a specified direction; characterized in that the nanostructure size design does not depend on the change of the polarization angle of the incident light or the incident angle; characterized in that the nanostructure size is matched according to the designed phase-amplitude-nanostructure size lookup table (LUT).

[0015] According to another aspect of the present invention, preferably, a single multilayer transmissive nanostructure of the metasurface array includes but is not limited to Si (nanopillar)-SiO2 (substrate)-Sb2Se3 (substrate), Si (nanopillar)-SiO2 (substrate)-Si (substrate), Sb2Se3 (nanopillar)-hydrogel (substrate)-Si (substrate); preferably, a single single-layer transmissive nanostructure includes but is not limited to Si (nanopillar)-SiO2 (substrate), Sb2Se3 (nanopillar)-TiO2 (substrate).

[0016] According to another aspect of the present invention, the metasurface array with multi-polarization angle response characteristics is used to perform phase, amplitude or complex amplitude modulation on the linear polarization components of multiple specific polarization angles of the light; the metasurface array with multi-incident angle response characteristics is used to perform phase, amplitude or complex amplitude modulation on the light at the multiple specific incident angles.

[0017] According to another aspect of the present invention, preferably, in order to achieve a smooth three-dimensional display effect without image jumps, the number of viewpoint images converged after phase modulation of the metasurface array subunits that simultaneously enter the user's pupil at the optimal viewing distance is two or more.

[0018] According to another aspect of the present invention, a method for performing three-dimensional display in a super multi-viewpoint three-dimensional display system is provided, which is characterized by comprising the following steps:

[0019] The display panel loads a coded viewpoint image sequence;

[0020] The metasurface array performs phase and / or amplitude modulation on linear polarization components of multiple specific polarization angles or light rays of multiple specific incident angles from the display panel, and converges light rays emitted by sub-pixels of the same group of viewpoint image display units to the same position;

[0021] At the optimal viewing distance, two or more adjacent viewpoint images enter the same pupil of the user, achieving a three-dimensional display effect.

[0022] According to another aspect of the present invention, the calculation of the phase shift of light before and after passing through the metasurface array nanostructure is related to the encoding method of the viewpoint image sequence of the display panel; the metasurface array nanostructure is related to the encoding method of the viewpoint image sequence of the display panel.

[0023] Compared with the prior art, the present invention has one or more of the following technical effects:

[0024] First, by using a metasurface array to replace the lens array and cylindrical lens array in the traditional ultra-multi-viewpoint three-dimensional display for light phase modulation, it is easier to achieve different requirements such as the number of viewing angles, viewing angle spacing, pixel size and depth range by adjusting the structural parameters and phase control methods, thereby improving the flexibility and freedom of design; at the same time, by adjusting the microstructure and material of the metasurface, the metasurface can be kept stable in a broadband range, and compared with the diffraction grating type ultra-multi-viewpoint three-dimensional display, there is no dispersion effect.

[0025] Secondly, by utilizing the multi-angle polarization response characteristics and / or multi-angle incident response characteristics of the metasurface array, the phase and direction of light can be controlled with high precision. Compared with the metasurface array that responds to a single polarization angle and / or a single incident angle, it can be combined with a multi-directional backlight module to achieve higher resolution and wider viewing angle three-dimensional display, improve image quality, and reduce unnecessary scattering and crosstalk between different viewing angles.

[0026] Third, the size of the metasurface array nanostructures is matched according to the designed phase-amplitude-nanostructure size lookup table (LUT). By precalculating the correspondence between the phase and the nanostructure, the required phase shift can be quickly found and the metasurface structure can be designed accordingly.

[0027] Fourth, the system has a higher light energy utilization rate. At the same time, the thin and light characteristics of the metasurface array further compress the system volume, making it suitable for miniaturized and integrated three-dimensional display devices such as portable and wearable displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to understand the details of the above features of the present invention, reference may be made to the embodiments for a more detailed description of the invention briefly summarized above. The accompanying drawings relate to preferred embodiments of the present invention and are described as follows:

[0029] Figure 1 It is a schematic structural diagram of a nano-pillar metasurface array three-dimensional display system with multi-angle polarization response according to a first preferred embodiment of the present invention;

[0030] Figure 2 A schematic diagram of encoding a single view synthesis image display unit according to a first preferred embodiment of the present invention;

[0031] Figure 3 A schematic diagram of a single nano-pillar type super-surface array nanostructure according to a first preferred embodiment of the present invention;

[0032] Figure 4 Schematic diagram of the corresponding relationship between a single cylindrical lens and a nano-column-type metasurface cylindrical lens array unit;

[0033] Figure 5Schematic diagram of the structure of a nano-column-type metasurface array three-dimensional display system that responds to multi-angle incidence according to a second preferred embodiment of the present invention. Specific embodiments

[0034] Various embodiments will now be described in detail, one or more examples of which are depicted in the figures. Each example is provided by way of explanation and is not meant to be limiting. For example, a feature depicted or described as part of one embodiment can be used in or combined with any other embodiment to produce yet another embodiment. The present invention is intended to include such modifications and variations.

[0035] In the following description of the drawings, the same reference numerals indicate the same or similar structures. Generally speaking, only the differences of individual embodiments will be described. Unless otherwise explicitly stated, the description of a part or aspect in one embodiment can also be applied to the corresponding part or aspect in another embodiment.

[0036] Example 1

[0037] See also Figure 1 , which shows a nano-pillar metasurface array three-dimensional display system with multi-angle polarization response, the system comprising:

[0038] The backlight module 110 is used to generate a light source with multi-directional collimated backlight.

[0039] Display panel 120, used for loading the encoded view synthesis image sequence;

[0040] Viewpoint coded images 121-124: obtained by coding 3D images acquired at different viewing angles, and used as a source of super-multi-viewpoint 3D display images;

[0041] The nano-column metasurface cylindrical lens array 130 is used to receive the viewpoint-coded image amplitude information from the display panel and phase-modulate the linear polarization components of the light at multiple specific polarization angles, so that the metasurface array transmits light and finally converges it to different viewpoints;

[0042] The nano-column type super-surface cylindrical lens array unit 131 is used to phase modulate the light emitted by the corresponding viewpoint coding image sub-pixel;

[0043] 140a, 140b: reconstructed three-dimensional objects a, b.

[0044] According to another preferred embodiment of the present invention, the display panel 120 includes LCD, LED, DMD or LPD; the viewpoint image display units 121-124 are viewpoint image sub-pixel units based on the cylindrical lens array display mode, and the viewpoint image display unit information corresponding to the incident light with different polarization angles is loaded onto the display panel according to the designed metasurface time division or space division multiplexing; the metasurface array 130 has a multi-angle polarization response characteristic, that is, under the designed linear polarization angle incidence conditions of 0°, 15°, 30°, 45°, and 60°, it has good amplitude modulation characteristics; the single nanostructure of the metasurface cylindrical lens array 130 is a multi-layer transmission type, and the single nanostructure of the metasurface array 130 is a nanocolumn structure.

[0045] According to another preferred embodiment of the present invention, the metasurface cylindrical lens array 130 comprises a layer of orderly arranged metasurface units. Each metasurface cylindrical lens unit corresponds to a group of refreshable viewpoint coding image units. Figure 1 As shown, the viewpoint coded image 121 loaded on the display panel 120 corresponds to a supersurface cylindrical lens array unit 131 of the supersurface cylindrical lens array 130, and different viewpoint coded image units correspond to different supersurface cylindrical lens array units. Since the light emitted by the display panel is non-polarized light, after phase modulation by the metasurface array 130 with multi-angle polarization response, the light emitted by the sub-pixels with the same name at each viewpoint converges to the same viewpoint position, and the light emitted by the sub-pixels with the same name at different viewpoints converges to different viewpoint positions, and the linear polarization components with different polarization angles converge to different angles, which are combined with the viewpoint image display unit loaded by the display panel in time division or space division multiplexing, and finally form a three-dimensional reconstructed image with a large viewing angle.

[0046] It is understandable that, similar to the traditional super multi-viewpoint 3D display system, the phase modulation effect of the metasurface cylindrical lens array 130 and the traditional cylindrical lens array should be consistent. Therefore, according to another preferred embodiment of the present invention, a method for designing a metasurface cylindrical lens array using the aforementioned phase-amplitude-nanostructure lookup table (LUT) method is also provided, which is characterized by comprising the following steps:

[0047] First, the electric field value E and transmittance T under different structural parameters are scanned within a certain range of nanostructure parameters using finite-difference time-domain (FDTD) simulation and / or rigorous coupled wave analysis (RCWA) numerical simulation methods. According to the scanning results, the corresponding nanostructure is selected as the structure of the lookup table (LUT), and finally, a metasurface nanostructure with multi-angle polarization response characteristics is designed in combination with the scanning results under angle polarization incidence. In order to meet the requirements of ultra-multi-viewpoint three-dimensional display, 8 phase-modulated metasurface nanostructures of 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4 should be designed respectively. The amplitude modulation value of each metasurface nanostructure under the incident light of the designed N polarization angles should be not much different and close to 1.

[0048] Secondly, the 3D model or 3D scene to be reproduced is recorded by a multi-view camera, the recorded viewpoint images are divided into N groups, and N viewpoint synthesis images are synthesized according to the viewpoint synthesis algorithm, and the encoded viewpoint synthesis image sequence is loaded onto the display panel by time division or space division multiplexing. Considering the visual persistence characteristics of the human eye, the refresh rate of the display panel should be at least (24*N) Hz when using time division multiplexing.

[0049] Third, phase encoding is performed on the cylindrical lens array matched to the viewpoint encoding image sequence to obtain phase encoding data;

[0050] Fourth, the phase-encoded data is discretized and mapped between 0 and 2π, and divided into 8 discrete levels: 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4;

[0051] Fifth, each part of the cylindrical lens is represented by an 8-order discrete phase modulation value, and the corresponding metasurface micro-nanostructure is found and replaced by the aforementioned phase-amplitude-nanostructure lookup table (LUT) method to obtain a metasurface cylindrical lens array unit, such as a metasurface cylindrical lens unit 131;

[0052] A phase discrete value of each cylindrical lens of the cylindrical lens array is matched to a metasurface nanostructure one by one by using a lookup table method, and finally a metasurface cylindrical lens array 130 is obtained;

[0053] The metasurface cylindrical lens array 130 is combined with the display panel 120 to form a large-viewing angle and ultra-multi-viewpoint three-dimensional display system based on the metasurface array, and the user finally observes the reconstructed three-dimensional images 140a and 140b at the viewing distance.

[0054] It can be understood that, compared with the lens array, the cylindrical lens array in the 3D display only modulates the viewpoint distribution in the horizontal direction, but does not modulate the viewpoint image distribution in the vertical direction. Therefore, the nanostructure of the metasurface cylindrical lens array should remain consistent in the vertical direction and be arranged periodically in the horizontal direction, see Figure 1 In addition, similar to the three-dimensional display based on the cylindrical lens array, the metasurface cylindrical lens array can be designed to have a certain tilt angle to reduce the difference between the horizontal resolution and the vertical resolution when reproducing the viewpoint and eliminate the moiré fringes.

[0055] According to another preferred embodiment of the present invention, see Figure 2 , showing the view synthesis image encoding method in the space division multiplexing mode. For example, a sub-pixel 125 simultaneously contains the viewpoint image amplitude information of incident light with N polarization angles. The view synthesis image encoding method in the space division multiplexing mode includes but is not limited to the following: Figure 2 The encoding method shown.

[0056] According to another preferred embodiment of the present invention, the eighth-order discrete phase distribution of a single cylindrical lens is matched with the orientation angle (θ) of the metasurface nanostructure nanocolumn by a lookup table (LUT) method, and finally a single metasurface cylindrical lens array unit is obtained, such as the metasurface cylindrical lens array unit 131.

[0057] According to another preferred embodiment of the present invention, the phase-amplitude-nanostructure lookup table (LUT) includes but is not limited to the correspondence between the phase-amplitude-nanopillar length (L) and width (W), the phase-amplitude-nanopillar material and the phase-amplitude-nanopillar orientation angle (θ).

[0058] According to another preferred embodiment of the present invention, without loss of generality, a single nano-pillar type single-layer transmission super surface micro-nano structure is taken as an example, and its schematic diagram is as follows: Figure 3 As shown. Using the finite-difference time-domain (FDTD) simulation and / or rigorous coupled wave analysis (RCWA) numerical simulation method, the height (H) and orientation angle (θ) of the nanopillar 310 are kept unchanged, TiO2 is selected as the material of the nanopillar 310 and SiO2 is selected as the material of the substrate 311. By scanning the length (L) and width (W) parameters of the supersurface nanostructure nanopillar 310, 8 supersurface micro-nano structures between 0 and 2π are optimized and designed. In the phase-amplitude-nanostructure size lookup table (LUT) designed for the 8 supersurface structures based on the nanopillar type, the phase modulation of the supersurface nanostructures corresponding to the 8 different nanopillar sizes is distributed in eight orders from 0 to 2π. When the incident light polarization angles are 0°, 15°, 30°, 45°, and 60°, respectively, the amplitude modulation is maintained at a high transmission characteristic of greater than or equal to 0.7.

[0059] According to another preferred embodiment of the present invention, for example Figure 4 , the eighth-order discrete phase distribution of the lens is matched with the length (L) and width (W) of the metasurface nanostructure nanocolumn through the lookup table (LUT) method, and finally a single metasurface column lens array unit is obtained, such as the metasurface column lens array unit 131.

[0060] According to another preferred embodiment of the present invention, the phase-amplitude-nanostructure lookup table (LUT) includes but is not limited to the corresponding relationship between the phase-amplitude-nanocolumn length (L) and width (W), the phase-amplitude-nanocolumn material and the phase-amplitude-nanocolumn orientation angle (θ). The following embodiments are the same.

[0061] Example 2

[0062] See also Figure 5 , which shows a nano-pillar metasurface array three-dimensional display system that responds to multi-angle incidence, the system comprising:

[0063] The multi-angle collimated backlight module 510 is used to generate collimated backlight at multiple angles.

[0064] Display panel 520, used for loading the encoded view synthesis image sequence;

[0065] Viewpoint coded images 521-524: obtained by encoding 3D images acquired at different viewing angles, and used as a source of super-multi-viewpoint 3D display images;

[0066] The nano-column metasurface cylindrical lens array 530 is used to receive the viewpoint-coded image amplitude information from the display panel and phase-modulate the light of the multiple specific incident angles, and finally the metasurface array transmits the light and converges it to different viewpoints;

[0067] The nano-column type metasurface cylindrical lens array unit 530 is used to phase modulate the light emitted by the corresponding viewpoint coded image sub-pixel;

[0068] 540a, 540b: reconstructed three-dimensional objects a, b.

[0069] According to another preferred embodiment of the present invention, the display panel 520 includes LCD, LED, DMD or LPD; the viewpoint image display units 521-524 are viewpoint image sub-pixel units based on the cylindrical lens array display mode, and the viewpoint image display unit information corresponding to different incident angles is loaded onto the display panel in a time-sharing manner according to the designed metasurface; the metasurface array 530 is single-layer encoded; a single nanostructure of the metasurface cylindrical lens array 530 is a multi-layer transmission type, and a single nanostructure of the metasurface array 530 is a nanocolumn structure.

[0070] According to another preferred embodiment of the present invention, the super surface cylindrical lens array 530 includes a layer of orderly arranged super surface units. Each super surface cylindrical lens unit corresponds to a group of refreshable viewpoint coding image units. Figure 5As shown, the viewpoint coded image 521 loaded on the display panel 520 corresponds to a super surface cylindrical lens array unit 531 of the super surface cylindrical lens array 530, and different viewpoint coded image units correspond to different super surface cylindrical lens array units. The multi-angle collimation backlight module is synchronously refreshed with the loaded image. After the phase modulation of the super surface array 530 that responds to multi-angle incidence, the light emitted by the sub-pixels with the same name at each viewpoint converges to the same viewpoint position, and the light emitted by the sub-pixels with the same name at different viewpoints converges to different viewpoint positions. The light at different incident angles is diffracted and propagated by the super surface array and converges to different angles, finally forming a three-dimensional reconstructed image with a large viewing angle.

[0071] It is understandable that, similar to the traditional super multi-viewpoint 3D display system, the phase modulation effect of the metasurface cylindrical lens array 530 and the traditional cylindrical lens array should be consistent. Therefore, according to another preferred embodiment of the present invention, a method for designing a metasurface cylindrical lens array using the aforementioned phase-amplitude-nanostructure lookup table (LUT) method is also provided, which is characterized by comprising the following steps:

[0072] First, a metasurface nanostructure with multi-polarization angle response characteristics is designed using finite-difference time-domain (FDTD) simulation and / or rigorous coupled wave analysis (RCWA) numerical simulation methods. In order to meet the requirements of ultra-multi-viewpoint 3D display, 8 phase-modulated metasurface nanostructures of 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4 should be designed respectively, and the amplitude modulation value of each metasurface nanostructure should be similar and close to 1 when illuminated by incident light of the designed N incident angles.

[0073] Secondly, the 3D model or 3D scene to be reproduced is recorded by a multi-view camera, the recorded viewpoint images are divided into N groups, and N viewpoint synthesis images are synthesized according to the viewpoint synthesis algorithm, and the encoded viewpoint synthesis image sequence is loaded onto the display panel in a time-division manner. Considering the visual persistence characteristics of the human eye, the refresh rate of the display panel should be at least (24*N) Hz when using time-division multiplexing.

[0074] Third, phase encoding is performed on the cylindrical lens array matched to the viewpoint encoding image sequence to obtain phase encoding data;

[0075] Fourth, the phase-encoded data is discretized and mapped between 0 and 2π, and divided into 8 discrete levels: 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4;

[0076] Fifth, each part of the cylindrical lens is represented by an 8-order discrete phase modulation value, and the corresponding metasurface micro-nanostructure is found and replaced by the aforementioned phase-amplitude-nanostructure lookup table (LUT) method to obtain a metasurface cylindrical lens array unit, such as a metasurface cylindrical lens unit 531;

[0077] A phase discrete value of each cylindrical lens of the cylindrical lens array is matched to a metasurface nanostructure one by one by using a lookup table method, and finally a metasurface cylindrical lens array 530 is obtained;

[0078] The metasurface cylindrical lens array 530 is combined with the display panel 520, and the multi-angle collimated backlight module is synchronously refreshed with the viewpoint synthetic image of the corresponding angle to form a large-viewing angle and ultra-multi-viewpoint three-dimensional display system based on the metasurface array. The user finally observes the reconstructed viewpoint images 540a and 540b at the viewing distance.

[0079] It can be understood that, compared with the lens array, the cylindrical lens array in the 3D display only modulates the viewpoint distribution in the horizontal direction, but does not modulate the viewpoint image distribution in the vertical direction. Therefore, the nanostructure of the metasurface cylindrical lens array should remain consistent in the vertical direction and be arranged periodically in the horizontal direction, see Figure 5 .

[0080] According to another preferred embodiment of the present invention, the eighth-order discrete phase distribution of a single cylindrical lens is matched with the orientation angle (θ) of the metasurface nanostructure nanocolumn by a lookup table (LUT) method, and finally a single metasurface cylindrical lens array unit is obtained, such as the metasurface cylindrical lens array unit 531.

[0081] According to another preferred embodiment of the present invention, the phase-amplitude-nanostructure lookup table (LUT) includes but is not limited to the correspondence between the phase-amplitude-nanopillar length (L) and width (W), the phase-amplitude-nanopillar material and the phase-amplitude-nanopillar orientation angle (θ).

[0082] According to another preferred embodiment of the present invention, without loss of generality, a single nano-pillar type single-layer transmission super surface micro-nano structure is taken as an example, and its schematic diagram is as follows: Figure 3As shown. Using the finite difference time domain (FDTD) simulation and / or rigorous coupled wave analysis (RCWA) numerical simulation method, the height (H) and orientation angle (θ) of the nanocolumn 310 are kept unchanged, TiO2 is selected as the material of the nanocolumn 310, and SiO2 is selected as the material of the substrate 311. By scanning the length (L) and width (W) parameters of the supersurface nanostructure nanocolumn 310, 8 supersurface micro-nano structures between 0 and 2π are optimized and designed. In the phase-amplitude-nanostructure size lookup table (LUT) designed for the 8 supersurface structures based on the nanocolumn type, the phase modulation of the supersurface nanostructures corresponding to the 8 different nanocolumn sizes is distributed in eight orders from 0 to 2π. When the incident angles of the incident light are 0°, 15°, 30°, 45°, and 60°, respectively, the amplitude modulation maintains a high transmission characteristic.

[0083] According to another preferred embodiment of the present invention, the eighth-order discrete phase distribution of the lens is matched with the length (L) and width (W) of the metasurface nanostructure nanocolumns by a lookup table (LUT) method, and finally a single metasurface lens array unit is obtained.

[0084] According to another preferred embodiment of the present invention, the phase-amplitude-nanostructure lookup table (LUT) includes but is not limited to the corresponding relationship between the phase-amplitude-nanocolumn length (L) and width (W), the phase-amplitude-nanocolumn material and the phase-amplitude-nanocolumn orientation angle (θ). The following embodiments are the same.

[0085] Compared with the prior art, the present invention has one or more of the following technical effects:

[0086] First, by using a metasurface array to replace the lens array and cylindrical lens array in the traditional ultra-multi-viewpoint three-dimensional display for light phase modulation, it is easier to achieve different requirements such as the number of viewing angles, viewing angle spacing, pixel size and depth range by adjusting the structural parameters and phase control methods, thereby improving the flexibility and freedom of design; at the same time, by adjusting the microstructure and material of the metasurface, the metasurface can be kept stable in a broadband range, and compared with the diffraction grating type ultra-multi-viewpoint three-dimensional display, there is no dispersion effect.

[0087] Secondly, by utilizing the multi-angle polarization response characteristics and / or multi-angle incidence response characteristics of the metasurface array, the phase and direction of light can be controlled with high precision. Compared with metasurface arrays that respond to a single polarization angle and / or a single incident angle, higher resolution and wider viewing angle three-dimensional displays can be achieved, image quality can be improved, and unnecessary scattering and crosstalk between different viewing angles can be reduced.

[0088] Third, the size of the metasurface array nanostructures is matched according to the designed phase-amplitude-nanostructure size lookup table (LUT). By precalculating the correspondence between the phase and the nanostructure, the required phase shift can be quickly found and the metasurface structure can be designed accordingly.

[0089] Fourth, the system has a higher light energy utilization rate. At the same time, the thin and light characteristics of the metasurface array further compress the system volume, making it suitable for miniaturized and integrated three-dimensional display devices such as portable and wearable displays.

[0090] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope of the invention, which is defined by the claims.

[0091] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention. The technical features in these embodiments that do not contradict each other can be combined with each other. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A system and method for realizing large viewing angle and multi-viewpoint three-dimensional display, characterized in that include: A backlight module for generating multi-directional collimated backlight; A display panel is used to load a coded viewpoint image sequence, and a metasurface array with multi-angle polarization response and / or multi-angle incidence response, which is used to receive the image intensity information of each viewpoint and perform phase and / or amplitude modulation on the linear polarization components of different polarization angles and / or light of different incident angles. Finally, the light is diffracted and propagated through the metasurface array to converge to different viewpoints.

2. The ultra-multi-viewpoint 3D display system according to claim 1, characterized in that A viewpoint image display unit of the display panel corresponds one-to-one to an array subunit of the metasurface array; the same group of viewpoint image display units converge to the same viewpoint after being phase-modulated by the corresponding metasurface array subunits, and different groups of viewpoint image display units converge to different viewpoints after being phase-modulated by the corresponding metasurface array subunits. Linear polarized light components with different polarization angles or light rays with different incident angles are diffracted and propagated by the metasurface array and converge to different angles, ultimately forming a three-dimensional reconstructed image with a large viewing angle.

3. The ultra-multi-viewpoint 3D display system according to claim 1-2, characterized in that The display panel includes LCD, LED, DMD or LPD; preferably, the viewpoint image display unit includes but is not limited to an element image unit based on an integrated imaging display mode, a viewpoint image sub-pixel unit based on a cylindrical lens array display mode, or a sub-pixel unit based on a diffraction grating display mode; optionally, the metasurface array has multi-angle polarization response characteristics or multi-angle incidence response characteristics; optionally, an array sub-unit of the metasurface array is a periodic structure or a non-periodic structure; optionally, a single nanostructure of the metasurface array is a multi-layer transmission type or a single-layer transmission type; optionally, a single nanostructure of the metasurface array includes but is not limited to nano-column type, nano-ring type, open resonant ring type, fan type, V-type, U-type, cylindrical type and other nanostructures.

4. The display panel according to claim 1-2, characterized in that: Preferably, the loaded viewpoint image sequence encoding method includes but is not limited to a sub-pixel viewpoint encoding method based on a lenticular array, a viewpoint encoding method based on an element image, or a sub-pixel viewpoint encoding method based on a diffraction grating.

5. The metasurface array according to claims 1-3, characterized in that: The nanostructure size design depends on the phase shift of light before and after passing through the metasurface array nanostructure; the phase shift depends on the incident light wave vector incident on the metasurface and the outgoing light wave vector emitted from the metasurface to a specified direction; the nanostructure size design does not depend on the change of the incident light polarization angle or the incident angle; the nanostructure size is matched according to the designed phase-amplitude-nanostructure size lookup table (LUT).

6. The metasurface array according to claims 1-5, characterized in that: A single multilayer transmissive nanostructure includes but is not limited to Si (nanopillar)-SiO2 (substrate)-Sb2Se3 (substrate), Si (nanopillar)-SiO2 (substrate)-Si (substrate), Sb2Se3 (nanopillar)-hydrogel (substrate)-Si (substrate); preferably, a single single-layer transmissive nanostructure includes but is not limited to Si (nanopillar)-SiO2 (substrate), Sb2Se3 (nanopillar)-TiO2 (substrate).

7. The metasurface array according to claims 1-6, characterized in that: The metasurface array with multi-polarization angle response characteristics is used to perform phase, amplitude or complex amplitude modulation on the linear polarization components of multiple specific polarization angles of the light; the metasurface array with multi-incident angle response characteristics is used to perform phase, amplitude or complex amplitude modulation on the light at the multiple specific incident angles.

8. According to the ultra-multi-viewpoint three-dimensional display system described in claims 1-4, preferably, in order to achieve a smooth three-dimensional display effect without image jumps, the number of viewpoint images converged after phase modulation of the metasurface array subunits that simultaneously enter the user's pupil at the optimal viewing distance is two or more.

9. A method for performing three-dimensional display using the ultra-multi-viewpoint three-dimensional display system according to any one of claims 1 to 8, characterized in that The following steps are involved: The display panel loads a coded viewpoint image sequence; The metasurface array performs phase and / or amplitude modulation on linear polarization components of multiple specific polarization angles or light rays of multiple specific incident angles from the display panel, and converges light rays emitted by sub-pixels of the same group of viewpoint image display units to the same position; At the optimal viewing distance, two or more adjacent viewpoint images enter the same pupil of the user, achieving a three-dimensional display effect.

10. The method for realizing 3D display by a super multi-viewpoint 3D display system according to claims 1-9, characterized in that: The calculation of the phase shift before and after the light passes through the metasurface array nanostructure is related to the encoding method of the viewpoint image sequence of the display panel; the metasurface array nanostructure is related to the encoding method of the viewpoint image sequence of the display panel.

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