Metasurface three-dimensional holographic display method based on holographic lenses

Abstract

A metasurface three-dimensional holographic display method based on holographic lenses (2). The method comprises: step 1, slicing a three-dimensional object (1) into N depth-layer planar images in the order from a first longitudinal depth to an Nth longitudinal depth, wherein N is a positive integer, one depth-layer planar image is superimposed with one holographic lens (2), and the greater the depth of the depth-layer planar image is, the greater the focal length of the corresponding holographic lens (2) is; step 2, using a metasurface unit structure (3) to perform phase encoding on phase information obtained after the N depth-layer planar images and N holographic lenses (2) are alternately superimposed one by one, so as to encode hologram phase information onto the metasurface structure (3) on a metasurface substrate (4); and step 3, using a three-dimensional metasurface holographic reconstruction system to realize the three-dimensional holographic display of the three-dimensional object (1). By means of the method, the computation time can be shortened, and the image quality can be improved.

Description

A metasurface three-dimensional holographic display method based on holographic lens

[0001] TECHNICAL FIELD: The present application relates to the technical field of holographic display, and in particular to a metasurface three-dimensional holographic display method based on holographic lens.

[0002] BACKGROUND: Human beings perceive the outside world through five senses, including vision, hearing, touch, taste and smell. A large number of studies have shown that vision is the main way for human beings to perceive the outside world, accounting for 80%. This shows the importance of vision in information acquisition. As a tool for transmitting visual information, display technology has undergone a long and continuous development process, accompanied by people's pursuit of visual information and the demand for exploration of the visual system.

[0003] The development of display technology has experienced a series of progress from static to dynamic, from black and white to color, from standard definition to Blu-ray, etc. However, these progressions are almost confined to the field of two-dimensional display. With the continuous evolution of technology and the improvement of human needs, people naturally expect to achieve more realistic three-dimensional display effects. Therefore, it can be predicted that future display technology will mainly focus on the development in the field of three dimensions. In the current three-dimensional display technology, holographic three-dimensional display technology is widely recognized as an excellent three-dimensional display technology with broad application prospects and development potential, because it can completely record and reconstruct the wave front of an object and provide all the depth information required by the human visual system. In addition, it has become one of the focuses of global research.

[0004] With the development of computer technology, metasurface three-dimensional holographic display has been widely used in computer holography. However, three-dimensional computer holography has the problem of large amount of calculation data, which has always to balance the calculation time and image quality, seriously restricting the display application. Although holographic lens has been applied in metasurface holographic display, the traditional method is limited in focal length and composite phase encoding, which can only integrate the target object with a single holographic lens and can only realize two-dimensional holographic display, but cannot achieve three-dimensional effect.

[0005] SUMMARY: The present application proposes a metasurface three-dimensional holographic display method based on holographic lens to solve the problems of long calculation time, large data volume and poor image quality in the prior art. On the basis of computer holography, the method integrates multiple layers of holographic lenses with different focal lengths, and combines the holographic lens with different depth images of the three-dimensional scene, thereby shortening the calculation time, improving the image quality and realizing three-dimensional display.

[0006] The technical solution of the present application is as follows:

[0007] A kind of super surface three-dimensional holographic display method based on holographic lens, comprising the following steps:

[0008] Step 1, three-dimensional object is cut into N depth layer planar images according to first longitudinal depth to N longitudinal depth, N is positive integer, one depth layer planar image is superimposed one holographic lens, the greater the depth of depth layer planar image, the greater the focal length of corresponding holographic lens;

[0009] Step 2, the phase information of N depth layer planar images and N holographic lenses after staggered superposition one by one is encoded using super surface unit structure, and the hologram phase information is encoded to the super surface structure on the super surface substrate;

[0010] Step 3, three-dimensional holographic display for the three-dimensional object is realized using three-dimensional super surface holographic reconstruction system.

[0011] In step 2, the phase map is generated using superposition calculation method, the phase map includes 1960*1200 phase points, each phase point has a phase value of 0-255, and the multi-layer depth phase is encoded according to the superposition of holographic lens.

[0012] In step 2, the super surface in the super surface structure is a geometric phase super surface or a resonance phase super surface or a propagation phase super surface.

[0013] In step 2, the material of the super surface unit structure is silicon, amorphous silicon, gold or aluminum, and the material of the super surface substrate is silicon or silicon dioxide.

[0014] In step 2, the length-width ratio, height and / or rotation angle of the super surface unit structure are controlled to generate different phases, which are matched and encoded with the phase map generated by the superposition calculation method.

[0015] The three-dimensional super surface holographic reconstruction system in step 3 includes laser, first linear polarizer, first quarter wave plate, super surface, microscope objective, second quarter wave plate, second linear polarizer and camera connected in sequence, the exit light of the laser is converted into circularly polarized light after passing through the first linear polarizer and the first quarter wave plate, the super surface of the coded hologram is excited, the image is enlarged by the microscope objective, the second quarter wave plate and the second linear polarizer filter zero noise, and the camera receives the holographic image.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] (1) The present application uses holographic lenses with different focal lengths to integrate images with different depths of field, realizes three-dimensional holographic display, and overcomes the problem that traditional holographic lens super surface holographic display is limited by focal length and can only be two-dimensional display, which is a new means.

[0018] (2) The method provided by the application reduces the calculation data amount of three-dimensional holography and improves the calculation speed.

[0019] (3) The method provided by the application reduces the interlayer crosstalk of three-dimensional holographic display and improves the image quality.

[0020] BRIEF DESCRIPTION OF DRAWINGS: FIG. 1 is a process schematic diagram of implementing a holographic lens-based metasurface three-dimensional holographic display method according to the application. FIG. 1 includes cutting a ring knot into four plane images according to depth, superimposing a plane image with a holographic lens, the greater the depth of the plane image, the greater the focal length of the corresponding holographic lens, and after the plane image and the holographic lens are superimposed layer by layer, the phase information of the hologram is encoded onto the metasurface structure on the metasurface substrate through phase encoding. In FIG. 1, 1 is a three-dimensional object (specifically a ring knot) cut into four layers according to depth, 2 is four holographic lenses with different focal lengths, 3 is the metasurface unit structure (rectangular column bodies with different orientations) obtained by phase encoding after the three-dimensional object and the holographic lenses with different focal lengths are superimposed layer by layer, and 4 is a metasurface substrate.

[0021] FIG. 2 is a schematic diagram of the structure of a three-dimensional metasurface holographic reconstruction system involved in implementing a holographic lens-based metasurface three-dimensional holographic display method according to the application.

[0022] FIG. 3 is a schematic diagram of three holographic lenses with different focal lengths. In FIG. 3, from left to right, 31 is a holographic lens with a focal length of 400 um, 32 is a holographic lens with a focal length of 700 um, and 33 is a holographic lens with a focal length of 1000 um.

[0023] FIG. 4 is an image of a three-dimensional target display object ring knot. The ring knot image in FIG. 4 has x-y plane information and z-direction depth information, and can be cut into layers according to depth.

[0024] FIG. 5 is a holographic lens-based metasurface three-dimensional holographic phase diagram involving three layers of depth of field.

[0025] FIG. 6 is a holographic lens-based metasurface three-dimensional holographic reconstruction diagram involving three layers of depth of field. In FIG. 6, from left to right, 61 is a holographic reconstruction image with a focal length of 400 um, 62 is a holographic reconstruction image with a focal length of 700 um, and 63 is a holographic reconstruction image with a focal length of 1000 um.

[0026] FIG. 7 is a holographic lens-based metasurface three-dimensional holographic phase diagram involving seven layers of depth of field.

[0027] Figure 8 is a holographic lens-based metasurface three-dimensional holographic reconstruction diagram involving seven layers of depth of field. From left to right in Figure 8, 81 is a holographic reconstruction image with a focal length of 400 um, 82 is a holographic reconstruction image with a focal length of 500 um, 83 is a holographic reconstruction image with a focal length of 600 um, 84 is a holographic reconstruction image with a focal length of 700 um, 85 is a holographic reconstruction image with a focal length of 800 um, 86 is a holographic reconstruction image with a focal length of 900 um, and 87 is a holographic reconstruction image with a focal length of 1000 um.

[0028] DETAILED DESCRIPTION: The present application will be described below in conjunction with the accompanying drawings (Figures 1-8) and examples.

[0029] Figure 1 is a process schematic diagram of a holographic lens-based metasurface three-dimensional holographic display method according to the present application. Figure 2 is a structural schematic diagram of a three-dimensional metasurface holographic reconstruction system involved in a holographic lens-based metasurface three-dimensional holographic display method according to the present application. Figure 3 is a schematic diagram of three holographic lenses with different focal lengths. Figure 4 is an image of a ring-shaped section of a three-dimensional target display object. Figure 5 is a holographic lens-based metasurface three-dimensional holographic phase diagram involving three layers of depth of field. Figure 6 is a holographic lens-based metasurface three-dimensional holographic reconstruction diagram involving three layers of depth of field. Figure 7 is a holographic lens-based metasurface three-dimensional holographic phase diagram involving seven layers of depth of field. Figure 8 is a holographic lens-based metasurface three-dimensional holographic reconstruction diagram involving seven layers of depth of field.

[0030] Referring to Figures 1-8, a holographic lens-based metasurface three-dimensional holographic display method includes the following steps:

[0031] Step 1, cutting a three-dimensional object into N depth layer plane images according to a first longitudinal depth to an Nth longitudinal depth, N being a positive integer, one depth layer plane image being superimposed with one holographic lens, the greater the depth of the depth layer plane image, the greater the focal length of the corresponding holographic lens;

[0032] Step 2, phase information after superimposing and interleaving N depth layer plane images and N holographic lenses one by one is phase-encoded using a metasurface unit structure, and the hologram phase information is encoded onto the metasurface structure on the metasurface substrate;

[0033] Step 3, a three-dimensional holographic display for the three-dimensional object is realized using a three-dimensional metasurface holographic reconstruction system.

[0034] The step 2 includes generating a phase map by using a superposition calculation method, the phase map includes 1960*1200 phase points, each phase point has a phase value of 0-255, and the multiple depth phases are encoded according to the superposition of the holographic lens. The super surface in the step 2 is a geometric phase super surface or a resonance phase super surface or a propagation phase super surface. The material of the super surface unit structure in the step 2 is silicon, amorphous silicon, gold or aluminum, and the material of the super surface substrate is silicon or silicon dioxide. The step 2 includes matching and encoding the phase map generated by using the superposition calculation method by controlling the aspect ratio, height and / or rotation angle of the super surface unit structure to generate different phases.

[0035] The three-dimensional super surface holographic reconstruction system in the step 3 includes a laser 21, a first linear polarizer 22, a first quarter wave plate 23, a super surface 24, a microscope objective 25, a second quarter wave plate 26, a second linear polarizer 27 and a camera 28 connected in sequence, the outgoing light of the laser 21 is converted into circularly polarized light after passing through the first linear polarizer 22 and the first quarter wave plate 23, the super surface 24 of the encoded hologram is excited, the image is enlarged by the microscope objective 25, the second quarter wave plate 26 and the second linear polarizer 27 filter zero-level noise, and the camera 28 receives the holographic image.

[0036] The present application relates to a kind of based on holographic lens's super surface three-dimensional holographic display method.The technical process of this method is based on the calculation holography, multiple different focal length holographic lenses are integrated therein, holographic lens is combined with the different depth image of three-dimensional scene, and it is encoded on the super surface with super high light field modulation capacity, three-dimensional holographic display is realized using super surface three-dimensional holographic reconstruction system.Multiple focal length holographic lens design and layer-by-layer superposition method are used, the difficulty that traditional holographic lens super surface holography can only two-dimensional display is broken through, the problems such as long calculation time, large data volume and poor image quality in prior art super surface three-dimensional calculation holography are solved.

[0037] A kind of based on holographic lens's super surface three-dimensional holographic display method, the flow of this method is when calculating hologram, the image of different depth of three-dimensional scene is added to holographic lens of different focal length, then multiple depth hologram superposition calculation is carried out, the hologram phase information obtained is encoded on super surface unit structure, three-dimensional super surface holographic display is realized using three-dimensional super surface holographic reconstruction system.

[0038] The holographic lens-based super surface three-dimensional holographic display method includes the following steps:

[0039] (1) a three-dimensional object is cut into different depth layers according to depth, and a holographic lens is superimposed on the image of each depth layer, the focal length of the holographic lens corresponds to the depth of the image, and the phase information after superposition is calculated;

[0040] (2) Using the unit structure of the metasurface to encode phase information;

[0041] (3) Using a three-dimensional metasurface holographic reconstruction system to realize three-dimensional holographic display.

[0042] The method of computer holography is:

[0043] (1) Cutting the three-dimensional scene with depth as a clue to form images of different depths;

[0044] (2) Adding holographic lenses with different focal lengths to holograms of different depths to reduce algorithm data volume and interlayer crosstalk and improve three-dimensional holographic display quality;

[0045] (3) Multi-depth hologram superposition calculation to generate a phase map.

[0046] The metasurface encoding method is:

[0047] (1) The metasurface can be any one of a geometric phase metasurface, a resonant phase metasurface, and a propagation phase metasurface;

[0048] (2) The unit structure material of the metasurface can be any one of silicon, amorphous silicon, gold, and aluminum, and the substrate of the metasurface can be silicon dioxide or silicon;

[0049] (3) By controlling the aspect ratio, height, and rotation angle of the unit structure of the metasurface to produce different phases, the phases are matched and encoded with the calculated phase map.

[0050] The three-dimensional metasurface holographic reconstruction system is: a three-dimensional holographic reconstruction system is composed of a laser, a linear polarizer, a quarter-wave plate, a microscope objective, a camera, and a metasurface. The outgoing light of the laser is converted into circularly polarized light after passing through the linear polarizer and the quarter-wave plate, exciting the metasurface of the encoded hologram, magnifying the image through the microscope objective, filtering the zero-level noise using the quarter-wave plate and the linear polarizer, and receiving the holographic image using the camera.

[0051] Referring to FIG. 1, a three-dimensional object "ring knot" is cut into four planar images according to depth, and an image on each depth layer is superimposed on a holographic lens whose focal length corresponds to the depth of the image. The phase information after superposition is calculated and encoded on the super surface unit structure. The number of layers can be set arbitrarily as needed. FIG. 2 is a three-dimensional super surface holographic reconstruction system. The outgoing light of the laser is converted into circularly polarized light after passing through a linear polarizer and a quarter-wave plate, and excites the super surface of the encoded hologram. The image is magnified by a microscope objective, and the zero-order noise is filtered by a quarter-wave plate and a linear polarizer. The holographic image is received by a camera. FIG. 3 is a holographic lens with different focal lengths generated in Example 1. FIGS. 4-6 are experimental results of a holographic lens-based super surface three-dimensional hologram (three layers of depth of field) in Example 2. FIGS. 7-8 are experimental results of a holographic lens-based super surface three-dimensional hologram (seven layers of depth of field) in Example 3.

[0052] Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present application should be understood in their usual sense by those skilled in the art to which the present application belongs.

[0053] In order to make the technical purposes, technical solutions and beneficial effects of the present application clearer, a holographic lens-based super surface three-dimensional holographic display method according to the embodiments of the present application is described below in combination with the drawings and specific exemplary embodiments.

[0054] Example 1: Holographic lenses with different focal lengths

[0055] The method comprises the following steps:

[0056] (1) As shown in FIG. 3, holographic lenses with focal lengths of 400 um (indicated by 31), 700 um (indicated by 32), and 1000 um (indicated by 33) are designed.

[0057] (2) The smaller the focal length, the larger the central circle, and the fewer the number of rings under the same area; the larger the focal length, the smaller the central circle, and the more the number of rings under the same area.

[0058] Example 2: Holographic lens-based super surface three-dimensional hologram (three layers of depth of field)

[0059] The method comprises the following steps:

[0060] (1) The target object ring knot (FIG. 4) is a three-dimensional object, and the image has depth information along the z direction in addition to the x-y plane. The image is cut into three layers according to depth.

[0061] (2) The cut seven-layer images of different depth of field are respectively superimposed on seven holographic lenses with different focal lengths, and the focal lengths of the holographic lenses are 400 um, 500 um, 600 um, 700 um, 800 um, 900 um and 1000 um.

[0062] (3) The phase diagram is generated by using the superposition calculation method, as shown in FIG. 5, the calculation time is only 0.36 seconds, the phase diagram contains 1960*1200 phase points, and each phase point has a phase value of 0-255. Due to the superposition of the holographic lens, the multi-layer depth phase is effectively encoded, and the phase diagram center has obvious phase mutation effect.

[0063] (4) The unit structure of the metasurface is selected as a nanometer column structure, the material is amorphous silicon, the nanometer column is 200 nm long, 100 nm wide and 500 nm high, and different angles are rotated to provide a phase consistent with the holographic phase diagram. The nanometer column is processed on a silicon dioxide substrate.

[0064] (5) The holographic display image is generated by using a holographic reconstruction system, as shown in FIG. 6, the laser with a wavelength of 808 nm is converted into circularly polarized light after passing through a linear polarizer and a quarter-wave plate, the metasurface of the encoded hologram is excited, the image is enlarged through a microscopic objective lens, the zero-level noise is filtered through a quarter-wave plate and a linear polarizer, and the holographic image is received by a camera.

[0065] (6) The holographic images of different depths are received by moving the camera forward and backward, the image at the first depth of the annular section is observed at the focal length 61, the image at the second depth of the annular section is observed at the focal length 62, and the image at the third depth of the annular section is observed at the focal length 63. The three-dimensional holographic display effect can be presented in the object space by splicing each layer, and the holographic image of each layer is clear without interlayer crosstalk.

[0066] Example 3: Metasurface three-dimensional hologram based on holographic lens (seven layers of depth of field)

[0067] The method comprises the following steps:

[0068] (1) The three-dimensional target object annular section (FIG. 4) is cut into seven layers as a z-direction depth clue.

[0069] (2) The cut seven-layer images of different depth of field are respectively superimposed seven holographic lenses with different focal lengths, and the focal lengths of the holographic lenses are respectively 400 um, 500 um, 600 um, 700 um, 800 um 900 um and 1000 um.

[0070] (3) Using superposition calculation method, phase map is generated, as shown in Figure 7, the calculation time is only 0.81 seconds, and the phase map contains 1600*1200 phase points, and each phase point has a phase value of 0-255. Due to the superposition of holographic lens, multiple depth phases are effectively encoded. Due to the large number of layers, the phase mutation area in the center of the phase map becomes larger.

[0071] (4) The unit structure of the metasurface is selected as a nano-cylindrical structure, the material is gold, the nano-cylindrical height is 600nm, and the diameter is 100nm-300nm. Different diameters are used to provide a phase consistent with the holographic phase map. The unit structure of the metasurface is processed on a silicon substrate.

[0072] (5) Using a holographic reconstruction system, a holographic display image is generated, as shown in Figure 8. The wavelength of the laser is 795nm. After the linear polarizer and the quarter-wave plate, the outgoing light is converted into circularly polarized light. The metasurface encoded hologram is excited, the image is enlarged through the microscope objective, the zero-level noise is filtered through the quarter-wave plate and the linear polarizer, and the camera receives the holographic image.

[0073] (6) By moving the camera forward and backward, holographic images of different depths are received. At focal length 81, the image of the first depth of the annular section is observed. At focal length 82, the image of the second depth of the annular section is observed. At focal length 83, the image of the third depth of the annular section is observed. At focal length 84, the image of the fourth depth of the annular section is observed. At focal length 85, the image of the fifth depth of the annular section is observed. At focal length 86, the image of the sixth depth of the annular section is observed. At focal length 87, the image of the seventh depth of the annular section is observed. Each layer is spliced to present a three-dimensional holographic display effect in the object space. The holographic image of each layer is clear, and there is no interlayer crosstalk. Due to the increase in the number of layers, the three-dimensional depth information is increased, and the holographic display effect is obviously improved.

[0074] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art.

[0075] The above-described embodiments are only the preferred embodiments of the present application, and do not limit the present application in any form. Any skilled person in the art can make more possible changes and decorations to the technical solution of the present application by using the disclosed technical content, or make modifications without departing from the scope of the technical solution of the present application. Therefore, any equivalent changes made according to the idea of the present application, without departing from the content of the technical solution of the present application, should be covered within the protection scope of the present application.

[0076] It is to be understood that the foregoing description is only illustrative of the embodiments of the application and that various modifications, changes, additions, and / or omissions can be made without departing from the scope and spirit of the disclosed embodiments. In addition, the description is not limited to the embodiments set forth herein as these embodiments are presented by way of example only. Furthermore, the described embodiments can be combined together in any and all manner without departing from the scope of the disclosure. Furthermore, each independent feature or component of any given assembly can constitute a separate embodiment.

[0077] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limit the present application; although the present application is described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

Claims

1. A metasurface three-dimensional holographic display method based on a holographic lens, characterized in that, Includes the following steps: Step 1: Cut the three-dimensional object into N depth layer plane images from the first vertical depth to the Nth vertical depth, where N is a positive integer. A holographic lens is superimposed on each depth layer plane image. The greater the depth of the depth layer plane image, the greater the focal length of the corresponding holographic lens. Step 2: The phase information of the N depth layer planar images and N holographic lenses are superimposed one by one using the metasurface unit structure for phase encoding, and the phase information of the hologram is encoded onto the metasurface structure on the metasurface substrate. Step 3: Use a three-dimensional metasurface holographic reconstruction system to achieve three-dimensional holographic display of the three-dimensional object.

2. The metasurface three-dimensional holographic display method based on a holographic lens according to claim 1, characterized in that, Step 2 includes generating a phase map using a superposition calculation method. The phase map contains 1960*1200 phase points, each with a phase value between 0 and 255. The multi-layer depth phase is encoded based on the superposition of the holographic lenses.

3. The metasurface three-dimensional holographic display method based on a holographic lens according to claim 1, characterized in that, Step 2 includes generating a phase map using a superposition calculation method. The phase map contains 1960*1200 phase points, each with a phase value between 0 and 255. The multi-layer depth phase is encoded based on the superposition of the holographic lenses.

4. The metasurface three-dimensional holographic display method based on a holographic lens according to claim 1, characterized in that, In step 2, the metasurface unit structure uses silicon, amorphous silicon, gold, or aluminum, and the metasurface substrate uses silicon or silicon dioxide.

5. The metasurface three-dimensional holographic display method based on a holographic lens according to claim 1, characterized in that, Step 2 involves controlling the aspect ratio, height, and / or rotation angle of the metasurface unit structure to generate different phases, and matching and encoding these phases with a phase map generated using a superposition calculation method.

6. The metasurface three-dimensional holographic display method based on a holographic lens according to claim 1, characterized in that, The three-dimensional metasurface holographic reconstruction system in step 3 includes a laser, a first linear polarizer, a first quarter-wave plate, a metasurface, a microscope objective, a second quarter-wave plate, a second linear polarizer, and a camera connected in sequence. The laser's output light is converted into circularly polarized light after passing through the first linear polarizer and the first quarter-wave plate, which excites the metasurface encoding the hologram. The image is magnified by the microscope objective, and the second quarter-wave plate and the second linear polarizer filter out zero-order noise. The camera receives the holographic image.

Images