A grating array, a 3D display device, and a 3D display method

Abstract

The present invention discloses a grating array, a 3D display device and a 3D display method. The grating array includes an input grating array and an output grating array disposed on a waveguide substrate. The input grating array couples incident light into the waveguide substrate and maintains the angular phase information of the incident light. The output grating array couples the light out of the waveguide substrate and maintains the angular phase information of the incident light. By means of the input grating array and the output grating array disposed on the waveguide substrate, the angular phase information of the incident light is restored. The overall device is thin and light, does not require multiple waveguides to cooperate, and reduces the processing difficulty.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic devices, and particularly to a grating array, a 3D display device, and a 3D display method. Background Art

[0002] Currently, the mainstream solutions for 3D display are glasses-type and autostereoscopic.

[0003] Typical glasses-type 3D displays include color difference type, polarization type, and active shutter type. They all use the parallax of the human eyes and project the corresponding images for the left and right eyes into the left and right eyes respectively. The brain then integrates these two images into a single image with spatial depth. Since the 3D display achieved by this principle is a spatial stereoscopic effect synthesized by the brain, there will be a feeling of discomfort after watching for a long time.

[0004] The representative of autostereoscopic 3D display is holographic display. Compared with glasses-type 3D displays, its advantage is that it can provide the full physical depth of field and true three-dimensional display. The disadvantage is that the dynamic refresh rate of holographic materials is not high enough to enable large-scale commercial applications.

[0005] Due to the above problems of traditional 3D displays, some institutions such as Magic Leap have tried to use the method of reproducing light fields to achieve scenes with real depth information. Although this enables our brains to process digital objects as naturally as real-world objects and is suitable for long-term use, the overall device is relatively complex and requires multiple layers of waveguides to cooperate. The processing of multiple layers of waveguides is difficult and the technical difficulty is high. Summary of the Invention

[0006] In order to solve the above technical problems, an object of the present invention is to provide a grating array, a 3D display device, and a 3D display method, which are 3D light field display solutions with good display effects.

[0007] According to one aspect of the present invention, there is provided a grating array, including: an input grating array and an output grating array disposed on a waveguide substrate,

[0008] The input grating array couples incident light into the waveguide substrate and maintains the angular phase information of the incident light;

[0009] The output grating array couples the light out of the waveguide substrate and restores the angular phase information of the incident light.

[0010] Compared with the prior art, the liquid crystal cell of the present invention has the following beneficial effects: through the input grating array and the output grating array disposed on the waveguide substrate, the output grating array restores the angular phase information of the incident light. The overall device is thin and light, does not require multiple layers of waveguides to cooperate, and reduces the processing difficulty.

[0011] Further, the input grating array includes a plurality of input gratings, and for the light rays with different incident angles in the incident light, there are corresponding input gratings and output gratings respectively;

[0012] The input grating is used to couple the light rays with the corresponding incident angle into the waveguide substrate, and the light rays propagate in the waveguide substrate at an angle greater than the total reflection angle towards the output grating array, and are coupled and output through the corresponding output grating.

[0013] The beneficial effect of adopting the above further technical solution is that for the light rays with different incident angles in the incident light, there are corresponding input gratings and output gratings respectively. The incident light rays of the light field are divided according to different incident angles. Different angles of light rays are selectively coupled through the input gratings and coupled into the waveguide substrate. The light rays propagate in the waveguide substrate at an angle greater than the total reflection angle towards the output grating array, and then are output from the waveguide substrate through the output grating. This can facilitate the collection of the light rays of the light field, couple all the information of this light field into the waveguide, and then be coupled and output to the human eye through the grating array.

[0014] Further, the input grating and the output grating include a transparent upper substrate and a lower substrate;

[0015] A polymer dispersed liquid crystal material is encapsulated between the upper substrate and the lower substrate, and the polymer liquid crystal material includes a polymer, an initiator, a liquid crystal, and a surfactant;

[0016] On one side of the upper substrate and the lower substrate close to the polymer dispersed liquid crystal material, there is a transparent conductive film. The distribution of the input grating polymer and liquid crystal is adapted to the light rays with the corresponding incident angle, and the light rays with the corresponding incident angle are coupled into the waveguide substrate.

[0017] The beneficial effect of adopting the above further technical solution is that the distribution of the input grating polymer and liquid crystal is adapted to the light rays with the corresponding incident angle, forming a liquid crystal-rich region and a polymer-rich region between the upper and lower substrates. After the conductive film is electrified, the refractive indexes of the liquid crystal-rich region and the polymer-rich region are different, thus forming a grating structure. The period and grating vector of the grating structure change with different diffraction angles, and the light rays with the corresponding incident angle are coupled into the waveguide substrate. The incident angles of the light rays that each input grating in the input grating array needs to couple are different. Therefore, the distribution of the polymer and liquid crystal of each input grating is different. Similarly, the distribution of the polymer and liquid crystal of each output grating is different. When the light rays with the corresponding incident angle are coupled and output, the angular phase information of the incident light rays is restored. Preferably, each input grating can couple the light rays within a cone angle into the waveguide, and there is no need to cooperate with multiple layers of waveguides to reduce costs.

[0018] Further, the liquid crystal is a mixed crystal, the difference between the ordinary light refractive index and the extraordinary light refractive index of the mixed crystal is 0.2 to 0.4, and the refractive index of the polymer is the same as the extraordinary light refractive index of the liquid crystal.

[0019] The beneficial effect of adopting the above further technical solution is that the birefringence of the liquid crystal is 0.2 to 0.4, which can improve the refractive index modulation degree of the entire material system and thus improve the diffraction efficiency of the grating.

[0020] Further, the upper substrate and the lower substrate are encapsulated by a sealant, the sealant is a border glue with a gasket, the gasket is a polystyrene sphere with a diameter not greater than 6 μm, and the border glue is a mixed glue composed of an ultraviolet glue and a thermosensitive glue.

[0021] The beneficial effect of adopting the above further technical solution is that it can control the thickness between the upper substrate and the lower substrate to be not greater than 6 μm, which can make the liquid crystal cell in a transparent state when not working, reduce energy consumption, and the gasket can facilitate the control of the thickness of the liquid crystal cell.

[0022] According to another aspect of the present invention, there is provided a 3D display device, including:

[0023] The grating array according to any one of the above;

[0024] A light source that provides incident light rays capable of forming a three-dimensional light field;

[0025] A spatial light modulator located between the light source and the grating array,

[0026] The incident light rays enter the input grating array of the grating array through the spatial light modulator. The function of the spatial light modulator is to perform intensity modulation on the light rays with different incident angles in the incident light rays by a timing method, and maintain the angular phase information of the light rays in each direction in the three-dimensional light field of the incident light rays.

[0027] Compared with the prior art, the 3D display device of the present invention has the following beneficial effects: The function of the spatial light modulator is to perform intensity modulation on the light rays in each direction of the incident light rays in units of pixels by a timing method, and perform timing arrangement on the light rays with different angles in the incident light rays.

[0028] With the help of a spatial light modulator (SLM), light rays pass through the SLM and become a light field with a certain field of view angle. The grating array can collect the light rays of the light field and couple the light rays of this light field into the waveguide substrate, and then couple and output the light rays to the human eye through the grating array to achieve light field display. By inputting the grating array to maintain the angular phase information of the incident light rays, the waveguide substrate propagates the light rays at an angle greater than the total reflection angle. After the grating couples the light rays into the waveguide substrate, the angular range of total reflection of the light rays is close, the occupied bandwidth is small, and the refractive index requirement for the waveguide substrate is small. The waveguide substrate greater than 1.5 can output a stereoscopic image with a large depth of field and a large field of view angle, without the need for an expensive waveguide substrate with a large refractive index, which can reduce costs. Preferably, the spatial light modulator is a phase type, which can perform phase modulation on light rays, is beneficial to achieving a stereoscopic depth of field effect, and outputs a stereoscopic image with a large depth of field and a large field of view angle.

[0029] Further, both the input gratings included in the input grating array and the output gratings included in the output grating array are m rows and n columns.

[0030] Each light ray emitted by each pixel of the spatial light modulator has an input grating corresponding to its position.

[0031] Each light ray emitted by each pixel of the spatial light modulator is coupled into the optical waveguide substrate through the input grating corresponding to its position.

[0032] The beneficial effect of adopting the above further technical solution is that the input grating and the output grating can be regarded as a liquid crystal cell composed of glass and a transparent conductive film plated on the glass. The liquid crystal cell is filled with a polymer-dispersed liquid crystal material to form a holographic grating. The incident angle of each light ray emitted by each pixel is specific. Each input grating array only needs to couple the light rays emitted by the corresponding pixels on the spatial light modulator (SLM), which is convenient for the grating array to accurately restore the angular phase information of each light ray in the light field; the grating array is used to couple all the light rays in all directions emitted from each point on the SLM image plane to the waveguide substrate, so as to realize that the array grating records the direction information of all the light rays in the entire light field.

[0033] Further, it further includes a control module, and the control module controls the power-on sequence of the spatial light modulator, the input grating, and the output grating, so that only one or one column of input gratings in each row of the input grating array is in the powered-on state at the same time.

[0034] The beneficial effects of adopting the above further technical solution are as follows: it can quickly and accurately control that only one liquid crystal cell in each row is applied with voltage at a moment, and at the same time control that the corresponding output grating is also applied with voltage, which is beneficial to accurately restore the angular phase information of each ray in the light field. Only one liquid crystal cell in each row works simultaneously, so that crosstalk between angles will not occur, and the angular phase information of each ray in the light field can be restored more accurately. The chip model of the control module can be selected as stm8 l.

[0035] Further, the current frequency applied to the input grating and / or output grating is 60mnHZ or 60nHZ, where m is the number of rows of the input grating and n is the number of columns of the input grating.

[0036] The beneficial effects of adopting the above further technical solution are as follows: the larger m and n are, the higher the resolution of the entire 3D display device is, which is beneficial to increasing the resolution of the 3D display device.

[0037] According to another aspect of the present invention, a 3D display method is provided, including the following steps:

[0038] Intensity modulation is performed on the incident light in each direction of the incident light by a timing method;

[0039] The light rays at different angles in the incident light are coupled into the optical waveguide matrix through the corresponding input gratings according to the modulated timing;

[0040] The output grating couples the light rays out of the waveguide matrix and maintains the angular phase information of each light ray in the incident light, thereby realizing three-dimensional display.

[0041] Compared with the prior art, the 3D display method of the present invention has the following beneficial effects: by the timing method, intensity modulation is performed on the incident light in each direction in units of pixels, so that a time difference is generated when light rays at different angles enter the waveguide matrix. Only the angular phase information of one angle of light rays needs to be restored at the same time, and a stereoscopic image with a large depth of field and a large viewing angle can be output without the need to cooperate with multiple waveguides. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic structural diagram of the grating array of the present invention;

[0043] Figure 2 It is a schematic structural diagram of the input grating;

[0044] Figure 3 It is a schematic diagram of the grating array collecting and outputting light rays within a certain angle;

[0045] Figure 4 It is a schematic structural diagram of the 3D display device;

[0046] Figure 5 Schematic diagram of encoding a light source ray output by a spatial light modulator for a 3D object

[0047] Figure 6 Schematic diagram of the corresponding relationship between the pixel points of the spatial light modulator and the input grating

[0048] Figure 7 Schematic diagram of the grating array collecting and outputting light rays

[0049] Figure 8 Schematic diagram of a 3D display device collecting and outputting light rays

[0050] Reference numerals shown in the drawings: 100 - light source; 200 - spatial light modulator; 300 - waveguide substrate; 310 - input grating array; 311 - input grating; 320 - output grating array; 321 - output grating; 400 - human eye; 501 - upper substrate; 502 - transparent conductive film; 503 - border adhesive; 504 - polymer liquid crystal material; 1210 - light ray a; 1211 - light ray c; 1220 - light ray b; 1221 - light ray d; 1310 - light ray e; 1320 - light ray f Detailed implementation manners

[0051] In order to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments

[0052] Embodiment 1:

[0053] As Figure 1 shown, a grating array includes: an input grating array and an output grating array disposed on a waveguide substrate

[0054] The input grating array couples incident light rays into the waveguide substrate and maintains the angular phase information of the incident light rays

[0055] The output grating array couples the light rays out of the waveguide substrate and maintains the angular phase information of the incident light rays. The light rays propagate in the waveguide substrate at an angle greater than the total reflection angle. The output grating array couples the light rays out of the waveguide substrate and restores the angular phase information of the incident light rays, which is beneficial to restoring each light ray in the light field when the light rays enter the human eye

[0056] Furthermore, the input grating array includes a plurality of input gratings. Light rays with different incident angles in the incident light rays each have a corresponding input grating and output grating. The input grating is used to couple the light rays with a corresponding incident angle into the waveguide substrate. The light rays propagate in the waveguide substrate at an angle greater than the total reflection angle towards the output grating array and are coupled out through the corresponding output grating. Specifically, asFigure 2 As shown, the input grating and the output grating include a transparent upper substrate and a lower substrate. A polymer-dispersed liquid crystal material is encapsulated between the upper substrate and the lower substrate. The polymer liquid crystal material includes a polymer, an initiator, a liquid crystal, and a surfactant. On one side of the upper substrate and the lower substrate close to the polymer-dispersed liquid crystal material, there is a transparent conductive film. The distribution of the polymer and the liquid crystal in the input grating is exposed in a laser interference field and is adapted to the light rays with corresponding incident angles. In this embodiment, the distribution of the polymer and the liquid crystal in the input grating is adapted to the light rays with corresponding incident angles, forming a liquid crystal-rich region and a polymer-rich region between the upper and lower substrates. After the conductive film is energized, the refractive indices of the liquid crystal-rich region and the polymer-rich region are different, thus forming a grating structure. The period d and the grating vector k of the grating structure change with different diffraction angles, coupling the light rays with corresponding incident angles into the waveguide substrate. The incident angles of the light rays that each input grating in the input grating array needs to couple are different. Therefore, the distribution of the polymer and the liquid crystal in each input grating is different. Similarly, the distribution of the polymer and the liquid crystal in each output grating is different. When coupling and outputting the light rays with corresponding incident angles, the angular phase information of the incident light rays is restored. The liquid crystal is a mixed crystal, and the difference between the ordinary light refractive index and the extraordinary light refractive index of the mixed crystal is 0.2 - 0.4. The refractive index of the polymer is the same as the extraordinary light refractive index of the liquid crystal. The upper substrate and the lower substrate are encapsulated by a sealant. The sealant is a border glue with a gasket. The gasket is a polystyrene sphere with a diameter not greater than 6 μm. In this embodiment, a polystyrene sphere with a diameter of 5 μm is selected. The border glue is a mixed glue composed of an ultraviolet glue and a thermal-sensitive glue. The polymer liquid crystal material includes 35 - 45 parts of liquid crystal, 35 - 45 parts of polymer, 8 - 12 parts of initiator, and 8 - 12 parts of surfactant. Taking an example, when the total weight of the polymer liquid crystal material is determined to be 5 g, the masses of each component are determined according to the mass ratio of each material: 2 g, 0.5 g, 2 g, 0.5 g, and they are sequentially added to a weighing bottle placed on an electronic balance, and the mixed material is emulsified in a dark room using an ultrasonic emulsifier for 48 hours to obtain. The surfactant is polyoxyethylene sorbitan monooleate, and its function is to reduce the surface tension of the material system and reduce the driving voltage of the material system. The initiator is a dye sensitive to laser, which can absorb the energy of the laser and promote the photopolymerization reaction. Its selection is determined according to the wavelength of the laser. When the excitation light is a 532 nm green laser, the initiator can be rose bengal. When the excitation light is a 632.8 nm red laser, the initiator can be methylene blue. After the conductive film is energized, the input grating couples the light rays with a preset incident angle into the optical waveguide substrate. As an alternative, the input gratings and the output gratings are combined into a two-dimensional array of rows and columns. Each input grating can couple the light rays within a cone angle into the waveguide. For example Figure 3As shown in the figure, a corresponding row of input gratings and output gratings on the grating array 301 is selected, and the corresponding input grating 311 and output grating 321 are selected. The input grating 311 can couple the light rays within a conical angle (the two limiting angle light rays are light ray a 1210 and light ray b 1220 respectively), so that the direction of the incident light rays remains unchanged. These two light rays are diffracted by the input grating 311 into light ray c 1211 and light ray d 1221 and propagate in the waveguide 300 at an angle greater than the total reflection angle. When reaching the output grating 321, the output light rays e 1310 and light ray f 1320 are output. The exit angles of light ray e 1310 and light ray f 1320 are symmetric with respect to the normal line to the incident angles of light ray a 1210 and light ray b 1220 respectively. At this time, only the gratings 311 and 321 are working. Therefore, the light rays propagating in the waveguide will not be diffracted when reaching the gratings 312 and 322, and still continue to propagate by total reflection. Through the input grating array and output grating array provided on the waveguide substrate, the angle and phase information of the incident light rays are restored. The overall device is thin and light, does not require multiple waveguides to cooperate, and reduces the processing difficulty.

[0057] As Figure 4 shown, this embodiment provides a 3D display device applying the above grating array. In addition to the grating array, it further includes: a light source, which provides incident light rays that can form a three-dimensional light field; a spatial light modulator located between the light source and the grating array. The incident light rays enter the input grating array of the grating array through the spatial light modulator. The function of the spatial light modulator is to modulate the intensity of the light rays with different incident angles in the incident light rays by a timing method, and maintain the angle and phase information of the light rays in each direction in the three-dimensional light field of the incident light rays, so that the light source can reproduce the light field of a three-dimensional object, such as Figure 5 , 6As shown, assume that a three-dimensional object ABCD is located behind the SLM. Arbitrarily select three points on the SLM. The light rays emitted from the three vertices A / B / D of the three-dimensional object pass through these three points on the SLM. These three points on the SLM modulate the light rays of the three vertices A / B / D respectively. The human eye can observe the stereoscopic information of the three vertices A / B / D on the SLM. With the help of a spatial light modulator (SLM), the light rays pass through the SLM and become a light field with a certain field of view angle. After the light rays in the 3D light field are phase-modulated by the spatial light modulator, they are irradiated on the input grating array of the waveguide substrate. According to the distance between the SLM and the liquid crystal cell array of the input grating array and the angular bandwidth of the liquid crystal cell, the range of the pixel point area that each grating can couple can be calculated. The grating array can collect the light rays of the light field and couple the light rays of this light field into the waveguide substrate, and then couple and output them into the human eye through the grating array to achieve light field display. In this embodiment, with the help of a spatial light modulator (SLM), preferably, the spatial light modulator is a phase type, which can perform phase modulation on the light rays, facilitating the realization of the stereoscopic depth of field effect and outputting a stereoscopic image with a large depth of field and a large field of view angle. The light rays pass through the SLM and become a light field with a certain field of view angle. The grating array can collect the light rays of the light field and couple the light rays of this light field into the waveguide substrate, and then couple and output them into the human eye through the grating array to achieve light field display. By maintaining the angle and phase information of the incident light rays through the input grating array, the waveguide substrate propagates the light rays at an angle greater than the total reflection angle. After the grating couples the light rays into the waveguide substrate, the angular range of total reflection of the light rays is close, occupying a small bandwidth and requiring a small refractive index for the waveguide substrate. The waveguide substrate only needs to be greater than 1.5 to output a stereoscopic image with a large depth of field and a large field of view angle, without the need for an expensive waveguide substrate with a large refractive index, which can reduce costs. Preferably, the spatial light modulator is a phase type, which can perform phase modulation on the light rays, facilitating the realization of the stereoscopic depth of field effect and outputting a stereoscopic image with a large depth of field and a large field of view angle.

[0058] As Figure 7As shown, both the input gratings included in the input grating array and the output gratings included in the output grating array are m rows and n columns. Only one column of the input gratings in each row of the input gratings is powered on at the same time. Each pixel on the SLM has a corresponding input grating 311 (in actual work, the pixels and the input gratings may not be in a one-to-one correspondence relationship. Each input grating can couple the light rays from a group of pixels, and the incident angles of these light rays can be within the range of the value of b). The polymer-dispersed liquid crystal material of the input grating 311 can allow the light rays with specific angle information emitted by the corresponding pixels on the SLM to pass through directly, and the output grating corresponding to the grating array outputs the light rays identical to the light rays with the specific angle information. The light rays coupled by each input grating 311 are transmitted in the waveguide at different total reflection angles to the optical waveguide substrate. Only one liquid crystal cell in each row of liquid crystal cells is in the working state at the same time. In this embodiment, the control module controls the power-on sequence of the spatial light modulator, the input gratings, and the output gratings. The light rays at different angles in the 3D light field are coupled into the optical waveguide substrate through different input gratings 311 of the input grating array after being modulated by the SLM. When the light rays are conducted to the corresponding input gratings of the output grating array, they are output from the optical waveguide substrate. The exit angles of the output light rays are symmetric about the normal line with the incident angles of the incident light rays (within the allowable error range), restoring the light rays in the 3D light field. Each grating can collect the light rays within a certain cone angle. The grating array has m rows and n columns. The larger m and n are, the higher the system resolution is. Since the light rays collected by each liquid crystal cell are transmitted in the waveguide at different total reflection angles and only one liquid crystal cell is working at the same time, crosstalk between angles will not occur, and the angle and phase information of each light ray in the light field can be restored more accurately.

[0059] A 3D display method includes the following steps:

[0060] Modulate the intensity of the incident light rays in each direction of the incident light rays in units of pixels by a timing method;

[0061] The light rays at different angles in the incident light rays are coupled into the optical waveguide substrate according to the modulated timing;

[0062] The output grating array couples the light rays out of the waveguide substrate, maintains the angular phase information of each light ray in the incident light rays, and realizes three-dimensional display. Specifically, the liquid crystal cell arrays of the input grating array and the output grating array are arranged. A voltage is applied to one or a column of input gratings 311 in the input grating array, so that only one or a column of input gratings in each row of the input grating array is in the energized state at the same time. The input grating 311 is directly coupled into the optical waveguide substrate. At the same time, a voltage is applied to the corresponding output gratings in the output grating array to restore the angular phase information of the light rays directly passing through the input grating 311. Correspondingly, a voltage with a frequency of 60mnHZ or 60nHZ is applied to the grating array, where m is the number of rows of the input grating and n is the number of columns of the input grating. The control module controls the power-on sequence of the spatial light modulator and the liquid crystal cells of the grating array, so that the human eye thinks that the light rays coupled by each input grating 311 arrive at the same time, that is, the 3D light field information modulated by the SLM can be collected. In this embodiment, the light source is a narrow-band LED or a laser light source, and the material selected for the waveguide substrate is heavy flint glass with a high refractive index and a thickness of 0.8 - 1.5 mm. As Figure 8 shown, only a group of corresponding input gratings and output gratings in the grating array are powered on and working at any time. Taking the case where only one input grating is in the energized state at the same time as an example, the power-on working sequence of the input gratings is: x1y1 → x1y2 → …… → x1yn → x2y1 → x2y2 → …… xmy1 → xmy2 → …… xmyn. Correspondingly, the power-on sequence of the output gratings is: x1y1 → x1y2 → …… → x1yn → x2y1 → x2y2 → …… xmy1 → xmy2 → …… xmyn. The light rays at a certain spatial angle are irradiated on a working grating in the input grating array 310, and after being conducted by it, the light rays with the same angle as the incident light rays are output by the corresponding output grating on the output grating array. A voltage with a frequency of more than 60mnHZ is applied to the grating array, so that the human eye thinks that the light rays conducted by each grating arrive at the same time, that is, the 3D light field information modulated by the SLM200 can be collected. By using the timing method, the intensity of the light rays in each direction of the incident light rays is modulated in units of pixels, so that there is a time difference when the light rays at different angles enter the waveguide substrate. Only the angular phase information of the light rays at one angle needs to be restored at the same time, and there is no need to cooperate with multiple waveguides to output a stereoscopic image with a large depth of field and a large viewing angle.

[0063] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solution formed by mutually replacing the above features with the technical features (but not limited to) disclosed in the present application that have similar functions.

Claims

1. A grating array, characterized in that, it includes an input grating array and an output grating array provided on a waveguide substrate; the input grating array couples incident light into the waveguide substrate and maintains the angular phase information of the incident light; the output grating array couples the light out of the waveguide substrate and restores the angular phase information of the incident light; the input grating array includes a plurality of input gratings, and for the light with different incident angles in the incident light, there are corresponding input gratings and output gratings; the input grating is used to couple the light with a corresponding incident angle into the waveguide substrate; the distribution of polymer and liquid crystal in the input grating is adapted to the light with a corresponding incident angle, and a liquid crystal-rich region and a polymer-rich region are formed between the upper and lower substrates. After the conductive film is energized, the refractive indexes of the liquid crystal-rich region and the polymer-rich region are different, thus forming a grating structure. The period d and grating vector k of the grating structure change with different diffraction angles, and the light with a corresponding incident angle is coupled into the waveguide substrate. The incident angles of the light that each input grating in the input grating array needs to couple are different; The input gratings and output gratings are combined into a two-dimensional array in rows and columns, and each input grating can couple the light within a cone angle into the waveguide.

2. The grating array according to claim 1, characterized in that, the light propagates in the waveguide substrate at an angle greater than the total reflection angle towards the output grating array and is coupled out through the corresponding output grating.

3. The grating array according to claim 2, characterized in that, the input grating and output grating include a transparent upper substrate and a lower substrate; a polymer-dispersed liquid crystal material is encapsulated between the upper substrate and the lower substrate, and the polymer-dispersed liquid crystal material includes a polymer, an initiator, a liquid crystal, and a surfactant; transparent conductive films are provided on one side of the upper substrate and the lower substrate close to the polymer-dispersed liquid crystal material. The distribution of polymer and liquid crystal in the input grating is adapted to the light with a corresponding incident angle, and the light with a corresponding incident angle is coupled into the waveguide substrate.

4. The grating array according to claim 3, characterized in that, the liquid crystal is a mixed crystal, the difference between the ordinary light refractive index and the extraordinary light refractive index of the mixed crystal is 0.2 - 0.4, and the refractive index of the polymer is the same as the extraordinary light refractive index of the liquid crystal.

5. The grating array according to claim 3, characterized in that, the upper substrate and the lower substrate are encapsulated by a sealant, the sealant is a border glue with a gasket, the gasket is a polystyrene sphere with a diameter not greater than 6 μm, and the border glue is a mixed glue composed of ultraviolet glue and thermosensitive glue.

6. A 3D display device, characterized in that, it includes: the grating array according to any one of claims 1 - 5; a light source, and the light source provides incident light that can form a three-dimensional light field; A spatial light modulator located between a light source and a grating array, and the incident light enters the input grating array of the grating array through the spatial light modulator. The function of the spatial light modulator is to modulate the intensity of the light with different incident angles in the incident light by a timing method, and maintain the angular phase information of the light in each direction in the three-dimensional light field of the incident light.

7. The 3D display device according to claim 6, wherein, both the input gratings included in the input grating array and the output gratings included in the output grating array are m rows and n columns, and the light emitted from each pixel of the spatial light modulator has an input grating corresponding to its position; the light emitted from each pixel of the spatial light modulator is coupled into the optical waveguide substrate through the input grating corresponding to its position.

8. The 3D display device according to claim 7, wherein, it further includes a control module; the control module controls the power-on sequence of the spatial light modulator, the input gratings, and the output gratings, so that only one or a column of input gratings in each row of the input grating array is in the powered-on state at the same time.

9. The 3D display device according to claim 7, wherein, the current frequency applied to the input grating and / or the output grating is 60mnHZ or 60nHZ, where m is the number of rows of the input grating and n is the number of columns of the input grating.

10. A 3D display method, wherein, for use in the 3D display device according to any one of claims 6-9; including the following steps: modulating the intensity of the light in each direction of the incident light by a timing method; the light with different angles in the incident light is coupled into the optical waveguide substrate through the corresponding input gratings according to the modulated timing; the output grating couples the light out of the waveguide substrate and maintains the angular phase information of each light ray in the incident light, thereby realizing three-dimensional display.

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