Augmented reality near-to-eye display system based on pixelated harmonic diffraction element

Abstract

The invention belongs to the technical field of display, and particularly provides an augmented reality near-to-eye display system based on a pixelated harmonic diffraction element, which comprises a color transparent display screen and a pixelated harmonic diffraction element which are closely arranged, and is characterized in that the color transparent display screen consists of a plurality of image pixels and is used for displaying a target image; light containing target image information is emitted to the pixelated harmonic diffraction element; the pixelated harmonic diffraction element is generated by dispersing a harmonic diffraction element pixel by pixel and consists of a plurality of discrete structural pixels, and the structural pixels are aligned with image pixels on the color transparent display screen one by one; each structural pixel on the pixelated harmonic diffraction element directionally diffracts light rays emitted by the image pixels on the aligned color transparent display screen to the crystalline lens optical center of the human eye and finally reaches the retina, the retina projection color near-to-eye display effect is formed, a complex projection light path in an existing augmented reality near-to-eye display system is avoided, and the display effect of the augmented reality near-to-eye display system is improved. The device has the advantages of simple structure, small size and light weight.

Description

Technical Field

[0001] The present invention belongs to the field of display technology, and in particular relates to an augmented reality near-eye display system based on a pixelated harmonic diffraction element. Background Art

[0002] Augmented reality near-eye display is a new interactive window that integrates virtual digital information and real physical information. It is widely used in military training, industrial manufacturing, surgical navigation and other fields due to its characteristics of virtual-real fusion, three-dimensional immersion, and real-time interaction. It is expected to become the next generation of human-computer interactive display platform. The optical module is the core component of the augmented reality near-eye display. Its performance is a key factor that directly affects the imaging quality and interactive experience. The design of the optical module needs to take into account the visual characteristics of the human eye and the requirements of ergonomics, and comprehensively consider important indicators such as field of view, eye movement range, light efficiency, angular resolution, component transmittance, distortion, volume and quality. From the current status of technological development, augmented reality near-eye display technology mostly adopts binocular parallax stereoscopic perspective display mode, and uses different types of optical modules (free-form optical components / geometric optical waveguides / diffraction optical waveguides / holographic optical waveguides as the mainstream) to fuse real scenes with virtual images. However, when it comes to consumer-level applications, augmented reality near-eye display optical modules still generally have their own limitations. For example, the field of view and size are balanced when designing free-form surface structures, and optical waveguide structures can achieve thin and light systems but the field of view is limited. In addition, there are problems such as low display quality, small depth range, and visual fatigue caused by the contradiction between convergence and focusing. Therefore, it will become very important to overcome these limitations through innovative optical architectures, innovative model designs, and the use of new principle optical components. Metasurface is an array of sub-wavelength electromagnetic control units arranged in an artificial way on a two-dimensional plane. It can arbitrarily control the amplitude, phase, polarization, and frequency parameters of light waves. It has the advantages of ultra-thinness, planarization, low loss, and easy integration. It is generally considered to be the next generation of new optical components. With the powerful light field control ability and the special advantages of thinness and flatness of metasurfaces, it can provide new solutions to break through the bottleneck problems of existing near-eye display systems. Therefore, metasurface optical technology is expected to become a powerful platform for researching and improving augmented reality near-eye displays.

[0003] At present, researchers at home and abroad have conducted exploratory research and beneficial attempts to apply metasurfaces in the field of augmented reality near-eye display. For example, in 2017, C. Hong et al. from the University of Washington in the United States first proposed a design scheme for an augmented reality near-eye display system based on a microdisplay and a metasurface. Compared with the near-eye display system based on a free-form reflector, the system has the advantages of small size and large field of view. However, the system can only respond to red light and cannot achieve color display. Later, in 2021, E. Bayati et al. from the same group at the University of Washington in the United States improved the above scheme and proposed a design scheme for an achromatic augmented reality near-eye display system based on a composite metasurface, in which the metasurface close to the human eye realizes an achromatic phase distribution for reflecting light from the display; the other metasurface is used to avoid the distortion of the real light field information caused by the achromatic metasurface, and has the advantages of large field of view, small volume, and achromaticity. However, the internal structure of the composite metasurface is complex and the characteristic size is extremely small, which leads to its complex manufacturing process and expensive processing cost. At the same time, the two-sided metasurface needs to be precisely aligned during the manufacturing process, which further increases the processing difficulty of the composite metasurface. In addition, Chinese patent 201811187305.2 discloses an augmented reality near-eye display system based on an ultra-microstructure, wherein the ultra-microstructure has a semi-transparent and semi-reflective function, which is used to reflect and converge the light emitted by the microdisplay to the pupil of the human eye, thereby achieving the effect of augmented reality near-eye display. However, the above three schemes all adopt a reflective optical system design, resulting in a large space between the microdisplay and the metasurface, which hinders the further reduction of the volume of the near-eye display system. In addition, Chinese patent 202210019355.X discloses a metasurface micro-nano near-eye display based on retinal display, including a transparent micro-display image source, a metasurface micro-nano focusing lens group, and a metasurface micro-nano compensation lens group, which has the advantages of large field of view and small volume. The ultra-surface micro-nano focusing lens group focuses the light beam information emitted by the transparent micro-display image source on the optical center of the human eye lens, and finally reaches the retina for imaging; the ultra-surface micro-nano compensation lens group can offset the focusing effect of the ultra-surface micro-nano focusing lens group, so that the light emitted by objects in the real external environment can enter the human eye normally without lens effect after passing through the ultra-surface micro-nano compensation lens group and the ultra-surface micro-nano focusing lens group; the pixel of the transparent micro-display image source is composed of three sub-pixels of red, green and blue, and the nano-column array of a single pixel on the ultra-surface micro-nano focusing lens layer corresponds to the pixel of a transparent micro-display image source, thereby realizing achromatic color display. However, the structure of the ultra-surface micro-nano lens group is complex and delicate, and in order to accurately modulate the phase, the length, width and rotation angle of the nano-columns of different pixels must be different, which makes the preparation of the structure extremely difficult and the processing cost expensive.In addition, the principle of achieving achromatic aberration in this scheme is that the nanocolumn array of a single metasurface pixel partitions and modulates the phase of the light emitted by the three sub-pixels of red, green and blue, thereby achieving the effect of dispersion suppression. However, the micro-display image source composed of multiple sub-pixels often has a low resolution and is difficult to achieve high-resolution display. In addition, when facing a micro-display image source with a single pixel wide spectrum light emission, this scheme is difficult to achieve a good achromatic aberration effect, which greatly limits the practicality of the scheme. On this basis, an augmented reality near-eye display system based on pixelated harmonic diffraction elements is proposed. Summary of the invention

[0004] The present invention mainly provides an augmented reality near-eye display system based on pixelated harmonic diffraction elements, which overcomes the common problems of high processing difficulty and high processing cost of achromatic metasurface optical devices used in augmented reality near-eye display systems at this stage, and aims to provide a low-cost, easy-to-process achromatic metasurface optical device, which cooperates with a color transparent display screen to achieve a large field of view, small volume, and achromatic augmented reality color near-eye display effect.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is:

[0006] An augmented reality near-eye display system based on a pixelated harmonic diffraction element comprises a color transparent display screen and a pixelated harmonic diffraction element which are arranged closely together, wherein the pixelated harmonic diffraction element is close to a human eye side, and the color transparent display screen is close to a real object side;

[0007] The color transparent display screen is composed of a plurality of image pixels, and is used to display a target image, and emits light containing target image information to be incident on a pixelated harmonic diffraction element;

[0008] The pixelated harmonic diffraction element is generated by discretizing the harmonic diffraction element pixel by pixel, and is composed of a plurality of discrete structural pixels, and the structural pixels are aligned one by one with the image pixels on the color transparent display screen;

[0009] Each structural pixel on the pixelated harmonic diffraction element diffracts the light emitted by the image pixel on the aligned color transparent display screen in a direction to the optical center of the lens of the human eye and finally reaches the retina, thereby forming the effect of retinal projection color near-eye display.

[0010] A further improvement is that the size of the structure pixel is equal to the size of the image pixel on the color transparent display screen, and the spacing between adjacent structure pixels is equal to the spacing between adjacent image pixels on the color transparent display screen.

[0011] A further improvement is that the design steps of the pixelated harmonic diffraction element are as follows:

[0012] S1: Determination of harmonic diffraction conditions: Determine the design main wavelength λ according to the luminous spectrum of the color transparent display m Harmonic diffraction coefficient P m Then, the harmonic diffraction condition is determined according to the harmonic diffraction achromatic principle, that is, the harmonic diffraction wavelength λ h Harmonic diffraction order P h :

[0013] λ m P m =λ h P h

[0014] S2: Phase calculation of the harmonic diffraction element: Establish the coordinate system of the display plane and the observation plane, record the distance between the two planes as d, record any position on the display plane as A(x,y,0), record the position of the optical center of the human eye lens on the observation plane as B(0,0,d), and then calculate the phase distribution of the harmonic diffraction element for:

[0015]

[0016] Wherein, mod(·) represents the remainder operation;

[0017] S3: Continuous morphology acquisition of harmonic diffraction element: Select the material of the harmonic diffraction element and calculate the refractive index n of the material. m Calculate the maximum structural height h of the harmonic diffraction element max for:

[0018]

[0019] Therefore, the height distribution h(x,y,0) of the harmonic diffraction element can be obtained as:

[0020]

[0021] That is the continuous morphology of the harmonic diffraction element;

[0022] S4: Stepping of harmonic diffraction elements: Establish the mapping relationship between the number of quantized steps of the harmonic diffraction element structure height and the diffraction efficiency, determine the number of steps N by comprehensively considering factors such as diffraction efficiency and processing accuracy, and then quantify the height distribution h(x, y, 0) of the harmonic diffraction element to obtain the stepped height distribution of the harmonic diffraction element. for:

[0023]

[0024] This is the multi-step morphology of the harmonic diffraction element, where round(·) represents the rounding operation;

[0025] S5: Discrete pixelation of harmonic diffraction element: Discrete the designed harmonic diffraction element according to the pixel size and pixel spacing of the color transparent display screen. Specifically, the color transparent display screen is used as a binary mask BM (x, y, 0), that is, the element value corresponding to the coordinate within the image pixel area is 1, and the element value corresponding to the coordinate outside the image pixel area is 0. Then, the stepped height distribution of the harmonic diffraction element is used. Multiplying by the binary mask BM(x,y,0) gives the height distribution of the pixelated harmonic diffraction element: for:

[0026]

[0027] At this point, the overall design of the pixelated harmonic diffraction element is completed.

[0028] A further improvement is that the light corresponding to the designed main wavelength and the harmonic diffraction wavelength emitted by each image pixel will propagate in the same direction after harmonic diffraction by the aligned structural pixels, thereby achieving an achromatic display effect.

[0029] A further improvement is that the color transparent display screen and the pixelated harmonic diffraction element have the function of transmitting the light emitted by real objects, so that the light emitted by real objects can also enter the human eye and eventually reach the retina, thereby realizing the superposition and fusion of the real object image and the image displayed on the color transparent display screen on the retina, forming an augmented reality color near-eye display effect.

[0030] A further improvement is that the color transparent display screen is any one of an organic light emitting diode display, a micron-level organic light emitting diode display, a micron-level inorganic light emitting diode display, and a nanometer-level inorganic light emitting diode display.

[0031] A further improvement is that the material of the pixelated harmonic diffraction element is quartz glass or K9 glass.

[0032] A further improvement is that the minimum feature size of the microstructure on the pixelated harmonic diffraction element is greater than 300 nm.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The augmented reality near-eye display system of the present invention is formed by closely attaching a color transparent display screen and a pixelated harmonic diffraction element, avoiding the complex projection optical path in the existing augmented reality near-eye display system, and has a simple structure, small size and light weight;

[0035] 2. The augmented reality near-eye display system of the present invention has an appearance similar to that of ordinary eyeglass lenses, and the pixelated harmonic diffraction element is close to one side of the human eye, thereby effectively reducing the exit pupil distance and expanding the field of view of the near-eye display;

[0036] 3. Compared with the retinal projection display method based on laser scanning technology, the structural pixels on the pixelated harmonic diffraction element of the present invention are aligned one by one with the image pixels on the transparent display screen, so that the light emitted by each image pixel on the color transparent display screen is directionally diffracted to the optical center of the lens of the human eye and finally reaches the retina, thereby forming a retinal projection display effect, avoiding the safety problem of laser focusing on the optical center of the lens, and improving the safety of use;

[0037] 4. The pixelated harmonic diffraction element in the present invention can guide the light corresponding to the designed main wavelength and the harmonic diffraction wavelength into the optical center of the human eye lens in the same direction and finally reach the retina, thereby achieving an achromatic display effect, solving the problem that the existing super-surface micro-nano near-eye display cannot adapt to the micro-display image source of single-pixel wide-spectrum luminescence;

[0038] 5. Compared with other metasurface optical devices used in augmented reality near-eye display systems, the pixelated harmonic diffraction element in the present invention has a larger characteristic size and does not require expensive electron beam lithography technology during processing, which helps to reduce processing difficulty and cost.

[0039] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of an augmented reality near-eye display system based on a pixelated harmonic diffraction element proposed by the present invention;

[0041] Figure 2 A schematic diagram of aligning a structural pixel on a pixelated harmonic diffraction element of the present invention with an image pixel on a color transparent display screen;

[0042] Figure 3 is a design flow chart of the pixelated harmonic diffraction element of the present invention;

[0043] Figure 4 A diagram showing the positional relationship between the display plane and the observation plane of the present invention;

[0044] Figure 5 A schematic diagram of light propagation of light of different wavelengths after passing through a pixelated harmonic diffraction element according to the present invention;

[0045] Figure 6 is the height distribution of the pixelated harmonic diffraction element in a specific embodiment of the present invention;

[0046] Figure 7 It is a partially enlarged three-dimensional distribution diagram of a 2mm×2mm area in the center of a pixelated harmonic diffraction element in a specific embodiment of the present invention.

[0047] Among them, 1-color transparent display screen; 101-image pixel; 2-pixelated harmonic diffraction element; 201-structural pixel. DETAILED DESCRIPTION

[0048] In order to facilitate understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings, in which several embodiments of the present invention are given, but the present invention can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the content disclosed by the present invention more thorough and comprehensive.

[0049] Reference Figure 1-7 The present invention proposes an augmented reality near-eye display system based on pixelated harmonic diffraction elements. Figure 1 As shown, it includes a color transparent display screen 1 and a pixelated harmonic diffraction element 2;

[0050] The color transparent display screen 1 is composed of a plurality of image pixels 101 and is used for displaying a target image. The light beam containing the target image information is emitted and incident on the pixelated harmonic diffraction element 2 .

[0051] The pixelated harmonic diffraction element 2 is generated by discretizing the harmonic diffraction element pixel by pixel, and can be regarded as composed of a plurality of discrete structural pixels 201. The structural pixels 201 are aligned one by one with the image pixels 101 on the color transparent display screen 1, as shown in FIG. Figure 2 As shown, the size of the structure pixel 201 is equal to the size of the image pixel 101 on the color transparent display screen 1 , and the spacing between adjacent structure pixels 201 is equal to the spacing between adjacent image pixels 101 on the color transparent display screen 1 .

[0052] The design process of the pixelated harmonic diffraction element 2 is as follows: Figure 3 As shown, the specific steps are as follows:

[0053] S1: Determination of harmonic diffraction conditions: Determine the design main wavelength λ according to the luminous spectrum of the color transparent display screen 1 m Harmonic diffraction coefficient P m Then, the harmonic diffraction condition is determined according to the harmonic diffraction achromatic principle, that is, the harmonic diffraction wavelength λ h Harmonic diffraction order P h :

[0054] λ m P m =λ h P h

[0055] S2: Phase calculation of harmonic diffraction element: Establish the coordinate system of the display plane and the observation plane, such as Figure 4As shown, the distance between the two planes is recorded as d, any position on the display plane is recorded as A(x,y,0), and the position of the optical center of the human eye lens on the observation plane is recorded as B(0,0,d). Then the phase distribution of the harmonic diffraction element is calculated. for:

[0056]

[0057] Wherein, mod(·) represents the remainder operation.

[0058] S3: Continuous morphology acquisition of harmonic diffraction element: Select the material of the harmonic diffraction element and calculate the refractive index n of the material. m Calculate the maximum structural height h of the harmonic diffraction element max for:

[0059]

[0060] Therefore, the height distribution h(x,y,0) of the harmonic diffraction element can be obtained as:

[0061]

[0062] That is the continuous morphology of the harmonic diffraction element.

[0063] S4: Stepping of harmonic diffraction elements: Establish the mapping relationship between the number of quantized steps of the harmonic diffraction element structure height and the diffraction efficiency, determine the number of steps N by comprehensively considering factors such as diffraction efficiency and processing accuracy, and then quantify the height distribution h(x, y, 0) of the harmonic diffraction element to obtain the stepped height distribution of the harmonic diffraction element. for:

[0064]

[0065] This is the multi-step morphology of the harmonic diffraction element, where round(·) represents a rounding operation.

[0066] S5: Discrete pixelation of harmonic diffraction element: Discrete the designed harmonic diffraction element according to the pixel size and pixel spacing of the color transparent display screen 1. Specifically, the color transparent display screen 1 is used as a binary mask BM (x, y, 0), that is, the element value corresponding to the coordinate within the image pixel 101 area is 1, and the element value corresponding to the coordinate outside the image pixel 101 area is 0. Then, the step height distribution of the harmonic diffraction element is used. Multiplying by the binary mask BM(x,y,0) gives the height distribution of the pixelated harmonic diffraction element: for:

[0067]

[0068] At this point, the overall design of the pixelated harmonic diffraction element 2 is completed.

[0069] In a preferred embodiment, each structural pixel 201 on the pixelated harmonic diffraction element 2 directionally diffracts the light emitted by the image pixel 101 on the aligned color transparent display screen 1 to the optical center of the lens of the human eye and finally reaches the retina, thereby forming the effect of retinal projection color near-eye display.

[0070] In a preferred embodiment, the pixelated harmonic diffraction element 2 is placed closely to the color transparent display screen 1, wherein the pixelated harmonic diffraction element 2 is close to the human eye side and the color transparent display screen 1 is away from the human eye side, that is, close to the real object side.

[0071] In a preferred embodiment, Figure 5 As shown, the light corresponding to the designed main wavelength and the harmonic diffraction wavelength emitted by each image pixel 101 will propagate in the same direction after being harmonically diffracted by the aligned structure pixel 201, thereby achieving an achromatic display effect. The light emitted by different image pixels 101 on the color transparent display screen 1 is directionally diffracted by the aligned structure pixel 201 and finally forms a viewpoint at the optical center of the lens of the human eye, thereby forming a retinal projection near-eye display effect.

[0072] In a preferred embodiment, the color transparent display screen 1 and the pixelated harmonic diffraction element 2 both have the function of transmitting light emitted by real objects, so that the light emitted by real objects can also enter the human eye and eventually reach the retina, thereby realizing the superposition and fusion of the real object image and the image displayed on the color transparent display screen 1 on the retina, thereby forming an augmented reality color near-eye display effect.

[0073] In the above technical solution, the color transparent display screen 1 is any one of an organic light emitting diode display (OLED), a micron-level organic light emitting diode display (Micro-OLED), a micron-level inorganic light emitting diode display (Micro-LED), and a nano-level inorganic light emitting diode display (Nano-LED).

[0074] In a preferred embodiment, the material of the pixelated harmonic diffraction element 2 is quartz glass or K9 glass.

[0075] In a preferred embodiment, the minimum feature size of the microstructure on the pixelated harmonic diffraction element 2 is greater than 300 nm.

[0076] Based on the above implementation, the color transparent display screen 1 in this embodiment is composed of 1136×640 image pixels 101, the size of each image pixel 101 is 36um×36um, and the spacing between adjacent image pixels 101 in the horizontal and vertical directions is 40um, then the pixelated harmonic diffraction element 2 is composed of 1136×640 different structural pixels 201, and the size of each structural pixel 201 is also 36um×36um, and the spacing between adjacent structural pixels 201 in the horizontal and vertical directions is also 40um. The luminous spectrum of the color transparent display screen 1 covers three bands of red, green and blue. We record the spectral range with a normalized transmission intensity greater than 0.5 as a highlight band, so the highlight bands of the red, green and blue spectra are 608-650nm, 505-550nm and 438-465nm respectively. The design main wavelength of the pixelated harmonic diffraction element 2 is set to 525nm, and the harmonic diffraction coefficient is 6. According to the corresponding formula, it can be calculated that when the harmonic diffraction order is 5, the harmonic diffraction wavelength is 630nm; when the harmonic diffraction order is 7, the harmonic diffraction wavelength is 450nm, so that after the directional diffraction of the pixelated harmonic diffraction element 2, the fifth-order diffraction light with a wavelength of 630nm, the sixth-order diffraction light with a wavelength of 525nm, and the seventh-order diffraction light with a wavelength of 450nm will propagate in the same direction into the optical center of the lens of the human eye and finally reach the retina, thereby achieving an achromatic color display effect. The material of the pixel grating array device 2 is K9 glass, and the refractive index is 1.523. It is assumed that the human eye is located on the central axis of the color transparent display screen 1, and the observation distance from the color transparent display screen 1 is 25mm. According to the calculation formula of the maximum structural height of the harmonic diffraction element, the maximum structural height h of the harmonic diffraction element can be calculated. max The quantized step number N of the harmonic diffraction element structure height is set to 256. Figure 3 After the design process of the pixelated harmonic diffraction element 2 shown in FIG. 1 , the height distribution of the designed pixelated harmonic diffraction element 2 can be obtained as shown in FIG. Figure 6 As shown, the local enlarged three-dimensional distribution diagram of the 2mm×2mm area in the center of the pixelated harmonic diffraction element 2 is as shown Figure 7 So far, the overall design of the pixelated harmonic diffraction element 2 is completed.

[0077] A preferred manufacturing process of the pixelated harmonic diffraction element 2 in this embodiment is as follows: first, the glass substrate is strictly cleaned, and then photoresist is coated on the surface of the substrate by spin coating to form a uniform photoresist layer, and then the pixelated harmonic diffraction element pattern is manufactured by laser direct writing photolithography technology to form a photoresist mask, and then the above-mentioned photoresist mask is pattern-transferred by ion beam etching technology. After the etching is completed, a pixelated harmonic diffraction element pattern is formed on the surface of the glass substrate, that is, an etched element, and finally the remaining photoresist on the top of the etched element is removed and cleaned, thereby completing the manufacture of the pixelated harmonic diffraction element 2.

[0078] Afterwards, the manufactured pixelated harmonic diffraction element 2 and the color transparent display screen 1 are integrated and adjusted under a microscope. When it is observed that the structural pixels 201 on the pixelated harmonic diffraction element 2 are aligned one by one with the image pixels 101 on the color transparent display screen 1, the positions of the color transparent display screen 1 and the pixelated harmonic diffraction element 2 are fixed, and then they are bonded and cured with glue, thereby forming an augmented reality color near-eye display system based on the color transparent display screen and the pixelated harmonic diffraction element.

[0079] The light emitted by each image pixel 101 on the color transparent display screen 1 is directionally diffracted by the corresponding structural pixel 201 on the pixelated harmonic diffraction element 2, and the light corresponding to the designed main wavelength and the harmonic diffraction wavelength will propagate in the same direction into the optical center of the lens of the human eye and finally reach the retina, thereby achieving the effect of achromatic retinal projection color near-eye display. At the same time, the light emitted by the real object successively passes through the color transparent display screen 1 and the pixelated harmonic diffraction element 2 into the human eye, and finally reaches the retina to form the image of the real object. The real object image on the retina is superimposed and fused with the image displayed on the color transparent display screen 1, and finally the effect of augmented reality color near-eye display is achieved.

[0080] In this embodiment, the display size of the color transparent display screen 1 is 45.44 mm×25.6 mm, the observation distance is 25 mm, and the calculated horizontal, vertical and diagonal field of view angles are 84.53°, 54.22° and 92.42°, respectively, which illustrates that the augmented reality near-eye display system based on pixelated harmonic diffraction elements proposed in the present invention has the advantage of a large field of view angle.

[0081] In summary, the present invention discloses an augmented reality near-eye display system based on a pixelated harmonic diffraction element. In the present invention, the augmented reality near-eye display system is formed by only two components, a color transparent display screen and a pixelated harmonic diffraction element, which are closely attached to each other. The appearance is similar to that of ordinary eyeglass lenses, avoiding complex projection light paths, and having the advantages of small size, light weight, and a large field of view. At the same time, since the pixelated harmonic diffraction element has achromatic characteristics, the system can achieve the effect of augmented reality color near-eye display. In addition, compared with other metasurface optical devices used in augmented reality near-eye display systems, the pixelated harmonic diffraction element in the present invention is a low-cost, easy-to-process metasurface optical device, which does not require expensive electron beam lithography technology during processing, thereby effectively reducing the processing difficulty and processing cost.

[0082] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An augmented reality near-eye display system based on pixelated harmonic diffraction elements, characterized in that: It comprises a color transparent display screen and a pixelated harmonic diffraction element which are closely arranged, wherein the pixelated harmonic diffraction element is close to a human eye side, and the color transparent display screen is close to a real object side; The color transparent display screen is composed of a plurality of image pixels, and is used to display a target image, and emits light containing target image information to be incident on a pixelated harmonic diffraction element; The pixelated harmonic diffraction element is generated by discretizing the harmonic diffraction element pixel by pixel, and is composed of a plurality of discrete structural pixels, and the structural pixels are aligned one by one with the image pixels on the color transparent display screen; Each structural pixel on the pixelated harmonic diffraction element diffracts the light emitted by the image pixel on the aligned color transparent display screen in a direction to the optical center of the lens of the human eye and finally reaches the retina, thereby forming the effect of retinal projection color near-eye display.

2. The augmented reality near-eye display system based on pixelated harmonic diffraction element according to claim 1, characterized in that: The size of the structure pixel is equal to the size of the image pixel on the color transparent display screen, and the spacing between adjacent structure pixels is equal to the spacing between adjacent image pixels on the color transparent display screen.

3. The augmented reality near-eye display system based on pixelated harmonic diffraction element according to claim 1, characterized in that: The design steps of the pixelated harmonic diffraction element are as follows: S1: Determination of harmonic diffraction conditions: Determine the design main wavelength λ according to the luminous spectrum of the color transparent display m Harmonic diffraction coefficient P m Then, the harmonic diffraction condition is determined according to the harmonic diffraction achromatic principle, that is, the harmonic diffraction wavelength λ h Harmonic diffraction order P h : l m P m =λ h P h S2: Phase calculation of the harmonic diffraction element: Establish the coordinate system of the display plane and the observation plane, record the distance between the two planes as d, record any position on the display plane as A(x,y,0), record the position of the optical center of the human eye lens on the observation plane as B(0,0,d), and then calculate the phase distribution of the harmonic diffraction element for: Among them, mod(·) represents the remainder operation; S3: Continuous morphology acquisition of harmonic diffraction element: Select the material of the harmonic diffraction element and calculate the refractive index n of the material. m Calculate the maximum structural height h of the harmonic diffraction element max for: Therefore, the height distribution h(x,y,0) of the harmonic diffraction element can be obtained as: That is the continuous morphology of the harmonic diffraction element; S4: Stepping of harmonic diffraction elements: Establish the mapping relationship between the number of quantized steps of the harmonic diffraction element structure height and the diffraction efficiency, determine the number of steps N by comprehensively considering factors such as diffraction efficiency and processing accuracy, and then quantify the height distribution h(x, y, 0) of the harmonic diffraction element to obtain the stepped height distribution of the harmonic diffraction element. for: This is the multi-step morphology of the harmonic diffraction element, where round(·) represents the rounding operation; S5: Discrete pixelation of harmonic diffraction element: Discrete the designed harmonic diffraction element according to the pixel size and pixel spacing of the color transparent display screen. Specifically, the color transparent display screen is used as a binary mask BM (x, y, 0), that is, the element value corresponding to the coordinate within the image pixel area is 1, and the element value corresponding to the coordinate outside the image pixel area is 0. Then, the stepped height distribution of the harmonic diffraction element is used. Multiplying by the binary mask BM(x,y,0) gives the height distribution of the pixelated harmonic diffraction element: for: At this point, the overall design of the pixelated harmonic diffraction element is completed.

4. The augmented reality near-eye display system based on pixelated harmonic diffraction element according to claim 1, characterized in that: The light rays corresponding to the designed main wavelength and the harmonic diffraction wavelength emitted by each image pixel will propagate in the same direction after harmonic diffraction by the aligned structural pixels, thereby achieving an achromatic display effect.

5. The augmented reality near-eye display system based on pixelated harmonic diffraction element according to claim 1, characterized in that: The color transparent display screen and the pixelated harmonic diffraction element both have the function of transmitting light emitted by real objects, so that the light emitted by real objects can enter the human eye and eventually reach the retina, thereby realizing the superposition and fusion of the real object image and the image displayed on the color transparent display screen on the retina, forming an augmented reality color near-eye display effect.

6. The augmented reality near-eye display system based on pixelated harmonic diffraction element according to claim 1, characterized in that: The color transparent display screen is any one of an organic light emitting diode display, a micron-level organic light emitting diode display, a micron-level inorganic light emitting diode display, and a nanometer-level inorganic light emitting diode display.

7. The augmented reality near-eye display system based on pixelated harmonic diffraction element according to claim 1, characterized in that: The material of the pixelated harmonic diffraction element is quartz glass or K9 glass.

8. The augmented reality near-eye display system based on pixelated harmonic diffraction element according to claim 1, characterized in that: The minimum characteristic size of the microstructure on the pixelated harmonic diffraction element is greater than 300 nm.

Images