Single-layer color holographic optical waveguide display device

Abstract

This application provides a single-layer color holographic optical waveguide display device. This application enables single-layer waveguide color display by using an internal and external coupling grating that can respond to image light from different fields of view, and by setting the grating periods of the internal and external coupling gratings to be the same, thereby realizing that fields of view corresponding to image light from different fields of view are interconnected. Compared to other optical waveguide color solutions, this application has advantages such as being thinner, having a simpler process, lower cost, and being advantageous for mass production.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority to a Chinese patent application submitted to the National Intellectual Property Administration Patent Office of China on May 7, 2024, with application number 202410552766.4, and with the title of invention "Single-layer color holographic optical waveguide display device," the entirety of which is incorporated herein by means of introduction.

[0002] Each embodiment of this application belongs to the field of AR display technology, and more particularly relates to a single-layer color holographic optical waveguide display device. [Background technology]

[0003] Diffraction optical waveguide display technology is an important development direction in the field of augmented reality (AR). Diffraction optical waveguide display mainly includes two types: surface relief gratings and holographic gratings. Due to the dispersion effect of the diffraction grating, incident light of different wavelengths will have different diffraction angles under the same order of diffraction. That is, image light of different colors will have different angles of transmission by total internal reflection in the waveguide. As a result, the field of view that can be achieved when displaying full color in a single-layer optical waveguide is relatively small, and due to the effect of the same diffraction grating, there are relatively large differences in diffraction efficiency corresponding to different wavelengths, resulting in relatively poor color uniformity of the image.

[0004] Therefore, in order to mitigate or solve the above-mentioned technical problems and realize full-color display of optical waveguides, one conventional technology is to solve the above problems by superimposing multilayer optical waveguides. However, this method requires the design of diffraction gratings so that each layer of optical waveguide corresponds to a different color channel. However, this method has problems such as a complex manufacturing process, high cost, low diffraction efficiency, and a relatively large volume for the multilayer waveguide. Another method is a single-layer waveguide multiplexing grating or a combination of multiple gratings, but this method has a complex design, low diffraction efficiency, and ghost image effects due to dispersion. [Overview of the project] [Means for solving the problem]

[0005] To solve or mitigate problems in the prior art, embodiments of this application provide a single-layer color holographic optical waveguide display device, which includes an image output device, an internal coupling grid, an external coupling grid, and an optical waveguide. The image output device includes a microdisplay and a collimating lens assembly, wherein the microdisplay outputs image light of three wavelengths: red, green, and blue, which is transmitted to an optical waveguide via the collimating lens assembly, and the three wavelengths of image light correspond to different fields of view. Both the internally bonded lattice and the externally bonded lattice are inclined hologram lattices. The lattice periods of the internally coupled lattice and the externally coupled lattice are the same. The internal coupling grating responds to image light of three wavelengths, red, green, and blue, which then propagates to the external coupling grating via the optical waveguide using total internal reflection. Finally, the external coupling grating emits a single-layer color display image in which Bragg angles corresponding to the three wavelengths of red, green, and blue are sequentially arranged and connected.

[0006] In one preferred embodiment of this application, the internal bonding grid and the external bonding grid are both composed of a polymer matrix and a liquid crystal, the refractive index of the polymer matrix is ​​1.45 to 1.65, and the thickness of the internal bonding grid and the external bonding grid is 2 μm to 10 μm. In one preferred embodiment of this application, the apparatus further includes a folding grid, The folded grating is installed in the optical waveguide, the grating period of the folded grating is smaller than the grating periods of the internal coupling grating and the external coupling grating, and the optical vectors of the internal coupling grating, the external coupling grating and the folded grating form a closed triangle.

[0007] In one preferred embodiment of this application, the inclined hologram grids are all transmission-type grids and / or reflection-type volume grids.

[0008] In one preferred embodiment of this application, the inclination angle of the transmissive grid is 45° to 71.5°, and the inclination angle of the reflective grid is 18.5° to 45°.

[0009] In one preferred embodiment of this application, the lattice period of the internal and external bonded lattices is 175 nm to 10 μm.

[0010] In one preferred embodiment of this application, the refractive indices of the internal bonding lattice and the external bonding lattice are 0.01 to 0.1.

[0011] In one preferred embodiment of this application, the thickness of the optical waveguide is 1 mm to 2.5 mm, and the refractive index is 1.5 to 2.0. [Effects of the Invention]

[0012] Compared to conventional technologies, the embodiment of this application provides a single-layer color holographic optical waveguide display device. This application enables single-layer waveguide color display by using an internal and external coupling grating that can respond to image light from different fields of view, and by setting the grating periods of the internal and external coupling gratings to be the same, thereby realizing that fields of view corresponding to image light from different fields of view are interconnected. Compared to other optical waveguide color solutions, this application has advantages such as being thinner, having a simpler process, lower costs, and being advantageous for mass production. [Brief explanation of the drawing]

[0013] The drawings described herein are provided to provide a further understanding of this application and constitute part of this application. The schematic embodiments and descriptions herein are for interpretive purposes only and do not constitute an unreasonable limitation of this application. Hereinafter, several specific embodiments of this application are described in detail in an exemplary but non-restrictive manner with reference to the drawings. The same reference numerals in the drawings indicate the same or similar components or parts. As those skilled in the art should understand, these drawings are not necessarily drawn to scale, and in the drawings, [Figure 1] This is a schematic diagram of the structure of a single-layer color holographic optical waveguide display device according to an embodiment of this application. [Figure 2] This is a schematic diagram of the structure of another single-layer color holographic optical waveguide display device according to an embodiment of this application. [Figure 3] These are schematic diagrams of different field-of-view distributions of microdisplays according to embodiments of this application. [Figure 4] This is a schematic diagram of the structure of a single-layer color holographic optical waveguide display device according to an embodiment of this application. [Figure 5] This is a schematic diagram of the image source display content according to an embodiment of the present application. [Figure 6] Examples (a) and comparative example (b) of Bragg diffraction distributions corresponding to different wavelengths of a transmission volume grating according to the embodiments of this application. [Modes for carrying out the invention]

[0014] To enable those skilled in the art to better understand the solutions of this application, the following clearly and completely describes the technical solutions in the embodiments of this application, linking them with the drawings of the embodiments. Clearly, the embodiments described are only some, and not all, embodiments of this application. All other embodiments derived from the embodiments of this application without the creative effort of those skilled in the art are all within the scope of protection of this application.

[0015] As shown in FIG. 1, an embodiment of the present application provides a single-layer color holographic optical waveguide display device, including an image output device 01, an internal coupling grating 02, an external coupling grating 04, and an optical waveguide 03. The image output device 01 outputs image light of different visual fields. After the image light of different visual fields is diffracted by the internal coupling grating 02, it is incident on the optical waveguide 03 in sequence, propagates to the external coupling grating 04 in the total reflection mode, is diffracted again by the external coupling grating 04, and after being emitted from the optical waveguide 03, enters the human eye for imaging display.

[0016] In an embodiment of the present application, the internal coupling grating 02 internally couples the image light output from the image output device 01 into the optical waveguide 03, transmits it in the form of total reflection within the optical waveguide 03, and when the image light is transmitted to the output end of the optical waveguide 03, it is diffracted again by the external coupling grating 04, and the image light is externally coupled from the optical waveguide 03. Through the design and process fabrication of the hologram grating, different wavelengths are separated in sequence by the diffraction effects of the internal coupling grating 02 and the external coupling grating 04, respectively corresponding Bragg angles, thereby realizing the display of images corresponding to respective colors under different visual fields, that is, the color display of a single optical waveguide 03 can be realized by the internal coupling grating and the external coupling grating.

[0017] Here, both the internal coupling grating 02 and the external coupling grating 04 are hologram gratings formed by polymer dispersed liquid crystal holographic exposure, and the grating periods of the internal coupling grating 02 and the external coupling grating 04 are the same. This embodiment can realize one-dimensional pupil expansion.

[0018] As shown in FIG. 2, the device further includes a folding grating 05. The folding grating 05 is installed on the optical waveguide 03. The grating period of the folding grating 05 is smaller than the grating periods of the internal coupling grating 02 and the external coupling grating 04, and the optical vectors of the internal coupling grating 02, the external coupling grating 04, and the folding grating 05 form a closed triangle.

[0019] In the embodiment of this application, both the internal coupling grid 02 and the external coupling grid 04 are inclined volume grids. The internal coupling grid 02 is responsible for internally coupling image light from different fields of view into the optical waveguide 03, the folding grid 05 expands and transmits light rays within the optical waveguide 03 along the grid direction, and the external coupling grid 04 expands light rays in another direction while simultaneously externally coupling light rays from the optical waveguide 03 to enter the human eye and capture an image. The embodiment of this application can achieve two-dimensional pupil enlargement.

[0020] Similarly, image light from different fields of view passes through a specific grating (optimized for grating period, tilt angle, and material refractive index modulation), allowing the image light from different fields representing the three colors to connect relatively well to form a complete image, achieving higher diffraction efficiency than surface relief gratings.

[0021] Specifically, as shown in Figures 3 and 4, in the embodiment of this application, the image output device 01 is a projection system, which consists of a microdisplay 01-1 and a collimating lens assembly 01-2. Here, the image light output from the microdisplay 01-1 consists of three parts: red (R), green (G), and blue (B), each corresponding to a different field of view, which are designated as view F1, view F2, and view F3. The optical waveguide 03, as an optical propagation carrier, has an incoming light region and an outgoing light region on its surface, the incoming light region corresponding to the internal coupling grating 02, and the outgoing light region corresponding to the external coupling grating 04. When incident light from different fields of view passes through the internal coupling grating 02, it enters the optical waveguide 03 sequentially due to the diffraction effect of the internal coupling grating 02, propagates to the external coupling grating 04 by total internal reflection, and is emitted from the optical waveguide 03 again by diffraction, entering the human eye and taking an image.

[0022] Due to the unique Bragg diffraction properties of holographic gratings, Bragg diffraction exhibits not only directional selectivity but also wavelength selectivity. Grating diffraction can be classified according to the type of grating and the monochromaticity of the light source. According to the grating classification, one is single-crystal Bragg diffraction, and the other is polycrystalline Bragg diffraction. Because the energy of Bragg diffraction is mainly concentrated at low diffraction orders (e.g., 0th, +1, or -1st order), it has relatively high diffraction efficiency and offers a technological advantage in displaying high brightness compared to surface relief grating optical waveguides 03. Furthermore, holographic gratings have different Bragg angles in response to incident light of different wavelengths that are reproduced.

[0023] JPEG2026521293000002.jpg15116

[0024] In the above equation, P is the period of the volume lattice, n is the refractive index of the medium surrounding the volume lattice, and λ r , λ g , λ b These correspond to the wavelengths of incident light in red (R), green (G), and blue (B), respectively, and θ r , θ g , θ b Since each corresponds to a different Bragg angle for incident light, incident light of different wavelengths does not have the effect of being transmitted under different fields of view, meaning that dispersion effects are almost nonexistent.

[0025] In the embodiments of this application, the micro-display image source may be a micro-display projector such as a micro-light-emitting diode (abbreviated as Micro-LED), a micro-organic light-emitting diode (abbreviated as Micro-OLED), or an off-axis optical projection system (abbreviated as LCOS), where the image content displayed by the image source is composed of a combination of three parts: red (R), green (G), and blue (B), each corresponding to a different field of view.

[0026] The hologram grating is composed of a polymer matrix and liquid crystal, manufactured by means of holographic exposure, and the periods of the internal-coupling and external-coupling volume gratings are the same. All of them may be transmission-type or reflection-type volume gratings, or a combination of transmission-type and reflection-type gratings.

[0027] As shown in FIGS. 5 and 6, the hologram grating responds to the wavelengths of three colors, red (R), green (G), and blue (B), in each visual field, and the Bragg angles corresponding to each wavelength are arranged and connected in sequence, ensuring that there is no overlapping situation in the visual fields (for example, for a visual field of 30° in the horizontal direction, θ r 、θ g 、θ b are respectively located within the visual field intervals of (-15°, -5°), (-5°, 5°), and (5°, 15°)).

[0028] In one embodiment of the present application, the hologram grating is an inclined volume grating. Here, the inclination angle of the reflection-type grating is 18.5° to 45°, and the inclination angle of the transmission-type grating is 45° to 71.5°. In one embodiment of the present application, the grating period of the hologram grating is 175 nm to 10 μm. In one embodiment of the present application, the thickness of the hologram grating is 2 μm to 10 μm. In one embodiment of the present application, the average refractive index of the polymer material is 1.45 to 1.65. In one embodiment of the present application, the refractive index of the hologram grating is 0.01 to 0.1. The thickness of the optical waveguide 03 is 1 mm to 2.5 mm, and its refractive index is 1.5 to 2.0, preferably ordinary glass with a refractive index of 1.52. The manufacturing cost is lower than that of high-refractive-index glass, and the glass transmittance is higher than 92%, and the haze is less than 5%.

[0029] The embodiment of this application involves manufacturing a gradient volume grating on a specific polymer material that responds to different wavelengths of red (R), green (G), and blue (B) in different fields of view using a holographic exposure method, and connecting the fields of view corresponding to the red (R), green (G), and blue (B) image light to each other, thereby realizing a single-layer waveguide color display. Compared to other optical waveguide color solutions, this application has advantages such as being thinner, having a simpler process, lower cost, high brightness, and having almost no dispersion, and is also advantageous for mass production.

[0030] Regarding the single-layer color optical waveguide display device according to the embodiment of this application, firstly, unlike other optical waveguide color schemes (current color optical waveguide displays are generally performed by superimposing multilayer optical waveguides or multilayer gratings, both of which cause volume or cost problems, and the multi-wavelength multiplexing scheme has high requirements for the manufacturing process, as well as low diffraction efficiency due to multiplexing and the problem of stray light), this application realizes color display by simply manufacturing a single-layer grating on a single-layer waveguide. By mainly adjusting the grating layout and structural parameters and combining them with polymer materials developed in-house, software simulations show that a connection in the viewing angle is achieved at different wavelengths through the same grating diffraction effect, and ultimately single-layer color optical waveguide display is realized without reducing diffraction efficiency.

[0031] Finally, it should be noted that the embodiments described above are merely for illustrative purposes and do not limit the technical proposal of this application. Although the present application has been described in detail with reference to the embodiments described above, it should be understood by those skilled in the art that the technical proposal described in the embodiments above can still be modified, or some or all of its technical features can be replaced with equivalent ones, but such modifications or replacements do not cause the essence of the technical proposal to deviate from the scope of the technical proposal of each embodiment of this application.

Claims

1. A single-layer color holographic optical waveguide display device comprising an image output device, an internal coupling grid, an external coupling grid, and an optical waveguide, The image output device includes a microdisplay and a collimating lens assembly, wherein the microdisplay outputs image light of three wavelengths: red, green, and blue, which is transmitted to an optical waveguide via the collimating lens assembly, and the three wavelengths of image light correspond to different fields of view. Both the internally bonded lattice and the externally bonded lattice are inclined hologram lattices. The lattice periods of the internally coupled lattice and the externally coupled lattice are the same. A single-layer color holographic optical waveguide display device characterized in that the internal coupling grating responds to image light of three wavelengths, red, green, and blue, and then propagates to the external coupling grating via the optical waveguide in a total internal reflection manner, and finally emits a single-layer color display image via the external coupling grating in which Bragg angles corresponding to the three wavelengths, red, green, and blue, are sequentially arranged and connected.

2. The single-layer color holographic optical waveguide display device according to claim 1, characterized in that both the internal bonding grid and the external bonding grid are composed of a polymer matrix and a liquid crystal, the refractive index of the polymer matrix is ​​1.45 to 1.65, and the thickness of the internal bonding grid and the external bonding grid is 2 μm to 10 μm.

3. The apparatus further includes a folding grid, The single-layer color holographic optical waveguide display device according to claim 1, characterized in that the folded grating is installed in the optical waveguide, the grating period of the folded grating is smaller than the grating periods of the internal coupling grating and the external coupling grating, and the optical vectors of the internal coupling grating, the external coupling grating and the folded grating form a closed triangle.

4. The single-layer color holographic optical waveguide display device according to claim 2, characterized in that the inclined hologram gratings are all transmission gratings and / or reflective volume gratings.

5. The single-layer color holographic optical waveguide display device according to claim 4, characterized in that the inclination angle of the transmissive grating is 45° to 71.5°, and the inclination angle of the reflective grating is 18.5° to 45°.

6. The single-layer color holographic optical waveguide display device according to claim 1, characterized in that the lattice periods of the internal coupling lattice and the external coupling lattice are 175 nm to 10 μm.

7. The single-layer color holographic optical waveguide display device according to claim 1, characterized in that the refractive indices of the internal coupling grating and the external coupling grating are 0.01 to 0.

1.

8. The single-layer color holographic optical waveguide display device according to claim 1, characterized in that the thickness of the optical waveguide is 1 mm to 2.5 mm and the refractive index is 1.5 to 2.0.

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