Optical waveguide with double-sided out-coupling structure

Abstract

The utility model relates to a kind of optical waveguide with double-sided coupling-out structure. Including: waveguide substrate, coupling-in unit, first coupling-out unit and second coupling-out unit, coupling-in unit and first coupling-out unit are located in the first surface of waveguide substrate, second coupling-out unit is set in the second surface of waveguide substrate opposite to first coupling-out unit, and second coupling-out unit is high-reflection-efficiency diffraction structure.Coupling-in unit is configured to couple image light into the waveguide substrate, part of the image light is diffracted by the first coupling-out unit, and the remaining light is reflected by the second coupling-out unit when it reaches the second coupling-out unit.

Description

Technical Field

[0001] This utility model relates to the field of optical waveguide technology, and in particular to an optical waveguide with a double-sided coupling structure. Background Technology

[0002] With the development of augmented reality technology, near-eye display devices have been widely used, and diffractive waveguides, as key optical components, have attracted much attention. In traditional single-sided coupled waveguides, during total internal reflection of the beam, there are non-overlapping areas between adjacent beams, resulting in periodic fluctuations in the intensity of the emitted light, which affects the uniformity of the display.

[0003] Specifically, please see Figure 1 A traditional optical waveguide 100' includes a waveguide substrate 110' with a refractive index of n' and a beam width of w'. During light transmission, due to the limitation of the thickness h' of the waveguide substrate 110', the primary and secondary total internal reflections may not be completely tightly fitted, resulting in the appearance of a dark area A'. The dark area affects the uniformity of light intensity distribution in the coupling area, reducing the display experience.

[0004] Existing solutions have certain limitations, such as increasing the beam width reducing energy utilization, reducing waveguide thickness being limited by mechanical strength, and increasing the refractive index being limited by material selection. Utility Model Content

[0005] This invention provides an optical waveguide with a double-sided coupling structure to improve the display effect of augmented reality display devices.

[0006] This utility model provides an optical waveguide with a double-sided coupling structure, comprising: a waveguide substrate, a coupling unit, a first coupling unit, and a second coupling unit. The coupling unit and the first coupling unit are located on a first surface of the waveguide substrate, and the second coupling unit is disposed on a second surface of the waveguide substrate opposite to the first coupling unit. The second coupling unit is a high-reflection-efficiency diffraction structure. The coupling unit is configured to couple image light into the waveguide substrate. A portion of the image light is diffracted and emitted by the first coupling unit, while the remaining light, upon reaching the second coupling unit, undergoes reflective diffraction and zero-order reflection before being diffracted and emitted by the first coupling unit.

[0007] Preferably, the first coupling unit is a periodic nanograting, including a plurality of periodically arranged grating ridges and grating slots between adjacent grating ridges, and the second coupling unit is a periodic nanograting with the same period as the first coupling unit, and the grating ridges of the second coupling unit are aligned with the grating ridges of the first coupling unit.

[0008] Preferably, the period of the first coupling unit is 200-600 nanometers, and the duty cycle of the grating is 1%-60%.

[0009] Preferably, the second coupling unit is a dielectric grating, and the surface of the second coupling unit is covered with a metal reflective layer.

[0010] Preferably, the second coupling unit is a high refractive difference all-dielectric grating, which adopts a Ta2O5 / SiO2 periodic multilayer film structure.

[0011] Preferably, the waveguide substrate is made of one of glass, polycarbonate, lithium niobate, and silicon carbide, with a refractive index ranging from 1.5 to 3, and the thickness of the waveguide substrate is 0.3 to 5.0 mm.

[0012] Compared with the prior art, this utility model provides an optical waveguide with a double-sided coupling structure, which has the following advantages:

[0013] 1. Through an innovative double-sided grating design, the coupling unit on the first surface is used for partial diffraction emission, and the second coupling unit on the second surface is used for reflective diffraction and zero-order reflection, thereby achieving a uniform distribution of the emitted beam. This effectively solves the "dark area effect" present in traditional single-sided coupling waveguides, significantly improves display uniformity, and enables effective control of beam density.

[0014] 2. The second coupling unit of the second surface preferably adopts a dielectric grating plus a metal reflective layer or a high refractive difference all-dielectric grating structure, which has high reflective diffraction efficiency and high visible light transmittance, ensuring high light energy utilization.

[0015] 3. The device has a simple structure and mature manufacturing process, and is suitable for various augmented reality display scenarios such as AR glasses and vehicle HUDs, and has broad application prospects. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a traditional optical waveguide;

[0017] Figure 2 This is a schematic diagram of the optical waveguide with a double-sided coupling structure according to the present invention;

[0018] Figure 3 This is a schematic diagram of the second coupling structure of the first embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of the second coupling structure of the second embodiment of the present invention. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0021] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] Please see Figure 2 The diffractive waveguide 100 with a double-sided coupling structure of this invention includes a waveguide substrate 110, a coupling unit 120, a first coupling unit 130, and a second coupling unit 140. The waveguide substrate 110 is in the form of a flat plate or a curved surface, including a first surface and a second surface arranged opposite to each other. In this embodiment, the coupling unit 120 and the first coupling unit 130 are located on the first surface of the waveguide substrate 110, and the second coupling unit 140 is disposed on the second surface opposite to the first coupling unit 130. The second coupling unit 140 is a diffractive structure with high reflection efficiency. The coupling unit 120 is configured to couple image light (as shown by the arrow in the figure) into the waveguide substrate 110. The image light is totally internally reflected inside the waveguide substrate. After being transmitted to the first coupling unit 130, part of the light is diffracted and emitted, while the remaining light continues to be totally internally reflected within the waveguide substrate 110. When the transmitted light reaches the second coupling unit 140, reflective diffraction and zero-order reflection occur.

[0024] The waveguide substrate 110 can be made of glass, polycarbonate, lithium niobate, or silicon carbide, with a refractive index ranging from 1.5 to 3 and a thickness of 0.3 to 5.0 mm. The first coupling unit 130 is a periodic nanograting, comprising multiple periodically arranged grating ridges and grating grooves between adjacent ridges, with a period of 200-600 nm. The period value depends on the wavelength of the incident light being controlled. The grating duty cycle is 1%-60%, and the grating depth is 20-400 nm, used to control uniform light output. The second coupling unit 140 is also a periodic nanograting with the same period as the first coupling unit 130. The grating ridges of the second coupling unit 140 are aligned with the grating ridges of the first coupling unit 130, with consistent orientation, preventing non-parallel coupling of image light and causing crosstalk, which would affect the imaging display.

[0025] Reference Figure 2 and Figure 3 In the first embodiment, the waveguide substrate 110 is made of polycarbonate material with a refractive index of 1.6 and a thickness of 0.8 mm. The first coupling unit 130 has a period of 400 nm, a duty cycle of 20%, and a depth of 150 nm. The second coupling unit 140 is a dielectric grating, which can be made of materials such as TiO2 / SiNx. The period of the second coupling unit 140 is the same as that of the first coupling unit 130. The surface of the second coupling unit 140 is covered with a metal reflective layer 150. The metal reflective layer 150 is made of materials such as silver, aluminum, or copper, has a reflectivity >90%, and a thickness of 50-100 nm, preferably 80 nm.

[0026] The light rays displaying the image first enter the waveguide substrate 110 through the coupling unit 120 and are propagated within the waveguide substrate 110. Partial diffraction occurs at the grating of the first coupling unit 130. Assuming an efficiency of η1 = 30-50%, there are dark areas between the diffracted beams. The remaining light rays are reflected and continue to be propagated by total internal reflection within the waveguide substrate 110. When the propagated light rays reach the second coupling unit 140 and the metal reflective layer 150, the metal reflective layer 150 blocks the light from leaking out. The light rays undergo reflective diffraction and 0th-order reflection at the second coupling unit 140 and the metal reflective layer 150. The reflective diffraction precisely fills the dark areas of the emitted beams on the upper surface, increasing the density of the emitted beams. The 0th-order reflected beams continue to propagate along the direction of total internal reflection and, after reaching the grating of the first coupling unit 130, excite a second diffraction emission. This cycle repeats, resulting in a uniform distribution of the emitted light rays.

[0027] Reference Figure 2 and Figure 4In the second embodiment, the waveguide substrate 110 is preferably made of glass with a refractive index of 1.5 and a thickness of 0.5 mm. The first coupling unit 130 has a period of 300 nm, a duty cycle of 30%, and a depth of 100 nm. The second coupling unit 140 is a high refractive difference all-dielectric grating, which adopts a Ta2O5 / SiO2 multilayer film structure. It is a periodic multilayer film structure composed of alternating high refractive index materials (Ta2O5, tantalum oxide) and low refractive index materials (SiO2, silicon dioxide), and has the same period as the first coupling unit 130.

[0028] The second coupling unit preferably adopts a dielectric grating with a metal reflective layer or a high refractive difference all-dielectric grating structure, which has high reflective diffraction efficiency and high visible light transmittance, ensuring high light energy utilization.

[0029] The working principle of this device is similar to that of Embodiment 1. The light rays from the image source that are used to display the image first enter the waveguide substrate 110 through the coupling unit 120 and are propagated within the waveguide substrate 110. Partial diffraction occurs at the grating of the first coupling unit 130, while the remaining light rays continue to be propagated by total internal reflection within the waveguide substrate 110. When the propagated light rays reach the second coupling unit, reflective diffraction and 0th-order reflection occur. The reflective diffracted beam precisely fills the dark area of ​​the emitted beam on the upper surface; the 0th-order reflected beam continues to propagate along the direction of total internal reflection and, upon reaching the first coupling unit 130, excites a second diffraction emission. This cycle repeats, resulting in a uniform distribution of the emitted light rays.

[0030] Compared with the prior art, this utility model provides an optical waveguide and a high-resolution display system based thereon, which has the following advantages:

[0031] 1. Through an innovative double-sided grating design, the coupling unit on the first surface is used for partial diffraction emission, while the second coupling unit on the second surface is used for reflective diffraction and 0th-order reflection. This achieves a uniform distribution of the emitted beam, effectively solving the "dark area effect" present in traditional single-sided coupled waveguides, significantly improving display uniformity, and enabling effective control of beam density.

[0032] 2. The second coupling unit of the second surface preferably adopts a dielectric grating plus a metal reflective layer or a high refractive difference all-dielectric grating structure, which has high reflective diffraction efficiency and high visible light transmittance, ensuring high light energy utilization.

[0033] 3. The device has a simple structure and mature manufacturing process, and is suitable for various augmented reality display scenarios such as AR glasses and vehicle HUDs, and has broad application prospects.

[0034] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. An optical waveguide with a double-sided coupling structure, characterized in that, include: The waveguide substrate comprises an input unit, a first output unit, and a second output unit. The input unit and the first output unit are located on a first surface of the waveguide substrate, and the second output unit is disposed on a second surface of the waveguide substrate opposite to the first output unit. The second output unit is a high-reflection-efficiency diffraction structure. The input unit is configured to couple image light into the waveguide substrate. A portion of the image light is diffracted and exited through the first output unit, while the remaining light, upon reaching the second output unit, undergoes reflective diffraction and zero-order reflection before being diffracted and exited through the first output unit.

2. The optical waveguide with a double-sided coupling structure according to claim 1, characterized in that, The first coupling unit is a periodic nanograting, including a plurality of periodically arranged grating ridges and grating slots between adjacent grating ridges. The second coupling unit is a periodic nanograting with the same period as the first coupling unit, and the grating ridges of the second coupling unit are aligned with the grating ridges of the first coupling unit.

3. The optical waveguide with a double-sided coupling structure according to claim 2, characterized in that, The period of the first coupling unit is 200-600 nanometers, and the duty cycle of the grating is 1%-60%.

4. The optical waveguide with a double-sided coupling structure according to claim 1, characterized in that, The second coupling unit is a dielectric grating, and the surface of the second coupling unit is covered with a metal reflective layer.

5. The optical waveguide with a double-sided coupling structure according to claim 1, characterized in that, The second coupling unit is a high refractive difference all-dielectric grating, which adopts a Ta2O5 / SiO2 periodic multilayer film structure.

6. The optical waveguide with a double-sided coupling structure according to claim 1, characterized in that, The waveguide substrate is made of one of glass, polycarbonate, lithium niobate, and silicon carbide, with a refractive index ranging from 1.5 to 3, and the thickness of the waveguide substrate is 0.3 to 5.0 mm.

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